Class _ 
 
 
 
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 Copyright N°_ 
 
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 COPYRIGHT DEPOSIT. 
 
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C^&^-*-*-r J^ yO^T^x.*^ 
 
TWENTIETH CENTURY HANDBOOK 
 
 FOR 
 
 STEAM ENGINEERS^ELECTRICIANS 
 
 WITH QUESTIONS AND ANSWERS 
 
 A PRACTICAL NONTECHNICAL TREATISE 
 
 On the Care and Management of Steam Engines, Boilers 
 and Electric Machinery. With full instructions in 
 Regard to the Intelligent Management of all Classes 
 of Steam Engines, Steam Turbines, Gas Engines, Air 
 Compressors and Elevators, both Electric and Hy- 
 draulic. CLThe section on Electricity is of especial 
 importance to all engineers. : : : : : 
 
 By CALVIN F. SWINGLE, M. E. 
 
 rj 
 
 Author of "Encyclopedia of Engineering," "Examination Questions 
 
 and Answers for Marine and Stationary Engineers," "Modern 
 
 Locomotive Engineering," and "Modern Steam Boilers." 
 
 ILLUSTRATED 
 
 CHICAGO 
 
 FREDERICK J. DRAKE & COMPANY 
 
 PUBLISHERS 
 
^ 
 
 Copyright 1916, 1913, 1910 and 1907 by FREDERICK J. DRAKE & CO. 
 Copyright 1903 by CALVIN F. SWINGLE 
 
 \o 
 
 
 FEB 3 1916 
 
 ©JI.A420648 
 
 
INTEODTTCTION. 
 
 Owing to the very generous reception accorded the first, 
 and second editions of the 20th Century Hand Book for 
 Steam Engineers; there having been over one hundred 
 thousand copies sold, the author was urged to revise, and 
 ) greatly enlarge the present edition, thus making it in a 
 sense an encyclopedia of practical information, covering 
 each department of work in which the stationary engineer 
 is likely to be called upon to engage in the pursuit of 
 his calling. In order to obtain a practical working knowl- 
 edge of steam engineering it is absolutely necessary that 
 the young man who desires to become a successful engineer 
 should start in the boiler-room, that he should thoroughly 
 familiarize himself with all of the details of boiler manage- 
 ment, and while his hands and eyes are thus gradually being 
 trained to the practical part of the work he should at the 
 same time be training his mind in the theoretical part by 
 reading and studying technical books and journals relative 
 to steam engineering. 
 
 Without a doubt the most successful operating engineers 
 are those who combine practice with theory, but the en- 
 gineer in charge of a steam plant should, in addition to 
 his other accomplishments, have at least sufficient technical 
 knowledge to enable him to ascertain, by measurements 
 and calculations, such very important points as the safe 
 working pressure of his boiler, the most economical point 
 of cut off for his engine, whether engine and boiler are 
 properly proportioned for the work to be performed, and 
 many ether details requiring his attention. 
 
 In the following pages the author proposes to deal mait?^ 
 
with the operation of steam engines, boilers, feed pumps, 
 and all the necessary adjuncts of a steam plant, while at 
 the same time considerable space will be devoted to the 
 design, construction, and erection of steam machinery, Gas 
 engines, Air compressors, and Elevators, both electric and 
 hydraulic. In the compilation of the section on Electricity 
 for engineers, special efforts have been put forth to adapt 
 the discussion of this important subject to the needs of 
 engineers, and electricians in charge of central stations; 
 or isolated plants of smaller capacity. Within the past 
 ten years there has been introduced a comparatively new 
 prime mover, in the shape of the steam Turbine, and judg- 
 ing from present indications it has come to stay. Therefore 
 it behooves engineers to make themselves acquainted with 
 it, and the sooner they do so the more will they be benefited 
 by the advent of this stranger. In these pages the au- 
 thor presents to his readers a plain practical description of 
 each of the leading types of steam Turbines now in use, 
 including an explanation of the principles controlling their 
 action, together with rules and instructions for guidance 
 in their operation. In order to facilitate the study of the 
 different subjects treated upon, a series of practical ques- 
 tions and answers will follow the close of each section. 
 And now with the hope that a study of the following pages 
 may prove to be a help to all into whose hands this book 
 may come, the author respectfully dedicates it to his fellow 
 craftsmen, the engineers of America. 
 
 Calvin F. Swingle. 
 
 L. 
 
The Boiler 
 
 Stationary boilers may be divided into four different 
 classes. The first and most simple type, and the one from 
 which the others have gradually evolved, is the plain cylin- 
 der boiler in which the heated gases merely pass under the 
 boiler, coming in contact only with the lower half of the 
 shell and then pass to the stack. These boilers are generally 
 of small diameter (about 30 in.) and great length (30 ft.). 
 
 Fig. 1 
 
 RETURN TUBULAR BOILER — SHOWING SETTING 
 
 Next comes the flue cylindrical boiler, which is somewhat 
 larger in diameter than the former, generally 40 in. diam- 
 eter and 20 to 30 ft. long, with two large flues 12 to 14 in. 
 diameter extending through it. The return tubular boiler, 
 
Steam Engineering 
 
 Fig. 2 
 front view of 250 h. p. cahall horizontal boiler 
 
 consisting of a shell with tubes of small diameter (2 to 4 in.) 
 extending from head to head through which the hot gases 
 from the furnace pass on their way to the stack. This 
 
 k 
 
Return Tubular Boiler 3 
 
 boiler, which comes in the third class, is probably more ex- 
 tensively used in the United States for stationary service 
 than any other type. The fourth class comprises the water 
 tube boilers, in which the water is carried in tribes 3 to 4 
 in. in diameter, sometimes vertical and sometimes inclined, 
 and connected at the top to one end of a steam drum, and 
 having the lower ends of the tubes connected to a mud 
 drum, which is also connected to the opposite end of the 
 steam drum, thus providing for a free circulation of the 
 water. Of the latter type there have been many different 
 kinds evolved during the last one hundred years, the ma- 
 jority of them having had but a brief existence, being com- 
 pelled to obey the inexorable law of the survival of the 
 fittest, and to-day there are a few excellent types of water 
 tube boilers which have become standard and are being ex- 
 tensively used. The margin of safety as regards disastrous 
 explosions appears to be in favor of the water tube boiler. 
 It is not contended that they are entirely exempt from the 
 danger of explosion. On the contrary, the percentage of 
 explosions of water tube boilers in proportion to the num- 
 ber in use is probably as large, if not larger, than it is with 
 boilers of the shell or return tubular type, but the results 
 are seldom so destructive of life or property, for the reason 
 that if one or more of the tubes give way the pressure is 
 released and the danger is past. 
 
 THE CAHALL WATER TUBE BOILER. 
 
 Figures 2 and 3 show, respectively, front and side views 
 of the Cahall horizontal water tube boiler. These boilers 
 are built in sizes of from 125 horsepower up to 850 horse- 
 power, in single units. The boilers are built for working 
 pressures of from 160 pounds per sq. in. up to 500 pounds 
 
4 Steam Engineering 
 
 per sq. in. The steam drums are made of the best open 
 hearth flange steel, the heads for the drums being of the 
 same material, hydraulically flanged. All the sheets are 
 beveled on the edges, bent into shape, and the rivet holes 
 drilled after bending. This insures absolutely round holes, 
 without crystallization, and allows calking of all seams, both 
 
 Fig. 3 
 side view of 250 h. p. c ah all horizontal boiler suspended 
 
 READY FOR BRICK WORK 
 
 inside and outside. In boilers, the working pressure of 
 which is not to exceed 160 lbs. to the sq. in., the longitudinal 
 seams in the drums are double riveted. In those of higher 
 working pressures, that is, from 160 to 500 lbs. per sq. in., 
 all of the horizontal seams are butt and double strapped 
 joints, with six rows of rivets. Each drum is provided at 
 both ends with the Cahall patent swinging man-head. The 
 
 
Cdhall Water Tube Boiler 5 
 
 action of this man-head is as follows: By loosening the 
 nuts, a slight push swings the head in similar to a door, 
 and when it is desired to again close it, it is pulled back to 
 its place, and, owing to its being hinged, the seats come to- 
 gether in exactly the same place every time, thus insuring 
 a tight joint. The flanges on the steam drums for the 
 steam and safety valve openings are all drop forged, from 
 flanged steel plates. Referring to Figure 3, it will be 
 noticed that each section of tubes is connected by nipples 
 to saddles on the steam drums. These saddles or cross 
 boxes are made from open hearth steel, which is melted 
 and run into molds. This steel, after cooling and anneal- 
 ing, presents all the chemical and physical properties of 
 regular boiler plate steel, physical tests on a large number 
 of coupons from these forms showing an elongation of over 
 25 per cent, a reduction in area of over 50 per cent, with a 
 tensile strength of over 60,000 lbs. to the square inch. 
 
 It can be seen from the side view of the boiler (Fig. 3) 
 that it stands on wrought iron supports and cross beams, 
 independent of the brickwork, so that the entire structure 
 is free to contract and expand without any strains occurring 
 either on the setting or on the boiler itself. In this method 
 of suspension, the entire framework is outside of the brick- 
 work, thereby avoiding the possibility of its burning away 
 or weakening through over-heating, as has frequently hap- 
 pened in the case of other designs. 
 
 The fronts for the boiler are what is known as the wrought 
 iron style — that is, the entire general framework of the 
 front is made up of wrought iron or steel beams, channels 
 and girders, and only the panels containing the door frames 
 are cast. This permits of a very light but rigid structure, 
 which it is impossible to crack from the application of in- 
 
Steam Engineering 
 
 L 
 
 Fig. 4 
 
 bear view of 250 h. p. c ah all horizontal boiler suspended 
 
 ready for brick work 
 
Cahall Water Tube Boiler 7 
 
 ternal heat, which has been heretofore one of the greatest 
 faults found with this type of boiler. 
 
 All the tubes used in this boiler are made of the best 
 knobbled charcoal iron, which though very much more ex- 
 pensive than the standard iron boiler tube, yet repays the 
 customer in future years for the additional investment in 
 first cost. The general fittings and trimmings of the boiler 
 are of the highest grade purchasable, the safety valves being 
 of the solid nickel seated type. The water column used is 
 either the Reliance or Pittsburg High and Low Water 
 Alarm. The blow-off valves are specially made under 
 patents owned by the Aultman & Taylor Machinery Co., 
 and are so designed that the discs are renewable at any 
 time, and both the disc and valve seat can be cleaned with- 
 out taking the valve apart. 
 
 It will be noticed in the illustration (Fig. 4) giving the 
 rear view of the boiler that these valves have two wheels, 
 one directly above the other, the upper one being smaller 
 than the lower. The larger wheel forces the disc down on 
 its seat, the smaller wheel revolves the spindle carrying the 
 disc. By revolving the larger wheel until the disc rests 
 lightly on its seat and then revolving the smaller wheel, the 
 disc is rotated on its seat, effectually clearing it of any ob- 
 structions that may have accumulated thereon. 
 
 The side cleaning doors for the boiler are of a new de- 
 sign, which permits the use of only one door instead of 
 two, and when the door is opened it is thrown back entirely 
 from the slot into which it fits, leaving a full, free opening 
 for the introduction of the steam hose, and when the door 
 is closed, wedge-shaped fire-brick tile, which line the door, 
 are pushed forward in a straight line into the opening, 
 making a perfectly smooth wall on the inside and an abso- 
 
8 Steam Engineering 
 
 lutely tight joint against the leakage of air into the setting. 
 Where very high pressures are to be used, say in excess 
 of 225 pounds to the square inch, the headers or manifolds 
 for the reception of the tubes are made of the same material 
 used in the cross-boxes on the drums, viz., special "flowed" 
 steel. 
 
 THE HEINE SAFETY BOILER. 
 
 Figure 5 shows a general view of the Heine water tube 
 boiler. 
 
 The boiler is composed of the best lap welded wrought 
 iron tubes, extending between and connecting the inside 
 faces of two "water legs," which form the end connections 
 between these tubes and a combined steam and water drum 
 or "shell," placed above and parallel with them. (Boilers 
 over 200 horsepower have two such shells.) These end 
 chambers are of approximately rectangular shape, drawn 
 in at top to fit the curvature of the shells. Each is composed 
 of a head plate and a tube sheet, flanged all around and 
 joined at bottom and sides by a butt strap of same material, 
 strongly riveted to both. The water legs are further stayed 
 by hollow stay bolts of hydraulic tubing, of large diameter, 
 so placed that two stays support each tube, and hand hole 
 and are subjected to only very slight strain. Being made 
 of heavy metal, they form the strongest parts of the boiler 
 and its natural supports. The water legs are joined to 
 the shell by flanged and riveted joints and the drum is 
 cut away at these two points to make connection with inside 
 of water leg, the opening thus made being strengthened 
 by bridges and special stays, so as to preserve the original 
 strength. 
 
 The shells are cylinders with heads dished to form 
 
1 
 
 Heine Safety Boiler 
 
 9 
 
 parts of a true sphere. The sphere is everywhere as strong 
 as the circle seam of the cylinder which is well known 
 to be twice as strong as its side seam. Therefore these 
 heads require no stays. Both the cylinder and its spherical 
 
 Fig. 5 
 375 h. p. heine boiler 
 
 heads are therefore free to follow their natural lines of 
 expansion when put under pressure. Where flat heads 
 have to be braced to the sides of the shell, both suffer local 
 distortions where the feet of the braces are riveted to them, 
 making the calculations of their strength fallacious. To 
 
10 Steam Engineering 
 
 the bottom of the front head a flange is riveted into which 
 the feed pipe is screwed. This pipe is shown in the cut 
 with angle valve and check valve attached. 
 
 On top of shell near the front end is riveted a steam noz- 
 zle 01 saddle, to which is bolted a tee. This tee carries the 
 steam valve on its branch, which is made to look either to 
 front, rear, right or left; on its top the safety valve is 
 placed. The saddle has an area equal to that of stop valve 
 and safety valve combined. The rear head carries a blow- 
 off flange of about the same size as the feed flange, and a 
 manhead curved to fit the head, the manhole supported by 
 a strengthening ring outside. On each side of the shell 
 a square bar, the tile-bar, rests loosely in flat hooks riveted 
 to the shell. This bar supports the side tiles whose other 
 ends rest on the side walls, thus closing in the furnace or 
 flue on top. The top of the tile bar is two inches below 
 low water line. The bars rise from front to rear at the rate 
 of one inch in twelve. When the boiler is set, they must 
 be exactly level, the whole boiler being then on an incline, 
 i. e., with a fall of one inch in twelve from front to rear. 
 
 It will be noted that this makes the height of the steam 
 space in front about two-tliirds the diameter of the shell, 
 while at the rear the water occupies two-thirds of the shell, 
 the whole contents of the drum being equally divided be- 
 tween steam and water. 
 
 The tubes extend through the tube sheets into which 
 they are expanded with roller expanders; opposite the end 
 of each and in the head plates is placed a hand hole of 
 slightly larger diameter than the tube, and through which 
 it may be withdrawn. These hand holes are closed by small 
 cast iron hand hole plates, which can be easily removed 
 for the purpose of cleaning or inspecting a tube. Figure 
 
Heine Safety Boiler 
 
 11 
 
 *t~ 3 
 
 — 
 
 \JT 
 
 3 
 
 
 Hf 
 
 Hi 
 
 Fig. 6 
 
 detail of water-leg, hand hole plates and yokes, etc., of 
 
 heine boilers 
 
12 
 
 L. 
 
 Steam Engineering 
 
 '"1 
 
 • ■ 
 
 Fig. 7 
 side sectional view of heine boiler 
 
 6 shows these hand hole plates, marked H. In the upper 
 corner one is shown in detail, H 2 being the top view, and 
 
Heine Safety Boiler 13 
 
 H 3 a side view, while H 1 is the yoke or crab placed outside 
 to support the bolt and nut. Figure 7 is a longitudinal 
 section showing inside construction. The mud drum D is 
 located well below the water line, parallel to and three 
 inches above the bottom of the shell. It is of oval section, 
 slightly smaller than the manhole. It is entirely enclosed, 
 except about eighteen inches of its upper portion at the 
 front end, which is cut away nearly parallel with the water 
 line. The mud drum D is made of strong sheet iron, with 
 cast iron heads, and its action is as follows : 
 
 The feed water enters it through the pipe F about one- 
 half inch above its bottom ; even if it has previously passed 
 the best heaters it is colder than the water in the boiler. 
 Hence it drops to the bottom, and, impelled by the pump 
 or injector, passes at a greatly reduced speed to the rear 
 of the mud drum. As it is gradually heated to near boiler 
 temperature it rises and flows slowly in reverse direction 
 to the open front of the mud drum ; here it passes over in a 
 thin sheet and is immediately swept backward into the 
 main body of water by the swift circulation, thus becom- 
 ing thoroughly mixed with it before it reaches the tubes. 
 During this process the mud, lime, salts, and other precipi- 
 tates are deposited as a sort of semi-fluid "sludge" near 
 the rear end of the mud drum, whence it is blown off at 
 frequent intervals through the blow-off valve N. As the 
 speed in the mud drum is only about one-fiftieth of that in 
 the feed water pipe, plenty of time is given for this action. 
 Any precipitates which may escape the mud drum at first, 
 will of course form a scale on the inside of the tubes, etc. 
 But the action of expansion and contraction cracks off scale 
 on the inside of a tube much faster than on the outside, 
 and then the circulation sweeps the small chips, like broken 
 
14 Steam Engineering 
 
 egg-shells, upward, and as they pass over the month of the 
 mnd drum they drop in the eddy, lose velocity in this slow 
 current and fall to the bottom, and, being pushed by the 
 feed current to the rear end, are blown off from the mud 
 drum with other refuse. On opening a Heine boiler after 
 some months' service, such bits of scale, whose shape identi- 
 fies them, are always found in the mud of the mud drum. 
 Very little loose scale is found on the bottom of the water 
 legs ; the current through the lower tubes, always the swift- 
 est, brushes too near the bottom to allow much to lodge 
 there. 
 
 This explanation of the action of the mud drum shows 
 how the inside of the tubes may be kept clean. To keep the 
 outside clear of soot and ashes which deposit on, and some- 
 times even bake fast to the tubes, each boiler is provided 
 with two special nozzles, with both side and front outlets, a 
 short one for the rear, a long one for the front. They are 
 of three-eighth inch gas pipe and each is supplied with 
 steam by a one-half inch steam hose. The nozzle is passed 
 through each stay bolt in turn, and thus delivers its side 
 jets on the three or four tubes adjacent, with the full force 
 of the steam, at the short range of two inches, knocking the 
 soot and ashes off completely, while the end jet carries 
 them into the main draft current, to lodge at points in 
 breeching or chimney base convenient for their ultimate 
 removal. An inspection of the cuts will show that the 
 stay bolts are so located that the nozzle can in turn be 
 brought to bear on all sides of the tubes. As soon as the 
 nozzle is withdrawn from the stay bolt this is closed air- 
 tight by a plain wooden plug. 
 
 In cleaning a boiler it is only necessary to remove every 
 fourth or fifth handhole plate in the front water leg; the 
 
Heine Safety Boiler 15 
 
 water hose, supplied with a short nozzle, can be entered in 
 all the adjacent tubes, owing to the ample dimensions of 
 the water leg. In the rear water leg only one or two hand- 
 holes in the lower row need be opened to let the water and 
 debris escape. The others in rear water leg are frequently 
 left untouched for years. A lamp or candle hung on a 
 wire through the manhead may be held opposite each tube 
 so that it can be perfectly inspected from the front. 
 
 The feed pipe F enters the mud drum through a loose 
 joint in front, and the blow-off pipe N is screwed tightly 
 into its rear head, passing by a steam-tight joint through 
 the rear head of the shell. Just under the steam nozzle is 
 placed a dry pipe A. L is a deflection plate, extending 
 from the front of the shell, and inclined upwards, beyond 
 the mouth of the front water leg. The throat or mouth 
 of each water leg is large, to equal in area the total tube 
 area, and where it joins the shell it increases gradually in 
 width by double the radius of the flange. In the setting, 
 the front water leg is placed firmly on a set of strong 
 cast iron columns, bolted and braced together by the door 
 frames, dead plate, etc., forming the fire front. This is the 
 fixed end. The rear water leg rests on rollers, free to 
 move on cast iron plates set in the lower masonry of the 
 rear wall. The brick work does not close in entirely to 
 the boiler, the space between being filled with tow or waste 
 saturated with fire clay or other refractory, but pliable 
 material, thus leaving the boiler and its walls each free 
 to move separately during expansion or contraction, with- 
 out disturbing any joints in the masonry. On the lower, 
 and between the upper tubes, are placed light fire brick 
 tiles. The lower tier extends from the front water leg to 
 within a few feet of the rear one, leaving there an upward 
 
16 Steam Engineering 
 
 passage across the rear ends of the tubes for the flame and 
 gases. The upper tier closes into the rear water leg, and 
 extends forward to within a few feet of the front one, thus 
 leaving an opening for the gases in front. The side tiles 
 extend from the side walls to tile bars, and close up to the 
 front water leg, and front wall, and leave open the final 
 uptake for the waste gases over the back part of the shell, 
 which is here covered above the water line with a row of 
 lock fire brick, resting on the tile bars. The rear wall, and 
 one parallel to it, are arched over the shell a few feet for- 
 ward, and form the uptakes. 
 
 THE BABCOCK & WILCOX WATER TUBE BOILER. 
 
 Description. Figure 8 presents a side view of the Bab- 
 cock & Wilcox boiler, and Figure 9 a partial section. 
 
 This boiler is composed of lap-welded wrought iron tubes, 
 placed in an inclined position and connected with each 
 other, and with a horizontal steam and water drum, by 
 vertical passages at each end, while a mud-drum is con- 
 nected to the rear and lowest point in the boiler. 
 
 The end connections are in one piece for each vertical 
 row of tubes, and are of such form that the tubes are "stag- 
 gered" (or so placed that each row comes over the spaces 
 in the previous row). The holes are accurately sized, made 
 tapering, and the tubes fixed therein by an expander. The 
 sections thus formed are connected with the drum, and 
 with the mud-drum also by short tubes expanded into 
 bored holes, doing away with all bolts, and leaving a clear 
 passageway between the several parts. The openings for 
 cleaning opposite the end of each tube are closed by hand- 
 hole plates, the joints of which are made in the most thor- 
 ough manner, by milling the surfaces to accurate metallic 
 
Babcock and Wilcox Boiler 
 
 17 
 
 Fig. S 
 
 SIDE VIEW OF BABCOCK & WILCOX BOILER OF WROUGHT STEEL 
 CONSTRUCTION 
 
18 Steam Engineering 
 
 contact, and are held in place by wrought-iron forged- 
 clamps and bolts. The) r are tested and made tight under 
 a hydrostatic pressure of 300 pounds per square inch,, iron 
 to iron, and without rubber packing or other perishable 
 substances. 
 
 The steam and water drums are made of flange iron or 
 steel, of extra thickness, and double riveted. They can 
 be made for any desired pressure, and are always tested 
 at 50 per cent above the pressure for which they are con- 
 structed. The mud-drums are of cast iron, as the best 
 material to withstand corrosion, and are provided with 
 ample means for cleaning. 
 
 Erection. In erecting this boiler, it is suspended entirely 
 independent of the brickwork, from wrought iron girders 
 resting on iron columns. This avoids any straining of the 
 boiler from unequal expansion between it and its enclosing 
 walls, and permits the brickwork to be repaired or re- 
 moved, if necessary, without in any way disturbing the 
 boiler. All the fixtures are extra heavy and of neat designs. 
 
 Operation. The fire is made under the front and higher 
 end of the tubes, and the products of the combustion pass 
 up between the tubes into a combustion chamber under the 
 steam and water drum; from thence they pass down be- 
 tween the tubes, then once more up through the spaces be- 
 tween the tubes, and off to the chimney. The water inside 
 the tubes, as it is heated, tends to rise towards the higher 
 end, and as it is converted into steam — the mingled col- 
 umn of steam and water being of less specific gravity than 
 the solid water at the back end of the boiler — rises through 
 the vertical passages into the drum above the tubes, where 
 the steam separates from the water and the latter flows 
 back to the rear and down again through the tubes in a con- 
 
Bab cock and Wilcox Boiler 
 
 19 
 
 Fig. 9 
 partial vertical section babcock & wilcox boiler 
 
20 
 
 Steam Engineering 
 
 tinuous circulation. As the passages are all large and 
 free, this circulation is very rapid, sweeping away the 
 steam as fast as formed, and supplying its place with wa- 
 
 Fig. 10 
 
 STANDARD FRONT OF BABCOCK & WILCOX BOILER 
 
 ter; absorbing the heat of the fire to the best advantage; 
 causing a thorough commingling of the water throughout 
 the boiler and a consequent equal temperature, and pre- 
 
 L 
 
Stirling Water Tube Boiler 21 
 
 venting, to a great degree, the formation of deposits or 
 incrustations upon the heating surfaces, sweeping them 
 away and depositing them in the mud-drum, whence they 
 are blown out. 
 
 The steam is taken out at the top of the steam-drum 
 near the back end of the boiler after it has thoroughly sep- 
 arated from the water, and to insure dry steam, a per- 
 forated dry-pipe is connected to the nozzle inside the drum. 
 
 THE STIRLING WATER-TUBE SAFETY BOILER. 
 
 The Stirling boiler, Figures 11 and 12, consists of three 
 tipper or steam drums, each connected by a number of tubes 
 (called a "bank") to a lower or mud drum. Suitably dis- 
 posed fire tile baffles between the banks direct the gases into 
 their proper course. Shorter tubes connect the steam spaces 
 of all upper drums, also water spaces of front, and middle 
 drums. The boiler is supported on a structural steel frame- 
 work, around which is built a brick setting, whose only 
 office is to provide furnace space, and serve as a housing to 
 confine the heat. The entire front is of metal of appro- 
 priate and artistic design. These parts, together with the 
 usual valves and fittings, constitute the completed boiler, 
 which represents the acme of simplicity and eliminates the 
 complication of the older types. 
 
 The drums vary from 36 to 54 inches in diameter and 
 are made of the best open hearth flange steel. The plates 
 extend the entire distance between heads, hence there are 
 no circular seams. The longitudinal seams — which are 
 double or triple riveted according to the working pressure 
 to be carried — are so placed that they are not exposed to 
 high temperature. The drum heads are hydraulically 
 dished to proper radius; each drum is provided with one 
 
22 Steam Engineering 
 
 manhole, and the manhole plate and arch bars are of 
 wrought steel; four manhole plates, which can be removed 
 in ten minutes, give access to the entire interior of the 
 boiler, and expose every tube end, rivet and joint. The 
 drum interiors are perfectly clear; there are no baffles, 
 stays, tie-rods, mud pipes or other obstructions in them. 
 
 The tubes are best lap-welded mild steel. They are 
 slightly curved at the ends to permit them to enter the 
 drums normally and to provide for free expansion of the 
 boiler when at work. The tubes are expanded directly 
 into reamed holes in tube sheets of the drums, hence the 
 annular recess between tubes and the cast headers of some 
 types of boiler is eliminated, and failure of tubes by pit- 
 ting through corrosion, caused by accumulation of soot in 
 these recesses, is avoided. There are no short nipples and 
 no tube joints in places which can be reached only by joint- 
 ed handles on the tube expander, rendering it impossible 
 to determine when the tube has been properly expanded. 
 In the Stirling boiler every tube end is visible and acces- 
 sible. As the entire weight of boiler and contents is sup- 
 ported on the steel frame work, cracking of the setting, 
 due to unequal settlements, is obviated, and no blocking is 
 needed when the brick work has to be repaired. The design 
 of frame work can be modified to suit special conditions. 
 The brick setting is so clearly shown in Figures 11 and 12 
 tli at an extended description is unnecessary. No special 
 shapes or other material not found in open market are need- 
 ed. Any necessary repairs to the brick work can be made 
 without disturbing the boiler connections. In the design of 
 the Stirling furnace it will be seen by reference to Figures 
 11 and L2, that a fire brick arch is sprung over the grates, 
 and immediately in front of the first bank of tubes. The 
 
4 
 
 
Stirling Water Tube Boiler 
 
 23 
 
 large triangular space between boiler front, tubes and mud 
 drum is available for a combustion chamber, and for instal- 
 lation of sufficient grate surface to meet the requirements 
 of the lowest grades of fuel. 
 
 Baffles and Course of Gases. The baffle walls rest di- 
 rectly upon the tubes, and guide the course of the gases up 
 the front bank, down the middle and up the rear bank, 
 thus bringing them into such intimate contact with the 
 
 H 
 
 JH 
 
 A ; -f* 
 
 ill 
 
 fH rfl m fi PUfl qua in 
 
 
 ELEVATION 
 FLAJ TILE 2 INCHES THICK 
 
 6 6&<S6 6 6 5 6 6 Wo 6 6 off 
 
 SECTION ON A-B 
 
 u v_L_ 
 
 Fig. 13 
 elevation and section of firetile baffles in stirling boilers 
 
 boiler surface that the heat is quickly and thoroughly ex- 
 tracted from them. In no other boiler are the gases com- 
 pelled to travel as far before reaching the stack, and the 
 effect upon economy is evident. The baffles are made of 
 plain rectangular firetile carried in stock by all fire-brick 
 dealers, in contrast to the special formed bricks (obtain- 
 able only from the manufacturer) required by many types 
 
24 Steam Engineering 
 
 of water-tube boiler. Another marked advantage of the 
 Stirling baffles is that since no tubes pass between or 
 through the tiles (see Fig. 13), they are not pried apart 
 and made leaky by distorted tubes; they can be removed 
 and replaced without disturbing a tube. Baffles built across 
 the tubes, as in many boilers, are damaged by pulling a 
 faulty tube through them, and can be repaired in but one 
 way — by removal of every tube necessary to permit a man 
 to crawl in and reach the defective spot. 
 
 Simplicity. There are no details of complicated shape; 
 no flat surfaces, tie-rods, water-legs, headers, return-bends, 
 outside circulating pipes to plug up; no multitudinous 
 handhole plates to be removed and packed with gaskets, 
 or to be ground and scraped to a fit whenever boiler is 
 opened; no baffles or mud pipes in the drums; no short 
 nipples, seams exposed to heat, or parts inaccessible for 
 cleaning. 
 
 Expansion and Contraction. In the Stirling, the mud 
 drum is not embedded in brickwork, but is suspended on 
 the tubes which connect it with the upper drums. 
 
 In consequence of this construction, not only may the 
 mud drum with perfect freedom move an amount repre- 
 senting the resultant expansion of the boiler, but any dif- 
 ference in expansion between the individual tubes, such 
 as caused when one side of the furnace is being cleaned 
 and other side is excessively hot, is taken up by the curve 
 in the tube. The boiler therefore stays tight, and is en- 
 tirely free from the stresses and frequent leaks caused by 
 unequal expansion of straight tubes rigidly connected at 
 each end to headers, water-legs, or large drums. It will 
 thus be seen that the bent tube performs in the boiler the 
 same function as an expansion loop in a steam line. 
 
Stirling Water Tube Boiler 25 
 
 Rapid Circulation. The path of the circulation in the 
 Stirling is as follows: The water is fed into upper rear 
 drum, passes down the rear bank of tubes to the lower 
 drum, thence up the front bank to forward steam drum. 
 Here the steam formed during passage up the front bank 
 disengages and passes through the upper row of cross 
 tubes into the middle drum, while the solid water passes 
 through the lower cross tubes into middle drum, then 
 down the middle bank to the lower drum, from which it is 
 again drawn up the front bank to retrace its former course 
 until it is finally evaporated. The steam generated in the 
 rear bank passes through cross tubes to the center drum. 
 
 The temperature of gases in contact with the tubes will 
 evidently be greatest at the bottom of the front bank, and 
 gradually decreases as the gases proceed along their course 
 to the breeching. Obviously then the velocity of water 
 circulation and quantity of steam generated will be a max- 
 imum in the front bank; in the rear bank there is a slow 
 circulation downward equal to the quantity of water evap- 
 orated in the other two banks. 
 
 Eapid circulation is essential for the following reasons : 
 
 (1) To keep all parts of the boiler at practically the 
 same temperature, thus eliminating severe stresses due to 
 unequal expansion. 
 
 (2) To permit quick raising of steam and rapid re- 
 sponse to sudden demands on the boiler capacity. 
 
 (3) To sweep away from the heating surfaces all steam 
 bubbles as fast as formed, and thereby prevent "steam 
 pockets," which quickly burn out the tubes. This is so 
 particularly the case where intense local heating occurs 
 due to use of gas or oil fuel, that some types of boiler fairly 
 well adapted to coal cannot be successfully used with these 
 fuels. 
 
26 Steam Engineering 
 
 The third requirement is met only indifferently or, not 
 at all in those types of boilers in which tubes often num- 
 bering as many as eighteen must discharge their entire con- 
 tent of steam and water through a narrow water-leg. or, 
 worse still, through a single nipple whose cross section is 
 equal to that of but one tube. At 150 pounds' gauge one 
 cubic foot of water, when converted into steam, will have 
 a volume of about 151 cubic feet. In consequence of this 
 great increase in volume, as soon as the boiler is forced, the 
 nipple area becomes insufficient, steam pockets form in 
 the lower tubes, which then become overheated, and buckle 
 and leak, and finally burn out. So inadequate are these 
 nipples and headers that recent experiments of M. Brull 
 have shown that in boilers whose circulation is constricted 
 by nipples or narrow water-legs, the circulation in the up- 
 per tubes reverses, that is, it goes from the front to rear 
 instead of in the opposite way, as intended. In conse- 
 quence of this, much matter suspended in the water is 
 swept into the bottom tubes, which fact, in connection with 
 the steam pockets, explains why those tubes so rapidly fail. 
 
 In the Stirling boiler there is no constriction of the cir- 
 culation, as each tube discharges directly into the drums, 
 without intervention of headers, nipples or water-legs. The 
 nearly vertical position of the tubes also promotes rapid 
 circulation, hence steam pockets cannot form, and a fruit- 
 ful cause* of interrupted service and tube renewals is thus 
 eliminated. 
 
 A most fruitful cause of burnt tubes is a piece of scale 
 which becomes detached and falls on the bottom of the 
 tube, and the spot under it is certain to burn out quickly. 
 The Stirling is free from this source of tube destruction, \ 
 because while the scale will not form in the hotter tubes r l 
 
Stirling Water Tube Boiler 27 
 
 unless the boiler is neglected, even if it does form owing to 
 such neglect and a piece becomes detached, it will slide 
 down to the mud drum instead of lodging. 
 
 Cleaning the Interior. By removing four manhole plates, 
 which can be done in ten minutes, the entire boiler interior 
 is accessible for cleaning. From the preceding discussion 
 it is evident that the precipitates are settled into the mud 
 drum, whence they are blown off at intervals; the scale is 
 practically confined to the rear bank of tubes, and by reason 
 of escaping the high temperatures it is soft and easily 
 detached. Consequently it happens in most cases that only 
 the rear bank needs cleaning each time the boiler is opened, 
 while the others need only occasional attention. The scale 
 is quickly and cheaply removed by a "turbine cleaner," 
 described and illustrated in the section on Boiler Opera- 
 tion. 
 
 Cleaning the Exterior. Ample cleaning doors are pro- 
 vided both in the sides and rear of the setting, so that the 
 exterior of the heating surfaces may be kept clean and all 
 accumulations of soot, ashes, etc., blown off as rapidly as 
 they form, by using a steam blower-pipe which is furnished 
 with every boiler. 
 
 Durability. By reason of the elimination of thick plates 
 and riveted joints exposed to the fire; cast metal of all 
 kinds; parts of irregular shape and uncertain strength; 
 stresses due to unequal expansion, multitudes of caps, joints 
 and nipples, and similar objectionable details, the Stirling 
 boiler is free from parts liable to get out of order. The 
 prevention of scale deposits in the hottest tubes; the per- 
 fect facilities for keeping the boiler clean; the rapidity of 
 vater circulation and impossibility of forming steam 
 ockets, all combine to protect the tubes against burning 
 
28 
 
 Steam Engineering 
 
 out. Hence the necessity of repairs to the boiler itself \S 
 extremely remote. The setting is simple and substantial 
 and not subject to derangement other than the natural 
 wear of surface lining. 
 
 MAXIM WATER-TUBE BOILER. 
 
 The Maxim water- tube boiler (Figs. 14 and 15) consists 
 of two drums, one above the other, connected by tubes. 
 
 Fig. 14 
 front elevation maxim boiler 
 
Maxim Water Tube Boiler 
 
 29 
 
 Each tube has two bends, thus providing for unequal ex- 
 pansion and contraction. The space between the tubes is 
 greater than the diameter of the tubes, so that any tube 
 can be passed through the space between. The tubes, which 
 are nearly vertical, are arranged in parallel rows, the lower 
 
 Fig. 15 
 maxim boiler 
 
 tube plates being cylindrical, and the bottom end of every 
 tube is opened to the lower drum, thus enabling the flue 
 dust, mud and loose scale to drop away from the heating 
 surface. There are no riveted joints exposed to the flames 
 or fire gases, and there are no cylinders subject to external 
 pressure. 
 
30 Steam Engineering 
 
 The heating surface is arranged so as to break up the 
 current of heated gases, which travels three times the length 
 of the tube, the form and direction of the gas current being 
 changed seven times between the furnace and chimney, 
 to insure a low temperature to the escaping gases. 
 
 The circulation is constant, the return circulation being 
 provided for by a third set of tubes, which are subjected 
 to the heat of the gases just before reaching the chimney. 
 As the cold feed water meets the gases as they leave the 
 boiler, the front section of the tube, which receives the 
 feed water, acts as an economizer and pun* tier. 
 
 The furnace of this type of boiler is constructed of fire- 
 brick, and is built under the boiler. Between the furnace 
 and each combustion chamber there is a throat contracted 
 to the proper size for drafts, the purpose being to insure a 
 better combustion bv an intimate mixture of s;ases. The 
 illustrations show a side view, sectional view through A B, 
 and a front view. 
 
 THE BIGELOW-HORNSBY WATER-TUBE BOILER. 
 
 The American rights to manufacture the Hornsby wa- 
 ter-tube boiler, which has been on the English market five 
 years, were recently acquired by the Bigelow Company, of 
 New Haven, Conn., hence in this country it will be known 
 as the "Bigelow-Hornsby" boiler. It has been re-designed 
 in a measure, to meet the requirements of American high- 
 pressure practice. A general idea of its construction may 
 be obtained from Fig. 16, which shows a section through 
 the setting. It will be noted that the boiler is supported 
 entirely from the overhead beams, leaving the lower part 
 free to respond to expansion stresses. The front tubes are 
 inclined at an angle of 68 degrees, and the rear units 
 
Bigelow-Hornsby Boiler 
 
 31 
 
 Fig. 16 
 
 SECTION THROUGH SETTING OF BIGELOW-HORNSBY BOILER 
 
 are vertical, as shown. Only two lengths of tubes are 
 used. Each section is independent of its neighbor, except 
 the nipples connecting with the steam drum and the equal- 
 
32 Steam Engineering 
 
 izing nipples which connect the bottom drums of the rear 
 sections. This flexible form of construction permits the 
 building of very large units, even larger than the 2,200- 
 horsepower Hornsby boilers at the Bow Street station of 
 the Charing Cross & London Electricity Works, where four 
 boilers containing 21,700 square feet of heating surface 
 evaporate in regular service 110,000 pounds of water per 
 hour. A large percentage of the heating surface is exposed 
 to the radiant heat of the furnace, and to the first pass of 
 gases, before these have reached any other heating surface. 
 The tubes of the front unit, which are located in front of 
 the baffles, comprise more than 12 per cent of the heating 
 surface of the boiler. 
 
 The feed-water is admitted into the bottom drum of the 
 rear unit and is advanced gradually from the coldest to 
 the hottest portion of the boiler, first passing up the entire 
 length of the tubes in the rear unit, then from the top of 
 those tubes to the unit immediately in front, down this 
 unit, and up the two front units and back through the 
 steam drum to the first vertical unit at the rear of the 
 steam drum. There is also, as may be conceived, a rapid 
 local circulation in each of the units while the general 
 circulation is going forward. The speed of the feed-water 
 up the rear unit being regulated by the amount of steam 
 generated, ample time is permitted for sediment and scale- 
 forming matter to be deposited in the bottom drum of 
 this unit. All liberation of steam from the water sur- 
 faces takes place in the upper drums and is entirely unre- 
 strained, the full area of the tube openings communicating 
 with the drums. The transfer of steam and water between 
 units occurs through separate nipples, and the water nip- 
 ples are required merely to care for the general circulation 
 through the boiler. 
 
Bigeloiv-Hornsby Boiler 
 
 33 
 
 The arrangement of this boiler is such that it can be 
 baffled so that the products of combustion are carried uni- 
 formly over the heating surfaces in thin layers, there being 
 no large unrestricted paths parallel to the heating surfaces 
 through which the gases can flow in their passage to the 
 
 Fig. 17 
 
 uptake. Fig. 17, which is a horizontal section through 
 some of the rear units, shows how they are arranged with 
 reference to the gas currents, and how the baffle-plates 
 serve to guide the gases through in substantially uniform 
 passages. 
 
34 Steam Engineering 
 
 The smoke flue can be taken off at the back of the boiler 
 at any point between the top and bottom. All the tubes 
 are straight and every tube in each section can be reached 
 for cleaning by the removal of a single manhole cover. 
 
 The boiler is built to a" factor of safety of five for 200 
 pounds working pressure, and it is stated that a test sec- 
 tion has been subjected to hydrostatic pressure of 1,000 
 pounds without rupture. The ratio of grate surface to 
 heating can be made as low as 1 to 26. 
 
 VTICKES VERTICAL WATER-TUBE BOILER. 
 
 This boiler (see Fig. 18) consists primarily of two cyl- 
 inders joined together by straight tubes, which are divided 
 by a fire brick tile passing through their center into two 
 compartments. The whole is then erected in a vertical 
 position and surrounded by brickwork. 
 
 Drum. The two cylinders are duplicates in their diam- 
 eter and general construction, but differ in height and ar- 
 rangement of convexed heads. The top cylinder, desig- 
 nated hereafter, from its use, as the steam drum, is the 
 longer, the length and diameter being varied in accordance 
 with the size of boiler desired and local requirements. 
 
 The bottom cylinder, designated hereafter, from its use, 
 as the mud drum, is the shorter, and is varied in the di- 
 mension as to diameter and length in accordance with the 
 power of boiler required and local conditions. Both drums 
 are closed at one end with the tube sheet, and at the other 
 end with convexed heads. 
 
 Tubes. The mud and steam drums are joined together 
 by the tubes, which are perfectly straight in themselves 
 and plumb, in position, when expanded into the two tube 
 sheets. They are arranged in parallel rows, from furnace 
 
Wiches Vertical Water Title Boiler 
 
 35 
 
 Fig. 18 
 wickes vertical water tube boiler 
 
 to stack, with a clear space between rows sufficient to per- 
 mit of introducing a small hoe for the purpose of removing 
 
36 Steam Engineering 
 
 any deposit of soot of of sediment which has fallen from 
 the tubes and accumulated on the mud drum tube sheet. 
 
 Manholes. In the convexed head of the steam drum 
 one large manhole, and a number of handholes, are placed, 
 and in the shell of the mud drum on a level with the floor 
 another manhole is placed. 
 
 This arrangement permits entering the boiler at the 
 highest and lowest points by simply breaking two joints, 
 from which points an examination may be made, or the 
 tubes cleaned'. By the introduction of heavy fire clay tile, 
 the tubes are divided into two compartments. The tubes 
 in the forward compartment are called the "risers," and 
 those in the rear compartment the "downcomers," since 
 the heat, and the water, mingled with steam, rise in the 
 forward tubes, and both heat and the water in a solid col- 
 umn descend in those forming the rear compartment, the 
 steam having passed into the upper drum. This gives the 
 heat two complete sweeps through the entire length of the 
 boiler, and the second sweep from above downward. The 
 heat in its double passage surrounds completely and closely 
 the tubes in both compartments. 
 
 Water Line. The water line in this boiler is maintained 
 in the steam drum, at a sufficient height to insure the com- 
 plete submersion of the tubes. 
 
 Baffle Plate. On a level with the water line, and ex- 
 tending over the tubes in the front compartment, is the 
 baffle plate, which deflects the water of circulation rising, 
 commingled with its steam, directly to the "downcomers," 
 and without splashing and spraying the steam room direct- 
 ly above with globules or masses of water. 
 
 Liberating Surface. Fully two-thirds of the entire area 
 of steam drum is liberating surface, and, as the liberation 
 
Wiclces Vertical Water Tube Boiler 37 
 
 takes place mainly over the "downcomers," it does so in the 
 quietest manner and in the absence of violent ebullition or 
 turmoil. 
 
 Steam Room. The large steam room is therefore en- 
 tirely free from water, and the steam outlet is the topmost 
 point, which is far away from the water line, in large boil- 
 ers the distance being from six to seven feet. On the other 
 hand, the blow-off is at the very lowest point, and where 
 all impurities are precipitated by gravity, and by separa- 
 tion due to the flow of the water of circulation. 
 
 Feed Water. The feed water may be introduced in the 
 steam drum directly into the "downcomers" and far below 
 the water line, or in the mud drum above the precipitated 
 sediment. The latter method, viz., introducing the feed 
 water into the mud drum is to be preferred. 
 
 Setting. The brick work setting of the Wickes boiler is 
 so arranged that it is entirely independent of the weight 
 of the boiler, and is therefore free to expand or contract as 
 its co-efficient may dictate, thus allowing the boiler to ex- 
 pand and contract in accordance with the special laws gov- 
 erning its change of form. 
 
 The gases of combustion are closely confined to the tubes, 
 after their generation in the furnace, and on their passage 
 to the stack. The direct flow of the heat is, by virtue of 
 the draft over the tile, and down by the shortest possible 
 route, or path of least resistance; while heat of radiation 
 rises naturally and surrounds the steam drum which, as 
 will be seen by reference to Fig. 18, is surrounded by brick 
 work to its top seam. It is claimed by the manufacturers 
 of this boiler that very dry steam is obtained from it, the 
 upper drum acting as a superheater. A damper, either sin- 
 gle or double wing, is placed in the setting at the point of 
 
38 Steam Engineering 
 
 exit of the gases. It is so designed as to allow the quick 
 and easy removal of the wings when cleaning is going on. 
 The foundation is so designed that by means of a door 
 through the circular brickwork, a man can enter under- 
 neath the boiler, examine the blow-off pipe and rivets, and 
 see that the bottom of the mud drum is kept well and heav- 
 ily painted. 
 
 ATLAS WATER-TUBE BOILER. 
 
 The design and construction of the Atlas water-tube 
 boiler will be easily comprehended by reference to Fig. 19, 
 which presents a full view of this boiler before setting. It 
 consists mainly of three drums, and two water-legs extend- 
 ing crosswise, and the tubes running lengthwise. The rear 
 water-leg is mounted on rollers in setting, in order to allow 
 for expansion, and contraction of the tubes. 
 
 An important and original feature in the general de- 
 sign is, that the water-legs are formed by the continuation 
 of the plates of which the shells of the front and rear 
 drums are composed. Thus no flanged plates, or riveted 
 seams whatever are exposed either to the fire or hot gases 
 at any point. The value of this form of construction lies 
 in the fact that it eliminates the possibility of the crystal- 
 lization of plates and rivets and consequent cracks, and an- 
 noying leaks at the seams arising from overheating and un- 
 equal expansion and contraction of double metal thickness, 
 due to exposure to flames and furnace gases of high tem- 
 perature. 
 
 Another exclusive and very valuable feature of the de 
 sign is the arrangement for passing the steam, after leav- 
 ing the vessels containing water, through a series of super- 
 heating tubes, wherein it loses every particle of moisture 
 
 ^ 
 
Atlas Water Tube Boiler 
 
 39 
 
 
 Fig. 19 
 atlas water tube boiler 
 
40 Steam Engineering 
 
 and is heated to a temperature many degrees higher than 
 that normal to its pressure. 
 
 Attention is directed to the fact that no matter how 
 large the boiler, there is only one steam drum, consequently 
 the entire product of the boiler can be piped out of a 
 single steam, opening. This means a large saving in the 
 cost of piping when compared to the expense incident to 
 installing other types of boilers, which in units of, say, 200 
 horsepower, or larger, necessarily have two longitudinal 
 drums to be connected together by the purchaser. 
 
 All parts of the Atlas boiler and the fixtures furnished 
 are designed for a safe working pressure of 160 pounds 
 per square inch with a safety factor of more than 5. 
 
 All materials have been selected with especial reference 
 to their adaptability to the service required. The shells 
 and heads of the drums and water-legs are open hearth 
 homogeneous flange steel, bearing the maker's stamp of 
 60,000 pounds tensile strength per square inch of section, 
 with not less than 50 per cent of ductility as indicated by 
 contraction of area at point of fracture under test; an 
 elongation of 25 per cent in a length of 8 inches, and guar- 
 anteed by the makers to be capable of bending down flat 
 upon itself when cold, red hot or after being heated to a 
 cherry red and quenched in cold water, without sign of 
 fracture. The chemical and physical properties are deter- 
 mined by thorough tests, and all plates must meet the re- 
 quirements of the best accepted practice. 
 
 The tubes are standard American lap welded, thoroughly 
 tested in all particulars before being expanded into place 
 by roller expanders and again after the boiler is assembled. 
 The tube-holes are accurately placed by template, then 
 reamed and neatly chamfered. 
 
Atlas Water Tube Boiler 41 
 
 Double-refined iron staybolts and braces, having an ulti- 
 mate tensile strength of 52,000 pounds per square inch of 
 section, an elastic limit of at least half the tensile strength 
 and an elongation of eighteen per cent in a length of 8 
 inches, are set to bear uniform tension. 
 
 The rivets are of mild steel and can be bent over cold 
 till the sides meet, without developing cracks on the outside 
 of the bent portion. All rivet holes are reamed to perfect 
 fairness, and the riveting wherever practicable is done by 
 hydraulic machinery, upsetting the rivet its full length, 
 completely filling the hole and forming a perfect head in 
 line with it. There are no riveted seams in the fire, or in 
 the path of the furnace gases. 
 
 All heads are first heated to a uniform bright red and 
 then flanged at a single operation in a hydraulic flanging 
 press. The bends in the plates forming the bottoms of 
 the water-legs are pressed cold under heavy pressure. There 
 is no distortion, either of heads or plates and there is a 
 total absence of marks resulting from frequent and partial 
 heating and hammering into shape. 
 
 No cast metals are used in any parts that are subjected 
 to tensile stresses, or furnace heat. The cast iron that is 
 used for handhole and manhole plates and yokes is good, 
 soft, grey iron, free from flaws or imperfections. 
 
 The rapid, steady, unimpeded flow of the water in the 
 course natural to expansion by exposure to heating sur- 
 face, bears important relation to the most economical utili- 
 zation of the heat units in the furnace gases, and is an es- 
 sential factor in the achievement of the highest efficiency 
 in the production of steam. Uniform temperature in all 
 parts exposed to furnace heat, which is so necessary to the 
 safety and durability of the boiler, cannot exist with faulty 
 circulation. 
 
42 
 
 Steam Engineering 
 
 Fig. 20 
 atlas water tube boiler — sectional view 
 
Atlas Water Tube Boiler 43 
 
 The water is fed into the purifier, whence it overflows 
 into the rear drum and passes down into the rear leg, 
 thence through the inclined tubes to the front leg and up- 
 ward into the front drum, where the globules of steam gen- 
 erated in the tubes are liberated and carried through the 
 superheating tubes to the steam drum. Meanwhile the 
 water continues its flow through the equalizing tubes to the 
 rear drum, joining the feed current at that point. The 
 regular movement of all the water in the circuit just de- 
 scribed, indicates uniform temperature in all the water- 
 tubes, and when an unimpeded circuit has been established 
 in the manner just explained, a maximum supply of dry 
 steam will be delivered. When the circulation is retarded 
 to sluggishness, the water does not so readily absorb the 
 heat, and wet steam and a smaller quantity of it must be 
 expected. It will be noted that while the design of this 
 boiler admits with equal facility the use of either the 
 vertical or the horizontal flame travel, the illustrations here- 
 with show the vertical, it being preferred for several 
 reasons, not the least important of which is that a more 
 uniform distribution of the heat arising from the grates 
 is obtained by first passing the gases upward through the 
 entire nest of tubes between the front end of the furnace, 
 and the first vertical baffle, thence downward between the 
 first and second baffles and finally upward again through 
 the entire nest of tubes between the second baffle, and the 
 rear water-leg. It is not difficult to understand that, 
 aside from all other considerations, the course of the heat- 
 ed gases as described is conducive to a more nearly equal 
 division of the units of heat among all the water-carrying 
 tubes than is possible with the horizontal travel which 
 concentrates by far the greatest degree of heat on the low- 
 
44 Steam Engineering 
 
 est tubes during almost their entire length. Uniform heat 
 distribution means uniform temperature, which logically 
 followed leads to the reasonable belief that the circulation, 
 which increases or decreases as the temperature goes up 
 or down, is of regular direction in all of the tubes, and 
 that each tube is doing its full share of the work. 
 
 Superheated steam has of late years been the subject of 
 much thought and experiment, and now the economical 
 utility of steam containing a number of degrees of super- 
 heat is quite generally understood. Ordinary steam at 
 100 pounds gauge pressure has a normal temperature 
 (omitting decimals) of 338° Fahr., and at 160 pounds its 
 normal temperature is 370° Fahr. The temperature in 
 excess of normal for steam of a given pressure is technic- 
 ally designated superheat. Steam that is in contact with 
 the water from which it was generated cannot be heated 
 above the temperature normal to its pressure. The process 
 of superheating must therefore take place subsequent to 
 the passage of the steam from the vessels containing water. 
 Superheat is obtained by exposing the steam to gases of a 
 higher temperature. The number of degrees of superheat 
 obtainable is governed by the temperature of the gases to 
 which the steam is exposed, and the duration of the ex- 
 posure. It is claimed for the Atlas water-tube boilers that 
 during various tests under actual working conditions they 
 have produced steam containing from 10 to 30 degrees of 
 superheat. 
 
 All users of steam are familiar with radiation losses in 
 steam pipes and the wastes in engine cylinders due to the 
 fact that at each stroke the new supply of steam is 
 brought into contact with the face of the piston and the 
 internal surfaces of the cylinder, which have been cooled 
 
Atlas Water Tube Boiler 45 
 
 by the exhaust of the previous stroke. When steam is 
 used at normal temperature, each degree of heat thus lost 
 means condensation and a proportional decrease of pres- 
 sure. When superheated steam is used there is no loss of 
 pressure until the steam is cooled to the temperature nor- 
 mal to the boiler pressure. Up to within the last few years 
 it was customary to equip each boiler with a mud drum. 
 Two very important facts, however, militated so seriously 
 against the mud drum that it is now eliminated from the 
 best boiler practice. In the first place a dangerously large 
 percentage of the substances in the feed water, which at 
 high temperatures become insoluble, would not gravitate 
 toward and settle within the mud drum according to the 
 plan laid out for them, and in the second place, the mud 
 drum proved in many cases little short of an aggravation 
 by reason of the constant and irremediable leakage of the 
 joints between the drum and the boiler, due to greater ex- 
 pansion and contraction of the boiler, the drum being nec- 
 essarily situated outside of the current of the hottest gases. 
 jfc Fig. 20, which is a sectional view of the Atlas water- 
 tube boiler as it appears set in brick work, shows a purify- 
 ing device which is hung loosely by strap hooks inside the 
 shell of the rear water drum, its depth gradually increasing 
 toward the blow-off end. 
 
 The water is fed into the shallow end and, the pan being 
 large and always full of, and surrounded by, hot water 
 and steam, it is raised to from 250° to 275° Fahr. before 
 it overflows into the main portion of the drum. 
 
 The overflow takes place entirely at the shallow end of 
 the pan, the top of that head being one inch lower than 
 the other head and the sides. It is a well-known fact that 
 water begins to clear itself when it reaches a temperature 
 
46 Steam Engineering 
 
 of 200° Fahr., and as the liberal dimensions of the pan 
 allow the water to remain in it a considerable time, prac- 
 tically all the scale-forming impurities are precipitated 
 to the bottom of the pan where they remain in a soft 
 sludge-like state pending the opening of the blow-off valve, 
 the frequency of which should be governed by the character 
 of the water and the rapidity of the accumulation. 
 
 It will be noted that aside from its open top, which is 
 several inches above the water line in the boiler, the pan 
 is water-tight. It is entirely practicable, therefore, to blow 
 off the sediment as often as desirable while the boiler is 
 under pressure without fear of reducing the water level 
 below the point of safety. 
 
 Corrosion is one of the inevitable effects of the accumu- 
 lation of mud and sediment on metal. Unlike purifiers 
 common to some other boilers, which consist of a pocket- 
 shelf built against the shell or one head of the boiler itself, 
 which, therefore, forms part of the purifier and is exposed 
 to the corrosive action of its contents, the purifier in the 
 Atlas boiler is self-contained and absolutely independent 
 of the boiler-shell or heads. The pan is made in sections 
 and when it finally deteriorates to an unserviceable point, 
 can be removed and replaced through the manhole with 
 little labor and small expense. 
 
 It is estimated that an incrustation of T Vinch will cause 
 a loss of 13 per cent of fuel, yg-inch 25 per cent, and so 
 on, and these figures are probably not far from correct. 
 Therefore, the purification of the feed water before it 
 reaches the surfaces exposed to the baking heat of the 
 furnace tends to a more economical use of fuel. It also 
 reduces cleaning labor and the cost of repairs and increases 
 the life of the boiler by avoiding the early disintegration 
 
Atlas Water Tube Boiler 
 
 47 
 
 
 of the metal which results from subjecting it to that intense 
 heat necessary to boil water through the additional thick- 
 
 Fig. 21 
 
 atlas water tube boiler 
 
 Section through Rear End Showing Water Purifier 
 
 ness due to a coating of scale. An individual hand-hole is 
 located opposite each end of each water tube. 
 
48 Steam Engineering 
 
 These hand-holes are of the diamond-oval shape, having 
 an accurately fitting plate, held in position by a suitable 
 yoke with bolt and nut, the construction being such that 
 the pressure on the inside of the boiler maintains the tight- 
 ness of the joint. Any one of these plates can be removed 
 and replaced through its own opening without disturbing 
 any of the others. The water tubes in this boiler being 
 absolutely straight, in order to clean them thoroughly on 
 the inside, it is only necessary to remove the front hand- 
 hole plates, insert a scraper and push the sediment back 
 into the rear water-leg, from which it may be easily re- 
 moved through a few of the hand-holes in the bottom row, 
 or through the blow-off. The internal condition of each 
 water tube may be determined without removing any of 
 the rear hand-hole plates by suspending a light through 
 the full length throat between the rear water-leg and 
 drum, and holding it in turn opposite the rear end of each 
 water tube, while looking through the open hand-holes in 
 front. Or, if the engineer prefers, the top row of rear 
 hand-hole plates may be removed, and the light inserted 
 and suspended, without entering the drum. 
 
 The interior of each of the three cross drums of the 
 Atlas boiler is reached through a large manhole in one 
 end. The edg6 of this manhole forms a deep flange at 
 right angles with the head, is faced true and provided with 
 an accurately fitted plate with yokes, bolts and nuts, all of 
 such proportions that this part of the head is as strong 
 as any other of like area. 
 
 MARZOLF WATER-TUBE BOILER. 
 
 Another design of water-tube boiler is shown in Fig. 22. 
 The object has been to construct a boiler so that the rela- 
 
Marzoif Water Tube Boiler 
 
 49 
 
 tive arrangements of the tubes, drum, and heat passages 
 are such as to obtain the most economical distribution of 
 
 
 Fig. 22 
 marzolf boiler — sectional view 
 
 heat. Another object is to facilitate the heating of the 
 water, and increase the circulation by arranging the drums, 
 
 . 
 
50 Steam Engineering 
 
 and a series of tubes so as to receive the direct applica- 
 tion of the heat from the furnace. 
 
 As shown, the drum A is located in the furnace and 
 connected to the drum B by tubes slightly bent at each end, 
 the drums A and B being connected to the drum C by simi- 
 lar tubes. As the flame and hot gases rise from the furnace, 
 they surround the water drum A and, striking the arch or 
 baffle wall D, follow along the inclined tubes E, which re- 
 ceive the direct application of the heat generated by the 
 combustion of the fuel. The extension of the bridge wall 
 is reduced in thickness above the grate, as shown at F, 
 forming a back wall which rises vertically behind the water 
 drum A, to a point close beneath the series of tubes E. 
 This wall is surmounted by a sloping wall G, which stands 
 adjacent to, and parallel with, the tubes E, and extends 
 toward the drum B. Owing to the baffle wall H, the hot 
 gases are forced up along the tubes E, and down through 
 the tubes I to the heating chamber K, tile roof of which is 
 found by the baffle wall H. The baffle wall L is inclined 
 downward parallel to and close to the rear of the series 
 of tubes J from a point directly behind the steam 
 drum B, to a point over the mud drum C, whereby the 
 heat and products of combustion are deflected downwards 
 among the tubes X. 
 
 The hot gases pass from the heating chamber to the 
 passage M between the lower end of the baffle wall and the 
 mud drum C to a draft passage located between the baffle 
 and the rear wall leading to the stack. 
 
 The heat thus not only acts directly upon the water-drum 
 A and upon the portions of the tubes X and E, located 
 within the furnace, but also upon the tubes E above the 
 furnace, upon the steam drum B, the tubes J and the mud 
 
Marzolf Water Tube Boiler 51 
 
 drum C. The portion of the tubes N which lies within the 
 heating chamber K also receives heat to some extent, al- 
 though the heat does not act directly upon them as upon 
 the other tubes. 
 
 The feed water supply to this boiler is admitted through 
 the drum C, and circulates through the tubes N, water 
 drum A, tubes E, steam drum B, and tubes J, back to the 
 mud drum, making one continuous circuit. As shown by 
 the illustration, the steam drum B is relatively larger and 
 consequently of much greater capacity than either of the 
 other two drums. It will be noticed that the tubes N" are 
 placed on an incline, owing to the mud drum being lo- 
 cated on a lower level than the water drum A, a design 
 intended to cause all sediment carried into the boiler to 
 gravitate to the mud drum C, from which it may be readily 
 removed through the usual blow-off. 
 
 DUPLEX WATER-TUBE BOILER. 
 
 In the Duplex water-tube boiler, Fig. 23, the features 
 which are most strongly emphasized hj the designers are: 
 Delivery of steam from the boiler in a superheated condi- 
 tion, without the use of a special superheater; removal of 
 steam from the boiler at a point where there is no ebulli- 
 tion, and elimination of a great many parts of the undu- 
 lating header type of boiler. The design of the boiler shows 
 absence of stay-bolted surfaces, the drums are not exposed 
 to the direct action of the fire, all seams or rivets are en- 
 tirely removed from contact with the heat, rigid connec- 
 tions are avoided between parts, and all joints are ex- 
 panded. 
 
 The Duplex boiler consists of two upper steam drums 
 connected by tubes. Short tubes expanded into the bottom 
 
52 
 
 Steam Engineering 
 
 — >L. r tt»-4 
 
 Fig. 23 
 duplex water tube boiler 
 
Duplex Water Tube Boiler 53 
 
 of the shell of the rear drum form the connection to a set 
 of headers below it, which are connected to the front drum 
 by tubes expanded into the shell of the latter. This com- 
 prises the upper generating system. These headers are 
 likewise connected to a drum situated below them by short 
 nipples, and this lower drum is in turn united to a set of 
 headers below, and similarly connected to, the front drum. 
 This comprises the lower generating system. The tubes are 
 inclined 20 degrees to insure rapid and positive circulation. 
 
 The drums are made in one sheet with no circular seams 
 except those connecting the heads to the shell. The longi- 
 tudinal seams are butt-strapped, either double or triple 
 riveted, as the pressure demands, and located on the out- 
 side of the shell. A pressed-steel manhole is placed on 
 the circumference of the shell for access to the interior of 
 the drums. 
 
 The headers are heavy, made of open-hearth steel, and 
 the section of the header to which the hand-hole plates are 
 secured is designed to be extra heavy, as is that portion 
 where the tubes enter the header, this latter being intended 
 to provide a wide tube seat and obviate the danger of leaky 
 tube joints. The headers are of long box-like form and 
 each header is designed to take in two vertical rows of 
 tubes. An elliptical hand-hole is placed opposite the ends 
 of two tubes through which the tubes are cleaned or re- 
 moved. This hand-hole is closed by an elliptical cap inside 
 the header held in position by a bolt secured with an out- 
 side crab. The joint between the cap seat and the header is 
 made tight with an asbestos gasket to avoid the necessity 
 of remilling the contact surfaces every time a cap is re- 
 
54 Steam Engineering 
 
 moved and replaced. In this construction the bolt and 
 crab are relieved of the strain of the boiler pressure. 
 
 The boiler tubes are 314 inches in diameter, of either 
 charcoal-iron, or steel lap-welded, expanded directly into the 
 shell of the drums or into the headers, and the ends are 
 belled over one-quarter of an inch. 
 
 A heavy steel framework incased in the brick setting 
 supports the boiler. On the sides and independent of the 
 boiler are built walls of brick about 17 inches in thickness. 
 The rear of the boiler is fitted with a sheet-iron casing pro- 
 tected with asbestos covering, the boiler being roofed over 
 with fire-tile supported by heavy T-irons. The boiler fronts 
 are of steel and doors of ornamental design are provided 
 for access to the headers. The frame-work is so designed 
 as to provide for the free expansion of all the tubes. The 
 two upper drums are set on lugs secured to the heads, the 
 lugs in turn being supported by the steel framework. The 
 rear lugs are first set on rollers which allow for the ex- 
 pansion of the tubes connecting the two drums. The hori- 
 zontal style of baffling is used. These baffles rest on the 
 tubes, and guide the gases along the lower bank, and the 
 horizontal circulating tubes. 
 
 Finally, the gases pass through the smoke outlet, which 
 may be located on the top of the boiler at the rear, or at a 
 point just under the rear drum. The course of the gases 
 is always upward, which is the free and natural passage for 
 them. The baffles are of the common rectangular shape, 
 which any dealer carries in stock. The upper and lower 
 banks of tubes comprise the active heating surface of this 
 boiler. The tubes that form the lower system are con- 
 nected at their rear ends to a large mud drum, which acts 
 
Duplex Water Tube Boiler 55 
 
 as a reservoir for water to insure an ample supply for the 
 bottom tubes at all times. The upper bank of tubes is 
 arranged in reverse of the lower, the tubes being connected 
 to the front drums at their front ends. All the tubes of 
 the upper system discharge independently into this drum. 
 The header ends of both banks of tubes are connected into 
 headers that are straight and of ample area. The tubes 
 are of easy access for the purpose of scraping off soot that 
 has been baked on in service. The feed water is introduced 
 in the upper rear drum, where any air that it contains may 
 be liberated. It then passes downward through the rear 
 circulating tubes and headers to the lower rear drum, where 
 any impurities present in the feed water may be deposited. 
 
 The passage of the water is then upward through the 
 lower bank of tubes, through the front headers to the 
 front drum. 
 
 At this point any steam that is generated separates from 
 the water, and passes across the steam tubes to the rear 
 drum, and is believed to be thoroughly dried out, and 
 slightly superheated in the process by coming in contact 
 with the hot gases surrounding these tubes. The water 
 passes across through the circulating, horizontal tubes to the 
 rear drum, thence downward again to the rear headers, and 
 thence up the upper bank of tubes into the front drum 
 again. By this time it is expected that the water will 
 have become heated to a very high temperature and, becom- 
 ing steam, it passes to the rear drum through the super- 
 heating tubes, becoming superheated on the route. 
 
 From this rear drum the steam is withdrawn, there 
 being no ebullition at this place, as experiment with a boiler 
 with glass heads on the rear drum has shown. The safety 
 
 _. 
 
56 Steam Engineering 
 
 valve is located on the front drum, where its sudden oper- 
 ation cannot throw water into the steam opening. The 
 spaces between the banks of tubes provide access to all 
 parts of the boiler inside the setting through doors in the 
 setting, and other openings in the setting permit the boiler 
 tubes to be cleaned by blowing with steam, or compressed 
 air. 
 
 The builders of this boiler, the Kobb-Mumford Boiler 
 Company, of South Framingham, Mass., have been carry- 
 ing on some very satisfactory experimental tests during 
 the past year. 
 
 ERIE CITY WATER-TUBE BOILER. 
 
 The Erie City Iron Works, of Erie, Penn., has added 
 to its line of products the boiler shown in the accompanying 
 illustrations, Figs. 24 to 26, the reproduced photographs 
 shown being from the experimental boiler at the Erie 
 shops. It is not claimed that the type is novel, but that 
 the Erie iron works will bring to its manufacture and ex- 
 ploitation refinements and improvement in detail and ex- 
 perience and facilities which should soon make a place for 
 it among the standard types. 
 
 Unite the three banks of tubes of a Stirling boiler in a 
 single upper drum, placed with its center directly over the 
 center of the lower one, and you have the type. The fur- 
 nace is an extension on the Dutch-oven plan, allowing 
 great flexibility in the adjustment of grate to heating sur- 
 face, and introducing the improved furnace conditions of 
 the reverberatory arch. Additional capacity is gained by 
 increasing the length of the drums and the number of 
 tubes sidewise, carrying with it increased width of fur- 
 
Erie City Water Tube Boiler 
 
 57 
 
 Fig. 24 
 erie city water tube boiler 
 
 nace and proportionate increase of grate surface, while 
 the length of the grate may be made such as to give the 
 desired ratio of grate to heating surface. 
 
 . 
 
58 
 
 Steam Engineering 
 
 The tubes are so spaced that any one of them may be 
 cut out, removed and replaced without interfering with 
 
 Fig. 25 
 side elevation erie city water tube boiler 
 
 any other. The entire boiler is suspended, as the engrav- 
 ings show, from the upper drum, giving perfect flexibility 
 
Erie City Water Tube Boiler 
 
 59 
 
 and freedom to adjust itself to varying conditions of tem- 
 perature and stress. The sufficiency of the expanded tube 
 
 Fig. 26 
 
 ENLARGED VIEW SHOWING SEPARATOR IN DRUM OF ERIE CITY BOILER 
 
 joints in the upper drum to sustain the weight thus brought 
 upon them has not only been tested out thoroughly in 
 
60 Steam Engineering 
 
 former boilers of this construction, but has been tried in 
 the boiler illustrated by means of hydraulic jacks and 
 found to be entirely adequate. 
 
 In this particular boiler the upper drum is 48 and the 
 lower 40 inches in diameter, with 11 rows of connecting 
 3-inch tubes and, with 22 tubes in each row, furnishing 
 2,377 square feet of water-heating surface. The front and 
 rear groups contain four rows each, the central group, three 
 rows. 
 
 The baffling is arranged to give three passes as shown, 
 the gases passing longitudinally through each group of 
 tubes. This gives a travel of the gas of something like 
 40 feet in contact with the heating surface, yet with such 
 freedom of passage that there was little drop in draft 
 pressure between the stack and the furnace when the boiler, 
 nominally rated at 238 horsepower, was developing over 
 500, and burning 36.7 pounds of coal per square foot of 
 grate. 
 
 At each end of the upper drum is a dry chamber, as 
 shown in the longitudinal section (Fig. 26), in which is 
 placed a separator upon each end of the steam-outlet pipe, 
 with the inlet facing toward the end of the drum and 
 away from the steam-liberating surface. The boiler ap- 
 pears to be one which will be well adapted to the large 
 units and intensive service demanded by the modern power 
 plant, especially those in which large amounts of power 
 are required for peak periods and where the ability to 
 stand forcing is particularly desirable. 
 
Setting Return Tubular Boilers 61 
 
 SETTING RETURN TUBULAR BOILERS. 
 
 In setting a return tubular boiler the prevailing cus- 
 tom has been to support on cast iron brackets resting upon 
 the side walls, which are liable in course of time to crum- 
 ble away and cause trouble. A great improvement is made 
 when we suspend such boilers from I-beams supported by 
 cast iron columns. Figures 27 and 28 show the setting of 
 this type of boilers either singly or in double batteries, by 
 means of suspension. In setting an even number of boil- 
 ers, as six or eight in one setting, it is best to divide them 
 into pairs so that not more than two boilers will be sus- 
 pended between supports. 
 
 The principal reason for this is that when the large sizes, 
 such as from 150 to 250 horsepower, are used, the size 
 I-beam required to safely carry this load between supports 
 is so large that it overbalances the cost of two or more 
 cast-iron columns. 
 
 In setting an odd number of boilers, such as three or five, 
 in a battery, columns are usually placed between the boilers 
 with a 2-inch air space all around the column, and an air 
 duct at the bottom of the setting which runs through from 
 the front to the back and connects with each air space 
 around the column. This allows a free circulation of air, 
 thus tending to keep the columns comparatively cool. In 
 setting boilers in this way, the columns and I-beams are 
 set in position first. The boiler is then hoisted to the proper 
 height by means of tackle, which is attached to the I-beams, 
 and when the boiler is brought to the proper height, the 
 U-bolts are slipped into place and fastened by nuts and 
 washers to the I-beams. 
 
62 
 
 Steam Engineering 
 
 This method abolishes the use of blocking and leaves all 
 of the space under the boilers clear for the brick work. 
 
 Fig. 27 
 
 The expansion is easily taken care of by the U-bolts and 
 hangers, and if the walls are properly set, they will show 
 
 ■ 
 
Setting Return Tubular Boilers 
 
 63 
 
 no cracks as they carry no weight, and are free to go and 
 come. The accompanying table, No. 1, has been carefully 
 worked out with a factor of safety of 5, and gives the dif- 
 ferent sizes and lengths of I-beams and columns required 
 
 Fig. 28 
 
 for boilers of 36 inches in diameter and 8 feet long, to 
 boilers of 90 inches in diameter and 20 feet in length, giv- 
 ing the total weight to be supported and the sizes, weights, 
 and positions of the columns, and I-beams required : 
 
64 
 
 Steam Engineering 
 
 Table 1 
 sizes and weights of columns and i-beams re 
 
 HORSE POWER 
 Dia. of boiler in inches 
 Length of tubes in feet 
 Length of curtain sheet 
 
 in inches , 
 
 Total weight of boiler 
 
 and water 
 
 Rear head to center of 
 
 hanger , 
 
 Center to cen. of hang'rs 
 Front head to center of 
 
 hanger 
 
 Distance between C of 
 
 supports (1 boiler) . . 
 Distance between C of 
 
 supports (2 boilers) . . 
 Length of I-beam for 
 
 1 boiler 
 
 Length of I-beam for 
 
 2 boilers 
 
 Size of I-beam required 
 
 for 1 boiler 
 
 Size of I-beam required 
 
 for 2 boilers. . . , 
 Weight per ft. of I-beam 
 
 for 1 boiler 
 
 Weight per ft. of I-beam 
 
 for 2 boilers 
 
 Length of cast-iron col. 
 Outside dia. of C. I. col. 
 
 for 1 boiler. .... 
 Outside dia. of C. I. col. 
 
 for 2 boilers. ... 
 Size of flange on ends of 
 
 col. for 1 boiler. 
 Size of flange on ends of 
 
 col. for 2 boilers. . . . 
 Thickness of C. I. col. 
 
 for 1 boiler. ... 
 Thickness of C. I. col. 
 
 for 2 boilers. .... 
 
 15 
 36 
 
 8 
 
 20 
 36 
 10 
 
 25 
 42 
 10 
 
 30 
 42 
 12 
 
 35 
 
 44 
 
 12 
 
 40 
 48 
 12 
 
 45 
 50 
 13 
 
 50 
 54 
 13 
 
 11 
 
 6500 
 
 11 
 
 7500 
 
 12 
 9400 
 
 12 
 10500 
 
 12 
 11500 
 
 14 
 13300 
 
 14 
 14200 
 
 14 
 15300 
 
 2-0 
 4-0 
 
 2-6 
 5-0 
 
 2-6 
 5-0 
 
 3-0 
 6-0 
 
 3-0 
 6-0 
 
 3-0 
 6-0 
 
 3-3 
 6-6 
 
 3-3 
 
 6-6 
 
 2-0 
 
 2-6 
 
 2-6 
 
 3-0 
 
 3-0 
 
 3-0 
 
 3-3 
 
 3-3 
 
 6-6 
 
 6-6 
 
 7-0 
 
 7-0 
 
 7-2 
 
 7-6 
 
 7-8 
 
 8-0 
 
 11-8 
 
 11-8 
 
 12-8 
 
 12-8 
 
 13-0 
 
 13-8 
 
 14-0 
 
 14-0 
 
 7-3 
 
 7-3 
 
 7-10 
 
 7-10 
 
 8-0 
 
 8-4 
 
 8-6 
 
 8-10 
 
 12-6 
 
 12-6 
 
 13-8 
 
 13-8 
 
 14-0 
 
 14-8 
 
 15-0 
 
 15-10 
 
 4 
 
 4 
 
 5 
 
 5 
 
 5 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 8 
 
 8 
 
 9. 
 
 9 
 
 9 
 
 10 
 
 7.5 
 
 7.5 
 
 9.75 
 
 9.75 
 
 9.75 
 
 12.25 
 
 12.25 
 
 12.25 
 
 12.25 
 8-0 
 
 12.25 
 8-0 
 
 18 
 8-6 
 
 18 
 8-6 
 
 21 
 8-8 
 
 21 
 9-3 
 
 21 
 9-5 
 
 25 
 10-0 
 
 4 
 
 4 
 
 4 
 
 4 
 
 4 
 
 5 
 
 5 
 
 5 
 
 5 
 
 5 
 
 5 
 
 5 
 
 5 
 
 6 
 
 6 
 
 6 
 
 9! 
 
 n 
 
 10 
 
 10 
 
 10 
 
 10! 
 
 10! 
 
 10! 
 
 10! 
 
 10! 
 
 12 
 
 12 
 
 12J 
 
 12! 
 
 12! 
 
 13! 
 
 ! 
 
 ! 
 
 ! 
 
 ! 
 
 ! 
 
 ! 
 
 1 
 
 1 
 
 I 
 
 1 
 
 1 
 
 i 
 
 % 
 
 5 
 
 1 
 
 1 
 
 60 
 54 
 15 
 
 14 
 
 17800 
 
 3-0 
 7-6 
 
 3-9 
 
 8-0 
 
 14-8 
 
 8-10 
 
 15-10 
 
 6 
 
 10 
 
 12.25 
 
 25 
 10-0 
 
 10J 
 
 13! 
 
 i 
 
 I 
 
Setting Return Tubular Boilers 
 
 65 
 
 Table 1 — continued, 
 quired in setting return tubular boilers. 
 
 70 
 60 
 14 
 
 75 
 60 
 15 
 
 1 80 
 60 
 16 
 
 90 
 66 
 15 
 
 100 
 66 
 16 
 
 125 
 
 72 
 16 
 
 150 
 72 
 
 18 
 
 16 
 
 20800 
 
 16 
 
 24800 
 
 1 16 
 ! 27200 
 
 17 
 30300 
 
 17 
 35000 
 
 18 
 40000 
 
 18 
 44000 
 
 3-6 
 7-0 
 
 3-9 
 
 7-6 
 
 4-0 
 
 8-0 
 
 3-9 
 
 7-6 
 
 4-0 
 
 8-0 
 
 4-0 
 
 8-0 
 
 4-6 
 9-0 
 
 3-6 
 
 3-9 
 
 4-0 
 
 3-9 
 
 4-0 
 
 4-0 
 
 4-6 
 
 9-0 
 
 9-0 
 
 9-0 
 
 9-6 
 
 9-6 
 
 10-0 
 
 10-0 
 
 16-2 
 
 16-2 
 
 16-2 
 
 17-2 
 
 17-2 
 
 18-2 
 
 18-2 
 
 10-0 
 
 10-0 
 
 10-0 
 
 10-6 
 
 10-6 
 
 11-0 
 
 11-0 
 
 17-4 
 
 17-4 
 
 17-4 
 
 18-4 
 
 18-4 
 
 19-5 
 
 19-5 
 
 7 
 
 7 
 
 7 
 
 7 
 
 7 
 
 8 
 
 8 
 
 12 
 
 12 
 
 12 
 
 12 
 
 12 
 
 15 
 
 15 
 
 15 
 
 15 
 
 15 
 
 15 
 
 15 
 
 18 
 
 18 
 
 31.5 
 
 10-8 
 
 31.5 
 
 10-8 
 
 31.5 
 10-8 
 
 40 
 11-2 
 
 40 
 11-2 
 
 42 
 12-0 
 
 42 
 12-0 
 
 5 
 
 5 
 
 5 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 6 
 
 8 
 
 8 
 
 111 
 
 111 
 
 111 
 
 111 
 
 111 
 
 12 
 
 12 
 
 14 
 
 14 
 
 14 
 
 141 
 
 141 
 
 15 
 
 15 
 
 ii 
 
 1 
 
 3 
 
 1 
 
 3 
 
 1 
 
 1 
 
 1 
 
 8 
 
 4 
 
 ] 
 
 1 
 
 1 
 
 1 
 
 1 
 
 175 
 
 78 
 18 
 
 18 
 
 48000 
 
 4-6 
 9-0 
 
 4-6 
 
 200 
 78 
 20 
 
 18 
 56000 
 
 5-0 
 10-0 
 
 i 
 
 5-0 
 
 10-6| 10-6 
 19-2 
 
 19-2 
 11-7 
 
 20-B 
 
 11-7 
 20-6 
 9 
 
 21 
 
 I 
 
 15 
 
 21| 
 
 60 60 
 12-6 12-6 
 
 121 121 
 
 16| 16 
 
 1 1 
 
 I 2 
 
 200 
 84 
 18 
 
 20 
 
 55000 
 
 4-6 
 9-0 
 
 4-6 
 
 11-0 
 
 20-2 
 
 12-0 
 
 21-6 
 
 9 
 
 15 
 
 21 
 
 60 
 13-0 
 
 121 
 
 16 
 
 1 
 
 1 
 
 225 
 84 
 20 
 
 20 
 
 67000 
 
 5-0 
 10-0 
 
 5-0 
 
 11-0 
 
 20-2 
 
 12-0 
 
 21-6 
 
 9 
 
 15 
 
 21 
 
 80 
 13-0 
 
 121 
 
 17 
 
 1 
 
 1 
 
 225 
 90 
 
 18 
 
 22 
 
 65000 
 
 4-6 
 9-0 
 
 4-6 
 
 11-6 
 
 21-2 
 
 12-6 
 
 22-6 
 
 9 
 
 15 
 
 21 
 
 80 
 13-10' 
 
 121 
 
 17 
 
 1 
 
 1 
 
 250 
 90 
 20 
 
 22 
 75000 
 
 5-0 
 
 10-0 
 
 5-0 
 
 11-6 
 
 21-2 
 
 12-8 
 
 22-6 
 
 10 
 
 15 
 
 25 
 
 80 
 13-10 
 
 6 
 
 8 
 
 131 
 
 17 
 
 1 
 
 . 
 
66 Steam Engineering 
 
 QUESTIONS AND ANSWERS. 
 
 1. What types of boilers are most commonly used for 
 stationary work ? 
 
 Ans. The horizontal tubular boiler and the water- tube 
 boiler. 
 
 2. Describe in general terms the horizontal tubular 
 boiler. 
 
 Ans. It consists of a shell having tubes of small diam- 
 eter, extending from head to head. 
 
 These tubes are located in the water space. 
 
 3. What is their function ? 
 
 Ans. To supply a passageway to the stack for the hot 
 gases from the furnace. 
 
 4. Does the water in the boiler receive heat from these 
 tubes? 
 
 Ans. It certainly does. 
 
 5. Describe the route taken by the smoke and hot 
 gases in the operation of a tubular boiler, 
 
 Ans. From the furnace, located under the front end 
 of the boiler, the gases pass under and along the sides of 
 the shell, back to the rear end, the upper part of which is 
 arched over. The route is here reversed, and the products 
 of combustion return through the flues towards the front 
 end and thence through the breeching into the stack. 
 
 6. Is this type of boiler economical in the burning of 
 fuel? 
 
 Ans. It can be made so if properly set and handled in 
 operation. 
 
 7. Describe in a general way the water-tube boiler. 
 Ans. It consists of a set, or sets of tubes 3 to 4 inches 
 
 in diameter, sometimes vertical, and sometimes inclined, 
 
Questions and Answers 67 
 
 and connected at the top to a steam drum, and at the bot- 
 tom to a mud drum. 
 
 8. What advantages as regards circulation of the water 
 has the water tube boiler ? 
 
 Ans. It provides for a free circulation. 
 
 9. Xame another advantage connected with the water 
 tube boiler. 
 
 Ans. The margin of safety from dangerous explosions. 
 
 10. Why is this? 
 
 Ans. Because if one or more tubes give way the pres- 
 sure is relieved. 
 
 11. What precautions should be observed in the design 
 and construction of a boiler? 
 
 Ans. The best materials should be used, the boiler 
 should be simple in design, and the workmanship should be 
 perfect. 
 
 12. Where should the mud drum be located? 
 
 Ans. In a place removed from the action of the fire. 
 
 13. What should be the capacity of the boiler relative 
 to its work? 
 
 Ans. It should have a steam and water capacity suf- 
 ficient to prevent any fluctuation in either the steam pres- 
 sure, or the water level, if properly fed. 
 
 14. Why should the water in a boiler circulate freely 
 and constantly? 
 
 Ans. In order to maintain all parts at as near the same 
 temperature as possible. 
 
 15. What should the strength of a boiler be, relative to 
 the strain it is liable to be subject to? 
 
 Ans. It should have a great excess of strength. 
 
 16. Is a combustion chamber an advantage to a boiler? 
 
68 Steam Engineering 
 
 Ans. It is, in order to complete the combustion of the 
 gases before they escape to the chimney. 
 
 17. How should a boiler be arranged with regard to 
 cleaning ? 
 
 Ans. All parts should be easily accessible for cleaning 
 and repairs. 
 
 18. What type of boiler is the Cahall? 
 Ans. It is a water-tube boiler. 
 
 19. Is it vertical or horizontal? 
 Ans. It is built either way. 
 
 20. What form of Cahall is generally used in central 
 power stations ? 
 
 Ans. The horizontal form. 
 
 20a. What is the range of pressures that these boilers 
 a/e built for? 
 
 Ans. From 160 to 500 pounds per square inch. 
 
 21. Describe the method of constructing the joints. 
 Ans. The sheets are beveled on the edges, bent into 
 
 shape, and rivet holes drilled after bending. 
 
 22. What is gained by so doing? 
 
 Ans. Absolutely round rivet holes and no crystalliza- 
 tion. 
 
 23. What type of riveted joint is used on the higher 
 pressure boilers? 
 
 Ans. Triple riveted, double strapped. 
 
 24. How are the tubes connected to the steam drum 
 in the Cahall boiler? 
 
 Ans. By nipples connected to saddles on the drum., 
 
 25. Does this boiler rest upon the brick work? 
 
 Ans. It does not, but is suspended free from the ma- 
 sonry. 
 
 26. What advantage is there in this style of setting? 
 
Questions and Answers 69 
 
 Ans. The entire structure is free to expand or contract 
 without causing any strains on either boiler or brick work. 
 
 27. Describe the Heine boiler. 
 
 A71S. It consists of one, and sometimes two shells on 
 drums resting upon water legs riveted to each end. These 
 water legs are connected by horizontal tubes. The water 
 fills the tubes, water legs, and partially fills the shell, leav- 
 ing the upper portion for steam space. 
 
 28. In the setting does this boiler occupy a horizontal 
 position ? 
 
 Ans. No. The shell and tubes have an incline of one 
 inch in twelve from front to rear. 
 
 29. What provision is made for cleaning and repairing 
 the tubes? 
 
 Ans. Hand-holes are located in the head plates oppo- 
 site each tube. 
 
 30. How are these hand-holes closed? 
 Ans. In the ordinary way, by plates. 
 
 31. Where is the mud drum located in the Heine boiler? 
 
 ^Ans. Inside the shell, near the bottom. 
 32. How is the Heine boiler supported in the setting? 
 Ans. The front or fixed end rests upon cast iron col- 
 umns. The rear water leg upon rollers. 
 
 33. Describe in brief the Babcock & Wilcox boiler. 
 Ans. It is composed of wrought iron tubes, placed in 
 
 an inclined position, and connected with each other, and 
 with a horizontal steam, and water drum by vertical headers. 
 
 34. Where is the mud drum in this boiler ? 
 
 Ans. In the rear, and connected to the lowest part of 
 the boiler. 
 
 35. What provision is made for cleaning the tubes in 
 the Babcock & Wilcox boiler? 
 
70 Steam Engineering 
 
 Ans. Through hand-holes in the headers, opposite each 
 tube? 
 
 36. How is this boiler supported in the setting? 
 Ans. It is suspended from wrought iron girders, en- 
 tirely independent of the brick work. 
 
 37. Describe in general terms the Stirling boiler. 
 
 Ans. It consists of three upper steam drums, each be- 
 ing connected by a number of tubes to a lower or mud 
 drum. 
 
 38. How are the steam spaces connected? 
 Ans. By shorter tubes. 
 
 39. How is the boiler supported? 
 
 Ans. On a structural steel frame work. 
 
 40. What provision is made for expansion and contrac- 
 tion of the tubes? 
 
 Ans. They are slightly curved near the ends. 
 
 41. How are the hot gases directed in their course 
 from furnace to stack? 
 
 Ans. By means of fire brick baffle walls. 
 
 42. How is the interior of this boiler cleaned ? 
 
 Ans. Four manholes are provided in the drums, by 
 which access to the interior of both the drums and tubes is 
 obtained. 
 
 43. What type of boiler is the Maxim boiler? 
 
 Ans. It is a water-tube boiler consisting of two drums, 
 one above the other, connected by tubes. 
 
 44. Describe the tubes. 
 
 Ans. Each tube has two bends, thus providing for un- 
 equal expansion or contraction. 
 
 45. How is the heating surface of the Maxim boiler 
 arranged ? 
 
Questions and Answers 71 
 
 Ans. It is so arranged that the current of heated gases 
 is made to travel three times the length of the tubes, the 
 direction of the current being changed seven times in its 
 route from furnace to stack. 
 
 46. What can be said of the Bigelow-Hornsby water- 
 tube boiler ? 
 
 Ans. Owing to the flexible form of its construction it 
 is possible to build it in very large units, 2,000 horsepower 
 and upwards. 
 
 47. What peculiar feature makes this possible? 
 
 Ans. Each section is independent of its neighbor, ex- 
 cept the nipples connecting with the steam drum, and the 
 equalizing nipples connecting the bottom drums of the 
 rear sections. 
 
 48. How is the boiler supported? 
 Ans. Entirely from overhead beams. 
 
 49. What percentage of the heating surface do the tubes 
 of the front unit comprise? 
 
 Ans. More than 12 per cent. 
 
 50. Where is the feed water first admitted? 
 Ans. Into the bottom drum of the rear unit. 
 
 51. Describe the course of the feed water. 
 
 Ans. The feed water is admitted into the bottom drum 
 of the rear unit, and is advanced gradually from the coldest 
 to the hottest portion of the boiler. 
 
 52. How is the speed of the feed water up the rear unit 
 regulated ? 
 
 Ans. By the amount of steam generated, ample time 
 being permitted for scale forming matter to be deposited 
 in the bottom drum of this unit. 
 
 53. Where does the liberation of steam take place? 
 Ans. In the upper drum. 
 
72 Steam Engineering 
 
 54. What can be said of this boiler regarding the utili- 
 zation of the heat? 
 
 Ans. It is baffled so that the products of combustion 
 are carried uniformly over the heating surfaces in thin 
 layers, the baffle plates serving to guide the gases through in 
 substantially uniform passages. 
 
 55. To what factor of safety is the Bigelow-Hornsby 
 boiler built? 
 
 Ans. Five for 200 pounds working pressure. 
 
 56. Describe in brief the Wickes vertical water-tube 
 boiler. 
 
 Ans. It consists of two cylinders joined together end- 
 ways by straight tubes, and erected in a vertical position. 
 
 57. What can be said of the top cylinder? 
 
 Ans. It is the longer, and is designated the steam drum. 
 
 58. What about the bottom cylinder? 
 
 Ans. It is the shorter, and is designated the mud drum. 
 Both cylinders vary in dimensions as to diameter and 
 length, according to the power required of the boiler. 
 
 59. Where are the manholes of the Wickes boiler? 
 Ans. One is placed in the convex head of the steam 
 
 drum ; there are also a number of hand-holes in this head. 
 A manhole is also placed in the lower or mud drum, near 
 the floor, thus permitting access to the top and bottom of 
 the boiler. 
 
 60. How are these tubes divided ? 
 
 Ans. By heavy fire-clay tile these tubes are divided into 
 two compartments. Those tubes in the front compart- 
 ment are called the "risers" and those in the rear the 
 "downcomers." 
 
 61. What can be said of the heat in its double passage? 
 
Questions and Answers 73 
 
 A ns. It surrounds completely, and closely the tubes in 
 both compartments. 
 
 62. Where is the water line in this boiler? 
 
 Ans. At a sufficient height in the steam drum to in- 
 sure the complete submersion of all the tubes. 
 
 63. How is the brick work setting of the Wickes water- 
 tube boiler arranged? 
 
 Ans. It is independent of the weight of the boiler, and 
 free to expand or contract. 
 
 64. Describe briefly the design of the Atlas water-tube 
 boiler. 
 
 Ans. It consists mainly of three drums and two water 
 legs extending crosswise, while the tubes extend lengthwise. 
 
 65. What is the original feature in the design of the 
 water legs? 
 
 Ans. They are formed by the continuation of front 
 and rear shell plates. 
 
 66. What other valuable feature is claimed for this 
 boiler ? 
 
 Ans. After the steam leaves the vessels containing water 
 it is -passed through a series of superheating tubes, and is 
 superheated. 
 
 67. Describe the course of the feed water. 
 
 Ans. It is fed first into the purifier, whence it over- 
 flows into the rear drum and down into the rear leg, thence 
 through the inclined tubes to the front leg, thence up into 
 the front drum, where the steam is liberated and carried 
 through superheating tubes to the steam drum. 
 
 68. What are the facilities for cleaning the water tubes 
 of this boiler? 
 
 Ans. An individual hand-hole is located opposite each 
 end of each water tube. 
 
74 Steam Engineering 
 
 69. How is the interior of each of the three cross drums 
 reached ? 
 
 Ans. Through a large manhole in each end. 
 
 70. Describe briefly the design and construction of 
 the Marzolf water-tube boiler. 
 
 Ans. It consists of three drums connected with each 
 other in triangular form. Drum A directly over the fire 
 is connected by tubes with drum B above it, and with drum 
 C in the rear and slightly below it. Drum C, which is the 
 mud drum, is also connected with drum B. The tubes are 
 each slightly bent. The steam is collected in drum B, which 
 is maintained about one-third full of water. 
 
 71. Describe in brief the action of the heat upon this 
 boiler. 
 
 Ans. It acts first upon the water in drum A over the 
 furnace, then by means of a baffle wall it is carried along 
 the inclined tubes to drum B, where it is deflected and car- 
 ried down along other inclined tubes to drum C, thence to 
 the stack. 
 
 71. How are the products of combustion caused to act 
 upon the lower bank of tubes? 
 
 Ans. By means of baffle walls located in the rear of 
 the furnace. 
 
 72. At what point in this boiler is the feed water ad- 
 mitted ? 
 
 Ans. At the lowest point, viz., the mud drum. 
 
 73. What are the principal advantages claimed for the 
 Duplex water-tube boiler? 
 
 Ans. Delivery of superheated steam; the removal of 
 steam from the boiler at a point where there is no ebul- 
 lition; the drums not exposed to the direct action of the 
 fire. 
 
Questions and Answers 75 
 
 74. Describe in brief the design of this boiler. 
 
 Ans. Two upper steam drums connected by tubes, a 
 mud drum at the bottom and rear which is connected to 
 the upper drums by headers and short nipples. The tubes 
 are inclined 20 degrees to insure rapid and positive cir- 
 culation. 
 
 75. How is this boiler supported? 
 Ans. Upon a heavy steel framework. 
 
 76. What is the leading feature in connection with 
 the Erie City water- tube boiler? 
 
 Ans. The three banks of tubes are practically vertical, 
 connected to upper, and lower drums, and spaced so that any 
 one of them may be cut out for repairs without interfering 
 with the others. 
 
 77. How do the products of combustion act upon this 
 boiler ? 
 
 Ans. The baffling is arranged to pass three times across 
 the tubes, and at each end of the upper drum is a dry 
 chamber. 
 
 78. Describe in brief the best method of supporting 
 horizontal tubular boilers. 
 
 Ans. By means of hangers suspended from I beams, 
 supported by cast iron columns. This takes the weight off 
 the side walls. 
 
 
. 
 
Boiler Construction 
 
 As it is of the highest importance not only to the engineer 
 in charge of the plant, but also to his assistants, and in 
 fact to all persons whose business compels them to be in 
 the vicinity of the boiler-room, that there should be abso- 
 
 i 
 
 
 AJL 
 
 
 Fig. 29 
 
 lutely no doubt as to the safe construction of the boilers, 
 and their ability to withstand the pressures under which 
 they are operated, the author has compiled the following 
 
 Fig. 30 
 
 by such eminent authorities as Dr. Thurston, Prof. Wm. 
 Kent, Dr. Peabody, D. K. Clark, Hutton and many other 
 experts have been consulted, and the author has also added 
 data regarding the construction and strength of boilers. 
 The deductions and reports of tests and experiments made 
 
 
 77 
 
 1 
 
78 
 
 Steam Engineering 
 
 the results of his own observations, collected during an 
 experience of thirty-five years as a practical engineer. 
 
 When steel was first introduced as a material for boiler 
 plate, it was customary to demand a high tensile strength, 
 70,000 to 74,000 pounds per square inch, but experience 
 and practice demonstrated in course of time that it was 
 much safer to use a material of lower tensile strength. It 
 was found that with steel boiler plate of high tenacity there 
 was great liability of its cracking, and also of certain 
 
 Fig. 31 
 
 changes occurring in its physical properties, brought about 
 by the variations in temperature to which it was exposed. 
 Consequently present-day specifications for steel boiler plate 
 call for tensile strengths running from 55,000 to 66,000 
 pounds, usually 60,000 pounds per square inch. Dr. Thurs- 
 ton gives what he calls "good specifications" for boiler steel 
 as follows: "Sheets to be of uniform thickness, smooth 
 finish, and sheared closely to size ordered." Tensile strength 
 to be 60,000 pounds per square inch for fire box sheets and 
 55,000 pounds per square inch for shell sheets. Working 
 
Boiler Construction ?$ 
 
 test : a piece from each sheet to be heated to a dark cherry 
 red, plunged into water at 60° and bent double, cold, under 
 the hammer. Such piece to show no flaw after bending. 
 The U. S. Board of Supervising Inspectors of Steam Ves- 
 sels prescribes, in Section 3 of General Eules and Kegula- 
 tions, the following method for ascertaining the tensile 
 strength of steel plate for boilers: "There shall be taken 
 from each sheet to be used in shell or other parts of boiler 
 which are subject to tensile strain, a test piece prepared in 
 form according in figure 32. The straight part in center 
 shall be 9 inches in length and 1 inch in width marked with 
 light prick punch marks at distances 1 inch apart, as shown, 
 spaced s& as to give 8 inches in length. The sample must 
 show, when tested, an elongation of at least 25 per cent in 
 a length of 2 inches for thickness up to % inch, inclusive ; 
 in a length of 4 inches for over *4 inch to T 7 e inches, in- 
 clusive ; in a length of 6 inches, for all plates over fy inches 
 and under 1% inches in thickness. The samples shall also 
 be capable of being bent to a curve of which the inner 
 radius is not greater than 1% times the thickness of the 
 plates, after having been heated uniformly to a low cherry 
 red and quenched in water of 82° F. 
 
 Punched and Drilled Plates. Much has been written on 
 this subject, and it is still open for discussion. If the 
 material is a good, soft steel, punched sheets are apparently 
 as strong and in some instances stronger than drilled ; espe- 
 cially is this the case with regard to the shearing resistance 
 of the rivets, which is greater with punched than with drilled 
 holes. 
 
 Concerning rivets and rivet iron and steel, Dr. Thurston 
 has this to say in his "Manual of Steam Boilers" : "Kivet 
 iron should have a tenacity in the bar approaching 60,000 
 
80 Steam Engineering 
 
 pounds per square inch, and should be as ductile as the very 
 best boiler plate when cold. A good %-inch iron rivet can 
 be doubled up and hammered together cold without ex- 
 hibiting a trace of fracture." The shearing resistance of 
 iron rivets is about 85 per cent and that of steel rivets 
 about 77 per cent of the tenacity of the original bar, as 
 shown by experiments made by Greig and Eyth. The re- 
 searches made by Wohler demonstrated that the shearing 
 strength of iron was about four- fifths of the tensile strength. 
 
 For the benefit of beginners, the following simple rules 
 are given for finding the percentage of efficiency, or in other 
 words the ratio of the strength of the riveted joint, to the 
 strength of the solid plate. In these calculations tlTe tensile 
 strength of the rivets was assumed to be 38,000 to 40,000 
 pounds per square inch. The highest efficiency is attained 
 in a riveted joint when the tensile strength of the rods from 
 which the rivets are cut approaches that of the plates, and 
 when the proportions of the joint are such that the tensile 
 strength of the plates, the shearing strength of the rivets, 
 and the crushing resistance of the rivets and plate, for a 
 given section or unit strip, are as nearly equal as it is 
 possible to secure them. 
 
 The shell should be made of homogeneous steel of about 
 60,000 pounds tensile strength. The thickness depending 
 upon the pressure to be carried. The term tensile strength 
 means that it would take a pull of 60,000 pounds in the 
 direction of its length to break a bar of the material one 
 inch square, or two inches wide by one-half inch thick, or 
 three-eighths of an inch thick by 2.67 in. wide. 
 
 The heads are generally made % inch thicker than the 
 shell. 
 
Boiler Construction 81 
 
 Riveting. Boiler rivets should be of good charcoal iron, 
 or a soft, mild steel of 38,000 pounds to 40,000 pounds, T. S. 
 No boiler is stronger than its weakest part, and it is evident 
 that a riveted joint has not the full strength of the solid 
 plate. In order to ascertain the safe working pressure of a 
 boiler it is necessary to first determine the strength of the 
 riveted seams, and the method of doing this is as follows : 
 Assume the boiler to be of the horizontal tubular type, 60 
 inches in diameter by 16 feet in length. The plates to be 
 of steel % in. thick, having a tensile strength of 60,000 
 pounds per square inch, the longitudinal seams to be double 
 riveted and the girth seams to be single riveted. The pitch 
 of the rivets, that is the distance from the center of one 
 rivet hole to the center of the next one in the same row, to 
 be for the double riveted seams 3% inches and for the 
 single riveted seams 2% inches. The diameter of the rivets 
 to be % inches and diameter of holes to be jf inches. 
 Assume the rivets to have a T. S. of 38,000 pounds per 
 square inch of sectional area. First, find strength of a 
 section of solid plate 3*4 inches wide, which is the width 
 between centers of rivet holes before punching. 
 
 Rule 1 Pitch X thickness X T. S. Thus, 3.25 X .375 X 
 60,000 = 73,125 pounds, strength of solid plate. 
 
 Second, find strength of net section of plate, meaning 
 that portion of plate left after deducting the diameter of 
 one hole {% inches, which expressed in decimals = .9375 
 inches from the width of plate before punching. 
 
 Rule 2. Pitch— diameter of hole X thickness X T. S. 
 Thus, 3.25— .9375X-375X60,000=52,031 pounds, strength 
 of net section of plate. 
 
 Third, find strength of rivets. In calculating the strength 
 of rivets in a double riveted seam, the sectional area of two 
 
82 Steam Engineering 
 
 rivets must be considered, taking one-half the area of two 
 
 rivets in the first row, and the area of another rivet in the 
 
 second row. The area of a %-inch rivet is .6013 inches, 
 
 but when in position it is assumed to fill the hole \% inches. 
 
 Consequently, its area would then be .69 inches and its 
 
 strength is found by Eule 3. 
 
 Rule 3. Sectional areaXT. S. Thus, .69X38,000=26,- 
 
 220 pounds, strength of one rivet, and multiplying by 2, 
 
 as there are two rivets, the result is 26,220X2=52,440 
 
 pounds, strength of rivets in the seam under consideration. 
 
 It thus appears that the plate is the weakest portion and 
 
 the percentage of strength retained is found by multiplying 
 
 52,031 by 100 and dividing by 73,125, the strength of solid 
 
 , , ™ 52,031X100 , 
 
 plate. Thus, WTT^ = 71.1 per cent. 
 
 The query might arise, why is the diameter of one rivet 
 hole deducted from the pitch when figuring the strength 
 of net plate? The answer is, that in punching the holes 
 one-half the diameter of each hole is cut from the section 
 designated, thereby reducing its width by just that amount. 
 
 The 71.1 per cent obtained by the calculation represents 
 the strength of the boiler as compared to the strength of 
 the sheet before punching, and should enter into all calcu- 
 lations for the safe working pressure. 
 
 It is usual in practice to figure the strength of a double- 
 riveted seam at 70 per cent of the strength of the solid 
 plate. The strength of triple-riveted butt joints may be 
 calculated by taking a section of plate along the first row 
 of rivets and estimate it as a single-riveted joint, then add 
 to this result the strength of rivets in the second and third 
 rows for a section of the same width. In properly designed 
 
Boiler Construction 83 
 
 triple-riveted butt joints the percentage of strength retained 
 is 88; and some recent achievements in designing have 
 shown the remarkable result of quadruple-riveted butt 
 joints retaining as high as 92 to 94 per cent of the strength 
 of the solid plate. 
 
 Bursting Pressure. The query might arise, why should 
 the longitudinal or side seams require to be stronger than 
 the girth or round about seams? The answer is, that the 
 force tending to rupture the boiler along the line of the 
 longitudinal seams is proportional to the diameter divided 
 by two, while the stress tending to pull it apart endwise is 
 only one-half that, or proportional to the diameter divided 
 by four. 
 
 To illustrate, let Fig. 29 represent the shell of the boiler 
 heretofore referred to, ignoring for the time being the 
 tubes and braces, and consider the boiler simply as a hollow 
 cylinder. Now the total force tending to rupture the boiler 
 along the line of the girth seams or in the direction of the 
 horizontal arrows=area of one head in square inchesX 
 pressure in pounds per square inch. It is true that the 
 pressure is exerted against both heads, but the area of one 
 head can only be considered for the reason that the two 
 stresses are exerted against each other just as in the case of 
 two horses pulling against each other, or in opposite direc- 
 tion on the same chain. The stress on the chain will be 
 what one horse (not both) pulls. To further illustrate, 
 suppose one of the horses to be replaced by a permanent 
 post or wall and let one end of the chain be attached thereto. 
 One head or one side of the boiler pulls against the other, 
 and the stress on the seams is the force with which each 
 (not both) pulls. Eeferring again to Fig. 29, area of one 
 head=60 2 X. 7854=2827.4 square inches. Suppose there is 
 
84 Steam Engineering 
 
 a pressure of 10 pounds per square inch in the boiler. Then 
 total stress on the girth seams=2827.4X 10=28,274 
 pounds. Opposed to this pull is the entire circumference 
 of the boiler, which is 60X3.1416=188.5 inches. There- 
 fore, dividing total pressure (28,274 pounds) by the cir- 
 cumference in inches (188.5) will give 150 pounds as the 
 stress on each inch of the girth seams. While the stress on 
 each inch of the longitudinal seams or along the line A B, 
 Fig. 29, and which is exerted in the direction of the vertical 
 arrows, is pressure (10 pounds) X one-half the diameter 
 (30 inches) =300 pounds. One-half the diameter is used 
 because the pressure in any direction is effective only on 
 the surface at right angles to that direction. 
 
 The formula for finding the bursting pressure of a boiler 
 may be expressed as follows : 
 
 B= — -^ in which B=bursting pressure. 
 
 T.S.=tensile strength. 
 T=thickness of sheet. 
 E=radius or one-half the diam. 
 Example. T.S. =55,000 pounds per square inch. 
 
 T=% inches (expressed decimally=.375 
 
 inches). 
 E=30 inches. 
 Then 55,000X.375-^30=687.5 pounds per square inch, 
 which is the pressure at which rupture would take place 
 provided there were no seams in the boiler and the original 
 strength of the sheet was retained, but, as has been seen, a 
 certain percentage of strength is lost through punching or 
 drilling the necessary rivet holes, and this must be taken 
 into account. 
 
Boiler Construction 85 
 
 The formula now becomes, for double riveting, 
 
 - T.S.XTX.70 . ,: , J. , u ., 
 
 13= — , m which the letters preserve the same 
 
 value as in the original formula, but the result is reduced 
 
 by multiplying by the decimal .70, which represents the 
 
 percentage of strength retained by double-riveted seams. 
 
 n + i -d -n 55,000X.375X.70 , 0i , 
 
 Consequently B will now= — — =481 pounds. 
 
 In case the seams are all single riveted .56 must be sub- 
 stituted for .70, and with triple-riveted butt joints .88 can 
 safely be used. 
 
 Safe Working Pressure. In order to ascertain the safe 
 working pressure of a boiler it is necessary first to calcu- 
 late the bursting pressure and divide this by another factor 
 called the factor of safety. The one most commonly used 
 for boilers is 5, or in other words the safe working pressure 
 = one-fifth the bursting pressure. In the case of the boiler 
 under consideration,- the safe pressure would be 481-^5=96 
 pounds, at which point the safety valve should blow off. 
 
 Bracing. Every engineer can easily ascertain for him- 
 self whether the boilers under his charge are properly braced 
 or not. The parts that require bracing are : all flat surfaces, 
 such as the sides and top of the fire-box in boilers of the 
 locomotive type, and those portions of the heads above and 
 below the tubes in horizontal tubular boilers, also the top 
 of the dome. 
 
 The stress per square inch of sectional area on braces 
 and stays should not exceed 6,000 pounds. It is customary 
 to consider the flange of the head and the top row of tubes 
 as sufficient bracing for a space two inches wide above the 
 
86 
 
 Steam Engineering 
 
 tubes and the same distance around the flange. Therefore 
 the part of the head to be braced will be the segment con- 
 tained within a line drawn two inches above the top row 
 of tubes and two inches inside the flange. 
 
 In order to ascertain the number of braces required for 
 a given boiler head, three factors are necessary : first, the 
 area of the segment in square inches ; second, the diameter 
 and T. S. of the braces, and third, the pressure to be carried. 
 By the use of Table 2 the areas of segments of boiler 
 heads ranging from 42 to 72 inches in diameter can easily 
 be obtained. Assume the boiler to be 60 inches in diame- 
 ter, distance from top of tubes to top of shell 24 inches. 
 Deduct 4 inches for surface braced by top row of tubes and 
 flange, leaving the height of segment to be braced 20 inches. 
 
 Table 2 
 
 Diameter 
 
 Distance from 
 
 Height of 
 
 Constant. 
 
 of Boiler. 
 
 Tubes to Shell. 
 
 Segment. 
 
 42 in. 
 
 15 in. 
 
 11 in. 
 
 .16314 
 
 44 in. 
 
 17 in. 
 
 13 in. 
 
 .1936 
 
 48 in. 
 
 19 in. 
 
 15 in. 
 
 .20923 
 
 54 in. 
 
 21 in. 
 
 17 in. 
 
 .21201 
 
 60 in. 
 
 24 in. 
 
 20 in. 
 
 .22886 
 
 66 in. 
 
 25 in. 
 
 21 in. 
 
 .214 
 
 72 in. 
 
 29 in. 
 
 25 in. 
 
 .24212 
 
 Rule, Multiply the square of the diameter of the boiler 
 by the constant number found in right hand column oppo- 
 site column headed diameter. 
 
 Example. 60X60X-22886=823.89 square inches, area 
 of segment to be braced. Find number of braces required. 
 Assume the braces to be lVs inches in diameter and of a 
 T. S. of 38,000 pounds per square inch of section. The 
 area of one brace will be .994 square inches, which X 6,000 
 pounds gives 5,964 pounds as the stress allowable on each 
 brace. Suppose the pressure to be carried is 100 pounds 
 
Boiler Construction 87 
 
 per square inch. There will be area of segment (823.89 
 square inches) X pressure (100 pounds) =82,389 pounds, 
 total stress. Dividing this result by 5,964 pounds (the 
 capacity of each brace) gives 13.8 braces as the number 
 needed. In practice there should be fourteen. 
 
 Having a T. S. of 38,000 pounds and using 6 as the 
 factor of safety, each brace could safely sustain a pull of 
 6,295 pounds. Therefore it is evident that the above men- 
 tioned load for each brace is well within the limit. For 
 convenience in calculating the areas of segments of circles, 
 other than those mentioned in Table 2, the following rule 
 is given : 
 
 Eeferring to Figure 30 it is desired to find the area of 
 the segment contained within the lines A B C E. It will 
 be necessary first to find the area of the sector bounded by 
 the lines ABCD. This is done by multiplying one-half 
 the length of the arc, A B C, by the radius, D B. Having 
 obtained the area of the sector, the next step is to find the 
 area of the triangle bounded by the lines A E C D and sub- 
 tract it from the area of the sector. The remainder will 
 be the area of the segment. Having found the area of the 
 surface to be braced, and the number of braces required, 
 it jiow becomes necessary to consider the spacing of the 
 same. 
 
 Rule. Divide area to be braced by the number of braces, 
 and extract the square root of quotient. 
 
 Example. 823.89-^14=58.8 square inches to be allotted 
 to each brace. Extract square root of 58.8 and the result is 
 7.68 inches, which is the length of one side of the square 
 which each brace will be required to sustain. 
 
 For internally fired boilers the same rules can be applied 
 except that the surfaces to be braced are generally of rec- 
 
88 Steam Engineering 
 
 tangular shape and consequently the area is more easily 
 figured than in the case of segments. That part of the 
 head below the tubes also requires to be braced, and two 
 braces are generally sufficient, as at A and B, Fig. 31. In 
 the case of domes it is safe to consider the portion of the 
 head within three inches of the flange as sufficiently braced. 
 Then suppose the dome to be 36 inches in diameter, there 
 will remain a circle 30 inches in diameter to be braced. 
 The circumference of this circle is 94.2 inches and the 
 pitch, or distance from center to center of the braces, being 
 7.6 inches, the number of braces required is found by divid- 
 ing 94.2 by 7.6, giving 12 braces. These braces should be 
 
 V lr J /Yo//ess fA*n 9" I 
 
 j Cj £L 
 
 " HI — 
 
 1 ' ' : i " ^ 
 
 Fig. 32 
 test piece 
 
 located along a line which is one-half the pitch, or 3.8 
 inches, within the circumference of the 30-inch circle. The 
 space immediately surrounding the hole cut for the steam 
 outlet will be sufficiently re-enforced by the flange riveted 
 on for the reception of the steam pipe. All holes cut in 
 boilers, such as man holes, hand holes, and those for pipe 
 connections, above two inches should be properly re-enforced 
 by riveting either inside or outside a wrought-iron or steel 
 ring or flange of such thickness and width as to contain at 
 least as much material as has been cut from the hole. 
 
 The preceding rules and calculations will serve to give 
 the young student an idea of the need of mathematics in 
 
Boiler Construction 
 
 89 
 
 boiler making, and the subject is to be pursued still farther 
 and deeper, thus enabling the engineer in charge of a steam 
 plant to calculate for himself whether or not his boilers are 
 working within the margin of safety. 
 
 The tables that follow have been compiled from the high- 
 est authorities and show the results of a long and exhaustive 
 series of tests and experiments made in order to ascertain 
 the proportions of riveted joints that will give the highest 
 efficiencies. 
 
 The following Table 3 gives the diameters of rivets for 
 various thicknesses of plates and is calculated according to 
 a rule given by Unwin : 
 
 Table 3 
 diameters of rivets. 
 
 Thickness of 
 
 Diameter of 
 
 Thickness of 
 
 Diameter of 
 
 Plate. 
 
 Rivet. 
 
 Plate. 
 
 Rivet. 
 
 1 in. 
 
 1 in | 
 
 ft in. 
 
 I in. 
 
 ft in. 
 
 T 9 e in. 
 
 S in. 
 
 i if in. 
 
 s in. 
 
 U in. 
 
 1 in. 
 
 It 1 * in. 
 
 & in. 
 
 i in. 
 
 I in. 
 
 11 in. 
 
 1 in. 
 
 ft in. 
 
 1 in. 
 
 14 in. 
 
 The efficiency of the joint is the percentage of the strength 
 of the solid plate that is retained in the joint, and it de- 
 pends upon the kind of joint and method of construction. 
 
 If the thickness of the plate is more than % inch, the 
 •joint should always be of the double butt type. 
 
 The diameters of rivets, rivet holes, pitch and efficiency 
 of joint, as given in the following Table 4, which was pub- 
 lished in the "Locomotive" several years ago, were adopted 
 at the time by some of the best establishments in the United 
 States : 
 
 Concerning the proportions of double-riveted butt joints, 
 Prof. Kent says : "Practically it may be said that we get 
 a double-riveted butt joint of maximum strength by mak- 
 
90 
 
 Steam Engineering 
 
 ing the diameter of the rivet about 1.8 times the thickness 
 of the plate, and making the pitch 4.1 times the diameter 
 of the hole/ 5 
 
 Table 4 
 proportions and efficiencies of riveted joints. 
 
 Inch. 
 
 Inch. Inch. Inch. Inch. 
 
 Thickness of plate \ 
 
 Diameter of rivet I 
 
 Diameter of rivet-hole ty 
 
 Pitch for single riveting 2 
 
 Pitch for double riveting 3 
 
 Efficiency, single-riveted joint 66 
 
 Efficiency, double-riveted joint 77 
 
 H 
 
 3 
 4 
 
 tt 
 
 I 
 
 if 
 
 2* 
 
 21 
 
 2t 3 * 
 
 2\ 
 
 31 
 
 31 
 
 31 
 
 31 
 
 .64 
 
 .62 
 
 .60 
 
 .58 
 
 .76 
 
 .75 
 
 .74 
 
 .73 
 
 Table 5 as given below is condensed from the report of a 
 test of double-riveted lap and butt joints. In this test the 
 tensile strength of the plates was 56,000 to 58,000 pounds 
 per square inch, and the shearing resistance of the rivets 
 (steel) was about 50,000 pounds per square inch. 
 
 Table 5 
 diameter and pitch of rivets— double-riveted joint. 
 
 Kind of 
 Joint. 
 
 Thickness of 
 Plate. 
 
 Diameter of 
 Rivet. 
 
 Ratio of Pitch 
 to Diameter. 
 
 Lap 
 Butt 
 Butt 
 Butt 
 
 1 inch 
 1 inch 
 1 inch 
 1 inch 
 
 0.8 inches 
 0.7 inches 
 1.1 inches 
 1.3 inches 
 
 3.6 inches 
 3.9 inches 
 4.0 inches 
 3.9 inches 
 
 Lloyd's rules, condensed, are as follows : 
 Table 6 
 
 LLOYD'S RULES— THICKNESS OF PLATE AND DIAMETER OF 
 
 RIVETS. 
 
 Thickness of 
 
 Diameter of 
 
 Thickness of 
 
 Diameter of 
 
 Plate. 
 
 Rivets. 
 
 Plate. 
 
 Rivets. 
 
 1 inch 
 
 I inch 
 
 i inch 
 
 1 inch 
 
 tV inch 
 
 I inch 
 
 \% inch 
 
 I inch 
 
 h inch 
 
 i inch 
 
 I inch 
 
 1 inch 
 
 & inch 
 
 $ inch 
 
 fk inch 
 
 1 inch 
 
 1 inch 
 
 'i inch 
 
 1 inch 
 
 1 inch 
 
 H inch 
 
 1 inch 
 
 
 
Boiler Construction 91 
 
 The following Table 7 is condensed from one calculated 
 by Prof. Kent, in which he assumes the shearing strength 
 of the rivets to be four-fifths of the tensile strength of the 
 plate per square inch, and the excess strength of the per- 
 forated plate to be 10 per cent. 
 
 Table 7 
 
 Pitch Efficiency 
 
 Thickness Diameter Single Double Single Double 
 
 of Plate. ot Hole. Riveting. Riveting. Riveting. Riveting. 
 
 Inches. Inches. Inches. Inches. Per Cent. Per Cent. 
 
 i I 2.04 3.20 57.1 72.7 
 
 & 1 2.30 3.61 56.6 72.3 
 
 I 1 2.14 3.28 53.3 70.0 
 
 I 11 2.57 4.01 56.2 72.0 
 
 T 9 <r 1 2.01 3.03 50.4 67.0 
 
 & II 2.41 3.69 53.3 69.5 
 
 & 14 2.83 4.42 55.9 71.5 
 
 1 1 1.91 2.82 47.7 64.6 
 
 § II 2.28 3.43 50.7 67.3 
 
 I II 2i>7 4 1 10 53 1 3 69.5 
 
 Another table of joint efficiencies as given by Dr. Thurs- 
 ton is as follows, slightly condensed from the original cal- 
 culation : 
 
 Table 8 
 
 Single riveting 
 
 Plate thickness iV I" T V 1" i" I" I" 1" 
 
 Efficiency 55 .55 .53 .52 .48 .47 .45 .43 
 
 Double riveting 
 
 Plate thickness I" T y i" 1" s" 1" 
 
 Efficiency 73 .72 .71 .66 .61 .63 
 
 The author has been at considerable pains to compile 
 Tables 9, 10 and 11, giving proportions and efficiencies of 
 single lap, double lap and butt, and triple-riveted butt joints. 
 The highest authorities have been consulted in the com- 
 putation of these tables arid great care exercised in the cal- 
 culations : 
 
 It will be noticed that in single-riveted lap joints the 
 highest efficiencies are attained when the diameter of the 
 
92 Steam Engineering 
 
 rivet hole is about 2 1/3 times the thickness of the plate, 
 and the pitch of the rivet 2% times the diameter of the 
 hole. 
 
 Table 9 
 proportions of single-riveted lap joints. 
 
 Thickness of 
 
 Diameter 
 
 of 
 
 Pitch of Rivet, 
 
 Efficiency, 
 
 Plate, Inches. 
 
 Rivet, Inches. 
 
 Inches. 
 
 Per Cent. 
 
 ft 
 
 i 9 <r 
 
 
 1.13 
 
 50.5 
 
 T 5 S 
 
 1 
 
 
 1.33 
 
 53.3 
 
 ft 
 
 tt 
 
 
 1.55 
 
 55.7 
 
 i 
 
 1 
 
 
 1.60 
 
 53.3 
 
 i 
 
 I 
 
 
 2.04 
 
 57.1 
 
 ft 
 
 I 
 
 
 1.87 
 
 53.2 
 
 ft 
 
 1 
 
 
 2.30 
 
 56.6 
 
 1 
 
 1 
 
 
 2.14 
 
 53.3 
 
 i 
 
 11 
 
 
 2.57 
 
 56.2 
 
 T 9 6 
 
 1 
 
 
 2.01 
 
 50.4 
 
 T 9 <f 
 
 11 
 
 
 2.41 
 
 53.3 
 
 ft 
 
 11 
 
 
 2.83 
 
 55.9 
 
 1 
 
 11 
 
 
 2.28 
 
 50.7 
 
 i 
 
 11 
 
 
 2.67 
 
 53.3 
 
 With the double-riveted joint it appears, according to 
 Table 10, that in order to obtain the highest efficiency, the 
 joint should be designed so that the diameter of the rivet 
 hole will be from 1 4/5 to 2 times the thickness of plate, 
 and the pitch should be from 3 1/3 to 3% times the diam- 
 eter of the hole. Concerning the thickness of plates Dr. 
 Thurston has this to say: "Very thin plates cannot be 
 well caulked, and thick plates cannot be safely riveted. The 
 limits are about % of an inch for the lower limit, and % 
 of an inch for the higher limit." The riveting machine, 
 however, overcomes the difficulty with very thick plates. 
 
 The triple-riveted butt joint with two welts, one inside 
 and one outside, has two rows of rivets in double shear and 
 one outer row in single shear on each side of the butt, the 
 pitch of rivets in the outer rows being twice the pitch of the 
 inner rows. One of the welts is wide enough for the three 
 
Boiler Construction 
 
 93 
 
 rows of rivets each side of the butt, while the other welt 
 takes in only the two close pitch rows. 
 
 Table 10 
 proportions of double-riveted lap and butt joints. 
 
 
 Thickness of 
 
 Diameter of 
 
 Pitch of 
 
 Efficiency, 
 
 
 Plate, Inches. 
 
 Rivet 
 
 Inches. 
 
 Rivet, Inches. 
 
 Per Cent. 
 
 
 i 5 s 
 
 
 & 
 
 1.71 
 
 67.1 
 
 
 & 
 
 
 i 
 
 2.05 
 
 69.5 
 
 
 i 
 
 
 1 
 
 2.46 
 
 69.5 
 
 
 1 
 
 
 I 
 
 3.20 
 
 72.7 
 
 
 A 
 
 
 £ 
 
 2.21 
 
 66.2 
 
 
 A 
 
 
 1 
 
 2.86 
 
 69.4 
 
 
 A 
 
 
 
 3.61 
 
 72.3 
 
 
 i 
 
 
 
 3.28 
 
 70.0 
 
 
 1 
 
 
 11 
 
 4.01 
 
 72.0 
 
 
 A 
 
 
 
 3.03 
 
 67.0 
 
 
 A 
 
 
 11 
 
 3.69 
 
 69.5 
 
 
 A 
 
 
 ii 
 
 4.42 
 
 71.5 
 
 
 i 
 
 
 ii 
 
 3.43 
 
 67.3 
 
 
 i 
 
 
 n 
 
 4.10 
 
 69.5 
 
 
 1 
 
 
 
 2.50 
 
 72.0 
 
 
 i 
 
 
 ii 
 
 3.94 
 
 74.2 
 
 
 l 
 
 
 1 1 
 J-4 
 
 4.10 
 
 76.1 
 
 When properly designed this form of joint has a high 
 efficiency, and is to be relied upon. Table 11 gives propor- 
 tions and efficiencies, and it will be noted that the highest 
 degree of efficiency is shown when the diameter of rivet 
 hole is from l 1 /^ to l 1 ^ times the thickness of plate, and 
 the pitch of the rivets is from 3% to 4 times the diameter 
 of the hole. This, of course, refers to the pitch of the close 
 rows of rivets, and not the two outer rows. 
 
 The highest efficiency is attained in a riveted joint when 
 the tensile strength of the rods from which the rivets are 
 cut approaches that of the plates, and when the propor- 
 tions of the joint are such that the tensile strength of the 
 plates, the shearing strength of the rivets, and the crushing 
 resistance of the rivets and plate, for a given section or 
 unit strip, are as nearly equal as it is possible to secure 
 them. 
 
94 
 
 Steam Engineering 
 
 Table 11 
 
 PROPORTIONS OF TRIPLE-RIVETED ] 
 
 BUTT JOINTS 
 
 WITH IN- 
 
 
 SIDE AND OUTSIDE WELT. 
 
 
 Thickness of 
 
 Diameter of 
 
 Pitch of 
 
 Pitch of Outer 
 
 Efficiency, 
 
 Plate, Inches. 
 
 Rivet, Inches. 
 
 Rivet, Inches. 
 
 Rows, Inches. 
 
 Per Cent. 
 
 i 
 
 8 
 
 3.25 
 
 6.5 
 
 84 
 
 & 
 
 tI 
 
 3.25 
 
 6.5 
 
 85 
 
 i 
 
 1 
 
 3.25 
 
 6.5 
 
 83 
 
 4 
 
 3.50 
 
 7.0 
 
 84 
 
 § 
 
 1 
 
 3.50 
 
 7.0 
 
 86 
 
 1 
 
 1* 
 
 3.50 
 
 7.0 
 
 85 
 
 i 
 
 11 
 
 3.75 
 
 7.5 
 
 86 
 
 l 
 
 11 
 
 3.87 
 
 7.7 
 
 84 
 
 A few examples of calculations for efficiency will be 
 given, taking the three forms of riveted joints in most com- 
 mon use. The following notation will be used throughout : 
 T. S.=Tensile strength of plate per square inch. 
 
 T=Thickness of plate. 
 
 C= Crushing resistance of plate and rivets. 
 
 A= Sectional area of rivets. 
 
 S= Shearing strength of rivets. 
 
 D=Diameter of hole (also diameter of rivets when 
 driven). 
 
 P=Pitch of rivets. 
 
 In the calculations that follow T. S. will be assumed to 
 be 60,000 pounds, S will be taken at 45,000 pounds, and 
 the value of C may be assumed to be 90,000 to 95,000. 
 
 DOUBLE-RIVETED LAP AND BUTT JOINTS. 
 
 Figure 33 shows a double-riveted lap joint. The style of 
 riveting in this joint is what is known as chain riveting. 
 
 In case the rivets are staggered, the same rules for cal- 
 culating the efficiency will hold as with chain riveting, for 
 the reason that with either style of riveting the unit strip 
 of plate has a width equal to the pitch or distance p. (Fig. 
 33.) 
 
Boiler Construction 95 
 
 The dimensions of the joint under consideration are as 
 follows: P=3 1 4 : inches, T= T 7 6 inch, D=l inch (which 
 is also diameter of driven rivet). 
 
 Fig. 33 
 double riveted lap joint 
 
 The strength of the unit strip of solid plate is PXTX 
 T. S.=85,312. 
 
 The strength of net section of plate after drilling is 
 P— DXTXT.S.=59,062. 
 
 The shearing resistance of two rivets is 2AXS=70,686. 
 
 The crushing resistance of rivets and plate is DX^XT 
 XC=78,750. 
 
 It thus appears that the weakest part of the joint is the 
 net strip or section of plate, the strength of which is 59,062 
 and the efficiency = 59,062 X 100-^85,312=69.2 per cent. 
 
 A double-riveted butt joint is illustrated by Fig. 34, and 
 the dimensions are as follows : 
 
 P, inner row of rivets=2% inches. 
 
 P', outer row of rivets=5% inches. 
 
 T of plate and butt straps= T 7 6 inch. 
 
 D of hole and driven rivet=l inch. 
 
 Failure may occur in this joint in five distinct ways, 
 which will be taken up in their order. 
 
96 
 
 Steam Engineering 
 
 1. Tearing of the plate at the outer row of rivets. The 
 net strength at this point is P— DXTXT.S., which, ex- 
 pressed in plain figures, results as follows: 5.5 — 1X-4375 
 X60,000=118,125. 
 
 Pig. 34 
 double riveted butt joint 
 
 2. Shearing two rivets in double shear and one in singly 
 shear. Should this occur, the two rivets in the inner row 
 would be sheared on both sides of the plate, thus being in 
 double shear. Opposed to this strain there are four sec- 
 tions of rivets, two for each rivet. Then at the outer row 
 of rivets in the unit strip there is the area of one rivet in 
 single shear to be added. The total resistance, therefore, 
 is 5AXS as follows: .7854X5X45,000=176,715. 
 
 3. The plate may tear at the inner row of rivets and 
 shear one rivet in the outer row. The resistance in this 
 case would be P'— 2DXTXT.S.+AXS as follows: 5.5 
 — 2X.4375X60,000+.7854X45,000=127,218. 
 
 4. Failure may occur by crushing in front of three 
 rivets. Opposed to this is 3DXTXC, or 1X3X-4375 
 X95,000=124,687. 
 
Boiler Construction 
 
 97 
 
 5. Failure may occur by crushing in front of two rivets 
 and shearing one. The resistance is represented by 2D XT 
 XC+1AXS; expressed in figures, 1X2X.4375X95,000+ 
 .7854X45,000=118,468. 
 
 The strength of a solid strip of plate 5^2 inches wide 
 before drilling is P'XTXT.S., or 5.5X-4375X60,000= 
 144,375, and the efficiency of the joint is 118,125X100-^- 
 144,375=81.1 per cent. 
 
 TRIPLE-RIVETED BUTT JOINT. 
 
 A triple-riveted butt joint is shown in Fig. 35, the dimen- 
 sions of which are as follows : 
 
 T= T V inch, D=-£f inch, A=.69 inch, T=3% inches, 
 ¥'=6% inches. 
 
 f K— P — > I 
 
 [I jj <jjj m 
 
 # m <% . # 3 % ' 
 o $ <& # # # 
 
 Q O Q ^ e © 
 & gj g g g I 
 
 Fig. 35 
 triple riveted butt joint 
 
 Failure may occur in this joint in either one of five ways. 
 
 1. By tearing the plate at the outer row of rivets where 
 the pitch is 6% inches. The net strength of the unit strip 
 at this point is P'-DXTXT.S., found as follows: 6.75— 
 .9375X.4375X60,000=152,578. 
 
98 Steam Engineering 
 
 2. By shearing four rivets in double shear and one in 
 single shear. In this instance, of the four rivets in double 
 shear, each one presents two sections, and the one in single 
 shear presents one, thus making a total of nine sections of 
 rivets to be sheared, and the strength is 9AXS, or .69 X 
 9X45,000=279,450. 
 
 3. Rupture of the plate at the middle row of rivets and 
 shearing one rivet. Opposed to this strain the strength is 
 P'— 2DXTXT.S.+1AXS, equivalent to 6.75— (.9375X 
 2) X-4375X60,000+. 69X90,000=190,068. 
 
 4. Crushing in front of four rivets and shearing one 
 rivet. The resistance in this instance is 4DXTXC+1AX 
 S, or .9375X4X.4375X90,000+.69X45,000=178,706. 
 
 5. Failure may be caused by crushing in front of five 
 rivets, four of which pass through both the inside and out- 
 side butt straps, while the fifth rivet passes through the in- 
 side strap only, and the resistance is 5DXTXC, equivalent 
 to .9375X5X90,000=184,570. 
 
 The strength of the unit strip of plate before drilling is 
 FXTXT.S., or 6.75X-4375X60,000=177,187, and the 
 efficiency is 152,578X100-^177,187=86 per cent. 
 
 With the constantly increasing demand for higher steam 
 pressures, the necessity for higher efficiencies in the riveted 
 joints of boilers becomes more apparent, and of late years 
 quadruple and even quintuple-riveted butt joints have in 
 many instances come into use. The quadruple butt joint 
 when properly designed shows a high efficiency, in some 
 cases as high as 94.6 per cent. Figure 36 illustrates a joint 
 of this kind, and the dimensions are as follows : 
 
 T=y 2 inch. 
 
 D=ff inch. 
 
 A=.69 inch. 
 
Boiler Construction 
 
 99 
 
 P, inner rows=3% inches. 
 
 P', 1st outer row=7 1 /2 inches. 
 
 P", 2d outer row=15 inches. 
 
 The two inner rows of rivets extend through the main 
 plate and both the inside and outside cover plates or butt 
 straps. 
 
 ->- 
 
 Fig. 36 
 quadruple riveted butt joint 
 
 The two outer rows reach through the main plate and 
 inside cover plate only, the first outer row having twice 
 the pitch of the inner rows, and the second outer row has 
 twice the pitch of the first. 
 
 Taking a strip or section of plate 15 inches wide (pitch 
 of outer row), there are four ways in which this joint may 
 fail. 
 
100 Steam Engineering 
 
 1. By tearing of the plate at the outer row of rivets. 
 The resistance is F'-DXTXT.S., or 15— .9375X-5X 
 60,000=421,875. 
 
 2. By shearing eight rivets in double shear and three 
 in single shear. The strength in resistance is 19AXS, or 
 .69X19X45,000=589,950. 
 
 3. By tearing at inner rows of rivets and shearing three 
 rivets. The resistance is P"— 4DXTXT.S.+3AXS, or 
 15— (.9375X4) X- 5X60,000+. 69X3X45,000=430,650. 
 
 4. By tearing at the first outer row of rivets, where the 
 pitch is 7% inches, and shearing one rivet. The resistance 
 is P"_ 2DXTXT.S.+AXS, or 15— (.9375X2) X-5 
 X60,000+. 69X45,000=424,800. 
 
 It appears that the weakest part of the joint is at the 
 outer row of rivets, where the net strength is 421,875. The 
 strength of the solid strip of plate 15 inches wide before 
 drilling. is P"XTXT.S., or 15X-5X60,000=450,000, and 
 the efficiency is 421,875X100-f-450,000=93!7 per cent. 
 
 Figure 37 shows another style of quadruple-riveted butt 
 joint. This joint is now used on nearly all high-grade 
 boilers of the horizontal return-tubular type, and it marks 
 about the practical limit of efficiency for riveted joints con- 
 necting plates of uniform thickness together. The methods 
 of failure to be considered are practically the same as in the 
 two preceding joints, except that there are more rivets 
 concerned in the calculations : 
 
 (1) Pulling apart of the sheets along net section A A. 
 
 (2) Pulling apart of the sheet along section D E F G 
 and shearing rivets A, B, C. 
 
 (3) Pulling apart of sheet along section D E F G and 
 crushing of rivets A, B, C in the strap. 
 
Boiler Construction 
 
 101 
 
 (4) Shearing rivets A, B, C in single shear and D, E, 
 F, G, H, I, J, K in double shear. 
 
 (5) Crushing of rivets D, E, F, G, H, I, J, K in plate 
 and A, B, C in the strap. 
 
 ©!© © © ©n 
 © ©_© © © ©jj 
 
 Fig. 37 
 quadruple riveted butt joint 
 
 (6) Crashing of rivets D, E, F, G, H, I, J, K in the 
 plate and shearing rivets A, B, C. 
 
 Using the numerical values previously given : 
 
 (1) (15.5— 1)X0.5625X55,000==448,580 pounds. 
 
102 Steam Engineering 
 
 (2) [ (15.5— 4)X0.5625X55,000] + (3X42,000X 
 0.7854) =454,739 pounds. 
 
 (3) [ (15.5— 4)X0.5625X55,000] + (3X0.4375X1 
 X 95,000) =480,465 pounds. 
 
 (4) (3X42,000X0.7854) +' (8X78,000X0.7854) = 
 589,050 pounds. 
 
 (5) (8X0.5625X1X95,000) + (3X0.4375X1X95,- 
 000) =552,187 pounds. 
 
 (6) (8X0.5625X1X95,000) + (3X42,000X0.7854) = 
 526,461 pounds. 
 
 The strength of the solid plate is 
 
 15.5X0.5625X55,000=479,528 
 pounds, and the failure of the sheet by pulling apart along 
 the net section A A is the one that determines the efficiency 
 of the joint, which is 
 
 =93.55 per cent. 
 
 479,528 
 
 Staying Flat Surfaces. The proper staying or bracing 
 of all flat surfaces in steam boilers is a highly important 
 problem, and while there are various methods of bracing 
 resorted to, still, as Dr. Peabody says, "the staying of a flat 
 surface consists essentially in holding it against pressure at 
 a series of isolated points which are arranged in regular or 
 symmetrical pattern." The cylindrical shell of a boiler 
 does not need bracing, for the very simple reason that the 
 internal pressure tends to keep it cylindrical. On the con- 
 trary, the internal pressure has a constant tendency to bulge 
 out the flat surface. Eule 2, Section >6, of the rules of the 
 U. S. Supervising Inspectors provides as follows: "No 
 braces or stays hereafter to be employed in the construction 
 
Boiler Construction 103 
 
 of boilers shall be allowed a greater strain than 6,000 
 pounds per square inch of section." 
 
 The method to be employed in staying a boiler depends 
 upon the type of boiler and the pressure to be carried. For- 
 merly when comparatively low pressures were used (60 to 
 75 pounds per square inch) the diagonal crow foot brace 
 was considered amply sufficient for staying the flat heads of 
 boilers of the cylindrical tubular type, both above and be- 
 low the tubes, but in the present age, when much higher 
 pressures are demanded, through stay rods are largely 
 employed. These are soft steel or iron rods 1*4 to 2 inches 
 in diameter, extending through from head to head, with a 
 
 Fig. 38 
 
 pull at right angles to the plate, thus having a great advan- 
 tage over the diagonal stay in that the pull on the diagonal 
 stay per square inch of section is more than 5 per cent in 
 excess of what a through stay would have to resist under 
 the same conditions of pressure. 
 
 The weakest portion of the crow foot brace when in 
 position is at the foot end, where it is connected to the 
 head by two rivets. With a correctly designed brace the 
 pull on these rivets is direct, and the tensile strength of the 
 material needs to be considered only, but if the form of the 
 brace is such as to bring the rivet holes above or below the 
 center line of the brace, or if the rivets are pitched too far 
 from the body of the brace, there will be a certain leverage 
 
104 
 
 Steam Engineering 
 
 exerted upon the rivets in addition to the direct pull. 
 Figure 38 shows a brace of incorrect design and Figs. 39 
 and 40 show braces designed along correct lines. 
 
 Fig. 39 
 
 Fig. 40 
 
 Other methods of staying, besides the crow foot brace and 
 through stays, consist of gusset stays, and for locomotives, 
 and other fire box boilers screwed stay bolts are employed 
 to tie the fire box to the external shell. The holes for these 
 stay bolts are punched or drilled before the fire box is put 
 in place. After it is in and riveted along the lower edge to 
 the foundation ring, or mud ring as it is sometimes called, 
 a continuous thread is tapped in the holes in both the out- 
 side plate and the fire sheet by running a long tap through 
 both plates. The steel stay bolt, is then screwed through 
 the plates and allowed to project enough at each end to 
 permit of its being riveted cold. Stay bolts are liable to 
 be broken by the unequal expansion of the fire box and 
 outer shell, and a small hole should be drilled in the center 
 of the bolt, from the outer end nearly through to the inner 
 end. Then in case a bolt breaks, steam or water will blow 
 out through the small hole, and the break will be discovered 
 
105 
 
 Fig. 41 
 
2U 
 
 Steam Engineering 
 
 at once. The problem of properly staying the flat crown 
 sheet of a horizontal fire box boiler, especially a locomotive 
 boiler, is a very difficult one and has taxed the inventive 
 genius of some of the most eminent engineers. 
 
 Before the invention of the Belpaire boiler, with its out- 
 side, or shell plate flat above the fire box, the only method 
 
 J.71W7J' 
 
 End Devotion, 
 knowing Attachment of Wong. Stays. 
 
 Fig. 42 
 
 •*— &¥"'* Half End Devotion 
 Half Section C-tX I of Smoke-Co*. 
 
 of staying the crown sheet was by the use of cumbersome 
 crown bars or double girders extending across the top of 
 the crown sheet, and supported at the ends by special cast- 
 ings that rest on the edges of the side sheets and on the 
 flange of the crown sheet. At intervals of 4 or 5 inches 
 crown bolts are placed, having the head inside the fire box 
 and the nut bearing on a plate on top of the girder. There 
 
Boiler Construction 107 
 
 is also a thimble for each bolt to pass through, between the 
 top of the crown sheet and the girder. These thimbles 
 maintain the proper distance between the crown sheet and 
 girder and allow the water to circulate freely. 
 
 The Belpaire fire box dispenses with girders, and permits 
 the use of through stays from the top of the flat outside 
 plate, through the crown sheet and secured at each end by 
 nuts, and copper washers. 
 
 For simplicity of construction and great strength the 
 cylindrical form of fire box known as the Morison corru- 
 gated furnace has proved to be very successful. This form 
 of fire box was in 1899 applied to a locomotive by Mr. 
 Cornelius Vanderbilt, at the time assistant superintendent 
 of motive power of the New York Central & Hudson Eiver 
 E. E. This furnace was rolled of %-inch steel, is 59 inches 
 internal diameter and 11 feet 2 1 / 4: inches in length. It 
 was tested under an external pressure of 500 pounds per 
 square inch before being placed in the boiler. It is carried 
 at the front end by a row of radial sling stays from the out- 
 side plate, and supported at the rear by the back head. 
 Figures 41 and 42 show respectively a sectional view, and 
 an end elevation of this boiler. It will be seen at once that 
 the question of stays for a fire box of this type becomes 
 very simple. The boiler has proved to be so satisfactory 
 that the company has since had many more of the same type 
 constructed. 
 
 Gusset stays are used mainly in boilers of the Lancashire 
 model, and are triangular-shaped plates sheared to the 
 proper form and having two angle irons riveted to the 
 edges that comes against the shell, and the head. The angle 
 irons are then riveted to the shell and the flat head. This 
 form of brace is simple and solid, but its chief defect is, 
 
108 
 
 Steam Engineering 
 
 that it is very rigid, and does not allow for the unequal ex- 
 pansion of the internal furnace flues and the shell. Fig. 43 
 illustrates a gusset stay and the method of applying it. 
 
 Fig. 43 
 
 Coming now to through stay rods, it is safe to say that 
 whenever, and wherever it is possible to apply them they 
 should be used. In all cases they should be placed far 
 enough apart to allow a man to pass between them for the 
 purposes of inspection and washing out of the boiler. 
 Through stay rods are usually spaced 14 inches apart hori- 
 zontally, and about the same distance vertically. The ends, 
 as far back as the threads run, are swaged larger than the 
 body, so that the diameter at the bottom of the thread is 
 greater than the diameter of the body. There are several 
 methods of applying through stays. One of the most com- 
 mon, especially for land boilers, is to allow the ends of the 
 rod to project through the plates to be stayed, and holding 
 them in place by a nut and copper washer, both inside and 
 outside the plate. Another and still better plan is to rivet 
 6-inch channel bars across the head, inside above the tubes, 
 the number of bars depending upon the height of the seg- 
 ment to be stayed. 
 
 The channel bars are drilled to correspond with the holes 
 that are drilled in the plate to receive the stay rods, which 
 latter are then secured by inside and outside nuts and cop- 
 
Boiler Construction 
 
 109 
 
 per washers. These channel bars act as girders, and serve 
 to greatly strengthen the head or flat plate. Fig. 44 will 
 serve to illustrate this method. 
 
 Fig. 44 
 
 Fig. 45 
 
 Sometimes a combination of channel bar and diagonal 
 crow foot braces is used, as shown by Fig. 45. 
 
110 Steam Engineering 
 
 A good form of diagonal crow foot stay is obtained by 
 using double crow feet, made of pieces of boiler plate bent 
 as shown by Fig. 46 and riveted to the plate by four rivets. 
 
 Fig. 46 
 
 A hole is drilled through the body of the crow foot, and 
 a bolt passing through this secures the forked end of the 
 stay. 
 
 Fig. 47 
 
 Another method of securing through stays to the heads 
 is shown by Fig. 47 and is applied where too many stay 
 rods would be required to connect all the points to be 
 
Boiler Construction 111 
 
 stayed. A tie iron is first riveted to the flat plate to be 
 stayed, and two V-shaped forgings are bolted to it as 
 shown. The through stay is then bolted to the forgings, 
 and thus two points in the flat head are supported by one 
 stay. It will readily be seen that this method will reduce 
 the number of through stay rods required. 
 
 Calculating the Strength of Stayed Surfaces. In calcu- 
 lations for ascertaining the strength of stayed surfaces, or 
 for finding the number of stays required for any given flat 
 surface in a boiler, the working pressure being known, it 
 must be remembered that each stay is subjected to the pres- 
 sure on an area bounded by lines drawn midway between 
 it and its neighbors. Therefore the area in square inches, 
 of the surface to be supported by each stay, equals the square 
 of the pitch or distance in inches between centers of the 
 points of connection of the stays to the flat plate. Thus, 
 suppose the stays in a certain boiler are spaced 8 inches 
 apart, the area sustained by each stay=8X8=64 square 
 inches, or assume the stay bolts in a locomotive fire box to 
 be pitched 4^£ inches each way, the area supported by each 
 stay bolt==4 1 / ^X4 1 /£=20 1 / 4 square inches. Again taking 
 through stay rods, suppose, for example, the through stays 
 shown in Fig. 44 to be spaced 15 inches horizontally and 
 14 inches vertically, the area supported by each stay=15 
 X 14=210 square inches. 
 
 The minimum factor of safety for stays, stay bolts and 
 braces is 8, and this factor should enter into all computa- 
 tions of the strength of stayed surfaces. 
 
 The pitch for stays depends upon the thickness of the 
 plate to be supported, and the maximum pressure to be 
 carried. 
 
112 Steam Engineering 
 
 In computing the total area of the stayed surface it is 
 safe to assume that the flange of the plate, where it is 
 riveted to the shell, sufficiently strengthens the plate for a 
 distance of 2 inches from the shell, also that the tubes act 
 as stays for a space of 2 inches above the top row. There- 
 fore the area of that portion of the flat head or plate 
 bounded by an imaginary line drawn at a distance of 2 
 inches from the shell and the same distance from the last 
 row of tubes is the area to be stayed. This surface may be 
 in the form of a segment of a circle, as with a horizontal 
 cylindrical boiler, or it may be rectangular in shape, as in 
 the case of a locomotive, or other fire box boiler. Other 
 forms of stayed surfaces are often encountered, but in gen- 
 eral the rules applicable to segments or rectangular figures 
 will suffice for ascertaining the areas. 
 
 The method of finding the area of the segmental portion 
 of the head above the tubes is as follows, using Table 12. 
 The diameter of the circle and the rise or height of the 
 segment being known, the area of the segment may be found 
 by the following rule: 
 
 Rule. Divide the height of the segment by the diameter 
 of the circle. Then find the decimal opposite this ratio in 
 the column headed "Area." Multiply this area by the 
 square of the diameter. The result is the required area. 
 
 Example. Diameter of circle=72 inches. Height of 
 segment=25 inches. 25-i-72=. 347, which will be found 
 in the column headed "Eatio," and the area opposite this 
 is .24212. Then .24212X72X72=1,255 square inches, 
 area of segment. 
 
Boiler Construction 
 
 113 
 
 The following examples of calculating the number of 
 braces, and the spacing of the same will serve to make the 
 matter plain. 
 
 A boiler is 66 inches in diameter, the working pressure 
 is 100 pounds per square inch. The distance from the top 
 row of tubes to the shell is 25 inches. Bequired, the num- 
 
 Table 12 
 
 AREAS OF SEGMENTS OF A CIRCLE. 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 
 .2 
 
 .11182 
 
 .243 
 
 .14751 
 
 .286 
 
 .18542 
 
 .329 
 
 .22509 
 
 
 .201 
 
 .11262 
 
 .244 
 
 .14837 
 
 .287 
 
 .18633 
 
 .33 
 
 .22603 
 
 
 .202 
 
 .11343 
 
 .245 
 
 .14923 
 
 .288 
 
 .18723 
 
 .331 
 
 .22697 
 
 
 .203 
 
 .11423 
 
 .246 
 
 .15009 
 
 .289 
 
 .18814 
 
 .332 
 
 .22792 
 
 
 .204 
 
 .11504 
 
 .247 
 
 .15095 
 
 .29 
 
 .18905 
 
 .333 
 
 .22886 
 
 
 .205 
 
 .11584 
 
 .248 
 
 .15182 
 
 .291 
 
 .18996 
 
 .334 
 
 .22980 
 
 
 .206 
 
 .11665 
 
 .249 
 
 .15268 
 
 .292 
 
 .19086 
 
 .335 
 
 .23074 
 
 
 .207 
 
 .11746 
 
 .25 
 
 .15355 
 
 .293 
 
 .19177 
 
 .336 
 
 .23169 
 
 
 .208 
 
 .11827 
 
 .251 
 
 .15441 
 
 .294 
 
 .19268 
 
 .337 
 
 .23263 
 
 
 .209 
 
 .11908 
 
 .252 
 
 .15528 
 
 .295 
 
 .19360 
 
 .338 
 
 .23358 
 
 
 .21 
 
 .11990 
 
 .253 
 
 .15615 
 
 .296 
 
 .19451 
 
 .339 
 
 .23453 
 
 
 .211 
 
 .12071 
 
 .254 
 
 .15702 
 
 .297 
 
 .19542 
 
 .34 
 
 .23547 
 
 
 .212 
 
 .12153 
 
 .255 
 
 .15789 
 
 .298 
 
 .19634 
 
 .341 
 
 .23642 
 
 
 .213 
 
 .12235 
 
 .256 
 
 .15876 
 
 .299 
 
 .19725 
 
 .342 
 
 .23737 
 
 
 .214 
 
 .12317 
 
 .257 
 
 .15964 
 
 .3 
 
 .19817 
 
 .343 
 
 .23832 
 
 
 .215 
 
 .12399 
 
 .258 
 
 .16051 
 
 .301 
 
 .19908 
 
 .344 
 
 .23927 
 
 
 .216 
 
 .12481 
 
 .259 
 
 .16139 
 
 .302 
 
 .20000 
 
 .345 
 
 .24022 
 
 
 .217 
 
 .12563 
 
 .26 
 
 .16226 
 
 .303 
 
 .20092 
 
 .346 
 
 .24117 
 
 
 .218 
 
 .12646 
 
 .261 
 
 .16314 
 
 .304 
 
 .20184 
 
 .347 
 
 .24212 
 
 
 .219 
 
 .12729 
 
 .262 
 
 .16402 
 
 .305 
 
 .20276 
 
 .348 
 
 .24307 
 
 
 .22 
 
 .12811 
 
 .263 
 
 .16490 
 
 .306 
 
 .20368 
 
 .349 
 
 .24403 
 
 
 .221 
 
 .12894 
 
 .264 
 
 .16578 
 
 .307 
 
 .20460 
 
 .35 
 
 .24498 
 
 
 .222 
 
 .12977 
 
 .265 
 
 .16666 
 
 .308 
 
 .20553 
 
 .351 
 
 .24593 
 
 
 .223 
 
 .13060 
 
 .266 
 
 .16755 
 
 .309 
 
 .20645 
 
 .352 
 
 .24689 
 
 
 .224 
 
 .13144 
 
 .267 
 
 .16843 
 
 .31 
 
 .20738 
 
 .353 
 
 .24784 
 
 
 .225 
 
 .13227 
 
 .268 
 
 .16932 
 
 .311 
 
 .20830 
 
 .354 
 
 .24880 
 
 
 .226 
 
 .13311 
 
 .269 
 
 .17020 
 
 .312 
 
 .20923 
 
 .355 
 
 .24976 
 
 
 .227 
 
 .13395 
 
 .27 
 
 .17109 
 
 .313 
 
 .21015 
 
 .356 
 
 .25071 
 
 
 .228 
 
 .13478 
 
 .271 
 
 .17198 
 
 .314 
 
 .21108 
 
 .357 
 
 .25167 
 
 
 .229 
 
 .13562 
 
 .272 
 
 .17287 
 
 .315 
 
 .21201 
 
 .358 
 
 .25263 
 
 
 .23 
 
 .13646 
 
 .273 
 
 .17376 
 
 .316 
 
 .21294 
 
 .359 
 
 .25359 
 
 
 .231 
 
 .13731 
 
 .274 
 
 .17465 
 
 .317 
 
 .21387 
 
 .36 
 
 .25455 
 
 
 .232 
 
 .13815 
 
 .275 
 
 .17554 
 
 .318 
 
 .21480 
 
 .361 
 
 .25551 
 
 
 .233 
 
 .13900 
 
 .276 
 
 .17644 
 
 .319 
 
 .21573 
 
 .362 
 
 .25647 
 
 
 .234 
 
 .13984 
 
 .277 
 
 .17733 
 
 .32 
 
 .21667 
 
 .363 
 
 .25743 
 
 
 .235 
 
 .14069 
 
 .278 
 
 .17823 
 
 .321 
 
 .21760 
 
 .364 
 
 .25839 
 
 
 .236 
 
 .14154 
 
 .279 
 
 .17912 
 
 .322 
 
 .21853 
 
 .365 
 
 .25936 
 
 
 .237 
 
 .14239 
 
 .280 
 
 .18002 
 
 .323 
 
 .21947 
 
 .366 
 
 .26032 
 
 
 .238 
 
 .14324 
 
 .281 
 
 .18092 
 
 .324 
 
 .22040 
 
 .367 
 
 .26128 
 
 
 .239 
 
 .14409 
 
 .282 
 
 .18182 
 
 .325 
 
 .22134 
 
 .368 
 
 .26225 
 
 
 .24 
 
 .14494 
 
 .283 
 
 .18272 
 
 .326 
 
 .22228 
 
 .369 
 
 .26321 
 
 
 .241 
 
 .14580 
 
 .284 
 
 .18362 
 
 .327 
 
 .22322 
 
 .37 
 
 .26418 
 
 
 .242 
 
 .14666 
 
 .285 
 
 .18452 
 
 .328 
 
 .22415 
 
 .371 
 
 .26514 
 
 
 ^ 
 
114 
 
 Steam Engineering 
 Table 12 — continued. 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 .372 
 
 .26611 
 
 .405 
 
 .29827 
 
 .438 
 
 .33086 
 
 .471 
 
 .36373 
 
 .373 
 
 .26708 
 
 .406 
 
 .29926 
 
 .439 
 
 .33185 
 
 .472 
 
 .36471 
 
 .374 
 
 .26805 
 
 .407 
 
 .30024 
 
 .44 
 
 .33284 
 
 .473 
 
 .36571 
 
 .375 
 
 .26901 
 
 .408 
 
 .303 22 
 
 .441 
 
 .33384 
 
 .474 
 
 .36671 
 
 .376 
 
 .26998 
 
 .409 
 
 .30220 
 
 .442 
 
 .33483 
 
 .475 
 
 .36771 
 
 .377 
 
 .27095 
 
 .41 
 
 .30319 
 
 .443 
 
 .33582 
 
 .476 
 
 .36871 
 
 .378 
 
 .27192 
 
 .411 
 
 .30417 
 
 .444 
 
 .33682 
 
 .477 
 
 .36971 
 
 .379 
 
 .27289 
 
 .412 
 
 .30516 
 
 .445 
 
 .33781 
 
 .478 
 
 .37071 
 
 .38 
 
 .27386 
 
 .413 
 
 .30614 
 
 .446 
 
 .33880 
 
 .479 
 
 .37171 
 
 .381 
 
 .27483 
 
 .414 
 
 .30712 
 
 .447 
 
 .33980 
 
 .48 
 
 .37270 
 
 .382 
 
 .27580 
 
 .415 
 
 .30811 
 
 .448 
 
 .34079 
 
 .481 
 
 .37370 
 
 .383 
 
 .27678 
 
 .416 
 
 .30910 
 
 .449 
 
 .34179 
 
 .482 
 
 .37470 
 
 .384 
 
 .27775 
 
 .417 
 
 .31008 
 
 .45 
 
 .34278 
 
 .483 
 
 .37570 
 
 .385 
 
 .27872 
 
 .418 
 
 .31107 
 
 .451 
 
 .34378 
 
 .484 
 
 .37670 
 
 .386 
 
 .27969 
 
 .419 
 
 .31205 
 
 .452 
 
 .34477 
 
 .485 
 
 .37770 
 
 .387 
 
 .28067 
 
 [ .42 
 
 .31304 
 
 .453 
 
 .34577 
 
 .486 
 
 .37870 
 
 .388 
 
 .28164 
 
 .421 
 
 .31403 
 
 .454 
 
 .34676 
 
 .487 
 
 .37970 
 
 .389 
 
 .28262 
 
 .422 
 
 .31502 
 
 .455 
 
 .34776 
 
 .488 
 
 .38070 
 
 .39 
 
 .28359 
 
 .4^3 
 
 .31600 
 
 .456 
 
 .34876 
 
 .489 
 
 .38170 
 
 .391 
 
 .28457 
 
 .424 
 
 .31699 
 
 .457 
 
 .34975 
 
 .49 
 
 .38270 
 
 .392 
 
 .28554 
 
 .425 
 
 .31798 
 
 .458 
 
 .35075 
 
 .491 
 
 .38370 
 
 .393 
 
 .28652 
 
 .426 
 
 .31897 
 
 .459 
 
 .35175 
 
 .492 
 
 .38470 
 
 .394 
 
 .28750 
 
 .427 
 
 .31996 
 
 .46 
 
 .35274 
 
 .493 
 
 .38570 
 
 .395 
 
 .28848 
 
 .428 
 
 .32095 
 
 .461 
 
 .35374 
 
 .494 
 
 .38670 
 
 .396 
 
 .28945 
 
 .429 
 
 .32194 
 
 .462 
 
 .35474 
 
 .495 
 
 .38770 
 
 .397 
 
 .29043 
 
 .43 
 
 .32293 
 
 .463 
 
 .35573 
 
 .496 
 
 .38870 
 
 .398 
 
 .29141 
 
 .431 
 
 .32392 
 
 .464 
 
 .35673 
 
 .497 
 
 .38970 
 
 .399 
 
 .29239 
 
 .432 
 
 .32941 
 
 .465 
 
 .35773 
 
 .498 
 
 .39070 
 
 .4 
 
 .29337 
 
 .433 
 
 .32590 
 
 .466 
 
 .35873 
 
 .499 
 
 .39170 
 
 .401 
 
 .29^35 
 
 .434 
 
 .32689 
 
 .467 
 
 .35972 
 
 .5 
 
 .39270 
 
 .402 
 
 .29533 
 
 .435 
 
 .32788 
 
 .468 
 
 .36072 
 
 
 
 .403 
 
 .29631 
 
 .436 
 
 .32887 
 
 .469 
 
 .36172 
 
 
 
 .404 
 
 .29729 
 
 .437 
 
 .32987 
 
 .47. 
 
 .36272 
 
 
 
 ber of diagonal crow foot braces that will be needed to sup- 
 port the heads above the tubes, also the sectional area of 
 each brace. The thickness of the head is % inch and 
 the T.S. =55,000 pounds per square inch. 
 
 Assume the head to be sufficiently strengthened by the 
 flange for a distance of 2 inches from the shell, the diameter 
 of the circle of which the segment above the tubes requires 
 to be stayed is reduced by 2+2=4 inches and will there- 
 fore be 66 — 4=62 inches. The rise or height of the seg- 
 ment above the tubes is 25 — 4=21 inches. Eequired, the 
 area. 21-^62=. 338. Looking down the column headed 
 "Ratio" in Table 12, area opposite .338 is .23358. Area of 
 
Boiler Construction 115 
 
 segment=.23358X62X62=897.88 square inches. The 
 total pressure on this area will be 897.88X100=89,788 
 pounds. 
 
 Assume the braces to be made of 1% inch round steel, 
 having a T.S. of 50,000 pounds per square inch and to be 
 designed in such a manner as to allow for loss of material 
 in drilling the rivet holes in the crow feet. Each brace will 
 have a sectional area of .994 square inches, and using 8 as 
 a factor of safety, the strength or safe holding power of each 
 stay may be found as follows: .994X50,000-^-8=6,212 
 pounds, and the number of stays required=89,788 pounds 
 (total pressure) divided by 6,212 pounds (strength of each 
 stay) =14.5, or in round numbers 15. If the stays are 
 made of flat bars of steel the sectional area should equal 
 that of the round stays, and the dimensions of the crow feet 
 of all stays should be such as to retain the full sectional 
 area of the body after the rivet holes are drilled. 
 
 Each stay is connected to the plate by two %-inch rivets, 
 having a T.S. of 55,000 pounds per square inch and a 
 shearing strength of 45,000 pounds per square inch. These 
 rivets are capable of resisting a direct pull of 10,818 pounds, 
 using 5 as a factor of safety; ascertained as follows: 2 A 
 X45,000-^5=10,818=strength of two rivets. They are 
 also subjected to a crushing strain, and the resistance to 
 this is DxC-^-5, which expressed in figures is .875X90,000 
 -4-5=15,750 pounds. 
 
 The proper spacing comes next, and is arrived at in the 
 following manner: 
 
 Area to be stayed=897.88 square inches. 
 
 Number of stays=15. 
 
 Area supported by each stay=897. 88-4-15=59. 8 square 
 inches. 
 
116 Steam Engineering 
 
 The square root of 59.8=7.75 nearly, which is the dis- 
 tance in inches each way that the stays should be spaced, 
 center to center. 
 
 If through stay rods are used in place of diagonal braces 
 for staying the boiler under consideration, the number and 
 diameter of the rods may be ascertained by the following 
 method : 
 
 Assuming the heads to be supported by channel bars, as 
 previously described, and that the stays are pitched 14 
 inches apart horizontally and 13 inches vertically, each stay 
 would be required to support an area of 14X13=182 square 
 inches, and the number of stays would be 897.88-^-182= 
 4.9, in round numbers 5. See Fig. 44. The pressure being 
 100 pounds per square inch, the total stress on each stay= 
 182X100=18,200 pounds. Assume the stay rods to be of 
 soft steel having a T.S. of 50,000 pounds per square inch, 
 and using a factor of safety of 8, the sectional area re- 
 quired for each stay will be found as follows: 18,200X8-^- 
 50,000=2.9 square inches, and the diameter will be found 
 as follows: 2. 9^-. 7854=3. 69, which is the square of the 
 diameter, and the square root of 3.69=1.9 inches, or prac- 
 tically 2 inches. The same methods of calculation are ap- 
 plicable to the staying of the heads below the tubes, also 
 for stay bolts in fire box boilers. 
 
 Strength of Unstayed Surfaces, A simple rule for find- 
 ing the bursting pressure of unstayed flat surfaces is that 
 of Mr. Nichols, published in the "Locomotive," February, 
 1890, and quoted by Prof. Kent in his "Pocket-book." 
 The rule is as follows: "Multiply the thickness of the 
 plate in inches by ten times the tensile strength of the ma- 
 terial used, and divide the product by the area of the head 
 in square inches." Thus, 
 
Boiler Construction 117 
 
 Diameter of head=66 inches. 
 Thickness of head=% inch. 
 
 Tensile strengths 55,000 pounds. 
 Area of head= 3,421 square mches. 
 
 %X55,000X10-t-3,421=100, which is the number of 
 pounds pressure per square inch under which the unstayed 
 head would bulge. 
 
 If we use a factor of safety of 8, the safe working pres- 
 sure would be 100-^-8=12.5 pounds per square inch, but 
 as the strength of the unstayed head is at best an uncertain 
 quantity it has not been considered in the foregoing calcu- 
 lations for bracing, except as regards that portion of it that 
 is strengthened by the flange. 
 
 In all calculations for the strength of stayed surfaces, 
 and especially where diagonal crow foot stays are used, the 
 strength of the rivets connecting the stay to the flat plate 
 must be carefully considered. A large factor of safety, 
 never less than 8, should be used, and the cross section of 
 that portion of the foot of the stay through which the rivet 
 holes are drilled should be large enough, after deducting 
 the diameter of the hole, to equal the sectional area of the 
 body of the stay. 
 
 Dished Heads. In boiler work where it is possible to 
 use dished, or "bumped up" heads as they are sometimes 
 called, this type of head is rapidly coming into use. Dished 
 heads may be used in the construction of steam drums, also 
 in many cases for dome-covers, thus obviating the necessity 
 of bracing. The maximum depth of dish, as adopted by 
 steel plate manufacturers April 4, 1901, is % of the diam- 
 eter of the head when flanged, and if the tensile strength 
 and quality of the plate from which the heads are made 
 are the same as those of the shell plate, the dished head 
 
118 Steam Engineering 
 
 becomes as strong as the shell, provided the head has the 
 same thickness, or is slightly thicker than the shell plate. 
 
 Welded Seams. A few boiler manufacturers have suc- 
 ceeded in making welded seams, thus dispensing with the 
 time-honored custom of riveting the plates together. A 
 good welded joint approaches more nearly to the full 
 strength of the material than can possibly be attained by 
 rivets, no matter how correctly designed the riveted joint 
 may be. The weld also dispenses with the necessity of 
 caulking, and a boiler having a perfectly smooth surface 
 inside, such as would be afforded by welded seams, would 
 certainly be much less liable to collect scale and sediment 
 than would one with riveted joints. But in order to make 
 a success of welded seams the material used must be of the 
 best possible quality, and great care and skill are required 
 in the work. 
 
 The Continental Iron Works of Brooklyn, New York, 
 exhibited at the St. Louis World's Fair in 1904, a welded 
 steel plate soda pulp digester without a single riveted joint. 
 The dimensions of this vessel, which may be likened to a 
 cylinder boiler without flues, were as follows: Thickness 
 of plate, % inch; diameter, 9 feet; length, 43 feet. The 
 heads were dished to the standard depth. The safe work- 
 ing pressure was 125 pounds per square inch. It appears 
 not only possible, but probable, that the process of welding 
 boiler joints may in time supplant the older custom of 
 riveting. 
 
 QUESTIONS AND ANSWERS. 
 
 79. What three principles should govern the design 
 and construction of steam boilers ? 
 
 Ans. First: They should be absolutely safe. Second: 
 
Boiler Construction 119 
 
 They should be economical in the consumption of fuel. 
 Third: They should be capable of furnishing dry steam. 
 
 80. What is meant by the term tensile strength as ap- 
 plied to boiler material ? 
 
 Ans. The number of pounds of pull that would be 
 required to break a bar of the material in the direction of 
 its length. 
 
 81. What is liable to occur in case the tensile strength 
 is too high ? 
 
 Ans. Cracking of the sheets, also certain changes in the 
 physical properties of the metal. 
 
 82. Which are the stronger, punched or drilled plates? 
 Ans. If the material is good soft steel, punched plates 
 
 show a greater shearing resistance. 
 
 83. What should be the tensile strength of rivet iron? 
 Ans. About 60,000 pounds per square inch. 
 
 84. What is a good test for a %-inch rivet? 
 
 Ans. It should stand being doubled up and hammered 
 together cold without being fractured. 
 
 85. What is the shearing resistance of iron rivets ? 
 Ans. About 85 per cent of the original bar. 
 
 86. What is the shearing resistance of steel rivets ? 
 Ans. 77 per cent of the original bar. 
 
 87. What is meant by efficiency of the joint? 
 
 Ans. The percentage of strength of the solid plate, that 
 is retained in the joint. 
 
 88. What should be the style of joint with sheets thicker 
 than y 2 inch? 
 
 Ans. It should be a double butt joint. 
 
 89. What should be the ratio of diameter of rivet to 
 thickness of plate for double butt joints? 
 
120 Steam Engineering 
 
 Ans. The diameter of the rivet should be about 1.8 
 times the thickness of sheet. 
 
 90. What should be the pitch of rivets? 
 
 Ans. Three and one-half to four times the diameter of 
 the hole. 
 
 91. Describe the triple riveted butt joint. 
 
 Ans. It has two welts or straps, one inside, and one 
 outside. 
 
 92. Is this a good form of joint? 
 Ans. It is. 
 
 93. What type of joint gives the highest efficiency? 
 Ans. A joint in which the tensile strength of the rods 
 
 from which the rivets are cut approaches that of the plates, 
 and when the proportions of the joint are such, that the 
 tensile strength of the rivets, and the crushing resistance 
 of the rivets and plate, for a given, or unit strip, are as 
 nearly equal as it is possible to make them. 
 
 94. In how many ways may failure occur in a double 
 riveted butt joint? 
 
 Ans. In five distinct ways. 
 
 95. Name the first manner of failure. 
 
 Ans. Tearing of the plate at outer row of rivets. 
 
 96. What is the second? 
 
 Ans. Shearing two rivets in double shear, and one in 
 single shear. 
 
 97. What is the third manner of failure? 
 
 Ans. Tearing of the plate at inner row of rivets, and 
 shearing one rivet in the outer row. 
 
 98. Describe the fourth method of failure. 
 Ans. Crushing in front of three rivets. 
 
 99. What is the fifth manner of failure? 
 
 Ans. Crushing in front of two rivets, and shearing one. 
 
Questions and Answers 121 
 
 100. How may a triple riveted butt joint fail? 
 
 Ans. First : By tearing the plate at the outer row of 
 rivets. Second: By shearing four rivets in double shear, 
 and one in single shear. Third : Eupture of the plate at 
 the middle row of rivets, and shearing one rivet. Fourth : 
 Crushing in front of four rivets, and shearing one rivet. 
 
 101. What is the efficiency of the quadruple riveted 
 butt joint? 
 
 Ans. In some cases as high as 94 per cent. 
 
 102. In what four ways may failure occur in this type 
 of joint? 
 
 Ans. First: By tearing the plate at the outer row of 
 rivets. Second: By shearing eight rivets in double shear, 
 and three in single shear. Third : By tearing at inner row 
 of rivets, and shearing three rivets. Fourth : By tearing at 
 first outer row of rivets where the pitch is 7^2 inches. 
 
 103. What is implied in the staying of a flat surface? 
 Ans. Holding it against pressure at a series of isolated 
 
 points, which are arranged in symmetrical order. 
 
 104. Does the cylindrical shell of a boiler need bracing? 
 Ans. No. 
 
 105. Why is this? ' 
 
 Ans. Because the internal pressure tends to keep it 
 cylindrical. 
 
 106. How are the heads sometimes stayed? 
 
 Ans. By through stay rods of soft steel, or iron l 1 /^ or 
 2 inches in diameter extending through from head to head. 
 
 107. What advantage has this form of stays? 
 Ans. The pull is at right angles to the plate. 
 
 108. What other methods of bracing the heads of high 
 pressure boilers are used? 
 
 Ans. Gusset stays, and dished heads. 
 
122 Steam Engineering 
 
 109. What is the minimum factor of safety for stays, 
 and braces? 
 
 Ans. Eight. 
 
 110. Give a simple rule for finding the bursting pres- 
 sure of unstayed flat surfaces. 
 
 Ans. Multiply the thickness of the plate in inches by 
 ten times the tensile strength and divide the product by 
 the area of the surface in square inches. 
 
 h 
 
Boiler Setting and Equipment 
 
 Setting. In the following remarks concerning boiler 
 setting, reference is had chiefly to the horizontal tubular 
 boiler. Owing to the many and varied styles of water-tube 
 boilers no prescribed set of rules is applicable, each builder 
 of this type of boiler having a set plan of his own for the 
 brick work, and these plans have already been illustrated 
 and described in the section on water-tube boilers. In the 
 case of internally fired boilers the matter of setting re- 
 solves itself into the simple point of securing a sufficiently 
 solid foundation, either of stone or brick laid in cement, 
 for the boiler to rest upon. 
 
 In the case of the horizontal tubular boiler, there are 
 two methods of support, one by suspension from I-beams 
 and girders, which has already been fully described; the 
 other by supporting the boiler upon brackets riveted to the 
 side sheets, and resting upon the side walls, and in such 
 settings particular attention should be paid to securing a 
 good foundation for the walls and great care exercised in 
 building them in such manner that the expansion of the 
 inner wall or lining will not seriously affect the outer walls. 
 This can be done by leaving an air space of two inches in 
 the rear and side walls, beginning at or near the level of 
 the grate bars and extending as high as the fire line, or 
 about the center line of the boiler. Above this height the 
 wall should be solid. Fig. 48 shows a plan and an end ele- 
 vation illustrating this idea. The ends of some of the 
 bricks should be allowed to project at intervals from th( 
 
 123 
 
124 
 
 Steam Engineering 
 
 outer walls across the air space, so as to come in touch with 
 the inner walls. 
 
 Where boilers are set in batteries of two or more, the 
 middle or party walls should be built up solid from the 
 foundation. All parts of the walls with which the fire 
 comes in contact should be lined with fire brick, every 
 fifth course being a header to tie the lining to the main 
 wall. 
 
 U 
 
 Fig. 48 
 
 Bridge walls should be built straight across from wall 
 to wall of the setting, and should not be curved to conform 
 to the circle of the boiler shell. The proper distance from 
 the top of the bridge wall to the bottom of the boiler varies 
 from eight to ten inches, depending upon the size of the 
 boiler. The space back of the bridge wall, called the com- 
 bustion chamber, can be filled in with earth or sand, and 
 should slope gradually downward from the back of the 
 bridge wall to the floor level at the rear wall, and should 
 be paved with hard burned brick. The ashes and soot can 
 then be easily cleaned out by means of a long-handled hoe 
 or scraper inserted through the cleaning out door, which 
 should always be placed in the back wall of every boiler set- 
 ting. 
 
 Back Arches. A good and durable arch can be made 
 for the back connection, extending from the back wall to 
 
Boiler Setting and Equipment 
 
 125 
 
 the boiler head, by taking flat bars of iron % x 4 inches, 
 cutting them to the proper length and bending them in 
 the shape of an arch, turning 4 inches of each end back 
 
 ■4* 
 
 y. 
 
 L<? 
 
 Fig. 49 
 
 
 Fig. 50 
 
 at right angles, as shown in Fig. 49. The distance O-B 
 should equal that from the rear wall to the boiler head, 
 and the height, O-A, should be about equal to O-B, and 
 should bring the point A about two inches above the top 
 
126 
 
 Steam Engineering 
 
 row of tubes. The clamp thus formed is filled with a 
 course of side arch fire brick, Fig. 50, and will form a 
 complete and self-sustaining arch, the bottom, B, resting 
 on the back wall, and the top, A, supported by an angle 
 iron riveted across the boiler head about three inches above 
 the top row of tubes. See Figs. 51 and 52. 
 
 Enough of these arches should be made so that when 
 laid side by side they will cover the distance from one side 
 
 Fig. 51 
 
 wall to the other across the rear end of the boiler. A fifty- 
 four-inch boiler would thus require six clamps, a sixty- 
 inch boiler seven clamps, and a seventy-two-inch boiler 
 would require eight clamps ; the length of a fire brick being 
 about nine inches. In case of needed repairs to the back' 
 end of the boiler the sections can be lifted off, thus giving 
 free access to all parts, and when the repairs are completed 
 the arches can be reset with very little trouble and much 
 less expense than the building of a solid arch would neces- 
 
Boiler Setting and Equipment 127 
 
 sitate. This form of segmental arch allows ample freedom 
 for expansion of the boiler, in the direction of its length, 
 without leaving an opening when the boiler contracts. 
 
 The crosswise construction of arch bars, while affording 
 equal facility in repair work, is necessarily more expensive 
 than the form here described, and is also open to the objec- 
 tion that it cannot follow the contracting boiler and main- 
 tain a tight joint or connection between the back arch and 
 the rear head above the tubes. 
 
 Boiler walls should always be well secured in both direc- 
 tions by tie rods extending throughout the entire length 
 and breadth of the setting, whether there be one boiler or a 
 battery of several. The bottom rods should be laid in place 
 at the floor level when starting the brick work, and the top 
 rods extending transversely across the boilers can be laid 
 on top of the boilers. The top rods extending from front 
 to back can be laid in the side walls, or rest on top of them. 
 All tie rods should be at least one inch in diameter, and 
 for batteries of several boilers they should be larger. The 
 rods should extend three or four inches beyond the brick 
 work, with good threads and nuts on each end to receive 
 the buck stays. In laying down the transverse tie rods 
 they should be located so as to allow the buck stays to bind 
 the brick work where the greatest concentration of heat 
 occurs. 
 
 Horizontal boilers should always be set at least one inch 
 lower at the back end than at the front, to make sure that 
 the rear ends of the tubes will be covered with water so long 
 as any appears in the gauge glass, provided of course that 
 the lower end of the glass is properly located with reference 
 to the top row of tubes, which will be discussed later on. 
 Upon the brick work and immediately under each lug of 
 
 ^ 
 
128 Steam Engineering 
 
 the boiler there should be laid in mortar a wrought or cast 
 iron plate several inches larger in dimension than the bear- 
 ing surface of the lug and not less than one inch in thick- 
 ness. Upon each of these plates there should be placed 
 two rollers made of round iron 1 or 1% in. in diameter, 
 and as long as the width of the lug. These rollers should 
 be placed at right angles to the length of the boiler, in 
 such a position that the lug will bear equally upon them. 
 The object af the rollers is to prevent disturbance of the 
 brick work by the endwise expansion and contraction of 
 the boiler. 
 
 It will be found very convenient when making tests to 
 have an opening into the combustion chamber back of the 
 bridge-wall, also in the back wall opposite the tubes, to in- 
 sert a pyrometer, or to connect a draft gage or gas sampler. 
 This can be accomplished by inserting a 1 14-inch pipe in 
 the wall flush with each side, and screwing a cap on the 
 outside. The inner end can be packed with asbestos fiber. 
 A %-inch hole drilled in the delivery pipe between the 
 valve and the nozzle will save drilling one by hand when 
 it is desired to insert a calorimeter. 
 
 Grate Surface. The number of square feet of grate sur- 
 face required depends upon the size of the boiler. A good 
 rule and one easy to remember is to make the length of the 
 grates equal to the diameter of the boiler. The width, of 
 course, will depend upon the construction of the furnace. 
 If the fire brick lining is built perpendicular, the width of 
 grate will be about equal to the diameter of the boiler. 
 On the other hand, if the lining is given a batter of three 
 inches, starting at the level of the grate, then the width 
 will be reduced six inches. It is customary to allow one 
 square foot of grate surface to every 36 sq. ft. of heating 
 
Boiler Setting and Equipment 129 
 
 surface. The distance of the grate-bars from the shell of 
 the boiler varies from 24 to 28 in., according to the dimen- 
 sions of the boiler. 
 
 Insulation All boilers should be well protected from 
 the cooling influence of outside air, if economy of fuel is 
 any object. The tops of horizontal boilers should be 
 covered with some kind of heat insulating material, or 
 arched over with common brick, leaving a space of two 
 inches, starting at the level of the grate, then the width 
 saving in fuel will far more than compensate for the extra 
 expense in a very short time. All cracks in the side and 
 rear walls should be carefully pointed up with mortar or 
 fire clay. One source of heat loss in return flue boilers is 
 short circuiting from the furnace to the breeching, caused 
 by the arches over the fire doors becoming loose and shaky, 
 and allowing considerable of the heat to escape directly to 
 the stack instead of passing under the boiler and through 
 the tubes. Another bad air leak often occurs at the back 
 connection when the arch rests wholly upon iron bars im- 
 bedded in the side walls. This leak, as has already been 
 noted, is caused by the expansion of the boiler, which 
 gradually pushes the arch away from the back head until, 
 in the course of time, there will be a space of % inch and 
 sometimes % inch between the head and the arch. The 
 obvious remedy for this is an arch that will go, and come 
 with the movement of the boiler, and such an arch can be 
 secured by building it in sections, as illustrated by Fig. 52, 
 and then riveting a piece of angle iron to the boiler head, 
 above the top row of tubes for the upper ends of the sec- 
 tions to rest upon, as already described. It will be seen 
 that within all possible range of boiler movement in either 
 direction the arch will, with this construction, always re- 
 main close to the head. 
 
130 
 
 Steam Engineering 
 
 Water Columns. Water columns should be so located 
 as to bring the lower end of the gauge glass exactly on a 
 level with the top of the upper row of tubes, thus always 
 affording a perfect guide as to the depth of water over the 
 tubes. Many gauge glasses are placed too low, and water 
 tenders and firemen are often deceived by them, unless their 
 positions with relation to the tubes are carefully noted. 
 
 Fig. 52 
 
 The only safe plan for an engineer to pursue in taking 
 charge of a steam plant is to seize the first opportunity for 
 noting this relation. When he has washed out his boilers 
 he may leave the top man-hole plates out while refilling 
 them, and when the water stands at about four inches over 
 the top row of tubes, the depth of water in the glass should 
 be measured. He should do this with every boiler in the 
 plant, and make a memorandum for each boiler. He will 
 
Boiler Setting and Equipment 131 
 
 then know his bearings with regard to the safe height of 
 water to be carried in the several gauge glasses. If he finds 
 any of them are too low, he should lose no time in having 
 them altered to conform to the requirements of safety. 
 The position of the lower gauge cock should be three 
 inches above the top row of tubes. 
 
 In making connections for the water column plugged 
 crosses should always be used in place of ells. Brass plugs 
 are to be preferred if they can be obtained ; but whether of 
 brass or iron, they should always be well coated with a paste 
 made of graphite and cylinder oil before they are screwed 
 in. They can then be easily removed when washing out the 
 boiler, so as to allow the scale, which is sure to form in the 
 lower connection, to be cleaned out. The best point at 
 which to connect the lower pipe with the boiler is in the 
 lower part of the head just below the bottom row of tubes, 
 and near the side of the boiler on which the water column 
 is to stand; l 1 /^ or iy 2 in. pipe should be used in all cases. 
 The top connection can be made either in the head near 
 the top, or in the shell. A % or 1 in. drain pipe should be 
 led into. the ash pit, fitted with a good reliable valve which 
 should be opened at frequent intervals to allow the mud 
 and dirt to blow out of the water column and its connec- 
 tions. This is a very important point, and great care should 
 be taken to keep the water column and all its connections 
 thoroughly clean at all times. 
 
 One of the best indications that some portion of the 
 connections between the water glass and the boiler is choked 
 or plugged with scale, is when there is no perceptible move- 
 ment of the water in the glass. When the connections are 
 free and the boiler is being fired, there is always a slight 
 movement of the water up and down in the glass, and when 
 
 . 
 
132 Steam Engineering 
 
 there is no perceptible movement it is time to look for the 
 cause at once. Many instances of burned tubes have oc- 
 curred, and even explosions caused by low water in boilers 
 while the gauge glass showed the water to be at a safe 
 height. But owing to the connections having become 
 plugged with scale, the water in the glass had no connec- 
 tion whatever with that in the boiler, and the water column 
 was therefore worse than useless. 
 
 The above remarks apply particularly to horizontal re- 
 turn tubular boilers. In the case of water tube boilers the 
 location of the gauge glass as regards height is governed 
 by the desired level of the water in steam drum, or drums. 
 
 Steam Gauges. As water columns are made at present 
 the steam gauge is usually connected at the top of the col- 
 umn. This makes a handsome and convenient connection, 
 although theoretically the proper method would be to con- 
 nect the steam gauge directly with the dome, or the steam 
 space of the shell. There should always be a trap or siphon 
 in the gauge pipe in order to retain the water of condensa- 
 tion, so as to prevent the hot steam from coming in con- 
 tact with the spring. 
 
 If at any time the water is drained from the siphon, care 
 should be exercised in turning on the steam again by al- 
 lowing it to flow in very slowly at first until the siphon is 
 again filled with water. 
 
 There are different types of steam gauges in use, but the 
 one most commonly used, and which no doubt is the most 
 reliable, is known as the Bourdon spring gauge (see Fig. 
 53). This gauge consists of a thin, curved, flattened metal- 
 lic tube, closed at both ends and connected to the steam 
 space of the boiler by a small pipe, bent at some portion of 
 its length into a curve or circle that becomes filled with 
 
Boiler Setting and Equipment 133 
 
 water of condensation, and thus prevents the hot live steam 
 from coming directly in contact with the spring, while at 
 the time the full pressure of steam in the boiler acts upon 
 
 Fig. 53 
 
 AUXILIARY SPRING PRESSURE GAUGE, SECTIONAL VIEW 
 
 the spring, tending to straighten it. The end or ends of 
 the spring being free to move, and connected by suitable 
 geared rack and pinion with the pointer of the gau^re, this 
 
 ^ 
 
134 
 
 Steam Engineering 
 
 hand or pointer is caused to move across the dial, thus indi- 
 cating the pressure of steam per square inch in the boiler. 
 When there is no pressure in the boiler the hand should 
 point to 0. 
 
 Fig. 54 
 
 AUXILIARY SPRING PRESSURE GAUGE 
 
 Steam gauges should be tested frequently by comparing 
 them with a test gauge that has been tested against a col- 
 umn of mercury. 
 
 The steam gauge and the safety valve should be com- 
 pared frequently by raising the steam pressure high enough 
 to cause the valve to open at the point for which it is set 
 to blow. 
 
Boiler Setting and Equipment 
 
 135 
 
 Safety Valves. The modern pop valve is generally re- 
 liable, but, like everything else, if it is allowed to stand 
 idle too long it is likely to become rusty and stick. There- 
 fore it should be allowed to blow off at least once or twice 
 a week in order to keep it in good condition. 
 
 Most pop valves for stationary boilers are provided with 
 a short lever, and if at any time the valve does not pop 
 when the steam gauge shows the pressure to be high 
 enough, it can generally be started by a light blow on the 
 lever with a hammer. 
 
 The ratio of safety valve area to that of grate surface is, 
 for the old style lever and weight valve, 1 sq. in. of valve 
 area for each 2 sq. ft. of grate surface, and for pop valves 
 1 sq. in. of valve area for each 3 sq. ft. of grate surface. 
 
 Each boiler in a battery should have its own safety valve, 
 and, in fact, be entirely independent of its mates as regards 
 safety appliances. 
 
 One example of safety valve computation will be given. 
 Suppose the grate surface of a boiler is 5X6=30 sq. ft., 
 
136 Steam Engineering 
 
 what should be the diameter of the lever safety valve? 
 The required area of the valve is 30-=-2 = 15 sq. in. Then 
 15-=-. 7854=19, which is the square of the diameter of the 
 valve. Extracting the square root of 19 gives 4.35 in. 
 diameter of valve. In actual practice one 5 in. or two 3 in. 
 lever safety valves would be required. If a pop valve is 
 to be used the required area i* 30-i-3=10 sq. in. Then 
 10-=-. 7854=12. 73=square of diameter of valve. Extract 
 the square root of 12.73 and the result is 3.6 in.=diameter 
 of valve. In practice a 4-in. valve would be required. 
 
 Eegarding the pressure at which a spring-loaded, or pop 
 safety valve will blow off, it is first necessary to ascertain 
 by experiment the force required to compress the spring. 
 The pressure at which a spring will yield depends not only 
 upon the shape and size of the material of which it is made, 
 the diameter, number and pitch of the coils, all of which 
 are measurable and determinable, but upon the nature and 
 condition of the material itself. 
 
 For instance, a spring of brass* will compress with less 
 pressure than one of steel, similar in every other respect, 
 and there is such a wide difference in steels that there will 
 be a great deal of difference in the action of steel springs 
 according to the kind of metal, degree of temper, etc. 
 
 The following rule may be used in calculations of this 
 character : 
 
 RULE. 
 
 Multiply the compression in inches by the fourth power 
 of the thickness of the steel in sixteenths of an inch, and 
 ~by 22 for round or 30 for square steel. Product I. 
 
 Multiply the cube of the diameter of the spring, meas- 
 ured from center to center of the coil (as on the line d, in 
 Fig. 55) in inches, by the number of free coils in the 
 
Boiler Setting and Equipment 137 
 
 spring, and by the area of the valve in square inches. 
 Product II. 
 
 Divide Product I by Product II and the quotient will be 
 the pressure per square inch at which the valve will blow 
 off.' 
 
 With a dead weight or a lever-loaded valve the force re- 
 quired to lift it remains the same, no matter how high the 
 valve lifts. The weights weigh no more if they are raised 
 an inch or two, and the leverage does not change, but with 
 the spring-loaded valve, the more the valve lifts the more 
 the spring is compressed, and the more force is required 
 to compress or hold it. It follows then that if an ordinary 
 valve were loaded with a spring it would simply crack open 
 and commence to sizzle when the pressure equaled the 
 force at which the spring was set, and that if this were 
 not enough to relieve the boiler the pressure would have 
 to increase, opening the valve more and more until the 
 steam blew off as fast as it was made. 
 
 But the ideal valve should stay on its seat until the 
 pressure reaches the desired limit, then open wide and dis- 
 charge the excess. This result is accomplished by the con- 
 struction shown in Fig. 56. With the first opening of the 
 valve the steam passes into the little "huddling chamber" 
 made by the cavity near the overhanging edge of the valve, 
 and a similar cavity surrounding the seat. The pressure 
 which accumulates here, acting on the additional area of 
 the valve, raises it sharply with the "pop" which gives the 
 valve its name, and it is sustained by the impact and re- 
 action of the issuing steam, until the pressure has subsided 
 sufficiently to allow the spring to overcome these actions. 
 
 A short space will be devoted to the consideration of the 
 lever safety valve also, as it may be of interest to some 
 students. 
 
138 
 
 Steam Engineering 
 
 The U. S. marine rule for lever valves. is here repeated: 
 "Lever safety valves to be attached to marine boilers shall 
 have an area of not less than one square inch to every two 
 
 ■SS^SSS>S>NS3\ 
 
 /SSS 
 
 Fig. 56 
 
 square feet of grate surface in the boiler, and the seats of 
 all such safety valves shall have an angle of inclination of 
 45° to the center line of their axis." 
 
 k 
 
Boiler Setting and Equipment 
 
 139 
 
 Fig. 57 
 inside view of a pop safety valve 
 
 In order to arrive at accurate results in lever safety 
 valve calculations it is necessary to know first the number 
 of pounds pressure exerted upon the stem of the valve by 
 
140 Steam Engineering 
 
 the lever itself, irrespective of the weight, also the weight 
 of the valve and stem, as all these weights, together with the 
 weight of the ball suspended upon the lever tend to hold 
 the valve down against the pressure of the steam. The 
 effective weight of the lever can be ascertained by leaving it 
 in its position attached to the fulcrum, and connecting a 
 spring balance scale to it at a point where it rests on the 
 valve stem. The weight of the valve and stem can also be 
 found by means of the scale. When the above weights are 
 known, together with the weight at the end of the lever and 
 its distance from the fulcrum, also the area of the valve and 
 its distance from the fulcrum, the pressure at which the 
 valve will blow can be found by the following rules : 
 
 Rule 1. Multiply the weight by its distance from the 
 fulcrum. Multiply the weight of the valve and lever by 
 the distance of the stem from the fulcrum and add this to 
 the former product. Divide the sum of the two products 
 by the product of the area of the valve multiplied by the 
 distance of its stem from the fulcrum. The result will 
 be pressure in pounds per square inch required to lift 
 the valve. 
 
 Example. Diameter of valve, 3 in." 
 
 Distance of stem from fulcrum, 3 in. 
 
 Effective weight of lever, valve and stem, 20 lbs. 
 
 Weight of ball, 50 lbs. 
 
 Distance of ball from fulcrum, 30 in. 
 
 Eequired pressure at which the valve will blow off, 50 X 
 30+20X3=1560. 
 
 Area of valve, 7.0686X3=21.2058. 
 
 1560—21.2058=73.57 pounds pressure. 
 
 AVhen the pressure at which it is desired the valve should 
 blow off is known, together with the weights of all the 
 

 Boiler Setting and Equipment 141 
 
 parts, the proper distance from the fulcrum at which to 
 place the weight is ascertained by Eule 2. 
 
 Rule 2. Multiply the area of the valve by the pressure, 
 and from the product subtract the effective weight of the 
 valve and lever. Multiply the remainder by the distance 
 of the stem from the fulcrum, and divide by the weight 
 of the ball. The quotient will be the required distance. 
 
 Example. Area of valve, 7.07 square inches. 
 To blow off at 75 pounds. 
 
 Effective weight of lever and valve, 20 pounds. 
 Weight of ball, 50 pounds. 
 Distance of valve stem from fulcrum, 3 inches. 
 7.07X75—20=510.25. 
 
 510. 25X3-^50=30. 6 inches, distance from fulcrum at 
 which to place the ball. 
 
 When the pressure is known, together with the distance 
 of the weight from the fulcrum, the weight of the ball is 
 obtained by Eule 3. 
 
 Rule 3. Multiply the area of the valve by the pressure, 
 and from the product subtract the effective weight of the 
 lever and valve. Multiply the remainder by the distance 
 of the stem from the fulcrum, and divide by the distance 
 of the ball from the fulcrum. The quotient will be the 
 required weight. 
 
 Example. Area of valve, 7.07 square inches. 
 
 Pressure in pounds per square inch, 80 pounds. 
 
 Effective weight of lever and valve, 20 pounds. 
 
 Distance of stem from fulcrum, 3 inches. 
 
 Distance of weight from fulcrum, 30 inches. 
 
 7.07X80—20=545.6. 
 
 545.6X3-^30=54.56 pounds, weight of ball. 
 
142 Steam Engineering 
 
 Safety valves, especially those of the lever type, are 
 liable to become corroded and stick to their seats if allowed 
 to go any great length of time without blowing. There- 
 fore it is good practice to raise the steam pressure to the 
 blowing off point at least two or three times a week, or 
 oftener, for the purpose of testing the valve. If it opens 
 and releases the steam at the proper point all is well, but 
 if it does not, it should be looked after forthwith. Gener- 
 ally the mere raising of the lever by hand, or a few taps 
 with a hammer if it be a pop valve, will free it and cause 
 it to work all right again; but if this treatment has to be 
 resorted to very often the valve should be taken down and 
 overhauled. In too many steam plants not enough im- 
 portance is attached to the safety valve. The fact is, it is 
 one of the most useful and important adjuncts of a boiler, 
 and if neglected serious results are sure to follow. 
 
 Fusible Plugs. A fusible plug should be inserted in 
 that part of the heating surface of a boiler which is first 
 liable to be overheated from lack of water. 
 
 In a horizontal tubular, or return flue boiler the proper 
 location for the fusible plug is in the back head about 
 iy 2 or 2 inches above the top row of tubes. In fire-box 
 boilers the plug can be put into the crown sheet directly 
 over the fire. These plugs should be made of brass with 
 hexagon heads and standard pipe threads, in sizes %, %, 
 1 inch, or even larger if desired. A hole drilled axially 
 through the center, and countersunk in the end that enters 
 the boiler is filled with an alloy of such composition that 
 it will melt and run out at the temperature of the dry 
 steam at the pressure carried in the boiler. Thus, if the 
 water should get below the plug the dry steam, coming in 
 contact with the fusible alloy, melts it and, escaping 
 
Boiler Setting and Equipment 143 
 
 through the hole in the plug, gives the alarm, and in ease 
 of fire-box or internally fired boilers the steam will gener- 
 ally extinguish the fire also. The hole is countersunk on 
 the inner end of the plug so as to retain the fusible metal 
 against the boiler pressure. These plugs should be looked 
 after each time the boilers are washed out, and all dirt 
 and scale should be cleaned off in order that the fusible 
 metal may be exposed to the heat. . 
 
 Another type of fusible plug consists of a small brass 
 cylinder into one end of which is screwed a plug filled with 
 a metal which will fuse at the temperature of dry steam 
 at the pressure which is to be carried in the boiler. The 
 other end of the cylinder is reduced and fitted with a small 
 stop valve and threaded to screw into a brass bushing in- 
 serted into the top of the boiler shell. This bushing also 
 receives at its lower end a piece of % or %-inch pipe which 
 extends downwards to within 2 inches of the top row of 
 tubes, or the crown sheet, if the boiler is internally fired. 
 The principle of the device is that in case the water falls 
 below the lower end of the pipe, steam will enter, fuse the 
 metal in the plug, and be free to blow and give warning of 
 danger. Some of these appliances are fitted with whistles 
 which are sounded in case the steam gets access to them. 
 But even with such devices, no engineer can afford to relax 
 his own vigilance and depend entirely upon the safety ap- 
 pliances to prevent accidents from low water. 
 
 Domes and Mud Drums. As a general proposition, both 
 mud drums and domes are useless appendages to steam 
 boilers. There are, no doubt, instances where they may 
 serve a purpose, but as a rule their use is of no advantage 
 to a boiler. Neither are the so-called circulating systems, 
 sometimes attached to return tubular boilers, of any real 
 
144 Steam Engineering 
 
 value. These consist of one or more 4 to 6-inch pipes 
 extending under the boiler from front to back through the 
 furnace, and the combustion chamber and connected to each 
 end of the boiler. 
 
 Blow Off Pipes. Blow off pipes should always be con- 
 nected with the lowest part of the water space of a boiler. 
 If there is a mud drum, then of course the blow off should 
 be connected with it ; . but if there is no mud drum, the 
 blow off should connect with the bottom of the shell, near 
 the back head, extend downwards to the floor of the com- 
 bustion chamber, and thence horizontally out through the 
 back wall, where the blow off cock can be located. 
 
 The best blow off cocks are the asbestos packed, iron-body 
 plug cocks, which are durable and safe. A globe valve 
 should never be used in a blow off pipe, because the scale 
 and dirt will lodge in it and prevent its being closed tight- 
 ly. A straight way, or gate valve is not so bad, but an 
 asbestos packed plug cock is undoubtedly the best and safest. 
 
 In order to protect the blow off pipe from the intense 
 heat, a shield consisting of a piece of larger pipe can be 
 slipped over the vertical part before it is connected. 
 
 Blow off cocks should be opened for a few seconds once 
 or twice a da) r , to allow the scale and mud to be blown out. 
 If neglected too long they are liable to become filled with 
 scale and burn out. A plan which is said to give good re- 
 sults is to connect a tee in the horizontal part of the pipe, 
 and from this tee run a 1 inch pipe to a point in the back 
 head at the water level. It is claimed that this will cause 
 a circulation of water in the pipe, and prevent the forma- 
 tion of scale. 
 
 A surface blow off is a great advantage, especially if the 
 water is muddy or liable to foam. By having the surface 
 
Boiler Setting and Equipment 145 
 
 blow off connected on a level with the water line a large 
 amount of mud, and other matter which is kept on the 
 surface by the constant ebullition can be blown out. 
 
 A combination surface blow off, bottom blow off, and cir- 
 culating system can be arranged by a connection such as 
 illustrated in Fig. 58. By closing cock A and opening 
 cocks B and C the bottom blow off is put in operation; by 
 closing B and opening A and C the surface blow off is 
 started, and by closing C and leaving A and B open the 
 device will act as a circulating system. The pipe should 
 be of the same size throughout. Blow off pipes should be 
 of ample size, never less than 1*4 inch, and from that to 
 2V2 inch, depending upon the size of the boiler. 
 
 Feed Pipes. Authorities differ in regard to the proper 
 location of the inlet for the feed pipe, but upon one point 
 all are agreed, namely, that the feed water, which is al- 
 ways at a lower temperature than the water in the boiler, 
 should not be allowed to come directly in contact with the 
 hot boiler sheets until its temperature has been raised to 
 within a few degrees of the temperature of the water in 
 the boiler. Certainly one of the most fruitful sources of 
 leaks in the seams, and around the rivets, is the practice of 
 introducing the feed water into the bottom either at the 
 back or front ends of boilers, as is too often the case. The 
 cool water coming directly in contact with the hot sheets 
 causes alternate contraction and expansion, and results in 
 leaks, and very often in small cracks in the sheet, the cracks 
 extending radially from the rivet holes. It would appear 
 that the proper method is to connect the feed pipe either 
 into the front head just above the tubes, or into the top 
 of the shell. The nipple entering the boiler should have 
 a long thread cut on the end which screws into the sheet, 
 
146 
 
 Steam Engineering 
 
 and to this end, inside the boiler there should be connected 
 another pipe which shall extend horizontally at least two- 
 thirds of the length of the boiler, resting on top of the tubes, 
 and then discharge. Or, what is till better, allow the in- 
 ternal pipe to extend from the entering nipple at the front 
 
 Fig. 58 
 
 end to within a few inches of the back head, then at right 
 angles across the top of the tubes to the other side, and from 
 there discharge downward. By this method the feed water 
 is heated to nearly, if not quite, the temperature of the 
 water in the boiler before it is discharged. One of the 
 objections to this system is the liability of the pipe inside 
 
 ifc^ 
 
Boiler Setting and Equipment 147 
 
 the boiler to become filled with scale and finally plugged 
 entirely. In such cases the only remedy is to replace it 
 with new pipe. But the great advantage of having the water 
 thoroughly heated before being discharged into the boiler 
 will much more than compensate for the extra expense of 
 piping, and the general idea of introducing the feed water 
 at the top, instead of at the bottom of the boiler is there- 
 fore recommended as being the best. 
 
 The diameters of feed pipes range from 1 inch for small 
 sized boilers, up to l 1 /^ an( i 2 inches for boilers of 54 to 72 
 inches in diameter. It is not good policy to have the feed 
 pipe larger than necessary for the capacity of the boiler; 
 because it then acts as a sort of cooling reservoir for the 
 feed water, and may cause considerable loss of heat. 
 
 For batteries of two or more boilers it is necessary to 
 run a main feed header, with branch pipes leading to each 
 boiler. The header should be large enough to supply all 
 the boilers at the same time, should it ever become necessary 
 to do so. The header can be run along the front of the 
 boilers just above the fire doors, with the branch pipes 
 running up on either side, clear of the flue doors and enter- 
 ing the front connection, or smoke arch, and the boiler head 
 at a point two inches above the tubes. There should always 
 be a valve in each branch pipe, between the check valve and 
 the header for the purpose of regulating the supply of 
 water to each boiler, and also for shutting off the pump 
 pressure in case of needed repairs to the check valve. An- 
 other valve should be placed between the check valve and 
 the boiler. By this arrangement it is always possible to get 
 at the check valve when it is out of order. 
 
148 Steam Engineering 
 
 FEED PUMPS. 
 
 Feed Pumps and Injectors. The belt driven power pump 
 is the most economical boiler feeder, but is not the most 
 convenient nor the safest. When the engine stops, the pump 
 stops also, and sometimes it happens that the belt gives 
 way, and the pump stops at just the time when the boiler 
 is being worked the hardest. 
 
 The modern double acting steam pump, of which there 
 are many different makes to choose from, is without doubt 
 the most reliable boiler feeding appliance and the one best 
 adapted to all circumstances and conditions, although it is 
 not economical in the use of steam, since the principle of 
 expansion cannot be carried out with the pump as with the 
 engine. 
 
 In selecting a feed pump care should be exercised to see 
 that it is of the proper size and capacity to supply the 
 maximum quantity of water that the boiler can evaporate. 
 This may be ascertained by taking into consideration the 
 amount of heating surface and the required consumption 
 of coal per square foot of grate surface per hour. First, 
 take the coal consumption. Assume the boiler to have 30 
 square, feet of grate surface, and that it is desired to burn 
 15 pounds of coal per square foot of grate per hour, which 
 is a good average with the ordinary hand fired furnace 
 using bituminous coal. Suppose the boiler is capable of 
 evaporating 8 pounds of water per pound of coal consumed. 
 Then 30X15X8=3,600 pounds of water evaporated per 
 hour. Dividing 3,600 by 62.4 (the weight of a cubic foot 
 of water in pounds) gives 57.6 cubic feet per hour, which, 
 divided by 60, gives 0.96 cubic feet per minute. This multi- 
 plied by 1,728 (number of cubic inches in a cubic foot) 
 gi^es 1,659 cubic inches per minute which the pump is 
 
Boiler Setting and Equipment 149 
 
 required to supply. Suppose the pump is to make forty 
 strokes per minute, and the length of stroke is five inches. 
 Then l,659-f-40=41.47 cubic inches per stroke, which, 
 divided by 5 (length of stroke in inches) gives 8.294 square 
 inches as the required area of water piston. 8.294-f-.7854= 
 10.56, which is the square of the corresponding diameter, 
 and the square root of 10.56=3.25. So, theoretically, the 
 size of the water end of the pump would be 3*4 inches in 
 diameter by 5 inches stroke; but as it is always safer to 
 have a reserve of pumping capacity, the proper size of the 
 pump would be 3y 2 inches in diameter, by 5 inches stroke, 
 With a steam cylinder of 6 or 7 inches in diameter. 
 
 There is another rule for ascertaining the size of the 
 feed pump, viz., by taking the number of square feet of 
 heating surface in the boiler and allow a pump capacity 
 of 1 cubic foot per hour for each 15 square feet of heating 
 surface. Thus, let the total heating surface of the boiler 
 be 786 square feet. Dividing this by 15 gives 52.4 as the 
 number of cubic feet of water required per hour, from which 
 the pump dimensions may be found in the same way as in 
 the preceding case. 
 
 In figuring on the capacity of a feed pump for a bat- 
 tery of two or more boilers, the total quantity of water 
 required by all the boilers must be taken into consideration. 
 All boiler-rooms should be supplied with at least two feed 
 pumps, so that if one breaks down there may always be 
 another one available. 
 
 Hard rubber valves are, all things considered, the best 
 for a boiler feed pump, as they are not affected by hot 
 water and do not hammer the seats like metallic composi- 
 tion valves do. Every boiler feed pump should be fitted 
 with a good sight-feed lubricator for cylinder oil. The 
 
150 Steam Engineering 
 
 steam valve mechanism of a steam pump is very sensitive 
 and delicate, and requires good lubrication in order to do 
 good work. In too many cases feed pumps are fitted with 
 an old style cylinder oil cup and there is generally more oil 
 on the outside of the valve chest than there is inside, while 
 the valve is bulldozed into working by frequent blows from 
 a convenient club. 
 
 The steam valves of all steam pumps are adjusted before 
 they are sent out from the factory, and most of them are 
 arranged so that the stroke may be shortened or lengthened 
 as the engineer desires. It is best, as a rule, to allow a 
 pump to make as long a stroke as it will without striking 
 the heads, because then the parts are worn evenly. 
 
 Sometimes an engineer is called upon to set the valves of 
 a duplex pump which have become disarranged. In such a 
 case he should proceed as follows: Place both pistons ex- 
 actly at mid-stroke. This may be done in two ways. First, 
 by dropping a plummet line alongside the levers connecting 
 the rock shafts with the spools on the piston rods. Then 
 bring the rods to the position where the. centers of the 
 spools will be in a vertical line with the centers of the 
 rock shafts. 
 
 The second method is to move the piston to the ex- 
 treme end of the stroke until it comes in contact with the 
 cylinder head. Then mark the rod at the face of the stuffing 
 box gland. Next move the piston to the other end of the 
 stroke and mark the rod at the opposite gland. Now make 
 a mark on the rod exactly half way between the two out- 
 side marks and move the piston back until the middle mark 
 is at the face of the gland and the piston will be at mid- 
 stroke. Having placed both pistons at mid-stroke, remove 
 the valve chest covers, and adjust the valves in their central 
 
Boiler Setting and Equipment 
 
 151 
 
 position, viz., so that they cover the steam ports. The valve 
 rod being in position, and connected to the rocker arms by 
 means of the short link, the nut or nuts securing the valve 
 to the rod should be so adjusted as to be equidistant from 
 the lugs on the valve, say ^ or % of an inch, according to 
 the amount of lost motion desired, which latter factor 
 governs the length of stroke in some makes of duplex 
 pumps, while in others it is controlled by tappets on the 
 
 Fig. 59 
 davis belt driven feed pump 
 
 valve rod outside of the valve chest. Care should be taken 
 while making these adjustments that the valve be retained 
 exactly in its central position. 
 
 Having set the valves correctly, move one of the pistons 
 far enough from mid-stroke to get a small opening of the 
 steam port on the opposite side, then replace the valve chest 
 covers and the pump will be ready to run. As these valves 
 
152 Steam Engineering 
 
 are generally made without any outside lap, a slight move- 
 ment of one of the pistons in either direction from its 
 central position will suffice to uncover one of the ports on 
 the other cylinder sufficiently to start the pump. 
 
 Sometimes duplex pumps "work lame," that is, one piston 
 will make a quick full stroke, while the other piston will 
 move very slowly, and just far enough to work the steam 
 valve of the opposite side. In the majorit)^ of cases this 
 irregular action is due to unequal friction in the packing 
 of the rods, or the packing rings on one of the pistons may 
 be worn out. 
 
 If one side of a duplex pump becomes disabled from any 
 cause, as breaking of piston rod in the water cylinder, for 
 instance, which is liable to happen, the pump may still be 
 operated in the following manner until duplicate parts to 
 replace the broken ones have been secured : Loosen the 
 nuts or tappets on the valve stem of the broken side and 
 place them far enough apart, so that the steam valve will 
 be moved through only a small portion of its stroke, thereby 
 admitting only steam enough to move the empty steam 
 piston and rod, and thus work the steam valve of the re- 
 maining side. The packing on the broken rod should be 
 screwed up tight, so as to create as much friction as pos- 
 sible; there being no resistance in the water end. In this 
 way the pump may be operated for several days or weeks 
 and thus prevent a shut down. 
 
 Large Boiler Feed Pumps. The plan of using one large 
 pump for feeding the boilers has recently been tried in 
 several large power stations. For instance, in the Ashley 
 Street Power House of the Union Electric Light and Power 
 Company of St. Louis, there was recently installed one large 
 Prescott steam pump to take the place of four smaller 
 ones which had been in use for feeding the boilers. 
 
Boiler Setting and Equipment 153 
 
 This pump is of the duplex compound condensing type, 
 having high-pressure steam cylinders 18 inches in diameter, 
 low-pressure steam cylinders 34 inches in diameter and 
 water plungers 17 inches in diameter, with 24-inch stroke in 
 each instance. The normal capacity of the pump is 1,800 
 gallons per minute, or 900,000 pounds of water per hour, 
 which is equal to 45,000 kilowatts at 20 pounds per kilo- 
 watt-hour. The present capacity of the Ashley street power 
 station is 36,000 kilowatts. 
 
 Fig. 60 
 worthington duplex boiler feed pump 
 
 The novel departure of installing a boiler feed-pump in 
 one large unit for this work will arouse the interest of engi- 
 neers, because it is customary to install several small units 
 for boiler-feed purposes in power plants of this size. But 
 as a matter of fact, this large pump is the consummation 
 of a process of evolution in this plant, which was at first 
 equipped with several small feed-pumps. 
 
 To produce the most economical results, the low-pressure 
 cylinders and their heads are steam- jacketed; the steam 
 valves are of the rotative type, there being one steam valve 
 for the high-pressure cylinders, and two each for the low- 
 pressure cylinders. The arrangement of two steam valves 
 
154 
 
 Steam Engineering 
 
 in the low-pressure steam cylinders reduces the clearance 
 to the lowest possible amount. The water end is of the pot- 
 form type, having four suction and discharge valves, 5% 
 inches in diameter, in each quarter of the suction and dis- 
 charge. The water plungers are of cast bronze of the out- 
 side end-packed type. 
 
 Fig. 61 
 
 phantom view of marsh independent steam pump 
 
 The boiler pressure carried is 175 pounds per square 
 inch. The pump operates against a pressure of 225 pounds 
 per square inch in the feed-water pipe system to the boilers. 
 This feed-water system is provided with a relief valve, and 
 the pump is controlled by a pressure governor. The boilers 
 are provided with thermostat valves, which allow the water 
 to flow into the boilers and maintain the proper level. All 
 of the automatic apparatus may be controlled by hand, 
 
Boiler Setting and Equipment 
 
 155 
 
 when desirable, for all the boilers, or for each boiler separ- 
 ately. Such occasions are very rare, however, as the pump 
 responds readily to changes in station load, and is under 
 perfect control of the automatic devices for controlling and 
 delivering the proper amount of feed-water to each boiler. 
 The feed-pipe system, in effect, is simply a system of 
 
 Fig. 62 
 
 the worthington compound steam pump 
 
 Piston Pattern, for General Service — For 150 Pounds Water 
 
 Pressure 
 
 water mains, in which the number of valves and fittings 
 liable to leak are reduced to a minimum. 
 
 Figures 62 and 63 show views of the Worthington boiler 
 feed pump, adaptable to large steam plants. In the ar- 
 rangement of steam cylinders shown in figure 62, the steam 
 is used expansively, thereby effecting a great saving. 
 
156 Steam Engineering 
 
 Figure 64 illustrates a type of pump which is rapidly 
 coming into favor for feeding boilers against high pressure.- 
 The steam pressures of from 150 to 200 pounds, which are 
 in common use, require a more substantial construction of 
 feed-pump than the lower pressures of a few years ago. 
 These machines are designed for high pressure and for 
 handling either hot or cold water. The steam ends are 
 made extra heavy and provided with extra strong bolting 
 for all joints, making them suitable for constant operation 
 under steam pressures up to 200 pounds per square inch. 
 The water ends are of the piston pattern, pot-valve type, 
 are of ample strength for working pressures up to 200 
 pounds and will easily stand test pressure of 300 pounds 
 per square inch. The piston-pattern construction requires 
 less room than the outside-packed machine of either the 
 center-packed, or end-packed type, and, furthermore, does 
 away with the large outside stuffing-boxes and excessive 
 amounts of drip. The pistons are fibrous-packed and are 
 readily accessible on removal of the cylinder-heads. 
 
 The valves are in special valve chambers* or pots, located 
 above the cylinders. This arrangement provides for con- 
 stant submergence of the pistons, and the reliability of 
 action of the machine consequent to such submergence. 
 Each pot contains one suction and one discharge valve, each 
 valve having an individual cover easily removable for in- 
 spection. Valves are of composition of the wing-guided 
 type, with bevel seats, and are of ample area for the re- 
 quirements of the service. A manifold connects the suction 
 openings of the various pots to a common suction inlet and 
 another manifold provides a common discharge outlet. 
 
 While designed primarily for boiler-feed purposes, these 
 pumps are very desirable machines for general service 
 
Boiler Setting and Equipment 
 
 157 
 
 against pressures not exceeding 200 pounds per square inch. 
 A good engineer will always take a pride in keeping his 
 feed pump in good condition, and if he has two or more 
 of them, which every steam plant of any consequence should 
 have, he will have an opportunity to keep his pumps in 
 good shape. The water pistons of most boiler feed pumps 
 are fitted to receive rings of fibrous packing. The best 
 
 Fig. 63 
 
 the worthingtox packed-plunger pump 
 Scranton Pattern — For 250 Pounds Water Pressure 
 
 packing for this purpose and one that will stand both hot 
 and cold water service is made of pure canvas cut in strips 
 of the required width, y 2 , %, % inches, etc., and laid to- 
 gether with a water proof cement having the edges for the 
 wearing surface. This packing is called square canvas 
 packing, and can be purchased in any size required for the 
 pump. The size is easily ascertained by placing the water 
 
158 
 
 Steam Engineering 
 
 piston, minus the follower plate, centrally in the water 
 cylinder and measuring the space between the piston and 
 
 Fig. 64 
 deane piston-pattern pot-valve-type boiler feed-pump 
 
 cylinder walls. This packing should not be allowed to 
 run for too long a time before renewing, for the reason 
 that pieces of it are liable to become loose, and be forced 
 
Boiler Setting and Equipment 159 
 
 along with the feed water on its way to the boiler and 
 lodge under the check valve,, holding it open and causing 
 no end of trouble. If the feed pump has to handle hot 
 water, or has to lift the water several feet by suction, the 
 packing rings should be looked after at least once a month. 
 Provisions for Testing, While considering feed pipes 
 and other apparatus necessarily appertaining to the feeding 
 of boilers, it is well to devote a short space also to the fit- 
 tings, and other devices required for successfully conducting 
 tests of the boiler and furnace. This subject is mentioned 
 here for the reason that the author considers that the nec- 
 essary fittings and appliances for making evaporative tests 
 properly belong to, and in fact are a part of, the feed 
 piping, and can be put in while the plant is being erected at 
 much less cost and trouble than if the matter is postponed 
 until after the plant is in operation. 
 
 Beginning then at the check valve, there should be a 
 tee located in the horizontal section of the feed pipe, as 
 near to the check valve as practicable, and between it and 
 the feed pump; or a tee can be used in place of an ell to 
 connect the vertical and horizontal sections of the branch 
 pipe where it rises in front of the boiler. One opening 
 of this tee is reduced to % or % inch to permit the attach- 
 ment of a hot water thermometer. (See Fig. 65). These 
 thermometers are also made angle-shaped at the shank, so 
 that if desired they can be screwed into a tee placed in 
 vertical pipe, and still allow the scale to stand vertically. 
 The thermometer is for the purpose of showing at what 
 temperature the feed water enters the boiler during the 
 test, and therefore should be as near the boiler as possible. 
 After the test is completed the thermometer may be taken 
 out and a plug inserted in its place. 
 
160 
 
 Steam Engineering 
 
 ;irm 
 
 Fig. 65 
 hot water thermo metee 
 
Boiler Setting and Equipment 161 
 
 The next requirement will be a device of some kind for 
 ascertaining the weight of water pumped into the boiler 
 during the test. In some well ordered plants each boiler is 
 fitted with a hot water meter in the feed pipe, but as this 
 arrangement is hardly within the reach of all, a substitute 
 equally as accurate can be made by placing two small water 
 tanks, each having a capacity of eight or ten cubic feet, in 
 the vicinity of the feed pump. These tanks can be made 
 of light tank iron, and each should be fitted with a nipple 
 and valw near the bottom for connection with the suction 
 side o'f the pump. The tops of the tanks may be left open. 
 If an open heater is used, and it is possible to place the 
 tanks low enough to allow a portion of the water from the 
 heater to be led into them by gravity, it will be desirable 
 to do so. A pipe leading from the main water supply, with 
 a branch to each tank, is also needed for filling them. One 
 of the feed pumps, of which there should always be at least 
 two, as already stated, is fitted with a tee in the suction pipe 
 near the pump to receive the pipe leading from the tanks. 
 During the test the. main suction leading to this pump 
 from the general supply should be kept closed, so that only 
 the water that passes through the tanks is used for feeding 
 the boiler. If the plant be a small one, with but one or 
 two boilers and only a single feed pump, the latter can be 
 made to do duty as a testing pump, because during the test 
 there will be no other boilers to feed besides the ones under 
 test. 
 
 If metal tanks are considered too expensive, two good 
 water-tight barrels can be substituted. Figure 66 will give 
 the reader a general idea of what is needed for obtaining the 
 weight of the water by the method just described. If a 
 closed heater is used and no other boilers are in service dur- 
 
162 
 
 Steam Engineering 
 
 ing the test, the cold water can be measured in the tanks 
 and pumped directly through the heater, but if it is nec- 
 essary to feed other boilers besides those under test, then 
 either a separate feed pipe must be run to the test boilers, 
 or else hot water meters will have to be put into the branch 
 pipes. 
 
 FtePWRreHSuepLy 
 
 ToFEfPPUMP 
 
 Fig. 66 
 
 In cases where a separate feed pipe must be put in for 
 the test boiler, and the water which is used for testing can- 
 not be passed through a heater, there should be a % or 1 
 inch pipe connected to the feed main, or header and leading 
 to the testing tanks, in order to allow a portion of the hot 
 feed water to run into and mix with the cold water in the 
 tanks as they are being filled, thus partially warming the 
 water before it <roe? to the boiler. 
 
Boiler Setting and Equipment 
 
 163 
 
 THE IXJECTOR. 
 
 The Injector. Although the injector is not generally 
 used for feeding stationary boilers, still a short study of the 
 
 Fig. 67 
 original form of the gifford injector 
 
 philosophy of its action may prove interesting, and useful 
 to engineers and water tenders. Consequently a space will 
 be devoted to this useful device for boiler feeding. 
 
164 Steam Engineering 
 
 Ever since the time of the invention of the injector in 
 1858 by that eminent French engineer Henri Giffard, and 
 its introduction into this country in 1860 by Wm. Sellers 
 & Co., of Philadelphia, it has been constantly improved 
 ■upon, and developed by various inventors and manufact- 
 urers. 
 
 How an Injector Works. How can an injector lift and 
 force large volumes of water into the boiler, against th£ 
 same or even higher pressure than that of the steam? 
 
 An injector works because the steam imparts sufficient 
 velocity to the water to overcome the pressure of the boiler. 
 
 This is a statement of fact; to explain the action, we 
 will take up the important parts of the question separately. 
 
 Why should an injector work? Let us assume that the 
 boiler pressure is 180 pounds — that is to say, every square 
 inch of the sheets, top and bottom, receives an internal 
 pressure of 180 pounds. If the thermometer is placed in- 
 side, it is found that both the water and the steam are at 
 the same temperature, 379°. But the steam contains more 
 heat than the water, because after water is heated, more 
 coal must be burned to break up the drops of water to 
 change them into steam; this heat is stored in the steam 
 and represents work done by the burning of the coal. 
 Steam not only exerts a pressure of 180 pounds per square 
 inch, but also can expand eight, to twenty-six times its 
 original volume, depending upon whether it exhausts into 
 the air or into a partial vacuum; water under the same 
 pressure would be discharged in a solid jet, and without 
 expansion. Either steam, or water can be used in the cylin- 
 der of an engine, or to drive the vanes of a steam or water 
 turbine, but one pound of steam is capable of much more 
 work than one pound-weight of water, on account of the 
 
Boiler Setting and Equipment 165 
 
 heat which has been used to change it into steam. This is 
 easily seen by comparing the velocities of discharge from 
 a steam nozzle and a water nozzle under 180 pounds pres- 
 sure; steam would expand while issuing, reaching at the 
 end of the nozzle a velocity of about 3,600 feet per second, 
 while the water, having no expansion, would have a velocity 
 of only 164 feet per second, about 1/22 of that of the 
 steam. The same weight of steam discharged per second 
 would therefore have vastly more power for doing work 
 than the water jet. 
 
 If a steam or water jet comes in contact with a body in 
 front of it, the tendency is to drive the body forward. The 
 force which tends to move the body is called "momentum," 
 and is equal to the weight of water or steam discharged by 
 the jet in one second, multiplied by its velocity per second. 
 If 1 pound of both the water and the steam are discharged 
 per second, the "momentum" of the steam jet is 3,600; 
 because 1 multiplied by 3,600=3,600; the momentum of 
 the water jet is 164. If the water jet discharged about 
 22 pounds per second, its momentum would be the same 
 as that of the steam, because 22 multiplied by 164 is nearly 
 3,600. The two jets are discharged under the same pres- 
 sure, but the steam has 22 times as much "momentum" or 
 force as the water jet; it could, therefore, easily enter a 
 boiler at 180 pounds pressure if we could reduce it to the 
 size of the hole of the water nozzle. 
 
 How ought an injector to work ? Here a practical diffi- 
 culty is reached. A steam jet 6 inches from the nozzle is 
 much larger than at the opening, and it would appear 
 almost impossible to make it enter a smaller tube. Even 
 at the narrowest part of the nozzle it is more than sixteen 
 times larger in diameter than a water jet discharging the 
 
166 Steam Engineering 
 
 same weight per second; therefore, if the steam is changed 
 to water without reducing its velocity, it would pass through 
 a hole one-sixteenth the diameter of the "steam nozzle" at 
 a velocity of 3,600 feet per second. The simplest and best 
 way to reduce its size is to condense it, and to use water for 
 this purpose, especially as water is needed in the boiler. 
 To condense the steam and utilize its velocity, the water 
 must be brought into close contact with it, without inter- 
 fering with the direct line of discharge ; a funnel, or "com- 
 bining tube" suitably placed will compel water to enter 
 evenly all around the steam jet. The mouth of this funnel 
 must not be too large, or too much water will enter and 
 swamp the jet; if too small, insufficient water will enter to 
 condense the steam. The effect of condensing the steam 
 is to reduce the diameter of the jet; therefore the funnel 
 or combining tube must be a smooth, converging taper, to 
 lead the combined jet of water and condensed steam into the 
 smaller hole of the delivery tube. The effect of the im- 
 pact of the steam is to give the water its momentum, so 
 that a solid stream shall issue from the lower end of the 
 tube. Each little drop of entering water is driven ahead 
 faster and faster by the vast number of little atoms of 
 steam moving hundreds of times as rapidly, until the steam 
 and water thoroughly combine into one swiftly-moving 
 jet of water and condensed steam, which contracts suffi- 
 ciently in diameter to enter the smaller delivery tube. 
 
 Why does the jet enter the boiler? The combined jet 
 now passes from the end of the combining tube into the 
 delivery tube; why does it enter the boiler? 
 
 If a pipe shaped like a fire-hose nozzle or a "delivery 
 tube" is connected to- a tank or boiler carrying 180 pounds, 
 the water will issue in a solid jet with a velocity of about 
 
Boiler Setting and Equipment 167 
 
 164 feet per second; or, if we could force water into the 
 tube at a speed of 164 feet per second at the same part of 
 the tube, this water would enter and fill up the boiler, or 
 tank against 180 pounds pressure. Therefore to enter the 
 boiler the combined jet of water and steam issuing from the 
 combining tube must have a velocity of at least 164 feet 
 per second. 
 
 Now, what is the velocity of the combined jet at the 
 lower end of the combining tube? If the steam nozzle 
 discharges one pound per second at 3,600 feet velocity, the 
 momentum of the steam is 1 multiplied by 3,600, or 3,600. 
 If the vacuum caused by the condensation of the steam 
 lifts and draws into the combining tube ten pounds of 
 water per second at a velocity of forty feet, its momentum 
 is 400; and that of the combined jet is 3,600 added to 400, 
 or 4,000. The weight of the combined jet is eleven pounds, 
 and at the time of entering the delivery tube its velocity 
 ought to be equal to 4,000 divided by 11, or 366 feet per 
 second; but as the water and the steam do not meet in 
 precisely the line of discharge ; there is a loss of. momen- 
 tum, and the velocity in the delivery tube is only 198 feet 
 per second. But the jet only needs a velocity of 164 feet to 
 enter the boiler, or tank carrying 180 pounds pressure, 
 therefore the actual jet in the delivery tube is able to over- 
 come a pressure of 206 pounds per square inch, or 26 
 pounds above that of the steam, because the velocity of a 
 jet of water under a head or pressure of 206 pounds would 
 be 198 feet per second. This excess is more than sufficient 
 to overcome the friction of the delivery piping and the 
 resistance of the main check valve. Therefore: 
 
 The action of the injector is due to the high velocity 
 with which a jet of steam strikes the water entering the 
 
168 
 
 Steam Engineering 
 
 combining tube, imparting to it its momentum, and form- 
 ing with it during condensation a continuous jet of smaller 
 diameter, having sufficient velocity to overcome the pres- 
 sure of the boiler. 
 
 The Sellers Improved Self-acting Injector, Description. 
 This injector is simply constructed and contains few operat- 
 ing parts. The lever is used in starting only, and the 
 water valve for regulation of the delivery. It is self-adjust- 
 ing, with fixed nozzle, and restarts automatically. All the 
 
 Fig. 68 
 the self-acting injector, class n improved 
 
 valve seats that may need refacing can be removed; the 
 body is not subject to wear and will last a lifetime. 
 
 The action is as follows (referring to Fig. 69) : Steam 
 from the boiler is admitted to the lifting nozzle by drawing 
 the starting lever (33) about one inch, without withdraw- 
 ing the plug on the end of the spindle (7) from the central 
 part of the steam nozzle (3). Steam then passes through 
 the small diagonal-drilled holes and discharges by the out- 
 side nozzle, through the upper part of the combining tube 
 
Boiler Setting and Equipment 
 
 169 
 
 (2) and into the overflow chamber, lifts the overflow valve 
 (30), and issues from the waste pipe (29). When water is 
 lifted the starting lever (33) is drawn back, opening the 
 forcing steam nozzle (3), and the full supply of steam dis- 
 charges into the combining tube, forcing the water through 
 the delivery tube into the boiler pipe. 
 
 At high steam pressure there is a tendency in all in- 
 jectors having an overflow to produce a vacuum in the 
 
 Fig. 69 
 the self-acting injector, class n improved 
 
 Sellers Standard Form 
 
 chamber (25). In the Improved Self- Acting Injector this 
 is utilized to draw an additional supply of water into the 
 combining tube by opening the inlet valve (42) ; the water 
 is forced by the jet into the boiler, increasing the capacity 
 about 20 per cent. 
 
 The water-regulating valve (40) is used only to adjust 
 the capacity to suit the needs of the boiler. The range is 
 unusually large. 
 
170 Steam Engineering 
 
 The cam lever (34) is turned toward the steam pipe to 
 prevent the opening of the overflow valve when it is desired 
 to use the injector as a heater, or to clean the strainer. The 
 joint between the body (25) and the waste-pipe (29) is 
 not subject to other pressure than that due to the discharg- 
 ing steam and water during starting ; the metal faces should 
 be kept clean and the retaining nut (32) screwed up tight. 
 
 To tighten up the gland of the steam spindle, push in the 
 starting lever (33) to end of stroke, remove the little nut 
 (5) and draw back the lever (33). This frees the cross- 
 head (8) and links (15), which can be swung out of the 
 way, and the follower (12) tightened on the packing to 
 make the gland steam-tight. 
 
 The injector is a reliable boiler feeder, and -is in fact 
 more economical than the steam pump, because the heat in 
 the steam used is all returned to the boiler, excepting the 
 losses by radiation. But the disadvantage attending the use 
 of the injector is that it will not work well with the feed 
 water at a temperature very much in excess of 100° F., 
 while a good steam pump, fitted with hard rubber valves, 
 will handle water at a temperature as high as 200° or 
 208° P., when the water flows to the pump by gravity from 
 a heater, or it will raise water from a receiving tank on a 
 short suction lift at a temperature of 150° or 160° F. 
 
 STEAM HEADERS AND CONNECTIONS. 
 
 The design, size and location of the main steam header, 
 and the connections between it and the boilers is a very 
 important problem, and should receive close attention. 
 
 If it was merely a case of uniting all boiler outlets into a 
 common pipe or header, regardless of the strains of expan- 
 sion, and ease of pipe fitting, the difficulties would be few. 
 
Boiler Setting and Equipment 171 
 
 The header should not only be a main for uniting all the 
 boilers, but it should also be of sufficient capacity to act as a 
 receiver-reservoir to counteract the effects of any momen- 
 tarily heavy demand for steam which would otherwise tend 
 to lift some of the water out of the boilers. The size of 
 the header may be determined by the following rule, viz., 
 let sectional area of main header equal, or slightly exceed 
 the sum of the areas of all boiler outlets connected with it. 
 Take for example a battery of four 72-inch by 18 feet 
 horizontal tubular boilers, each having 6-inch outlets. By 
 reference to the table of areas and circumferences of circles 
 it will be seen that the area of a circle 6 inches in diameter 
 equals 28.274. Therefore the combined areas of the four 
 outlets is 28.274X4=113 square inches, and reference to 
 the table again will show that a 12-inch pipe will be re- 
 quired for the header. It is best to have the header of a 
 uniform diameter throughout its length, as it will then 
 have the greatest storage capacity possible, and the supply 
 to the .largest engine or steam user should be taken from as 
 near the middle of the header as possible. 
 
 The location of the header must be determined by local 
 conditions, and by the relative positions of the boilers to the 
 engine room, but the header should be so located that all 
 valves, joints and connections are easily accessible, and so 
 that the valves can be conveniently operated from a fixed 
 platform, or from the top of the boilers. It should not be 
 necessary to use a movable ladder to control any steam 
 valve on the header, as the chances are that the ladder would 
 not be in its place in time of emergency or accident. 
 Locating the header in front of the boilers over the firing 
 space should be avoided if possible, as any leakage would 
 be liable to discomfort the firemen. A good location is 
 
172 Steam Engineering 
 
 along the top of the boilers near the rear, the header being 
 supported by brick piers built upon the boiler-setting walls. 
 
 All boiler connections should enter the header at the 
 top and the outlets should also be taken from the top to 
 insure that any water in the header will not be carried over 
 to engine, but will be drained off at the proper place. It is 
 not necessa^ to pitch the header for draining, provided 
 that the drain connection is made close to the point where 
 the heaviest draft of steam is taken. If the header is level, 
 the movement of the steam toward the heaviest outlet will 
 naturally cause the water in the bottom of the header to 
 flow in the same direction. A good arrangement for drain- 
 ing a header is to use a cross at the heaviest, outlet, with 
 the outlet connection taken from the top opening, and the 
 lower opening fitted with a blind flange tapped for drain- 
 age, but the use of a good high-pressure trap attached to 
 the drain opening of the header, and discharging into a 
 return tank, hot-well, or open heater is the most reliable 
 method of drainage. 
 
 Valves. The question of valves is next in order. The 
 day of the single valve in each boiler connection is passing. 
 Many cities by ordinance now require two valves in each 
 connection, and many engineers know only too well what it 
 means to crawl into a boiler with a leaky valve on top of 
 them. This condition can be eliminated by the use of two 
 valves. Globe valves should be avoided on account of the 
 turns in the steam path, gate and angle valves being pref- 
 erable. One of the neatest, and most efficient arrange- 
 ments is to use two angle valves, one on top of the header 
 and the other on top of the boiler. 
 
 Automatic stop and check-valves are daily finding favor, 
 and are coming into general use. These valves which are 
 
Boiler Setting and Equipment 173 
 
 adaptations of the ordinary check-valve, are generally made 
 in the angle type to set over the boiler outlet. The disk 
 falls to its seat when the flow of steam reverses, so that if 
 a tube should blow out the automatic stop and check, or 
 non-return valve would close because of the unbalanced 
 pressure, thereby isolating the disabled boiler from the 
 others. The advantages of such an arrangement are fully 
 apparent. The check disk in these valves is not attached 
 to the valve-stem, but the valve can be used as an ordinary 
 stop-valve by screwing the stem down until it holds the 
 disk securely on its seat. It is impossible to open this type 
 of valve when the boiler is out of commission, and this in 
 itself is a safety item to be considered by those who have 
 to enter boilers for cleaning or repairs. The non-return 
 valve will also close if the boiler becomes sluggish in gen- 
 erating steam, and will not open until the pressure equals 
 that in the header. The valve should be equipped with an 
 outside lever, or indicating device which will clearly show 
 whether it is open or closed. 
 
 There are a few types of non-return valve which have an 
 added feature of closing if the velocity should increase in 
 the regular direction beyond the normal rate, which might 
 easily be caused by the bursting of a pipe or joint in the 
 piping system. The location^ of the automatic stop and 
 check-valves should be as near as possible to the boiler 
 outlets. Where the ordinary angle or gate valves are used, 
 they should preferably have rising stems to readily indicate 
 whether the valve is open or closed. 
 
 Superheaters. The location of the superheater in the 
 boiler setting is a very important point, but there are cer- 
 tain rules and reasons that help to determine where it 
 1 should be placed in a particular type of boiler. The tern- 
 
174 Steam Engineering 
 
 perature of superheated steam at 150 pounds pressure super- 
 heated 200 degrees is 566 degrees, and if it were desired 
 to place a superheater in a boiler to meet such conditions, 
 it is evident that if the temperature of the escaping gases 
 were 500 degrees it would be impossible to place the super- 
 heater near the uptake. It would be necessary to place the 
 superheater at some point in the setting where there would 
 be a sufficient temperature drop between the gases and the 
 superheating surface to cause the necessary heat transfer. 
 The nearer the furnace, the greater will be the temperature 
 drop from the gases to the steam, and a greater heat trans- 
 fer per square foot of heating surface per hour. Therefore, 
 for a given degree of superheat the superheater that is 
 placed closest to the furnace will require the least heating 
 surface per horse-power, and for a given design the super- 
 heater having the least heating surface is the cheapest to 
 build. . 
 
 If the superheater is placed at such a point in the setting 
 that the gases exceed 1,000 degrees, it is necessary to pro- 
 vide for flooding with water whenever the flow of steam 
 through the superheater is stopped or during the raising 
 of steam. Except in certain special cases flooding is objec- 
 tionable, and the superheater should be placed just beyond 
 the point where the average temperature of the gases has 
 reached 1,000 degrees. In the average water-tube boiler 
 having a furnace temperature of 2,500 degrees, and an up- 
 take temperature of 500 degrees, 75 per cent of the total 
 amount of steam has been generated when the gases have 
 passed over 40 per cent of the heating surface and have 
 dropped to a little less than 1,000 degrees. 
 
 Besides the above there are other considerations, such as 
 adaptability to the design of the boiler, and accessibility 
 for cleaning and repairs. 
 
Boiler Setting and Equipment 175 
 
 The superheater contained within the boiler setting is 
 the most efficient type for degrees of superheat not exceed- 
 ing 200. It has the added advantage that it does not require 
 any additional space for its installation, except in some cases 
 an increase in the height of the boiler. It can be installed 
 without any additional piping over that required for a 
 simple boiler. If properly located it will deliver a fairly 
 uniform temperature of steam, and will automatically fol- 
 low the fluctuations in the boiler load. Whenever it is 
 necessary to cut out a superheater, only one unit is lost and 
 the other units will take care of the loss by carrying an 
 overload, thus preventing any wide temperature change in 
 the piping system, or an appreciable loss in economy. 
 
 In the boiler-setting type, the superheater is forced when- 
 ever the boiler is forced, but the temperature of the escaping 
 steam may fluctuate on account of leaving the fire doors 
 open too long, or firing too heavily or irregularly. Where 
 there are a number of boilers in a battery the temperature 
 of the steam at the engines should not vary, as the fluctua- 
 tions in temperature do not occur at the same time in all 
 the boilers, and therefore the average of all the boilers should 
 be nearly constant. Superheaters of this type can be de- 
 signed so that they will compound on overload; that is, 
 the degree of superheat will increase with the load up 
 to a certain amount. 
 
 The freedom of expansion of each of the elements of 
 heating surface is very important and should be given care- 
 ful consideration. The U-bend provides absolute freedom, 
 and cannot produce any strain on the joints, provided its 
 movement is not restrained by hangers, or clamps. In de- 
 signs where straight or slightly curved tubes are expanded 
 at each end into manifolds, considerable trouble is experi- 
 
 
176 Steam Engineering 
 
 enced with leaky joints due to the difference in expansion 
 of the tubes and the rigidity of the manifolds. 
 
 In properly designed all-steel superheaters very few re- 
 pairs will be required, but just as careful provisions should 
 • be made for such repairs as if they were of frequent occur- 
 rence. All the expanded joints, and all the manifold cover- 
 plates should be easily accessible for inspection and repairs. 
 
 HYDRAULICS FOR ENGINEERS. 
 
 Among the many difficult problems that are continually 
 coming up for engineers to solve, there is none more per- 
 plexing than the correct calculation of the quantity of 
 water which will be discharged in a given time from pipes 
 of various sizes, and under the many different heads or 
 pressures. Problems in hydraulics, as given by the majority 
 of writers on engineering, are usually in elaborate algebraic 
 equations, which, to the ordinary working engineer, are 
 very perplexing, at least the author has found them to be so 
 in his experience. Therefore with a view of assisting his 
 brother engineers in the solution of problems along this 
 line which they may be called upon to solve, the author has 
 spent considerable time and labor in searching for and 
 compiling a few rules and examples for hydraulic calcula- 
 tions in plain arithmetic, which he hopes may be of benefit. 
 
 First, to find velocity of flow in the pump, or in other 
 words, piston speed. 
 
 Rule. Multiply number of strokes per minute by length 
 of stroke in feet, or fractions thereof. 
 
 Second, the velocity of flow in the discharge pipe is in 
 inverse ratio to the squares of the diameters of the pipe, 
 and the water cylinder of pump. 
 
Boiler Setting and Equipment 111 
 
 Thus, a pump cylinder is 6 inches in diameter, and the 
 piston speed is 100 feet per minute; the discharge pipe 
 being 3 inches in diameter. What is the velocity of flow 
 in the pipe ? 
 
 Example, Q =4. In this case the velocity in the 
 
 pipe is four times that in the pump, and 100X4=400 feet 
 per minute, velocity for water in the discharge pipe. 
 
 Third, to find velocity in feet per minute necessary to 
 discharge a given quantity of water in a given time. 
 
 Rule. Multiply the number of cubic feet to be dis- 
 charged by 144 and divide by area of pipe in inches. 
 
 Fourth, to find area of pipe when the volume and velocity 
 of water to be discharged are known. 
 
 Rule. Multiply volume in cubic feet by 144 and divide 
 by the velocity in feet per minute. 
 
 Fifth, one of the first requisites in making correct calcu- 
 lations of the quantity of water discharged from any sized 
 pipe is to obtain the velocity of flow per second. There 
 are several rules for doing this, among which the following 
 appear to be the plainest and most simple : 
 
 Rule 1. Multiply the square root of the head in inches 
 by the constant 27.8. For instance, assume the head to be 
 100 feet=l,200 inches. The square root of 1,200 is 35 
 nearly, then 35X27-8=973 inches=81 feet per second 
 velocity. 
 
 Rule 2. Multiply the square root of the head in feet by 
 the constant 8, as follows: The square of 100=10 and 
 10X8=80 feet velocity per second. 
 
 Rule 3. Multiply twice the acceleration of gravity by the 
 head in feet, and extract the square root of product. The 
 
178 Steam Engineering 
 
 acceleration of gravity may be considered the constant num- 
 ber 32, neglecting decimals, 32X2X100=6,400. Square 
 root of 6,400=80 feet per second. 
 
 In many instances it is more convenient to use the 
 pressure in pounds per square inch as shown by gauge, in- 
 stead of the height or head, and we can then apply Eule 4. 
 
 Rule Jf. Multiply the square root of the pressure in 
 pounds per square inch by the constant number 12.16 as 
 follows : Pressure due to 100-foot head=44 pounds, nearly. 
 Square root of 44=6.6, which multiplied by 12.16=80.2 
 feet velocity per second. 
 
 Having ascertained the velocity of flow, we may now 
 proceed to calculate the weight of water in pounds per sec- 
 ond discharged from any size of pipe, neglecting for the 
 time being the loss in pressure caused by friction from 
 elbows and bends in the pipe and also the peculiar shape 
 assumed by a stream of water flowing through pipes, or 
 conduits when there is no resistance except the pressure of 
 the atmosphere, and friction caused by long distance trans- 
 mission. 
 
 We will take for our calculation a four-inch pipe from 
 which the water has a free flow under a head of 100 feet, 
 which gives a velocity of 80 feet per second. 
 
 Rule 5. Divide the velocity in feet per second, by the 
 constant 2.3, and multiply the quotient by the area of dis- 
 charge pipe in square inches. 80-f-2.3=34.7. Xow the 
 area of a four-inch pipe is 12.57 square inches, and 34.7 
 X 12.57=436 pounds discharge per second. 
 
 In order to get the matter clearly before ns, let us assume 
 that we have a section of four-inch pipe just 80 feet in 
 length and that it lies in a horizontal position and is filled 
 solidly full of water. It will contain area, 12.57 square 
 
Boiler Setting and Equipment 179 
 
 inches X length, 960 inches=12,067.2 cubic inches of water, 
 and as one pound of water occupies a space of 27.7 cubic 
 inches, we therefore have 12,067.2-^27.7=436 pounds of 
 water, and at a velocity of 80 feet per second our pipe will 
 be emptied and refilled continuously each second. We 
 have also Eule 6 to find the number of cubic feet dis- 
 charged per minute when the velocity per minute is known. 
 
 Rule 6. Multiply the area of pipe in square inches by 
 the velocity in feet per minute and divide by the constant 
 144. 
 
 Example. Area of 4-inch pipe=12.57 square inches. 
 Velocity of flow=80 feet per second=4,800 feet per min- 
 ute. 
 
 Then — — — -7 =419 cubic feet per minute=6.99 cubic 
 
 144 r 
 
 feet per second, which multiplied by 62.3 pounds (weight 
 of 1 cubic foot) =435.4 pounds per second. 
 
 As stated before, no allowance is made by the above rules 
 for friction or other retarding influences, but for ordinary 
 purposes in connection with a steam plant a deduction of 
 25 per cent is probably sufficient. Of course if the water is 
 being discharged into an elevated tank, or against direct 
 pressure of any kind, the resistance in pounds per square 
 inch or, the height in feet must be deducted from the im- 
 pelling pressure or head. Let us assume, for instance, that 
 our 4 inch pipe is discharging water into a tank at an ele- 
 vation of 75 feet above the level of the pump, and that to 
 reach the tank requires 100 feet of pipe with two 90° ells 
 and one straight-way valve. "We wish to discharge 500 
 gallons per minute into the tank, and will therefore require 
 a velocity of about 13 feet per second, which will necessitate 
 
180 Steam Engineering 
 
 a pressure of a little more than 1 pound per square inch to 
 be maintained at the pump over and above all resistance. 
 Xow the resistance to be overcome in this case will be : 
 Pressure per square inch due to 75-foot head. . . .32.5 lbs. 
 Friction loss due to length of pipe and velocity. . . 7.43 lbs. 
 
 Friction loss due to two 90° ells 2.16 lbs. 
 
 Friction loss due to straight-way valve 2 lbs. 
 
 Total . . ..42.29 lbs. 
 
 Eequiring a pressure of say 43 pounds per square inch, or 
 about the equivalent of 100 feet head at the pump. 
 
 Again, suppose that in place of the elevated tank we 
 have 1,000 feet of 8-inch horizontal pipe with a 4-inch 
 delivery at the end farthest from the pump, and three 
 branch pipes each 100 feet long and 4 inches in diameter 
 with one 90° ell, one straightway valve, connected at in- 
 tervals to the 8-inch main, and it is required to discharge in 
 all 1,000 gallons per minute, or at the rate of 250 gallons 
 per minute for each 4-inch delivery. The friction loss for 
 each 100 feet in length of 8-inch pipe at a velocity of 13 
 feet per second is .94 pounds, and for each 100 feet of 4-inch 
 pipe it is 1.89 pounds. Likewise the friction loss for each 
 90° ell is 1.08 pounds, and for a straight-way valve .2 
 pounds, at the above velocity. The total resistance there- 
 fore to be overcome is as follows : 
 
 For 1,000 feet of 8-inch pipe 941bs.X10= 9.4 lbs. 
 
 For 300 feet of 4-inch pipe 1.89 lbs.X 3= 5.67 lbs. 
 
 For four 90° ells 1.08 lbs.X 4= 4.32 lbs. 
 
 For four straight-way valves 2 lbs.X 4= .8 lbs. 
 
 Total . . . 20.19 lbs. 
 
 Consequently the pressure required at the pump will be 
 about 22 pounds per square inch, equal to a head of 50 feet. 
 
Boiler Setting and Equipment 
 
 181 
 
 Table 13 
 pressure of water. 
 
 The pressure of water in pounds per square inch for every foot in heigh* 
 to 260 feet ; and then by intervals to 3,000 feet head. By this table, from 
 the pounds pressure per square inch, the feet head is readily obtained ; and 
 vice versa. 
 
 
 u 
 
 
 u 
 
 
 u 
 
 
 u 
 
 
 u 
 
 rt 
 
 ft 
 
 
 0J 
 
 ft 
 
 
 <u 
 
 ft 
 
 -a 
 
 (U 
 
 ft 
 
 
 V 
 
 V 
 
 <u c 
 
 V 
 
 <u ~ 
 
 <U 
 
 v C 
 
 <U 
 
 <v c 
 
 V 
 
 <U C 
 
 M 
 
 3 . 
 
 K 
 
 3 . 
 
 H 
 
 3 . 
 
 ffi 
 
 3 . 
 
 X 
 
 3 . 
 
 
 oo rj> 
 
 
 
 
 oo rr" 
 
 
 oo -? 
 
 
 
 <u 
 
 tf> 00 
 
 <u 
 
 00 CO 
 
 <u 
 
 oo co 
 
 <D 
 
 w> oo 
 
 <u 
 
 <*> CO 
 
 u 
 
 <u 
 
 V 
 
 V 
 
 <D 
 
 <U 
 
 <D 
 
 <v 
 
 <y 
 
 <L> OT 
 
 Ph 
 
 u 
 
 h 
 
 
 fr 
 
 
 h 
 
 
 Ph 
 
 
 1 
 
 0.43 
 
 64 
 
 27.72 
 
 127 
 
 55.01 
 
 190 
 
 82.30 
 
 253 
 
 109.59 
 
 2 
 
 0.86 
 
 65 
 
 28.15 
 
 128 
 
 55.54 
 
 191 
 
 82.63 
 
 254 
 
 110.03 
 
 3 
 
 1.30 
 
 66 
 
 28.58 
 
 129 
 
 55.88 
 
 192 
 
 83.17 
 
 255 
 
 110.46 
 
 4 
 
 1.73 
 
 67 
 
 29.02 
 
 130 
 
 56.31 
 
 193 
 
 83.60 
 
 256 
 
 110.89 
 
 5 
 
 2.16 
 
 68 
 
 29.45 
 
 131 
 
 56.74 
 
 194 
 
 84.03 
 
 257 
 
 111.32 
 
 6 
 
 2.59 
 
 69 
 
 29.88 
 
 132 
 
 57.18 
 
 195 
 
 84.46 
 
 258 
 
 111.76 
 
 7 
 
 3.03 
 
 70 
 
 30.32 
 
 133 
 
 57.61 
 
 196 
 
 84.80 
 
 259 
 
 112.19 
 
 8 
 
 3.46 
 
 71 
 
 30.75 
 
 134 
 
 58.04 
 
 197 
 
 85.33 
 
 260 
 
 112.62 
 
 9 
 
 3.89 
 
 72 
 
 31.18 
 
 135 
 
 58.48 
 
 198 
 
 85.76 
 
 261 
 
 113.06 
 
 10 
 
 4.33 
 
 73 
 
 31.62 
 
 136 
 
 58.91 
 
 199 
 
 86.20 
 
 262 
 
 113.49 
 
 11 
 
 4.76 
 
 74 
 
 32.05 
 
 137 
 
 59.34 
 
 200 
 
 86.63 
 
 270 
 
 116.96 
 
 12 
 
 5.20 
 
 75 
 
 32.48 
 
 138 
 
 59.77 
 
 201 
 
 87.07 
 
 275 
 
 119.12 
 
 13 
 
 5.63 
 
 76 
 
 32.92 
 
 139 
 
 60.21 
 
 202 
 
 87.50 
 
 280 
 
 121.29 
 
 14 
 
 6.06 
 
 77 
 
 33.35 
 
 140 
 
 60.64 
 
 203 
 
 87.93 
 
 285 
 
 123.45 
 
 15 
 
 6.49 
 
 78 
 
 33.78 
 
 141 
 
 61.07 
 
 204 
 
 88.36 
 
 290 
 
 125.62 
 
 16 
 
 6.93 
 
 79 
 
 34.21 
 
 142 
 
 61.51 
 
 205 
 
 88.80 
 
 295 
 
 127.78 
 
 17 
 
 7.36 
 
 80 
 
 34.65 
 
 143 
 
 61.94 
 
 206 
 
 89.21 
 
 300 
 
 129.95 
 
 18 
 
 7.79 
 
 81 
 
 35.08 
 
 144 
 
 62.37 
 
 207 
 
 89.66 
 
 305 
 
 132.12 
 
 19 
 
 8.22 
 
 82 
 
 35.52 
 
 145 
 
 62.81 
 
 208 
 
 90.10 
 
 310 
 
 134.28 
 
 20 
 
 8.66 
 
 83 
 
 35.95 
 
 146 
 
 63.24 
 
 209 
 
 90.53 
 
 315 
 
 136.46 
 
 21 
 
 9.09 
 
 84 
 
 36.39 
 
 147 
 
 63.67 
 
 210 
 
 90.96 
 
 320 
 
 138.62 
 
 22 
 
 9.53 
 
 85 
 
 36.82 
 
 148 
 
 64.10 
 
 211 
 
 91.39 
 
 325 
 
 140.79 
 
 23 
 
 9.96 
 
 86 
 
 37.25 
 
 149 
 
 64.54 
 
 212 
 
 91.83 
 
 330 
 
 142.95 
 
 24 
 
 10.39 
 
 87 
 
 37.68 | 
 
 150 
 
 64.97 
 
 213 
 
 92.20 
 
 335 
 
 145.12 
 
 25 
 
 10.82 
 
 88 
 
 38.12 
 
 151 
 
 65.40 
 
 214 
 
 92.69 
 
 340 
 
 147.28 
 
 26 
 
 11.20 
 
 89 
 
 38.55 
 
 152 
 
 65.84 
 
 215 
 
 93.13 
 
 345 
 
 149.45 
 
 27 
 
 11.69 
 
 90 
 
 38.98 | 
 
 153 
 
 66.27 
 
 216 
 
 93.56 
 
 350 
 
 151.61 
 
 28 
 
 12.12 
 
 91 
 
 39.42 
 
 154 
 
 66.70 
 
 217 
 
 93.99 
 
 355 
 
 153.78 
 
 29 
 
 12.55 
 
 92 
 
 39.85 
 
 155 
 
 67.14 
 
 218 
 
 94.43 
 
 360 
 
 155.94 
 
 30 
 
 12.99 
 
 93 
 
 40.28 
 
 156 
 
 67.57 
 
 219 
 
 94.86 
 
 365 
 
 158.10 
 
 31 
 
 13.42 
 
 94 
 
 40.72 
 
 157 
 
 68.00 
 
 220 
 
 95.30 
 
 370 
 
 160.27 
 
 32 
 
 13.86 
 
 95 
 
 41.15 
 
 158 
 
 68.43 
 
 221 
 
 95.73 
 
 375 
 
 162.45 
 
 33 
 
 14.29 
 
 96 
 
 41.58 
 
 159 
 
 68.89 
 
 222 
 
 96.16 
 
 380 
 
 164.61 
 
 34 
 
 14.72 
 
 97 
 
 42.01 
 
 160 
 
 69.31 
 
 223 
 
 96.60 
 
 385 
 
 166.78 
 
 35 
 
 15.16 
 
 98 
 
 42.45 
 
 161 
 
 69.74 
 
 224 
 
 97.03 
 
 390 
 
 168.94 
 
 36 
 
 15.59 
 
 99 
 
 42.88 
 
 162 
 
 70.17 
 
 225 
 
 97.46 
 
 395 
 
 171.11 
 
 37 
 
 16.02 
 
 100 
 
 43.31 
 
 163 
 
 70.61 
 
 226 
 
 97.90 
 
 400 
 
 173.27 
 
 38 
 
 16.45 
 
 101 
 
 43.75 
 
 164 
 
 71.04 
 
 227 
 
 98.33 
 
 425 
 
 184.10 
 
 39 
 
 16.89 
 
 102 
 
 44.18 
 
 165 
 
 71.47 
 
 228 
 
 98.76 
 
 450 
 
 195.00 
 
 40 
 
 17.32 
 
 103 
 
 44.61 
 
 166 
 
 71.91 
 
 229 
 
 99.20 
 
 475 
 
 205.77 
 
 41 
 
 17.75 
 
 104 
 
 45.05 
 
 167 
 
 72.34 
 
 230 
 
 99.63 
 
 500 
 
 216.58 
 
 42 
 
 18.19 
 
 105 
 
 45.48 
 
 168 
 
 72.77 
 
 231 
 
 100.00 
 
 525 
 
 227.42 
 
 43 
 
 18.62 
 
 106 
 
 45.91 
 
 169 
 
 73.20 
 
 232 
 
 100.49 
 
 550 
 
 238.25 
 
 44 
 
 19.05 
 
 107 
 
 46.34 
 
 170 
 
 73.64 
 
 233 
 
 100.93 
 
 575 
 
 249.09 
 
 45 
 
 19.49 
 
 108 
 
 46.78 
 
 171 
 
 74.07 
 
 234 
 
 101.39 
 
 600 
 
 259.90 
 
 46 
 
 19.92 
 
 109 
 
 47.21 
 
 172 
 
 74.50 
 
 235 
 
 101.79 
 
 625 
 
 270.73 
 
 47 
 
 20.35 
 
 110 
 
 47.64 
 
 173 
 
 74.94 
 
 236 
 
 102.23 
 
 650 
 
 281.56 
 
182 
 
 Steam Engineering 
 
 Table 13 — continued. 
 
 
 u 
 
 
 u 
 
 
 u 
 
 
 Ih 
 
 
 u 
 
 T3 
 
 
 as 
 
 
 T3 
 
 
 a3 
 
 
 
 
 <u 
 
 <u c 
 
 <D 
 
 <L> g 
 
 <L> 
 
 <d d 
 
 a 
 
 <U g 
 
 <v 
 
 <U r-' 
 
 w 
 
 Ih.Jh 
 
 3 . 
 
 w 
 
 5l1 
 
 H 
 
 Ih.S 
 
 H 
 
 3 . 
 
 H 
 
 Ih.S 
 
 3 . 
 
 
 £ o 4 
 
 
 £ cr 
 
 
 £ cr 1 
 
 
 1/3 rr 1 
 
 
 £ o 4 
 
 V 
 
 £ W 
 
 <D 
 
 £ w 
 
 <u 
 
 £ w 
 
 <u 
 
 ^ w 
 
 <L) 
 
 £ w 
 
 <D 
 
 <U 
 
 <u 
 
 aj 
 
 <u 
 
 a 
 
 <u 
 
 <L> 
 
 V 
 
 a 
 
 h 
 
 Ih 
 
 h 
 
 Ih 
 
 Ph 
 
 h 
 
 Ph 
 
 ft 
 
 Ph 
 
 ft 
 
 Ph 
 
 48 1 
 
 20.79 
 
 ill 
 
 48.08 
 
 174 
 
 75.37 
 
 237 
 
 102.66 
 
 675 
 
 292.40 
 
 49 
 
 21.22 
 
 112 
 
 48.51 
 
 175 
 
 75.80 
 
 238 
 
 103.09 
 
 700 
 
 303.22 
 
 50 
 
 21.65 
 
 113 
 
 48.94 
 
 176 
 
 76.23 
 
 239 
 
 103.53 
 
 725 
 
 314.05 
 
 51 
 
 22.09 
 
 114 
 
 49.38 
 
 177 
 
 76.67 
 
 240 
 
 103.96 
 
 750 
 
 324.88 
 
 52 | 
 
 22.52 
 
 115 
 
 49.81 
 
 178 
 
 77.10 
 
 241 
 
 104.39 
 
 775 
 
 335.72 
 
 53 
 
 22.95 
 
 116 
 
 50.24 
 
 179 
 
 77.53 
 
 242 
 
 104.83 
 
 800 
 
 346.54 
 
 54 | 
 
 23.39 
 
 117 
 
 50.68 
 
 180 
 
 77.97 
 
 243 
 
 105.26 
 
 825 
 
 357.37 
 
 55 
 
 23.82 
 
 118 
 
 51.11 
 
 181 
 
 78.40 
 
 244 
 
 i05.96 
 
 850 
 
 368.20 
 
 56 | 
 
 24.26 
 
 119 
 
 51.54 
 
 182 
 
 78.84 
 
 245 
 
 106.13 
 
 875 
 
 379.03 
 
 57 
 
 24.69 
 
 120 
 
 51.98 
 
 183 
 
 79.27 
 
 246 
 
 106.56 
 
 900 
 
 389.86 
 
 58 
 
 25.12 
 
 121 
 
 52.41 
 
 184 
 
 79.70 
 
 247 
 
 106.99 
 
 925 
 
 400.70 
 
 59 : 
 
 25.55 
 
 122 
 
 52.84 
 
 185 
 
 80.14 
 
 248 
 
 107.43 
 
 950 
 
 411.54 
 
 60 
 
 25.99 
 
 123 
 
 53.28 
 
 186 
 
 80.57 
 
 249 
 
 107.85 
 
 975 
 
 422.35 
 
 61 
 
 26.42 
 
 124 
 
 53.71 
 
 187 
 
 81.00 
 
 250 
 
 108.20 
 
 1000 
 
 433.18 
 
 62 
 
 26.85 
 
 125 
 
 54.15 
 
 188 
 
 81.43 
 
 251 
 
 108.73 
 
 1500 
 
 649.70 
 
 63 
 
 1 
 
 27.29 
 
 126 
 
 54.58 
 
 189 
 
 81.87 
 
 252 
 
 109.16 
 
 2000 
 3000 
 
 866.30 
 1,299.50 
 
 QUESTIONS AND ANSWERS. 
 
 111. What two methods of support are generally used 
 in the setting of horizontal tubular boilers ? 
 
 Arts. First: By suspension from I beams and girders, 
 and secondly by means of brackets riveted to the side sheets, 
 and resting upon the side walls. 
 
 112. How are water tube boilers usually supported in 
 the setting? 
 
 Ans. By suspension. 
 
 113. What important details should be looked after 
 concerning the brick work? 
 
 Ans. The foundations should be good, and the walls 
 built in such manner as to take care of the expansion and 
 contraction. 
 
 114. How is this accomplished? 
 
Questions and Answers 183 
 
 Ans, By leaving an air space of two inches in the side 
 and rear walls beginning at the level of the grate bars, and 
 extending up to about the center line of the boiler. 
 
 115. What kind of brick should be used for inside 
 lining ? 
 
 Ans. Fire brick of good quality. 
 
 116. How should bridge walls be built for horizontal 
 tubular boilers ? 
 
 Ans. Straight across from wall to wall. 
 
 117. About what distance from the bottom of the boiler 
 should this wall be ? 
 
 Ans. Eight to ten inches. 
 
 118. Where is the combustion chamber? 
 Ans. It is the space back of the bridge wall. 
 
 119. How should boiler walls be secured? 
 
 Ans. By means of tie rods extending the entire length, 
 and breadth of the setting. 
 
 120. What are the buck stays? 
 
 Ans. They are strong cast-iron, or wrought-iron bars 
 placed vertically upon the outside of the walls, and secured 
 to the tie rods. 
 
 121. Should horizontal tubular boilers be set perfectly 
 level lengthwise? 
 
 Ans. It is better that they be set about one inch lower 
 at the back end, than at the front end. 
 
 122. Give one of the main reasons for this style of 
 setting. 
 
 Ans. When washing out the boiler, the mud and water 
 will more easily drain towards the blow off pipe. 
 
 123. What is the usual ratio of grate surface to heating 
 surface ? 
 
184 Steam Engineering 
 
 Ans. One square foot of grate surface to each 36 square 
 feet of heating surface. 
 
 124. At what point should the glass water-gauge be 
 located ? 
 
 Ans. In such a position as to bring the lowest visible 
 portion of the gauge glass exactly on a level with the top of 
 the upper row of tubes of a horizontal tubular boiler. With- 
 other types of boilers the lowest end of the gauge glass 
 should always be on a level with the danger point. 
 
 125. Why should the above rules be observed in locating 
 a water column? 
 
 Ans. Because when the water level in the glass begins 
 to draw near to the lower end of glass the engineer or water 
 tender will have an infallible guide to warn him to get 
 busy. 
 
 126. What is a good indication that the connections of 
 the water glass are choked or plugged with scale? 
 
 Ans. When. there is no movement of the water in the 
 glass. 
 
 127. Why should there be a trap, or siphon in the pipe 
 connecting the steam gauge to the boiler? 
 
 Ans. To prevent the hot steam from coming into con- 
 tact with the spring of the gauge. 
 
 128. How may the steam gauge, and safety valve be 
 tested in comparison with each other? 
 
 Ans. By occasionally raising the steam pressure higli 
 enough to cause the valve to open at the point for which 
 it is set to blow. 
 
 129. Is the pop valve reliable as a safety valve? 
 
 Ans. It is, if not allowed to stand idle too long and 
 become rusty. 
 
 130. How often should it be allowed to blow off? 
 
Questions and Answers 185 
 
 Ans. At least twice a week. 
 
 131. Are lever safety valves used to any extent? 
 
 Ans. They are still in use to some extent, but are rapidly 
 being superseded by pop valves. 
 
 132. What is the function of a fusible plug? 
 
 Ans. The fusible alloy of which it is composed will melt 
 when it comes in contact with dry steam/ and allow the 
 steam to blow a warning. 
 
 133. Where is the fusible plug located? 
 
 Ans. In that portion of the heating surface of a boiler 
 which is first liable to be overheated from lack of water. 
 
 134. Are Domes and Mud drums necessary parts of 
 boilers ? 
 
 Ans. They are not as a rule. 
 
 135. Where should the blow off pipe always be con- 
 nected ? 
 
 Ans. With the lowest part of the water space. 
 
 136. Should the blow off cock be opened while the 
 boiler is under pressure ? 
 
 Ans. Yes, for a few seconds, once, or twice each day. 
 
 137. Is a surface blow off any advantage? 
 Ans. It is, especially if the water is muddy. 
 
 138. What precautions should be observed with regard 
 to inlet for feed water? 
 
 Ans. The feed water should not be allowed to come 
 directly in contact with the hot boiler sheets until its 
 temperature is equal to, or near that of the water within 
 the boiler. 
 
 139. How may this be brought about? 
 
 Ans. By means of feed water heaters, and internal coils 
 of pipe through which the feed water is caused to pass. 
 
 140. What is the most economical style of feed pump ? 
 
 J 
 
186 Steam Engineering 
 
 Ans. The belt-driven power pump. 
 
 141. Is it the most reliable, or safest? 
 Ans. It is not. 
 
 142. What is the most reliable boiler feeding device, for 
 all conditions of stationary practice? 
 
 Ans. The double acting steam pump. 
 
 143. What* precautions should be observed in figuring 
 on the capacity of a feed pump for a battery of two or 
 more boilers ? 
 
 Ans. To take into account the total quantity of water 
 required by all of the boilers; and let the capacity of the 
 pump be equal to it, 
 
 144. In connection with feed apparatus for boilers, 
 what other fittings and devices should be installed? 
 
 Ans. There should be a tee located in the horizontal 
 section of the feed pipe near the check valve, and between it 
 and the feed pump. One opening of this tee is to be re- 
 duced to % or x /2 inch to receive a hot water thermometer 
 for testing the temperature of the feed water when making 
 evaporative tests, etc. 
 
 145. What other provisions along this line should be 
 made ? 
 
 Ans. Tanks for weighing the feed water — also a sep- 
 arate feed pipe to the boiler under test, also means for 
 weighing the coal burned during test. 
 
 146. Is the injector an efficient boiler feeder? 
 
 Ans. It is in locations where there is not very much 
 exhaust steam available for heating the feed water. 
 
 147. When, and by whom was the injector invented? 
 /ins. In the year 1858, by Henri Giffard. 
 
 148. Why does an injector force water into a boiler 
 that is under steam pressure? 
 
Questions and Answers 187 
 
 Ans. Because the steam passing through the injector 
 imparts sufficient velocity to the water to overcome the 
 boiler pressure. 
 
 149. Why does an injector lift water from a lower level ? 
 
 Ans. Because the condensation of the steam in the com- 
 bining tube creates a vacuum there, and in the suction 
 pipe connected with it. 
 
 150. How may the size of the steam header for a battery 
 of boilers* be determined? 
 
 Ans. The sectional area of the header should equal or 
 slightly exceed the sum of the areas of all the boiler outlets 
 to be connected with it. 
 
 151. Where should all connections except for drainage, 
 enter, and leave the main header? 
 
 Ans. At the top. 
 
 152. How many valves should there be in each boiler 
 connection leading to the header ? 
 
 Ans. Xever less than two. 
 
 153. What kind of valves are best for this purpose? 
 Ans. Automatic stop, and check valves. 
 
 154. What is the most efficient type of superheater for 
 practical purposes? 
 
 Ans. The one that is contained within the boiler setting. 
 
 155. How is the velocity of flow, or piston speed per 
 minute of a pump ascertained? 
 
 Ans. Multiply number of strokes per minute by length 
 of stroke in feet, or fractions thereof. 
 
 156. The piston speed being known, how is the velocity 
 of flow in the discharge pipe found ? 
 
 Ans. The velocity of flow in the discharge pipe is in 
 inverse ratio to the squares of the diameters of the pipe and 
 the water cylinder of pump. 
 
188 Steam Engineering 
 
 157. When it is required to discharge a certain quantity 
 of water from a given size of pipe in a given time, how 
 may the velocity of flow in feet per minute be found ? 
 
 . . Ans. Multiply the number of cubic feet to be discharged 
 by 144 and divide by area of pipe in inches. 
 
 158. When the volume of water to be discharged and 
 the velocity of flow are known, how is the area of the pipe 
 obtained ? 
 
 Ans. Multiply volume in cubic feet by 144, and divide 
 by velocity in feet per minute. 
 
 159. What is meant by "acceleration of gravity/" and 
 what constant number represents it in connection with 
 hydraulics ? 
 
 Ans. Acceleration of gravity is the increase in velocity 
 caused by the actual weight of the water, and is represented 
 by the constant 32. 
 
 160. What per cent of allowance is ordinarily made for 
 friction in water pipes? 
 
 Ans. A deduction of 25 per cent is sufficient. 
 
Feed Water Heaters 
 
 Feed Water Heaters. One great source of economy in 
 fuel is the utilization of all the available exhaust steam for 
 
 Fig. 70 
 
 baragwanath steam jacket 
 
 feed water heater 
 
 ■■■-tilll.:::!^;^- ■■■- :=■- 
 
 Fig. 71 
 
 INTERIOR VIEW OF OPEN 
 HEATER 
 
 heating the feed water before it enters the boiler. Of 
 course if the main engines are condensing, the exhaust from 
 
 189 
 
190 Steam Engineering 
 
 that source is not directly available, except by interposing 
 a closed heater between the cylinder and the condenser, 
 or by using the water of condensation for feeding the 
 boilers. This can be done with safety, provided a surface 
 condenser is used, but with a jet condenser or an open 
 heater in which the exhaust mingles with the water, it is 
 advisable to have an oil separator to prevent the oil from 
 getting into the boilers. 
 
 Exhaust heaters are of two kinds, open and closed. In 
 the open heater the exhaust steam mingles directly with 
 the water, and a portion of it is condensed. A well-designed 
 open exhaust heater will raise the temperature of the water 
 to very nearly the boiling point, 212° P. These heaters 
 should be set so that the water will flow by gravity from 
 them to the feed pump. In the closed type of exhaust 
 heaters the exhaust steam and the water are kept separate. 
 In some styles the steam passes through tubes, which are 
 surrounded by water, while in others the water fills the 
 tubes, which are in turn surrounded by the steam. In 
 either case the water in the closed heater is under the full 
 boiler pressure, while the feed pump is in operation, be- 
 cause the heater is between the pump and the boiler, while 
 with the open heater the pump is between the heater and 
 the boiler. 
 
 The saving effected by heating the feed water with ex- 
 haust steam can be easily ascertained by the use of a 
 thermometer, a steam table, and a simple arithmetical cal- 
 culation. First, find by thermometer the temperature of 
 the water before entering the heater; find its temperature 
 as it leaves the heater. Next ascertain by table 17 the 
 number of heat units above 32° F. in the water at each of 
 Jie two temperatures. Subtract the less from the greater, 
 
Fig. 72 
 
 SQUARE OPEN HEATER 
 
192 Steam Engineering 
 
 and the remainder will be the number of heat units added 
 to the water by the heater. Next find by table 17 the num- 
 ber of heat units above 32 °F. in the steam at the pressure 
 ordinarily carried in the boiler, and subtract from this the 
 number of heat units in the water before it enters the 
 heater. The result will be the number of heat units that 
 would be required to convert the water into steam of the 
 required pressure, provided no heater were used. . Then to 
 find the percentage of saving effected by the heater, multi- 
 ply the number of heat units added to the water by the 
 heater by 100, and divide by the number of heat units re- 
 quired to convert the unheated water into steam, from the 
 initial temperature at which it enters the heater. 
 
 Example. Assume the boiler to be carrying 100 pounds 
 gauge pressure. Suppose the temperature of the water 
 before entering the heater is 60° F., and that after leaving 
 the heater its temperature is 202° F., what is the percentage 
 of saving due to the heater ? The solution of the problem 
 is as follows: 
 
 Boiler pressure by gauge=100 pounds. 
 
 Initial temperature of feed water =60° F. 
 
 Heated temperature of feed water=202° ]?. 
 
 Prom Table 17 it is found that 
 
 Heat units in water at 202° F.=170.7. 
 
 Heat unit in water at 60° F.=28.01. 
 
 Heat units added to water by heater=170.7 — 28.01= 
 142.69. 
 
 Heat units in steam at 100 pounds gauge pressures 
 1185.0. 
 
 Heat units to be added to water at 60° F. to make steam 
 of 100 pounds gauge pressure=1185.0— 28.01 = 1156.99. 
 
Feed Vfater Heaters 193 
 
 Percentage of saving effected by the use of the heater 
 142.69X100 
 
 1156.99 
 
 - = 12.33 percent. 
 
 Suppose the coal consumed under this boiler amounts to 
 two tons per day at a cost of $3.00 per ton, or a fuel cost 
 of $6.00 per day. Then the saving in dollars and cents due 
 to the heater in the foregoing example would be 12.33 per 
 cent of $6.00, or $0.7398 (74 cents) per day. 
 
 Hoppes Class E Heater. Figure 74 is a side sectional 
 elevation of a Hoppes class E open feed-water heater, Fig. 
 75 being an end sectional view of the same. Although this 
 heater has been on the market several years, it has recently 
 been improved, and embodies features not hertofore shown. 
 The shell of the heater is cylindrical and the heads are 
 "bumped," a design calculated to resist pressure, and also 
 to prevent pulsations due to the impulses of the exhaust. 
 The interior of the heater is provided with laj^ers of trough- 
 shaped pans arranged in tiers and designed tc afford a 
 large amount of heating surface. To avoid corrosion the 
 pans are of cast-iron, as are also the bottom of the shell, 
 the lower ends of the center posts, and all other parts with 
 which the water comes in contact. The shell may be en- 
 tirely cast-iron, however, if desired. In the back end of the 
 heater is located a large oil catcher, through which the ex- 
 haust passes. See Fig. 74. 
 
 The principle of operation is, to provide that the flow of 
 water from the cast-iron troughs at the top be so gradual 
 that the water will be distributed over the edges of the 
 pans in a thin film, and over the sides and ends so gently 
 that it will, follow the bottom contour of each pan to the 
 lowest point before dropping off into the pan beneath. 
 
194 
 
 Steam Engineering 
 
 fcj"f v 1 vp 
 
 ilfimr - ii,f < .v„ ! iriv,r. 
 
 Fig. 73 
 closed feed water heater 
 
 While the water is following the under side of the pans, 
 the exhaust steam will come in direct contact with, and heat 
 
Feed Water Heaters 
 
 195 
 
 it to the temperature of the exhaust. Lime and other solids 
 which may be held in solution in the water will, when 
 liberated by the heat, form mostly on the under side of the 
 pans and hence will not detract from the efficiency of the 
 process, as the same direct action of the exhaust on the 
 water will continue as when the pans are clean. 
 
 In open heaters of large size the regulation and 
 distribution of water so as to obtain the best results are im- 
 
 Pig. 74 
 sectional elevation of hoppes class r feed-water heater 
 
 portant. In the Hoppes apparatus the water is regulated 
 to the heater by a float in a separate float-chamber operat- 
 ing a double-disk balanced valve of the company's manu- 
 facture. Branch pipes from the main feed-pipe are con- 
 nected to the shell at the top, and these branches have ex- 
 tensions inside the heater to which are attached flanged 
 tees. To the flanges of these tees are bolted flanged inverted 
 L-shaped pipes, the long arms of which extend below the 
 water level of the feed troughs in the top of the heater. 
 
196 
 
 Steam Engineering 
 
 Disks with orifices of proper and equal size are placed be- 
 tween the flanges of the L-shaped feed-pipes and the tees, 
 and by this means the water is equally distributed into the 
 various tiers of pans. 
 
 When it is desired to feed two or more heaters in multiple, 
 an equal distribution of water is given to all the heaters 
 by using a single regulating valve on the main water inlet, 
 and branching the same to the heaters to be supplied. 
 
 Fig. 75 
 end sectional view of hoppes class r heater 
 
 A feature recently added is an overflow dam, at the rear 
 end of the heater, which is intended to act as a skimmer 
 and also to add to the capacity of the overflow pipe by in- 
 creasing the head on the outlet without causing the water 
 to rise higher in the heater. The drip from the oil separator 
 is piped into the chamber formed by the dam, but this may 
 
Feed Water Heaters 197 
 
 have a separate connection, if prefeired. Filters are pro- 
 vided on request, but it is believed that the large amount 
 of lime-catching surfaces obviates the necessity for their 
 use in most cases. 
 
 These heaters are built in sizes ranging from 50 to 
 30,000 horse-power. 
 
 Heaters, especially those of the closed type, should have 
 capacity sufficient to supply the boiler for fifteen or twenty 
 minutes. There would then be a body of water continually 
 in the heater in direct contact with the heating surface, and 
 as it passes slowly through it will receive much more heat 
 than if rushed through a heater that is too small. All 
 heaters and feed pipes should be well protected by some 
 good insulating covering to prevent loss of heat by radia- 
 tion. In some cases the exhaust steam, or a portion of it at 
 least, can be used to advantage in an exhaust injector. This 
 device, where it can be used at all, is economical in that it 
 not only feeds the boiler, but also heats the water without 
 the use of live steam. But it will not force the water against 
 a pressure much above 75 pounds to the square inch, and 
 if the initial temperature of the water is much above 75 °F. 
 the exhaust injector will not handle it. Heaters which use 
 live steam direct from the boilers heat the feed water to a 
 much higher temperature, so that they act as purifiers by 
 removing a large portion of the scale-forming impurities 
 before the water enters the boiler. Live steam heaters, 
 however, are not to be considered as economizers of heat. 
 
 MECHANICAL STOKERS. 
 
 - The principles governing the operation of mechanical or 
 automatic stokers are in the main correct, viz., that the 
 supply of coal and air is continuous, and that provision is 
 
Mechanical Stokers 
 
 199 
 
 made for the regulation of the supply of fuel according to 
 the demand upon the boiler for steam; also that the in- 
 termittent opening and closing of the furnace doors, as in 
 hand firing, thereby admitting a large volume of cold air 
 directly into the furnace on top of the fire, is avoided. 
 
 Mechanical stokers have within the last twelve years 
 been largely adopted in the United States, especially in sec- 
 tions where bituminous coal is the principal fuel. The 
 disadvantages attending their use are : 
 
 Fig. 77 
 cahall vertica boiler with chain grate stoker attached 
 
 First, that the cost of properly installing them is so 
 great that their use is practically prohibited to the small 
 manufacturer. 
 
 Second, that in case of a sudden demand upon the boilers 
 for more steam the automatic stoker cannot respond as 
 promptly as in hand firing, although this objection could 
 no doubt be met by skillful handling. 
 
200 Steam Engineering 
 
 Third, the extra cost for power to operate them, al- 
 though this is probably offset by the diminished expense 
 for labor required, as compared to hand firing. 
 
 There are many different types of mechanical stokers, 
 and automatic furnaces, but they may for convenience be 
 grouped into four general classes. In class one, the grate 
 consists of an endless chain of short bars that travel in a 
 horizontal direction over sprocket wheels, operated either 
 by a small auxiliary engine or by power derived from an 
 overhead line of shafting in front of the boilers. 
 
 In class two may be included stokers having grate bars 
 somewhat after the ordinary type as to length and size, but 
 having a continuous motion up and down or forward and 
 back. This motion, though slight, serves to keep the fuel 
 stirred and loosened, thus preventing the firing from be- 
 coming sluggish. The grate bars in this class of stokers 
 are either horizontal, or inclined at a slight angle, and their 
 constant motion tends to gradually advance the coal from 
 the front to the back end of the furnace. 
 
 Class three includes stokers having the grate bars steeply 
 inclined. Slow motion is imparted to the grates, the coal 
 being fed onto the upper end, and forced forward as fast 
 as required. 
 
 Class four includes an entirely different type of stoker, 
 in that the fresh coal is supplied underneath the grates, 
 and is pushed up through an opening left for the purpose 
 midway of the furnace. The gases, on being distilled, im- 
 mediately come in contact with the hot bed of coke on top, 
 and the result is good combustion. In this type of stoker, 
 steam is the active agent used for forcing the coal up into 
 the furnace, either by means of a long, slowly revolving 
 screw, as in the American stoker, or a steam ram, as with 
 
Mechanical Stokers 
 
 201 
 
 the Jones under-feed stoker. A forced draft is employed, 
 and the air is blown into the furnace through tuyeres. 
 
 Fig. 78 
 
 mansfield chain grate stoker 
 
 Showing How it Can Be Withdrawn from under Boiler 
 
 When these stokers are intelligently handled they give good 
 results, especially with cheap bituminous coal. The clinker 
 formed on the grate bars or dead plates is easily removed. 
 
202 
 
 Steam Engineering 
 
 The coal is supplied to mechanical stokers, either by be- 
 ing shoveled by hand into hoppers in front of, and above 
 the grates, or, as is the case in most of the large plants 
 using them, it is elevated by machinery and deposited in 
 chutes, through which it is fed to each boiler by gravity. 
 Stokers of the chain grate variety are usually constructed 
 so that they may be withdrawn from underneath the boiler 
 in case repairs are necessary. The coal, either nut or 
 screenings, is fed into a hopper in front of and above the 
 
 yfcA Pit. 
 
 Fig. 79 
 playford stoker 
 
 level of the grate, and is. slowly carried along towards the 
 rear end. The ash drops from the grate as it passes over 
 the sprocket wheel at the rear. 
 
 Fig. 76 shows a battery of Babcock & Wilcox water-tube 
 boilers fitted with chain grate stokers. The buckets for 
 elevating the coal to bins overhead, from whence it is fed by 
 gravity to the stokers, are not shown. These buckets or 
 carriers may also be utilized for conveying the ashes from 
 the boiler-room. 
 

 Mechanical Stokers 
 
 203 
 
 Fi2\ 77 is a sectional view of a vertical Cahall boiler with 
 a Mansfield chain grate stoker, and Fig. 78 shows the same 
 stoker withdrawn from the boiler. 
 
 The Coxe mechanical stoker operates upon the same gen- 
 eral principles as do those previously described, being of 
 
 Fig. 80 
 vicars mechanical stoker 
 
 the chain grate type; but it has in addition a series of air 
 chambers just underneath the upper traveling grate. These 
 air chambers are made of sheet iron, and are open at the top 
 and provided with dampers for regulating the air pressure 
 for different sections of the grate. The air blast is sup- 
 
204 Steam Engineering 
 
 plied by a fan. Another feature of this stoker is a water 
 chamber for the bottom section of the grate to travel 
 through on its return. 
 
 The Play ford stoker has wrought iron T bars extending 
 across the furnace and attached to the traveling chains. 
 These T bars carry the small cast iron sections composing 
 the grate. A screw conveyor is also placed in the ash pit 
 for the purpose of carrying the ashes from the rear to the 
 front of the pit. Fig. 79 is a sectional view of the Playford 
 stoker attached to a water-tube boiler. 
 
 In class two may be included stokers having the grates in- 
 clined more or less. In some varieties the grates incline 
 from front to rear, while in others they are made to incline 
 from the side walls toward the center line of the furnace. 
 
 In the Vicars mechanical stoker the grate bars are some- 
 what of the shape of the ordinary grate, and lie in two tiers 
 in a horizontal position. The lower or back tier next the 
 bridge wall is stationary, and is placed there for the pur- 
 pose of catching what coal is carried over the ends of the 
 upper or moving grate bars. These have a slow reciprocat- 
 ing motion which gradually moves the hot coke back 
 towards the bridge wall. The coal is fed from a hopper 
 into two compartments, from which it is pushed by recipro- 
 cating plungers onto a coking plate and from thence it 
 passes to the grate bars. The motion of these bars has 
 several intermediate variations, from a state of rest to a 
 movement of Sy 2 inches. They have a simultaneous move- 
 ment forward by which the fuel is advanced, but on the 
 return movement the bars act at separate intervals. In this 
 manner the fuel remains undisturbed by the return motion 
 of the grates. Fig. 80 illustrates this stoker. 
 
Mechanical Stokers 
 
 205 
 
 Fig. 81 
 furnace view, wilkinson stoker 
 
 In the Wilkinson stoker, Fig. 81, the grate bars are hol- 
 low and are set at an angle of 20°, the inclination being 
 from front to back. Each bar is stepped along its fire 
 
206 
 
 Steam Engineering 
 
 surface, and on the rise is perforated with a long, narrow- 
 slot. A steam pipe extends along the front of the furnace, 
 
 Fig. 82 
 wilkinson stoker 
 
 and from this pipe small branch pipes lead into the ends 
 of the grate bars, which latter are in fact a series of hollow 
 trunks with their front ends open. When in operation a 
 
Mechanical Stokers 
 
 207 
 
 steam blast is admitted to each of the several trunk grate 
 bars through the small branch pipes, and this blast induces 
 an air current of more or less pressure, which finds an 
 outlet through the narrow slots in the stepped fire surface 
 of the grates, and directly into and through the burning 
 mass of fuel. A slow reciprocating motion is imparted to 
 the grates by means of cranks and links operated from an 
 
 Fig. 83 
 
 THE MURPHY AUTOMATIC FURNACE 
 
 overhead shaft; see Fig. 82. These cranks are set alternate- 
 ly at 90° with each other, thus giving a forward movement 
 to one-half of the grate bars, while at the same time the 
 other half is moving backward. In this manner the fuel 
 is kept slowly moving down the inclined grates. 
 
 The Murphy Automatic Furnace, a sectional view of 
 which is shown in Fig. 83, has the grates inclined inwards 
 from the side walls, while a fire brick arch is sprung fron? 
 
208 Steam Engineering 
 
 side to side to cover the entire length of the grate. The 
 coal is shoveled or fed by carrier into the coal magazines, 
 one on each side, as shown in the cut. If the furnace is 
 placed directly under the boiler it necessitates putting 
 these coal magazines within the side walls, but as the 
 Murphy furnace is usually constructed at the present day 
 as an outside furnace, the coal magazines are independent 
 of the boiler walls. 
 
 The bottom of each magazine is used as a coking plate, 
 against which the upper ends of the inclined grates rest. 
 On the central part of this plate is an inverted open box. 
 This is termed the "stoker box," and it is moved back and 
 forth across the face of the coking plate by means of a 
 shaft with pinions that mesh into racks under each end of 
 the box. By means of this motion of the stoker boxes the 
 coal is pushed forward to the edge of the coking plate and 
 from thence it slowly passes down over the inclined grates 
 toward the center of the furnace. At this point the slowly 
 rotating clinker breaker grinds the clinker and other refuse 
 and deposits them in the ash pit. 
 
 Above the coking plates are the "arch plates," upon 
 which the bases of the fire brick arch rest. These plates 
 are ribbed, the ribs being an inch apart, and, the arch rest- 
 ing upon these ribs, there is thus provided a series of air 
 ducts by means of which the air, already heated by having 
 been admitted in front and passed through the flues over 
 the arch, is conducted into the furnace above the grates 
 and comes directly in contact with the gases rising from 
 'the coking fuel. Air is also admitted under the coking 
 plate and, passing up through the grates, serves to keep 
 them cool and also furnishes the needed supply to the 
 burning coke as it slowly moves down toward the center. 
 
Mechanical Stokers 209 
 
 The fuel is aided in its downward movement by the con- 
 stant motion of the grates, one grate of each pair being 
 moved up and down by a rocker at the lower end. 
 
 Motion is imparted to the various moving parts of this 
 furnace by means of a reciprocating bar extending across 
 the outside of the entire front, and to which all the work- 
 ing parts are attached by links and levers. This bar is 
 operated by a small engine at one side of the setting, the 
 power required being about one horsepower per furnace. 
 
 Fig. 84 
 sectional perspective of the roney mechanical stoker 
 
 The Roney stoker consists of a set of rocking stepped 
 grate bars, inclined from the front toward the bridge wall. 
 The angle of inclination is 37°. A dumping grate oper- 
 ated by hand is at the bottom of the incline for the purpose 
 of receiving and discharging the clinker and ash. This 
 dumping grate is divided into sections for convenience in 
 handling. 
 
 The coal is fed onto the inclined grates from a hopper in 
 front. The grate bars rock through an arc of 30°, assum- 
 
210 Steam Engineering 
 
 ing alternately the stepped, and the inclined positions. Fig. 
 84 is a sectional perspective view of this stoker and illus- 
 trates the working parts. 
 
 The grate bars receive their motion through the medium 
 of a rocker bar and connecting rod. A shaft extending 
 across the front of the stoker under the coal hopper car- 
 ries an eccentric that gives motion to the connecting rod 
 and also to the pusher in the coal hopper. This pusher, 
 working back and forth, feeds the coal over the dead plates 
 onto the grates, and its range of motion is regulated by a 
 
 Fig. 85 
 
 feed wheel from no stroke, to full stroke, according to the 
 demand for coal. The motion of the grate bars may also 
 be regulated by a sheath nut working on a long thread on 
 the connecting rod. Each grate bar consists of two parts, 
 viz., a cast iron web fitted with trunnions on each end that 
 rest in seats in the side bearer, and a fuel plate having the 
 under side ribbed to allow a free circulation of air. 
 
 The fuel plate is bolted to the web and carries the fuel. 
 The grates lie in a horizontal position across the furnace 
 in the form of steps, and ample provision is made for the 
 
M e cli a n ica I Sto Jeers 
 
 211 
 
 admission of air through the slotted webs. A fire brick 
 arch is also sprung across the furnace, covering the upper 
 portion of the grate. 
 
 Fig. 86 
 new roney stoker as it appears in furnace 
 
 This arch, being heated to a high temperature, serves in 
 a measure to partly coke the coal as it passes under it. Air 
 is also admitted on top of the coal at the front. This air 
 
212 Steam Engineering 
 
 is heated by its passage through a perforated tile over the 
 dead plate and adjoining the fire brick arch. Fig. 85 
 shows the location of the arch and tile. 
 
 The Westinghouse Machine Company has recently de- 
 signed an improved model of the Eoney mechanical stoker. 
 Some of the most important features in connection with 
 its design is, that the number of complete grate bars has 
 been reduced one-half over that used with the old type of 
 stoker. The tops, webs, guards and dumping grates are 
 interchangeable. The grate bars automatically center 
 themselves in the side bearings by their own weight; they 
 may also be re-distributed so as to equalize wear over all 
 parts of the furnace. The guard and dumping grates are 
 interchangeable without disturbing the side or center bear- 
 ings. Fig. 86 shows the stoker as it appears in a furnace 
 setting. 
 
 For the upper four grates a non-sifting type of top is 
 used, provided with abutting, horizontal ledges to prevent 
 the fine fuel from sifting through the bars, and at the 
 same time permit a free entrance of the air. For each 
 square foot of grate exposed to the fire, 7.4 square feet of 
 surface is cooled by the air, giving 7.4 times the cooling 
 effect of the flat-top grate bar. 
 
 As will be seen from Fig. 87, the grate proper consists 
 of a number of thin plates set on edge in V-grooves. These 
 hook over a trussed web, and are held in place by a key- 
 rod slipped in from the end. They are, therefore, easily re- 
 moved. One of the principal advantages of the sectional 
 grate-bar tops is, that it reduces the amount of scrap when 
 they have been sufficiently worn to be discarded. In this 
 stoker no bolts are used, and any part can be removed 
 without disturbing the other. 
 
Mechanical Stohers 
 
 213 
 
 Fig. 87 
 
 roney stoker 
 
 Showing Construction of Grate 
 
214 Steam Engineering 
 
 The new type of guard prevents the fire from sliding into 
 the ash-pit when the dumping grate is operated. As the 
 lower end of the guard is now raised, instead of cutting 
 through the fire, as formerly, it not only makes it possible 
 to dislodge from the fire all clinker formed at the bottom, 
 but also provides an unobstructed descent for the ash and 
 clinker separately. When dropped to its normal position, 
 it permits the lower edge of the fire to settle quietly 
 without a tendency to slide. 
 
 The new dumping grate is hinged about one-third for- 
 ward, dumping both front and rear. Being nearly bal- 
 anced, it is very easily operated. The upward motion of 
 the dumping grate breaks up any clinker bridge tending 
 to form between the grates and bridge-wall. 
 
 In mechanical stokers of the under-feed type the air is 
 supplied by forced draft. 
 
 The American stoker consists of a horizontal conveyor 
 pipe into which the coal is fed from a hopper. The diam- 
 eter of this pipe depends upon the quantity of coal to be 
 burned, and varies from 4 1 /2 inches for the smaller sizes 
 up to 9 and 10 inches for the larger sized stokers. The 
 length of the conveyor pipe for the standard 10-inch stoker 
 is 72 inches. Attached to the outer end of this conveyor 
 pipe, and forming a part of it, is an iron box containing a 
 reciprocating steam motor, which, through the medium of 
 a rocker arm, and pawl and ratchet wheel, drives a screw 
 conveyor shaft that slowly revolves within the pipe, thus 
 forcing the coal forward and up through another box or 
 trough, which latter is wholly within the furnace. Extend- 
 ing around the top edges of this box, and on a level with 
 the grate bars, there is a series of tuveres through which 
 the air is forced. 
 
Mechanical Stokers 
 
 215 
 
 Fig. 88 
 typical setting of american stoker under a return tubular 
 
 BOILER 
 
 These tuyeres, being at a high temperature, serve to heat 
 the air in its passage through them, thus greatly aiding 
 combustion. Fig. 88 is a longitudinal sectional view of 
 this stoker. 
 
216 Steam Engineering 
 
 The speed of the screw conveyor is regulated by the hand 
 throttle of the motor, according to the demand for coal. 
 With the 9-inch standard stoker from 350 to 1,200 pounds 
 of coal per hour may be burned. Fig. 89 is a view of the 
 American stoker before being placed in position in the 
 furnace. 
 
 The air jets, passing out from the tuyeres in a horizontal 
 direction, and from opposite sides, cut through the rounded 
 bed of coal and the gases are thus ignited and consumed 
 immediately after being distilled from the coal, while the 
 pressure of the coal rising from underneath forces the al<- 
 ready coked fuel over the edges of the trough or box onto 
 the grates which occupy the space between the side walls 
 and the coal trough. The air is first delivered from the 
 fan into the air box that surrounds the coal trough on 
 three sides and from thence it passes to the tuyeres. If 
 this stoker is properly handled very good results may be 
 obtained by -its use, but, like all other devices for burning 
 coal under boilers, it is bad policy to endeavor to force it 
 beyond its capacity. 
 
 In the Jones under- feed stoker the coal is pushed for- 
 ward and up into the furnace through a cast iron retort or 
 trough. The impelling force is a steam ram connected to 
 the outer end of the retort, and the speed of the ram is 
 regulated automatically by the steam pressure, or by hand 
 as desired. The coal is supplied to the ram through a cast 
 iron hopper having a capacity of 125 to 140 pounds. 
 
 Force draft is also employed in this stoker, the air being 
 conducted from the fan or blower through galvanized iron 
 pipes into the closed ash pit, which really forms an air box, 
 as the space on either side of the retort that is usually 
 occupied by grate bars is in this case covered by solid cast 
 
Mechanical Stokers 
 
 217 
 
 Fig. 89 
 standard 8 and 9 inch american stokers 
 
 A — Coal hopper; B — Conveyor pipe; C — Tuyeres for intro- 
 ducing air to the fuel ; D — Opening to wind-box for air connec- 
 tions; E — Wind-box for supplying air to tuyeres ; K — Automatic 
 steam motor for driving conveyor ; R — Air pipe to wind-box ; 
 S — Gas ducts for returning volatile products from entering coal 
 to furnace. 
 
218 Steam Engineering 
 
 iron dead plates, upon which the coked fuel lies until it is 
 consumed. These plates, being hot, serve to heat the air 
 coming in contact with them in its passage to the cast iron 
 tuyeres through which it passes to the bed of burning fuel 
 in the retort. Air entirely surrounds the retort on the sides 
 and back end, and is at a constant pressure in the ash 
 pit, but can only pass into the furnace through the tuyeres, 
 the jets of air cutting through the rounded heap of in- 
 candescent fuel from opposite sides, and in a direction in- 
 clined upwards. 
 
 Fig. 90 
 
 Coal is supplied to the hopper either by hand, or by 
 mechanical means where the plant is fitted with coal- 
 handling machinery. The opening through which it passes 
 from the hopper to a position in front of the ram is 8x10 
 inches in size. Each charge of the steam ram carries for- 
 ward 15 to 20 pounds of coal. Connected to the ram, and 
 moving in conjunction with it is a long rod extending 
 through the retort near the bottom. Upon this rod are 
 carried shoes that act as auxiliary plungers and facilitate 
 the movement of the coal. 
 
 Fig. 90 is a sectional view of the Jones stoker, showing 
 the machine full of coal, with the ram readv to make a 
 
Mechanical Stokers 219 
 
 charge. Fig. 91 shows the stoker complete before being 
 placed in the furnace. 
 
 It is claimed by the builders of under-feed stokers, and 
 the claim appears to have good foundation, that by pushing 
 the green coal up, so as to meet the upper crust of glowing 
 fuel the gases on being distilled immediately come in con- 
 tact with, and are consumed by the burning mass, and the 
 formation of smoke is thus prevented. Both the Jones 
 under-feed, and the American stokers have proved to be 
 very successful in the burning of the cheaper bituminous 
 coals of the West. One feature tending to commend them 
 
 is the fact that practically all of the coal is utilized, there 
 being no waste caused by the slack coal or fine screenings 
 dropped through the grate bars into the ash pit uncon- 
 sumed. 
 
 A good substitute for the mechanical stoker is an outside 
 furnace, by which is meant a boiler installation having the 
 furnace in front of, instead of underneath the boiler. One 
 of the principal hindrances to good combustion in the ordi- 
 nary type of boiler furnace is the fact that the temperature 
 of the boiler shell or water tubes with which the gaseous 
 products of combustion come in contact can never be higher 
 than the temperature of the water contained within the 
 
220 Steam Engineering 
 
 boiler. This temperature ranges from 297° for steam at 
 50 pounds gauge pressure, up to 407° for 255 pounds 
 pressure, while the temperature of the furnace, according 
 to Dr. Thurston and other high authorities, ranges from 
 2,010° to 2,550°. 
 
 It is evident that perfect combustion does not take place 
 until these high temperatures are reached. Each time the 
 furnace is charged with fresh coal, especially if the boiler 
 be hand-fired, a large volume of volatile gases is liberated, 
 but not consumed. If these gases are allowed to immediate- 
 ly come in contact with a comparatively cool surface, as 
 for instance the heating surface of the boiler, the result is 
 a cooling, of the gases, incomplete combustion and the 
 formation of smoke and soot. If, on the other hand, the 
 furnace is so constructed that these gaseous products first 
 impinge against hot surfaces, such as fire brick arches or 
 bafflers that have a temperature corresponding to that of 
 the furnace, good combustion is assured. This condition 
 is in a large degree attained by the use of outside furnaces, 
 that permit the construction of a fire brick arch to cover 
 the entire grate surface. 
 
 The Burke furnace, patented by James V. Burke of 
 Chicago, is a notable example of this type of furnace. It is 
 applicable to any type of stationary boiler. Fig. 92 shows 
 this furnace as applied to tubular boilers. It consists of a 
 fire brick arch extending from 6 to 8 feet outwards from 
 the boiler front, and of a width to correspond to the diame- 
 ter of the boiler. The arch rests securely upon brick work 
 inclosed in a well ventilated iron casing. There is prac- 
 tically no heat radiated from this furnace, all the heat gen- 
 erated by it passing to the boiler. The central portion of 
 the grate bars consists of shaking grates, while the side bars 
 are stationary and inclined. 
 
Mechanical Stokers 
 
 221 
 
 Fig. 93 is a sectional view and will serve to illustrate 
 the construction of this furnace. The coal is fed through 
 pockets on top on each side of the arch, the larger furnaces 
 having two pockets on each side and the smaller sizes one. 
 
 Front View. 
 
 Fig. 92 
 
 burke furnace 
 
 The doors in front are only opened for the purpose of 
 cleaning fires, or when first starting fires. The air is sup- 
 plied by way of the ash pit, passing up through the grate 
 bars. A portion of the air supply is also drawn through 
 the ventilators and passes to the upper part of the furnace. 
 
222 
 
 Steam Engineering 
 
 The arch extends under the front end of the boiler 6 or 8 
 inches, and there is a bridge wall about 4 feet back from 
 the front, against which the gases from the furnace im- 
 pinge. 
 
 There are 42 square feet of grate surface in the larger 
 sizes, and 22 square feet in the smaller size. Good com- 
 bustion is attained in this furnace, owing to the fact that 
 the gases as they are distilled from the coal come imme- 
 
 
 Cfioss Sect/oh. 
 
 Fig. 93 
 burke furnace 
 
 diately in contact with the highly heated surface of the 
 arch directly over the fire. 
 
 Stoker selection and stoker installation furnish prob- 
 lems requiring a high order of mechanical skill, knowledge 
 of many details and freedom from bias and prejudice. 
 Each installation must be studied individually, and the size 
 and type of stoker and subsidiary details of grate, draft, 
 furnace, etc., determined only after an exhaustive consider- 
 
Mechanical Stokers 223 
 
 ation of all points. Thus and only thus may the highest 
 economy be realized, for it is economy primarily that must 
 be sought and secured in this day of keen competition, with 
 a smokeless stack as a secondary consideration. 
 
 It is a fact, well recognized by all students of boiler* fur- 
 nace combustion, that smoke suppression does not neces- 
 sarily mean fuel economy, while it is universally recog- 
 nized that when combustion is complete with fuel economy 
 at its highest, there can be no smoke. 
 
 The very considerable initial cost of installing mechan- 
 ical stokers may no longer be regarded as a species of 
 speculation, but as a sound investment that returns a 
 truly marvelous annual dividend. It is not overstating 
 the facts, as well recognized by progressive and studious 
 engineers that there is no other single piece of power plant 
 equipment that will pay a richer dividend on its cost than 
 a properly constructed, properly selected, properly installed 
 mechanical stoker. 
 
 It is totally impossible to duplicate the condition of a 
 stoker-fired furnace with one in which the coal is fed by 
 hand through the firedoor. 
 
 MECHANICAL DRAFT. 
 
 Application of mechanical draft assumes three general 
 forms : First, induced draft by the installation of fans 
 to serve as a chimney. Second, forced draft by applying 
 fans to force air beneath boiler grates. Third, the com- 
 bination of induced and forced draft, obtained by fans ap- 
 plied to serve both purposes, or by separate fans for each. 
 Many large plants are now installed where this combina- 
 tion is employed, the combined forced and induced draft 
 system being brought about on account of equipping the 
 
224 Steam Engineering 
 
 boilers with any make of stokers, outside of the chain type 
 or those having the open ash pit. Air, under a pressure 
 of one and one-fourth to two ounces, is delivered to the 
 stokers by a forced draft fan, the separate induced draft 
 fan, or fans being connected in the ordinary manner, with 
 the boiler breeching, with or without economizer in con- 
 nection, and discharge the gases through a steel stack into 
 the atmosphere. Under this class may also be included 
 the method of burning powdered fuel in suspension. The 
 practicability of the system has been thoroughly demon- 
 strated by tests extending over a number of months, but, 
 while the system has shown a marked degree of efficiency, 
 it has seldom been made use of in practice. The selection 
 of the proper type to render the highest economy, primarily 
 depends upon the fuel to be consumed, and the various 
 conditions of the steam plant to be outfitted. It is readily 
 seen that no single one of these three applications of me- 
 chanical draft will give the best results in all cases, but that 
 every boiler plant must be carefully treated individually. 
 Mechanical Induced Draft is by no means a new idea, 
 yet it is only within a few years that the same draft has 
 been much used or installed on a large scale. Previously 
 it had been used, with a few exceptions, for the purpose of 
 improving poor draft by helping out an insufficient or an 
 overloaded chimney. The largest and most successful ap- 
 plications of mechanically induced draft have been made 
 in connection with feed water heaters designed to utilize 
 the waste heat of the flue gases, and known as fuel econo- 
 mizers. This form of feed-water heaters has been manu- 
 factured in England for over fifty years. They have, how- 
 ever, been imported for many years, as their value as a fuel 
 saving device is well established. Their successful opera- 
 
Mechanical Draft 225 
 
 tion is so dependent upon good draft that no well-informed 
 engineer would think of installing an economizer without 
 making provision for much better draft than the boilers 
 would require without it. On account of the reducing ef- 
 fect on the draft, caused by lowering the temperature of 
 the gases and retarding their flow by the mechanical inter- 
 ference of the pipes, it cannot be considered good engineer- 
 ing to attach an economizer to a chimney less than 200 feet 
 in height. The best working economizers in connection 
 with chimneys are those where the chimney is considerably 
 over 200 feet high. 
 
 Forced Draft has been used for years, the original instal- 
 lations being principally for burning refuse materials, and 
 for assisting boiler draft of natural low efficiency. The 
 advancement to popular favor has been of healthy but grad- 
 ual growth. In the early stage it was commonly supposed 
 that what would now be called in mechanical draft a high 
 air pressure was absolutely essential to best results. As this 
 type of mechanical draft has developed, it is noticeable that 
 in succeeding representative plants, the velocity of air has 
 gradually decreased, until now it is generally recognized 
 that forced draft outfits show the best results where a suf- 
 ficient air volume is used at the lowest pressure which se- 
 cures complete combustion. Practice has established the 
 fact that this is more economical than using the same 
 quantity of air at double the velocity, because of less liabil- 
 ity to blow holes, less unconsumed particles carried up to 
 the stack, and less horse power consumed by the fan. 
 
 As is at once understood, the term "forced draft" used 
 in connection with a steam plant refers to the forcing of the 
 air under the grates. The favorite point of introduction 
 into most boilers is through the bridge wall at the rear end 
 
226 Steam Engineering 
 
 of the grates. Where this arrangement is not feasible, 
 however, quite as efficient results are obtained through side 
 walls, or further in front, using properly arranged dampers 
 with convenient accessories for manipulation. 
 
 Occasionally objections to forced draft are urged, on the 
 ground that with its use there is an outward leakage of 
 gases, and blow holes through boiler fires at different grate 
 intervals. Such results only occur with poor applications 
 and installation details, or with improper firing. The meth- 
 od of introduction of the air to the grates, and the appli- 
 ances therefor, figure conspicuously in the securing of max- 
 imum economy and efficiency. 
 
 Where the air supplied to the fan is taken from an air 
 chamber built around, or through the smoke breeching — 
 and herein is embodied an important saving — the tempera- 
 ture of the air supply, and consequently the temperature of 
 the furnace is raised w r hile the temperature of the gases in 
 the breeching is reduced. With natural draft this would 
 tend to reduce the velocity in the stack. It is highly de- 
 sirable that the fan be driven by an individual engine, with 
 the valve controlling the steam supply thereto equipped 
 with the special arrangement for governing the speed of 
 the engine, according to the draft requirements. In brief, 
 the principle of this consists of automatically supplying 
 more steam to the engine when the boiler pressure lowers, 
 and less steam when the steam pressure increases. This 
 has been brought to so fine a point that practically a con- 
 stant pressure is maintained on the boilers with proper 
 firing. 
 
 Direct advantages exist in favor of forced draft where 
 certain conditions exist. The chimney of a given steam 
 plant may be capable of handling the boilers, excepting un- 
 
1 
 
 Mechanical Draft 
 
 227j 
 
 Fig. 94 
 buffalo mechanical draft apparatus 
 Horizontal Tandem Fans— Casing and Economizer Partly Re- 
 moved to Show Damper 
 
 der adverse conditions of weather, when a blower properly 
 applied needs only .to be started and run during such pe- 
 riods. While the capacity of a chimney, either with forced 
 or natural draft, is limited, the natural efficiency may be 
 
 j 
 
228 
 
 Steam Engineering 
 
 materially increased, so that if more boilers have been 
 added than the chimney will properly handle without some 
 assistance, this may be afforded by the proper application 
 of a blower to force air into the ash-pit. 
 
 Fig. 94 shows part of a large steam plant equipped with 
 an induced draft apparatus supplied by the Buffalo Forge 
 
 Fig. 95 
 three-quarter housing steel plate fan with double hori- 
 zontal engine 
 
 Co., Buffalo, N. Y. A portion of the casing is removed in 
 order to show the location of the economizer. 
 
 Fig. 95 shows another style of fan having double hori- 
 zontal engines, one on each side of the crank shaft, which is 
 extended into the fan, and forms a direct-attached machine 
 by reason of the fan wheel being placed on the opposite end 
 of the shaft. But one of the engines is intended for use at 
 
Mechanical Draft 229 
 
 a time, the other rod being disconnected and held in reserve 
 in case of an accident, although the design is such that 
 both may be operated simultaneously, if desired. In the 
 construction of this engine, the desirable point of being able 
 to quickly change from the right to the left-hand engine, 
 or the reverse, at the same time keeping a perfect balance, 
 has been embodied. This feature is accomplished in the 
 following manner : The disc is made sufficiently heavy on 
 the side on which the pin is placed to counterbalance the 
 crank and connections when the left-hand engine connected 
 to the crank is in use. Then when the left-hand engine is 
 disconnected and the right-hand engine is connected up, 
 the pocket provided in the disc on the opposite side from 
 the pin is filled with shot, and the balance re-established for 
 the right-hand engine, when the left-hand engine is held in 
 reserve. The pocket in which the shot is placed is stopped 
 with a threaded plug inserted with a screw-driver and 
 makes a neat finish. It may be filled or emptied in a few 
 seconds' time. The crank shaft is of forged steel, of ample 
 proportions, which is a distinguishing feature of Buffalo 
 Steam Fans. Sufficient space is left between the crank and 
 the disc for the eccentric, and a bearing of ample wearing 
 proportions. The valves employed are of the piston type, 
 carefully fitted up with cages, and snap ring packing. They 
 are attached to the valve stem by a simple, efficient method, 
 which permits of the removal of the valve with the great- 
 est ease. Other general construction details are similar to 
 those found in the Buffalo center-crank engines. 
 
 The illustration shows a large fan in three-quarter steel 
 plate housing, the lower portion of the scroll being brick- 
 work, and is used for blowing a battery of stationary boiler 
 fires- 
 
230 Steam Engineering 
 
 Combined induced and forced draft applied to a bat- 
 tery of boilers is somewhat unusual, but the Buffalo Special 
 Steel Plate Fans have been thus employed with excellent 
 results. The combined system being employed because of 
 equipping the boilers with stokers, requiring a closed ash 
 pit. Certain special boilers are designed particularly for 
 induced and forced draft, and to these have applications 
 been made, with the result of obtaining more than a regular 
 amount of steaming capacity within a given space. Ordi- 
 nary boilers have also been thus outfitted with considerably 
 increased capacity. 
 
 The combination may be installed in two ways, as fol- 
 lows : First, with two separate fans, one an induction, and 
 the other an eduction fan. Second, with a single fan of 
 special construction, having a web or divided wheel and 
 two inlets, one to receive the intake of gases from the boiler 
 stack, and the other to receive fresh air, the amount handled 
 being regulated by an oscillating damper. The former 
 arrangement is necessitated for the special boiler construc- 
 tion alluded to, and is also applicable to large steam plants 
 with ordinary, water-tube, or tubular boilers with or without 
 equipments of economizers, and burning fuel of low grades. 
 The fan for forcing air under the grates is usually some- 
 what the smaller of the two. 
 
 The more simple plants of combined induced and forced 
 draft employ the one fan arrangement, which is built with 
 two inlets and takes in unheated air on one side. Connec- 
 tion, by means of a suitable pipe, is made with the chimney 
 flue or smoke breeching of the boiler to the other side of 
 the fan, thereby taking in the larger part of the flue gases. 
 These are mixed with the fresh air taken in from the other 
 side of the fan as it leaves the outlet and is being 
 
Mechanical Draft 231 
 
 delivered to the ash-pit of the furnaces. From thence the 
 air is forced through the grates to the fuel bed. Dampers 
 are used on each side to regulate the proportion of air and 
 flue gases admitted to the fan. Eecently published tests of 
 such apparatus using Buffalo Special Steel Plate Fans, 
 show an average temperature of the air discharged under 
 the grates of 235 degrees, and naturally a great gain in 
 efficiency over the same boilers without the device. 
 
 The importance of good draft, either natural or arti- 
 ficial, for supplying sufficient oxygen for the economical 
 combustion of fuel has long been recognized by intelligent 
 engineers. The gain, both in efficiency and capacity, ob- 
 tained by the rapid and energetic combustion of fuel, and 
 the resulting high furnace temperatures is well established. 
 Its importance has been generally conceded only within a 
 few years. To obtain this high furnace temperature re- 
 quires draft sufficiently strong to deliver an abundant sup- 
 ply of oxygen to the furnace. 
 
 CHIMNEYS. 
 
 Chimneys are required for two purposes — first, to carry 
 off obnoxious gases; second, to produce a draft, and so fa- 
 cilitate combustion. The first requires size, the second 
 height. 
 
 The weight of gas to be carried off by a chimney in a 
 given time depends upon three things — size of chimney, 
 velocity of flow, and density of gas. But as the density 
 decreases directly as the absolute temperature, while the 
 velocity increases, with a given height, nearly as the square 
 root of the temperature, it follows that there is a tempera- 
 ture at which the weight of gas delivered is a maximum. 
 This is about 550° above the surrounding air. Tempera- 
 
232 Steam Engineering 
 
 ture, however, makes so little difference, that at 550° 
 above, the quantity is only four per cent greater than at 
 300°. Therefore, height and area are the only elements 
 necessary to consider in an ordinary chimney. 
 
 The intensity of draft is, however, independent of the 
 size, and depends upon the difference in weight of the out- 
 side and inside columns' of air, which varies nearly as the 
 product of the height into the difference of temperature. 
 This is usually stated in an equivalent column of water, 
 and may vary from to possibly 2 inches. 
 
 After a height has been reached to product draft of suf- 
 ficient intensity to burn fine, hard coal, provided the area 
 of the chimney is large enough, there seems no good me- 
 chanical reason for adding further to the height, whatever 
 the size of the chimney required. Where cost is no consid- 
 eration, there is no objection to building as high as one 
 pleases; but for the purely utilitarian purposes of steam 
 making, equally good results might be attained with a 
 shorter chimney at much less cost. 
 
 The intensity of draft required varies with the kind and 
 condition of the fuel, and the thickness of the fires. Wood 
 requires the least, and anthracite screenings the most. The 
 strong draft required for burning the smaller sizes of an- 
 thracite coal necessitates a very tall chimney, unless forced 
 blast is used. 
 
 Generally a much less height than 100 feet cannot be 
 recommended for a boiler, as the lower grades of fuel can- 
 not be burned as they should be with a shorter chimney. 
 
 A round chimney is better than square, and a straight 
 flue better than a tapering, though it may be either larger 
 or smaller at the top without detriment. 
 
Chimneys 233 
 
 The effective area of a chimney for a given power varies 
 inversely as the square root of the height. The actual area, 
 in practice, should be greater, because of retardation of ve- 
 locity due to friction against the walls. On the basis that 
 this is equal to a layer of air two inches thick over the 
 whole interior surface, and that a commercial horsepower 
 requires the consumption on an average of 5 pounds of coal 
 per hour, we have the following formulas : 
 
 0.3 H 
 
 E= -— =A— 0.6 VA 1 
 
 H=3.33 E yX7 2 
 
 S=12 VE+4 3 
 
 D=13.54 VE+4 4 
 
 /0.3H 2 \ 
 
 n=l o 
 
 (Tj 
 
 in which H=horsepower ; h— .height of chimney in feet; 
 E=erfective area, and A=actual area in square feet; S= 
 side of square chimney, and D=dia. of round chimney in 
 inches. Table 15 is calculated by means of these formulas. 
 To find the draft of a given chimney in inches of water : 
 Divide 7.6 by the absolute temperature of the external air 
 ( TsL= t-\-Jf.60); divide 7.9 by the absolute temperature of 
 the gases in the chimney (T c =t'-\-460) ; subtract the latter 
 from the former, and multiply the remainder by the height 
 of the chimney in feet. This rule, expressed in a formula, 
 would be : 
 
 d=h 
 
 (*.6 7.9 \ 
 
234 Steam Engineering 
 
 To find the height of a chimney, to give a specific draft 
 power, expressed in inches of water: Proceed as above, 
 through the first two steps, then divide the given draft 
 power by the remainder, the result is the height in feet. 
 Or, by formula : 
 
 d 
 
 lr- 
 
 7.6 7.9 
 
 To find the maximum efficient draft for any given 
 chimney, the heated column being 600° F., and the ex- 
 ternal air 62° : Multiply the height above grate in feet by 
 .007, and the product is the draft power in inches of water. 
 
 The diagram, Fig. 96, shows the draft, in inches, of wa- 
 ter for a chimney 100 feet high, under different tempera- 
 tures, from 50° to 800° above external atmosphere, which 
 is assumed at 60°. The vertical scale is full size, and each 
 division is 1/20 of an inch. It also shows the relative 
 quantity, in pounds of air, which would be delivered, in the 
 same time, by a chimney under the same differences of 
 temperature. It will be seen that practically nothing can 
 be gained by carrying the temperature of the chimney 
 more than 350° above the external air at 60°. 
 
 To determine the quantity of air, in pounds, a given 
 chimney will deliver per hour, multiply the distance in 
 inches, at given temperature, on the diagram, Fig. 96, by 
 1,000 times the effective area in square feet, and by the 
 square root of the height in feet. This gives a maximum. 
 Friction in flues and furnace may reduce it greatly. 
 
 The external diameter of a brick chimney at the base 
 should be one-tenth the height, unless it be supported by 
 
Chimneys 
 
 235 
 
 some other structure. The "batter" or taper of a chim- 
 ney should be from y 1 ^ to 14 inch to the foot on each side. 
 
 \ 
 
 JIT 
 
 \ 
 M_ \ 
 
 -A 
 
 •t OC 
 
 ... JjlL 
 
 5 V 
 
 \ 
 
 
 i i 
 
 
 S 1 
 
 1 
 
 8 
 
 £ - -L 
 
 i'l tl 
 
 1 
 
 11 
 
 i .......... 
 
 I 
 
 8 " 
 
 'I 
 
 s - 
 
 8 
 
 | 
 
 \\ 
 
 8 " 
 
 s --- 
 
 ' 
 
 
 1 
 
 Fig. 96 
 
 Thickness of brick work: one brick (8 or 9 inches) for 
 25 feet from the top, increasing y 2 brick (4 or 4 1 /2 inches) 
 for each 25 feet from the top downwards. 
 
236 
 
 Steam Engineering 
 
 If the inside diameter exceed 5 feet the top length 
 should be 1% bricks, and if under 3 feet it may be Vo 
 brick for ten feet. 
 
 Table 14 
 
 theoretical draft pressure in inches of water in a 
 chimney 100 peet high. 
 
 (For other heights the draft varies directly as the height.) 
 
 Temp, 
 in 
 
 TEMP. OF EXTERNAL AIR. (Barometer 30 Inches.) 
 
 Chimney 
 Fahr. 
 
 0° 
 
 10° 
 
 20 Q 
 
 30° 
 
 40° 
 
 50° 
 
 60° 
 
 70° 
 
 80° 
 
 90* 
 
 100* 
 
 200° 
 
 220 
 
 240 
 
 260 
 
 280 
 
 300 
 
 320 
 
 340 
 
 360 
 
 380 
 
 400 
 
 420 
 
 440 
 
 460 
 
 480 
 
 500 
 
 .453 
 .488 
 .520 
 .555 
 .584 
 .611 
 .637 
 .662 
 .687 
 .710 
 .732 
 .753 
 .774 
 .793 
 .810 
 .829 
 
 .419 
 .453 
 
 .488 
 .528 
 .549 
 .576 
 .603 
 .638 
 .653 
 .676 
 .697 
 .718 
 .739 
 .758 
 .776 
 .791 
 
 .384 
 .419 
 .451 
 .484 
 .515 
 .541 
 .568' 
 .593 
 .618 
 .641 
 .662 
 .684 
 .705 
 .724 
 .741 
 .760 
 
 .353 
 
 .388 
 .421 
 .453 
 .482 
 .511 
 .538 
 .563 
 .588 
 .611 
 .632 
 .653 
 .674 
 .694 
 .710 
 .730 
 
 .321 
 .355 
 
 .388 
 .420 
 .451 
 .478 
 .505 
 .530 
 .555 
 .578 
 .598 
 .620 
 .641 
 .660 
 .678 
 .697 
 
 .292 
 .326 
 .359 
 .392 
 .422 
 .449 
 .476 
 .501 
 .526 
 .549 
 .570 
 .591 
 .612 
 .632 
 .649 
 .669 
 
 .263 
 
 .298 
 .330 
 .363 
 .394 
 .420 
 .447 
 .472 
 .497 
 .520 
 .541 
 .563 
 .584 
 .603 
 .620 
 .639 
 
 .234 
 .269 
 .301 
 .334 
 .365 
 .392 
 .419 
 .443 
 .468 
 .492 
 .513 
 .534 
 .555 
 .574 
 .591 
 .610 
 
 .209 
 .244 
 .276 
 .309 
 .340 
 .367 
 .394 
 .419 
 .444 
 .467 
 .488 
 .509 
 .530 
 .549 
 .566 
 .586 
 
 .182 
 .217 
 .250 
 .282 
 .313 
 .340 
 .367 
 .392 
 .417 
 .440 
 .461 
 .482 
 .503 
 .522 
 .540 
 .559 
 
 .157 
 .192 
 .225 
 .257 
 .288 
 .315 
 .342 
 .367 
 .392 
 .415 
 .436 
 .457 
 .478 
 .497 
 .515 
 .534 
 
 The available draft will be the tabular values, less the 
 amount consumed by friction in the stack. In stacks 
 whose diameter is determined by the formulae, the net draft 
 will be 80% of the tabular values. Hence to obtain from 
 the table the height of stack necessary to produce a net 
 draft of say 0.6 inches, the theoretical draft will be 0.6 X 
 1.25=0.75 inches, which can be got with a stack 100 feet 
 high with flue-gas temperature of 420° F., and air temper- 
 ature of 0° F., or a stack 125 feet high when the air tem- 
 perature is 60° F. 
 
Chimneys 
 
 237 
 
 * 00 00 i I - — O O BO BO X rl'lO^ On 4^ *- 00 CO 00 00 to to to M 
 
 * x to oo co 4-^ x to oo o 4-^ x to oo o >+-■ x to ;c oo oo oo — 1 4- i-i oc 
 
 CJlWKH as oo oo ~1 00 li • 
 
 -^ 05 Otrf^ CO K3 IO I-* M M • 
 
 CO 01 00 10 00 J- C ~1 4 
 
 to oooo-ao CHQoeoMCO" 
 
 c« to m bo x oo on J- oo ' ' t o ^ • 
 
 oo ■+- oo cr oo oo oo — 4~ o» >— x • 
 -q j> oo on o« 4- o< bo x oc bo to • 
 
 04^1: O 00 -J UI ^ oo to ■ 
 oa o« i^ oc cj x oo to on ^ • 
 
 rf^MCO-Jrf^tO^CO-qOOCHCO' 
 
 ClB04^l0B0B0O00-gC0O0C' 
 COlOO0©O04^-vl4*C5tO0CCO- 
 
 4- oc oo oo to to ro to i-* m m i~i m- 
 
 00 © 05 00 CO OS 4 ' X 08 4- to O 00 CO On • 
 
 0( 0O 4- O BO X O OO -1 00 rJ M 1 4- BO On ■ 
 -1 r- tc X O -HO OO OO 00 X 10 OO BO 10 M • 
 
 4^ 4> 00 00 00 to I o to to -i t-i M Hi 
 
 -1 OO BO 01 tO 00 On 00 C -1 01 00 ^ BO -1 • 
 
 ^h^0^00O004>00-3o^O0T<XX- 
 
 OX J> 4> 00 00 00 to to tO I- 1 M ^ 1- 1 
 
 O OO I O X 4- O -1 4- *-* X OO 4^ i-k BO • 
 
 :; o o i; oi o-i o. o o :: c x x • 
 
 — X 01 C 10 OC oo to -10O-1 O H- h-i. 
 
 10 1 M M C BO BO BO X X -1 -1 OO On 01 4- 4- OO 00 OO 00 tO to tO I- 1 h-i 
 -110 -1 tO 05 i-i 00 O OO O On O 4~ BO 4^ X 'OO X Ol tO O -1 J> to BO 00 
 
 Ml-i \ 
 
 M O OO X -q -1 OO OH OT J> 00 OO tO tO M i-i »-* 
 
 wwwpoopwpp^xcoxwpwtoppo^oi^wwtOM 
 m bo © on on bo bo -i to m 4^ m to -t bo bo con bo oo b oo 'oo o U 'o> ^q 
 
 OOOOOB04AXtOCn^XXX^004>0-5tOO-q^t-^oo4>(-'-q 
 
 Diameter 
 in Inches. 
 
 8 2 
 
 ►h X 71 
 
 &1 I 
 
 0^>? 
 
 2. w n> c 
 
 N 
 
 w 
 
 75 
 
 o 
 
 3 
 
 72 
 
 /row Chimneys. In many places iron stacks are pre- 
 ferred to brick chimneys. Iron stacks require to be kept 
 
238 Steam Engineering 
 
 well painted to prevent rust, and generally, where not 
 bolted down, they need to be braced by rods or wires to 
 surrounding objects. With four such braces attached to an 
 angle iron ring at 2/3 the height of stack, and spreading 
 laterally at least an equal distance, each brace should have 
 an area in square inches equal to .001 the exposed area of 
 stack (diam. X height) in feet. 
 
 Stability, or power to withstand the overturning force 
 of the highest winds, requires a proportionate relation be- 
 tween the weight, height, breadth of base, and exposed 
 area of the chimney. This relation is expressed in the 
 equation 
 
 dh 2 
 C =W, 
 
 b 
 
 in which d=the average breadth of the shaft ; h=its height ; 
 b=the breadth of base, — all in feet; W=weight of chim- 
 ney in pounds, and C=a co-efficient of wind pressure per 
 square foot of area. This varies with the cross-section of 
 the chimney, and=56 for a square, 35 for an octagon, and 
 28 for a round chimney. Thus a square chimney of aver- 
 age breadth of 8 feet, 10 feet wide at base and 100 feet 
 high, would require to weigh 56X8X100X10=448,000 
 pounds to withstand any gale likely to be experienced. 
 Brickwork weighs from 100 to 130 pounds per cubic foot, 
 hence such a chimney must average 13 inches thick to be 
 safe. A round stack could weigh half as much, or have 
 less base. 
 
 Pure Air is a mixture of oxj^gen and nitrogen in follow- 
 ing proportions: by volume 20.91 parts oxygen to 79.09 
 parts nitrogen; by weight 23.15 parts oxygen to 76.85 parts 
 nitrogen. Air in nature always contains other constituents 
 
Chimneys 239 
 
 such as dust, carbon dioxide, ammonia, ozone and water 
 vapor. 
 
 Air being perfectly elastic, the density of the atmos- 
 phere decreases in geometrical ratio with the altitude. This 
 fact has an important bearing on proportions of furnaces 
 and stacks located in high altitudes, as will later appear. 
 The atmospheric pressure for different altitudes is given 
 in Table 23. 
 
 WEIGHT AXD VOLUME OF AIR. 
 
 A cubic foot of air at 60° and under average atmos- 
 pheric pressure, at sea level, weighs 536 grains, and 13.06 
 cubic feet weigh one pound. Air expands or contracts an 
 equal amount with each degree of variation in tempera- 
 ture. Its weight and volume at any temperature # under 
 30 inches of barometer may be found within less than one- 
 half of one per cent by the following formula, in which 
 W= weight in pounds of one cubic foot, Y= volume in 
 cubic feet, per pound, and T=absolute temperature, or 
 460° added to that by the thermometer, =t+460. 
 
 40 r 
 
 r 40 
 
 Eor any condition of pressure and temperature the fol- 
 lowing formulas are very nearly exact: 
 
 V r 
 
 W=2.71— V= t=2.1!lVp— 460 
 
 r 2.71p 
 
 in which p is pressure above absolute vacuum. The same 
 formulae answer for any other gas by changing the co- 
 efficient. 
 
240 Steam Engineering 
 
 Table 16 
 
 VOLUME AND WEIGHT OF AIR AT VARIOUS TEMPERA- 
 TURES, AND ATMOSPHERIC PRESSURE. 
 
 Weight of one 
 Cu. Ft. in Lbs. 
 
 .077884 
 .077133 
 .076400 
 .075667 
 .074950 
 .074260 
 .073565 
 .072894 
 .072230 
 .071580 
 .070942 
 .069698 
 .068500 
 .067342 
 .066221 
 .065140 
 .064088 
 .063072 
 .062090 
 .061134 
 .060210 
 .059313 
 .059135 
 .058442 
 .057596 
 .056774 
 .055975 
 .055200 
 .054444 
 .053710 
 ,052994 
 .052297 
 .050959 
 .049686 
 .048476 
 .047323 
 .046223 
 .044920 
 .043686 
 .042520 
 .041414 
 .040364 
 .039365 
 .038415 
 .037510 
 .035822 
 .034280 
 • .032865 
 
 Temperature in 
 
 Volume of one 
 
 Degrees Fahr. 
 
 Pound Cu. Ft. 
 
 50 
 
 12.840 
 
 55 
 
 12.964 
 
 60 
 
 13.090 
 
 65 
 
 13.216 
 
 70 
 
 13.342 
 
 75 
 
 13.467 
 
 80 
 
 13.593 
 
 85 
 
 13.718 
 
 90 
 
 13.845 
 
 95 
 
 13.970 
 
 100 
 
 14.096 
 
 110 
 
 14.346 
 
 120 
 
 14.598 
 
 130 
 
 14.849 ' 
 
 140 
 
 15.100 
 
 150 
 
 15.352 
 
 160 
 
 15.603 
 
 170 
 
 15.854 
 
 180 
 
 16.106 
 
 190 
 
 16.357 
 
 200 
 
 16.606 
 
 210 
 
 16.860 
 
 212 
 
 16.910 
 
 220 
 
 17.111 
 
 230 
 
 17.362 
 
 240 
 
 17.612 
 
 250 
 
 17.865 
 
 260 
 
 18.116 
 
 270 
 
 18.367 
 
 280 
 
 18.621 
 
 290 
 
 18.870 
 
 300 
 
 19.121 
 
 320 
 
 19.624 
 
 340 
 
 20.126 
 
 360 
 
 20.630 
 
 380 
 
 21.131 
 
 400 
 
 21.634 
 
 425 
 
 22.262 
 
 450 
 
 22.890 
 
 475 
 
 23.518 
 
 500 
 
 24.146 
 
 525 
 
 24.775 
 
 550 
 
 25.403 
 
 575 
 
 26.031 
 
 600 
 
 26.659 
 
 650 
 
 27.913 
 
 700 
 
 29.172 
 
 750 
 
 30.428 
 
Questions and Answers 241 
 
 QUESTIONS AXD ANSWERS. 
 
 161. Is a feed water heater an economical factor in the 
 equipment of a boiler plant? 
 
 Ans. It certainly is, provided exhaust steam is used for 
 heating. 
 
 162. How many kinds of exhaust heaters are there? 
 Ans. Two, viz. : Open, and closed. 
 
 163. Describe in brief terms the action of a so-called 
 open heater. 
 
 Ans. The exhaust steam mingles directly with the 
 water, and a portion of it is condensed. 
 
 164. Describe the operation of a closed heater. 
 
 Ans. The exhaust steam and the water are kept sep- 
 arate. In some cases the steam passes through tubes that 
 are surrounded by water, and in other types the water 
 fills the tubes that are surrounded by steam. 
 
 165. What difference exists between the two kinds of 
 heater ? 
 
 Ans. The closed heater is under full boiler pressure 
 when the feed pump is working, while the open heater is 
 not because the feed pump is between it and the boiler. 
 
 166. What per cent of saving in fuel may be effected 
 by the use of a heater? 
 
 Ans. From 12 to 15 per cent. 
 
 167. Of what capacity should a feed water heater be, 
 relative to the boilers ? 
 
 Ans. It should have capacit)^ sufficient to supply the 
 boilers for 15 or 20 minutes. 
 
 168. Can the exhaust injector be used for feeding 
 boilers. 
 
 Ans. It can if the boiler pressure does not exceed 75 
 pounds. 
 
242 Steam Engineering 
 
 169. What advantages are gained by the use of mechan- 
 ical stokers? 
 
 Ans. Kegulation of the supply of fuel to meet the de- 
 mand for steam; also the opening and closing of furnace 
 doors is avoided. 
 
 170. What are the disadvantages attending the use of 
 mechanical stokers? 
 
 Ans. First, cost of installation. Second, in case of a 
 sudden demand for steam the mechanical stoker cannot re- 
 spond as quickly as in hand firing. Third, extra cost for 
 power to operate them. 
 
 171. Into how many classes are mechanical stokers 
 grouped ? 
 
 Ans. Four. 
 
 172. Enumerate, and briefly describe. 
 
 Ans. Class one — An endless chain of short grate bars 
 that travel horizontally over sprocket wheels. 
 
 Class two — Grate bars similar to the ordinary type hav- 
 ing a continuous motion up and down, or forward and 
 back, the bars being either horizontal or slightly inclined. 
 
 Class three — Grate bars steeply inclined and having a 
 slow motion. 
 
 Class four — Under feed stoker in which the coal is pushed 
 up onto the grate by means of a revolving screw, or steam 
 ram. 
 
 173. In what three forms is mechanical draft used for 
 boiler. 
 
 Ans. First — Induced draft. 
 
 Second — Forced draft, in which fans force air beneath 
 the grates. 
 
Questions and Answers 243 
 
 Third — A combination of induced and forced draft. 
 
 174. Is a good draft necessary for the efficient opera- 
 tion of steam boilers? 
 
 Ans. It certainly is. The economical combustion of 
 fuel cannot be accomplished without a good draft. 
 
 175. For what two purposes are chimneys required? 
 Ans. First, to carry off obnoxious gases. Second, to 
 
 create sufficient draft for the combustion of the fuel. 
 
 176. What factor governs the intensity of the draft, 
 independent of the dimensions of the chimney? 
 
 Ans. The difference in weight of the outside and in- 
 side columns of air. 
 
 177. What is the best shape of chimney? 
 Ans. Bound, with a straight flue. 
 
 178. What is the weight, and volume of air at a tem- 
 perature of 60°, and under average atmospheric pressure 
 at sea level? 
 
 Ans. One cubic foot weighs 536 grains, and 13.06 cubic 
 feet weigh one pound. 
 
r 
 
Care and Operation of Boilers 
 
 Duties. The first act of the engineer on entering his 
 boiler-room when he goes on duty should be to ascertain 
 the exact height of the water in his boilers. This he can 
 do by opening the valve in the drain pipe of the water 
 column, allowing it to blow out freely for a few seconds, 
 then close it tight and allow the water to settle back in 
 the glass. This should be done with each boiler under 
 steam, not only once, but several times during the day. 
 ]STo engineer should be satisfied with a general squint along 
 the line of gauge glasses, but he should either go himself, 
 or else instruct his fireman, or water tender to make the 
 rounds of each boiler and be sure that the water is all right. 
 
 The instructions regarding the cleaning of fires, and 
 firing, refer particularly to hand fired boilers. Mechani- 
 cal stokers will be taken up in their regular order. 
 
 The next thing to be looked after is the fire. If the 
 plant is run continuously day and night it is the duty 
 of the firemen coming off watch to have the fires clean, 
 the ash pits all cleaned out, a good supply of coal on the 
 floor, and everything in good order for the oncoming force. 
 A good fireman will take pride in always leaving things in 
 neat shape for the man who is to relieve him. 
 
 Cleaning Fires. With some varieties of coal this is a 
 comparatively easy task, especially if the boilers are fitted 
 with shaking grates. With a coal that does not form a 
 clinker on the grate bars, the fires can be kept in good 
 condition by cleaning them twice or three times in twenty- 
 
 245 
 
246 Steam Engineering 
 
 four hours, as the larger part of the loose ashes and non- 
 combu&tible can be gotten rid of by shaking the grates 
 and using the slice bar at intervals more or less frequent; 
 but such coals are generally considered too expensive to use 
 in the ordinary manufacturing plant, and cheaper grades 
 are substituted. 
 
 Fire Tools. For cleaning fires successfully and quickly, 
 the following tools should be provided; a slice bar, a fire 
 hook, a heavy iron or steel hoe, and a light hoe for clean- 
 ing the ash-pit. It is unnecessary to describe these tools, 
 as they are familiar to all engineers. A suggestion as to 
 the kind of handles with which they should be fitted may be 
 of benefit. The working ends of the aforesaid tools having 
 been made and each welded to a bar of 1 or 1% inch round 
 iron and 10 or 12 inches long, take pieces of 1 or 1%- inch 
 iron pipe cut to the length desired for the handles and weld 
 the shanks of the tools to them. To the other end of the 
 pipe weld a handle made of round iron somewhat smaller 
 than the shank. By using pipe handles the weight of the 
 tools is considerably lessened, and they will still be suffi- 
 ciently strong. The labor of cleaning the fire will thus be 
 greatly lightened. When a fire shows signs of being foul 
 and choked with clinker, preparations should be made at 
 once for cleaning it by allowing one side to burn down as 
 low as possible, putting fresh coal on the other side alone. 
 When the first side has burned as low as it can without 
 danger of letting the steam pressure fall too much, take the 
 slice bar and run it in along the side of the furnace on 
 top of the clinker and back to near the bridge wall, then 
 using the door jamb as a fulcrum, give it a quick strong 
 sweep across the fire and the greater part of the live coals 
 will be pushed over to the other side. What remains of 
 
Care and Operation of Boilers 247 
 
 the coal not yet consumed can be pulled out upon the floor 
 with the light hoe and shoveled to one side, to be thrown 
 back into the furnace after the clinker is taken out. Hav- 
 ing now disposed of the live coal, take the slice bar and 
 run it along on top of the grates, loosening and breaking 
 up the clinker thoroughly, after which take the heavy hoe 
 and pull it all out on the floor. A helper should be ready 
 with a pail of water, or, w^hat is still better, a small rubber 
 hose connected to a cold water pipe running along the 
 boiler fronts for this purpose, and put on just enough 
 water to quench the intense heat of the red hot clinker as it 
 lies on the floor. When the grates are cleaned, close the 
 door, and with the slice bar in the other side push all the 
 live coal over to the side just cleaned, where it should be 
 leveled off and fresh coal added. After this has become 
 ignited, treat the other side in the same way. An expert 
 fireman will thus clean a fire with very little loss in steam 
 pressure, and practically no waste of coal. 
 
 Disposal of the Ashes. The problem of disposing of the 
 ashes in large power plants is quite a serious one, and any 
 device that tends to lessen the cost of labor, and shorten the 
 time consumed in conveying the ashes from the boiler 
 room certainly merits the attention of chief engineers. 
 
 The suction confeyor system of the Darley Engineering 
 Company, Chicago, a general view of which is shown in 
 Fig. 97, consists essentially of four parts, as follows: 
 
 1. Conveyor Pipe. 
 
 2. Separator. 
 
 3. Exhauster. 
 
 4. Water Jet. 
 
 The conveyor pipe line is made in three sizes and ca- 
 pacities, namely, 6", 8" and 10", of iron or steel pipe. The 
 
248 
 
 Steam Engineering 
 
 Fig. 97 
 
 diagram showing a complete suction conveyor system as 
 
 applied to handling ashes from boilers 
 
 conveyor pipe, as far as possible, is run in straight lines. 
 It is generally placed beneath the surface, but can be ele- 
 vated or run anywhere to suit conditions. 
 
Care and Operation of Boilers 
 
 249 
 
 The separator, which is in reality an expansion cham- 
 ber, also serves as a storage tank for storing the conveyed 
 material. This separator is always placed at the end of 
 the conveyor run. It serves to catch the material conveyed 
 and hold it until it can be drawn (by gravity through an 
 
 Fig. OS 
 
 ASH CONVEYOR EXHAUSTER SET DRIVEN BY STEAM TURBINE 
 
 under-cut gate) into cars, carts or barges. This separator 
 is located in the most convenient position for the purpose. 
 The separator can be made any size, to hold any predeterm- 
 ined amount of material, or for a time run of the conveyor 
 of any fixed duration. These separators can also be mount- 
 ed over bins or bunkers of large or small size, if such addi- 
 
250 
 
 Steam Engineering 
 
 tional bin storage capacity is required. Separators are gen- 
 erally built of cylindrical form and of steel plate construc- 
 tion with a cone top and bottom. For certain work and on 
 small sized plants, they can be made rectangular, or of an 
 irregular shape. They can also be made of concrete, either 
 square or round, with small cone top of steel plate. They 
 are always made water tight. 
 
 Fig. 99 
 ash conveyor — exhauster set driven by induction motor 
 
 The Exhauster (Figs. 98 and 99) consists essentially of 
 a rotating impeller, surrounded by a suitable case, with an 
 intake air opening at the center, and a discharge opening 
 at the circumference. In appearance, it is similar to the 
 centrifugal pump. The efficiency depends largely upon 
 the design of the impeller and casing, and on the proper 
 shaping of these parts. In actual practice some conditions 
 call for other types. For instance, for a small, simple lay 
 
 v. 
 
Care and Operation of Boilerj 251 
 
 out, an ordinary exhaust fan can be used, whereas for cer- 
 tain complicated and extensive work, a cycloidal blower is 
 best adapted for the purpose. It can be either steam, or 
 motor driven for alternating or direct current. These ma- 
 chines are ' very strong in construction, and will operate 
 under adverse conditions with a very low cost for main- 
 tenance, and are especially suitable for this class of work. 
 
 Just before entering the separator, the conveyed mate- 
 rial passes through a water jet, located in the conveyor 
 pipe. This jet is composed of %" holes, spaced 1" cen- 
 ters, and serves two purposes, viz., it takes the heat out 
 of the hot material, such as ashes, etc., and eliminates all 
 dust when the material is dusty. In this way all dust is 
 kept out of the exhauster. 
 
 In the case of an ashes conveyor, the intakes are placed 
 in front of the ash pits of the boilers, or at any other de- 
 sired place, and the ashes are hoed or shoveled from the 
 ash pits into these intakes, whence they disappear through 
 the pipe line at a higher velocity. The conveyor pipe line 
 will take them away as fast as they are fed to the intakes. 
 When not in use, a cast iron cover is placed over these 
 intakes. These covers are lifted off when material is to be 
 fed to the conveyor. 
 
 The size of the intake opening is slightly smaller in diam- 
 eter than that of the pipe line, so that any piece of material 
 that passes the intake opening will be conveyed freely 
 through the conveyor pipe. 
 
 As the hardest wear comes on the elbows, a patented 
 split elbow is used, having an interchangeable wearing back, 
 about 3" thick, made of hard iron. These wearing backs 
 will last from 10 to 18 months, and are quickly replaced 
 when worn out, and can be replaced without interfering 
 
252 
 
 Steam Engineering 
 
 with the working of the conveyor, and at trifling cost. 
 Patented fittings with interchangeable wearing back are 
 also used when required. 
 
 Owing to the higher velocity of the air in the central 
 portion of the pipe, the tendency is to convey the material 
 in suspension in the center of the pipe. That this is a fact 
 
 Fig. 100 
 exhauster set driven by direct current motor 
 
 can be readily seen on looking into a conveyor pipe in 
 operation. 
 
 This fact prevents serious wear on the pipe, and from 
 observation of plants in use up to two and one-half years, 
 shows that an ordinary steel pipe, handling ashes, will last 
 for years. 
 
 No material comes in contact with any moving part of 
 this conveyor, and it is dustless in operation. These facts 
 
Care and Operation of Boilers 253 
 
 should appeal to engineers, especially those who have had 
 experience with mechanical conveyors in handling ashes. 
 
 There is absolutely no corrosion of the conveyor pipe, 
 as the great rush of air through the pipe keeps same per- 
 fectly dry under all conditions. 
 
 The following table gives capacities, etc. : 
 with convenient accessories for manipulation. 
 
 Size of Capacity 
 
 Conveyor. per minute. 
 
 6" 200 lbs. 
 
 8" 300 lbs. 
 
 1CT 500 lbs. 
 
 Firing. ISTo definite set of rules for hand firing can be 
 laid down that will be suitable for all steam plants, or for 
 the many different kinds of coal used. Some kinds of coal 
 need very little stirring or slicing, while others that have 
 a tendency to coke, and form a crust on top of the fire need 
 to be sliced quite often. 
 
 Every engineer, if he is at all observant, should be able 
 to judge for himself as to the best method of treating the 
 coal he is using, so as to get the most economical results. A 
 few general maxims may be laid down. First, keep a clean 
 fire; second, see that every square inch of grate surface is 
 covered with a good live fire ; third, keep a level fire, don't 
 allow hills and valleys, and yawning chasms to form in the 
 furnace, but keep the fire level; fourth, when cleaning the 
 fire always be sure to clean all the clinkers and dead ashes 
 away from the back end of the grates at the bridge wall, 
 in order that the air may have a free passage through the 
 grate bars, because this is one of the best points in the fur- 
 nace for securing good combustion, provided the bridge 
 wall is kept clean from the grates up. 
 
254 Steam Engineering 
 
 By keeping the back ends of the grate bars and the face 
 of the bridge wall clean, the air is permitted to come in 
 contact with the hot fire brick, and thus one of the greatest 
 aids to good combustion is utilized. Don't allow the fire 
 to become so deep and heavy that the air cannot pass up 
 through it, because without a good supply of air good com- 
 bustion is impossible. When the chimney draft is good the 
 quality of cold air admitted underneath the grate bars may 
 be easily regulated by leaving the ash-pit doors partly open. 
 
 The amount of opening required can be ascertained by a 
 little experimenting and depends upon the intensity of 
 the draft, and the condition of the fire. With a clean, light 
 fire, and the air spaces in the gates free from dead ashes, a 
 slight opening of the ash-pit doors will suffice to admit all 
 the air required beneath the grates. But if the fire is 
 heavy and the grates are clogged, a larger opening will be 
 necessary. In firing bituminous coal containing a large 
 percentage of volatile (light or gaseous matter), the best 
 results can be obtained by leaving the fire doors slightly 
 open for a few seconds immediately aftei throwing in a 
 fresh fire. The reason for doing this is that the volatile 
 matter in the coal flashes into flame the instant it comes 
 in contact with the heat of the furnace, and if a sufficient 
 supply of oxygen is not present just at this particular time 
 the combustion will be imperfect, and the result will be 
 the formation of carbon monoxide or carbonic oxide gas, 
 and the loss of about two-thirds of the heat units contained 
 in the coal. This loss can be guarded against in a great 
 measure by a sufficient volume of air, either through the 
 fire doors directly after putting in a fresh fire, or what is 
 still better, providing air ducts through the bridge wall or 
 side walls which will bring the air in on top of the firs. 
 
Care and Operation of Boilers 255 
 
 Each pound of coal requires for its complete combustion 
 12 pounds, or about 150 cubic feet of air, and the largest 
 volume of air is needed just after fresh coal has been added 
 to the fire. 
 
 Cleanliness. In order to get the best results, great care 
 should be taken that the tubes be kept clean and free from 
 soot. Especially does this apply to horizontal return tubu- 
 lar boilers, for the reason that when the tubes become 
 clogged with soot the efficiency of the draft is destroyed, 
 and the steaming capacity of the boiler is greatly reduced. 
 Soot not only stops the draft, but it is a non-conductor of 
 heat. In some batteries of boilers where an inferior grade 
 of coal is used and the draft is poor, it is absolutely neces- 
 sary to scrape or blow the tubes at least once a day in order 
 to enable the boilers to generate sufficient steam. 
 
 As to the process of cleaning there are various devices on 
 the market, both for blowing the soot out by means of a 
 steam jet and also for scraping the inside of the tubes. 
 The steam jet, if properly made and used with a high 
 pressure and dry steam, does very satisfactory work, but 
 is should not be depended upon exclusively to keep the 
 tubes clean, because in process of time a scale will form in- 
 side the tubes that nothing but a good scraper will remove. 
 For that reason it is good practice to use the scraper two 
 or three times a week at least. When the boiler is cooled 
 down for washing out, the bottom of the shell should be 
 cleaned of all accumulations of dust and ashes, the com- 
 bustion chamber, back of the bridge wall cleaned out, and 
 the back flue sheet or head swept off and examined, and if 
 there is a fusible plug in the back head the scale should be 
 scraped from it, both inside and outside the boiler, because 
 if it is covered with scale, neither the water, nor the heat 
 can come in contact with it, and it will be non-effective. 
 
256 Steam Engineering 
 
 Washing Out. The length of time that a boiler can be 
 run safely and economically after having been washed out 
 depends upon the nature of the feed water. If the water 
 is impregnated to a considerable extent with scale forming 
 matter, the boiler should be washed out every two weeks 
 at the least, and in some cases of particularly bad water it 
 becomes necessary to shorten the time to one week. To 
 prepare a boiler for washing the fire should be allowed to 
 burn as low as possible and then be pulled out of the 
 furnace, the furnace doors left slightly ajar, and the damper 
 left wide open in order that the walls may gradually cool. 
 It is as bad a practice to cool a boiler off too suddenly as 
 it is to fire it up too quick, because the sudden change of 
 temperature either way has an injurious effect on the seams, 
 contracting or expanding the plates, according as it is 
 cooled or warmed, and thus creating leaks and very often 
 small cracks radiating from the rivet holes, and becoming 
 larger with each change of temperature, until finally the 
 strength of the steam is destroyed and rupture takes place. 
 After the boiler has become comparatively cool and there is 
 no pressure indicated by the steam gauge the blow off cock 
 may be opened and the water allowed to run out. The 
 gauge cocks, and also the drip to the water column should 
 be left open to allow the air to enter and displace the water. 
 Otherwise there will be a partial vacuum formed in the 
 boiler and the water will not run out freely. 
 
 A boiler should not be blown out, that is, emptied of 
 water while under pressure. The sudden change of tem- 
 perature is sure to have a bad effect upon the sheets and 
 seams. Suppose for instance that all the water is blown 
 out of a boiler under a pressure of 20 pounds by the steam 
 gauge. The temperature of steam at 20 pounds is 260° F., 
 
Care and Operation of Boilers 257 
 
 and it may be assumed that the metal of the boiler is at or 
 near that temperature also. Assume the temperature of 
 the atmosphere in the boiler-room to be 60° F. There will 
 then be a range of 260°— 60°=200° temperature for the 
 boiler to pass through within a short time, which will cer- 
 tainly have a bad effect, and besides this the boiler shell will 
 be so hot that the loose mud and sediment left after the 
 water has run out is liable to be baked upon the sheets, 
 making it much harder to remove. 
 
 While inside the boiler the boiler washer should closely 
 examine all the braces and stays, and if any are found 
 loose or broken they should be repaired at once before the 
 boiler is used again. The soundness of braces, rivets, etc., 
 can be ascertained by tapping them with a light hammer. 
 
 Renewing Tubes. As it is practically impossible to pre- 
 vent scale from forming on the outside of the tubes of 
 horizontal tubular boilers unless the feed water is expection- 
 ally good, and as the tubes will in course of time become 
 leaky where they are expanded into the heads, the engineer 
 if he has a battery of two or more, should take advantage 
 of the first opportunity that presents itself to take out of 
 service the boiler that shows the most signs of deterioration 
 and take out the tubes, and after cleaning them of scale by 
 scraping and hammering or rolling in a tumbling cylinder, 
 he should select those that are still in good condition and 
 have them pieced out at the ends, making them almost as 
 good as new. 
 
 All tube failures reduce to four classes : 
 
 (1) Pitting, which causes pin holes to be formed. 
 
 (2) Defective welds, which cause the tube to open, as 
 in A, Fig. 101. 
 
258 
 
 Steam Engineering 
 
 (3) An initial bagging resulting in a rupture, as in B. 
 
 (1) Scabbing and blistering, as in C. 
 
 In the first case the tube is not enlarged, and may be 
 drawn through a tube sheet, without disturbing other tubes, 
 though usually with difficulty, owing to deposits on the 
 outer surface. 
 
 Fig. 101 
 photographs showing distention of tubes at point of 
 
 RUPTURE 
 
 In the other cases, the tubes become larger than their 
 original size, hence they cannot be drawn through the tube 
 sheet, water-leg or header, unless they are split and collapsed 
 inch by inch for their entire length beyond the point of 
 failure, and if they also pass through cross baffles the en- 
 largement will pull out the bricks and destroy the baffle. 
 
Care and Operation of Boilers 259 
 
 To remove a tube in this way is the work of days, and in 
 consequence the actual method used is to cut out all tubes 
 — numbering at times half a dozen below the defective one 
 — and to avoid destroying the baffles these tubes are cut into 
 several pieces. 
 
 In case the tubes are all taken out of the boiler for 
 repairs the boiler washer will have a good opportunity to 
 thoroughly clean the inside of the boiler, and if there are 
 any loose rivets they should be replaced and leaky or sus- 
 picious looking seams chipped and caulked. If there are 
 indications of corrosion or pitting, a stiff paste or putty 
 made of plumbago mixed with a small proportion of cylin- 
 der oil may be applied to the affected parts with good 
 results. 
 
 Feed Water. There is no steam plant of any consequence 
 that does not have more or less exhaust steam, or returns 
 from a steam heating system, which can be utilized for 
 heating the feed water before it enters the boiler. Cold 
 water should never be pumped into a boiler that is under 
 steam when it is possible to prevent it. 
 
 In feeding a boiler the speed of the feed pump should 
 be so gauged as to supply the water just as fast as it is 
 evaporated. The firing can then be even and regular. 
 
 If the supply of feed water should suddenly be cut off, 
 owing to breakage of the pump or bursting of a water main, 
 and no other source of supply was available, the dampers 
 should be immediately closed, or if there should be no 
 damper in the breeching, the draft may be stopped by 
 opening the flue doors. The fires should then be deadened 
 by shoveling wet or damp ashes in on top of them, or if the 
 ashes cannot be readily procured, bank the fires over with 
 green coal broken into fine bits. This, with the draft all 
 
260 Steam Engineering 
 
 shut off, will deaden the fires, while the engine still running 
 will gradually use up the extra steam. If the water should 
 get dangerously low in the boilers the fires may be pulled, 
 provided they have become deadened sufficiently, but they 
 should never be pulled while they are burning lively, be- 
 cause the stirring will only serve to increase the heat, and 
 the danger will be aggravated. 
 
 Connecting a Recently Fired Up Boiler. After a boiler 
 has been washed out, filled with water, and fired up, the 
 next move is to connect it with the main battery. The 
 steam in the boiler to be connected having been raised to 
 the same pressure as that in the battery; the connecting 
 valve should be opened slightly, just enough to permit a 
 small jet of steam to pass through, which can be heard by 
 placing the ear near the body of the valve. This jet of 
 steam may be passing from the battery into the newly con- 
 nected boiler, or vice versa. Whichever way it passes, the 
 valve should not be opened any farther until the flow of 
 steam stops, which will indicate that the pressure has been 
 equalized. It will then be found that the valve will move 
 much easier, and it may be gradually opened until it is 
 wide open. 
 
 Foaming. Water carried with the steam from the boiler 
 to the engine, even if in small quantities, is very detri- 
 mental to the successful operation of the engine, as it 
 w r ashes the oil from the walls of the cylinder, thereby in- 
 creasing the friction, and unless a plentiful supply of oil 
 is entering the cylinder, cutting of the piston rings will 
 take place. There is also danger of breaking a cylinder 
 head, or of bending the piston rod if the water conies in too 
 large quantities. 
 
Care and Operation of Boilers 261 
 
 There are certain kinds of water which have a natural 
 tendency to foam, especially such as contain considerable 
 organic matter, and the more severe the service to which 
 the boiler is put the more will the water foam, until it is 
 practically impossible to locate the true level of the water 
 in the boilers, and the only recourse the water tender has 
 is to keep his feed pump running at such a speed as will, 
 in his judgment supply the water as fast as it goes out of 
 the boilers. It is a dangerous condition to say the least, 
 and the only remedy for it is either a change to a different 
 kind of water, or if this is not possible, then an increase in 
 the number of boilers, which would make it possible to 
 supply sufficient steam for the engine without being com- 
 pelled to fire the boilers so hard. 
 
 Priming. By which is meant the carrying over of water 
 in the form of fine spray mingled with the steam, is not so 
 dangerous as foaming and yet it causes much loss in the 
 efficiency of a boiler or engine. It can be prevented to a 
 large extent by placing a baffle plate in the steam space of 
 the boiler directly under the dome or outlet to the connec- 
 tion with the steam main. 
 
 The following rules are compiled from those issued by 
 various boiler insurance companies in this country and 
 Europe — they apply to all boilers except as otherwise noted : 
 
 1. Safety Valves. Great care should be exercised to 
 see that these valves are ample in size and in working order. 
 Overloading, or neglect frequently leads to the most dis- 
 astrous results. Safety valves should be tried at least 
 once every day to see that they will act freely. 
 
 2. Pressure Gauge. The steam gauge should stand at 
 zero when the pressure is off, and it should show the same 
 pressure as the safety valve when that is blowing off. If 
 
262 Steam Engineering 
 
 not, then one is wrong, and the gauge should be tested by 
 one known to be correct. 
 
 3. Water Level. The first duty of an engineer before 
 starting, or at the beginning of his watch, is to see that 
 the water is at the proper height. Do not rely on glass 
 gauges, floats or water alarms, but try the gauge cocks. 
 If they do not agree with water gauge, learn the cause and 
 correct it. Water level in Babcock & Wilcox boilers should 
 be at center of drum, which is usually at middle gauge. 
 It should not be carried above. 
 
 4. Gauge Cocks and Water Gauges must be kept clean. 
 Water gauge should be blown out frequently, and the glasses, 
 and passages to gauge kept clean. The Manchester, Eng- 
 land, Boiler Association attributes more accidents to in- 
 attention to water gauges than to all other causes put to- 
 gether. 
 
 5. Feed Pump, or Injector. These should be kept in 
 perfect order, and be of ample size. No make of pump can 
 be expected to be continuously reliable without regular and 
 careful attention. It is always safe to have two means of 
 feeding a boiler. Check valves, and self-acting feed valves 
 should be frequently examined and cleaned. Satisfy your- 
 self that the valve is acting when the feed pump is at work. 
 
 6. Low Water. In case of low water, immediately cover 
 the fire with ashes (wet if possible) or any earth that may 
 be at hand. If nothing else is handy use fresh coal. Draw 
 fire as soon as it can be done without increasing the heat. 
 Neither turn on the feed, start or stop engine, nor lift 
 safety valve until fires are out, and the boiler cooled down. 
 
 7. Blisters and Cracks. These are liable to occur in 
 the best plate iron. When the first indication appears there 
 must be no delay in having it carefully examined and 
 properly cared for. 
 
Care and Operation of Boilers 263 
 
 8. Fusible Plugs, when used, must be examined when 
 the boiler is cleaned, and carefully scraped clean on both 
 the water and fire sides, or they are liable not to act. 
 
 9. Firing. Fire evenly and regularly, a little at a time. 
 Moderately thick fires are most economical, but thin firing 
 must be used where the draught is poor. Take care to keep 
 grates evenly covered, and allow no air-holes in the fire. 
 Do not "clean" fires oftener than necessary. With bi- 
 tuminous coal, a "coking fire," i. e., firing in front, and 
 shoving back when coked, gives best results, if properly 
 managed. 
 
 10. Cleaning. All heating surfaces must be kept clean 
 outside and in, or there will be a serious waste of fuel. The 
 frequency of cleaning will depend on the nature of fuel 
 and water. As a rule, never allow over -^ inch scale or soot 
 to collect on surfaces between cleanings. Hand-holes should 
 be frequently removed, and surfaces examined, particularly 
 in case of a new boiler, until proper intervals have been 
 established by experience. 
 
 Water tube boilers are provided with extra facilities for 
 cleaning, and with a little care can be kept up to their 
 maximum efficiency, where tubulars, or locomotive boilers 
 would be quickly destroyed. For inspection, remove the 
 hand-holes at both ends of the tubes, and by holding a 
 lamp at one end and looking in at the other, the condition 
 of the surface can be fully seen. Push the scraper through 
 the tube to remove sediment, or if the scale is hard use the 
 chipping scraper made for that purpose. Water through 
 a hose will facilitate the operation. In replacing hand- 
 hole caps, clean the surfaces without scratching or bruising, 
 smear with oil, and screw up tight. Examine mud-drum 
 and remove the sediment therefrom. 
 
264 Steam Engineering 
 
 The exterior of tubes can be kept clean by the use of 
 blowing pipe and hose through openings provided for that 
 purpose. In using smoky fuel, it is best to occasionally 
 brush the surfaces when steam is off. 
 
 11. Hot Feed-Water. Cold water should never be fed 
 into any boiler when it can be avoided, but when necessary 
 it should be caused to mix with the heated water before 
 coming in contact with any portion of the boiler. 
 
 12. Foaming. When foaming occurs in a boiler, check- 
 ing the outflow of steam will usually stop it. If caused by 
 dirty water, blowing down and pumping up will generally 
 cure it. In cases of violent foaming, check the draft and 
 fires. 
 
 13. Air Leaks. Be sure that all openings for admission 
 of air to boiler or flues, except through the fire, are care- 
 fully stopped. This is frequently an unsuspected cause of 
 serious waste. 
 
 14. Blowing Off. If feed-water is muddy or salt, blow 
 off a portion frequently, according to condition of water. 
 Empty the boiler every week or two, and fill up afresh. 
 When surface blow-cocks are used, they should be often 
 opened for a few minutes at a time. Make sure no water 
 is escaping from the blow-off cock when, it is supposed to 
 be closed. Blow-off cocks, and check-valves should be ex- 
 amined every time the boiler is cleaned. 
 
 15. Leaks. When leaks are discovered, they should be 
 repaired as soon as possible. 
 
 16. Blowing Off for Washing. Never empty the boiler 
 while the brickwork is hot. 
 
 17. Filling Up. Never pump cold water into a hot 
 boiler. Many times leaks, and, in shell boilers, serious 
 weaknesses, and sometimes explosions are the result of 
 such an action. 
 
Care and Operation of Boilers 265 
 
 18. Dampness. Take care that no water comes in con- 
 tact with the exterior of the boiler from any cause, as it 
 tends to corrode and weaken the boiler. Beware of all 
 dampness in seatings or coverings. 
 
 19. Galvanic Action. Examine frequently parts in con- 
 tact with copper or brass, where water is present, for signs 
 of corrosion. If water is salt or acid, some metallic zinc 
 placed in the boiler will usually prevent corrosion, but it 
 will need attention and renewal from time to time. 
 
 20. Rapid Firing. In boilers with thick plates, or 
 seams exposed to the fire, steam should be raised slowly, 
 and rapid or intense firing avoided. AYith thin water tubes, 
 however, and adequate water circulation, no damage can 
 come from that cause. 
 
 21. Standing Unused. If a boiler is not required for 
 some time, empty and dry it thoroughly. If this is im- 
 practicable, fill it quite full of water, and put in a quantity 
 of common washing soda. External parts exposed to damp- 
 ness should receive a coating of linseed oil. 
 
 22. General Cleanliness. All things about the boiler 
 room should be kept clean and in good order. Negligence 
 tends to waste and decay. 
 
 Miscellaneous. In burning coal under a boiler, it should 
 be remembered that the object is to transfer as many as 
 possible of the total heat units contained in the coal to the 
 water in the boiler, and that any failure to do this shows a 
 lack of engineering ability. 
 
 No leak or waste is too small to deserve attention and 
 unceasing viligance is the price of economy. The grates, if 
 hand-fired, should be of standard shaking pattern, and the 
 fire kept thin enough so that it can be kept clean and bright 
 without too much overhead slicing. Every time that the 
 
266 Steam Engineering 
 
 furnace door is opened for the introduction of coal or for 
 cleaning the fire in any way, there is a distinct loss of 
 efficiency on account of the inrush of cold air. Most 
 boiler-room fires suffer from too much meddling. It is 
 undoubtedly better in all plants of any size to install me- 
 chanical stokers, there being the double advantage of a 
 uniform feed of fuel, and a definite air supply, just suffi- 
 cient to maintain combustion. 
 
 HEATIXG SURFACE. 
 
 For a fire-box boiler of the vertical type, the area of the 
 flue sheets minus the sectional area of the flues, plus the 
 area of the fire-box plus the inside area of the flues consti- 
 tutes the heating surface. If the boiler is a horizontal in- 
 ternally fired boiler, the heating surface will consist of, 
 first, area of three sides of the fire-box ; second, area of the 
 crown sheet; third, area of flue sheets minus sectional area 
 of flues ; fourth, inside area of the flues. 
 
 In estimating the area of the fire-box, the area of the fire 
 door should be subtracted therefrom. If the fire-box be 
 circular, as in the case of a vertical boiler, the area may 
 be obtained by first finding by measurements the diame- 
 ter, which multiplied by 3.1416 will give the circumfer- 
 ence. Then multiply this result by the height or the dis- 
 tance between the grate bars and the flue sheet. In the 
 case of water tube boilers the outside area of the tubes 
 must be taken. Two examples will be given illustrating 
 methods of calculating heating surface: 
 
 First, take a horizontal tubular boiler, diameter 72 in., 
 length 18 ft., having sixty-two 4% in, flues: find area of 
 lower half of shell. 
 
Care and Operation of Boilers 267 
 
 Circumference= diameter X 3.1416=18.8496 ft. 
 
 One-half of the circumference multiplied by the length 
 ^required area. Thus, 18.8496-^-2X18=169.64 sq. ft. 
 
 Next find heating surface of back head below the water 
 line. Total area=72 2 X .7854=4071.5 sq. in. Assume 
 two-thirds of this area to be exposed to the heat, 2/3 of 
 4071.5=2714.3 sq. in. From this must be deducted the 
 sectional area of the tubes. In giving the size of boiler 
 tubes the outside diameter is taken. The tubes being 4!/2 
 in.; the area of a circle 4 x /2 in. in diameter is 15.9 sq. in. 
 Number of flues, 62X15.9=985.8 sq. in. = sectional area 
 of tubes. The heating surface of the back head therefore= 
 2714.3—985.8=1728.5 sq. in. Dividing this by 144, to 
 reduce to feet, we have 12 sq. ft. 
 
 Next find inside area of tubes. The standard thickness 
 of a 4% in - tube=.134 in. The inside diameter therefore 
 will be 4.5 — (2X-134)=4.23 in., and the circumference 
 will be 4.23X3.1416=13.29 in., and the inside area will be 
 13.29Xlength, 18 ft.,=216 in. Thus 216X13.29-f-l44= 
 19.93 sq. ft., inside area of one flue. There being 62 flues, 
 the total heating surface of tubes is 19.93X62=1235.66 
 sq. ft. The heating surface of the front head is found in 
 the same manner as that of the back head, with the excep- 
 tion that the whole area should be figured instead of two- 
 thirds, for the reason that the entire surface is exposed to 
 the heat, although that portion above the water line may 
 be considered as superheating surface. The heating surface 
 of front head would be: area 4071.5 — sectional area of 
 tubes 985.8=3085. i sq. in.=21.43 sq. ft. 
 
 The total heating surface of the boiler is thus found to 
 be 1438.73 sq. ft., divided up as follows : 
 
 , 
 
268 Steam Engineering 
 
 Lower half of shell, 169.64. sq. ft. 
 
 Back head, 12.00 sq. ft. 
 
 Tubes, 1235.66 sq. ft. 
 
 Front head, 21.43 sq. ft. 
 
 1438.73 sq. ft. 
 
 Next taking a vertical fire-box boiler of the following 
 dimensions : diameter of fine sheet, and also of fire-box, 50 
 in. ; height of fire-box above grate bars, 30 in. ; number of 
 flues, 200; size of flues, 2 in.; length of flues, 7 ft. 
 
 First, find heating surface in flue sheet. 
 
 Area of circle, 50 in. in diameter=l,963.5 sq. in. 
 
 Sectional area of 2 in. flue=3.14 sq. in., which multi- 
 plied by 200=628 sq. in., total sectional area of tubes. The 
 heating surface of one flue sheet therefore will be 1,963.5 — 
 628-^144=9 sq. ft. 
 
 Assuming that the tops of the flues are submerged, the 
 area of the top flue sheet will also be 9 sq. ft. Then heating 
 surface of flue sheets=9X2=18 sq. ft. 
 
 Second, find heating surface of tubes. The standard 
 thickness of a 2 in. flue is .095 in. The inside diameter 
 will consequently be 2 — (.095X2)=1.8 in., and the cir- 
 cumference will be 1.8X3.1416=5.66 in. The length of 
 the flue being 7 ft., or 84 in., the inside area will be 5.66 X 
 84-^144=3.3 sq. ft., and multiplying this result by 200 we 
 have 200X3.3=660 sq. ft. as the heating surface of the 
 flues. 
 
 Third, find heating surface of the fire-box. Diameter of 
 fire-box=50 in., which multiplied by 3.1416=157.08, which 
 is the circumference. The height being 30 in., the total 
 area will be 157.08X30-^144=32.7 sq. ft. Allowing 1 sq. 
 ft. as the area of the fire door, will leave 31.7 sq. ft. heating 
 
Care and Operation of Boilers 269 
 
 surface of fire-box. The heating surface of the boiler 
 will be: 
 
 For the flue sheets, 18 sq. ft. 
 
 For the flues, 660 sq. ft. 
 
 For the fire-box, 31.7 sq. ft. 
 
 Total, 709.7 sq. ft. 
 
 The above methods may be applied in estimating the 
 heating surface of any boiler, provided in the case of water 
 tube boilers that the outside in place of the inside area of 
 the tubes be figured. 
 
 Reducing Loss in Handling Coal. In large coal-hand- 
 ling systems used in power plants of considerable capacity, 
 there is often a chance to save a few dollars in operation if 
 the station staff is on the alert to cut down wastes. In a 
 good sized plant there are frequently several hundred con- 
 veyer buckets to be driven, and a twenty or twenty-five 
 horse-power engine, or motor may be needed to operate the 
 system at its full capacity. With the most careful lubrica- 
 tion and skilled attention, the friction load of the conveyer 
 system may amonnt to forty or fifty per cent of the power 
 required when operating with the buckets full. If care is 
 not taken to shut down the conveyer promptly after the 
 delivery of coal to the bunkers or when the collection of 
 ashes has ceased, the power loss may be felt in the year's 
 operating expense of the auxiliaries. 
 
 The operation of the endless conveyer chain, empty, once 
 or twice a week for purposes of oiling or greasing may cost 
 perhaps ten dollars a year for the extra power used, com- 
 pared with lubricating when the conveyer is handling fuel. 
 In larger conveyer installations two men are often needed 
 to apply the oil or grease as each bucket passes by, a third 
 
270 Steam Engineering 
 
 man being on hand to fill the cans. If this work can be 
 arranged to be done when the conveyer is delivering coal, 
 a desirable gain will be made, since there are always points 
 in the travel of the conveyer belt or buckets where they are 
 empty and thus readily inspected in detail, or oiled in any 
 part. 
 
 Two other frequent sources of waste in the handling of 
 a coal-conveyor system are, in the pocket lights, and the 
 steam lines which may be in. use. Current is wasted through 
 failure to cut off the incandescents as soon as they are not 
 needed in the recesses of the pocket, and when several 
 steam-pipe branch lines are used in connection with hoist- 
 ing engines, if a main valve is not installed at the entrance 
 of the pocket or tower, leakages in the separate valves are 
 liable to prove expensive. 
 
 QUESTIONS AXD ANSWERS. 
 
 179. What is one of the most important duties of the 
 engineer when he goes on watch ? 
 
 Ans. To ascertain the exact height of the water in his 
 boilers. 
 
 180. Describe the correct method of doing this. 
 
 Ans. Open the valve in the drain pipe of the water col- 
 umn, and allow the water to blow out freely for a few 
 seconds, then close the valve and note the level of the water 
 when it settles back in the gauge glass. 
 
 181. "What is the next important step in beginning the 
 day's work ? 
 
 Ans. To see that the fires are cleaned, and in good con- 
 dition. 
 
 182. In firms: boiler^ by hand, what is the first and 
 most important rule to be observed? 
 
Questions and Answers 271 
 
 Ans. Keep a clean fire. 
 
 183. What is the second rule? 
 
 Ans. See that every square inch of grate surface is 
 
 covered with a good live fire. 
 
 181. Give the third rule regarding firing by hand. 
 
 Ans. Keep a level fire. 
 
 185. What is the fourth rule? 
 
 Ans. When cleaning the fire, always clean all clinkers 
 and dead ashes away from the back end of the grates and 
 the bridge wall. 
 
 186. Why should this be done? 
 
 Ans. In order to allow a free passage of the air through 
 the grate bars, so as to promote combustion. 
 
 187. If the plant runs continuously, day and night, 
 what is one of the important duties of the fireman coming 
 off watch? 
 
 Ans. To leave clean fires, clean ash pits, and a good 
 supply of coal ready for the oncoming force. 
 
 188. How long a time should the fires be allowed to 
 burn before cleaning? 
 
 Ans. This depends upon the quality of the coal. With 
 a coal that does not clinker on the grate bars, an interval 
 of 7 or 8 hours may elapse between cleanings, but with the 
 average soft coal the fires should not be allowed to burn 
 longer than 4 or 5 hours without cleaning. 
 
 189. What is one of the greatest aids to good combustion 
 in a hand-fed furnace? 
 
 Ans. A clean bridge wall, kept as hot as possible. 
 
 190. What precautions should be observed regarding 
 the depth of the fire? 
 
 Ans. It should not be allowed to become so deep and 
 heavy as to prevent the air from passing up through it 
 freely 
 
272 Steam Engineering 
 
 191. How should the position of the ash-pit doors be 
 regulated ? 
 
 Ans. With a clean, light fire, a slight opening will be 
 sufficient, but with a heavy fire, and the grates clogged with 
 ashes, a larger opening is necessary. 
 
 192. How can the best results be secured in firing 
 bituminous coal ? 
 
 Ans. By leaving the fire doors slightly open for a few 
 seconds immediately after throwing in a fire. 
 
 193. What reason is there for doing this? 
 
 Ans. Because the volatile matter in the coal flashes into 
 flame the instant it comes in contact with the heat of the 
 furnace, and unless there is sufficient supply of oxygen 
 present just then, the combustion will be imperfect. 
 
 194. What is the result of this imperfect combustion? 
 
 Ans. The formation of carbonic oxide gas, and the con- 
 sequent loss of about two-thirds of the heat units contained 
 in the coal. 
 
 195. How may this loss be prevented in a great meas- 
 ure? 
 
 Ans. By admitting a sufficient volume of aii*, either 
 through the fire doors, directly after throwing in a fresh 
 fire, or, better still, providing air ducts through the bridge 
 wall, or side walls, which will direct the air in on top of 
 the fire. 
 
 196. How much air is required for the complete com- 
 bustion of one pound of coal? 
 
 Ans. By weight 12 pounds — by volume 150 cubic feet. 
 
 197. What precaution is necessary regarding the tubes 
 of a boiler in order to get the best results from the fuel ? 
 
 Ans. The tubes should be kept clean and free from soot 
 and scale. 
 
Questions and Answers 273 
 
 198. Should the steam jet cleaner be depended upon 
 alone for cleaning the tubes ? 
 
 Ans. No. The scraper should also be used. 
 
 199. How should safety valves be looked after? 
 
 Ans. They should be ample in size, never overloaded, 
 and should be tested at least once a day to see that they 
 act freely. 
 
 200. At what point should the steam gauge pointer 
 stand when the pressure is off? 
 
 Ans. It should stand at zero. 
 
 201. What should be done in case of low water in a 
 boiler ? 
 
 Ans. The fire should be covered immediately with ashes, 
 earth, or if neither is available use fresh coal. Draw the 
 fire as soon as it can be done without increasing the heat. 
 
 202. Should the rate of feeding the water be increased, 
 in case of extremely low water in the boiler? 
 
 Ans. It should not, neither should the engine be stopped 
 or the safety valve lifted, until the fires are out, and the 
 boiler cooled down. 
 
 203. In case of indications of cracks or blisters appear- 
 ing on the boiler sheets, what should be done ? 
 
 Ans. There shomld be no delay in making repairs. 
 
 204. What should be done with fusible plugs when used ? 
 Ans. They should be cleaned and carefully scraped on 
 
 both water and fire sides at each washing out. 
 
 205. How may the most economical results regarding 
 fuel be attained with a steam boiler ? 
 
 Ans. By keeping the heating surfaces clean, both inside 
 and outside, also careful firing, a little at a time, but keep- 
 ing the grates covered. 
 
 206. Should cold water ever be fed into a boiler when 
 it is under pressure ? 
 
r 
 
 274 Steam Engineering 
 
 Ans. Not when it can be avoided. 
 
 207. How may foaming usually be stopped? 
 
 Ans. By checking the outflow of steam, by blowing 
 down and pumping up, or by checking the draft and fires. 
 
 208. Should air be allowed to pass to the boiler or tubes, 
 except through the furnace ? 
 
 Ans. It should not, as it will cause a waste of fuel. 
 
 209. What should be done with leaks when discovered? 
 Ans. They should be repaired as soon as possible. 
 
 210. What precautions should be observed when pre- 
 paring to empty a boiler for washing out, or other pur- 
 poses ? 
 
 Ans. Allow it to cool down until there is no steam pres- 
 sure, and until the brick work is cool also. 
 
 211. When firing up a boiler what course should be 
 pursued ? 
 
 Ans. Steam should be raised very slowly, and rapid fir- 
 ing avoided. 
 
 212. What bad results follow too rapid firing up of a 
 boiler ? 
 
 Ans. Straining of the joints and seams caused by un- 
 equal expansion. 
 
 213. What should be done with a boiler that is to 
 stand idle for any length of time? 
 
 Ans. It should be emptied, and thoroughly dried. In 
 case this is impracticable, fill it full of water, and put in 
 a quantity of washing soda. 
 
 214. How long a time may a boiler be safely operated 
 between dates of washing out ? 
 
 Ans. This depends upon the nature of the feed water. 
 The time should never be longer than two weeks, and with 
 very bad water, the boiler should he washed out once a 
 week. 
 
Questions and Answers 275 
 
 215. Besides cleaning the boiler inside, what other very 
 important work should the boiler washer perform while 
 inside the boiler ? 
 
 Ans. He should closely examine all braces, stays, and 
 rivets by tapping them with a hammer. An} r loose or de- 
 fective parts can usually be detected in this way. 
 
 216. Describe four ways in which tube failures may 
 occur. 
 
 Ans. 1. Pitting. 2. Defective welds. 3. Bagging. 4. 
 Scabbing and blistering. 
 
 217. How may a great saving in fuel be effected with 
 regard to the feed water ? 
 
 Ans. By heating it with the exhaust steam from engines 
 and pumps before passing it to the boilers. 
 
 218. Describe the available heating surface of a station- 
 ary boiler, of either type, return tubular or water tube. 
 
 Ans. The lower half of the shell, and heads, and the 
 combined cross sectional area of all the tubes. 
 
 219. What should be the location of the water gauge 
 glass, relative to the water level in the boiler? 
 
 Ans. It should be located at such a height as to bring 
 the lower end of the glass tube on a level with the danger 
 point for low water in the boiler. 
 
 220. Where should the lower gauge cock be located 
 relative to the danger point ? 
 
 Ans. About three inches above. 
 
 222. Should an engineer or water tender depend entirely 
 upon the water gauge glasses ? 
 
 Ans. He should not, but should frequently open and try 
 the gauge cocks. 
 
 223. What should be done with the entire water column 
 several times a day? 
 
276 Steam Engineering 
 
 Ans. It should be blown out thoroughly. 
 
 224. What should be done with the safety valves in 
 order to make them reliable ? 
 
 Ans, They should be allowed to blow off at least twice a 
 week. 
 
 225. Why is this necessary? 
 
 Ans. Because the valves are liable to become corroded, 
 and stick to their seats if not attended to properly. 
 
 226. What is the rule for finding the bursting pressure 
 of boilers? 
 
 Ans. Multiply the tensile strength by the thickness and 
 divide by one-half the diameter of the shell. 
 
 227. How may the safe working pressure of a boiler be 
 ascertained ? 
 
 Ans. By dividing the bursting pressure by five. 
 
 228. What is the rule for ascertaining the velocity of 
 flow in a pump? 
 
 Ans. Multiply the number of strokes per minute by 
 length of stroke in feet. This will give piston speed. 
 
 229.. How may velocity of flow in the discharge pipe of 
 a pump be found ? 
 
 Ans. Divide square of diameter of water piston by the 
 square of the diameter of pipe, and multiply by piston speed 
 per minute. 
 
 230. What is the rule for finding velocity in feet per 
 minute required to discharge a given quantity of water in 
 a given time ? 
 
 Ans. Multiply number of cubic feet to be discharged by 
 144 and divide by area of pipe in inches. 
 
 231. When the volume and velocity of water to be dis- 
 charged are known, how may the area of the pipe be ascer- 
 tained ? 
 
Questions and Answers 211 
 
 Arts. Multiply volume in cubic feet by 144 and divide 
 by velocity in feet per minute. 
 
 232. What is one of the main requisites in the success- 
 ful burning of coal in a boiler furnace? 
 
 Ans. A good draft. 
 
 233. What is a common cause of lost economy in the 
 operation of boilers? 
 
 Ans. Air leaks in the brick settings. 
 
 234. Mention another source of loss in connection with 
 mechanical stokers. 
 
 Ans. The dead area of grate that is covered with a thin 
 layer of clinker, and ash. 
 
 235. What is meant by the expression "priming?" 
 Ans. Carrying over into the cylinder of water in the 
 
 form of fine spray mingled with the steam. 
 
 236. How may this be prevented to a large extent? 
 Ans. By placing a baffle plate in the steam space of the 
 
 boiler, directly under the dome. Steam separators may 
 also be employed for this purpose. 
 
 237. What should be the principal object in view in 
 burning coal under a boiler? 
 
 Ans. To transfer as many as possible of the total heat 
 units in the coal, to the water in the boiler. 
 
278 
 
 Steam Engineering 
 
 Table 17 
 
 properties of saturated steam. 
 
 >> 
 
 u 
 
 g 
 
 
 Tota 
 
 Heat 
 
 
 cu 
 
 jjj 
 
 +> 
 
 3 
 o 
 
 
 
 above 
 
 32° F. 
 
 ^ 
 
 B 
 
 C <u 
 
 o . 
 
 
 Absolute 
 
 Pressure 
 
 bs. per Sq. 
 
 ft 
 
 £ « 
 
 cu 
 
 p 
 
 
 
 
 "o 
 > 
 
 13 
 
 v o 
 
 ft . 
 
 tH 
 
 [t, CO 
 
 £ 1 
 o 
 
 u 
 
 6 8 
 
 the Steam 
 
 H 
 eat-units 
 
 .2J 
 
 C 
 
 U 
 
 
 £ K 
 
 t— 1 
 
 
 P4 
 
 £ 
 
 29.74 
 
 .089 
 
 32. 
 
 0. 
 
 1091.7 
 
 1091.7 
 
 208.080 
 
 3333.3 
 
 .0003 
 
 29.67 
 
 .122 
 
 40. 
 
 8. 
 
 1094.1 
 
 1086.1 
 
 154,330 
 
 2472.2 
 
 .0004 
 
 29.56 
 
 .176 
 
 50. 
 
 .18. 
 
 1097.2 
 
 1079.2 
 
 107,630 
 
 1724.1 
 
 .0006 
 
 29.40 
 
 .254 
 
 60. 
 
 28.01 
 
 1100.2 
 
 1072.2 
 
 76,370 
 
 1223.4 
 
 .0008 
 
 29.19 
 
 .359 
 
 70. 
 
 38.02 
 
 1103.3 
 
 1065.3 
 
 54,660 
 
 875.61 
 
 .0011 
 
 28.90 
 
 .502 
 
 80. 
 
 48.04 
 
 1106.3 
 
 1058.3 
 
 39,690 
 
 635.80 
 
 .0016 
 
 28.51 
 
 .692 
 
 90. 
 
 58.06 
 
 1109.4 
 
 1051.3 
 
 29,290 
 
 469.20 
 
 .0021 
 
 28.00 
 
 .943 
 
 100. 
 
 68.08 
 
 1112.4 
 
 1044.4 
 
 21,830 
 
 349.70 
 
 .0028 
 
 27.88 
 
 1. 
 
 102.1 
 
 70.09 
 
 1113.1 
 
 1043.0 
 
 20,623 
 
 334.23 
 
 .0030 
 
 25.85 
 
 2. 
 
 126.3 
 
 94.44 
 
 1120.5 
 
 1026.0 
 
 10,730 
 
 173.23 
 
 .0058 
 
 23.83 
 
 3. 
 
 141.6 
 
 109.9 
 
 1125.1 
 
 1015.3 
 
 7,325 
 
 118.00 
 
 .0085 
 
 21.78 
 
 4. 
 
 153.1 
 
 121.4 
 
 1128.6 
 
 1007.2 
 
 5,588 
 
 89.80 
 
 .0111 
 
 19.74 
 
 5. 
 
 162.3 
 
 130.7 
 
 1131.4 
 
 1000.7 
 
 4,530 
 
 72?50 
 
 .0137 
 
 17.70 
 
 6. 
 
 170.1 
 
 138.6 
 
 1133.8 
 
 995.2 
 
 3,816 
 
 61.10 
 
 .0163 
 
 15.67 
 
 7. 
 
 176.9 
 
 145.4 
 
 1135.9 
 
 990.5 
 
 3,302 
 
 53.00 
 
 .0189 
 
 13.63 
 
 8. 
 
 182.9 
 
 151.5 
 
 1137.7 
 
 986.2 
 
 2,912 
 
 46.60 
 
 .0214 
 
 11.60 
 
 9. 
 
 188.3 
 
 156.9 
 
 1139.4 
 
 982.4 
 
 2,607 
 
 41.82 
 
 .0239 
 
 9.56 
 
 10. 
 
 193.2 
 
 161.9 
 
 1140.9 
 
 979.0 
 
 2,361 
 
 37.80 
 
 .0264 
 
 7.52 
 
 11. 
 
 197.8 
 
 166.5 
 
 1142.3 
 
 975.8 
 
 2,159 
 
 34.61 
 
 .0289 
 
 5.49 
 
 12. 
 
 202.0 
 
 170.7 
 
 1143.5 
 
 972.8 
 
 1,990 
 
 31.90 
 
 .0314 
 
 3.45 
 
 13. 
 
 205.9 
 
 174.7 
 
 1144.7 
 
 970.0 
 
 1,846 
 
 29.60 
 
 .0338 
 
 1.41 
 
 14. 
 
 209.6 
 
 178.4 
 
 1145.9 
 
 967.4 
 
 1,721 
 
 27.50 
 
 .0363 
 
 0.00 
 
 14.7 
 
 212.0 
 
 180.9 
 
 1146.6 
 
 963.7 
 
 1,646 
 
 26.36 
 
 .0379 
 
Properties of Saturated Steam 
 Table 1 7 — continued 
 
 279 
 
 
 
 
 Total Heat 
 
 
 V 
 
 S 
 
 o 
 
 u& 
 
 3 C 
 
 en 
 & CD 
 
 Ih 
 
 Geo 
 
 H to 
 
 A 
 
 above 32° F. 
 
 Latent Heat 
 
 H-h 
 
 Heat-units 
 
 & 
 
 > 
 
 .£ 8 
 
 <u o 
 ^ . 
 
 o . 
 
 [£, co 
 
 V 
 
 ^3 
 
 M 
 
 CJ »*-« -t-> 
 
 £ S 
 
 i— i 
 
 1 2 
 
 £ -a- 
 
 .2J 
 
 4J O 
 
 0.3 
 
 15 
 
 213.3 
 
 181.9 
 
 1146.9 
 
 965.0 
 
 1,614 
 
 25.90 
 
 .0387 
 
 1.3 
 
 16 
 
 216.3 
 
 185.3 
 
 1147.9 
 
 962.7 
 
 1,519 
 
 24.33 
 
 .0411 
 
 2.3 
 
 17 
 
 219.4 
 
 188.4 
 
 1148.9 
 
 960.5 
 
 1,434 
 
 23.00 
 
 .0435 
 
 3.3 
 
 18 
 
 222.4 
 
 191.4 
 
 1149.8 
 
 958.3 
 
 1,359 
 
 21.80 
 
 .0459 
 
 4.3 
 
 19 
 
 225.2 
 
 194.3 
 
 1150.6 
 
 956.3 
 
 1,292 
 
 20.70 
 
 .0483 
 
 5.3 
 
 20 
 
 227.9 
 
 197.0 
 
 1151.5 
 
 954.4 
 
 1,231 
 
 19.72 
 
 .0507 
 
 6.3 
 
 21 
 
 230.5 
 
 199.7 
 
 1152.2 
 
 952.6 
 
 1,176 
 
 18.84 
 
 .0531 
 
 7.3 
 
 22 
 
 233.0 
 
 202.2 
 
 1153.0 
 
 950.8 
 
 1,126 
 
 18.03 
 
 .0555 
 
 8.3 
 
 23 
 
 235.4 
 
 204.7 
 
 1153.7 
 
 949.1 
 
 1,080 
 
 17.30 
 
 .0578 
 
 9.3 
 
 24 
 
 237.8 
 
 207.0 
 
 1154.5 
 
 947.4 
 
 1,038 
 
 16.62 
 
 .0602 
 
 10.3 
 
 25 
 
 240.0 
 
 209.3 
 
 1155.1 
 
 945.8 
 
 998 
 
 16.00 
 
 .0625 
 
 11.3 
 
 26 
 
 242.2 
 
 211.5 
 
 1155.8 
 
 944.3 
 
 962 
 
 15.42 
 
 .0649 
 
 12.3 
 
 27 
 
 244.3 
 
 213.7 
 
 1156.4 
 
 942.8 
 
 929 
 
 14.90 
 
 .0672 
 
 13.3 
 
 28 
 
 246.3 
 
 215.7 
 
 1157.1 
 
 941.3 
 
 898 
 
 14.40 
 
 .0696 
 
 14.3 
 
 29 
 
 248.3 
 
 217.8 
 
 1157.7 
 
 939.9 
 
 869 
 
 13.91 
 
 .0719 
 
 15.3 
 
 30 
 
 250.2 
 
 219.7 
 
 1158.3 
 
 938.9 
 
 841 
 
 13.50 
 
 .0742 
 
 16.3 
 
 31 
 
 252.1 
 
 221.6 
 
 1158.8 
 
 937.2 
 
 816 
 
 13.07 
 
 .0765 
 
 17.3 
 
 32 
 
 254.0 
 
 223.5 
 
 1159.4 
 
 935.9 
 
 792 
 
 12.68 
 
 .0788 
 
 18.3 
 
 33 
 
 255.7 
 
 225.3 
 
 1159.9 
 
 93^.6 
 
 769 
 
 12.32 
 
 .0812 
 
 19.3 
 
 34 
 
 257.5 
 
 227.1 
 
 1160.5 
 
 933.4 
 
 748 
 
 12.00 
 
 .0835 
 
 20.3 
 
 35 
 
 259.2 
 
 228.8 
 
 1161.0 
 
 932.2 
 
 728 
 
 11.66 
 
 .0858 
 
 21.3 
 
 36 
 
 260.8 
 
 230.5 
 
 1161.5 
 
 931.0 
 
 709 
 
 11.36 
 
 .0880 
 
 22.3 
 
 37 
 
 262.5 
 
 232.1 
 
 1162.0 
 
 929.8 
 
 691 
 
 11.07 
 
 .0903 
 
 23.3 
 
 38 
 
 264.0 
 
 233.8 
 
 1162.5 
 
 928.7 
 
 674 
 
 10.80 
 
 .0926 
 
 24.3 
 
 39 
 
 265.6 
 
 235.4 
 
 1162.9 
 
 927.6 
 
 658 
 
 10.53 
 
 .0949 
 
 25.3 
 
 40 
 
 267.1 
 
 236.9 
 
 1163.4 
 
 926.5 
 
 642 
 
 10.28 
 
 .0972 
 
 26.3 
 
 41 
 
 268.6 
 
 238.5 
 
 1163.9 
 
 925.4 
 
 627 
 
 10.05 
 
 .0995 
 
 27.3 
 
 42 
 
 270.1 
 
 240.0 
 
 1164.3 
 
 924.4 
 
 613 
 
 9.83 
 
 .1018 
 
 28.3 
 
 43 
 
 271.5 
 
 241.4 
 
 1164.7 
 
 923.3 
 
 600 
 
 9.61 
 
 .1040 
 
 29.3 
 
 44 
 
 272.9 
 
 242.9 
 
 1165.2 
 
 922.3 
 
 587 
 
 9.41 
 
 .1063 
 
 30.3 
 
 45 
 
 274.3 
 
 244.3 
 
 1165.6 
 
 921.3 
 
 575 
 
 9.21 
 
 .1086 
 
 31.3 
 
 46 
 
 275.7 
 
 245.7 
 
 1166.0 
 
 920.4 
 
 563 
 
 9.02 
 
 .1108 
 
 32.3 
 
 47 
 
 277.0 
 
 247.0 
 
 1166.4 
 
 919.4 
 
 552 
 
 8.84 
 
 .1131 
 
 33.3 
 
 48 
 
 278.3 
 
 248.4 
 
 1166.8 
 
 918.5 
 
 541 
 
 8.67 
 
 .1153 
 
 34.3 
 
 49 
 
 279.6 
 
 249.7 
 
 1167.2 
 
 917.5 
 
 531 
 
 8.50 
 
 .1176 
 
 35.3 
 
 50 
 
 280.9 
 
 251.0 
 
 1167.6 
 
 916.6 
 
 520 
 
 8.34 
 
 .1198 
 
 36.3 
 
 51 
 
 282.1 
 
 252.2 
 
 1168.0 
 
 915.7 
 
 511 
 
 8.19 
 
 .1221 
 
 37.3 
 
 52 
 
 283.3 
 
 253.5 
 
 1168.4 
 
 914.9 
 
 502 
 
 8.04 
 
 .1243 
 
 38.3 
 
 53 
 
 I 284.5 
 
 254.7 
 
 1168.7 
 
 914.0 
 
 492 
 
 7.90 
 
 .1266 
 
 39.3 
 
 54 
 
 285.7 
 
 256.0 
 
 1169.1 
 
 913.1 
 
 484 
 
 7.76 
 
 .1288 
 
 40.3 
 
 55 
 
 286.9 
 
 257.2 
 
 1169.4 
 
 912.3 
 
 476 
 
 7.63 
 
 .13U 
 
 41.3 
 
 56 
 
 288.1 
 
 258.3 
 
 1169.8 
 
 911.5 
 
 468 
 
 7.50 
 
 .1333 
 
 42.3 
 
 57 
 
 289.1 
 
 259.5 
 
 1170.1 
 
 910.6 
 
 460 
 
 7.38 
 
 .1355 
 
 43.3 
 
 58 
 
 290.3 
 
 260.7 
 
 1170.5 
 
 909.8 
 
 453 
 
 7.26 
 
 .1377 
 
 44.3 
 
 59 
 
 I 291.4 
 
 261.8 
 
 1170.8 
 
 909.0 
 
 446 
 
 7.14 
 
 .1400 
 
 45.3 
 
 60 
 
 1 292.5 
 
 262.9 
 
 1171.2 
 
 908.2 
 
 439 
 
 7.03 
 
 .1422 
 
 46.3 
 
 61 
 
 1 293.6 
 
 264.0 
 
 1171.5 
 
 907.5 
 
 432 
 
 6.92 
 
 .1444 
 
 47 3 
 
 62 
 
 294.7 
 
 265.1 
 
 1171.8 
 
 906.7 
 
 425 
 
 6.82 
 
 .1466 
 
 48.3 
 
 63 
 
 I 295.7 
 
 266.2 
 
 1172.1 
 
 905.9 
 
 419 
 
 6.72 
 
 .1488 
 
280 
 
 Steam Engineering 
 Table 1 7 — continued 
 
 
 
 
 Total Heat 
 
 
 V 
 
 B 
 
 o 
 
 £►5 
 
 
 above 32° F. 
 
 
 a 
 
 o . 
 
 p 
 
 Absolute 
 
 Pressure 
 
 s. per Sq. 
 
 & CO 
 C tu 
 O £ 
 
 Q 
 
 
 
 
 J3 
 
 "o 
 
 > 
 
 CD Ml 
 
 
 CO rT 1 
 
 u 
 
 W CO 
 
 M 
 
 i ■ 
 
 .23 
 
 Tig 
 
 ®S 
 
 
 
 -4_> V 
 
 4_> <D 
 
 
 
 U J 
 
 ■M ° 
 
 
 
 
 
 
 
 
 rH 
 
 49.3 
 
 64 
 
 296.8 
 
 267.2 
 
 1172.4 
 
 905.2 
 
 413 
 
 6.62 
 
 .1511 
 
 50.3 
 
 65 
 
 297.8 
 
 268.3 
 
 1172.8 
 
 904.5 
 
 407 
 
 6.53 
 
 .1533 
 
 51.3 
 
 66 
 
 298.8 
 
 269.3 
 
 1173.1 
 
 903.7 
 
 401 
 
 6.43 
 
 .1555 
 
 52.3 
 
 67 
 
 299.8 
 
 270.4 
 
 1173.4 
 
 903.0 
 
 395 
 
 6.34 
 
 .1577 
 
 53.3 
 
 68 
 
 300.8 
 
 271.4 
 
 1173.7 
 
 902.3 
 
 390 
 
 6.25 
 
 .1599 
 
 54.3 
 
 69 
 
 301.8 
 
 272.4 
 
 1174.0 
 
 901.6 
 
 384 
 
 6.17 
 
 .1621 
 
 55.3 
 
 70 
 
 302.7 
 
 273.4 
 
 1174.3 
 
 900.9 
 
 379 
 
 6.09 
 
 .1643 
 
 56.3 
 
 71 
 
 303.7 
 
 274.4 
 
 1174.6 
 
 900.2 
 
 374 
 
 6.01 
 
 .1665 
 
 57.3 
 
 72 
 
 304.6 
 
 275.3 
 
 1174.8 
 
 899.5 
 
 369 
 
 5.93 
 
 .1687 
 
 58.3 
 
 73 
 
 305.6 
 
 276.3 
 
 1175.1 
 
 898.9 
 
 365 
 
 5.85 
 
 .1709 
 
 59.3 
 
 74 
 
 306.5 
 
 277.2 
 
 1175.4 
 
 898.2 
 
 360 
 
 5.78 
 
 .1731 
 
 60.3 
 
 75 
 
 307.4 
 
 278.2 
 
 1175.7 
 
 897.5 
 
 356 
 
 5.71 
 
 .1753 
 
 61.3 
 
 76 
 
 308.3 
 
 279.1 
 
 1176.0 
 
 896.9 
 
 351 
 
 5.63 
 
 .1775 
 
 62.3 
 
 77 
 
 309.2 
 
 280.0 
 
 1176.2 
 
 896.2 
 
 347 
 
 5.57 
 
 .1797 
 
 63.3 
 
 78 
 
 310.1 
 
 280.9 
 
 1176.5 
 
 895.6 
 
 343 
 
 5.50 
 
 .1819 
 
 64.3 
 
 79 
 
 310.9 
 
 281.8 
 
 1176.8 
 
 895.0 
 
 339 
 
 5.43 
 
 .1840 
 
 65.3 
 
 80 
 
 311.8 
 
 282.7 
 
 1177.0 
 
 894.3 
 
 334 
 
 5.37 
 
 .1862 
 
 66.3 
 
 81 
 
 312.7 
 
 283.6 
 
 1177.3 
 
 893.7 
 
 331 
 
 5.31 
 
 .1884 
 
 67.3 
 
 82 
 
 313.5 
 
 284.5 
 
 1177.6 
 
 893.1 
 
 327 
 
 5.25 
 
 .1906 
 
 68.3 
 
 83 
 
 314.4 
 
 285.3 | 
 
 1177.8 
 
 892.5 | 
 
 323 
 
 5.18 
 
 .1928 
 
 69.3 
 
 84 
 
 315.2 
 
 286.2 
 
 1178.1 
 
 891.9 
 
 320 
 
 5.13 
 
 .1950 
 
 70.3 
 
 85 
 
 316.0 
 
 287.0 
 
 1178.3 
 
 891.3. 
 
 316 
 
 5.07 
 
 .1971 
 
 71.3 
 
 86 
 
 316.8 
 
 287.9 
 
 1178.6 
 
 890.7 
 
 313 
 
 5.02 
 
 .1993 
 
 72.3 
 
 87 
 
 317.7 
 
 288.7 
 
 1178.8 
 
 890.1 
 
 309 
 
 4.96 
 
 .2015 
 
 73.3 
 
 88 
 
 318.5 
 
 289.5 
 
 1179.1 
 
 889.5 
 
 306 
 
 4.91 
 
 .2036 
 
 74.3 
 
 89 
 
 319.3 
 
 290.4 
 
 1179.3 
 
 888.9 
 
 303 
 
 4.86 
 
 .2058 
 
 75.3 
 
 90 
 
 320.0 
 
 291.2 
 
 1179.6 
 
 888.4 
 
 299 
 
 4.81 
 
 .2080 
 
 76.3 
 
 91 
 
 320.8 
 
 292.0 
 
 1179.8 
 
 887.8 
 
 296 
 
 4.76 
 
 .2102 
 
 77.3 
 
 92 
 
 321.6 
 
 292.8 
 
 1180.0 
 
 887.2 
 
 293 
 
 4.71 
 
 .2123 
 
 78.3 
 
 93 
 
 322.4 
 
 293.6 
 
 1180.3 
 
 886.7 
 
 290 
 
 4.66 
 
 .2145 
 
 79.3 
 
 94 
 
 323.1 
 
 294.4 
 
 1180.5 
 
 886.1 
 
 287 
 
 4.62 
 
 .2166 
 
 80.3 
 
 95 
 
 323.9 
 
 295.1 
 
 1180.7 
 
 885.6 
 
 285 
 
 4.57 
 
 .2188 
 
 81.3 
 
 96 
 
 324.6 
 
 295.9 
 
 1181.0 
 
 885.0 
 
 282 
 
 4.53 
 
 .2210 
 
 82.3 
 
 97 
 
 325.4 
 
 296.7 
 
 1181.2 
 
 884.5 
 
 279 
 
 4.48 
 
 .2231 
 
 83.3 
 
 98 
 
 326.1 
 
 297.4 
 
 1181.4 
 
 884.0 
 
 276 
 
 4.44 
 
 .2253 
 
 84.3 
 
 99 
 
 326.8 
 
 298.2 
 
 1181.6 
 
 883.4 
 
 274 
 
 4.40 
 
 .2274 
 
 85.3 
 
 100 
 
 327.6 
 
 298.9 
 
 1181.8 
 
 882.9 
 
 271 
 
 4.36 
 
 .2296 
 
 86.3 
 
 101 
 
 328.3 
 
 299.7 
 
 1182.1 
 
 882.4 
 
 268 
 
 4.32 
 
 .2317 
 
 87.3 
 
 102 
 
 329.0 
 
 300.4 
 
 1182.3 
 
 881.9 
 
 266 
 
 4.28 
 
 .2339 
 
 88.3 
 
 103 
 
 329.7 
 
 301.1 
 
 1182.5 
 
 881.4 
 
 264 
 
 4.24 
 
 .2360 
 
 89.3 
 
 104 
 
 330.4 
 
 301.9 
 
 1182.7 
 
 880.8 
 
 261 
 
 4.20 
 
 .2382 
 
 90.3 
 
 105 
 
 331.1 
 
 302.6 
 
 1182.9 
 
 880.3 
 
 259 
 
 4.16 
 
 .2403 
 
 91.3 
 
 106 
 
 331.8 
 
 303.3 
 
 1183.1 
 
 879.8 
 
 257 
 
 4.12 
 
 .2425 
 
 92.3 
 
 107 
 
 332.5 
 
 304.0 
 
 1183.4 
 
 879.3 
 
 254 
 
 4.09 
 
 .2446 
 
 93.3 
 
 108 
 
 333.2 
 
 304.7 
 
 1183.6 
 
 878.8 
 
 252 
 
 4.05 
 
 .2467 
 
 94.3 
 
 109 
 
 333.9 
 
 305.4 
 
 1183.8 
 
 878.3 
 
 250 
 
 4.02 
 
 .2489 
 
 95.3 
 
 110 | 
 
 334.5 
 
 306.1 
 
 1184.0 
 
 877.9 
 
 248 
 
 3.98 
 
 .2510 
 
 96.3 
 
 111 
 
 335.2 
 
 306.8 
 
 1184.2 
 
 877.4 
 
 246 
 
 3.95 
 
 .2531 
 
 97.3 
 
 112 
 
 335.9 
 
 307.5 
 
 1184.4 
 
 876.9 
 
 244 
 
 3.92 
 
 .2553 
 
Properties of Saturated Steam 
 Table 17 — continued. 
 
 281 
 
 u C 
 3>H 
 
 c 
 
 
 Total Heat 
 
 
 
 c 
 
 o 
 
 
 
 above 32° F. 
 
 ^ 
 
 6 
 
 5 £ 
 
 ^3 
 
 W . 
 
 ££c? 
 
 P4 
 
 
 
 
 J3 
 
 'Zw 
 
 .sw 
 
 P V 
 
 
 
 be 
 
 Absolu 
 
 Pressui 
 
 Lbs. per S 
 
 Q 
 
 u 
 
 <U CO 
 
 In the Steam 
 H 
 Heat-units 
 
 Latent H 
 
 H-h 
 Heat-uni 
 
 O 
 > 
 
 v o 
 
 H 
 
 ■M ° 
 
 98.3 
 
 113 
 
 336.5 
 
 308.2 
 
 1184.6 
 
 876.4 
 
 242 
 
 3.88 
 
 .2574 
 
 99.3 
 
 114 
 
 337.2 
 
 308.8 
 
 1184.8 
 
 875.9 
 
 240 
 
 3.85 
 
 .2596 
 
 100.3 
 
 115 
 
 337.8 
 
 309.5 
 
 1185.0 
 
 875.5 
 
 238 
 
 3.82 
 
 .2617 
 
 101.3 
 
 116 
 
 338.5 
 
 310.2 
 
 1185.2 
 
 875.0 
 
 236 
 
 3.79 
 
 .2638 
 
 102.3 
 
 117 
 
 339.1 
 
 310.8 
 
 1185.4 
 
 874.5 
 
 234 
 
 3.76 
 
 .2660 
 
 103.3 
 
 118 
 
 339.7 
 
 311.5 
 
 1185.6 
 
 874.1 
 
 232 
 
 3.73 
 
 .2681 
 
 104.3 
 
 119 
 
 340.4 
 
 312.1 
 
 1185.8 
 
 873.6 
 
 230 
 
 3.70 
 
 .2703 
 
 105.3 
 
 120 
 
 341.0 
 
 312.8 
 
 1185.9 
 
 873.2 
 
 228 
 
 3.67 
 
 .2764 
 
 106.3 
 
 121 
 
 341.6 
 
 313.4 
 
 1186.1 
 
 872.7 
 
 227 
 
 3.64 
 
 .2745 
 
 107.3 
 
 122 
 
 342.2 
 
 314.1 
 
 1186.3 
 
 872.3 
 
 225 
 
 3.62 
 
 .2766 
 
 108.3 
 
 123 
 
 342.9 
 
 314.7 
 
 1186.5 
 
 871.8 
 
 223 
 
 3.59 
 
 .2788 
 
 109.3 
 
 124 
 
 343.5 
 
 315.3 
 
 1186.7 
 
 871.4 
 
 221 
 
 3.56 
 
 .2809 
 
 110.3 
 
 125 
 
 344.1 
 
 316.0 
 
 1186.9 
 
 870.9 
 
 220 
 
 3.53 
 
 .2830 
 
 111.3 
 
 126 
 
 344.7 
 
 316.6 
 
 1187.1 
 
 870.5 
 
 218 
 
 3.51 
 
 .2851 
 
 112.3 
 
 127 
 
 345.3 
 
 317.2 
 
 1187.3 
 
 870.0 
 
 216 
 
 3.48 
 
 .2872 
 
 113.3 
 
 128 
 
 345.9 
 
 317.8 
 
 1187.4 
 
 869.6 
 
 215 
 
 3.46 
 
 .2894 
 
 114.3 
 
 129 
 
 346.5 
 
 318.4 
 
 1187.6 
 
 869.2 
 
 213 
 
 3.43 
 
 .2915 
 
 115.3 
 
 130 
 
 347.1 
 
 319.1 
 
 1187.8 
 
 868.7 
 
 212 
 
 3.41 
 
 .2936 
 
 116.3 
 
 131 
 
 347.6 
 
 319.7 
 
 1188.0 
 
 868.3 
 
 210 
 
 3.38 
 
 .2957 
 
 117.3 
 
 132 
 
 348.2 
 
 320.3 
 
 1188.2 
 
 867.9 
 
 209 
 
 3.36 
 
 .2978 
 
 118.3 
 
 133 
 
 348.8 
 
 320.8 
 
 - 1188.3 
 
 867.5 
 
 207 
 
 3.33 
 
 .3000 
 
 119.3 
 
 134 
 
 349.4 
 
 321.5 
 
 1188.5 
 
 867.0 
 
 206 
 
 3.31 
 
 .3021 
 
 120.3 
 
 135 
 
 350.0 
 
 322.1 
 
 1188.7 
 
 866.6 
 
 204 
 
 3.29 
 
 .3042 
 
 121.3 
 
 136 
 
 350.5 
 
 322.6 
 
 1188.9 
 
 866.2 
 
 203 
 
 3.27 
 
 .3063 
 
 122.3 
 
 137 
 
 351.1 
 
 323.2 
 
 1189.0 
 
 865. 8 
 
 201 
 
 3.24 
 
 .3084 
 
 123.3 
 
 138 
 
 351.8 
 
 323.8 
 
 1189.2 
 
 865.4 
 
 200 
 
 3.22 
 
 .3105 
 
 124.3 
 
 139 
 
 352.2 
 
 324.4 
 
 1189.4 
 
 865.0 
 
 199 
 
 3.20 
 
 .3126 
 
 125.3 
 
 140 
 
 352.8 
 
 325.0 
 
 1189.5 
 
 864.6 
 
 197 
 
 3.18 
 
 .3147 
 
 126.3 
 
 141 
 
 353.3 
 
 325.5 
 
 1189.7 
 
 864.2 
 
 196 
 
 3.16 
 
 .3169 
 
 127.3 
 
 142 
 
 353.9 
 
 326.1 
 
 1189.9 
 
 863.8 
 
 195 
 
 3.14 
 
 .3190 
 
 128.3 
 
 143 
 
 354.4 
 
 326.7 
 
 1190.0 
 
 863.4 
 
 193 
 
 3.11 
 
 .3211 
 
 329.3 
 
 144 
 
 355.0 
 
 327.2 
 
 1190.2 
 
 863.0 
 
 192 
 
 3.09 
 
 .3232 
 
 130.3 
 
 145 
 
 355.5 
 
 327.8 
 
 1190.4 
 
 862.6 
 
 191 
 
 3.07 
 
 .3253 
 
 131.3 
 
 146 
 
 356.0 
 
 328.4 
 
 1190.5 
 
 862.2 
 
 190 
 
 3.05 
 
 .3274 
 
 133.3 
 
 148 
 
 357.1 
 
 329.5 
 
 1190.9 
 
 861.4 
 
 187 
 
 3.02 
 
 .3316 
 
 135.3 
 
 150 
 
 358.2 
 
 330.6 
 
 1191.2 
 
 860.6 
 
 185 
 
 2.98 
 
 .3358 
 
 140.3 
 
 155 
 
 360.7 
 
 333.2 
 
 1192.0 
 
 858.7 
 
 179 
 
 2.89 
 
 .3463 
 
 145.3 
 
 160 
 
 363.3 
 
 335.9 
 
 1192.7 
 
 856.9 
 
 174 
 
 2.80 
 
 .3567 
 
 150.3 
 
 165 
 
 365.7 
 
 338.4 
 
 1193.5 
 
 855.1 
 
 169 
 
 2.72 
 
 .3671 
 
 155.3 
 
 170 
 
 368.2 
 
 340.9 
 
 1194.2 
 
 853.3 
 
 164 
 
 2.65 
 
 .3775 
 
 160.3 
 
 175 
 
 370.5 
 
 343.4 
 
 1194.9 
 
 851.6 
 
 160 
 
 2.58 
 
 .3879 
 
 165.3 
 
 180 
 
 372.8 
 
 345.8 
 
 1195.7 
 
 849.9 
 
 156 
 
 2.51 
 
 .3983 
 
 170.3 
 
 185 
 
 375.1 
 
 348.1 
 
 1196.3 
 
 848.2 
 
 152 
 
 2.45 
 
 .4087 
 
 175.3 
 
 190 
 
 377.3 
 
 350.4 
 
 1197.0 
 
 846.6 
 
 148 
 
 2.39 
 
 .4191 
 
 180.3 
 
 195 
 
 379.5 
 
 352.7 
 
 1197.7 
 
 845.0 
 
 144 
 
 2.33 
 
 .4296 
 
 185.3 
 
 200 
 
 381.6 
 
 354.9 
 
 1198.3 
 
 843.4 
 
 141 
 
 2.27 
 
 .4400 
 
 190.3 
 
 205 
 
 383.7 
 
 357.1 
 
 1199.0 
 
 841.9 
 
 138 
 
 2.22 
 
 .4503 
 
 195.3 
 
 210 
 
 385.7 
 
 359.2 
 
 1199.6 
 
 840.4 
 
 135 
 
 2.17 
 
 .4605 
 
 200.3 
 
 215 | 
 
 387.7 
 
 361.3 
 
 1200.2 
 
 838.9 
 
 132 
 
 2.12 
 
 .4707 
 
r 
 
 282 
 
 Steam Engineering 
 Table 1 7 — continued 
 
 
 t— i 
 
 
 Total Heat 
 
 
 
 6 
 
 o 
 
 u G 
 
 
 above 
 
 32° F. 
 
 
 £ 
 
 C <L» 
 
 o . 
 
 pjl-H 
 
 
 ft 
 
 c <u 
 H bo 
 
 M 
 
 
 
 a in 
 
 a 
 
 
 «^ 
 
 
 Absolute 
 
 Pressure 
 
 s. per Sq 
 
 
 £ g 
 
 >3 w 
 
 o 
 > 
 <u 
 > 
 
 
 
 CJ 
 
 J3 
 h-1 
 
 
 
 
 
 tf 
 
 
 jj o 
 
 205.3 
 
 220 
 
 389.7 
 
 362.2 
 
 1200.8 
 
 838.6 
 
 129 
 
 2.06 
 
 .4852 
 
 245.3 
 
 260 
 
 404.4 
 
 377.4 
 
 1205.3 
 
 827.9 
 
 110 
 
 1.76 
 
 .5686 
 
 285.3 
 
 300 
 
 417.4 
 
 390.9 
 
 1209.2 
 
 818.3 
 
 96 
 
 1.53 
 
 .6515 
 
 485.3 
 
 500 
 
 467.4 
 
 443.5 
 
 1224.5 
 
 781.0 
 
 59 
 
 .94 
 
 1.062 
 
 685.3 
 
 700 
 
 504.1 
 
 482.4 
 
 1235.7 
 
 753.3 
 
 42 
 
 .68 
 
 1.470 
 
 985.3 
 
 1000 
 
 546.8 
 
 528.3 
 
 1248.7 
 
 720.3 
 
 30 
 
 .48 
 
 2.082 
 
Combustion 
 
 Combustion, as the term is used in steam engineering, 
 is the rapid chemical combination of oxj^gen with carbon, 
 hydrogen, and sulphur, with the accompaniment of heat 
 and light. The substance which combines with the oxygen 
 is the combustible. The combustion is perfect when the 
 combustible is oxidized to the highest possible degree ; thus, 
 conversion of carbon into carbon dioxide (C0 2 ) represents 
 perfect combustion, while its conversion to monoxide (CO) 
 is imperfect combustion, since the monoxide can be further 
 burned and finally converted into C0 2 . 
 
 Kindling Point. As in many other chemical processes, 
 a certain degree of heat is necessary to cause the union of 
 the oxygen and combustible; the temperatures necessary 
 to cause this union are the kindling temperatures, and are 
 approximately as given in the following table by Stromeyer : 
 
 Table 18 
 kindling temperatures. 
 
 Lignite Dust 300° F 
 
 Sulphur 470 
 
 Dried Peat 435 
 
 Anthracite Dust 570 
 
 Coal 600 
 
 Cokes Red Heat 
 
 Anthracite Red Heat 750 
 
 Carbon Monoxide Red Heat 1211 
 
 Hydrogen 1030 or 1290 
 
 The Oxygen necessary for combustion is supplied from 
 the air. Its density is 1.10521 (Air=l) ; its weight 
 0.088843 pounds per cubic foot at 32° F., and atmospheric 
 pressure; its atomic weight is 16 ; a pound of air contains 
 
 283 
 
284 
 
 Steam Engineering 
 
 0.2315 pounds of oxygen, and 1 pound of oxygen is con- 
 tained in 4.32 pounds of air. 
 
 Carbon (C), the most abundant combustible, has atomic 
 weight of 12, and reaches the boiler furnace as a constituent 
 of oil, gas, coal, charcoal, wood, etc. 
 
 Hydrogen (H) occurs free in small quantity in some 
 fuels, but is usually in combination with the carbon. Its 
 atomic weight is 1; its density is 0.0692 (Air=l) ; and its 
 weight per cubic foot at 32° F. and atmospheric pressure 
 is 0.00559 pounds. The heating value of 1 pound of pure 
 carbon is rated at 14,500 heat units, while 1 pound of hydro- 
 gen gas contains 62,000 heat units. 
 
 Coal. Analysis of coal shows that it contains moisture, 
 fixed carbon, volatile matter, ash and sulphur in various 
 proportions according to the quality of the coal. Table 19 
 deduced from a few of the many valuable tables of analysis 
 of the coals of the United States will show the composition 
 of the principal bituminous coals in use in this country for 
 
 Table 19 
 composition of various coals. 
 
 
 
 Mois- 
 
 Vola- 
 
 Fixed 
 
 
 Sul- 
 
 State 
 
 Kind of Coal 
 
 ture 
 
 tile 
 Matter 
 
 Carbon 
 
 Ash 
 
 phur 
 
 Pennsylvania 
 
 Youghiogheny 
 
 1.03 . 
 
 36.49 
 
 59.05 
 
 2.61 
 
 0.81 
 
 Pennsylvania 
 
 Connellsville 
 
 1.26 
 
 30.10 
 
 59.61 
 
 8.23 
 
 0.78 
 
 West Virginia 
 
 Quinimont 
 Fire Creek 
 
 0.76 
 
 18.65 
 
 79.26 
 
 1.11 
 
 0.23 
 
 West Virginia 
 
 0.61 
 
 22.34 
 
 75.02 
 
 1.47 
 
 0.56 
 
 E. Kentucky 
 
 Peach Orchard 
 
 4.60 
 
 35.70 
 
 53.28 
 
 6.42 
 
 1.08 
 
 E. Kentucky 
 
 Pike County 
 
 1.80 
 
 26.80 
 
 67.60 
 
 3.80 
 
 0.97 
 
 Alabama 
 
 Cahaba 
 
 1.66 
 
 33.28 
 
 63.04 
 
 2.02 
 
 0.53 
 
 Alabama 
 
 Pratt Co.'s 
 
 1.47 
 
 32.29 
 
 59.50 
 
 6.73 
 
 1.22 
 
 Ohio 
 
 Hocking Valley 
 
 6.59 
 
 35.77 
 
 49.64 
 
 8.00 
 
 1.59 
 
 Ohio 
 
 Muskingum Valley 
 
 3.47 
 
 37.88 
 
 53.30 
 
 5.35 
 
 2.24 
 
 Indiana 
 
 Block 
 
 8.50 
 
 31.00 
 
 57.50 
 
 3.00 
 
 
 Indiana 
 
 Block 
 
 2.50 
 
 44.75 
 
 51.25 
 
 1.50 
 
 
 W. Kentucky 
 
 Nolin River 
 
 4.70 
 
 33.24 
 
 54.94 
 
 11.70 
 
 2.54 
 
 W. Kentucky 
 
 Ohio County 
 
 3.70 
 
 30.70 
 
 45.00 
 
 3.16 
 
 1.24 
 
 Illinois 
 
 Big Muddy 
 
 6.40 
 
 30.60 
 
 54.60 
 
 8.30 
 
 1.50 
 
 Illinois 
 
 Wilmington 
 
 15.50 
 
 32.80 
 
 39.90 
 
 11.80 
 
 
 Illinois 
 
 screenings 
 
 14.00 
 
 28.00 
 
 34.20 
 
 23.80 
 
 
 Illinois 
 
 Duquoin 
 
 8.90 
 
 23.50 
 
 60.60 
 
 7.00 
 
 
Combustion 285 
 
 steam purposes. Two samples are selected from each of 
 the great coal producing states, with the exception of 
 Illinois, from which four were taken. 
 
 The process of combustion of fuel consists in the union 
 of the carbon and hydrogen of the fuel with the oxygen of 
 the air. Each atom of carbon combines with two atoms of 
 oxygen, and the energetic vibration set up by their com- 
 bination is heat. Bituminous coal contains a large per- 
 centage of volatile matter which is released and flashes into 
 flame when the coal is thrown into the furnace, and unless 
 air is supplied in large amounts at this stage of the com- 
 bustion there will be an excess of smoke, and consequent 
 loss of carbon. On the other hand there is a loss in ad- 
 mitting too much air because the surplus is heated to the 
 temperature of the furnace without aiding the combustion, 
 and will carry off to the chimney just as many heat units 
 as were required to raise it from the temperature at which 
 it entered the furnace, to that at which it enters the uptake. 
 It will therefore be seen that a great advantage will be 
 gained by first allowing the air that is needed above the 
 fire to pass over or through heated bridge walls, or side 
 walls. Some kinds of coal need more air for their com- 
 bustion than do others, and good judgment and close ob- 
 servation are needed on the part of the fireman to properly 
 regulate the supply. 
 
 Sulphur (S, atomic weight 32) is found in most coals 
 and in some oils. It is usually present in a combined form, 
 either as sulphide of iron, or sulphate of lime ; in the latter 
 form it has no heating value. Its presence in fuel is ob- 
 jectionable, because the gases formed from its combustion 
 attack the metal of the boiler and cause rapid corrosion, 
 particularly in presence of moisture. 
 
w ' 
 
 286 Steam Engineering 
 
 Nitrogen (N) is drawn into the furnace with the air. 
 Its atomic weight is 14; its density is 0.9701 (Air=l) ; 
 its weight per cubic foot at 32° F. and atmospheric pres- 
 sure is .07831 pounds; each pound of air at atmospheric 
 pressure contains 0.7685 pounds of nitrogen, and 1 pound 
 of nitrogen is contained in 1.301 pounds of air. 
 
 Nitrogen performs no useful office in combustion, and 
 passes through the furnace without change. It dilutes the 
 air, absorbs heat and reduces the temperature of the prod- 
 ucts of combustion, and is the chief source of heat loss in 
 furnaces. 
 
 Combining Weights. When chemical elements unite to 
 form a new compound they do so in definite proportions 
 which are always the same, and the union produces heat, 
 the quantity of which is also invariable. Thus, a pound of 
 carbon, when carbon dioxide is formed, will always unite 
 with 2 2-3 pounds of oxygen, and give off 14,600 B. T. U. 
 As an intermediate step the carbon might unite with 1 1-3 
 times its weight of oxygen, and produce 4,450 B. T. IT., but 
 in its further conversion to C0 2 it would unite with an 
 additional 1 1-3 times its weight of oxygen and evolve the 
 other 10,150 B. T. IT., since the heat developed in any 
 chemical combination depends upon the initial, and final 
 states, and not upon any intermediate change. 
 
 Carlorific Value of Fuel. The amount of heat liberated 
 per pound of fuel undergoing perfect combustion is called 
 the calorific value of the fuel. 
 
 Some boilers will make steam more economically by 
 partly closing the ash-pit doors, while others require the 
 same doors to be kept wide open. The quantity of air re- 
 quired for the combustion of one pound of coal is, by 
 volume, about 150 cubic feet; by weight, about 12 pounds. 
 
Combustion 287 
 
 The temperature of the furnace is usually about 2,500°, 
 in some cases reaching as high as 3,000°. The temperature 
 of the escaping gases should not be much above nor below 
 400° F. for bituminous coal. The waste heat in the escap- 
 ing gases can be utilized to great advantage by passing 
 them through what are called economizers before they es- 
 cape into the chimney. These economizers consist of coils, 
 or stacks of cast iron pipe placed within the flue or breeching 
 leading from the boilers to the chimney and are enveloped 
 in the hot gases, while the feed water is passed through 
 the pipes on its way to the boilers, the result being that 
 considerable heat is thus imparted to the feed water that 
 would otherwise go to waste. 
 
 In order to attain the highest economy in the burning 
 of coal in boiler furnaces two factors are indispensable, 
 viz., a constant high furnace temperature, and quick com- 
 bustion, and these factors can only be secured by supplying 
 the fresh coal constantly just as fast as it is burned, and 
 also by preventing as much as possible the admission of 
 cold air to the furnace. This is why the automatic or 
 mechanical stoker, if it be of the proper design, is more 
 economical and causes less smoke than hand firing. The 
 fireman when he puts in a fire is prone to shovel in a good 
 supply all at once, and this has the tendency to greatly 
 reduce the temperature of the furnace, while at the same 
 time it retards combustion. On the other hand the me- 
 chanical stoker supplies the coal continuously only as fast 
 as it is required and no faster, and the furnace doors to 
 not need to be opened at all, by which a large volume of 
 cold air is prevented from entering the furnace and reduc- 
 ing the temperature. The author does not wish to be under- 
 stood as recommending the adoption and use of mechanical 
 
288 Steam Engineering 
 
 stokers to replace hand firing, but he draws this contrast 
 between the two methods of firing in order that it may be 
 of some benefit to the thousands of honest toilers who earn 
 a livelihood by shoveling coal into boiler furnaces. 
 
 The problem of the economical use of coal and the abate- 
 ment of the smoke nuisance, especially in our large cities, 
 has of late years become so serious that it is to the interest 
 of every engineer, and especially every fireman, to use the 
 utmost diligence, care and good judgment in the use of 
 coal, and to emulate as much as possible the methods of the 
 mechanical stoker. 
 
 Heat, All matter, whether solid, liquid or gaseous, con- 
 sists of molecules, or atoms, which are in a state of continual 
 vibration, and the result of this vibration is heat. The 
 intensity of the heat evolved depends upon the degree of 
 agitation to which the molecules are subject. 
 
 Heat Effects. When heat is added to or taken from a 
 body, either the temperature of the body is altered, or its 
 volume is varied, or its state is changed. Thus, if heat be 
 added to water under atmospheric pressure,, the temperature 
 of the water increases until it reaches 212° F. If more 
 heat be added and the pressure remains unchanged, the 
 temperature does not further increase, but the water evapor^ 
 ates into steam. Heat thus changes water from a liquid to 
 a gaseous state. If heat be abstracted from water the tem- 
 perature is reduced until it reaches 32° F., after which any 
 diminution of heat does not further decrease the tempera- 
 ture, until the liquor is converted into a solid, or ice. The 
 quantity of heat passing from one body to another can thus 
 be estimated by the effects produced. Therefore heat is 
 something that can be both transferred and measured. 
 
 The general effect of heat on a body is to increase its 
 
Heat 289 
 
 volume. If heat be abstracted from a body the contrary 
 effect ensues, and the volume is diminished. Hence the 
 general principle, to which, however, there are some ex- 
 ceptions, that heat expands and cold contracts. These 
 effects, arising from a change of temperature, are produced 
 in very different degrees according to the nature of the 
 bodies. They are small in solids, greater in liquids, and 
 greater still in gases. 
 
 It is w r ell known that the work expended in friction 
 apparently is lost as regards mechanical work; that heat 
 is developed when friction occurs; that the greater the 
 friction the greater is the amount of heat produced. Ex- 
 periments have proved that the amount of heat generated 
 by friction is exactly equivalent to the amount of work 
 lost, whence it is shown that heat, like mechanical work 
 is one of the forms of energy. 
 
 Thermometers. In consequence of the uniform expan- 
 sion of mercury and its great sensitiveness to heat, it is the 
 fluid most commonly used in the construction of thermome- 
 ters. In all thermometers the freezing and the boiling 
 point of water, under mean atmospheric pressure at sea 
 level, are assumed as two fixed points, but the division of 
 the scale between these two points varies in different coun- 
 tries, hence there are in use three thermometers, known as 
 the Fahrenheit, the Centrigrade or Celsius, and the Reau-r 
 mur. In the Fahrenheit, the space between the two fixed 
 points is divided into 180 parts; the boiling point is marked 
 212, and the freezing point is marked 32, and zero is a 
 temperature which, at the time this thermometer was in- 
 vented, was incorrectly imagined to be the lowest tempera- 
 ture attainable. In the Centrigrade and the Reaumur 
 scales the distance between the two fixed points is divided 
 
290 
 
 Steam Engineering 
 
 Table 20 
 compaeison of thermometer scales. 
 
 I 
 
 Fahrenheit 
 
 Centigrade 
 
 Reaumur 
 
 —460.66 
 
 —273.70 
 
 —218.96 
 
 
 
 —17.77 
 
 —14.22 
 
 10 
 
 —12.23 
 
 —9.77 
 
 20 
 
 —6.67 
 
 —5.33 
 
 30 
 
 —1.11 
 
 —0.88 
 
 32 
 
 0. 
 
 0. 
 
 39.1 
 
 3.94 
 
 3.15 
 
 50 
 
 10. 
 
 8. 
 
 75 
 
 23.89 
 
 19.11 
 
 100 
 
 37.78 
 
 30.22 
 
 200 
 
 93.34 
 
 74.66 
 
 212 
 
 100. 
 
 80. 
 
 250 
 
 121.11 
 
 96.88 
 
 300 
 
 148.89 
 
 119.11 
 
 350 
 
 176.67 
 
 141.33 
 
 Absolute Zero 
 
 Freezing Point 
 
 Maximum Density of 
 Water 
 
 Boiling Point 
 
 F=9-5 C+32° = 9-4 E+32° 
 C=5-9(F— 32°) =5-4 E. 
 B=4-5C=4-9(F— 32°). 
 
 into 100 and 80 parts, respectively. In each of these two 
 scales the freezing point is marked 0, and the boiling point 
 is marked 100 in the Centigrade, and 80 in the Eeaumur. 
 Each of the 180, 100, or 80 divisions is termed a degree. 
 Table 20 and the appended formulas are useful for con- 
 verting one scale to another. 
 
 1 
 
 Absolute zero. At 32° F. a perfect gas expands ■ 
 
 492.66 
 part of its volume, if its temperature is increased one de- 
 gree and its pressure remains constant. This rate of ex- 
 pansion holds good at all temperatures above the freezing 
 point, in the case of the gas, which would double its volume 
 if under a constant pressure its temperature were raised to 
 32°+492.66=524.66° F., while under a diminution of 
 temperature it would shrink and finally disappear at a 
 temperature of 492.66—32=460.66° below zero F. 
 
Heat 291 
 
 Therefore the temperature 460.66°, or for the sake of 
 simplicity, 461° F. is taken as absolute zero. 
 
 Until as late as the beginning of the nineteenth century 
 two rival theories in regard to the nature of heat had been 
 advocated by scientists. The older of these theories was that 
 heat was a material substance, a subtle, elastic fluid termed 
 caloric, and that this fluid penetrated matter something 
 like water penetrates a sponge. But this theory was shown 
 to be false by the wonderful researches and experiments of 
 Count Eumford at Munich, Bavaria, in 1798. 
 
 By means of the friction, between two heavy metallic 
 bodies placed in a wooden trough filled with water, one of 
 the pieces of metal being rotated by machinery driven by 
 horses, Count Eumford succeeded in raising the tempera- 
 ture of the water in two and one-half hours from its original 
 temperature of 60° to 212° F., the boiling point, thus 
 demonstrating that heat is not a material substance, but 
 that it is due to vibration or motion, an internal commotion 
 among the molecules of matter. This theory, known as 
 the Kinetic theory of heat, has since been generally ac- 
 cepted, although it was nearly fifty years after Eumford 
 advocated it in a paper read before the Eoyal Society of 
 Great Britain in 1798, before scientists generally became 
 converted to this idea of the nature of heat, and the science 
 of thermo-dynamics was placed on a firm basis. 
 
 During the period from 1840 to 1849 Dr. Joule made a 
 series of experiments which not only confirmed the truth 
 of Count Bumford's theory that heat was not a material 
 substance, but a form of energy which may be applied to or 
 taken away from bodies, but Joule's experiments also es- 
 tablished a method of estimating in mechanical units or foot 
 pounds the amount of that energy. This latter was a most 
 
292 Steam Engineering 
 
 important discovery, because by means of it the exact rela- 
 tion between heat and work can be accurately measured. 
 
 The first law of thermo-dynamics is this: Heat and 
 mechanical energy, or work are mutually convertible. That 
 is, a certain amount of work will produce a certain amount 
 of heat, and the heat thus produced is capable of producing 
 by its disappearance a fixed amount of mechanical energy 
 if rightly applied. The mechanical energy in the form of 
 heat which, through the medium of the steam engine, has 
 revolutionized the world, was first stored up by the sun's 
 heat millions of years ago in the coal which in turn, by 
 combustion, is made to release it for purposes of mechanical 
 work. 
 
 The general principles of Dr. Joule's device for meas- 
 uring the amount of work in heat are illustrated in Fig. 
 102. It consists of a small copper cylinder containing a 
 known quantity of water at a known temperature. Inside 
 the cylinder and extending through the top was a vertical 
 shaft to which were fixed paddles for stirring the water. 
 Stationary vanes were also placed inside the cylinder. Mo- 
 tion was imparted to the shaft through the medium of a 
 cord or small rope coiled around a drum near the top of 
 the shaft and running over a grooved pulley or sheave. To 
 the free end of the cord a known weight was attached. 
 This weight was allowed to fall through a certain distance, 
 and in falling it turned the shaft with its paddles, which in 
 turn agitated the water, thus producing a certain amount 
 of heat. To illustrate, suppose the weight to be 77.8 pounds, 
 and that by means of the crank at the top end of the shaft 
 it has been raised to the zero mark at the top of the scale. 
 (See Fig. 102.) One pound of water at 39.1° F. is poured 
 into the copper cylinder, which is then closed and the weight 
 
Heat 
 
 293 
 
 released. At the moment the weight passes the 10 foot 
 mark on the scale, the thermometer attached to the cylinder 
 will indicate that the temperature of the water has been 
 raised one degree. Then multiplying the number of pounds 
 in the weight by the distance in feet through which it fell 
 
 We, 3 ht ft/fa 
 
 O- frank 
 
 P - fiaddies 
 £ V-Jtabc/va*y Vantf 
 
 r~££e*mom etc* 
 
 -z 
 
 j 
 
 - f 
 
 - i 
 
 - 1 
 -I 
 
 fir* 
 
 Fig. 102 
 
 will give the number of foot pounds of work done. Thus, 
 77.8 poundsXIO feet=778 foot pounds. 
 
 The heat unit or British thermal unit (B. T. U.) is the 
 quantity of heat required to raise the temperature of one 
 pound of water one degree, or from 39° to 40° F., and 
 
294 Steam Engineering 
 
 the amount of mechanical work required to produce a 
 unit of heat is 778 foot pounds. Therefore the mechanical 
 equivalent of heat is the energy required to raise 778 pounds 
 one foot high, or 77.8 pounds 10 feet high, or 1 pound 778 
 feet high. Or again, suppose a one-pound weight falls 
 through a space of 778 feet or a weight of 778 pounds falls 
 one foot, enough mechanical energy would thus be de- 
 veloped to raise a pound of water one degree in tempera- 
 ture, provided all the energy so developed could be utilized 
 in churning or stirring the water, as in Joule's machine. 
 Hence the mechanical equivalent of heat is 778 foot pounds. 
 
 Specific Heat. The specific heat of any substance is 
 the ratio of the quantity of heat required to raise a given 
 weight of that substance one degree in temperature, to the 
 quantity of heat required to raise an equal weight of water 
 one degree in temperature when the water is at its maxi- 
 mum density, 39.1° P. To illustrate, take the specific heat 
 of lead, for instance, which is .031, while the specific heat 
 of water is 1. That means that it would require 31 times 
 as much heat to raise one pound of water one degree in 
 temperature as it would to raise the temperature of a pound 
 of lead one degree. 
 
 The following table gives the specific heat of different 
 substances in which engineers are most generally interested : 
 
Heat 295 
 
 Table 21 
 specific heat of various substances. 
 
 Water at 39.1" F 1.000 
 
 Ice at 32° F 504 
 
 Steam at 212° F 480 
 
 Mercury , 033 
 
 Cast iron 130 
 
 Wrought iron . 113 
 
 Soft steel 116 
 
 Copper 095 
 
 Lead 031 
 
 Coal 240 
 
 Air 238 
 
 Hydrogen 3.404 
 
 Oxygen 218 
 
 Nitrogen 244 
 
 Sensible Heat and Latent Heat. The plainest and most 
 simple definition of these two terms is that given by Sir 
 Wm. Thomson. He says: "Heat given to a body and 
 warming it is sensible heat. Heat given to a body and not 
 warming it is latent heat." Sensible heat in a substance 
 is the heat that can be measured in degrees of a thermome- 
 ter, while latent heat is the heat in any substance that is 
 not shown by the thermometer. 
 
 To illustrate this more fully a brief reference to some 
 experiments made by Professor Black in 1762 will no doubt 
 make the matter plain. It will be remembered that at that 
 early date comparatively little was known of the true 
 nature of heat, hence Professor Black's investigations and 
 discoveries along this line appear all the more wonderful. 
 He procured equal weights of ice at 32° F. and water at the 
 same temperature, that is, just at the freezing point, and 
 placing them in separate glass vessels suspended the vessels 
 in a room in which the uniform temperature was 47° F. 
 He noticed that in one-half hour the water had increased 
 7° F. in temperature, but that twenty half hours elapsed 
 before all of the ice was melted. Therefore he reasoned that 
 twenty times more heat had entered the ice than had entered 
 
296 Steam Engineering 
 
 the water, because at the end of twenty half hours when 
 the ice was all melted the water in both vessels was of the 
 same temperature. The water having absorbed 7° of heat 
 during the first half hour must have continued to absorb 
 heat at the same rate during the whole of the twenty half 
 hours, although the thermometer did not indicate it. From 
 this he calculated that 7°X20=140° of heat had become 
 latent or hidden in the water. 
 
 In another experiment Professor Black placed a lump 
 of melting ice, which he estimated to be at a temperature 
 of 33° F. on the surface, in a vessel containing the same 
 weight of water at 176° F., and he observed that when the 
 whole of the ice had been melted the temperature of the 
 water was 33° F., thus proving that 143° of heat (176°— 
 33°) had been absorbed in melting the ice and was at that 
 moment latent in the water. By these two experiments 
 Professor Black established the theory of the latent heat of 
 water, and his estimate was very near the truth because 
 the results obtained since that time by the greatest experi- 
 menters show that the latent heat of water is 142 heat units, 
 or B. T. U. 
 
 Black's experiment for ascertaining the latent heat in 
 steam at atmospheric pressure was made in the following 
 simple manner : He placed a flat, open tin dish on a hot 
 plate over a fire and into the dish he put a small quantity 
 of water at 50° F. In four minutes the water began to 
 boil, and in twenty minutes more it had all evaporated. 
 In the first four minutes the temperature had increased 
 212° — 50° = 162°, and the temperature remained at 
 212° throughout the twenty minutes that it required to 
 evaporate all the water, despite the fact that the water 
 had been receiving heat during this period at the same rate 
 
Heat 297 
 
 as during the first four minutes. He therefore reasoned 
 that in the twenty minutes the water had absorbed five 
 times as much heat as it had in the four minutes, or 160° X 
 5=810°, without any sensible rise in temperature. There- 
 fore the 810° became latent in the steam. Owing to the 
 crude nature of the experiment Professor Black's estimate 
 of the number of degrees of latent heat in steam was in- 
 correct, as it has been proven by many famous experimenters 
 since then that the latent heat of steam at atmospheric 
 pressure is 965.7 B. T. U. 
 
 It will thus be perceived that what is meant by the term 
 latent heat is that quantity of heat which becomes hidden, 
 or latent when the state of a body is changed from a solid 
 to a liquid, as in the case of melting ice, or from a liquid 
 to a gaseous state, as with water evaporated into steam.. 
 But the heat so disappearing has not been lost, on the 
 contrary it has, while becoming latent, been doing an im- 
 mense amount of work, as can easily be ascertained by 
 means of a few simple figures. It has been seen that a 
 heat unit is the quantity of heat required to raise one 
 pound of water one degree in temperature and also that the 
 mechanical equivalent of heat, or, in other words, the 
 mechanical energy stored in one- heat unit is equal to 778 
 foot pounds of work. 
 
 A horse power equals 33,000 foot pounds of energy in 
 one minute of time, and a heat unit=778-i-33,000=:.0236, 
 or about 1-43 of a horse-power. The work done by the 
 heat which becomes latent in converting one pound of ice 
 at 32° F. into water at the same temperature=142 heat 
 unitsX?78 foot pounds=110,476 foot pounds, which di- 
 vided by 33,000 equals 3.34 horse-power. Again, by the 
 evaporation of one pound of water from 32° F. into steam 
 
298 Steam Engineering 
 
 at atmospheric pressure, 965.7 units of heat become latent 
 in the steam and the work done=965. 7X778=751,314 
 foot pounds=22.7 horse-power. It will thus be seen what 
 tremendous energy lies stored in one pound of coal, which 
 contains from 12,000 to 14,500 heat units, provided all 
 the heat could be utilized in an engine. 
 
 Total Heat of Evaporation. In order to raise the tem- 
 perature of one pound of water from the freezing point, 
 32° F., to the boiling point, 212° F., there must be added 
 to the temperature of the water 212°— 32° = 180°. This 
 represents the sensible heat. Then to make the water boil 
 at atmospheric pressure, or, in other words, to evaporate it, 
 there must still be added 965.7 B. T. IT., thus 180+965.7= 
 1,145.7, or in round numbers 1,146 heat units. This repre- 
 sents what is termed the total heat of evaporation at at- 
 mospheric pressure and is the sum of the sensible and latent 
 heat in steam at that pressure. But if a thermometer were 
 held in steam evaporating into the open air, as, for instance, 
 in front of the spout of a tea-kettle, it would indicate but 
 212° F. 
 
 When steam is generated at a higher pressure than 212°, 
 the sensible heat increases and the latent heat decreases 
 slowly, while at the same time the total heat of evaporation 
 slowly increases as the pressure increases, but not in the 
 same ratio. As, for instance, the total heat in steam at 
 atmospheric pressure is 1,146 B. T. U., while the total heat 
 in steam at 100 pounds gauge pressure is 1,185 B. T. IT., 
 and the sensible temperature of steam at atmospheric pres- 
 sure is 212°, while at 100 pounds gauge pressure the tem- 
 perature is 338 and the latent heat is 876 B. T. IT. 
 
Water 299 
 
 WATER.. 
 
 Water. The elements that enter into the composition of 
 pure water are the two gases, hydrogen and oxygen, in the 
 following proportions : 
 
 Hydrogen Oxygen 
 
 By volume . . . . 2 1 
 
 By weight 11.1 88.9 
 
 Perfectly pure water is not attainable, neither is it de- 
 sirable nor necessary to the welfare of the human race, 
 because the presence of certain proportions of air and 
 ammonia add greatly to its value as an agent for manu- 
 facturing purposes and for generating steam. The nearest 
 approach to pure water is rain water, but even this contains 
 2.5 volumes of air to each 100 volumes of water. Pure 
 distilled water, such for instance as the return water from 
 steam heating systems, is not desirable for use alone in a 
 boiler, as it will cause corrosion and pitting of the sheets, 
 but if it is mixed with other wat?r before going into the 
 boiler its use is highly beneficial, as it will prevent to a 
 certain degree the formation of scale and incrustation. 
 Nearly all water used for the generation of steam in boilers 
 contains more or less scale-forming matter, such as the 
 carbonates of lime and magnesia, the sulphates of lime and 
 magnesia, oxide of iron, silica and organic matter, which 
 latter tends to cause foaming in boilers. 
 
 The carbonates of lime and magnesia are the chief causes 
 of incrustation. The sulphate of lime forms a hard crystal- 
 line scale which is extremely difficult to remove when once 
 formed on the sheets and tubes of boilers. Of late years 
 the intelligent application of chemistry to the analyzing of 
 
300 Steam Engineering 
 
 feed waters has been of great benefit to engineers and steam 
 users, in that it has enabled them to properly treat the 
 water with solvents either before it is pumped into the 
 boiler, or by the introduction into the boiler of certain scale 
 preventing compounds made especially for treating the 
 particular kind of water used. Where it is necessary to 
 treat water in this manner great care and watchfulness 
 should be exercised by the engineer in the selection and 
 use of a boiler compound. 
 
 From ten to forty grains of mineral matter per gallon 
 are held in solution by the w r aters of the different rivers, 
 streams and lakes; well and mine water contain still more. 
 
 Water contracts and becomes denser in cooling until it 
 reaches a temperature of 39.1° F., its point of greatest 
 density. Below this temperature it expands and at 32° F. 
 it becomes solid or freezes, and in the act of freezing it ex- 
 pands considerably, as every engineer who has had to deal 
 with frozen water pipes can testify. 
 
 Water is 815 times heavier than atmospheric air. The 
 weight of a cubic foot of water at 39.1° is approximately 
 62.5 pounds, although authorities differ on this matter, 
 some of them placing it at 62.379 pounds, and others at 
 62.425 pounds per cubic foot. As its temperature increases 
 its weight per cubic foot decreases until at 212° F. one cubic 
 foot weighs 59.76 pounds. 
 
 The table which fallows is compiled from various sources 
 and gives the weight of a cubic foot of water at different 
 temperatures. 
 
Water 
 
 301 
 
 Table 22 
 weight of cu. ft. of water 
 
 Temper- 
 
 Weight per 
 
 Temper- 
 
 Weight per 
 
 Temper- 
 
 Weight per 
 
 ature 
 
 Cubic Foot 
 
 ature 
 
 Cubic Foot 
 
 ature 
 
 Cubic Foot 
 
 32° F. 
 
 64.42 lbs. | 
 
 132° F. 
 
 61.52 lbs. || 230° F. 
 
 59.37 lbs. 
 
 42° 
 
 62.42 || 142° 
 
 | 61.34 
 
 | 240° 
 
 59.10 
 
 52° 
 
 62.40 
 
 152° 
 
 61.14 
 
 | 250° 
 
 58.85 
 
 62° 
 
 62.36 
 
 162° 
 
 | 60.94 
 
 | 260° 
 
 58.52 
 
 72° 
 
 62.30 172° 
 
 60.73 
 
 I 270° 
 
 58.21 
 
 82 a 
 
 62.21 
 
 182° 
 
 | 60.50 
 
 | 300° 
 
 57.26 
 
 92° 
 
 62.11 | 
 
 192° 
 
 60.27 
 
 | 330° 
 
 56.24 
 
 102° 
 
 62.00 
 
 i 202° 
 
 60.02 
 
 | 360° 
 
 55.16 
 
 112° 
 
 61.86 |'| 212° 
 
 | 59.76 
 
 | 390° 
 
 54.03 
 
 122° 
 
 61.70 
 
 | 220° 
 
 59.64 
 
 420° 
 
 52.86 
 
 The boiling point of water varies according to the pres- 
 sure to which it is subject. In the open air at sea level 
 the boiling point is 212° F. When confined in a boiler 
 under steam pressure the boiling point of water depends 
 upon the pressure and temperature of the steam, as, for 
 instance, at 100 pounds gauge pressure the temperature of 
 the steam is 338° F., to which temperature the water must 
 be raised before its molecules will separate and be converted 
 into steam. In the absence of any pressure, as in a perfect 
 vacuum, water boils at 32° F. temperature. In a vacuum 
 of 28 inches, corresponding to an absolute pressure of .943 
 pounds, water will boil at 100°, and in a vacuum of 26 
 inches, at which the absolute pressure is 2 pounds, the boil- 
 ing point of water is 127° F. On the tops of high moun- 
 tains in a rarefied atmosphere, water will boil at a much 
 lower temperature than at sea level, for instance at an alti- 
 tude of 15,000 feet above sea level water boils at 184° F. 
 
 Table 23 gives the boiling point of water at various alti- 
 tudes above sea level, also the atmospheric pressure in 
 pounds per square inch. 
 
302 
 
 Steam Engineering 
 
 Table 23 
 boiling point of water at various altitudes. 
 
 Boiling Point 
 
 Altitude above 
 
 Atmospheric 
 
 
 in degrees 
 
 Sea Level. 
 
 Pressure. 
 
 Barometer, 
 
 Fahrenheit. 
 
 Feet. 
 
 Pounds per 
 square inch. 
 
 Inches. 
 
 184 
 
 15,221 
 
 8.19 
 
 16.79 
 
 185 
 
 14,649 
 
 8.37 
 
 17.16 
 
 186 
 
 14,075 
 
 8.56 
 
 17.54 
 
 187 
 
 13,498 
 
 8.75 
 
 17.93 
 
 188 
 
 12,934 
 
 8.94 
 
 18.32 
 
 189 
 
 12,367 
 
 9.13 
 
 18.72 
 
 190 
 
 11,799 
 
 9.33 
 
 19.13 
 
 191 
 
 11,243 
 
 9.53 
 
 19.54 
 
 192 
 
 10,685 
 
 9.74 
 
 19.96 
 
 193 
 
 10,127 
 
 9.95 
 
 20.39 
 
 194 
 
 9,579 
 
 10.16 
 
 20.82 
 
 195 
 
 9,031 
 
 10.38 
 
 21.26 
 
 196 
 
 8,481 
 
 10.60 
 
 21.71 
 
 197 
 
 7,932 
 
 10.82 
 
 22.17 
 
 198 
 
 7,381 
 
 11.05 
 
 22.64 
 
 199 
 
 6,843 
 
 11.28 
 
 23.11 
 
 200 
 
 6,304 
 
 11.52 
 
 23.59 
 
 201 
 
 5,764 
 
 11.76 
 
 24.08 
 
 202 
 
 5,225 
 
 12.01 
 
 24.58 
 
 203 
 
 4,697 
 
 12.25 
 
 25.08 
 
 204 
 
 4,169 
 
 12.51 
 
 25.59 
 
 205 
 
 3,642 
 
 12.77 
 
 26.11 
 
 206 
 
 3,115 
 
 13.03 
 
 26.64 
 
 207 
 
 2,589 
 
 13.29 
 
 27.18 
 
 208 
 
 2,063 
 
 13.57 
 
 27.73 
 
 209 
 
 1,539 
 
 13.84 
 
 28.29 
 
 210 
 
 1,025 
 
 14.12 
 
 28.85 
 
 211 
 
 512 
 
 14.41 
 
 29.42 
 
 212 
 
 Sea-Level 
 
 14.70 
 
 30.00 
 
 STEAM. 
 
 Steam. Having discussed to some extent the physical 
 properties of water, it is now in order to devote some time 
 to the study of the nature of steam, which is simply water 
 in its gaseous form, made so by the application of heat. 
 
 As has been stated in another portion of this book, mat- 
 ter consists of molecules or atoms inconceivably small in 
 size, yet each having an individuality, and in the case of 
 solids or liquids, each having a mutual cohesion or attrac- 
 tion for the other, and all being in a state of continual vi- 
 bration, more or less violent according to the temperature 
 of the body. 
 
1 
 
 Steam 303 
 
 The law of gravitation which holds the universe together, 
 also exerts its wonderful influence on these atoms, and 
 causes them to hold together with more or less tenacity 
 according to the nature of the substance. Thus it is much 
 more difficult to chip off pieces of iron or granite than it 
 is of wood. But in the case of water and other liquids the 
 atoms, while they adhere to each other to a certain extent, 
 still they are not so hard to separate, in fact, they are to 
 some extent repulsive to each other, and unless confined 
 within certain bounds the atoms will gradually scatter and 
 spread out, and finally either be evaporated or sink out of 
 sight in the earth's surface. Heat applied to any substance 
 tends to accelerate the vibrations of the molecules, and if 
 enough heat is applied it will reduce the hardest sub- 
 stances to a liquid or gaseous state. 
 
 The process of the generation of steam from water is 
 simply an increase of the natural vibrations of the mole- 
 cules of the water, caused by the application of heat until 
 they lose all attraction for each other and become instead 
 entirely repulsive, and unless confined will fly off into 
 space. But being confined they continually strike against 
 the sides of the containing vessel, thus causing the pressure 
 which steam or any other gas exerts when under confine- 
 ment. 
 
 Of course steam, like other gases, when under pressure, 
 is invisible, but the laws governing its action are well 
 known. These laws, especially those relating to the expan- 
 sion of steam, will be more fully discussed in the section 
 on the Indicator. The temperature of steam in contact 
 with the water from which it is generated, as for instance 
 in the ordinary steam boiler, depends upon the pressure 
 under which it is generated. Thus at atmospheric pres- 
 
304 Steam Engineering 
 
 sure its temperature is 212° F. If the vessel is closed and 
 the pressure increased the temperature of the steam and 
 also that of the water rises. 
 
 Saturated Steam. When steam is taken directly from 
 the boiler to the engine without being superheated, it is 
 termed saturated steam. This does not necessarily imply 
 that it is wet and mixed with spray and moisture. 
 
 Superheated Steam. When steam is conducted into or 
 through a vessel or coils of pipe separate from the boiler 
 in which it was generated, and is there heated to a higher 
 temperature than that due to its pressure, it is said to be 
 superheated. 
 
 Dry Steam. When steam contains no moisture it is said 
 to be dry. Dry steam may be either saturated or super- 
 heated. 
 
 Wet Steam. When steam contains mist or spray inter- 
 mingled it is termed wet steam, although it may have the 
 same temperature as dry saturated steam of the same pres- 
 sure. 
 
 During the further consideration of steam in this book, 
 saturated steam will be mainly under discussion, for 
 the reason that this is the normal condition of steam as 
 used most generally in steam engines. 
 
 Total Heat of Steam. The total heat in steam includes 
 the heat required to raise the temperature of the water 
 from 32° F. to the temperature of the steam plus the heat 
 required to evaporate the water at that temperature. This 
 latter heat becomes latent in the steam, and is therefore 
 called the latent heat of steam. 
 
 The work done by the heat acting within the mass of 
 water and causing the molecules to rise to the surface is 
 termed by scientists internal work, and the work done in 
 
Steam 305 
 
 compressing the steam already formed in the boiler, or in 
 pushing it against the superincumbent atmosphere, if the 
 vessel be open, is termed external work. There are, there- 
 fore, in reality three elements to be taken into consideration 
 in estimating the total heat of steam, but as the heat ex- 
 pended in doing external work is done within the mass it- 
 self it may, for practical purposes, be included in the 
 general term latent heat of steam. 
 
 Density of Steam. The expression density of steam 
 means the actual weight in pounds, or fractions of a pound 
 avoirdupois of a given volume of steam. This is a very 
 important point for young engineers especially to remem- 
 ber, so as not to get the two terms, pounds pressure and 
 pounds weight, mixed, as some are prone to do. 
 
 Volume of Steam. By this term is meant the volume 
 as expressed by the number of cubic feet in one pound 
 weight of steam. 
 
 Relative Volume of Steam. This expression has refer- 
 ence to the number of volumes of steam produced from 
 one volume of water. Thus the steam produced by the 
 evaporation of one cubic foot of water from 39° F. into 
 steam at atmospheric pressure will occupy a space of 1646 
 cubic feet, but, as the steam is compressed and the pres- 
 sure allowed to rise, the relative volume of the steam be- 
 comes smaller, as for instance at 100 pounds gauge pres- 
 sure the steam produced from one cubic foot of water will 
 occupy but 237.6 cubic feet, and if the same steam was com- 
 pressed to 1,000 pounds absolute or 985.3 pounds gauge 
 pressure it would then occupy only 30 cubic feet. 
 
 The condition of steam as regards its dryness may be 
 approximately estimated by observing its appearance as it 
 issues from a pet cock or other small opening into the 
 
306 Steam Engineering 
 
 atmosphere. Dry, or nearly dry steam containing abjajit 
 1 per cent of moisture will be transparent close to the 
 orifice through which it issues, and even if it is of a gray- 
 ish white color it may be estimated to contain not over 2 
 per cent of moisture. 
 
 Steam in its relation to the engine should be considered 
 in the character of a vehicle for transferring the energy, 
 created by the heat, from the boiler to the engine. For 
 this reason all steam drums, headers and pipes should be 
 thoroughly insulated in order to prevent, as much as pos- 
 sible, the loss of heat or energy by radiation. 
 
 There is a wide difference in the value of different sub- 
 stances for protection from radiation, their value varying 
 nearly in the inverse ratio of their conducting power for 
 heat, up to their ability to transmit as much heat as the 
 surface of the pipe will radiate, after which they become 
 detrimental, rather than useful, as covering. This point 
 is reached nearly at baked clay or brick. 
 
 Table 2i shows the relative value of various non-con- 
 ductors of heat, and table 25 gives the loss of heat from 
 steam pipes protected, and unprotected. 
 
 Where two values are given in table 24 for the same 
 substance the lower one is for the denser condition. 
 
 A smooth or polished surface is of itself a good protec- 
 tion, polished tin or Russia iron having a ratio, for radia- 
 tion, of 53 to 100 for cast iron. Mere color makes but lit- 
 tle difference. 
 
 Hair or wool felt, and most of the better non-conduc- 
 tors, have the disadvantage of becoming soon charred from 
 the heat of steam at high pressure, and sometimes of tak- 
 ing fire therefrom. 
 
 ''Mineral wool," a fibrous material made from blast fur- 
 nace slag, is the best non-combustible covering, but is quite 
 
Steam 307 
 
 brittle, and liable to fall to powder where much jarring 
 exists. 
 
 Air space alone is one of the poorest of non-conductors, 
 though the best owe their efficiency to the numerous mi- 
 nute air cells in their structure. This is best seen in the 
 value of different forms of carbon, from cork charcoal to 
 anthracite dust, the former being three times as valuable 
 for this purpose, though in chemical constitution they are 
 practically identical. 
 
 Any suitable substance used to prevent the escape of 
 steam heat should not be less than one inch thick. 
 
 Table 24 
 relative value of non-conducting materials. 
 
 Substance Value 
 
 *Loose Wool 3.35 
 
 ♦Loose Lampblack 1.12 
 
 * Geese Feathers 1.08 
 
 ♦Felt, Hair or Wool 1. 
 
 ♦Carded Cotton 1. 
 
 ♦Charcoal from Cork .87 
 
 Mineral Wool 68 to .83 
 
 Fossil Meal 66 to .79 
 
 * Straw Rope, wound spirally .77 
 
 ♦Rice Chaff, loose .76 
 
 Carbonate Magnesia 67 to .76 
 
 ♦Charcoal from Wood 63 to .75 
 
 ♦Paper 50 to .74 
 
 * Cork .71 
 
 ♦Sawdust 61 to .68 
 
 Paste of Fossil Meal anH Hair fi3 
 
 Wood Ashes ^61 
 
 * Wood, across grain 40 to .55 
 
 Loam, dry and open _ .55 
 
 Chalk, ground, Spanish white .51 
 
 Coal Ashes 35 to .49 
 
 Gas-house Carbon .47 
 
 Asbestos Paper .47 
 
 Paste of Fossil Meal and Asbestos .47 
 
 Asbestos, fibrous .36 
 
 Plaster of Paris, dry .34 
 
 Clay, with vegetable fiber .34 
 
 Anthracite Coal, powdered .29 
 
 Coke in lumps .27 
 
 Air Space, undivided 14 to .22 
 
 Sand .17 
 
 Baked Clay, Brick .07 
 
 Glass .05 
 
 Stone .02 
 
 * Combustible, and sometimes dangerous. 
 
308 Steam Engineering 
 
 The following table gives the loss of heat from steam 
 pipes, naked and clothed with wool or hair felt, of dif- 
 ferent thickness, the steam pressure being assumed at 75 
 pounds and the external air at 60 °, 
 
 ^ 
 
Steam 
 
 303 
 
 Ci 4* tO M *^*^ © 
 
 Thickness of Covering 
 in inches 
 
 
 MtO 
 
 : CDOOCOCipCD 
 
 • bo^bo^^ib 
 
 Loss in Units 
 
 per foot run 
 
 per hour 
 
 to 
 
 5' 
 
 o 
 
 p* 
 
 2*. 
 5' 
 
 3 
 
 n> 
 
 o 
 a 
 
 H 
 m 
 
 
 
 w 
 
 a 
 *—* 
 
 > 
 
 w 
 
 H 
 W 
 
 o 
 
 t— 1 
 
 W 
 
 H 
 K 
 O 
 
 a 
 
 r 1 
 
 H 
 
 
 M 
 
 • CDCO© OOIO 
 
 Ratio of Loss 
 
 
 • Ml- 1 
 
 • C5M-3 OtCOM 
 
 • CO CO M -3 M to 
 
 Feet in Length 
 per H. P. lost 
 
 
 MMCO 
 
 to to 4^ -q hooo 
 
 CO 00 4* CO ^lOO 
 rf*. M ^ b tO b 00 
 
 Loss in Units 
 
 per foot run 
 
 per hour 
 
 4* 
 
 5' 
 
 o 
 P* 
 
 g> 
 
 E»" 
 
 3 
 n 
 
 
 M 
 
 b b J- 1 m co *4^ b 
 
 CS-IMOO OOiO 
 
 Ratio of Loss 
 
 o 
 w 
 
 in 
 
 MM 
 
 rfkM-J4*. tOM 
 tO 00 4* OT 00 00 00 
 4* Ci Ut M *» tO C5 
 
 Feet in Length 
 per H. P. lost 
 
 Table 25 
 of heat from s 
 
 MM' fl5 
 CO^CiMOO. to 
 CO 4^ Oi M ^1 : rf* 
 
 ^i to to b to • M 
 
 Loss in Units 
 
 per foot run 
 
 per hour 
 
 05 
 
 5' 
 
 o 
 ts* 
 
 a. 
 (3* 
 
 3 
 
 a> 
 
 n> 
 •i 
 
 • i -1 
 
 © b m m co r b 
 ot a © -i o • © 
 
 4*O5OJ0O©« © 
 
 Ratio of Loss 
 
 CDOOOXCOM* 
 COOOO^' or 
 OOO^O^* CO 
 
 Feet in Length 
 per H. P. lost 
 
 H 
 
 > 
 
 MtO' -^ 
 C04^-5tOM« tO 
 4*050100©: CD 
 
 cob to cob* bo 
 
 Loss in Units 
 
 per foot run 
 
 per hour 
 
 GO 
 
 5' 
 O 
 tt 
 
 a. 
 p' 
 3 
 
 a> 
 
 a 
 i 
 
 2 
 
 • M 
 
 b b ^ •-* oo t b 
 
 4*05©-3©» O 
 -JCOC005M' o 
 
 Ratio of Loss 
 
 
 © ~q 4* tO,!- 1 • 
 
 -q to 4^ Oi Oi • 4» 
 
 t04*CO©M- O 
 
 Feet in Length 
 per H. P. lost 
 
 
 • M 
 
 MCO. o 
 
 4* 05 © 00 © • -1 
 
 pi © 00 CH h- 1 *. ^1 
 
 to CO b CO ^1 • 4* 
 
 Loss in Units 
 
 per foot run 
 
 per hour 
 
 M 
 
 to 
 
 5' 
 
 o 
 
 & 
 
 St 
 5' 
 
 3 
 
 n> 
 n 
 
 
 1.000 
 
 '.280 
 .172 
 .091 
 .056 
 .042 
 
 Ratio of Loss 
 
 
 -3CHCOMM. 
 COOl^-ll- 1 • co 
 OlCO©©4*« M 
 
 Feet in Length 
 per H. P. lost 
 
 
310 Steam Engineering 
 
 Flow of Steam Through Pipes. The approximate 
 weight of any fluid which will flow in one minute through 
 any given pipe with a given head or pressure may be found 
 by the following formula: 
 
 in which TF=weight in pounds avoirdupois, d=diameter 
 in inches, D— density or weight per cubic foot, p 1 =the 
 initial pressure, p 2 =pressure at end of pipe, and L= 
 the length in feet. Table 26 gives, approximately, the 
 weight of steam per minute which will flow from various 
 initial pressures, with one pound loss of pressure through 
 straight smooth pipes, each having a length of 240 times 
 its own diameter. 
 
 For sizes of pipe below 6-inch, the flow is calculated 
 from the actual areas of "standard" pipe of such nominal 
 diameters. 
 
 For horsepower, multiply the figures in the table by 2. 
 For any other loss of pressure, multiply by the square root 
 of the given loss. For any other length of pipe, divide 
 2J+0 by the given length expressed in diameters, and mul- 
 tiply the figures in the table oy the square root of this 
 quotient, which will give the flow for 1 lb. loss of pres- 
 sure. Conversely, dividing the given length by 240 will 
 give the loss of pressure for the flow given in the table. 
 
 The loss of head due to getting up the velocity, to the 
 friction of the steam entering the pipe, and passing elbows 
 and valves, will reduce the flow given in the tables. The 
 resistance at the opening, and that at a globe valve, are 
 each about the same as that for a length of pipe equal to 
 
Steam 
 
 311 
 
 MMM 
 OOOOOOOOOOOOM 
 
 Initial Pressure by 
 Gauge. Pounds 
 per Square Inch. 
 
 CO 00 tO tO tO tO bO tO tO M M M M 
 
 co © bo ^i 01 4* co m. © go © co m 
 
 ~1 © 4^ I- 1 © ©tO-^MtOtOXtO 
 
 3 
 
 o 
 
 o 
 
 en 
 n> 
 
 3 
 
 5' 
 
 B' 
 
 •a 
 
 o 
 
 c 
 
 3 
 P- 
 
 1 
 
 s* 
 
 O 
 3 
 o 
 
 o 
 
 p* 
 
 CO 
 
 O 
 
 •-t 
 O 
 Crt 
 Ui 
 
 C 
 *\ 
 
 
 > 
 
 W 
 H 
 W 
 
 ^ 
 
 O 
 *j 
 
 hd 
 
 hj 
 W 
 
 l-H 
 
 3 
 
 o 
 
 m 
 w 
 
 r 
 w 
 
 o 
 
 H 
 O 
 
 *i 
 
 w 
 > 
 o 
 W 
 
 Jo 
 
 © 
 
 
 
 (—1 
 
 > 
 w 
 
 H 
 
 W 
 
 © pi Ol 4^ *» 4»> 4>> CO CO CO tO tO JO 
 
 U©kci©^bito©©cocDbi© 
 
 ©^©©Oli-^OlXX^-q^Ol 
 
 35 Ol rfi. CO CO tO M O O © GO Ci Ol 
 © 4*. CO © © 4* ^3 '© J- 1 to M CD Ci 
 
 -^^©©tOMOltOh-^XXOl 
 
 
 COtOtOtOtOtOtOI- l l- 1 l- 1 l- l l-il- 1 
 © ^ Ol 4^ CO tO h-i © X © 4^ tO © 
 
 ^^^bibicobb^bi^jbih- 1 
 
 ©OlC0Olt0tO4^~5X4^©4^Ol 
 
 to 
 
 4^4^COCOCOCOCOtOtOtOtOMH-i 
 Ol M co p OT CO M p ^ 4^ to GO pi 
 
 x ^ ^ © co oi '© bi co x © x to 
 
 COI-^MI-iCSOlCO-^rf^CiOOlO 
 
 to 
 
 -^©©©OlOlOl4*4s«.4>-C0C0tO 
 Ol X CO O GO Ol tO GO 4* O p h* Ol 
 
 4*. © © ^ m to © © o co co © m 
 
 tO4^©4^©tO©~3©lO©C0tO 
 
 CO 
 
 WlOKMOOOXOO^OCi^ 
 X©-3i- l ~3^01©t0 01Ci~l© 
 
 III 1 
 
 4 15 6 | 8 10 1 12 
 
 tO O CD X -1 © Ol 4^ 'CO tO i-i CD -1 
 
 GO ^1 tO CO p -1 -1 -q p CO O CO p 
 
 4^bGOCDCOCO^l4^CobUcDM 
 
 CO0OtOtOtOtOtOtOl- l l- l >-H- A M 
 CO©X©Ol4*CO©© XDiCOi-i 
 pi pi tO p GO pi M 05 CO M M ^ M 
 
 toU©©©a^coco©x©cD© 
 
 Oi010lOl4^4^4^4^COCOCOtOtO 
 tO-^IOO<XOlCOO^l4^00lO 
 ^1 M p Ol 4^ p CO 4^ 4* O to GO p 
 
 ^coxc^co©co©bi©©toM 
 
 ©©XX-l~J©©©O14^4^C0 
 © i-i c;i -^ -1 CO CD Ol O 4^ GO i- 1 CO 
 p GO tO h-i Q0 p p M tO ^1 p Ol © 
 
 ©©k>bi©co©bicox^icoco 
 
 ^COIOMMOO^OOOO-IOJ*. 
 Q0 Ol Ol © 4* X tO C'l XOmhO 
 
 tO © CO GO 4* CD Ol ^ tO CD © GO CO 
 
 (OtOtCMMUMMMHM 
 
 CO M © © 00 -3 © Ol 4^ tO )-i © -3 
 
 ~3©©-^C04^4*COr^CD4>.-l© 
 ©©X©©tOtOOl©M~3©tO 
 
 M 
 
 Ol 
 
 COCOtOtOtOtOtOtOtOMI-i|-il-* 
 4*. t-» © X © Ol 4* rc © X © 4^ t- 1 
 X -3 4^ © X Ol © 4* -1 X -1 CO © 
 
 CO©©Ot~3©4^XX©©CO© 
 
 X 
 
 o 
 
 o 
 
 H 
 W 
 
 > 
 
 W 
 
 o 
 o 
 
 C/3 
 
 W 
 
 to 
 
312 Steam Engineering 
 
 114 diameters divided by a number represented by 1+ 
 (3.6-^diameter). For the sizes of pipes given in the table, 
 these corresponding lengths are : 
 
 I 1 II 2 2i 3 4 5 6 8 10 12 15 18 
 20 25 34 41 47 52 60 66 71 79 84 88 92 95 
 
 The resistance at an elbow is equal to 2/3 that of a 
 globe valve. These equivalents — for opening, for elbows, 
 and for valves — must be added in each instance to the ac- 
 tual length of pipe. Thus a 4 in. pipe, 120 diameter 
 (40 feet) long, with a globe valve and three elbows, would 
 be equivalent to 120+60+60+ (3X40) =360 diameters 
 long; and 360-^240=1%. It would therefore have iy 2 
 pounds loss of pressure at the flow given in the table, or 
 deliver (l-^-yi%=.816) 81.6 per cent of the steam 
 with the same (1 pound) loss of pressure. 
 
 Flow of Steam From a Given Orifice. Steam of any 
 pressure flowing through an opening into any other pres- 
 sure, less than three-fifths of the initial, has practically a 
 constant velocity, 888 feet per second, or a little over ten 
 miles per minute; hence the amount discharged in pounds 
 is proportionate to the weight or density of the steam. To 
 ascertain the pounds, avoirdupois, discharged per minute, 
 multiply the area of opening in inches, by 370 times the 
 weight per cubic foot of the steam. (See Table 17.) 
 
 Or the quantity discharged per minute may be approx- 
 imately found by Eankine's formula : 
 
 W=6 a p-i-7 
 in which W=weight in pounds, a=area in square inches, 
 and p=absolute pressure. The theoretical flow requires 
 to be multiplied by £=0.93, for a short pipe, or 0.63 for 
 a thin opening, as in a plate, or a safety valve. 
 
Steam 313 
 
 Where the steam flows into a pressure more than 2/3 
 the pressure in the boiler : 
 
 TF=1.9 a fcVG>— 8)8 
 in which 8= difference in pressure between the two sides, 
 in pounds per square inch, and a, p, and Jc as above. 
 
 To reduce to horsepower, multiply by 2. 
 
 Where a given horsepower is required to flow through 
 a given opening, to determine the necessary difference in 
 pressure : 
 
 ■j 
 
 p \p 2 H.P, 
 
 °~ 2 ^4 14a 2 & 
 
 QUESTIONS AXD ANSWERS. 
 
 238. What is meant by the term combustion as used in 
 steam engineering? 
 
 Ans. It is the rapid chemical combination of oxygen 
 with the carbon, hydrogen and sulphur in the fuel with 
 the accompaniment of heat and light. 
 
 239. What is meant by the symbol C0 2 ? 
 
 Ans. C0 2 represents perfect combustion, viz., the cre- 
 ation of carbon dioxide. 
 
 240. What is the most abundant combustible in nature ? 
 Ans. Carbon. 
 
 241. How many heat units are contained in one pound 
 of pure carbon? 
 
 Ans. 14,500. 
 
 242. What is the heating value of one pound of hydro- 
 gen gas? 
 
 Ans. 62,000. 
 
 243. Give the composition of coal. 
 
314 Steam Engineering 
 
 Ans. Fixed carbon, volatile matter, ash and sulphur in 
 
 various proportions, depending upon the quality of the 
 coal. 
 
 24:4:. Is sulphur desirable as a constituent of coal? 
 
 Ans. It is not. The gases formed from its combustion 
 attack the metal of the boiler, causing corrosion. 
 
 245. What office does nitrogen perform in combustion? 
 Ans. No useful office. Bather it is a detriment, and 
 
 in fact is the chief source of loss in furnaces. It is drawn 
 in with the air. 
 
 246. What is meant by the term calorific value of fuel ? 
 Ans. The amount of heat liberated per pound of fuel 
 
 undergoing perfect combustion. 
 
 248. What are economizers in connection with a boiler 
 plant ? 
 
 Ans. Coils or stacks of cast iron pipe placed within the 
 smoke flue, or breeching and surrounded by the hot gases 
 while the water is passed through the pipes on its way to 
 the boilers, thus receiving an additional amount of heat. 
 
 249. What two factors are necessary in order to attain 
 economy in the burning of coal? 
 
 Ans. A constant high furnace temperature and quick 
 combustion. 
 
 250. Define the term heat. 
 
 Ans. Heat is the result of the vibration of the mole- 
 cules or atoms composing matter. 
 
 251. Upon what does the intensity of heat depend? 
 Ans. Upon the rapidity of the agitation to which the 
 
 molecules are subject. 
 
 252. What are the general effects of heat? 
 
 Ans. When heat is added to, or taken away from a 
 body the temperature of the body is altered and its volume 
 is varied. 
 
Steam 315 
 
 253. What is absolute zero? 
 
 Arts. It is that degree of temperature at which, owing 
 to the intense cold, a perfect gas would disappear. Abso- 
 lute zero is 461° below the zero of the Fahrenheit ther- 
 mometer. 
 
 254. What is a heat unit (B. T. II.) ? 
 
 Arts. It is the quantity of heat required to raise the tem- 
 perature of one pound of water one degree, or from 39° 
 to 40° F. 
 
 255. What is the mechanical equivalent of heat? 
 Arts. 778 foot pounds; in other words, 778 pounds 
 
 raised one foot high. 
 
 256. What is the specific heat of any substance? 
 
 Ans. The ratio of the quantity of heat required to raise 
 a given weight of that substance one degree in tempera- 
 ture, to the quantity of heat required to raise an equal 
 weight of water one degree when the water is at its maxi- 
 mum density, viz., 39.1° F. 
 
 257. What is latent heat? 
 
 Ans. Heat given to a body and not warming it. 
 
 258. What is sensible heat? 
 
 Ans. Heat given to a body and warming it. 
 
 259. Of what is pure water composed? 
 
 Ans. By volume — Hydrogen 2 parts, oxygen 1. 
 
 By weight — Hydrogen 11.1 parts, oxygen 88.9. 
 
 260. Is perfectly pure water desirable for use in a steam 
 boiler ? 
 
 Ans. It is not, as it will cause corrosion and pitting of 
 the sheets. 
 
 261. What two ingredients in water are the chief causes 
 of incrustation in boilers ? 
 
 Ans. The carbonates of lime and magnesia. 
 
316 Steam Engineering 
 
 262. What is steam ? 
 
 Ans. Steam is the vapor of water generated by an in- 
 crease of the natural vibrations of molecules of the water 
 through the application of heat. 
 
 263. "What is saturated steam? 
 
 A ns. Steam taken directly from the boiler to the engine 
 without being superheated. 
 
 264. What is superheated steam? 
 
 Ans. Steam that has been heated to a higher tempera- 
 ture than that due to its pressure. 
 
 265. "What should be done with all pipes through which 
 live steam is conducted for purposes of heating, or power? 
 
 Ans. They should be well protected by a covering, in 
 order to prevent loss of heat by radiation. 
 
 266. In what respect should steam be considered in its 
 relation to the engine? 
 
 Ans. As a vehicle for transferring the heat energy from 
 the boiler to the engine. 
 
Evaporation Tests 
 
 Evaporation Tests. The object of making evaporation 
 tests of steam boilers is primarily to ascertain how many 
 pounds of water the boilers are evaporating per pound of 
 coal burned; but these tests can and should be made to 
 determine several other important points with reference 
 to the operation of the boilers, as for instance: 1. The 
 efficiency of the boiler and furnace as an apparatus for the 
 consumption of fuel and the evaporation of water ; whether 
 this apparatus is performing its guaranteed duty in this 
 respect, and how it compares with a known standard. 2. 
 To determine the relative economy of different varieties of 
 coal, also to determine the relative value of fuels other than 
 coal, such as oil, gas, etc. 3. To ascertain whether or not 
 the boilers as they are operated under ordinary every day 
 conditions are being run as economically as they should be. 
 4. In case the boilers, owing to an increased demand for 
 steam, fail to supply a sufficient quantity without forcing 
 the fires, whether or not additional boilers are needed, or 
 whether the trouble could be overcome by»a change pf con- 
 ditions in operating them. 
 
 Tests for the last three purposes named can be made by 
 the regular engineering force of the plant, but in case a 
 controversy should arise between the maker of the boiler 
 and the purchaser regarding the first mentioned point, viz., 
 the guaranteed efficiency of the boiler or the furnace, the 
 services of experts in boiler testing may be resorted to. 
 
 Preparing for a Test. All testing apparatus should be 
 kept in such shape that it will not take three or four days 
 
 317 
 
318 Steam Engineering 
 
 to get it ready for making a test. On the contrary, it can 
 be and should be always kept in condition ready for use, 
 so that the preparations for making a test will occupy but 
 a short time. A small platform scale sufficiently large for 
 weighing a wheel-barrow load of coal should also be pro- 
 vided in addition to the apparatus heretofore described. 
 
 The capacity of each of the two tanks illustrated in Fig. 
 66, can be determined in two ways, either by measuring 
 the cubical contents of each or by placing them one at a 
 time on the scales, filling them with water to within a few 
 inches of the top, and note the weight. Also make a per- 
 manent mark on the inside at the water level. The water 
 should then be permitted to run out until within an inch 
 or so of the outlet pipe near the bottom, where another 
 plain mark should be made, after which the empty tank 
 should be again weighed, then by subtracting the last 
 weight from the first the exact number of pounds of water 
 that the tank will contain between the top and bottom 
 marks can be determined and a note made of it. 
 
 It is much more convenient to have each tank contain 
 the same quantity of water, although not absolutely neces- 
 sary. The tanks should also be numbered 1 and 2 re- 
 spectively in order to prevent confusion in keeping a record 
 of the number of tanks full of water used during the test. 
 Care should be exercised to have the water with which the 
 tanks are filled while on the scale, at or near the same tem- 
 perature as that at which it is to be fed into the boiler dur- 
 ing the test. Otherwise there is liability of error owing 
 to the variation in the weight of water at different tem- 
 peratures. In order to guard against this, the capacity in 
 cubic feet of each tank between the top and bottom marks 
 should be ascertained by measuring the distance between 
 the marks, also the diameter, or, if the tanks be square, the 
 
Evaporation Tests 319 
 
 length of one Bide, after which the cubical contents can be 
 easily figured and noted down. By knowing the capacity 
 in cubic feet of each tank all possibility of error in the 
 weight of feed water will be eliminated. 
 
 The scales for weighing the coal can be fitted with a 
 temporary wooden platform large enough to accommodate 
 a wheel-barrow, and after it has been balanced with the 
 empty barrow on it, the record of weight of coal burned 
 during the test can be easily kept. 
 
 The same barrow should be used throughout the test, 
 and to save complications in estimating the weight, the 
 same number of pounds of coal should be filled in the 
 barrow each load. The coal passer will learn in a short 
 time to fill the barrow to within a few pounds of the same 
 weight each load by counting the shovelsful and the dif- 
 ference can easily be adjusted by having a small box of 
 coal near the scale from which to take a few lumps to bal- 
 ance the load, or if there is too much coal in the barrow 
 some of it can be thrown into the box. 
 
 At least two separate tally sheets should be provided, 
 marked respectively coal and water, and the one for coal 
 placed near the scale, and care should be taken that each 
 load is tallied as soon as it is weighed. The tally sheet for 
 water should be near the measuring tanks and as soon as 
 a tank is emptied it should be tallied. The temperature 
 of the feed water should be taken at least every thirty 
 minutes, or oftener if possible, from a thermometer placed 
 in the feed pipe near the check valve. The readings should 
 be noted and, at the expiration of the test, the average 
 taken. 
 
 To Find the Cubic Contents of a Barrel. To find the 
 cubic contents of a barrel, square the largest diameter, then 
 multiply by 2, then add the square of the head diameter; 
 
320 Steam Engineering 
 
 multiply this sum by the length of the cask and that prod- 
 uct by 0.2618. For example, a barrel whose largest di- 
 ameter is 21 inches, head diameter 18 inches and height 
 33 inches: 21X21X2=882; 18X18=324; 324+882= 
 1206; 1206X33=39,798; 39,798X0.2618=10,419.11 cubic 
 inches. Dividing by 231 for gallons gives 45.10 gallons. 
 
 If the object of the test is to ascertain the efficiency of 
 the boiler and furnace it is absolutely necessary that the 
 boiler and all its appurtenances be put in good condition, 
 by cleaning the heating surface both inside the boiler and 
 outside, scraping and blowing the soot out of the tubes, if 
 it be a return tubular boiler, and blowing the soot and ashes 
 from between the tubes if it is a water tube boiler. All 
 dust, soot and ashes should be removed from the outside 
 of the shell and also from the combustion chamber and 
 smoke connections. The grate bars and sides of the fur- 
 nace should be cleared of all clinker, and all air leaks made 
 as close as possible. The boiler and all its water connec- 
 tions should be free from leaks, especially the blow-off 
 valve or cock. If any doubt exists as to the latter it should 
 be plugged or a blind flange put on it. It is very essential 
 that there should be no way for the water to leak out of 
 the boiler, neither should any water be allowed to get 
 into the boiler during the test except that which .is 
 measured by passing through the tanks. 
 
 In making an efficiency test it is essential that the boiler 
 should be run at its fullest capacity from the beginning to 
 the end of the test. Therefore arrangements should be 
 made to dispose of the steam as fast as it is generated. If 
 the boiler is in a battery connected with a common header, 
 its mates can be fired lighter during the test, but if there 
 is but the one boiler in use a waste steam pipe should be 
 
Evaporation Tests 321 
 
 temporarily connected through which the surplus steam, if 
 there is any, can be discharged into the open air through 
 a valve regulated as required. Before starting the test the 
 boiler should be thoroughly heated by having been run 
 several hours at the ordinary rate. The fire should then be 
 cleaned and put in good condition to receive fresh coal. 
 
 At the time of beginning the test the water level should 
 be at o^ near the height ordinarily carried, and its position 
 marked by tying -a cord around one of the guard rods of 
 the gauge glass, and, to prevent all possibility of error, the 
 height of the water in the glass should be measured and a 
 note made of it. Note also the time that the first lot of 
 weighed coal is fed to the furnace, and record it as the 
 starting time. The steam pressure should be noted at the 
 beginning of the test, and at regular intervals during the 
 progress of the test in order that the average pressure may be 
 obtained. 
 
 At the close of the test all of the above conditions should 
 be as nearly as possible the same as at the beginning; the 
 quantity, and condition of the fire should be the same, also 
 the steam pressure and water level. This can be ac- 
 complished only by careful work towards the close of the 
 test. 
 
 During the progress of the test care should be exercised 
 to prevent any waste of coal, especially in cleaning the fire. 
 The ash made during the test must not be wet down until 
 after it is weighed, as in all calculations for combustible 
 and non-combustible matter in the coal the ash should be 
 dry. 
 
 The duration of the test should be at least ten hours if 
 it is possible to continue it for that length of time. The 
 feed pump should be kept running at such speed as will 
 
322 Steam Engineering 
 
 supply the water to the boiler as fast as it is evaporated, 
 and no faster. If at the close of the test a portion of water 
 is left in the last tank tallied it can be measured, and de- 
 ducted from the total. And if any weighed coal is left 
 on the floor it should be weighed back and deducted from 
 the total weight. If the boiler is fed by an injector in- 
 stead of a pump during the test, the injector should receive 
 steam directly from the boiler under test through a well 
 protected pipe. Also, the temperature of the feed water 
 should be taken from the measuring tanks, or at least from 
 the suction side of the injector, for the reason that the 
 water in passing through the injector receives a large quan- 
 tity of heat imparted to it by live steam directly from the 
 boiler. Therefore the temperature of the water after it 
 leaves the injector would not be a true factor for figuring 
 the evaporation. 
 
 Determination of the Percentage of Moisture in the 
 Steam. This is an important point in estimating the re- 
 sults of an evaporation test for the reason that each pound 
 weight of moisture in the steam as it leaves the boiler rep- 
 resents a pound of water that has not been evaporated into 
 steam, and should therefore be deducted from the total 
 weight of water fed into the boiler during the test. 
 
 The steam should be tested for moisture by taking 
 samples of it from the steam pipe or header as near the 
 boiler as possible in order to guard against additional 
 moisture caused by condensation. 
 
 Practically all saturated steam contains water, varying 
 in amount from a fraction of one per cent when the steam 
 is generated in a properly designed boiler fed with good 
 water, to five per cent or even more when the feed water is 
 bad, or the boilers are of defective design. Not only is the 
 
Evaporation Tests 323 
 
 heat absorbed by raising this water from the boiler feed 
 temperature to the steam temperature practically wasted, 
 but the water causes further loss by increasing the initial 
 condensation in the engine cylinder ; it also interferes with 
 proper cylinder lubrication, causes knocking in the engine, 
 and water hammer in the steam pipe. 
 
 Quality of Steam. The percentage weight of steam, in 
 a mixture of steam and water, is called the quality of the 
 steam, Thus steam of quality 99.5 contains one-half of 
 one per cent by weight of moisture. 
 
 Calorimeters. The apparatus used to determine the 
 moisture in steam is called a calorimeter, though the name 
 is inapt, since the instrument is in no sense a measurer of 
 heat. The first form used was the "barrel calorimeter." 
 In this apparatus liability of error is so great that its use 
 is practically abandoned. Modern calorimeters are usually 
 of either the throttling or separator type. 
 
 Throttling Calorimeter. Figure 103 shows a section 
 through a typical form of the instrument. Steam is drawn 
 from the vertical pipe by a nipple arranged as later de- 
 scribed, passes around the first thermometer cup as shown, 
 then through a hole about y^-inch diameter in the disk as 
 shown. It next passes around the lower thermometer cup, 
 after which it is permitted to escape. Thermometers are 
 inserted into the cups, which are then filled with cylinder 
 oil, and when the whole apparatus is heated the tempera- 
 ture of the steam before, and after passing through the 
 hole in the disk is noted. 
 
 The instrument and pipes leading to it should be thor- 
 oughly covered to diminish the radiation loss. 
 
 When steam passes from a higher to a lower pressure, 
 as in this case, no work has to be done in overcoming a re- 
 
324 
 
 Steam Engineering 
 
 sistance; hence assuming there is no loss from radiation, 
 the quantity of heat is exactly the same after passing the 
 disk as it was ahead of it. Suppose that the higher steam 
 pressure is 150 pounds by gauge, and the lower pressure 
 that of the atmosphere. The total heat in a pound of dry 
 steam at the former pressure is 1193.5 B. T. U. and at the 
 latter pressure is 1146.6 B. T. XL, difference, 46.9 B. T. U. 
 
 TQ ATMOSPHEB£ 
 
 Fig. 103 
 throttling calorimeter and sampling pipe 
 
 As this heat still exists in the steam of lower pressure, its 
 
 effect is to superheat that steam. Assuming the specific 
 
 heat of steam to be 0.48, the steam will then be superheated 
 
 46.9 
 
 =97.7 degrees. Suppose, however, the steam had 
 
 0.48 
 
 contained one per cent, of moisture. Before any super- 
 heating could occur, this moisture would have to be evap- 
 orated into steam of atmospheric pressure. Since the latent 
 heat of steam at atmospheric pressure is 965.8 B. T. U. 
 
Evaporation Tests 325 
 
 it follows that the one per cent, of moisture would require 
 
 9.658 B. T. U. to evaporate it, leaving only 46.9 — 9.658= 
 
 37.242 B. T. U. available for superheating, hence the super- 
 
 37.242 
 
 heat would be =77.6° as against 97.7 degrees in the 
 
 0.48 
 
 preceding case. In a similar manner the degree of super- 
 heat for other amounts of moisture can be determined, 
 and the action of the throttling calorimeter is based on 
 this fact as will now be shown. 
 
 Let i?=total heat of steam at boiler pressure. 
 L=latent heat of steam at boiler pressure. 
 7&=total heat of steam at reduced pressure after 
 
 passing the disk. 
 ^^temperature of saturated steam at the reduced 
 
 pressure. 
 i 2 = temperature of steam after expanding through 
 opening in the disk. 
 0.48=specific heat of saturated steam. 
 i #=proportion of moisture in the steam. 
 The difference between the B. T. TJ.'s in a pound of steam 
 at boiler pressure and after passing the disk is the heat 
 which must evaporate the moisture in the steam, and then 
 do the superheating, hence. 
 
 H—h=xL—0M (t 2 —t 1 ) y therefore 
 11— h— 0.48 (t 2 —t 1 ) 
 
 X= [61 
 
 L 
 
 Almost invariably the lower pressure is taken as that 
 of the atmosphere where 7i=1146.6 and ^=212, hence 
 the formula becomes 
 
 H— 1146.6— 0.48 (X— 212) 
 
 X—- — ■ [71 
 
326 Steam Engineering 
 
 For practical work it is more convenient to dispense with 
 the upper thermometer in the calorimeter, and substitute 
 an accurate steam gauge whose readings are more easily 
 noted. 
 
 Sources of Error. There are two. The first is that the 
 specific heat of superheated steam, while given as 0.48 is 
 far from being certain, and only future investigation can 
 determine the true value. The second source of error is 
 loss of heat by radiation. Evidently from the moment the 
 steam enters the sampling nipple it is losing heat, hence 
 when it passes through the small opening and into the 
 lower pressure the heat available for evaporating moisture, 
 and superheating will be diminished by just the amount 
 lost by radiation, hence the value of t 2 will be lower than 
 it should be. This is sometimes corrected for as follows: 
 A valve in the steam pipe beyond the calorimeter nipple 
 is closed, and the steam left in a quiescent state for about 
 ten minutes, and it is assumed that by doing this all the 
 moisture in the steam will settle out, and that a sample of 
 steam drawn from the pipe will be dry. Steam is then 
 allowed to flow through the calorimeter and the tempera- 
 ture of the lower thermometer is noted. Let T denote this 
 temperature. Since the sample of steam was assumed to 
 be dry it follows that if there were no loss from radiation 
 the value of T would be that due to all of the liberated 
 heat being absorbed in superheating the steam of lower 
 temperature. There is, however, a loss of radiation, and 
 the effect of this is to condense some of the steam of lower 
 pressure, and the water thus formed must be evaporated 
 before any superheating can be done. Let x 1 represent the 
 proportion of water thus formed, then evidently 
 H—h—OAS (T—tJ 
 
Evaporation Tests 327 
 
 Now this amount of water was not in the steam orig- 
 inally, but was caused by condensation in the instrument, 
 hence the true amount of moisture in the steam, which 
 may be denoted by X, will be 
 
 H-h-OAS {t-tj 
 X=x — z*= ■ 
 
 H— h— 0.48 (T—t ± ) 
 
 L 
 
 0.48 (T— U) 
 
 [83 
 
 L 
 
 The disadvantages of this method are: [1) It assumes 
 that during the test the boiler pressure will remain the 
 same as it was when T was determined, which is seldom 
 practicable; (2) It assumes that the sample of steam 
 drawn into the instrument when determining T was ab- 
 solutely dry, although experiment has shown that this as- 
 sumption is not necessarily true. Notwithstanding these 
 facts, formula [8] is much used by engineers because of 
 its simplicity and convenience, and any error due to its 
 use is of no practical significance. 
 
 There are many forms of throttling calorimeter, all of 
 which operate on precisely the same principle as the simple 
 design shown in Fig. 103. An extremely convenient and 
 compact design is shown in Fig. 104. It consists of two 
 concentric cylinders screwed to a cap containing a ther- 
 mometer cup. The steam pressure is measured by a gauge 
 placed in the supply pipe, or any other convenient place. 
 Steam passes through the opening A, expands to atmos- 
 pheric pressure, and its temperature at this pressure is 
 measured by a thermometer placed in the cup C. To pre- 
 vent radiation losses the annular space between the two 
 
328 
 
 Steam Engineering 
 
 cylinders is used as a jacket, and is supplied with steam 
 through the hole B. 
 
 The limits of the throttling calorimeter at sea level are 
 from about four per cent of moisture at eighty pounds 
 pressure to six per cent at 200 pounds pressure. If there 
 is a greater content of moisture the liberated heat is in- 
 
 D 
 
 E — 
 
 Fig. 104 
 compact throttling calorimeter 
 
 sufficient to evaporate it, and superheat the steam thus 
 generated. 
 
 Separating Calorimeter. The separating calorimeter 
 (Fig. 105) mechanically separates the entrained water 
 from the steam and collects it in a reservoir, where its 
 amount is either indicated by a gauge glass or determined 
 
Evaporation Tests 
 
 329 
 
 by draining if off and weighing it. The steam passes out 
 of the calorimeter through an orifice of known size, so 
 
 Fig. 105 
 separating calorimeter 
 
 that either its total amount can be calculated, or it can be 
 weighed as later described. To avoid radiation errors, the 
 calorimeter should be well covered with non-conducting 
 
330 Steam Engineering 
 
 material. This instrument is not limited in capacity theo- 
 retically, but if the amount of moisture is very large, the 
 readings should be checked by passing the discharged steam 
 through a throttling calorimeter ; that is, a small separator 
 should be used between the steam pipe and a throttling 
 calorimeter, and the sum of the percentages obtained from 
 the two instruments be taken as the moisture in the steam. 
 In the separating calorimeter, the amount of steam 
 passing through the orifice can be determined by Xapier's 
 empirical formula, 
 
 pa 
 Pounds of steam per second= — 
 
 70 
 
 In which p= absolute pressure in pounds per square inch, 
 and a=area of orifice in square inches. 
 
 There is liability of considerable error in determining 
 the area of such small orifices, and further, the flow of 
 steam soon wears the orifice larger. A more accurate 
 method of determining the weight of steam passing through 
 is to convey it through a hose into a barrel of water resting 
 on a platform scale. The weight of the barrel and con- 
 tained water having been noted before and after the steam 
 is run in, the difference is the weight of steam condensed. 
 The moisture caught in the separating calorimeter can be 
 weighed in the same way. If W is the weight of steam 
 condensed, w the weight of moisture from the separating 
 calorimeter, and x the per cent of moisture in the steam, 
 then 
 
 lOOw 
 x= L9] 
 
 W+w 
 
 Location of Sampling Nipple. The principal source of 
 inaccuracy in calorimeter determinations is failure to secure 
 
Evaporation Tests 331 
 
 an average sample of steam. It is extremely doubtful 
 whether such a sample is ever secured. To dimmish the 
 liability of error the instrument should be located as near 
 as possible to the point where the sample is drawn off. 
 
 Taking an Observation. Locate the sampling nipple as 
 above directed, attach the instrument as close to it as pos- 
 sible, and cover all exposed parts to preveni radiation. If 
 the throttling calorimeter be used, locate the steam gauge 
 on the pressure side, and the thermometer on the expansion 
 side. To take an observation, note simultaneously the 
 gauge reading and the thermometer reading, and from 
 these the content of moisture may be determined by use of 
 formula [7]. If the separating calorimeter be used, attach 
 to the separator outlet a piece of hose which terminates in 
 a vessel of water on a platform scale graduated to read to 
 1/100 of a pound. Similarly connect the steam outlet to 
 another vessel of water resting on an equally sensitive 
 scale. Xote in each case the weight of each vessel includ- 
 ing the water it contains. "When ready to take an obser- 
 vation, blow out the instrument thoroughly, so there will 
 be no water in the separator. Then simultaneously close 
 the separator drip, and insert the steam hose into its 
 vessel of water. When the separator has accumulated a 
 sufficient quantity of water, close the valve at the main 
 steam pipe, thus cutting off the supply of steam to the 
 instrument, remove the steam hose from the vessel of water 
 into which it was inserted, and empty the separator water 
 into its vessel on the scale. Xote the final weight of each 
 vessel and contents, then the differences between final, 
 and original weights will be respectively, the weight of 
 moisture collected by the separator, and the weight of 
 steam from which the moisture was taken, hence the pro- 
 portion of moisture can be computed from formula [9]. 
 
332 Steam Engineering 
 
 Before taking any calorimeter observations, steam should 
 be allowed to flow through freely until the instrument is 
 thoroughly heated up. 
 
 Moisture in the Coal. This can generally be obtained 
 from the reports of the geologist of the state in which the 
 coal is mined, or from the dealer, although the former is 
 the most reliable. The percentage of moisture must be 
 deducted from the total weight of coal in figuring the 
 weight of combustible. 
 
 Measuring the Chimney Draft. A good draft is indis- 
 pensable for obtaining economical results in an evapora- 
 tion test. The draft can be easily regulated by a damper 
 to suit the conditions. Chimney draft is ordinarily meas- 
 ured by a draft gauge connected with the smoke flue near 
 the chimney. The usual form of draft gauge is a glass 
 tube bent in the shape of the letter U. (See Fig. 106.) 
 One leg is connected to the flue by a small rubber hose, 
 while the other is open to the atmosphere. The tube is 
 partly filled with water, which will, when there is no draft, 
 stand at the same height in both legs. When connected 
 to the chimney or flue the suction will cause the water in 
 the leg to which the hose is attached to rise, while the level 
 of the water in the other leg will be equally depressed, and 
 the extent of the variation in fractions of an inch is the 
 measure of the draft. Thus the draft is referred to as 
 being .5, .7 or .75 inches. The draft should not be less 
 than .5 inches in any case to insure good results. 
 
 The Barrus draft gauge is illustrated in Fig. 107. It 
 consists of a U-tube made of -^j-incli glass, surmounted 
 by two larger tubes, or chambers, each having a diameter 
 of 2 1 /2~:mch. Two different liquids which will not mix, 
 and which are of different color, are used. The movement 
 
Evaporation Tests 
 
 333 
 
 of the line of demarcation is proportional to the difference 
 in the areas of the chambers and of the U-tube connecting 
 them below. The liquids generally employed are alcohol 
 colored red and a certain grade of lubricating oil. A 
 
 r^r^ 
 
 
 
 
 
 
 
 i 
 
 
 
 
 / 
 
 
 
 f 
 
 
 ■ 
 
 ^^ 
 
 7 
 
 i 
 
 
 • 
 
 ■ 
 
 ••- 
 
 : . .-: 
 
 ^^ 
 
 s ^ d> 
 
 r g- ,j|{ 
 
 U 
 
 p3| 
 
 
 r 
 
 □ 
 
 Fig. 106 
 
 Fig. 107 
 barrus' draft gauge 
 
 multiplication varying from eight to ten times is obtained 
 under these circumstances; in other words, with %-inch 
 draft the movement of the line of demarcation is some 2 
 inches. The instrument is calibrated by referring it to 
 the ordinary U-tube gauge. 
 
334 
 
 Steam Engineering 
 
 Ellison s Gauge. In this form of gauge the lower por- 
 tion of the ordinal XT-tube has been replaced by a tube 
 slightly inclined to the horizontal, as shown in Fig. 108, 
 By this arrangement anjr vertical motion in the left hand 
 upright tube causes a very much greater travel of the 
 liquid in the inclined tube, thus permitting extremely 
 small variation in the draft pressure to be read with fa- 
 cility. 
 
 The gauge is first leveled by means of the small level 
 attached to it, both legs being open to the atmosphere. 
 The liquid is then adjusted (by adding to or taking from 
 
 Fig. 108 
 ellison's draft gauge outline 
 
 it) until its meniscus rests at the zero point on the right. 
 The left hand leg is then connected to the source of draft 
 by means of a piece of rubber tubing. Under these cir- 
 cumstances, a rise of level of one inch in the left hand 
 vertical tube causes the meniscus in the inclined tube to 
 pass from the point to 1.0. The scale is divided into 
 tenths of an inch, and the subdivisions are hundredths of 
 an inch. 
 
 The right hand leg of the instrument bears two marks. 
 By filling the tube to the lower of these the range of the 
 instrument is increased one-half inch, i. e., it will record 
 draft pressures from to 1% inches. Similarly, by filling 
 
 
Evaporation Tests 335 
 
 to the upper mark, the range is increased to 2 inches* 
 When so used the observed readings in the scale are to be 
 increased by one-half or one-inch, as the case may be. 
 
 The makers recommend the use of a non-drying oil 
 for the liquid, usually a 300° test refined petroleum, but 
 water suffices for all practical purposes. 
 
 Flue Gas Analysis. The object of the flue-gas analysis 
 is to determine from a sample of the gas the amount of 
 excess air admitted, the degree of completeness of the com- 
 bustion of the carbon, and the amount and distribution of 
 the heat losses due to the excess air and incomplete com- 
 bustion. The quantities actually determined by the analy- 
 sis are the relative proportions of carbon dioxide (C0 2 ), 
 carbon monoxide (CO), and oxygen (0) in the gases. 
 Although the analysis does not directly determine the 
 amount of nitrogen present in the flue-gases, yet its actual 
 amount, as well as that of the air supply, may readily be 
 ascertained by calculation. When air is drawn through an 
 opening, like an ash-pit door, sometimes an anemometer 
 can be used for ascertaining the velocity through the area, 
 and the air supply be determined by these means. 
 
 A pound of carbon requires for complete combustion, 
 2.67 pounds of oxygen, or a volume of 32 cubic feet at 
 60° F., and the gaseous product, carbon dioxide (C0 2 ), 
 when cooled occupies precisely the same volume as the oxy- 
 gen, viz., 32 cubic feet. If the oxygen is mixed with nitro- 
 gen in the same proportion as it is found in air (20.91 O 
 and 79.09 X), the volume of the carbon dioxide (C0 2 ) 
 after combustion, and also its proportion to nitrogen, is 
 the same as that of the oxygen; hence, for complete com- 
 bustion of carbon, with no excess of air, the volumetric 
 analysis of the flue gases is, 
 
336 Steam Engineering 
 
 Carbon dioxide CO 2 =20.91% 
 
 Carbon monoxide CO =N"one 
 
 Oxygen =N"one 
 
 Nitrogen N =79.09% 
 
 If the supply of air is in excess of that required to supply 
 the oxj^gen needed, the combined volumes of the carbon 
 dioxide and oxygen are still the same as that of the oxygen 
 before combustion; consequently, for the complete com- 
 bustion of pure carbon, the sum of the percentages by vol- 
 ume of the carbon dioxide and oxygen in the flue gases 
 must always be 20.91, no matter what the supply of air 
 may be. 
 
 Carbon monoxide (CO) produced by imperfect com- 
 bustion of carbon, occupies twice the volume of the oxygen 
 entering into its composition, and renders the volume of 
 the, flue gases greater than that of the air supply in the 
 proportion of 
 
 100 
 . , hence 
 
 100—y 2 the % of CO 
 when pure carbon is the fuel, the sum of the percentages 
 of carbon dioxide, oxygen, and one-half the carbon mon- 
 oxide must be in the same ratio to the nitrogen as is oxy- 
 gen in the air, viz. 20.91 to 79.09. 
 
 Or sat Apparatus. The analysis of the flue-gases is best 
 made for practical purposes by means of the Orsat appara- 
 tus shown in Fig. 109. The operation is as follows: 
 Exactly 100 cc of the gas sample are drawn into the 
 graduated measuring burette, A, and then passed in suc- 
 cession into the U-form absorbing vessels, *D, E, F, each 
 time being returned to and measured in A. In passing 
 into the U-shaped vessels, the gas displaces the liquid 
 contained therein, driving it up into the other legs. A 
 

 Evaporation Tests 
 
 337 
 
 portion of the fluids, however, adheres to the glass tubes 
 placed in the vessels for that purpose, and comes in inti- 
 mate contact with the gas. Each vessel absorbs a different 
 constituent. D is filled with a solution of potassium 
 hydroxide and takes up the carbon dioxide; E contains 
 
 Fig. 109 
 orsat apparatus for flue-gas analysis 
 
 pyrogallic acid, which removes the oxygen; and F absorbs 
 the carbon monoxide in a solution of cuprous chloride. 
 The reduction in volume measured in A gives the per- 
 centage of each constituent gas. 
 
 J 
 
338 Steam Engineering 
 
 The connections to A are made through the glass stop 
 cocks M, and the capillary tube C. The movement of the 
 gases is produced by lowering or raising the bottle L, which 
 is connected to the lower part of A by the rubber tube S, 
 and is partially filled with water. When a measurement 
 is taken, the level of the water in A and L must be the 
 same, so that all measurements are taken at atmospheric 
 pressure. A constant temperature of the gas in A is main- 
 tained by the water in the surrounding cylinder shown. 
 
 The sample is drawn into the apparatus through the 
 cock B, which also serves to connect the capillary tube to 
 the atmosphere, the latter connection being through the 
 spindle of the cock; this permits the removal of any excess 
 of gas above 100 cc that may have been drawn into A. Be- 
 fore the sample is drawn, the vessels D, E and F should 
 have their respective liquids raised to the cocks M which 
 can then be closed, and the atmospheric pressure acting 
 through the other leg, which is open, will keep them filled. 
 The burette A and the capillary tubes should be filled with 
 water up to the cock B. All this can easily and quickly 
 be done by raising and lowering L, and opening and closing 
 cocks M and B. The absorption of oxygen and carbon 
 monoxide is very slow, and the gas should be passed back 
 and forth a number of times until a reduction of volume 
 is no longer indicated. 
 
 As the pressure of the gases in a flue is less than the 
 atmospheric pressure, they will not, of themselves, flow 
 through the rubber or metal tubing connecting to the 
 analyzing apparatus; but by filling the instrument two or 
 three times and discharging it into the atmosphere through 
 cock B, the air can be removed from the connecting tubing 
 and a sample of the gas be obtained. For rapid work, an 
 
Evaporation Tests 339 
 
 aspirator can be used for drawing the gas from the tube 
 in a constant stream. If this is used there is less danger 
 of an admixture of air. It is sometimes desirable to take 
 a sample that represents an average during half an hour, 
 or an hour, and in this case a metal, or glass vessel with 
 a stop-cock at both top and bottom, and filled with water, 
 can be connected through the upper stop-cock to the flue, 
 and the bottom cock then be opened. The water will 
 gradually drip out, drawing the gas into the vessel. The 
 time taken to fill it can be regulated by the lower cock. 
 
 The result of a flue-gas analysis depends both on the 
 manner and time of taking the sample, and to get at the 
 average composition of the gas, a number of determina- 
 tions should be made on samples from different parts of 
 the flue. 
 
 The analysis made by the Orsat apparatus is volumetric ; 
 if the analysis by weight is required it can be found from 
 the volumetric analysis as follows: 
 
 Multiply the percentages by volume by the molecular 
 weight of the gas, and divide by the sum of all the prod- 
 ucts; the quotient ivill be the percentage by weight. 
 
 The molecular weights are as follows: 
 
 Carbon dioxide 44 
 
 Carbon monoxide 28 
 
 Oxygen 32 
 
 Nitrogen 28 
 
 Calculations for Efficiency of the Plant. Having thus 
 successfully conducted the test to its close, and being armed 
 with all the data heretofore noted, the engineer is now 
 ready to compute the results. 
 
 If the test is made for the purpose of determining the 
 efficiency of the boiler and setting as a whole, including 
 
340 Steam Engineering 
 
 grate, chimney draft, etc., then the result must be based 
 upon the number of pounds of water evaporated per pound 
 of coal. This latter phrase includes not only the purely 
 combustible matter in the coal, but the non-combustible 
 also, as ash, moisture, etc. Some varieties of western coal 
 contain as high as 12 to 14 per cent, of moisture, and the 
 ability of the furnace to extract heat from the mass is to 
 be tested, as well as the ability of the boiler to absorb and 
 transmit that heat to the water. Therefore the efficiency 
 of the boiler and furnace= 
 
 Heat absorbed per pound of coal. 
 Heating value of one pound of coal. 
 
 Efficiency of the Boiler. The heating surface of the 
 boiler must transmit heat from the hot furnace gases on 
 one side, to the water on the other. This transmission of 
 heat is very rapid through the metal of the boiler, but the 
 accumulation of scale on the interior, and soot on the ex- 
 terior surfaces greatly obstructs the flow of heat and renders 
 the heating surface inefficient. 
 
 If the test is to determine the efficiency of the boiler 
 itself as an absorber of heat, then the combustible alone 
 must be considered in working out the final result. Thus, 
 
 Efficiency of boiler= 
 
 Heat absorbed per pound of combustible. 
 Heating value of one pound of combustible. 
 
 When making a series of tests for the purpose of com- 
 paring the economical value of different varieties of coal, 
 the conditions should be as nearly uniform as possible; 
 that is, let the tests be made under ordinary working con- 
 ditions, and with the same boiler or boilers, and if possible 
 with the same fireman. 
 
Evaporation Tests 341 
 
 The following is a record of one of many evaporation 
 tests made by the author, and is introduced here for the 
 purpose of illustrating methods of computing the results 
 to be obtained from the various data. The rather large 
 
 Date of test 
 
 Duration of test, 12 hours. 
 Boiler, return tubular, 72 in. diameter, 18 ft. long, 62-4J in. tubes. 
 
 Kind of coal, Pocahontas ; average steam pressure 85 lbs. 
 
 Weight of coal consumed 11,100 lbs. 
 
 Weight of water apparently evaporated 107,187 lbs. 
 
 Weight of dry ash returned 8.1 per cent.= 900 lbs. 
 
 Moisture in the coal 2.0 per cent.= 222 lbs. 
 
 Moisture in the steam 1.0 per cent.= 1,071 lbs. 
 
 Dry coal corrected for moisture 10,878 lbs. 
 
 Weight of combustible 9,978 lbs. 
 
 Water corrected for moisture in the steam 106,116 lbs. 
 
 W T ater evaporated into dry steam, from and at 212° 117,788 lbs. 
 
 Water evaporated per lb. of coal, actual conditions 9.65 lbs. 
 
 Water evaporated per lb. of coal, from and at 212° 10.61 lbs. 
 
 Water evaporated per lb. of combustible, from and at 212° . . 11.81 lbs. 
 
 Water evaporated per lb. of dry coal, from and at 212° 10.82 lbs. 
 
 Water evaporated per hr. per sq. ft. of heating surface 6.22 lbs. 
 
 Coal burned per sq. ft. of grate surface per hour 25 lbs. 
 
 Horsepower developed by boiler during test 284.5 
 
 Temperature of feed water, average 141° 
 
 Temperature of chimney gases, average 400° 
 
 Square feet of grate surface 36 
 
 Square feet of heating surface 1,576 
 
 Ratio of grate surface to heating surface 43.7 
 
 quantity of coal burned per square foot of grate surface 
 per hour (25 pounds) is owing to the fact that the boiler 
 was run to its full capacity, the coal burning clean, and 
 forming no clinker. The chimney draft also was excep- 
 tionally good, giving a large unit of evaporation per square 
 foot of heating surface per hour. The low temperature of 
 the escaping gases is due to the fact that they were returned 
 over the top of the boiler before passing to the chimney. 
 
 The results obtained will be taken up in their regular 
 order beginning with, first, water evaporated into dry steam 
 from and at 212°. As it may be of benefit to some, a 
 short definition of the meaning of the above expression is 
 here given. 
 
342 Steam Engineering 
 
 The term "equivalent evaporation," or the evaporation 
 from and at 212°, assumes that the feed water enters the 
 boiler at a temperature of 212° and is evaporated into steam 
 at 212° temperature and at atmospheric pressure. As for 
 instance, if the top man hole plate were left out, or some 
 other large opening in the steam space allowed the steam 
 to escape into the atmosphere as fast as it was generated. 
 Owing to the variation in the temperatures of the feed 
 water used in different tests, and also the variation in the 
 steam pressure, it is absolutely necessary that the results 
 of all tests be brought by computation to the common basis 
 of 212° in order to obtain a just comparison. 
 
 The process by which this is done is as follows: Ee- 
 ferring to the record of the test it is seen that the steam 
 pressure average was 85 pounds gauge pressure, or 100 
 pounds absolute, and that the temperature of the feed water 
 was 141°. Eef erring again to Table 17, physical proper- 
 ties of steam, it will be seen that in a pound of steam at 
 100 pounds absolute pressure there are 1,181.8 heat units, 
 and in a pound of water at 141° temperature there are 
 109.9 heat units. It therefore took 1,181.8—109.9= 
 1,071.9 heat units to convert one pound of feed water at 
 141° into steam at 85 pounds pressure. To convert a pound 
 of water at 212° into steam at atmospheric pressure, and 
 212° temperature requires 965.7 heat units, and the 1,071.9 
 heat units would evaporate 1,071.9^-965.7=1.11 pounds 
 water from and at 212°. The 1.11 is the factor of evapora- 
 tion for 85 pounds gauge pressure and 141° temperature 
 of feed water, and by multiplying "water corrected for 
 moisture in the steam" (see record of test), 106,116 pounds, 
 by 1.11, the weight of water which could have been evapo- 
 rated into steam from and at 212° is obtained, which is 
 
Evaporation Tests 
 
 343 
 
 117,788 pounds. The factor of evaporation is based upon 
 
 the steam pressure and the temperature of the feed water 
 
 in any test and the formula for ascertaining it is as fol- 
 
 H— h 
 
 lows: Factor= , in which H=total heat in the 
 
 965.7 
 
 steam and h=total heat in the feed water. It is used in 
 
 shortening the process of finding the evaporation from and 
 
 at 212 ° y and Table 26 gives the factor of evaporation for 
 
 various pressures and temperatures. 
 
 Table 26 
 factors of evaporation. 
 
 
 BB 
 
 .a 
 
 c/j 
 
 (A 
 
 en 
 
 CO 
 
 .a 
 
 CO 
 
 
 JQ 
 
 a 
 
 £2 
 
 g>8 
 
 s?8 
 
 
 
 si 
 
 bfiO 
 
 (DO 
 3tH 
 
 
 <D© 
 
 3H 
 
 t3 a 
 
 U 
 
 Ph 
 
 u 
 PL, 
 
 OS 
 
 V 
 
 u 
 
 Ph 
 
 Ph 
 
 ■ Ph 
 
 W CO 
 
 u 
 
 Ph 
 
 O en 
 
 co 
 <u 
 
 Ph 
 
 w co 
 V 
 
 Ph 
 
 212° 
 
 1.027 
 
 1.030 
 
 1.032 
 
 1.035 
 
 1.037 
 
 1.039 
 
 1.041 
 
 1.043 
 
 1.047 
 
 200° 
 
 1.039 
 
 1.042 
 
 1.045 
 
 1.047 
 
 1.050 
 
 1.052 
 
 1.054 
 
 1.056 
 
 1.059 
 
 191° 
 
 1.049 
 
 1.052 
 
 1.054 
 
 1.057 
 
 1.059 
 
 1.061 
 
 1.063 
 
 1.065 
 
 1.069 
 
 182° 
 
 1.058 
 
 1.061 
 
 1.064 
 
 1.066 
 
 1.069 
 
 1.071 
 
 1.073 
 
 1.075 
 
 1.078 
 
 173° 
 
 1.067 
 
 1.070 
 
 1.073 
 
 1.076 
 
 1.078 
 
 1.080 
 
 1.082 
 
 1.084 
 
 1.087 
 
 164° 
 
 1.077 
 
 1.080 
 
 1.083 
 
 1.085 
 
 1.087 
 
 1.090 
 
 1.091 
 
 1.093 
 
 1.097 
 
 152° 
 
 1.089 
 
 1.092 
 
 1.095 
 
 1.098 
 
 1.100 
 
 1.102 
 
 1.104 
 
 1.106 
 
 1.109 
 
 143° 
 
 1.099 
 
 1.102 
 
 1.105 
 
 1.107 
 
 1.109 
 
 1.111 
 
 1.113 
 
 1.115 
 
 1.119 
 
 134° 
 
 1.108 
 
 1.111 
 
 1.114 
 
 1.116 
 
 1.119 
 
 1.121 
 
 1.123 
 
 1.125 
 
 1.128 
 
 125° 
 
 1.118 
 
 1.121 
 
 1.123 
 
 1.126 
 
 1.128 
 
 1.130 
 
 1.132 
 
 1.134 
 
 1.137 
 
 113° 
 
 1.130 
 
 1.133 
 
 1.136 
 
 1.138 
 
 1.140 
 
 1.143 
 
 1.145 
 
 1.146 
 
 1.150 
 
 104° 
 
 1.138 
 
 1.142 
 
 1.145 
 
 1.148 
 
 1.150 
 
 1.152 
 
 1.154 
 
 1.156 
 
 1.159 
 
 95° 
 
 1.149 
 
 1.152 
 
 1.154 
 
 1.157 
 
 1.159 
 
 1.161 
 
 1.163 
 
 1.165 
 
 1.169 
 
 86° 
 
 1.158 
 
 1.161 
 
 1.164 
 
 1.166 
 
 1.169 
 
 1.171 
 
 1.173 
 
 1.174 
 
 1.178 
 
 77° 
 
 1.167 
 
 1.170 
 
 1.173 
 
 1.176 
 
 1.178 
 
 1.180 
 
 1.182 
 
 1.184 
 
 1.187 
 
 65° 
 
 1.180 
 
 1.183 
 
 1.186 
 
 1.188 
 
 1.190 
 
 1.192 
 
 1.194 
 
 1.196 
 
 1.200 
 
 56° 
 
 1.189 
 
 1.192 
 
 1.195 
 
 1.197 
 
 1.200 
 
 1.202 
 
 1.204 
 
 1.206 
 
 1.209 
 
 47° 
 
 1.199 
 
 1.201 
 
 1.204 
 
 1.207 
 
 1.209 
 
 1.211 
 
 1.213 
 
 1.215 
 
 1.218 
 
 38° 
 
 1.208 
 
 1.211 
 
 1.214 
 
 1.216 
 
 1.218 
 
 1.220 
 
 1.222 
 
 1.224 
 
 1.228 
 
 Second, water evaporated per pound of coal actual con- 
 ditions=water apparently evaporated divided by coal con- 
 sumed=9.65 pounds. No accurate estimate regarding the 
 quality of the coal or the efficiency of the boiler can be 
 made from this figure (9.65 pounds). It can be used, 
 
344 Steam Engineering 
 
 however, in estimating the cost of fuel for generating the 
 steam ; as, for instance, if the boiler is supplying steam to 
 an engine that uses 30 pounds of steam per house-power 
 per hour, it will require 30-^9. 65=3.1 pounds of coal per 
 horse-power per hour ; the "actual conditions" under which 
 the boiler is being operated being the pressure of steam 
 required by the engine and the temperature of the feedi 
 water. > 
 
 Third, water evaporated per pound of coal from and at 
 212°=water evaporated into dry steam from and at 212° 
 -^coal consumed=10.61 pounds. This figure is the proper 
 one to use in comparing the relative economic values of 
 different varieties of coal tested with the same boiler or 
 boilers. 
 
 Fourth, w T ater evaporated per pound of combustible from 
 and at 212°=water evaporated into dry steam from and 
 at 212° -^weight of combustible=11.81 pounds. This re- 
 sult is the one to be used for ascertaining the efficiency of 
 the boiler, and the percentage of efficiency is found by 
 dividing the heat absorbed by the boiler per pound of com- 
 bustible by the heat value of one pound of combustible. 
 The average heat value of bituminous and semi-bituminous 
 coals is not far from 15,000 heat units per pound of com- 
 bustible. In the evaporation of 11.81 pounds of water 
 from and at 212° the heat absorbed was 11.81X965.7= 
 11,4.04.9 heat units. The efficiency of the boiler therefore 
 was 
 
 11,404.9X100 
 
 =76 per cent. 
 
 15,000 
 
 In like manner to ascertain the efficiency of the boiler 
 and furnace as a whole, the water evaporated from and 
 at 212° per pound of coal is taken. Thus 10.61X965.7 
 
Evaporation Tests 345 
 
 = 10,246 heat units absorbed from each pound of coal. 
 
 N~ow assuming that there were 13,500 heat units in each 
 
 pound of the coal used in the test, the per cent of efficiency 
 
 of boiler and furnace was 
 
 10,246X100 
 
 =75.9. 
 
 13,500 
 
 Fifth, water evaporated per pound of dry coal from 
 and at 212°=water evaporated into dry steam from and 
 at 212° divided by coal corrected for moisture. Thus, 
 117,788-^10.878=10.82 pounds. This result is useful 
 for calculating the results of tests of the same grade of 
 coal, but differing in the degree of moisture in each. 
 
 Sixth. Boiler horse-power. The latest decision of the 
 American Society of Mechanical Engineers (than whom 
 there is no better authority) regarding the horse-power of 
 a boiler is as follows: "The unit of commercial horse- 
 power developed by a boiler shall be taken as 34% units 
 of evaporation per hour. That is, 34 1 /2 pounds of water 
 evaporated per hour from a feed temperature of 212° 
 into steam of the same temperature. This standard is 
 equivalent to 33,317 B.T.U. per hour. It is also practically 
 equivalent to an evaporation of 30 pounds of water from a 
 feed water temperature of 100° F. into steam of 70 pounds 
 gauge pressure." 
 
 According to this rule the horse-power developed by the 
 boiler during the test under consideration=water evap- 
 orated into dry steam from and at 212°, 117,788 pounds 
 ^-12 hours-^34.5=284.5 horse-power. 
 
346 Steam Engineering 
 
 QUESTIONS AND ANSWERS. 
 
 267. What is the primary object of an evaporation test? 
 Ans. To ascertain how many pounds of water the boilers 
 
 are evaporating per pound of coal burned. 
 
 268. What other important points relative to boiler 
 operation may be determined hj these tests? 
 
 Ans. There are four. First — To determine the efficiency 
 of the plant as an apparatus for the consumption of fuel, 
 and the evaporation of water. Second — To determine the 
 relative economy of different varieties of coal, and other 
 fuels. Third — To determine whether or not the boilers 
 are being operated as economically as they might be. 
 Fourth — To determine whether the boilers are being over 
 worked. 
 
 269. In what condition should the testing apparatus 
 be maintained? 
 
 Ans. In first-class condition, ready to be used at any 
 time for making a test. 
 
 270. What should be done with the boiler, and all of 
 its appurtenances preparatory to making a test? 
 
 Ans. They should be put in good condition, by clean- 
 ing, etc. 
 
 271. How should the boiler under test be operated 
 during the test? 
 
 Ans. At its full capacity. 
 
 272. Where should the water level be at the beginning, 
 and close of the test? 
 
 Ans. At the height ordinarily carried, and its position 
 should be marked by tying a cord around one of the guard 
 rods of the gauge glass. 
 
 273. How long should the test last? 
 Ans. About 10 hours. 
 
Questions and Answers 347 
 
 274. How is the percentage of moisture in the steam 
 determined ? 
 
 Ans. By means of the calorimeter. 
 
 275. How many, and what kind of calorimeters are 
 used for this purpose? 
 
 Ans. Two. The throttling calorimeter, and separating 
 calorimeter. 
 
 276. Upon what principle does the throttling calori- 
 meter act? 
 
 Ans. Upon the principle of temperatures. 
 
 277. How does the separating calorimeter act? 
 
 Ans. It mechanically separates the water from a known 
 volume of steam passing through it. 
 
 278. In what other manner may the condition of steam 
 regarding its dryness be approximated? 
 
 Ans. By observing its appearance as it issues from a 
 pet cock, or other small opening. 
 
 279. How will steam containing 1 or 2 per cent of 
 moisture appear under such conditions ? 
 
 Ans. It will be transparent close to the orifice from 
 
 which it issues. 
 
 280. How is the chimney draft measured? 
 Ans. By means of a draft gauge. 
 
 281. What is the usual form of draft gauge? 
 Ans. A glass tube bent in the shape of. the letter U. 
 
 282. Describe the action of a draft gauge. 
 
 Ans. One leg of the U tube is connected to the chimney 
 by a small rubber hose. The other leg is open to the at- 
 mosphere. The tube is partly filled with water, which 
 when there is no draft will stand at the same height in 
 both legs. 
 
348 Steam Engineering 
 
 283. When there is a draft and the rubber hose is con- 
 nected to the chimney how is the water in the U tube 
 affected ? 
 
 Ans. The draft suction causes the water in the leg to 
 which the hose is connected, to rise while the level of the 
 water in the other leg will be equally depressed. 
 
 284. How is the intensity of the draft thus estimated? 
 Ans. In fractions of an inch, .5, .7 or .75 inches. 
 
 285o What is the object of flue gas analysis? 
 
 Ans. There are three. First — To determine the amount 
 of excess air admitted to the furnace. Second — To de- 
 termine the character of the combustion. Third — To as- 
 certain the heat losses. 
 
 286. What weight of oxygen is required for the com- 
 plete combustion of one pound of carbon? 
 
 Ans. 2.67 pounds. By volume, 32 cubic feet. 
 
 287. What gaseous combination is produced by com- 
 plete combustion? 
 
 Ans. Carbon dioxide (C0 2 ). 
 
 288. What is the result of imperfect combustion? 
 Ans. Carbon monoxide (CO). 
 
 289. How is the efficiency of the boiler and furnace 
 ascertained through an evaporation test? 
 
 Ans. By weighing the coal consumed and the water 
 evaporated during a certain number of hours and dividing 
 the number of pounds of water evaporated by the number 
 of pounds of coal consumed. This will give number of 
 pounds water evaporated per pound oi coal. 
 
 290. What is meant by the term "equivalent evapora- 
 tion?" 
 
 Ans. It assumes that the feed water enters the boiler 
 at a temperature of 212°, and is evaporated into steam at 
 212° and at atmospheric pressure. 
 
Questions and Answers* 349 
 
 291. Why is this standard necessary in evaporation 
 tests ? 
 
 Ans. Because of the variations in the temperature of 
 the feed water used in different tests. 
 
 292. What is meant by boiler horse-power? 
 
 Ans. The evaporation of 34 1 /2 pounds water from a 
 feed temperature of 212° into steam of the same tempera- 
 ture; or the evaporation of 30 pounds water from a feed 
 temperature of 100° into steam at 70 pounds gauge pres- 
 sure. 
 
 293. What is meant by the expression "total heat of 
 evaporation ?" 
 
 Ans. The sum of the sensible heat plus the latent- heat, 
 at boiling point. 
 
 294. What is steam in its relation to the engine? 
 Ans. It is merely a vehicle for transferring the neat 
 
 energy from the boiler to the engine shaft. 
 
^ 
 
Steam Engines 
 
 Fig. 110 
 beynoids combined vertical and horizontal engine 12,000 
 
 HORSE-POWER CYLINDERS, 44x88x60. 
 
 Built by Allis-Chalmers Company 
 
 Steam engines may be divided into two general classes, 
 viz., simple and compound. 
 
 A simple engine may be either condensing or non-con- 
 densing, but its leading characteristic is, that the steam is 
 
 351 
 
352 Steam Engineering 
 
 used in but one cylinder, and from thence it is exhausted 
 either into the atmosphere or into a condenser. 
 
 A compound engine is one in which the steam is made 
 to do work in two or more cylinders before it is allowed 
 to exhaust, and this class of engine may be either condens- 
 ing or non-condensing. 
 
 In a non-condensing engine the pressure of the atmos- 
 phere, amounting to 14.7 pounds per square inch at sea 
 level, is constantly in resistance to the motion of the piston. 
 Therefore the exhaust pressure cannot fall below the atmos- 
 pheric pressure, and is generally from two to five pounds 
 above it, caused by the resistance of bends and turns in the 
 exhaust pipe, or other causes which tend to retard the free 
 passage of the steam. 
 
 The advantage, from an economical point of view, of 
 exhausting the steam into a condenser in which a vacuum 
 is maintained, will be fully set forth in the section on 
 Indicator Work. 
 
 CONDENSERS. 
 
 Condensers are of two classes, viz., jet condensers and 
 surface condensers. 
 
 In a jet condenser the steam is exhausted into an air- 
 tight iron vessel of any convenient shape, generally cylin- 
 drical and of suitable size, and is there condensed by com- 
 ing in contact with a jet of cold water, admitted in the 
 form of a spray. The air pump, which also maintains a 
 vacuum in the condenser, draws this water, together with 
 the condensed steam, away from the condenser. 
 
 The surface condenser, like the jet condenser, consists 
 of an air-tight iron vessel, either cylindrical or rectangular 
 in shape, but unlike the jet condenser, it is fitted with a 
 
Condensers 353 
 
 large number of brass or copper tubes of small diameter, 
 through which cold water is forced by a pump, called a 
 circulating pump. A vacuum is also maintained in the 
 body of the condenser by the air pump, and the steam 
 exhausting into this is condensed by coming in contact 
 with the cool surface of the tubes. Or, as is often the case, 
 the exhaust steam passes through the tubes in place of 
 around them, and the condensing water is forced into and 
 through the body of the condenser, the vacuum in this case 
 
 Fig. Ill 
 
 CROSS COMPOUND DIRECT CONNECTED CORLISS ENGINE, ALLIS- 
 CHALMERS COMPANY 
 
 being maintained in the tubes. Owing to the fact that in 
 a surface condenser the steam does not mix with the water, 
 a larger quantity of condensing water is required than in 
 a jet condenser, but on the other hand, an advantage is 
 gained by having the pure water of condensation ; in other 
 words, the condensed steam, which may be returned to the 
 boilers along with the regular feed water supply, and will 
 greatly aid in preventing the formation of scale, while the 
 water of condensation as it comes from a jet condenser, 
 
354 Steam Engineering 
 
 being mixed with oil and other impurities, is not, as a rule, 
 suitable to be fed to boilers. 
 
 There are many different types of jet condensing ap- 
 paratus, in some of which no air pump is used ; their action 
 being based somewhat upon the principle of the injector 
 used for feeding boilers. In this type of jet condenser 
 the supply of condensing water is drawn from outside pres- 
 sure, either from an overhead tank or other source, and 
 passing into an annular enlargement of the exhaust pipe, 
 is discharged downwards in the form of a cylindrical sheet 
 
 Fig. 112 
 tandem compound engine, buckeye engine company 
 
 of water into a nozzle which gradually contracts. The 
 exhaust steam, entering at the same time, is condensed, 
 and the contracting neck of the cone shaped nozzle gradu- 
 ally brings the water to a solid jet, and it rushes through 
 the nozzle with a velocity sufficient to create a vacuum. 
 This type of condenser can only be used where the dis- 
 charge pipe has a free outlet. 
 
 The jet condenser with air pump attached is the most 
 reliable as well as economical for general purposes, for the 
 reason that with this type the supply of condensing water 
 may be drawn from a well or other source lower than the 
 
Condensers 
 
 355 
 
 level of the condenser. These condensers are also generally 
 fitted with a "force injection/' as it is called, which is 
 simply a connection between the condenser and water main 
 
 Fig. 113 
 knowles jet condenser 
 
 or tank, for the purpose of letting cold water into the con- 
 denser to condense the exhaust steam when starting the 
 engine, and thus aid in forming a vacuum. When a good 
 
356 Steam Engineering 
 
 vacuum has been established and the engine is running up 
 to speed, the force injection may be shut off, and the water 
 will flow into the condenser from the well by suction. The 
 above refers to engines in which the air pump receives its 
 motion directly from the engine. 
 
 Another type of jet condensing apparatus is the inde- 
 pendent air pump and condenser, which is still better, for 
 the reason that the air pump, which is simply an ordinary 
 double acting steam pump, may be started independently 
 of the engine, and, in fact, before the engine is started, 
 thus creating a vacuum in the condenser, and greatly facili- 
 tating the starting of the engine. Another great advantage 
 in the independent condensing apparatus is, that there is 
 not so much danger of the w T ater backing up into the 
 cylinder in case of a sudden shut down of the engine, be- 
 cause the air pump may be kept in operation, thus relieving 
 the condenser of water; whereas, if the air pump gets its 
 motion from the engine, it will of course stop when the 
 engine stops, and unless the injection water is shut off 
 immediately after closing the throttle there is great danger 
 of the cylinder becoming flooded with water, resulting very 
 often in a broken cylinder head, or a bent piston rod. 
 
 The quantity of water required to condense the exhaust 
 steam of an engine is determined by three factors : First, 
 the density, temperature and volume of the steam to be 
 condensed in a given time; second, the temperature of the 
 overflow or discharge, and third, the temperature of the 
 injection water. For instance, the temperature of the in- 
 jection water may be 35° in the winter and 70° in the 
 summer. Or it may be desired to keep the overflow at as 
 high a temperature as possible for the purpose of feeding 
 the boilers. Again, the . pressure, and consequently the 
 
Condensers 357 
 
 temperature of the exhaust steam as it enters the condenser, 
 varies with different engines, and often with the same en- 
 gine, according as the load is light or heavy. Therefore 
 the only accurate method of estimating the amount of con- 
 densing water required per minute or per hour, under any 
 and all conditions, is to first ascertain the weight of water 
 required to condense one pound weight of steam at the tem- 
 perature and pressure at which the steam is being ex- 
 
 Fig. 114 
 worthington surface condenser, with air and circulating 
 
 PUMP 
 
 hausted. In these calculations the total heat in the steam 
 must be considered. This means not only the sensible 
 heat, but the latent heat also. 
 
 The formula for solving the above problem may be ex- 
 
 H— T 
 
 pressed as follows : =W, in which 
 
 T— I 
 
 H=total heat in the steam, 
 T=temperature of the overflow, 
 

 358 
 
 Steam Engineering 
 
 I = temperature of the injection water, 
 
 W=weight of water required to condense one pound 
 weight of steam. 
 
 To illustrate, suppose the absolute pressure of the ex- 
 haust, as shown by the indicator diagram, is 7 pounds. 
 Referring to Table 17, it will be seen that the total heat 
 in steam at 7 pounds absolute is 1135.9 heat units. As- 
 sume the temperature of the overflow to be 110°, which is 
 
 Fig. 115 
 siphon condenser 
 
 as high as is consistent with a good vacuum. Now the 
 total heat to be absorbed from each pound weight of steam 
 in this case would be 1135.9—110=1025.9 B. T. U. 
 
 Suppose the temperature of the condensing water to 
 be 55° and the temperature of the overflow being 110°, 
 there will be 110° — 55° =55° of heat absorbed by each 
 pound of water passing into, and through the condenser, 
 and the number of pounds of water required to condense 
 
Condensers 359 
 
 one pound weight of steam under the above conditions 
 will equal the number of times 55 is contained in 1025.9. 
 Expressed in plain figures the calculation is 
 
 1135.9—110 
 
 =18.65 pounds. 
 
 110—55 
 
 In order to ascertain the quantity of condensing water 
 required per house-power per hour, it is only necessary to 
 know the number of pounds weight of steam consumed by 
 the engine per horse-power per hour, as shown by the indi- 
 cator diagram, and multiply this by the weight of condens- 
 ing water required per pound of steam, as found by the 
 above solution. 
 
 Thus, suppose the steam consumption of the engine to 
 be 17 pounds per I. H. P. per hour. Then 17X18.65= 
 317.05 pounds per hour, which reduced to gallons=38.2 
 gallons. 
 
 Or, if the steam consumption is not known, and the 
 w r eight only of condensing water required per hour is de- 
 sired, regardless of the horse-power developed by the en- 
 gine, it will be necessary, first, to estimate the total volume 
 of steam exhausted per hour and calculate its weight from 
 its known pressure. 
 
 Thus, assume the engine to be 24X48 inches, and the 
 E. P. M. to be 80. Then the piston displacement will equal 
 area, of piston less one-half area of rod multiplied by length 
 of stroke. Eef erring to Table 27, the area of a circle 24 
 inches in diameter=452.39 square inches. Suppose the 
 piston rod to be 4.5 inches in diameter, its area, according 
 to Table 27, is 15.904 square inches, one-half of which= 
 7.952 square inches. The effective area of the piston now 
 becomes 452.39 — 7.952=444.43 square inches, and the pis- 
 ton displacement equals 444.43X48=21332.64 cubic inches. 
 
360 Steam Engineering 
 
 Dividing this by 1728 (number of cubic inches in a cubic 
 foot) gives 12.34 cubic feet of piston displacement. The 
 total volume of steam exhausted per minute, therefore, 
 will be 12.34X2X80=1974,4 cubic feet. 
 
 The absolute pressure of the exhaust may again be 
 assumed to be 7 pounds per square inch. Eeferring to 
 Table 17, the weight of one cubic foot of steam at 7 
 pounds absolute is .0189 pounds, and the total weight of 
 steam exhausted per minute, therefore, would be 19 74.4 X 
 .0189=37.3 pounds, and if 18.65 pounds water is required 
 to condense one pound of steam, the quantity required per 
 minute would be 37.3X18.65=695.8 pounds, or per hour, 
 41748 pounds, equal to 5029 gallons. This is at the rate 
 of 8.7 pounds, or a little more than one gallon per revolu- 
 tion for a 24X48 inch, simple condensing engine. Table 
 28 gives the quantity of injection water required per revolu- 
 tion for different types of condensing engines. 
 
Condensers 
 
 361 
 
 Table 27 
 
 AREAS AND CIRCUMFERENCES OF CIRCLES. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 .25 
 
 .049 
 
 .7854 
 
 19 
 
 283.529 
 
 59.690 
 
 .5 
 
 .1963 
 
 1.5708 
 
 19.25 
 
 291.039 
 
 60.475 
 
 1.0 
 
 .7854 
 
 3.1416 
 
 19.5 
 
 298.648 
 
 61.261 
 
 1.25 
 
 1.2271 
 
 3.9270 
 
 20 
 
 314.160 
 
 62.832 
 
 1.5 
 
 1.7671 
 
 4.7124 
 
 20.25 
 
 322.063 
 
 63.617 
 
 2 
 
 3.1416 
 
 6.2832 
 
 20.5 
 
 330.064 
 
 64.402 
 
 2.25 
 
 3.9760 
 
 7.0686 
 
 21 
 
 346.361 
 
 65.973 
 
 2.5 
 
 4.9087 
 
 7.8540 
 
 21.25 
 
 354.657 
 
 06.759 
 
 3 
 
 7.0686 
 
 9.4248 
 
 21.5 
 
 363.051 
 
 67.544 
 
 3.25 
 
 8.2957 
 
 10.210 
 
 22 
 
 380.133 
 
 69.115 
 
 3.5 
 
 9.6211 
 
 10.995 
 
 22.25 
 
 388.822 
 
 69.900 
 
 4 
 
 12.566 
 
 12.566 
 
 22.5 
 
 397.608 
 
 70.686 
 
 4.25 
 
 14.186 
 
 13.351 
 
 23 
 
 415.476 
 
 72.256 
 
 4.5 
 
 15.904 
 
 14.137 
 
 23.25 
 
 424.557 
 
 73.042 
 
 5 
 
 19.635 
 
 15.708 
 
 23.5 
 
 433.731 
 
 73.827 
 
 5.25 
 
 21.647 
 
 16.493 
 
 24 
 
 452.390 
 
 75.398 
 
 5.5 
 
 23.758 
 
 17.278 
 
 24.25 
 
 461.864 
 
 76.183 
 
 6 
 
 28.274 
 
 18.849 
 
 24.5 
 
 471.436 
 
 76.969 
 
 6.25 
 
 30.679 
 
 19.635 
 
 25 
 
 490.875 
 
 78.540 
 
 6.5 
 
 33.183 
 
 20.420 
 
 25.25 
 
 500.741 
 
 79.325 
 
 7 
 
 38.484 
 
 21.991 
 
 25.5 
 
 510.706 
 
 80.110 
 
 7.25 
 
 41.282 
 
 22.776 
 
 26 
 
 530.930 
 
 81.681 
 
 7.5 
 
 44.178 
 
 23.562 
 
 26.25 
 
 541.189 
 
 82.467 
 
 8 
 
 50.265 | 
 
 25.132 
 
 26.5 
 
 551.547 
 
 83.252 
 
 8.25 
 
 53.456 
 
 25.918 
 
 27 
 
 572.556 
 
 84.823 
 
 8.5 
 
 56.745 
 
 26.703 
 
 27.25 
 
 583.208 
 
 85.608 
 
 9 
 
 63.617 
 
 28.274 
 
 27.5 
 
 593.958 
 
 86.394 
 
 9.25 
 
 67.200 
 
 29.059 
 
 28 
 
 615.753 
 
 87.964 
 
 9.5 
 
 70.882 
 
 29.845 
 
 28.25 
 
 626.798 
 
 88.750 
 
 10 
 
 78.540 
 
 31.416 
 
 28.5 
 
 637.941 
 
 89.535 
 
 10.25 
 
 82.516 
 
 32.201 
 
 29 
 
 660.521 
 
 91.106 
 
 10.5 
 
 86.590 
 
 32.986 
 
 29.25 
 
 671.958 
 
 91.891 
 
 11 
 
 95.033 
 
 34.557 
 
 29.5 
 
 683.494 
 
 92.677 
 
 11.25 
 
 99.402 
 
 35.343 
 
 30 
 
 706.860 
 
 94.248 
 
 11.5 
 
 103.869 
 
 36.128 
 
 30.25 
 
 718.690 
 
 95.033 
 
 12 
 
 113.097 
 
 37.699 
 
 30.5 
 
 730.618 
 
 95.818 
 
 12.25 
 
 117.859 
 
 38.484 
 
 31 
 
 754.769 
 
 97.3S9 
 
 12.5 
 
 122.718 
 
 39.270 
 
 31.25 
 
 766.992 
 
 98.175 
 
 13 
 
 132.732 
 
 40.840 
 
 31.5 
 
 799.313 
 
 98.968 
 
 13.25 
 
 137.886 
 
 41.626 
 
 32 
 
 804.249 
 
 100.53 
 
 13.5 
 
 143.130 
 
 42.411 
 
 32.25 | 
 
 816.86 
 
 101.31 
 
 14 
 
 153.938 
 
 43.982 
 
 33 
 
 855.30 
 
 103.67 
 
 14.25 
 
 159.485 
 
 44.767 
 
 33.25 
 
 868.30 
 
 104.45 
 
 14.5 
 
 165.130 
 
 45.553 
 
 33.5 
 
 881.41 
 
 105.24 
 
 15 
 
 176.715 
 
 47.124 
 
 34 
 
 907.92 
 
 106.81 
 
 15.25 
 
 182.654 
 
 47.909 
 
 34.25 
 
 921.32 
 
 107.60 
 
 15.5 
 
 188.692 
 
 48.694 
 
 34.5 
 
 934. 82 
 
 108.38 
 
 16 
 
 201.062 
 
 50.265 
 
 35 
 
 962.11 
 
 109.95 
 
 16.25 
 
 207.394 
 
 51.051 
 
 35.25 
 
 975.90 
 
 110.74 
 
 16.5 
 
 213.825 
 
 51.836 
 
 35.5 
 
 989.80 
 
 111.52 
 
 17 
 
 226.980 
 
 53.407 
 
 36 
 
 1017.8 
 
 113.09 
 
 17.25 
 
 233.705 
 
 54.192 
 
 36.25 
 
 1032.06 
 
 113.88 
 
 17.5 
 
 240.520 
 
 54.978 
 
 30.5 
 
 1046.35 
 
 114.66 
 
 18 
 
 254.469 
 
 56.548 
 
 37 
 
 1075.21 
 
 116.23 
 
 18.25 
 
 261.587 
 
 57.334 
 
 37.25 
 
 1089.79 
 
 117.01 
 
 18.5 
 
 268.803 
 
 58.119 
 
 37.5 
 
 1104.46 
 
 117.81 
 
 . 
 
362 
 
 Steam Engineering 
 Table 27 — continued 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 38 
 
 1134.11 
 
 119.38 
 
 57 
 
 2551.76 
 
 179.07 
 
 38.25 
 
 1149.08 
 
 120.16 
 
 57.25 
 
 2574.19 
 
 179.85 
 
 38.5 
 
 1164.15 
 
 120.95 
 
 57.5 
 
 2596.72 
 
 180.64 
 
 39 
 
 1194.59 
 
 122.52 
 
 58 
 
 2642.08 
 
 182.21 
 
 39.25 
 
 1209.95 
 
 123.30 
 
 58.25 
 
 2664.91 
 
 182.99 
 
 39.5 
 
 1225.42 
 
 124.09 
 
 58.5 
 
 2687.83 
 
 183.78 
 
 40 
 
 1256.64 
 
 125.66 
 
 59 
 
 2733.97 
 
 185.35 
 
 40.25 
 
 1272.39 
 
 126.44 
 
 59.25 
 
 2757.19 
 
 186.14 
 
 40.5 
 
 1288.25 
 
 127.23 
 
 59.5 
 
 2780.51 
 
 186.92 
 
 41 
 
 1320.25 
 
 128.80 
 
 60 
 
 2827.44 
 
 188.49 
 
 41.25 
 
 1336.40 
 
 129.59 
 
 60.25 
 
 2851.05 
 
 189.28 
 
 41.5 
 
 1352.65 
 
 130.37 
 
 60.5 
 
 2874.76 
 
 190.06 
 
 42 
 
 1385.44 
 
 131.94 
 
 61 
 
 2922.47 
 
 191.64 
 
 42.25 
 
 1401.98 
 
 132.73 
 
 61.25 
 
 2946.47 
 
 192.42 
 
 42.5 
 
 1418.62 
 
 133.51 
 
 61.5 
 
 2970.57 
 
 193.21 
 
 43 
 
 1452.20 
 
 135.08 
 
 62 
 
 3019.07 
 
 194.78 
 
 43.25 
 
 1469.13 
 
 135.87 
 
 62.25 
 
 3043.47 
 
 195.56 
 
 43.5 
 
 1486.17 
 
 136.65 
 
 62.5 
 
 3067.96 
 
 196.35 
 
 44 
 
 1520.53 
 
 138.23 
 
 63 
 
 3117.25 
 
 197.92 
 
 44.25 
 
 1537.86 
 
 139.01 
 
 63.25 
 
 3142.04 
 
 198.71 
 
 44.5 
 
 1555.28 
 
 139.80 
 
 63.5 
 
 3166.92 
 
 199.50 
 
 45 
 
 1590.43 
 
 141.37 
 
 64 
 
 3216.99 
 
 201.06 
 
 45.25 
 
 1608.15 
 
 142.15 
 
 64.25 
 
 3242.17 
 
 201.85 
 
 45.5 
 
 1625.97 
 
 142.94 
 
 64.5 
 
 3267.46 
 
 202.68 
 
 46 
 
 1661.90 
 
 144.51 
 
 65 
 
 3318.31 
 
 204.20 
 
 46.25 
 
 1680.01 
 
 145.29 
 
 65.25 
 
 3343.88 
 
 204.99 
 
 46.5 
 
 1698.23 
 
 146.08 
 
 65.5 
 
 3369.56 
 
 205.77 
 
 47 
 
 1734.94 
 
 147.65 
 
 66 
 
 3421.20 
 
 207.34 
 
 47.25 
 
 1753.45 
 
 148.44 
 
 66.25 
 
 3447.16 
 
 208.13 
 
 47.5 
 
 1772.05 
 
 149.22 
 
 66.5 
 
 3473.23 
 
 208.91 
 
 48 
 
 1809.56 
 
 150.79 
 
 67 
 
 3525.66 
 
 210.49 
 
 48.25 
 
 1828.46 
 
 151.58 
 
 67.25 
 
 3552.01 
 
 211.27 
 
 48.5 
 
 1847.45 
 
 152.36 
 
 67.5 
 
 3578.47 
 
 212.06 
 
 49 
 
 1885.74 
 
 153.93 
 
 68 
 
 3631.68 
 
 213.63 
 
 49.25 
 
 1905.03 
 
 154.72 
 
 68.25 
 
 3658.44 
 
 214.41 
 
 49.5 
 
 1924.42 
 
 155.50 
 
 68.5 
 
 3685.29 
 
 215.20 
 
 50 
 
 1963.50 
 
 157.08 
 
 69 
 
 3739.28 
 
 216.77 
 
 50.25 
 
 1983.18 
 
 157.86 
 
 69.25 
 
 3766.43 
 
 217.55 
 
 50.5 
 
 2002.96 
 
 158.65 
 
 69.5 
 
 3793.67 
 
 218.34 
 
 51 
 
 2042.82 
 
 160.22 
 
 70 
 
 3848.46 
 
 219.91 
 
 51.25 
 
 2062.90 
 
 161.00 
 
 70.25 
 
 3875.99 
 
 220.70 
 
 51.5 
 
 2083.07 
 
 161.79 
 
 70.5 
 
 3903.63 
 
 221.48 
 
 52 
 
 21-3.72 
 
 163.36 
 
 71 
 
 3959.20 
 
 223.05 
 
 52.25 
 
 2144.19 
 
 164.14 
 
 71.25 
 
 3987.13 
 
 223.84 
 
 52.5 
 
 2164.75 
 
 164.19 
 
 71.5 
 
 4015.16 
 
 224.62 
 
 53 
 
 2206.18 
 
 166.50 
 
 72 
 
 4071.51 
 
 226.19 
 
 53.25 
 
 2227.05 
 
 167.29 
 
 72.25 
 
 4099.83 
 
 226.98 
 
 53.5 
 
 2248.01 
 
 168.07 
 
 72.5 
 
 4128.25 
 
 227.75 
 
 54 
 
 2290.22 
 
 169.64 
 
 73 
 
 4185.39 
 
 229.34 
 
 54.25 
 
 2311.48 
 
 170.43 
 
 73.25 
 
 4214.11 
 
 230.12 
 
 54.5 
 
 2332.83 
 
 171.21 
 
 73.5 
 
 4242.92 
 
 230.91 
 
 55 
 
 | 2375.83 
 
 172.78 
 
 74 
 
 4300.85 
 
 232.48 
 
 55.25 
 
 2397.48 
 
 173.57 
 
 74.25 
 
 4329.95 
 
 233.26 
 
 55.5 
 
 I 2419.22 
 
 174.35 
 
 74.5 
 
 4359.16 
 
 234.05 
 
 56 
 
 I 2463.01 
 
 175.92 
 
 75 
 
 4417.87 
 
 235.62 
 
 56.25 
 
 I 2485.05 
 
 I 176.71 
 
 75.25 
 
 4447.37 
 
 236.40 
 
 56 5 
 
 I 2507.19 
 
 | 177 5 
 
 75.5 
 
 [ 4476.97 
 
 237.19 
 
Condensers 
 
 363 
 
 Table 27 — continued 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 76 
 
 4536.37 
 
 238.76 
 
 87.5 
 
 6013.21 
 
 274.89 
 
 76.25 
 
 4566.36 
 
 239.55 
 
 88 
 
 6082.13 
 
 276.46 
 
 76.5 
 
 4596.35 
 
 240.33 
 
 88.5 
 
 6151.44 
 
 278.03 
 
 77 
 
 4656.63 
 
 241.90 
 
 89 
 
 6221.15 
 
 279.60 
 
 77.25 
 
 4686.92 
 
 242.69 
 
 89.5 
 
 6291.25 
 
 281.17 
 
 77.5 
 
 4717.30 
 
 243.47 
 
 90 
 
 6371.64 
 
 282.74 
 
 78 
 
 4778.37 
 
 245.04 
 
 90.5 
 
 6432.62 
 
 284.31 
 
 78.25 
 
 4809.05 
 
 245.83 
 
 91 
 
 6503.89 
 
 285.88 
 
 78.5 
 
 4839.83 
 
 246.61 
 
 91.5 
 
 6573.56 
 
 287.46 
 
 79 
 
 4901.68 
 
 248.19 
 
 92 
 
 6647.62 
 
 289.03 
 
 79.25 
 
 4932.75 
 
 248.97 
 
 92.5 
 
 6720.07 
 
 290.60 
 
 79.5 
 
 4963.92 
 
 249.76 
 
 93 
 
 6792.92 
 
 292.17 
 
 80 
 
 5026.56 
 
 251.33 
 
 93.5 
 
 6866.16 
 
 293.74 
 
 80.5 
 
 5089.58 
 
 252.90 
 
 94 
 
 6939.79 
 
 295.31 
 
 81 
 
 5153.00 
 
 254.47 
 
 94.5 
 
 7013.81 
 
 296.88 
 
 81.5 
 
 5216.82 
 
 256.04 
 
 95 
 
 7088.23 
 
 298.45 
 
 82 
 
 5281.02 
 
 257.61 
 
 95.5 
 
 7163.04 
 
 300.02 
 
 82.5 
 
 5345.62 
 
 259.18 
 
 96 
 
 7238.25 
 
 301.59 
 
 83 
 
 5410.62 
 
 260.75 
 
 96.5 
 
 7313.80 
 
 303.16 
 
 83.5 
 
 5476.00 
 
 262.32 
 
 97 
 
 7389.81 
 
 304.73 
 
 84 
 
 5541.78 
 
 263.89 
 
 97.5 
 
 7466.22 
 
 306.30 
 
 84.5 
 
 5607.95 
 
 265.46 
 
 98 
 
 7542.89 
 
 307.88 
 
 85 
 
 5674.51 
 
 267.04 
 
 98.5 
 
 7620.09 
 
 309.44 
 
 85.5 
 
 5741.47 
 
 268.60 
 
 99 
 
 7697.70 
 
 311.02 
 
 86 
 
 5808.81 
 
 270.17 
 
 99.5 
 
 7775.63 
 
 312.58 
 
 86.5 | 
 
 5876.55 
 
 271.75 
 
 100 | 
 
 7854.00 
 
 314.16 
 
 87 
 
 5944.66 
 
 273.32 
 
 
 
 
 Table 28 
 quantity of injection water for jet condensers. 
 
 Injection Temp. 50°. Overflow Temp. 110°. 
 
 
 
 WATER PER REV. 
 
 Low Press. 
 
 Single Exp. 
 
 Double Exp. 
 
 Triple Exp. 
 
 Cylinder. 
 
 Engines. 
 
 Engines. 
 
 Engines. 
 
 
 Lbs. 
 
 Galls. 
 
 Lbs. 
 
 Galls. 
 
 Lbs. 
 
 Galls. 
 
 20 in. x 36 in. 
 
 4.2 
 
 .5 
 
 3.9 
 
 .47 
 
 3.6 
 
 .43 
 
 22 ' 
 
 x 36 " 
 
 5.1 
 
 .61 
 
 4.8 
 
 .57 
 
 4.4 
 
 .53 
 
 24 * 
 
 ' x 42 " 
 
 7. 
 
 .84 
 
 6.6 
 
 .79 
 
 6. 
 
 .72 
 
 26 ' 
 
 x 42 " 
 
 8.3 
 
 1. 
 
 7.8 
 
 .93 
 
 7.2 
 
 .87 
 
 28 * 
 
 x 48 " 
 
 11. 
 
 1.45 
 
 10.4 
 
 1.24 
 
 9.5 
 
 1.14 
 
 30 * 
 
 x 48 " 
 
 12.6 
 
 1.52 
 
 11.7 
 
 1.41 
 
 10.8 
 
 1.3 
 
 32 ' 
 
 x 54 " 
 
 16.2 
 
 1.95 
 
 15. 
 
 1.81 
 
 13.9 
 
 1.68 
 
 34 ' 
 
 x 54 " 
 
 18.3 
 
 2.2 
 
 17.0 
 
 2.05 
 
 15.8 
 
 1.9 
 
 36 ' 
 
 x 60 " 
 
 22.8 
 
 2.75 
 
 21.2 
 
 2.55 
 
 19.6 
 
 2.36 
 
 38 « 
 
 x 60 " 
 
 25.5 
 
 3.07 
 
 23.7 
 
 2.85 
 
 21.9 
 
 2.64 
 
 40 ■ 
 
 x 66 " 
 
 31. 
 
 3.73 
 
 28.8 
 
 3.45 
 
 26.7 
 
 3.2 
 
 44 ' 
 
 x 66 " 
 
 37.5 
 
 4.51 
 
 34.8 
 
 4.2 
 
 32.2 
 
 3.8 
 
 48 ' 
 
 x 72 " 
 
 48.5 
 
 5.84 
 
 45. 
 
 5.42 
 
 41.7 
 
 5.. 
 
 52 ' 
 
 x 72 " 
 
 57. 
 
 6.89 
 
 53.1 
 
 6.4 
 
 49.2 
 
 5.9 
 
 56 ' 
 
 x 72 " 
 
 66. 
 
 7.9 
 
 61.5 
 
 7.41 
 
 57. 
 
 6.8 
 
 60 ' 
 
 x 72 " 
 
 75.6 
 
 9. 
 
 70.5 
 
 8.5 
 
 65.3 
 
 7.8 
 
 64 " x 72 " 
 
 85. 
 
 10. 
 
 80. 
 
 9.6 | 74. 
 
 8.9 
 
364 
 
 Steam Engineering 
 
 Table 29 
 size of air-pumps— single acting. 
 
 One Stroke of Pump per Rev. of Engine. 
 
 
 SIZE OF PUMP. 
 
 Low-Press. 
 Cylinder. 
 
 Single Exp. 
 Engines. 
 
 Double Exp. 
 Engines. 
 
 Triple Exp. 
 Engines. 
 
 Dia. Stroke 
 
 Dia. Stroke 
 
 Dia. Stroke 
 
 Dia. Stroke 
 
 20 in. x 36 in. 
 22 in. x 36 in. 
 24 in. x 42 in. 
 26 in. x 42 in. 
 28 in. x 48 in. 
 30 in. x 48 in. 
 32 in. x 54 in. 
 34 in. x 54 in. 
 36 in. x 60 in. 
 38 in. x 60 in. 
 40 in. x 66 in. 
 44 in. x 66 in. 
 48 in. x 72 in. 
 52 in. x 72 in. 
 56 in. x 72 in. 
 60 in. x 72 in. 
 64 in. x 72 in. 
 
 15 Yz in. x 8 in. 
 154 in. x 10 in. 
 YIYat in. x 10 in. 
 19^4 in. x 10 in. 
 21Y2 in. xlOin. 
 2134 in. xl2in. 
 2434 in. x 12 in. 
 264 in. x 12 in. 
 294 in. xl2in. 
 31 in. x 12 in. 
 3434 in. x 12 in. 
 33^4 in. x 15 in. 
 38 in. x 15 in. 
 41^ in. x 15 in. 
 44}/2 in. x 15 in. 
 4734 in. x 15 in. 
 51 in. x 15 in. 
 
 15 in. x 8 in. 
 16^ in. x 8 in. 
 1754 in. x 10 in. 
 1834 in. x 10 in. 
 21^ in. xlOin. 
 2234 in. x 10 in. 
 24 in. x 12 in. 
 25^ in. x 12 in. 
 284 in. x 12 in. 
 30 in. x 12 in. 
 33 in. x 12 in. 
 32^ in. x 15 in. 
 37 in. x 15 in. 
 40 in. x 15 in. 
 43 in. x 15 in. 
 464 in. x 15 in. 
 49^ in. x 15 in. 
 
 14^ in. x Sin. 
 16 4 in. x 8 in. 
 164 in. xlOin. 
 18 in. x 10 in. 
 2034 in. x 10 in. 
 
 22 in. x 10 in. 
 
 23 in. x 12 in. 
 244 in. x 12 in. 
 274 in- x 12 in. 
 2834 in. x 12 in. 
 3134 in. x 12 in. 
 3434 in. x 12 in. 
 35^4 in. x 15 in. 
 384 in. x 15 in. 
 42 in. x 15 in. 
 444 in. x 15 in. 
 47 in. x 15 in. 
 
 Multiple Cylinder Engines. As has been already ex- 
 plained, a compound engine is one in which the steam is 
 made to do work in two or more cylinders, and the secret 
 of success in this type of engine is due to three factors, 
 viz., (1) a high initial pressure, (2) the expansion of the 
 steam to the greatest extent, and (3) reducing as much 
 as possible the losses caused by cylinder condensation. Prof. 
 Thurston has wisely said that "Maximum expansion, as 
 nearly adiabatic as practicable, is the secret of maximum 
 efficiency." 
 
 Horizontal — Vertical. Of the several types of multiple 
 expansion engines, the two cylinder or double expansion 
 engine appears to be best adapted to central power station 
 service, owing to the excessive load variation. Figure 110 
 shows the horizontal vertical type. It has many advantages, 
 especially in large units. First, the low pressure cylinder 
 
Compound Engines 365 
 
 can be arranged vertically and thereby avoid the excessive 
 friction due to the weight of so large a piston; second, the 
 cylinders being arranged one vertical and the other hori- 
 zontal and both acting upon the same crank pin, gives 
 four impulses for each revolution of the crank. The cut 
 represents a pair of such engines with two cranks, the 
 cranks being keyed to one shaft and at right angles to each 
 other make eight impulses for each revolution, a still 
 greater improvement in turning effect. This type of en- 
 gine is particularly valuable in electric service, with the 
 armature between the engines, and makes a very compact 
 and desirable arrangement. 
 
 Cross Compound. A cross compound engine consists of 
 two cylinders, one high pressure, and the other low pressure. 
 Each cylinder has its own connecting rod and crank, the 
 cranks being set at opposite ends of the main engine shaft, 
 and at an angle of 90° to each other. The two cylinders 
 are connected by piping, and there is generally a receiver 
 between them, into which the high pressure cylinder ex- 
 hausts, and is held in reserve until the opening of the low 
 pressure admission valve. Figure 111 shows a cross com- 
 pound engine, the receiver being underneath the floor. The 
 power unit shown in figure 110 may be considered as con- 
 sisting of two cross compound engines. 
 
 Tandem Compound. In the tandem compound, the two 
 cylinders are arranged tandem to each other, as shown in 
 Figure 112. The advantage claimed for this type of com- 
 pound engine is that it gives a much shorter and more 
 direct route for the exhaust steam, in its passage from the 
 high to the low pressure cylinders. 
 
 Two Low Pressure Cylinders. Where large units are 
 required, it frequently happens that the low pressure cylin- 
 der figures beyond the capacity of the station for handling 
 
366 
 
 Steam Engineering 
 
 the work. To meet this limitation, two low pressure cylin- 
 ders, each of one-half the total area, may be employed ; both 
 cylinders being connected with one receiver, three cranks 
 are employed, one in the center and one on each end of 
 same shaft and keyed at 120 degrees to each other. 
 
 Table 30 
 numbers, their square roots and cube roots. 
 
 c3 ° 
 
 d 
 
 o ^j 
 
 a 
 
 6 
 
 <v ^ 
 
 * 2 
 
 6 
 
 a <j 
 
 c3 ° 
 
 6 
 
 % o 
 
 3 ° 
 
 Xfl 
 
 £ 
 
 ^ 
 3 O 
 
 0;v; 
 
 « 
 
 £ 
 
 *5 ° 
 3 o 
 
 3 O 
 
 fe 
 
 -5 ° 
 
 3 ° 
 
 5 
 
 ■9 ° 
 
 c3* 
 
 3.16 
 
 I 10. 
 
 2.15 
 
 4.24 
 
 18. 
 
 2.62 
 
 5.10 
 
 26. 
 
 2.96 
 
 5.83 
 
 34. 
 
 3.24 
 
 3.19 
 
 10.2 
 
 2.16 
 
 4.26 
 
 18.2 
 
 2.63 
 
 5.12 
 
 26.2 
 
 2.96 
 
 5.84 
 
 34.2 
 
 3.24 
 
 3.22 
 
 10.4 
 
 2.18 
 
 4.28 
 
 18.4 
 
 2.64 
 
 5.14 
 
 26.4 
 
 2.97 
 
 5.86 
 
 34.4 
 
 3.25 
 
 3.25 
 
 10.6 
 
 2.19 
 
 4.30 
 
 18.6 
 
 2.64 
 
 5.16 
 
 26.6 
 
 2.98 
 
 5.87 
 
 34.6 
 
 3.26 
 
 3.28 
 
 10.8 
 
 2.20 
 
 4.33 
 
 18.8 
 
 2.65 
 
 5.18 
 
 26.8 
 
 2.99 
 
 5.89 
 
 34.8 
 
 3.26 
 
 3.31 
 
 11. 
 
 2 22 
 
 4.35 
 
 19. 
 
 2.66 
 
 5.19 
 
 27. 
 
 3.00 
 
 5.91 
 
 35. 
 
 3.27 
 
 3.34 
 
 11.2 
 
 2'.24 
 
 4.38 
 
 19.2 
 
 2.67 
 
 5.21 
 
 27.2 
 
 3.01 
 
 5.92 
 
 35.2 
 
 3.27 
 
 3.37 
 
 11.4 
 
 2.25 
 
 4.40 
 
 19.4 
 
 2.68 
 
 5.23 
 
 27.4 
 
 3.01 
 
 5.94 
 
 35.4 
 
 3.28 
 
 3.40 
 
 11.6 
 
 2.27 
 
 4.43 
 
 19.6 
 
 2.69 
 
 5.25 
 
 27.6 
 
 3.02 
 
 5.96 
 
 35.6 
 
 3.28 
 
 3.43 
 
 11.8 
 
 2.28 
 
 4.45 
 
 19.8 
 
 2.70 
 
 5.27 
 
 27.8 
 
 3.03 
 
 5.98 
 
 35.8 
 
 3.29 
 
 3.46 
 
 12. 
 
 2.29 
 
 4.47 
 
 20. 
 
 2.71 
 
 5.29 
 
 28. 
 
 3.03 
 
 6.00 
 
 36. 
 
 3.30 
 
 3.49 
 
 12.2 
 
 2.30 
 
 4.50 
 
 20.2 
 
 2.72 
 
 5.30 
 
 28.2 
 
 3.04 
 
 6.01 
 
 36.2 
 
 3.30 
 
 3.52 
 
 12.4 
 
 2.32 
 
 4.52 
 
 20.4 
 
 2.72 
 
 5.32 
 
 28.4 
 
 3.04 
 
 6.03 
 
 36.4 
 
 3.31 
 
 3.55 
 
 12.6 
 
 2.33 
 
 4.54 
 
 20.6 
 
 2.73 
 
 5.34 
 
 28.6 
 
 3.05 
 
 6.04 
 
 36.6 
 
 3.32 
 
 3.58 
 
 12.8 
 
 2.34 
 
 4.56 
 
 20.8 
 
 2.74 
 
 5.36 
 
 28.8 
 
 3.06 
 
 6.06 
 
 36.8 
 
 3.32 
 
 3.60 
 
 13. 
 
 2.35 
 
 4.58 
 
 21. 
 
 2.75 
 
 5.38 
 
 29. 
 
 3.07 
 
 6.08 
 
 37. 
 
 3.33 
 
 3.63 
 
 13.2 
 
 2.37 
 
 4.60 
 
 21.2 
 
 2.76 
 
 5.39 
 
 29.2 
 
 3.07 
 
 6.09 
 
 37.2 
 
 3.33 
 
 3.66 
 
 13.4 
 
 2.38 
 
 4.63 
 
 21.4 
 
 2.77 
 
 5.41 
 
 29.4 
 
 3.08 
 
 6.11 
 
 37.4 
 
 3.34 
 
 3.69 
 
 13.6 
 
 2.39 
 
 4.65 
 
 21.6 
 
 2.78 
 
 5.43 
 
 29.6 1 
 
 3.08 
 
 6.12 
 
 37.6 
 
 3.34 
 
 3.71 
 
 13.8 
 
 2.40 
 
 4.67 
 
 21.8 
 
 2.79 
 
 5.45 
 
 29.8 
 
 3.09 
 
 6.14 
 
 37.8 
 
 3.35 
 
 3.74 
 
 14. 
 
 2.41 
 
 4.69 
 
 22. 
 
 2.80 
 
 5.47 
 
 30. 
 
 3.10 
 
 6.16 
 
 38. 
 
 3.36 
 
 3.76 
 
 14.2 
 
 2.42 
 
 4.71 
 
 22.2 
 
 2.80 
 
 5.49 
 
 30.2 
 
 3.10 
 
 6.17 
 
 38.2 
 
 3.37 
 
 3.79 
 
 14.4 
 
 2.43 
 
 4.73 
 
 22* 4 
 
 2.81 
 
 5.50 
 
 30.4 
 
 3.11 
 
 6.19 
 
 38.4 
 
 3.37 
 
 3.82 
 
 14.6 
 
 2.44 
 
 4.75 
 
 22.6 
 
 2.82 
 
 5.52 
 
 30.6 
 
 3.12 
 
 6.20 
 
 38.6 
 
 3.38 
 
 3.85 
 
 14.8 
 
 2.45 
 
 4.77 
 
 22.8 
 
 2.83 
 
 5.54 
 
 30.8 
 
 3.13 
 
 6.22 
 
 38.8 
 
 3.38 
 
 3.87 
 
 15. 
 
 2.46 
 
 4.79 
 
 23. 
 
 2.84 
 
 5.56 
 
 31. 
 
 3.14 
 
 6.24 
 
 39. 
 
 3.39 
 
 3.90 
 
 15.2 
 
 2.48 
 
 4.81 
 
 23.2 
 
 2.84 
 
 5.58 
 
 31.2 
 
 3.14 
 
 6.25 
 
 39.2 
 
 3.39 
 
 3.92 
 
 15.4 
 
 2.49 
 
 4.83 
 
 23.4 
 
 2.85 
 
 5.60 
 
 31.4 
 
 3.15 
 
 6.27 
 
 39.4 
 
 3.40 
 
 3.95 
 
 15.6 
 
 2.50 
 
 4.85 
 
 23.6 
 
 2.86 
 
 5.61 
 
 31.6 
 
 3.16 
 
 6.28 
 
 39.6 
 
 3.41 
 
 3.98 
 
 15.8 
 
 2.51 
 
 4.87 
 
 23.8 
 
 2.87 
 
 5.63 
 
 31.8 
 
 3.17 
 
 6.30 
 
 39.8 
 
 3.41 
 
 4.00 
 
 16. 
 
 2.52 
 
 4.89 
 
 24. 
 
 2.88 
 
 5.65 
 
 32. 
 
 3.17 
 
 6.32 | 
 
 40. 
 
 3.42 
 
 4.03 
 
 16.2 
 
 2.53 
 
 4.90 
 
 24.2 
 
 2.88 
 
 5.67 
 
 32.2 
 
 3.18 
 
 6.33 | 
 
 40.2 
 
 3.42 
 
 4.05 
 
 16.4 
 
 2.54 
 
 4.92 | 
 
 24.4 
 
 2.89 
 
 5.68 
 
 32.4 
 
 3.18 
 
 6.35 | 
 
 40.4 
 
 3.43 
 
 4.08 
 
 16.6 
 
 2.55 
 
 4.95 
 
 24.6 
 
 2.90 
 
 5.70 
 
 32.6 
 
 3.19 
 
 6.36 | 
 
 40.6 
 
 3.43 
 
 4.10 
 
 16.8 
 
 2.56 
 
 4.97 
 
 24.8 
 
 2.91 
 
 5.72 
 
 32.8 
 
 3.19 
 
 6.38 | 
 
 40.8 
 
 3.44 
 
 4.12 
 
 17. 
 
 2.57 
 
 5.00 | 
 
 25. 
 
 2.92 
 
 5.74 
 
 33. 
 
 3.20 
 
 6.40 | 
 
 41. 
 
 3.45 
 
 4.14 
 
 17.2 
 
 2.58 
 
 5.02 
 
 25.2 
 
 2.92 
 
 5.76 
 
 33.2 
 
 3.20 
 
 6.41 | 
 
 41.2 
 
 3.45 
 
 4.17 
 
 17.4 
 
 2.59 
 
 5.04 | 
 
 25.4 
 
 2.93 
 
 5.77 
 
 33.4 
 
 3.21 
 
 5.43 | 
 
 41.4 
 
 3.46 
 
 4.19 
 
 17.6 
 
 2.60 
 
 5.06 
 
 25.6 
 
 2.94 
 
 5.79 
 
 33.6 
 
 3.22 
 
 6.45 1 
 
 41.6 
 
 3.46 
 
 4.22 
 
 17.8 
 
 2.61 
 
 5.08 
 
 25.8 
 
 2.95 
 
 5.81 
 
 33.8 
 
 3.23 
 
 6.46 | 
 
 4i.8 : 
 
 3.47 
 
 Triple Expansion Engine. In the triple expansion en- 
 gine the steam is expanded successively in three cylinders, 
 
Compound Engines 
 
 367 
 
 each larger in diameter than its predecessor. There is first 
 the high pressure cylinder, second the intermediate cylin- 
 der, and third the low pressure cylinder, from which the 
 steam exhausts into the condenser. Very high initial pres- 
 sure (200 to 225 pounds per square inch) is necessary with 
 this type of engine, as well as the quadruple expansion en- 
 gine consisting of four cylinders, in order to get good effi- 
 ciency. The two latter types of multiple expansion en- 
 gines, viz., the triple and quadruple expansion are best 
 adapted to pumping station work, rather than to the high 
 speeds, and variable loads of the central power station. 
 Owing to present day limitations on boiler pressure, the 
 most desirable number of expansions in each cylinder of 
 the different types of condensing engines should be 
 about as given in Table 31. 
 
 Table 31 
 number of expansions. 
 
 
 « on 
 
 CO 
 
 c 
 —. o 
 £'S5 
 
 o c 
 
 ^a 
 
 X 
 
 Expansions in Each Cylinder. 
 
 TYPE 
 
 1st. 
 
 2nd. 
 
 3rd. 
 
 4th. 
 
 Single expansions 
 
 65 
 145 
 185 
 265 
 
 7 
 22 
 30 
 
 48 
 
 7. 
 
 4.8 
 3.2 
 2.7 
 
 4.6 
 3.1 
 2.65 
 
 3.0 
 2.6 
 
 
 Double expansions 
 
 
 Triple expansions 
 
 
 Quadruple expansions 
 
 2.55 
 
 The Steam Jacket. Authorities differ as to the advan- 
 tages derived from the steam jacket for the low pressure 
 cylinder of a compound engine. There is no doubt that 
 in the case of an engine furnishing power for shop pur- 
 poses during working hours only, which implies that the 
 service is not continuous, or rather that the engine is in 
 service only ten or twelve hours out of twenty-four, the 
 steam jacket is of great benefit in keeping the cylinder and 
 
368 Steam Engineering 
 
 valve chest warm, and thus preventing the severe strains 
 which would result from the contraction and expansion of 
 the metal. The weight of steam per indicated horse-power 
 per hour that is condensed in the jacket varies from 1.7 
 pounds to 3.8 pounds, the average being about 2.3 pounds; 
 while the economy of the thoroughly steam- jacketed cylin- 
 der over the jacketless one varies from 3 pounds to as high 
 as 7.9 pounds of steam per I. H. P. per hour, or an average 
 of about 4 pounds less steam consumed per H. P. H. by the 
 use of the jacket, after deducting the weight of steam con- 
 sumed in the jacket. Judging from all the authorities 
 whom the writer has been able to consult, and also from 
 his own practical experience along this line, it seems plain 
 that an actual saving of from 5 to 15 per cent in the con- 
 sumption of steam can be effected by the judicious use of 
 the steam jacket. In other words, if an engine with un- 
 jacketed cylinders consumes steam at the rate of 20 pounds 
 per H. P. H. the same engine with its cylinders jacketed 
 would develop the same amount of power with a consump- 
 tion of only 16 pounds or 17 pounds per H. P. H. besides 
 the advantage of having the cylinders always warm and 
 ready for operation. 
 
 QUESTIONS AND ANSWERS. 
 
 295. Into what two general classes are steam engines 
 divided. 
 
 Ans. Simple and compound. 
 
 296. Describe a simple engine. 
 
 Ans. A simple engine may be either condensing or non- 
 condensing, but its leading characteristic is, that the steam 
 is used in but one cylinder. 
 
 297. What is a condensing engine? 
 
Questions and Answers 369 
 
 Ans. One in which the exhaust steam is passed into an 
 air-tight vessel in which a vacuum is maintained, the ex- 
 haust steam being there condensed by coming in contact 
 with cold water, or a series of tubes through which cold 
 water is being circulated. 
 
 298. Describe a compound engine? 
 
 Ans. A compound engine is one in which the steam is 
 made to do work in two or more cylinders before it is al- 
 lowed to exhaust. 
 
 299. How is this accomplished ? 
 
 Ans. By causing the exhaust steam from the first, or 
 high pressure cylinder, to pass into a second cylinder of 
 larger diameter, and, if the engine be triple or quadruple 
 expansion, from thence into a third or fourth cylinder, 
 the diameters of which increase in regular ratio. 
 
 300. What is a non-condensing engine? 
 
 Ans. One from which the steam exhausts directly into 
 the atmosphere, or is used for heating purposes before 
 passing out into the open air. 
 
 301. What disadvantage does a non-condensing engine 
 constantly labor under? 
 
 Ans. The pressure of the atmosphere amounting to 
 14.7 pounds per square inch is constantly in resistance to 
 the motion of the piston. 
 
 302. Mention several other causes that tend to increase 
 the back pressure upon the piston of a non-condensing en- 
 gine. 
 
 Ans. The resistance of bends and turns in the exhaust 
 pipe, also causing the exhaust to pass through feed water 
 heaters or heating coils. 
 
 304. What is back pressure? 
 
 Ans. Pressure that tends to retard the forward stroke 
 of the piston. 
 
370 Steam Engineering 
 
 305. What advantage has a condensing engine over a 
 non-condensing engine? 
 
 Ans. The atmospheric pressure is removed from in front 
 of the piston to a degree corresponding to the height of 
 the vacuum that is maintained in the condenser. 
 
 306. How many classes of condensers are there in gen- 
 eral use? 
 
 Ans. Two; jet condensers and surface condensers. 
 
 307. Describe a jet condenser. 
 
 Ans. One in which the steam is exhausted into an air- 
 tight vessel, and is there condensed by coming in contact 
 with a jet or spray of cold water. 
 
 308. How is this water removed? 
 
 Ans. By means of the air pump, which also maintains 
 a vacuum in the condenser. 
 
 309. Describe a surface condenser. 
 
 Ans. It is an air-tight vessel, either cylindrical or 
 rectangular in shape, fitted with a large number of brass 
 or copper tubes, of small diameter, through which the cold 
 water is forced by the circulating pump. A vacuum is 
 maintained in the body of the condenser by the air pump, 
 and the steam exhausted into this is condensed by coming 
 in contact with the cool surface of the tubes. In some 
 cases the steam passes through the tubes in place of around 
 them, the condensing water being forced into and through 
 the body of the condenser, and. the vacuum being main- 
 tained in the tubes. 
 
 310. Describe an injector condenser. 
 
 Ans. A condenser in which the cold water is forced 
 through an annular enlargement of the exhaust pipe, and 
 passing down into a nozzle which gradually contracts. The 
 
Questions and Ansivers 371 
 
 exhaust steam entering at the same time is condensed, the 
 water rushing through the nozzle with a velocity sufficient 
 to create a vacuum. 
 
 311. About what quantity of water is required per 
 horse-power per hour to condense the exhaust steam from 
 an engine? 
 
 Ans. About 38 to 40 gallons, depending upon the tem- 
 perature of the condensing Water. 
 
 312. What^ three factors are necessary to insure good 
 economy with multiple cylinder engines ? 
 
 Ans. First — A high initial pressure. Second — Expan- 
 sion of the steam to greatest extent possible. Third — Pro- 
 tecting the surfaces of the cylinders from cooling influences. 
 
 313. Describe a cross compound engine. 
 
 Ans. An engine consisting of two cylinders, each hav- 
 ing its own connecting rod and crank, the cranks being 
 set at opopsite ends of the engine shaft, and at an angle 
 of 90° to each other. The high pressure cylinder exhausts 
 into the low pressure cylinder, usually through a receiver. 
 
 314. Describe a tandem compound engine. 
 
 Ans. An engine having the two cylinders arranged tan- 
 dem to each other, with a common piston rod, and connect- 
 ing rod. 
 
 315. What advantage is gained by this design? 
 
 Ans. A much shorter and more direct route for the 
 exhaust steam in its passage from the high to the low pres- 
 sure cylinder. 
 
r 
 
Valves and Valve Setting 
 
 It goes without saying that every man who aspires to be 
 an engineer should endeavor to thoroughly acquaint him- 
 self with the principles governing the -action of valves, as 
 well as the details of valve adjustment. But it must be 
 remembered that this knowledge cannot be acquired in a 
 day or a week, or even months. True, a man may be 
 able to learn some of the alphabet of valve lore in a com- 
 paratively short time, but the more practical experience 
 he has in the work, the more will he realize the supreme 
 need of mastering all the details of the process. 
 
 The common D slide valve, simple as it appears, is 
 capable of furnishing problems over which savants have 
 puzzled themselves. 
 
 The development of the full amount of power of which 
 the engine is capable, its efficiency and economical use of 
 steam, and its regular and quiet action are, in the largest 
 degree, dependent upon the correct adjustment of its valve, 
 or valves. 
 
 There are many different types of valves for controlling 
 the admission and release of steam to and from the cylin- 
 ders of engines, but the basic principles governing the ad- 
 justment of all, whether slide, poppet, rotative, piston, etc., 
 are exemplified in the action of the common D slide valve, 
 viz., the admission of the steam to the cylinder, its cut off 
 and release, and the closure of the exhaust, each and all 
 of which events are to take place at the proper moment 
 during one stroke of the piston. 
 
 373 
 
374 
 
 Steam Engineering 
 
 In order to properly perform these important functions 
 the valve must have lead and lap. The various terms re- 
 lating to valve action are plainly defined in the section on 
 "Definitions," and it is unnecessary to repeat them here. 
 If the outside lap is increased admission will be later and 
 cut off earlier, and if it be desired to keep the lead the 
 same it will be necessary to move the eccentric forward, 
 which will make the other events, cut off, release and com- 
 pression, earlier also. If the inside lap is increased the 
 result will be an earlier closing of the exhaust and in- 
 creased compression. 
 
 These propositions refer mainly to engines of the single 
 valve variety in which one valve controls the admission and 
 distribution of the steam for both ends of the cylinder. 
 In engines of the four-valve type, having a separate steam 
 and exhaust valve for each end of the cylinder, each in- 
 dividual valve may be adjusted independently of the others, 
 as will be explained later on, and in the case of engines 
 having separate eccentrics, one for the steam, and one for 
 the exhaust valves, the adjustment becomes still more per- 
 fect. 
 
 We will first study the action of the D slide valve by 
 referring to Fig. 116, which is a sectional view of a valve, 
 valve seat and ports. The valve is represented at mid travel 
 
Valves and Valve Setting 375 
 
 or in its central position. S P, SP are the steam ports, 
 and E P is the exhaust port. The projections marked X 
 at each foot of the arch inside the valve represent inside 
 lap, and may be added to or taken from the inside edges of 
 the valve, according as more or less compression is desired. 
 The dotted lines,, L, L represent outside lap. 
 
 Motion is imparted to the valve through the medium 
 of the eccentric. If the valve had neither lap nor lead the 
 position of the eccentric on the crank shaft would be just 
 90°, or one-quarter of a circle, ahead of the crank, but as 
 more or less lap as well as lead is required, it becomes 
 
 Fig. 117 
 
 necessary to move the eccentric still farther ahead of the 
 crank, and this farther advance is termed angular advance, 
 lap angle for lap, and lead angle for lead. 
 
 Assuming the piston to be at the end of the stroke to- 
 wards the crank, in other words, the engine to be on the 
 dead center, the first function of the valve is lead or ad- 
 mission, illustrated by Fig. 117. Owing to the valve hav- 
 ing both lap and lead, the position of the highest point of 
 the eccentric will be assumed in this case to be 120° ahead 
 of the crank, the position of the latter being at*0°. 
 
 Exhaust opening has also occurred at the opposite end 
 of the cylinder. The second function is full port opening, 
 Fig. 118, the crank having moved through 60° and the 
 
376 
 
 Steam Engineering 
 
 eccentric is now at 180°, the farthest point of its throw 
 in that direction, the valve being at the end of its travel. 
 At this point it might be well to note a matter about which 
 some persons are liable to become confused, simple as it is, 
 viz., that the travel of a slide valve equals twice the port 
 opening plus twice the outside lap. For instance, suppose 
 
 Fig. IIS 
 
 the width of each steam port to be 1% inches and the out- 
 side lap to be 1 inch. In Fig. 118 the valve is at the ex-' 
 treme end of its travel towards the right and is about to 
 return. It first covers port number one=li4 inches. Next 
 it moves to mid travel lap number one— 214 inches. Its 
 next move is lap number two=3 1 / 4 inches, and lastly it 
 
 -* — «fc 
 
 Fig. 119 
 
 uncovers port number two=4 1 /2 inches, which is its travel. 
 To return to the third function of the valve or cut off, 
 Fig. 119. The crank has now traversed 120°, and the high- 
 est point of the eccentric is at 60° on the return circle, a 
 point equivalent to 240° of the circle described by the 
 crank. 
 
Valves and Valve Setting 
 
 377 
 
 The fourth function is when compression begins at the 
 head end of the cylinder, Fig. 120. The crank is now at 
 150°, the piston being near the end of the stroke and the 
 eccentric has reached 90° of the return circle, or three- 
 quarters of the crank circle, while the crank has still to 
 travel 30° in order to complete the first one-half of its 
 
 Fig. 120 
 
 circle. At this point we can study the effect of inside lap, 
 because if the valve has no inside lap, release on the crank 
 end will begin almost at the same moment that compres- 
 sion takes place at the head end, but by adding inside lap, 
 compression can be caused to take place earlier and release 
 later. 
 
 Fig. 121 
 
 The next event is admission at the head end of the 
 cylinder, Fig. 121. The crank has now arrived at 180°, 
 having completed one-half of a revolution; the piston is 
 at the end of the stroke, and the eccentric is at 120° on 
 the return path. Fig. 122 serves to better illustrate the 
 relative positions of the crank pin and eccentric during the 
 
378 
 
 Steam Engineering 
 
 stroke. The inner circle represents the path described by 
 the high point of the eccentric, and the large circle that of 
 the crank pin. The radius C 2 of the small circle represents 
 the throw of the eccentric, and the distance C L is the lap 
 of the valve plus .the lead. The point of intersection of the 
 vertical line, L 1, with the eccentric circle locates the posi- 
 tion of the highest point of the eccentric, and the line CB, 
 
 /<" — 
 
 7~~"~ 
 
 
 t[\ 
 
 
 / \«n 
 
 ©• \ 
 
 
 \ 1 / 
 
 f%o { 
 
 14 
 
 96- 
 
 Fig. 122 
 
 drawn from the center of the crank shaft through this point, 
 indicates the angular advance which in this case is 30°, 
 represented by the angle ABC. The figures 1, 2, 3, 4, 5 
 indicate the position of the high point of the eccentric at 
 the moment of each function of the valve. The action 
 of the valve can be more graphically illustrated by means 
 of valve diagrams, of which there are several different 
 kinds, notably the Bilgram and Zeuner. The Zeuner dia- 
 gram will be made use of in this instance. 
 
Valves and Valve Setting 
 
 379 
 
 Figure 123 shows the total movement of the valve, re- 
 gardless of lap and lead. First draw line C 1 to represent 
 the center line of the engine. Xext draw line C 4 perpen- 
 dicular to the line of centers, with C as the center of the 
 crank shaft. The radius of the semi-circle D, 1, 2, 3, 4, 5, 
 
 ¥ 
 
 Valv£ TRavet =? 
 Rqc(/\sS' or £ccenfc/t//y =r 
 Fig. 123 
 
 
 6 equals the radius of eccentricity. Line C D represents 
 the position of the crank when the valve is at mid travel 
 or in its central position, D being the location of the crank 
 pin. Bef erring back *to Fig. 116, the valve is there shown 
 in its central position, and supposed to be moving in the 
 direction of the arrow in order to admit steam to the crank 
 
380 Steam Engineering 
 
 end of the cylinder. Again referring to Fig. 123, draw line 
 C A in such a position that the angle ABC will equal the 
 angular advance of the eccentric, which we will assume in 
 this case to be 30°. 
 
 This will bring the high point of the eccentric at B while 
 the crank, as before stated, is at D. Next using line C A 
 as the diameter, draw a circle about it called the valve 
 circle. Now suppose the crank to be turning in the direc- 
 tion of the arrows. At position D the crank line is just 
 about to cut into the valve circle, the valve being central. 
 When the crank gets to position 1 the valve has moved 
 the distance C E. When the crank is at 2 the valve has 
 moved the distance C M, and when the crank arrives at 3 
 the valve has moved to the limit of its travel from its cen- 
 tral position, and it now begins the return movement. The 
 motion of the valve is comparatively slow at this point 
 for the reason that the high point of the eccentric is now 
 passing the center at 7. The distance the valve has moved 
 backward while the crank has moved from 3 to 4 is the 
 distance B F, while F C represents its distance from the 
 central position, and G- C the same when the crank is at 5. 
 When the crank arrives at 6 and its line has left the valve 
 circle, the valve is again central. Figure 123 merely shows 
 the movement of the valve through one-half of its travel 
 without giving any details regarding port openings, cut 
 off, etc. 
 
 In Fig. 124 the influence of outside lap is delineated. 
 According to the dimensions of the valve under considera- 
 tion the outside lap is one inch. The diagram is drawn 
 precisely as in Fig. 123, and in addition strike an arc 
 representing the outside lap, using C as the center with a 
 radius equal to the outside lap. As before, the crank is at 
 
Valves and Valve Setting 
 
 381 
 
 D and the valve central. When the crank has moved to E 
 and its line cuts the intersection of the outside lap and 
 valve circles, the valve has moved the distance C H, just 
 equal to the outside lap, and the port begins to uncover at 
 .this point. Then by the time the crank gets to the center, 
 
 v 
 
 Fig. 124 
 
 1, the port is open the distance L 0, which is the lead, in 
 this case %-inch. This position of the valve is shown in 
 Fig. 117. 
 
 The position of the crank when cut off takes place is 
 ascertained by drawing a line, C G 5, through the inter- 
 
382 
 
 Steam Engineering 
 
 section of the outside lap and valve circles, where the valve 
 is on its return movement (see Fig. 119). Thus far no 
 account has been taken of release and compression, and in 
 order to determine the position of the crank when these 
 events occur it will be necessary to draw the valve circle 
 
 
 1 / / \ 
 
 
 7 
 
 
 \? ft ^\ 
 
 
 2 
 
 B 
 
 10 
 
 V^/f 1 
 
 j V 
 
 \ / / 
 
 \\J // 
 
 1 
 
 • 
 
 
 
 \/«(\,e Tftavet 
 
 - v4'- \ 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 Fig. 125 
 
 for the opposite movement of the valve, for be it remem- 
 bered that the movement of the valve so far considered has 
 been only one-half of its travel ; that is, it has moved from 
 its central position towards the head end of the cylinder, 
 and back again. We have seen how it has thus performed 
 the functions of admission, full port opening and cut off 
 
Valves and Valve Setting 
 
 383 
 
 for the crank end of the cylinder, and now by referring 
 to Pig. 125 it will be seen at what point of the stroke the 
 remaining events, viz., release and compression, occur. 
 
 Draw a second valve circle, Fig. 125, diametrically oppo- 
 site the first. Also draw an arc with a radius equal to the 
 
 v> 7 
 
 \ A 
 
 '/// 
 
 Fig. 126 
 
 inside lap, which in this case is assumed to be one-half inch. 
 When the crank gets to the position 7 its center line cuts 
 the intersection of the inside lap and valve circles, and 
 release begins. When the crank arrives on the center 8, 
 the valve has moved the distance C T from central position ; 
 but C X of this distance has been occupied by the inside 
 
384 
 
 Steam Engineering 
 
 lap, therefore the lead on the exhaust is represented by the 
 distance X T. When the crank on its return stroke arrives 
 at the position marked 10, its line again cuts the inter- 
 section of the inside lap and valve circles and compression 
 takes place, as in Fig. 120. By dropping perpendiculars 
 
 C > 
 
 \ M 
 
 J>' 
 
 K-* 
 
 \ 
 
 Fig. 127 
 
 from the positions of the crank at 1, 5, 7 and 10 an indi- 
 cator diagram may be drawn showing the performance of 
 an engine with this style of valve. 
 
 Figure 126 shows the effect of decreasing the angular 
 advance, that is, setting the eccentric back towards the 
 
Valves and Valve Setting 385 
 
 crank. In this instance the eccentric is set bacK 10°, thus 
 making the angle of abvance 20° instead of 30°, as before. 
 The full lines represent the new angle, while the dotted 
 circles and lines indicate the valve and its movements as 
 drawn at first. A shows the original point of admission 
 and A' the position of the crank when admission takes place 
 with the lesser angle of advance. Similarly, E and R' show 
 the old and new points of release, and C and C the com- 
 pression. The two different points of cut off are also in- 
 dicated. It will be observed that all of these events occur 
 later and the lead also is diminished. 
 
 In locomotives, and also in some types of adjustable cut 
 off engines, the travel of the valve may be varied at will, 
 and the effect of decreasing the valve's travel is illustrated 
 by Fig. 127, the full lines showing the decreased travel and 
 its influence, and the dotted lines showing the original. 
 Admission and release occur later, while cut off and com- 
 pression take place earlier, and the lead is less. The travel 
 of the valve as indicated in Fig. 127 has been decreased 
 one inch, making it Sy 2 inches in place of 4% inches as 
 before. 
 
 Figure 128 shows the result of increasing the outside 
 lap. The lap has been increased in this case from 1 inch, 
 as originally drawn, to l 1 /^ inches, as indicated by the full 
 lines, while the dotted lines show the lap as it was before 
 being changed. The effect of this change is to cause less 
 lead, a later admission and an earlier cut of!, but compres- 
 sion and release are not affected for the reason that these 
 latter events are controlled by the inside lap, which has 
 not been changed. 
 
 In Fig. 125 the valve is shown as cutting off the steam 
 when the crank has completed 120°, or two-thirds of the 
 
386 
 
 Steam Engineering 
 
 half revolution, but the point of cut off on the indicator 
 diagram shows that the piston has traveled 7/9 of the 
 stroke. This discrepancy is due to the obliquity of the 
 connecting rod, as it will be seen by looking at the valve 
 diagram, Fig. 125, that the crank must travel farther to 
 
 Fig. 128 
 
 complete the stroke from this point than the piston does. 
 In order to cause the valve to cut off earlier, say at one- 
 half stroke, it will be necessary to do one of two things, 
 either to increase the outside lap, which would have a 
 tendency to cause admission to occur too late, or the angle 
 of advance may be increased sufficient to cause cut off to 
 
Valves and Valve Setting 
 
 387 
 
 take place at half stroke, but to do this alone would cause 
 admission to occur too early. Therefore the proper thing 
 to do is to increase both the angle of advance and the 
 outside lap. Figure 129 shows how this can be done with- 
 out decreasing the travel of the valve. The angle of ad- 
 
 Fig. 129 
 
 vance, A B C, is now 50°, where before it was 30°, as in 
 Fig. 125. 
 
 The valve is central when the crank is at position 1 ; 
 the high point of the eccentric being at point 4. The out- 
 side lap, which before was 1 in., has had 7/16 in. added 
 
388 Steam Engineering 
 
 to it, making it 1 7/16 in. When the crank gets to D the 
 port is just commencing to open, and with the crank on 
 the center at 2, the lead is *4 in. 
 
 It will readily be seen at this point that by increasing 
 the outside lap still more the lead can be diminished, and 
 the point of cut off made still earlier, but this would result 
 in a still further reduction of the power of the engine, 
 which has already been considerably reduced, as shown by 
 the diminished area of the indicator diagram as compared 
 with the one in Fig. 125. When the crank gets to position 
 3 the valve has reached the limit of its travel, and the port 
 
 Fig. 130 
 
 is open the distance A a, which is as far as the outside lap 
 will permit. With the crank at point 4 cut off occurs. 
 But with the increased angular advance and the inside 
 lap remaining as it was before, viz., i/o in., release would 
 occur too early. Therefore it will be necessary to increase 
 the inside lap sufficient to cause release and compression to 
 take place at as near the proper points as possible. In this 
 instance % in. has been added, making the inside lap % 
 in., and release takes place with the crank at position 5, 
 while compression begins at 6. These points may also be 
 changed by simply adding to, or decreasing the inside lap. 
 It should be noted that in the foregoing discussion of 
 valve gear it is understood that the valve stem moves in 
 
Valves and Valve Setting 389 
 
 the same direction as the eccentric rod, that is, the direc- 
 tion of motion is not reversed by a rocker arm interposed 
 between the eccentric and the valve. 
 
 The first step in the operation of valve setting is to place 
 the engine on the dead center, which means that the piston 
 is at the end of the stroke, and the centers of the main 
 shaft, crank pin and crosshead pin, or wrist pin, as it is 
 sometimes called, are in line (see Fig. 130). When mov- 
 ing the engine to place it on the center it should always 
 be turned in the direction in which it is to run. This is 
 to guard against any errors which might result from lost 
 
 Fig. 131 
 
 motion or looseness m the reciprocating parts. Turn the 
 fly wheel around until the crosshead is almost to the end 
 of the stroke, say within a half inch of it, as at Fig. 131. 
 Then with a steel scriber or penknife mark the location 
 of the crosshead on the guides A, also provide a secure rest- 
 ing place upon the floor of the engine-room for a marker 
 to be placed against the rim of the wheel. This rest should 
 be firmly fastened to the floor in order that its position 
 may not be changed during the operation of valve setting. 
 Place the marker against the wheel, as at B, and mark the 
 point with a center punch or cold chisel. Next turn the 
 engine carefuly until the crosshead completes the stroke 
 and moves back on the return stroke until the mark A is 
 
390 Steam Engineering 
 
 in line again. Make another mark on the rim of the wheel 
 opposite the marker at C. This position of the engine is 
 shown in Fig. 132, and it will be seen that the crank is 
 now as much above the center as it was below in Fig. 131. 
 Now with a. pair of large dividers ascertain the middle or 
 half distance between marks B and C and put another mark 
 D, at this point. Then turn the engine a complete revolu- 
 tion until mark D comes opposite the pointer, Fig. 130, 
 and the engine will be on the true center. 
 
 At this point the question may arise, why not simply 
 reverse the motion and back the wheel up until the mark 
 
 Fig. 132 
 
 D is in line with the marker? The answer is, that while 
 this would undoubtedly save considerable labor, yet it 
 would almost certainly result in an error, on accoui^t of the 
 lost motion of the moving parts, which would permit of 
 considerable movement of the wheel before any movement 
 of the crosshead would take place if the wheel was turned 
 back. The result would be that when mark D came to 
 be opposite to the pointer, the crank woulc} not be on the 
 true center. The. next move is to see that the eccentric 
 rod is adjusted to the proper length. If there is a rocker 
 arm, connect the eccentric rod in its proper place, leaving 
 the valve rod disconnected for the time being. Then ad- 
 just the length of the rod so that when the eccentric is 
 
Valves and Valve Setting 
 
 391 
 
 turned around on the shaft the rocker arm will vibrate 
 equal distances on each side of a plummet line suspended 
 through the center of the pin upon which the arm turns, 
 as in Fig. 133. Before connecting the valve rod the valve 
 
 
 £eee;ti/itc &xt 
 
 31 
 
 / 
 
 KV 
 
 Fig. 133 
 
 should be put in its central position and marked. To do 
 this it will be necessary to first ascertain the outside lap. 
 
 The most accurate method of doing this is to take the 
 valve out and measure the distances between the outside 
 edges of the steam ports, as at B, Fig. 134. Then measure 
 the width of the valve from edge to edge, as at A. Then 
 
392 
 
 Steam Engineering 
 
 A — B-^2=the outside lap. For instance, A=8.5 in., B= 
 6.5 in. Then 8.5—6.5=2, and 2 divided by 2=1 in., 
 which is the lap. The inside lap should also be measured 
 at this point for convenience, and the measurements pre- 
 served for future reference. The inside lap is ascertained 
 by measuring the distance between the inside edges of the 
 ports and the distance across the arch of the valve from one 
 inside edge to the other (see Fig. 134) and dividing the 
 
 Fig. 134 
 
 difference by 2. For instance, the distance F is 4 in., and 
 
 4—3 
 
 E is 3 in.; then =.5 in., making the inside lap ^ in. 
 
 2 
 To place the valve central, measure the width of the 
 outside lap each way from the outside edges of the steam 
 ports and mark the points on the valve seat with a sharp 
 lead pencil. Then place the valve with edges on the marks 
 and it will be central. To insure accuracy, measurements 
 should also be taken from the outside edges of the steam 
 ports to the ends of the seats. Having fixed the valve in 
 
Valves and Valve Setting 393 
 
 its central position, replace the stem and if it is secured in 
 the valve by nuts, as in Fig. 134, care should be taken to 
 leave a little play for the valve between the nuts, otherwise 
 it is liable to become stuck, and held off the seat when it 
 gets hot and expands. Make a center punch mark C, on 
 the edge of the valve chest directly over the valve stem, 
 and placing one leg of a tram or pair of dividers in the 
 mark, with the other leg describe a mark on the top of 
 the valve as at D, thus marking the valve in its central 
 position. 
 
 Now with the rocker arm perpendicular, the eccentric 
 rod having been previously adjusted, connect the valve rod 
 to the rocker, and turn the eccentric to the limit of its 
 throw in one direction, and measure the distance the valve 
 has traveled from its central position. Then turn the ec- 
 centric around to its extreme throw in the other direction, 
 and if the valve travels the same distance from its central 
 position in the opposite direction the lengths of the rods, 
 are correct, but if not correct, the necessary change can 
 usually be made by shifting the nuts on the valve stem, 
 or if the valve is secured to the stem by a yoke the change 
 can be made in the rod. 
 
 Having succeeded in getting the correct travel for the 
 valve, the next step is to set the eccentric. With the 
 engine on the dead center, turn the eccentric around on 
 the shaft in the direction in which the engine is to run, 
 so as to take up all the play in the valve stem and other 
 moving parts, and with the tram, or dividers watch the 
 valve until it has moved away from its central position by 
 the amount of its outside lap, plus the lead it is desired 
 to give the valve. For instance, if the valve has one inch 
 outside lap and the lead is to be % in., the valve should be 
 
394 Steam Engineering 
 
 moved away from its central position 1% in., and also 
 away from the end of the cylinder at which the piston is. 
 The steam port for that end should now be open % in., 
 and the eccentric should be ahead of the crank one-quarter 
 turn plus the angular advance required for the outside 
 lap and lead, or if as previously explained, the motion, of 
 the eccentric is reversed by a rocker arm the eccentric 
 should be behind the crank by the same amount. Tighten 
 the set screws holding the eccentric on to the shaft and 
 turn the engine around until it is on the opposite center. 
 Then if the lead is the same on each center the valve is set 
 correctly. If the lead is not the same, move the valve on 
 the stem toward the end having the most lead, a distance 
 equal to one-half the difference between the two leads. If 
 the lead as equalized is more than is desired move the 
 eccentric back on the shaft until the correct lead opening 
 is secured, then tighten the set screws permanently, and 
 with a sharp cold chisel make a plain mark on the shaft, 
 and opposite to this another mark on the eccentric. This 
 will save considerable trouble in case the eccentric should 
 slip or be accidentally moved from its true position at any 
 time. 
 
 Although the common D slide valve as applied to sta- 
 tionary engines usually has its point of cut off fixed, yet 
 there are many types of variable automatic cut off engines 
 with single slide valves of various patterns, such as box 
 valves in which the steam passes through the valve, piston 
 valves, in which the steam either passes through or around 
 the ends of the valve, so-called gridiron valves, and various 
 other types. Such valves are generally applied to high speed 
 engines, and are actuated by eccentrics which are under the 
 control of shaft governors which vary the position of the 
 
Valves and Valve Setting 
 
 395 
 
 eccentric with relation to the crank according to the load 
 that is on the engine, thus regulating the point of cut off 
 so as to maintain a constant speed, while the throttle is 
 kept wide open. "While the details of setting all the var- 
 ious styles of valves, including the Corliss or four-valve 
 type, differ considerably from those required in setting the 
 D valve, yet the same principles govern the operation, no 
 matter what kind of a valve is to be adjusted. 
 
 fty? .\w\vcv\w wwww A\vva 
 
 Fig. 135 
 
 In all types of reciprocating engines the same factors 
 affecting the distribution of the steam are present, viz., the 
 outside or steam lap affecting admission and cut off, and 
 the inside or exhaust lap affecting release and compression. 
 While the D valve (and other types of single valves) com- 
 bines these four principal factors within itself (that is, 
 two steam laps and two exhaust laps), it should be noted 
 that in the four-valve type of engine the same factors are 
 distributed among four valves, each valve performing its 
 own particular function in controlling the distribution of 
 the steam for the end of the cylinder to which it is at- 
 tached. Also each valve may be adjusted to a certain de- 
 
396 Steam Engineering 
 
 gree independently of the others, and this fact goes far 
 towards explaining why engines of this type, with the dis- 
 engaging valve gear, are so much more economical in the 
 use of steam than are those with the ordinary fixed cut off. 
 Thus, for instance, the steam valves of a Corliss engine 
 may be adjusted to cut off the steam at any point, from 
 the very beginning up to one-half of the stroke, without in 
 the least affecting the release or compression, because these 
 events are controlled by the exhaust valves. 
 
 In some of the modern improved makes of four-valve 
 engines there are two eccentrics, one for the steam and the 
 other for the exhaust valves. This arrangement permits 
 of still greater latitude in adjustments for the economical 
 use of steam. 
 
 As the Corliss engine is a prominent and familiar type 
 of the four valve detaching cut off engine, and embodies 
 the main features of nearly all engines belonging to that 
 class, it will be used to illustrate the method of setting 
 the valves on a four valve engine. 
 
 Fig. 135 is a sectional view of the cylinder, steam and 
 exhaust chests, and the valve chambers of a Corliss engine. 
 1 and 2 are the steam valves, and 3 and 4 the exhaust valves. 
 The valves work in cylindrical chambers accurately bored 
 out, the face of the valve being turned off to fit steam 
 tight. They are what is termed rotative valves, that is, 
 they receive a semi-rotary motion from the wrist plate, 
 which in turn is actuated by the eccentric. 
 
 In Fig. 135 the piston is shown as just ready to begin 
 the stroke towards the left. Admission is taking place at 
 valve 2 and release at valve 3, valves 1 and 4 being closed. 
 The arrows show the direction in which the valves move. 
 Motion is transmitted from the wrist plate to the valves by 
 
Valves and Valve Setting 
 
 397 
 
 means of short connecting rods and cranks attached to the 
 valve stems. These rods are, or at least should be, fitted 
 with right and left hand threads or turn buckles for the 
 purpose of lengthening or shortening the rods while set- 
 ting the valves. 
 
 The valve gear of a Corliss engine with a single eccentric 
 is shown in Fig. 136. The connections of the exhaust 
 valves with the wrist plate are positive, and the travel of 
 these valves is fixed, being a constant quantity, but the con- 
 
 
 Jw~~T 
 
 
 
 ^2 
 
 C 
 
 f (•/ 
 
 *_ 
 
 8 
 
 1 
 
 1 
 
 3 
 
 ( ©\ 
 
 I©) 
 
 
 cr\% 
 
 If 
 
 llVf 
 
 3 S 
 
 1 
 
 Wm 
 
 Fig. 136 
 
 nections of the steam valves with the wrist plate are de- 
 tachable, being under the control of the governor. Various 
 designs of releasing mechanism are in use by different 
 builders, but the same general principles govern the oper- 
 ation of all, viz., that the valve is quickly opened at .the 
 commencement of the stroke when the wrist plate has its 
 fastest motion, and that the governor trips the releasing 
 mechanism at that point in the stroke at which it is de- 
 sired that cut off should take place, and that the valve is 
 then quickly closed by means of a vacuum dash pot or, as 
 
398 
 
 Steam Engineering 
 
 in some types of engines, by a spring. Connection is made 
 between the wrist plate and rocker arm by means of the 
 hook rod, so-called because it hooks over the wrist plate pin, 
 and can easily be disconnected in case it is desired to work 
 the valves by hand, as in warming up the engine prepar- 
 atory to starting up. 
 
 Fig. 137 
 
 Eef erring to Fig. 136, A is the wrist plate, B and C are 
 the dash pot rods, D, D' the dash pots and H E the hook 
 rod. G and G' represent the governor rods, and the figures 
 1, 2, 3 and 4 indicate the valve rods with turn buckles for 
 changing their lengths. 
 
Valves. and Valve Setting 399 
 
 As in setting the slide yalve, the first requisite in setting 
 Corliss, valves is to put the engine on the center, the method 
 of doing which has been fully described. Next adjust the 
 length of the hook rod, if it is adjustable, if not, then the 
 eccentric rod so that the wrist plate will vibrate equal dis- 
 tances each way from its central position which is marked 
 on top of the hub. (See Fig. 137.) It will be noticed 
 that there are four marks, A, B, C and D. Marks A and 
 B are on the hub of the wrist plate and the stationary 
 flange against which it turns, and when they are in line, 
 indicate that the wrist plate is central. Marks C and D 
 are on the stationary flange at equal distances each way 
 from B, and when the engine is running. mark A should 
 travel to the right until it is in line with D and to the left 
 until in line with C, or it may happen that A will travel 
 past C and D or perhaps not quite to them, but which 
 ever it does, it should stop at equal distances from them. 
 This adjustment should be carefully made before setting 
 the valves, because if any change is. made in the lengths 
 of the eccentric rod or hook rod after the valves are once 
 set it will seriously affect the action of all the valves. 
 
 The method of adjusting the rocker arm so that it will 
 vibrate correctly has been already described and it is very 
 desirable that its travel should be equidistant in either di- 
 rection from a vertical position, but if it is found that the 
 hook rod is non-adjustable as to length and that the wrist 
 plate still vibrates too far in one direction, then the adjust- 
 ment must be made on the length of the eccentric rod, 
 which can be screwed into or out of the strap. The vibra- 
 tion of the wrist plate should then be tested by turning 
 the eccentric around on the shaft in the direction the engine 
 is to run. When this is found to be correct the next step 
 
400 
 
 Steam Engineering 
 
 is to remove the back bonnets from the valve chambers. 
 Fig. 138 represents one of the steam valves and Fig. 139 
 one of the exhaust valves, each with back bonnet removed, 
 showing the ends of the valves. 
 
 I 
 
 i 
 
 h 
 
 Fig. 138 
 
 The working edges of the valve, as well as the ports of 
 a Corliss engine, cannot be seen when the valves are in place, 
 owing to the fact that the circular ends of the valves fill 
 the spaces at the ends of the valve chambers, but certain 
 
 % 
 
 i 
 
 Fig. 139 
 
 marks will be found on the ends of the valves, and cor- 
 responding marks on the faces of the chambers which serve 
 as a guide in setting the valves. Eeferring to Fig. 138, 
 mark V on the end of the valve is in line with the edge of 
 
Valves and Valve Setting 401 
 
 the valve, and P indicates the edge of the port. The same 
 letters apply to Fig. 139. Having removed the bonnets 
 and found the marks, temporarily secure the wrist plate 
 in its central position by tightening one of the set screws 
 on the eccentric. Then connect the valve rods, adjusting 
 their lengths so that the steam valve will have from *4 to 
 9/16 in. lap, as in Fig. 138, and the exhaust valves from 
 3*2 to jq in. opening, as in Fig. 139. These figures 
 vary according to the size of the engine, the smaller figures 
 being for small size engines, and the larger figures apply 
 to large sizes. 
 
 In adjusting the steam valves be sure and note the direc- 
 tion in which they turn to open. In most Corliss engines 
 the arm of the crank to which the valve rod is connected 
 extends downwards from the valve stem, as in Fig. 136. 
 This will cause the valve to move towards the wrist plate 
 in opening. After the valve rods have been properly ad- 
 justed as to length, place the engine on either center by 
 the method previously explained, and move the eccentric 
 around on the shaft in the direction in which the engine 
 is to run until it is far enough ahead of the crank to allow 
 the steam valve the proper amount of lead opening, which 
 will vary according to the size of the engine. Table 32 
 gives the lap and lead for various sizes of Corliss engines 
 from 12 to 40 in. bore. Having tightened the eccentric 
 set screws, turn the engine around to the opposite center 
 and note whether the lead is the same on each end. If 
 there is a difference it can generally be equalized by slightly 
 altering the length of one of the valve rods. The valves 
 should also be adjusted by means of the indicator at the 
 first opportunity, as that is the only absolutely correct 
 method. 
 
402 
 
 Steam Engineering 
 Table 32 
 
 Size o 
 
 f Engine 
 
 Lap of Steam 
 
 Lead Opening of 
 
 Lead Opening of 
 
 Valve 
 
 Steam Valve 
 
 Exnaust Valve 
 
 12 
 
 nches 
 
 1 inch 
 
 s 1 ^ inch 
 
 5^ inch 
 
 14 
 
 nches 
 
 t 5 6 inch 
 
 & inch 
 
 sfe inch 
 
 16 
 
 nches 
 
 T 5 6 inch 
 
 ye inch 
 
 sz inch 
 
 18 
 
 nches 
 
 1 inch 
 
 tV inch 
 
 is inch 
 
 20 
 
 nches 
 
 1 inch 
 
 T V inch 
 
 iV inch 
 
 22 
 
 nches 
 
 1 inch 
 
 tV inch 
 
 . T V inch 
 
 24 
 
 nches 
 
 iV inch 
 
 s 3 2 inch 
 
 s 3 2 inch 
 
 26 
 
 nches 
 
 -h inch 
 
 s 3 2 inch 
 
 s 3 2 inch 
 
 28 
 
 nches 
 
 T 7 F inch 
 
 & inch 
 
 5 3 2- inch 
 
 30 
 
 nches 
 
 h inch 
 
 s 3 2 inch 
 
 § inch 
 
 32 
 
 nches 
 
 i inch 
 
 5 3 2 inch 
 
 § inch 
 
 34 
 
 nches 
 
 i inch 
 
 § inch 
 
 § inch 
 
 36 
 
 nches 
 
 i inch 
 
 § inch 
 
 § inch 
 
 38 
 
 nches 
 
 is inch 
 
 § inch 
 
 tV inch 
 
 40 
 
 nches 
 
 T 9 6 inch 
 
 § inch 
 
 T 3 <j inch 
 
 42 
 
 inches 
 
 t 9 6 inch 
 
 1 inch 
 
 Y5 inch 
 
 The next point to receive attention is the adjustment of 
 the lengths of the horizontal rods extending from the 
 governor to the releasing mechanism, so that the steam 
 valves will cut off at equal points in the stroke. This is 
 done by raising the hook rod clear of the wrist plate pin, 
 and with the bar provided for the purpose move the wrist 
 plate to either one of its extreme positions as shown by the 
 marks on the hub (see Fig. 137) and holding it in this 
 position adjust the length of the governor rod for the steam 
 valve (which will then be wide open) so that the boss or 
 roller which trips the releasing mechanism is just in con- 
 tact, or within 1/32 in. of it. Then move the wrist plate 
 to the other extreme of its travel and adjust the length of 
 the other rod in the same manner. To prove the accuracy 
 of the adjustment, raise the governor balls to their medium 
 position, or about where they would be when the engine is 
 running at its normal speed and block them there. Then 
 having again connected the hook rod to the wrist plate, 
 turn the engine around in the direction in which it is to 
 run, and when the valve is released, measure the distance 
 
Valves and Valve Setting 
 
 403 
 
 upon the guide that the crosshead has traveled from the 
 end' of the stroke. Now continue to turn the engine in the 
 same direction until the other valve is released, and 
 measure the distance that the crosshead has traveled from 
 the opposite end of the stroke, and if the cut off is equalized 
 these two distances will be the same. If there is a dif- 
 ference, lengthen one rod and shorten the other until the 
 point of cut off is the same for both ends. 
 
 Fig. 140 
 
 The lengths of the dash pot rods should also be adjusted 
 so that when the plunger is at the bottom of the dash pot 
 the valve lever will engage the hook. 
 
 After all adjustments have been made, tighten the lock 
 nuts on all the rods. 
 
 Fig. 140 shows the wrist plate of a Eeynolds Corliss 
 engine in its central position ready for adjusting valve 
 connections. The parts broken away show the steam and 
 exhaust valves in their respective positions as regards lap. 
 The valves shown are single ported. 
 
404 
 
 Steam Engineering 
 
 Fig. 141 shows the position of the wrist plate of a Rey- 
 nolds Corliss engine, when the crank is on the center and 
 the eccentric set so as to give the steam valves the proper 
 
 amount of lead. * The exhaust valves will be correct if they 
 have been set according to table 32 — the wrist plate being 
 central. 
 
 Fig. 142 shows the wrist plate of a heavy duty or re- 
 liance type Reynolds Corliss engine in its central position, 
 
Valves and Valve Setting 405 
 
 ready for adjusting the lengths of the valve rods. The 
 valves in this type of engines are double ported. 
 
 Fig. 143 shows the position of the wrist plate of a heavy 
 duty or reliance type Eeynolds Corliss engine, when the 
 crank is on the center, and the eccentric set so as to give 
 the steam valves the correct lead. These valves are double 
 ported, and the exhaust valves will be correct if set ac- 
 cording to table 32. 
 
 
 
 Fig. 143 
 
 Reynolds Long Range Cut Off. Fig. 144 shows the 
 valve gear side of an Allis-Chalmers engine equipped with 
 the long range cut off which is designed to give a maximum 
 cut-off for power, and the essential feature of the steam 
 valves is, that they have a negative lap or opening when in 
 mid-position, the cut-off being made entirely by the gov- 
 ernor through the knock-off cam. 
 
 Eeferring to Fig. 145, the steam and exhaust valves on 
 one end of the cylinder are shown -with the valve-gear re- 
 moved and the valves and ports in cross-section, while on 
 the other end the valve-cranks have been left in place, and 
 
Fig. 144 
 
 VALVE-GEAR SIDE OF REYNOLDS LONG-RANGE CUT-OFF ENGINE 
 
Valves and Valve Setting 407 
 
 show their relative position to the valves at the opposite 
 end. The steam and exhaust wrist-plates are shown at A 
 and B, respectively, and above A is shown the travel circle 
 C of the steam eccentric; below is the exhaust circle D. 
 In these circles the crank position is at c and e is the ec- 
 centric | position. The steam valve-crank is indicated by 
 E, the exhaust valve-crank by F; G is the bell-crank and 
 H the knock-off cam. On the other end of the cylinder 
 where the valves and ports are in cross-section, the dotted 
 lines E', F', G' and H' denote the center lines of the same 
 parts on that end, and the arcs at the ends of these lines 
 show the respective positions of the pin centers. From each 
 end of these arcs the center lines show the positions of the 
 pins when they reach their respective extremes of travel. 
 
 In Fig. 145 the wrist-plates and all connected parts are 
 shown in their central positions, at which the exhaust 
 valves are lapped, as is usual in practice, but the steam 
 valves are open on both ends when they are hooked up. If 
 hooked up and not released the steam valves would be open 
 from the beginning of one stroke up to 75 per cent of the 
 return stroke, but when the knock-off cam-pin center is at 
 a, the cut-off will be carried out to about seven-eights or 
 eleven-twelfths of the stroke, and the cut-off will occur 
 just before the steam valve on the opposite end picks up for 
 lead. When the knock-off cams are in the position repre- 
 sented by the lines H and H', Fig. 145, the cut-off will 
 occur at about three-eights of the stroke, and when the 
 knock-off pin center is at b the valves will remain lapped, 
 being dropped before they can open. If the regulator is 
 allowed to drop down so the knock-off cam-pin will reach 
 the point c, the valves will not pick up and will remain 
 lapped. This peculiarity must be thoroughly fixed in 
 mind. 
 
408 
 
 Steam Engineering 
 
 Fig. 145 
 
 In Fig. 146 the valve-cranks are in their extreme posi- 
 tions, and the eccentrics likewise, with everything ready to 
 start in the direction of the arrows. On the crank end the 
 steam valve is lapped, and the exhaust valve is open, while 
 
 .. 
 
Valves and Valve Setting 
 
 409 
 
 Fig. 146 
 
 -reverse conditions exist on the head end. On all other 
 types of valve-gear the eccentrics would be advanced 90 
 degrees when the valves are lapped, but on this engine the 
 steam valve is lapped when the eccentric is on its extreme 
 
410 Steam Engineering 
 
 position. The exhaust valves are the same as on any other 
 double-eccentric Corliss engine. 
 
 Setting the Valves. Bearing these points in mind we 
 may proceed to set the valves. The amounts of lap and 
 lead and the positions of the cranks from the center lines 
 given herewith are for engine cylinders of 36, 42, 48, and 
 60-inch stroke. 
 
 First set the wrist-plates central and clamp them in 
 place ; then adjust#the lengths of the rods so that the steam 
 valves are open JJ inch, as shown in Fig. 145, and the 
 exhaust valves are lapped -^ inch. If the rod lengths 
 are right the center lines of the cranks E and E' will coin- 
 cide, the pins of the cranks F and F' will be one-half inch 
 from the center line, as shown, and the pins on each end. 
 of the bell-cranks G and G' will be 2% inches and -fy 
 inch from the center lines. "When the valves have been 
 set with the wrist-plates central, release the wrist-plates 
 and roll the eccentrics around the shaft to test them, and 
 the reach-rod?, and see that they are of the right length 
 to make the wrist-plate travel equally each side of the 
 center line. 
 
 Then place the crank on center, and pull the steam ec- 
 centric around enough to give aV-inch lead, and make it 
 fast. Next move the engine around in its direction of 
 travel to about 95 degrees of its stroke, and move the ex- 
 haust eccentric around until the exhaust valve on the same 
 end is just opening or releasing. Make the exhaust ec- 
 centric fast, and move the engine around its full revolu- 
 tion and check off the valves on the other end, and the ex- 
 haust closure. Then set the regulator up to its central 
 position and adjust the lengths of the rods from the lever 
 to the knock-off cams, so that the pins of the cams H and 
 
Valves and Valve Setting 
 
 411 
 
 H' will set % inch of the center line, as in Fig. 145. 
 Let the regulator down and hook up the wrist-plates; then 
 pull the engine around to make sure that the steam valves 
 are released on each stroke alternately, at not later than 
 eleven-twelfths of the stroke, and always before the other 
 valve picks up. 
 
 Fig. 147 
 
 The Greene Wheelock Engine. In this engine, each 
 cylinder is equipped with four valves of the Hill gridiron 
 type, two steam and two exhaust to each cylinder, and each 
 valve is driven by a separate eccentric. This type of valve 
 and gear gives a large port opening, with a minimum of 
 travel, which in connection with the Greene cut off on the 
 steam, and the toggle motion on the exhaust valves, gives 
 
412 
 
 Steam Engineering 
 
 the quickest action at the right time to both. A minimum 
 lap is also obtained with the aid of the gear. It is there- 
 fore very important that the movements of the valve and 
 gear be thoroughly understood, and great care be used in 
 adjusting it. The valve plugs contain the valve seats as 
 an integral part of the plug. These are in turn remov- 
 able for repairs, as are also the valves when in position. 
 
 Fig. 148 
 
 To the plug is attached the head that holds the working 
 parts of the valve mechanism. 
 
 The arrangement of the valves beneath the cylinder as 
 in the Wheelock system, allows short ports, small clearance 
 volume, and a free discharge for the water of condensation 
 through the exhaust. The throttle also is beneath, and ad- 
 mits steam to the steam chest under the cylinder. There 
 are four eccentrics, one for each valve. These eccentrics 
 
Valves and Valve Setting 41 3 
 
 are of small size and short throw, and receive their motion 
 from the eccentric shaft extending from the back cylinder 
 head, alongside the engine frame to the main crank shaft, 
 from which it receives rotary motion through bevel gear. 
 
 An understanding of the valve plugs and their location 
 may be had by reference to Figs. 147, 148, 149. Fig. 147 
 shows a longitudinal section of the cylinder, and the cross- 
 section of the valve plug at A. This view gives the loca- 
 tion of the inlet (steam) valve and seat at a and the out- 
 let (exhaust) valve and seat at b, the steam chest B B 
 forming a jacket for part of the cylinder, as well as admit- 
 ting the steam through the inlet a into the cylinder. From 
 the cylinder the steam passes out through the outlet b into 
 the exhaust passage C. 
 
 Fig. 148 is a cross-section of the cylinder through the 
 clearance space and a longitudinal of the valve plug in that 
 end of the cylinder, showing the back of the inlet valve seat, 
 with the outlet valve cut away. 
 
 Fig. 149 is a view of the valve plug with all of the parts 
 assembled. This view shows the inlet or steam valve 
 side of the plug. The inlet valve is at a ; the spring which 
 holds it to its seat when not under steam pressure is at b ; 
 and c is the pusher crank which actuates the valve by means 
 of a cam at d, which comes in contact with the latch of the 
 valve-stem head e. This is fastened to the inlet valve- 
 stem by clamp bolts. The inlet valve-stem screws into the 
 nut f, so that by loosening the clamp bolts of the head e 
 and turning the rod, an adjustment of the valve setting 
 can be made, as will be shown later. 
 
 The inlet valve is opened by the pusher cam pushing 
 it forward, but is released from this cam through the 
 means of a trip cam on the bottom of the valve-plug head-, 
 
r 
 
 414 
 
 Steam Engineering 
 
 Fig. 149 
 
 which is connected to the governor-rods. When released 
 by the trip cam, the valve cuts off by means of the steam 
 pressure on the valve-stem controlled by a dash-pot ar- 
 rangement in the valve-plug head to which the other end 
 of the rod is attached. 
 
Valves and Valve Setting 415 
 
 The outlet valve is inside of the valve plug under the 
 strut g. The position of this valve in relation to the inlet 
 can be noted by reference to Fig. 147, where the cross-sec- 
 tion of the valves and seats is shown. The outlet valve is 
 actuated by the eccentric acting on the toggle joint h, con- 
 nected between the two pairs of links, from the point i, 
 where it is fixed, and the joint j, where the link is fastened 
 to the valve-rod head k on the outlet valve-stem. 
 
 Instructions For Proper Setting. The following in- 
 structions are from the builders of these engines, and if 
 adhered to will give proper setting of the valves. The pre- 
 vious illustrations will aid to a full understanding of these 
 operations. 
 
 For reference and a means of checking off the action of 
 the valves it is stated that "A-size" valves have ^Vi ncn 
 lap, with %-inch travel, and are generally used on cylin- 
 ders up to and including 16 inches in diameter; "B-size" 
 valves have T Vinch lap, with l^s-inch travel, and are 
 generally used on cylinders from 18 to 26 inches in di- 
 ameter, inclusive; "C-size" valves have 14-inch lap, with 
 1%-inch travel, and are used on cylinders from 28 inches 
 in diameter upward. 
 
 When starting to adjust the valves, first have all ec- 
 centrics loose on the cylinder shaft, and, second, determine 
 the direction the cylinder shaft is to run, and always rotate 
 the eccentrics in the same direction, whether loose on the 
 shaft, or when the shaft and eccentrics turn together. 
 
 To Adjust the Travel of the Steam Valves. On the 
 edge of the pusher crank a line is made in the shop, and 
 on the side of the plug head, next to the pusher crank, a 
 corresponding line is made (where the arrow points). 
 When the line on the pusher crank corresponds exactly 
 
416 Steam Engineering 
 
 with the line on the side of the plug head, the pusher plate 
 is vertical. This is its most backward position. 
 
 Adjust the eccentric-rod for this valve to such a length 
 that in turning the eccentric around on the shaft the line 
 on the edge of the pusher crank comes back to correspond 
 exactly with the line on the plug head at each revolution. 
 Then, by shimming, adjust the bridge-supporting trip cam, 
 so that the steam valve will travel % of an inch on "A- 
 size," 1% inches on "B-size," and 1% inches on "C-size," 
 but bear in mind that the valve must trip at the end of its 
 travel and the bridge must not be so low that the valve 
 will carry the full stroke without tripping. The roller 
 of the lifter must be in position for full travel. 
 
 To Set the Steam Valves. On the steam valve-stem, four 
 scratch lines are made. These lines represent the valve 
 on its lap, the valve just opening, the valve wide open, and 
 the valve pushed in until it strikes the plug. With each 
 valve-gear a steel-wire tram is sent. Just above the valve- 
 stem on the plug-head casting, a prick-punch mark will be 
 found. Loosen up the inlet stem head on the stem, then 
 shove the valve back until it strikes the plug. If the valve 
 is set correctly, the tram with one end in the mark on the 
 plug head casting should with the other end meet the first 
 scratch line on the valve-stem (nearest the outside end of 
 stem). If the point of the tram does not coincide with 
 this line, the valve-stem should be screwed in or out until 
 it does. The valve should then be let back so that the 
 dasher strikes the head, and the inlet stem head be brought 
 back against the pusher plate when the pusher plate is ver- 
 tical, leaving 1/64 inch clearance between the pusher and 
 latch plates. It will then be found that the point of the 
 tram will correspond with the fourth mark on the stem, 
 with the valve closed. 
 
Valves and Valve Setting 417 
 
 When the valve is moved forward so that the tram point 
 corresponds with the third line on the stem, the valve is 
 just closing or opening, and when moved farther so that it 
 corresponds with the second line, the valve is wide open. 
 The travel of the valve should be between the second, third 
 and fourth points spoken of, and it should trip just as the 
 tram point corresponds with the second line from the out- 
 side end. Then, with the piston on dead center, the ec- 
 centric should be revolved on the shaft to bring the steam 
 valve ^2 of an inch open on the crank end and 3/64 of 
 an inch on the head end. The eccentric should then be 
 clamped to the shaft, and the valve is set. 
 
 To Adjust the Exhaust Valves. On the outside of the 
 plug head are four prick-punch marks. On the outside of 
 the outlet stem head where the tram rests is another prick- 
 punch mark. This is for one point of tram. 
 
 To Adjust Valves For Lap. The eccentric rod should 
 be disconnected from the eccentric. Shove the valve back 
 as far as it will go. With the valve in this position, the 
 outside end of the tram should fall into the fourth mark 
 on outside of the plug head nearest the cylinder. If it 
 does not, loosen up the nut holding the outlet stem head, 
 and screw the stem in or out sufficiently to make the tram 
 come into the fourth mark. Then tighten up the nut hold- 
 ing the outlet stem head, connect the eccentric-rod to the 
 eccentric, lengthen or shorten this eccentric rod so that 
 the travel of the valve due to one revolution of the eccen- 
 tric will move the tram from the first to the third prick- 
 punch mark ; and no farther. 
 
 The eccentric should then be set so that when the piston 
 is about 5 inches from the end of the return stroke, the ex- 
 haust valve should have just closed, and the tram point 
 would fall into the second mark on the plug head. 
 
418 
 
 Steam Engineering 
 
 Fig. 150 
 the fitchburg engine, showing the valve gear 
 
Valves and Valve Setting 
 
 419 
 
 As these valves must be set while the valves are out of 
 sight, a strict adherence to these rules of adjustment must 
 be followed, care being taken to be accurate on all points. 
 
 Fig. 151 
 cross section of steam valve, fitchburg engine 
 
 The. Fitchburg Engine. This engine is fitted with four 
 valves of the piston type. Motion is imparted to the steam 
 valves by a shaft governor eccentric, acting through rods 
 
• 420 Steam Engineering 
 
 A and B, and wrist-cranks C and D, Fig. 150. The ex- 
 haust valves have a common stem, and receive their motion 
 from a fixed eccentric through rods F, and E, Fig. 150. 
 The construction of the steam valve is illustrated in Fig. 
 151. The valve is held in place on the stem A by the nut 
 B. Eings C and D fit into, and bind in place, taper plug 
 E, E, which is used to set out expansible ring F, F. G, GK 
 are adjustment bolts, used for adjusting ring F, F, to wear. 
 To adjust the ring, first slacken nut B just enough to allow 
 ring F freedom to expand or contract, then to expand it 
 slacken the bolts G, G, and run the set-screws H in until 
 the required expansion is accomplished. If too tight, re- 
 verse the process by first slackening set screws H, and then 
 tighten bolts G. During the process the valve should be 
 tested for tightness by rocking it back and forth with the 
 starting bar. 
 
 Fig. 152 shows the steam and exhaust valves for one end 
 of the cylinder. The exhaust valve A is solid. The steam 
 valve B is double ported, and balanced as shown in Fig. 
 151. Eef erring to Fig. 152, the valve motion is on the 
 center of its travel, the valves being lapped. In this posi- 
 tion rocker arms C and D should stand vertical, exactly at 
 right angles to the center line of the engine, and the wrist- 
 cranks E and F should be in like position, with the cams 
 G and H as shown, and the valve rod so adjusted that the 
 valves have their proper lap. When all of the rods are 
 properly adjusted as to length, the rocker-arms, and wrist- 
 cranks will travel an equal distance on each side of the 
 center line on which they rest in Fig. 152. Nut J on the 
 steam reach rod has a right-and-left thread in it, and by 
 loosening the lock nuts and turning the center, the length 
 of this rod may be changed so as to bring the wrist-cranks 
 
Valves and Valve Setting 
 
 421 
 
 in line. Fig. 151 shows the steam valve just on the point 
 of opening. The arrows indicate the direction of flow of 
 the steam. 
 
 fe 
 
 Fig. 152 
 
 Fig. 153 shows the same valve at full opening, and the 
 wrist cranks at the extreme position of their travel in that 
 direction. The governor eccentric is also at its maximum 
 
r 
 
 422 
 
 Steam Engineering 
 
 throw, and on its center. One steam valve is full open, 
 and the other one is closed. When the positions are re- 
 
 Fig. 153 
 
 versed, and the eccentric is on the other center, the steam 
 valve here shown will be back in the position shown in Fig. 
 152, and the crank-end valve will be full open. The ex- 
 
Valves and Valve Setting 423 
 
 haust valves should be so adjusted that they will close, and 
 open alternately at about seven-eights of the stroke of the 
 engine. The travel of the steam valves equals the distance 
 W (Fig. 152) or the width of the bridge X, plus the width 
 of the valve port Y. The steam valve is given this travel 
 through the medium of the cams, and herein lies the pe- 
 culiarity of this valve motion. The largest part of the cam 
 slot is of the same radius that the driving pin and roll on 
 the wrist-crank pass through, so that when the pin is 
 moving down and away from the steam chest and back 
 again to the position shown in Fig. 152, the valve is at 
 rest. This is for a period of one-half the engine revolu- 
 tion. To illustrate this fact, remember that while the 
 wrist-crank is in the position shown in Fig. 152, it is on 
 the center or half of its travel. Supposing the eccentric 
 to move so that the wrist-pin moves from K to L and back 
 again; the engine has completed one-half its revolution. 
 Now while the same wrist-pin is traveling from the position 
 shown in Fig. 152 to that in Fig. 153, the motion of open- 
 ing is given in one-fourth of the engine revolution, and on 
 moving back to the central position the valve has cut off 
 and lapped in one-fourth of the revolution. To prevent a 
 too sudden action of the valve, the slot is just enough off 
 from the point M to the end to start the cam and valve in 
 motion slightly before the valve opens. 
 
 The steam valve is balanced by having the steam pres- 
 sure on all sides, with the exception of the area of the valve 
 stem on one end. The steam valves admit, and the ex- 
 haust valves release steam over their inside ends. The 
 steam valves receive motion indirectly, on account of the 
 wrist-cranks. The exhaust valve motion is direct. The 
 steam and exhaust eccentrics both lead the crank. 
 
424 
 
 Steam Engineering 
 
 Fig. 154 shows the relative position of the crank and 
 steam eccentric at about the point A on the dotted line 
 E X, or it is about 90 degrees plus 37 degrees for lap and 
 lead ahead of the crank, and the exhaust eccentric is ap- 
 proximately at 90 degrees ahead of the crank. This lat- 
 ter fact may be useful to know in the event of a slipped 
 eccentric and the minimum time for adjustment. 
 
 Fig. 154 
 
 Fig. 152 shows both eccentrics at 90 degrees, while Fig. 
 153 shows the lead of the steam valve distorted, for clear- 
 ness of ilustration, but the wrist-crank is in the same ap- 
 proximate position as when the crank is on the center and 
 the eccentric is, at its greatest throw, advanced to the point 
 shown in Fig. 154. While in this position the steam is cut 
 off at about three-fourths stroke. The angle of advance 
 grows less and less as the eccentric is thrown across the 
 shaft by the action of the governor from higher speed, 
 
Valves and Valve Setting 425 
 
 thus accomplishing the regulation of speed. For a full 
 understanding of this action refer to Fig. 154. The action 
 is as follows : As long as the engine is below speed, the ec- 
 centric is kept in its longest throw by the tension of the 
 springs, and steam follows about three-fourths of the stroke, 
 but as soon as the proper speed is reached, centrifugal 
 action causes the weights H to overcome the tension of the 
 springs and to move outward in the direction of the arrow,- 
 at the same time lengthening the springs. By means of 
 the connecting rods G G, the outward motion of the weights 
 turns the suspension arms C upon their fulcra and the 
 ears B, the eccentric is carried across the shaft from S to- 
 ward E, and as the arcs by the centers B B are in oppo- 
 site curves they compensate each other, and the center S 
 of the eccentric follows a straight line in its movement, 
 preserving a constant lead opening, or otherwise, as de- 
 sired. This manifestly decreases the eccentricity, and in- 
 creases the advance of the eccentric, giving an earlier cut- 
 off to the valve until, when the eccentric is swung squarely 
 back of the crank, the valve opens only the lead, there be- 
 ing all points between this and extreme cut-off for varia- 
 tion. Upon the least diminution of speed the springs have 
 more power than the centrifugal force of the weights, and 
 the motion of the parts is arrested and turned in the op- 
 posite direction, giving a later cut-off, as more work is per- 
 formed by the engine. 
 
 How to Set and Adjust the Valves. Having now dis- 
 cussed the motion, the idea is to get a working knowledge 
 of how to set the valves and adjust them and the governor 
 for various conditions. The location of the governor case 
 is determined by placing the engine on one dead center, 
 and rolling the case around on the shaft until the off set 
 
426 Steam Engineering 
 
 of the eccentric is on the opposite side of the shaft from 
 the crank pin. Then roll carefully into such position that 
 when (with the springs removed) the eccentric is thrown 
 back and forth across the shaft no end motion is given the 
 valve rod. At this place tighten the governor case firmly 
 upon the shaft, and roll the shaft to the opposite dead 
 center and again move the eccentric back and forth across 
 the shaft, and roll, and if there is at this end any end mo- 
 tion to the valve-rod, change the position of the governor 
 case on the shaft enough to make the motion just half as 
 much, then fasten the governor case firmly in this final 
 position by drilling into the shaft for the point of the set- 
 screw, and then tightening the clamp bolts to place solidly. 
 Put in the springs and tighten them until the proper num- 
 ber of revolutions is obtained, being sure to tighten up the 
 springs that go through the counterbalance which hangs 
 nearest the springs (when the governor is at rest) about 
 three-fourths of an inch more than the springs on the other 
 side. 
 
 The travel of the exhaust valves can first be evened up 
 before their eccentric is tightened upon the shaft by rolling 
 the eccentric around the shaft to its extreme throw at each 
 end. It should then be set so that the port is just closed 
 when the crosshead has traveled a little less than seven- 
 eighths of its stroke, and the set screw firmly screwed upon 
 the shaft. 
 
 To adjust the steam valves, place the latch of the hook 
 in the center of the half-spiral slot and clamp the hook 
 firmly by its lever, evening up the movement of the wrist- 
 cranks by the right and left nut in the valve-rod, so that 
 in a revolution of the engine shaft they rock evenly each 
 side of a vertical line drawn from the centers of their 
 
Valves and Valve Setting 427 
 
 shafts. Set the engine exactly on one dead center, and 
 move the small valve rod attached to the head end valve in, 
 and out of its cam until the port is opened the proper lead, 
 in usual cases one-sixteenth of an inch, and tighten the set- 
 crew in the neck of the cam upon the rod firmly. Roll the 
 engine to opposite center and set the other valve in the 
 same way. After the valves are thus set as closely as pos- 
 sible, if practicable they should be adjusted by use of the 
 indicator, when the engine is under partial or full load, as 
 no mere measurements can ever set the valves exactly right 
 in any engine. The exhaust valves of the low-pressure 
 cylinder can be set the same as for the high-pressure 
 cylinder. 
 
 The shaft governor depends for its action upon the cen- 
 trifugal power of the two weights nearest the rim, which, 
 through the connecting-rods, move the counterbalancing 
 weights to which the eccentric is attached and thus carry 
 the eccentric across the shaft, altering the throw of the 
 valve-rod and the point of closure of the admission valves. 
 The centrifugal power of the weight arms being exerted 
 against the springs, and the more the weight arms are 
 thrown out toward the rim, the earlier the point of cut-off, 
 it follows that to increase the speed of the engine, tighten 
 the springs or take off some the weight ; and to decrease the 
 speed, loosen the springs or add more weight. The springs 
 should not be stretched much over l 1 /^ times the length of 
 the coil when unstretched. The speed of the engine may 
 be changed several revolutions by adjusting the tension of 
 the springs. A small amount of friction should be main- 
 tained between the face of the eccentric and the governor 
 case to prevent dancing, and this is secured by the springs 
 and washers on the ends of the pins which carry the 
 
428 Steam Engineering 
 
 counterbalance weights. Once adjusted, they are right for 
 a long time. 
 
 Adding to the centrifugal weight arms and increasing 
 the tension of the springs makes the governor more sen- 
 sitive. 
 
The Governor 
 
 The proper regulation of speed is a very important point 
 in the operation of engines, and in order to attain this most 
 desirable object, due attention must be paid to the governor. 
 If the governor is what is known as a throttling governor 
 (see Fig. 155), the principles of which are explained in 
 
 Fig. 155 
 throttling governor 
 
 the section on "definitions," care should be taken to not 
 pack the small valve stem too tight, nor allow the packing 
 to become hard from long usage. The packing nut should 
 be left loose enough to allow a slight leakage of steam past 
 the stem. This will keep it lubricated, and the slightest 
 
 429 
 
430 Steam Engineering 
 
 variation of the governor balls will be transmitted to the 
 valve, and the speed will be regular. 
 
 If the engine has an automatic cut off mechanism actu- 
 ated by a fly ball governor, it is obvious that all the moving 
 parts of the governor should work with as little friction as 
 possible. Good oil and enough of it should be used. Par- 
 ticular attention should be paid to the dash pot connected 
 with the governor, the object of which is to regulate the 
 variations of the governor and prevent a jerky movement. 
 It often happens, especially with new engines, that the 
 small piston in the dash pot fits too snug, and the conse- 
 quence is that it sticks ; causing the governor to be slow in 
 responding to changes in the speed of the engine. 
 
 It is a good plan sometimes to take the dash pot piston 
 out, and putting it in a lathe, reduce its diameter slightly, 
 and also round off the sharp edges. The oil used in the 
 dash pot should not be allowed to become gummy by being 
 used too long without changing it for fresh oil. 
 
 SHAFT GOVERNORS. 
 
 Shaft Governors. Many automatic cut off engines, 
 especially those of the high speed type, are fitted with isoch- 
 ronal, or shaft governors. There are various styles of 
 these governors, but all, or nearly all of them control the 
 admission of steam to the cylinder, and consequently the 
 point of cut off by varying the angular advance of the 
 eccentric, which in such engines is free to move across the 
 shaft, being entirely under the control of the governor. 
 
 Very close regulation is generally obtained by the use of 
 shaft governors, but particular attention should be given 
 to the lubrication of the steam valve, which, with this class 
 of engines, is generally a slide valve of some description, 
 
Shaft Governors 431 
 
 and although it may be ever so nicely balanced, yet if it 
 does not get sufficient oil, the friction due to dry surfaces 
 rubbing together, will put extra work on the governor, 
 and the speed is liable to be irregular. 
 
 The general principle controlling the action of shaft- 
 governors is clearly explained in the section on "defini- 
 tions," and need not be restated here. A few examples 
 of the various makes of this type of governor will be given. 
 The shaft governor, or "governor eccentric" as it is called, 
 which is attached to the Fitchburg engine is described in 
 connection with that engine. (See Fig. 154.) 
 
 Fig. 156 shows the shaft governor of the Eussell engine, 
 which is also a four valve high speed engine. 
 
 This governor is of the centrifugal type and regulates by 
 advancing the eccentric, or retarding it in its position in 
 relation to the crank, thus hastening or holding the point 
 of cut off without altering the travel, and the lap of valve 
 remaining the same. The weights are pivoted at the ends 
 of the arm by the pins near the rim of the wheel, and their 
 outward motion is resisted by springs. The eccentric is 
 fastened to each weight arm by links, and is counterweighted 
 to offset the weight of the reciprocating parts attached. 
 The governor is very simple, and easily understood. 
 
 On a right-hand engine running over, the parts will be 
 mounted as in Fig. 156, with the right-hand weight arm 
 hanging down and the left-hand arm in the position shown. 
 This arrangement also holds good for a left-hand engine 
 running under. 
 
 To change from a right-hand engine running over, to a 
 left-hand engine running under, the wheel would be turned 
 around side for side. On a right-hand engine running 
 under or a left-hand engine running over, the weight arm 
 
432 
 
 Steam Engineering 
 
 will hang downward on the left, the pin being placed in 
 the vacant hole seen at the top of the spoke. To change 
 from a right-hand engine running under, to a left-hand 
 engine running over, turn the wheel around side for side. 
 In other words the weight must always follow the pivot 
 pin of its arm in the direction of engine travel. 
 
 When first working the engine up to speed for the pur- 
 pose of adjusting the governor, screw up on the springs and 
 
 Fig. 156 
 centrifugal governor 
 
 keep setting the weights out farther on the arms, until the 
 speed and sensitiveness are about right. 
 
 Then to get more speed, set up on the springs or take 
 off weight. 
 
 To get less speed, slacken the springs or add weight. 
 
 To make the governor less sensitive, slacken the springs 
 and take off weight. 
 
Shaft Governors 433 
 
 To make the governor more sensitive, set up on the 
 springs and add weight. 
 
 To correct for sluggishness, set up on the springs. 
 
 Generally speaking, when the governor regulates closely 
 and a change in speed is desired, the spring tension should 
 not be changed, but the desired speed should be obtained 
 by changing the weights. More weight gives less speed, 
 and less weight more speed. Moving the weights toward 
 the rim of the wheel, or moving the spring clip on the 
 weight arm toward the weight to get more purchase, has 
 the effect of less weight. Moving the weights toward the 
 hub of the wheel, or the spring clip away from the weight, 
 has the effect of more weight. 
 
 To move the spring clip too far affects the sensitiveness 
 of the governor as well as the speed, and a radical change 
 should not be made without the advice of the builders. 
 When changes of tension on the spring or in the amount 
 of weight are made in any way, the same amount of change 
 should always be made on each spring or weight, as the 
 case may be. To change the direction of rotation on one 
 of these engines, turn the eccentrics to positions opposite 
 to those for the initial direction, and hang the weight arms 
 according to the directions here given. 
 
 Fig. 157 shows the Atlas shaft governor which regulates 
 the supply of steam to the engine by lengthening, or short- 
 ening the valve travel, according as the load increases or 
 diminishes. 
 
 The movement of the governor parts thus not only con-* 
 trols the speed of the engine under changes of load how- 
 ever wide, but also offers proper conditions for low steam 
 consumption. 
 
434 
 
 Steam Engineering 
 
 The eccentric is pivoted on the same side of the shaft 
 as the crank, and as the eccentric swings across the shaft, 
 decreasing valve travel, the lead is well maintained 
 throughout all working conditions of the engine, insuring 
 prompt opening of the steam ports, with consequent proper 
 steam distribution. 
 
 Fig. 157 
 
 atlas automatic shaft governor 
 
 Four- Valve Center Crank Type 
 
 The important principle of inertia is made effective in 
 this governor by the manner of weight suspension. This 
 is combined with a very strong centrifugal element, with- 
 out which no governor is reliable. 
 
 The Atlas engine company also supply a so-called inertia, 
 or dead wheel governor for use on their automatic heavy 
 duty (side crank) engines. This governor occupies less 
 space than does the band-wheel type, but is nevertheless a 
 governor of great power, because of the large inertia ele- 
 
Shaft Governors 435 
 
 ment stored in the wheel. This wheel is not keyed to the 
 shaft, but is free to turn thereon and by such motion 
 through link connection with the eccentric, combined with 
 the centrifugal action of two weights, the eccentric is 
 shifted across the shaft, changing the angle of advance. 
 
 Fig. 158 shows a view of this governor. Both of these 
 governors have spiral springs acting in compression, not in 
 tension. 
 
 Fig. 158 
 
 the atlas automatic shaft governor 
 
 Side Crank Type 
 
 Figs. 159 and 160 show views of the Armington and Sims 
 shaft governor, which differs in some respects from those 
 already described, notably in that it has two eccentrics, one 
 working inside the other. Eef erring to Fig. 159 it will 
 be seen that it consists of a wheel which is fixed to the 
 engine shaft, to which are hinged the weights 1, 1 ; these 
 weights are controlled by springs, one end of the same be- 
 
436 
 
 Steam Engineering 
 
 ing seated in a pocked fixed on the spoke of the wheel, or 
 in some cases attached directly to rim of wheel ; the inner 
 eccentric, marked G, having ears attached, is placed close 
 to the regulator wheel, and is free to turn upon the shaft ; 
 from these ears rods 2, 2 are connected with the weights: 
 
 Fig. 159 
 armington and sims shaft governor 
 
 on the outside of the inner eccentric and free to turn is 
 placed an eccentric ring D, from which a rod 3 is connected 
 to the toe of one of the weights; on this outer eccentric 
 ring is placed the usual eccentric strap, to which is directly 
 attached the valve rod. To avoid confusion, these are not 
 shown in the cut. 
 
Shaft Governors 
 
 437 
 
 It will be seen that when the engine is running at its 
 greatest velocity the weights, due to the centrifugal force 
 overcoming the springs, will be out, consequently the posi- 
 tion of the eccentrics will be as shown in Fig. 159, which 
 gives the valve its least travel and shortest cut-off. The 
 
 Fig. 160 
 armington and sims shaft governor 
 
 eccentricity of the two combined eccentrics is then the dis- 
 tance shown at A, in the cut. 
 
 Taking now the other extreme position shown in Fig. 
 160 when the engine has its heaviest load, requiring later 
 cut off. The position of the weights will then be as shown 
 in the cut, and it will be seen that when the weights are in 
 
438 Steam Engineering 
 
 this position, the inner eccentric has been, moved back, and 
 the outer eccentric forward or in the opposite direction, 
 and the eccentricity by this combined movement is in- 
 creased as shown at B ; this is sufficient to allow the steam 
 to follow the piston to about seven-tenths of the stroke. 
 This gives a wide range of valve action, practically from 
 simple lead at A, Fig. 159, to admission during seven- 
 tenths of the stroke, and causes very quick and sensitive 
 action resulting in close regulation. The lead of the valve 
 remains constant at all positions of the eccentrics. 
 
 QUESTIONS AND ANSWERS. 
 
 316. What inportant features in the operation of an 
 engine are dependent upon a correct adjustment of the 
 valves ? 
 
 Ans. The efficiency of the engine, the economical use 
 of steam, and the regular and quiet action of the engine. 
 
 317. How many different types of valves are there in 
 general use? 
 
 Ans. Slide, poppet, rotative, piston, gridiron, etc. 
 
 318. What are the basic principles governing the ad- 
 justment of the valves of an engine, regardless of the type ? 
 
 Ans. Admission, cut-off, release, and exhaust closure; 
 each of these functions to occur at the proper moment dur- 
 ing one stroke of the piston. 
 
 319. Name two important functions of a valve. 
 Ans. Lap and lead. 
 
 320. What is the effect of increasing outside lap? 
 Ans. Later admission, and an earlier cut off. 
 
 321. What results from increasing inside lap? 
 
 Ans. Earlier exhaust closure, and an increased conpres- 
 sion. 
 
Questions and Answers 439 
 
 322. What advantage has an engine of the four valve 
 type over a single valve engine? 
 
 Ans. Each individual valve may be adjusted in- 
 pendently of the others. 
 
 323. If a valve had neither lap nor lead what would 
 be the position of the eccentric relative to the crank? 
 
 Ans. 90° ahead of the crank. 
 
 324. What is meant by the term "angular advance/' and 
 why is it necessary ? 
 
 Ans. The distance that the high point of the eccentric 
 is set ahead of a line at right angles with the crank. It is 
 necessary in order to give the valve lap, and lead. 
 
 325. What is the first function of the valve at the com- 
 mencement of the stroke ? 
 
 Ans. Lead, or admission. 
 
 326. What is the second function? 
 Ans. Full port opening. 
 
 327. What is the travel of a valve equal to? 
 
 Ans. Twice the port opening plus twice the outside lap. 
 
 328. What is the third function of the valve? 
 A?is. Cut off. 
 
 329. What is the fourth function? 
 Ans. Exhaust closure, or compression. 
 
 330. What will be the effect if the valve has no inside 
 lap? 
 
 Ans. An early release, and no compression. 
 
 331. What is meant by "radius of eccentricity?" 
 Ans. One half the travel of the valve. 
 
 332. What is an eccentric? 
 
 Ans. A mechanical device for converting rotary into 
 reciprocating motion. Its center of revolution is apart 
 from its center of formation. 
 
440 Steam Engineering 
 
 333. What is the "throw" of an eccentric? 
 
 Ans. The distance from the center of the eccentric to 
 the center of the shaft. 
 
 334. What is meant by eccentric position? 
 
 Ans. The location of the highest point of the eccentric 
 relative to the center of the crank pin, expressed in degrees. 
 
 335. What is valve travel? 
 
 Ans. The distance covered by the valve in its move- 
 ment. 
 
 336. What is lap? 
 
 Ans. The amount that the ends of the valve project 
 over the edges of the ports when the valve is at mid travel. 
 
 337. What is inside lap? 
 
 Ans. The lap of the inside, or exhaust edge of the valve 
 over the inside edge of the port. 
 
 338. What is outside lap ? 
 
 Ans. ' The lap of the outside edge of the valve over the 
 outside edge of the port. 
 
 339. What is lead? 
 
 Ans. The amount that the port is open when the crank 
 is on the dead center. 
 
 340. Why must a valve have outside lap ? 
 
 Ans. Because admission and cut off are controlled 
 thereby. 
 
 341. Why should a valve have inside lap ? 
 
 Ans. In order that release and compression may be 
 properly controlled. 
 
 342. What is the effect of decreasing the angular ad- 
 vance ? 
 
 Ans. All the important functions of the valve occur 
 later. 
 
 343. What results follow from decreasing the travel of 
 the valve 
 
Questions and Answers 441 
 
 Ans. Less lead, a later admission and release, and an 
 earlier cut off and compression. 
 
 344. What is meant by automatic or variable cut off? 
 Ans. A system in which full boiler pressure is constantly 
 
 maintained in the valve chest, the speed being regulated by 
 the governor controlling the point of cut off. 
 
 345. What is meant by fixed cut off? 
 
 Ans. When the point of cut off remains the same, re- 
 gardless of the load, the speed being regulated by throttling 
 the steam. 
 
 346. What three changes must be made in order to 
 cause an earlier cut off on an engine that has a fixed cut off ? 
 
 Ans. First — Increase the angular advance. Second — 
 Increase the outside lap. Third — Increase the inside lap. 
 
 347. What is the first step in valve setting? 
 Ans. To place the engine on the dead center. 
 
 348. What is meant by the dead center? 
 
 Ans. When the piston is at the end of the stroke, and 
 the centers of the crank shaft, crank pin, and cross head 
 pin are in line. 
 
 349. What rule should be observed in turning an en- 
 gine to place it on the dead center? 
 
 Ans. Always turn it in the direction in which it is to 
 run. 
 
 350. Why is this necessary? 
 
 Ans. In order to guard against errors which might 
 result from lost motion in the parts. 
 
 351. Having placed the engine on the dead center, what 
 is to be done next ? 
 
 Ans. Adjust the eccentric rod to the proper length? 
 
 352. What should be done with the valve before con- 
 necting it with the eccentric rod ? 
 
 Ans. It should be placed at mid travel, and marked. 
 
442 Steam Engineering 
 
 353. What is necessary before the valve can be placed 
 in its central position? 
 
 Ans. The exact amount of outside lap must be known. 
 
 354. What amount of lead is usually given to the valve ? 
 Ans. From ^ in. to % in. depending upon the size of 
 
 the engine. 
 
 355. What is the function of the governor? 
 
 Ans. To properly regulate the speed of the engine. 
 
 356. Explain the action of a governor? 
 
 Ans. Its action is based upon the principle of the cen- 
 trifugal, and centripetal forces, which cause the balls or 
 weights attached to the arms, to fly outward or inward as 
 their speed of revolution increases or decreases. 
 
 357. In what manner is this movement of the balls 
 caused to regulate the speed? 
 
 Ans. In the pendulum or fly ball governor, the motion 
 is transferred by means of levers and rods to the cut of! 
 mechanism. In the shaft governor the changes in the 
 position of the weights change the angular advance of the 
 eccentric, thus causing an earlier or later cut off, according 
 as the load is light, or heavy. 
 
 358. In what way does the throttling governor regulate 
 the speed of an engine? 
 
 Ans. It controls the position of a valve in the steam 
 pipe, opening or closing it according as the engine needs 
 more, or less steam to maintain a regular speed. 
 
 359. What is compression? 
 
 Ans. If the exhaust port is closed by the valve, just be- 
 fore the piston reaches the end of stroke, a portion of the 
 steam will be entrapped in the cylinder, and being ahead 
 cf the piston will be compressed. 
 
 37-0. Is there any advantage in this? 
 
Questions and Answers 443 
 
 Ans. Yes. The steam thus compressed acts as a cush- 
 ion for the piston, preventing shock or jar to the moving 
 parts on reaching the end of the stroke. 
 
 361. What is an adjustable cut off? 
 
 Ans. One in which the point of cut off may te adjusted 
 by a hand wheel attached to the valve stem of a throttling 
 governor. 
 
_-- 
 
Definitions 
 
 In order to facilitate the study and analysis of indicator 
 diagrams, the following definitions of technical terms, some 
 of which have already been explained in another part of 
 this book, are here given. 
 
 Absolute pressure. Pressure reckoned from a perfect 
 vacuum. It equals the boiler pressure plus the atmospheric 
 pressure. 
 
 Boiler pressure or gauge pressure. Pressure above the 
 atmospheric pressure as shown by the steam gauge. 
 
 Initial pressure. Pressure in the cylinder at the begin- 
 ning of the stroke. 
 
 Terminal pressure (T. P.). The pressure that would ex- 
 ist in the cylinder at the end of the stroke provided the 
 exhaust valve did not open until the stroke was entirely 
 completed. It may be graphically illustrated on the diagram 
 by extending the expansion curve by hand to the end of 
 the stroke. It is found theoretically by dividing the pres- 
 sure at point of cut off by the ratio of expansion. Thus, 
 absolute pressure at cut off=100 lbs., ratio of expansions 
 5; then 100-^5=20 lbs., absolute terminal pressure. 
 
 Mean effective pressure (M. E. P.). The average pressure 
 acting upon the piston throughout the stroke minus the 
 back pressure. 
 
 Bach pressure. Pressure which tends to retard the for- 
 ward stroke of the piston. Indicated on the diagram from 
 a non-condensing engine by the height of the back pressure 
 line above the atmospheric line. In a condensing engine 
 the degree of back pressure is shown by the height of the 
 
 445 
 
446 Steam Engineering 
 
 back pressure line above an imaginary line representing 
 the pressure in the condenser corresponding to the degree 
 of vacuum in inches, as shown by the vacuum gauge. 
 
 Total or absolute bach pressure, in either a condensing 
 or non-condensing engine, is that indicated on the diagram 
 by the height of the line of back pressure above the line 
 of perfect vacuum. 
 
 Ratio of expansion. The proportion that the volume of 
 steam in the cylinder at point of release bears to the volume 
 at cut off. Thus, if the point of cut off is at one-fifth of 
 the stroke, and release does not take place until the end 
 of the stroke, the ratio of expansion, or in other words, the 
 number of expansions, is 5. When the T. P. is known the 
 ratio of expansion may be found by dividing the initial 
 pressure by the T. P. 
 
 Wire drawing. When through insufficiency of valve 
 opening, contracted ports, or throttling governor, the steam 
 is prevented from following up the piston at full initial 
 pressure until the point of cut off is reached, it is said to 
 be wire drawn. It is indicated on the diagram by a grad- 
 ual inclination downwards of the steam line from the ad- 
 mission line to the point of cut off. Too small a steam pipe 
 from boiler to engine will also cause wire drawing, and fall 
 of pressure. 
 
 Condenser pressure may be defined as the pressure exist- 
 ing in the condenser of an engine, caused by the lack of a 
 perfect vacuum. As, for instance, with a vacuum of 25 
 in. there will still remain the pressure due to the 5 in. which 
 is lacking. This will be about 2.5 lbs. 
 
 Vacuum. That condition existing within a closed vessel 
 from which all matter, including air, has been expelled. 
 It is measured by inches in a column of mercury contained 
 
Definitions 447 
 
 within a glass tube a little over 30 in. in height, having its 
 lower end open and immersed in a small open vessel filled 
 with mercury. The upper end of the glass tube is con- 
 nected with the vessel in which the vacuum is to be pro- 
 duced. When no vacuum exists the mercury will leave the 
 tube and fill the lower vessel. When a vacuum is main- 
 tained in the condenser, or other vessel, the mercury will 
 rise in the glass tube to a height corresponding to the de- 
 gree of vacuum. If the mercury rises to the height of 30 
 in. it indicates a perfect vacuum, which means the absence 
 of all pressure within the vessel, but this condition is never 
 realized in practice ; the nearest approach to it being about 
 28 in. 
 
 For purposes of convenience the mercurial vacuum gauge 
 is not generally used, it having been replaced by the Bour- 
 don spring gauge, although the mercury gauge is used for 
 testing. 
 
 The vacuum in a condenser is generally maintained by 
 an air pump, although it can be produced and maintained 
 by the mere condensation of the steam as it enters the con- 
 denser by allowing a spray of cold water to strike it. The 
 steam when it first enters the condenser drives out the air 
 and the vessel is filled with steam which, when condensed, 
 occupies about 1,600 times less space than it did before be- 
 ing condensed, hence a partial vacuum is produced. 
 
 While the vacuum in a condenser cannot be considered 
 as power at all, yet it occupies the anomalous position of 
 increasing, by its presence, the capacity of the engine for 
 doing work. This is owing to the fact that the atmospheric 
 pressure, or resistance which is always ahead of the piston 
 in a non-condensing engine is, in the case of a condensing 
 engine, removed to a degree corresponding to the height of 
 
448 Steam Engineering 
 
 the vacuum, thus making available just so much more of 
 the pressure behind the piston. Thus, if the average steam 
 pressure throughout the stroke is 30 lbs. and there is a 
 vacuum of 26 in. maintained in the condenser, there will 
 be 13 lbs. of resistance per square inch removed from in 
 front of the piston, thus making available 30+13=43 lbs. 
 pressure per square inch. 
 
 Absolute zero has been fixed by calculation at 461.2° be- 
 low the zero of the Fahrenheit scale. 
 
 Piston displacement. The space or volume swept through 
 by the piston in a single stroke. Found by multiplying 
 the area of piston by length of stroke. 
 
 Piston clearance. The distance between the piston and 
 cylinder head when the piston is at the end of the stroke. 
 
 Steam clearance, ordinarily termed clearance. The space 
 between the piston at the end of the stroke and the valve 
 face. It is reckoned in per cent of the total piston dis- 
 placement. 
 
 Horse power (H. P.). 33,000 pounds raised one foot 
 high in one minute of time. 
 
 Indicated horse power (I. PL. P.). The horse power as 
 shown by the indicator diagram. It is found as follows : 
 
 Area of piston in square inches XM. E. P. X piston speed 
 in feet-f-33,000. 
 
 Piston speed. The distance in feet traveled by the piston 
 in one minute. It is the product of twice the length of 
 stroke expressed in feet, multiplied by the number of revolu- 
 tions per minute. 
 
 R. P. M. Revolutions per minute. 
 
 Net horse power. I. H. P. minus the friction of the en- 
 gine. 
 
Definitions 449 
 
 Compression. The action of the piston as it nears the 
 end of the stroke, in reducing the volume, and raising the 
 pressure of the steam retained in the cylinder ahead of the 
 piston by the closing of the exhaust valve. 
 
 Boyle's or Mariotte's law of expanding gases. "The pres- 
 sure of a gas at a constant temperature varies inversely as 
 the space it occupies." Thus, if a given volume of gas is 
 confined at a pressure of 50 lbs. per square inch and it is 
 allowed to expand to twice its volume, the pressure will fall 
 to 25 lbs. per square inch. 
 
 Adiabatic curve. A curve representing the expansion 
 of a gas which loses no heat while expanding. Sometimes 
 called the curve of no transmission. 
 
 Isothermal curve. A curve representing the expansion 
 of a gas having a constant temperature but partially in- 
 fluenced by moisture, causing a variation in pressure accord- 
 ing to the degree of moisture or saturation. It is also 
 called the theoretical expansion curve. 
 
 Expansion curve. The curve traced upon the diagram 
 by the indicator pencil showing the actual expansion of 
 the steam in the cylinder. 
 
 First law of thermodynamics. Heat and mechanical 
 energy are mutually convertible. 
 
 Power. The rate of doing work, or the number of foot 
 pounds exerted in a given time. 
 
 Unit of work. The foot pound, or the raising of one 
 pound weight one foot high. 
 
 First law of motion. All bodies continue either in a 
 state of rest or of uniform motion in a straight line, except 
 in so far as they may be compelled by impressed forces to 
 change that state. 
 
 Work. Mechanical force or pressure cannot be con- 
 
450 Steam Engineering 
 
 sidered as work unless it is exerted upon a body and causes 
 that body to move through space. The product of the 
 pressure multiplied by the distance passed through and 
 the time thus occupied is work. 
 
 Momentum. Force possessed by bodies in motion, or 
 the product of mass and density. 
 
 Dynamics. The science of moving powers or of matter 
 in motion, or of the motion of bodies that mutually act upon 
 each other. 
 
 Force. That which alters the motion of a body, or puts 
 in motion a body that was at rest. 
 
 Maximum theoretical duty of steam is the product of the 
 mechanical equivalent of heat, viz., 778 ft. lbs. multiplied 
 by the total heat units in a pound of steam. Thus, in one 
 pound of steam at 212° reckoned from 32° the total heat 
 equals 1,146.6 heat units. Then 778X1,146.6 equals 892,- 
 054.8 ft. lbs.=maximum duty. 
 
 Steam efficiency may be expressed as follows : 
 
 Heat converted into useful work 
 
 and maximum efficiency 
 
 Heat expended 
 
 can only be attained by using steam at as high an initial 
 pressure as is consistent with safety, and at as large a ratio 
 of expansion as possible. The percentage of efficiency of 
 steam used at atmospheric pressure in a non-expansive en- 
 gine is very low; as, for instance, the heat expended in the 
 evaporation of one pound of water at 32° into steam at 
 atmospheric pressure= 1,146.6 heat units, and the volume 
 of steam so generated=26.36 cu. ft. 
 
 One cubic foot of steam at 212° contains energy equal 
 to 144X14.7=2,116.8 ft. lbs., and 26.36 cu. ft.=2,116.8 
 X 26.36=55,798.84 ft. lbs., which divided by the mechani- 
 cal equivalent of heat, viz., 778 ft. lbs.=71.72 heat units, 
 
Definitions 451 
 
 available for useful work. The per cent of efficiency there- 
 
 71.72X100 
 
 fore is =6.2 per cent. But suppose the initial 
 
 1,116.6 
 
 pressure to have been 200 lbs. absolute, and that the steam 
 
 is allowed to expand to thirty times its original volume. 
 
 The heat expended in evaporating a pound of water at 32° 
 
 into steam at 200 lbs. absolute pressure=l,198.3 heat units, 
 
 and the volume of steam so generated=2.27 cu. ft. The 
 
 average pressure during expansion would be 29.34 lbs. per 
 
 square inch and the volume when expanded thirty times 
 
 would equal 2.27X30=68.1 cu. ft. 
 
 One cubic foot of steam at 29.31 lbs. pressure equals 
 114X29.31=4,224.96 ft. lbs., and 68.1 cu. ft. will equal 
 4224.96X68.1=287,719.7 ft. lbs. of energy, which divided 
 by the equivalent, 778, equals 370.2 heat units, and the per 
 
 cent of efficiency will be tttttt^ — =30.8 per cent. 
 
 J 1198.3 r 
 
 Engine efficiency. If the engine is considered merely as 
 
 a machine for converting into useful work the heat energy 
 
 in the steam regardless of the cost of fuel, its efficiency 
 
 may be expressed as follows : 
 
 Heat converted into useful work 
 
 Total heat received in the steam 
 Example. Assume an engine to be receiving steam at 
 95 lbs. absolute pressure, that the consumption of dry 
 steam per horse power per hour equals 20 lbs., that the 
 friction of the engine amounts to 15 per cent, and that the 
 temperature of the feed water is raised from 60° to 170° 
 by utilizing a portion of the exhaust. 
 
 In a pound of steam at 95 lbs. absolute there are 1,180.7 
 heat units, and in a pound of water at 170° there are 
 
452 Steam Engineering 
 
 138.6 units of heat, but 28.01 of these heat units were in 
 the water at its initial temperature of 60°. Therefore the 
 total heat added to the water by the exhaust steam equals 
 138.6—28.01=110.59 heat units, and the total heat in 
 each pound of steam to be charged up to the engine is 1,180.7 
 - — 110.59=1,070.11, and the total for each horse power de- 
 veloped per hour will be 1,070.11X20=21,402.2 heat units. 
 A horse power equals 33,000 ft. lbs. per minute, or sixty 
 times 33,000=1,980,000 ft. lbs. per hour. From this must 
 be deducted 15 per cent for friction of the engine, leaving 
 1,683,000 ft. lbs. for useful work. Dividing this by the 
 equivalent, viz., 778 ft. lbs., gives 2,163.2 heat units as the 
 heat converted into one horse power of work in one hour, 
 and the percentage of efficiency of the engine will be 
 
 2,163.2X100 
 
 =10.1 per cent. 
 
 21,402.2 
 
 Efficiency of the plant as a whole includes boiler and 
 
 engine efficiency, and is to be figured upon the basis of 
 
 Heat converted into useful work 
 
 Calorific or heat value of fuel 
 
 Horse power constant of an engine is found by multiply- 
 ing the area of the piston in square inches by the speed of 
 the piston in feet per minute and dividing the product by 
 33,000. It is the power the engine would develop with one 
 pound mean effective pressure. To find the horse power of 
 the engine, multiply the M. E. P. of the diagram by this 
 constant. 
 
 Logarithms. A series of numbers having a certain rela- 
 tion to the series of natural numbers, by means of which 
 many arithmetical operations are made comparatively easy. 
 The nature of the relation will be understood by considering 
 two simple series, such as the following, one proceeding 
 
 * = 
 
Definitions 453 
 
 from unity in geometrical progression and the other from 
 in arithmetical progression: 
 
 Geom. series, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, etc. 
 
 Arith. series, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, etc. 
 
 Here the ratio of the geometrical series is 2 and any 
 term in the arithmetical series expresses how often 2 has 
 been multiplied into 1 to produce the corresponding term 
 of the geometrical series. Thus, in proceeding from 1 to 
 32 there have been 5 steps or multiplications by the ratio 
 2; in other words, the ratio of 32 to 1 is compounded 5 
 times of the ratio of 2 to 1. The above is the basic princi- 
 ple upon which common logarithms are computed. 
 
 Hyperbolic logarithms. Used in figuring the M. E. P. 
 of a diagram from the ratio of expansion and the initial 
 pressure. Thus, hyperbolic logarithm of ratio of expansion 
 + 1 multiplied by absolute initial pressure, and divided by 
 ratio of expansion=mean forward pressure. From this 
 deduct total back pressure and the remainder will be mean 
 effective pressure. The hyperbolic logarithm is found by 
 multiplying the common logarithm by the constant 2.302- 
 585. Table 33 gives the hyperbolic logarithms of numbers 
 usually required in calculations of the above nature. 
 
454 
 
 . Steam Engineering 
 
 Table 33 
 hyperbolic logarithms. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 1.01 
 
 0.0099 
 
 3.00 
 
 1.0986 
 
 5.00 
 
 1.6094 
 
 7.00 
 
 1.9459 
 
 9.00 
 
 2.1972 
 
 1.05 
 
 0.0487 
 
 3.05 
 
 1.1151 
 
 5.05 
 
 1.6194 
 
 7.05 
 
 1.9530 
 
 9.05 
 
 2.2028 
 
 1.10 
 
 0.0953 
 
 3.10 
 
 1.1341 
 
 5.10 
 
 1.6292 
 
 7.10 
 
 1.9600 
 
 9.10 
 
 2.2083 
 
 1.15 
 
 0.1397 
 
 3.15 
 
 1.1474 
 
 5.15 
 
 1.6390 
 
 7.15 
 
 1.9671 
 
 9.15 
 
 2.2137 
 
 1.20 
 
 0.1823 
 
 3.20 
 
 1.1631 
 
 5.20 
 
 1.6486 
 
 7.20 
 
 1.9740 
 
 9.20 
 
 2.2192 
 
 1.25 
 
 0.2231 
 
 3.25 
 
 1.1786 
 
 5.25 
 
 1.6582 
 
 7.25 
 
 1.9810 
 
 9.25 
 
 2.2246 
 
 1.30 
 
 0.2623 
 
 3.30 
 
 1.1939 
 
 5.30 
 
 1.6677 
 
 7.30 
 
 1.9879 
 
 9.30 
 
 2.2310 
 
 1.35 
 
 0.3001 
 
 3.35 
 
 1.2090 
 
 5.35 
 
 1.6771 
 
 7.35 
 
 1.9947 
 
 9.35 
 
 2.2354 
 
 1.40 
 
 0.3364 
 
 3.40 
 
 1.2238 
 
 5.40 
 
 1.6864 
 
 7.40 
 
 2.0015 
 
 9.40 
 
 2.2407 
 
 1.45 
 
 0.3715 
 
 3.45 
 
 1.2384 
 
 5.45 
 
 1.6956 
 
 7.45 
 
 2.0018 
 
 9.45 
 
 2.2460 
 
 1.50 
 
 0.4054 
 
 3.50 
 
 1.2527 
 
 5.50 
 
 1.7047 
 
 7.50 
 
 2.0149 
 
 9.50 
 
 2.2513 
 
 1.55 
 
 0.4382 
 
 3.55 
 
 1.2669 
 
 5.55 
 
 1.7138 
 
 7.55 
 
 2.0215 
 
 9.55 
 
 2.2565 
 
 1.60 
 
 0.4700 
 
 3.60 
 
 1.2809 
 
 5.60 
 
 1.7228 
 
 7.60 
 
 2.0281 
 
 9.60 
 
 2.2618 
 
 1.65 
 
 0.5007 
 
 3.65 
 
 1.2947 
 
 5.65 
 
 1.7316 
 
 7.65 
 
 2.0347 
 
 9.65 
 
 2.2670 
 
 1.70 
 
 0.5306 
 
 3.70 
 
 1.3083 
 
 5.70 
 
 1.7405 
 
 7.70 
 
 2.0412 
 
 9.70 
 
 2.2721 
 
 1.75 
 
 0.5596 
 
 3.75 
 
 1.3217 
 
 5.75 
 
 1.7491 
 
 7.75 
 
 2.0477 
 
 9.75 
 
 2.2773 
 
 1.80 
 
 0.5877 
 
 3.80 
 
 1.3350 
 
 5.80 
 
 1.7578 
 
 7.80 
 
 2.0541 
 
 9.80 
 
 2.2824 
 
 1.85 
 
 0.6151 
 
 3.85 
 
 1.3480 
 
 5.85 
 
 1.7664 
 
 7.85 
 
 2.0605 
 
 9.85 
 
 2.2875 
 
 1.90 
 
 0.6418 
 
 3.90 
 
 1.3610 
 
 5.90 
 
 1.7750 
 
 7.90 
 
 2.0668 
 
 9.90 
 
 2.2925 
 
 1.95 
 
 0.6678 
 
 3.95 
 
 1.3737 
 
 5.95 
 
 1.7834 
 
 7.95 
 
 2.0731 
 
 9.95 
 
 2.2976 
 
 2.00 
 
 0.6931 
 
 4.00 
 
 1.3863 
 
 6.00 
 
 1.7918 
 
 8.00 
 
 2.0794 
 
 10.00 
 
 2.3026 
 
 2.05 
 
 0.7178 
 
 4.05 
 
 1.3987 
 
 6.05 
 
 1.8000 
 
 8.05 
 
 2.0857 
 
 10.25 
 
 2.3273 
 
 2.10 
 
 0.7419 
 
 4.10 
 
 1.4010 
 
 6.10 
 
 1.8083 
 
 8.10 
 
 2.0918 
 
 10.50 
 
 2.3514 
 
 2.15 
 
 0.7654 
 
 4.15 
 
 1.4231 
 
 6.15 
 
 1.8164 
 
 8.15 
 
 2.0988 
 
 10.75 
 
 2.3749 
 
 2.20 
 
 0.7885 
 
 4.20 
 
 1.4351 
 
 6.20 
 
 1.8245 
 
 8.20 
 
 2.1041 
 
 11.00 
 
 2.3979 
 
 2.25 
 
 0.8110 
 
 4.25 
 
 1.4469 
 
 6.25 
 
 1.8326 
 
 8.25 
 
 2.1102 
 
 12.00 
 
 2.4849 
 
 2.30 
 
 0.8329 
 
 4.30 
 
 1.4586 
 
 6.30 
 
 1.8405 
 
 8.30 
 
 2.1162 
 
 13.00 
 
 2.5626 
 
 2.35 
 
 0.8544 
 
 4.35 
 
 1.4701 
 
 6.35 
 
 1.8484 
 
 8.35 
 
 2 1222 
 
 14.00 
 
 2.6390 
 
 2.40 
 
 0.8755 
 
 4.40 
 
 1.4816 
 
 6.40 
 
 1.8563 
 
 8.40 
 
 2. 1282 
 
 15.00 
 
 2.7103 
 
 2.45 
 
 0.8961 
 
 4.45 
 
 1.4929 
 
 6.45 
 
 1.8640 
 
 8.45 
 
 2.1342 
 
 16.00 
 
 2.7751 
 
 2.50 
 
 0.9163 
 
 4.50 
 
 1.5040 
 
 6.50 
 
 1.8718 
 
 8.50 
 
 2.1400 
 
 17.00 
 
 2.8332 
 
 2.55 
 
 0.9361 
 
 4.55 
 
 1.5151 
 
 6.55 
 
 1.8795 
 
 8.55 
 
 2.1459 
 
 18.00 
 
 2.8903 
 
 2.60 
 
 0.9555 
 
 4.60 
 
 1.5260 
 
 6.60 
 
 1.8870 
 
 8.60 
 
 2.1518 
 
 19.00 
 
 2.9444 
 
 2.65 
 
 0.9746 
 
 4.65 
 
 1.5369 
 
 6.65 
 
 1.8946 
 
 8.65 
 
 2.1576 
 
 20.00 
 
 2.9957 
 
 2.70 
 
 0.9932 
 
 4.70 
 
 1.5475 
 
 6.70 
 
 1.9021 
 
 8.70 
 
 2.1633 
 
 21.00 
 
 3.0445 
 
 2.75 
 
 1.0116 
 
 4.75 
 
 1.5581 
 
 6.75 
 
 1.9095 
 
 8.75 
 
 2.1690 
 
 22.00 
 
 3.0910 
 
 2.80 
 
 1.0296 
 
 4.80 
 
 1.5686 
 
 6.80 
 
 1.9169 
 
 8.80 
 
 2.1747 
 
 23.00 
 
 3.0355 
 
 2.85 
 
 1.0473 
 
 4.85 
 
 1.5790 
 
 6.85 
 
 1.9242 
 
 8.85 
 
 2.1804 
 
 24.00 
 
 3.1780 
 
 2.90 
 
 1.0647 
 
 4.90 
 
 1.5892 
 
 6.90 
 
 1.9315 
 
 8.90 
 
 2.1860 
 
 25.00 
 
 3.2189 
 
 2.95 
 
 1.0818 
 
 4.95 
 
 1.5994 
 
 6.95 
 
 1.9387 
 
 8.95 
 
 2.1916 
 
 30.00 
 
 3.3782 
 
 Steam consumption per horse power per hour. The 
 weight in pounds of steam exhausted into the atmosphere, 
 or into the condenser in one hour, divided by the horse 
 power developed. It is determined from the diagram by 
 selecting a point in the expansion curve just previous to 
 the opening of the exhaust valve, and measuring the absolute 
 pressure at that point. Then the piston displacement up 
 to the point selected, plus the clearance space, -expressed in 
 
 __ - 
 
Definitions 455 
 
 cubic feet, will give the volume of steam in the cylinder, 
 which multiplied by the weight per cubic foot of steam at 
 the pressure as measured will give the weight of steam con- 
 sumed during one stroke. From this should be deducted 
 the steam saved by compression as shown by the diagram, 
 in order to get a true measure of the economy of the engine. 
 Having thus determined the weight of steam consumed for 
 one stroke, multiply it by twice the number of strokes per 
 minute and by 60, which will give the total weight con- 
 sumed per hour. This divided by the horse power will 
 give the rate per horse power per hour. 
 
 Cylinder condensation and reevaporation. When the ex- 
 haust valve opens to permit the exit of the steam there is a 
 perceptible cooling of the walls of the cylinder, especially 
 in condensing engines when a high vacuum is maintained. 
 This results in more or less condensation of the live steam 
 admitted by the opening of the steam valve; but if the 
 exhaust valve is caused to close at the proper time so as to 
 retain a portion of the steam to be compressed by the piston 
 on the return stroke, a considerable portion of the water 
 caused by condensation will be reevaporated into steam by 
 the heat and consequent rise in pressure caused by com- 
 pression. 
 
 Ordinates. Parallel lines drawn at equal distances apart 
 across the face of the diagram, and perpendicular to the 
 atmospheric line. They serve as a guide to facilitate the 
 measurement of the average forward pressure throughout 
 the stroke, or the pressure at any point of the stroke if 
 desired. 
 
 Eccentric. A mechanical device used in place of a crank 
 for converting rotary into reciprocating motion. An eccen- 
 tric is in fact a form of crank in which the crank pin, cor- 
 responding to the eccentric sheave, embraces the shaft, but 
 
456 Steam Engineering 
 
 owing to the great leverage at which the friction between 
 the sheave and the strap acts, compared with its short turn- 
 ing leverage, it can only be used to advantage for the pur- 
 pose named above. 
 
 Eccentric throw is the distance from the center of the 
 eccentric to the center of the shaft. This definition also 
 applies to the term "radius of eccentricity." 
 
 Eccentric position. The location of the highest point 
 of the eccentric relative to the center of the crank pin, 
 measured or expressed in degrees. 
 
 Angular advance. The distance that the high point of 
 the eccentric is set ahead of a line at right angles with the 
 crank. In other words, the lap angle plus the lead angle. 
 If a valve had neither lap nor lead, the position of the high 
 point of the eccentric would be on a line at right angles with 
 the crank; as for instance, the crank being at 0° the eccen- 
 tric would stand at 90°. 
 
 Valve travel. The distance covered by the valve in its 
 movement. It equals twice the throw of the eccentric. This 
 refers to engines having a fixed cut off. In the case of an 
 engine with a variable automatic cut off, the travel of the 
 cut off valve is regulated by the governor. 
 
 Lap. The amount that the ends of the valve project 
 over the edges of the ports when the valve is at mid travel. 
 
 Outside or steam lap. The amount that the end of the 
 valve overlaps or projects over the outside edge of the steam 
 port. 
 
 Inside lap. The lap of the inside or exhaust edge of the 
 valve over the inside edge of the port. 
 
 Lead. The amount that the port is open when the crank 
 is on the dead center. The object of giving a valve lead is 
 to supply a cushion of live steam which, in conjunction with 
 
Definitions 457 
 
 that already confined in the clearance space by compression, 
 shall serve to bring the moving parts of the engine to rest 
 quietly at the end of the stroke, and also quicken the action 
 of the piston in beginning the return stroke. 
 
 Compression. Closing of the exhaust passage before the 
 steam is entirely exhausted from the cylinder. A certain 
 quantity of steam is thus compressed into the clearance 
 space. 
 
 Throttling governor. Used to regulate the speed of en- 
 gines having a fixed cut off. The governor controls the 
 position of a valve in the steam pipe, opening or closing it 
 according as the engine needs more or less steam in order 
 to maintain a regular speed. 
 
 Automatic or variable cut of. In engines of this type 
 the full boiler pressure is constantly in the valve chest and 
 the speed of the engine is regulated by the governor con- 
 trolling the point of cut off, causing it to take place earlier 
 or later, according as the load on the engine is lighter or 
 heavier. 
 
 Fixed cut off. This term is applied to engines in which 
 the point of cut off remains the same regardless of the load, 
 the speed being regulated by a throttling governor as ex- 
 plained above. 
 
 Isochronal or shaft governor. This device in which the 
 centrifugal and centripetal forces are utilized, as in the 
 fly ball governor, is generally applied to automatic cut off 
 engines having reciprocating or slide valves. It is attached 
 to the crank shaft, and its function is to change the position 
 of the eccentric, which is free to move across the shaft 
 within certain prescribed limits, but is at the same time 
 attached to the governor. The angular advance of the 
 eccentric is thus increased or diminished, in fact is entirely 
 
458 Steam Engineering 
 
 under the control of the governor, and cut off occurs earlier 
 or later according to the demands of the load on the engine. 
 Adjustable cut off. One in which the point of cut off 
 may be regulated or adjusted by hand by means of a hand 
 wheel and screw attached to the valve stem, the supply of 
 steam being regulated by a throttling governor. 
 
 QUESTIONS AND ANSWERS. 
 
 362. What is absolute pressure? 
 
 Ans. Pressure reckoned from a perfect vacuum. 
 
 363. What is gauge pressure? 
 
 Ans. Pressure above atmospheric pressure. 
 
 364. What is initial pressure? 
 
 Ans. Pressure in the cylinder at the beginning of the 
 stroke. 
 
 365. What is terminal pressure? 
 
 Ans. Pressure in the cylinder at the end of the stroke. 
 
 366. What is mean effective pressure (M. E. P.) ? 
 Ans. The average pressure acting upon the piston 
 
 throughout the stroke. 
 
 367. What is back pressure? 
 
 Ans. Pressure tending to retard the forward stroke of 
 the piston. 
 
 368. What is absolute back pressure? 
 
 Ans. Back pressure measured from a perfect vacuum. 
 
 369. What is the ratio of expansion? 
 
 Ans. The relative volume of steam in the cylinder at 
 point of release, compared to volume at cut off. 
 
 370. What is wire drawing of steam? 
 
 Ans. Eestricted passage of the steam caused by too 
 small a steam pipe. 
 
 371. What is condenser pressure? 
 
Questions and Answers 459 
 
 Ans. Pressure existing in the condenser caused by the 
 lack of vacuum. 
 
 372. What is vacuum? 
 
 Ans. That condition existing within a closed vessel from 
 i which all matter, including air has been expelled. 
 
 373. What is absolute zero? 
 Ans. 461.2° below zero Fahr. 
 
 374. What is piston displacement? 
 
 Ans. The space swept through by the piston in a single 
 stroke. 
 
 375. What is piston clearance? 
 
 Ans. The distance between the piston and cylinder head 
 at the end of the stroke. 
 
 376. What is steam clearance? 
 
 Ans. The distance between the piston at end of stroke, 
 and the valve face. 
 
 377. What is a horse power (H. P.) ? 
 
 Ans. 33,000 lbs. raised one foot in one minute of time. 
 
 378. What is indicated horse power (I. H. P.) ? 
 
 Ans. The horse power as shown by the indicator dia- 
 gram. 
 
 379. What is piston speed? 
 
 Ans. The distance in feet traveled by the piston in one' 
 minute. 
 
 380. Give the rule for figuring the horse power? 
 
 Ans. Area of piston in square inchesXM. E. P.Xpiston 
 speed—33,000. 
 
 381. What is net horse power? 
 Ans. I. H. P. minus engine friction. 
 
 382. Define Boyle's law of expanding gases? 
 
 Ans. Pressure at constant temperature varies inversely 
 as the space it occupies. 
 
L 
 
 460 Steam Engineering 
 
 383. What is an adiabatic curve? 
 
 Ans. The curve of expanding gas that loses no heat 
 while expanding. 
 
 384. What is an isothermal curve? 
 
 Ans. The curve of an expanding gas of constant tem- 
 perature, but influenced by moisture. 
 
 385. What is an expansion curve? 
 
 Ans. The curve traced upon the diagram by the indi- 
 cator pencil. 
 
 386. Define the first law of thermodynamics. 
 
 Ans. Heat and mechanical energy are mutually con- 
 vertible. 
 
 387. What is power? 
 
 Ans. The rate of doing work. 
 
 388. What is the unit of work? 
 
 Ans. The foot pound, viz., the raising of one pound, 
 one foot high. 
 
 389. Define the first law of motion? 
 
 Ans. All bodies continue either in a state of rest, or of 
 uniform motion in a straight line, uniecs compelled by im- 
 pressed forces to change that state. 
 
 390. What is work, mechanically considered? 
 Ans. Pressure X distance passed throughXtime. 
 
 391. What is momentum? 
 Ans. Mass X density. 
 
 392. What is dynamics? 
 
 Ans. The science of moving powers. 
 
 393. What is force? 
 
 Ans. That which alters the motion of a body, or puts 
 in motion a body that was at rest. 
 
 394. Define the maximum theoretical duty of steam? 
 Ans. Mechanical equivalent of heat X total heat units 
 
 in a pound of steam? 
 
Questions and Answers 461 
 
 395. How may steam efficiency be expressed? 
 
 Ans. Heat converted into useful work-=-heat expended. 
 
 396. How may engine efficiency be expressed? 
 
 Ans. Heat converted into useful work-i-total heat re- 
 ceived in the steam. 
 
 397. How may efficiency of the plant be expressed? 
 Ans. Heat converted into useful work-f-calorific, or heat 
 
 value of the fuel. 
 
 398. What is horse power constant? 
 
 Ans. The power the engine would develop with one 
 pound M. E. P. 
 
 399. What is meant by steam consumption per H. P. 
 per hour? 
 
 Ans. Weight in pounds of steam used-f-H. P. developed ? 
 
 400. What are ordinates as applied to indicator dia- 
 grams ? 
 
 Ans. Parallel lines drawn at equal distances across the 
 face of the diagram, perpendicular to atmospheric line, 
 
The Indicator 
 
 One of the greatest aids to the economical operation of 
 the steam engine is the indicator, and it is the privilege of 
 every engineer to have at least an elementary, if not a 
 thorough knowledge of its principles and working. The 
 time devoted to the study of the indicator, and in its appli- 
 cation to the engine, is time well spent, and in the end will 
 well repay the student of steam engineering. 
 
 Inventor. The indicator was invented, and first applied 
 to the steam engine by James Watt, whose restless genius 
 was not satisfied with a mere outside view of his engine as 
 it was running, but he desired to know more about the 
 action of the steam in the cylinder, its pressure at different 
 portions of the stroke, the laws governing its expansion 
 after being cut off, etc. Watt's indicator, although crude 
 in its design and construction, contained embodied within 
 it all of the principles of the modern instrument. 
 
 Principles. These principles are: 
 
 First. The pressure of the steam in the engine cylinder 
 throughout an entire revolution, against a small piston in 
 the cylinder of the indicator, which in turn is controlled 
 or resisted in its movement by a spring of known tension, 
 so as to confine the stroke of the indicator piston within a 
 certain small limit. 
 
 Second. The stroke of the indicator piston is communi- 
 cated by a multiplying mechanism of levers and parallel 
 motion to a pencil moving in a straight line. The distance 
 through which the pencil moves being governed by the 
 
 463 
 
464 Steam Engineering 
 
 pressure in the engine cylinder and the tension of the 
 spring. 
 
 Third. By the intervention of a reducing mechanism 
 and a strong cord, the motion of the piston of the engine 
 throughout an entire revolution is communicated to a small 
 drum attached to, and forming a part of the indicator. The 
 movement of the drum is rotative, and in a direction at 
 right angles to the movement of the pencil. The forward 
 stroke of the engine piston causes the drum to rotate through 
 part of a revolution and at the same time a clock spring 
 connected within the drum is wound up. On the return 
 stroke the motion of the drum is reversed, and the tension 
 of the spring returns the drum to its original position and 
 also keeps the cord taut. 
 
 To the outside of the drum a piece of blank paper of 
 suitable size is attached and held in place by two clips. 
 Upon this paper the pencil in its motion up and down 
 traces a complete diagram of the pressures and other in- 
 teresting events transpiring within the engine cylinder dur- 
 ing the revolution of the engine. In fact the diagram 
 traced upon the paper is the compound result of two con- 
 current movements. First, that of the pencil caused by the 
 pressure of the steam against the indicator piston; second, 
 that of the paper drum caused by, and coincident with, the 
 motion of the engine piston. The upper end of the indica- 
 tor cylinder is always open to the atmosphere, the steam 
 acting only upon the underside of the small piston, and 
 when the cock connecting the cylinders of the engine and 
 indicator is closed, both ends of the indicator cylinder are 
 open to atmospheric pressure, and the pencil then stands 
 at its neutral position. If now the pencil is held against 
 the paper and the drum rotated either by hand or by con- 
 
The Judical or 
 
 465 
 
 necting it with the cord, a horizontal line will be traced. 
 This line is called the atmospheric line, meaning the line 
 of atmospheric pressure, and it is a very important factor 
 in the study of the diagram. 
 
 Fig. 161 
 sectional view crosby indicator 
 
 Figure 161 shows a sectional elevation of the Crosby 
 indicator, and will give the student a good idea of its in- 
 terior construction. Figure 162 shows the spring. 
 
466 Steam Engineering 
 
 If the engine is a non-condensing engine the pencil in 
 tracing the diagram will, or at least, should not fall below 
 the atmospheric line at any point, but will on the return 
 stroke trace a line called the line of back pressure at a dis- 
 tance more or less above the atmospheric line and very 
 nearly parallel with it. If the engine is a condensing en- 
 gine the pencil will drop below the atmospheric line while 
 tracing the line of back pressure on the diagram, and the 
 
 Fig. 162 
 crosby indicator spring 
 
 distance this line is below the atmospheric line will depend 
 upon the number of inches of vacuum in the condenser. 
 
 As before stated, the length of stroke of the indicator 
 piston, and the pencil movement as well is controlled by a 
 spiral steel spring which acts in resistance to the pressure 
 of the steam. These springs are made of different tensions 
 in order to be suitable to different steam pressures and 
 speeds, and are numbered 20, 40, 60, etc., the number 
 meaning that a pressure per square inqh in the engine 
 
The Indicator 
 
 467 
 
 cylinder corresponding to the number on the spring will 
 cause a vertical movement of the pencil through a distance 
 
 Fig. 163 
 
 improved tabor indicator with outside connected spring 
 
 Ashcroft Mfg. Co., N. Y. 
 
 of one inch. Thus, if a number 20 spring is used and the 
 pressure in the cylinder at the commencement of the stroke 
 
468 Steam Engineering 
 
 is 20 lbs. per square inch, the pencil will be raised one 
 inch, or if the pressure is 30 lbs., the pencil will travel 1% 
 in., and if there is a vacuum of 20 in. in the condenser, 
 the pencil will drop y 2 in. below the atmospheric line for 
 the reason that 20 in. of vacuum corresponds to a pressure 
 of about 10 lbs. less than atmospheric pressure or an abso- 
 lute pressure of about 4 lbs. If a 60 spring is used a pres- 
 sure of 60 lbs. in the engine cylinder will be required to 
 raise it one inch, or 90 lbs. to raise it l 1 /^ inches. Figure 
 163 shows the" Tabor indicator, with outside connected 
 spring. The spring is placed on top of the small cylinder, 
 which arrangement removes it from the influence of the heat 
 of the steam in the cylinder, and leaves it subject only to 
 the temperature of the surrounding atmosphere. It is 
 claimed that as a result of this, the accuracy of the spring 
 is insured, and that no allowance need to be made in its 
 manufacture for expansion caused by the high temperature 
 to which it is subject when located within the cylinder. 
 Another good feature of this design is, that the spring can 
 be easily removed without disconnecting any one part of 
 the instrument in case it is desired to change springs. 
 
 Figure 164 shows a view of the American indicator with 
 outside connected spring. 
 
 The spring remains cool and can be changed without 
 removing the piston or allowing the indicator to cool. It 
 is in line with the piston, and is supported by two standards 
 connected at the top by a cross bar, having a screw for at- 
 taching the upper end of the spring. The lower end is 
 connected to the top of the piston. The piston rod and 
 connections are made hollow and as light as possible to pre- 
 vent error from the inertia of the moving parts. 
 
 To remove the spring, unscrew the nurled nut at the top 
 until the end of the spring is released, and turn the spring 
 
The Indicator 
 
 46? 
 
 Fig. 164 
 american outside spring indicator 
 
470 Steam Engineering 
 
 until it is free from the base. To prevent the piston from 
 turning while removing the spring, insert a steel pin, fur- 
 nished with the indicator, in holes in the spring base. 
 
 Figure 165 shows the three-way cock for attaching the 
 indicator to the cylinder of the engine. 
 
 Reducing Mechanism. Probably the only practically 
 universal mechanism for reducing the motion of the cross- 
 head is the reducing wheel, a device in which, by the em- 
 ployment of gears and pulleys of different diameters, the 
 
 Fig. 165 
 
 motion is reduced to within the compass of the drum, and 
 the device is applicable to almost any make of engine, 
 whether of high or low speed. Some makers of indicators 
 attach the reducing wheel directly to the indicator, thus 
 producing a neat and very convenient arrangement. 
 
 Figure 166 illustrates a Crosby reducing wheel with the 
 indicator mounted in place. The reducing motion is en- 
 tirely distinct from the indicator, and terminates at the 
 bottom with a swivel joint by which it is attached to the 
 indicator cock. On top, the arm of the reducing motion 
 
The Indicator 
 
 471 
 
 is finished to receive the swivel joint of the indicator itself, 
 which is attached, as shown in the figure, in such a position 
 
 Fig. 166 
 crosby indicator and reducing motion assembled 
 
 that the cord pulley of the indicator drum is directly over 
 the small sheave about which the cord from the paper 
 barrel is passed. Fig. 167 shows this position to better ad- 
 
472 
 
 Steam Engineering 
 
 vantage. The principal object sought and attained by 
 this design and arrangement of reducing wheel and indi- 
 cator is rigidity. As the wheel or its frame does not de- 
 pend from the indicator proper, the strength of the com- 
 bination is good. The pull of the cross-head is resisted and 
 
 Fig. 1C7 
 
 the cord is returned by the helical spring A, Fig. 168, con- 
 tained in the horizontal spring case B. Adjustment of this 
 spring is made by the milled head which closes the outer 
 end of the case and carries one end of the spring. This 
 head slips over the squared end of the horizontal shaft D, 
 
The Indicator 
 
 473 
 
 and is secured in place by the thumb screw E. The shaft 
 is carried on ball bearings F and G in the frame H, and 
 
 l yrtVrtfr&rt*^^ 
 
 £L 
 
 K3«***WK*gg3gC 
 
 Je$° 
 
 Fig. 168 
 sectional view of crosby reducing motion 
 
 the web and gear I of the small sheave are a part of the 
 horizontal shaft. On this small sheave are the bushings J 
 
474 Steam Engineering 
 
 which are taken ofi or added to, to get the proper ratio of 
 motion for the paper drum. The bushings are held in place 
 by a flange K, and thumb screw L. 
 
 The main frame H is a casting, and from it depends the 
 vertical shaft M, upon which revolves the sleeve 1ST carrying 
 the smaller of the bevel gears and the cord-receiving sheave 
 0. Beneath the large sheave and turning therewith is a 
 screw engaging with the cross-head P which carries the 
 cord guide Q. The cross-head is prevented from turning by 
 two guide pins E and S, upon which it slides, and these 
 pins are supported by a plate T at the bottom of the vertical 
 shaft. This plate is secured by an hexagonal nut U. The 
 arm carrying the cord guide is clamped around the cross- 
 head, and may be turned to lead in any direction. Above 
 the bottom plate T is a stiff four-leaved spring V to receive 
 the cross-head without shock in case it is allowed to run 
 way down, as it would by the breakage of the cord. 
 
 When ready to use the reducing motion, first mount the 
 wheel frame on the indicator cock, and the indicator on the 
 frame, as shown in Figs. 166 and 167. Then, after deter- 
 mining the size of bushing to go on the small sheave, put 
 it in place and secure it under the flange K with the nut L. 
 Pass the cord from the paper drum once around the small 
 sheave, slipping the end through the hole in the flange and 
 securing it to the cleat thereon. Be sure that there is 
 enough cord on the large sheave to accommodate the long- 
 est engine stroke for which the wheel will be used. Then 
 pass the end through the guide pulley Q and there fasten 
 it to resist the tension of the spring, leaving enough more 
 cord to reach the cross-head of the engine. The cross-head 
 P of the reducing motion must be just low enough for the 
 guide pulley to lead the cord from the bottom flange of the 
 
The Indicator 
 
 475 
 
 large sheave, as shown in Fig. 166. Then the cord from the 
 paper drum must be brought down and around the small 
 sheave to the hole in the flange, so that while the motion 
 is at rest, as in Fig. 166, it will pass around the sheave, in 
 the direction of its travel, far enough to pass over the cir- 
 cumference of the bushing on the sheave. Before fasten- 
 ing to the cleat, the cord must be drawn taut, so that the 
 paper drum will have just left its rest stop. 
 
 Fig. 169 
 
 , To alter the tension on the recoil spring of this reducing 
 motion, remove the nut E, and grasping the milled head 
 C between the thumb and forefinger, pull it from the case 
 far enough to allow it to be turned. Then twist it to the 
 right, if more tension is desired, and allow it to slide onto 
 the square end of the horizontal shaft again and replace the 
 nut. To reduce the tension of the spring, allow the milled 
 head to fall back to the left. 
 
476 
 
 Steam Engineering 
 
 If at any time the horizontal shaft D appears to be loose 
 in its bearings and needs adjustment, remove nut E, grasp 
 the head W in the fingers and back it off from its place. 
 This will carry the spring, case and milled head from their 
 positions and expose the adjustment X and its lock nut Y. 
 Back off the lock nut and adjust the bearings with the other 
 nut, after which lock the two nuts together again. Always 
 try the bearings again after setting up on the lock nut. 
 
 Fig. 170 
 
 One of the most accurate and easily applied devices for 
 reducing the motion of the piston is the wooden pendulum 
 in its various forms. (See Figs. 169, 170 and 171.) It 
 consists of a flat strip of pine or other light wood of a 
 length not less than one and a half times the stroke of the 
 engine, and if made longer it will be better. It should be 
 from % to % in. thick and have an average width of about 
 4 in. If the engine to be indicated is horizontal the bar or 
 
The Indicator 
 
 477 
 
 pendulum is to be pivoted at a fixed point directly above, and 
 in line with the side of the crosshead, as that is generally 
 the most convenient point of attachment. The pivot can 
 be fixed to a permanent standard bolted to the frame of 
 the engine, or it may be secured to the ceiling of the room 
 or even to a post fastened to the floor. If the engine is 
 vertical the bar can be pivoted to the wall of the room, 
 or a strong post firmly secured to the floor. The con- 
 
 Fig. 171 
 
 nection with the crosshead is best accomplished by means 
 of a short bar or link. A convenient length for this bar is 
 one-half the stroke of the engine. To locate the correct 
 point for the pivot, assuming the length of the short bar 
 to be one-half the length of the stroke, proceed as follows : 
 Place the engine on the center with the crosshead at the 
 end of the stroke towards the crank. Then having pre- 
 viously bored a hole for the pivot in one end of the pendu- 
 
478 
 
 Steam Engineering 
 
 him bar, and in the other end a hole for connecting with 
 the link, suspend the pendulum by a temporary pin, as a 
 large wood screw, directly above and in line with the stud 
 or bolt hole which has previously been tapped into the 
 crosshead at any convenient point. The pendulum should 
 be temporarily suspended at such a height that when it 
 hangs perpendicular the hole in its lower end will line up 
 accurately with the hole or stud in the crosshead. Now 
 swing the pendulum in either direction a distance equal to 
 
 Fig. 172 
 
 the length of the link (one-half the stroke of the engine) 
 from the crosshead connection and note the distance that 
 the bottom hole is above a straight edge laid horizontal 
 and in line with the center of the stud in the crosshead. 
 This will give the total vibration of the free end of the link 
 from a line parallel with the line of the engine, and the 
 permanent location of the pivot should be one-half of this 
 distance below the temporary point of suspension. This 
 
The Indicator 479 
 
 will allow the link to vibrate equally above and below the 
 center of its connection with the crosshead. Fig. 172 shows 
 a complete connection of this character. 
 
 Sometimes the end is slotted and thus directly connected 
 to the stud in the crosshead, dispensing with the link. In 
 this case it is necessary to locate the pivot at a point per- 
 pendicular to the center of travel of the stud in the cross- 
 head. (See Fig. 169.) The link connection is to be pre- 
 ferred, however. The cord can be attached to the pendulum 
 at a point near the pivot which will give the desired length 
 of diagram. This point can be determined by multiplying 
 the length of the pendulum by the desired length of dia- 
 gram and dividing the product by the stroke. For con- 
 venience these terms should be expressed in inches. Thus, 
 assume stroke of engine to be 48 in., length of pendulum 
 iy 2 times length of stroke=72 in. Desired length of dia- 
 gram 3 in. Then 72X3-^-48=4.5 in., which is the distance 
 from center of pivot to point of connection for the cord. 
 This can be either a small hole bored through the pendulum, 
 or a wood screw to which the cord can be attached. From 
 this point the cord should be led over a guide pulley located 
 at such height that when the pendulum is vertical the cord 
 will leave it at right angles. After leaving the guide pulley 
 the cord can be carried at any angle desired. One of the 
 neatest and most easily applied devices for reducing the 
 motion of the crosshead is the pantograph. (See Fig. 173.) 
 No dimensions are essential except that it shall be made 
 reasonably strong of some light, tough variety of wood, 
 and that the pins and holes be nicely fitted to each other so 
 that while the movement may be free there shall at the 
 same time not be too much lost motion. The pantograph 
 should be of such capacity that it will just close up nicely 
 
 . 
 
480 
 
 Steam Engineering 
 
 when the engine is at mid stroke and open out nicely when 
 at its extreme travel. The two ends, C and D, are each to 
 be fitted with a pin extending through far enough so that 
 pin C can be hooked into a hole or socket on the crosshead, 
 while pin D rests in a socket in the top of a post secured 
 to the floor at a point opposite the center of travel of the 
 crosshead, and of such height as will allow the pantograph 
 to lie in a horizontal position. Also the distance of the post 
 from the guides must be adjusted so as to allow the device 
 
 Fig. 173 
 
 to close up at mid stroke, and open out at full stroke with- 
 out any straining of the parts. The point F of connection 
 for the cord will always have a motion parallel with, and 
 simultaneous with, that of the crosshead ; the pin to which 
 the cord is attached can be set in any one of the holes that 
 will give the desired length for the diagram. The motion 
 given by this device is accurate, although it may become 
 necessary in some cases, especially with long stroke engines, 
 to introduce a guide pulley to carry the cord from the 
 pantograph. 
 
The Indicator 481 
 
 Attaching the Indicator. The cylinders of most engines 
 at the present time are drilled and tapped for indicator 
 connections before they leave the shop, which is eminently 
 proper, as no engine builder, or purchaser either, should 
 be satisfied with the performance of a new engine until 
 after it has been accurately tested and adjusted with the 
 indicator. 
 
 The main requirements in these connections are that the 
 holes shall not be drilled near the bottom of the cylinder 
 where water is likely to find its way into the pipes, neither 
 should they be in a location where the inrush of steam 
 from the ports will strike them directly, nor where the 
 edge of the piston is liable to partly cover them when at 
 its extreme travel. An engineer before he undertakes to 
 indicate an engine should satisfy himself that all these 
 requirements are fulfilled. Otherwise he is not likely to 
 obtain a true diagram. The cock supplied with the indicator 
 is threaded for one-half inch pipe, and unless the engine 
 has a very long stroke it is the practice to bring the two 
 end connections together at the side or top of the cylinder, 
 and at or near the middle of its length, where they can be 
 connected to a three way cock. The pipe connections 
 should be as short and as free from elbows as possible in 
 order that the steam may strike the indicator piston as 
 nearly as possible at the same moment that it acts upon 
 the engine piston. 
 
 The work of taking diagrams is very much simplified 
 by having both ends of the cylinder connected to one com- 
 mon tee or a three way cock as above described, but for 
 long stroke engines there should be two indicators, one for 
 each end and the diagrams should be taken simultaneously 
 if it is desired to adjust the valves by the indicator. In 
 
482 Steam Engineering 
 
 this case an assistant would be required to manipulate one 
 of the instruments. 
 
 The pipes should always be thoroughly blown out by 
 allowing the steam to blow through the open cock during 
 several revolutions of the engine, before connecting the 
 indicator. If this is not done there is a moral certainty 
 that grit and dirt will get into the cylinder of the indicator, 
 where the presence of the least atom of grit will cause the 
 delicate instrument to work badly. 
 
 Selecting a Spring. The proper number of spring to 
 use depends upon the boiler pressure in the case of an auto- 
 matic cut off engine, but for an engine with a fixed cut off 
 and throttling governor the number of the spring to be 
 selected will depend upon the initial pressure in the cylinder. 
 A convenient rule is to select a spring numbered one-half 
 as high as the pressure; for instance, if the boiler pressure 
 is 80 lbs., use a Xo. 40 spring, which will give a diagram 
 2 in. in height. 
 
 Care of the Instrument. The indicator should be cleaned 
 and oiled both before and after using. The best material 
 for wiping it is a clean piece of old soft muslin of fine 
 texture, as there is not so much liability of lint sticking to 
 or getting into the small joints. Use good clock oil for the 
 joints and springs, and before taking diagrams it is a good 
 practice to rub a small portion of cylinder oil on the piston 
 and the inside of the cylinder, but when about to put the 
 instrument away these should be oiled with clock oil also. 
 None but the best cord should be used for connecting the 
 paper drum with the reducing motion, as a cord that is 
 liable to stretch will cause trouble. Suitable cord and also 
 blank diagrams can generally be secured from firms manu- 
 facturing and selling indicators. After the indicator has 
 
The Indicator 483 
 
 been screwed on to the cock connecting with the pipe, the 
 cord must be adjusted to the proper length before hooking 
 it on to the drum. This must be done while the engine is 
 running, by taking hold of the loop on the cord connected 
 with the reducing motion with one hand, and with the 
 other hand grasp the hook on the short cord attached to 
 the drum, then by holding the two ends near each other 
 during a revolution or two it will be seen whether the long 
 cord needs to be shortened or lengthened. 
 
 The length of the diagram is determined by the point 
 of connection of the cord to the pendulum as has been 
 heretofore explained. Care should be exercised in placing 
 the paper on the drum, to see that it is stretched tight and 
 firmly held by the clips. The pencil point having been 
 first sharpened by rubbing it on a piece of fine emery cloth 
 or sand paper should be adjusted by means of the pencil 
 stop with which all indicators should be provided, so that 
 it will have just sufficient bearing against the paper to 
 make a fine, plain mark. If the pencil bears too hard on 
 the paper it will cause unnecessary friction and the diagram 
 will be distorted. The best method of ascertaining this fact 
 and also whether the travel of the drum is equally divided 
 between the stops, is to place a blank diagram on the drum, 
 connect the cord and while the engine makes a revolution 
 hold the pencil against the paper. Then unhook the cord, 
 remove the paper and if the travel of the drum is not di- 
 vided correctly it can be changed. 
 
 Having thus arranged all the preliminary details, place 
 a fresh blank on the drum, being careful to keep the pencil 
 out of contact with it, connect the cord, open the cock ad- 
 mitting steam to the indicator and after the pencil has 
 made a few strokes to allow the cylinder to become warmed 
 
484 Steam Engineering 
 
 up, then gently swing it around to the paper drum and 
 hold it there while the engine makes a complete revolution. 
 Then move the pencil clear of the paper, close the cock 
 and unhook the cord. Now trace the atmospheric line by 
 holding the pencil against the paper while the drum is 
 revolved by hand. This method of tracing the atmospheric 
 line is preferable to that of tracing it immediately after 
 closing the cock and while the drum is still being moved 
 by the engine, for the reason that there is not so much 
 liability of getting the atmospheric line too high owing to 
 the presence of a slight pressure of steam remaining under 
 the indicator piston for a second or two just after closing 
 the cock; also the line drawn by hand will be longer than 
 one drawn while the drum is moved by the motion of the 
 engine, and will therefore be more readily distinguished 
 from the line of back pressure. 
 
 Having secured a truthful diagram, it now remains to 
 take as many as are desired, and if the object is to set the 
 valves of the engine, the diagrams from each end of the 
 cylinder should follow each other as quickly as possible in 
 order that the conditions of load and steam pressure may 
 be the same. When the indicator is connected so that dia- 
 grams can be taken from both ends without changing it, 
 the above conditions can generally be realized. But if 
 diagrams can only be taken from one end at a time, the 
 only way to arrive at correct conclusions in relation to the 
 adjustment of the valves will be to see that the boiler pres- 
 sure is practically the same at the time of taking diagrams 
 from either end and that the position of the governor is 
 also the same, assuming that the load on the engine is 
 practically constant. This applies of course to an auto- 
 matic cut off. 
 
The Indicator 
 
 485 
 
 As soon as the diagrams are taken the following data 
 should be noted upon them: The end of the cylinder, 
 whether head or crank; boiler pressure; and time when 
 taken. Other data can be added afterwards. If the engine 
 is an automatic cut off of the Corliss type, and the point of 
 cut off on one end does not coincide with the other, the 
 difference can generally be adjusted while the engine is 
 running by changing the length of the rods extending 
 from the governor to the tripping device. These rods are, 
 or should be, fitted with right and left threads on the ends 
 for this purpose. Any changes in the valves, such as giv- 
 ing them more lead, compression, etc., and which neces- 
 sitates changing the length of the reach rods connecting 
 them with the wrist plate, will have to be made while the 
 engine is stopped, although with slow speed engines and 
 the exercise of caution it is possible to make alterations in 
 these rods while the engine is running. 
 
 DIAGRAM ANALYSIS. 
 
 Before proceeding to the study of indicator diagrams, it 
 is well to define the different points, lines and curves of a 
 
 Fig. 174 
 
 diagram in order that the young student may get these 
 matters firmly fixed in his mind, and that there may be 
 no confusion. 
 
486 Steam Engineering 
 
 Eef erring to Fig. 174, from C to B is the compression 
 curve, which in this particular diagram is somewhat lighter 
 than is ordinarily given to engines. This is due to the fact 
 that the engine from which Fig. 174 was taken is of slow 
 speed and long stroke, and therefore does not require as 
 heavy a cushion as does a high speed, short stroke engine,, 
 
 From B to D is the admission line, which being practi- 
 cally perpendicular to the atmospheric line A, shows suffi- 
 cient lead and ample port area. From D to E is the steam 
 line. Cut oflE occurs at E, and from E to F is the expansion 
 curve. At F the point of release is quite sharply defined, 
 as it should be. From F to Gr is the exhaust line, and from 
 G to C the line of back pressure, sometimes called the line 
 of counter pressure for the reason that the pressure indi- 
 cated by it acts counter or in opposition to the forward 
 pressure of the steam on the piston. This engine is a 
 simple condensing engine, and the nearness of the back 
 pressure line to the line of perfect vacuum V shows that an 
 excellent vacuum was maintained in the condenser. 
 
 It should be noted that all of the diagrams referred to 
 in the following pages are reproductions of actual diagrams 
 taken under ordinary working conditions. Figs. 175, 176 
 and 177 are reproductions of diagrams taken from a Cooper 
 Corliss non condensing engine. 
 
 The dimensions of the engine are as follows : Diameter 
 of piston, 34 in. ; length of stroke, 42 in. 
 
 At the time Fig. 175 was taken the boiler pressure was 
 105 lbs., but it was increased a few months later to 110 lbs., 
 as was the load also, when Figs. 176 and 177 were taken. 
 
 These diagrams are fairly good working cards, but there 
 are some defects which it might be well to point out. 
 
 Eef erring to Fig. 175, it will be noticed that the initial 
 pressure at s, on the head end, is 94 lbs., while on the crank 
 
Diagram Analysis 
 
 487 
 
 end the initial pressure runs up to 99 lbs. above the atmos- 
 pheric line. 
 
 Fig. 175 
 
 This decrepancy is caused by insufficient lead on the 
 head end, plainly shown by the inclination inward of the 
 admission line, and the rounded corner at s. 
 
488 
 
 Steam Engineering 
 
 The compression is excessive, especially on the head end, 
 as indicated by the curve at L. 
 
 < ^ 
 
 These two factors, lead and compression, may always be 
 distinguished by observing the character of the admission 
 line. 
 
 L 
 
Diagram Analysis 
 
 489 
 
 
 Fig. 177 
 
 
 A curve, such as shown at L, denotes too early closure 
 of the exhaust, and the rounded corner at % and inward 
 
490 Steam Engineering 
 
 inclination of the admission line from 1 to s is a pretty sure 
 indication that the steam lead is not sufficient. 
 
 The diagram from the crank end is much better, although 
 there is more compression than is needed. 
 
 The cut-off is not equalized, that on the crank end takes 
 place earlier in the stroke than the same event does on the 
 head end, and the consequence is that the M. E. P. for the 
 head end is 60.4 lbs. while the M. E. P. for the crank end 
 is 54.4 lbs. (see Pig. 177), a difference of 6 lbs. more 
 pressure per square inch being exerted against the piston 
 as it travels from the head end of the cylinder, than there 
 is exerted against it as it travels from the crank end, and 
 this unequal strain, or push is felt by the moving parts 
 of the engine 160 times a minute, the engine making 80 
 E. P. M. 
 
 It is unnecessary to again emphasize the need of care 
 and good judgment in the adjustment and equalizing of the 
 points of cut off. On an engine, a very simple calculation 
 will be sufficient. 
 
 The diameter of the piston under consideration is 34 in., 
 area 907.92 sq. in., pressure per sq. in. 6 lbs. Then 907.92 
 X6=5447.52 lbs., which divided by 2,000=2.72 tons more 
 pressure against the piston when traveling from the head 
 end, than there is on the return stroke. 
 
 Figure 176 is a much better appearing diagram, the lead 
 on the head end having been slightly increased, thus practi- 
 cally equalizing the initial pressure, and improving the 
 rounded corner at s. 
 
 The variation in the points of cut off at c. o. still exists, 
 and the compression is still too great. 
 
 As before stated, the three diagrams shown are all from 
 the same engine and figure 177 is introduced for the pur- 
 
Diagram Analysis 491 
 
 pose of illustrating the method of obtaining the M. E. P. 
 by the use of ordinates, as they are termed, they being the 
 vertical lines, drawn in order to facilitate the measurement 
 of the pressures shown by the steam line, and expansion 
 curve above the line of atmospheric pressure, or if the en- 
 gine is a condensing engine these measurements must be 
 made from the vacuum line, as drawn by the indicator 
 pencil. 
 
 The first requisite in this process is to correctly draw 
 these ordinates, spacing them equidistant apart. 
 
 First draw lines 1 and 2 at each end of the diagram, and 
 perpendicular to the atmospheric line. 
 
 Then measure the distance between these two lines, and 
 this distance, whatever it may be, should be divided into 
 ten equal spaces, although it is not absolutely necessary 
 that there should be ten spaces, as any other number of 
 spaces w T ill serve, provided they are of equal width. 
 
 Ten is usually chosen, owing to the fact that this num- 
 ber is the most convenient to use in calculations. 
 
 In Fig. 177 the distance across the face of the diagram 
 from line 1 to line 2 is found to be nearly 3^f in. or 63 
 sixteenths, which divided by 10 equals a little more than 6 
 sixteenths or % in. 
 
 Therefore the width of the spaces will be % in. and the 
 vertical lines should be drawn that distance apart. 
 
 Having drawn the lines, the next step is to measure the 
 pressure by using the scale corresponding to the spring 
 that was used. These different scales 40, 50, 60, 80, etc. 
 are supplied by the makers of the indicator, and should ac- 
 company each outfit. 
 
 Again referring to Fig. 177, beginning at the head end, 
 lay the scale along the middle of the first space with the 
 
 J 
 
492 Steam Engineering 
 
 zero mark on the compression curve, and the pressure from 
 c to s is found to be 64 lbs. 
 
 This is the effective pressure exerted against the piston 
 at this point in the stroke notwithstanding the fact that the 
 boiler pressure was 110 lbs. 
 
 Eight here the query might arise, why this decrease in 
 pressure ? and it might be well to explain the cause of it. 
 
 The actual work area of the diagram is only that portion 
 confined within its own boundary lines as traced by the 
 pencil when in motion. The lines of atmospheric pressure, 
 and vacuum are traced by hand, and their purpose is to 
 facilitate measurements only. 
 
 Therefore the pressure can only be measured from points 
 c and s in the two spaces at the beginning of the stroke. 
 
 It is evident therefore that too much compression, or too 
 much lead tends to lessen the work area of the diagram at 
 the beginning of the stroke, thus placing a limit on the 
 capacity of the engine for doing work. 
 
 Measurements for pressure on the remaining spaces of 
 Fig. 177 may be made from the atmospheric line, except 
 that when measuring the diagrams from the crank end the 
 same rule governs the measurement of the pressure in the 
 space at the beginning of the stroke, viz., measure from the 
 compression curve, c, to the steam line s. The pressure in 
 this case is found to be 67 lbs. 
 
 In space two (crank end) the pressure measured from 
 the atmospheric line is found to be 96 lbs., and on the head 
 end it is 95 lbs. 
 
 After all the ten spaces have been measured, say from 
 the head end, and the results added together, it is found 
 that the total is 604, which divided by 10 equals 60.4 lbs., 
 which is the M. E. P. for that end. 
 
Diagram Analysis ■ 493 
 
 Proceeding in the same manner with the crank end the 
 M. E. P. is found to be 54.4 lbs. 
 
 The cause of this difference of 6 lbs. between the two 
 diagrams, and its effect upon the engine has already been 
 explained. 
 
 In order to obtain the average M. E. P. it is necessary to 
 add the two results together and divide the sum by 2, thus : 
 60.4+54.4-^2=57.4 lbs. 
 
 Before proceeding to calculate the H. P. there is another 
 factor to be considered, viz., the back pressure, which is 
 always present in a greater or less degree, and which in 
 Fig. 177 is found to be 4 lbs.; ascertained by measuring 
 with the scale the distance from the atmospheric line to 
 the line of back pressure, B. P. 
 
 This 4 lbs. is to be deducted from the average M. E. P. ; 
 thus 57.4 — 4=53.4 lbs., which is the net pressure for power 
 calculations. 
 
 It should be noted that the number of the spring used 
 on Fig. 177 was 60. 
 
 The process of ascertaining the M. E. P. by ordinates, 
 and also by the use of the planimeter will be enlarged upon 
 later on in this discussion. 
 
 Great care should be exercised in these calculations, es- 
 pecially in taking measurements of the pressure by the use 
 of ordinates, on diagrams taken from engines using steam 
 of high initial pressure, 150 to 250 lbs. per sq. in., where 
 springs of high tension (80 to 125 lbs.) are required. 
 
 The lines on such scales are so close together, and the 
 figures are so small, that it is very difficult to distinguish 
 them. However, there are other and more simple methods 
 that can be used, and the results are just as accurate. 
 
494 
 
 Steam Engineering 
 
 Figures 178 and 179 are reproductions of diagrams 
 taken from a 14x30 in. engine, and are introduced for the 
 purpose of showing the need of care and good judgment 
 in the selection of a spring. 
 
 Fig. 178 
 
 -J/J 
 
 Fig. 179 
 
 The boiler pressure at the time the cards were taken was 
 90 lbs. per sq. in. but a 60 spring was used, when a much 
 better diagram might have been secured with a 50 spring. 
 
Diagram Analysis 495 
 
 The fluctuations in the steam lines S to C are caused 
 by the spring being of too high tension, and they are brought 
 about in the following manner. 
 
 Initial pressure is high enough at the beginning of the 
 stroke to run the admission line up to 82 lbs. on the head 
 end of Fig. 178 and to 78 lbs. on the crank end, but the high 
 tension of the 60 spring immediately causes the indicator 
 piston to drop slightly, and remain so until about l-12th 
 of the stroke is completed, when the steam pressure slowly 
 overcomes the tension of the spring, and the pencil again 
 slowly rises, and remains steady until cut off occurs. 
 
 The same defect appears in Fig. 179 taken from this 
 engine running with a somewhat lighter load. 
 
 The engine is 14x30 in. running at a speed of 100 E. P. 
 M. The exhaust steam passes through heating coils in a 
 dry kiln,, which accounts for the high back pressure lines 
 on the diagrams. 
 
 Aside from the above mentioned defects the diagrams 
 are good. The valves appear to be properly adjusted for 
 compression, lead, and cut off, these events all occurring in 
 their regular order. 
 
 Unequal cut of. The unequal division of forces, or 
 pressures acting alternately upon the piston of a steam en- 
 gine, to propel it back and forth, may be likened, in a 
 measure, to two men working a ratchet drill, or pumping 
 a hand car. 
 
 If one of the men is a small, weak man and his partner 
 is a big strong-armed man, the result will be that the big 
 man will do most of the work, even though the small man 
 may be willing enough, and does all that he is able to do. 
 
 With an engine, this unequal division of pressures, in 
 other words, unequal cut off, may be easily remedied through 
 the instrumentality of the indicator. 
 
496 
 
 Steam Engineering' 
 
 The bad effects of unequal cut off will make themselves 
 felt, and heard also in time. The engine will not develop 
 the power that it is capable of developing, the coal con- 
 sumption per H. P. per hour will be greater than it should 
 be, and it will be a much harder task to keep the engine 
 running smoothly under such conditions than it would be 
 if the cut off was equalized, and the mean effective pres- 
 sures were the same or nearlv so for each stroke. 
 
 Fig. ISO 
 
 Figure 180 is a reproduction of a diagram taken from a 
 Corliss engine 30 in. bore by 48 in. stroke, running 82 
 B. P. M. 
 
 One of the minor defects of the diagram is that it occu- 
 pies too much space, meaning that it is too high, and too 
 long. The fault in height is caused by using too light a 
 spring in the indicator, allowing the indicator piston to 
 rise too high. 
 
 The boiler pressure at the time the cards were taken was 
 120 lbs., but the spring used was a 50 lbs. spring, when it 
 should have been a 60 lb. 
 
Diagram Analysis 497 
 
 The spring, or scale as it is often designated, should be 
 selected in accordance with the boiler, or gauge pressure. 
 
 For instance, if the gauge pressure is 120 lbs. a 60 spring 
 should be used. If the gauge pressure is 90 or 100 lbs. 
 a 50 spring is strong enough. 
 
 A good rule to observe in this matter is, to use a spring, 
 or scale of as nearly one-half the gauge pressure as it is 
 possible to get it. 
 
 The diagram will then be about 1% in. in height, which 
 is much more easily measured than one that is two inches 
 in height, such as Fig. 180 shows. 
 
 Of course it must be understood that these measure- 
 ments are to be made from the atmospheric line A. 
 
 The cause of the excessive length of the diagram is too 
 long a stroke of the reducing motion. This is easily 
 remedied also. 
 
 A convenient length for a diagram is from two to two 
 and a half inches. 
 
 The lead and compression lines shown at 1-1, Fig. 180, 
 are practically perfect. It is plain from these lines that 
 lead begins where compression lets go, which is as it should 
 be. 
 
 The admission lines 1 to 2 on both crank and head ends 
 are good also, and indicate prompt opening of the steam 
 ports. 
 
 The release at K' also shows good economy, and there is 
 practically no back pressure on the piston for either stroke. 
 
 But here is where our favorable criticism of Fig. 180 
 ends, except that we might say with reference to the ex- 
 pansion curve, 3 to R', of the crank end diagram, that it 
 compares favorably with the theoretical expansion curve. 
 
 The main trouble with the engine, as shown by the dia- 
 
498 
 
 Steam Engineering 
 
 gram is unequal cut off, that on the head end being con- 
 siderably later in the stroke than it should be, while cut off 
 on the crank end occurs a little too soon. 
 
 This is also shown by measurement of the mean effective 
 pressures, that on the crank end being 42.1 pounds while 
 that from the head end is 48.2 pounds, showing that there 
 is 48.2 minus 42.1 equals 6.1 pounds more M. E. P. on the 
 head end than on the crank end. 
 
 This means that the piston which is 30 inches in di- 
 ameter having an area of 706.86 square inches has 706. 86x 
 6.1 equals 4311.84 pounds more pressure exerted against 
 
 Fig. 181 
 
 its surface during the stroke from the head of the cylinder 
 than it has on the opposite stroke. 
 
 It also means that the strains are unequally divided so 
 far as regards the moving parts of the engine. The en- 
 gineer in charge reports that he has lots of trouble with his 
 engine in his efforts to keep it running quietly, but this is 
 to be expected considering the unequal cut offs, and the dif- 
 ference in the pressures upon the piston at each stroke. 
 
 The H. P. developed by the engine as indicated by Fig. 
 180 is 564.8. 
 
Diagram Analysis 
 
 499 
 
 Effects of Wire Drawing. Fig. 181 is from a Buckeye ; 
 automatic cut off engine having a shaft governor and, what 
 is termed a riding cut off, that is the cut off valve slides to 
 and fro on the back of the main valve. The engine is hor- 
 izontal non-condensing, the cylinder being 28 in. bore by 
 56 in. stroke, and, at the time the diagram was taken, de- 
 veloped 357.58 horse power with a piston speed of 728 ft. 
 per minute. The steam consumption per I. H. P. per hour 3 
 was 26 pounds, a rather high rate, but this was owing to 
 the fact that the engine was located too far from the boil-» 
 ers, and as there were a large number of elbows in the steam 
 
 Fig. 182 
 
 pipe the pressure was greatly reduced at the engine. Thus 
 wire drawing of the steam was caused, which is plainly in- 
 dicated by the downward inclination of the steam line, D E. 
 
 In a well proportioned engine having a steam pipe of 
 sufficiently large area, the steam line should parallel the 
 atmospheric line up to the point of cut off. Fig. 181 in- 
 dicates proper release of the steam at F, and the back pres- 
 sure from G to C, which is 3 pounds above the atmospheric 
 line, shows a reasonably free passage of the exhaust steam. 
 
 Figs. 182 to 187 illustrate diagrams from three new ver- 
 tical Corliss engines supplying power for an electric light- 
 ing plant, which the author was requested to test and ad- 
 
500 
 
 Steam Engineering 
 
 just after they had been in operation a few months. The 
 valves had previously been set by the erecting engineer at 
 the time the engines were set up. Each one of these en- 
 gines exhausted into a separate condenser of the Jet type, 
 into which the condensing water was forced under pressure, 
 and from which the overflow was discharged by gravity 
 into a sewer. There was no air pump and as a consequence 
 the vacuum maintained was very low, usually from 10 to 
 15 in., and at times still less, so that the beneficial results 
 of condensing were only partially realized. 
 
 Fig. 183 
 
 For convenience the diagrams from each engine will be 
 treated in numerical order, beginning with engine No. 1. 
 This engine was 24x48 inches, running 70 E. P. M., with 
 a boiler pressure of 68 pounds. A 40 spring was used in 
 the indicator. The principal defect was the lack of suffi- 
 cient lead on both ends, as indicated by the inclination in- 
 ward of the admission lines and the rounded corners of the 
 steam lines at the beginning of the stroke. (See Fig. 182.) 
 There was also more compression, especially on the bottom 
 end, than was necessary, considering the size of the engine, 
 and the speed. The necessary changes having been made, 
 the indicator was again applied and the diagram, Fig. 183, 
 
Diagram Analysis 501 
 
 was obtained, which shows the distribution of the steam to 
 be satisfactory, although at the time of taking this di- 
 agram the boiler pressure was only 60 pounds, while it 
 should have been 68 or 70 pounds, because with the latter 
 pressure still better results could have been attained. The 
 I. H. P. was 235 and the steam used per I. H. P. per hour 
 was 18 pounds. 
 
 Fig. 184 is the original diagram from engine No. 2, and 
 shows bad valve adjustment all around, with the exception 
 of lead on the top end. The variation in the points of 
 cut off is the worst feature; cut off taking place on the 
 bottom at 29 per cent, of the stroke, while on the top end 
 
 Fig. 184 
 
 it does not occur until the piston has traveled through 42 
 per cent, of the stroke. There is more compression also 
 than is needed. This engine was 18x42 inches, running 
 at a speed of 78 E. P. M., and the steam consumption, ac- 
 cording to diagram Fig. 184, was 33 lbs. per I. H. P. per 
 hour. Having equalized the cut off and reduced the com- 
 pression by making the necessary changes in the valve gear, 
 the indicator was again applied, resulting in diagram Fig. 
 185, which may be considered practically perfect. The 
 boiler pressure was 68 pounds and the spring used was a 
 No. 40. The steam consumption was reduced to 22 pounds 
 per I. H. P. per hour as compared to 33 lbs. in Fig. 184. 
 
 J 
 
502 
 
 Steam Engineering 
 
 Figs. 186 and 187 represent diagrams from engine No. 
 3, which was the same size as No. 1, viz., 24x48 in., and 
 running at 72 E. P. M. The original diagram, Fig. 186, 
 shows too little lead on both ends, but especially on the top. 
 There is also lack of compression on the bottom end. The 
 
 Fig. 185 
 
 boiler pressure was 60 pounds, and the scale of spring 40. 
 Fig. 187, taken after the necessary adjustments had been 
 made, shows much better valve performance. The horse 
 power developed was 251 and the steam consumption was 
 20.5 pounds per I. H. P. per hour. The rather high rate 
 
 Fig. 186 
 
 of steam consumption for this engine as compared with 
 engine No. 1, which was the same size but consumed only 
 18 pounds of steam per I. H. P. per hour, was due to two 
 causes. First, a low vacuum; second, low initial pressure 
 necessitating a late cut off. 
 
Diagram Analysis 
 
 503 
 
 Figs. 188 to 191 are reproductions of diagrams taken 
 from a new horizontal non-condensing engine which had 
 been running about eight or nine months when it fell to 
 the author's lot to apply the indicator to the engine, not 
 only for the purpose of adjusting the valve motion, but 
 
 Fig. 187 
 
 also to make a series of tests for the purpose of ascertaining 
 the amount of power delivered by the engine to each one of 
 several different departments which were receiving power 
 from this source. 
 
 Fig. 188 
 
 The dimensions of the engine were as follows: bore of 
 cylinder, 32 in.; stroke, 5 ft. At the time Fig. 188 was 
 taken the engine was making 62 E. P. M. and the boiler 
 pressure was only 50 pounds. A 30 spring was used. 
 Although the load on the engine was very light at the time, 
 
504 
 
 Steam Engineering 
 
 yet the diagram served as a guide to some extent in set- 
 ting the valves, and by taking off the bonnets from the 
 valve chests and making the necessary changes in the ad- 
 justment by the marks on the valves a pretty fair job was 
 
 Fig. 1S9 
 
 made of it, as will be seen by referring to Fig. 189. The 
 reducing motion was a pantograph, and as it is very easy 
 to vary the travel of the paper drum with this motion, 
 diagrams of different lengths were taken until the one which 
 
 Fig. 190 
 
 appeared to be the most satisfactory was obtained. The 
 slight hump in the expansion curve immediately after cut 
 off, was probably caused by a speck of dirt or grit which 
 momentarily checked the indicator piston on the down 
 
Diagram Analysis 
 
 505 
 
 stroke. The compression on the crank end is not sufficient 
 and the exhaust valve rod on that end was slightly length- 
 ened, resulting in the production of diagram Fig. 190. In 
 this diagram the familiar hump in the crank end expan- 
 sion curve reappears, but in a different location, being 
 nearer the end of the stroke. It will also be noticed that 
 the length of Fig. 190 has been considerably reduced from 
 that of Fig. 188, it being about one inch shorter. 
 
 Head 
 
 Fig. 191 
 
 The boiler pressure and the load on this eng were 
 gradually increased from time to time, from 50 pounds, 
 and a light load (as shown by Fig. 188) to 60 pounds and 
 335 horse power (as indicated by Fig. 189 taken some three 
 months later), and when Fig. 191 was taken, about two 
 years and eight months later, the boiler pressure had been 
 increased to 87 pounds and the I. H. P. was over 700. 
 
 Diagram Fig. 191 shows good economy in the use of 
 steam in spite of the fact that the cut off occurs rather late. 
 

 506 
 
 Steam Engineering 
 
 There is no back pressure worth mentioning, the back pres- 
 • sure line forming part of the atmospheric line through the 
 largest part of the stroke. The reason for this is that the 
 areas of the exhaust ports, as well as the exhaust pipe were 
 sufficiently large to permit a free passage for the steam. 
 The exhaust pipe, also, was made as short and direct as 
 possible and all superfluous elbows were dispensed with. 
 The steam consumed per I. H. P. per hour as per diagram 
 Fig. 191 was 22.3 pounds, and the horse power developed 
 was 710.6. 
 
 IS6 
 
 Fig. 192 
 
 Figs. 192 to 194, inclusive, represent diagrams from a 
 Buckeye engine 24x48 inches, and are introduced for the 
 purpose of emphasizing the need of caution and good judg- 
 ment in setting valves by the indicator when the load on 
 the engine is variable. Fig. 192, which was the first to be 
 taken, would seem to indicate that the valve was badly ad- 
 justed, but when Fig. 193 was taken immediately after- 
 wards, the cause of the trouble became apparent. The 
 engine was furnishing power for operating an electric street 
 
Diagram Analysis 
 
 507 
 
 railway on a small scale, and the variation in the points 
 of cut off was caused by the stopping and starting of the 
 cars. 
 
 Fig. 193 is a notable example of the quick and delicate 
 action of the shaft governor, as it will be seen that during 
 four successive revolutions there was a different load each 
 time, as shown by the diagram from the crank end. 
 
 Fig. 198 
 
 Fig. 194 was secured by quick manipulation of the in- 
 Ftrument when it was known that the load was to be steady 
 iqx a few seconds. 
 
 Fig. 195 is from an Atlas single valve automatic cut off 
 engine with shaft governor. This engine was 16x24 
 inches, running at 105 R. P. M., and at the time the di- 
 agram was taken the boiler pressure was only 50 pounds. 
 The spring used was a No. 30. The diagram is a fairly 
 
 Owing to the variation 
 
 good one for the type of engine. 
 
508 
 
 Steam Engineering 
 
 in the angular advance of the single eccentric actuated by 
 a shaft governor, the degree of compression varies with the 
 point of cut off in the single valve engine, the compression 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 <* 
 
 *> 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 k» 
 
 tl 
 
 \ 
 
 
 
 
 
 
 
 
 
 N. 
 
 1 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 23 
 
 k- 
 
 
 
 
 
 
 
 
 
 
 *e 
 
 e 
 
 $*»*£;* 4* 5r ^* . 
 
 
 fc 
 
 ^^^^S&Mfc^j 
 
 
 
 
 
 
 
 Fig 
 
 . 194 
 
 
 
 
 
 
 being higher with an early cut off than it is when cut off 
 occurs later in the stroke. The loop at A is caused by too 
 
 Fig. 195 
 
 much lead which, together with the compression, caused a 
 momentary rise in the pressure above the normal. The 
 lead at B is approximately correct. The difference in ter- 
 
Diagram Analysis 
 
 509 
 
 minal pressures at C and D is the result of shifting of the 
 points of cut off caused by variations in the load. The 
 back pressure lines are almost identical with the atmos- 
 
 
 Fig. 196 
 
 pheric line, showing that the exhaust is in no way restricted 
 or cramped. I. H. P. is 65.7 and steam consumption 21 
 pounds per I. H. P. per hour. 
 
 Fig. 197 
 
 Figs. 196 and 197 are diagrams taken from a cross com- 
 pound condensing Corliss engine. The high pressure cylin- 
 der was 24x48 inches, and the low pressure cylinder was 
 44x48 in. The steam from the high pressure exhausted 
 
510 Steam Engineering 
 
 into a receiver, and from thence into the low pressure cylin- 
 der. The receiver pressure was 5.3 pounds above atmos- 
 pheric pressure. The ratio of piston areas was 3.36 to 1. 
 That is, the area of the low pressure piston was 3.36 times 
 the area of the high pressure piston, which was about the 
 correct ratio for the pressure carried, viz., 84 pounds gauge 
 or 99 pounds absolute. A No. 40 spring was used on the 
 high pressure and a No. 12 on the low pressure cylinder. 
 The number of expansions in the two cylinders was 14. 
 Thus, the ratio of expansion in the high pressure cjdin- 
 der was 4.5 and in the low pressure the ratio was 3.1. 
 Then 4.5X3.1 = 14; or, Thus, initial pressure=99 pounds 
 absolute, terminal pressure in L. P. cylinder = 7 pounds 
 absolute; then 99-^7=14. 
 
 To illustrate the process of finding the M. E. P. without 
 the use of ordinates when the absolute initial and terminal 
 pressures and the number of expansions in each cylinder 
 are known, the following problems will be worked out : 
 
 Find M. E. P. in L. P. cylinder. 
 
 First, find initial pressure. 
 
 Rule. T. P. multipled by number of expansions. Thus, 
 7X3.1=21.7 pounds absolute initial pressure in L. P. 
 cylinder. 
 
 Second, find mean forward pressure (M. F. P.). 
 
 Rule. Multiply initial pressure by hyperbolic logarithm 
 of number of expansions plus 1, and divide product by num- 
 ber of expansions. Thus the Iryperbolic logarithm of 3.1 
 
 21.7X2.1314 
 
 =1.1314, to which add 1=2.1314. Then — — — = 
 
 3.1 
 
 14.9 pounds M. F. P. Deduct from this the back pressure, 
 which was 5 pounds absolute. Thus, 14.9 — 5=9.9 pounds 
 M. E. P. in L. P. cylinder. 
 
Diagram Analysis 511 
 
 Next find M. E. P. in H. P. cylinder. 
 
 First, find T. P. in H. P. cylinder. 
 
 This will equal the initial pressure in the L. P. cylinder 
 -\-2 per cent, for loss in the receiver. Thus, 2 1.7 +.4= 
 22.1 pounds, terminal pressure in H. P. cylinder. 
 
 Second, find initial pressure in H. P. cylinder. 
 
 Rule. Multiply T. P. by number of expansions. Thus, 
 22.1X4.5=99.4 pounds absolute initial pressure in H. P. 
 cylinder. 
 
 Third, find mean forward pressure (M. F. P.). 
 
 The hyperbolic logarithm of 4.5=1.5041, add 1=2.5041. 
 
 99.4X2.5041 
 Then — : =55 pounds, M. F. P. in H. P. cylin- 
 
 4.5 
 
 der. Deduct back pressure 22.1; thus, 55 pounds — 22.1 
 pounds=32.9 pounds, M. E. P. in H. P. cylinder. 
 
 The ratio of piston areas being 3.36 to 1, it may be of 
 interest to pursue the subject a little farther and ascertain 
 how the distribution of the steam in the two cylinders cor- 
 responds to the ratio of areas. The ratio and pressures 
 may be expressed as follows : 
 
 Eatio of areas — H. P. cylinder, 1 ; L. P. cylinder, 3.36. 
 M. E. P.— H. P. cylinder, 32.9 ; L. P. cylinder, 9.9 pounds 
 whicn is very nearly correct ; sufficiently so for all practical 
 purposes, and clearly demonstrates that with the intelligent 
 use of the indicator it is possible to so adjust the valves, 
 and establish the points of cut off on a compound, or triple 
 expansion engine, that the work done in each cylinder w r ill 
 be practically the same. As for instance, the product of 
 the area of the H. P. piston and the M. E. P.= 14,883.6 
 pounds, and that of the L. P. piston X M. E. P.=15,052.9 
 pounds, a difference of only 169.3 pounds. If the two pro- 
 ducts had been equal, the horse power exerted in the two 
 
 j 
 
512 
 
 Steam Engineering 
 
 cylinders would have been the same. As it was, the horse 
 power of the H. P. cylinder was 263.4 and that of the L. P. 
 cylinder was 266.4, showing a difference of only three horse 
 power in the amount of work done in each cylinder. 
 
 Fig. 198 was taken from one of a pair of Fishkill Cor- 
 liss engines connected to a common crank shaft. The en- 
 gines were each 24x48 inches, and run at 65 E. P. M., with 
 a boiler pressure of 65 pounds. They were equipped with 
 a jet condenser, and a bucket plunger air pump served for 
 both engines. These engines had been in continuous 
 service for nearly seventeen years when the author was 
 
 Fig. 198 
 
 called upon to indicate them and adjust the valves. A 
 diagram taken at the same time from the mate of this en- 
 gine was very nearly an exact counterpart of Fig. 198. 
 The horse power, as shown by Fig. 198, was 248, and the 
 steam per I. H. P. per hour was 15.2 pounds. The vacuum 
 gauge showed 27 inches and a 50 spring was used. 
 
 Figs. 199 and 200 are from an old Fishkill Corliss en- 
 gine 16X42 inches, to which the author applied the indi- 
 cator, after he had set the valves, according to the ordin- 
 ary rules for valve setting, by the marks placed on the ends 
 of the valves and valve chests. These diagrams are in- 
 troduced especially for the purpose of showing the need of 
 
Diagram Analysis 
 
 513 
 
 exercising the greatest of care to prevent dirt or grit of 
 any kind from getting into the indicator cylinder. After 
 the indicator pipes had been blown out sufficiently, as it 
 was thought, the indicator, which was a thoroughly reli- 
 able instrument, was attached and diagram Fig. 199 was 
 
 Fig. 199 
 
 obtained. It showed the valve adjustment to be very 
 nearly correct, but the perfectly straight steam lines, and 
 the sharp corners and sudden drop at cut off were a puzzle, 
 especially in an old engine where the valves and valve seats 
 
 Fig. 200 
 
 were known to be much worn down. After taking several 
 more diagrams with precisely the same result, the indicator 
 was removed, and upon taking out the piston a quantity of 
 dirt was found on it, and also on the inside of the cylinder. 
 This fully explained the cause of the sharp corners, etc., 
 
514 Steam Engineering 
 
 on the diagram. After the indicator had been cleaned and 
 oiled it was again connected, and Fig. 200 was produced, 
 which is a truthful presentation of the performance of the 
 steam in the cylinder. 
 
 Many diagrams are misleading, owing to causes similar 
 to the above, and a diagram with too sharp angles at cut 
 off, or release should be regarded with suspicion until it is 
 proved beyond all doubt to be truthful. 
 
 Fig. 201 represents a diagram from a vertical non-con- 
 densing engine 14x16 inches, with riding cut off, which the 
 author was called upon to adjust. This engine was nearly 
 new, having been run but a few months, and although the 
 
 Fig. 201 
 
 size of it w T as ample to do all the work required, yet it had 
 failed, so far, to supply one-half the power needed. After 
 taking the diagram and making a few outside investiga- 
 tions, the cause of the trouble was apparent. Indeed, the 
 wonder was that the engine had supplied as much power as 
 it had under the circumstances. 
 
 First. It was situated too far from the boiler plant, 
 being fully 1,200 feet, and although a pressure of 85 
 pounds was carried at the boilers and the steam was con- 
 veyed through a 6-inch pipe, yet owing to the many drains 
 on the pipe for heating buildings, running other small en- 
 gines, etc., by the time the steam reached the engine in 
 question the pressure was reduced so much that a 30 spring 
 
Diagram Analysis 515 
 
 1 u 
 
 was found to be too strong, although that was the scale of 
 Fig. 201. 
 
 Second, the end of the exhaust pipe was found to be sub- 
 merged in a nearby pond of water to which it had been 
 carried, probably with a view of making a condensing en- 
 gine out of it ! It was also found that there were no less 
 than four superfluous elbows in the exhaust pipe that could 
 easily be dispensed with. The diagram shows that the cut 
 off was practically useless. That the back pressure was 
 nearly 6 pounds above the atmosphere, and that the engine 
 was using 55 pounds of steam and 7 pounds of coal per 
 
 Fig. 202 
 
 horse power per hour, all of which conditions were about as 
 bad as they could be. 
 
 After increasing the lead and adjusting the cut off a 
 No. 16 spring was used and Fig. 202 was produced which, 
 although still showing late admission, is an improvement 
 over the original diagram. The initial pressure being only 
 30 pounds above the atmosphere, further work with the in- 
 dicator was deferred until changes were made in the steam 
 and exhaust pipes, by which the initial pressure was in- 
 creased to 55 pounds and the exhaust pipe was freed of 
 extra turns and raised from its watery grave into the open 
 air. The engine has since then given perfect satisfaction. 
 
516 
 
 Steam Engineering 
 
 Fig. 203 is from a Buckeye automatic cut off engine 
 18x36 inches. The engine had been running for several 
 years with the valves in the condition shown by the di- 
 agram, and in the meanwhile, the load having been in- 
 creased from time to time, the engine finally refused to 
 run up to speed and something had to be done. The 
 superintendent of the plant said that he had an idea that 
 something was the matter with the engine but could not 
 ascertain what it was, and so he finally called upon the 
 author to apply the indicator. The result was that diagram 
 Fig. 203 was obtained, showing that the principle cause of 
 
 Fig. 203 
 
 the trouble was unequal cut off. After equalizing the cut 
 off and increasing the lead on the crank end by a small 
 fraction diagram Fig. 204 was taken, and after this the 
 engine gave no further trouble. The depression in thd 
 steam lines might have been rectified to some extent by in- 
 creasing the boiler pressure, thus giving a higher initial 
 pressure and an earlier cut off. The speed of the engine 
 was 94 R. P. M., with a boiler pressure of 70 pounds. A 
 40 spring was used with the indicator. 
 
 In order to more fully illustrate the process of ascertain- 
 ing the M. E. P. without dividing the diagram into ordi- 
 nates, the following computation is given together with 
 
Diagram Analysis 517 
 
 rules, etc. In this process two important factors are neces- 
 sary, viz., the absolute initial pressure, and the absolute ter- 
 minal pressure, and they can both be obtained from the 
 diagram by measuring with the scale adapted to the spring 
 used. Thus, in Fig. 204 the absolute initial pressure 
 measured from the line of perfect vacuum V to line B is 
 77 pounds, and the absolute terminal pressure measured 
 from V to line B' is 21 pounds. The ratio, or number of 
 expansions, is found thus : 
 
 Rule, Divide the absolute initial pressure by the abso- 
 lute terminal pressure; thus, 77-^21=3. 65=number of 
 expansions. 
 J3L 
 
 Fig. 204 
 
 Second. Find mean forward pressure. 
 
 Rule. Multiply absolute initial pressure by the hyper- 
 bolic logarithm of number of expansions plus 1, and divide 
 product by number of expansions. Thus, referring to Table 
 33, it will be seen that the hyperbolic logarithm of 3.65 is 
 
 77X2.2947 
 
 1.2947, to which 1 must be added. Then =48.4 
 
 3.65 
 
 pounds, which is the absolute mean forward pressure. From 
 
 this deduct. the absolute back pressure, which is 16 pounds or 
 
 1 pound above atmosphere; thus, 48.4 — 16=32.4 pounds 
 
 M. E. P. 
 
518 Steam Engineering 
 
 Third. Find I. H. P. 
 
 Area of piston minus one-half area of rod X M. E. P. 
 
 X piston speed in feet per minute, divided by 33,000. 
 
 250.96X32.4X564 
 
 Thus (the diameter of rod being 3 in.), ■ 
 
 33,000 
 
 = 138.9 I. H. P. 
 
 The steam consumption per I. H. P. per hour may also 
 be computed by means of Table 34, which was originally 
 calculated by Mr. Thomson, and is based upon the follow- 
 ing theory : 
 
 A horse power=33,000 feet pounds per minute, or 
 1,980,000 feet pounds per hour, or 1,980,000X12=23,- 
 760,000 inch pounds per hour, meaning that the same 
 amount of energy required to lift 33,000 pounds one foot 
 high in one minute of time would lift 23,760,000 pounds 
 one inch high in one minute of time. Now if an engine 
 were driven by a fluid that weighed one pound per cubic 
 inch, and the mean effective pressure of this fluid upon the 
 piston was one pound per square inch, it would require 23,- 
 760,000 pounds of the fluid per horse power per hour. But, 
 if in place of the heavier fluid we substitute pure distilled 
 water of which it requires 27.648 cubic inches to weigh one 
 pound, the consumption per I. H. P. per hour will be con- 
 siderably less; as, for instance, 23,760,000^27.648=859,- 
 375 pounds, which would be the rate per hour of the water 
 driven engine if the M. E. P. of the water was one pound 
 per square inch, and if the M. E. P. was increased to 20 
 pounds then twenty times more power would be developed 
 with the same volume of water, but the weight of water 
 consumed per H. P. per hour would be proportionately 
 less. Now if the engine is driven by steam it will consume 
 just as much less water in proportion as the water required 
 
Diagram Analysis 519 
 
 to make the steam is less in volume than the steam used. 
 Therefore if the above constant number, 859,375, be di- 
 vided by the M. E. P. of any diagram, and by the volume 
 of the terminal pressure, the quotient will be the water (or 
 steam) consumption per I. H. P. per hour. 
 
 Eeferring to Table 34, the numbers in the W columns 
 are the quotients obtained by dividing the constant; 859,- 
 375, by the volumes of the absolute pressures given in the 
 columns under T. P. and which represent terminal pres- 
 sures. The table is considerably abridged from the orig- 
 inal, which was very full and complete, the pressures ad- 
 vancing by tenths of a pound from 3 pounds to 60 pounds ; 
 but it is seldom that in ordinary practice there is needed 
 such accuracy. If at any time, however, a diagram should 
 show a terminal pressure not given in the table, the correct 
 factor for that pressure can be easily found by dividing 
 the constant 859,375, by the relative volume of the pres- 
 sure as found in Table 17 of the properties of saturated 
 steam. 
 
 Eeferring again to Fig. 204, it is seen that the terminal 
 pressure is 21 pounds absolute, and by reference to Table 
 34 and glancing down column T. P. until 21 is reached, it 
 will be seen that the number opposite .in column W is 
 732.69. This number divided by the M. E. P. of the 
 diagram Fig. 204, which is 32.4 pounds, gives 22.6 pounds 
 per I. H. P. per hour as the steam consumption. The rate 
 thus found makes no allowance for clearance and compres- 
 sion, however, and these two very important items will be 
 treated upon in succeeding pages. 
 
520 
 
 Steam Engineering 
 
 Table 34 
 power factors. 
 
 T. P. 
 
 W. 
 
 T. P. 
 
 W. 
 
 T. P. 
 
 W. 
 
 3 
 
 117.30 
 
 13. 
 
 466.57 
 
 23 
 
 798. lu 
 
 3.5 
 
 135.75 
 
 13.5 
 
 483.43 
 
 23.5 
 
 814.39 
 
 4 
 
 153.88 
 
 14 
 
 500.22 
 
 24 
 
 830.64 
 
 4.5 
 
 171.94 
 
 14.5 
 
 517.07 
 
 24.5 
 
 846.96 
 
 5 
 
 186.75 
 
 15 
 
 533.85 
 
 25 
 
 863.25 
 
 5.5 
 
 207.60 
 
 15.5 
 
 550.64 
 
 25.5 
 
 879.49 
 
 6 
 
 225.24 
 
 16 
 
 567.36 
 
 26 
 
 895.70 
 
 6.5 
 
 242.97 
 
 16.5 
 
 584.10 
 
 26.5 
 
 911.86 
 
 7 
 
 260.54 
 
 17 
 
 600.78 
 
 27 
 
 927.99 
 
 7.5 
 
 278.06 
 
 17.5 
 
 617.40 
 
 27.5 
 
 944.07 
 
 8 
 
 295.44 
 
 18 
 
 633.96 
 
 28 
 
 960.12 
 
 8.5 
 
 312.80 
 
 18.5 
 
 650.46 
 
 28.5 
 
 976.27 
 
 9 
 
 330.03 
 
 19 
 
 666.90 
 
 29 
 
 992.38 
 
 9.5 
 
 347.27 
 
 19.5 
 
 683.38 
 
 29.5 
 
 1008.46 
 
 10 
 
 364.40 
 
 20 
 
 699.80 
 
 30 
 
 1024.50 
 
 10.5 
 
 381.57 
 
 20.5 
 
 716.27 
 
 30.5 
 
 1040.51 
 
 11 
 
 398.64 
 
 21 
 
 732.69 
 
 31 
 
 1056.48 
 
 11.5 
 
 415.73 
 
 21.5 
 
 749.06 
 
 31.5 
 
 1072.42 
 
 12 
 
 432.72 
 
 22 
 
 765.38 
 
 32 
 
 1088.32 
 
 12.5 
 
 449.69 
 
 22.5 
 
 781.76 
 
 32.5 
 
 1104.35 
 
 Fig. 205 is from a Hamilton Corliss non-condensing en- 
 gine 32% in. bore by 72 in. stroke. A No. 60 spring was 
 used, the boiler pressure being 85 pounds gauge. The 
 I. H. P. was 652.2 and the steam consumption per I. H. P. 
 per hour was 22.9 pounds. 
 
 -4 
 
 Fig. 205 
 
 There are but few points about the diagram that are 
 open to criticism. The compression is rather high for so 
 large an engine and the steam lines should be maintained 
 more nearly horizontal up to the point of cut off. 
 
Diagram Analysis 
 
 521 
 
 Steam Consumption from Indicator Diagrams. In cal- 
 culating the steam consumption of an engine, two very im- 
 portant factors must not be lost sight of, viz., clearance and 
 compression. Especially is this the case in regard to clear- 
 ance when there is little or no compression, for the reason 
 that the steam required to fill the clearance space at each 
 stroke of the engine is practically wasted, and all of it 
 passes into the atmosphere or the condensor, as the case 
 may be, without having done any useful work, except to 
 merely fill the space devoted to clearance. On the other 
 hand, if the exhaust valve is closed before the piston com- 
 
 Fig. 206 
 
 pletes the return stroke, the steam then remaining in the 
 cylinder will be compressed into the clearance space and can 
 be deducted from the total volume which, without compres- 
 sion, would have been exhausted at the terminal pressure. 
 Figs 206 and 207, which are reproductions of diagrams 
 taken by the author while adjusting the valves on a 16x 
 42 inch Corliss engine, will serve to graphically illustrate 
 this point. Fig. 206, which was the first one to be taken, 
 shows no compression. The point of admission at A is 
 plainly defined by the square corner at the extreme end of 
 the stroke. The clearance of this engine is 4 per cent, of 
 
522 Steam Engineering 
 
 the volume of the piston displacement. The engine being 
 16 inch bore by 42 inch stroke, the piston displacement is 
 found by the following calculation: Area of piston,. 201.06 
 square inches X stroke, 42 inches=8444.52 cubic inches. 
 The volume of clearance space is equal to 8444.52 cubic 
 inches X .04=337.78 cubic inches, which divided by 1,728 
 = .195 cubic feet. 
 
 By reference to Fig. 207, taken after adjusting the valves 
 for compression, it will be noticed that the steam is there 
 compressed to 37 pounds, the compression curve beginning 
 at C and ending at B. There is therefore compressed dur- 
 
 Fig. 207 
 
 ing each stroke a volume of steam equal to .195 cubic feet 
 at a pressure of 37 pounds gauge, or 52 pounds absolute. 
 
 One cubic foot of steam at 52 pounds absolute pressure 
 weighs .1243 pounds, and .195 cubic feet will weigh .1243 
 X.195=.0242 pounds. 
 
 The engine was running at 70 E. P. M., or 140 strokes 
 per minute. Thus, according to Fig. 207, the total weight 
 of steam compressed and doing useful work during one 
 hour, and which without compression would have passed 
 out through the exhaust pipe, is equal to .0242X140X60 
 =203.28 pounds. 
 
Diagram Analysis 523 
 
 Now in order to estimate the steam consumption of the 
 above engine from diagram Fig. 206, it would be necessary 
 to account for all the steam occupying not only the volume 
 of 'the piston displacement at the end of the stroke, but the 
 clearance as well, for the reason, as before stated, that it 
 would all be released before exhaust closure. This would 
 equal 8444.52 cubic inches + 337.78 cubic inches=8782.3 
 cubic inches, which divided by 1,728=5.08 cubic feet each 
 stroke, or 10.16 cubic feet each revolution. 
 
 The absolute terminal pressure of Fig. 206 is 20 pounds. 
 One cubic foot of steam at this pressure weighs .0507 
 pounds, and the weight of steam consumed each revolution 
 would therefore be 10.16X-0507=.515 pounds, which mul- 
 tiplied by 70 E. P. M. =36.05 pounds per minute, or 2,163 
 pounds per hour. The horse power developed by the engine 
 at the time was 80. Therefore the steam consumption per 
 I. H. P. per hour=2,163-^80=27 pounds. 
 
 Eeferring again to Fig. 207 it will be remembered that 
 the total weight of steam compressed during one hour was 
 203.28 pounds. The weight of steam consumed per hour, 
 therefore, equals 2,163—203.28=1959.7 pounds. 
 
 Owing to compression, the work area of Fig. 207 is some- 
 what smaller than that of Fig. 206, amounting in fact to 
 the area of the irregular figure enclosed between the points 
 A, B and C. The work represented by this figure amounts 
 to a very small proportion of the total work indicated by 
 Fig. 206, still in order to arrive at correct conclusions, it 
 should be deducted therefrom. 
 
 Assuming the negative work to be equal to .55 horse 
 power, we have 80 — .55=79.45 I. H. P. as the work repre- 
 sented by Fig. 80. As the total weight of steam consumed 
 in one hour was 1959.7 pounds, the steam consumption per 
 
524 Steam Engineering 
 
 I. H. P. per hour will be 1959.7-^-79.45=24.67 pounds, a 
 saving by compression of 2.33 pounds per H. P. per hour, 
 besides the great advantage of having a cushion of steam 
 in contact with the piston at the termination of the stroke, 
 thus bringing the moving parts of the engine to rest quietly 
 without shock or jar. 
 
 The steam consumption may also be computed from the 
 diagram, regardless of the dimensions of the cylinder or 
 the horse power developed. The mean effective pressure 
 and also the absolute terminal pressure must, however, be 
 
 Fig. 208 
 
 known. This method has already been referred to, but in 
 the computation therein made, no correction was made for 
 clearance and compression. 
 
 Having reviewed these two factors at considerable length 
 it will now be in order to more fully explain the methods 
 of treating diagrams when it is desired to make these cor- 
 rections. 
 
 First, draw vertical lines C and D, Fig. 208, at each end 
 of the diagram, and perpendicular to the atmospheric line. 
 Draw line V, representing perfect vacuum, 14.7 pounds 
 below the atmospheric line, as indicated on the scale adapted 
 
Diagram Analysis 
 
 525 
 
 to the diagram, which in this case is 50 pounds to the inch. 
 Continue the expansion from K, where release begins, until 
 it intersects line D V, from which point the absolute ter- 
 minal pressure can be measured. 
 
 Having ascertained the terminal pressure, which for Fig. 
 208 is 30 pounds, draw line D E, which may be called the 
 consumption line for 30 pounds. The terminal being 30 
 pounds, refer to Table 34 and find in column W, opposite 
 30 in column T. P., the number 1,024.5. Divide this num- 
 ber by the M. E. P. which in Fig. 208 is 41 pounds, and 
 the quotient, which is 24.99 pounds, is the uncorrected rate 
 
 *L-^-rr^"^ _ hi 
 
 -' L 
 
 
 • A 
 
 ! \v 
 
 Fig. 209 
 
 
 
 of steam consumption. This rate stands for the total con- 
 sumption throughout the whole stroke represented on the 
 diagram by the distance from D to C, which measures 3.25 
 inches, but it is evident that there is a small portion of the 
 return stroke, that indicated by the distance from E to C, 
 during which the steam compressed in the clearance space 
 should not be charged to the consumption rate, but should 
 be deducted therefrom. In order to do this, multiply the 
 uncorrected rate by the distance from D to E, which is 
 3% inches, or 3.125 inches, and divide the product by the 
 distance from D to C, 3^ inches, or 3.25 inches. Thus, 
 
526 
 
 Steam Engineering 
 
 24.99X3. 125-^3.25=24.03 pounds, which is the corrected 
 rate and represents a saving by compression of 24.99 — 24.03 
 =.96 pounds, or nearly 3.7 per cent. 
 
 In many cases the terminal pressure greatly exceeds the 
 compression, an illustration of which is given in Fig. 209 
 which is a reproduction of a diagram from an old Wheelock 
 engine. It now becomes necessary to extend the compres- 
 sion curve to L, a point equidistant from the vacuum line 
 with the terminal at E. The consumption line E. L. now 
 
 Fig. 210 
 
 becomes longer than the stroke line E. M., therefore the 
 corrected rate will exceed the uncorrected rate by just so 
 much; as for instance, terminal pressure=34 pounds. The 
 factor, as per Table 34,=1152.26, and the M. E. P. of the 
 diagram is 47 pounds. Then, 1,152.26-^47=24.5 pounds, 
 uncorrected rate; 24.5X3.125 inches (distance E. L.)-^-3 
 inches (distance E. M.) =25.52 pounds, corrected rate, a 
 loss of a little more than one pound, or about 4 per cent. 
 
 There is another class of diagrams very frequently en- 
 countered in which the terminal pressure is considerably 
 
Diagram Analysis 527 
 
 below the compression curve, and in order to compute the 
 consumption rate by the above method it becomes necessary 
 to continue the compression curve downwards until it meets 
 the terminal, as illustrated at A, Fig. 210, which is a fric- 
 tion diagram from a Buckeye engine. E is the point of 
 release, D A represents the consumption line, and D C the 
 stroke. The terminal is 8.5 pounds, and the factor for that 
 pressure, according to Table 34, is 312.8. Dividing this 
 number by the M. E. P., which was 7 pounds, gives 4-1.6 
 pounds as the uncorrected rate. The distance D to A, where 
 the compression curve intersects the consumption line, is 
 2.625 inches, and the total length of the diagram C to D 
 is 3.375 inches. Then 44.6X2.625-^3.375=35 pounds as 
 the corrected rate. The extremely high rate is owing to 
 the fact that the engine was running light, no load except 
 a line of empty shafting. 
 
 Theoretical Clearance. The expansion and compression 
 curves of a diagram are created by the expansion and com- 
 pression of all the steam admitted during the stroke. This 
 includes the steam in the clearance space as well as in the 
 cylinder proper. It is evident, therefore, that the volume 
 of the clearance is one of the factors controlling the form 
 of these curves, and when the clearance is known a correct 
 expansion or isothermal curve may be theoretically con- 
 structed, as will be explained later on. Also if the actual 
 curves, either expansion or compression, of a diagram as- 
 sume an approximately correct form, the clearance, if not 
 already known, may be determined theoretically from them ; 
 although too much confidence should not be put in the re- 
 sults as they are liable to show either too little, or too much 
 clearance, generally the latter, especially if figured from 
 the compression curve. 
 
528 
 
 Steam Engineering 
 
 For the benefit of those who may desire to test this method 
 of ascertaining the percentage of clearance of their en- 
 gines, several illustrations will be given of its application 
 to actual diagrams taken from engines in which the clear- 
 ance was known. 
 
 Fig. 211 is from an engine in which the clearance was 
 known to be 5 per cent. As compression cuts but a very 
 small figure in this diagram, the expansion curve alone will 
 be utilized for obtaining the theoretical clearance, and the 
 process is as follows: 
 
 Fig. 211 
 
 Select two points, C and E, in the curve as far apart as 
 possible, but be sure that they are each within the limits of 
 the true curve. Thus C is located just after cut off takes 
 place, and E is at a point just before release begins. From 
 C draw line C D parallel with the atmospheric line. From 
 D draw line D E, and from C draw line C E, both perpen- 
 dicular to the atmospheric line. Then from E draw line 
 E E, forming a rectangular parallelogram, C D E E, with 
 two opposite corners, C and E, within the curve. Now 
 
Diagram Analysis 
 
 529 
 
 through the other two corners, D and E, draw the diagonal 
 D E, extending it downwards until it intersects the vacuum 
 line V. From this point erect the vertical line V W, which 
 is the theoretical clearance line. 
 
 To prove the result proceed as follows: Measure the 
 length of diagram from F to G, which in this case is 3.75 
 inches, representing piston displacement. Next measure 
 the distance from F to the clearance line V W, which is 
 3.91 inches, representing piston displacement with volume 
 of clearance added. Then 3.91 — 3. 75=. 16, which repre- 
 sents volume of clearance; and .16 X 100-^-3. 75=4.3 per 
 cent, which is approximately near the actual clearance, 
 which, as before stated, was 5 per cent. 
 
 cl I V 
 
 Fig. 212 
 
 Fig. 212 serves to illustrate the same method applied to 
 the compression curve. This diagram is a reproduction of 
 one taken from the low pressure cylinder of a large com- 
 pound condensing Corliss engine in which the actual clear- 
 ance was 2.25 per cent. Two points, G and H, are selected 
 in the compression curve, and from them the parallelogram 
 G H I K is erected with two of its opposite corners, G and 
 H, well within the limits of the curve, while through the 
 other two corners, I and K, the diagonal I K C is drawn 
 intersecting the vacuum line at C, thus locating the point 
 
r 
 
 530 Steam Engineering 
 
 from which the clearance line C D can be drawn. The 
 measurements in this case are as follows: 
 
 Total length of diagram, E to F=3.75 inches. 
 
 Distance from clearance line, D C, to F=3.875 inches. 
 
 Volume of clearance=3.875 — 3. 75=. 125 inches. 
 
 .125Xl00-f-3.75=3.33 per cent clearance, which is 1.08 
 per cent more than the known clearance. 
 
 However, notwithstanding the liability to error in many 
 cases, still this method of computing clearance may often 
 be utilized to good advantage. 
 
 Another and more practical method of measuring clear- 
 ance is as follows: Place the engine on the dead center. 
 Eemove the valve chest cover and take out the valve. Close 
 the cylinder cock on that end of the cylinder to which the 
 piston has been moved, leaving the cock on the opposite end 
 of the cylinder open and disconnected from its drip pipe, 
 so as to give an opportunity for catching any water that may 
 leak past the piston while measuring the clearance space. 
 Then having first provided a known weight of water, al- 
 ways making sure of having a little more than enough, pour 
 it into the steam port until the clearance space is filled to 
 a level with the valve seat. When this is done, weigh the 
 water that is left and deduct it from the original quantity, 
 and the remainder will be the number of pounds of water 
 required to fill the clearance, from which it is an easy mat- 
 ter to compute the number of cubic inches or cubic feet in 
 the space devoted to clearance. If any water leaks past the 
 piston during the operation it should be weighed and de- 
 ducted from the total quantity poured into the port. 
 
 In the case of an engine having the valve chest on the 
 side of the cylinder it will be necessary to close the steam 
 port either by blocking the valve against it or by fitting a 
 
Diagram Analysis 531 
 
 piece of soft wood into it, making it water tight. The 
 water can then be poured into the clearance space through 
 a pipe connected to the indicator opening in that end of the 
 cylinder. Care should be exercised to allow a vent for 
 the air to escape as it is displaced by the water. 
 
 The Theoretical Expansion Curve. According to Boyle's 
 law the volume of all elastic gases is inversely as their 
 pressures, and steam being a gas conforms substantially to 
 this law; although the expansion curves of indicator dia- 
 grams are affected more or less by the loss of heat trans- 
 mitted through the cylinder walls, and by the change in 
 the temperature of the steam produced by the changes in 
 pressure during the progress of the stroke. The pressure 
 generally falls more rapidly during the first part of the 
 stroke, and less rapidly during the last portion than it 
 should in order to conform strictly to the above law, and the 
 terminal pressure usually is greater than it should be to 
 agree with the ratio of expansion. But this fullness of the 
 expansion curve of the diagram near the end compensates 
 in a measure for the too rapid fall near the beginning of 
 the stroke. Therefore, if the engine is in fairly good condi- 
 tion with the valves properly adjusted, and not leaking, and 
 the piston rings are steam tight, it may be assumed that the 
 expansion of the steam in the cylinder takes place according 
 to Boyle's law and it is found that the expansion curve 
 drawn by the indicator practically coincides with a hyper- 
 bolic curve constructed according to that law. 
 
 Fig. 213 graphically illustrates the application of the 
 hyperbolic law to the expansion of gases. The horizontal 
 lines represent volumes and the vertical lines represent 
 pressures. The base line, A F, represents the full stroke of 
 a piston in the cylinder of an engine, and the vertical line 
 
532 
 
 Steam Engineering 
 
 A I represents the pressure of the steam at the commence- 
 ment of the stroke. 
 
 Suppose there is no clearance and that the steam has 
 been admitted rip to point H when it is cut off. The rect- 
 angle A B H I is the product of the pressure multiplied 
 by the volume of the steam thus admitted. When the 
 piston has traveled from A to C the volume of the steam has 
 been doubled and the pressure C L has been reduced to just 
 one-half what it was at A I, but the area of the rectangle 
 
 fl 
 
 h 
 
 Hi 
 
 J 
 
 c_--^ / 
 
 
 
 
 y — • '1 
 
 
 
 
 Af 
 
 Fig. 213 
 
 JO C J? A 
 
 A C L M is equal to the area of the initial rectangle, and, 
 as before, is the product of the pressure C L multiplied by 
 the volume AC. As the piston travels still farther, as 
 from A to D, the steam is expanded to four volumes while 
 the pressure at D K will only be one-fourth that of the 
 initial pressure; but the new rectangle A D K N is still 
 equal in area to either of the others, A B H I or A C L M. 
 The same law applies to each of the remaining rectangles ; 
 A E G representing five volumes and one-fifth of the 
 initial pressure, and A P E P representing six times the 
 
Diagram Analysis 
 
 533 
 
 initial volume and one-sixth of the initial pressure, but 
 each having the same area as the initial rectangle A B H I. 
 Now the area of the rectangle A B H I represents the work 
 done by the steam up to the point of cut off, and the area 
 of the hyperbolic figure enclosed by the lines B H R F 
 represents the work done by the expansion of the steam after 
 cut off occurs. 
 
 This area and the amount of work it represents may be 
 computed by means of the known relations of hyperbolic 
 surfaces with their base lines; as for instance, if the base 
 
 Fig. 214 
 
 lines A B, A C, A D, etc., extend in geometrical ratio, as 
 1, 2, 4, 8, 16, etc., the successive areas, B H L C, B H K D, 
 B H G E, etc., increase in arithmetical ratio, as 1, 2, 3, 4, 
 etc. 
 
 On the principles of common logarithms, which represent 
 in arithmetical ratio natural numbers in geometrical ratio, 
 tables of hyperbolic logarithms (see table 33) have been com- 
 puted for the purpose of facilitating the calculation of 
 areas of work due to different degrees of expansion. 
 
 A theoretical curve may be constructed conjointly with 
 the actual expansion curve of a diagram by first locating 
 
534 Steam Engineering 
 
 the clearance and vacuum lines, and then pursuing the 
 method illustrated by Fig. 214. A curve so produced is 
 called an isothermal curve, meaning a curve of the same 
 temperature. 
 
 Eef erring to Fig. 214, suppose, first, that it is desired to 
 ascertain how near the expansion curve of the diagram 
 coincides with the isothermal curve, at or near the point 
 of cut ofT. Select point E near where release begins, but 
 still well within the expansion curve. From this point draw 
 the vertical line, E T, parallel with the clearance line, V S. 
 Then draw the horizontal line, S T, parallel with the at- 
 mospheric line, and at such a height above it as will equal 
 the boiler pressure as measured by the scale adapted to the 
 diagram; such measurement to be made from the atmos- 
 pheric line to correspond with the gauge pressure. From 
 T draw the diagonal T V, and from E draw the horizontal 
 line E D parallel with the atmospheric line. From D, 
 where this line intersects T V, erect the perpendicular D E, 
 thus forming the parallelogram E D E T, and as line T V 
 passes through two of its opposite angles and meets the 
 junction of the clearance and vacuum lines, the other two 
 angles, E and E, will be in the theoretical curve, and E be- 
 ing the starting point, it is obvious that this curve must 
 pass through E, which would be the theoretical point of 
 eut off on the steam line S T. 
 
 Two important points in the theoretical curve have now 
 been located, viz., E as the cut off, and E as the point of 
 release. In order to obtain intermediate points, draw any 
 desired number of lines downward from points in S T, as 
 1, 2, 3, 4, 5, etc., and continue them downwards far enough 
 to be sure that they will meet the intended curve, and from 
 the same points in S T draw diagonals 1 V, 2 V, 3 V, 4 V, 
 
Diagram Analysis 
 
 535 
 
 5 V, etc., all to converge accurately at V. From the inter- 
 section of these diagonals with D E draw horizontal lines 
 parallel with V V, and the points of junction of these lines 
 with the vertical lines will be points in the theoretical curve. 
 It will now be an easy matter to trace the curve through 
 these points. If, on the other hand, it be desired to com- 
 pare the curves toward the exhaust end of the diagram, 
 draw lines E D and E T, Fig. 215, also T E, locating E 
 near where release commences, after which draw line E D, 
 completing the parallelogram E T E D, fixing E as a point 
 in the theoretical curve started at E. After drawing the 
 
 Fig. 215 
 
 diagonal T V, proceed in the same manner as before to 
 locate the intermediate points. 
 
 It will be observed that in order to ascertain the perform- 
 ance of the steam near the beginning of the stroke, the 
 starting point of the isothermal curve must be near the 
 point of release, and conversely, if the starting point of the 
 curve is located near the point of cut off and coincident 
 with the actual curve, the test will apply towards the end 
 of the stroke. It is not to be expected that the expansion 
 curve of any diagram taken in practice will conform strictly 
 to the lines of the isothermal curve, especially towards the 
 
536 
 
 Steam Engineering 
 
 latter end of the stroke, owing to the reevaporation of water 
 resulting from the condensation of steam which was re- 
 tained in the cylinder by the closing of the exhaust valve. 
 This reevaporation commences just as soon as the tempera- 
 ture of the steam, owing to reduction of pressure due to 
 expansion, falls below the temperature of the cylinder walls, 
 and it continues at an increasing rate until release occurs.* 
 The tendency of this reevaporation, or generation of steam 
 within the cylinder during the latter portion of the stroke 
 is to raise the terminal pressure considerably above what 
 
 7 
 
 
 ,'c 
 
 S 
 
 So 
 
 
 ^ — *~~ 
 
 ]S 
 
 
 / s 
 
 7o 
 
 
 / / 
 
 R 
 
 
 ' / 
 
 loo 
 
 
 • / 
 
 SJ 
 
 
 ' s 
 
 5o 
 
 
 s> 
 
 H5 
 
 
 ^'^ 
 
 
 
 
 35 
 
 
 - 
 
 s&*^ 
 
 3o 
 
 R 
 
 ^ — 
 
 . 2t> 
 
 c 
 
 J 
 
 A 
 
 V 
 
 Y . 
 
 Fig. 216 
 
 it would be if true isothermal expansion took place. The 
 terminal pressure may also be augmented by a leaky steam 
 valve, while, on the other hand a leaky piston would cause 
 a lowering of the terminal and an increase in the back 
 pressure. 
 
 The Adiabatic Curve. If it were possible to so protect, 
 or insulate the cylinder of a steam engine that there would 
 be absolutely no transmission of heat either to or from 
 the steam during expansion, a true adiabatic curve or "curve 
 of no transmission" might be obtained. The closer the 
 actual expansion curve of a diagram conforms to such a 
 
Diagram Analysis 537 
 
 curve, the higher will be the efficiency of ihe engine as a 
 machine for converting heat into work. 
 
 Fig. 216 illustrates a method of figuring a curve which, 
 while not strictly adiabatic, will be near enough for all 
 practical purposes, while at the same time it will give the 
 student an opportunity to study the laws governing the 
 expansion of saturated steam. 
 
 To draw the curve, first locate the clearance and vacuum 
 lines V S and V V. Next locate point E in the expansion 
 curve near where release begins, making this the starting 
 point, and also the point of coincidence of the expansion 
 curve with the adiabatic curve. The other points in the 
 curve are located from the volumes of steam at different 
 pressures during expansion; the pressures being measured 
 from the line of perfect vacuum, and the volumes from the 
 clearance line. 
 
 The absolute pressure at E, Fig. 216, is 26 pounds. From 
 point B erect the perpendicular E T. Also draw horizontal 
 line E 26 parallel with the vacuum line and at a height 
 equal to 26 pounds above vacuum line V V, as shown by 
 the scale, which in this case was 40. The length of line 
 E 26, measured from E to the clearance line, is 3^ inches, 
 or 3.0625 inches. By reference to Table 17 it will be seen 
 that the volume of steam at 26 pounds absolute, as com- 
 pared with water at 39°, is 962. Now if the length of line 
 E 26 be divided by this volume, and the quotient multi- 
 plied by each of the volumes of the other pressures repre- 
 sented at points 30, 35, 40, 45, etc., up to the initial pres- 
 sure, the products will be the respective distances from the 
 clearance line of points in the adiabatic curve. These 
 points can be marked on the horizontal lines drawn from 
 the clearance line to line E T. 
 
538 
 
 Steam Engineering 
 
 Starting with line E 26, it has been noted that its length 
 is 3.0625 inches, and that the volume was 962. 3.0625-4- 
 962=. 003. Then the volume of steam at 30 pounds is 
 8-41, which being multiplied by .003=2.5 inches, the length 
 of line 30. Xext the volume at 35 pounds=728. Multiply- 
 ing this volume by .003=2.1 inches, length of line 35, and 
 so in like manner for each of the other points. 
 
 The process involves considerable figuring and careful 
 and accurate measurements, which should be made with a 
 
 steel rule with decimal graduations. It is not expected that 
 the cut Fig. 216 will be found accurate enough in its meas- 
 urements to serve as a standard: it being intended only to 
 serve as an illustration of the process. The diagram from 
 which the illustration was drawn was taken from a 600 
 H. P. engine situated some 200 feet from the boilers, and 
 there was a considerable cooling of the steam by the time it 
 reached the engine, the effect of which is apparent. The 
 curve produced by the measurements is shown by the broken 
 line. The process can be applied to any diagram. 
 
Diagram Analysis 539 
 
 Power Calculations. The area of the piston (minus one- 
 lialf the area of rod) multiplied by the M. E. P., as shown 
 by the diagram, and this product multiplied by the number 
 of feet traveled by the piston per minute (piston speed) 
 will give the number of foot pounds of work done by the 
 engine each minute, and if this product be divided by 33,000, 
 the quotient will be the indicated horse power (I. H. P.) 
 developed by the engine. 
 
 Therefore one of the first requisites in power calculations 
 is to ascertain the M. E. P. Beginning with the most 
 simple, though only approximately correct, method of ob- 
 taining the average pressure, as illustrated by Fig. 217, 
 draw line A B touching at A and cutting the diagram in 
 such manner that the space D above it will equal in area 
 spaces C and E taken together, as nearly as can be estimated 
 by the eye. Then with the scale measure the pressure along 
 the line F G at the middle of the diagram, which will be 
 the M. E. P. 
 
 The process is based upon the theory that the average 
 width of any tapering figure is its width at the middle of 
 its length. This method should not be relied upon as accu- 
 rate, but is convenient at times when it is desired to make 
 a rough estimate of the horse power of an engine. 
 
 Ordinates. The method of calculating the M. E. P. by 
 the use of ordinates has already been alluded to, and will 
 be here enlarged upon. The process consists in drawing 
 any convenient number of vertical lines perpendicular to 
 the atmospheric line across the face of the diagram, spac- 
 ing them equally, with the exception of the two end spaces, 
 which should be one-half the width of the others, for the 
 iea c on that the ordinates stand for the centers of equal 
 spaces, as for instance, line 1, Fig. 218, stands for that 
 
540 
 
 Steam Engineering 
 
 portion of the diagram from the end to the middle of the 
 space between it and line 2. xlgain, line 2 stands for the 
 remaining half of the second space and the first half of 
 the third, and so on. This is an important matter, and 
 should be thoroughly understood, because if the spaces are 
 all made of equal width, and measurements are taken on 
 the ordinates, the result will be incorrect, especially in the 
 case of high initial pressure and early cut off, following 
 which the steam undergoes great changes. 
 
 ss 
 
 /o./ 
 7 
 
 U 7 4 + /o -Zi.y/Ut/I.FI 3 
 
 2.3. v .n£p< 
 
 JUazKEi 
 
 3 
 
 Fig. 218 
 
 If the spaces are all made equal, the measurements will 
 require to be taken in the middle of them, and errors are 
 liable to occur, whereas if spaced as before described, the 
 measurements can be made on the ordinates, which is much 
 more convenient and will insure correct results. Any num- 
 ber of ordinates can be drawn, but ten is the most conven- 
 ient and is amply sufficient, except in case the diagram is 
 excessively long. For spacing the ordinates, dividers may 
 be used, or a parallel ruler may be procured from the 
 makers of the indicator; but one of the most convenient 
 and easily procurable instruments for this purpose is a 
 
Diagram Analysis 541 
 
 common two-foot rule, and the method of using it is illus- 
 trated in Fig. 218. 
 
 First draw vertical lines at each end of the diagram, 
 perpendicular to the atmospheric line, and extending down- 
 wards to the vacuum line, or below it if necessary, in order 
 to have a point on which to lay the rule. In Fig. 218 
 points A and B are found to be the most convenient. Now 
 lay the rule diagonally across the diagram, touching at A 
 and B, and the distance will be found to be 3% inches, or 
 60 sixteenths. 
 
 Suppose it be desired to draw 10 ordinates. Divide 60 
 by 10, which will give 6 sixteenths, or % inches as the 
 width of the spaces, but as the two end spaces are to be 
 one-half the width of the others, there will be 11 spaces 
 altogether, the two outer ones having a width equal to one- 
 half of % or T 3 6. Now apply the rule again in the same 
 manner, touching at points A and B, and with a sharp 
 pointed pencil begin at A and mark the location of the first 
 ordinate according to the rule, at a distance of -^ from the 
 end. Then % from this mark make another one, which will 
 locate the second ordinate, and proceed in like manner to 
 locate the others. The last two or three marks generally 
 come below the diagram, and if the diagram be taken from 
 a condensing engine it may be necessary to tack it on to a 
 larger sheet of paper in order to get these points. Having 
 correctly located the ordinates, they may now be drawn 
 perpendicular to the atmospheric line or vacuum line, either 
 of which will answer. 
 
 It should be noted that, owing to the diagonal position 
 of the rule with relation to the atmospheric line, the spaces 
 are not of the actual width as described by the rule, but this 
 is unimportant, so long as they are of a uniform width. 
 
542 Steam Engineering 
 
 This method can be applied to any diagram, no matter 
 what its length may be, and point B may be located at any 
 distance below the atmospheric or vacuum lines, wherever 
 it is the most convenient for the subdivisions on the rule, 
 sixteenths, eighths, etc., so long as it is in line with the end 
 of the diagram. Having thus drawn the ordinates, the 
 M. E. P. may be found by measuring the pressure expressed 
 by each one, using for this purpose the scale adapted to the 
 spring used, adding all together and dividing by the num- 
 ber of ordinates which will give the average pressure. 
 
 Eef erring to Fig. 218, begin with ordinate No. 1 on the 
 diagram, from the head end of the cylinder. In this case 
 a 40 spring was used. Lay the scale on the ordinate with 
 the zero mark where it intersects the compression curve. 
 The pressure is seen to be 49 pounds. Set this down at that 
 end of the card and measure the pressure along ordinate 
 Xo. 2, which is 55 pounds. Proceed in this manner to 
 measure all the ordinates, placing the resulting figures in 
 a column, after which add them together and divide by 10. 
 The result is 26.71 pounds, which is the mean forward pres- 
 sure (M. P. P.). To obtain the mean effective pressure, 
 deduct the back pressure, which is represented by the dis- 
 tance of the exhaust line of the diagram -above the atmos- 
 pheric line in a non-condensing engine, and in a condensing 
 engine the back pressure is measured from the line of per- 
 fect vacuum, 14.7 pounds, according to the scale below the 
 atmospheric line. 
 
 In Fig. 218 the back pressure is found to be 3 pounds. 
 Therefore the M. E. P. of the head end will be 26.71—3= 
 23.71 pounds. On the crank end the M. F. P. is 27.23 
 pounds, and 27.23—3=24.23 pounds=M. E. P. The 
 average effective pressure on the piston, therefore, will be 
 23.71 + 24.23-^-2=23.97 pounds. 
 
Diagram Analysis 
 
 543 
 
 Unless great care is exercised in the measurements, errors 
 are liable to occur in applying this method, especially with 
 scales representing high pressures, as 60, 80, etc. The most 
 sonvenient and reliable method is to take a narrow strip 
 of paper of sufficient length, and starting at one end, apply 
 its edge to each ordinate in succession, and mark their 
 lengths on it consecutively, with the point of a knife blade 
 or a sharp pencil. Having thus marked on the paper the 
 total length of all the ordinates, ascertain the number of 
 inches and fractions of an inch thereon, the fractions to be 
 
 Fig. 210 
 
 expressed decimally, and divide by the number of ordinates. 
 The quotient will be the average height of the diagram, and 
 as the scale expresses the number of pounds pressure for 
 each inch, or fraction of an inch in height, if the average 
 height of the diagram be multiplied by the number of the 
 scale, the product will be the M. F. P. 
 
 Eeferring again to Fig. 218, if the lengths of the ordinates 
 drawn on the head end diagram be measured, their sum will 
 be found to be 6 8/12 or 6.666 inches. Dividing this by 
 
544 Steam Engineering 
 
 10 gives .666 inches as the average height. The mean for- 
 ward pressure will then be as follows: .666X40=26.64 
 pounds, or practically the same as found by the other 
 method. 
 
 Fig. 219 illustrates a type of diagram frequently met 
 with, and one which requires somewhat different treatment 
 in estimating the power developed. It will be noticed that, 
 owing to light load and early cut off, the expansion curve 
 drops considerably below the atmospheric line, notwith- 
 standing that the engine from which this diagram was 
 taken is a non-condensing engine. When release occurs at 
 
 E, and the exhaust side of the piston is exposed to the atmos- 
 phere, the pressure immediately rises to a point equal to, 
 or slightly above, that of the atmosphere. 
 
 Fig. 219 was taken during a series of experiments made 
 by the author for the purpose of ascertaining the friction 
 of shafting and machinery, and the engine it was obtained 
 from is a Buckeye 24x48 inches. The boiler pressure at 
 the time was only 40 pounds, and a No. 20 spring was used. 
 The ordinates are drawn according to the method illustrated 
 in Fig. 218. By placing the rule on points A and B, the 
 distance between those two points is found to be 3% inches, 
 or 58 sixteenths. Dividing this by 10 gives 5.8 sixteenths, 
 or nearly % inches, as the width of the spaces ; the two end 
 spaces being one-half of this, or T 3 6 inches wide. The first 
 five ordinates, counting from A, express forward pressure, 
 represented by the arrows. The remaining five ordinates, 
 counting from B, express counter or back pressure, repre- 
 sented by the arrows pointing in the opposite direction. 
 Measuring the pressures along the first five ordinates, and 
 adding them together, gives 63.1 pounds, which divided by 
 5 gives 12.65 pounds as the mean forward pressure (M. 
 
 F. P.). 
 
Diagram Analysis 545" 
 
 Then figuring up the counter pressure in the same man- 
 ner on the other five ordinates, beginning at B, the result 
 is 4.25 pounds. The M. E. P. therefore will be 12.65—4.25 
 = 8.4 pounds. 
 
 Obtaining the M. E. P. with the Planimeter. The area 
 of the diagram represents the actual work done by the 
 steam acting upon the piston. In a non-condensing engine 
 the lower, or exhaust line of the diagram must be either 
 coincident with or slightly above the atmospheric line in 
 order to express positive work. Any deviation of this line, 
 either above or below the atmospheric line, represents 
 counter pressure, the amount of which may be ascertained 
 by measurements with the scale, and should be deducted 
 from the mean forward pressure. 
 
 On the other hand, the exhaust line of a diagram from 
 a condensing engine falls more or less below the atmos- 
 pheric line, according to the degree of vacuum maintained, 
 .and the nearer this line approaches the line of perfect 
 vacuum, as drawn by the scale, 14.7 pounds below the at- 
 mospheric line, the less will be the counter pressure, which 
 in this case is expressed by the distance the exhaust line is 
 above that of perfect vacuum. 
 
 The prime requisite therefore in making power calcu- 
 lations from indicator diagrams is to obtain the average 
 height or width of the diagram, supposing it were reduced 
 to a plain parallelogram instead of the irregular figure which 
 it is. 
 
 The planimeter, Figs. 220-221, is an instrument which 
 will accurately measure the area of any plane surface, no 
 matter how irregular the outline or boundary line is, and 
 it is particularly adapted for measuring the areas of indi- 
 cator diagrams, and in cases where there are many diagrams 
 
546 
 
 Steam Engineering 
 
 to work up, it is a very convenient instrument and saves 
 much time and mental effort. In fact, the planimeter has 
 
 Fig. 220 
 
 COFFIN AVERAGER OR PLANIMETER 
 
 of late years become an almost indispensable adjunct of the 
 indicator. It shows at once the area of the diagram in 
 square inches and decimal fractions of a square inch, and 
 
Diagram Analysis 
 
 547 
 
 when the area is thus known it is an easy matter to obtain 
 the average height by simply dividing the area in inches by 
 the length of the diagram in inches. Having ascertained 
 the average height of the diagram in inches or fractions 
 of an inch the mean or average pressure is found by multi- 
 
 Fig. 221 
 
 plying the height by the scale. Or the process may be made 
 still more simple by first multiplying the area, as shown 
 by the planimeter in square inches and decimals of an inch, 
 by the scale, and dividing the product by the length of the 
 diagram in inches. The result will be the same as before, 
 and troublesome fractions will be avoided. 
 
548 Steam Engineering 
 
 QUESTIONS AND ANSWERS. 
 
 401. "What two important points are gained by the use 
 of the indicator? 
 
 Ans. First — It shows the average pressure upon the 
 piston throughout the stroke. Second— It shows the action 
 of the valve or valves in admission, cut off and release of 
 the steam. 
 
 402. What is the first principle of the indicator? 
 
 Ans. Pressure of the steam in the engine cylinder dur- 
 ing an entire revolution, against a small piston in the cylin- 
 der of the indicator. 
 
 403. What resistance is in front of the indicator piston? 
 Ans. A spiral spring of known tension. 
 
 404. What is the second principle of the indicator? 
 Ans. By means of a multiplying mechanism of levers, 
 
 the stroke of the indicator piston is communicated to a 
 pencil moving in a straight line. 
 
 405. What is the third principle of the indicator? 
 Ans. By means of a reducing mechanism and cord, the 
 
 motion of the engine piston during an entire revolution is 
 imparted to a small rotating drum, to which is attached a 
 piece of blank paper. 
 
 406. How is a diagram obtained? 
 
 Ans. The pencil is held against the paper and thus traces 
 a diagram of the action of the steam within the engine 
 cylinder. 
 
 407. What is the atmospheric line? 
 
 Ans. A line drawn by the indicator pencil before. com- 
 munication is established between engine cylinder and indi- 
 cator cylinder. 
 
 408. Where should a diagram from a non-condensing 
 engine appear relative to the atmospheric line? 
 
Questions and Answers 549 
 
 Ans. It should appear above the atmospheric line. 
 
 409. Where should the diagram from a condensing en- 
 gine appear? 
 
 Ans, Partly above, and partly below the atmospheric 
 line. 
 
 410. What is the best reducing motion to use? 
 Ans. The reducing wheel. 
 
 411. How is the indicator attached to the engine cylin- 
 der? 
 
 Ans. By means of half-inch pipe tapped into the side of 
 the cylinder near the ends. 
 
 412. How are the springs numbered? 
 
 Ans. They are made for various pressures, and num- 
 bered accordingly. 
 
 413. What is a good rule to follow in selecting a spring? 
 Ans. Select one numbered one-half as high as the boiler 
 
 pressure, which will give a diagram about two inches high. 
 
 414. What data should be noted upon the diagrams 
 when they are taken? 
 
 Ans. Boiler pressure; time when taken, and which end 
 of cylinder, head, or crank. 
 
 415. What pressure must always be deducted from the 
 mean forward pressure (M. F. P.) in calculations for 
 power ? 
 
 Ans. The back pressure. 
 
 416. What bad effects follow unequal cut off? 
 
 Ans. The engine will not develop the power that it is 
 capable of — uneven strains will be set up. 
 
 417. What is a convenient size for a diagram? 
 Ans. iy 2 or 2 inches high, and 2 or 2% inches long. 
 
 418. What precaution regarding the pipe connections 
 of the indicator should always be observed before taking 
 diagrams ? 
 
550 Steam Engineering 
 
 Ans. They should be thoroughly blown out, and cleaned 
 of all dirt. 
 
 419. How is the ratio of expansions found? 
 
 Ans. Divide absolute initial pressure by absolute ter- 
 minal pressure. 
 
 420. Xame a very important factor in the calculation 
 of steam consumption of an engine. 
 
 Ans. The clearance space. 
 
 421. What is one of the first requisites in power calcu- 
 lations? 
 
 Ans. To ascertain the M. E. P. 
 
 422. How is this done? 
 
 Ans. In several ways., for instance by means of ordinates, 
 or it may be obtained by the use of the Planimeter. 
 
Friction and Lubrication 
 
 Next to the all important problems of keeping the water 
 in the boilers at the proper level, and maintaining a suffi- 
 cient supply of steam, comes the proper lubrication of the 
 bearings, and other rubbing surfaces on the engine. If 
 these are not oiled as they should be, the efficiency of the 
 engine will be reduced, and besides there is a constant 
 danger of some one of the heavy bearings becoming heated, 
 and most likely cause a shut-down. 
 
 In discussing the problem of lubrication it is well to first 
 study the laws of friction of plane surfaces in contact. 
 
 There are five of these laws which are commonly accepted 
 relative to this subject. 
 
 Friction is the resistance caused by the motion of a body 
 when in contact with another body that does not partake 
 of its motion, and the laws that control this resistance are 
 as follows: 
 
 First — Friction will vary in proportion to the pressure 
 on the surfaces, that is if the pressure increases, the fric- 
 tion will be increased, and vice versa. 
 
 Second — Friction is independent of the areas of the sur- 
 faces in contact, but if the pressure, or friction be distributed 
 over a larger area, the liability of heating and abrasion be- 
 comes less than it would be if the friction is concentrated 
 on a smaller area. 
 
 Third — Friction increases with the roughness of the sur- 
 faces, and decreases as the surfaces become smoother. 
 
 Fourth — Friction is greatest at the beginning of motion. 
 Greater force is required to overcome the friction at the 
 
 551 
 
552 Steam Engineering 
 
 instant of starting to move a body, than is required after 
 motion has commenced. 
 
 Fifth — Friction is greater between soft bodies than it 
 is between hard bodies. 
 
 These five laws were formulated in the years 1831-33 by 
 Gen. Arthur Morin, a French engineer, who made many 
 experiments relating to the friction of plane surfaces in 
 contact, but numerous experiments in later years by many 
 eminent engineers have demonstrated that these laws are 
 not altogether rigid, and that they can only be accepted in 
 so far as they relate to the friction of dry surfaces in con- 
 tact, or lubricated surfaces moving under light pressures, 
 and at slow speed. As friction is always a resisting, and 
 retarding factor, its tendency is to bring everything in ma 
 tion to a state of rest. With machinery in motion the frici 
 tion between the surfaces of the parts moving in contact 
 tends to cause them to adhere to each other. 
 
 Therefore in order to successfully and economically oper- 
 ate the machinery, it is absolutely necessary that a lubri- 
 cant be used that will distribute itself over these surfaces, 
 and thus prevent them from coming in direct contact with 
 each other. 
 
 Friction, however, is useful in many ways, as for in- 
 stance, the friction of the belt in contact with the rim of 
 the pulley causes power to be transmitted from the engine 
 to the machines throughout the shop. Then also the fric- 
 tion or adhesion of the driving wheels of the locomotive 
 makes it possible for the engine to start a heavy train and 
 keep it moving. 
 
 The friction of the brake shoes on the car wheels makes it 
 possible to stop a train in much less time than if it were 
 allowed to stop of its own accord. 
 
Friction 
 
 553 
 
 There are two kinds of friction in mechanics, viz., the 
 friction of solids, and the friction of liquids. It is the 
 friction of solids that the engineer has to deal with mainly, 
 and this kind of friction for convenience may be again 
 divided into two classes, viz., rolling friction, as for in- 
 stance a journal revolving in its bearings, or a crank pin 
 in its brasses, and second, sliding friction, as the cross-head 
 on the guides, or the piston traveling back and forth in the 
 cylinder. 
 
 >LBS. 
 
 w^ 7 
 
 
 
 L 
 B 
 S 
 
 
 
 1 y ' 
 
 *%. 
 
 
 Fig. 222 
 
 Co-Efficient of Friction. By this term is meant the re- 
 lation that the power required to move a body, bears to the 
 weight or pressure on that body. 
 
 This definition may be expressed in another, and per- 
 haps plainer form, as follows: 
 
 The co-efficient of friction is the ratio between the resist- 
 ance to motion, and the perpendicular pressure, and is de- 
 termined by dividing the amount of the former by the 
 latter. Figures 222 and 223 will serve to illustrate in a 
 graphic manner the second law of friction, and also explain 
 one method of determining the co-efficient of friction. 
 
 M 
 
554 
 
 Steam Engineering 
 
 A block of iron or other metal is* drawn across the sur- 
 face of the table top by means of weights suspended from a 
 cord attached to one end of the. block, and passing over a 
 small pulley or roller at* one end of the table. The block 
 has a flat surface on one side, while on the opposite side 
 there are four small projections or legs, one on each corner, 
 and each leg has a sectional area of one square inch. The 
 size of the block may be assumed to be 8 inches wide, 12 
 inches long and 2 inches thick, and its weight may be taken 
 at 50 pounds. In Figure 222 the block is placed upon the 
 
 LBS | 
 
 
 
 7 
 
 
 11 
 
 
 
 L 
 
 
 
 
 
 B 
 
 
 
 
 
 S 
 
 
 
 
 
 
 
 
 
 
 ^~ 
 
 . 
 
 ^' 
 
 
 
 
 Fig. 228 
 
 table with its flat, or largest bearing surface down. This 
 surface has an area of 8 inches by 12 inches=96 square 
 inches in contact with the surface of the table, and it is 
 found that by placing weights on the cord until the block 
 begins to move, and keep moving requires a weight of 7 
 pounds. Xow it might be supposed that if the block were 
 reversed so that it would rest on its four legs it could be 
 moved across the table with much less weight on the cord 
 than was required in the position shown in Figure 222, but 
 such is not the case, as shown by Figure 223 and which can 
 also be mathematicallv demonstrated. 
 
Friction 555 
 
 In the' experiment illustrated in Figure 222 the co-effi- 
 cient of friction is resistance 7 pounds divided by weight 
 or pressure 50 pounds=.14; that is it requires a force of 
 14 pounds to move one pound of weight. The pressure 
 per square inch of area=weight 50 pounds divided by area 
 96 square inches=.52 pounds. The co-efficient being .14 
 pounds, the pull per square inch of surface required to move 
 the block is .52 X .14=. 0729 pounds, which multiplied by 
 the total area 96 square inches equals 6.9888 or practically 
 7 pounds. Eeferring to Figure 223 where the block is 
 reversed, and stands on four legs, each leg having an area 
 of one square inch in contact with the surface of the table, 
 the total contact is four square inches, but the pressure re- 
 mains the same, viz., 50 pounds. Therefore the pressure 
 per square inch of area=50-^4=12.5 pounds, which when 
 multiplied by the co-efficient .14 equals 1.75, which is the 
 pull per square inch of surface, and there being 4 square 
 inches, the total pull= 1.75X4= 7 pounds. It will thus be 
 seen that the extent of surface in contact does not affect the 
 friction so long as the weight or pressure remains constant, 
 but by allowing the larger area of surface to come into con- 
 tact with the table surface thus distributing the pressure 
 over a greater area, reduces the liability of heating and 
 abrasion because the pressure per square inch is so much 
 less. 
 
 In machine design, especially engine bearings, and crank 
 pins, the object should be to obtain as large a surface as 
 possible in order that the pressure per square inch may be 
 reduced. By making the bearings of proper proportions, 
 by using bearing metals having the greatest anti-friction 
 value, by keeping the shafting in line, and by the use of 
 the best and most suitable lubricants, and lubricating de- 
 
556 
 
 Steam Engineering 
 
 vices, or by using self-oiling bearings wherever possible, the 
 friction losses may be reduced to a very small percentage 
 of the total power developed by the engine. Modern engine 
 construction, and methods of lubrication have in recent 
 years been brought to such a degree of mechanical refine- 
 ment that the friction loss per horse power is only 2 or 3 
 per cent. This low per cent of friction loss has been brought 
 
 Fig. 224 
 
 about in the case of high speed engines by properly pro- 
 portioning, and balancing the rotating parts, and by the 
 use of lubricating apparatus that keeps the bearing con- 
 tinuously flooded in a bath of oil. 
 
 Great care should be exercised by the engineer in the 
 selection of piston rod, and valve stem packing, and in its 
 application and adjustment, as otherwise there will be con- 
 siderable friction loss, especially if the packing is unsuit- 
 
Friction 
 
 557 
 
 able or becomes hard from too long service, or has been 
 screwed up too tightly. 
 
 Prof. Chas. H. Benjamin, in a paper presented at the 
 meeting of the A. S. M. E. December, 1900, gives the re- 
 sults of a series of tests made by himself, at the Case School 
 of Applied Science, in Cleveland, Ohio, to determine the 
 amount of friction caused by various kinds of piston pack- 
 in. Figure 224 shows the device used by Prof. Benjamin in 
 making the tests. 
 
 Figure 225 is a sectional view of the same machine, which 
 consisted of a cast iron cylinder 6x12 inches, fitted at each 
 
 Fig. 225 
 
 end with a suitable head, and stuffing box and gland 
 arranged for a two-inch piston rod. The rod was given a 
 reciprocating motion, through the medium of a slotted cross- 
 head, and crank, and a pulley on the crank shaft was con- 
 nected by a belt to a dynamometer. Steam was admitted to 
 the cylinder through the pipe shown in Figure 224 and the 
 water of condensation was drawn off at the bottom, while 
 a steam gauge showed the pressure in the cylinder. The 
 gland nuts were usually tightened with the fingers only, 
 but when a wrench was used, a spring balance was attached, 
 and the turning moment was noted. The stroke of the rod 
 was 4.25 inches, and the revolutions were 200 per minute, 
 
558 
 
 Steam Engineering 
 
 giving a piston speed of 141 feet per minute. Seventeen 
 different kinds of packing were used, the materials of which 
 were rubber, cotton, asbestos, hemp, lead, and flax. 
 
 Some of these packings were combined with mica, graph- 
 ite, and paraffme. The various packings were fitted accord- 
 ing to the directions of the makers, and the routine of the 
 tests as they were conducted was as follows: 
 
 The machine was first run without packing, in order to 
 determine the friction of the empty apparatus. The pack- 
 ing was then inserted, and steam turned on, the gland nuts 
 being tightened just sufficient to prevent leakage, and the 
 packing was then tested under various pressures, each test 
 lasting from 15 to 40 minutes. The gland nuts were then 
 tightened with the wrench, and spring balance to various 
 pressures, and other sets of readings taken, after which 
 
 Table 35 
 
 
 
 
 c x 
 
 rt 
 
 
 
 
 3 
 
 
 
 
 to 
 
 c 
 
 
 P4 
 
 h'3 
 
 C tfi ■ 
 
 
 3 
 
 w 
 
 O w 
 
 t> 
 
 ifi u 
 
 
 o 
 a 
 
 fin 
 
 .Is 
 
 'u 
 
 H 
 
 
 WJBf 
 
 be <u 
 
 
 Remarks on Leakage, etc. 
 
 
 O 
 
 
 2 s 
 
 Ch'~ 
 
 
 c 
 
 6 
 
 3c 
 
 > « 
 
 O 
 
 .0 
 
 
 2 
 
 £ 
 
 H 
 
 < 
 
 K 
 
 
 1 
 
 5 
 
 22 
 
 .091 
 
 .085 
 
 Moderate leakage. 
 
 2 
 
 8 
 
 40 
 
 .049 
 
 .048 
 
 Easily adjusted ; slight leakage. 
 
 3 
 
 5 
 
 25 
 
 .037 
 
 .036 
 
 Considerable leakage. 
 
 4 
 
 5 
 
 25 
 
 .159 
 
 .176 
 
 Leaked badly. 
 
 5 
 
 5 
 
 25 
 
 .095 
 
 .081 
 
 Oiling necessary ; leaked badly. 
 
 6 
 
 5 
 
 25 
 
 .368 
 
 .400 
 
 Moderate leakage. 
 
 7 
 
 5 
 
 25 
 
 .067 
 
 .067 
 
 Easily adjusted and no leakage. 
 
 8 
 
 .5 
 
 25 
 
 .082 
 
 .082 
 
 Very satisfactory ; slight leakage. 
 
 9 
 
 3 
 
 15 
 
 .200 
 
 .182 
 
 Moderate leakage. 
 
 10 
 
 3 
 
 
 .275 
 
 
 Excessive leakage. 
 
 11 
 
 5 
 
 25 
 
 .157 
 
 .172 
 
 Moderate leakage. 
 
 12 
 
 5 
 
 25 
 
 .266 
 
 .330 
 
 Moderate leakage. 
 
 13 
 
 5 
 
 25 
 
 .162 
 
 .230 
 
 No leakage; oiling necessary. 
 
 14 
 
 5 
 
 25 
 
 .176 
 
 .276 
 
 Moderate leakage ; oiling necessary. 
 
 15 
 
 5 
 
 25 
 
 .233 
 
 | .255 
 
 Difficult to adjust ; no leakage. 
 
 16 
 
 5 
 
 25 
 
 .292 
 
 .210 
 
 Oiling necessary ; no leakage. 
 
 17 
 
 5 
 
 25 
 
 .128 
 
 .084 
 
 No leakage. 
 
Friction 
 
 559 
 
 cylinder oil was applied to the rod, and the difference in 
 friction, noted. These tests were measured by means of a 
 Flather recording dynamometer, and a Weber box gear 
 dynamometer, the readings being taken at short intervals 
 and averaged. The results of these tests are summed up in 
 Tables 35 and 36. Table 35 gives a summary of the re- 
 sults, showing the average horse power absorbed by each 
 packing at various pressures, and for purpose of compari- 
 son, the power at 50 pounds of steam pressure. Table 36 
 shows the increased friction caused by tightening the gland 
 nuts, and also the beneficial effect of oiling the rod. The 
 different packings are numbered. 
 
 The general conclusions arrived at from this series of 
 tests are as follows: 
 
 First — That the softer rubber, and graphite packings 
 absorb less power in friction than the harder kinds do. 
 
 Second — That oiling the piston rod will reduce the fric- 
 tion of any kind of packing. 
 
 Table 36 
 
 oj 
 
 
 
 
 
 
 .s 
 
 Horse 
 
 :-power Consumed by Each Box, 
 
 when 
 
 H. P. 
 
 Before 
 
 ^4 
 
 Pressure was Applied to Gland Nuts 
 
 by 
 
 and After 
 
 c2 
 
 
 a Seven-inch Wrench 
 
 
 Oiling 
 
 Rod. 
 
 c 
 
 3 
 
 5 Lbs. 
 
 8 Lbs. 
 
 10 Lbs. 
 
 12 Lbs. 
 
 14 Lbs. 
 
 16 Lbs. 
 
 Dry 
 
 Oiled 
 
 i 
 
 .120 
 
 
 .136 1 
 
 
 
 
 
 3 
 
 
 
 
 . . . . .... 
 
 
 
 .055 
 
 .021 
 
 4 
 
 
 
 ^248 
 
 .303 
 
 
 '.390 
 
 .154 
 
 .123 
 
 5 
 
 
 
 .220 
 
 
 
 
 
 
 6 
 
 
 
 .348 
 
 .430 
 
 
 
 .323 
 
 .194 
 
 7 
 
 
 
 .126 
 
 .228 1 .260 
 
 '.330 
 
 [340 
 
 .067 
 
 .053 
 
 8 
 
 
 
 .363 
 
 .500 | .535 
 
 .520 
 
 .533 
 
 .533 
 
 .236 
 
 9 
 
 
 
 .666 
 
 .... i .... 
 
 
 
 .666 
 
 .636 
 
 11 
 
 
 
 .405 
 
 .454 | .... 
 
 
 
 .454 
 
 .176 
 
 12 
 
 
 
 .161 
 
 .242 I .359 
 
 !454 
 
 
 .454 
 
 .122 
 
 13 
 
 
 
 .317 
 
 .394 .582 | 
 
 
 
 
 15 
 
 
 
 .526 
 
 
 
 
 
 
 16 
 
 
 
 .327 
 
 .860 
 
 
 
 
 
 17 
 
 
 
 .198 
 
 .277 1 .380 
 
 
 
 
 
560 Steam Engineering 
 
 Third — That there is almost no limit to the friction loss 
 that can be caused by the injudicious use of the wrench. 
 
 Variations of friction of lubricated surfaces occur with 
 every change of condition of either the bearing or journal 
 surfaces, or of the lubricant applied to them. The condi- 
 tions that produce the greatest differences in ordinary lubri- 
 cation are, the nature and quality of the lubricant, the 
 nature and condition of the wearing surfaces, and the speed, 
 pressure, and temperature. 
 
 Lubricating Oils. The engineer in charge of a plant will 
 always find on the market a wide range of petroleum prod- 
 ucts to choose from to meet the various conditions that will 
 show up in the proper lubrication of the machinery under 
 his charge. The ordinary facilities of the engine room do 
 not usually afford means to make elaborate tests of oils, and 
 other lubricants, but an engineer can make valuable com- 
 parative tests of different grades of oil on his engine, or 
 other machinery. 
 
 For instance by means of a thermometer placed in the 
 bearing, with the bulb resting on the shaft, or immersed 
 in the oil chamber, the temperature of the bearing may 
 be noted, while it is being lubricated with various grades 
 of oils, and their qualities thus determined. Of course 
 in tests of this kind, care should be taken that the rate of 
 oil feed, the belt tension, the pressure on the bearings, and 
 the speed remain as near constant as possible, and an allow- 
 ance should also be made for any difference in the tempera- 
 ture of the room during the tests. A good and efficient 
 lubricant should possess the following characteristics : 
 
 First, sufficient "body" to keep the surfaces apart, but 
 the greatest possible fluidity consistent with this. 
 
 Second, a minimum co-efficient of "internal" friction in 
 actual service. 
 
Lubrication 561 
 
 Third, must not dry or "gum," and must not contain free 
 acids or other corrosive ingredients. 
 
 Fourth, must not be readily thinned, vaporized or ignited 
 by heat, or stiffened by the cold encountered in the service 
 to be performed. 
 
 Fifth, must be absolutely free from all gritty foreign 
 substances. 
 
 Sixth, it must be especially adapted to the conditions for 
 which it is chosen. 
 
 Experience has proved that in lubrication the best is 
 nearly always the cheapest in the end, and that the consumer 
 can better afford to use the highest priced lubricants the 
 market affords, than accept those of lower value as a gift. 
 
 The cost of lubrication is not merely the market price 
 of lubricants, but their cost plus the cost of the friction ac- 
 companying their use. The value, not the cost, of the lub- 
 ricant, is the point worthy of greatest consideration. "What 
 it will do, not what it costs per pound or per gallon. ISTo 
 greater error can be made than to economize upon the 
 quality of lubricants, for even under the most extravagant 
 conditions the cost of lubricants represents but a very small 
 fraction of the cost of fuel, and repairs and depreciation 
 of poorly lubricated engines and machinery. 
 
 The best lubricant for a bearing under normal conditions 
 may not do so well after heating commences, a thick viscous 
 oil which under ordinary conditions on high speed machin- 
 ery would be comparatively wasteful of power is often an 
 excellent lubricant for a hot bearing, and for the following 
 reason: an engineer on finding a bearing heating up will 
 apply the ordinary oil freely, and at the same time loosen 
 up the bolts so as to allow for increased expansion and 
 free flow of oil; if the heating continues, and the engine 
 
562 Steam Engineering 
 
 or machinery must be kept in operation at all hazards, he 
 will turn to his cylinder oil, apply it freely, and often with 
 good results. The reason of this is that the cylinder oil, 
 owing to its high fire test (from 550 to 600) became thin 
 and limpid without burning, and flowed freely between 
 the close-fitting surfaces and kept them apart, and at the 
 same time, absorbed the heat that would otherwise have 
 gone into the metal and carried it away, while the engine 
 oil, being of lower flash test, vaporized, and if the bearing 
 got hot enough, caught fire. 
 
 In many cases the use of pure graphite or plumbago, as 
 it is sometimes called, will prove to be beneficial, especially 
 on heavy bearings that are inclined to heat. 
 
 The essential function of graphite is that of an auxiliary, 
 or accessory lubricant, with which to perfect and maintain 
 the working surfaces in a condition of high polish and great 
 smoothness, so that the oils and greases used as the actual 
 lubricating film may the more successfully perform their 
 particular service. They have only to separate two highly- 
 polished and perfectly fitted surfaces and to reduce friction 
 to the lowest possible point. 
 
 Graphite allows the safe and satisfactory use of less oil 
 or grease than would otherwise be necessary, because there 
 is far less actual wearing out of the oil between the smooth 
 surfaces. 
 
 Inasmuch as metallic wear is nearly eliminated, the oil 
 does not become rapidly charged with fine metal particles 
 and lose its lubricating value. 
 
 Thinner lubricants can generally be used. Graphite in- 
 creases the endurance and efficiency of oil, and grease lubri- 
 cants because it relieves them of a very great part of the 
 duty they otherwise have to perform. 
 
Lubrication 563 
 
 Whether graphite is fed at regular intervals or only 
 occasionally the results are much the same, inasmuch as 
 the coating of graphite persists for a considerable period 
 after application. 
 
 In 1902 Professor W. F. M. Goss of Purdue University 
 conducted a long series of tests to determine the value of 
 Dixon's Flake Graphite as a general lubricant for bearings, 
 and as applied to railroad air brake equipment. 
 
 The tests extended over a period of many months and 
 were made, not to create arguments in favor of Dixon's 
 Graphite but to enlarge the sum of information on the 
 subject of graphite lubrication. 
 
 The following extracts are taken from the report : 
 
 "From the earlier and rather limited uses of graphite 
 in lubrication, the field has gradually widened to include its 
 use with light oils, with water, and, in some cases, unmixed 
 with other materials. It is no longer regarded merely as a 
 material for an emergency, but now has a place in the 
 ordinary and usual routine of the engineer's day. 
 
 "The demand for graphite has come because men charged ' 
 with the responsibility of keeping machinery moving have 
 found it beneficial in their work, and not because manu- 
 facturers and plant owners pressed its use upon them. 
 
 "It is not to be presumed that because a material is sold 
 as graphite it will give good results in lubrication ; it must 
 be free from grit and other impurities and properly graded 
 for the work. . . . 
 
 "Graphite does not behave like oil, but associates itself 
 with one or the other of the rubbing surfaces. It is worked 
 into every crack and pore in the surfaces and fills them, 
 and if the surfaces are ill-shaped or irregularly worn, the 
 graphite fills in and overlays until a new surface or more 
 

 564 Steam Engineering 
 
 regular outline is produced. When applied to a well fitted 
 journal the rubbing surfaces are coated with a layer so thin 
 as to appear hardly more than a slight discoloration. If, 
 on the other hand, the parts are poorly fitted, a veneering 
 of graphite of varying thickness, which in the case of a 
 certain experiment was found as great as ^ inch, will re- 
 sult. The character of this veneering is always the same, 
 dense in structure, capable of resisting enormous pressure, 
 continuous in service without apparent pore or crack, and 
 presenting a superficial finish that is wonderfully smooth 
 and delicate to the touch." 
 
 In the lubrication of the interior wearing surfaces of the 
 valves, and cylinders of steam engines, conditions will be 
 met which are altogether different from those encountered 
 in the lubrication of bearings and journals. 
 
 In the latter case, the working and comparing of one oil 
 with another, and the results obtained can be easily deter- 
 mined by noting the changes of temperature, etc., but in 
 internal lubrication, the conditions are altogether different. 
 
 In the case of journals and bearings, the oil can be ap- 
 plied directly to the surface to be lubricated; in cylinder 
 lubrication one must depend upon the flow of steam to con- 
 vey the oil to the parts or wearing surfaces requiring lubri- 
 cation. 
 
 The points that govern the conditions of interior lubri- 
 cation are : The conditions of the surfaces, the steam pres- 
 sure, the amount of moisture in the steam, the piston speed, 
 weight and fit of the moving parts, and the make or type 
 of the engine. 
 
 An automatic cut off engine with balanced, or piston 
 valves will usually require less oil than an engine with a 
 heavy unbalanced valve. 
 
Lubrication 565 
 
 A large cylinder whose piston is supported by a "tail-rod" 
 is more easily lubricated than one whose heavy piston drags 
 back and forth over the bottom of the cylinder. 
 
 An oil to be used as a cylinder lubricant in order to give 
 good results must possess certain essential properties. 
 
 It must be of high flash test, so that it will not volatilize, 
 or vapome when in contact with the hot steam: it must 
 have good viscosity, or body when in contact with the hot 
 surfaces, and should adhere to, and form a coating of oil 
 so as to prevent wear and reduce as much as possible the 
 friction of the moving parts. 
 
 While the quality of a cylinder oil as shown by the use 
 of testing instruments will give one a general idea of its 
 lubricating value, the engineer who is studying the question 
 of cylinder lubrication can determine more accurately its 
 exact value by experimenting on his engines, and pumps 
 and under the conditions peculiar to his own plant. 
 
 LUBRICATING APPLIANCES. 
 
 Lubricating Appliances. The successful lubrication of 
 an engine depends in a large measure upon the character 
 of the appliances that are used 'to convey the lubricant to 
 the wearing surfaces. 
 
 For steam cylinder lubrication the hydrostatic, or sight 
 feed type of lubricator is in most general use; this type 
 of lubricator depends for its operation upon the displace- 
 ment of the oil by a body of water which is formed by the 
 condensing of the steam in the condensing chamber of the 
 lubricator, the water in passing into the oil chambers dis- 
 places the oil, forcing it up through the sight-feed glass, 
 whence it flows through the discharge pipe to the cylinder. 
 
 The construction and operation of this class of lubrica- 
 
566 
 
 Steam Engineering 
 
 tors will be better understood by reference to Figures 226 
 and 227. Figure 226 is an exterior view of the well-known 
 Detroit sight-feed lubricator, while Figure 227 is a sectional 
 view showing the interior construction. The pipe P shown 
 in Figure 227 connects with a passage from the condenser 
 A-2 Figure 226 and when the water feed valve A-4 Figure 
 
 Fig. 223 
 exterior view detroit lubricator 
 
 226 is opened, the water in the condenser will pass down 
 the pipe P to the bottom of the lubricator, and, being 
 heavier than oil, will stay at the bottom, the oil floating 
 above it. The pipe S Figure 227 leads from the lower 
 sight-feed arm to the upper part of the body of the lubri- 
 cator. The action of the lubricator is as follows : 
 
Lubricating Appliances 
 
 567 
 
 The body x\-l is filled with oil. Steam from the main 
 steam pipe passes in the connecting pipes above the lubri- 
 cator, and condenses, filling the condenser A-2 and part of 
 the pipe above it with water. The steam also passes into 
 the support arm and through the internal tube T into the 
 sight-feed glass, where it condenses, filling the glass with 
 water. 
 
 Fig. 227 
 interior view detroit lubricatob 
 
 As soon as the valve A-4 is opened, the oil in the body 
 of the lubricator is subjected to the pressure of the column 
 of water extending through the pipe P, the condenser and 
 part of the pipe above it, amounting to about 2 pounds to 
 the square inch, and in addition to the pressure of the steam 
 
568 Steam Engineering 
 
 above the water, amounting to say 100 pounds to the square 
 inch, or a total pressure of about 102 pounds to the square 
 inch. This we may call the positive pressure. Liquids 
 communicate pressure equally in all directions, so the oil 
 in the body of the lubricator will press in every direction 
 with a force of about 102 pounds to the square inch. It will 
 therefore press down through the tube S with this force of 
 102 pounds to the square inch. Then, if the valve A- 7 is 
 opened, a force acting in the opposite direction is en- 
 countered, which we may call the back pressure. When 
 the lubricator is connected as shown, this back pressure will 
 consist of the column of water in the sight-feed glass, and 
 in addition, the steam pressure back of this column entering 
 through the support arm, and amounting to 100 pounds to 
 the square inch. 
 
 The positive steam pressure being just the same as the 
 back steam pressure, these two forces will neutralize each 
 other, and we have left, the positive pressure of the column 
 of water extending through the pipe P, the condenser and 
 part of the pipe above it, and the back pressure of the 
 column of water in the sight-feed glass. As the latter is 
 much less than the positive pressure, the drop of oil is forced 
 through the nozzle. As soon as it leaves the nozzle it is 
 no longer acted upon by the positive pressure, and it rises 
 through the water in the glass from the force of gravity, it 
 being lighter than the water. After rising through the 
 sight-feed glass it floats through the tube T, Figure 227, 
 and through the support arm into the main steampipe and 
 goes with the current of steam to the steam chest and 
 cylinder. The positive pressure must always be greater than 
 the back pressure, or the lubricator will not work. 
 
 For instance, if a lubricator be connected to a horizontal 
 steampipe by being suspended below it, the back pressure 
 
Lubricating Appliances 
 
 569 
 
 would be greatly increased, and in order to get sufficient 
 positive pressure the condensing pipe should rise 18 inches 
 to 24 inches above the horizontal steampipe and then de- 
 scend to the condenser. This will give a column of water 
 for positive pressure higher than the column of water 
 which acts as back pressure. 
 
 TO RE-FILL AND OPERATE. 
 
 Close valves A-4 and A-7. Open drain valve A-8, then 
 remove filler plug A-3 and the water will drain out rapidly. 
 
 Improved 
 
 'tER VALVE 
 <fr FILLING CAP 
 
 r REGULATING VAIVE 
 
 Fig. 228 
 powell lubricator 
 A, Oil reservoir. B, Filling cup. C, Valve to regulate oil 
 drops. D, Shut-off valve. E, Packing nuts. F, Drain valve. 
 H, coupling for condensing pipe. JJ, Sight feed and index 
 glasses. K, Plug for removing and inserting glasses. M, Con- 
 densing chamber. N, Valve to regulate water from the con- 
 denser. V, Valve to drain sight feed glass. R, Attaching shank 
 and valve. 
 
570 
 
 Steam Engineering 
 
 When water is all out, close valve A-8, fill with oil, and re- 
 place filler ping A-3. Then open valve A-4, and regulate 
 the flow of oil with valve A-7. The valve A-9 is to be 
 closed only when desiring to shut off steam from the lubri- 
 cator in case of accidental breakage of the glass, or when 
 there is danger from freezing. Before starting the lubri- 
 cator, time should be allowed for the sight-feed glass, and 
 
 Fig. 229 
 Powell's duplex condenser locomotive lubricator 
 
 condensing chamber to fill with water from condensation. 
 When there is danger from freezing when lubricator is not 
 in use, empty the lubricator, and leave open valves A-4, 
 A-8 and A-6. Then close valve A-9 and the small angle 
 valve in condensing pipe above the lubricator. 
 
 Figure 228 shows an external view of the Powell lubri- 
 cator "Class A," for single cylinder engines, and Figures 
 
Lubricating Appliances 
 
 571 
 
 229 and 230 show exterior, and sectional views of the 
 Powell duplex condenser and double, up-feed lubricator for 
 use on compound and triple expansion engines. In this 
 lubricator there may be two or three sight-feeds combined 
 with one oil chamber. The letters designate the different 
 parts, and the operation of this lubricator will be easily 
 understood by a study of Figure 230. 
 
 Fig. 230 
 description of internal parts 
 A, Oil chamber. CC, Oil drop regulating valves. EE, Brass 
 protecting shields. F, Drain valve. GG, Removable plugs to 
 clean oil tubes. HH, Packing nuts. II, Adjustable rings. 
 JJ, Sight glasses. KK, Removable cages to replace glasses. 
 MM, Condensers. N, Water valve. T, Connecting coupling to 
 boiler. VV, Cleaning valves for sight glasses. W, Water tube. 
 X, Water and oil trap. 
 
572 
 
 Steam Engineering 
 
 The force feed, or mechanically operated lubricator, has 
 come into favor largely within recent years, and it certainly 
 has the merit of being positive, while at the same time it is 
 not wasteful of oil, being governed by the speed of the en- 
 gine or pump that it is lubricating. This type of lubricator 
 is made in single, double, triple, and quadruple style, and 
 is operated by attaching the connecting rod of the oil pump 
 
 Fig. 231 
 manzel quadruple feed, oil pump 
 
 to any movable part of the engine that will give it a recipro- 
 cating motion. 
 
 Figure 231 shows the Manzel quadruple feed oil pump. 
 These pumps are also made with five and six feeds. Man- 
 zel Brothers Co. also make an agitating force, and sight- 
 feed oil pump for the purpose of feeding graphite mixed 
 with the oil. Graphite being a mineral and not easily sus- 
 pended in oil it has always been a rather difficult problem 
 
Lubricating Appliances 
 
 573 
 
 to feed it properly along with the oil, but the device illus- 
 trated in Figure 232 has proved to be very successful in 
 feeding the mixture of oil and graphite. The action of this 
 appliance will be easily comprehended by a reference to 
 Figure 232. The spiral agitating device that revolves in 
 the cup is operated by means of the belt-drive on the wheel, 
 
 Fig. 232 
 the manzel agitating, force and sight feed oil pump 
 
 and bevel gears on the cup. The construction is simple 
 and durable. Two fillers are used, one for oil and one for 
 graphite. Xo fixed rule can be laid down for the amount 
 of graphite to be used, as some engines require more than 
 others. Two or three good teaspoonfuls to a pint of valve 
 oil, would be a good rule to start on, and the engineer can 
 
574 Steam Engineering 
 
 then watch results and ascertain for himself the proper 
 quantity to use. 
 
 Another rule might be, three teaspoonfuls of graphite 
 per day for a 150 horse power engine. 
 
 To Attach the Manzel Oil Pump. Place the pump on 
 the frame of an engine, or pump where it is most conven- 
 ient to get motion. It can be bolted to a stud or stand. 
 Attach connecting rod of the pump to any movable part 
 that travels back and forth such as a valve rod to an en- 
 gine, or rocker arm of a pump. Connect the pipe to the 
 pump cylinder. Use % inch pipe for % pint and pint 
 pumps, and *4 inch pipe for all other sizes; the end of 
 pumps and check valves are threaded for these sizes, and 
 run to, and enter the steam line or steam chest above or 
 below the throttle, as desired. Equip the oil pipes as near 
 as possible to the steam line with check valve; the end 
 marked "S" toward the steam line. By using a reducer, % 
 inch pipe can be used on the larger size pump. 
 
 The feed on the "Manzel Improved" Pump is regulated 
 while in operation on the engine, on the upper plungers. 
 To increase the feed, screw plunger inward, to decrease the 
 feed, screw plunger outward, then tighten lock-nut. Partic- 
 ular attention is called to the regularity of the feed that is 
 obtained on these pumps under all conditions. They can 
 be regulated to feed from nothing or one drop to a stream of 
 oil with every stroke of the plunger. 
 
 Another good force feed lubricator is the Dietz high 
 pressure force feed lubricator made by the Pearl Manu- 
 facturing Co. of Buffalo, New York. This device is made 
 either single, or double acting, and with from one to six 
 feeds. 
 
 Figure 233 shows a double acting three-feed Deitz high 
 pressure lubricator, and it is claimed by the manufacturers 
 
Lubricating Appliances 
 
 575 
 
 that it will feed any mixture of oil and graphite without 
 becoming clogged, owing to the fact that the valves are of 
 the poppet type, and made of steel, and when not opened 
 
 Fig. 233 
 dietz high pressure force feed lubricator 
 
 by the cams, are held to their seats by a strong spiral spring 
 in addition to the pressure. This oil pump is fitted with a 
 crank, by means of which it may be worked by hand, in 
 starting, or should an extra amount of oil be required at 
 
576 
 
 Steam Engineering 
 
 L 
 
 Fig. 234 
 rochester force feed lubricator with monitor sight feed 
 
 appliance 
 
 any time. The pump is driven in the usual way by con- 
 necting to the valve rod of the engine and the feed is 
 regulated by varying the travel of the rocker arm. 
 
 Figure 234 shows the Eochester force feed lubricator, 
 as it appears with the Monitor sight-feed attachment 
 
Lubricating Appliances 577 
 
 screwed onto the delivery pipe, by means of which the engi- 
 neer is enabled to see the drops of oil as they are being fed 
 to the cylinder or bearings. The number and size of the 
 drops can be regulated to suit the requirements of the 
 engine. 
 
 QUESTIONS AND ANSWERS. 
 
 423. What is one of the most important problems con- 
 nected with engine operation ? 
 
 Arts. The proper lubrication of the bearings. 
 
 424. What is friction? 
 
 Arts. The resistance caused by the motion of a body in 
 contact with another body that does not partake of its 
 motion. 
 
 425. What is the first law of friction? 
 
 Arts. Friction varies in proportion to the pressure on 
 the surfaces in contact. 
 
 426. Define the second law of friction. 
 
 Arts. Friction is independent of the areas of surface in 
 contact. 
 
 427. What is the third law of friction? 
 
 Ans. Friction increases with the roughness of the sur- 
 faces, and decreases as the surfaces become smoother. 
 
 428. What is the fourth law of friction ? 
 
 Ans. Friction is greatest at the beginning of motion. 
 
 429. Give the fifth law of friction? 
 
 Ans. Friction is greater between soft bodies than it is 
 between hard bodies. 
 
 430. When, and by whom were these laws first formu- 
 lated?' 
 
 Ans. In 1831-33 by Gen. Arthur Morin, a French en- 
 gineer. 
 
578 Steam Engineering 
 
 431. What is the tendency of friction with machinery 
 in operation? 
 
 Ans. It tends to cause the parts to adhere to each other. 
 
 432. How may this friction be largely obviated? 
 Ans. By proper lubrication of the rubbing surfaces. 
 
 433. Does friction serve any good purpose? 
 
 Ans. Yes, for instance the friction of the belt in con- 
 tact with the rim of the pulley, also the friction of the 
 driving wheels of a .locomotive. 
 
 434. How many kinds of friction are there in connec- 
 tion with machinery in operation ? 
 
 Ans. Two, viz., the friction of solids, and the friction 
 of liquids. 
 
 435. What is meant by the term co-efficient of friction? 
 Ans. The ratio of the power required to move a body, 
 
 and the pressure on that body. 
 
 436. What should be the object sought in the design 
 of engine bearings? 
 
 Ans. To obtain as large a rubbing surface as possible. 
 
 437. Mention some of the qualities that a good lubri- 
 cating oil should possess. 
 
 Ans. It should have a good "body" — must not dry or 
 "gum ;" must not be easily thinned by heat, or thickened by 
 cold. Must be free from all gritty substances. 
 
 438. What is the proper kind of oil to use on a bearing 
 that has started to heat ? 
 
 Ans. Cylinder oil, owing to its high fire test. 
 
 439. Is graphite, or plumbago a good lubricant? 
 Ans. It is in many cases. 
 
 440. What is the essential function of graphite ? 
 Ans. It is an auxiliary, or accessory lubricant. 
 
 441. Mention some of the points that govern interior 
 lubrication of engine parts. 
 
Questions and Answers 579 
 
 Ans. The conditions of the surfaces ; the steam pressure ; 
 the amount of moisture in the steam ; piston speed ; weight, 
 and fit of moving parts, etc. 
 
 442. What properties should a good cylinder oil possess ? 
 Ans. It must be of high flash test; must have good 
 
 viscosity, or body when in contact with hot surfaces. 
 
 443. Upon what does the successful lubrication of an 
 engine largely depend? 
 
 Ans. Upon the character of the lubricating appliances 
 used. 
 
 444. What system of lubrication for cylinders, and 
 valves is most largely used? 
 
 Ans. The hydrostatic, or sight-feed type of lubricator. 
 
 445. What other system has come into extensive use in 
 late years? 
 
 Ans. The force feed, or mechanically operated oil pump. 
 
The Steam Turbine 
 
 Although the turbine principle of utilizing the heat 
 energy in steam and converting it into useful work has 
 been experimented upon for many years, it is only since 
 the inauguration of the twentieth century that steam tur- 
 bines have been brought to the front as efficient power 
 producers. 
 
 The piston of the reciprocating engine is driven back 
 and forth by the static expansive force of the steam, while 
 in the steam turbine not only the expansive force is made 
 to do work, but a still more important element is utilized, 
 viz., the kinetic energy, or heat energy latent in the steam, 
 and which manifests itself in the rapid vibratory motion of 
 the particles of steam expanding from a high, to a low 
 pressure, and this motion the steam turbine transforms 
 into work. 
 
 Xotwithstanding the fact that much has been said and 
 written during the past four years regarding the steam 
 turbine, the machine is to-day a mystery to thousands of 
 engineers, not because they do not desire information upon 
 the subject, but because of a lack of opportunities for ob- 
 taining that information. The author therefore considers 
 that a space devoted to this subject would no doubt be of 
 benefit to his readers. 
 
 The steam turbine is simple and compact in design, hav- 
 ing few working parts as compared with the reciprocating 
 engine, and any engineer who is capable of operating and 
 caring for an engine of the latter type, can also run and 
 take care of a steam turbine. But, as in the case of the 
 
 581 
 
582 
 
 Steam Engineering 
 
 L 
 
 Fig. 235 
 four westinghouse-parsons steam turbines 
 
The Steam Turbine 
 
 583 
 
 reciprocating engine, the engineer in charge of a turbine 
 plant should be familiar with the interior construction of 
 the machines under his charge, and he should know what 
 to do, and what to avoid in order to keep them in continual 
 and efficient operation. 
 
 Fig. 236 
 
 The steam turbine in principle, and even in type is not 
 new, being in fact the first heat motor of which we have 
 any record in steam engineering. 
 
 One of the earliest descriptions of a device for convert- 
 ing the power of steam into work was recorded by Hero, 
 a learned writer who flourished in the city of Alexandria 
 
584 
 
 Steam Engineering 
 
 in Egypt, in the second century before Christ. Hero de- 
 scribes a machine called an Aeolipile or "Ball of Aeolus," 
 illustrated in Fig. 236. B is the boiler under which a 
 fire was made. G is a hollow metallic globe that revolved 
 on trunnions C and D, one of which terminated in a pivot 
 at E, while the other was hollow and conveyed the steam 
 generated in the boiler B to the interior of the globe or 
 ball, from which it escaped through the hollow bent tubes 
 H and I, and the reaction of the escaping steam caused the 
 
 
 v 
 
 kOTfcl 
 
 Fig. 237 
 
 globe to revolve. This was the first steam turbine, and 
 it worked on the reaction principle. 
 
 Many centuries later, in the year A. D. 1629, Branca, 
 an Italian, described an engine which marks a change in 
 the method of using the steam. Branca' s engine consisted 
 of a boiler A, Fig. 237, from which the steam issued through 
 a straight pipe, and impinged upon the vanes of a hori- 
 zontal wheel carried upon a vertical shaft, causing it to 
 revolve. This device was the germ of the impulse tur- 
 
The Steam Turbine 585 
 
 bine, and these two principles, viz., reaction and impulse, 
 either one or the other, and sometimes a combinaticn of 
 both, are the fundamental principles upon which the suc- 
 cessful steam turbines of the present age operate. 
 
 Steam expanding through a definite range of tempera- 
 ture and pressure exerts the same energy whether it issues 
 from a suitable orifice or expands against a receding piston. 
 
 Two transformations of energy take place in the steam 
 turbine; first, from thermal to kinetic energy; second, 
 from kinetic energy to useful work. The latter alone pre- 
 sents an analogy to the hydraulic turbine. 
 
 The radical difference between the two turbines lies in 
 the low density of steam as compared to water, and the 
 wide variation of its volume under varying temperatures 
 and pressures. 
 
 A cubic foot of steam under 100 lbs. pressure, if allowed 
 to discharge into a vacuum of 28 inches, would attain a 
 theoretical velocity of 3,860 feet per second and would 
 exert 59,900 ft. lbs. of energy. 
 
 A law of turbo-mechanics specifies that in order to ob- 
 tain the highest efficiency in the operation of turbines 
 (whether water or steam) the relation between bucket 
 speed and fluid speed, (steam in this case), should be as 
 follows : 
 
 For purely impulse wheels, bucket speed equals one-half 
 of jet speed. 
 
 For reaction wheels, bucket speed equals jet speed. 
 
 Assuming the velocity of the jet of steam issuing from 
 the nozzle to be 4,000 feet per second, this would mean 
 a peripheral speed of 2,000 feet per second for an im- 
 pulse wheel, and for a wheel 1 foot in diameter the speed 
 would be 38,100 E. P. M. But such a speed is beyond 
 
586 
 
 Steam Engineering 
 
 the limits of strength of material, and the speed of steam 
 turbines is accordingly kept within the bounds of safety, 
 and strength of material. 
 
 Form of Blade. — The blades or buckets should be of 
 such form, and curvature as will permit the steam to ex- 
 pand to the desired final, or terminal pressure with the 
 »mallest possible friction and eddy current losses. As to 
 directing the flow in the desired course, the direction of 
 
 Fig. 238 
 
 W- 
 
 exit from the guide, and rotating wheel is of the greatest 
 importance. In order to get the desired angle, the last 
 part of the blade should be kept straight, at least to the 
 foot of the perpendicular dropped from A x , or the length 
 A B in Fig. 238. From there on, the channel should lead 
 in easy curvature to the angle a x . The construction ac- 
 cording to a in Fig. 238 would obviously be too sharp, and 
 would cause the steam stream to separate from the wall. 
 
The Steam Turbine 587 
 
 The construction according to b would suffice, and the 
 wheel radius would depend, above all, upon how far we 
 wish to diminish the shock at entrance. For the profile b 
 the angle a x is taken as the slope of the blade back, from 
 which we obtain for the guiding blade surface the some- 
 what large angle a/. This would be more favorable with c, 
 and d, but the latter would obviously give a needlessly 
 long steam path. Besides, a pointing of /the blade such 
 that a x is half of a/, as is shown dotted at d, could be con- 
 sidered just as correct as the first mentioned. By drawing 
 the absolute steam path and finding the decrease of peri- 
 pheral speed, we get useful results concerning the regu- 
 larity of delivering work. 
 
 The proper length of the channel, or steam path can 
 only be determined by practical experience, and with a 
 given curvature the ratio of length to breadth can be con- 
 sidered fairly constant. 
 
 Stuffing Boxes. — The stuffing boxes are the most im- 
 portant and delicate part of the steam turbine. As they 
 are subjected to high temperature on account of their 
 proximity to the steam space, the problem of getting rid of 
 their own heat of friction becomes all the more difficult. 
 The advantage of the stuffing box used on reciprocating 
 engines, where the rod for part of the time is exposed to 
 the air, and cools at least its surface by radiation, cannot 
 be considered with the rotating shaft. Water-cooling may 
 be an effective means, but creates considerable loss by con- 
 densation in the surrounding steam spaces. 
 
 The majority of designers get around this difficulty by 
 avoiding contact between packing and shaft, and secure 
 tightness only by the least possible clearance. This is the 
 principle of the so-called "labyrinth stuffing box" that was 
 
588 
 
 Steam Engineering 
 
 first generally used by Parsons. This is shown in Fisr. 
 
 o %i xj O 
 
 239, in which A is the shafts B the stuffing box. The rings 
 
 y x y 
 
 Fig. 239 
 labarynth stuffing box 
 
 on both parts form alternately a narrow space x, and a 
 large space y. The velocity of the steam flowing through 
 this narrow space is destroyed by eddy-currents in the 
 
 Fig. 240 
 
 Fig. 241 
 
 large space, so that for further velocity, a part of the drop 
 in pressure is utilized. With a large number of rings, 
 and with very small spaces x, the loss is greatly decreased. 
 
 _ 
 
The Steam Turbine 
 
 589 
 
 It also seems to have a favorable influence when the steam 
 in leaving this narrow space flows radially inwards, that is, 
 it helps to overcome its centrifugal force. 
 
 Fig. 240 shows the stuffing box of a Schuh turbine. No 
 provision is here made for enlarged spaces, but the neces- 
 sary throttling is accomplished by the great length of the 
 labyrinth path. The designer hoped to limit his clearance 
 to 1 mm. (0.039 in.). The outer box is made in two parts. 
 
 Fig. 242 
 
 Fig. 241 shows a stuffing box by the same designer, built 
 of rings, in which the inner rings are loose, but are made 
 with a neat fit. 
 
 The Bateau stuffing box is shown in Fig. 242. The 
 main part consists of the shaft, a, enclosed by a close fit- 
 ting box b, of suitable metal. The steam leaking through 
 this space flows into chamber c, where a constant pressure 
 of about 12 lbs. absolute is maintained by a reducing valve. 
 From the valve the steam is led to a condenser. Chamber 
 c, is kept steam tight from the outside by two bronze rings 
 
590 
 
 Steam Engineering 
 
 d, d, each made in three parts, which are held against the 
 shaft with slight pressure by the spiral springs e. A pres- 
 sure in an axial direction is caused by springs f. The 
 chambers of all the stuffing boxes of the turbine are con- 
 nected together. Thus a portion of the steam that leaves 
 the high pressure chamber will be drawn into the low pres- 
 sure side. When running light, partial vacuum exists in 
 all the stuffing boxes, the reducing valve allowing live 
 
 Fig. 243 
 
 steam to enter, thus preventing air from being drawn in. 
 
 Steam is led in Figs. 240 and 241 through the ring 
 passages, and excludes thereby the air, so that the vacuum 
 does not suffer. 
 
 The construction of a turbine stuffing box as steam tight 
 as that of the steam engine is still an unsolved problem. 
 For this reason we might add the excellent stuffing box of 
 Schwabe, that is used in steam-engine work, shown in 
 Fig. 243. This consists of a large number of rings D 
 
The Steam Turbine 591 
 
 made in three parts, held together by a circumferential 
 spiral spring. These rings (for the steam engine) press 
 on one another, and should either not touch the shaft at 
 all, or with only the slightest pressure. With turbines, the 
 soft packing at the outer end will of course be omitted, 
 and the rings must be prevented from turning, and so con- 
 structed as to be tight against either pressure or vacuum. 
 The inside and outside ends of the box are provided with 
 means for oiling. 
 
 The Regulation of the Steam Turbine. — The regulation 
 in the majority of different systems is acomplished by sim- 
 ple throttling, thus decreasing, at the very beginning, the 
 available work of the steam, and consequently the economy 
 of the turbine. The loss is measured by the product of the 
 increase of entropy and the absolute temperature of the 
 exhaust steam, which can easily be determined from the 
 entropy tables. 
 
 The ideal conditions would be to constantly work with a 
 full initial pressure, and to make all cross-sections of steam 
 passages suitable to the power required. Constructively, 
 this idea is most easily applicable to the single stage im- 
 pulse turbine, in which the nozzles are opened or closed one 
 after another by means of a regulator. 
 
 The following description of the construction, and prin- 
 ciples controlling the action of the leading types of steam 
 turbines manufactured in the United States is presented, 
 with the hope that it may prove to be not only interesting, 
 but instructive as well, to the student. 
 
 It may be said in general of the steam turbine, that it 
 has passed the experimental stage, and has come to the 
 front as an efficient power producer, having a bright 
 future before it. It has solved the problem of using super- 
 
592 Steam Engineering 
 
 heated steam, owing to the absence of all rubbing parts 
 exposed to the steam. This permits the use of steam of 
 high temperature, thus making it possible to realize the 
 advantages of economical operation. 
 
 
The Westinghouse-Parsons Steam 
 Turbine 
 
 The Westinghouse-Parsons Steam Turbine operates on 
 both impulse and reaction principles, and by a system of 
 compounding, which will be explained later on, the peri- 
 pheral velocity of the machine has been so reduced as to 
 
 Fig. 244 
 
 bring it within practical limits, while at the same time the 
 power value of the steam is utilized to a high degree of 
 efficiency. 
 
 The speed of the Westinghouse-Parsons turbine varies 
 from about 750 B. P. M. for a 5,000 K. W. machine, to 
 3,600 E. P. M. for a 400 K. W. turbine. 
 
 593 
 
594 Steam Engineering 
 
 The Westinghouse-Parsons turbine is fundamentally 
 based upon the invention of Mr. Charles A. Parsons, who, 
 while experimenting with a reaction turbine constructed 
 along the lines of Hero's engine, conceived the idea of 
 combining the two principles, reaction and impulse, and 
 also of causing the steam to flow in a general direction 
 parallel with the shaft of the turbine. This principle of 
 parallel flow is common to all four types of turbines, but 
 is perhaps more prominent in the Westinghouse-Parsons, 
 and less so in the De Laval. 
 
 Fig. 235 shows a general view of four Westinghouse- 
 Parsons steam turbines, and Fig. 244 shows a 600 H. P. 
 machine with the upper half of the cylinder, or stator as it 
 is termed, thrown back for inspection. Fig.. 245 is a sec- 
 tional view of a Westinghouse-Parsons turbine, and it will 
 be noticed that there are three sections or drums, gradually 
 increasing in diameter from the inlet A, to the third and 
 last group of blades. This arrangement may be likened 
 in some measure to the triple compound reciprocating 
 engine. 
 
 Fig. 246 shows the complete revolving part of a 3^000 
 H. P. turbine. Its weight is 28,000 lbs., length over all 
 19 feet 8 inches, and 12 feet 3 inches between bearings; 
 the largest diamater, 6 feet. 
 
 By reference to Fig. 244 it will be seen that the inside 
 of the cylinder is studded with rows of small stationary 
 blades, and that the rotor or' revolving part of the ma- 
 chine is also fitted with rows of small blades, similar in 
 shape and dimensions to the' stationary blades. When the 
 upper half of the cylinder is in position, each row of sta- 
 tionary blades fits in between two corresponding rows of 
 moving blades. This arrangement may perhaps be better 
 
Westinghouse-Parsons Steam Turbine 595 
 
 Fig. 245 
 
 SECTION OF STANDARD WESTINGHOUSE SINGLE FLOW TURBINE 
 
596 
 
 Steam Engineering 
 
 understood by reference to Fig. 247, which illustrates the 
 relation of the stationary blades to the moving blades when 
 in position, and also shows by the arrows the course of the 
 steam and its change of direction caused by the stationary 
 blades. 
 
 For the purpose of explanation the moving blades or 
 vanes may be considered as small curved paddles pro- 
 jecting from the surface of the rotor, and there is a large 
 number of them, as for instance, taking a 400 K. W. ma- 
 chine, there are 16,095 moving blades and 14,978 sta- 
 tionary blades, a total of 31,073. 
 
 Fig. 246 
 
 The stationary vanes, as previously explained project 
 from the inside surface of the cylinder. Both stationary 
 and moving vanes are similar in shape, and are made of 
 hard drawn material, and they are set into their places 
 and secured by a caulking process. The blades vary in size 
 from Yo to 7 in. in length, according to where they are 
 used. Referring to Fig. 244, it will be observed that the 
 shortest blades are placed at what might be termed the 
 steam end of each section or drum of the rotor and cylinder, 
 and that their length gradually increases, corresponding 
 
Westinghouse-Parsons Steam Turbine 597 
 
 with the increased volume of steam, until a mechanical 
 limit is reached, when a new group of blades begins on a 
 succeeding drum of larger diameter. Eeferring to Fig. 
 247, which is a sectional view of four rows of blades, it will 
 be noticed that all the blades, whether stationary or mov- 
 ing, have the same curvature. Also that the curves are set 
 opposite each other. The reason for this will be apparent 
 as the diagram is studied. The steam at pressure P first 
 comes in contact with row 1 of stationary blades. It 
 expands through this row, and in expanding the pressure 
 falls to P'. 
 
 (^ C^ CL C C CvC C C sTAT, °7 ARy blades 
 
 )) )) )) )) J 3 )) D 
 
 CCCCAOCC 
 
 J> i> )) J) K)) TJ1 
 
 MOVING BLADES 
 )N)\RY BLADES 
 MOVING BLADES 
 
 Fig. 247 
 
 The energy in the steam is converted into velocity, and 
 it impinges upon row 2 of moving blades, driving them 
 around in their course by impulse, A second expansion 
 now occurs in row 2, and again the energy is converted into 
 velocity, but this time the reaction of the steam as it leaves 
 the blades of row 2 also tends to impel them around in 
 their course. The moving blades thus receive motion from 
 two causes — the one due to the impulse of the steam strik- 
 ing them, and the other due to the reaction of the steam 
 leaving them. 
 
598 Steam Engineering 
 
 This cycle is repeated in rows 3 and 4, and so on through- 
 out the length of the rotor until the exhaust end is reached. 
 
 It should be noted that the general direction taken by 
 the steam in its passage through the turbine is in the form 
 of a spiral or screw line about the rotor. The clearance 
 between the blades as they stand in the rows is % in. for 
 the smallest size blades and % in. for the larger ones, 
 gradually increasing from the inlet to the exhaust. In the 
 5,000 K. W. machine the clearance at the exhaust end be- 
 tween the rows of blades is 1 in. It will thus be seen that 
 there is ample mechanical clearance, also allowance for 
 lateral motion for adjustment of the rotor, although this is 
 very slight, as the -rotor is balanced at all loads and pres- 
 sures by the balancing pistons PPP, Fig. 245, to which 
 reference is now made. These pistons revolve within the 
 cylinder, but do not come in mechanical contact with it; 
 consequently there is no friction. The diameter of each 
 piston corresponds to the diameter of one of the three 
 drums. 
 
 The steam entering the chamber A through valve V 
 presses against the turbine blades and goes through doing 
 work by reason of its velocity. It also presses equally in 
 the opposite direction against the first piston P, and so 
 the shaft or rotor has no end thrust. On leaving the first 
 group of blades and striking the second group the pressure 
 in either direction is again equalized by the balance port 
 E allowing the steam to press against the second balance 
 piston P. The same event occurs at group three, the 
 steam acting upon the third piston P. 
 
 The areas of the balancing pistons are such that, no 
 matter what the load may be, or what the steam pressure 
 or exhaust pressure may be, the correct balance is main- 
 
Westinghouse-Parsons Steam Turbine 599 
 
 tained and there is practically no end thrust. Below is 
 shown a pipe E connecting the back of the balancing pis- 
 tons with the exhaust chamber. This arrangement is for 
 the purpose of equalizing the pressure at this point with 
 the pressure in the exhaust chamber. 
 
 It might be thought that the blades, on account of their 
 being so light and thin, would wear out very fast, but ex- 
 perience so far shows that they do not. This may be ac- 
 counted for in two ways. First, the reduction of the 
 velocity of the steam, the highest velocity in the Parsons 
 turbine not exceeding 600 ft. per second; secondly, the 
 light steam thrust on each blade, said to be equal to about 
 1 oz. avoirdupois. This is far within the bending strength 
 of the material. A steam strainer is also placed in the 
 admission port, to prevent all foreign substances from en- 
 tering the turbine. 
 
 A rigid shaft and thrust or adjustment bearing accu- 
 rately preserves the clearances, which are larger in this 
 turbine than in other types, owing to the fact that the 
 entire circumference of the turbine is constantly filled 
 with working steam when in operation. 
 
 The bearings shown in Fig. 245 are constructed along 
 lines differing from those of the ordinary reciprocating 
 engine. The bearing proper is a gun metal sleeve, see Fig. 
 248, that is prevented from turning by a loose-fitting 
 dowel. Outside of this sleeve are three concentric tubes 
 having a small clearance between them. This clearance is 
 kept constantly filled with oil supplied under light pres- 
 sure, which permits a vibration of the inner shell or sleeve 
 and at the same time tends to restrain or cushion it. This 
 arrangement allows the shaft to revolve about its axis of 
 gravity, instead of the geometrical axis, as would be the 
 
600 
 
 Steam Engineering 
 
 case if the bearing were of the ordinary construction. The 
 journal is thus to a certain degree a floating journal, free 
 to run slightly eccentric according as the shaft may hap- 
 pen to be out of balance. 
 
 -.' iiii &» • - - -' 
 
 k^^A 
 
 Fig. 248 
 
 A flexible coupling is provided, by means of which the 
 power of the turbine is transmitted to the dynamo or other 
 machine it is intended to run. The oil from all the bear- 
 
W estingliouse-P arsons Steam Turbine 601 
 
 ings drains back into a reservoir, and from there it is forced 
 up into a chamber, where it forms a static head, which 
 gives a constant pressure of oil on all the bearings. A 
 secondary valve is located at Vs, by means of which high 
 pressure steam may be admitted to the steam space E on 
 the same principle that high pressure steam is admitted to 
 the low pressure cylinder of a compound engine. This 
 valve opens automatically in cases of emergency, such as 
 overload, failure of the condenser to work, etc. 
 
 The shaft, where it passes through either cylinder head, 
 is packed with a water seal packing, consisting of a small 
 paddle wheel attached to the shaft, which, through centri- 
 fugal action, maintains a static pressure of about 5 lbs. per 
 sq. in. in the water seal, thus preventing all leakage while 
 at the same time it is frictionless. 
 
 Governor. — The speed of the Westinghouse-Parsons tur- 
 bine is regulated by a fly ball governor constructed in such 
 manner that a very slight movement of the balls serves to 
 produce the required change in the supply of steam. Fig. 
 249 is a diagram of the governor mechanism. The ball 
 levers swing on knife edges instead of pins. The gover- 
 nor works both ways, that is to say, when the levers are 
 oscillating about their mid position a head of steam corre- 
 sponding to full load is being admitted to the turbine, and 
 a movement from this point, either up or down, tends to 
 increase or to decrease the supply of steam. 
 
 Eeferring to Fig. 249„ B is a piston directly connected 
 to the admission valve. Steam is admitted to this piston 
 under control of the pilot valve A, which has a slight but 
 continuous reciprocating motion derived from the eccentric 
 rod C, and the function of the governor is to vary the plane 
 of oscillation of this valve, thus causing it to admit more 
 
602 
 
 Steam Engineering 
 
 or less steam to piston B. The admission valve, being 
 actuated exclusively by piston B, is thus caused to remain 
 open for a longer or shorter period of! time, according to 
 the load upon the turbine. 
 
 The vibrations of the admission valve, although very 
 slight, are continuous and regular, about 165 per minute, 
 and are transmitted primarily by means of an eccentric, 
 the rod of which is shown at C, Fig. 249. 
 
 Fig. 249 
 
 The governor sleeve is used as a floating fulcrum, and 
 the points D and E are fixed. By means of this very 
 ingenious device the steam is admitted to the turbine in 
 puffs, either long or short, according to the demand for 
 steam. At full load the puffs merge into an almost con- 
 tinuous blast. When the load has increased to the point 
 where the valve is wide open continuously, a full head of 
 steam is being admitted. Beyond this the secondary valve 
 comes into action, thus keeping the speed up to normal. 
 
Westinghouse-Parsons Steam Turbine 
 
 603 
 
 The rotor requires perfect balancing to insure quiet 
 runnings but this is easily accomplished in the shop by 
 means of a balancing machine used by the builders. 
 
 Steam turbines generally show higher efficiency in the 
 use of steam than reciprocating engines do, and this fact 
 is due to three leading causes. First, it is possible with 
 the turbine to use highly superheated steam which, owing 
 to the difficulties attending lubrication, could not be used 
 in the reciprocating engine. Second, a larger proportion of 
 the heat contained in the steam is converted into work, for 
 
 Fig. 250 
 new blading material 
 
 the reason that the steam is allowed to expand to a much 
 lower pressure, and into a higher vacuum. In addition to 
 this, the velocity of the expanding steam is utilized in a 
 much higher degree in the turbine as compared with the re- 
 ciprocating engine. Third, mechanical friction or lost 
 work is reduced to the minimum. Under test a 400 K. W. 
 Westinghouse-Parsons steam turbine, using steam at 150 
 lbs. initial pressure and superheated about 180°, consumed 
 11.17 lbs. of steam per brake horse power hour at full load. 
 The speed was 3,550 E. P. M. and the vacuum was 28 in. 
 
604 Steam Engineering 
 
 With dry saturated steam the consumption was 13.5 lbs. 
 per B. H. P. hour at full load, and 15.5 lbs. at one-half 
 load. 
 
 A 1,000 K. "W. machine, using steam of 150 lbs. pres- 
 sure and superheated 140°, exhausting into a vacuum of 
 28 in., showed the very remarkable economy of 12.66 lbs 
 of steam per E. H. P. per hour. 
 
 A 1,500 K. W. Westinghouse-Parsons turbine, using dry 
 saturated steam of 150 lbs. pressure with 27 in. vacuum, 
 consumed 14.8 lbs. steam per E. H. P. hour at full load, 
 and 17.2 lbs. at one-half load. 
 
 The Westinghouse machine company have recently in- 
 troduced a new blade material which is now used in all 
 Westinghouse turbines. It is a copper-coated steel blade, 
 or, as designated by the builder, "Monnot metal," in which 
 the copper coating (seen in Fig. 250) is chemically welded 
 to the steel so thoroughly that the blades can be drawn to 
 the desired shape from the original ingot, without weaken- 
 ing the union between the copper and steel. The process 
 of drawing makes the copper coating somewhat thicker at 
 the inlet and outlet edges of the blade, though the remain- 
 ing portions of the blade surfaces are coated with an abso- 
 lutely uniform thickness of copper. The only portion of 
 the blade where steel is exposed, is the small surface of the 
 tip of the blade where, however, corrosion is the least detri- 
 mental, for should the tips corrode, the copper coating 
 would still remain intact, thus leaving the working blade 
 surfaces untouched and the blade clearances unaltered. 
 
 Figs. 251 and 252 show sectional elevations of the double 
 flow type of steam turbines now being manufactured by the 
 Westinghouse company, in addition to the standard single 
 flow turbine already described. 
 
Westinghouse-Parsons Steam Turbine 
 
 605 
 
 Fig. 251 
 section of westinghouse double flow turbin^ 
 
606 
 
 Steam Engineering 
 
 Fig. 252 
 
 westinghouse double flow low-pressure turbine 
 
 Sectional Elevation 
 
 Fig. 251 shows the machine as adapted for using steam 
 of high initial pressure, in fact an impulse turbine, in which 
 the steam admitted first to the nozzle block, is expanded 
 
Westinghouse-Parsons Steam Turbine 607 
 
 in nozzles arranged about the periphery, and impinges 
 upon the impulse buckets of the central rotation wheel. 
 There are two rows of moving blades upon the impulse 
 wheel, with an intermediate set of reversing blades as 
 shown. Issuing from the delivery side of this wheel with 
 its velocity energy practically all abstracted, the steam 
 passes, as shown by the arrow, to an intermediate set of 
 Parsons blading. As this blading has no counterpart upon 
 the other side of the turbine, the pressure upon it must be 
 counterbalanced, and this is done by making the extension 
 of the hub by which the impulse wheel is keyed to the shaft, 
 into a piston or dummy of the mean diameter of the inter- 
 mediate stage, as shown at P. After passing the inter- 
 mediate stage the steam divides, one portion passing 
 directly to the low-pressure blading at the left, while the 
 rest passes through the hollow shell of the rotor to the 
 similar pressure blades upon the right. As these sections 
 are equal and symmetrical they counterbalance each other, 
 so that no further dummies are required than the small 
 one already referred to. 
 
 For regulating the steam supply in accordance with the 
 load, two methods other than that of simple throttling with 
 its sacrifice of temperature head are available. 
 
 The admission area may be varied by the cutting in and 
 out of nozzles. 
 
 The duration of the time of admission through a con- 
 stant area may be varied. 
 
 The first is the Curtis method, impracticable for a full- 
 admission turbine like the Parsons ; the second, that which 
 has been developed by the Westinghouse engineers for the 
 Parsons as they build it. The adoption of the partial ad- 
 mission for first stage in the double flow machine gave the 
 
608 Steam Engineering 
 
 Westinghouse designers their option of the two methods, 
 but they have preferred to continue the variable duration 
 puff system, already described in connection with single 
 flow machines. A disadvantage of the variable nozzle 
 method of regulation is, that if the area of the nozzles of 
 the succeeding stages is correctly proportioned to pass 
 along the steam admitted by a certain number of primary 7 
 nozzles, it will be too great when fewer nozzles are in 
 action, and too small when there are more. This will 
 result in a considerable variation of the pressure in the 
 succeeding stages, and of the pressure ratios of expansion 
 and jet velocity acquired in those stages, and interfere 
 with the designer's intention with regard to the distribu- 
 tion of work and the relation of blade to jet velocity. This 
 could be overcome only by adjusting the nozzles of the suc- 
 ceeding individual stages in harmony with those of the 
 initial stage. 
 
 If, on the other hand, the passages through the turbine 
 are permanently arranged in the correct relation to each 
 other, this relation will persist whether the flow is con- 
 tinuous or intermittent, and the energy developed can be 
 regulated to the demand by making the flow more nearly 
 continuous, as the load approaches the rated capacity of 
 the machine. So far as the change in initial pressure due 
 to the alternate letting on and shutting off of the steam is 
 concerned, theory indicates, and experiment proves that 
 where the expansion in each stage is but a small part of 
 the total range, as in the Parsons turbine, the initial and 
 terminal pressures of each stage rise and fall, resulting in 
 a fairly constant pressure ratio at each successive expan- 
 sion; in other words, for small ranges, and throttle gov- 
 erning, the nozzle and blade areas are reasonably correct 
 
~\Yestinghouse-Parsons Steam Turbine 609 
 
 through, a wide range of load and pressure distribution. 
 For this reason the impulse section of the Westinghouse 
 turbine., doing, say, only one-fifth of the total work, is 
 properly proportioned for a wide range in load and may be 
 governed without resorting to intermediate nozzle control, 
 and without sacrifice of economy and fractional loads. 
 
 Advantage Gained. — The balancing pistons have been re- 
 duced to a minimum. In the single-flow types the high- 
 pressure dummy occupies fully one-half of the total dummy 
 piston length on the shaft, while the low-pressure piston 
 is 2y% times the high-pressure diameter. 
 
 A reduction of nearly 50 per cent in shaft span between 
 bearings. Owing to the rotor construction a better loading 
 of the shaft is also obtained; that is, the rotor weight is 
 transmitted to the shaft at points nearer the bearings than 
 in the single-flow rotor, where the weight is largely dis- 
 tributed. 
 
 An increase to about double rotative speed made possible 
 by the reduction in shaft span and loading; that is, to a 
 general greater rigidity of the double-flow construction. 
 
 A reduction of about 70 per cent in the bulk of the main 
 parts of the machine with practically the same output. 
 
 Internal cylinder stresses due to high-pressure and high- 
 temperature steam are avoided by isolating the incoming 
 steam within separate nozzle chambers, so that the main 
 body of the turbine is subjected to steam having not much 
 over 75 pounds gauge pressure with practically no super- 
 heat. 
 
 The bulk of the low-pressure stage is better distributed 
 and the length of the low-pressure blades greatly reduced 
 by subdividing this stage into two parts located at opposite 
 ends of the rotor. 
 
 As will be plain from what has preceded, the advantages 
 
610 
 
 Steam Engineering 
 
 sought in this form of turbine are constructional and me- 
 chanical rather than economic. For high-pressure work 
 the standard Westinghouse-Parsons single-flow turbine will 
 be built up to capacities of 3,000 kilowatts; above 5,000 
 kilowatts all units will be built upon the double-flow prin- 
 
 Fig. 253 
 
 3,000 K. W. WESTINGHOUSE DOUBLE FLOW STEAM TURBINE 
 
 ciple. The latter construction will also be used for the 
 low-pressure turbines to which it is so admirably adapted, 
 as shown in Fig. 252, which is a section of the Westing- 
 house low-pressure, double-flow, steam turbine designed 
 for utilizing the exhaust steam from non-condensing recip- 
 rocating engines. Fig. 253 shows a view of a double-flow 
 steam turbine without the generator attached. 
 
The Curtis Steam Turbine 
 
 In the Curtis turbine the heat energy in the steam is 
 imparted to the wheel-, both by impulse and reaction, but 
 the method of admission differs from that of the Westing- 
 house-Parsons, in that the steam is admitted through ex- 
 panding nozzles in which nearly all of the expansive force 
 of the steam is transformed into the force of velocity. The 
 steam is caused to pass through one, two, or more stages 
 of moving elements, each stage having its own set of ex- 
 panding nozzles, each succeeding set of nozzles being greater 
 in number and of larger area than the preceding set. The 
 ratio of expansion within these nozzles depends upon the 
 number of stages, as, for instance, in a two-stage machine, 
 the steam enters the initial set of nozzles at boiler pres- 
 sure, say 180 lbs. It leaves these nozzles and enters the 
 first set of moving blades at a pressure of about 15 lbs., 
 from which it further expands to atmospheric pressure in 
 passing through the wheels and intermediates. Trom the 
 pressure in the first stage the steam again expands through 
 the larger area of the second stage nozzle to a pressure 
 slightly greater than the condenser vacuum at the entrance 
 to the second set of moving blades, against which it now 
 impinges, and passes through still doing work, due to 
 velocity and mass. 
 
 From this stage the steam passes to the condenser. If 
 the turbine is a four-stage machine and the initial pressure 
 is 180 lbs., the pressure at the different stages would be dis- 
 tributed in about the following manner: Initial pressure, 
 180 lbs.; first stage, 50 lbs.; second stage, 5 lbs.; third 
 
 611 
 
612 
 
 Steam Engineering 
 
 stage, partial vacuum, and fourth stage, condenser vacuum. 
 
 Fig. 254 gives a general view of a 5,000 K. W. turbine 
 
 and generator. The generator is shown at the top, while 
 
 the turbine occupies the middle and lower section. A por- 
 
 Fig. 254 # 
 
 5,000 K. W. CURTIS STEAM TURBINE DIRECT CONNECTED TO 5.000 K. W. 
 THREE-PHASE ALTERNATING CURRENT GENERATOR 
 
 tion of the inlet steam pipe is shown, ending in one nozzle 
 group at the side. There are three groups of initial noz- 
 zles, two of which are not shown. The revolving parts of 
 this unit are set upon a vertical shaft, the diameter of the 
 
Curtis Steam Turbine 613 
 
 shaft corresponding to the size of the unit. For a machine 
 having the capacity of the one illustrated by Fig. 254 the 
 diameter of the shaft is 14 in. 
 
 The shaft is supported by, and runs upon a step bearing 
 at the bottom. This step bearing consists of two cylindrical 
 cast iron plates, bearing upon each other and having a 
 central recess between them into which lubricating oil is 
 forced under pressure by a steam or electrically driven 
 pump, the oil passing up from beneath. A weighted ac- 
 cumulator is sometimes installed in connection with the 
 oil pipe as a convenient device for governing the step bear- 
 ing pumps, and also as a safety device in case the pumps 
 should fail, but it is seldom required for the latter pur- 
 pose, as the step bearing pumps have proven, after a long 
 service in a number of cases, to be reliable. The vertical 
 shaft is also held in place and kept steady by three sleeve 
 bearings, one just above the step, one between the turbine 
 and generator, and the other near the top. These guide 
 bearings are lubricated by a standard gravity feed system. 
 It is apparent that the amount of friction in the machine 
 is very small, and as there is no end thrust caused by the 
 action of the steam, the relation between the revolving and 
 stationary blades may be maintained accurately. As a con- 
 sequence, therefore, the clearances are reduced to the mini- 
 mum. 
 
 The Curtis turbine is divided into two or more stages, 
 and each stage has one, two or more sets of revolving 
 blades bolted upon the peripheries of wheels keyed to the 
 shaft. There are also the corresponding sets of stationary 
 blades, bolted to the inner walls of the cylinder or casing. 
 As in the Westinghouse-Parsons type, the function of the 
 stationary blades is to give direction to the flow of steam. 
 
614 Steam Engineering 
 
 Fig. 255 illustrates one stage of a 500 K. W. turbine in 
 course of construction. It will be observed that there are 
 three wheels, and that in the spaces between these wheels 
 the stationary buckets or vanes are placed, being firmly 
 bolted to the casing. Fig. 256 shows sections of both 
 revolving and stationary buckets ready to be placed in 
 
 Fig. 255 
 500 k. w. curtis steam turbine in course of construction 
 
 position. The illustration in Fig. 255 shows the lower or 
 last stage. The clearance between the revolving and sta- 
 tionary blades is from £$ to ^ in., thus reducing the 
 wasteage of steam to a very low percentage. The diameters 
 of the wheels vary according to the size of the turbine, 
 that of a 5,000 K. W. machine being 13 ft. 
 
Curtis Steam Turbine 
 
 615 
 
 REVOLVING BUCKETS FOR CURTIS STEAM TURBINE 
 
 stationary buckets for curtis steam turbine 
 Fig. 256 
 
 Fig. 257 shows a nozzle diaphragm with its various 
 openings, and it will be noted that the nozzles are set at 
 an angle to the plane of revolution of the wheel. 
 
616 
 
 Steam Engineering 
 
 Fig. 258 is a diagram of the nozzles, moving blades and 
 stationary blades of a two-stage Curtis steam turbine. The 
 steam enters the nozzle openings at the top, controlled by 
 
 •S ttsorr? <T/7e5 £. 
 
 i 
 
 r««««««««« 
 
 mm 
 
 ma<«m««««e 
 
 A/ozz/<§ 
 St-otL/'or-tor^ J3 /<><*&& 
 
 /VoZZte ZD/t=r/=>/->r~acfrr\ 
 
 Moving fl/oafe^ 
 
 3£o£/or7C3rr~i^ 
 
 A7ov/r>£T /3/o<=/gs 
 
 St,at. /or^ctr-c^ 
 
 cccccccccccccccccccccc 
 
 I I I I I I 
 
 Fig. 258 
 
 DIAGRAM OF NOZZLES AND BUCKETS IN CURTIS STEAM TURBINE 
 
 the valves shown, the regulation of which will be explained 
 later on. In the cut Fig. 258 two of the valves are open, 
 and the course of the steam through the first stage is indi- 
 
 
 L 
 
Curtis Steam Turbine 617 
 
 cated by the arrows. After passing successively through 
 the different sets of moving blades and stationary blades 
 in the first stage, the steam passes into the second steam 
 chest. The flow of steam from this chamber to the second 
 stage of buckets is also controlled by valves, but the func- 
 tion of these valves is not in the line of speed regulation, 
 but for the purpose of limiting the pressure in the stage 
 chambers, in a manner somewhat similar to the control of 
 the receiver pressure in a two-cylinder or three-cylinder 
 compound reciprocating engine. 
 
 The valves controlling the admission of steam to the 
 second, and later stages differ from those in the first group 
 in that they partake more of the nature of slide valves and 
 may be operated either by hand, or automatically ; in fact, 
 they require but very little regulation, as the governing 
 is always done by the live steam admission valves. 
 
 Action of the Steam in a Two-stage Machine. — As prev- 
 iously stated, the steam first strikes the moving blades in 
 the first stage of a two-stage machine at a pressure of about 
 15 lbs. above atmospheric pressure, but with great velocity. 
 From this wheel it passes to the set of stationary blades 
 between it and the next lower wheel. These stationary 
 blades change the direction of flow of the steam and cause 
 it to impinge the buckets of the second wheel at the proper 
 angle. 
 
 This cycle is repeated until the steam passes from the 
 first stage into the receiving chamber, or steam chest for the 
 second stage. Its passage from this chamber into the 
 second stage is controlled by valves, which, as before stated, 
 are regulated either by hand, or automatically. The course 
 of the steam through the nozzles and blades of the second 
 stage is clearly indicated by the arrows, and it will be 
 noted that steam is passing through all the nozzles. 
 
618 Steam Engineering 
 
 At this point it might be well to consider the question 
 which no doubt arises in the mind of the student in his 
 efforts to grasp the underlying principles in the action of 
 the steam turbine. Why is it that the impingement of the 
 steam, at so low a pressure, against the blades or buckets 
 of the turbine, imparts such a large amount of energy 
 to the shaft? 
 
 The answer is, because of velocity, and a good example 
 of the manner in which velocity may be made to increase 
 the capacity of an agent to do work is illustrated in the 
 following way: Suppose that a man is standing within 
 arm's length of a heavy plate glass window and that he 
 holds in his hand an iron ball weighing 10 lbs. Suppose 
 the man should place the ball against the glass and press 
 the same there with all the energy he is capable of exerting. 
 He would make very little, if any, impression upon the 
 glass. But suppose that he should walk away from the 
 window a distance of 20 ft. and then exert the same amount 
 of energy in throwing the ball against the glass, a different 
 result would ensue. The velocity with which the ball would 
 impinge the surface of the glass would no doubt ruin the 
 window. Now, notwithstanding the fact that weight, energy 
 and time involved were exactly the same in both instances, 
 yet a much larger amount of work was performed in the 
 latter case, owing to the added force imparted to the ball 
 by the velocity with which it impinged against the glass. 
 
 Speed Regulation. — The governing of speed is accom- 
 plished in the first set of nozzles, and the control of the 
 admission valves here is effected by means of a centrifugal 
 governor attached to the top end of the shaft. This gover- 
 nor, by a very slight movement, imparts motion to levers, 
 which in turn work the valve mechanism. The admission 
 
Curtis Steam Turbine 
 
 619 
 
 of steam to the nozzles is controlled by piston valves, which 
 are actuated by steam from small pilot valves which are in 
 turn under the control of the governor Fig. 259 shows the 
 
 Fig. 259 
 
 GOVERNOR FOR 5,000 K. W. TURBINE 
 
 form a governor for a 5,000 K. "W. turbine, and Fig. 260 
 shows the electrically operated admission valves for one 
 set of nozzles. 
 
620 
 
 Steam Engineering 
 
 Speed regulation is affected by varying the number of 
 nozzles in flow, that is for light loads fewer nozzles are open, 
 and a smaller volume of steam is admitted to the turbine 
 wheel, but the steam that is admitted impinges the moving 
 blades with the same velocity always, no matter whether 
 the volume be large or small. With a full load and ail the 
 nozzle sections in flow, the steam passes to the wheel in a 
 broad belt and steady flow. 
 
 Fig. 260 
 electeically operated valve 
 
 In addition to the method just described, of actuating 
 the addmission valves by steam, the General Electric Com- 
 pany, manufactures of the Curtis Turbine, have recently 
 introduced a system of hydraulicaly operated valves for 
 speed regulation. 
 
 These valves are also of the poppet type, and each is 
 closed by a helical spring in compression. In the closed 
 position they are held tight by steam pressure, against 
 which they are opened. The valves on one machine are all 
 
Curtis Steam Turbine 
 
 621 
 
 duplicates, and are opened in rotation by cams (one for 
 each valve) mounted on a shaft, each cam being given in 
 succession an angular advance over its predecessor. This 
 
 Fig. 261 
 cam shaft is rotated by the piston in a hydraulic cylinder, 
 the cylinder being mounted either on the generator or 
 valve casing. 
 
622 Steam Engineering 
 
 The valves open gradually; that is there will be throt- 
 tling on the opening, or closing valve, before the next one 
 in either side is opened or closed, so that the exact amount 
 of steam required can be admitted for any definite load. 
 Fig. 261 shows a section of the hydraulic cylinder, and 
 controlling valve. The position of piston A is controlled 
 by a balanced piston valve B. The liquid under pressure 
 is admitted at C, and discharged at D. The rod E is con- 
 nected with the governor, and rod F with the piston rod. 
 
 Operation. — The rod E receives its motion from the 
 governor, and occupies a fixed position for any given speed 
 between the limits through which the governor is designed 
 to operate. The lever arms Gr and G', and H and H' are 
 so proportioned that the piston A will occupy a definite 
 fixed position to correspond with any position of rod E. 
 
 Therefore as the crosshead K transmits its motion 
 through connecting rod 1ST; (see Fig. 262) to the crank 
 L on the cam shaft M, there will be a fixed number of 
 valves open for any position of the governor. While the 
 turbine is operating at a fixed speed, the piston valve will 
 occupy a central position, closing both ports and P. 
 When there is a drop in speed, the governor causes rod E 
 to move down, thus opening part to discharge, and port 
 P to admit liquid under piston A which them moves up- 
 wards, opening more valves to satisfy the demand for steam. 
 In moving up the piston transmits its motion through rod 
 F to the piston valve B, restoring it to the central position. 
 When operating on a fixed, or slightly varying load, the 
 main piston should not continuously move over a distance 
 greater than that corresponding to the lap of the piston 
 valve, and under no condition of governing should the 
 main piston continually travel back and forth over a dis- 
 
Curtis Steam Turbine 
 
 b23 
 
 Fig. 262 
 
 tance greater than this. Any larger movements should 
 only occur when greater or less power is demanded for 
 
624 Steam Engineering 
 
 considerable variation in load. Any continuous opening 
 and closing of the valves during a steady load is an indi- 
 cation of excessive friction in the governor rigging, or pis- 
 ton valve, and it should be eliminated as soon as possible. 
 
 It is essential that the pistons on the piston valve B, 
 Fig. 261 be reduced in diameter at their centers ^ in. 
 as indicated in the illustration. If this is not done it may 
 be responsible for sticking of the piston valve, thereby in- 
 terfering with the satisfactory regulation of the machine. ■ 
 
 For different machines the connections may be altered, 
 and in some the operation is reversed, by crossing the ports, 
 so that the piston A will move in the same direction as the 
 piston valve B, and. in the application of the gear to later 
 machines of large capacity, it has been found advisable to 
 place the cylinder horizontal, operating crank shafts of 
 valve casings by means of rack and pinion with bevel gear 
 transmission, or with racks operating directly on pinions 
 on cam shafts, but the principle of operation is the same, 
 only modified in application to suit particular cases. 
 
 Adjustment. — With the piston A, and the piston valve 
 B, both in their mid positions, the rod F should be of such 
 a length that the lever G will be horizontal. The connect- 
 ing rod N is adjusted so that with piston A at the extreme 
 end of its up stroke, all the steam valves are open, and the 
 first one just ready to close. With the piston A in this 
 position (i. e., at the extreme end of its stroke,) and the 
 governor at the low speed position, the rod- E should be 
 adjusted so that the piston valve B, will be in its mid 
 position. 
 
 Precautions. — (1) It is absolutely essential that all con- 
 nections between governor and valve be entirely free from 
 friction. 
 
Curtis Steam Turbine 625 
 
 (2) The piston valve B must move freely for the whole 
 length of its stroke, so that if the rod E be disconnected 
 from the arm G, the valve will drop of its own weight, 
 either with pressure on or off. 
 
 (3) There must be absolutely no binding at any of the 
 joints through the whole travel. 
 
 (4) The liquid used must be entirely free from dirt, or 
 grit, of any nature. 
 
 (5) On the main steam valves; in the closed position, 
 when the roller has ridden off of the cam, it must not press 
 on the cam shaft, as this will prevent valve seating properly. 
 
 (6) The piston valve and bore must be perfectly round 
 and absolutely straight, or an excessive leakage will be 
 established on one side of the valve, causing it to bind. 
 
 (7) The pressure exerted by the main valve springs in 
 the open position must be in excess of that sufficient to 
 overcome steam pressure on rod, and any friction that may 
 exist in packing. 
 
 (8) The plate below main valve springs must be a slid- 
 ing fit in guides at all temperatures. 
 
 (9) Care must be taken in the adjustment of the length 
 of the rods E and F, that in no position of the governor, or 
 piston, can the piston valve become jammed at the end of 
 its stroke. 
 
 (10) A heavy oil must not be used or the action will be 
 sluggish. 
 
 Piping. — -Fig. 263 shows a diagram of piping for a ma- 
 chine using oil to operate the valves. This is supplied by the 
 same pumps that furnish lubrication for the guide bearings. 
 A relief valve E, is adjusted to the desired pressure for 
 operating the gear. When the speed is constant and the 
 valve not taking any oil, the excess supplied by pumps will 
 be discharged through this relief valve. 
 
626 
 
 Steam Engineering 
 
 The special reducing valve shown in Fig. 264, and at S, 
 Fig. 263, is provided to control the amount of oil supplied 
 to the bearings. 
 
 This valve can be closed, or adjusted over a wide range, by 
 altering the effective length of baffler. 
 
 Referring to Fig. 263, the tank marked "air chamber" is 
 
 O/ZSupp/y for Bearings 
 
 Wranfi 
 
 "ft Oro/r> /l/r Cnamoer 
 
 p 
 
 ""'- 0//PtsMp3 
 
 Suction s fte/,ef Va/ve 
 
 Fie. 3 
 
 Fig. 263 
 
 provided in order to give a reserved capacity of oil should 
 the pumps for any reason stop, and also to form an air- 
 cushion on the system. The valve at the top of this tank 
 should be kept closed, and the oil allowed to compress the 
 air contained in the tank, and from time to time the tank 
 should be completely emptied and refilled with air. The 
 
Curtis Steam Turbine 
 
 627 
 
 emptying can be easily accomplished by opening the three- 
 way valve to discharge to the oil tank. This need not in- 
 terfere with the operation of the machine. After the air 
 chamber is emptied, valve J should be closed, and the three- 
 way valve open to admit oil to the chamber. 
 
 OUMr 
 
 -* 
 
 Fig. 264 
 
 In installations where oil is used for the turbine step 
 bearing, oil for the operating gear and bearings may be 
 taken from the high pressure pipe line, on the pump side 
 of the step baffler, through a reducing valve. The piping 
 
628 
 
 Steam Engineering 
 
 system remains as shown diagramatlcally in Fig. 263 except 
 for change in source of supply of operating fluid. 
 
 In case the station installation includes an air compres- 
 
 Fig. 265 
 
 sor, this equalizing tank may be piped in the system, the 
 connection being made on the side of the tank (as provided 
 for). The refilling of the tank is thus much simplified, 
 and its capacity for emergency operation greatly increased. 
 
Curtis Steam Turbine 6£t 
 
 Care should be taken to insure tightness of both valve con- 
 trolling air supply to tank, and pet cock at the top. 
 
 Step Bearing. — Fig. 265 is a section through the cast iron 
 step blocks. The lower block in the illustration has two 
 holes drilled in it to match the two dowel pins seen project- 
 ing from the other block. There is another hole through 
 the center of the lower block threaded for %" pipe — The 
 step lubricant (oil or water) is forced up through this hole, 
 and out between the raised edges in a film, thus floating the 
 rotating elements of the turbine on a frictionless disk of 
 lubricant. The upper side of the top step block is counter- 
 bored to fit the lower end of the turbine shaft, in which 
 there is also a slot for the reception of a key that is fitted 
 across the top end of the step block. 
 
 The counterbore centers the block, the dowel-pins guide 
 the key into the slot, and the key causes the block to turn 
 with the shaft. These are all close fits, and when it be- 
 comes! necessary to remove the block for inspection or re- 
 pairs, it must be pulled off by means of a screw introduced 
 into a threaded hole in the under side of the lower block. 
 The whole is supported by, and rests upon a large screw that 
 passes up through a block of cast-iron which has a threaded 
 bronze bushing that forms the nut for the screw. The 
 large block termed the cover plate is held to the base of the 
 turbine by eight l 1 /^ in ch cap screws. A good idea of the 
 construction may be gained by reference to Fig. 266 which 
 is a section of the lower portions. It will be noticed that the 
 % in. oil supply pipe passes up through the entire length 
 of the large step supporting screw, and connects with the 
 oil passage through the lower step block. 
 
 Clearance. — With the Curtis turbine, the matter of clear- 
 ance is very important. There must be no rubbing contact 
 
630 
 
 Steam Engineering 
 
 between the revolving and stationary buckets. Neither 
 must there be too much clearance. Provision is therefore 
 made for inspection, and adjustment of the clearance in the 
 following manner. A two inch hole is drilled and tapped 
 
 .Steam 
 Supply 
 
 OilTDraia 
 
 TJ-*— Oil Supply 
 
 Fig. 266 
 
 into each stage, sometimes opposite a row of moving blades 
 and sometimes opposite the stationary blades. 
 
 Two inch plugs are screwed into these holes, to be re- 
 moved when an inspection is to be made. The clearance is 
 
Curtis Steam Turbine 631 
 
 not uniform in all the stages, but is least in the first stage, 
 and greatest in the last. The clearances in each stage of a 
 1500 K W machine for instance are as follows: 1st stage 
 0.06 to 0.08, 2nd stage 0.08 to 0.1, 3d stage 0.08 to 0.1, 
 4th stage 0.08 to 0.2. 
 
 These clearances are measured by clearance gages, which 
 are tapering slips of steel about %-in. wide accurately 
 ground and graduated by markings, the difference in thick- 
 ness of the gage between graduations being 0.001-in., the 
 graduations being %-in. apart. 
 
 When it is desired to measure the clearance, one of the 
 2 inch plugs is taken out, and a clearance gage which has 
 previously been rubbed with red lead is inserted between 
 the revolving and stationary buckets as far as it will go, 
 and then pulled out. 
 
 The red lead marking on the gage will show how far it 
 went in, and the nearest graduation in thousandths of an 
 inch will show the clearance, after noting which, the red 
 lead is rubbed on the gage again, and it is tried on the 
 other side, and if there is any difference either high or low 
 it is corrected by placing the wheel as nearly in the middle 
 of the clearance space as possible, which is done by means 
 of the step supporting screw shown in Fig. 266. 
 
 The clearance may be adjusted while the machine is run- 
 ning at full speed in the following manner: turn the step 
 supporting screw until the wheels are heard or felt to rub 
 slightly, then mark the screw, and turn it in the opposite 
 direction until the wheels rub again. After marking the 
 screw at this point, it should be turned back half way be- 
 tween the two marks. 
 
 This method of adjusting the clearance requires great 
 skill, and experience, and it would seem that the gage 
 method is to be preferred for safety. 
 
632 Steam Engineering 
 
 Packing. — The shaft of the Curtis turbine is packed with 
 carbon packing, where it passes through the top head of the 
 wheel case. This packing consists of blocks of carbon made 
 into rings, each ring consisting of three segments which 
 break joints. These rings are fitted to the shaft with a 
 slight clearance, and soon get a smooth polish which is not 
 only frictionless but steam tight. The rings are held close 
 to the shaft either by light springs, or the pressure of the 
 steam in the case. 
 
 The Baffler. — This is a device for restricting the flow of 
 water, or oil to the step and guide bearing. Its most im- 
 portant function is to steady the flow from the pump, and 
 maintain a constant oil film as the pressure varies with the 
 load, and in cases where several machines are operating on 
 the same step-bearing system, the baffler fixes the flow to 
 each machine. The amount, and pressure of oil or water 
 required to float a turbine, and lubricate the guide bearing 
 depend upon each other, and also upon the condition of the 
 step bearing. Usually from 4% to 5% gallons per min- 
 ute flowing under a pressure of from 425 to 450 lbs. per sq. 
 in. is found to be correct for a 1500 K W machine; of 
 course larger machines require a heavier pressure. The area 
 of the step bearing must be considered also. The principle 
 upon which the baffler operates is as follows : into the barrel 
 or body of the device is inserted a plug which is simply a 
 square threaded worm, the length of which, and the dis- 
 tance it enters the barrel of the baffler determining the 
 amount of flow. The more turns that the water must pass, 
 the less will be the flow. 
 
The De Laval SteamTurbine 
 
 The De Laval steam turbine, the invention of Carl 
 De Laval of Sweden, is noted for the simplicity of its con- 
 struction and the high speed of the wheel — 10,000 to 30,000 
 E. P. M. The difficulties attending such high velocities 
 are, however, overcome by the long, flexible shaft and the 
 ball and socket type of bearings, which allow of a slight 
 flexure of the shaft in order that the wheel may revolve 
 about its center of gravity, rather than the geometrical 
 center or center of position. All high speed parts of the 
 machine are made of forged nickel steel of great tensile 
 strength. But one of the most striking features of this 
 turbine is the diverging nozzle, also the invention of De 
 Laval. 
 
 It is well known that in a correctly designed nozzle the 
 adiabatic expansion of the steam from maximum to mini- 
 mum pressure will convert the entire static energy of the 
 steam into kinetic. Theoretically this is what occurs in 
 the De Laval nozzle. The expanding steam acquires great 
 velocity, and, the energy of the jet of steam issuing from 
 the nozzle is equal to the amount of energy that would be 
 developed if an equal volume of steam were allowed to 
 adiabatically expand behind the piston of a reciprocating 
 engine, a condition, however, which for obvious reasons 
 has never yet been attained in practice with the reciprocat- 
 ing engine. But with the divergent nozzle the conditions 
 are different. 
 
 Kef erring to Fig. 267, a continuous volume of steam 
 at maximum pressure is entering the nozzle at E, and, pass- 
 
 633 
 
634 
 
 Steam Engineering 
 
 ing through it, expands to minimum pressure at F, the 
 temperature of the nozzle being at the same time constant, 
 and equal to the temperature of the passing steam. The 
 
 Fig. 267 
 de laval nozzle 
 
 principles of the De Laval expanding nozzle are in fact 
 more or less prominent in all steam turbines. The facilities 
 for converting heat into work are increased by its use, and 
 
De Laval Steam Turbine 
 
 635 
 
 the losses by radiation and cooling influences are greatly 
 lessened. 
 
 The De Laval steam turbine is termed by its builders 
 a high-speed rotary steam engine. It has but a single 
 wheel, fitted with vanes or buckets of such curvature as 
 
 Fig. 268 
 the de laval turbine wheel and nozzles 
 
 has been found to be best adapted for receiving the im- 
 pulse of the steam jet. There are no stationary or guide 
 blades, the augular position of the nozzles giving direction 
 to the jet. Fig. 268 shows the form of wheel and the 
 nozzles. The nozzles are placed at an angle of 20° to the 
 
636 Steam Engineering 
 
 plane of motion of the buckets, and the course of the 
 steam is shown by the illustration. 
 
 The heat energy in the steam is practically devoted to 
 the production of velocity in the expanding or divergent 
 nozzle, and the velocity thus attained by the issuing jet 
 of steam is about 4,000 ft. per second. To attain the 
 maximum of efficiency the buckets attached to the peri- 
 phery of the wheel against which this jet impinges should 
 have a speed of about 1,900 ft. per second, but, owing to 
 the difficulty of producing a material for the wheel strong 
 enough to withstand the strains induced by such a high 
 speed, it has been found necessary to limit the peripheral 
 speed to 1,200 or 1,300 ft. per second. 
 
 Fig. 269 shows a De Laval steam turbine motor of 300 
 H. P., which is the largest size built up to the present 
 time, its use having been confined chiefly to light work. 
 
 The turbine illustrated in Fig. 269 is shown directly 
 connected to a 200 K. W. two-phase alternator. The 
 steam and exhaust connections are plainly shown, as also 
 the nozzle valves projecting from the turbine casing. The 
 speed of the turbine wheel and shaft is entirely too high 
 for most practical purposes, and it is reduced by a pair of 
 very perfectly cut spiral gears, usually made 10 to 1. 
 These gear wheels are made of solid cast steel, or of cast 
 iron with steel rims pressed on. The teeth in two rows 
 are set at an angle of 90° to each other. This arrange- 
 ment insures smooth running and at the same time checks 
 any tendency of the shaft towards end thrust, thus dis- 
 pensing with a thrust bearing. 
 
 The working parts of the machine are clearly illustrated 
 in Fig. 270, and a fairly good conception of the assembling 
 
De Laval Steam Turbine 
 
 637 
 
 Fig. 269 
 
 of the various members, and especially the reducing gears, 
 may be had by reference to Fig. 271, which shows a 110 
 
63b 
 
 Steam Engineering 
 
 Fig. 270 
 
 H. P. turbine and rotary pump with the upper half of the 
 gear case and field' frame ramoved for purposes of inspec- 
 
De Laval Steam Turbine 
 
 639 
 
 Fig. 271 
 
 tion. The slender shaft is seen projecting from the center 
 of the turhine case, and upon this shaft are shown the 
 
640 Steam Engineering 
 
 small pinions meshing into the large spiral gears upon the 
 two pump shafts. 
 
 Eef erring to Fig. 270, A is the turbine shaft, B is the 
 turbine wheel, and C is the pinion. As the turbine wheel 
 is by far the most important element, it will be taken up 
 first. It is made of forged nickel steel, and it is claimed 
 by the builders, the De Laval Steam Turbine Co., of Tren- 
 ton, New Jersey, that it will withstand more than double 
 the normal speed before showing any signs of distress. A 
 clear idea of the construction of the wheel and buckets 
 may be had by reference to Fig. 268. The number of 
 buckets varies according to the capacity of the machine. 
 There are about 350 buckets on a 300 H. P. wheel. The 
 buckets are drop forged, and made with a bulb shank 
 fitted in slots milled in the rim of the wheel. 
 
 Fig. 272 is a sectional plan of a 30 H. P. turbine con- 
 nected to a single dynamo, and Fig. 273 is a sectional ele- 
 vation of the same. 
 
 The steam, after passing the governor valve C, Fig 273, 
 enters the steam chamber D, Fig. 272, from whence it is 
 distributed to the various nozzles. The number of these 
 nozzles depends upon the size of the machine, ranging 
 from one to fifteen. They are generally fitted with shut- 
 off valves (see Fig. 269) by which one or more nozzles can 
 be cut out when the load is light. This renders it possible 
 to use steam at boiler pressure, no matter how small the 
 volume required for the load. This is a matter of great 
 importance, especially where the load varies considerably, 
 as, for instance, there are plants in which during certain 
 hours of the day a 300 H. P. machine may be taxed to its 
 utmost capacity and during certain other hours the load 
 on the same machine may drop to 50 H. P. In such cases 
 
Fig. 272 
 
642 Steam Engineering 
 
 the number of nozzles in action may be reduced by closing 
 the shut-off valves until the required volume of steam is 
 admitted to the wheel. This adds to the economy of the 
 machine. After passing through the nozzles, the steam, 
 as elsewhere explained, is now completely expanded, and 
 in impinging on the buckets its kinetic energy is trans- 
 ferred to the turbine wheel. Leaving the buckets, the 
 steam now passes into the exhaust chamber G, Fig. 272, 
 and out through the exhaust opening H, Eig. 273, to the 
 condenser or atmosphere as the case may be. 
 
 The gear is mounted and enclosed in the gear case I, 
 Fig. 272. J is the pinion made solid with the flexible 
 shaft and engaging the gear wheel K. This latter is 
 forced upon the shaft L, which, with couplings M, connects 
 to the dynamo, or is extended for other transmission. 
 
 0, Fig. 273, is the governor held with a taper shank in 
 the end of the shaft L, and by means of the bell crank P 
 operates the governor valve C." The flexible shaft is sup- 
 ported in three bearings, Fig. 272. Q and E are the pin- 
 ion bearings and S is the main shaft bearing which carries 
 the greater part of the weight of the wheel. This bearing 
 is self-aligning, being held to its seat by the spring and cap 
 shown. 
 
 T, Fig. 272, is the flexible bearing, being entirely free to 
 oscillate with the shaft. Its only purpose is to prevent 
 the escape of steam when running non-condensing, or the 
 admission of air to the wheel case when running condens- 
 ing. The flexible shaft is made very slender, as will be 
 observed by comparing its size with that of the rotary pump 
 shaft in Fig. 271. It is by means of this slender, flexible 
 shaft that the dangerous feature of the enormously high 
 speed of this turbine is eliminated. 
 
De Laval Steam Turbine 
 
 643 
 
 Fig. 273 
 
644 
 
 Steam Engineering 
 
 The governor is of the centrifugal type, although dif- 
 fering greatly in detail from the ordinary fly ball governor, 
 as will be seen by reference to Fig. 274. It is connected 
 directly to the end of the gear wheel shaft. Two weights 
 B are pivoted on knife edges A with hardened pins C, 
 bearing on the spring seat D. E is the governor body 
 fitted in the end of the gear wheel shaft K and has seats 
 
 
 Fig. 274 
 
 milled for the knife edges A. It is afterwards reduced in 
 diameter to pass inside of the weights and its outer end is 
 threaded to receive the adjusting nut I, by means of which 
 the tension of the spring, and through this the speed of the 
 turbine, is adjusted. When the speed accelerates, the 
 weights, affected by centrifugal force, tend to spread apart, 
 and pressing on the spring seat at D push the governor 
 
Be Laval Steam Turbine 645 
 
 pin G to the right, thus actuating the bell crank L and cut- 
 ting off a part of the flow of steam. 
 
 It has been found necessary with this turbine, when 
 running condensing, to introduce a valve termed a vacuum 
 valve, also controlled by the* governor, as it has been found 
 that the governor valve alone is unable to hold the speed 
 of the machine within the desired limit. The function of 
 the vacuum valve is as follows: The governor pin G act- 
 uates the plunger H, which is screwed into the bell crank 
 L, but without moving the plunger relative to said crank. 
 This is on account of the spring M being stiffer than the 
 spring 1ST, whose function is to keep the governor valve open 
 and the plunger H in contact with the governor pin. When 
 a large portion of the load is suddenly thrown off, the 
 governor opens, pushing the bell crank in the direction of 
 the vacuum valve T. This closes the governor valve, which 
 is entirely shut off when the bell crank is pushed so far that 
 the screw barely touches the vacuum valve stem J. 
 Should this not check the speed sufficiently, the plunger 
 H is pushed forward in the now stationary bell crank, and 
 the vacuum valve is opened, thus allowing the air to rush 
 into the space P in which the turbine wheel revolves, and 
 the speed is immediately checked. 
 
 The main shaft and dynamo bearings are ring oiling. 
 The high-speed bearings on the turbine shaft are fed by 
 gravity from an oil reservoir, and the drip oil is collected 
 in the base and may be filtered and used over again. 
 
 The fact that the steam is used in but a single stage or 
 set of buckets and then allowed to pass into the exhaust 
 chamber might appear at first thought to be a great loss 
 of kinetic energy, but, as has been previously stated, the 
 static energy in the steam as it enters the nozzles is con- 
 
646 
 
 Steam Engineering 
 
 verted into kinetic energy by its passage through the diver- 
 gent nozzles, and the result is a greatly increased volume of 
 steam leaving the nozzles at a tremendous velocity, but at 
 a greatly reduced pressure — practically exhaust pressure — 
 impinging against the buckets of the turbine wheel and 
 thus causing it to revolve. 
 
 Fig. 275 
 
 Efficiency tests of the De Laval turbine show a high econ- 
 omy in steam consumption, as for instance, a test made, by 
 Messrs. Dean and Main of Boston, Mass., on a 300 H. P. 
 turbine, using saturated steam at about 200 lbs. pressure 
 per sq. in. and developing 333 Brake H. P., showed a steam 
 consumption of 15.17 lbs. per B. H. P., and the same ma- 
 chine, when supplied with superheated steam and carrying 
 
De Laval Steam Turbine 647 
 
 a load of 352 B. H. P., ronsumed but 13.94 lbs. per B. 
 H. P. These results compare most favorably with those of 
 the highest type of reciprocating engines. 
 
 Fig. 275 shows a cross section of a 300 H. P. De Laval 
 wheel, showing the design necessary for withstanding th& 
 high centrifugal stress to which these wheels are subjected. 
 All De Laval wheels are tested to withstand the centrifugal 
 stress of twice their normal velocity without showing signs 
 of fatigue. 
 
 A characteristic feature of the De Laval steam turbine is 
 that none of its running parts are subject to the full press- 
 ure of the steam, as the steam is fully expanded in the nozzle 
 before it reaches the turbine wheel. This feature, which 
 will not be found in any other heat motor, is of great value 
 and promising future in the direction of using high press- 
 ures with resultant increase in economy of fuel. The restric- 
 tion as to the steam pressure that can be used is found only 
 with the boiler, and as far as the steam turbine itself is con- 
 cerned, it has been operated successfully with a pressure as 
 high as 3,000 lbs. per square inch. 
 
L^ 
 
Allis-Chalmers Steam Turbine 
 
 Fig. 276 shows a general view of the Allis-Chalmers 
 steam turbine, and although it is essentially of the "Par- 
 sons" type, still there are a number of modifications in 
 details of construction, as compared with the Westinghouse- 
 Parsons steam turbine, some of which, no doubt may be 
 considered as adding to the efnciencj r , and durability of 
 the machine. 
 
 Fig. 277 is a sectional view of the "elementary" Parsons 
 type of steam turbine, and its various parts are described 
 as follows : 
 
 Main bearings, A and B. Thrust bearing, E. Steam 
 pipe C. Main throttle valve, D, which is balanced, and 
 operated by the governor. Steam enters the cylinder 
 through passage E, passes to the left through the alternate 
 rows of stationary and revolving blades, leaving the cylinder 
 at F and passes into the condenser, or atmosphere through 
 passage G. H, J and K are the three steps or stages of the 
 machine. L, M and N" are the three balance pistons. 0, P 
 and Q are the equalizing passages, connecting the balance 
 pistons with the corresponding stages. 
 
 Fig. 278 shows a sectional veiw of the "Parsons" turbine 
 with the Allis-Chalmers modifications. L and M are the 
 two balance pistons at the high pressure end. Z is a smaller 
 balance piston placed in the low pressure end, yet having 
 the same effective area as did the larger piston 1ST shown in 
 Fig. 277. and Q are the two equalizing passages for 
 pistons L and M. Passage P is omitted in this construc- 
 tion, and balance piston Z is equalized with the third stage 
 
 649 
 
Fig. 270 
 the allis-chalmers steam turbine 
 
Alhs-Clialmers Steam Turbine 
 
 651 
 
 pressure at Y. Valve V is a by-pass valve to allow of live 
 steam being admitted to the second stage of the cylinder 
 in case of a sudden overload. This by-pass valve is the 
 equivalent of the by-pass valve used to admit live steam to 
 
 T == .| 
 
 ELEMENTARY PARSONS TYPE STEAM TURBINE 
 
 Fig. 277 
 
 the low pressure cylinder of a compound reciprocating en- 
 gine. Valve V is arranged to be operated, either by the 
 governor or by hand, as the conditions may require. Fric- 
 
 FIG.3 
 
 ELEMENTARY PARSONS TURBtC WITH ALUS-CHALMERS MOOT CATI0N8 
 
 Fig. 278 
 
 tionless glands made tight by water packing are provided 
 at S and T where the shaft passes out of the cylinder. The 
 shaft is extended at U and connected to the generator shaft 
 by a flexible coupling. 
 
652 Steam Engineering 
 
 The action of the steam, and the general arrangement of 
 
 the stationary, and moving blades is practically the same 
 
 in the two turbines, with the exception that, in the larger 
 
 sizes of the Allis-Chalmers turbine the "balance" pistons for 
 
 rrprrr 
 
 >t 
 
 rrrrrrr 
 
 T 
 
 MOVING 
 BLADES 
 
 STATrONARY 
 BLADES 
 
 MOVING 
 BLADES 
 
 STATIONARY 
 BLADES 
 
 MOVING 
 BLADES 
 
 STATIONARY 
 BLADES 
 
 Fig. 279 
 
 Showing Arrangement of Blading and Course of the Steam in 
 Parsons Steam Turbine 
 
 neutralizing the end thrust, are arranged in a different 
 manner, the largest one of the three pistons (piston X — 
 Fig. 277) is replaced by a smaller balance piston. 
 
 This piston presents the same effective area for the steam 
 to act upon, as did the larger piston, for the reason that th£ 
 
Allis-Chalmers Steam Turbine 653 
 
 working area of the latter in its original location consisted 
 only of the annular area included between its periphery 
 and the periphery of the next smaller piston. The 
 pressure of the steam is brought to bear upon this 
 equalizing piston in its new position, by means of passages 
 or ports through the body of the rotor, connecting the third 
 stage of the cylinder with the supplementary cylinder, in 
 which the piston revolves. Fig. 279 shows the arrangement 
 of blading, the course of the steam being indicated by the 
 arrows. The clearances between the edges of the revolving 
 and stationary blades, as shown in the cut are relatively 
 out of proportion to the actual clearances allowed. 
 
 This clearance is preserved by means of a small thrust- 
 bearing provided inside the housing of the main bearing. 
 
 This thrust-bearing can be adjusted to locate and hold 
 the rotor in such a position as will allow sufficient clear- 
 ance to prevent actual contact between the moving and 
 stationary blades, and yet reduce the leakage of steam to 
 a minimum. 
 
 The method by which the blades are fitted to and held 
 in the rotor and cylinder of the Allis-Chalmers steam tur- 
 bine is as follows: Each blade is individually formed by 
 special machine tools, so that its root or foot is of an an- 
 gular, or dove-tail shape, and at its tip there is a projection. 
 In order that the roots of the blade may be firmly held in 
 position, a foundation ring, A, Fig. 280, is provided, which 
 after being formed to a circle of the proper diameter, has 
 slots cut in it by a special milling machine. 
 
 These slots are formed of dove-tail shape to receive the 
 roots of the blades, and are at the same time accurately 
 spaced, and inclined so as to give the required pitch and 
 angles to the blades. 
 
654 
 
 Steam Engineering 
 
 The foundation rings are also of dove-tail snape in cross- 
 section, those holding the stationary blades are inserted 
 in dove-tail grooves in the cjdinder and those holding the 
 revolving blades being pressed into the rotor or spindle. 
 
 The rings are firmly held in their places by key-pieces 
 driven into place and upset into under-cut grooves, thus 
 positively locking the whole structure together, and making 
 
 Fig. 2S0 
 
 it practically impossible for a blade to get out of place. 
 
 The tips of the blades are held and firmly bound together 
 by a shroud-ring, B, Fig. 280. 
 
 The shroud-rings are made channel-shape, in cross-sec- 
 tion, the flanges being made thin in order to prevent 
 dangerous heating in case of accidental contact with either 
 the walls of the cylinder or the surface of the rotor. 
 
Allis-Chalmers Steam Turbine 655 
 
 The bearings of this turbine are of the self-adjusting 
 ball and socket type, designed for high speed. Shims are 
 provided for proper alignment. The lubrication of the 
 four bearings, two for the turbine, and two for the gen- 
 erator, is accomplished by supplying an abundance of oil 
 to the middle of each bearing and allowing it to flow out 
 at the ends where it is caught, passed through a cooler, 
 and pumped back to the bearings. 
 
 The fact that the oil is supplied in large quantities to 
 the bearings does not involve a heavy oil bill. 
 
 The journals are practically floating on films of oil, thus 
 preventing that "wearing out" of the oil that occurs when 
 it is supplied in small "doses." 
 
 The governor is driven from the turbine shaft by means 
 of cut gears working in an oil-bath. 
 
 The governor operates a balance throttle valve by means 
 of a relay, except in very small sizes in which the valve 
 is w r orked direct. 
 
 In order to .provide for any possible accidental derange- 
 ment of the main governing mechanism, an entirely sep- 
 arate safety, or over-speed governor is furnished. This 
 governor is driven directly by the turbine shaft without 
 the intervention of gearing, and is so arranged and adjusted 
 that if the turbine should reach a predetermined speed above 
 that for which the main governor is set, the safety governor 
 will come into action and trip a valve, shutting off the 
 steam and stopping the turbine. A strainer is provided 
 through which the steam is passed before admission to 
 the turbine. 
 
 For connecting the rotors of the turbine and generator 
 a special type of flexible coupling is used to provide for any 
 slight inequality in the wear of the bearings, to permit 
 
656 Steam Engineering 
 
 axial adjustment of the turbine spindle, and to allow for 
 differences in expansion. This coupling is so made that it 
 can be readily disconnected for the removal of the turbine 
 spindle, or of the revolving field of the generator. Provi- 
 sion is made for ample lubrication of the adjoining faces 
 of the coupling.* The coupling is enclosed in the bearing 
 housing, so that it is completely protected against damage, 
 and cannot cause injury to the attendants. 
 
 Waste of heat by radiation is prevented in the following 
 manner : 
 
 The hot parts of the turbine, up to the exhaust chamber 
 are covered with an ample thickness of non-conducting 
 material and lagged with planished steel. 
 
 For large Allis-Chalmers turbines the bedplate is di- 
 vided into two parts, one carrying the low-pressure end 
 of the turbine and the bearings of the generator, the other 
 carrying the high-pressure end of the turbine. The tur- 
 bine is secured to the former, while the latter is provided 
 with guides which permit the machine to slide back and 
 forth with differences of expansion caused by varying tem- 
 perature, at the same time maintaining the alignment. 
 
 Fig. 281 shows the spindle, or rotor of the Allis-Chalmers 
 turbine. The rings which carry the blades are pressed on 
 the shaft. Fig. 282 illustrates the blades as they appear 
 when fitted on to the rotor. The shroud ring protecting 
 the tips of the blades is also shown in place. Fig. 283 
 shows another view of the blade construction. This is a 
 half-ring of blades inserted in the foundation ring before 
 being placed upon the rotor. 
 
 Fig. 284 shows several rows of stationary blades as they 
 appear, fitted in the cylinder of an Allis-Chalmers steam 
 turbine. 
 
Allis-Chalmers Steam Turbine 
 
 657 
 
 Fig. 281 
 rotor of allis-chalmers steam turbine 
 
658 
 
 Steam Engineering 
 
 
 Fig. 282 
 Starting Up. — As a rule in preparing to start a steam 
 turbine, especially one of the "Parsons/' type, the first 
 
Allis-Chalmers Steam Turbine 509 
 
 move is to open the throttle slightly, to allow as much steam 
 as possible to flow through the turbine without causing it 
 to start. This requires but a few seconds, and about an 
 equal period of time is required to start the auxiliary oil 
 pump. The inlet valve is always left open to the surface 
 condensers, so they are always full of water. The outlet valve 
 is quickly opened a certain number of turns, which is known 
 to be sufficient for all purposes, and this is easily done be- 
 fore the moderate amount of steam flowing through has had 
 time to heat the condenser unduly. By this time the oil 
 is sufficiently high in the reservoir to permit the turbine to 
 be started very slowly, and it doubtless warms up rather 
 more evenly when turning over than when standing. When 
 the oil has reached its normal level in the reservoir, the 
 turbine is given more steam, and the field cut in. 
 
 The principal precautions to be observed are, not to start 
 without properly warming up, also to be certain that the oil 
 is circulating freely through the bearings. 
 
 The vacuum should not be on until the water glands seal, 
 and care should be taken not to run on vacuum without a 
 load on the turbine. 
 
 If a turbine vibrates objectionably when started after a 
 moderate time has been allowed for warming, say 6 minutes 
 for a 500-kilowatt, 10 minutes for a 2000-kilowatt, and 15 
 or,perhaps 20 minutes for larger sizes, it is highly probable 
 that there is something structurally wrong with it, and any 
 longer period will do but little, if any, good ; furthermore, 
 it will be subject to mysterious "spells" or "fits" of vibra- 
 tion upon changes of load or vacuum. 
 
 In Operation. — The throttle, and inlet gages should be 
 closely watched, to see that neither the pressure, nor the 
 steam temperature varies much. The vacuum should also 
 
660 
 
 Steam Engineering 
 
 Fig. 283 
 
Allis-Chalmers Steam Turbine 
 
 661 
 
 be kept constant, as well as the water glands, and those 
 pressures indicated by the oil gages. The temperature of 
 the oil flowing to and from the bearings should not exceed 
 135° Fahr.— . 
 
 Fig. 284 
 
 Shows a Number of Rows of Stationary Blades Fitted in the 
 
 Cylinder of an Allis-Chalmers Steam Turbine 
 
 The governor parts also should be oiled at regluar 
 intervals. 
 
 Stopping the turbine is practically the reverse of start- 
 ing, the successive steps being as follows : starting the aux- 
 
662 Steam Engineering 
 
 iliary oil pump, freeing it of water and allowing it to run 
 slowly ; removing the load gradually ; breaking the vacuum 
 when the load is almost zero, shutting off the condenser 
 injection and taking care that the steam exhausts freely 
 into the atmosphere ; shutting off the gland water when the 
 load and vacuum are off; pulling the automatic stop to 
 trip the valve and shut off steam and, as the speed of the 
 turbine decreases, speeding up the auxiliary oil pump to 
 maintain pressure on the bearings; then, when the turbine 
 has stopped, shutting down the auxiliary oil pump, turning 
 off the cooling water, opening the steam chest drains and 
 slightly oiling the oil inlet valve-stem. During these 
 operations the chief particulars to be heeded are: not to 
 shut off the steam before starting the auxiliary oil pump 
 nor before the vacuum is broken, and not to shut off the 
 gland water with vacuum on the turbine. The automatic 
 stop should also remain unhooked until the turbine is about 
 to be started up again. 
 
 General Suggestions. — Water used in the glands of the 
 turbine must be free from scale-forming impurities, and 
 should be delivered at the turbine under a steady pressure 
 of not less than 15 pounds. The pressure in the glands 
 will vary from 4 to 10 pounds. This water may be warm. 
 In the use of water for the cooling coils and of oil for the 
 lubricating system, nothing more is required than ordiriary 
 good sense dictates. An absolutely pure mineral oil must 
 be supplied, of a nonfoaming charcter, and it should be 
 kept free through filtering from any impurities. 
 
 These suggestions apply more particularly to steam tur- 
 bines of the "Parsons" type, exhausting into condensers. 
 For turbines built to be run non-condensing the portion 
 relating to vacuum does not of course apply. 
 
Hamilton-Holzwarth Steam Turbine 
 
 In order to thoroughly understand the underlying prin- 
 ciples of the steam turbine, and the action of the steam 
 within it, one must get definitely fixed in his mind this 
 fact, viz., that there is no similarity between it and the 
 reciprocating engine, and the action of the steam upon the 
 piston in driving it back and forth. In fact, there is more 
 similarity between the reciprocating engine and the rotary 
 engine than there is in the case of the turbine. In the 
 rotary engine the steam pushes a piston in the same manner 
 as it does in the reciprocating engine, with the exception 
 that the piston of the rotary engine travels entirely around 
 the shaft, while the piston of the reciprocating engine 
 travels back and forth in a straight line motion. It will 
 be much easier to get a clear idea of the action of the tur- 
 bine if one will for the time being drop all knowledge he 
 may have of reciprocating and rotary engines. He will 
 then be able to more readily grasp, and better understand 
 the action of the steam turbine. 
 
 One of the most comprehensive, and at the time most 
 simple explanations of the action of the steam upon the 
 blades of the turbine, and also upon the piston of the 
 reciprocating engine, in both of which cases rotary motion 
 is produced, but in two different ways, is given by Hans 
 Holzwarth. He says: "Take a large wheel which is 
 fastened to a vertical shaft. Grasp this wheel at the rim 
 at a certain point, and walk continuously around the shaft, 
 always retaining the hold, like a horse walking around 
 a capstan fastened to a bar or pole which he pulls after him. 
 
 663 
 
664 Steam Engineering 
 
 Or stand still in a certain spot and take the wheel by the 
 rim and cause it to revolve (like opening and closing a 
 valve by hand), by changing hands so that the whole rim 
 is constantly revolving." 
 
 The first illustration clearly explains the manner in 
 which the shaft of the reciprocating engine is caused to 
 revolve, by means of the static expansion force of the steam 
 acting upon the crank pin, through the medium of 
 the piston, piston rod, cross head, and connecting 
 rod. In the second illustration, in which the man 
 turns the wheel by simply standing still in one place, and 
 causing the wheel to revolve by grasping the rim and giv- 
 ing it a push, first with one hand, and then with the other, 
 we have a simple explanation of how the steam causes the 
 shaft of the turbine to revolve, by a constant series of 
 pushes, or impulses against the movable blades that are key 
 seated to the drum, which in turn is keyed to the shaft, 
 the moving blades representing the rim of our wheel. 
 
 Every one knows that in order to be able to turn the 
 aforesaid wheel the man must have a good floor to stand 
 upon, and he must also have a good foothold on the floor, 
 because he exerts the same amount of pressure on the 
 floor, that he exerts against the rim of the wheel. This 
 explains why there must be stationary blades, as well as 
 revolving blades in a turbine. 
 
 The actual pressure exerted upon any single blade in a 
 turbine is in reality very light. Take, for example, a 300 
 K. W. Westinghouse turbine. There are altogether in a 
 machine of this size 31,073 blades, of which 16,095 are mov- 
 ing blades. The pressure that each blade exerts in turning 
 the shaft is a little over one ounce, but owing to the large 
 number of blades, and the velocity of the steam, the power 
 is developed. 
 
Hamilton-Hohwarth Steam Turbine 
 
 665 
 
 
 Fig. 285 
 hamilton-holzwarth steam turbine 
 
 The Hamilton-Holzwarth steam turbine resembles in 
 many respects the Westinghouse-Parsons turbine, prominent 
 
£66 Steam Engineering 
 
 of which is that it is a full stroke turbine ; that is, the steam 
 flows through it in one continuous belt, or veil in a screw 
 line, the general direction being parallel with the shaft. 
 But unlike the Parsons type, the steam in the Hamilton- 
 Holzwarth turbine is made to do its work only by impulse, 
 and not by impulse and reaction combined. The smaller 
 sizes are built in a single casing or cylinder, but for units 
 of 750 K. W. and larger there are two parts, viz., high 
 and low pressure, thus resmbling in some respects a com- 
 pound reciprocating engine. 
 
 The Hamilton-Holzwarth steam turbine is based upon 
 and has been developed from the designs of Prof. Eateau, 
 of Paris, and is being manufactured in this country by 
 the Hooven-Owens-Eentschler Co., of Hamilton, Ohio. It 
 is horizontal, and placed upon a rigid bed plate of the box 
 pattern. All steam, oil and water pipes are within and 
 beneath this bed plate, as are also the steam inlet valve and 
 the regulating and by-pass valves. 
 
 There are no balancing pistons in this machine, the 
 axial thrust of the shaft being taken up by a thrust ball- 
 bearing. The interior of the cylinder is divided into a 
 series of stages by stationary discs which are set in grooves 
 in the cylinder, and are bored in the center to allow the 
 shaft, or rather the hubs of the running wheels that are 
 keyed to the shaft, to revolve in this bore. 
 
 Clearance. — The clearance allowed is as small as prac- 
 ticable, as it is in this clearance between the revolving hub 
 and the circumference of the bore of the stationary disc 
 that the leakage losses occur. It should be noted that be- 
 tween each two stationary discs there is located a running 
 wheel, and that the clearance between the running vanes 
 and the stationary vanes is made as slight as is consistent 
 
Hamilton-Holzivarth Steam Turbine 667 
 
 with safe practice; otherwise leakage would occur here 
 also, and besides this there would be a distortion of the 
 steam jet and entrainment of the surrounding atmosphere, 
 resulting in a rapid decline in economy if the clearance 
 between the stationary and moving elements was not re- 
 duced to as small a fraction as possible. 
 
 As before stated, the stationary discs are firmly secured 
 to the interior walls of the casing. At intervals on the 
 outside periphery of these discs are located the stationary, 
 or guide vanes. These are made of drop forged steel. They 
 are set in a groove on the outside edge of the disc and 
 fastened with rivets. Both disc and vanes are then ground, 
 giving the vanes the profile that they should have for the 
 most efficient expansion of the steam. After this is done 
 a steel ring is shrunk on the outside periphery of the vanes 
 and the steam channels in the disc. These discs are then 
 placed in the grooves in the casing at regular intervals, 
 and in the spaces between them are the running wheels. 
 
 The casing is divided into an upper and lower half. The 
 running wheels are built with a cast steel hub having a 
 steel disc riveted on to each side, thus forming a circum- 
 ferential ring space into which the running vanes are 
 riveted. A thin steel band or rim is tied on the outer edge 
 of the vanes, thus forming an outer wall to the steam 
 channels and confining the steam within the vanes. These 
 vanes are also milled on both edges, on the influx, and 
 efflux side of the wheel, thus forming them to the shape 
 corresponding to the theoretical diagram. 
 
 In all steam turbines one of the main requisites for a 
 quiet-running machine is that the revolving element or 
 rotor shall be perfectly balanced. The rotary body of the 
 Hamilton-Holzwarth turbine consists of a plurality of run- 
 
668 Steam Engineering 
 
 ning wheels, each one of which is balanced by itself before 
 being placed upon the shaft. All the bearings are lubri- 
 cated in a thorough manner by oil forced up into the bot- 
 tom bushing or shell under slight pressure. Flexible coup- 
 lings are used between the high and low-pressure shafts, 
 and for connecting the turbine shaft to the generator shaft 
 or other shaft to be driven. By means of the thrust ball- 
 bearing on the exhaust end of the turbine the shaft may 
 be adjusted in an axial direction in such a manner as to 
 accurately preserve the desired position of the running 
 wheels. 
 
 Fig. 285 shows a general view of the Hamilton-Holz- 
 warth turbine, and the action of the steam within the ma- 
 chine may be described as follows: After leaving the 
 steam separator that is located beneath the bed plate, the 
 steam passes through the inlet or throttle valve, the stem 
 of which extends up through the floor near the high- 
 pressure casing and is protected by a floor stand and 
 equipped with a hand wheel, shown in Fig. 285. The 
 steam now passes through the regulating valve. From this 
 valve it is led through a curved pipe to the front head of 
 the high pressure casing or cylinder. In this head is a 
 ring channel into which the steam enters, and from which 
 it flows through the first set of stationary vanes. In these 
 vanes the first stage of expansion occurs. 
 
 Construction of the Stationary Blade. — A stationary 
 blade is constructed in the following manner: A circular 
 cast-iron disc a, Fig. 286, has a bore b corresponding to 
 the diameter of the shaft, with the necessary clearance. 
 On the outer circumference of this disc there is cut a 
 groove c. The stationary guides, consisting of a vane of 
 proper curvature and the adjoining piece, are of drop- 
 
Hamilton-Holzwarth Steam Turbine 
 
 669 
 
 forged steel, milled on all sides of the adjoining piece which 
 fits into the circular groove c. These vanes are arranged 
 all around the circumference so that one adjoining piece 
 touches another and they are held in place and fastened 
 securely, by rivets e, to the disk. The outer circumference 
 of these vanes is turned off to the right size, and then a 
 steel ring f is shrunk over them. This shrunk ring pro- 
 jects into the grooves of the housing. 
 
 Fig. 286 
 
 The Running Wheel. — While in the stationary blade the 
 weight is not of great importance, in the running wheel it 
 is very essential to reduce the weight as much as possible. 
 It will be readily understood that the lighter the running 
 wheels are, the less the bearings will have to support, and 
 therefore the shorter they may be constructed, and the 
 better they will work. Furthermore, by keeping down the 
 weight of the running wheel the shaft diameter is kept 
 within small limits. This determines the bore of the sta- 
 tionary blade, and with that the circular space between the 
 bore of the stationary blade and the shaft can be kept 
 
670 
 
 Steam Engineering 
 
 within small limits; therefore in the construction of this 
 running wheel every dead and unnecessary weight is 
 avoided. 
 
 The running wheel is made up as follows: A steel hub 
 or spider a., Fig. 287, has a bore b fitting closely to the 
 shaft diameter. On both side of the hub are riveted steel 
 discs c. The groove on the outer circumference of the 
 steel disc is turned out and forms a receptacle for the 
 running vanes. The running vane itself consists of the 
 
 Fig. 287 
 
 properly curved blade, with an adjoining piece made in one 
 section of drop-forged steel. The adjoining piece is fin- 
 ished and fits closely into the grooves of the steel disc. The 
 running vanes are held in place and rigidly connected to 
 the steel discs by rivets d, so that the centrifugal force of 
 each vane is taken up by a rivet and transmitted through 
 the rivet to the steel disc. The outer edge f of the vane is 
 turned off and thus provided with an annular groove form- 
 ing a receptacle for the steel band g, which is tied all 
 around the wheel. It is held in place and secured to the 
 
Hamilton-Holzwarth Steam Turbine 671 
 
 vanes by riveting over the projecting ends of the vanes. 
 The ends of the band are brazed together. 
 
 Eeference to Fig. 288, which is a vertical section of this 
 turbine, will serve to make more clear the action of the 
 steam within the machine. The turbine casing a, is made 
 of cast iron of cylindrical shape, and split in the horizontal 
 axis, into the upper half, a, and the lower half, b. In the 
 horizontal points the two halves are bolted together steam 
 tight. The lower half, b, is cast together with the pedestal, 
 c, which is the support for the low pressure bearing, d, and 
 the groove, e, for the stuffing box, f. The outlet opening, 
 g, is arranged in the lower half, b. This lower half is sup- 
 ported on pads of the bed plate, h, with two feet extending 
 on the sides, and fastened thereto. The front head, i, is 
 bolted steam tight to the flange, k, on the front side of 
 the casing. In front of the head, i, is located the regu- 
 lating mechanism pedestal, 1, which combines the high 
 pressure bearing with the housing for regulating mechan- 
 ism, n, and housing, o, for the governor, p. A live steam 
 pipe, g', is connected to an inlet valve, r, and this to a main 
 regulating valve, s, to the inlet flange of the front head, i. 
 The passage of the steam into this front or high pressure 
 head has already been referred to. In the grooves cut in 
 the housing are the stationary blades, t, and in the space 
 between the two following stationary blades is the running 
 wheel, u. All running wheels fit on the shaft, v, and are 
 keyed to the shaft. The shaft, v, is supported in the high 
 pressure bearing, m, on one end, and in the low pressure 
 bearing, d, on the other end. The low pressure bearing 
 has an arrangement which allows the adjustment of the 
 shaft, v, lengthwise in the direction of the turbine. On 
 the outer end of the shaft is the coupling, w, keyed to the 
 
£72 
 
 Steam Engineering 
 
 \ I 
 
 Fig. 288 
 
 hamilton-holzwarth steam turbine 
 
 Sectional Elevation 
 
HamiUon-Holzwarth Steam Turbine 
 
 673 
 
 shaft. This coupling allows connection to be made to 
 the generator, pump, or blower, which is to be driven by 
 the turbine. 
 
 The flow of the steam from the inlet valve, r, to the 
 exhaust outlet, g, and the manner of the working of the 
 steam in the turbine is as follows : The steam passing 
 through the main regulating valve, s, enters the circular 
 channel of the front head, i, and from here it flows through 
 a circular slot to the first stationary blade, t. Opposite this 
 circular slot is arranged a multitude of vanes, x, Fig. 289, 
 
 Fig. 289 
 
 which give the steam the right expansion in the right 
 direction. With this velocity attained in the stationary 
 blades, the steam impinges upon the vanes, u, of the first 
 running wheel, and the bore of the housing can be kept 
 within larger limits, because the steam flowing through 
 the vanes is prevented from flowing rapidly outward by 
 means of a band secured around the outer circumference 
 of the running wheel. 
 
 The running vanes conform in section somewhat to the 
 Parsons type, but the action of the steam upon them, and 
 
674 Steam Engineering 
 
 also within the stationary vanes is different. The expan- 
 sion of the steam, and consequent development of velocity 
 takes place entirely within the stationary vanes, which also 
 change the direction of flow of the steam, and distribute 
 it in the proper manner to the vanes of the running wheels, 
 which, according to the claims of the makers, the steam 
 enters and leaves at the same pressure, thus allowing the 
 wheel to revolve in a uniform pressure. 
 
 In the low-pressure casing, which is larger in diameter 
 than the high-pressure, the steam is distributed in the 
 same manner as it is in the high-pressure casing. There 
 is, however, in the front head of the low-pressure casing 
 an additional nozzle through which live steam may be ad- 
 mitted in case of overload. The design of this nozzle is 
 such that the live steam entering and passing through it, 
 and controlled by the governor exerts no back pressure on 
 the steam coming from the receiver, but, on the contrary, 
 its action is similar to the action of an injector, that is, it 
 tends to suck the low-pressure steam through the first set 
 of stationary vanes of the low-pressure turbine. 
 
 The first stationary disc of the low-pressure turbine has 
 guide vanes all around its circumference, so that the steam 
 enters the turbine in a full cylindrical belt, interrupted only 
 by the guide vanes. To provide for the increasing volume 
 as the steam expands in its course through the turbine, the 
 areas of the passages through the distributers and running 
 vanes must be progressively enlarged. The gradual in- 
 crease in the dimensions of the stationary vanes permits 
 the steam to expand within them, thus tending to maintain 
 its velocity, while at the same time the vanes guide the 
 steam under such a small angle that the force with which 
 it impinges the vanes of the next running wheel is as 
 
Hamilton-Hohwarth Steam Turbine 675 
 
 effective as possible. The curvature of the vanes is such 
 that the steam while passing through them will increase its 
 velocity in a ratio corresponding to its action. 
 
 The purpose of the stationary discs is, as has been stated, 
 to distribute the steam to the running wheel. They also 
 take the back pressure of the steam as it impinges the 
 vanes of the running wheels, thus in a sense acting as 
 balancing pistons. 
 
 The governor is of the spring and weight type, adapted 
 to high speed, and is designed especially for turbine govern- 
 ing. It is directly driven by the turbine shaft, revolving 
 with the same angular velocity. Its action is as follows: 
 Two discs keyed to the shaft drive, by means of rollers, 
 two weights sliding along a cross bar placed at right angles 
 through the shaft and compressing two springs against 
 two nuts on the cross bar. Every movement of the weights, 
 caused by increasing or decreasing the angular velocity of 
 the turbine shaft, is translated by means of levers to a 
 sleeve which actuates the regulating mechanism. These 
 levers are balanced so that no back pressure is exerted upon 
 the weights. The whole governor is closed in by the discs, 
 one on each side, and a steel ring secured by concentric 
 recesses to the discs. In order to decrease the friction 
 within the governor and regulating mechanism, thrust 
 ball-bearings and frictionless roller-bearings are used. 
 
 As previously stated, the regulating valve is located be- 
 neath the bed plate. One side of it is connected by a curved 
 pipe with the front head of the high-pressure cylinder, and 
 the other side is connected with the inlet valve. The regu- 
 lating valve is of the double-seated poppet valve type. 
 Valves and valve seats are made of tough cast steel, to 
 avoid corrosion as much as possible, and the valve body is 
 made of cast iron. 
 
676 Steam Engineering 
 
 Immediately below the regulating valve and forming a 
 part of it in one steam chamber is located the by-pass regu- 
 lating valve. Thus the use of a second stuffing box for 
 the stem of this valve is avoided. The function of this 
 valve is to control the volume of the live steam supply that 
 flows directly to the by-pass nozzles in the front head of 
 the low-pressure casing. This valve is also a double-seated 
 poppet valve. 
 
 The main regulating valve is not actuated directly by 
 the governor, but by means 1 of the regulating mechanism. 
 The construction and operation of this regulating mechan- 
 ism is as follows: The stem of the regulating valve is 
 driven by means of bevel gears by a shaft that is supported 
 in frictionless roller-bearings. 
 
 On this shaft there is a friction wheel that the governor 
 can slide across the face of a continuously revolving fric- 
 tion disc by means of its sleeve and bell crank lever. This 
 revolving disc is keyed to a solid shaft which is driven by 
 a coupling from a hollow shaft. This hollow shaft is driven 
 by the turbine shaft through the medium of a worm gear. 
 The solid shaft, with the continuously revolving friction 
 disc, can be slightly shifted by the governor sleeve so that 
 the two friction discs come into contact when the sleeve 
 moves, that is, when the angular velocity changes. If this 
 change is relatively great, the sleeve will draw the periodi- 
 cally revolving friction disc far from the center of the 
 always revolving one, and this disc will quickly drive the 
 stem of the regulating valve and the flow of steam will thus 
 be regulated. As soon as the angular velocity falls below 
 a certain percentage of the normal speed', the driving fric- 
 tion disc is drawn back by the governor, the regulating 
 valve remains open and the whole regulating mechanism 
 rests or stops, although the shaft is still running 
 
Hamilton-Hohwarth Steam Turbine 677 
 
 Should the angular velocity of the shaft reach a point 
 2.5 per cent higher than normal, the governor will shut 
 down the turbine. If an accident should happen to the 
 governor, due to imperfect material or breaking or weaken- 
 ing of the springs, the result would be a shut-down of the 
 turbine. 
 
 In order to change the speed of the turbine while run- 
 ning, which might be necessary in order to run the machine 
 parallel with another prime mover, a spring balance is 
 provided, attached to the bell crank lever of the regulating 
 mechanism. The hand wheel of this spring balance is 
 outside of the pedestal for regulating mechanism and near 
 the floor-stand and hand wheel. With this spring balance 
 the speed of the turbine may be changed 5 per cent either 
 way from normal. 
 
 All the bearings of the turbine are thoroughly lubricated 
 with oil forced under pressure by the oil pump driven by 
 means of worm gearing by the turbine itself. After flowing 
 through the bearings the oil is passed through a filter, and 
 from thence to the oil tank located within the bed plate, 
 from whence it is taken by the oil pump. All revolving 
 parts are enclosed, and the principal part of the regulating 
 mechanism operates in a bath of oil. 
 
 The Stuffing-Box. — An effective means of packing a 
 swiftly revolving shaft is a long sleeve surrounding the 
 shaft with a very small radial clearance. The reason for 
 this will be found in the throttling action of the steam par- 
 ticles revolving with the shaft. These steam particles have 
 a tendency to fly outwardly and so prevent the steam from 
 passing axially through the small clearance between the 
 shaft and the sleeve. The reader will readily understand 
 that it would not be practical to use such a long sleeve in 
 
678 
 
 Steam Engineering 
 
 the construction of a steam turbine, as this arrangement 
 would considerably increase the length of the free shaft. 
 For the reason that the deflection of the shaft depends 
 upon the third power of the free length of the shaft, it is 
 absolutely necessary to restrict this free length as much as 
 possible. 
 
 Fig. 290 
 
 In the Hamilton-Holzwarth turbine, use is made of the 
 telescopic idea; that is the entire length of the sleeve is 
 split into several parts, and these single parts are shifted 
 together. In Fig. 290 the ring A screwed upon the shaft 
 projects axially into a groove of the ring B, and revolves 
 within it. The ring B does not move at all, but is held in 
 place, and pressed tightly against the turbine casing by 
 means of the ring C which presses against the bushing of 
 
Hamilton-Hohwarth Steam Turbine 679 
 
 the bearing. By screwing the ring C on the ring B, both 
 rings are forced axially in opposite directions. From the 
 casing S the steam seeking to escape, flows axially to T. 
 From there it flows back to XL, and then forward to V, 
 being very much throttled in the process. The ring B has 
 an annular groove which must be packed with soft packing. 
 Any accumulating water is collected in the chamber W, in 
 the bushing of the bearing, from whence it is properly 
 drained. The ring E serves only the purpose of tightening 
 the threads between rings C and B. 
 
k. 
 
The Rateau Steam Turbine 
 
 The Eatean turbine is purely an impulse turbine, using 
 wheels of thin platec pressed into a slightly conical form. 
 These are mounted on a common shaft, and separated from 
 each other by division walls. The first wheels have partial 
 peripheral admission, so that the peripheral velocity may be 
 high from the very beginning without using too short 
 blades. The guide blades are set into division walls, and 
 the rotating blades are bent from a single piece of bronze, 
 or steel plate, and are riveted to the double turned rim of 
 the wheel-disc. The shaft bearings were originally built 
 as part of the cover of the turbine, but now are made inde- 
 pendent. At the low pressure end the shaft is made steam 
 tight by means of a simple stuffing box, into which suffi- 
 cient water is allowed to flow to secure steam tightness. 
 As the same pressure exists on both sides of each rotating 
 wheel, the axial thrust has only the small value due to the 
 pressure on the area of the end of the front journal. 
 
 Fig. 291 shows a sectional view of the machine, in which 
 it is to be noted that the wheel discs are riveted to their 
 hubs. 
 
 Fig. 292 shows a view of the turbine with generator, and 
 oil equipment. The construction of the wheels, and division 
 walls can easily be seen in Figs. 293, 294 and 295. The 
 construction according to the latter figure, with division 
 walls made in sections is preferred, because after taking 
 away the casing cover, all the interior parts are easily 
 accessible. 
 
 681 
 
682 
 
 Steam Engineering 
 
 Fig. 291 
 The most recent Rateau turbine is of the action type, 
 that is to say, expansion of the steam is fully carried out in 
 
 _ 
 
Rateau Steam Turbine 
 
 683 
 
 Fig. 292 
 the distributor for each group consisting of a distributor 
 and one moving wheel. The steam therefore acts by its 
 
684 
 
 Steam Engineering 
 
 velocity and not by its pressure. These turbines are more- 
 over multicellular, that is to say, they consist of a certain 
 number of elements, each element comprising one dis- 
 tributor and one moving wheel. 
 
 This turbine has been developed by the firm of Sautter- 
 
 V' ' & 
 
 ~ ^ 
 
 m 
 
 I 
 
 
 m 
 
 ;' y 
 
 
 ■ . 
 
 - .,/ 
 
 
 §1 
 
 * 
 
 
 \ 
 
 sjeHp 
 
 
 '--Wj^tm 
 
 WBK 
 
 
 V ';;.; 
 
 
 
 B 
 
 Fig. 293 
 
 Hartley of Paris, France, from designs by Prof. A. Eateau, 
 who is also the inventor of the Eateau steam regenerator, 
 through which the exhaust from non-condensing recipro- 
 cating engines may be passed to a low-pressure turbine, 
 thus resulting in the development of power from steam 
 which otherwise would be wasted. A very complete and 
 
Rateau Steam Turbine 685 
 
 successful installation of this character has been in opera- 
 tion for some time at the extensive steel works of the Inter- 
 national Harvester Company at Chicago, 111., and judging 
 from the results of an exhaustive series of tests conducted 
 by Mr. P. G. Gaesch, and published in the June, 1907, 
 issue of "Power," the system possesses considerable merit. 
 The following description of the installation at the Har- 
 vester Company's plant, is supplied by courtesy of the 
 Western Electric Co., of Chicago. 
 
 Fig. 294 
 
 The Steam Regenerator, or accumulator, consists of a 
 cylindrical wrought-steel shell % of an inch in thickness, 
 11 feet 6 inches in diameter, and 30 feet long, having a 
 central horizontal diaphragm which divides the regenerator 
 into two similar compartments. In each compartment 
 there are six elliptical tubes or steam-distributing conduits, 
 A, Fig. 296, which extend from end to end in pairs, and 
 are so placed as to leave spaces, B, between them. (The 
 
686 
 
 Steam Engineering 
 
 sectional view is from another installation and only shows 
 four tubes.) Baffle plates, C, are arranged above the space 
 between each pair of tubes. The spaces surrounding the 
 conduits, and, under certain conditions, even the conduits 
 themselves, are filled with water to the extent that the top 
 of the latter is usually submerged three or four inches. 
 The sides of the conduits are perforated with a great many 
 %-inch holes to allow of the lateral escape of steam through 
 
 Fig. 295 
 
 the water, with, occasionally, a further escape from the 
 bottom openings. A large baffle plate in the upper steam 
 <space serves for a perfect separation of entrained moisture 
 from the steam. The steam enters by the pipe shown at the 
 left hand of the side elevation, passes to the interior of the 
 elliptical tubes, and escapes into the spaces through the 
 perforations. The circulation of the water takes place in 
 the direction of the arrows; the baffle plates placed above 
 each pair of tubes prevent the water from being thrown 
 
Rateau Steam Turbine 687 
 
 liico the steam space. This flow of steam gives an extreme 
 degree of steam saturation to the water; and the slight 
 back pressure which at first might be expected, owing to the 
 head of water above the rows of perforations, is thereby, 
 reduced to insignificant proportions. 
 
 When the supply of steam from main engine ceases, the 
 water liberates part of the heat it has absorbed, and an even 
 flow of low-pressure steam is given off, while the steady 
 demand of the turbine reduces the pressure in the accumu- 
 lator, causing the steam still retained in the tubes to escape, 
 maintaining the circulation of the water, and facilitating 
 the liberation of the steam. Experience has shown that the 
 whole of the contained water participates in the regenera- 
 tive action. The steam is taken from the top of the ac- 
 cumulator to the turbine, and the pressure can be regu- 
 lated by the relief valve shown. The water level is main- 
 tained constant by a ball float contained in a small tank 
 arranged at the back of the regenerator. Generally there is 
 a slight overflow at all times, representing among other 
 things the "make up" from the exhaust steam supply. The 
 regenerator at this plant has a capacity of 55 tons of water, 
 sufficient by actual test to deliver all the steam for a 50 
 per cent overload on the turbine for a period of 430 
 seconds. At full load this would correspond to a period 
 of 390 seconds. The regenerator or accumulator is fitted 
 with the following accessories : First, an adjustible relief 
 valve, which regulates the limits of pressure in the accumu- 
 lator, and allows the steam to escape when the turbine is 
 stopped, or working on a light load ; it also prevents back 
 pressure in the cylinders of the reciprocating engine. 
 
 This valve may be connected to the condenser so that in 
 case the turbine is shut down for a period, the main engines 
 may have the benefit of the vacuum. 
 
688 
 
 Steam Engineering 
 
 L 
 
 Fig. 296 
 
 plan and elevation of low-pressure turbine installation, 
 
 with transverse and longitudinal sections of 
 
 regenerator 
 
 Second, a non-return water valve, necessary with water 
 accumulators, to prevent any possibility of reflux of water 
 toward the main engines during periods of stoppage. 
 
Bateau Steam Turbine 689 
 
 Third, automatic level regulators, and gauge glasses, and 
 automatic drains. 
 
 Fourth, piping beginning at the inlet of the receiving 
 drum, including the steam header and mains from the 
 regenerator to the turbine, the exhaust piping from the 
 turbine, and condenser, and the piping between the con- 
 denser and air pump. 
 
 Fifth, a vertical receiving drum 9 feet in diameter, and 
 22 feet long, with baffle plates, and separating chambers, 
 the function of which is to allow the ready escape of steam 
 from the main engines without increase of back pressure 
 on the system. The expansions allowed in this drum con- 
 duce to a more even flow of steam in the steam regenerator. 
 
 Sixth, a 30-inch barometric condenser of the Alberger 
 type, complete with air cooler, exhaust entrainer, expan- 
 sion joint, and an air pump 8x6x12 inches. 
 
 The exhaust steam from a 42x60 Mcintosh & Hemphill, 
 rolling mill engine, passes through the regenerator and into 
 a Eateau low-pressure turbine, to the shaft of which is 
 connected two direct current generators, each of 250 K. W. 
 capacity, at 250 volts, and designed so that they may be 
 operated in parallel. The bearings are of the ring oiled 
 reservoir type, with water jackets. The plant is designed 
 with a view of adding another similar unit, but the evidence 
 of the tests shows that a 750 K. W. unit can be operated 
 with the steam that is available, without allowance for the 
 steam (about 6,000 lbs. per hour) that is available from 
 auxilliary machinery. 
 
 Part of these auxiliaries already exhaust into an open 
 feed water heater, but the steam regenerator, constituting 
 a perfect feed heating device, can more appropriately re- 
 ceive all the steam from the auxiliaries, with the advantage 
 of some addition to the capacity of the turbine equipment. 
 
690 
 
 Steam Engineering 
 
 Fig. 297 shows a view of the regenerator and attached 
 equipment. 
 
 The leading objects of the tests made by Mr. Gaesch were, 
 first to determine the steam consumption of the turbine 
 
 Fig. 297 
 rateau regenerator, and attached condenser 
 
 per unit of power, and second, to measure the actual 
 amount of steam available for the use of the turbine as 
 delivered from the main engine. 
 
Bateau Steam Turbine 691 
 
 Space prohibits a detailed description of the method of 
 conducting the) tests, and the results derived therefrom. 
 
 The average brake horse power developed by the turbine 
 according to the report of one of the tests was 544 with a 
 steam consumption per B. H. P. per hour of 37 lbs. The 
 average steam pressure at the turbine was 16.6 lbs. absolute. 
 The average I. H. P. of the main engine during the same 
 test was 820, with a steam consumption of 61.2 lbs. per 
 I. H. P. per hour. The total weight of steam available 
 per hour from regenerator to turbine was 56.100 lbs. 
 
 The main engine, the dimensions of which have already 
 been given, was a reversing rolling mill engine. The stuff- 
 ing box used in the Eateau turbine is clearly illustrated in 
 Figs. 240 to 243. 
 
The Reidler-Stumpf Steam Turbine 
 
 This turbine is manufactured in Germany and its essen- 
 tial characteristics are the peculiarly formed, parallel re- 
 turn buckets derived from the Pelton water wheel, also the 
 rectangular nozzles that allow a homogeneous jet of steam 
 to be directed against the wheel* Fig. 298 shows a view 
 
 Fig. 298 
 
 of one of the wheels, and Fig. 299 shows sections of a 
 bucket, and nozzle. 
 
 The buckets are worked out of a solid forged wheel with 
 a milling cutter, consequently they are very strong, and 
 durable. 
 
 693 
 
r 
 
 69-4 
 
 Steam Engineering 
 
 The steam jet enters the bucket C from the nozzle B, and 
 is deflected through an angle of 180 degrees, the direction 
 
 Fig. 299 
 
 L 
 
 of its exit being parallel to that of its entrance, as shown 
 by the arrows (Fig. 299). 
 
Reidler-Stumpf Steam Turbine 
 
 695 
 
 This type of wheel has but a one-sided discharge — Fig. 
 300 shows another type of this turbine, in which the sta- 
 
 Fig. 300 
 
 tionary buckets D, of the reverse guide are opposed to the 
 rotating buckets C of the wheel in such a manner as to 
 form a continuous closed cylinder in which the steam in 
 
696 
 
 Steam Engineering 
 
 its course through the wheel continually whirls or spirals 
 around and around. With this type of turbine the steam 
 enters the bucket wheel from the nozzle as shown in Fig. 
 299, but instead of escaping after it has passed once 
 through the bucket, it is caught by the guide or stationary 
 bucket and returned to the wheel, this process being re- 
 peated again and again until practically all of the energy 
 in the steam has been abstracted. 
 
 Fig. 301 
 Fig. 301 shows a portion of the rim of this style of 
 wheel with its symmetrical double buckets. The steam jet 
 is split into two symmetrical parts by the sharp middle par- 
 tition. The direction of flow of the two steam streams 
 is now reversed, and they are returned to the middle plane 
 of the wheel by the reverse blades, and again brought to the 
 wheel as a united jet. Nearly the entire periphery has 
 primary, or secondary admission, and as a result of this 
 the fan work of the idle blades is reduced to a minimum. 
 
Disposal of the Exhaust Steam of 
 Steam Turbines 
 
 As in the case of the reciprocating engine, the highest 
 efficiency in the operation of the steam turbine is obtained 
 by allowing the exhaust steam to pass into a condenser, 
 and experience has demonstrated that it is possible to main- 
 tain a higher vacuum in the condenser of a turbine than in 
 that of a reciprocating engine. This is due, no doubt, to 
 the fact that in the turbine the steam is expanded down 
 to a much lower pressure than is possible with the recipro- 
 cating engine. 
 
 The condensing apparatus used in connection with steam 
 turbines may consist of any one of the modern improved 
 systems, and as no cylinder oil is used within the cylinder 
 of the turbine, the water of condensation may be returned 
 to the boilers as feed water. If the condensing water is 
 foul or contains matter that would be injurious to the 
 boilers, a surface condenser should be used. If the water 
 of condensation is not to be used in the boilers, the jet 
 system may be employed. Another type of condenser that 
 is being successfully used with steam turbines is the Bulk- 
 ley injector condenser. 
 
 Among the steam turbines that were on exhibition at the 
 St. Louis exposition in 1904 the Westinghouse-Parsons and 
 the General Electric Curtis turbines were each equipped 
 with Worthington surface condensers, fitted with improved 
 auxiliary apparatus consisting of dry vacuum pumps, either 
 horizontal of the well-known Worthington type, or rotative 
 
 697 
 
698 Steam Engineering 
 
 motor-driven, a hot well pump, and a pump for disposing 
 of the condensed steam from the exhaust system. The two 
 latter pumps were of the Worthington centrifugal type. 
 The Hamilton-Holzwarth turbine was equipped with a 
 Smith- Vaile surface condenser, fitted with a duplex double- 
 acting air pump, a compound condensing circulating pump 5 
 and a rotative dry vacuum pump, motor-driven. The 
 vacuum maintained was high, 28 to 28.5 in. 
 
 As an instance of the great gain in economy effected by 
 the use of the condenser in connection with the steam tur- 
 bine, a 750 K. W. Westinghouse-Parsons turbine, using 
 steam of 150 lbs. pressure not superheated and exhausting 
 into a vacuum of 28 in., showed a steam consumption of 
 13.77 lbs. per B. H. P. per hour, while the same machine 
 operating non-condensing consumed 28.26 lbs. of steam per 
 B. H. P. hour. Practically the same percentage in economy 
 effected by condensing the exhaust applies to the other 
 types of steam turbines. 
 
 With reference to the relative cost of operating the sev- 
 eral auxiliaries necessary to a complete condensing outfit, 
 the highest authorities on the subject place the power con- 
 sumption of these auxiliaries at from 2 to 7 per cent of the 
 total turbine output of power. A portion of this is re- 
 gained by the use of an open heater for the feed water, 
 into which the exhaust steam from the auxiliaries may 
 pass, thus heating the feed water and returning a part of 
 the heat to the boilers. 
 
 A prime requisite to the maintenance of high vacuum, 
 with the resultant economy in the operation of the con- 
 densing apparatus, is that all entrained air must be ex- 
 cluded from the condenser. There are various ways in 
 which it is possible for air to find its way into the con- 
 
Disposal of Exhaust Steam 699 
 
 densing system. For instance, there may be an improperly 
 packed gland, or there may be. slight leaks in the piping, or 
 the air may be introduced with the condensing water. This 
 air should be removed before it reaches the condenser, and 
 it may be accomplished by means of the "dry" air pump. 
 
 This dry air pump is different from the ordinary air 
 pump that is used in connection with most condensing 
 systems. The dry air pump handles no water, the cylinder 
 being lubricated with oil in the same manner as the steam 
 cylinder. The clearances also are made as small as possi- 
 ble. These pumps are built either in one or two stages. 
 
 A barometric or a jet condenser may be used, or a surface 
 condenser. The latter type lessens the danger of entrained 
 air, besides rendering it possible to return the condensed 
 steam, which is pure distilled water, to the boilers along 
 with the feed water, a thing very much to be desired in 
 localities where the water used for feeding the boilers is 
 impregnated with carbonate of lime, or other scale-form- 
 ing ingredients. 
 
 In comparing the efficiency of the reciprocating engine 
 and the steam turbine it is not to be inferred that recipro- 
 cating engines would not give better results at high vacuum 
 than they do at the usual rate of 25 to 26 in., but to reach 
 and maintain the higher vacuum of 28 to 28.5 in. with the 
 reciprocating engine would necessitate much larger sizes 
 of the low-pressure cylinder, as also the valves and exhaust 
 pipes, in order to handle the greatly increased volume of 
 steam at the low pressure demanded by high vacuum. 
 
 The steam turbine expands its working steam to within 
 1 in. of the vacuum existing in the condenser, that is, if 
 there is a vacuum of 28 in. in the condenser there will be 
 27 in. of vacuum in the exhaust end of the turbine cylinder. 
 
700 Steam Engineering 
 
 On the other hand, there is usually a difference of 4 or 5 
 in (2 to 2.5 lbs.) between the mean back pressure in the 
 cylinder of a reciprocating condensing engine, and the 
 absolute back pressure in the condenser. 
 
 It therefore appears that the gain in economy per inch 
 increase of vacuum above 25 in. is much larger with the 
 turbine than it is with the reciprocating engine. Mr. J. E. 
 Bibbins estimates this gain to be as follows : between 25 and 
 28 in. there is a gain of S 1 /^ to 4 per cent per inch of in- 
 crease, and at 28 in. 5 per cent. These results have been 
 obtained by means of exhaustive tests conducted by Mr. 
 Bibbins. Other high authorities on the steam turbine all 
 agree as to the great advantages to be derived by incurring 
 the extra expense of erecting a condensing plant that is 
 capable of maintaining the high vacuum necessary to high 
 efficiency. 
 
 Another method by which the steam consumption of the 
 turbine may be materially decreased, and a great gain in 
 economy effected is by superheating the steam. The amount 
 of superheat usually specified is 100°, and the apparatus 
 employed for producing it may be easily mounted in the 
 path of the waste gases. The steam may thus be super- 
 heated without extra cost in fuel, and an increase of 8 to 
 10 per cent in economy effected. The independent super- 
 heater requires extra fuel and labor, and the gain in this 
 case is doubtful, but there can be no question as to the wis- 
 dom of utilizing the waste flue gases for superheating the 
 steam. 
 
 As previously stated, the steam turbine is peculiarly 
 adapted for the use of highly superheated steam, and high 
 vacuum, and in these two particulars it excels the recipro- 
 cating engine. At the present time many large plants are 
 
Disposal of Exhaust 701 
 
 equipped with turbine engines that are giving the best of 
 results, and the outlook for the future employment of this 
 type of power producer is certainly very promising. 
 
 Surface Condensers. — The demand for efficient service in 
 the production of power by both the reciprocating engine, 
 and the steam turbine has resulted in bringing to bear upon 
 the design of the surface condenser, some of the thought, 
 study and experiment which have heretofore been expended 
 upon the other factors of the power plant. Up to within 
 the past few years the surface condenser consisted princi- 
 pally of an indiscriminate collection of tubes within a metal 
 box, with a flood of water following what happened to be the 
 path of least resistance, with tubes subjected upon the steam 
 side to a shower of water of condensation, keeping the steam 
 from contact, and with pockets and quiet corners for steam 
 and air and water, with an air-pump large enough for what- 
 ever happened, and little attention paid to the getting of 
 the air into it, the surface condenser has satisfied the mod- 
 erate demands of the past, and awaited the demands created 
 by the turbine, and the strenuous central station man for 
 scientific treatment along rational lines. 
 
 In a condenser taking care of 200,000 pounds of steam 
 per hour, over 55 pounds of water are made upon the tubes 
 per second. If this has to drip down over the bank below 
 the point at which it is formed, it can readily be seen that 
 the lower tubes are going to be busy cooling off feed-water 
 instead of condensing steam, and that the greater rate of 
 condensation will occur upon the upper tubes. By arrang- 
 ing the tubes in banks, the condensation from each of which 
 is quickly drawn to the side and disposed of, by leading 
 the steam to a positive and rapid flow among those tubes 
 in a direction counter to the flow of the water, so that the 
 
702 Steam Engineering 
 
 final contact of the condensed steam and air is with the 
 coolest water, and by subdividing the flow so that the circu- 
 lating water travels positively and rapidly past every square 
 foot of the cooling surface, the condenser is made to con- 
 dense eighten or twenty instead of six pounds of steam per 
 hour per square foot of surface. The significance of this, 
 not only in first cost and space occupied, but in mainte- 
 nance charges where, as in some of the large stations upon 
 the Atlantic seaboard, tubes have to be renewed once in 
 about three years, is easy to appreciate, and it is not the tube 
 which is condensing lots of steam, but rather that which is 
 loafing in an air pocket or an eddy, that is the most likely 
 to corrode. 
 
 Notwithstanding the liability to corrosion of the tubes 
 of surface condensers, many of the large engine plants, and 
 practically all steam turbine plants have been equipped 
 with surface condensers. This is due largely to the saving 
 effected by returning the pure water of condensation to 
 the boilers. But unless the condenser tubes are closely 
 watched for signs of corrosion, there is danger of having 
 in the course of time a mixture of cylinder oil and con- 
 denser leakage along with the water of condensation, which 
 would be a very undesirable boiler feed. This applies to 
 reciprocating engine plants. On the other hand a surface 
 condenser in connection with a steam turbine is a better 
 investment. The turbine water of condensation contains 
 no lubricating oil and condenser leakage is the only source 
 of trouble to be feared. To maintain this condenser leak- 
 age at the lowest practicable minimum is extremely im- 
 portant, as this will seriously affect (if the hot-well water 
 is used for boiler feed) the percentage of corrosive and 
 scale-forming elements fed into the boilers. Even under 
 
Disposal of Exhaust 703 
 
 normal surface-condenser operation there is a small leakage, 
 through the packing at the ends of the tubes, and to. this 
 is added leakage due to corrosion.. 
 
 The danger of corrosion attacking the tubes of surface 
 condensers is much greater in localities upon, or near the 
 sea coast where the condensing water is largely impreg- 
 nated with salt. 
 
 QUESTIONS AND ANSWERS. 
 
 446. Explain the chief points of difference between 
 the action of the reciprocating steam engine, and the steam 
 turbine. 
 
 Ans. The piston of the reciprocating engine is driven 
 back and forth by the static expansive force of the steam; 
 while in the steam turbine, not only is this static expansive 
 force made to do work, but the velocity of the steam in ex- 
 panding from a high, to a low pressure is also utilized in 
 turning the rotor of the turbine. 
 
 447. What other important factors enter into the opera- 
 tion of a steam turbine? 
 
 Ans. The principles of reaction and impulse. 
 
 448. Name several of the more important advantages 
 that the turbine has over the reciprocating engine. 
 
 Ans. First, highly superheated steam of a high initial 
 pressure may be used in the turbine. Second, a larger 
 proportion of the heat in the steam may be converted into 
 work with the turbine. Third, there is much less friction 
 with the turbine. 
 
 449. What is the most economical method of disposing 
 of the exhaust steam from a turbine? 
 
 Ans. By allowing it to pass into a condenser. 
 
704 Steam Engineering 
 
 450. ^Vill the turbine expand the steam to as low a 
 pressure as the reciprocating engine will? 
 
 Ans. Yes, and even lower. 
 
 451. What type of condensing apparatus is necessary 
 with the steam turbine. 
 
 Ans. The same kind that is used on reciprocating en- 
 gines. 
 
 452. How low will a well regulated turbine allow the 
 steam to expand ? 
 
 Ans. To within one inch of the vacuum existing in 
 the condenser. 
 
 453. What is the theoretical velocity of steam under 
 100 lbs. pressure if allowed to discharge into a vacuum of 
 28 inches? 
 
 Ans. 3860 feet per second. 
 
 454. How many ft. lbs. of energy would one cubic ft. 
 of steam thus exert? 
 
 Ans. 59,900 ft. lbs. 
 
 455. What is the ratio of bucket speed to jet speed for 
 impulse wheels. 
 
 Ans. Bucket speed equals one-half of jet speed. 
 
 456. What should be the ratio between bucket speed 
 and jet speed, for reaction wheels. 
 
 Ans. 1 to 1. That is, the two speeds should be equal. 
 
 457. What should be the form or curvature of the 
 blades, or buckets? 
 
 Ans. They should be of such form as will permit expan- 
 sion of the steam with the least amount of friction, or eddy 
 currents. 
 
 458. How are the stuffing boxes of steam turbines usu- 
 ally kept cooled? 
 
 Ans. By means of water applied in various ways. 
 
Questions and Answers 705 
 
 459. How is the speed of steam turbines usually regu- 
 lated? 
 
 Ans. By simple throttling. 
 
 460. What are the ideal conditions under which a tur- 
 bine should work? 
 
 Ans. A full initial pressure, and all cross sections of 
 steam passages to be suitable to the power required. 
 
 461. Of what type is the Westinghouse-Parsons turbine ? 
 Ans. It is both an impulse and reaction turbine. 
 
 462. How are the clearances between the blades pre- 
 served in this turbine? 
 
 Ans. By means of balancing pistons on the shaft. 
 
 463. What is the usual velocity of the steam in the 
 Westinghouse-Parsons turbine ? 
 
 Ans. 600 ft. per second. 
 
 464. How does the efficiency of steam turbines compare 
 with that of reciprocating engines? 
 
 Ans. It is generally higher. 
 
 465. How is the heat energy in the steam imparted to 
 the wheels of the Curtis turbine? 
 
 Ans. Both by impulse and reaction. 
 
 466. Describe the method of admission in the Curtis 
 turbine. 
 
 Ans. The steam is admitted through expanding nozzles 
 in which nearly all of the expansive force of the steam is 
 transformed into the force of velocity. The steam is caused 
 to pass through one, two, or more stages of moving ele- 
 ments, each stage having its own set of expanding nozzles, 
 each succeeding set of nozzles being greater in number and 
 of larger area than the preceding set. 
 
 467. What is the ratio of expansion in these nozzles? 
 
706 Steam Engineering 
 
 Ans. The ratio of expansion within these nozzles de- 
 pends upon the number of stages, as, for instance, in a two- 
 stage machine, the steam enters the initial set of nozzles at 
 boiler pressure, say 180 lbs. It leaves these nozzles and 
 enters the first set of moving blades at a pressure of about 
 15 lbs. 
 
 468. In a four-stage machine, with 180 lbs initial pres- 
 sure, what would be the pressures at the different stages? 
 
 Ans. First stage, 50 lbs. ; second stage, 5 lbs. ; third 
 stage, partial vacuum, and fourth stage, condenser vacuum. 
 
 469. How are the revolving parts of the Curtis turbine 
 supported ? 
 
 Ans. Upon a vertical shaft, which in turn is supported 
 by, and runs upon a step bearing at the bottom. 
 
 470. How is this step bearing lubricated? 
 
 Ans. Oil is forced under pressure by a steam or elec- 
 trically driven pump, the oil passing up from beneath. 
 
 471. How is the speed of the Curtis turbine regulated? 
 Ans. By varying the number of nozzles in flow. 
 
 472. How are the clearances adjusted in the Curtis 
 turbine ? 
 
 Ans. By means of the large step screw at the bottom. 
 
 473. How is the shaft packed to prevent steam leakage? 
 Ans. With carbon blocks made into rings fitting the 
 
 shaft. 
 
 474. What type of turbine is the De Laval? 
 Ans. It is purely an impulse wheel. 
 
 475. "What is the speed of the wheel? 
 
 Ans. From 10,000 to 30,000 revolutions per minute. 
 
 476. How is the heat energy in the steam utilized in 
 the De Laval turbine? 
 
 Ans. In the production of velocity. 
 
Questions and Answers 707 
 
 477. What is the velocity of the steam as it issues from 
 the expanding nozzles and impinges against the buckets ? 
 
 Ans. About 4,000 ft. per second. 
 
 478. What is the usual peripheral speed of the wheel? 
 Ans. 1,200 to 1,300 feet per second. 
 
 479. Of what type is the Allis-Chalmers steam turbine? 
 Ans. It is essentially of the Parsons type. 
 
 480. How are the clearances between the revolving and 
 stationary blades preserved? 
 
 Ans. By a thrust bearing. 
 
 481. What kind of bearings has the Allis-Chalmers 
 turbine ? 
 
 Ans. Self-adjusting ball and socket bearings. 
 
 482. What is the first move in preparing to start a 
 steam turbine? 
 
 Ans. Open the throttle slightly and allow a small vol- 
 ume of steam to flow through in order to warm the tur- 
 bine. 
 
 483. What should be done next? 
 Ans. Start the auxiliary oil pump. 
 
 484. What are the principal precautions to be observed 
 when starting a steam turbine? 
 
 Ans. To see that the turbine is properly warmed, also 
 to be certain that the oil is circulating freely through the 
 bearings. 
 
 485. What type of turbine is the Hamilton-Holzwarth 
 steam turbine? 
 
 Ans. It is an impulse turbine. 
 
 486. Describe in brief its construction? 
 
 Ans. There are no balancing pistons in this machine, 
 the axial thrust of the shaft being taken up by a thrust 
 ball-bearing. The interior of the cylinder is divided into 
 
708 Steam Engineering 
 
 a series of stages by stationary discs which are set in 
 grooves in the cylinder and are bored in the center to allow 
 the shaft, or rather the hubs of the running wheels that are 
 keyed to the shaft, to revolve in this bore. 
 
 487. In what respect does this turbine resemble a com- 
 pound reciprocating engine? 
 
 Ans. The steam is first admitted to the high pressure 
 casing, and from there it passes into the low pressure cas- 
 ing, which is larger in diameter. 
 
 488. Describe the action of the steam upon the blades? 
 Ans. The expansion of the steam takes place entirely 
 
 within the stationary blades, which also change the direc- 
 tion of its flow, distributing it to the running vanes. 
 
 489. What additional function do the stationary vanes 
 perform ? 
 
 Ans. They take the back pressure, thus acting as balanc- 
 ing pistons. 
 
 490. What type of governor has this turbine? 
 Ans. The spring and weight type. 
 
 491. How are the bearings lubricated? 
 
 Ans. The oil is forced into the bearings under pressure 
 by an oil pump. 
 
 492. Of what type is the Eateau steam turbine? 
 
 Ans. It is an impulse turbine having wheels of thin 
 plates, slightly conical. 
 
 493. How is the rotor balanced? 
 
 Ans. The same pressure exists on both sides of each 
 rotating wheel. 
 
 494. Does the steam act by velocity or pressure ? 
 Ans. By velocity in this case. 
 
 495. What are the essential features of the Eeidler- 
 Stumpf steam turbine ? 
 
Questions and Answers 709 
 
 Arts. The peculiar form of bucket, and the parallel 
 return of the steam. 
 
 496. What is meant by parallel return of the steam? 
 Ans. The steam enters the buckets through nozzles, 
 
 and is deflected through an angle of 180 degrees, thus leav- 
 ing the rotating buckets in a direction parallel to that of 
 its entrance. 
 
 497. Describe the action of the steam within the Eeid- 
 ler-Stumpf turbine. 
 
 Ans. Instead of escaping after having once passed 
 through the buckets, it is caught by the guides or stationary 
 buckets and returned to the wheel; this process being re- 
 peated again, and again until all of the energy in the steam 
 has been made to do work. 
 
 498. How many types of this turbine are there? 
 
 Ans. Two, viz. : The single flow, and the double flow. 
 
 499. How is the highest efficiency obtained in the oper- 
 ation of the steam turbine ? 
 
 Ans. By allowing the exhaust steam to pass into a 
 condenser. 
 
 500. Is it possible to maintain as high vacuum with 
 the turbine as with a reciprocating engine? 
 
 Ans. Experience demonstrates that a higher vacuum 
 may be maintained in the condenser of a turbine than is 
 possible with reciprocating engines. 
 
 501. What kind of condensing apparatus may be used 
 with steam turbines? 
 
 Ans. Any one of the modern improved types. 
 
 502. What is required in order to maintain a high 
 vacuum in any type of condenser? 
 
 Ans. That all entrained air be excluded. 
 
 503. How may this be accomplished? 
 
710 Steam Engineering 
 
 Ans. By means of a dry air pump. 
 
 504:. In what manner does the dry air pump differ from 
 an ordinary air pump ? 
 
 Ans. The dry air pump handles no water, and the clear- 
 ances are made as small as possible. 
 
 505. To what extent does the steam turbine expand its 
 working steam? 
 
 Ans. To within one inch of the vacuum existing within 
 the condenser. 
 
 506. Is the steam turbine adapted to the use of super- 
 heated steam? 
 
 Ans. It is. Highly superheated steam may be used, and 
 a high vacuum maintained. 
 
 507. Is the water of condensation from turbines desir- 
 able for boiler feed ? 
 
 Ans. It is, for the reason that it contains no lubricating 
 oil, and is a comparatively pure water. 
 
The Gas Engine 
 
 The gas engine differs structurally from the steam engine 
 
 in two particulars, it is much more ponderous than a steam 
 
 engine of equal output and has usually a much heavier 
 
 crank-shaft. The difference in total weight must not be 
 
 laid to the higher mean pressures exerted in the cylinder, 
 
 for, in engines of a certain power, the mean pressure in 
 
 the gas-engine cylinder will be higher than that in the 
 
 steam-engine cylinder, so that for a given power per stroke, 
 
 the gas engine may have the smaller cylinder. But the 
 
 four-stroke-cycle gas engine has only one working stroke 
 
 n four. For a given power, therefore, its cylinder area 
 
 nust be four times the area of the steam-engine cylinder, 
 
 >er pound of mean effective pressure. Since this latter 
 
 rill be as 3 to 2, approximately, the actual cylinder area 
 
 will be as 2.66 to 1, or the diameter ratio will be 1.63 to 1. 
 
 Approximately the gas engine appears fully 50 per cent 
 
 le larger when its piston speed is the same as that of the 
 
 earn engine. This is a very strong inducement to the 
 
 esigner to produce an engine which shall do work in both 
 
 ids of the cylinder. Such a design, however, necessitates 
 
 I piston-rod stuffing-box, gland and cooling devices. It 
 
 evolves double the number of explosions per minute in 
 
 the cylinder and it renders possible a reduction of the 
 
 cylinder ratio, as compared with a steam engine, to 1.33 
 
 to 1. Regarding single acting, or double acting gas engines, 
 
 the difference in stress on the crank shaft must be taken 
 
 into account. A single-acting engine produces a torsion in 
 
 the shaft which is reversed on the next stroke when the 
 
 711 
 
712 Steam Engineering 
 
 shaft is pushing back the piston. Keversing stresses are 
 about 50 per cent more destructive than stresses in one 
 direction only. The crank-shaft strength ratio is thus not 
 simply 4:1, as between a four-stroke and a one-stroke 
 method of working, but it is as 6:1, or diametrally as 
 1.8 :1, the strength varying as the cube of the diameter. 
 This is why gas-engine crank shafts are so very large and 
 this point must be of great importance on the score of cost. 
 Indeed the four-stroke engine embodies a large amount of 
 material which does very little work during a large pro- 
 portion of its working hours. 
 
 The gas engine is a prime mover which derives its power 
 or energy from the heat generated by the combustion within 
 its cylinder, of a mixture of gas and air in the proper pro- 
 portion to form an explosive. The combustion of this 
 charge of gas and air is occasioned under a close or heavy 
 compression, a result of the inward movement of the piston 
 after the charge is admitted- and all valves closed. The 
 result of igniting this mixture under the heavy compres- 
 sion is what is commonly called an explosion, which is 
 nothing more than a quick burning or rapid combustion 
 of the mixture. This sudden explosion causes a high degree 
 of heat within the cylinder behind the piston, and. the re- 
 sultant high initial pressure against the piston drives it 
 forward, and, through the medium of connecting rod and 
 crank, mqtion is imparted to the main engine shaft. The 
 original gas engines, and a majority of the smaller sizes 
 of today, operate upon the Beau de Eochas cycle or four 
 stroke cycle, sometimes termed the Otto cycle, meaning that 
 an engine completes a cycle in four acts, defined as follows : 
 (1) Induction — During an outstroke of the piston, air and 
 gas in suitable proportions are drawn into the cylinder. (2) 
 
The Gas Engine 713 
 
 Compression — The following instroke compresses the com- 
 bustible mixture into the clearance space. (3) Explosion 
 — Ignition of the compressed charge causes a rapid rise of 
 pressure and subsequent expansion of products. (4) Ex- 
 pulsion — The expanded gases are expelled by the returning 
 piston. In this type of gas engine, two revolutions of the 
 crank shaft are necessary in order to complete one cycle. 
 
 Many small engines and some of those of largest power 
 are designed upon the 2-stroke cycle, which is as follows : 
 (1) Compression of the charge. (2) Ignition, explosion 
 and expansion, and at the end of the stroke the exhaust 
 products are expelled and the cylinder filled by a mixture 
 of gas and air under pressure. In the two cycle engine, 
 two compression chambers are necessary, due to the fact 
 that in this type of gas engine consisting of two cylinders, 
 either side by side, or tandem, the charge of gas and air 
 is being received in one qdinder, while the previous charge 
 in the other cylinder is being compressed, preparatory to 
 explosion. A two-cycle engine thus explodes a charge, and 
 receives an impulse at each revolution. It is important to 
 admit only pure air and gas into engine cylinders. Dust 
 and grit, or tarry matters cause rapid wear of interior sur- 
 faces. Care is also necessary to insure the induction of 
 cold charges, in order that maximum density of gas and air 
 may be obtained. 
 
 The usefulness of the gas engine as a prime mover is 
 greatly enhanced by the fact that suitable power gas may 
 now be produced from almost any form of commercial fuel ; 
 the cheapness or relative fuel value of the combustible hav- 
 ing very little bearing on the value for power purposes of 
 the gas produced. For the efficient generation of steam 
 the choice of coals is confined within narrow limits ; for gas 
 
714 Steam Engineering 
 
 production relatively wide limits exist. Thus gas engines 
 are operating with practically the same thermal efficiency 
 on fuel gases ranging from 1,500 B. T. IT. per cubic foot, 
 to 90 B. T. U. per cubic foot. The former is a rich dis- 
 tillate from oil refining, the latter a waste product from 
 blast furnaces. The one contains practically no combusti- 
 ble, the other as high as 8 per cent. 
 
 Table 37 gives the origin, and some of the properties of 
 the usual commercial gases; Table 38 of the usual con- 
 stituent gases. 
 
 The power derived from the combustion of these gases 
 is, however, far more uniform than at first appears from 
 their relative calorific value. For perfect combustion a defi- 
 nite amount of air must be mixed with the gas, depend- 
 ing upon the amount of combustibles to be neutralized by 
 the oxygen in the air. For instance Pittsburg natural gas 
 requires about 10 to 12 cu. ft. of air per cubic foot of gas, 
 while for producer gas about equal volumes of gas and air 
 are required. The calorific value of the mixture entering 
 the gas engine cylinder thus forms the basis of all calcula- 
 tions rather than the heat of the gas itself, and in this 
 respect relatively little difference exists between the heat 
 value of suitable mixtures, whether the gas be rich or poor. 
 For this reason the gas engine is enabled to work efficiently 
 with most gases, however lean, provided of course that they 
 are properly cleaned or purified from sulphur — no dust — 
 no tar, etc. 
 
 Combustion. — In gas engine work it is important to 
 obtain a speed of combustion neither too rapid nor too 
 sluggish. Much then depends upon the relative constitu- 
 ents of the gas. Hydrogen burns with the greatest rapidity 
 — seven times faster than methane, and if present in large 
 
The Gas Engine 715 
 
 quantities, forms an undesirable element with high com- 
 pressions, on account of its tendency to premature ignition 
 from the heat of compression. On the other hand, the 
 comparatively sluggish combustion of methane and other 
 heavy hydro-carbons, and the presence of large quantities 
 of inert gases such as C0 2 and X tends to retard the com- 
 bustion of hydrogen, so that a permanent gas, although 
 containing a high percentage of hydrogen, if modified by 
 a high percentage of more sluggish gases, will prove to be 
 a suitable power gas. If, on the other hand, sufficient 
 sluggish constituents are not present, compression in the 
 engine must be largely reduced. Thus blue water gas (un- 
 carburetted) is unsuited to gas engine work on this ac- 
 count. Enriched with oil gas (carburetted), water gas be- 
 comes somewhat more adaptable; likewise crude oil water 
 gas. 
 
 Coke oven gas may become unsuitable if drawn off for 
 too long a period during the coking process. In most 
 forms of modern by-product coke ovens the richer gases are 
 drawn off during the first 40 or 50 per cent of the coking 
 period (10 hrs. in 24 hr. coke, 16 hrs. in 30 hr. coke) ; 
 those gases given off during the latter part being used for 
 heating the ovens. During the latter period tne percent- 
 ages of methane and hydrogen are rapidly reversed so that 
 hydrogen may run as high as 60 or 70 per cent of the total 
 volume of gas, which makes it quite unfit for power work. 
 The gas delivery must, therefore, be carefully controlled, 
 if utilized for power purposes. 
 
 Blast furnace gas, which is simply the product of more 
 or less incomplete combustion of carbon in a coke furnace, 
 contains less than one-third combustible matter, but forms 
 an excedingly satisfactory fuel gas. It is comparatively 
 
Table 37 
 commercial power gases— general properties. 
 
 ~ 
 
 O 
 
 «c 
 
 OC 
 
 -<i 
 
 OS 
 
 m 
 
 ■H 
 
 00 
 
 to 
 
 - 
 
 
 Blast Gas 
 
 O 
 O 
 
 ft 
 
 > 
 
 3 
 
 3* 
 
 p 
 
 
 
 
 5 
 
 3 
 3. 
 
 
 c 
 
 hd 
 1 
 
 
 0- 
 
 3 
 
 
 fD 
 
 O 
 P 
 
 O 
 
 i 
 
 p 
 
 ft 
 "I 
 
 O 
 P 
 Cfl 
 
 P 
 
 fD 
 •t 
 
 O 
 P 
 
 
 _ 
 
 O 
 
 EL 
 
 O 
 p 
 
 Cfl 
 
 O 
 
 C 
 p 
 
 CO 
 
 2 
 
 p 
 
 3 
 >-t 
 
 EL 
 
 O 
 p 
 
 Cfl 
 
 > 
 
 By-nroduct of blast furnaces. — Conver- 
 sion of fixed C in coke into CO by 
 air blast. Some CO2 formed. 
 
 Cfl 
 
 cr 
 ^p 
 
 P 
 
 ° 1 
 I* 
 
 3 < 
 » 
 
 ft* 
 
 Cfl 
 
 1 
 
 O 
 
 
 
 > 
 
 3- 
 
 8g 
 
 3 
 
 Cf) 1 "^ 
 
 p p 
 
 « 
 
 pg 
 
 p* 
 
 Cfl 
 
 Bituminous coal. Breaking up of vola- 
 tile hydro-carbons and conversion of 
 fixed carbon into CO. 
 
 Obtained from coal, coke, peat, lignite 
 or wo. 1. Largely incomplete oxida- 
 tion of carbon to CO by a steam air 
 blast. H2O decomposes into free H. 
 Some CO2 formed. 
 
 
 
 m 
 
 p Cfl 
 fD 2*. 
 
 3 
 
 cr 
 
 q Cfl 
 CLp 
 
 ftg 
 
 
 
 3JP 
 
 • 3 
 
 CL 
 
 O 
 
 3* 
 H 
 
 a 
 
 
 
 C^ft 3" 
 ^ LT. 
 
 CLO 
 
 3 3 
 
 Crq O 
 fD •■+» 
 
 3 w 
 rt>ft 
 
 fD 3 
 cl 
 
 - 
 3 
 
 &> M. 
 
 £3 
 
 2 w 
 
 3 3 
 
 rr^ 
 ? c 
 a en 
 -t 
 3 ft 
 
 as 
 
 r 
 2.5* 
 
 CTfD 
 P -t 
 
 3S 
 
 -i 3 
 
 Cfl 
 
 O 
 
 3,'< 
 3-0 
 
 IS 
 
 cr~> 
 3 
 
 Cfl 
 O -~ 
 
 ?S' 
 
 
 
 
 
 Cfl 
 
 fD 
 
 CL 
 
 ft 
 
 ft % 
 
 en £" 
 
 < 
 
 
 
 £1 
 
 Cfl' 
 
 p* 
 
 0" 
 
 3 
 
 
 
 
 
 p^ 
 
 3* 
 O 
 
 O* 
 
 Cfl 
 
 fD 
 CL 
 
 < 
 
 p 
 r? 3. 
 
 ~l N 
 
 crq 5' 
 pcrq 
 
 Cfl 
 
 
 3 
 
 CL 
 ft 
 
 o_ 
 
 d 
 
 Cfl 
 fD 
 CL 
 
 O 
 
 ft 
 3 
 H 
 O* 
 
 3* 
 
 
 
 fD bL 
 
 ?q O 
 fD crq 
 p 0" 
 
 rf p 
 
 §T 
 
 CO 
 
 Cfl 
 
 •t 
 
 
 3 
 
 CL 
 ft 
 O 
 O 
 
 3 
 *o 
 
 
 Cfl 
 
 ft 
 
 CL 
 
 
 
 s 
 
 
 
 1— 1 
 
 Gas very lean, dusty, and sluggish. Dif- 
 ficult to clean except mechanically. 
 Excellent gas for engines taking high 
 compressions. 
 
 Gas practically clean, except dust. Most 
 suitable for small producers. Fuel 
 rather expensive. 
 
 Gas free from tar, — requiring little 
 cleaning. Excellent power gas. Buck- 
 wheat size coal may be used. 
 
 Richest of producer gases. Tar distil- 
 late difficult to remove. Most grades 
 of coal suitable, including slack, lig- 
 nite and wood. 
 
 Cheapest and best of artificial fuel gases, 
 lean and comparatively slow burning. 
 Made from any grade fuel. 
 
 Rich gas, high in H, and rather snappy. 
 Free from impurities, except S. Man- 
 ufacturing cost low. 
 
 Pure gas, too snappy (high in H) for 
 gas engines. More suitable if enriched 
 with oil gas. Rather expensive gas 
 for general power purposes. 
 
 Gas should be drawn off during early 
 part of coking run. Good gas, rather 
 high in H & S, requiring much puri- 
 fication. 
 
 Excellent gas, resembling natural gas. 
 Not hard to clean. Manufacturing 
 costs usually too high for general 
 power purposes. 
 
 Very rich in hydro-carbons. Liable to 
 carbon deposits. Seldom used for 
 power except in small oil (petrol) 
 engines. 
 
 1— 1 
 
 CL 
 
 2Lft 
 EL 
 
 ^9 
 -1 
 
 3 fD 
 
 3* 
 
 qqorq 
 P 
 
 Cfl 
 
 ft 
 
 £.5 
 
 fD 3* 
 co » 
 
 §"§ 
 
 ft " 
 p 
 
 3 •-» 
 
 3,5 ST 
 
 • ft 
 
 1 
 
 O 
 W 
 
 H 
 O 
 
 t73 
 
 ife. 
 
 -1 
 
 ; 
 
 W 
 
 re 
 
 u 
 
 a 
 
 
 
 01 
 
 00 
 
 CO 
 
 M 
 
 P P T3 
 
 5/1 3 . X 
 ft 
 
 C 
 
 ft * 
 •1 
 
 _ 
 
The Gas Engine 
 
 717 
 
 Table 38 
 constituents of power gases. 
 
 Gas 
 
 Heating 
 
 Value 
 
 
 
 Name 
 
 Chemical 
 Symbol 
 
 B.T.U. 
 
 Cu. Ft. 
 
 Net 
 
 Rela- 
 tive 
 
 t^naractenstics — Where 
 Found 
 
 Hydrogen 
 
 H 
 
 278 
 
 1 
 
 Element formed from decom- 
 position of steam (H2O) 
 r hydro - carbon c m- 
 pounds. Burns very rap- 
 idly with high flame tem- 
 perature. 
 
 Oxygen 
 
 O 
 
 
 
 
 Element, not considered a 
 combustible as it displaces 
 an equal amount of (O) in 
 air for combustion. 
 
 Nitrogen 
 
 N 
 
 
 
 
 Element. Inert gas entering 
 with air (N-79%, 0-21%). 
 Retards speed of combus- 
 tion. 
 
 Carbon Monoxide 
 or Carbonic Oxide 
 
 CO 
 
 326 
 
 1.17 
 
 Valuable constituent. Prod- 
 uct of incomplete combus- 
 tion (oxidation) of C in 
 presence of excess carbon. 
 
 Carbon Dioxide 
 
 co 2 
 
 
 
 
 Inert gas. Product of com- 
 plete combustion of C. 
 Occurs in all producer and 
 blast gases. Retards speed 
 of combustion. 
 
 Methane or Marsh 
 Gas 
 
 CH 4 
 
 913 
 
 3.29 
 
 Most valuable constituent 
 evolved by natural or ar- 
 tificial decomposition of 
 vegetable matter, coal or 
 crude oils. 
 
 Acetylene 
 Ethylene Off de- 
 fiant Gas 
 Ethane 
 Benzene or Benzol 
 
 C 2 H 2 
 C 2 H 4 
 C 5 H 6 
 C 6 H 6 
 
 1427 
 1490 
 1615 
 3955 
 
 51.4 
 
 53.6 
 
 58.1 
 
 131.5 
 
 J 
 
 Higher hydro-carbons, usu- 
 ally as "illuminants" — 
 occur in small quantities 
 . in the richer gases, liber- 
 ated during destructive 
 distillation of coal or oil 
 — Acetylene used alone 
 for lighting. 
 
 Carbon 
 
 C 
 
 
 
 C oxidizes to CO (incom- 
 plete) and CO2 (com- 
 plete). CO oxidizes to 
 CO2. 
 
 Sulphur 
 
 S 
 
 
 
 S oxidizes to SO 2 forming 
 H2SO4 (sulphuric acid) 
 with water. 
 
718 Steam Engineering 
 
 slow burning, thus permitting compressions as high as 
 160-200 lbs. per sq. in. and can be cleansed of dust without 
 great difficulty; no tar is, of course, encountered. Owing 
 to the fact that nearly 40 per cent less heat is contained 
 in a cu. ft. of blast furnace gas mixture than with natural 
 gas, larger cylinders are provided on blast furnace gas 
 engines for developing the same horse power. The slight 
 increase in friction is, however, largely overcome by in- 
 creased thermal efficiency due to higher compression, and 
 gas engines designed for this gas give practically the same 
 efficiency as those operating on richer gases. 
 
 Induction. — The charge of gas and air in definite propor- 
 tions is drawn into the cylinder by the suction of the engine 
 piston, and the velocity of entry is in direct proportion to 
 the piston speed. The air valve is usually opened before 
 the gas valve, but inasmuch as there is no suction created 
 until the opening of the air valve, some makers set the 
 valves so that the gas valve is approaching its maximum 
 lift by the time that the air valve has commenced to open, 
 thus ensuring a well mixed charge. Usually, however, the 
 settings are arranged so that the first portion of the in- 
 duced charge is of air only, then air and gas, and finally 
 air with the small quantity of gas swept in by the still 
 moving current of air from the passages connecting the gas 
 and air valve seats. The cams operating the valves are 
 carefully designed to permit maximum lift with swift, but 
 gradual opening and closing, to accord with the induced 
 velocity set up by the linear speed of the piston at each 
 point of the stroke. The air valve, governing the entry of 
 the entire charge, is opened well in advance of the inner 
 dead center of the engine, and is kept from closing until 
 after the outer dead center, so that full effect of the mo- 
 
The Gas Engine 719 
 
 mentum imparted to the entering gases at the highest rate 
 of piston speed can be utilized without restriction, it being 
 possible by such means to obtain a better filled cylinder. 
 
 Compression. — Modern practice in gas engine design 
 aims at securing the economical advantages coincident with 
 high compression pressures, but the limit of allowable max- 
 imum compression pressure depends upon the relative pro- 
 portion of hydro-carbon gases, and hydrogen contained in 
 the mixture or charge admitted to the cylinder. Hydro- 
 gen will ignite at a much lower temperature than the other 
 constituents, and owing to the additional heat during com- 
 pression, it becomes necessary to so design the relative 
 volumes of piston displacement, and clearance, that self 
 ignition is practically impossible. With blast furnace gas 
 containing only about two per cent of hydrogen, compres- 
 sion pressures .of 200 lbs. per sq. in. and over may be 
 safely used, and with producer gas, 150 to 200 lbs. are com- 
 mon and safe pressures, but with illuminating gases the 
 maximum is placed at 120 lbs. per sq. in. unless special 
 precautions are taken to insure efficient cooling and clean- 
 ing of the cylinders. This is effected by the injection of 
 water or cold air through the clearance spaces and valve 
 ports during the charging stroke, or by pressure during 
 compression. 
 
 Ignition. — The increase of compression pressures, and 
 the use of poor gases for power purposes has brought elec- 
 trical ignition devices into common use. Hot tubes of 
 porcelain or hecnum are still used for engines designed to 
 suit illuminating gas, but the impossibility of quickly ad- 
 justing the instant of explosion when running, the rapid 
 deterioration of timing valves, and cost of renewals have 
 emphasized the superior advantages of electrical firing. 
 
720 Steam Engineering 
 
 While with petrol engines the current from a primary or 
 secondary battery is utilized with intensifying coil, and 
 jump sparking plug, the usual method adopted for gas 
 engines is that of a positive break by mechanical separation 
 of two electrodes through which current is passing from a 
 magneto machine. In a magneto the lines of force flowing 
 between opposite poles of a permanent magnet of great 
 strength are alternately deflected from, and passed through 
 an interposed armature by means of a shield or deflector 
 operated by suitable mechanism from the half speed shaft. 
 Upon maximum rapidity of the armature cutting the mag- 
 netic lines of force a strong current is induced in the wind- 
 ings and passes through a circuit formed by an insulated 
 wire connected to a fixed, well-insulated electrode through 
 the second and movable electrode in electrical contact with 
 the engine frame and through this to the armature. It is 
 of course very necessary to time the mechanism making the 
 "break" so that it synchronizes with the period of the most 
 powerful induced current in the armature. Most of the 
 difficulties encountered with magnetos have been owing 
 to the slipping of the actuating mechanism from the coned 
 seating on the armature spindle, but once the correct set- 
 ting has been noted and marked, attendants nave found 
 that very little other attention is necessary. 
 
 Primary Batteries. — Those used are of two kinds, dry 
 and wet batteries. Before the dry cell became so common, 
 the cell that was used mostly for bells, and other open cir- 
 cuit work, (by open circuit work is meant intermittent work, 
 like a bell that rings occasionally, or ignition purposes; a 
 closed circuit is one where the current flows continuously) 
 was the wet sal ammoniac cell. The elements in this cell 
 are commonly carbon and zinc; the earlier types had the 
 
The Gas Engine 721 
 
 carbon contained in a porous cup and surrounded by broken 
 carbon and the depolarizer, but the later and more im- 
 proved forms have the depolarizer compound mixed with 
 the carbon, and the whole formed into a cylinder, while the 
 zinc element is in the form of a pencil or rod about three- 
 eighths of an inch in diameter and passes through a por- 
 celain sleeve in the center of the carbon so that it is insu- 
 lated from it. This form of zinc exposes very little sur- 
 face to the solution, and the internal resistance of the cell 
 is high. Some makers have endeavored to overcome this 
 by making a large sheet zinc, which either encloses the 
 carbon, or is enclosed by it. This increases the amperes that 
 can be drawn from the cell, but unfortunately, as there is 
 no porous cup to help resist it, local action soon takes place 
 and the cell soon runs down, even if it is not worked, while 
 the small pencil zincs will stand for years; but their ampere 
 output is low, from 3 to 6 at a voltage of 1.6 so that as a 
 rule they are not as good as the dry cell for ignition pur- 
 poses, unless connected in series parallel, when they will 
 give good service. 
 
 The Copper Oxide Battery is another type that is fre- 
 quently used. This battery has elements composed of cop- 
 per oxide compressed into a flat firm plate, and a zinc plate, 
 both of which are suspended in a solution of caustic potash ; 
 the voltage is very low, a little less than 1 volt per cell, but 
 the amperage is very high. In fact, the batteries are sold 
 on an ampere rating very similar to that of storage bat- 
 teries. The ampere hours capacity of the cell determining 
 its price (an ampere hour, is one ampere flowing for one 
 hour, or its equivalent). These cells are usually arranged 
 so that all parts fail at nearly the same time, that is, the 
 solution is exhausted at the same time that the elements 
 
722 Steam Engineering 
 
 are used up, so at the end of each run all that is left is 
 the jar and element holders. It should be borne in mind 
 when installing cells of this character, that on account of 
 their low voltage it is necessary to install one cell for each 
 volt wanted. 
 
 The Storage Battery is perhaps the best battery for 
 spark producing purposes, as its voltage is high, starting at 
 2 volts, and working strongly till towards the last, when it 
 drops to 1.8 and should be recharged while its amperage is 
 very high ; in fact, drawing current from a storage cell has 
 been likened to taking water from a pail, one can get any 
 quantity that it contains, from a drop at a. time to the whole 
 amount by tipping the pail over. In the same way current 
 can be taken from a storage cell by regulating the resistance 
 so that any amount can be drawn off from .001 of an 
 ampere, to several hundred amperes. 
 
 A Storage Cell consists of several grids or skeleton 
 frames of lead which are filled part of them with red lead 
 for the positive plates, and the rest with litharge for the 
 negative plates; under the action of the electric current, 
 these turn into plain lead for the negative, and peroxide of 
 lead for the positive. These are immersed in a mixture of 
 sulphuric acid and water, about 6 parts of water to 1 of 
 acid, and then subjected to the action of an electric cur- 
 rent, and while they do not (as their name might indicate) 
 "store electricity" a chemical action takes place which 
 renders them capable of giving off a large proportion of 
 the current which they receive. 
 
 A Dry Battery is not, as its name might indicate, dry ; it 
 is, rather a moist battery, for as soon as it becomes "dry" 
 its usefulness is ended. This is one reason why it is neces- 
 sary to be certain that the batteries are new and fresh when 
 buying them. 
 
The Gas Engine 723 
 
 As commonly made^ a dry battery consists of a round 
 zinc case, which forms one of the elements, and which con- 
 tains a piece of carbon in the center that forms the other 
 element. This carbon element is made in various shapes 
 according to the manufacturer's ideas, as each maker is 
 striving to get as large a surface as possible in order to 
 reduce the internal resistance of the cell and get a large 
 output in amperes. The carbon is usually surrounded by 
 some powdered carbon containing what is called the "de- 
 polarizer" (though this depolarizer may be incorporated in 
 the exciting paste). This depolarizer has a great influence 
 on the life of the cell for the reason that, under the action 
 of the exciting fluid when the cell is working, bubbles of 
 hydrogen form on the carbon and to quite an extent insu- 
 late it, thus preventing the action of the excitant on it, 
 so much so that it seriously weakens the action or output 
 of the cell. The depolarizer to a great extent counteracts 
 this by absorbing the bubbles and thus sustains the cell, 
 keeping the output more nearly uniform. When a cell is 
 "run down," a rest allows this depolarizer to continue its 
 action, and after a time the cell will be found in much better 
 condition, though as both the exciting fluid and the de- 
 polarizer are weakened, it will never be as good as before. 
 
 The exciting fluid is a solution of sal ammoniac with 
 other ingredients added. The precise formulas are kept 
 secret by the manufacturers, but plaster of paris, mixed 
 with oxide of zinc and other chemicals, which keep the 
 plaster in an open and porous condition so that the excit- 
 ing fluid and gases can easily pass through it, are used. 
 This mixture is firmly packed in the space between the 
 carbon and the zinc after a piece of blotting paper has been 
 rolled up and placed next to the zinc to act as a porous 
 
724 Steam Engineering 
 
 cup to prevent actual contact between the mixture and 
 the zinc. 
 
 The usual test for a dry cell is with an ampere meter, 
 and they are rated as to what they will show ; for instance 
 one showing less than ten amperes is considered as poor, 
 while one showing twenty-five amperes is considered excel- 
 lent. This style of testing and rating, while it is the only 
 convenient and quick way known at the present time, is 
 not very reliable owing to the uncertainty as to the exact 
 condition of the cell. According to ohms law, current in 
 amperes equals electromotive force in volts divided by 
 
 E 
 
 resistance in ohms; expressed by the formula C = — . Now 
 
 the internal resistance of the cell may be high, and the 
 result is that when drawn upon for current this resistance 
 will restrict the volume of flow to a low reading on the 
 ammeter, or if the internal resistance of the cell is low a 
 larger volume of current will flow, and the reading of the 
 ammeter will be higher, while the voltage remains the same. 
 
 Of course the low reading may just as well come from 
 the cell not being in good condition and having very little 
 in it. While on the other hand the low internal resistance 
 and high reading cell is exposed to the dangers of local 
 action, that is, the current works inside of the cell itself, 
 wearing it out while standing in much the same way that a 
 leak might start in a pail of water if the sides and bottom 
 w r ere extremely thin. 
 
 Another element of uncertainty lies in the internal 
 resistance of the ampere meters used for testing. If the 
 resistances of its working coils are low, it will show high 
 reading, if they are high the readings will be low, for the 
 reason that the small voltage of the cell cannot push the 
 
The Gas Engine 725 
 
 heavy current through against the high resistance of the 
 meter; some meters are supplied with a conducting cord 
 to reach across where it is difficult to get at the cells. A 
 decided difference in the reading will be noticed when us- 
 ing this cord for the same reason spoken of above, as the 
 resistance of the cord, while it is small, cuts down the 
 current very appreciably. While the high resistance me- 
 ters are not favorites with the battery dealers, for the rea- 
 son that they do not show amperage enough, they are the 
 best for practical use as they do not draw so heavily on the 
 battery, and as soon as one gets accustomed to how low 
 cells can be worked, according to their particular meter 
 reading, it matters very little what that reading is, provid- 
 ed that it does not change. 
 
 One trouble with the common cheap meters is, that they 
 depend for their accuracy upon the difference in pull be- 
 tween a permanent magnet and an electro magnet which 
 is energized by the cell to be tested. As long as the strength 
 of the permanent magnet remains the same, the reading 
 remains the same, but as the permanent magnets are us- 
 ually made from cast iron, the magnetism does not remain 
 the same, but it is continually getting weaker. As the 
 electro magnet remains practically the same, this allows it 
 to pull the needle further and further as the permanent 
 magnet weakens more and more so that the readings are 
 continually getting higher and higher; for this reason it 
 is well to have the meter tested occasionally in series with 
 some large standard make. 
 
 From the foregoing it can be easily seen that all connec- 
 tions should be kept clean and tight, for dirt adds greatly 
 to the resistance that the battery has to overcome. A dirty 
 connection is a hard trouble to find at times when the wir- 
 
726 Steam Engineering 
 
 ing runs through obscure places as it usually does around 
 ordinary gas engines. A loose connection will also cause lots 
 of trouble and be difficult to find for the reason that it 
 will work at times, and not at other times, giving one the 
 impression that the trouble may be in the carbureter, or 
 plug. 
 
 Magnet Ignition. — There are three types of magneto 
 ignition. The most recent type is the inductor type of 
 magneto, which has no moving wires, commutators or 
 brushes and which generates a sine wave of alternating 
 current. 
 
 The second type is a dynamo type of magneto, which has 
 a commutator and brushes, and a little drum wound ar- 
 mature, and which has a permanent magnetic field. This 
 type of magneto is merely a dynamo with permanent 
 magnets instead of electric magnets for its field. 
 
 The third type is an alternating current magneto which 
 is equipped with its own circuit breaker and distributor, 
 commonly called a high tension magneto. This type of 
 magneto is also often made with a circuit breaker and 
 distributor, and a primary winding on it, which operates 
 on a coil, external to the magneto. It is a low tension 
 magneto, but is also frequently called a high tension mag- 
 neto, on account of its producing a jump spark. 
 
 Spark Coils. — Soft platinum points should not be 
 used but an alloy of such percentage of iridium and plat- 
 inum as will permit a very hard and dense point, and one 
 which will not weld itself together as soon as it warms up. 
 It must be borne in mind that pure platinum is a very soft 
 and spongy metal, and will weld together at temperatures 
 extremely low for welding heat. 
 
 Irido platinum contact points require a very much higher 
 temperature before they will weld or seize together. 
 
The Gas Engine 727 
 
 In the construction of spark coils the very best of in- 
 sulating material should be employed, and after the wind- 
 ings are made, they should be pumped out in a hot vacuum, 
 thus exhausting all of the air and moisture and they should 
 then be impregnated while under vacuum with a dielec- 
 tric of heat and moisture resisting qualities, which would 
 seal up the windings, making them impervious to mois- 
 ture, and preventing all electrical discharges and leakage 
 between its turns and layers. 
 
 This method of treating spark coils is quite recent, and 
 is by no means as yet universal among the various spark 
 coil builders. If spark coils were all built properly, with 
 the proper kind of windings, and the proper kind of 
 vibrators used, and the coils used in connections with the 
 proper kind of timers, that is, timers which do not have an 
 unnecessarily long period of contact, it would be found that 
 the battery consumption could be reduced very materially. 
 
 Proper timing of ignition devices has a direct result 
 upon the economical working of the engine. If the mech- 
 anism is set too early on the compression stroke, combustion 
 of the charge occurs at, or before the inner dead center of 
 the engine, resulting in violent shocks, excessive strain 
 upon the piston, connecting rod, and bearings and in- 
 volving great waste of power. If too late, the piston has 
 commenced to accelerate under the influence of momentum 
 stored up in the flywheel, so that the explosive force follows 
 the piston without attaining its maximum thrusting effort, 
 and with some loss of compression pressure, due to the re- 
 expansion of the charge before ignition is effected. 
 
 The speed of flame propagation varies with the per- 
 centage of hydrogen contained in combustible mixtures, 
 and it is convenient for means to be provided to adjust the 
 
728 Steam Engineering 
 
 instant of ignition to suit varying qualities of gas. For 
 this reason many makers fit a device permitting an attend- 
 ant to set the "break" at the most suitable instant, and 
 there is no doubt that with such facilities a careful man 
 can thus obtain good results even with very variable mix- 
 tures such as often occur with poor gases generated by pro- 
 ducers. Some leading manufacturers, however, realize 
 that, by carelessness or neglect, the provision of such means 
 of adjustment is liable to misuse, and they prefer to ar- 
 range two firing points only — one very late for starting up 
 at slow speeds, and another for normal speeds, the varia- 
 tions in inflammability of charges being deemed of less 
 importance than the variations of the average skill and 
 intelligence of attendants. 
 
 The Explosive Mixture* — "Theoretically, ignition must 
 be effected early enough and be so efficient that the whole 
 of the power charge is ignited when the piston reaches the 
 inner dead center position. Thus the condition of max- 
 imum heat development will occur with the minimum 
 cooling surface, and in a space which is specially designed 
 to withstand high temperatures and pressures. Purity, 
 calorific value, temperature and compression of the mix- 
 ture, as well as the position and efficiency of the sparking 
 apparatus, the form of combustion chamber and other con- 
 ditions, will cause inflammation to spread faster, or slower, 
 which phenomenon becomes quite clearly visible on the 
 indicator card, provided the latter be taken on a drum 
 with continuous travel. 
 
 In several types of large modern gas engines the point 
 of mixing the gas and air is rather superficially treated, 
 
 * Franz Ehrich Junge. 
 
The Gas Engine 729 
 
 while Keichenbach, who certainly deserves consideration 
 as an authority on the subject, puts very much emphasis 
 on this feature in all his designs from the earliest down 
 to the very latest. It is interesting to examine what- has 
 actually been done to clarify this question, and which view 
 the serious student of the gas problem is justified in 
 holding. 
 
 Gas and air properly mixed in chemical proportions, so 
 that just sufficient oxygen is present in the combination to 
 ensure perfect combustion, will give the highest temperature 
 of explosion which it is possible to obtain. Above and be- 
 low this ideal condition there is a wide range of inflamma- 
 bility wherein more or less oxygen in the form of air may 
 be mixed with the gas, than is necessary for its chemical 
 combustion, so that a mixture of such composition will yet 
 ignite but will burn at a slower rate of flame propagation 
 and, consequently, will not develop the maximum tem- 
 perature corresponding to its calorific value. If with a cer- 
 tain gas there be mixed about 4.7 times the amount of air 
 that is necessary to establish the condition of chemical 
 balance, the mixture will be that which is theoretically 
 best suited for adoption in gas-engine practice. Theory 
 and practice often differ, and so it is found advantageous 
 to employ in actual practice far more air in the internal 
 combustion process than is theoretically required. The 
 reasons are threefold: To reduce temperatures all round, 
 to prevent premature explosions which might be provoked 
 by the high heat of compression, and to supply to the gas, 
 even when poorly mixed with the air, always sufficient 
 oxygen for combustion, and consequently to reduce the loss 
 of unburnt gases leaving the exhaust to a minimum. 
 
 If one examines by thermodynamic calculation the com- 
 bustion efficiency of lean mixtures under whatever cyclic 
 
730 Steam Engineering 
 
 conditions they may be transformed into work, it will be 
 found that maximum economy is attained by compressing 
 the weakest mixture to the highest possible degree, but here 
 again one is confronted by an upper limit which is rigidly 
 drawn by the lack of inflammability of such mixtures. 
 Desire for thermal excellence of the working process forces 
 us to approach this upper limit as much as possible, but the 
 decreasing calorific value of the power charge per unit of 
 contents, and the decreasing capacity of the engine keeps 
 the actual practice far below this extreme ideal. In 
 average practice it is customary, at normal loads and with 
 lean gases, to work with a surplus of air of from 30 to 40 
 per cent over what is theoretically required; with gases 
 of high heat value, even more air is provided, so that the 
 dynamic medium in the engine cylinder possesses a calor- 
 ific value of from 44 to 62 B. t. u. per cubic foot." 
 
 Explosion and Expansion. The mean pressure upon the 
 area of the piston throughout the stroke is, of course, of 
 great importance and directly affects the power given out 
 from the engine. High initial explosion pressures per se do 
 not create the most powerful efforts behind the piston, 
 neither are low terminal expansion pressures indicative of 
 maximum economy. 
 
 Exhaust. Before the expansion, or power stroke is fully 
 completed the exhaust valve commences to open — usually 
 when the piston has still to travel one-tenth of its stroke. 
 
 On small high speed engines the exhaust valve should 
 open 15 to 40° before center on the power stroke depend- 
 ing on the size and the speed of the engine. The last part 
 of the power stroke is not noticeably effective in delivering 
 power to the crank shaft and the exhaust valve is opened 
 early to get rid of the heat after it has done its work. In 
 
Gas Engine Valve Setting 
 
 731 
 
 an engine with 6-inch stroke the piston travels only {% 
 inch in the last 40° of the power stroke as shown in Figs. 
 303 and 304. The exhaust valve should never close before 
 dead center on the scavenging stroke. 
 
 For slow moving engines with large, easy valve ports 
 and passages, the exhaust opening may be fixed at 15 to 20° 
 before center instead of 40°, and the inlet opening and 
 closing points may be fixed at center to 10° after center. 
 
 ■ 
 
732 
 
 Steam Engineering 
 
 For very high speed engines the inlet closing should be 
 delayed to 30 or 40° past center instead of 20° as shown. 
 A point to keep in mind is that it is impossible to change 
 the time a valve opens without changing the closing time 
 correspondingly earlier or later, unless a new cam of dif- 
 ferent design is used. This is indicated by A and B, Fig. 
 303. If, for example, it is desired to open the valve later 
 without changing the closing point at B, the cam must be 
 made so the beginning of the lift at point A will be carried 
 around further toward B. 
 
 fxhavst valve closes 
 
 Tnlet Valve closes 
 
 Fig. 804 
 
 If an engine is known to be properly timed and is to be 
 taken apart it will save much trouble later, to see that the 
 gears are marked as shown at C, Fig. 303, before taking 
 the machine to pieces. The gears can then be readily 
 reassembled and the timing will be just as before. The 
 terminal expansion pressures are about 25 to 30 lbs. 
 above atmosphere, and the velocity with which the burnt 
 product leaves the cylinder due to such pressure imparts 
 considerable momentum to the column of escaping gases, 
 
Gas Engine Valve Setting 733 
 
 thus helping to effect their thorough evacuation. With 
 long exhaust pipes not unduly restricted, the energy of the 
 moving column of gases is taken advantage of. 
 
 Valve Timing. — Timing the valves of a gas engine means 
 practially the same thing as "setting" the valves of a 
 steam engine. It means to so set the gears, cams, and con- 
 tributory adjustments that admission and exhaust valves 
 will be opened and closed at a point a certain number of 
 degrees from dead center in the travel of the crank, and 
 with relation to the piston stroke. The first thing, there- 
 fore, is to know positively just when the crank is on the 
 dead centers. The piston is, of course, at the extreme ends 
 of its sroke when the crank is at dead center. Owing, how- 
 ever, to the fact that the crank moves a number of degrees 
 on each side of the center without perceptible movment of 
 the piston, it is impossible to tell accurately when dead 
 center is reached by watching the position of the piston. 
 Guess work will not do. 
 
 The following instructions apply more particularly to 
 the smaller sized, high speed engines. Large sized engines 
 will be taken up later on. 
 
 Fig. 305 illustrates a simple, accurate method of finding 
 the dead centers. First provide a stationary pointer on 
 the engine as at C. It will be better if this pointer can be 
 arranged close to the face of the flywheel. As the flywheel 
 is keyed securely to the crank shaft its movement corre- 
 sponds to the movement of the crank. Now turn the crank 
 to one side of center as shown by the full lines in the 
 drawing ; insert a rod, A, through a hole in the head letting 
 it rest firmly against the piston ; make a mark on the face 
 of the flywheel at D as indicated by the stationary pointer, 
 C ; also make a mark, B, on the rod, A. Now turn the 
 
734 
 
 Steam Engineering 
 
 crank to the other side of center as shown by the dotted 
 lines; when the mark, B, on rod A, is at the same position 
 as before with relation to its' guide, and to the piston the 
 crank will be at exactly the same distance from center as 
 before; now make the mark, E, on the face of the flywheel 
 
 Fig. 305 
 
 as indicated by the pointer C. As marks D and E are at 
 equal distances on each side of center, it follows that in 
 bisecting the distance from D to E, as shown, and bringing 
 the central mark, F, to the fixed pointer, C, we will bring 
 the crank to the exact dead center for that end of the stroke. 
 The opposite center is found in the same way. After the 
 
Gas Engine Valve Setting 735 
 
 dead center marks are made on the flywheel the stationary 
 pointer, which is left permanently in position, will show 
 at any time when the crank is on dead center. 
 
 Fig. 305, shows valves in the head one of which has been 
 removed to insert the rod, A, for finding the exact dead 
 centers. The valve stem guide makes a good guide for the 
 rod, A, of similar size. Where the valves are not in the 
 head, any other opening, as for spark ping or igniter may 
 be utilized by making a special block to fit the opening and 
 drilling in it a guide hole for the rod A. 
 
 By measuring the distance in inches before or after the 
 dead center mark on the flywheel to the point at which the 
 valves open and close, the number of degrees can be quickly 
 determined. For example, suppose we find the exhaust 
 valve opening 10 inches (as measured in the face of the fly- 
 wheel) before the crank reaches center on the power stroke 
 of the piston. If the flywheel is 25 inches in diameter we 
 have 25" X 3.1416=78.54 circumference of the wheel; 
 (360° always represents the circumference of a wheel of 
 any size) then we have 360°-i-78. 54=4.58° for every inch 
 on the face of the 25 inch flywheel. If as stated the ex- 
 haust valve is opening 10 inches before center we have 
 4.58° X 10=45.8° before dead center at the end of the 
 power stroke. The closing point of the exhaust valve and 
 the movement of the inlet valve (if it is operated with a 
 cam and gear) can be checked up in the same way. 
 
 Owing to the fact referred to that the crank moves a 
 number of degrees at the ends of its stroke without 
 perceptible movement of the piston, there is a range of 15 
 or 20° in valve setting within which it is difficult to detect 
 material difference under equal conditions of port passages 
 and engine speed. In fact it is the valve lift, size and 
 
736 Steam Engineering 
 
 length of inlet and exhaust passages, and the engine speed, 
 or corresponding speed of the gas flow that decide the best 
 valve setting for any particular engine. If the engine runs 
 slowly, and the inlet valve and passage are of ample size, 
 the intake valve may open and close at dead center with ex- 
 cellent results. If the incoming charge comes into the cylin- 
 der at high speed, as is usually the case with high speed 
 engines, a late closing of the inlet valve is necessary, because 
 of the greater vacuum following the piston, and the inertia 
 or moving force of the incoming charge. A late opening 
 of the intake valve (from 10 to 20° past center) is recom- 
 mended to secure better action of the carbureter. 
 
 Relative Efficiency of Power Gases. Apart from the 
 calorific values of one cubic foot of the various powergases 
 when burnt in sufficient air to support complete combus- 
 tion, it is necessary to differentiate them in terms of calor- 
 ific value per cubic foot of gas and air mixture when only 
 just sufficient air is present. For gas engines, however, 
 it is necessary to dilute the gas still further in order to 
 control ignition as, varying with the percentage of hy* 
 drogen present, theoretical mixtures are impossible, owing 
 to risks of pre-ignition and violent shocks caused by the 
 rapidity of the propagation of flame. Experience has 
 determined that while hydrogen is of the greatest value in 
 obtaining good results, yet it is important that its volume 
 should be only about 7 per cent in gas engine mixtures. 
 
 Gas Engine Indicator. — The principles governing the 
 action of the gas engine indicator are precisely similar 
 to those of the steam engine indicator which has 
 already been described in the section on steam engines. 
 The only difference between the two instruments lies in 
 the details of construction, the gas engine indicator being 
 
Gas Engine Indicator 
 
 737 
 
 more strongly made in order to withstand the sudden shock, 
 and higher pressure of that engine, as compared with the 
 steam engine. Firms manufacturing indicators make a 
 combined steam and gas engine indicator, the piston used 
 for indicating gas engines being one half the area of the 
 piston used for steam engines, and as the same springs may 
 be. used with either piston, the scale is doubled when the 
 
 Fig. 306 
 
 smaller piston is used. Fig. 306 shows a Crosby combined 
 gas, and steam engine indicator with the small piston in 
 place for gas engine work. The pencil arm is of extra 
 strength to withstand the shock due to the explosive press- 
 ure exerted upon the piston. The drum is of small dia- 
 meter and extremely light to reduce the effect of inertia to 
 a minimum. 
 
738 
 
 Steam Engineering 
 
 The tension of the drum spring may be readily changed 
 in accordance with the speed of the engine upon which the 
 indicator is to be used. The initial vertical position of the 
 pencil point with respect to the drum may be raised or 
 
 Fig. 306a 
 
 lowered on the paper according to the size of the diagram 
 to be taken. 
 
 Fig. 306 A shows the new Crosby indicator designed for 
 taking continuous diagrams. The drum is designed to use 
 
Gas Engine Indicator 
 
 739 
 
 a roll of paper 2 inches wide and 12 feet long, upon which 
 is made in the operation of the indicator a series of dia- 
 grams. In the center of and concentric with the drum is 
 a cylinder upon which the paper is wound as it is used. 
 When the roll is exhausted, the cylinder can be withdrawn 
 through an opening in the top of the drum and the paper 
 easily detached. Above the cylinder is a knurled head 
 
 Fig. 306b 
 
 loosely attached to the drum spindle which can be adjusted 
 to take continuous diagrams, varying in number from 6 to 
 100 per feet of paper. 
 
 Fig. 306b shows the Crosby reducing wheel with Detent — 
 This detent when applied to the reducing wheel does not 
 affect the connection between it and the engine; and does 
 not allow the cord leading from the indicator drum to the 
 

 740 
 
 Steam Engineering 
 
 Fig. 307 
 
 tabor indicator with outside spring 
 
 Combined Steam and Gas Engine Type 
 
 *i 
 
Gas Engine Indicator 
 
 741 
 
 reducing wheel to slacken. When the clutch is thrown in, 
 the indicator drum is revolved to the end of the stroke and 
 held there by the drumcord, while the mechanism of the 
 detent controls the cord leading from the reducing wheel 
 to the cross-head of the engine. 
 
 When the clutch is released, and the motion of the engine 
 is again communicated to the drum, the latter takes up the 
 
 Fig. 308 
 
 motion without shock from the point where it stopped, 
 because it starts from a state of rest at the end of the stroke. 
 This is important, for if a drum is stopped and held by a 
 detent in mid-stroke, where the piston is running at its 
 highest speed, at the release of the detent, the drum will 
 necessarily start again at such highest speed with a shock. 
 Moreover, as such a detent must engage at the highest 
 speed, it often fails to operate and always wears rapidly. 
 
742 Steam Engineering 
 
 Fig. 307 is the Tabor combined steam and gas engine 
 indicator, and is supplied with two sizes of pistons as in the 
 case of the indicator just mentioned. The spring is placed 
 outside of the indicator cylinder in order that the hot gases 
 from the engine will not affect the temper of the spring, 
 and thereby change the scale. 
 
 Fig 308 shows the piston, piston rod, cap and spring, 
 removed from the indicator for cleaning. 
 
 Fig 309 shows the parallel motion, or straight line mo- 
 tion of the Tabor indicator. The curved cam slot provides 
 
 Fig. 309 
 
 for a perfectly true vertical motion of the pencil, and fur- 
 ther provides rigidity and tends to reduce vibration. 
 
 This indicator is made with the regular i/o-inch area 
 piston and cylinder for steam, and is furnished with a 
 secondary and longer piston of 14-inch area which operates 
 in the upper portion of the cock tube, to give the necessary 
 increase in range to the spring, for extremely high pres- 
 sures. This style indicator can be made with either size 
 standard drum. 
 
 All indicators of this type, employing a pressure piston 
 and spring, require careful calibration where extreme 
 accuracy is essential. On account of the inertia of the 
 
Gas Engine Indicator 
 
 743 
 
 piston and pencil mechanism, and that of the oscillating 
 drum, engines of very high speed cannot he indicated by 
 the forms of indicator just described. They have been 
 found to be reasonably accurate at speeds as high as 500 
 revolutions per minute, although at this speed they can be 
 used successfully only by experienced hands. 
 
 Indicators for High Speed. — To overcome this objection 
 and to be able to indicate engines of speeds as high as 2,000 
 revolutions per minute or more, indicators employing a 
 beam of light thrown upon a sensitive photographic plate 
 
 ACETYLENE 
 BURNER 
 •^Pl^. TUBE 
 
 CAAPtNTIlK 
 
 GROUND 
 
 CI ASS 
 
 ^SCAECN 
 
 r^ 
 
 -TOP OF TRIPOD STAND 
 
 Fig. 310 
 
 are now used. In this case a small mirror is caused to 
 move in two planes at right angles to each other, one move- 
 ment being produced by the motion of the piston, the other 
 by the pressure, which is transmitted through a thin steel 
 diaphragm. The angular motion of the mirror is so small, 
 and the parts so light that the effect of inertia becomes 
 practically negligible. 
 
 Fig. 310 shows the general appearance, and Fig. 311 two 
 sections of one type of the indicator referred to. This in- 
 strument is called the Hospitalier-Carpenter Manograph 
 and is manufactured in Paris. 
 
744 
 
 Steam Engineering 
 
 Some makers manufacture special heavy indicators with 
 14-inch pistons to suit the pressures involved in gas engine 
 indication. Springs from 80 pounds to 200 pounds scale 
 are very efficient in recording expansion, combustion and 
 compression lines, as these effects are all high pressure. 
 If the low pressure lines, such as the suction and exhaust, 
 do not show up to advantage when taken with high scale 
 springs, low scale springs of from 10 lbs. to 30 lbs. may be 
 used for obtaining those lines. 
 
 ftEPermoft ftccxANiSM 
 
 m^mmz^^uX 
 
 END VIEW SECTION 
 
 TOP VIEW SECTION 
 
 Fig. 311 
 high speed engine indicator 
 
 Diagrams from Gas Engines. — The process of obtaining 
 indicator diagrams from gas engines being similar to steam 
 engine practice, it is not necessary to repeat a description 
 of it. Attention will therefore be devoted to several 
 reproductions of typical diagrams from gas engine. Fig. 
 312 shows a characteristic diagram from a four cycle engine. 
 On the forward stroke of the engine the piston draws into 
 the cylinder a charge of explosive mixture, the pencil of the 
 indicator tracing the line A-B. It will be seen that this 
 line drops slightly below the atmospheric line A-F. This 
 
Gas Engine Indicator 
 
 745 
 
 slight drop is due to the partial vacuum produced within 
 the cylinder during the "suction stroke" of the engine. 
 From point B, the piston returns to its original position 
 compressing the mixture in the clearance space, the indi- 
 cator tracing the line B-C, which is known as the compres- 
 sion curve. At this point ignition takes place with a sud- 
 den increase in pressure, the indicator tracing the line 
 C-D, which is nearly vertical. On the next or third stroke, 
 the gases are expanded to point E, at which time the exhaust 
 
 *- 
 
 Fig. 312 
 
 valve opens, the indicator having traced the line D-E, which 
 is known as the expansion curve. At E there is a drop in 
 pressure as the gases issue from the exhaust port and from 
 F to A the gases are swept from the cylinder which causes 
 a line to be drawn by the indicator slightly above the atmos- 
 pheric line A-F, as shown. This completes the cycle. The 
 vertical distance from the atmospheric line to point C is 
 proportioned to the compression pressure above atmosphere ; 
 the distance to point D is proportional to the explosion or 
 maximum pressure, and the distance to point E is pro- 
 portional to the release pressure. 
 
 . A 
 
746 
 
 Steam Engineering 
 
 Figure 313 shows a card from a two-port two-cycle gas 
 engine. It will be noticed that the suction and exhaust 
 lines are absent, the suction stroke being completed in an 
 enclosed crank case, or a separate cylinder or pump. The 
 exhaust takes place at A and requires about one-tenth of 
 
 ^LTspoa 
 
 Fig. 313 
 
 the stroke. The exhaust and inlet ports are covered, and 
 uncovered by the piston and are definitely fixed points. 
 
 Figure 314 shows a very good diagram, where combus- 
 tion is very nearly complete, the mixture of air and gas 
 being practically correct. The ignition line points slightly 
 
 Fig. 314 
 
 to the right at the top, and is nearly perpendicular. The 
 exhaust is shown to open at the right time about ninety 
 degrees of the stroke. The suction and exhaust lines run 
 very near the atmospheric line, thereby denoting correctly 
 proportioned inlet, and exhaust valves and passages for 
 same. 
 
Gas Engine Indicator 
 
 747 
 
 Figure 315 shows a condition existing when the suction 
 to the cylinder is in some way choked, the suction line of 
 the card or diagram being away below the atmospheric line. 
 This condition may be caused by the valve being too small, 
 improper setting of the valve, too small an area of the suc- 
 
 Fig. 315 
 
 tion pipe, which may be caused in some cases by too many 
 bends or short elbows. 
 
 In figure 316, the exhaust line is shown at too great a 
 height above the atmospheric line, thus showing that the 
 discharge of exhaust gases is choked. In theory, there 
 
 A2&93 
 
 Fig. 316 
 
 should be no back pressure, during the exhaust stroke, but 
 in actual practice a pressure is recorded, varying in differ- 
 ent makes of engines. 
 
 Back pressure as shown in the diagram figure 316 may 
 result from the following conditions: The exhaust valve 
 
748 Steam Engineering 
 
 being too small in area, setting of valve incorrect, too long 
 an exhaust pipe, too many bends or too small a diameter 
 of same. 
 
 If the compression curve B C, Fig. 312, shows a lack of 
 sufficient compression pressure and all other conditions 
 are perfect, this is probably due to leaky piston rings, 
 valves, or joints. 
 
 Figure 317 shows a low spring card and gives the differ- 
 ent lines. The suction line is shown starting at C, the 
 point where the exhaust line strikes the atmospheric line, 
 and extending to the point 'A where the compression line 
 commences. 
 
 Fig. 317 
 
 The mean effective pressure of gas engine diagrams is 
 found by precisely the same method as that pursued with 
 diagrams from steam engines. 
 
 Indicated Horse Power. — This is a computation based 
 upon the mean effective pressure developed at each ex- 
 plosion and is usually calculated from the same formula 
 used in connection with steam engines: 1. H. P.= 
 
 PLAN 
 
 where P=mean effective pressure ; L=length 
 
 33,000 
 
 of stroke (ft.); A=area of cylinder; N=number of ex- 
 plosions per minute. This formula does not discriminate 
 between mechanical friction and losses in "fluid" friction. 
 
Gas Engine Indicator 749 
 
 To get acurate results it is necessary to obtain the mean 
 effective pressure after measuring the indicator diagrams 
 recorded during both "power" and "cut-out" cycles as also 
 "compression" and "suction" cards. 
 
 It requires a considerable knowledge of gas engine prac- 
 tice to make use of the above formula. What is needed 
 is one that is more arbitrary and fits the majority of cases 
 and, moreover, requires the use of only a few facts, such 
 as the diameter of cylinder, length of stroke and revolu- 
 tions per minute. Such a formula will be of great value 
 in estimating the probable power a gas engine should de- 
 velop if well designed and properly built. 
 
 Such a formula is given as follows : 
 
 VXr. p m. 
 I. H. P.= 
 
 10,000 
 
 which means that the indicated horse power is equal to 
 the volume of the cylinder in cubic inches multiplied by 
 the number of revolutions per minute and divided by 
 10,000. The constant used varies from 9,000 to 14,000, 
 depending upon certain types of engines; 10,000 is an 
 average figure to use for four cycle engines. The brake 
 horse power will be from 65 to 85 per cent of the result 
 obtained ; 80 per cent may be taken as an average : 
 For example, a 6 1 / 4 ,/ x9" engine at 300 r. p. m. gave by 
 test 7.2 horse power. 
 
 The area of the piston is 33.2 square inches and the 
 volume of the cylinder is 298.8 cubic inches; multiplying 
 by 300 and dividing by 10,000 gives 9.0 indicated horse 
 power, or for a mechanical efficiency of 80 per cent 7.2 
 brake horse power. 
 
 Economy of Gas Engines. — As fuel is ordinarily used, 
 at present, for light, heat and power, the losses are so 
 
750 Steam Engineering 
 
 great that, of the total calorific value of the coal, less than 
 5 per cent on an average is converted into useful work, 
 while the largest and best power stations utilize only about 
 10 per cent. 
 
 With gas-engine-driven units, however, fuel economy is 
 the distinguishing characteristic, resulting in a delivery 
 at the engine shaft of not less than 16 to 20 per cent of 
 the energy contained in the fuel. 
 
 Notably is this true of lignite coal, immense quantities 
 of which are to be found in various parts of the country. 
 The calorific value of such coal averages only about 8,000 
 B. T. U. per pound as fired; but, when utilized in a gas 
 producer and gas engine, it is possible to develop a brake 
 horse power on less than 2 pounds of lignite. 
 
 Owing to the difficulty of securing, with this fuel, proper 
 combustion under a steam boiler, the gas producer offers 
 practically the only means of using it on a commercial 
 basis. 
 
 The same is true of slack coal, bone coal, etc. 
 
 A recent bulletin of the United States Geological sur- 
 vey calls attenion to the possibilities, of the producer gas 
 plant, as above indicated, and states that lignite beds 
 underlying from 20,000,000 to 30,000,000 acres of public 
 land, heretofore supposed to be practically useless, are 
 now shown to have a large value for power development. 
 This is of particular importance to the West, making pos- 
 sible a great industrial development there. 
 
 Producers now made will also successfully gasify nearly 
 all grades of bituminous coal, as well as anthracite, or coke. 
 
 Additional Advantages of Gas Engines. — The standby 
 losses during a period of idleness are practically negligible, 
 
Producer Gas 751 
 
 and are included in the fuel estimate per .brake horse power 
 as given above, leakage losses are reduced and the smoke 
 nuisance is abolished. 
 
 In localities where the water supply is scarce, or of poor 
 quality, a gas power plant offers additional advantages, 
 and, by the use of cooling towers, the water consumption 
 can be reduced to a very small quantity. 
 
 PRODUCER GAS. 
 
 Producer gas, whether from anthracite or bituminous 
 coal, lignite, wood, charcoal, or coke, is remarkably uni- 
 form in quality, and a very desirable gas if properly cleansed 
 from dust, tar and sulphur. As practically all the combus- 
 tible matter of coke and charcoal is fixed carbon, these 
 fuels are most readily gasified, and on this account are 
 favorite fuels for small gas plants of the suction producer 
 type. Anthracite coal contains a small quantity of vola- 
 tile matter, but is also a very desirable fuel, the gas requir- 
 ing but little cleaning. Bituminous coal, lignite and wood, 
 although giving a desirable power gas, at the same time 
 yield considerable amounts of hydro-carbon vapors con- 
 densible in the form of tar and pitch, the removal of 
 which from the gas is attended with some difficulty. 
 
 Complete producer gas plant equipments may be had of 
 several types, suited either to bituminous or non-bituminous 
 fuels, and with, or without apparatus for the reclamation 
 of by-products, such as ammonia, tar and other hydro- 
 carbons. The majority of these systems are simple in con- 
 struction and operation, and yield a net efficiency consid- 
 erably in excess of the steam boiler plant. 
 
 In localities where natural gas is not available, the pro- 
 ducer gas plant affords a comparatively simple, and inex- 
 
752 
 
 Steam Engineering 
 
 pensive means of generating a suitable fuel gas. It is less 
 complicated in its workings than the average steam plant, 
 and its efficiency is higher, as will be seen by reference to 
 
 Poroont cf Uoat in Coal 
 
 Fig. 318 
 comparative efficiency of gas and steam plant 
 
 Fig. 318, which compares the net work obtainable from 
 coal in modern .well-equipped steam and gas plants of 
 moderate size. The producer transmits 75 per cent of the 
 
Producer Gas 753 
 
 fuel energy, the boiler 70 per cent; the gas engine delivers 
 at the shaft 25 per cent of the energy supplied, the steam 
 engine 13 per cent; as a whole the gas plant realizes over 
 17 per cent of the fuel energy, the steam plant about 8 per 
 cent. On this basis the gas plant could afford to use fuel 
 costing twice as much as steam fuel; as a matter of fact 
 it can utilize fuel much cheaper and of such low grade as 
 to be quite unsuited for efficient boiler working. 
 
 The gas producer takes the coal, ignites it, and by sup- 
 plying a limited amount of air, and a proportionate amount 
 of water keeps the fire at a dull red glow, just the right 
 temperature to produce a good uniform quality of gas and 
 prevent formation of clinkers. As the load on the engine 
 is varied a greater or lesser quantity of gas is required but 
 it is important that the quality or heat power remain the 
 same. 
 
 At present three distinct types of gas producer are offered 
 to the power user. They are the suction producer, the 
 steam-pressure producer, and the induced down-draft 
 producer. 
 
 The Suction Producer. — In this type the fuel is fed into 
 the generator from a hopper at the top. Ashes and clinkers 
 are removed from the bottom, and air is usually admitted 
 below the grate, first passing through economizers, where 
 it is heated and passed over a body of hot water to absorb 
 the necessary moisture. In some makes of producer the 
 air is admitted direct from the engine room, and a small, 
 regulated amount of water is fed into a space prepared 
 around the grate, where it is evaporated and is carried as 
 steam along with the air up into the fuel bed. 
 
 In this type of producer, coke or anthracite coal can 
 only be used and not even these fuels in the very small 
 
754 Steam Engineering 
 
 sizes. It is not easy to note the condition of the fire, as the 
 generator cannot be opened at the top without admitting 
 air and causing a poor mixture of gas ; the only thing to do 
 in this emergency is to feed in more coal to stop the chim- 
 ney holes in the fire-bed, or quickly insert a poker bar and 
 thoroughly tamp the fuel. The latter is the better way, 
 even though it has to be done blindly. 
 
 In operating this type of producer, trials and tribula- 
 tions may be many and varied, depending largely upon how 
 the producer is made and the basis of its horse power rat- 
 ing. A suction gas producer rated at more than 12!/2 
 pounds of coal per square foot of grate area, or area of fuel- 
 bed cross-section, is very apt to be too small, and a pro- 
 ducer so small for the power it has to develop that it must 
 be driven to furnish sufficient gas will immediately develop 
 clinker troubles, variable gas troubles or excess C0 2 . If 
 an attempt is made to correct clinker troubles with an over- 
 supply of steam, an excess of hydrogen will result, with its 
 attendant engine difficulties of back-firing, or premature 
 explosions. 
 
 Even with a producer of the proper size, the regulation 
 of the volume of steam or water to the volume of air must 
 be closely watched. Too frequent raking of the fire will 
 waste good fuel, and induce draft holes through the fuel 
 bed. Too much poking from the top will pack the fire, 
 and necessitate an increased vacuum. Too fine a fuel will 
 produce the same troubles, and any coal that fuses easily 
 will not do for this type of producer. Anthracite running 
 high in slate mixture tends to run high in sulphur, and 
 high sulphur with slate makes bad clinkers at any time, 
 and if the fire is forced at all will soon necessitate a shut- 
 down to clean out. The producer should be of ample size 
 
 ^ 
 
The Gas Producer 
 
 755 
 
 Fig. 319 
 monahan suction producer 
 
 — 10 pounds of coal per square foot of internal area- 
 rated on l 1 /^ pounds of coal per horse power hour. 
 
 -and 
 
756 
 
 Steam Engineering 
 
 It is not good practice to use a suction gas-producer 
 plant of over 150 horse power when the engine has to' 
 draw the gas from the producer by the vacuum in the 1 
 cylinder. Sizes larger than this should be equipped with 
 exhaust fans which will relieve the engine of this work, the 
 
 Fig. 320 
 sectional view of monahan producer 
 
 exhausters being driven by motors, or other auxiliary 
 power. 
 
 The Monahan Suction Producer. — This producer, a full 
 view of which is shown in Fig. 319, is of the suction type, 
 and consists of the usual generator, scrubber, and equalizing 
 tank. The vaporizer for supplying steam to the fuel bed 
 
The Gas Producer 
 
 757 
 
 is an upper extension of the generator, but is located so 
 that the hot gases from the fuel bed do not impinge square- 
 ly on the bottom of the vaporizer. This is clearly shown in 
 the sectional view, Fig. 320, in which the revolving grate, 
 and air heater are also shown. The scrubber is of the wet, 
 coke-filled type, and the equalizing tank is a simple drum 
 
 Fig. 321 
 
 STEAM KEGULATOB 
 
 within an equalizing chamber formed in its cover, and 
 separated from the drum by a rubber diaphragm. 
 
 A small vent in the cover allows air to pass in or out 
 slowly, forming a sort of brake on the fluctuations of pres- 
 sure within the drum. The regulator controlling the ad- 
 mission of steam to the fuel bed is shown in section in 
 Fig. 321. The outlet at the bottom is connected to the 
 ash pit of the generator. The upper intake admits air 
 
758 
 
 Steam Engineering 
 
 only, and the intake near the middle admits steam. When 
 running light the suction is insufficient to pull down the 
 valve, and air alone passes through the fire. As the load 
 
 Fig. 322 
 smith automatic suction gas producer 
 
 increases, the increasing suction gradually pulls down the 
 valve (which is a piston valve) until the steam ports are 
 uncovered to an extent depending upon the load. This 
 
The Gas Producer 759 
 
 arrangement prevents the chilling of the fire with steam at 
 very light loads, and graduates the supply for heavier 
 loads. 
 
 Smith Suction Producer. — Pig. 322 shows a view of the 
 Smith Automatic Suction gas producer, built by the Smith 
 Gas Power Co., Lexington, Ohio — Fig. 323 is a sectional 
 view of the regulator, which is also shown in perspective 
 in Fig. 324 mounted upon the superheater with which this 
 producer is equipped. The hot exhaust from the gas engine 
 is piped into this superheater which heats the incoming air 
 for the producer and turns the proportionate amount of 
 
 Water FfgQ 
 
 Fig. 323 
 
 water required into steam. The regulator consists of a 
 curved iron tube E through which the air is drawn into the 
 superheater, then on and through the fire bed in the pro- 
 ducer. Vane V, Fig. 323, is located in the curved tube 
 and is connected to water cylinder G which is mounted on 
 knife edge bearings so it will rotate freely. The vane V 
 and the connecting arm H are accurately balanced by the 
 adjustable weight K. Weight L serves to counteract the 
 pressure of the air which passes with more or less force 
 (according to the needs of the engine) through curved 
 tube E. The water cylinder G is supplied with a needle 
 
760 
 
 Steam Engineering 
 
 valve feed at N" and an overflow next to its axis. The feed 
 water from needle valve N runs directly into the air 
 passage E. 
 
 It will be readily seen that when more air is passing 
 through the curved tube E the vane V will be drawn down 
 rotating water cylinder G. As the water keeps its level 
 there will be more head water above the needle valve feed 
 
 Fig. 324 
 N, causing an increase in the water feed in proportion to 
 the increase of air. When the load on the engine runs 
 light, and less air is drawn through tube E, there is less 
 pressure on vane V, and the weight L rotates water cylinder 
 G in the opposite direction, decreasing the head of water 
 on needle valve N". The proportion of water and air under 
 all the varying conditions is thus automatically held uni- 
 
The Gas Producer 761 
 
 form. As the flow of the column of air passing through the 
 curved tube E, and past vane V is practically constant there 
 are no sudden fluctuations of the vane and water cylinder 
 but a smooth gradual adjustment to meet the any changing 
 conditions. 
 
 This machine is arranged to operate either up draft 
 or down draft as may be required, and can be utilized on 
 anthracite, semi-anthracite, coke, charcoal, lignite, wood or 
 bituminous coal, as conditions may require. The machine 
 is a straight suction producer and is complete in all par- 
 ticulars as shown in Fig. 322. The gas pipe at the upper 
 left hand corner passes directly to the engine. 
 
 The Steam-Pressure Producer. — This type has an upward 
 draft, the air being drawn in around a steam jet through a 
 Korting nozzle of the Bunsen type. Anthracite and coke 
 are the only kinds of fuel available, unless tar extractors, 
 and other expensive mechanical auxiliaries are provided to 
 clean the gas. When the producer is equipped with such 
 cleaning apparatus, bituminous coals or fuels containing 
 volatile hydrocarbons may be used, but as these are con- 
 densed and washed out of the gas, the thermal efficiency of 
 the producer is reduced to the extent of the loss of the heat 
 units contained in the extracted hydrocarbons, which are 
 the richest part of the fuel. 
 
 With a pressure producer it is necessary to have gas- 
 storage capacity, so that gas-holders must be provided 
 regardless of the kind of fuel used, and these must hold 
 enough gas to run the engine while the fire is being poked, 
 and the ashes removed. Coal is fed through a tightly clos- 
 ing hopper on top of the generator, and ashes are removed 
 from the bottom when the generator is not in operation. It 
 is almost impossible to poke, or bar the fire while the pro- 
 
762 Steam Engineering 
 
 ducer is running, as any outlet for this purpose will be 
 flooded with burning gas escaping under whatever pressure 
 the steam jet is maintaining at the time. 
 
 Induced Down-Draft Producer. — In the down-draft pro- 
 ducer the gas is drawn down through the fire by an ex- 
 hauster or fan, and forced by the exhauster through the 
 main to the point of use. There is probably more horse- 
 power of these producers in use than in all of the others 
 put together, but they are mostly of large size and the 
 plants only number about one-fourth of the total. 
 
 Essentially these are bituminous-coal producers. They 
 are operated with an open top, where the fire is seen by 
 the operator, and any blow-holes or passages in the fire 
 are easily closed by the use of the poker or tamping bar, 
 and fresh fuel is fed as necessary. The volatile hydro- 
 carbons of the fuel, being distilled at the top of the fuel 
 bed, mix with the in-drawn air and steam, and pass down 
 through the bed of incandescent carbon, where they com- 
 bine with the other gases and leave at the bottom of the 
 producer, as a fixed non-condensable gas. This combina- 
 tion of gases then passes directly into the bottom of a 
 vertical tubular boiler and out at the top, thence into the 
 bottom of the wet scrubber, where the outlet is under water 
 to form a seal and prevent the gas from returning to the 
 producer. From the top of the wet scrubber the gas passes 
 to the exhauster, and is forced through the dry scrubber to 
 the gas-holder. 
 
 The boiler, which is a part of the producer installation, 
 supplies a large part of the steam necessary for the pro- 
 ducer, and also the amount necessary to run the engine 
 driving the exhauster. This steam is made from the heat 
 given up by the gas in its passage through the boiler, and 
 
The Gas Producer 763 
 
 all heat that is not absorbed by the water is delivered up 
 to the wet scrubber. Once a week these producers have to 
 be entirely cooled down to be cleaned, and as the steam 
 pressure in the boiler is down at this time, an auxiliary 
 boiler has to be provided to start up again. Some time 
 during the week, especially toward the last days, the fuel 
 beds become so clogged with the accumulation of ashes and 
 clinkers, that water-gas runs have to be made every few 
 moments; the load on the engine driving the exhauster 
 increases, and both these conditions so increase the demand 
 for steam that the auxiliary boiler has to be brought into 
 use. 
 
 For continuous 24-hour service with this type of producer 
 it is necessary to have a spare unit, in order that it can 
 take the place of the one that has been in service for a week. 
 A single spare unit in an installation of a large number of 
 units does not add a very large percentage to the original 
 investment, but a spare unit to a single outfit nearly doubles 
 the cost. The following timely suggestions regarding gas 
 engine practice are presented by the Gas Power Section of 
 the A. S. M. E. : 
 
 "Engine Efficiency. Should be expressed in terms of 
 effective heat value, until a combined gas-vapor cycle comes 
 into use. For the present, let us not confound a definite 
 engine efficiency by introducing the indefinite factor of 
 latent heat of water vapor. Engine efficiencies should be 
 given for full, to half load at least: 
 
 "Producer Capacity. The producer should be rated upon 
 its ability to gasify coal. It would be more accurate to 
 rate on B. t, u. of standard gas, but this is impracticable. 
 Should the builder desire to rate on a special coal, he might 
 insert a clause limiting some of the constituents. In speci- 
 
764 Steam Engineering 
 
 fying sizes, a maximum as well as a minimum screen should 
 be mentioned. A mixture of many sizes packs the producer 
 as badly as a very small fuel. As a usual thing the flexi- 
 bility of the producer will more than meet the overload 
 possibilities of the engine. 
 
 "Producer Efficiency. Can only be specified in terms 
 of B. t. u. output, involving volumetric measurement, which 
 it is usually impossible to determine except by calibration 
 of the engine. As we are dependent upon the engine as a 
 gas meter, we must be consistent, and determine the effi- 
 ciency of the producer in like terms, that is, the ratio 
 between heat output in standard gas, and heat input in 
 fuel for the fire. 
 
 "Producer Regulation. An important point is the prop- 
 erty of the producer as regards the regulation of heat value 
 of the gas, and its pressure as delivered to the engine. Qual- 
 ity regulation is covered by the engine-capacity clause 
 'with gas of not less than so many B. t. u. heat value per 
 cubic foot/ 
 
 "Hydrogen Content. This may be expressed as a per- 
 centage by volume of the gas, a percentage by volume of 
 combustible in the gas, a percentage of the heat value of 
 the gas per mixture, or a percentage by volume of the mix- 
 ture. The last appears to be the most explanatory. The 
 first conveys no impression of the commercial value of the 
 gas. The second is better in this respect. The third pre- 
 sents widely varying values." 
 
 ALLIS-CHALMERS GAS EXGIXE. 
 
 Figure 325 presents a view of a four cycle, double acting 
 tandem gas engine as built by Allis-Chalmers Companay, of 
 Milwaukee, Wis. This engine is using natural gas. Fig. 
 
Allis-Chalmers Gas Engine 765 
 
 326 shows a four cycle double acting twin-tandem gas 
 engine by the same company. 
 
 The distinctive features of the gas engines built by Allis- 
 Chalmers Co., or those which appeal most strongly to engi- 
 neers who have seen them in service, are the extreme sim- 
 plicity of design, the solidity of construction, and the quiet 
 operation. Maximum overloads are handled as easily, and 
 
 Fig. 325 
 
 allis-chalmers four-cycle, double-acting, tandem gas engine 
 
 direct-connected to an allis-chalmers continuous 
 
 current generator — natural gas used 
 
 with the same freedom from vibration that characterize 
 their operation under normal conditions; the engines turn 
 their centers as quietly as a slow-running Corliss machine 
 and with apparent indifference to the rapid changes in load 
 which they are often called upon to sustain. 
 
766 Steam Engineering 
 
 While the engines are, as a whole, exceptionally rigid and 
 heavy, the weight is concentrated in the frame, cylinders, 
 and tie pieces in the direct line of stresses to which an 
 engine of this type is subjected. In the frame is illustrated 
 the principal difference between European and American 
 design. This frame is designed for a side crank, in place 
 of the double throw crank which represents the standard 
 practice abroad. The stresses transmitted to the frame in a 
 side crank engine are very great, but, even in the largest 
 sized gas engines, they are no greater than Allis-Chalmers 
 Company has for many years successfully provided for in 
 steam engine practice. 
 
 The jaw, which is subjected to peculiarly severe stress, 
 is made in a form to insure maximum strength of the cast- 
 ing, and is further strengthened by two steel tie bolts car- 
 ried above the shaft, which are made of sufficient size to 
 carry their proportion of the load without appreciable 
 elongation. This construction eliminates entirely any bend- 
 ing stresses in the frame at this point. 
 
 The engine frames for the 2,500 K. W. units weigh 
 approximately 90 tons each, and one-half of each frame is 
 buried in the foundation, in order to raise the floor line 
 to a point which will make the slides on the valve gear 
 readily accessible. 
 
 The pistons and rods are water-cooled, water being in- 
 troduced at the center and flowing forward to a discharge 
 in the frame for the front piston, and backward to a dis- 
 charge in the tail guide for the rear piston, each piston 
 having its separate supply. For dismantling or for cleans- 
 ing, the rod is made in two parts joined at the central slide, 
 the rear half going out at the back of the engine and the 
 other half going through the frame, which is made open 
 at the top for convenience. 
 
ALLIS-CHALMERS, FOUR-CYCLE, DOUBLE-ACTING TWIN-TANDEM GAS 
 ENGINES, EACH OF 2,000 H. P. CAPACITY 
 
 Driving Allis-Chalmers Alternating Current Generators in the 
 Power House of the Milwaukee-Northern Railway, Port Wash- 
 ington, Wis, 
 
768 Steam Engineering 
 
 The Valve Gear. — On twin tandems the valve gear is 
 located between the engines, concentrating it in such a way 
 as to make it very convenient for the operating engineer. 
 
 This gear is of Allis-Chalmers Co/s stratification type, 
 and the engine operates with constant compression, thus 
 tending to insure smooth running under the highly varia- 
 ble loads to which it is subjected. The inlet gear is ex- 
 tremely simple, consisting of a main inlet valve of the 
 single beat poppet type, eccentric operated, thus insuring 
 long life and quiet running. The mixture of the air and 
 gas is thoroughly effected before entering the cylinder by 
 means of a patented annular mixing chamber located under 
 the main inlet bonnet; the design and operation of this 
 device is such that, at the instant of closing of the main 
 inlet valve, there is practically no explosive mixture left 
 outside the cylinder. The gas valve is of the double beat 
 poppet type, controlled by a variable lift rolling lever 
 operated by a single link connection to the main inlet, the 
 lift -of the valve and consequently the amount of gas ad- 
 mitted, and the time of admission being regulated by the 
 governors. The exhaust gear is of the single beat poppet 
 valve type, eccentric operated, and is in this respect a 
 duplicate of the main inlet gear. A feature of this engine 
 is the location of the exhaust bonnet with its valve at the 
 bottom of the cylinder, where all the dirt is removed by the 
 action of the exhaust gases, and the provision of a substan- 
 tial jack to lower the entire exhaust mechanism out of 
 place to allow inspection and regrinding of the valve, which 
 also serves to swing the valve chamber, with the valve and 
 its operating mechanism complete, out to one side where it 
 can be reached by the crane hoist. The removal of one pin, 
 either in the inlet, or exhaust mechanism, is all that is 
 
Allis-Chalmers Gas Engine 769 
 
 necessary to allow the removal of either the inlet or exhaust 
 bonnets, with their valves and entire operating apparatus, 
 without disturbing any adjustment whatever. 
 
 The igniters are electrically controlled, and so arranged 
 that the time of ignition may be regulated by a single hand 
 wheel. Direct current at 80 volts is used in the ignition 
 system. Duplicate independent igniters are provided at 
 each end of the cylinder to insure prompt firing of low 
 heat value gases, and also to avoid the danger of shut down 
 due to short circuit. 
 
 The air starting device consists of a small poppet inlet 
 air valve at each end of each cylinder, operated by the 
 layshaft. Air is admitted to each cylinder in turn at what 
 would be the working stroke. As the high compression 
 carried prevents the engine from stopping on the dead 
 center, this arrangement insures the prompt starting of 
 even a tandem engine without the use of a barring gear. 
 These engines being twin tandem will, of course, start from 
 any position. 
 
 Lubrication. — All wearing surfaces, including the main 
 bearings, slides, crank and cross-head pins, are arranged for 
 a continuous oiling system and the cylinders are lubricated 
 by carefully timed admission of the cylinder oil, sight-feed 
 oil pumps being used. 
 
 The engines shown in Fig. 326 are of the following 
 dimensions: Each engine has four cylinders 32 inches in 
 diameter by 42 inches stroke, and operates at 107 revolu- 
 tions per minute. Each unit is rated at 1,000 K. W. but 
 both engines and generators were designed for large over- 
 load capacities. 
 
 The engines shown in Fig. 302 are said to have the larg- 
 est cylinder diameter of any gas engine yet built in the 
 
770 
 
 Steam Engineering 
 
 United States, the dimentions being M inches diameter by 
 54 inches stroke. 
 
 WESTINGHOUSE GAS EXGINE. 
 
 Figs. 327 arid 328 show respectively front and rear views 
 of the Westinghouse gas engine of the vertical type. These 
 
 Fig. 327 
 
 westinghouse three-cylinder vertical gas engine 
 
 Front View — Direct Connected Type 
 
 builders also manufacture a horizontal heavy, duty double 
 acting type of gas engine of large capacity. 
 
 Fig. 329 is a vertical section through one of the West- 
 inghouse cylinders, showing the gas and air distribution, 
 water jacket, and also shows the valve gear. The inlet and 
 exhaust valves are located at opposite ends of the vertical 
 cylinder diameter, as shown in Fig. 329. Both valves, at 
 
Westinghouse Gas Engine 
 
 771 
 
 each end of a cylinder, are operated by a single eccentric 
 through wipers and rocker-arms; this construction is also 
 shown in Fig. 329. The exhaust valve is of the mushroom 
 type, hollow, with a tube extending up the stem into the 
 center of the head for discharging the cooling water; the 
 water is introduced through the annular passage between 
 
 Fig. 328 
 
 westinghouse three-cylinder vertical gas engine 
 
 Rear View — Belted Type 
 
 the outlet tube and the wall of the valve-stem. The valve 
 cage sets into a circular housing projecting downward from 
 the cylinder. 
 
 The main inlet valve is of the simple disk type, and is 
 opened and released by the eccentric and wiper levers 
 always at the same points of the piston travel. There is 
 mounted on the valve-stem, however, a cylindrical valve 
 
772 
 
 Steam Engineering 
 
 Jig. 329 
 valve gear, westinghouse gas engine 
 
Westinghouse Gas Engine 773 
 
 which controls the quantity of air and gas admitted, this 
 being under the control of the governor. It is not shown 
 in Fig. 329, but the connection for the governor rod is 
 shown. The cylindrical valve fits closely in the bore of the 
 valve cage, and has ports in its wall which correspond to 
 the ports leading into the cage from the air and gas pass- 
 ages. When the admission valve is on its seat, the ports 
 in the cylindrical valve are above those in the cage wall, 
 and the latter are therefore closed, preventing gas from 
 backing up into the air passage. When the inlet valve is 
 depressed by the valve-gear, the cylindrical valve goes with 
 it, and its ports then come into horizontal alignment with 
 the air and gas ports in the wall. The governor controls 
 the quantity of air and gas admitted by rotating the cylin- 
 drical valve on the disk-valve stem; in the full-load posi- 
 tion the ports are all in exact alignment when the valve is 
 depressed, and at lesser loads the valve is twisted around by 
 the governor so as to shut off part of the port opening. The 
 four cylindrical valves of one side of the engine are all con- 
 nected together by reach-rods, so that the governor adjusts 
 all four valves simultaneously and alike. The two sets of 
 regulating gear are connected by double reach-rods, so that 
 there is no lost motion between the two sides. The pistons 
 are centered in the cylinders by adjustments at the three 
 crossheads. Each piston is equipped with four sectional 
 packing rings; the sections of each ring are joined by brass 
 keepers and set out by flat steel springs. The piston-rods 
 are hollow, of course, to admit and discharge cooling water 
 to and from the pistons, and they are turned without any 
 camber. 
 
 Governor. — In the Westinghouse gas engine, regulation 
 is obtained through two elements, governor and mixing 
 valve. The flyball governor or regulator is geared direct 
 
774 Steam Engineering 
 
 to the main engine shaft. From the rise and fall of the 
 governor sleeve, with corresponding changes in speed, the 
 essential motion is derived for operating the mixing valve 
 through a simple and direct linkage. With this mechanism 
 the governor is able to record without the least delay the 
 slightest change in speed of the engine, due to change in 
 load. 
 
 A slight range in speed is desirable for parallel operated 
 units. This is provided for by two springs on the mixing 
 valves, which can be adjusted while the engine is running, 
 so as to alter the position of the governor. 
 
 Mixing Valve. — This important detail part accomplishes 
 in a single mechanism two fundamental functions — one, the 
 proper proportioning of air and gas, and the other, the con- 
 trol of the quantity of mixture delivered to the cylinders. 
 A vertical free moving cylindrical valve with suitable ports 
 is surrounded by two independent sleeves, correspondingly 
 ported, capable of rotation by handles through a small arc 
 as indicated by two graduated dials. By rotating these 
 sleeves, when the engine is running on a certain kind of 
 gas, it is easy to "feel" for the best mixture. The mixing 
 valve then accomplishes the desired regulation as controlled 
 by the governor. In producer gas plants, foreign matter 
 such as dust and tar makes it difficult to keep this type of 
 valve in working order, so that a poppet type is used in- 
 stead, operating on the same principle. 
 
 In the Westinghouse engines the "make and break" or 
 "hammer break" type igniter is employed, this type having 
 been found by experience to be the least susceptible to irreg- 
 ular working, and to give the longest life. Essentially the 
 "make and break" system, comprises a source of electrical 
 current and a spark plug, inserted through the walls of the 
 
Westinghouse Gas Engine 
 
 775 
 
 combustion chamber. This interrupts the current at the 
 proper moment, causing an electrical discharge across the 
 opening in the circuit, the heat from which starts combus- 
 tion of the compressed gas mixture. 
 
 An igniter plug is shown in Fig. 330. To obtain the 
 necessary interruption, one of the poles of the igniter is 
 stationary, the other movable, and actuated from the out- 
 
 Fig. 330 
 
 IGNITER 
 
 side by a trip. This igniter mechanism interrupts the cur- 
 rent flow only at the beginning of each power stroke. The 
 opposing contact points are protected by tips of platinum, 
 or other heat resisting metal. 
 
 Starting. — While small gas motors may readily be started 
 by hand with a turn of the fly wheel, such a method is quite 
 impracticable in large engines. An automatic system has 
 
776 Steam Engineering 
 
 been incorporated in the Westinghouse engine by which 
 compressed air under 100-250 pounds pressure (according 
 to the size of the engine), is admitted at the proper moment 
 to one of the cylinders which then operates, for the instant, 
 as an air motor. During the succeeding rotation of the 
 engine, the other power cylinders are carried through their 
 respective cycles, and normal combustion begins in one or 
 the other upon the second or third revolution. Compressed 
 air is then shut off, the air valves automatically return to 
 their seats, and normal combustion in the remaining cylin- 
 der begins. 
 
 SNOW GAS ENGINES. 
 
 The Snow twin unit has cylinders 16 inches in diameter 
 by 30 inches stroke. The cranks are set at 90 degrees apart, 
 thus giving four impulses to the shaft per revolution. The 
 combustion chamber is on the side, with the inlet valves in 
 the top, and the exhaust valve in the bottom of each com- 
 bustion chamber. 
 
 The engine speed is regulated by cut-off valves which, 
 under control of the governor, shut off both the gas and 
 air supply sooner or later in the suction strokes, according 
 to the speed changes. The arrangement of inlet valves for 
 one end of a cylinder is shown by Fig. 331. The air and 
 gas pass to the mixing chamber M through separate ports, 
 shown closed by the valve discs A and G, respectively. From 
 the mixing chamber the mixture is admitted to the cylinder 
 by the main inlet valve I at the beginning of the suction 
 stroke ; at the point in the stroke determined by the gover- 
 nor, the cut-off valve A G is released and allowed to close 
 under the influence of its spring. The baffling disc B is 
 adjustable so as to obtain the desired proportion of gas to. 
 
 ■ 
 
Snow Gas Engine 
 
 in 
 
 Fig. 331 
 
 sectional elevation of inlet and cut-off valves and gear, 
 
 snow gas engine 
 
 air, the adjustment being made by means of the knurled 
 head N, which is locked in the proper position by the set- 
 screw s. The shank of the baffling disc serves also as a 
 
778 
 
 Steam Engineering 
 
 guide for the lower end of the stem of the cut-off valve. 
 The valve discs A and G are connected by a short barrel D, 
 the whole being a single casting. The gas valve G is pro- 
 vided with a tapered seat, and the valve-stem is adjusted 
 in the block at its upper end until both discs seat simul- 
 taneously. 
 
 Fig. 332 
 end elevation of inlet and cut-off mechanism. 
 
 ENGINE 
 
 SNOW GAS 
 
 The main inlet valve I is opened and closed always at 
 the beginning, and termination of the suction stroke, by the 
 inlet rocker-arm (Fig. 332), and its stem is linked to a 
 short rocker-arm E, Fig. 331, to the other end of which is 
 pivoted a block arranged to slide vertically in a guide. To 
 this block is hung the pivoted latch L, shown in Fig. 332, 
 the end of which normally engages a dog on the block 
 
Snow Gas Engine 779 
 
 which is screwed on the upper end of the stem of the cut-off 
 valve. When the main inlet valve is opened, the latch L 
 lifts the discs A and G of the cut-off valve. At the proper 
 point of the suction stroke, the cam C, Fig. 332, engages a 
 lug and draws the drag-link over, thereby pulling out the 
 latch L and allowing the cut-off valve to drop. The drag- 
 link is pivotally attached to a lug on the latch L, and its 
 other end is curved around the cut-off shaft S, the upper 
 leg of the bend resting on the journal box and holding the 
 link in place as it slides back and forth. Before the suc- 
 ceeding suction stroke begins, the cam C has turned to the 
 "low" side and the latch L is thrown into engagement with 
 the valve-stem dog by a small helical spring. When the 
 cut-off valve drops, it is cushioned by the inverted cup E, 
 Fig. 331, acting as a dash-pot, the plug F constituting the 
 plunger. The cut-off cam-shaft S rotates continuously at 
 one-half the crank-shaft speed, and its angular position 
 with respect to that of the crank-shaft is adjusted by the 
 governor through the well-known "floating" bevel gear. 
 
 DU BOIS TANDEM GAS ENGINE. 
 
 The Du Bois Iron Works, Du Bois, Penn., has devel- 
 oped and is now building a line of single-acting tandem 
 gas engines which embody several interesting features. 
 Fig. 333 is a view of one of these engines, from which it 
 will be evident that the design conforms to the standard 
 European practice of locating the inlet valves in the top, 
 the exhaust valves in the bottom, and the valve-gear shaft 
 alongside of the cylinders. Another characteristic Euro- 
 pean feature is the use of center-crank construction. Be- 
 yond these few points, however, the design cannot be said 
 to follow strictly any classified practice. 
 

 
 ^Li^J 
 
 mi 
 
 
 
 /I§»fly 
 
 
 
 
 B^ 
 
 
 {SB iaSf ) 
 
 
 1 
 
 
 f\« »pAg 
 
 
 \ 
 
 11 
 
 1 «fHi^ 
 I I ( 
 
 sTlsw fli ^MP9S^«uK^si3^^^^^\ 
 
 
 ^Wgfft 
 
 m^ 
 
 
 
 tr;#;i/ia-J;>r.'r A-. 
 
 
 
 
 
 Fig. 333 
 du bois tandem gas engine 
 
Du Bo is Gas Engine 
 
 781 
 
782 Steam Engineering 
 
 The longitudinal section, Fig. 334, gives an excellent 
 idea of the internal construction of the engine, and shows 
 clearly the unusual method employed for packing the 
 piston-rod hole in the rear end of the front cylinder. 
 Instead of providing a stationary packing cage, and having 
 the rod slide through rings contained therein, the packing 
 rings are put on the rod, like those on the piston, and they 
 slide back and forth with the rod in a sleeve formed in the 
 head of the front cylinder and a rearward extension of it. 
 It might seem at first glance that this arrangement would 
 entail an unduly long engine structure, but the fact is that 
 even if stationary packing rings were mounted in a housing 
 in the cylinder head, the engine could not be shortened up 
 without sacrificing accessibility to the rear piston, and ease 
 of dismounting the front cylinder head. Fig. 335 is a view 
 of the piston rod with its packing rings and the flanged 
 sleeve to which the rear piston is bolted. 
 
 The pistons are of the trunk type, and are built with con- 
 vex heads, in order to obtain the requisite strength with a 
 moderate weight of metal. 
 
 The construction of the water jackets, cylinder heads, 
 connecting rod and crank case is so clearly shown by Fig. 
 334 as to require no verbal description. The crank shaft, 
 crank cheeks, and pin are all cast in one piece of steel ; the 
 balancing weights are bolted on. 
 
 Valves, Valve Gear and Governor. — Simple, flat poppet 
 valves of forged steel, with beveled seats, are used through- 
 out the engine, and the need for cooling the exhaust valves 
 in larger sizes is obviated by the use of auxiliary exhaust 
 ports uncovered by the pistons at the end of the forward 
 stroke. These ports consist of a series of round holes 
 through a rib connecting the water-jacket wall and the 
 
Du Bois Gas Engine 
 
 783 
 
 Fig. 336 
 cross section through cylinder and valve chambers, du bois 
 
 gas engine 
 
 cylinder barrel, and they are drilled, instead of being cored, 
 in order to obtain absolute accuracy in dimension and loca- 
 
784 
 
 Steam Engineering 
 
 tion. The inlet and exhaust valves of each cylinder are 
 opened by a cam, two push rods and four rocker arms, as 
 indicated in Fig. 336. Boilers are provided, of course, to 
 take the thrust of the cam and to deliver the motion of the 
 rocker arms to the valve stems. 
 
 s=^=s=?i 
 
 Fig. 337 
 
 cross section through cylinder, mixing-valve chamber and 
 
 governor, du bois gas engine 
 
 One mixing valve serves both cylinders, as indicated in 
 Fig. 334, where the mixing valve is shown immediately 
 above the rear end of the piston-rod packing sleeve. Fig. 
 337 shows more of the details. The valve stem carries two 
 
Du Bois Gas Engine 785 
 
 pistons, the upper one controlling the air supply by vary- 
 ing the space between its upper edge and the top of the 
 cage, and the lower one varying the gas supply by means 
 of ports in its wall and corresponding ports in the wall of 
 its cage. The proportion of gas to air is adjusted manually 
 by means of the butterfly valves in the supply passages, 
 except in such cases as require variation of the mixture 
 proportions, simultaneously with variation in the quantity 
 of mixture admitted. For such conditions, the lever which 
 raises and lowers the mixing valve is also linked to the 
 butterfly valves, the linkage being adjusted so that the mix- 
 ture is made richer as the load decreases (and the com- 
 pression is reduced), and poorer as the load increases. This 
 automatic mixture control is not necessary except when run- 
 ning on very lean gases. The mechanism is adjusted usu- 
 ally to give the best mixture proportions at full rated load, 
 but a wide range of adjustment is practicable. 
 
 The governor is of the flyball type, but differs essentially 
 from the common construction, as Fig. 337 clearly shows. 
 The spindle is driven through spiral gears from the cam 
 shaft, and the balls and sliding member are inclosed in a 
 stationary housing, as shown in Fig. 337. The governor 
 gears are located between the forward cam and the main 
 shaft; consequently, the angular velocity of the governor 
 is not disturbed or made irregular by the tensional yield- 
 ing of the cam shaft" to the stresses imposed by the cams 
 and valve mechanism. The cam shaft is driven from the 
 crank shaft through spiral gears running in an oil bath. 
 
 Ignition. — Igniters of the mechanical make-and-break 
 class are used. The reciprocating mechanism which trips 
 each igniter is driven by an eccentric on the cam shaft, as 
 shown by Fig. 338. The individual igniter is timed by 
 
786 
 
 Steam Engineering 
 
 KM i 
 
 • I 
 
 j§ 
 
 : 
 
 ^— «*» 
 
 ^B 
 
 
 '■"""• ' J ' ' i ■■iiimirtiBWWBWMB '^^MfflKlHlP' ^ v 
 
 *l 
 
 Fig. 338 
 du bois igniter mechanism 
 
 means of the vertical handle near the cylinder; this raises 
 or lowers the horizontal finger with the bent end which 
 trips the igniter, and thereby alters the point of ignition. 
 
 .V 
 
Du Bois Gas Engine 787 
 
 The reach rod leading from the igniter mechanism to the 
 left extends to the other igniter, and adjustment of this rod 
 to the right or left retards or advances the timing of both 
 igniters simultaneously. The levers to which the ends of 
 this rod are pivoted are fastened to the ends of sleeves 
 which are eccentric to the rocker studs, and the igniter 
 rockers are mounted on these sleeves; turning the sleeves 
 on the studs alters the relation between the rockers and the 
 igniter triggers and thereby changes the timing. A handle 
 at the middle of the reach rod serves for manipulating it, 
 and a clamp holds it wherever it is set. 
 
 The engine is arranged so as to be oiled by a central 
 gravity-feed system. Since the piston trunks are more 
 than full-stroke length, they always cover the oil holes 
 in the cylinder walls; timed lubrication is therefore 
 unnecessary. 
 
 The engine is equipped with a valve in the head of the 
 rear cylinder for starting with compressed air, and the 
 valve disc is located at the inner face of the cylinder head, 
 so that when it is closed no pocket is formed in the com- 
 bustion-chamber wall. This construction is shown in Fig. 
 334. The indicator openings are provided with similar 
 valves, as shown in Fig. 336. This drawing also shows 
 the unusual feature of a water- jacketed exhaust pipe with 
 which every Du Bois engine is equipped. Another unusual 
 feature, although not original on this engine, is the injec- 
 tion of cooling water into the exhaust pipe ; this cools the 
 exhaust gases so suddenly that a muffler is not required. 
 The water jacket around the exhaust pipe is chiefly for the 
 purpose of obviating the exposure of dangerously hot sur- 
 faces where attendants are likely to come in contact with 
 them, although the water jacket also cools the exhaust gases 
 considerably. 
 
788 
 
 Steam Engineering 
 
 The compression pressure is about 140 pounds absolute 
 for natural gas, and 180 pounds for producer gas, and the 
 engine can be changed from the one to the other compres- 
 sion in a few minutes. 
 
 THE TOWER GAS ENGINE. 
 
 Fig. 339 shows a view of the Tower heavy duty gas 
 engine built by the Tower Engineering Company, Buffalo, 
 
 Fig. 339 
 200 h. p. tower gas engine 
 
 1ST. Y. This engine is designed for using producer gas, 
 and has some very pronounced features embodying the best- 
 practice and the most recent development in gas engine 
 design. 
 
Tower Gas Engine 789 
 
 The engine is of the three cylinder, vertical, single acting 
 type operating on the four stroke-cycle principle. It is 
 rated at 200 h. p. upon producer gas of approximately 135 
 b. t. u. per cubic foot measured under standard conditions 
 of 62° Fahr. temperature and 30 in. mercury pressure. 
 The cylinders are each 16 ^2 in. diameter and the stroke 
 is 18 inches. The area of the piston is 213.8 sq. in., the . 
 piston displacement is 3850 cu. in. The piston speed under 
 normal operation of 257 r. p. m. is 771 feet per minute. 
 The mean effective pressure in each cylinder as calculated 
 from the above data is 53 pounds per sq. in. of piston area. 
 
 The height of the engine is 12 1 /9 feet, the length 14 1/6 
 feet, the width 8^2 feet, the floor space occupied is 120 sq. 
 ft. 
 
 The weight of the complete engine with its fittings is 
 61,000 pounds which gives a weight of metal of 305 pounds 
 per horse power. Each of the two fly wheels is seven feet 
 in diameter and weighs 10,000 pounds. The peripheral 
 speed of the wheels is 5,600 feet per minute which is far 
 too low to give any cause for fly wheel explosions. Provi- 
 sion is made for belting off one fly wheel if necessary, 
 and for barring the engine over, during times of inspection 
 from the other, by means of holes drilled in the face of the 
 fly wheel. 
 
 The crank shaft is of forged open hearth steel with high 
 ultimate, and elastic limits, combined with reasonable ductil- 
 ity to suit the conditions of service. The matter of crank 
 'shafts for vertical three cylinder engines has received con- 
 siderable study of late, in view of the fact that there have 
 been several breakages of late, in engines of supposedly 
 good design. The pressures exerted on the crank at the 
 time of the explosion are very great and, due to the rotation 
 
790 Steam Engineering 
 
 of the crank shaft, the stresses are reversed from tension 
 to compression so that if any defects or initial stresses are 
 in the material, there is great liability to rupture due to 
 "fatigue" or crystallization of the metal. The use of the 
 best material, of good proportions, and large bearing sur- 
 faces, easy to adjust and keep in correct alignment is the 
 solution of the crank shaft problem. The two end crank 
 shaft bearings are each 20 in. long and the two center 
 bearings are each 14 in. long, with wedge take-up adjust- 
 ments. The diameter of the crank shaft is 8 in., that of 
 the crank pin bearings is 8^2 in., with a length of 7% in. 
 The piston pin has a diameter of 5% in.,, and the length 
 of the bearing surface is 8 in. The oil reservoir supplies 
 a sight feed indicating distributer in full view of the 
 engineer. There are separate oil feeds piped from this dis- 
 tributer to each of the bearings, and the engineer can easily 
 adjust the flow to each bearing, and with a glance of his 
 eye observe whether oil is going to every bearing or not. 
 The feeding device starts and stops with the engine, the oil 
 is collected in the pit of the crank case, passes through the 
 filter, and is pumped to the reservoir with little waste. 
 
 The cylinder heads contain the 'nlet and exhaust valves of 
 the poppet type; the latter is water cooled. The valves 
 themselves are placed in cages which may be readily re- 
 moved from the cylinder heads. The construction is such 
 that neither valve can fall into the cylinder — a very wise 
 precaution, as engines have been badly damaged by having 
 an inlet valve drop into a cylinder. 
 
 The valves are operated by eccentrics which are encased, 
 and dip into a bath of oil. The entire eccentric shaft can 
 be exposed for inspection by lifting the cover of the case. 
 
 The governor case, as shown to the right under the end of 
 the eccentric case in the illustration, encloses two fly-balls 
 
Tower Gas Engine 791 
 
 immersed in oil, running at engine speed. The cover to 
 the case can be removed for easy inspection. Means are 
 provided for changing the speed of the engine, while run- 
 ning, by turning a knurled adjusting nut. Connections are 
 made to the governor valve by two reach rods; one to con- 
 trol the gas, and one to control the air supply. 
 
 The governor valve, for controlling the quality of the 
 mixture, and the compression of the engine, is multiported 
 and operates on ball bearings to insure minimum friction 
 and sensitiveness. An indicator is provided to show, at all 
 times, the position of gas and air ports at all conditions of 
 load. The adjustment provided on the reach rods and 
 governor, allows of the variation of air and gas separately, 
 or the adjustment of both simultaneously, while engine is 
 operating. 
 
 The special feature of ignition is important. Two spark 
 plugs are used in a plate, and by throwing a lever either 
 plug may be thrown into service. 
 
 A defective plug may thus be removed without losing a 
 power stroke. An adjustable timing device, allows the tim- 
 ing of each cylinder separately, or advancing and retarding 
 the spark in all the cylinders at the same time. 
 
 No batteries are used. The cylinder, cylinder head, 
 exhaust valve and exhaust manifold are water cooled. 
 "Water is piped to each cylinder independently, and connec- 
 tion is made externally from cylinder, to cylinder head. 
 The water from the cylinder head is discharged into an 
 open funnel so that the engineer can see at a glance that 
 each cylinder is getting its proper share of cooling water. 
 This is an important matter to consider as practice has 
 shown that cylinders heat differently, and trouble due to 
 one hot cylinder may seriously injure the engine. 
 
792 Steam Engineering 
 
 The starting of the engine is effected by compressed air. 
 The auxiliary apparatus consists of two air storage tanks, 
 a two cylinder air compressor, and a 4 horse power gasoline 
 engine. 
 
 THE REEVES GAS ENGINE, 
 
 Figures 340 and 341 show views of the Eeeves gas engine 
 built by the Eeeves Engineering Co., Mt. Vernon Ohio. 
 
 Fig. 340 
 eeeves three-cylinder gas engine 
 
 This engine is designed to be operated on natural or pro- 
 ducer gas, and can also be operated on gasoline if necessary. 
 
 As will be noted by the illustrations these engines are of 
 the vertical, multiple cylinder single acting type. 
 
 The crank shafts and connecting rods on this engine are 
 forged without welds from open hearth steel. Crank pin 
 
Reeves Gas Engine 
 
 793 
 
 bearings are of marine type, and cast from phosphor bronze ; 
 the adjustment of wear on these bearings being made by a 
 special system of liners, each one consisting of a number 
 of sheets of brass, each being 0.003 of an inch in thick- 
 ness and a number made into a unit constitute a liner. In 
 
 Fig. 341 
 sectional view of the reeves gas engine 
 
 making an adjustment the removal of one sheet on each 
 side gives equal adjustment all over the bearing. The pin 
 is made from tool steel, hardened and ground to exact size. 
 Pistons are of special hard gray iron, and are unusually 
 long affording a liberal wearing surface. By referring to 
 
794 Steam Engineering 
 
 Fig. 341 the extreme length of the piston will be apparent. 
 It will also be noted that the packing ring system consists 
 of five narrow rings, four at top for holding compression 
 and one ring at the bottom which acts as an oil retainer, 
 making lasting compression possible. 
 
 The cylinder head has no offset firing chambers and the 
 surface exposed to heat is thereby reduced to a minimum, 
 which together with the high compression gives low fuel 
 consumption. To protect the gasket between the cylinder 
 and the cylinder head from the firing of the charge, the 
 cylinder head is fitted with a male flange which projects 
 and makes a close fit in to a corresponding counterbore in 
 the cylinder. The valve stem guides on both intake and 
 exhaust are made from close grained cast iron bushings in- 
 serted in the cylinder head. 
 
 The cylinder head is thoroughly water jacketed, and has 
 a system for injecting cooling water directly around the 
 exhaust valve seat. 
 
 Cylinders are cast from semi-steel, the flange for bolting 
 same to housing being set three inches from end of cylinder. 
 The extension below this flange is a slip fit to correspond 
 to bore in housing; this centralizes the cylinder on the bed 
 and also adds to the rigidity. They are bolted (at the bot- 
 tom) direct to the housings, which consruction allows for 
 contraction and expansion without throwing cylinder out 
 of true. 
 
 The governor is the throttling type, the engine taking 
 impulses regularly, each impulse being graduated by gover- 
 nor according to load the engine is carrying. The engine 
 is fitted with a patent proportional throttle valve, which 
 gives a constant proportion of air and fuel under all loads. 
 
 Either jump spark, or make and break ignition is fitted, 
 according to the charcter of work or fuel on which engine 
 
Reeves Gas Engine 795 
 
 is to be operated. For natural gas, or gasoline the jump 
 spark is undoubtedly the best, but for producer gas a 
 mechanically operated system of make and break spark is 
 used. 
 
 The timer is arranged so that the firing point can be 
 changed while the engine is in motion. 
 
 The spark plug is located directly underneath the inlet 
 valve. 
 
 Splash lubrication has been abandoned, and* its place is 
 taken by an individual oiler on each bearing. All drip oil 
 is collected in the base of the engine and drawn off through 
 a drain pipe in the back. All lubrication devices are ac- 
 cessible on outside for oiling while the engine is in oper- 
 ation. Each cylinder has two sight feed lubricators, located 
 on opposite sides of cylinder. 
 
 THE GASOLINE ENGINE. 
 
 The principles governing the action of the gasoline engine 
 are essentially the same as those of the gas engine. In 
 fact the term, "gas engine" applies equally well to gasoline 
 and oil engines, and there is very little difference in their 
 action. An engine using gas may be easily changed to use 
 gasoline, or a gasoline engine may, by a few simple changes, 
 be fitted to use natural, or artificial gas. The principal dif- 
 ference between the gas engine proper, and those engines 
 such as gasoline, oil, etc., that use a liquid fuel is, that with 
 the latter the gas is generated within the engine itself while 
 in operation, whereas with the former the gas is supplied 
 from outside sources. In early gas engine practice a gas- 
 oline or oil vapor gas was made by passing air in close prox- 
 imity to a large surface of the liquid fuel. The air was 
 thus saturated with the vapor of the gasoline or oil, and be- 
 
796 
 
 Steam Engineering 
 
 came a vapor gas similar to artificial or natural gas. This 
 vapor gas was piped to the engine and mixed with air in 
 proper proportion to secure the quickest and best com- 
 bustion. This principle of mixing is used now with natu- 
 ral, artificial and producer gas. The next development in 
 the use of liquid fuel was the mixer or carbureter by which 
 a minute quantity of the gasoline or oil is measured and 
 supplied with each charge of air entering the engine cjdin- 
 
 Fig. 342 
 
 der. With the stationary, single cylinder, industrial en- 
 gines in common use the device for measuring the liquid 
 fuel is called a mixer, and is usually made a part of the 
 engine. A gasoline or fuel pump and constant level over- 
 flow cup is provided so that the gasoline tank may be located 
 outside of the building in compliance with insurance reg- 
 ulations about the storage of gasoline. For multiple cylin- 
 
The Gasoline Engine 797 
 
 der, and lighter engines the measuring device is called 
 a carbureter, and is generally an accessory to the engine. 
 
 Fig. 342 shows the principle of the constant level overflow 
 Mixer System commonly employed in the single cylinder 
 stationary engine. A is the constant level overflow cup 
 showing how the gasoline or liquid fuel rises in the spray 
 nozzle, F, to the same level maintained in the cup. B is 
 the pipe from the gasoline pump, and C is the overflow pipe 
 that leads the surplus gasoline back to the tank which, as 
 stated, may be outside the building if so required. D is 
 the gasoline regulator, E the air regulator, F the spray 
 nozzle and G the short passage to the inlet valve of the 
 engine. At a given speed the engine draws in a certain 
 amount of air by the regulator, E. The air rushing past 
 spray nozzle, F, draws a small quantity of gasoline, meas- 
 ured by regulator, D, from the spray nozzle, and carries it 
 into the cylinder of the engine. The natural heat in trw 
 air supply, assisted by the heat of the cylinder, turns the gas- 
 oline spray into a gas that burns like a flash or "explodes''" 
 when compressed and ignited by the engine, provided of 
 course that the right proportion of air and gasoline has 
 been obtained. This is easily known by adjusting the fuel 
 and air regulators, and observing the action of the engine, 
 especially under load. The greatest amount of air with the 
 least amount of gasoline for the strongest pull at a given 
 speed will be the correct position for the regulators. For 
 easy starting the air regulator should be closed a little, then 
 opened again when the engine gets up speed. 
 
 Fig. 343 is an illustration of a 1908 accessory carbureter, 
 such as is commonly used on multiple cylinder and light 
 motors, although it is applicable to any type of engine. A 
 float, M, controlling a valve, 0, takes the place of pump and 
 
798 
 
 Steam Engineering 
 
 overflow system shown in Fig. 342, maintaining a constant 
 level of the fuel in the spray nozzle, L. The float chamber 
 is placed around the spray nozzle so that in traction or 
 marine work, involving various angles and positions of the 
 machine, there will be no variation of the fuel level in the 
 spray nozzle. The fuel tank is usually placed above the 
 
 Fig. 343 
 
 carbureter, and connected by pipe P to float valve 0. The 
 liquid fuel is thus fed to the float chamber by gravity. By 
 using a light air pressure in the tank it may be placed 
 below the carbureter but this is not often done. The mixer 
 as shown in Fig. 342 is designed for a given engine speed. 
 If the engine speed is changed the air and gasoline regu- 
 lators must also be changed to get the best results. The 
 
The Gasoline Engine 
 
 799 
 
 carbureter is generally designed to automatically adjust 
 itself to a considerable range of engine speed. Thus in 
 Fig. 343 the air for starting, and slow speed enters at I. 
 As the engine speed increases the compensating valve, G, 
 opens, more air is admitted and the syphon force exerted 
 on the spray nozzle, L, is kept in fairly accurate proportion 
 to the requirements of the engine. 
 
 .system attache ^gfip Nw jr> 
 
 Fig. 344 
 
 K is a butterfly throttle valve for governing either auto- 
 matically, or positively the amount of mixture admitted to 
 the engine, and thus controlling the speed and power. Some 
 makers connect the needle valve, A, to the throttle lever, K, 
 in such a way that on full open throttle the needle valve is 
 given additional opening. Other designs like the one illus- 
 trated in Fig. 343 depend entirely on the compensating 
 valve for the proportion of liquid fuel and air, covering the 
 range of speed and power required of the engine. Aside 
 
800 Steam Engineering 
 
 from the differences in regulation and control, the essential 
 principles of the overflow, and float feed systems are prac- 
 tically the same. 
 
 Fig. 344 illustrates the principle of the generator or mix- 
 ing valve, a very common method of measuring the liquid 
 fuel for making each charge of gas for a gas engine. The 
 liquid fuel (generally from a tank higher than the valve) 
 is supplied to the fuel regulator, D. When the intake 
 stroke of the engine draws air through the valve a small 
 quantity of gasoline or fuel oil, measured by regulator, D, 
 is drawn from the drilled opening to the valve seat, G. 
 When not in action the valve is held to its seat by a light 
 tension spring, thus preventing the continued flow of the 
 liquid fuel. This type of mixer or measuring device is 
 especially well suited to two port two cycle engines, but has 
 been successfully employed by large numbers of four cycle 
 engines as well. E is a regulator for the stroke of the valve. 
 F is a butterfly valve for controlling the amount of mixture 
 admitted and the speed and power of the engine. 
 
 Where insurance regulations or other considerations 
 make it desirable to dispense with a considerable gravity 
 head of fuel, the pump and overflow systems may be at- 
 tached as shown in the drawing, Fig. 344. A is the over- 
 flow cup showing the small quantity of head fuel supply. 
 B is the pipe from the gasoline pump, and C the pipe lead- 
 ing the overflow back to the tank. 
 
 Owing to the pulsations of the valve on some types of 
 engines a small amount of vapor is blown back from the 
 valve with each stroke. A piece of pipe, 8 or 10 inches 
 long, to be attached as indicated by H will effect quite a 
 saving of gasoline or fuel oil. 
 
 These illustrations show the principles of the various 
 devices now in general use, for making gas out of gasoline, 
 
The Gasoline Engine 801 
 
 kerosene or other liquid fuel. It must be kept in mind that 
 they are chiefly measuring devices, and depend on the heat 
 of the incoming air and the heat of the cylinder for the 
 vaporization or gasification of the liquid measured for each 
 charge. The lighter and more volatile the liquid fuel the 
 better the vaporization. This is the reason gasoline is so 
 generally used. The complete vaporization of the heavier 
 oils and spirits such as kerosene and alcohol requires special 
 attention for equally successful results. Even gasoline in 
 cold weather needs hot air for the first few charges in 
 starting. Some makers of engines provide a generating 
 cup to hold a small amount of gasoline for heating the 
 intake pipe for easy starting in cold weather. 
 
 The higher the speed of the engine the less time there 
 is for the thorough gasification of the measured liquid for 
 each charge. The heat of the cylinder has less effect. The 
 use of multiple cylinders has brought greatly increased 
 practical speeds. These facts, together with the very desir- 
 able purpose of serving each cylinder of an engine with 
 an equal quantity of an equally carbureted mixture, seems 
 likely to bring further improvements in gas generating 
 devices for liquid fuel. The present practice is to put the 
 measuring mixer, carbureter or generator valve, as the 
 case may be, as close to the cylinder intake valves as possi- 
 ble, and depend principally on the heat of the cylinders for 
 completing the gasification. A complete gasification of the 
 charge before it reaches the cylinders would certainly add 
 to the fuel economy, smoothness and reliability of action 
 in high speed multiple cylinder engines, if it can be accom- 
 plished in a practical way, and without possible ignition of 
 the mixture in the carbureter and intake manifold. 
 
802 Steam Engineering 
 
 LUBRICATION OE GAS ENGINES 
 
 Engines which are air cooled require more lubrication in 
 the cylinders, as well as a heavier oil because the tempera- 
 ture of the metal is invariably higher, than where the water 
 cooled system is in use. 
 
 An oil suitable for this purpose must have three charac- 
 teristic points, i. e., a good body, low in carbon, and lastly 
 it must have a very high fire test. That is, the temperature 
 at which the vapor coming from the oil would ignite should 
 not be lower than 500 to 600 degrees. 
 
 Any lubricant leaving a large amount of carbon or resi- 
 due should be carefully avoided. 
 
 For the crank and crankshaft bearings, the same grade 
 of lubricant as is used for the cylinder gives the best re- 
 sults, and the amount should be three to four drops per 
 minute with the gravity system and a proportionately small 
 amount with the force feed system. 
 
 This method of lubrication is now being adopted on a 
 large number of gas engines because of its reliability. A 
 tank holding a quantity of oil is located at some convenient 
 point on the engine. A small force pump is worked from 
 the crank, or cam shaft as the case may be, and forces the 
 oil through brass or copper tubes directly to the bearings 
 and by means of check valves located at the pump and also 
 near the sight feed a pressure of several pounds to the 
 equare inch is obtained and each drop of oil is assured of 
 reaching the proper place. This system requires practically 
 no attention other than an occasional refilling of the tanks. 
 
 Where grease cups are used the caps or plungers should 
 be screwed down at least two turns each hour. If a small 
 quantity of graphite, about one tablespoonful to one pound 
 of grease is used, one full turn of the cap or plunger each 
 
Lubrication of Gas Engines 803 
 
 hour will be sufficient. The graphite and grease should be 
 thoroughly mixed before filling the cup. 
 
 The fact that the lubricators are feeding is not a sign 
 that the oil is reaching the proper place. Be sure the ducts 
 are open and the lubricant goes to the bearing. 
 
 Where the splash system of lubrication is used the oil 
 holder or base should be carefully cleaned before each fill- 
 ing. Wipe the inside of the holder with waste or a piece 
 of cloth, being careful to remove all the particles of grit 
 and sediment which will collect on the sides and bottom. 
 
 Cylinder Lubrication. — In cylinder lubrication extreme 
 caution should be exercised. Just enough oil should be used 
 to thoroughly lubricate the piston and no more. An excess 
 will be burned by the high heat, and will form carbon on 
 the rings, cylinder walls and piston. This carbon will, in 
 a short time, become heated causing pre-ignition and in a 
 four cycle engine frequent regrinding of the valves will be 
 necessary. The piston rings will also stick, causing them 
 to wear uneven, and thereby much of the compression will 
 be lost, as well as a large amount of the power which should 
 be delivered. 
 
 From eight to ten drops of oil per minute should be 
 delivered to the cylinder, where common cups or in other 
 words where the gravity system is used. With force feed 
 this amount may be. cut to five or six drops a minute, as 
 they are much larger. An excess of oil in the cylinder 
 will make itself known by the smoke from the exhaust pipe. 
 
 QUESTIONS AND ANSWERS. 
 
 508. In what respect does the gas engine differ from tne 
 steam engine structurally? 
 
 Ans. It is a much more ponderous machine than a steam 
 
804 Steam Engineering 
 
 engine of equal output, and usually requires a. much heavier 
 crank shaft. 
 
 509. Why should this be? 
 
 Ans. Because the ordinary four-stroke-cycle, gas engine 
 has only one working stroke in four, and requires four 
 times as much cylinder area for a given amount of work, 
 as would a steam engine for the same work. 
 
 510. Define the difference between a single acting four 
 stroke cycle and a double acting or two stroke cycle gas 
 engine in their operation. 
 
 Ans. In the four stroke engine two revolutions of the 
 crank are required for one cycle. In the double acting or 
 two stroke, the cycle is completed in one revolution of the 
 crank. 
 
 511. Why are gas engine crank shafts made larger in 
 proportion than those of steam engines? 
 
 Ans. In order that they may withstand the increased 
 torsional strains. 
 
 512. What causes the pressure behind the piston of the 
 gas engine? 
 
 ' Ans. The combustion within the cylinder of a charge 
 of gas and air properly mixed to form an explosive,- and 
 admitted at the proper moment. 
 
 513. When is this proper moment? 
 
 Ans. When the piston is at the end of its instroke 
 ready to start outward. 
 
 514. Define the stages of a four cycle engine. 
 
 Ans. First, induction; during an out stroke of the 
 piston, air and gas are drawn into the cylinder in the 
 proper proportions. Second, compression; on the return 
 stroke the piston compresses this combustible mixture 
 into the clearance space. Third, explosion; ignition of the 
 
Questions and Answers 805 
 
 compressed charge causes a rapid rise of pressure and sub- 
 sequent expansion of products. Fourth, expulsion; the 
 expanded gases are expelled by the returning piston. 
 
 515. Define the stages of a two cycle gas engine. 
 
 Ans. First, compression of the charge. Second, igni- 
 tion, explosion, and expansion, and at the end of the 
 stroke the expanded products are expelled, and the cylinder 
 filled by another charge of air and gas under pressure. 
 
 516. How many compression chambers are needed for 
 the two cycle gas engine? 
 
 Ans. Two; for the reason that this type of gas engine 
 requires two cylinders, either side by side, or tandem, and 
 the charge of gas and air is being received in one cylinder, 
 while the previous charge in the other cylinder is being 
 compressed preparatory for explosion. 
 
 517. How is the usefulness of the gas engine as a prime 
 mover made apparent? 
 
 Ans. By the fact that a suitable power gas may now be 
 produced from almost any kind of commercial fuel. 
 
 518. What are the relative volumes of gas and air re- 
 quired for combustion in a gas engine? 
 
 Ans. This depends upon the kind of gas. Natural gas 
 requires 10 to 12 cu. ft. of air per cubic feet of gas, while 
 producer gas requires equal volumes of gas and air. 
 
 519. Is blast furnace gas suitable for fuel gas? 
 
 Ans. Yes, because it is slow burning, thus permitting 
 high compression. 
 
 520. To what pressures may it be compressed? 
 Ans. 160 to 200 lbs. per sq. in. 
 
 521. Is there as much heat in a given volume of blast 
 furnace gas as in the same volume of natural gas ? 
 
 Ans. No, there is about 40 per cent less. 
 
806 Steam Engineering 
 
 522. How is the charge of gas and air drawn into the 
 cylinder of a gas engine ? 
 
 Ans. By the suction of the piston. 
 
 523. What precaution should be observed regarding 
 the admission of the air and gas? 
 
 Ans. The air should be pure and free from dust, and 
 the gas should not contain tarry matters if it can be 
 avoided. 
 
 524. How are the induction valves usually set? 
 
 Ans. So that the first portion of the charge is air only, 
 then air and gas, and finally air with a small quantity of 
 gas. 
 
 525. How is the air valve controlling the entry of the 
 entire charge adjusted? 
 
 Ans. It is set to open well in advance of the inner dead 
 center of the engine, and is kept from closing until after 
 the outer dead center. 
 
 526. Why is this valve so set? 
 
 Ans. In order that the full effect of the momentum 
 imparted to entering gases at the highest rate of piston 
 speed may be utilized. 
 
 527. Upon what does the allowable compression pres- 
 sure depend? 
 
 Ans. Upon the relative proportions of hydro-carbon 
 gases, and hydrogen contained in the mixture. 
 
 528. What per cent of hydrogen is considered within 
 the limits of safety ? 
 
 Ans. Not over 7 per cent. 
 
 529. What are the usual compression pressures carried 
 with blast furnace gas ? 
 
 Ans. 200 lbs. per sq. in. 
 
 530. What pressure may be safely carried when pro- 
 ducer gas is used ? 
 
Questions and Answers 807 
 
 Ans. From 150 to 200 lbs. per sq. in. 
 
 531. If illuminating gas is used, what is the maximum 
 safe pressure? 
 
 Ans. 120 lbs. per sq. in. 
 
 532. How is the cylinder cooled and cleaned? 
 
 Ans. By the injection of water or cold air through 
 the clearance spaces, and valve ports during the charging 
 stroke, or by pressure during compression. 
 
 533. What other methods are available for cooling the 
 cylinder and piston rod ? 
 
 Ans. By means of a water jacket that surrounds the 
 cylinder. The piston rod may be hollow and water cir- 
 culated through it. 
 
 534. How is the charge of gas and air ignited? 
 
 Ans. Formerly by hot tubes , of porcelain or hecnum, 
 which are still used to some extent, but at the present day 
 electrical ignition devices are used principally. 
 
 535. What kind of electrical devices are used for this 
 purpose ? 
 
 Ans. Primary batteries, storage batteries, and magneto 
 machines, or the current may be taken from the lighting, 
 or power circuit. 
 
 536. How many types of primary batteries are in com- 
 mon use? 
 
 Ans. Two — Dry and wet batteries. 
 
 537. What are the elements commonly used in the wet 
 battery ? 
 
 Ans. Carbon and zinc immersed in a jar or cell con- 
 taining a solution of sal ammoniac, or sulphate of copper. 
 
 538. Describe the copper oxide battery. 
 
 Ans. It consists of a plate of copper oxide, and a zinc 
 plate, both being immersed in a solution of caustic potash. 
 
808 Steam Engineering 
 
 539. What is the usual voltage of these cells? 
 Ans. From 1 to 2 volts per cell. 
 
 540. Describe in brief the construction of the storage 
 cell? 
 
 Ans. It consists of gridded frames of lead, part of which 
 are filled with red lead for the positive plates, and those for 
 tthe negative plates are filled with litharge, all being im- 
 fmersed in a solution of 6 parts of water to 1 part of sul- 
 phuric acid. 
 
 541. How is a dry battery made? 
 
 Ans. A round zinc case forms one of the elements, and 
 a piece of carbon in the center of the case forms the other 
 element. 
 
 542. Are there any other ingredients? 
 
 Ans. Yes — A mixture of powdered manganese, carbon, 
 and flour is packed around the carbon, while the rest of the 
 can is filled with a plaster mixture of oxide of zinc and 
 flour, and the whole is soaked in a solution of sal ammo- 
 niac and zinc chloride. 
 
 543. In what manner does the electric current ignite 
 the charge of gas in the cylinder? 
 
 Ans. By means of the jump spark caused by alternately 
 making and breaking the circuit. 
 
 544. What is one of the most important features con- 
 nected with ignition? 
 
 Ans. To see that ignition occurs at the proper moment. 
 
 545. At what point in the stroke of the piston should 
 ignition occur? 
 
 Ans. This depends upon the quality of the gas used. 
 With the maximum allowable percentage of hydrogen, igni- 
 tion should not occur until after the piston has passed the 
 inner dead center. Otherwise the result will be violent 
 shocks, and strains upon the working parts. 
 
Questions and Answers 809 
 
 546. Do high initial explosions create the most powerful 
 efforts behind the piston? 
 
 Ans. They do not. 
 
 547. What are the usual terminal pressures for gas 
 engines ? 
 
 Ans. 25 to 30 lbs. above atmospheric pressure. 
 
 548. How is the horse power of a gas engine calculated? 
 
 Ans. Usually from the same formula used in connec- 
 tion with the steam engine, and the computation is based 
 upon the mean effective pressure developed at each ex- 
 plosion. 
 
 549. What percentage of the total calorific value of 
 the coal is usually converted into useful work with the 
 steam engine? 
 
 Ans. From 5 to 10 per cent. 
 
 550. What percentage of the energy contained in the 
 fuel is it possible to utilize with a modern gas-driven unit? 
 
 Ans. From 16 to 20 per cent. 
 
 551. How many type of apparatus are in use for the 
 production of gas for power? 
 
 Ans. Three : the suction producer, the steam pressure 
 producer, and the induced down draft producer. 
 
 552. What kind of fuel must be used in the suction, 
 and steam pressure producers? 
 
 Ans. Coke, or anthracite coal. 
 
 553. What kind of fuel is the induced down draft pro- 
 ducer adapted for? 
 
 Ans. Bituminous coal. 
 
 554. How may gas engine efficiency be expressed? 
 Ans. In terms of heat value. 
 
 555. Is there any difference of importance between a 
 gas engine, and a gasoline or oil engine ? 
 
810 Steam Engineering 
 
 Ans. None of any importance. A gas engine may be 
 easily converted into a gasoline engine, or vice versa. 
 
 556. Wherein lies the principal difference between the 
 two kinds of engines? 
 
 Ans. In the gas engine proper the gas is supplied to 
 the cylinder by the producer. In the gasoline engine the 
 gas is generated within the cylinder, from a charge of 
 gasoline. 
 
 557. How may the action of the gas within the cylinder 
 of a gas engine be ascertained ? 
 
 Ans. By means of diagrams taken with an indicator. 
 
 558. Is there any difference between a steam engine in- 
 dicator, and an indicator adapted for gas engines ? 
 
 Ans. None in principle. The gas engine indicator is 
 made somewhat stronger owing to the high pressures used. 
 
Modern Types of Oil Engines 
 
 Diesel Engine. — This engine is built in both the four-cycle and 
 two-cycle styles. Vaporization of the oil takes place within the 
 cylinder itself, where the pressure of compression is carried suffi- 
 ciently high to cause combustion of the fuel. The oil is injected 
 through a valve at the top of the cylinder, which is vertical, and 
 as the fuel enters the cylinder after the period of compression, 
 about 600 pounds pressure per square inch is required for the 
 injection. This pressure is supplied by an independent air com- 
 pressor. The air necessary to support combustion is introduced 
 through an air inlet valve. 
 
 Figure 1 represents cross-sections of the working cylinder and 
 head of a stationary two-stroke motor. The arrangement of slots 
 in the cylinder wall, through which the exhaust gases leave the 
 working cylinder, as the piston comes near the lower dead point, 
 
 FIG. 1 
 
 Sectional view of Diesel two-stroke cycle engine. 
 
 810a 
 
810& 
 
 Steam Engineering 
 
 is, of course, a typical feature of two-stroke motors. This ar- 
 rangement is an undoubted advantage over four-stroke motors, 
 which discharge their exhaust gases through valves. The admis- 
 sion of scavenging and charging air is affected through four 
 valves, arranged symmetrically in the cylinder head. 
 
 As seen from the figure, the piston comprises at its upper end 
 a cooling compartment, pistons above a given size having to be 
 cooled with water or oil. Telescoping tubes through which a 
 water jet in free contact with air is projected directly against the 
 bottom of the piston serve to admit and carry away cooling water, 
 an arrangement which avoids any stuffing boxes. 
 
 It is true that the two-stroke process entails the use of a spe- 
 cial scavenging pump to discharge the exhaust gases. Four-stroke 
 motors, which are more simple from a constructive point of view, 
 
 FIG. 2 
 
 Section of Diesel two-stroke marine engine. 
 
Oil Engines 
 
 810c 
 
 are therefore generally preferable for small and medium installa- 
 tions. In connection with large units, the addition of an air 
 pump, however, is of much less importance, the more so as the 
 pump discharging the scavenging air works at very low pres- 
 sures and accordingly under extremely favorable conditions. On 
 the other hand, the reduction in weight is of paramount import- 
 ance for large units, the frames, bases and flywheels of large 
 
 FIG. 3 
 
 Scheme of injection air regulation. 
 
 Diesel Engine. 
 
 four-stroke motors being so heavy that their transportation and 
 erection entail serious difficulties. 
 
 The two-stroke Diesel motor resembles the four-stroke type as 
 far as its outside arrangement is concerned. The cylinders are 
 likewise vertical; their jackets are cast of one piece with the 
 frame, the working cylinders are encased and the piston is de- 
 signed as crosshead. Apart from the compressed air pump, which 
 
810d 
 
 Steam Engineering 
 
 serves to introduce fuel oil into the cylinder and to start the en- 
 gine, two-stroke motors comprise a scavenging air pump arranged, 
 in accordance with local conditions, in the basement or above the 
 floor. The scavenging air valves, like the other valve, are ar- 
 ranged in the cylinder head. The exhaust valves are, however, 
 replaced by slots in the working cylinder, and the fuel supply is 
 regulated automatically in accordance with the load on the en- 
 gine. All motors of this type have an attachment for changing 
 speed during operation. 
 
 Figure 2 shows a cross-section through a directly reversible 
 Sulzer-Diesel marine engine, which has likewise been designed as 
 two-stroke. 
 
 In connection with large units the special regulation developed 
 by the constructors would seem to deserve more than passing 
 notice. These engines are thus in a position to deal with any 
 sudden fluctuations in load with least variation in speed and at the 
 same time can be readily connected up in parallel with any other 
 prime movers of the same or any different type, such as steam 
 engines, gas motors and water turbines. The working of the 
 regulator will be understood by referring to Figure 3. 
 
 The governor controls, in accordance with its adjustment, all the 
 factors on which the output of the engine depends. These factors 
 in the case of Diesel motors are the amount of fuel injected, the 
 amount and pressure of the injection air required for vaporizing 
 and injecting the fuel, as well as the variable admission of the 
 vaporizer valve in accordance with the amounts of air and fuel. 
 The amount of fuel, as well as the amount of pressure of the 
 injection air, are adjusted for directly from the regulator. The 
 regulation of the amount of injection air in the present instance 
 is affected by adjusting a slide fitted into the suction conduit of 
 the first stage of the injection air pump. The adjustment of the 
 duration of opening of the fuel valve, on account of the valve re- 
 sistance, however, requires much more energy, so that the action 
 of the regulator itself would not be sufficient. A pilot valve S 
 has therefore been provided, which is operated by the pressure 
 
 FIG. 4 
 
 Hornsby-Akroyd horizontal engine. 
 
Oil Engines 
 
 810e 
 
 from one of the stages of the injection air pump. In the present 
 instance the pressure obtaining between the first stage 1, and the 
 second stage k, of the injection pump is used for this purpose, 
 the conduit u serving to transmit this pressure to the pilot valve S. 
 Horxsby-Akroyd Oil Engine. — In this engine, a sectional view of 
 which is shown in Figure 4, the oil is first introduced in liquid 
 form into the vaporizer shown at the back of the cylinder. The 
 heat necessary for vaporizing the oil is supplied at starting by 
 external lamps, but when the engine is in operation the continued 
 combustion of the fuel supplies sufficient heat for both vaporiza- 
 
 FIG. 5 
 
 Hornsby-Akroyd vertical engine. 
 
 ^ 
 
810/ 
 
 Steam Engineering 
 
 13 Oil spraying" nozzle. 
 
 14 Control lever. 
 
 15 Hand hole cover. 
 
 16 Crankpin brasses. 
 
 17 Flywheel. 
 
 18 Governor weight. 
 
 19 Cam. 
 
 FIG. 6 
 
 Names of Parts. 
 
 20 Stud carryinsr governor weight. 
 
 21 Crankcase end plate. 
 
 22 Wrist pin bushing. 
 
 23 Exhaust pipe flange. 
 
 24 Speed control segment. 
 
 25 Bracket carrying control lever. 
 
Oil Engines 8100 
 
 tion and ignition. Air necessary for combustion is introduced into 
 the cylinder during the suction period of the cycle, this being a 
 four-cycle engine. Thus the cylinder becomes .charged with air 
 and the vaporizer becomes filled with a spray of oil, both events 
 occurring simultaneously. During the compression period the 
 air in the cylinder, being forced into the vaporizer, becomes prop- 
 erly mixed with the oil and an explosive mixture is formed. The 
 deposit of carbon frequently found where crude oil is used does 
 not enter the cylinder nor come in contact with the piston or 
 piston rings, but is formed in the vaporizer cap. A flange cover 
 at the back of the cap allows the quick removal of this deposit 
 periodically, usually about every sixty hours of running. In the 
 vertical type of the Hornsby-Akroyd engine, shown in section in 
 Figure 5, the vaporizer is placed horizontally on the side of the 
 cylinder, while the air and exhaust valves are located in housings 
 in the top cover. As is the case with the horizontal type, shown 
 in Figure 4, the ignition of the gases in the cylinder is caused 
 automatically by the heat of compression, together with the heat 
 stored in the walls of the vaporizer. The method of governing 
 consists in the automatic lengthening and shortening of the stroke 
 of the oil supply pumps, thus giving very close regulation. 
 
 Remington Oil Engine. — The Remington oil engine is of the 
 vertical type, operating on the two-stroke cycle, the fuel being 
 introduced into the combustion chamber as a liquid and gasified 
 within this chamber. The engine is valveless, the gases being 
 moved into and out of the cylinder through ports uncovered by 
 the movement of the piston, which itself performs also the func- 
 tion of a pump. The action is as follows: 
 
 On the up-stroke of the piston a partial vacuum is created in 
 the enclosed crankcase, causing air to rush in when the bottom 
 of the piston uncovers the inlet port seen directly under the exhaust 
 port (23), Figure 6. On the next down-stroke this air is com- 
 pressed in the crankcase to about four or five pounds pressure per 
 square inch. Meanwhile the mixture of oil, vapor and air al- 
 ready in the cylinder is burning and expanding. When the piston 
 approaches the end of its down-stroke, it uncovers the exhaust 
 port (23), permitting the burnt charge to escape, until its pressure 
 reaches that of the atmosphere. Directly afterward the transfer 
 port on the opposite side of the cylinder is uncovered by the pis- 
 ton, thereby allowing a portion of the air compressed in the crank- 
 case to rush into the cylinder, where it is deflected upwards by the 
 shape of the top of the piston and caused to fill the cylinder, there- 
 by expelling the remainder of the burnt charge. The piston now 
 starts upward, compressing the fresh charge of air into the hot 
 cylinder head. Near the end of the stroke a small oil pump, 
 mounted on the crankcase and controlled by the governor, injects 
 the proper amount of oil through the nozzle (13), Figure 7, into 
 the compressed and heated air. 
 
 This oil is atomized in a vertical direction through a hole near 
 the end of the nozzle. It is therefore vaporized and gasified be- 
 fore there is a possibility of its reaching the cylinder walls. 
 
 The spray of oil is ignited by the nickel steel plug (12), which 
 is kept red hot by the explosions, because the iron walls surround- 
 ing it are protected from radiation by the hood (11). By the 
 burning of the oil spray in the air the pressure is gradually in- 
 creased and the piston forced downward, this being the power or 
 impulse stroke. Near the end of the down-stroke the exhaust 
 port is again uncovered and the burnt gases discharged. 
 
 The operations above described take place in the cylinder and 
 crankcase with every revolution. Each up-stroke of the piston 
 draws fresh air into the crankcase and compresses the air trans- 
 ferred to the cylinder. Each down-stroke is a power stroke and 
 at the same time compresses the air in the crankcase prepara- 
 
810ft 
 
 Steam Engineering 
 
 tory to transferring- it to the cylinder by its own pressure at the 
 end of the stroke. 
 
 The same volume of air enters the cylinder under all conditions, 
 and the power is regulated by modifying the stroke of the oil 
 pump, which may be done by hand or automatically by the gov- 
 ernor in the flywheel. 
 
 1 Cylinder head. 
 
 2 Cylinder. 
 
 3 Piston. 
 
 4 Wrist pin. 
 
 5 Connecting rod. 
 
 6 Counter balance weights. 
 
 FIG. 7 
 
 Names of Parts. 
 
 7 Main bearing cap. 
 
 8 Crankshaft and crankpin. 
 
 9 Crank oil hole. 
 
 10 Crankcase. 
 
 11 Hood on cylinder head. 
 
 12 Igniter plug of nickel steel. 
 
Oil Engines SlOi 
 
 Governor and Control. — The governor is of the centrifugal type. 
 It has an L-shaped weight (18), Figure 7, pivoted to the piece 
 (20) attached to the flywheel. As the engine speed increases the 
 weight (18) tends to swing outward toward the flywheel rim, and 
 thereby moves the arm attached to it so as to shift the cam (19) 
 along the crankshaft toward the left in the figure. 
 
 This cam turns with the shaft, and operates the kerosene oil 
 pump. According to the position of the cam on the shaft, it will 
 impart to the pump plunger a long or a short stroke, thereby in- 
 jecting more or less oil into the cylinder. The long lever pivoted 
 on the bracket (25) moves with the cam (19) and is used for 
 controlling the engine's speed by hand. To stop the engine the 
 handle (14) of the lever is pulled towards the flywheel, thereby 
 interrupting the pump action altogether. 
 
 The handle of the control lever can be fitted with an adjustable 
 speed regulator when required. This device is for use on marine 
 engines to enable the operator to slow down the engine. The 
 speed regulator does not interfere with the action of the governor, 
 but acts in conjunction with it. Whatever the speed of the 
 engine may be, it is under the control of the governor. The engine 
 can be controlled from the pilot house if such an arrangement 
 is desirable. 
 
 All Remington oil engines are built to operate on all grades of 
 ordinary kerosene oil, while several sizes are built especially to 
 operate on lower grade, semi-refined fuels, which have a variety 
 of names and composition, such as fuel oil, Diesel oil, distillate, 
 solar oil, gas oil, etc. 
 
 Starting. — To start the engine, the hollow cast-iron projection 
 rising from the cylinder head is heated by the kerosene torch 
 furnished with the engine. When it is hot, a single charge of oil 
 is injected into the cylinder by working the hand lever connected 
 with the pump. The flywheel is now turned smartly backward, 
 thereby compressing the charge, which ignites before the piston 
 reaches the highest point, and starts the engine in the forward 
 direction. 
 
 After the engine has been started the starting torch may be 
 extinguished. Ignition will take place continuously and the engine 
 will not miss fire under varying loads. 
 
 Cylinder. — The cylinder is provided with a water jacket extend- 
 ing practically its full length. This insures thorough cooling of 
 the piston and increases the efficiency of the lubrication. 
 
 This water jacket is provided with two long hand hole plates on 
 opposite sides of the cylinder, which may be conveniently removed 
 for inspecting and removing sediment from the water jacket space. 
 
 Ignition. — Rising from the center of the head is a hollow cast- 
 iron projection, which contains the nickel steel igniter plug by 
 which the oil gas is ignited. This plug is practically indestrucible 
 by heat, and as it is permanently located at an exact point found 
 correct by trial, it fires the charge at the right moment under 
 all conditions. 
 
 Fuel Pump. — The fuel pump is made of bronze. The valves are 
 made of bronze and are specially designed with very large areas 
 and are very carefully fitted and ground. The plunger is made 
 of tool steel and is hardened and ground. A bronze cup strainer 
 is attached to the lower end of the pump to prevent sediment or 
 foreign matter from reaching the pump valves. 
 
 Head. — The cylinder head is cast separately from the cylinder 
 and has no water jacket about it. The packing between the head 
 and cylinder is copper-asbestos. The head can be removed any 
 number of times without injuring the packing. The nuts which 
 hold the head are fitted to the cylinder studs so that they can be 
 removed without pulling out the studs. 
 
Air Compression 
 
 The compression of air always develops heat, and owing 
 to the fact that compressed air always cools down to the 
 temperature of the surrounding medium before it is used, 
 there is a certain amount of work lost through the dissi- 
 pation of this heat, the lost work being represented by the 
 mechanical equivalent of the dissipated heat. In order to 
 have a given volume of compressed air, at a given pressure 
 at the locality where it is to be utilized for industrial pur- 
 poses it is necessary to carry a higher pressure in the air 
 compressor, for the reason that the heat of compression 
 increases the volume of the air, and the work done in main- 
 taining this excess pressure is work lost, heat energy dissi- 
 pated. Another source of loss of power in air compression 
 is the friction of the air in the pipes through which it is 
 conveyed. Then there are dead spaces to be kept filled; 
 leakages; the resistance offered by the valves; insufficient 
 valve area, and various other causes of loss. The loss of the 
 heat developed by compression is unavoidable. All of the 
 mechanical energy that the compressor-piston exerts upon 
 the air taken into the cylinder is converted into heat, and 
 this heat being dissipated by radiation and conduction, its 
 mechanical equivalent is lost work. It might be inferred 
 from the above statement that the work, or in other words, 
 the heat energy expended in running an air compressor, is 
 expended upon a useless toy, merely for amusement; but 
 not so, because the compressed air, when it again reaches 
 thermal equilibrium with the surrounding atmosphere, ex- 
 pands and does work by reason of that intrinsic energy 
 
 811 
 
812 Steam Engineering 
 
 which is exerted by it in the effort it always makes to change 
 from a given temperature, and volume, to a state of total 
 absence of heat, and indefinite expansion. It is unnecessary 
 to enlarge upon the usefulness of the air compressor, nor 
 to mention the many ways in which compressed air is made 
 to conduce to the welfare and comfort of man, as these 
 facts are well known. A short section will be devoted to a 
 discussion of the various methods employed in the utiliza- 
 tion of this great natural force. 
 
 Air compression is generally accomplished by one of the 
 two methods, technically termed Isothermal, wherein the 
 heat of compression is carried away as fast as it is devel- 
 oped; and Adiabatic in which no heat is removed from the 
 air, and a consequent rise of temperature attends the 
 operation. Diagrams indicating the line of compression 
 will demonstrate the resulting loss of power, due to not 
 extracting the heat developed by compression. 
 
 In the first case the compressed air will be delivered at a 
 temperature corresponding to that at which it entered the 
 cylinder. 
 
 In the second, the air delivered under pressure will be 
 at the high terminal temperature corresponding to that 
 pressure. The first kind of compression is the theoretical 
 ideal; but impossible of attainment. The second method 
 of compression is the one which all pneumatic engineers 
 endeavor to avoid as much as possible. The actual results 
 secured in the best compressors are intermediate between 
 these, but nearer to the second. Other things being equal, 
 the economy of an air compressor is proportional to the 
 degree in which the heat of compression is removed as 
 fast as it is developed. The efficiency of the compressor, 
 therefore, may be said to depend upon the effectiveness of 
 
Fig. 345 
 
 the largest air compressor in the world 
 
 Ingersoll- Sergeant Corliss Air Compressor — Compound Steam 
 
 and Compound Air Cylinders with Semi-Tangye Frame. Steam 
 
 Cylinders, 32 and 60 Inches; Air Cylinders, 52*4 and 32^ 
 
 Inches; Stroke, 72 Inches. 
 
 j 
 
814 Steam Engineering 
 
 the cooling devices adopted, provided that what is gained 
 in this way is not elsewhere wasted in whole or in part. 
 After long experience modern practice in air compressor 
 design recognizes only two practical methods of removing 
 the heat of compression: viz., jacket cooling and inter- 
 cooling. These will be considered in order. 
 
 Jacket Cooling. — Jacket cooling seeks to remove the heat 
 of compression as it arises, through the cylinder walls which 
 are kept at a low temperature by cold water circulating in 
 a surrounding jacket. A brief consideration of the condi- 
 tions will show that jacketed barrel cooling alone can be 
 only a partial and very unsatisfactory solution of the 
 problem. 
 
 With the piston at the beginning of its stroke, the maxi- 
 mum cold cylinder surface is exposed and the cylinder is 
 filled with air at its lowest pressure and temperature. As 
 the piston advances, pressure and temperature increase, 
 while the exposed area of cooling surface diminishes; and 
 when the maximum pressure and temperature are attained 
 near the end of the stroke, there is practically none of the 
 cylinder walls exposed except on the other, or intake, side 
 of the piston; and if the head, too, is jacketed, it alone 
 remains to exert any cooling influence. Furthermore, 
 throughout the stroke only the outside layer of the air can 
 be in contact with the cold surface and, air being a poor 
 conductor of heat, none of the heat from the interior of the 
 air volume is absorbed in the cooling water. Cylinder 
 jacketing is advisable and even essential, in keeping the 
 metal of the working parts at a low temperature, prevent- 
 ing the coking of lubricant upon the cylinder walls and 
 other evils of a hot machine. But it cannot of itself be con- 
 sidered as an adequate solution of the problem of cooling 
 during compression. 
 
o 
 
 H 
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 H 
 
 W 
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 4 
 
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 M 
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 W 
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 50 
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 Ingersoll-Sergeant Corliss High Pressure Air Compressor — 
 Compound Steam and Four Stage Air Cylinders with Semi- 
 Tangye Frame. Steam Cylinders, 20 and 40 Inches ; Air Cylin- 
 ders, 37%, 20%, 12y 2 and 6 Inches; Stroke, 48 Inches; Capacity, 
 2,000 Cubic Feet Per Minute. Pressure, 950 Pounds. 
 
816 Steam Engineering 
 
 However, in those constructions involving the use of a 
 piston inlet tube and valve, not only the barrels but the 
 heads and inlet valves, too, are chilled ; and the piston and 
 tube themselves are kept relatively very cold. Thus the 
 air enters through a cold passage, is in contact on all sides 
 with cold metal throughout the stroke and the maximum 
 effect obtainable from jacketing alone is secured. 
 
 Compound Compression — Intercooling. — If at several 
 points in the stroke, the piston should be stopped for a 
 moment and the air, already partially compressed and 
 heated, be withdrawn long enough to be cooled by some 
 external means to its initial temperature, and then returned 
 to the cylinder to be further compressed, it is evident that 
 a fairly uniform temperature could be maintained in the 
 air volume throughout the range of pressures from initial 
 to terminal. The result would be in effect nearly that of 
 isothermal compression. But while mechanical considera- 
 tions forbid in practice such repeated starting and stopping 
 of the piston, practically the same results may be secured 
 by carrying on the process of compression in several cylin- 
 ders, in the first of which a given low pressure is reached, 
 and the air, at this pressure is discharged through a cool- 
 ing device to a second cylinder, in which it is compressed 
 to a still higher pressure, and discharged through another 
 cooler to a third cylinder for compression to a higher pres- 
 sure, the process being repeated until the required pressure 
 is reached. Such a process, developed to a practical work- 
 ing basis is the compound method of air compression in 
 multi-stage cylinders which has become practically standard 
 in air compressors for the higher pressures. 
 
 Multistage Compression. — Theoretically there is a gain 
 in compound compression, regardless of the pressure, but 
 
Air Compression 817 
 
 with the lower pressures the saving is so small as to be offset 
 by the greater expense and complication involved in having 
 several cylinders, and the losses that are unavoidable in the 
 operation of the additional parts. After extended expe- 
 rience, makers of air compressors have fixed upon 70 to 100 
 lbs. gauge as the maximum terminal pressure that can be 
 best attained in simple cylinders, and for pressures from 
 75 lbs. up they have adopted compound compression in two, 
 three, and four stage machines, the number of stages in- 
 creasing with the pressure required at terminal. At high 
 altitudes, however, with large volumes, and expensive fuel, 
 this dividing line may come at a lower pressure. It is 
 elastic, and depends somewhat upon the conditions* 
 
 The cylinder ratios in a correctly designed compound air 
 compressor are such that the final temperature, and the 
 mean effective pressures are equal in all cylinders, and all 
 of the pistons are therefore equally loaded. The air com- 
 pressed in the first cylinder to a pressure determined by 
 the cylinder ratios is discharged through the outlet valves 
 to an intercooler, where it is split up into thin streams 
 passing over cold surfaces. The best practice involves a 
 nest of tubes through which cold water circulates, and over, 
 and between which the stream of air passes, a complete 
 breaking up and subdivision of the stream being secured 
 by baffle plates, and the tubes themselves. In cases of very 
 high pressure the air may pass through the tubes, for struc- 
 tural reasons. A properly designed intercooler having 
 sufficient cooling area for the volume of air may reduce the 
 temperature of the air compressed in the first cylinder to 
 at least outgoing water temperature. 
 
 From the intercooler this air, entering the second cylinder 
 cold, is compressed to a higher pressure and again 
 
818 
 
 Steam Engineering 
 
 Fig. 347 
 
 ingersoll-sergeant class u a-2" three stage straight line 
 
 steam driven air compressor 
 
Air Compression 819 
 
 reaches a temperature about the same as that attained in 
 the first cylinder. In two stage machines this air will be 
 discharged directly to the receiver without further cooling, 
 unless conditions are such as to render advisable the use 
 of an aftercooler. In three stage machines the second 
 cylinder will be known as the intermediate, from which the 
 air w T ill pass to the second intercooler, undergo a second 
 reduction of temperature, and enter the third cylinder for 
 final compression to required pressure. 
 
 It is seen that multi-stage compression is in effect iden- 
 tical w T ith the theoretical process already suggested, in which 
 the compressing piston was stopped and the air cooled at 
 intervals during the stroke. The maximum cooling effect 
 and saving is secured by making the inter coolers of ample 
 proportions, and providing for the splitting-up of the air 
 stream into thin sheets exposed to cooling action. 
 
 Reduced Strains. — When compression is carried on in a 
 single cylinder, the difference in the pressures at the begin- 
 ning and end of stroke is the total difference between initial 
 and terminal pressures, implying a great variation in 
 strains on the driving mechanism and the structure of the 
 machine. The greatest strains come near the end of the 
 stroke, and are almost instantly relieved when the inlet 
 valves open. Thus the terminal strain on a 20-inch cylin- 
 der having 314 square inches area at 100 pounds pressure 
 will be 31,400 pounds or nearly 16 tons. At 100 revolu- 
 tions this strain is repeated 200 times per minute and de- 
 .mands a very rugged construction. This is a condition not 
 conducive to easy operation in any but the most massively 
 proportioned compressors. In compound compression, on 
 the other hand, the difference between initial and terminal 
 pressures in each cylinder is but a fraction of the total 
 
820 Steam Engineering 
 
 range of pressure. The pressures, furthermore, are par- 
 tially balanced in the several cylinders. The working 
 strains on valves and other parts are consequently greatly 
 diminished, resulting in a greatly reduced wear and liability 
 to breakage, and securing free lubrication and a noticeable 
 improvement in the smooth, easy operation of the machine. 
 These are all facts which contribute to continuous and satis- 
 factory service, with the least possible adjustment and 
 attention. 
 
 As a matter of fact, compounding the air cylinders 
 transfers so much of the load from the later to the earlier 
 part of the stroke .that the maximum terminal strain on 
 bearings is reduced fully 45 per cent over those in single 
 stage compression ; in the above case, from 3,140 "ton min- 
 utes" to 1,727 — obviously a much easier proposition, me- 
 chanically. Misled by this point, it has been common 
 practice to reduce the weight and size of bearings accord- 
 ingly, the mistake being evident, however, when it is remem- 
 bered that the stoppage of circulating water in the cooler 
 at once raises the load on the low pressure piston ; while a 
 broken or damaged outlet valve on the high pressure cylin- 
 der may at any moment throw the same load on all parts 
 as with a single cylinder machine. 
 
 Improved Steam Economy. — The more equable distribu- 
 tion of the load throughout the stroke in compound com- 
 pression, just noted, also aids in securing a higher economy 
 in steam consumption at the other end of the machine ; for 
 it makes possible an earlier cut-off in the steam-cylinder and 
 a consequently greater steam expansion with its attendant 
 saving; late cut-offs not being so necessary to prevent "cen- 
 tering". Multi-stage compression with effective intercoolers 
 between stages, also permits a higher piston speed, which is 
 another factor in steam economy. 
 
Air Compression 
 
 821 
 
 Higher Volumetric Efficiency. — The air remaining in the 
 clearance space at the end of the stroke must be expanded 
 
 Fig. 348 
 
 an illustration oe the ''straight line" principle 
 
 Showing the Arrangement of the Crosshead, Pistons, Piston 
 
 Rods and Connecting Rods of the Class "A" Machine 
 
 on the return stroke to atmospheric pressure before free 
 air can enter through the inlet valves. The higher the pres- 
 
 ^d 
 
822 Steam Engineering 
 
 sure in this clearance space, the greater will be the volume 
 of expansion and the lower the intake efficiency of the 
 cylinder. 
 
 In single stage compression, the clearance pressure is the 
 working pressure, while in compound compression, clear- 
 ance pressure in each cylinder is terminal pressure in that 
 cylinder. But in the intake cylinder this terminal pressure 
 is low usually not over 25 lbs. when the final working pres- 
 sure is 100 lbs. The volumetric efficiency of compound 
 compression cylinders is higher for this reason, the clear- 
 ance in the low pressure cylinders only being in question. 
 Another condition conducive to high volumetric efficiency 
 resulting from compound compression is the fact that term- 
 inal pressures, and consequently terminal temperatures are 
 lower than in single stage cylinders. 
 
 The cylinder walls, and more particularly the heads, with 
 the valves and ports which may be in the heads, are there- 
 fore kept much cooler, and the entering air is not much 
 heated by contact with these parts. A third element enter- 
 ing into the question of capacity is the reduced leakage in 
 stage compression cylinders, through valves, and past pis- 
 tons and rods, with consequent loss of power. It is evident 
 that the higher the pressure the greater the liability to 
 leakage ; and the smaller range of partly balanced pressures 
 in multi-stage cylinder reduces this loss. 
 
 Drier Air. — One of the greatest difficulties encountered 
 in air power transmission is the freezing of the moisture 
 in the air, either in the pipe line, or at the exhaust ports of 
 the air motors. One of the great advantages of the subdi- 
 vision of compression into several stages lies in the oppor- 
 tunity it affords for cooling the compressed air at inter- 
 mediate stages to a temperature at which its moisture will 
 
Air Compression 823 
 
 be precipitated. Of course, practically all of this condensa- 
 tion occurs in the inter, and af tercoolers : and herein ap- 
 pears the necessity for a design which will pass the air at 
 low velocity with full opportunity for cooling on the water 
 tubes. The moisture in suspension is withdrawn through 
 the drain pipe. It is needless to say that unless some pro- 
 vision is made for arresting and withdrawing the condensed 
 water from the intercooler, the value of the latter as an air 
 drier is lost ; for the moisture is carried over into the com- 
 pression cylinders, producing a condition of cutting and 
 leakage in valves and rings and finally working out into the 
 pipe line. Aftercoolers are in some instances as important 
 as intercoolers in removing moisture. 
 
 Better Lubrication. — If air be compressed in a single 
 cylinder from atmospheric pressure and temperature of 
 60° F. to a final pressure of 100 pounds, the maximum 
 temperature attained may be 484° F. This temperature 
 is manifestly destructive to common lubricants, and oils of 
 ordinary quality are burned into a solid, gritty, coke-like 
 or gummy substance which gives the very reverse of proper 
 lubrication, unless proper jacketing devices are employed 
 to keep the parts cold. This deposit, moreover, collecting 
 in ports and valves, may so obstruct and clog them as to 
 cause leakage, and throw an added load on the compressor. 
 If, however, this same volume of air be compressed in the 
 first cylinder to a pressure of 25 pounds, the highest tem- 
 perature which can be reached is only 233° — a heat which 
 will not leave a deposit or destroy the lubricating qualities 
 of good oils such as should be used in compressor work. 
 This air, passing through the intercooler, will be brought 
 back to about the original temperature of 60° and com- 
 pressed (in a two stage compressor) from 25 to 100 pounds 
 
824 Steam Engineering 
 
 in the second cylinder. Here the maximum temperature 
 attained will be but little (if any) in excess of that in the 
 first cylinder, since the heat of compression is a function 
 of the number of compressions, and is almost wholly inde- 
 pendent of the initial pressure. In multi-stage compressors, 
 therefore, the conditions of temperature are seen to be most 
 conducive to thorough lubrication of pistons and valves, 
 tending toward durability and tightness of working parts, 
 with long life and high efficiency of the machine. 
 
 For pressures exceeding 100 pounds per square inch, for 
 economy and safety, compounding is recommended, and 
 for pressures exceeding say 400 pounds per square inch, 
 multi-stage compression. 
 
 For pressures under 100 pounds per square inch, factors 
 must enter into consideration upon which local conditions 
 have a bearing, viz., first cost, comparing cost of installa- 
 tion of single, and two stage machines, cost of fuel, and 
 horse power developed. 
 
 Table 39 of horse powers developed under multi-stage 
 compression is upon the following basis: Water- jacketed 
 cylinders with temperature of air reduced to 60° F. in the 
 intercoolers. Atmosphere at 60°. Three per cent approxi- 
 mately allowed for friction of piston for each cylinder. 
 
Table 39 
 
 horsepower required to compress 100 cubic feet 
 
 free air from atmosphere to various 
 
 pressures. 
 
 Gauge 
 
 Pressure, 
 Pounds. 
 
 One-Stage 
 
 Compression, 
 
 D. H. P. 
 
 Gauge 
 
 Pressure, 
 Pounds. 
 
 Two- Stage 
 
 Compression, 
 
 D. H. P. 
 
 Four-Stage 
 
 Compression, 
 
 D. H. P. 
 
 10 
 
 3.60 
 
 60 
 
 11.70 
 
 10.80 
 
 15 
 
 5.03 
 
 80 
 
 13.70 
 
 12.50 
 
 20 
 
 6.28 
 
 100 
 
 15.40 
 
 14.20 
 
 25 
 
 7.42 
 
 200 
 
 21.20 
 
 18.75 
 
 30 
 
 8.47 
 
 300 
 
 24.50 
 
 21.80 
 
 35 
 
 9.42 
 
 400 
 
 27.70 
 
 24.00 
 
 40 
 
 10.30 
 
 500 
 
 29.75 
 
 25.90 
 
 45 
 
 11.14 
 
 600 
 
 31.70 
 
 27.50 
 
 50 
 
 11.90 
 
 700 
 
 33.50 
 
 28.90 
 
 55 
 
 12.67 
 
 800 
 
 34.90 
 
 30.00 
 
 60 
 
 13.41 
 
 900 
 
 36:30 
 
 31.00 
 
 70 
 
 14.72 
 
 1000 
 
 37.80 
 
 31.80 
 
 80 
 
 15.94 
 
 1200 
 
 39.70 
 
 33.30 
 
 90 
 
 17.06 
 
 1600 
 
 43.00 
 
 35.65 
 
 100 
 
 18.15 
 
 2000 
 2500 
 3000 
 
 45.50 
 
 37.80 
 39.06 
 40.15 
 
 
 
 Table 40 
 
 
 
 CONTENTS OF CYLINDER IN CUBIC FEET FOR EACH FOOT 
 
 IN LENGTH. 
 
 Diameter 
 
 1 
 
 Cubic 
 
 1 
 
 | Diameter 
 
 Cubic 
 
 1 
 
 | Diameter 
 
 Cubic 
 
 in Inches. 
 
 Contents. 
 
 | in Inches. 
 1 
 
 Contents. 
 
 | in Inches. 
 
 ! 
 
 Contents. 
 
 1 
 
 .0055 
 
 m 
 
 .4175 
 
 21 
 
 2.405 
 
 154 
 
 .0085 
 
 9 
 
 .4418 
 
 2154 
 
 2.521 
 
 iy 2 
 
 .0123 
 
 954 
 
 .4668 
 
 22 
 
 2.640 
 
 \y A 
 
 .0168 
 
 9 l A 
 
 .4923 
 
 225^ 
 
 2.761 
 
 2 
 
 .0218 
 
 934 
 
 .5185 
 
 23 
 
 2.885 
 
 254 
 
 .0276 
 
 10 
 
 .5455 
 
 23 y 2 
 
 3.012 
 
 2^ 
 
 .0341 
 
 1054 
 
 .5730 
 
 24 
 
 3.142 
 
 23/ 4 
 
 .0413 
 
 ioy 2 
 
 .6013 
 
 25 
 
 3.409 
 
 3 
 
 .0491 
 
 10 y 4 
 
 .6303 
 
 26 
 
 3.687 
 
 354 
 
 .0576 
 
 11 
 
 .6600 
 
 27 
 
 3.976 
 
 3^ 
 
 .0668 
 
 1154 
 
 .6903 
 
 28 
 
 4.276 
 
 SVa 
 
 .0767 
 
 1154 
 
 .7213 
 
 29 
 
 4.587 
 
 4 
 
 .0873 
 
 113/4 
 
 .7530 
 
 30 
 
 4.909 
 
 454 
 
 .0985 
 
 12 
 
 .7854 
 
 31 
 
 5.241 
 
 4y 2 
 
 .1105 
 
 1254 
 
 .8523 
 
 32 
 
 5.585 
 
 4M 
 
 .1231 
 
 13 
 
 .9218 
 
 33 
 
 5.940 
 
 5 
 
 .1364 
 
 isy 2 
 
 .9940 
 
 34 
 
 6.305 
 
 554 
 
 .2503 
 
 14 
 
 1.069 
 
 35 
 
 6.681 
 
 5V2 
 
 .1650 
 
 uy 2 
 
 1.147 
 
 36 
 
 7.069 
 
 5tt 
 
 .1803 
 
 15 
 
 1.227 
 
 37 
 
 7.468 
 
 6 
 
 .1963 
 
 15 ^ 
 
 1.310 
 
 38 
 
 7.886 
 
 654 
 
 .2130 
 
 16 
 
 1.396 
 
 39 
 
 8.296 
 
 ey 2 
 
 .2305 
 
 165^ 
 
 1.485 
 
 40 
 
 8.728 
 
 63/4 
 
 .2485 
 
 17 
 
 1.576 
 
 41 
 
 9.168 
 
 7 
 
 .2673 
 
 ny 2 
 
 1.670 
 
 42 
 
 9.620 
 
 7*4 
 
 .2868 
 
 18 
 
 1.767 
 
 43 
 
 10.084 
 
 7H 
 
 .3068 
 
 1854 
 
 1.867 
 
 44 
 
 10.560 
 
 734 
 
 .3275 
 
 19 
 
 1.969 
 
 45 
 
 11.044 
 
 8 
 
 .3490 
 
 195^ 
 
 2.074 
 
 46 
 
 11.540 
 
 854 
 
 .3713 
 
 20 
 
 2.182 
 
 47 
 
 12.048 
 
 8/ 2 
 
 .3940 
 
 2oy 2 
 
 2.292 
 
 48 
 
 12.566 
 
826 
 
 Steam Engineering 
 
 Air compression at mountain, or high altitudes is con- 
 siderably more expensive than at sea level. This is due to 
 the fact that the capacity of the compressor decreases in 
 a greater ratio than does the power necessary to compress. 
 At an altitude of 10,000 feet above sea level this extra 
 expense amounts to over 20 per cent. Table 41 gives the 
 efficiencies of the compressor at various altitudes. 
 
 Table 41 
 
 efficiencies of air compressors at different 
 altitudes. 
 
 ft 
 
 Barometric Pressure 
 
 Com- 
 r Cent 
 
 "o 
 
 0. 
 
 u u 
 
 
 
 
 Ph 
 
 .5 
 
 
 d 
 
 
 
 'Ot^ 
 
 
 
 CO . 
 
 T3 D< 
 
 l&s 
 
 
 CD cu 
 CO U. 
 
 CD P 4-1 
 
 £ 
 
 M g 
 
 CC/3 
 
 3 C o 
 
 CO Ui 
 
 fjCffl 
 
 < 
 
 
 P-i a 
 
 *3.£ u 
 
 CO CD 
 
 O d) CD 
 
 
 
 30.00 
 
 14.75 
 
 100 
 
 
 
 
 
 1000 
 
 28.88 
 
 14.20 
 
 97 
 
 3 
 
 1.8 
 
 2000 
 
 27.80 
 
 13.67 
 
 93 
 
 7 
 
 3.5 
 
 3000 
 
 26.76 
 
 13.16 
 
 90 
 
 10 
 
 5.2 
 
 4000 
 
 25.76 
 
 12.67 
 
 87 
 
 13 
 
 6.9 
 
 5000 
 
 24.79 
 
 12.20 
 
 84 
 
 16 
 
 8.5 
 
 6000 
 
 23.86 
 
 11.73 
 
 81 
 
 19 
 
 10.1 
 
 7000 
 
 22.97 
 
 11.30 
 
 78 
 
 22 
 
 11.6 
 
 8000 
 
 22.11 
 
 10.87 
 
 76 
 
 24 
 
 13.1 
 
 9000 
 
 21.29 
 
 10.46 
 
 73 
 
 27 
 
 14.6 
 
 10000 
 
 20.49 
 
 10.07 
 
 70 
 
 30 
 
 16.1 
 
 11000 
 
 19.72 
 
 9.70 
 
 68 
 
 32 
 
 17.6 
 
 12000 
 
 18.98 
 
 9.34 
 
 65 
 
 35 
 
 19.1 
 
 13000 
 
 18.27 
 
 8.98 
 
 63 
 
 37 
 
 20.6 
 
 14000 
 
 17.59 
 
 8.65 
 
 60 
 
 40 
 
 22.1 
 
 15000 
 
 16.93 
 
 8.32 
 
 58 
 
 42 
 
 23.5 
 
 Table 42 gives the volume in cu. ft. of free air that will 
 flow from circular openings, of diameter from 1/64 in. to 2 
 inches, and under pressure of from 2 lbs. to 100 lbs. per 
 sq. in. 
 
Air Compression 
 
 827 
 
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 Steam Engineering 
 
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 Equivalent Vol- 
 ume oi Free Air 
 Discharged per 
 Minute. 
 
 1 Inch. 
 
 VA Inch. 
 \y 2 Inch. 
 
 2 Inch. 
 
 2Y 2 Inch. 
 
 3 Inch. 
 
 4 Inch. 
 
 5 Inch. 
 
 6 Inch. 
 
 7 Inch. 
 
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830 
 
 Steam Engineering 
 
 As before stated there is considerable loss of pressure 
 caused by friction of compressed air in its passage through 
 pipes, and the resistance offered by elbows and valves. 
 Table 43 gives the loss of pressure due to friction for every 
 100 feet of pipe varying in diameter from 1 inch to 14 
 inches, with an initial pressure of 80 lbs at the receiver. 
 
 For the compression part only, of the stroke when com- 
 pressing and delivering air from one atmosphere to a given 
 gauge pressure in a single cylinder, the mean effective pres- 
 sure is always lower than the mean effective pressure for 
 the whole work. This is shown for both Adiabatic, and 
 Isothermal compression by Table 44. 
 
 Table 44 
 
 mean effective pressures. 
 
 Gauge Pressure 1 
 
 Gauge Pressure 2 
 
 Gauge Pressure 3 
 
 Gauge Pressure 4 
 
 Gauge Pressure 5 
 
 Gauge Pressure 10 
 
 Gauge Pressure 15 
 
 Gauge Pressure 20 
 
 Gauge Pressure 25 
 
 Gauge Pressure 30 
 
 Gauge Pressure 35 
 
 Gauge Pressure 40 
 
 Gauge Pressure 45 
 
 Gauge Pressure 50 
 
 Gauge Pressure 55 
 
 Gauge Pressure 60 
 
 Gauge Pressure 65 
 
 Gauge Pressure 70 
 
 Gauge Pressure 75 
 
 Gauge Pressure 80 
 
 Gauge Pressure 85 
 
 Gauge Pressure 90 
 
 Gauge Pressure 95 
 
 Gauge Pressure 100 
 
 Adiabatic 
 
 Isothermal 
 
 Compression 
 
 Compression 
 
 .44 
 
 .43 
 
 .96 
 
 .95 
 
 1.41 
 
 1.4 
 
 1.86 
 
 1.84 
 
 2.26 
 
 2.22 
 
 4.26 
 
 4.14 
 
 5.99 
 
 5.77 
 
 7.58 
 
 7.2 
 
 9.05 
 
 8.49 
 
 10.39 
 
 9.66 
 
 11.59 
 
 10.72 
 
 12.8 
 
 11.7 
 
 13.95 
 
 12.62 
 
 15.05 
 
 13.48 
 
 15.98 
 
 14.3 
 
 16.89 
 
 15.05 
 
 17.88 
 
 15.76 
 
 18.74 
 
 16.43 
 
 19.54 
 
 17.09 
 
 20.5 
 
 17.7 
 
 21.22 
 
 18.3 
 
 22. 
 
 18.87 
 
 22.27 
 
 19.4 
 
 23.43 
 
 19.92 
 
 Table 45 will serve to show the requirements at sea level, 
 of rock drills driven by compressed air, and Table 46 gives 
 the increase of pressure required at various altitudes. The 
 
Air Compression 
 
 831 
 
 factor of multiplication is also given in Table 46 for the 
 different altitudes and pressures. 
 
 Table 45 
 
 approximate amount of air required at sea level 
 for specific sizes rock drills. 
 
 
 Cvlinder. . . 
 
 9 
 
 2\ 21 
 
 21 3 
 
 31 
 
 3^ 31 
 
 Diam. of Hole Drilled. .1-11 
 
 n-n 1-2 : 
 
 LI-2J 11-3 
 
 11-3 
 
 11-3 li-3 
 
 A 
 
 r Pressure. 
 
 Air C 
 
 Dmpression at 
 feet per 
 
 Sea Level 
 minute of 
 
 :>f one Drill — Cubic 
 free air. 
 
 
 60 
 
 60 
 
 65 70 
 
 80 90 
 
 100 
 
 110 120 
 
 
 70 
 
 70 
 
 75 80 
 
 90 105 
 
 115 
 
 125 135 
 
 
 80 
 
 80 
 
 85 90 
 
 100 115 
 
 130 
 
 140 150 
 
 
 90 
 
 85 
 
 90 95 
 
 115 130 
 
 140 
 
 150 170 
 
 
 100 
 
 95 
 
 100 110 
 
 125 140 
 
 155 
 
 170 185 
 
 
 
 
 Table 46 
 
 
 
 
 FACTORS FOR 
 
 COMPUTING REQUIREMENTS 
 
 FOR 
 
 DRILLS 
 
 
 
 AT VARIOUS ALTITUDES. 
 
 
 
 £"« 
 
 u ~ 
 
 FACTOR OF 
 
 MULTIPLICATION 
 
 v > 
 
 Ph & 
 
 
 
 
 
 
 i-J 
 
 T'OO 
 
 
 
 
 
 
 £ c c 
 r o 
 
 2 ,, * 
 
 
 Pre 
 
 5sure at Dri 
 
 11 
 
 
 ^3 «< 
 
 
 
 
 
 
 B> 
 
 
 
 
 
 
 .5 o 
 
 Jj£ j 
 
 60 Lbs. 
 
 70 Lbs. 
 
 80 Lbs. 
 
 90 Lbs. 
 
 100 Lbs. 
 
 « 
 
 < ^^ 
 
 
 
 
 
 
 
 14.7 
 
 1.00 
 
 1.133 
 
 1.26 
 
 1.40 
 
 1.535 
 
 500 
 
 14.45 
 
 1.015 
 
 1.15 
 
 1.28 
 
 1.425 
 
 1.563 
 
 1,000 
 
 14.12 
 
 1.03 
 
 1.17 
 
 1.31 
 
 1.45 
 
 1.59 
 
 1,500 
 
 13.92 
 
 1.048 
 
 1.19 
 
 1.33 
 
 1.48 
 
 1.62 
 
 2,000 
 
 13.61 
 
 1.06 
 
 1.21 
 
 1.35 
 
 1.50 
 
 1.645 
 
 3,000 
 
 13.10 
 
 1.10 
 
 1.25 
 
 1.40 
 
 1.55 
 
 1.70 
 
 4,000 
 
 12.61 
 
 1.131 
 
 1.287 
 
 1.443 
 
 1.60 
 
 1.755 
 
 5,000 
 
 12.15 
 
 1.17 
 
 1.33 
 
 1.495 
 
 1.652 
 
 1.81 
 
 6,000 
 
 11.75 
 
 1.20 
 
 1.37 
 
 1.537 
 
 1.705 
 
 1.87 
 
 7,000 
 
 11.27 
 
 1.24 
 
 1.42 
 
 1.59 
 
 1.76 
 
 1.935 
 
 8,000 
 
 10.85 
 
 1.282 
 
 1.465 
 
 1.645 
 
 1.825 
 
 2.00 
 
 9,000 
 
 10.45 
 
 1.32 
 
 1.51 
 
 1.70 
 
 1.90 
 
 2.07 
 
 10,000 
 
 10.10 
 
 1.365 
 
 1.56 
 
 1.755 
 
 1.968 
 
 2.143 
 
 Installation. — It should be the first care in installing 
 an air compressor to provide it with a suitable foundation. 
 The compressors are self-contained and need foundations 
 only of such design and strength as will insure the com- 
 pressor remaining rigidly in place. A poor foundation costs 
 
832 Steam Engineering 
 
 almost as much as a good one, and as a compressor is 
 usually a permanent fixture, it is advisable to put in a good 
 foundation. 
 
 Blue prints are usually furnished showing location and 
 proper size of foundation bolts for each machine, from 
 which a template can be made by which the foundation bolts 
 can be accurately located. It is of great importance that 
 space should be left around foundation bolts so that they 
 may be left free to move. The setting of the compressor 
 is rendered much easier by taking this precaution. A good 
 way to do is to put a short piece of pipe around each foun- 
 dation bolt, carrying it up with the foundation, thus leav- 
 ing the desired space behind it. In case a concrete founda- 
 tion is installed, the pipe should be full length around each 
 rod. 
 
 Setting Compressor. — After the compressor has been 
 placed in position, block the compressor off the foundation 
 about % inch by means of iron wedges, upon which the 
 compressor should set level. Then the cement should be run 
 into the bolt holes, and also between the base of the com- 
 pressor and foundation to insure true bearing all around. 
 
 Pipe Connections. — The steam and exhaust pipes should 
 be as free from L's as possible, and should be used only in 
 so far as is demanded by expansion of pipes. All pipes 
 should be thoroughly cleaned before starting the com- 
 pressor, so that metal chips from cutting pipes may not be 
 carried into the steam chest and score the valves and seats. 
 
 Proper allowance should be made for the expansion of 
 the steam pipes in connecting them up. 
 
 A drain pipe or bleeder should be provided for live 
 steam, connection being made directly above throttle valve 
 and with the drain, so that the water of condensation may 
 
Air Compression 833 
 
 not have to pass through the steam cylinders. If steam 
 connection for the compressor is taken from the main 
 steam line instead of direct from the boilers, the connec- 
 tion should be taken from the top of the steam pipe, thus 
 avoiding the carrying of condensation. 
 
 The cocks and drains provided for both steam and air 
 ends should be opened after the pump ceases operation, so 
 that the water may be thoroughly drained, thereby avoiding 
 any possibility of freezing. 
 
 In connecting water pipe to jacket around the air cylin- 
 der care should be exercised to allow for proper drainage of 
 cooling surface and pipes. In cold weather the water 
 should be drained, or breakage from freezing might occur 
 in cylinder or jacket. 
 
 In piping air discharge pipe use lead in all joints, and 
 screw up tight, as air leaks are expensive. 
 
 INGERSOLL-RAND AIR COMPRESSOR. 
 
 Fig. 347 shows a view of an Ingersoll-Eand Class "A" 
 straight line air compressor. Its distinctive principle is 
 the direct application of power to resistance, being in itself 
 a distinct unit. This is clearly shown in Fig. 348. In the 
 single stage types the heads, and barrel of the air cylinder 
 are completely water jacketed, thus insuring economical 
 compression. 
 
 This is supplemented in the two stage Class "A-2" types 
 by a horizontal intercooler of effective design. In three 
 stage modifications, high and intermediate pressure cylin- 
 ders, with their valves and high pressure intercooler, are 
 completely submerged in water-box coolers. 
 
 Fig. 349 will serve to give to the student a good idea of 
 the internal construction of this type of air compressors, 
 
834 
 
 Steam Engineering 
 
 each part being numbered and the designation of the parts 
 given in the caption. 
 
 The Meyer cut-off valve gear is clearly shown in the 
 steam end, and the Ingersoll-Sargeant piston inlet valves 
 are shown in the air cylinder, an enlarged view of which is 
 presented in Fig. 350. Formerly all Class "A" com- 
 pressors, except 30-inch stroke machines, were fitted with 
 A5 Air and A14 Steam Regulators, now called "Unloader" 
 and "Regulator." 
 
 Fig. 350 
 ingersoll-sergeant piston inlet valve cylinder 
 
 The standard governor for all Class "A" compressors 
 is the type known as the "Air-Ball" Governor. 
 
 Unloader and Regulator. — The function of the unloader 
 and regulator is to take the load off the air piston 
 when the pressure reaches the desired point, and, 
 at the same instant, to throttle the supply of steam 
 to a point just sufficient to keep the compressor 
 

 
 *■ ■ l 
 
 ■ 
 
 '• •: I 
 
 • -. 
 
 ■ 
 
 
 .■ 
 
 

 FlO. 349 INGERSOLL-f 
 
Inger soil-Rand Air Compressor 835 
 
 turning over. When the pressure of air goes down 
 past the limit, usually ten pounds below the running press- 
 ure, the load is thrown on and the steam again admitted, 
 when compression is resumed in the regular way. This 
 is accomplished as follows: When the weighted lever is 
 down the pipes leading from the unloader to the discharge 
 valves, and to the steam regulator cylinder (No. 155), are 
 filled with air at receiver pressure. The result of this is 
 that the discharge valves act in the nature of check valves, 
 letting the compressed air out of the cylinder, but not in 
 again, and the steam regulator valve (No. 92) is held open, 
 thus admitting of the compression and discharge of the air. 
 When the air pressure rises above the point at which the air 
 is to be carried the weight will lift, resulting in the air 
 (which was under pressure in the pipes referred to) being 
 exhausted. When this pressure is relieved the discharge 
 valves throw wide open, and stay wide open, the result 
 being, of course, that the inlet valves are held shut, the 
 piston has receiver pressure on both sides, and moves back 
 and forth in equilibrium. At the same instant the steam 
 regulator valve closes to a point which admits just enough 
 steam to overcome the engine friction and keep it moving 
 fast enough to prevent centering. The extent to which 
 the steam regulator valve closes is regulated by screwing the 
 adjusting nut (No. 158), Fig. 349, one way or the other, 
 when the compressor is running without a load, until the 
 proper speed is secured. The pressure at which the com- 
 pressor ceases to discharge air into the receiver may be de- 
 termined by the weights hung on the regulator. The safety- 
 valve on the receiver is set to blow at about ten pounds 
 above the regulator pressure, and in practice should rarely 
 or never blow. See that the stop-cocks on the pipes leading 
 
836 Steam Engineering 
 
 from the regulator to the discharge valves are wide open. 
 
 The causes for the regulator not working properly, if the 
 pipes are clear, are to be looked for as follows. 
 See that packing is not too tight, and that the steam valve 
 moves freely. See that valve (No. 146) moves freely. See 
 that plunger (No. 142) moves freely, and that lever does 
 not bind. An occasional cleaning out with kerosene may 
 be necessary if there is any tendency to gum up, which is 
 rarely the case. 
 
 To Remove Inlet Valves. — Loosen the jam nut on the 
 air piston rod, and screw rod out of swivel block; remove 
 back head (No. 99), on air cylinder; slide air piston 
 out on plank; remove piston rings; unscrew screw plugs 
 (No. 107) ; remove inlet valve pins (No. 106) ; these 
 are tapered and can be started out with a drift sent with 
 the compressor for that purpose. When these pins are all 
 out the valves can be removed, and the whole operation 
 can be performed in a short time. 
 
 The valves can then be inspected, and proper repairs 
 made. If there is any deposit of dust or gum in the piston, 
 it can be removed while it is out. If new inlet valves are to 
 be put in, the seat should be scraped, so as to allow the 
 valves to seat air-tight; but this will rarely be necessary. 
 If the valve pins are worn flat where the valve has been 
 striking them, put in a new set of pins when replacing the 
 valve, or turn the pins around so that the valve has a true 
 surface of the pin to strike against. Do not set the pins 
 so that valve will strike against a sharp corner on same, 
 as it tends to wear the valve very rapidly. When putting 
 in valves it is best to use new pins. 
 
 When replacing the piston, those ends of the rings 
 having the same marks should go together; thus, 1-1, 2-8 
 
Ingersoll-Rand Air Compressor 837 
 
 and 3-3 go together. A piece of stout cord lapped around 
 the rings and tied will hold them in place until slipped 
 beyond the counterbore, after which the cord is to be re- 
 moved. 
 
 To Set the Cut-Off Eccentric. — Different portions of 
 the stroke are laid out along the cross-head slide in reference 
 to each end of the stroke; the cut-off valves are screwed 
 on the rod together, and the cross-head being set at any 
 desired part of the stroke the cut-off valve is moved (by 
 turning the hand wheel) so that it just cuts off the port 
 on the main valve. The cross-head is then moved to a 
 corresponding position at the other end of the stroke, when 
 the other cut-off valve should just close the port on main 
 valve. If it does not, the valve Stem should be lengthened 
 or shortened in the eye piece, or one cut-off valve can be 
 put on the stem a thread or two sooner than the other, thus 
 equalizing them for both ends of the stroke. 
 
 There is only one position where they will cut off exactly 
 the same on both ends, and if varied from this the cut-off 
 will be different on both ends of the stroke, being greater 
 relatively on one side if increasing the cut-off, and less 
 relatively on the same side when diminishing the cut-off. 
 
 In other words the cut-off valve may be arranged to close 
 correctly at one half (or any other fixed part of the stroke) 
 but at one fourth cut-off, one valve will be a little ahead of 
 the other, and at three-fourths cut-off the opposite end will 
 be the other way, so that the best that can be done with this 
 style of cut-off is to obtain one correct point of cut-off; 
 that may be one half, or any other desired point, but at 
 all other points it will not be exactly correct. A good way 
 ,to get the engine on its exact dead center is as follows: 
 Turn the fly-wheels till the piston is within an inch or so 
 
838 Steam Engineering 
 
 of the end of its stroke. Scribe a fine vertical line across 
 the edge of the cross-head and guides; scribe another line 
 across the face of the fly-wheel, horizontally, or any con- 
 venient part of the rim, guiding the scriber across the plan- 
 ed edge of a board nailed rigidly in position. Now turn 
 past the centre till the cross-head comes back exactly to the 
 line, and scribe across the straight edge on the rim again. 
 Now draw another line across the rim, exactly half way 
 between the first two, and when the fly-wheel is turned to 
 bring this last line even with the straight edge, the engine 
 will be exactly on the dead centre. The centre at the other 
 end of the stroke may be marked in the same way, after 
 which you can turn to either centre instantly and without 
 liability of error. 
 
 Air Ball Governor. — This device is at the same time a 
 speed regulator or governor, and a means for holding a con- 
 stant air pressure in the receiver. It consists of a special 
 balanced throttle valve, the spindle of which is connected 
 to a fly-ball governor belted from the engine shaft. This 
 throttles the steam supply when the engine speed exceeds 
 the desired limit. 
 
 At one side of the governor is a small air cylinder, the 
 piston of which presses against a lever on which is a sliding 
 weight. This cylinder is connected with the air receiver. 
 The inner end of the weighted lever connects with the 
 spindle of the balanced throttle through a link which 
 makes the action of the small air cylinder independent of 
 the fly-ball governor, so that when the pressure in the 
 receiver exceeds that for which the governor is set, the 
 weighted lever is raised, and the balance throttle closed to 
 a point which admits steam enough to turn the machine 
 over at the speed necessary to supply a volume of air equal 
 to that being drawn from the receiver. 
 
Ingersoll-Rand Air Compressor 
 
 839 
 
 If from any cause the air pressure in the receiver drops, 
 the weighted lever is allowed to drop, by the decrease of 
 pressure in the small cylinder. This opens the throttle, 
 admitting more steam to the engine. If an air pipe should 
 break, or too great a demand is made upon the compressor, 
 keeping the air pressure down so that the air piston does 
 not work, the engine speeds up to a point where the centrif- 
 ugal governor partially closes. 
 
 Setting Meyer Slide Fa/t'tfs.— Set the main eccentric, 
 actuating the lower valve, so that the angle centre advance 
 is somewhere near fifteen degrees, thus : 
 
 Fig. 351 
 mason pump governor 
 
 Put the crank on either dead centre and set the main 
 valve at that end so that it has about l-64th inch lead, and 
 set the nuts against valve temporarily ; now turn the wheels 
 to the other dead centre, and see how far the port edge of 
 valve is from the edge of port. Whatever this distance 
 is, the valve should be moved one-half this distance along 
 its stem, by loosening the nuts on one side and screwing 
 up on the other. When this distance has been exactly di- 
 vided the nuts should be jammed up tight, so that they 
 
840 
 
 Steam Engineering 
 
 just bear against the valve. The valve stem will then be 
 of the correct length. With the crank at dead center move 
 the eccentric around so that the valve has 1/64 inch lead, 
 and fasten the eccentric there ; then turn the crank to the 
 opposite dead center, and note if the lead is the same — if 
 not, average it as close as possible. 
 
 Fig. 352 
 
 MASON PUMP GOVERNOR — SECTIONAL VIEW 
 
 Mason Pump Governor. — Figs. 351 and 352 show the 
 Mason Pump Governor which is used only on compressors 
 for the Pohle air lift outfits, or in case a constant speed is 
 desired irrespective of the load. 
 
 The Mason Pump Governor attaches directly to the 
 eccentric rod of the compressor, and operates a balanced 
 
Mason Pump Governor 841 
 
 valve placed in the steam pipe, thereby exactly weighing the 
 amount of steam to the needs of the compressor and econo- 
 mizing the same. By using the Mason Governor the com- 
 pressor can be set or changed to run any required speed, 
 which will be maintained in spite of variation in load or 
 steam pressure. As all the working parts of the governor 
 are immersed in oil, the wear is reduced to a minimum. 
 
 The Mason Governor consists of a cylindrical shell or 
 reservoir filled with oil or glycerine. The plunger AA 
 (Fig. 352) is connected through the arm I to some re- 
 ciprocating part of the pump or engine, and works in uni- 
 son with the strokes of the compressor, thereby drawing the 
 works in unison with the strokes of the compressor, thereby 
 drawing the oil up through the check valves DD into the 
 chambers JJ, whence it is forced alternatelv through the 
 passages BB, through another set check valves into the pres- 
 sure chamber EE. The oil then returns through the orifice 
 C, the size of which is controlled by a key inserted at N, 
 into the lower chamber, to be repumped as before. In case 
 the engine works more rapidly than is intended, the oil is 
 pumped into the chamber EE faster than it can escape 
 through the outlet C, and the piston GG is forced upward, 
 raising L with its weight and throttling the steam. In 
 case the compressor runs slower than is intended, the re- 
 verse action takes place, the weight on the end of the lever 
 L forces the piston GG down and more steam is let on. As 
 the orifice at C can be increased or diminished by adjusting 
 the screw at N", the governor can be set to maintain any 
 desired speed. The piston GG fits over the stationary 
 piston forming an oil dash pot, thereby preventing fluctua- 
 tion of the governor. This dash pot is fed from pressure 
 chamber E through a passage which is controlled by an 
 
842 Steam Engineering 
 
 adjusting screw K, which is set by a screwdriver (after re- 
 moving the cap screw T). It requires no further attention 
 when once adjusted. 
 
 The governor is placed on the compressor, where the 
 requisite motion can be obtained for operating it, and also 
 in such a way that a rod can be run from the knuckle joint 
 on the top lever to the valve in the steam pipe. Now place 
 the valve in the pipe so that the stem shall be in a direct 
 line with the knuckle joint on the lever, pull out the valve 
 stem to its full extent, then, with the ball on the governor 
 in its lowest position, connect the valve rod with the lever. 
 The governor is then ready to fill. To do this remove the 
 plug in the top of the gauge glass, and with a good clean, 
 light grade of mineral oil fill the governor about half full. 
 The governor is then ready for work. 
 
 To Start. — First start the compressor at about the de- 
 sired speed, and get it working well ; then, placing the key 
 in the key-hole on the side of the governor, turn to the right 
 until the speed of the compressor has diminished . slightly. 
 Then open the throttle valve wide, and the compressor will 
 be under full control of the governor. Should there be 
 much jumping, or fluctuating of the ball remove the screw 
 T, insert a small screwdriver, and screw adjusting screw 
 in at K until it ceases. After the governor has run a little 
 while it will be found that the oil in the glass gauge has 
 lowered considerably. It should then be refilled, so that the 
 glass will stand about half full when the governor is at 
 work. Under no circumstances should the gauge be full, 
 as it will prevent the ball from coming down and opening 
 the valve when the steam lowers. As there is no pressure 
 upon the gauge, the governor may be refilled while in 
 motion by removing the plug in the top of the gauge glass. 
 
Dallett Air Compressor 843 
 
 THE DALLETT AIR COMPRESSOR. 
 
 Fig. 353 shows a sectional elevation of the Dallett Air 
 Compressor built by the Thomas H. Dallett Company of 
 Philadelphia, Pa. This compressor incorporates the essen- 
 tial features of having all parts requiring adjustment or 
 renewals readily accessible, and employing a liberal amount 
 of metal, so placed as to insure rigidity in operation. 
 
 The frame is of the open-fork center-crank type, de- 
 signed to obtain on each size of compressor a greater range 
 of capacity by substituting, when desired, a cylinder of the 
 next larger size than the standard to operate at 100 pounds 
 pressure. 
 
 The main bearings are lined with babbitt metal, which is 
 thoroughly peened in to obviate shrinkage, and then bored 
 and scraped to fit the crankshaft. The duplex-belt, duplex- 
 steam and single-steam machines are supported on deep, 
 rigid sub-bases, thus making the entire machine self-con- 
 tained. 
 
 The steam cylinder and valve gear of the steam-driven 
 machines are designed to give high efficiency. All steam 
 ports are short and direct, and the clearance has been re- 
 duced to a minimum. A plain D balanced slide valve is 
 used on the small and medium-sized machines, and the 
 Meyer balanced adjustable cutoff valve in the larger ma- 
 chines. To provide efficient insulation, all steam cylinders 
 are lagged with mineral wool and jacketed with sheet 
 steel. 
 
 The governor of the steam-driven machine is equipped 
 with a safety-stop device. The governor pulley is situated 
 on the end of the shaft outside of the fly-wheel on the 
 single-steam machine, thus bringing the flywheel as close 
 to the bearing as possible. Formerly, in the case of duplex 
 
844 
 
 Steam Engineering 
 
 Fig. 353 
 sectional elevation of dallett steam driven air compressor 
 
 compressors with compound steam cylinders, if the ma- 
 chine stopped with the high-pressure side on the dead 
 
Dallett Air Compressor 845 
 
 center, it would not start automatically, due to the fact that 
 the high-pressure side takes steam from the line. This 
 trouble has been overcome by using a reducing valve which 
 reduces the live-steam pressure for use in the low-pressure 
 cylinder. The air and steam cylinders are tied together 
 and held in position by means of an internally flanged tie 
 or distance piece. 
 
 Mechanically operated inlet valves are supplied on any 
 size of compressor if desired. These valves are ground to 
 gage and the valve holes lapped to size. 
 
 The air-intake and discharge valves are special features 
 of these compressors. The intake valve is of the automatic 
 poppet type, contained in a malleable-iron cage. 
 
 ALLIS-CHALMERS AIR COMPRESSOR. 
 
 For single-stage air compressors, and in the high-pressure 
 cylinders of two-stage air compressors, the Allis- Chalmers 
 Company, of Milwaukee, uses as a standard the arrange- 
 ment of valves shown in Fig. 354. Eotary valves are used 
 for the inlet, and plain, single-beat poppet valves for the 
 discharge. The inlet valves are driven by an eccentric on 
 the main shaft, and, by means of the wrist-plate, they are 
 given the quick opening and closing, and the slow move- 
 ment when the ports are covered and the valves under 
 pressure, which is characteristic of the Corliss valve-gear. 
 The inlet ports are of ample size, short and direct, and the 
 air is* guided into the cylinder by an easy curve, thus re- 
 ducing the entering friction, and insuring the complete 
 filling of the cylinder with as little loss in pressure, and at 
 as nearly the outside pressure as possible. 
 
 The discharge valves are of the drawn-steel cup type and 
 open automatically when the pressure in the cylinder equals 
 the discharge pressure. 
 
846 
 
 Steam Engineering 
 
 A modification of the valve-gear shown by Pig. 454 is 
 illustrated in Fig. 355. In this gear the inlet valves are 
 operated the same as in Fig. 354, but the discharge valves 
 are mechanically closed, being free to open automatically, 
 and positively closed by plungers operated by connections 
 to a wrist-plate driven by an eccentric on the main shaft. 
 The movement of the plungers of the discharge valves is 
 
 Fig. 354 
 air cylinder with automatic discharge- 
 compressor 
 
 -ALLIS-CHALMERS AIR 
 
 so timed as to positively bring the valves to their seats just 
 as the piston reaches the end of its stroke, thus avoiding 
 any slip of air back by the valves and also to avoid slam- 
 ming when the piston commences to return. As soon as 
 the valves are closed the plungers recede, leaving the valves 
 held to their seats by the discharge air pressure until that 
 point in the return stroke of the piston is reached where 
 
Allis-Chalmers Air Compressor 
 
 847 
 
 Fig. 355 
 aib cylinder with mechanical discharge valve — allis-chal- 
 mers air compressor 
 
 J 
 
848 
 
 Steam Engineering 
 
 the pressure in the cylinder equals the discharge pressure, 
 when the valves are free to open automatically. In closing, 
 the air between the plunger and valve forms a cushion 
 which is so adjusted, and gradually reduced that the valve 
 is brought gently to its seat without noise or pounding. 
 
 A third type of valve-gear is shown in Fig. 356. In this 
 both the inlet and discharge valves are of the rotary pat- 
 
 i 
 
 
 
 
 
 91 ^ 
 
 
 
 
 Fig. 356 
 air cylinder with mechanical discharge valve- 
 mers air compressor 
 
 -ALLIS-CHAL- 
 
 tern, positively operated by independent eccentrics on the 
 main shaft. The inlet valves are the same as described in 
 the two preceding types. The discharge valves are so propor- 
 tioned and adjusted as to close positively just as the piston 
 reaches the end of its stroke, and to open at any predeter- 
 mined maximum discharge pressure required. In addition 
 to the rotary discharge valves, the cylinder is fitted with 
 
Allis-Chalmers Air Compressor 849 
 
 auxiliary poppet valves of the steel-cup type, which serve 
 as relief valves in case the eccentric should slip; or for 
 allowing the air to be discharged from the cylinder, should 
 the pressure, for any cause, fall below that at which the 
 main discharge valves are set to open. 
 
 QUESTIONS AND ANSWERS. 
 
 599. What is one of the results of compressing air? 
 Ans. The development of heat. 
 
 560. What amount of work is lost by the development 
 and dissipation of this heat? 
 
 Ans. The work represented by the mechanical equiva- 
 lent of the' heat developed. 
 
 561. Mention another cause of more or less lost work 
 in air compression? 
 
 Ans. Friction of the air in the pipes through which it 
 is conveyed. 
 
 562. By what two methods is air compression generally 
 accomplished ? 
 
 Ans. Isothermal, by which the heat of compression is 
 carried away as fast as developed ; and adiabatic, by which 
 no heat is removed from the air. 
 
 563. Which of the two is the ideal method of com- 
 pression ? 
 
 Ans. The isothermal. 
 
 564. Is it possible of attainment? 
 Ans. Not entirely. 
 
 565. What may be said of the adiabatic method? 
 Ans. It is one which should be avoided as much as 
 
 possible. 
 
 566. What are the actual results secured in the best 
 compressors ? 
 
850 Steam Engineering 
 
 Ans. They are intermediate between the two meth- 
 ods just mentioned, but nearer to the second method. 
 
 567. Upon what does the efficiency of an air compres- 
 sor depend principally? 
 
 Ans. Upon the effectiveness of the cooling devices. 
 
 568. How many practical methods of removing the 
 heat of compression are there? 
 
 Ans. Two — jacket cooling, and intercooling. 
 
 569. Is jacket cooling of the compressor-cylinder ef- 
 fective ? 
 
 Ans. Not entirely, except with single-stage compres- 
 sion. 
 
 570. What is an intercooler? 
 
 Ans. It is a cooling device interposed between the 
 cylinders of a compound or multi-stage machine, through 
 which the air passes on its way from one cylinder to 
 the next one. 
 
 571. Describe the process of compression by the multi- 
 stage method? 
 
 Ans. A multi-stage compressor has two or more cylin- 
 ders, the intake or low pressure cylinder being the lar- 
 gest in diameter, and in which the air is first compressed 
 to a low pressure, and then passed on into the next cylin- 
 der which is of smaller diameter, where the air is com- 
 pressed to a still higher pressure, and so on in increasing 
 ratio. 
 
 572. How should the cylinder ratios be proportioned? 
 Ans. So that the M. E. P. and the final temperature 
 
 are equal in all the cylinders. 
 
 573. Describe the construction of an intercooler? 
 Ans. It usually consists of a nest of tubes through 
 
 which cold water circulates, and between which the stream 
 of air passes. 
 
Questions and Answers 851 
 
 574. Which method, single-stage, or multi-stage, ap- 
 proaches nearest to the theoretical ideal? 
 
 Ans. The multi-stage, with intercoolers. 
 
 575. Mention another point in favor of multi-stage 
 compression ? 
 
 Ans. It permits a higher piston speed, thus econo- 
 mizing in steam. 
 
 576. What is one of the greatest difficulties encoun- 
 tered in air power transmission? 
 
 Ans. Freezing of the moisture in the air, either in 
 the pipe line, or at the exhaust ports of the air motors. 
 
 577. How may this condition be avoided to a large 
 extent ? 
 
 Ans. By the proper cooling of the air during compres- 
 sion, which will precipitate the moisture, which may then 
 be withdrawn by drain pipes. 
 
 578. What would be the resultant temperature of air 
 compressed from atmospheric pressure, and 60° Fahr., to 
 a final pressure of 100 lbs., provided there was no cooling 
 device ? 
 
 Ans. 484° Fahr. 
 
 579. What effect would this have upon the cylinder 
 lubricant ? 
 
 Ans. It would be burned, and be useless. 
 
 580. What would be the temperature of the same 
 volume of air if compressed in the first, or intake cylinder 
 of a multi-stage machine to a pressure of 25 lbs.? 
 
 Ans. 233° Fahr. 
 
 581. If passed through an intercooler on its way to 
 cylinder No. 2, what would its temperature be? 
 
 Ans. It would be brought back to its original tem- 
 perature of 60° Fahr. and enter the second cylinder under 
 . a pressure of 25 lbs. 
 
852 Steam Engineering 
 
 582. What would the temperature of the same air be 
 if compressed in cylinder No. 2 from 25 lbs. to 100 lbs. 
 pressure ? 
 
 Ans. It would be but little in excess of that attained 
 in the first cylinder, viz., 233° Fahr. 
 
 583. Why would it not attain the temperature stated 
 in the answer to question 578, viz., 484° Fahr.? 
 
 Ans. Because the heat of compression is a function of 
 the number of compressions, and practically independent 
 of the initial pressure. 
 
 584. Why is air compression at high altitudes more ex- 
 pensive than at sea level? 
 
 Ans. Because the capacity of the compressor decreases 
 in a greater ratio than does the power necessary to com- 
 press. 
 
 585. At an elevation of 10,000 ft. above sea level, 
 what is the increase in expense ? 
 
 Ans. Over 20 per cent. 
 
 586. What should be the first care in the installation 
 of an air compressor? 
 
 Ans. To provide a suitable foundation. 
 
 587. What precautions should be observed in the pip- 
 ing? 
 
 Ans. First, there should be as few L's as possible, and 
 second, all pipes should be thoroughly cleaned before start- 
 ing the compressor; third, allowance should be made for 
 expansion. 
 
 588. What is the function of the unloader on the In- 
 gersoll-Eand air compressor? 
 
 Ans. To take the load off the air piston when the pres- 
 sure reaches the desired point. 
 
 589. What is the function of the regulator? 
 
Questions and Answers 853 
 
 Ans. To regulate the supply of steam to the steam 
 end of the compressor. 
 
 590. What type of air inlet valves is this compressor 
 equipped with? 
 
 Ans. Piston inlet valves. 
 
 591. Describe the action of these valves? 
 
 Ans. The air enters and passes through the piston, thus 
 tending to keep it cooled. 
 
 592. What is the function of the Mason pump gov- 
 ernor, with which some air compressors are equipped? 
 
 Ans. To maintain a constant speed regardless of the 
 load. 
 
 593. What kind of inlet valves is the Dallett air com- 
 pressor fitted with? 
 
 Ans. Either mechanically operated valves, or auto- 
 matic poppet valves, as desired. 
 
 594. With what type of valves are the Allis-Chalmers 
 air compressors usually equipped? 
 
 Ans. Eotary valves for the inlet, and single-beat poppet 
 valves for the discharge. 
 
 595. How are the inlet valves operated? 
 
 Ans. By an eccentric on the main shaft, and a wrist 
 plate. 
 
 596. What other type of valve-gear are some of these 
 compressors equipped* with? 
 
 Ans. Both inlet, and discharge valves are actuated by 
 independent eccentrics on the main shaft. 
 
¥ 
 
 l 
 
Refrigeration 
 
 The process of refrigeration consists in the abstraction 
 of heat from a substance, and if air, water, or ice is at 
 hand at a lower temperature than it is desired to attain 
 in the body or substance to be cooled, the cooling element 
 may be employed to perform the refrigeration directly 
 without the aid of a machine. 
 
 If a temperature of 32 degrees and not lower is de- 
 sired ice can be used directly, but if it is necessary to 
 reach a temperature lower than 32 degrees, a mixture of 
 salt and ice or other freezing mixture must be used. 
 
 By mixing one pound of calcium chloride with 0.7 lbs. 
 of snow a solution is produced which will give a tempera- 
 ture of 67° below zero. But freezing mixtures are too 
 expensive to be used for practical purposes, and it there- 
 fore becomes necessary to employ machinery. 
 
 The theory and practice of mechanical refrigeration are 
 based upon the two first laws of thermo-dynamics, that 
 is to say, first: that mechanical energy and heat are 
 mutually convertible; and second, that an external agent 
 is necessary in order to complete or bring about the trans- 
 formation. 
 
 The generally accepted theory concerning the nature of 
 heat together with definitions of the terms, specific heat, 
 latent heat, the mechanical equivalent of heat, etc., are 
 fully discussed in another section of this book and there- 
 fore it will not be necessary to enlarge upon these sub- 
 jects in this connection except to state that the phrase 
 commonly used, "heat is generated by compression," is 
 
 855 
 
856 Steam Engineering 
 
 somewhat misleading, because the amount of heat in the 
 universe is a fixed quantity, and the intrinsic energy 
 possessed by any gas is, under given conditions a quantity 
 that can be actually calculated. Thus if a pound of 
 air at a temperature of 70 degrees Fahrenheit, and at 
 normal atmospheric pressure be taken as an example, the 
 total quantity of energy it possesses is at once known.' 
 If this air be placed in a compressor, and its volume be 
 reduced to say one-half of its original volume, and if 
 this be done so rapidly that there is no time for heat to 
 escape at the end of the compression, that is to say, adia- 
 batically or instantaneous compression without transmis- 
 sion of heat, then its energy, will have been increased by 
 the amount of work done upon it. Its static pressure 
 will be increased, and its temperature will also have risen, 
 by reason of its changed state or condition internally. 
 Now if the temperature be reduced to its former amount, 
 that is to say, to 70 degrees Fahrenheit, its volume will 
 contract, so that a small additional quantity of air will 
 have to be forced in in order that the pressure may re- 
 main unchanged as the temperature is reduced. It will 
 be seen that there will be now, consequently upon the 
 above, rather more than a pound of air to deal with at 
 the higher pressure, and this is what actually occurs in 
 practice, but is a point which is easily overlooked. Now 
 if this air be allowed to expand in a cylinder, it will 
 give up more of its heat in tfrder to overcome the resist- 
 ance, and in this way it will lose or part with more heat. 
 The amount of work done is shown by the indicator card, 
 and can be estimated. The mechanical work done by the 
 air in this expansion is exactly the same as that done 
 upon it during its compression, but there is in addition 
 the further loss of energy, due to the internal work done 
 
Refrigeration 857 
 
 in the air during the expansion, so that what has been 
 done to the air during the entire process has been to 
 extract some of its original store of heat, thus reducing 
 its temperature; and the cold air is now ready to restore 
 its deficiency at the expense of the surrounding hotter 
 bodies. 
 
 It should be borne ; in mind by the student that all 
 bodies contain more or less heat and that heat can neither 
 be created nor destroyed because it remains a fixed quan- 
 tity throughout the universe. 
 
 Therefore the only method by which the temperature 
 of a body or substance can be reduced is by the trans- 
 ference of more or less of the heat contained in the body 
 to some other body or substance. 
 
 The work demanded of a refrigerating machine is to 
 extract heat from a body, say from the air in an enclosed 
 space, such as a refrigerating chamber, and by the ex- 
 penditure of mechanical energy, to sufficiently raise the 
 temperature of this heat to admit of its being carried 
 away by a suitable external agent, the latter being most 
 usually water, which is not only the cheapest one avail- 
 able, but also has a greater capacity for heat, weight for 
 w r eight, than any other known substance, and is taken as 
 the standard of comparison, its specific heat being taken 
 as unity. 
 
 A refrigerating or ice-making machine may then prop- 
 erly be defined as a heat-pump for the simple reason that 
 its main function is the abstraction of heat from one 
 body (the body to be cooled), and continuously and auto- 
 matically transferring that heat to the refrigerating or: 
 cooling agent. 
 
858 Steam Engineering 
 
 REFRIGERATING MACHINES. 
 
 The various inventions for refrigerating and ice-making 
 that are now in rise, can be conveniently classified for the 
 present purpose under the following five principal heads, 
 viz. : 
 
 First, those wherein the more or less rapid dissolution, 
 or liquefaction of a solid is utilized to abstract heat. 
 This is, strictly speaking, more a chemical process. 
 
 Second, those wherein the abstraction of heat is effected 
 by the evaporation of a portion of the liquid to be cooled, 
 the process being assisted by an air-pump. This is known 
 as the vacuum system. 
 
 Third, those wherein the abstraction of heat is effected 
 by the evaporation of a separate refrigerating agent of 
 a more or less volatile nature, which agent is subsequently 
 restored to its original physical condition by mechanical 
 compression and cooling. This is called the compression 
 system. 
 
 Fourth, those wherein the abstraction of heat is ef- 
 fected by the evaporation of a separate refrigerating agent 
 of more or less volatile nature under the direct action 
 of heat, which agent again enters in solution with a 
 liquid. This is termed the absorption system. 
 
 Fifth, those wherein air or other gas is first compressed, 
 then cooled, and afterwards permitted to expand whilst 
 doing work, or practically by first applying heat, so as 
 to ultimately produce cold. These are usually designated 
 as cold-air machines. 
 
 Of the various systems of refrigeration using different 
 refrigerating mediums, only two, namely, the ammonia 
 compression system and the ammonia absorption system 
 have come into anything like general use in this country, 
 
Refrigerating Machines 859 
 
 and these two systems the author proposes to take up and 
 discuss in a practical way beginning with the compression 
 system. 
 
 A compression plant consists of a high-pressure system 
 made up of a condensing coil surrounded by cooling water, 
 with pipes connecting it to the compressor and regulating 
 valve, and a low-pressure system consisting of an evapo- 
 rating coil surrounded by brine, or open to the cold cham- 
 ber, with connecting pipes. A small brine pump for circu- 
 lating the brine is required. 
 
 In this system the process of refrigeration is divided 
 into three distinct stages, viz., compression, condensation, 
 and expansion. 
 
 Anhydrous ammonia is selected as the refrigerating 
 medium on account of its low boiling point ( — 28.6° F.), 
 its high latent heat of vaporization, its non-corrosive 
 effect on iron and steel, and because the pressures under 
 which it is used are such as to render it perfectly safe 
 to handle with properly constructed apparatus. 
 
 When nitrogen and hydrogen combine to form ammonia, 
 one volume of nitrogen unites with three volumes of hy- 
 drogen, hence the chemical formula of ammonia is XH 3 . 
 As the atomic weight of nitrogen is 14 and of hydro- 
 gen 1, the formula also indicates that 14 parts, by weight, 
 of nitrogen, combine with 3 parts of hydrogen, to create 
 17 parts of ammonia. 
 
 Gaseous ammonia can be liquefied at a pressure of 128 
 lbs. to the square inch, at a temperature of 70° Fahr., and 
 at a pressure of 150 lbs. at a temperature of 77° Fahr., 
 the pressure required to produce liquefaction rising very 
 rapidly with the temperature. To liquefy by cold it re- 
 quires to be reduced to a very low temperature, viz., — 85.5° 
 Fahr, 
 
860 Steam Engineering 
 
 The gaseous ammonia is drawn into the ammonia com- 
 pressor, or pump, and is there compressed to a pressure 
 varying from 125 to, 175 pounds per square inch. 
 
 During this compression, the latent heat of the vapor 
 (that is, that quantity of heat which was imparted to it 
 to effect its expansion from a liquid to a vapor) is con- 
 verted into active or sensible heat. 
 
 The vapor, under this high pressure, is forced into the 
 condenser, consisting of a series of pipes over which cold 
 water is allowed to flow (atmospheric condenser), or 
 through pipe coils submerged in a body of cold water 
 (submerged condenser), where the now active and sen- 
 sible heat developed during compression is transferred 
 to the cooling water, thus withdrawing from the vapor 
 that heat which was necessary to keep it in a gaseous 
 condition, and re-converting it into a liquid at the tem- 
 perature and pressure existing in the condenser. 
 
 The ammonia, so liquefied in the condenser, is then 
 allowed to pass in small quantities through a regulating 
 or expansion valve into pipe coils placed in the rooms 
 to be cooled, or in a bath of brine, when it again expands 
 into a vapor, owing to the lower pressure maintained in 
 such pipes, taking up from whatever substance surrounds 
 it, an amount of heat exactly equivalent to that which was 
 given up during condensation. 
 
 The expanded vapor is then drawn back into the com- 
 pressor, again compressed, condensed, and expanded, the 
 cycle of operation being repeated indefinitely with the 
 same ammonia, which is used continuously and which 
 never comes in contact with the substance to be refrig- 
 erated. 
 
 There are two systems of refrigeration by compression* 
 viz., the "wet" system and the "dry" system. 
 
Refrigerating Machines 861 
 
 A dry compression plant with an expansion evaporating 
 system requires: 
 
 One. A medium size compressor. 
 
 Two. A large size evaporating system. 
 
 Three. A large amount of ammonia. 
 
 On the other hand, a wet compression plant having a 
 wet compression evaporating sytem requires : 
 
 One. A large size compressor. 
 
 Two. A medium size evaporating system. 
 
 Three. A medium quantity of ammonia. 
 
 According to Vollman the "wet" system has the fol- 
 lowing advantages over the "dry" compression system: 
 
 One. "By allowing the ammonia vapors to return to 
 the compressor in a partially wet state, we are enabled to 
 work with a higher back pressure, thereby having the am- 
 monia gas in the refrigerator pipes of a higher density 
 than if the vapors were perfectly dry. Furthermore, we 
 are enabled to keep the refrigerator pipes partially filled 
 with liquid ammonia, in consequence of which the surface 
 of the refrigerator can be materially reduced." 
 
 Two. "By keeping the compressor parts at a cool tem- 
 perature, the compressor draws in a greater amount of 
 vapors than where the parts are highly overheated. With 
 a dry compressor, although the cylinder is water- jacketed, 
 the internal parts are kept at a very high temperature, 
 and when the dry ammonia vapors are drawn into the 
 compressor, they immediately get heated up, and by ex- 
 panding prevent the compressor from drawing in its full 
 amount of vapors." 
 
 Three. "By keeping the compressor at a cool tempera- 
 ture, the compressor oil which is taken into the compres- 
 sor through the stuffing box cannot evaporate, but is kept 
 
862 Steam Engineering 
 
 in its liquid state, and as such deposited in the oil col- 
 lector." 
 
 Four. "With the wet compressor system, the engineer 
 in charge knows if sufficient ammonia is circulated through 
 the system or not, by placing his hand on the delivery pipe. 
 If this is fairly warm, a sufficient amount of ammonia is 
 passed through the system." 
 
 Eegarding Tollman's theory (2), that a larger vol- 
 ume of vapor could be handled by the wet compressor at 
 each stroke, the fact must not be overlooked that the in- 
 terchange of heat between the ammonia and the walls 
 of the compressor cylinder is much greater than is gen- 
 erally anticipated. With the vapor wet after compression, 
 the capacity of the plant is reduced, and also the coefficient 
 of performance, so that this condition should be avoided. 
 When superheating is allowed, the capacity is increased, 
 but again the ideal coefficient of performance is reduced 
 slightly. Experiments seem to indicate, however, that a 
 moderate amount of superheat, say 10° to 20°, results in 
 a decided improvement in efficiency. This may be due 
 to the reduction thereby caused in the mechanical losses 
 inside the cylinder, and also in the heat leakage into the 
 ammonia vapor from the cylinder walls during compres- 
 sion. But this is more or less counterbalanced by the 
 widening of the temperature range, so that the coefficient 
 of performance may be reduced, may remain steady, or 
 may be increased according to the charge of ammonia 
 present. 
 
 On the whole there does not seem to be much to choose 
 between "wet" and "dry" compression. The former gives 
 a slightly higher coefficient of performance, the latter a 
 slightly greater amount of refrigeration. 
 
Linde Ice Machine 863 
 
 THE LINDE ICE MACHINE. 
 
 As the Linde ice machine, Fig. 357, is a good example 
 of the workings of the "wet" or humid system, a short de- 
 scription of the construction and operation of the machine 
 will be given. 
 
 The theory of the action of the Linde machine is as 
 follows : 
 
 "So long as ammonia vapor is in a humid or saturated 
 condition (that is, while still in contact with any of its 
 originating liquid), temperature and pressure are func- 
 tions of one another, and to a given temperature belongs 
 a certain pressure. 
 
 "On the contrary, when ammonia (now properly called 
 a gas) is not in contact with any of its mother liquid, its 
 temperature may be very much higher than that corre- 
 sponding to its pressure. 
 
 "For example, the pressure of the steam in a boiler de- 
 pends entirely upon its temperature, which is always equal 
 to that of the remaining water. It is therefore evident 
 that in the case of steam, while in contact with the origi- 
 nating water, temperature and pressure are interdepen- 
 dent. 
 
 "Separate the steam from the water, and apply heat (su- 
 perheat it), and it may have the same pressure at widely 
 different temperatures." 
 
 When a gas or vapor is compressed, the heat equiva- 
 lent of the mechanical work of compression tends to raise 
 its temperature, and consequently its pressure, more rap- 
 idly than would be the case if it would be maintained at 
 constant temperature. 
 
 In the compression of a dry gas, unless heat is with- 
 drawn by means of a water-jacket, or other cooling device, 
 
864 
 
 Steam Engineering 
 
 
 
 K 
 
 c 
 
 co 
 S 
 
Linde Ice Machine 
 
 865 
 
 the adiabatic curve will be traced on the indicator dia- 
 gram. This is the curve which represents the compression 
 or expansion of a gas without loss or gain of heat. 
 
 In the Linde machine the cooling of the vapor in the 
 compression cylinder is effected by the introduction into 
 the latter of a small quantity of liquid ammonia with 
 the gas or vapor at the commencement of each stroke, 
 
 VSOTHS.RMAU • 
 
 AOViNa>NT\C 
 
 m 
 
 (0 
 
 J 
 
 o 
 
 in 
 
 Spring 60 
 
 M. E. P. 59 Lbs. 
 
 Vv... Area 0.05° 
 
 .......... Area 0.69° 
 
 Dry Gas. 
 Fig. 358 
 
 whereby it is cooled down to a refrigerating temperature. 
 The ammonia is carried back to the compressor in a sat- 
 urated condition, and the heat of compression is taken 
 care of in the unexpanded ammonia which in the form of 
 fog or vapor, entered the compressor on the suction stroke. 
 The diagrams Figs. 358 and 359 illustrate the compara- 
 tive efficiency of this method of cooling the compression 
 
866 
 
 Steam Engineering 
 
 cylinder, termed the "wet" system, and the other method 
 wherein a water-jacket system is employed termed the 
 "dry" gas system. 
 
 The initial volume and pressure, and the terminal pres- 
 sure are the same in each case. In the compression of 
 the dry gas, the compression curve necessarily follows for 
 a considerable distance the adiabatic line. 
 
 <SOTHS.RMAU '• 
 
 Spring 60 
 M. E. P. 53 Lbs. 
 Area 0.4°' 
 .. Area 0.34° 
 
 Saturated Vapor. 
 Fig. 359 
 
 This for the reason that the gas coming into the cylin- 
 der from the expansion coils is at a temperature of — 5° 
 F. and no heat can be transmitted from it to the cooling 
 water in the water-jacket until the temperature of the 
 gas has been raised above that of the water, which is prob- 
 ably 60° to 70° F. 
 
Linde Ice Machine 
 
 867 
 
 The compression curve then leaves the adiabatic and 
 during the last part of the stroke, before the discharge 
 valve opens, approaches the isothermal line. 
 
 In the compression of saturated vapor, the unexpanded 
 ammonia begins immediately to absorb the heat of com- 
 pression, and the compression curve at once leaves the 
 adiabatic and approaches the isothermal line, making a 
 
 Fig. 360 
 sectional view of the linde compressor cylinder and valves 
 
 diagram that is much smaller in area and which therefore 
 represents work requiring less power. 
 
 The efficiency ratio of any cylinder cooling device is 
 found by dividing the area between the actual compression 
 curve and the adiabatic curve, by the total area between 
 the adiabatic and isothermal curves. 
 
 "Assuming that the diagrams shown are from eighteen 
 by thirty inch double-acting compressors, running at fifty 
 
868 Steam Engineering 
 
 revolutions per minute, the effective horse-power required 
 for the compression of the saturated vapor would be 
 102.1 horse-power, as against 113.7 horse-power for the 
 dry-gas machine, a gain of 10.2% in favor of the humid 
 system of operation/' 
 
 Fig. 360 shows a sectional view of the Linde compres- 
 sor cylinder, piston and valves. 
 
 It will be observed that the piston and heads are 
 spherical and of the same radius. The valve discs con- 
 form absolutely to this radius, and when the valves are 
 seated these discs are exactly flush with the heads. 
 
 The clearance between the piston and the cylinder head 
 is very small, being only ^ in., therefore the clearance 
 losses are very small, being less than two per cent, of the 
 total cylinder volume. The cylinders are made of clear, 
 hard iron, tested to 1,000 lbs. hydrostatic pressure. The 
 finishing cut through the cylinder is made after it is 
 placed in the frame, the final cut on crosshead guides 
 being taken at the same time, and on the same boring 
 bar, thus insuring their correct alignment. Proper open- 
 ings are provided for the application of the indicator. 
 
 The lubrication of the piston is accomplished in large 
 measure by the moisture in the ammonia itself. Oil is 
 used to seal the stuffing box against the leakage of am- 
 monia. Very little of this oil is carried into the cylinder 
 on the piston rod. 
 
 The piston is ground on the tapered shoulder of the 
 piston rod, and is secured by lock nuts, as shown in Fig. 
 360. The follower head is then screwed on and held 
 firmly in place by the flush nut, which in turn is pre- 
 vented from backing off by a screw set into the face of 
 the follower and riveted over. Those who have expe- 
 rienced the annoying effect of pistons working loose on 
 
Linde Ice Machine 869 
 
 the rod will appreciate the advantages of this method, per- 
 mitting, as it does, the ready removal of the piston when 
 necessary, while at the same time absolutely precluding 
 the possibility of its accidentally becoming loose. Many 
 serious accidents have resulted from inattention to this 
 detail. The piston is packed with removable bull rings 
 and cast-iron packing rings. 
 
 The valves are of large area, the discharge valve being 
 placed at the lowest point of the cylinder, insuring the 
 perfect draining of any liquid present at the end of the 
 compression period. The importance of this feature can- 
 not be overestimated; the many records of compressors 
 wrecked by the piston coming in contact with incompres- 
 sible liquid being familiar to all users of this class of 
 machinery. The stems and discs are of the finest forged 
 steel, set in cast-steel housings. The valve lift is gov- 
 erned by positive stops and controlled by springs. The 
 suction valve is provided with a safety stop to prevent 
 its falling into the cylinder. 
 
 The Linde stuffing-box is shown in section, in Fig. 361 
 — to which reference is now made. The numbers 2, 4, 
 5, 9, 10, 12 and 14 indicate composition packing rings. 
 These should never be used solid but should be cut as 
 shown in sketch "A." Numbers 3, 6, 8 and 11 repre- 
 sent metal rings, made from pure tin. They are intended 
 to keep the rubber rings in proper condition. These rings 
 should always be one-sixteenth of an inch larger than the 
 rod, and should never be cut in two, as otherwise they 
 are apt to score the rod. If necessary to put in new metal 
 rings, disconnect the piston rod from the crosshead and 
 slip the rings over the end of the rod. Under no circum- 
 stances pack the compressor without the metal rings. 
 
Fig. 361 
 sectional view of linde stuffing box 
 
Linde Ice Machine 
 
 871 
 
 Number 7 designates the lantern which forms an oil 
 storage in the middle of the stuffing box. The oil supply 
 is taken in at the point marked "a" through a pipe con- 
 nection from the oil trap. This passage being always 
 open, the oil is forced into the stuffing-box by the high 
 pressure gas in the oil trap, keeping this stuffing-box 
 and lantern always full, and instantly replacing what little 
 oil is carried into the cylinder on the rod. Number 13 
 is the stuffing-box gland which is supplied with oil through 
 
 Fig. 362 
 12-ton linde ice machine- 
 
 -MOTOR OPERATED 
 
 the inlet "b" from a small oil pump operated from the 
 main shaft. This oil overflows at "c" and is led back 
 to the oil pan to be recirculated. 
 
 Number 15 is the oil gland which should be kept just 
 tight enough to keep the oil in the stuffing-box gland. 
 The points of contact with the rod are numbers 1, 13, 
 and 15, and they must fit the rod properly. If it becomes 
 scored and is turned down, these parts must be rebab- 
 bitted. 
 
872 Steam Engineering 
 
 When repacking be sure to place the different parts of 
 the packing in strict accordance with the above instruc- 
 tions and with the cut shown, insuring the best results. 
 Great care should be used not to tighten the stuffing 
 gland 13 more than is necessary to prevent the ammonia 
 from leaking. 
 
 The Linde compressor is of the horizontal double-acting 
 type, and consequently the lines of strain are brought 
 close to, and parallel with the foundations. The machine 
 is so constructed, as to be easily attached to any steam 
 engine, either by being direct connected, or by belting 
 from a counter shaft. In small plants, electric motors 
 are often used for operating these machines. Fig. 362 
 shows an installation of this kind. 
 
 DE LA VERGXE REFRIGERATING MACHINE. 
 
 In the De La Vergne refrigerating machine the cooling 
 of the heated gas is effected by passing it through pipes 
 surrounded by running water. The characteristic feature 
 of this machine consists in the patented system for pre- 
 venting the occurrence of any leakage of gas taking place 
 past the stuffing-box, piston, and valves, and of extract- 
 ing the heat from the gas during compression, by the 
 simple device of injecting into the compressor, at each 
 stroke, a certain quantity of oil or other suitable lubricat- 
 ing fluid. By means of this sealing, lubricating, and cool- 
 ing oil, not only are the stuffing-box, piston, and valves 
 effectually sealed, and the heat developed during compres- 
 sion taken up, but all clearances are entirely filled up. 
 This latter is a matter of great importance, as it ensures 
 a complete discharge of the gas from the pump cylinder, 
 and obviates the above-mentioned loss of power and effi- 
 ciency. 
 
De La Vergne Refrigerator 
 
 873 
 
 This method of sealing the stuffing-box and piston pre- 
 vents leakage and consequent introduction of air into 
 the pump, or wasting of the refrigerating gas at each 
 alternate stroke of the piston without necessitating the 
 packing of piston so tightly as to cause excessive friction. 
 Fig. 363 shows a sectional view of a double-acting De La 
 Vergne compressor fitted with Louis Block's arrangement 
 of valves, the main object of which is to secure the dis- 
 charge of the oil at the lower end of the cylinder taking 
 place immediately after all the gas is gone and not be- 
 
 Fig. 363 
 double-acting type of de la vergne ammonia compressor 
 
 fore, as in the latter case re-expansion will take place, 
 resulting in loss of efficiency of the pump. To effect this, 
 two valves are provided in the lower end of the compressor 
 cylinder, one above the other. 
 
 Either, or both of these valves may open on the down 
 stroke of the piston, until the latter covers the upper 
 one, when only the lower one is left open to the condenser. 
 During the remainder of the stroke of the piston, after 
 the lower valve is also closed, the other or upper one 
 opens communication with an annular chamber formed 
 in the said piston. In the bottom of this annular chain- 
 
874 Steam Engineering 
 
 ber are provided, moreover, valves which open as soon 
 as all the other outlets from the underside of the piston 
 are closed, to ensure which they are loaded with springs, 
 so arranged as to require somewhat more pressure to 
 open them than the discharge valves on the side of the 
 cylinder. The gas, and afterwards the oil, then all pass 
 out through the piston, no trace of the former being 
 present at the completion of the down stroke. In this 
 manner the oil system of sealing can be advantageously 
 retained, and the pump will work as well at the lower 
 side as the upper. 
 
 Fig. 364 shows a complete installation of a refrigera- 
 ting plant on the De La Vergne system, the vertical com- 
 pressor being driven by a horizontal engine. The cir- 
 culation of the ammonia, and the sealing oil is as fol- 
 lows: A is the compressor cylinder, double-acting, and 
 similar in construction to that shown in section in Fig. 
 363. E is the steam engine cylinder. B is the pipe 
 through which the gas is drawn from the evaporating 
 coils into the compressor A. The gas is then discharged 
 by the action of the compressor through the pipe C, into 
 the pressure tank D, where the sealing oil or liquid falls 
 to the bottom. Suitable cast-iron baffle plates are fitted 
 in the upper portion of the pressure tank, which serve 
 to retain the oil, and insure its deposition. From the 
 pressure tank d the gas which still retains the heat due 
 to compression, passes through pipe e into the bottom 
 or lower pipe of the condenser f, wherein, by the cooling 
 action of cold water running over the pipes, the heated 
 gas is first cooled and then liquefied. The ammonia, in 
 this liquid condition, is then led by the small liquid pipes 
 G, through the liquid header h, into the storage tank I, 
 from whence it flows through the pipe J into the lower 
 
Fig. 364 
 complete installation of a de la vergne refrigerating plant 
 
876 Steam Engineering 
 
 part of the separating tank k, which latter must be con- 
 stantly maintained at the very least three-quarters full. 
 L is a pipe of small bore, through which the liquid am- 
 monia is forced, by reason of the pressure to which it 
 is now subjected, to the expansion cock or valve, through 
 which it is injected into the evaporating or expansion 
 coil n which is situated in the room or chamber to be 
 refrigerated or cooled. 
 
 The ammonia gas resulting from the expansion and 
 evaporation of the liquid ammonia in the evaporating or 
 expansion coil K, having absorbed or taken up the heat 
 from the surrounding atmosphere, passes away through 
 the pipes o and b, back again into the compressor cylin- 
 der, and the cycle of operations of compressing, etc., are 
 again performed as above. 
 
 Secondly. Following the course of the oil employed 
 for sealing, lubricating, and cooling purposes, which, as 
 previously mentioned, is heated with the gas during com- 
 pression, and is passed into the tank D, to the bottom of 
 which it falls. From the bottom of the tank D. the heated 
 oil is conducted through a pipe a to the lowermost pipe 
 of the oil-cooler b, which is practically similar in con- 
 struction, but on a smaller scale, to the ammonia con- 
 denser, and is likewise cooled by sprayed or atomized 
 cold water. After being sufficiently reduced in tempera- 
 ture in the oil-cooler b, the oil flows through the pipe c, 
 strainer d, and pipe e, into the oil pump f, which latter 
 is so constructed that it delivers the cooled oil into the 
 compressor, distributing it to either side of the piston or 
 plunger during its compression stroke, that is to say, in 
 such a manner that no oil is furnished during the suction 
 stroke of the piston, but only during the time of com- 
 pressing, thereby cooling the gas during its period of 
 
De La Vergne Refrigerator 
 
 877 
 
 heating. The heated oil, after leaving the compressor, 
 then again returns, together with the hot compressed gas, 
 to the pressure tank D, and follows the same round through 
 the oil-cooler b, strainer d, and oil pump i, back to the 
 compression cylinder. It will be obvious that the oil, as 
 well as the ammonia, is used over and over again, no loss 
 or waste of either taking place except that which may 
 occur through leakage. 
 
 Fig. 365 
 diagram from de la vergne compressor 
 
 Any small quantities of oil, however, that may be car- 
 ried over with the current of the gas from the pressure 
 tank D into the condenser f, pass along with the liquid 
 ammonia into the separating tank k, where, by reason 
 of its greater weight, this oil falls to, and collects at the 
 bottom of the tank. As soon as a sufficient quantity of 
 oil has become thus deposited, it is drawn off, and passed 
 through the oil cooler back to the oil pump. The oil 
 reservoir or tank is also connected to the oil pump f. 
 When the apparatus is employed for the manufacture of 
 
878 Steam Engineering 
 
 ice, the evaporating coils N are placed in a tank contain- 
 ing brine, sufficient space being left between them to 
 allow of the insertion of cans or moulds containing the 
 water to be frozen. As before stated, the exhaust steam 
 of the engine driving the compressor is condensed and 
 purified, and supplies the water to be made into ice. 
 
 The various parts are clearly indicated in Fig. 364 — 
 and the routes taken by the ammonia, the sealing oil, the 
 lubricating and cooling oil, and the steam are shown by 
 the arrows. 
 
 THE TRIUMPH ICE MACHINE. 
 
 Fig. 366 shows a sectional view of the compressor cylin- 
 der and valves of the Triumph double-acting ammonia 
 compressor. 
 
 It will be seen from the illustration that the compres- 
 sor is provided with five valves, viz., three suction valves 
 and two discharge valves, the third, or auxiliary suction 
 valve, being much lighter than the main valves, and per- 
 fectly balanced, and it being claimed by the makers tending 
 greatly to increase the economy of the machine. 
 
 Obviously the main suction valves must necessarily be 
 of sufficient dimensions to admit the charge quickly at 
 the commencement of each stroke, and the springs con- 
 trolling them must consequently have an appreciable ten- 
 sion. It will be readily seen that owing to this fact the 
 pressure of the gas in the cylinder, during admission, 
 must be less than it is in the suction pipe by an amount 
 equal to the tension of these springs. By the use of the 
 above mentioned third, or auxiliary suction valve, which 
 is comparatively light, and is consequently operated with 
 a very light spring, the pressures in the compressor pump 
 
Triumph Ice Machine 
 
 879 
 
 are equalized, and a fuller charge is obtained at each 
 stroke, thereby increasing the efficiency of the machine. 
 v The valves comprise each a guard screwed on to the 
 stem, fitted inside a cage, and so ribbed as to reduce the 
 port area, the bottom of the stem being enlarged for that 
 reason. Stems extending from both the suction and dis- 
 charge valves to the exterior, and passing through stuffing- 
 boxes, admit of their being adjusted from the outside, 
 
 Fig. 366 
 
 double-action horizontal type of triumph ammonia 
 
 compressor 
 
 and any desired degree of tension being put upon the 
 springs. The object of this arrangement is to adjust the 
 machine for working at different pressures, and the rela- 
 tive temperatures thereof. 
 
 There are three packing compartments in the piston- 
 rod stuffing-box, and it is fitted with a suitable relief valve 
 communicating with the suction. The heads are formed 
 concave, and of a radius which enables a larger valve 
 area to be secured. The principal shut-off valves are of 
 
V 
 
 880 Steam Engineering 
 
 such a form of construction as to admit of their being 
 packed while the machine is working, and a feature in 
 the design of this machine which is of by no means in- 
 considerable advantage, is that every portion of the com- 
 pressor is easily accessible. 
 
 CONSOLIDATED REFRIGERATING MACHINE. 
 
 Fig. 367 shows the general form of the Consolidated 
 ice-making and refrigerating machine. It is a compres- 
 sion type of machine, having two single-acting, vertical 
 compressors, and either a horizontal or a vertical engine, 
 which is connected to a center crank, on either side of 
 which are large journal bearings. Power thus transmitted 
 to the shaft is regulated by two flywheels which are of 
 sufficient weight to carry the engine smoothly over the 
 point of maximum compression, and to deliver the power 
 to the compressor. 
 
 It is an advantage to have the crank in the center of 
 the shaft, and to place a flywheel between the engine crank 
 and each pump crank, because this construction gives 
 uniformity and steadiness of motion and diminishes tor- 
 sional strain, vibration and friction of the crank shaft. 
 It also permits the use of a long-stroke Corliss engine, since 
 the stroke of the engine is not limited to the stroke of the 
 ammonia pump, as is the case where the compressor and 
 engine are connected to the same crank pin. In this way, 
 the builders claim to effect a saving of from 10 to 15 
 per cent in the steam consumption. 
 
 Heavy pump columns terminate at the bottom in broad 
 flanges bolted to a substantial foundation plate, cast in 
 one piece and provided with four journal bearings for 
 the crank shaft. Convenient stairways and galleries are 
 
Consolidated Ice Machine 
 
 8. 1 
 
 provided to furnish access to the upper part of the ma- 
 chine. As seen in Fig. 368 the compressor or ammonia 
 pump is single-acting, compressing only on the up-stroke, 
 and the gas has free entrance to, and exit from the cylin- 
 
 Fig. 307 
 vertical consolidated refrigerating machine 
 
 der below the piston, thus keeping the pump cylinder and 
 piston cool. 
 
 An oil chamber, which effectually seals the stuffing-box 
 around the pump piston rod, is formed in the lower part 
 of the pump. As the pressure on the stuffing-box end of 
 
882 
 
 Steam Engineering 
 
 Fig. 368 
 
 CROSS-SECTION OF THE SIMPLE-ACTING AMMONIA COMPRESSOR 
 
 the pump is only the direct evaporator pressure, there is 
 no chance for the escape of ammonia. Equalization of 
 
Consolidated Ice Machine 
 
 883 
 
 the temperature and cooling of the compressor is effected 
 by encasing it in a copper water jacket. 
 
 In the construction of the piston, no bolts or nuts are 
 used, and there are, therefore, no cavities or chambers 
 into which the gas can be compressed. Since the piston 
 travels flush with the pump head, all of the gas is ex- 
 
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 Fig. 369 
 suction valve showing safety device 
 
 pelled at each stroke. The pistons are fitted with spring 
 rings that are first turned elliptical, and afterward re- 
 turned on a mandrel until they fit the cylinder exactly. 
 
 As shown in Fig. 368 the stuffing-boxes are operated 
 by a worm-gear device so that, while the machine is run- 
 ning, a turn of the hand-wheel accurately adjusts the 
 
884 Steam Engineering 
 
 stuffing-box gland and thus makes unnecessary the dif- 
 ferent and frequently dangerous use of a wrench or span- 
 ner and also avoids the possibility of cutting the piston 
 rod by uneven adjustment of the gland. 
 
 Connections for the suction and discharge pipes are 
 made outside of the pump head so that, when it is de- 
 sired to remove the head, neither of these connections need 
 be disturbed. Discharge and suction valves, compressor 
 heads, piston and piston rods, all are easily removed with- 
 out breaking any ammonia connections. 
 
 Fig. 368 shows the suction and discharge valves which 
 are located in the pump head. The suction valve, Fig. 369, 
 is balanced, thus allowing the pump to fill with expanded 
 gas from the evaporator with no loss of pressure. As 
 shown in Fig. 369, the valves are provided with a safety 
 device which renders it impossible for them to get into 
 the cylinder. Cushioning of the discharge valves ensures 
 noiseless action and, since both suction and discharge 
 valves are set in steel cages, and held in position in the 
 pump head by means of yokes and set screws, it is but 
 a moment's work to remove a valve and put a duplicate 
 in place. 
 
 As seen in Fig. 367 the machine is driven by a Feath- 
 erstone Corliss engine resting on substantial base plates 
 which are extended on one side for the dashpots. The 
 valve motion is of the improved Corliss type, having the 
 liberating catches made of hardened steel of such form 
 that eight wearing surfaces are available, by change of 
 position, each new position restoring the valve motion to 
 its original setting. 
 
 Horizontal Type. In this form, the Featherstone ma- 
 chine is built with a horizontal engine and a horizontal, 
 double-acting compressor, and has a straight crank shaft 
 
Fig. 370 
 
 HORIZONTAL DOUBLE-ACTING MACHINE 
 
886 Steam Engineering 
 
 with the flywheel placed in the middle between the two 
 main bearings as shown in Fig. 370. These machines are 
 mounted on the heavy duty Tangye frame which is almost 
 universally used by builders of double-acting compressors. 
 Provision is made for cooling the compressor cylinder by 
 means of a water jacket so that it may be operated as a 
 dry, or humid gas machine. As shown in Fig. 370, the 
 machine is driven by a Featherstone-Corliss engine, hav- 
 ing a heavy frame similar to that of the compressor, but 
 any type of engine may be used and, if necessary, the 
 compressor can be driven by belt. 
 
 Figure 371 shows the manner in which the compressor 
 cylinders are pressed into the frame so as to form a water 
 jacket. The valves are placed in the compressor head in 
 a way that will permit of their easy removal and, since 
 the discharge valves are located at the lowest part of 
 the cylinder, perfect draining at the end of the compres- 
 sion period is assured. This makes it impossible for the 
 machine to be wrecked by the piston coming in contact 
 with an incompressible liquid at the end of the stroke. 
 The clearance is less than ^ inch, thus giving good 
 efficiency by permitting the piston to discharge all of 
 the gas at each stroke, so that on commencing a new 
 stroke, gas is immediately drawn into the cylinder. 
 
 In the horizontal machine, the valves are like those 
 used in the consolidated compressors, the stems and discs 
 being of forged steel set in cast-steel housings. Lift 
 of the valves is given by cushion springs and controlled 
 by compression springs and the suction valves are of the 
 Featherstone safety type, so that it is impossible for them 
 to fall into the cylinder. The piston is screwed to the 
 piston rod by a jam nut, and the connecting rod is pro- 
 
Fig. 371 
 section of compressor showing water jacket 
 
888 Steam Engineering 
 
 vided with adjustable wedges for taking up the wear of 
 the boxes. 
 
 In a double-acting, ammonia compressor, the stuffing- 
 box is one of the most vital parts. Referring to Fig. 372, 
 letters A, B, C, D, E and F indicate composition split 
 packing rings and letters Q, R, S, IT, V and W denote 
 pure tin rings of .an inside diameter ■£$ inch larger than 
 that of the piston rod. These rings should never be split. 
 
 J is a lantern which forms an oil storage reservoir in 
 the stuffing-box, the oil being taken in at the point marked 
 K from a pipe connected to the oil trap. This passage 
 being always open, the oil is forced into the stuffing-box 
 by the high pressure of the gas in the oil trap, thus keep- 
 ing the lantern full and instantly replacing what little 
 oil is carried into the cylinder by the rod. L is a lantern 
 which at the point marked M has a pipe connection to 
 the suction line so that any ammonia gas which may have 
 escaped the packing rings C, D, E and F is drawn back. 
 By this device, packing rings A and B have to withstand 
 only the suction pressure. N is the stuffing-box gland 
 which has a chamber supplied with oil through from 
 a small rotary oil pump operated from the main shaft. 
 P is the oil gland which should be kept just tight enough 
 to keep the oil in the stuffing-box gland. 
 
 Points of contact with the rod are G, H and I and 
 they are made an exact fit. If the rod becomes scored 
 and is turned down, these parts must be rebabbitted. To 
 tighten the stuffing-box gland it is only necessary to ad- 
 just the nut T, which is a pinion nut and is in mesh 
 with the inside gear and the other two pinion nuts. 
 
 As shown in Fig. 373, the dashpot is of a special de- 
 sign, and allows for the adjustment of both vacuum and 
 cushion. It is placed on an extension of the cylinder foot 
 
Consolidated Ice Machine 
 
 889 
 
 Fig. 372 
 stuffing-box of the double-acting compressor 
 
 and connected by the usual vertical link rod to the crank 
 on the valve stem. The central cylinder A acts as a 
 
890 
 
 Steam Engineering 
 
 guide and piston, while the pot B rises and falls, and 
 by so doing draws air into the chamber C through the 
 passage D, the vacuum C being regulated by the position 
 of the needle valve E. As the pot falls, air escapes from 
 C through valve H, and the fall is free until the lower 
 end of the pot cushions into a chamber K formed by 
 drawing up the ring F by means of the screw G. The 
 position of F determines the amount of the cushioning 
 and the leather washer E prevents hammering at the end 
 of the fall. 
 
 Fig. 373 
 section of the dash pot 
 
 Double-pipe Ammonia Condenser. This type of con- 
 denser consists of two series of coils, one within the ether, 
 and is usually built in four different forms having 2-inch 
 and 1.25-inch, 2.5-inch, 3-inch and 2-inch pipes or, 
 having the upper outside pipes 2.5 inches and the lower 
 pipes with all of the inner pipes 1.25 inch. Of these forms, 
 the first is used most extensively, but the second is used 
 whenever extra strong pipe is required, and the third when 
 
Double Pipe Ammonia Condenser 
 
 891 
 
 extremely dirty water is to be handled. The ammonia cir- 
 culates downwards through the annular space between the 
 two sets of pipe coils. By this arrangement a compara- 
 tively small charge of ammonia is required, owing to the 
 narrowness of the space between the pipes. 
 
 Occupying small space, the condenser can be placed in 
 a basement or other convenient place. Since the flow of 
 
 Fig. 374 
 return bend for the atmospheric condenser 
 
 ammonia gas and the cooling water are in opposite di- 
 rections, the hottest gas comes in contact with the hottest 
 water and thus fully utilizes the cooling effect of the water. 
 Fig. 374 shows a sectional view of the atmospheric 
 condenser return bend, and Fig. 375 a view of the return 
 bend which is used for the double-pipe ammonia con- 
 denser and also for the brine cooler. Fig. 376 shows 
 
892 
 
 Steam Engineering 
 
 the double-pipe condenser in which, owing to the con- 
 struction of the return bend, it is possible to remove and 
 replace any length of pipe without tearing down the 
 whole coil as is necessary where double-pipe connections 
 are made with screwed bends. 
 
 Condensers are furnished complete with gas, liquid, 
 pump-out, and water headers and one of the special fea- 
 tures is the construction of the liquid and purge head- 
 ers which are made with special tee valves. Owing to 
 the design, additional sections can be added at any time 
 as enlargement of the plant may require. 
 
 Fig. 375 
 double-pipe return bend 
 
 Pig. 377 shows a double-pipe brine cooler, which is 
 built on the same general plan as the ammonia con- 
 denser, but is made of 2 and 3-inch pipes. Liquid am- 
 monia enters and is expanded in the bottom pipe and the 
 gas is drawn off at the top, while the brine is pumped 
 into the top and circulates downward, through the an- 
 nular space between the two pipes. 
 
 There are two distinct methods of utilizing refriger- 
 ation, viz., the Brine System and the Direct Expansion 
 System. In the former the coils of pipe in which the 
 ammonia is expanded are placed in a tank containing a 
 

 Fig. 376 
 double-pipe ammonia condenser 
 
Fig. 377 
 double-pipe brine cooler 
 
Brine, and Direct Expansion Systems 895 
 
 solution of salt, or calcium chloride of such density as 
 to insure a low freezing point. This body of brine, after 
 being reduced to a low temperature by the transfer of 
 its heat to the expanding ammonia, is pumped through 
 coils of pipe in the rooms to be cooled, taking up from 
 the atmosphere of such rooms a part of its heat. It is 
 then returned to the brine tank, recooled and again cir- 
 culated through the rooms. 
 
 In the direct expansion system, the expansion pipes 
 are placed in the rooms to be cooled, the heat necessary 
 for the expansion of the ammonia being drawn directly 
 from the atmosphere surrounding the pipes. 
 
 Of the two systems, the direct expansion system is 
 probably the most efficient as may be seen by the follow- 
 ing summary of its advantages over the brine system : 
 
 1st. All intermediate agencies are dispensed with, the 
 refrigeration being produced at the place where it is uti- 
 lized. Every transfer of energy means loss. The brine 
 tank, even if insulated, furnishes immense surface for 
 loss by radiation. 
 
 2d. The whole plant is much simpler, considerable aux- 
 iliary apparatus, such as pumps, etc., is unnecessary, the 
 requirement of power is therefore reduced, and repairs are 
 correspondingly lessened. 
 
 3d. The expansion surface is enlarged and better dis- 
 tributed, making possible the using of the entire capacity 
 of the compressor to the best advantage. 
 
 4th. The ammonia is expanded at a much higher tem- 
 perature and pressure, and is therefore drawn back to the 
 compressor at higher density, resulting in the machine cir- 
 culating a much greater weight of ammonia per minute. 
 Each pound of ammonia has just so much potential re- 
 frigerating energy, and the capacity of a compressor is 
 
896 Steam Engineering 
 
 therefore dependent solely upon the weight of ammonia 
 pumped in a given time. For example, if it is desired 
 to maintain a temperature of 32° F. in a certain room, 
 it will require a compressor displacement of 22 per cent 
 more with the brine system than with direct expansion. 
 
 5th. The brine system is much more expensive to in- 
 stall, owing to the far greater quantity of pipe required, 
 the additional pumps, tanks, etc. 
 
 One of the advantages claimed for the brine system is 
 the ability to store refrigerating energy in the brine tank, 
 which may be drawn upon during the night, thus ren- 
 dering the continued operation of the compressor unnec- 
 essary. It has been claimed that by doing this the fuel 
 consumption is reduced; but this is not good logic, since 
 just so much work must be done to produce a given quan- 
 tity of refrigeration, and it makes no difference whether 
 this work is distributed throughout the twenty-four hours, 
 or is crowded into a shorter period. If the work is to 
 be done in a short time the compressor must be corre- 
 spondingly larger. 
 
 The development of the ice-making industry during 
 the past ten years has been astonishingly rapid. This 
 may be attributed to the fact that the ice-using public 
 has come to a realization of the vast superiority, from 
 a hygienic standpoint, of manufactured, over natural ice, 
 and to the further fact that owners of electric light plants, 
 mills, water-works and other power plants have found 
 that the ice-making business is one that is peculiarly 
 adapted to being operated in combination with other in- 
 dustries requiring the use of power. 
 
 Ice Making. Ice is made artificially by either the can 
 system or plate system. 
 
JTTTTnX 
 
 3t2Z 
 
 S 
 
 F\\ 
 
 
Ice Making 897 
 
 In order to obtain absolutely pure and crystal ice by 
 this system, a complete distilling and filtering process 
 must be employed. Water, when evaporated into steam, 
 parts with all of its impurities; the steam is condensed, 
 the water of condensation being entirely pure. All the 
 air must then be expelled from it, as otherwise it will 
 freeze into opaque or so-called "snow" ice. 
 
 The inserted illustration, Fig. 378, shows an arrange- 
 ment for the production of can ice from distilled water. 
 The compression and condensation of the ammonia is 
 carried on as already described, the ammonia being ex- 
 panded in expansion coils placed in the freezing tank. 
 (18.) 
 
 The steam generated in the boiler is first used to drive 
 the steam-engine. The exhaust steam then passes to the 
 steam condenser (10), first passing through an oil ex- 
 tractor (9), where any lubricating matter which has been 
 carried along from the cylinder is removed. The steam 
 condenser is designed on the same principle as the am- 
 monia condenser, being a series of pipes over which cool- 
 ing water is allowed to flow. The exhaust steam is not 
 usually sufficient to make the full capacity of ice, and 
 sufficient live steam is therefore supplied to the steam 
 condenser to make up the deficiency. The water result- 
 ing from the condensing of the steam passes to the skim- 
 mer (11), where any oil that may pass the oil extractor 
 is removed. 
 
 From the skimmer the water goes to the re-boiler (12), 
 at the bottom of which is placed a small steam coil by 
 means of which the water is kept boiling and the air con- 
 tained in it expelled. It then passes to the flat cooler 
 (13), an apparatus similar to a condenser, where its tem- 
 perature is reduced to that of the cooling water available. 
 
ARRANGEMENT OF AN ICE PLANT. 
 
898 Steam Engineering 
 
 Thence it is led to the filters (14), which are furnished 
 in duplicate so that one may be shut off and cleaned with- 
 out interfering with the operation of the plant. In 
 special cases, where the nature of the water requires it, 
 sponge, silicate, or bone charcoal filters are used. From 
 the filters the water passes to the cold-water storage tank 
 (15), which contains an ammonia expansion coil. By the 
 use of the coil the distilled water is reduced to the freez- 
 ing temperature before going into the freezing cans. 
 
 By means of a can filler (17), so arranged 'that the 
 water is automatically shut off when the can is filled 
 to the proper depth, the galvanized iron freezing cans are 
 filled with distilled water from the cold-water tank. The 
 freezing tank (18) is usually made of iron or steel and 
 thoroughly insulated at the bottom and sides. It is pro- 
 vided with suitable hardwood frame and covers, and has 
 an efficient agitating device for keeping the brine in mo- 
 tion. The brine acts as a medium for the transfer of 
 the heat from the distilled water within the cans to the 
 expanding ammonia in the expansion coils, which are 
 placed longitudinally of the tank and between which the 
 cans are inserted. 
 
 The ice when frozen is hoisted out of the tank by 
 means of the hoisting apparatus (19). The ice is 
 loosened from the cans by the use of warm water from 
 the condenser, either by employing a sprinkling apparatus 
 (20) or by dipping the can bodily into a tank. 
 
 Table 47 gives the number of cubic feet of ammonia 
 gas required per minute per ton of refrigeration in twenty- 
 four hours: 
 
Ice Making 
 
 899 
 
 Table 47 
 
 cubic feet of gas that must be pumped per minute at 
 
 different condenser and suction pressures, to 
 
 produce one ton of refrigeration 
 
 in twenty-four hours. 
 
 to 
 a 
 
 O 
 
 P& 
 
 
 Temperature 
 
 of the Gas 
 
 in Degrees 
 
 F. 
 
 
 
 u 
 
 3 . 
 bo en o* 
 
 c £gq 
 
 'life 
 
 o a 
 
 65° 
 
 70° 
 
 75° 
 
 80° 
 
 85° 
 
 90° 
 
 95° 
 
 100° 
 
 105° 
 
 fa w 
 
 
 Correspondin 
 
 g Con 
 
 denser 
 
 Pressure (gauge), 
 
 
 
 
 
 
 pounds per square inch. 
 
 
 
 u oj 
 O 3^ 
 
 Ut/1 
 
 103 
 
 115 
 
 127 
 
 139 
 
 153 
 
 168 
 
 184 
 
 200 
 
 218 
 
 
 
 
 
 
 
 
 
 
 
 G. Pres. 
 
 
 
 
 
 
 
 
 
 
 —27 
 
 1 
 
 7.22 
 
 7.3 
 
 7.37 
 
 7.46 
 
 7.54 
 
 7.62 
 
 7.70 
 
 7.79 
 
 7.88 
 
 —20 
 
 4 
 
 5.84 
 
 5.9 
 
 5.96 
 
 6.03 
 
 6.09 
 
 6.16 
 
 6.23 
 
 6.30 
 
 6.43 
 
 —15 
 
 6 
 
 5.35 
 
 5.4 
 
 5.46 
 
 5.52 
 
 5.58 
 
 5.64 
 
 5.70 
 
 5.77 
 
 5.83 
 
 —10 
 
 9 
 
 4.66 
 
 4.73 
 
 4.76 
 
 4.81 
 
 4.86 
 
 4.91 
 
 4.97 
 
 5.05 
 
 5.08 
 
 — 5 
 
 13 
 
 4.09 
 
 4.12 
 
 4.17 
 
 4.21 
 
 4.25 
 
 4.30 
 
 4.35 
 
 4.40 
 
 4.44 
 
 
 
 16 
 
 3.59 
 
 3.63 
 
 3.66 
 
 3.70 
 
 3.74 
 
 3.78 
 
 3.83 
 
 3.87 
 
 3.91 
 
 5 
 
 20 
 
 3.20 
 
 3.24 
 
 3.27 
 
 3.30 
 
 3.34 
 
 3.38 
 
 3.41 
 
 3.45 
 
 3.49 
 
 10 
 
 24 
 
 2.87 
 
 2.9 
 
 2.93 
 
 2.96 
 
 2.99 
 
 3.02 
 
 3.06 
 
 3.09 
 
 3.12 
 
 15 
 
 28 
 
 2.59 
 
 2.61 
 
 2.65 
 
 2.68 
 
 2.71 
 
 2.73 
 
 2.76 
 
 2.80 
 
 2.82 
 
 .20 
 
 33 
 
 2.31 
 
 2.34 
 
 2.36 
 
 2.38 
 
 2.41 
 
 2.44 
 
 2.46 
 
 2.49 
 
 2.51 
 
 25 
 
 39 
 
 2.06 
 
 2.08 
 
 2.10 
 
 2.12 
 
 2.15 
 
 2.17 
 
 2.20 
 
 2.22 
 
 2.24 
 
 30 
 
 45 
 
 1.85 
 
 1.87 
 
 1.89 
 
 1.91 
 
 1.93 
 
 1.95 
 
 1.97 
 
 2.00 
 
 2.01 
 
 35 
 
 51 
 
 1.70 
 
 1.72 
 
 1.74 
 
 1.76 
 
 1.77 
 
 1.79 
 
 1.81 
 
 1.83 
 
 1.85 
 
 Absorption Process. Besides ammonia, there are various 
 other refrigerating agents employed in the compression 
 system, among which may be mentioned ether, methyl- 
 chloride, sulphurous acid, and carbonic acid, but space will 
 not permit a further discussion of the compression system, 
 and the absorption process will now be taken up. 
 
 The principle involved in the operation of apparatus 
 for the abstraction of heat by the evaporation of a sepa- 
 rate refrigerating agent of a volatile nature under the 
 direct action of heat, and without the use of power, which 
 agent again enters into solution with a liquid, is, more 
 a chemical, or physical action than a mechanical one. It 
 is founded upon the fact of the great capacity possessed 
 by water for absorbing a number of vapors having low 
 
900 Steam Engineering 
 
 boiling points, and of their being readily separable there- 
 from again, by heating the combined liquid; hence it is 
 commonly known as the absorption process. 
 
 The absorption process was invented by Ferdinand 
 Carre about the year 1850. This system involves the 
 continuous distillation of ammoniacal liquor, and requires 
 the use of three distinct sets of appliances, viz. : 
 
 First, for distilling, condensing and liquefying the am- 
 monia. Second, for producing cold, by means of a re- 
 frigerator, and absorber, a condenser, a concentrator and 
 a rectifier. Third, pumps for forcing the liquor from 
 the condenser into the generator for redistillation. The 
 three operations are each distinct from the other, but 
 when the apparatus is in actual work they must be con- 
 tinuous, and are dependent upon one another, forming 
 separate stages of a closed cycle. 
 
 An advantage of the absorption process is that the bulk 
 of the heat required for performing the work is applied 
 direct without being transformed into mechanical power. 
 The first machines, however, constructed upon this prin- 
 ciple were very imperfect in operation, by reason of the 
 impossibility of securing an anhydrous product of dis- 
 tillation, and as the ammonia distilled over contained as 
 much as 25 per cent of water, a very large expenditure of 
 heat was required for evaporation, and the working of 
 the apparatus, moreover, was rendered intermittent. This 
 was owing to the distillation, which is the most important 
 operation, and has of necessity to be executed in a rapid 
 manner, being, in the first machines, very imperfectly ef- 
 fected, and the liquor resulting therefrom being naturally 
 much diluted with water. Another serious result of the 
 above defect was the accumulation of weak liquor in the 
 
Absorption System 
 
 901 
 
902 Steam Engineering 
 
 refrigerator, and the consequent necessity for constant ad- 
 ditions of ammonia. 
 
 Fig. 379 illustrates an ammonia absorption, refrigerat- 
 ing device, one of a leading American type, and will give 
 a clear idea of the operation in general of the system. 
 
 A constant pressure of about 150 lbs. per square inch 
 is maintained in the generator, and to prevent this pres- 
 sure from being exceeded, a safety valve is provided on 
 the dome o. f the generator. The gas that escapes through 
 this safety valve is led through a suitable pipe to a small 
 water tank, where it is absorbed. The operation is as 
 follows : 
 
 The aqua ammonia is first introduced into the genera- 
 tor, the gas or vapor expelled therefrom by heat into 
 the condenser; and, so that the process may be carried out 
 continuously and not be arrested by the exhaustion of the 
 solution, the exhausted or impoverished liquor is slowly 
 drawn off at the bottom of the generator, an equal vol- 
 ume of fresh strong solution being constantly inserted 
 at the top thereof. The united effects of the cooling and 
 pressure produce liquefaction of the ammoniacal gas or 
 vapor in the condenser, and the liquid ammonia passes 
 to the refrigerator. It will be seen that the ammoniacal 
 gas or vapor from the tubes of the refrigerator is re- 
 absorbed, and a rich solution is formed to feed the gen- 
 erator, the absorbing water used being that withdrawn 
 exhausted from the latter. Thus the generator and the 
 condenser will keep up a continuous supply of the liquid, 
 and the refrigerator will continue to freeze successive 
 charges of water in the ice-cans or cases, provided, how- 
 ever, that the requisite heat to vaporize or gasify the am- 
 monia is supplied to the generator. If, therefore, the 
 entire apparatus be perfectly fluid-tight, as it is theo- 
 
Absorption System 903 
 
 retically supposed to be, no escape could take place by 
 leakage or otherwise, and the same materials would go 
 on indefinitely producing the same uniform effect. 
 
 In starting a machine constructed on the absorption 
 principle it must be first blown through to expel all the 
 air. In Carre's apparatus the air escaping from the ab- 
 sorber is conducted by a suitable pipe into what is known 
 as a purger, where it is passed below the surface of water 
 to absorb or retain any ammonia that would otherwise 
 escape with the air. 
 
 A large amount of water is required for cooling pur- 
 poses in the condenser or liquefier, and absorber, and a 
 considerable consumption of fuel is also necessary to heat 
 the generator, when this is performed directly by means 
 of a furnace. When, however, this is effected by steam- 
 heated pipes, or, by coils of pipe heated by the exhaust 
 steam from an engine, or even by direct or live steam 
 from a boiler, there is a considerable saving on this head. 
 Steam or other motive power is likewise required for 
 driving the force pump. 
 
 The operation of Keece's improved apparatus is briefly 
 as follows: 
 
 The charge of liquid ammonia (the ordinary commer- 
 cial quality of a density of 26° Beaume) is vaporized by 
 the application of heat, and the mixed vapor of water 
 and ammonia passed to the vessels called the analyzer, 
 and the rectifier, wherein the bulk of the water is con- 
 densed at a comparatively high temperature, and is re- 
 turned to the generator. The ammoniacal vapor or gas is 
 then passed to the condenser, where it is treated in a 
 substantially similar manner to that in Carre's apparatus, 
 that is to say, it is caused to liquefy under the combined 
 action of the condensation effected bv the cooling water 
 
904 Steam Engineering 
 
 circulating around the condenser tubes, and of the pres- 
 sure maintained in the generator. The liquid ammonia 
 (in this case practically anhydrous) is then used in the 
 refrigerator, and the vapor therefrom, whilst still under 
 considerable tension, is admitted from the refrigerator to 
 a cylinder fitted with a slide valve, and entry and ex- 
 haust ports, practically similar to those of a high pressure 
 steam-engine, and is thus utilized to drive the force pump 
 for returning the strong solution to the generator, after 
 which it is passed into the absorber, where it meets, and 
 is taken up by, the weak liquor from the generator, and 
 the strong liquor so formed is forced back into the gen- 
 erator by means of a force pump. 
 
 The important features of the absorption machine are 
 the expansion valve, the absorber and the strength of the 
 liquor. The expansion valve should be handled very care- 
 fully, as it is delicate and will not bear rough usage. 
 
 The expansion valve may be likened to a throttle valve 
 on a full-stroke engine. If opened wide, or more than is 
 necessary to operate the machine a little above its ca- 
 pacity, it will draw on the generator as a wide-open pipe 
 will draw on a boiler, and it will take from the generator 
 more liquor than can be separated in the rectifier; and 
 when it passes the rectifier it must go through into the 
 cooler. As this liquor cannot evaporate at that tempera- 
 ture, it will plug up the cooler. This is termed a "boil- 
 over." 
 
 Shutting off the gas valve also necessitates shutting off 
 the expansion valve and the machine stops working, with 
 the consequent raising of temperatures. Also, when the 
 machine is purged and the gas and expansion valves are 
 opened, 10 or 12 degrees in temperature will be lost, as it 
 will be an hour or more before the machine gets to work 
 
Absorption System 905 
 
 reducing temperatures again, and if there is still bad 
 liquor in the condenser, to come over, the machine will 
 want purging again soon, with another rise in tempera- 
 ture. 
 
 The Absorber, The efficiency of the machine depends 
 upon the condition of the absorber. If the absorber is 
 cool, and free from air or poor gas, the cooler will give 
 off its gas with ease. As long as the water and absorber 
 are cool, it is difficult to know about the spray at the 
 top. This spray device is simply a valve with three oblique 
 holes. 
 
 If one side of the absorber gets warmer than the other, 
 the valve should be turned down slightly, say one-eighth 
 of a turn, and by a little manipulation the temperature 
 of the entire absorber may be evenly maintained. If a 
 small scale, or dirt should get over a hole, it will close 
 that much of the valve. This valve does not regulate the 
 flow of the poor liquor, but rather its distribution over the 
 coils. The flow of the poor liquor is regulated by the 
 valve near the exchanger, that at the generator being used 
 only to shut off the poor liquor entirely. There should 
 be just sufficient poor liquor thrown over to absorb the 
 gas. More than this puts an extra load on the ammonia 
 pump, exchanger and absorber. 
 
 At this point is where the expense of the absorption 
 machine comes to be considered, as regards water, and also 
 the capacity of the machine, the whole being limited by 
 the amount of gas the absorber will take over from the 
 cooler. When the absorber is cold, the poor liquor within 
 it will have a large absorbing capacity, and it will take 
 gas from the cooler even if it is gas of medium high 
 percentage, but if the absorber becomes warmer, it will 
 have less absorbing power, and do less work. If the tern- 
 
906 Steam Engineering 
 
 perature cannot be improved because of insufficient water, 
 then the liquor coming over should be made weaker by 
 turning more heat on the generator, and distilling more 
 of the gas over into the condenser, which will carry a 
 larger amount in storage. Under these conditions, the 
 cooler will also need more gas, and this will tend to 
 weaken the whole charge in the generator, thus requir- 
 ing a higher temperature in the coils, and a higher pres- 
 sure to distill the necessary gas from the weakened charge. 
 
 With the cooling water at a temperature of 60° or lower, 
 a low pressure machine will operate at atmospheric pres- 
 sure. With the water at 70°, the steam pressure may have 
 to be raised two or three pounds; and if the temperature 
 of the water is 75°, the pressure will need to be increased 
 to 10 pounds. The pressures required depend upon the 
 amount of heating surface in the generator. With water 
 at a temperature of 60° the pressure in the generator may 
 be from 90 to 100 pounds; but with the water at 75°, it 
 will be necessary to carry generator pressure at 150 to 160 
 pounds. 
 
 It is possible to ascertain at any time whether or not 
 the absorber is taking hold well, by observing the frost on 
 the gas pipe. If this frost continues white, and keeps on 
 accumulating, it is an indication that the absorber is 
 working uniformly. If the frost begins to thaw, either 
 the absorber has let go, or the cooler has become foul. 
 The pipe at the bottom of the absorber should have a swivel 
 joint, thus making it possible to swing it into or out of 
 a pail of water. This is for the purpose of testing for 
 the presence of air in the system. To make a test, place 
 a bucket of cold water under the outlet, and open the 
 valve one-eighth or one-quarter turn. If air is present, 
 bubbles will rise to the surface of the water without noise. 
 
Absorption System 907 
 
 Should there be but few bubbles, accompanied by a crack- 
 ling sound similar to that made by water into which steam 
 is being blown, it indicates the presence of gas, showing 
 that this portion of the machine is all right. If, when air 
 bubbles are rising, a lighted match be held over the pail 
 of water and a pale yellow flame results, it shows that 
 there is some foul gas mixed with air. 
 
 Half way up the absorber there is another purge pipe 
 for drawing off foul gas. If this valve is slightly opened 
 and the gas issuing therefrom is lighted, and continues to 
 burn of itself, it shows foul gas, and the pipe should be 
 turned into a pail of water until good gas comes, which 
 can be told by the crackling sound. Do not make the 
 mistake of holding a light under it only to light it. Am- 
 monia gas will burn (if a light is kept under it) with a 
 very similar flame. The pail of water tells the story. 
 
 There should be sufficient anhydrous ammonia in the 
 system for the cooler to have all it wants, and allow the 
 generator to keep a few inches in the condenser gage all 
 the time, with the steam pressure down to the low point. 
 This is with a cool absorber, and it is sometimes possible 
 to have the liquor in a cool absorber so rich that the pump 
 will not take it, the gas separating out in the pump, a 
 condition which will be shown in the glass gage of the 
 absorber, as when the pump lets go, the absorber fills up, 
 and the liquor in the glass will effervesce like soda water. 
 The remedy is to weaken the charge by throwing more of 
 the gas over into the condenser, for a reservoir, and start 
 the pump by pressure from the condenser. 
 
 The Generator. The coils for steam in the generator 
 go in at about the center, and return near the bottom. 
 When starting up a generator cold, do so easily, taking 
 plenty of time. If possible, the better plan is to turn 
 
908 Steam Engineering 
 
 steam on at the bottom and let it work its way upward. 
 If it is a large machine with a flange joint in the center, 
 by turning steam on strong at the top, the top will be 
 heated, and expand and open the joint at the bottom. 
 Should this occur, stop the heat and let it cool. Take off 
 one nut at a time, oil it and put it back and pull it up 
 tight. This may stop it once or twice, only do not hurry 
 the heating of the generator. 
 
 As soon as there is sufficient pressure to raise the liquor 
 over through the weak-liquor pipe, open the valve and 
 when the liquor shows in the absorber start the pump. 
 This sets up a circulation in the generator and the danger 
 is over. When the pressure is shown to be sufficient to 
 liquefy the gas, which will be at 70 pounds, and it does 
 not show on the gage in the condenser, open the expan- 
 sion valve slightly so as to start circulation. The top 
 of the steam coils is about at the center of the generator. 
 
 It is a good plan to make a gage from a pine strip 
 marked in inches and half inches and fasten it to the 
 gage fittings, with a mark showing the top of the coils. 
 The charge in the generator should always be kept above 
 the coils and usually near the top of the generator. This 
 level will change, depending on the gas in the condenser 
 and cooler, and the liquor in the absorber. Sometimes, 
 purging the cooler will raise the lev£l in the generator 
 4 or 5 inches. When a lot of the anhydrous ammonia is 
 sent over into the condenser the level will be changed. 
 
 If there is no leakage around the ammonia pump, all 
 loss will be of anhydrous ammonia, and it must be re- 
 plenished with the same. Should there be leakage of 
 liquor, it can be replenished with aqua ammonia, or with 
 water and anhydrous ammonia. If water is used, it should 
 
Absorption System 909 
 
 be pure, distilled water, as impure water would cause foul 
 gases. 
 
 The troubles caused by allowing the charge to get below 
 the generating coils are two: If allowed for more than a 
 short time the ammonia will corrode the pipes, and the 
 hot pipes in the gas will decompose the gas. This will 
 be shown up around the cooler, the frost everywhere being 
 excessively heavy, as though everything was frozen up, and 
 the gage on the absorber will show about as good vacuum 
 as a condensing engine. The temperature of the brine 
 will be high, as that is the only thing that does not show 
 any low temperatures. The only remedy is a good charge 
 of anhydrous ammonia and purging out the bad gas. 
 
 Rectifier. The rectifier is for drying out the gas and 
 should be run cool enough to chill off the moisture but not 
 cool enough to liquefy the gas, or any portion of it, as it 
 would drain back into the generator and have to be dis- 
 tilled again. The last passage of water is through this 
 vessel, and there is a bypass around it for the water so 
 that the temperature can be regulated. There are ther- 
 mometers for the rectifier, and water leaving it. 
 
 If considerable water is used because of the absorber, 
 a large amount will go through the bypass. If water is 
 economized and the absorber is warm, all of it may go 
 through the rectifier. The thermometer should not register 
 below 110°. The drain pipe should feel warm to the 
 hand. 
 
 Dirty Coils. The condenser and absorber coils are liable 
 to the same trouble where the water becomes warm and 
 the flow sluggish. Corrosion, in the form of "barnacles" 
 sets in, and the pipes gradually become filled. These coils 
 have headers at both top and bottom and each coil has a 
 valve at both ends. 
 
910 Steam Engineering 
 
 There should be an air compressor on the premises 
 capable of maintaining a pressure of 80 pounds through 
 an open %-inch pipe. The headers should be connected 
 to the air line, and also to a water pressure, with %-inch 
 pipe; the feed line will do. 
 
 Once a week the ammonia should be shut oil, or rather, 
 the machine should be stopped and the water drawn from 
 the coils, the bottom valves closed, and air turned on. 
 There should be a valve for the bottom header, in the 
 bottom of the flange, which should be opened, and then 
 the valves on the coils should be opened separately and 
 the air allowed to blow through. The deposit will be soft 
 and will easily clear out. After air has blown through, 
 turn on the water in the same manner and wash the coils 
 out. While the machine is idle, the brine temperature 
 may have gone up one or two degrees, but it will readily 
 come down again. 
 
 If the coils are badly coated the machine will have to be 
 stopped for two or three days. The ammonia will have to 
 be drawn from the condenser and absorber, as if warmed 
 up the expansion would cause too much pressure. In 
 drawing off the ammonia be careful not to reduce it too 
 low all at once, or the freezing effect will be so great 
 as to freeze the water coils. 
 
 Have prepared a sufficient quantity of a strong potash 
 solution, draw the water from the coils, fill them with 
 potash and let it stand for twenty-four hours, or longer 
 if the machine can be spared. When the potash is drawn 
 off, turn on the water from the small cleaning pipe and 
 fill the coils. Close the valve to within one-half turn and 
 turn on the air. Open one valve at the bottom of the 
 coil header and keep it open until the water runs clear, 
 then close that one and open another. After all have been 
 
Absorption System 911 
 
 blown, begin with the first and go over them again. They 
 may require four or five blowings out before they will be 
 clean. 
 
 When air and water issue from a pipe together, it will be 
 noticed that it issues with a series of explosions, which 
 appear to take place all through the coil and may be 
 thought to do the cleaning, but this method has little 
 effect without the potash. Water at from 125 to 150 de- 
 grees appears to do better work than cold water, as the 
 vapor from the warm water makes the explosions stronger. 
 
 Brine. — For brine, chloride of calcium should be used 
 instead of chloride of sodium, because it cleans the pipes 
 better, prevents corrosion, and will carry lower tempera- 
 tures. Care should be taken to get the purest, but even 
 with this there is a sludge that will stop circulation in 
 small pipes, and sometimes in good-sized pipes. Place a 
 steam pipe in the tank for dissolving purposes and do 
 not fill the tank full of water after the calcium is placed 
 in it. When the mixing tank is charged, turn on steam 
 until the tank boils, then close the steam valve. Skim 
 off the scum that rises. It will be necessary to wait until 
 the brine cools before pumping it into the system, other- 
 wise it would raise temperatures. The skimming can be 
 done without heating, but not as much of the impurities 
 will rise as by heating, and not much time is gained, as 
 the dissolving is so much slower. Heating saves lots of 
 cleaning later, also. 
 
 Danger in Ammonia Fumes. — In case of accident, am- 
 monia is a bad thing, as it takes but a small amount to 
 overcome a person. Acetic acid is an antidote and is 
 found in ordinary vinegar. A sponge soaked in vinegar 
 and put over the nose will enable anyone to work in a 
 strongly impregnated atmosphere, as far as breathing is 
 
912 Steam Engineering 
 
 concerned, but the eyes would not be protected. To work 
 under such conditions it is necessary to wear a helmet, 
 which should be kept charged at all times at 125 pounds 
 pressure and regulated so that it will take one-half hour 
 to reduce the pressure to 25 pounds. 
 
 Should anyone be in danger of suffocation, breathing 
 the fumes from vinegar will neutralize it. Drinking warm 
 milk will relieve a person partly suffocated from ammonia 
 or any gas. 
 
 Workers around ammonia should not forget the strong 
 affinity it has for water and the absorbing power of water. 
 When there is a small leak of even the gas under pres- 
 sure, a piece of water-soaked waste put over it will remove 
 all trouble until the water is thoroughly saturated with it. 
 
 It is a good idea to practice using water for even unim- 
 portant leaks so as to be accustomed to it. A 1-inch hose 
 and a 2 1 /2-i n di hose under water pressure should always 
 be handy, as by their use a big leak could be drowned; 
 and these would be thought of instantly if one were ac- 
 customed to the use of water to take care of ammonia 
 fumes. 
 
 There are various devices for detecting leaks, but the 
 best is white litmus paper. This can be procured free 
 from the dealer in ammonia. Take a strip ^-inch wide 
 and about IV2 inches long. With a thread, tie it onto a 
 small stick 15 to 18 inches long. When using it, moisten 
 it in water and hold it to the suspected place. Tf there 
 is a leak the paper will turn red and the shade of red 
 will show how strong the leak is. Litmus paper will de- 
 tect leaks that cannot be smelled. Turn it away from the 
 leak into pure air and it again becomes white. It can 
 be used until completely worn out, all that is necessary, 
 when using it, being to moisten it. 
 
Absorption System 913 
 
 For putting screwed fittings together, or for material 
 to put on flanges, use litharge and glycerine; for sheet 
 packing, use pure rubber. Do not get fittings intended 
 simply to receive the pipe that is to be screwed into 
 them ; get special ammonia extra-heavy fittings, either with 
 a stuffing-box at each end of the fitting, in which rubber 
 packing should be used or fittings with a lead ring in 
 each outlet, and with provision to put in shot and allow 
 a plug to be screwed in the top to force the shot down 
 on the pipe. 
 
 Weak-liquor Pipe. — In regard to the weak-liquor pipe, it 
 should be remembered that as the pressure in the genera- 
 tor is carried higher the flow through this line is increased 
 unless throttled. 
 
 Charging. — When charging a new compression system, 
 proceed as follows: 
 
 Make a proper connection between the outlet valve of 
 ihe flask and the manifold where there are three valves. 
 After creating a vacuum in the system close the right 
 hand valve and open the other two. Carefully open the 
 valve on the flask and the pressure will force the am- 
 monia into the system, where it will expand and destroy 
 the vacuum. To prevent this as much as possible use 
 plenty of water on the condensers. Start up the compres- 
 sor and run it slowly until all of the ammonia is out of 
 the flask, when the bottom of it will begin to freeze. Care 
 should be taken to have the outlet valve at the lowest part 
 of the flask. Eun the compressor until the back pressure 
 gauge indicates zero, close the two valves used to admit 
 the ammonia, and let the machine stand for about 15 
 minutes, before changing any of the valves on the system. 
 
 With the absorption system there is no compressor with 
 which to create a vacuum in the pipes, but if the whole 
 
914 Steam Engineering 
 
 system is filled with steam before it is used at all, it will 
 drive out the air, then by using water on the condenser 
 and in the brine tank, this steam may be condensed and 
 a vacuum formed for testing, as with the compression 
 system. A light steam pressure will answer every pur- 
 pose in this case. The absence of a pump also prevents 
 the high pressure air test. 
 
 When charging the absorption system a partial vacuum 
 may be secured as already described, when the pressure 
 in the ammonia flask will cause the contents to escape 
 into the system. Ammonia flasks should be weighed both 
 before and after charging, so that the amount used may 
 be definitely known. It is a good plan to test ammonia 
 before putting it into a system, by drawing a small quan- 
 tity of it out of the flask and, seeing that it will evaporate 
 without leaving any sediment. 
 
 Starting. — When starting a compression system, open 
 the regulating valve on the discharge pipe slightly at first, 
 but do not allow the compressor to pump a vacuum on 
 the coils, for the regulating valve should be open until 
 there is perhaps 15 pounds back pressure, although there 
 is no cast-iron rule for this purpose. It is well to cal- 
 culate on about one-tenth of the high pressure, for the 
 low or suction pressure side, so that if 200 pounds is 
 carried on one, about 20 pounds will be right for the 
 other. This is one of the many points that each engineer 
 must decide for himself, for it will depend on circum- 
 stances. When the brine is warm, a high pressure on 
 the condenser side is advisable, so that the full benefits 
 of expansion may be secured, but if the brine is cooler, it 
 is evident that a lower pressure will answer the purpose. 
 High pressures are expensive, as it requires more steam 
 to pump against them, and this should be taken into ac- 
 
Absorption System 915 
 
 count, for there is no necessity of freezing the suction pipe 
 back into the engine room, where the heat will cause water 
 to drop on the machinery and the floor. When frost shows 
 on the suction pipe just beyond the brine tank, or just out- 
 side of whatever room is to be cooled, it shows that the 
 best results are secured. 
 
 In some cases, however, where a double-acting compres- 
 sor is in use, it may become necessary to freeze back to 
 the compressor in order to prevent undue accumulation of 
 heat in the cylinder which would cause the machine to 
 work at a disadvantage, and might burn out the fibrous 
 packing around the rod, or injure the metallic packing, if 
 such is used. On the other hand if the frost reaches back 
 to the cylinder of a single-acting compressor, it may do 
 much damage by freezing up the packing, so that here, as 
 elsewhere about a refrigerating plant, much depends upon 
 the good judgment of the engineer. 
 
 When running with wet compression, the discharge pipe 
 should never get very warm, but with dry compression it 
 may be hot enough to burn the hand, without doing any 
 damage. 
 
 If trouble is encountered in keeping the stuffing-boxes 
 tight on a vertical single-acting compressor, it may be due 
 to the presence of weak liquor on the cylinder head, which 
 flows down the piston rod, and causes an unpleasant odor 
 to fill the room. If the glands are tightened up to stop 
 it, the rods may be scored and badly damaged. 
 
 The safest method is to take the packing out, and allow 
 this weak liquor to run out, and if there is a collar next 
 to the rod, it may be necessary to take out the piston 
 and sponge the liquor out, as the collar will prevent it 
 from running out. Care must be taken to prevent oil 
 from passing the oil separator. The oil should be purged 
 
916 Steam Engineering 
 
 out and not allowed to pass over into the coils where it 
 is not wanted. If it does get into them, it is necessary to 
 disconnect the pipes and blow live steam through them 
 until it is all driven out. If they are badly coated, it 
 may be necessary to clean them out with a solution of 
 soda ash, and then blow steam through them, and after- 
 wards air under pressure, to purify them. 
 
 Whenever a serious leak develops on the high pressure 
 side of the apparatus, the valves must be so manipulated 
 that the ammonia will be drawn from this side over into 
 the suction side, while the compressor is run at a slow 
 speed, when the proper valves should be shut to keep it 
 locked up there until the repairs are completed. If the 
 leak is on the suction side, the liquid valve must be closed 
 and all of the ammonia pumped up into the condenser, 
 then by closing the valve on the top of the condenser it 
 may be retained there until the machine is again ready 
 for use. Incompetent men in charge of these machines, 
 have been known to allow all of the ammonia to escape 
 into the air, when there was a leak in the pipes, to the 
 extreme disgust of the neighbors, and the detriment of 
 the owners, but in a majority of cases this is entirely 
 unnecessary. 
 
 When it is time to shut down a machine of this kind, 
 the liquid valve should be closed, and the suction pres- 
 sure reduced to zero. Do not pump a vacuum at this 
 time, for it may cause the system to be filled with air 
 before starting up again. 
 
 Properties of Ammonia. — Ammonia is composed of one 
 part of nitrogen and three parts of hydrogen, represented 
 by the formula NH 3 . It is a colorless gas, possessing a 
 pungent odor. It is much lighter than air, having a 
 specific gravity of 0.58, that of air being 1. 
 
Properties of Ammonia 917 
 
 It can be obtained from the air, from sal ammoniac, 
 nitrogenous constituents of plants and animals by process 
 of distillation ; as a matter of fact, there are very few sub- 
 stances free from it. 
 
 Ammonia in itself is a slight lubricant, and has no effect 
 whatsoever on iron or steel, of which ice machinery is con- 
 structed. It will eventually purge and scour the entire 
 system clean to the metal surfaces, the loose foreign matter 
 being caught in the separators and interceptors provided 
 for this purpose. 
 
 At the present day almost all the sal ammoniac and 
 ammonia liquors are prepared from ammoniacal liquid a 
 by-product obtained in the manufacture of coal gas and 
 coke. Although ordinarily existing as a gas, it may be 
 condensed to a liquid by cooling, and applying pressure. 
 Liquid anhydrous ammonia formed in this way boils under 
 atmospheric pressure at 28.5 degrees below zero, and its 
 latent heat of evaporation is about 562 British thermal 
 units at 32 degrees F., at which temperature 1 pound of 
 the liquid evaporated under atmospheric pressure will oc- 
 cupy 21 cubic feet. 
 
 Pure ammonia liquid is colorless, having a peculiar 
 alkaline odor, and caustic taste. It turns red litmus paper 
 blue. Compared with water, its weight or specific gravity 
 at 32 degrees F. is about % of water, or 0.6364. One 
 cubic foot of liquid ammonia weighs 39.73 pounds, one 
 gallon weighs 5.3 pounds, one pound of the liquid 
 at 32 degrees will occupy 21.017 cubic feet of space when 
 evaporated at atmospheric pressure. The specific heat of 
 ammonia gas, as determined by Eegnault (capacity for 
 heat), is 0.50836. Its latent heat of evaporation, as deter- 
 mined by the highest authorities, is not far from 560 ther- 
 mal units at 32 degrees, at which temperature one pound 
 
918 
 
 Steam Engineering 
 
 of liquid evaporated under a pressure of fifteen pounds per 
 square inch, will occupy twenty-one cubic feet. 
 
 Table 48 gives the properties of saturated ammonia. 
 
 Table 48 
 
 PROPERTIES OF SATURATED AMMONIA— (Wood). 
 
 The critical pressure of ammonia is 115 atmospheres ; critical tempera- 
 ture at 266° F. (Dewar) ; critical volume .00482 (calculated). 
 
 Tempera- 
 ture 
 
 Pressure, 
 
 absolute 
 
 c 
 .2 
 
 cd 
 
 • N 
 
 O W 
 
 a.ti 
 
 > s 
 
 X J* 
 
 £-5 
 
 u 
 O 
 Cu . 
 
 > 
 
 "33 
 
 > a 
 
 '3 . 
 
 ■S3 
 
 > a 
 
 3 
 
 m 
 3 
 
 So 
 
 <u 
 
 P 
 
 IS 
 
 *o 
 
 w 
 < 
 
 u . 
 
 CO & 
 
 3" 
 
 O . 
 
 ■M O 
 
 be rt 
 *53 
 
 — 40 
 
 — 35 
 
 — 30 
 
 420.66 
 425.66 | 
 430.66 
 
 1540.9 
 1773.6 
 2035.8 
 
 10.59 
 12.31 
 14.13 
 
 579.67 
 576.69 
 573.69 
 
 48.23 
 48.48 
 | 48.77 
 
 531.44 
 
 528.21 
 524.92 
 
 24.37 
 
 21.29 
 18.66 
 
 .0234 
 .0236 
 .0237 
 
 .0410 
 .0467 
 .0535 
 
 — 25 
 
 — 20 
 
 — 15 
 
 435.66 
 440.66 
 445.66 
 
 2329.5 
 2657.5 
 3022.5 
 
 16.17 
 18.45 
 20.99 
 
 570.68 
 567.67 
 564.64 
 
 49.06 
 49.38 
 49.67 
 
 521.62 
 518.29 
 514.97 
 
 16.41 
 14.48 
 12.81 
 
 .0238 
 .0240 
 .0242 
 
 .0609 
 .0690 
 .0779 
 
 — 10 
 
 — 5 
 
 
 450.66 
 455.66 
 460.66 
 
 3428.0 
 3877.2 
 4373.5 
 
 23.77 
 25.93 
 30.37 
 
 561.61 
 558.56 
 555.50 
 
 49.99 
 50.31 
 
 50.68 
 
 511.62 
 
 508.25 
 504.82 
 
 11.36 
 
 10.12 
 
 9.04 
 
 .0243 
 .0244 
 .0246 
 
 .0878 
 .0988 
 .1109 
 
 4- 5 
 4- 10 
 4- 15 
 
 465.66 
 470.66 
 475.66 
 
 4920.5 
 5522.2 
 6182.4 
 
 34.17 
 38.55 
 42.93 
 
 553.43 
 549.35 
 546.26 
 
 50.84 
 51.13 
 51.33 
 
 501.59 
 
 498.22 
 494.93 
 
 8.06 
 7.23 
 6.49 
 
 .0247 
 .0249 
 .0250 
 
 .1241 
 .1384 
 .1540 
 
 4- 20 
 + 25 
 4- 30 
 
 480.66 
 485.66 
 490.66 
 
 6905.3 
 7695.2 
 8596.0 
 
 47.95 
 53.43 
 59.41 
 
 543.15 
 540.03 
 536.92 
 
 51.61 
 51.80 
 52.01 
 
 491.54 
 488.23 
 484.91 
 
 5.84 
 5.26 
 4.75 
 
 .0252 
 .0253 
 .0254 
 
 .1712 
 .1901 
 .2105 
 
 4- 35 
 4- 40 
 4- 45 
 
 495.66 
 500.66 
 505.66 
 
 9493.9 
 10512 
 11616 
 
 65.93 
 73.00 
 80.66 
 
 533.78 
 530.63 
 527.47 
 
 52.22 
 52.42 
 52.62 
 
 481.56 
 478.21 
 474.85 
 
 4.31 
 3.91 
 3.56 
 
 .0256 
 .0257 
 .0260 
 
 .2320 
 
 .2583 
 .2809 
 
 4- 50 
 4- 55 
 4- 60 
 
 510.66 
 515.66 
 520.66 
 
 12811 
 14102 
 15494 
 
 88.96 
 
 97.93 
 
 107.60 
 
 524.30 
 521.12 
 517.23 
 
 52.82 
 53.01 
 53.21 
 
 471.48 
 468.11 
 464.72 
 
 3.25 
 2.96 
 2.70 
 
 .0260 
 .0260 
 .0265 
 
 .3109 
 .3379 
 .3704 
 
 4- 65 
 4- 70 
 4- 75 
 
 525.66 
 530.66 
 535.66 
 
 16993 
 18605 
 20336 
 
 118.03 
 129.21 
 141.25 
 
 514.73 
 511.52 
 508.29 
 
 53.38 
 53.57 
 53.76 
 
 461.35 
 
 457.85 
 454.53 
 
 2.48 
 2.27 
 2.08 
 
 .0266 
 .0268 
 .0270 
 
 .4034 
 .4405 
 
 .4808 
 
 4- 80 
 4- 85 
 4- 90 
 
 540.66 
 545.66 
 550.66 
 
 22192 
 24178 
 26300 
 
 154.11 
 
 167.86 
 182.8 
 
 504.66 
 501.81 
 498.11 | 
 
 53.96 
 54.15 
 
 54.28 | 
 
 450.70 
 447.66 
 443.83 | 
 
 1.91 
 1.77 
 1.64 
 
 .0272 
 .0273 
 .0274 
 
 .5252 
 .5649 
 .6098 
 
Properties of Ammonia 
 
 919 
 
 Table 48 — continued 
 
 Tempera- 
 ture. 
 
 Pressure, 
 absOTUte. 
 
 c 
 
 .2 
 
 u 
 
 43 
 
 u 
 
 43 
 
 a 
 u 
 
 u 
 
 a 
 
 T3 
 
 *o 
 
 
 
 
 O 3 
 
 a 
 *»^ 
 
 „ en 
 
 u C 
 
 43 3 
 
 ga 
 
 <U 
 
 43 3 
 
 ^a 
 
 c 
 
 u 
 V 
 44 
 
 c 
 
 a£ 
 cd 
 
 M-. O 
 
 o 
 
 > 
 
 .2* 
 
 ~ 3 
 
 Ml O 
 
 o 
 
 a~ 
 
 J3 
 > 
 
 3 2 
 
 V) 
 V 
 
 U 
 
 bo 
 v 
 
 Q 
 
 s 
 
 15 
 
 < 
 
 u 
 
 Im 
 
 5" 
 
 u 
 
 + 95 
 
 + 100 
 + 105 
 
 555.66 
 560.66 
 565.66 
 
 28565 
 30980 
 33550 
 
 198.37 
 215.14 
 232.98 
 
 495.29 
 491.50 
 
 488.72 
 
 54.41 
 54.54 
 54.67 
 
 440.88 
 436.96 
 434.08 
 
 1.51 
 
 1.39 
 
 1.289 
 
 .0277 
 .0279 
 .0281 
 
 .6622 
 .7194 
 .7757 
 
 + 110 
 + 115 
 + 120 
 
 570.66 
 575.66 
 580.66 
 
 36284 
 39188 
 42267 
 
 251.97 
 272.14 
 293.49 
 
 485.42 
 482.41 
 
 478.79 
 
 54.78 
 54.91 
 55.03 
 
 430.64 
 427.40 
 423.75 
 
 1.203 
 1.121 
 1.041 
 
 .0283 
 
 .0285 
 .0287 
 
 .8312 
 .8912 
 .9608 
 
 + 125 
 + 130 
 + 135 
 
 585.66 
 590.66 
 595.66 
 
 45528 
 48978 
 52626 
 
 316.16 
 340.42 
 365.16 
 
 475.45 
 472.11 
 468.75 
 
 55.09 
 55.16 
 55.22 
 
 420.39 
 416.94 
 413.53 
 
 .9699 
 .9051 
 .8457 
 
 .0289 
 .0291 
 .0293 
 
 1.0310 
 1.1048 
 1.1824 
 
 + 140 
 + 145 
 + 150 
 
 600.66 
 605.66 
 610.66 
 
 55483 
 60550 
 64833 
 
 392.22 
 420.49 
 450.20 
 
 465.39 
 462.01 
 458.62 
 
 55.29 
 55.34 
 55.39 
 
 410.09 
 406.67 
 402.23 
 
 .7910 
 .7408 
 .6946 
 
 .0295 
 .0297 
 .0299 
 
 1.2642 
 1.3497 
 1.4696 
 
 + 155 
 + 160 
 + 165 
 
 615.66 
 620.66 
 625.66 
 
 69341 
 74086 
 79071 
 
 481.54 
 514.40 
 549.04 
 
 455.22 
 451.81 
 448.39 
 
 55.43 
 55.46 
 55.48 
 
 399.79 
 396.35 
 392.94 
 
 .6511 
 
 .6128 
 .5765 
 
 .0302 
 .0304 
 .0306 
 
 1.5358 
 1.6318 
 1.7344 
 
 Testing Anhydrous Ammonia. — It is essential that the 
 purity of the liquid anhydrous ammonia, or the strength of 
 the aqua ammonia solution shall be up to standard and to 
 determine this point tests must be made. Aqua ammonia 
 is usually guaranteed to be not less than 26 degrees Baume 
 scale and its density can readily be measured with the 
 hydrometer. Liquid anhydrous can be tested by the use 
 of an ordinary glass testing tube 12 inches long or, if this 
 cannot be had, take a piece of 1-inch pipe and cap one end. 
 Securely fasten a piece of stiff wire about 12 inches long 
 around the tube or pipe so that it can be held about a foot 
 away from the hand and, after securing a piece of pipe 
 of the same size as the cylinder valve, bend the threaded 
 end so that the pipe will stand vertical when in position on 
 
920 Steam Engineering 
 
 the cylinder. Slip the test tube over the pipe almost to the 
 bottom or about as far as it will go, open the cylinder 
 valve gently, and draw a certain number* of inches of the 
 liquid into the tube, gradually withdrawing it from the 
 bent pipe as it fills. When the desired amount of liquid 
 ammonia has been drawn into the tube, remove it from the 
 pipe and, after noting carefully the exact amount of an- 
 hydrous ammonia, pour the liquid into a shallow vessel and 
 set it in cold water, or on a block of ice. Under these con- 
 ditions the ammonia will boil and evaporate quickly, and 
 any residue remaining is the amount of moisture and im- 
 purities originally in the liquid ammonia drawn into the 
 tube. Dividing the amount of residue by the quantity of 
 the liquid drawn into the tube and multiplying by 100 
 gives the percentage of moisture and impurities. Before 
 the liquid is drawn into the tube a little of the gas should 
 be allowed to escape in order to purge the bent pipe. 
 
 Hydrometers. — From among the instruments frequently 
 used to ascertain the specific gravity of liquids, and by 
 inference their strength, we mention those called hydro- 
 meters as based on the Archimedian principle. They are 
 generally made of a weighted body (usually of glass), hav- 
 ing a thinner stem at the upper end provided with a scale 
 divided into degrees. The degrees may be arbitrary, or 
 show specific gravities or the strength of some particular 
 liquid or solution in per cents ; in the latter case the instru- 
 ment is called saccharometer, salometer, alcoholometer, 
 acidometer, alkalimeter, etc., according to the liquid it is 
 designed to test. Hydrometers for different liquids or pur- 
 poses, provided they cover the same range of specific gravi- 
 ties, may be used for either liquid when the relation their 
 degrees bear to each other is known. 
 
Questions and Answers 921 
 
 QUESTIONS AND ANSWERS. 
 
 597. Of what does the process of refrigeration consist? 
 Ans. In the abstraction of heat from a substance. 
 
 598. Describe a freezing mixture that will give a tem- 
 perature of 67 degrees below zero. 
 
 Ans. A mixture of one pound of calcium chloride, and 
 0.7 lbs. of snow. 
 
 599. Upon what are the theory, and practice of mechan- 
 ical refrigeration based? 
 
 Ans. Upon the two first laws of thermo-dynamics. 
 
 600. What is the first of these laws? 
 
 Ans. Mechanical energy and heat are mutually con- 
 vertible. 
 
 601. Define the second law. 
 
 Ans. An external agent is necessary to complete or 
 bring about this transformation. 
 
 602. Is heat generated by compression, or by any other 
 means ? 
 
 Ans. It is not generated but developed, because there 
 is a fixed amount of heat in the universe which can neither 
 be increased nor diminished. 
 
 603. What is the result of compressing one pound of 
 air at 70 degrees temperature and at atmospheric pressure, 
 to one half its original volume ? 
 
 Ans. An increase in its static pressure, also an increase 
 in its temperature. 
 
 604. In order that the higher pressure may be main- 
 tained, as the temperature is reduced, what is necessary ? 
 
 Ans. A small additional quantity of air will have to be 
 forced into the compressor cylinder. 
 
 605. If the pound of compressed air be allowed to ex- 
 pand in a cylinder what will be the result? 
 
922 Steam Engineering 
 
 Ans. A portion of the heat developed by compression 
 will be given up. 
 
 606. What can be said of the mechanical work done 
 by this air in its expansion? 
 
 Ans. In amount it is exactly the same as that done upon 
 it during its compression. 
 
 607. How is the temperature of a body or substance 
 reduced ? 
 
 Ans. >By transferring more or less of the heat con- 
 tained in the body to some other substance or body. 
 
 608. What work is demanded of a refrigerating ma- 
 chine ? 
 
 Ans. To extract heat from a body, and by the expendi- 
 ture of mechanical energy to sufficiently raise the temper- 
 ature of this heat to admit of its being carried away by a 
 suitable external agent, usually water. 
 
 609. How may a refrigerating machine be defined, and 
 what is its main function? 
 
 Ans. As a heat pump, its main function being the 
 abstraction of heat from the body to be cooled, and trans- 
 ferring that heat to a cooling agent. 
 
 610. How may the various devices for refrigeration and 
 ice making be classified? 
 
 Ans. Under five principal heads. 
 
 611. Explain the action of apparatus belonging to 
 class one. 
 
 Ans. Heat is abstracted from the body to be cooled, 
 by the dissolution or liquefaction of a solid, as for instance 
 the cooling of water with ice. 
 
 612. Describe the vacuum system? 
 
 Ans. The abstraction of heat is effected by the evapora- 
 tion of a portion of the liquid to be cooled, the process 
 being assisted by an air pump. 
 
Questions and Answers 923 
 
 613. How is refrigeration effected in machines belong- 
 ing to the third class? 
 
 Ans. By the evaporation of a separate refrigerating 
 agent, which is subsequently restored to its original physi- 
 cal condition by mechanical compression and cooling. 
 
 614. Describe the fourth or absorption system. 
 
 Ans. Heat is abstracted by the evaporation of a sepa- 
 rate refrigerating agent, under the direct action of heat, 
 which agent again enters in solution with a liquid. 
 
 615. Describe the action of machines belonging to the 
 fifth class, known as cold air machines ? 
 
 Ans. Air, or other gas is first compressed, then cooled, 
 and afterwards permitted to expand while doing work. 
 
 616. What two systems have come into general use in 
 the United States? 
 
 Ans. The ammonia compression system, and the am- 
 monia absorption system. 
 
 617. What are the three distinct stages in the com- 
 pression system? 
 
 Ans. Compression, condensation, and expansion. 
 
 618. What is the refrigerating agent or medium used 
 in the compression system? 
 
 Ans. Anhydrous ammonia. 
 
 619. Of what does ammonia consist, and what is its 
 chemical formula? 
 
 Ans. One part of nitrogen, and three parts of hydro- 
 gen. Its chemical formula is NH 3 . 
 
 620. Under what two conditions may gaseous ammonia 
 be liquefied? 
 
 Ans At a pressure of 128 lbs. per sq. in., and a tem- 
 perature of 70° Fahr., or a pressure of 150 lbs, and a tem- 
 perature of 77° Fahr. It may also be liquefied by cold if 
 its temperature be reduced to 85.5° Fahr. below zero. 
 
924 Steam Engineering 
 
 621. To what pressure is gaseous ammonia usually 
 compressed ? 
 
 Ans From 125 to 175 lbs. per sq. in. 
 
 622. Of what does a compression plant consist? 
 
 Ans. Of a high pressure system made up of a condens- 
 ing coil surrounded by cooling water, and a low pressure 
 system consisting of an evaporating coil surrounded by 
 brine, or open to the room to be cooled. 
 
 623. What takes place during compression? 
 
 Ans. The latent heat of the vapor is converted into 
 active, or sensible heat. 
 
 624. How is the vapor condensed, or liquefied? 
 
 Ans. It is forced into and through the condenser coils 
 which are submerged in a body of cold water, or over which 
 cold water is flowing, and the sensible heat developed dur- 
 ing compression is thus transferred to the cooling water. 
 
 625. How are the refrigerating qualities of the am- 
 monia in its liquefied state utilized? 
 
 Ans. It is allowed to pass in small quantities from the 
 condenser into pipe coils placed in the rooms to be cooled, 
 when it again expar;ds into a vapor, and takes up an 
 amount of heat exactly equivalent to that given up during 
 condensation. 
 
 626. After being expanded into vapor, what becomes 
 of it? 
 
 Ans. It is drawn back into the compressor, again com- 
 pressed, condensed, and expanded, the cycle of operations 
 being repeated indefinitely. 
 
 627. How many, and what are the systems of refrigera- 
 tion by compression? 
 
 Ans. Two — the wet system, and the dry. 
 
 628. Describe the theory of the wet system. 
 
Questions and Answers 925 
 
 Ans. The ammonia vapor is cooled by the injection 
 into the compressor cylinder of a small quantity of liquid 
 ammonia at the beginning of each stroke, and it is carried 
 from the cooling room back to the compressor in a sat- 
 urated state. It is thus kept in contact with a small por- 
 tion of its originating fluid, and is kept comparatively cool. 
 
 629. Upon what does the pressure of steam in a boiler 
 depend ? 
 
 Ans. Upon its temperature, which is always the same as 
 that of the water in the boiler. 
 
 630. What are the relations of temperature and pres- 
 sure in the case of steam while in contact with the originat- 
 ing water? 
 
 Ans. They are interdependent. 
 
 631. What is the result if the steam is superheated? 
 Ans. It may still be of the same pressure, but its tem- 
 perature will be higher. 
 
 632. What results from the compression of a dry gas 
 without cooling? 
 
 Ans Its temperature may be much higher than that 
 corresponding to its pressure. 
 
 633. What does the Adiabatic curve as traced by the 
 indicator represent? 
 
 Ans. The compression, or expansion of a gas without 
 loss or gain of heat. 
 
 634. Describe in brief the construction of the cylinder 
 heads, and valves in the Linde ice machine. 
 
 Ans. The piston and cylinder heads are spherical, and 
 of the same radius, and the valve discs conform to this 
 radius. 
 
 635. What is the clearance between piston and cylin- 
 der head ? 
 
 Ans One thirtv-second of an inch. 
 
926 Steam Engineering 
 
 636. How is the piston lubricated? 
 
 Ans. In a large measure by the moisture in the am- 
 monia vapor. 
 
 637. In the De La Vergne refrigerating machine how 
 is the heated gas cooled? 
 
 Ans. By passing it through coils of pipe surrounded 
 by running water. 
 
 638. How many valves has the Triumph ice machine? 
 Ans. Five, three suction valves, and two discharge 
 
 valves. 
 
 639. What advantage is said to be gained by the use 
 of the third suction valve? 
 
 Ans. That it tends to increase the economy of the ma- 
 chine. 
 
 640. Describe the construction of a double pipe am- 
 monia condenser. 
 
 Ans. It consists of two series of coils, one within the 
 other. 
 
 641. How many methods are there of utilizing the 
 brine system? 
 
 Ans. Two; the brine system, and the direct expansion 
 system. 
 
 642. Describe in brief the brine system. 
 
 Ans. The coils of pipe in which the ammonia is ex- 
 panded are submerged in a solution of salt, or calcium 
 chloride. This brine after being reduced to a low tempera- 
 ture is pumped through coils of pipe in the rooms to be 
 cooled. 
 
 643. Describe the direct expansion system. 
 
 Ans. The expansion coils are placed in the rooms to be 
 cooled, and the cooling is effected directly by the expansion 
 of the ammonia. 
 
 644. Which one of the two systems is the most efficient ? 
 
Questions and Answers 927 
 
 Ans. The direct expansion system. 
 
 645. Mention a few of the advantages that this system 
 has over the brine system. 
 
 Ans. First — All intermediate agencies are dispensed 
 with. Second — The whole plant is much simpler. Third 
 — A larger expansion surface. 
 
 646. By what two systems is ice made or manufactured ? 
 Ans. The can system and the plate system. 
 
 647. Mention other refrigerating agents besides am- 
 monia that may be used in the compression system ? 
 
 Ans. Ether, methyl-chloride, sulphurous acid, and car- 
 bonic acid. 
 
 648. How is refrigeration effected in the absorption 
 system ? 
 
 Ans. .By the continuous distillation of ammoniacal 
 liquor. 
 
 649. What advantage appertains to the absorption 
 system ? 
 
 Ans. The bulk of the heat required for the work is 
 applied direct without being transformed into mechanical 
 power. 
 
 650. What pressure is usually maintained in the gen- 
 erator ? 
 
 Ans. 150 lbs. per sq. in. 
 
 651. Mention the more important features of the ab- 
 sorption machine? 
 
 Ans. The expansion valve, the absorber, and the 
 strength of the liquor. 
 
 652. Upon what does the efficiency of the machine 
 mostly depend? 
 
 Ans. Upon the condition of the absorber. If it is cool 
 and free from air, or poor gas, better results will be 
 realized. 
 
928 Steam Engineering 
 
 653. What should be done if one side of the absorber 
 should get warmer than the other ? 
 
 Ans. The spray valve should be turned down slightly, 
 say one-eighth of a turn. 
 
 654. Mention one of the troubles in the operation of 
 this system. 
 
 Ans. A filling up of the coils with scale and dirt. 
 
 655. What is the remedy in such cases? 
 
 Ans. Stop the machine once a week, drain the coils, and 
 blow them out with compressed air. 
 
 656. How is anhydrous ammonia formed? 
 
 Ans. By condensing ammonia gas to a liquid, and 
 applying pressure. 
 
 657. Under atmospheric pressure, what is the boiling 
 point of anhydrous ammonia? 
 
 Ans. 28.5 degrees delow zero Fahr. 
 
 658. What is the specific gravity of liquid ammonia 
 compared with water? 
 
 Ans. At 32° Fahr. it is about % that of water, or 
 0.6364. 
 
 659. What is its latent heat of evaporation? 
 
 Ans. At 32 degrees temperature it is 560 thermal units. 
 
 660. If evaporated at 32° Fahr. and atmospheric pres- 
 sure, how much space will one pound occupy? 
 
 Ans. Twenty-one cubic feet. 
 
 L 
 
Elevators — Electric and Hydraulic 
 
 As the majority of stationary engineers, especially in 
 large cities and towns, have more or less to do with ele- 
 vators, either electric or hydraulic, the author deems it 
 fitting and proper that a section should be devoted to this 
 subject. 
 
 Therefore, the construction and operation of electric and 
 hydraulic elevators will be taken up in order, and although 
 the subject-matter will have to be somewhat condensed for 
 want of space, still the leading types, including the numer- 
 ous improvements which have been developed during the 
 past ten years will be illustrated, and the mechanism de- 
 scribed. 
 
 OTIS TRACTION ELEVATOR. 
 
 In the Otis traction elevator the working parts have b^en 
 reduced to the simplest possible elements. The elevator 
 engine, a view of which is presented in Fig. 380, consists 
 essentially of a motor traction driving sheave, and a brake 
 pulley, the latter enclosed with a pair of powerful springs 
 actuated, electrically released brake shoes, all compactly 
 grouped, and mounted on a heavy iron bed plate. 
 
 Instead of the high speed motor used with the geared 
 electric elevator, a slow speed shunt-wound motor designed 
 especially for the service is used. The armature shaft 
 which is of high tensile steel, of unusually large diameter 
 serves merely as a support for the load, and on it are 
 mounted the brake pulley and the traction driving sheave. 
 
 929 
 
930 Steam Engineering 
 
 The actual drive from the armature to the sheave is effect- 
 ed through the engagement of projecting arms on each, 
 cushioned by rubber buffers, thus entirely eliminating all 
 tortional strains to the shaft, and the use of keys. In this 
 machine all intermediate gearing between motor and driv- 
 ing member is dispensed with, by the use of the slow speed 
 motor, and the result is, that the starting, accelerating, re- 
 tarding and stopping events are each, and all, remarkably 
 even and quiet. 
 
 Fig. 380 
 otis tbaction elevator 
 
 The driving cables, from one end of which the car is 
 supported, while to the other end the counterweight is 
 attached, pass partially around the traction driving sheave 
 in lieu of a drum, continuing under an idler leading sheave, 
 thence again around the driving sheave, thereby forming a 
 complete loop around these two sheaves, which arrange- 
 ment results in the necessary tractive effort for lifting the 
 car. One of the striking advantages resulting from this 
 
 ^ 
 
Electric Elevators 931 
 
 arrangement of cables, and the method of driving the same 
 is the decrease in traction which follows the striking on the 
 bottom of the shaft of either the car or the counterweight, 
 and the consequent minimizing of the lifting power of the 
 machine, until normal conditions are resumed. Inasmuch 
 as in any properly constructed elevator the parts are so 
 arranged that the member (car or counterweight) which 
 is at the bottom of the shaft must strike and come to rest 
 before the other member can possibly come in contact with 
 the overhead work, it will readily be seen that the above 
 mentioned decrease in tractive effort is a valuable, and 
 effective safety feature inherent in this type of elevator, j 
 The controller is so designed in connection with the 
 motor, that the initial retarding of the car in bringing the 
 same to stop is independent of the brake, the latter being 
 requisitioned to bring the car to a final positive stop and to 
 hold it at the landings. 
 
 The motor is also governed in such a way, electrically, as 
 to prevent its attaining any excessive speed with the car no 
 matter what the load in same may be. 
 
 In designing the controlling equipment, one of the fea- 
 tures demanding greatest consideration, in view of the very 
 high speed at which the cars run, is the automatic retard- 
 ing of their speed and the final positive stopping of same, 
 automatically, at the upper and lower terminals of travel. 
 This result is very satisfactorily attained with the installa- 
 tion, in the elevator hatchway, of two groups of switches 
 located respectively at the top and bottom of the shaft, each 
 switch in the series being opened one after another, as the 
 car passes, resulting in a reduction of speed until the open- 
 ing of the final switch brings the car to a positive stop, 
 applying the brake. This operation is entirely independent 
 
932 
 
 Steam Engineering 
 
 of the operator in the car and is effective even though the 
 car operating device be left in the full speed position. 
 
 Another feature of security of the greatest interest and 
 importance is provided in the Otis Patented Oil Cushion 
 Buffers. (See Fig. 381.) These are placed in the hoistway, 
 one under the car and one under the counterweight, and 
 
 Fig. 3S1 
 
 OTIS PATENTED SPRING RETURN OIL BUFFER 
 
 are arranged to bring either the car or the counterweight to 
 a positive stop, through the telescoping of the buffer — this 
 occurring at a carefully calculated rate of speed, which is 
 regulated by the escape of oil from one chamber of the 
 buffer to another. The buffers have been proven capable 
 by test of bringing a loaded car safely to rest from full 
 
Electric Elevators 
 
 933 
 
 speed, and in this respect are unique among elevator safety 
 features of comparatively low cost. 
 
 The usual safety devices installed in connection with 
 modern high grade apparatus are used with this type of 
 elevator, including speed governors, wedge clamp safety 
 devices for gripping the rails in case of the car attaining 
 excessive speed, and potential switches. 
 
 OTIS GEARED TRACTION ELEVATOR. 
 
 The modern adaptation, in the Otis Traction Elevator, of 
 the traction principle for elevator service which utilizes 
 the patented feature of operating the car by means of driv- 
 
 Fig. 382 
 
 OTIS DIRECT CURRENT TRACTION MACHINE FOR OVERHEAD INSTAL- 
 LATION 
 
 ing the cables direct from the motor without the interven- 
 tion of retarding rigging, showed so conclusively the merits 
 of that principle that the question naturally arose as to the 
 
934 Steam Engineering 
 
 feasibility of employing this method of drive in the low 
 speed machines as well. The result was the introduction 
 of what is commercially known as the Otis Geared Trac- 
 tion Elevator which embodies many of the good points of 
 its larger contemporary. 
 
 It might be well to state here that the traction principle 
 is neither new nor experimental, as is instanced by its use 
 in the familiar type of carriage hoist, this being in reality 
 a low duty hand power traction elevator driven by means 
 of a hemp rope; also this method of drive has been em- 
 ployed on dumb-waiters for some time. However, as ap- 
 plied to the high speed passenger machines used in our tall 
 office buildings, it must be referred to as a comparatively 
 new and improyed development of former types. 
 
 The Geared Traction machine is similar in appearance 
 to the standard drum machine, except that a multi-grooved 
 driving sheave is mounted in place of the drum, and a non- 
 vibrating idler leading sheave takes the place of the vibrat- 
 ing sheave necessary on the drum type. The car and the 
 counterbalance weight hang directly from the driving 
 sheave — one from either end of the cables — in precisely the 
 same manner as with the Otis Traction Elevator ; the neces- 
 sary amount of traction being obtained by the extra turn 
 resulting from passing around the idler sheave. 
 
 The machines are built in two classes, double screw, and 
 single screw, depending upon the duty required. 
 
 The double screw machine is designed for the heavier 
 duties, and the gearing consists of a right and left hand 
 worm, see Fig. 383, accurately cut from a solid forging. 
 This worm, coupled directly to the electric motor, runs 
 submerged in oil and meshes with two large bronze gear 
 wheels, which in turn mesh with each other. The effect of 
 the three-point drive thus obtained, in conjunction with 
 
Electric Elevators 935 
 
 the right and left hand thread, is the entire elimination of 
 end thrust on the worm shaft — a most desirable feature. 
 The complete gear is fully protected in an oil tight iron 
 case and is well lubricated in every part. 
 
 To the forward gear wheel, that is the one furthest from 
 the motor, there is bolted the iron buffer-neck, or what 
 might be termed the driving spider. It is constructed in 
 such a way that the use of keys is unnecessary to effect the 
 drive, inasmuch, as the flange of the buffer-neck is bolted 
 with through bolts directly to the bronze gear wheel near 
 
 Fig. 383 
 
 THREE POINT DRIVE 
 
 its periphery, and by means of four extending arms on its 
 opposite end engages with similar arms on the driving 
 sheave. A mechanically strong and perfect drive is thus 
 obtained. The shaft passing through the driving sheave 
 and buffer-neck serves merely as a support for the moving 
 loads and is subject to absolutely no tortional strains. In 
 order to protect the gears and elevator car from possible 
 vibrations, large rubber buffers are placed under slight 
 compression between the arms of the sheave and those of 
 the buffer-neck. 
 
936 Steam Engineering 
 
 The machine is equipped with a mechanically applied, 
 and electrically released double shoe brake. The shoes are 
 applied against a pulley of ample diameter and width to 
 dissipate any heat generated, and serves as a coupling be- 
 tween the motor shaft and the worm shaft. 
 
 The brake shoes are normally bearing against the pulley 
 with a pressure corresponding to the compression of the 
 two helical springs. When current is admitted to the 
 solenoid brake magnet, and then only, the action of the 
 springs for the time is overcome, so that the shoes are 
 released. It will be seen, therefore, that the brake will 
 apply with full force should a failure of current occur; 
 resulting in an immediate stop of the elevator. 
 
 The motor is compound wound, and runs at about eight 
 hundred revolutions per minute at full car speed and load. 
 The series field is used only at starting to obtain a highly 
 saturated field in the shortest possible time, and is then 
 short-circuited, leaving the motor to run as a plain shunt 
 wound type. 
 
 In stopping, a comparatively low resistance field is 
 thrown across the armature, providing a dynamic brake 
 action and a gentle slowing down of the car, the mechanical 
 brake being called upon only to effect the final stop and to 
 hold the load at rest. Eesistance in series with this "Extra 
 Field," as it is called, is controlled by magnets which de- 
 pend, in their operation, on the speed of the armature. 
 It is therefore evident that the dynamic, or retarding effect 
 of the field is proportional to the speed, and therefore to 
 the load in the elevator car, hence good stops under all 
 conditions are easily obtained. 
 
 To meet the demands in districts where alternating cur- 
 rent is in use, the same apparatus described is furnished 
 
Electric Elevators 
 
 937 
 
 except that the direct current motor and controller give 
 place to an alternating current motor and controller. 
 
 The alternating current machines are made in two classes 
 also, single and double screw. The cut, Fig. 384, repre- 
 sents a double screw machine designed for basement in- 
 
 Fig. 384 
 
 otis alternating current double screw traction machine 
 Designed for Basement Installations 
 
 stallations. The brake is slightly different in appearance 
 but performs the same functions as does the direct current 
 brake. 
 
 The safeties used on the Otis Traction Elevators are 
 found on the geared traction elevators. The main differ- 
 ence between the two machines being the ability to use on 
 
938 
 
 Steam Engineering 
 
 the latter a small high speed motor with gearing, instead 
 of the large, slow speed and more expensive motor of the 
 Otis Traction Elevator. 
 
 Fig. 385 
 magnet controller 
 
 Fig. 385 shows the Otis electric magnet controller, and 
 Fig. 386 shows the standard car switch. With this operating 
 device the current is automatically and gradually admitted 
 to the motor, enabling the operator to start and stop the 
 car without shock or jar. This controlling device is con- 
 
Electric Elevators 939 
 
 structed to secure the motor against damage by any over- 
 load, or excess of current; these features are automatic in 
 their operation, are independent of the operator in the 
 car, and are designed to prevent more current being ad- 
 mitted to the motor than is required to do the maximum 
 work of the elevator. 
 
 Fig. 3S6 
 
 OTIS LEVER CAR SWITCH 
 
 Electro magnets are employed throughout, thereby elim- 
 inating the use of all rheostats, sliding contacts, or other 
 easily deranged devices. The contacts and wearing parts 
 in the controlling mechanism are of ample dimensions to 
 meet the severe conditions, and exacting requirements of 
 elevator operation and control. 
 
 Careless Operation. — The waste of power caused by the 
 careless operation of electric elevators is well worth consid- 
 
940 Steam Engineering 
 
 eration. The following timely suggestions are quoted from 
 an article by C. M. Bipley in the September, 1909, issue of 
 Power : 
 
 "An electric passenger elevator driven by a 30-horse- 
 power motor on a 220-volt circuit is generally fused for 150 
 amperes. Assuming that it requires four seconds for the 
 car to gain its maximum speed, and that electric service 
 costs 10 cents per kilowatt-hour, the cost of merely start- 
 ing the elevator will figure out as follows : 
 
 150X220X4=132,000 watt-seconds; 
 
 132,000-^3600=36.6 watt-hours or 
 
 0.0366 kilowatt hour; 
 
 0.0366X10=0.366 cent, or over a third 
 
 of a cent. 
 
 "In a building with, let us say, one elevator, serving six 
 floors continually for eight hours, this waste in power would 
 be considerable if the operator had to make one unneces- 
 sary start on each trip, or two unnecessary starts for each 
 round trip. If this car made 84,000 round trips in a year, 
 the power waste would cost over $60. And if this average 
 held good in buildings with ten elevators instead of one, 
 with 24-hour service instead of 8-hour service, and with 20 
 stories instead of six stories, the loss would amount to 
 something over $3,000. The wear and tear on switch con- 
 tacts, controller contacts, controller magnets, commutator, 
 armature, steel worm, bronze gear or gears, thrust plates, 
 ball bearings, armature bearings, drum-shaft bearings, the 
 ear cables, the counterweight cables and the back-drum 
 cables are all materially increased also by increased 
 starting." 
 
 Table 49 gives some interesting and instructive data 
 regarding the starting and running current, fuse capacity, 
 etc., of various sized motors for Otis elevators. 
 
Electric Elevators 
 
 941 
 
 Fig. 3S7 
 
 DOUBLE WORM AND GEAR ELECTRIC ELEVATOR, OVERHEAD INSTAL- 
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Electric Elevators 
 
 943 
 
 1 
 
 Pig. 388 
 single wgiul and gear electric elevator, basement instal- 
 LATION 
 
944 Steam Engineering 
 
 In addition to the waste of power caused by unnecessary 
 starts, there is the tremendous strain to which the appar- 
 atus and cables are subjected when the car is suddenly 
 stopped on the down trip; there is also the liability of 
 burning out armatures by hasty reversals. Most elevator 
 controllers are designed now so that the current cannot be 
 sent through the motor in the reverse direction until the 
 armature has ceased revolving. But there are many con- 
 trollers still in use which are not so equipped, and motors 
 operated with such controllers can easily be damaged by 
 suddenly reversing the car switch before the motor has 
 stopped revolving. If an elevator operator reverses his 
 switch to the "down" position before the motor has fully 
 ceased rotating in the "up" direction, the effective voltage 
 at the armature terminals will be practically the sum of 
 the line voltage and the counter electro-motive force of the 
 armature, instead of the difference between the line voltage 
 and the counter electro-motive force, or almost twice the 
 line voltage, with nothing to oppose it but the very low 
 resistance of the armature winding and connections. This 
 would result in a flow of an enormous current — sufficient 
 to burn up the armature in short order — if the safety fuses 
 did not melt promptly. 
 
 HYDRAULIC ELEVATORS. 
 
 The mechanism of a hydraulic elevator consists of a 
 cylinder and piston, the piston being connected by one 
 or more piston rods to a cross-head which carries the 
 sheaves over which run the lifting cables from which 
 the car is suspended. By means of suitable valves, and con- 
 trolling mechanism operated from the car, water, under 
 pressure from compression, or gravity tank systems, or 
 
Hydraulic Elevators 
 
 945 
 
 Fig. 389 
 
 from street mains where sufficient pressure is available, is 
 caused to flow into, and out of the cylinder, thus causing 
 
946 Steam Engineering 
 
 the piston to move from one end of the cylinder to the 
 other, and back again. This motion of the piston -and 
 cross-head to and fro imparts motion to the lifting cables 
 which pass over sheaves at the top of the elevator hatchway, 
 and which hold in suspension the car, thus moving it up 
 or down, according as the water flows into or out of the 
 water cylinder. 
 
 The motion of the piston transmitted to the cable is 
 multiplied to a greater or less degree, according to the 
 design of the elevator, by being caused to pass over sheaves 
 designed for that purpose. 
 
 Thus the ratio of increase in speed may be anywhere 
 from 2 to 1, to 12 to 1, to meet the requirements due to the 
 nature of the service, whether freight or passenger. The 
 height of the building also controls in a large measure the 
 speed, for instance in very tall buildings the elevators may 
 be geared as high as 12 to 1. 
 
 The cylinders of hydraulic elevators are made either ver- 
 tical, or horizontal depending upon local conditions. If 
 the floor space is restricted, vertical cylinders are used, 
 but in cases where space above the basement floor for the 
 accommodation of vertical machines cannot be easily ob- 
 tained, it is the usual practice to place horizontal cylin- 
 ders in the basement. Vertical cylinders are usually geared 
 three and four to one, although ratios of from two to one, 
 up to six to one are quite common. 
 
 Fig. 389 presents a view of a low pressure vertical cylin- 
 der hydraulic elevator geared two to one. The cut shows 
 the general arrangement of the mechanism, from base- 
 ment to top sheave. This type of hydraulic elevator is 
 operated by the movement of the hand rope n, which passes 
 around a sheave at the side of the valve chamber, and 
 moves the valve by means of a rack and pinion gear. 
 
Hydraulic Elevators 947 
 
 Kope n then passes under two small sheaves at the bottom 
 of the elevator hatchway, and from thence up to the top 
 of the hatchway, and over another small sheave. One side 
 of this hand rope passes through the car, and by pulling 
 this side up the operator causes the car to descend, and by 
 pulling the rope down the car will ascend. Near the top, 
 and bottom of the hatchway two balls m and m' are placed 
 upon the hand rope. They are large enough to prevent 
 their passing through the openings in the floor, and roof 
 of the car through which the hand rope passes. When the 
 car ascending strikes the upper ball m, the latter is carried 
 up with the car, thus pulling up the hand rope, and moving 
 the control valve back to the stop position. Should the car 
 fail to stop, the valve will be carried past the stop position, 
 w^hich will connect both ends of the cylinder, and the car 
 will start to descend. If, however, every part is properly 
 adjusted, this reversal of the motion of the car cannot 
 occur, because under such conditions, the car will stop 
 when the valve is closed. If by any mishap the car should 
 run away, and go beyond the normal limit of its travel, the 
 control valve would be slightly opened in the opposite direc- 
 tion, just sufficient to develop a retarding force and thus 
 stop the car. The action is the same when the car approaches 
 the bottom, as it will then strike ball m', which will be 
 carried down, thereby closing the operating valve. Balls 
 m and m' are in fact automatic top and bottom limit stops, 
 and constitute one of the most valuable safety devices with 
 which elevators are equipped. 
 
 Another valuable device is the speed limit, which usually 
 consists of stops mounted at some convenient point in the 
 hatchway, and set above and below balls m and m'. so as to 
 limit the distance through which the latter can be moved. 
 
948 
 
 Steam Engineering 
 
 In some cases additional stop balls are used, on account of 
 its not being convenient to place stops to act directly upon 
 m and m'. The positions of these stops which limit the 
 amount of opening of the valve, are determined experi- 
 
 Fig. 390 
 
 mentally when the elevator is installed. The movement of 
 the car is kept steady by guides M, M, Fig. 389. In the 
 construction shown in Fig. 389 these guides are made of 
 hard wood. At the top of the car adjustible shoes are 
 
Hydraulic Elevators 
 
 949 
 
 provided, which slide freely against the guides. At the 
 bottom the car is guided by jaws formed in a safety device, 
 or "safety" as it is termed. It is made of hard wood blocks, 
 the dimensions varying from 4 inches thick by 11 inches 
 wide in the smaller sizes, to 5 in. x 15 in. in the larger 
 sizes. The jaws of this safety are reinforced with massive 
 iron castings, and on one side are provided with a wedge 
 that can be adjusted in position by means of screws, and on 
 
 Fig. 391 
 
 the opposite side with another wedge that can be forced 
 between the guide and the jaw to stop the car if one of the 
 lifting ropes breaks, or the car attains an excessive velocity 
 from any cause. 
 
 By reference to Fig. 390, and also to Fig. 391, which 
 shows one end of the safety device, its construction and 
 operation will be clearly understood. 
 
 In Fig. 391 the governor rope rod L is shown only in 
 the end elevation. Kef erring to Fig. 390 it will be seen that 
 
950 Steam Engineering 
 
 the two lifting ropes that run down to either side of the 
 car are connected with the ends of a rocking lever C. This 
 lever C, as shown in Fig. 391, is pivoted at D', hence if 
 either one of the lifting ropes breaks, the end of the lever 
 it is attached to will drop down. The shaft II which 
 extends under the car from one side to the other, carries at 
 its ends a lever L' which, when raised lifts the wedge N 
 and forces it into the space between the guide M and the 
 side of the jaw of the safety plank. Whichever way the 
 lever C may be tilted by the breaking of one of the lifting 
 ropes, it will rotate shaft H and lever L' in the proper 
 direction to throw up wedges N, thereby locking the car 
 against the stationary guides M. 
 
 The levers on shaft H are sufficiently long to strike the 
 guides M, when raised high enough, and are sharp at the 
 ends so that they will cut into the guides. 
 
 It might be thought that if the wedge N is only raised 
 far enough to catch in the space between the guide M and 
 the safety-plank jaw it would be forced upward so tightly 
 as to stop the car without further assistance. This would 
 be the case if the wedge had a sufficiently long taper, but 
 if it were so proportioned, it would require an enormously 
 strong jaw to resist the bursting strain ; moreover, the car 
 would be so tightly wedged that it would require a greater 
 force to release it than could be easily obtained. 
 
 With the wedges of the proportions used, it is necessary 
 to make the lever that lifts the wedge so that it will dig 
 into the guide, and as the car moves down through, say, a 
 foot or two in coming to a stop, the lever shaves the side 
 of the guide, thereby not only forcing the wedge tighter 
 against the guide, but producing an additional retarding 
 force. When a car is caught by the safety, all that is neces- 
 
Hydraulic Elevators 
 
 951 
 
 sary to release it is to start in the upward direction, and the 
 force exerted by the lifting cylinder is enough to overcome 
 the friction of the wedges against the guides. 
 
 In the foregoing it is shown how this safely acts, provid- 
 ing one of the ropes breaks. Elevator cars, however, seldom 
 drop when one of the ropes breaks, but frequently attain 
 
 Fig. 392 
 
 a very high velocity when the ropes do not break, and on 
 that account it is necessary to arrange the safety so that 
 it will act when the speed reaches a certain stage regard- 
 less of the cause of increased velocity. This is accom- 
 plished by means of the Otis safety governor, shown 
 mounted on one of the overhead beams in Fig. 389, and in 
 detail in Fig. 392. This device is driven by the rope L, 
 
yo2 Steam Engineering 
 
 which is made fast to one end of lever G' as shown in 
 Fig. 389. The spring that holds G' is strong enough to keep 
 the lever in its normal position and rotate the safety gov- 
 ernor at a velocity proportional to the speed of the car. 
 Eeferring to Fig. 392 it will be seen that the governor may 
 be adjusted by means of the spring on the spindle, to act at 
 any desired velocity. The governor driving rope passes ^ 
 through the clamping jaws H H', and when the governor 
 speed becomes great enough to lift the rod Z and throw 
 the jaws together, the rope will be clamped. Then, as the 
 rope cannot move, the outer end of the lever G' on the 
 safety plank will be held stationary as the car descends; 
 hence, the shaft H will be rotated, throwing the safety 
 wedges 1ST into action to stop the car. It is evident that 
 the car can descend only as far as the upward movement of 
 the end of lever G' and the compression of the spring on 
 L will permit, before the rope will be compelled to slide 
 through the clamps H, H' of the governor. As the distance 
 through which the spring can be compressed, plus the move- 
 ment of the end of G' is only a few inches, it is evident 
 that unless the car is stopped very short, the rope L must 
 break if it cannot slide through clamps H, H\ The dis- 
 tance in which the car will stop is always considerably more 
 than the compression of the spring plus the movement of 
 the end of G' ; hence, while it is necessary for H H' to 
 clamp the rope tight enough to move G', the pressure must 
 not be so great as to prevent the rope from slipping. For 
 the same reason, in order to make the safety governor 
 reliable it is necessary that the operating rope shall be in 
 just as good condition as the elevator lifting ropes. The 
 failure to inspect this rope properly, and make sure that 
 it is at all times in perfect condition has been a prolific 
 cause of accidents. 
 
Hydraulic Elevators 
 
 953 
 
 Fig. 393 
 
 The jaws of the safety plank and the wedge N should be 
 kept clean and in proper adjustment at all times. As the 
 
WZ^ 
 
 954 Steam Engineering 
 
 guides M have to be kept well lubricated, it can be easily 
 seen that if the safety jaws are neglected they will soon 
 become clogged with a mixture of grease and dust, and this 
 may give a considerable trouble by causing the wedge to 
 stick to the side of the guide and thus go into action when 
 everything else is running properly. The wedge 1ST, and 
 the adjusting wedge on the opposite side of the guide, will 
 gradually wear away. For this reason the latter should 
 be set up as often as required to keep the proper amount 
 of clearance between the guide, and the safety jaw. If the 
 clearance is too great, the wedge N is liable to not catch 
 firmly when called into action, and if the clearance is too 
 small, the safety is liable to act when not required. 
 
 The operating valve shown in Fig. 389 is the same in 
 principle as the one shown in section in Fig. 393, but it 
 has several details of construction not shown in the latter. 
 Its design is shown more in detail in Fig. 394, which is a 
 sectional elevation of the valve, and casing. The casing 
 is made in three parts marked 7, 8 and 9. Part 7 forms 
 the top, and provides a dome, into which the rack 6 on the 
 end of the valve rod can rise as the valve is lifted by the 
 rotation of the pinion on the end of the shaft A. This 
 shaft carries at its outer end the hand rope sheave shown 
 at the side of the valve in Fig. 389. The parts 7 and 8 are 
 divided at the center of the shaft A, and form a bearing 
 for the latter. 
 
 The lower part 9 which is the valve casing proper, has 
 ports 10 and 11 for connection with the lower end of the 
 circulating pipe, and the lower end of the cylinder, in the 
 manner indicated in Fig. 393. That portion into which 
 the circulating pipe is connected forms a separate casting 
 in Fig. 389, and the casing 9 is bolted to it. Port 12 in 
 part 9 of the valve casing is for the purpose of connecting 
 
Hydraulic Elevators 
 
 955 
 
 Fig. 394 
 
956 Steam Engineering 
 
 with the pressure-water supply if for any reason it is not 
 desired to have this connection made in the circulating 
 pipe. The valve casing is lined with brass tubing 4 and 3. 
 Lining 4 is simply for the purpose of providing a smooth 
 surface for the cup packing of V to slide against. Lining 
 3 is provided for the purpose of making ports of such a 
 character that the cup packings of V may be able to slide 
 over them freely. 
 
 If the ports were large openings, the packings could not 
 pass over them, because on the up movement they would be 
 caught by the edges of the ports. With the brass linings 
 this trouble is overcome by perforating the brass with a 
 large number of small holes, about one-quarter of an inch 
 in diameter. The combined area of the holes is much 
 larger than would be required in a single port, this increase 
 in opening being provided so as to reduce the friction of 
 the water running through the holes by reducing the 
 velocity of flow. 
 
 The pressure of the water tends to force the valve piston 
 V up, and the other piston V down, and as both pistons 
 are the same in diameter, the valve is balanced. Never- 
 theless the force required to move the valve is considerable, 
 owing to the friction of the cup packings, caused by the 
 pressure of the water acting upon the entire surface of the 
 leather in contact with the brass linings of the valve casing. 
 
 On this account the pinion on the shaft A, through which 
 the valve is moved, is made very small, while the hand rope 
 sheave is large — about 20 inches in diameter — so that while 
 the valve travels a few inches in either direction the hand 
 rope has to be pulled through a distance of from two to 
 four feet, according to the size of the valve and the speed of 
 car. For high car speeds the hand rope movement is in- 
 creased, so that the automatic top and bottom stops may 
 
 . 
 
Hydraulic Elevators 957 
 
 be able to arrest the movement of the car without making 
 the stop abruptly. Eeference to Fig. 394 will show that 
 the lower head that clamps packing 2 is made tapering. 
 This is done in order to prevent too quick a closure of the 
 outlet from the lower end of the cylinder when the valve is 
 moved down to stop the car on the up trip ; otherwise the 
 stop would be too abrupt. Even with this precaution it 
 is possible for the operator to close the valve too quickly; 
 therefore a check valve is inserted in the passage connect- 
 ing the valve casing with the cylinder. 
 
 This check is directly under the lower end of the circu- 
 lating pipe, so that if the operator closes the valve too sud- 
 denly the descent of the piston within the cylinder will not 
 be arrested instantly, but the piston will slowly continue 
 its movement and gradually force the water under it to 
 pass through the relief check valve, into the circulating 
 pipe, and thus into the top end of the cylinder. If the 
 operator moves the hand rope so quickly on the down trip 
 as to produce a violent stop, the piston will continue to rise 
 in the cylinder, and the water above it which cannot pass 
 to the lower end of the cylinder on account of the valve 
 being closed, will be forced back through the inlet pipe I to 
 the pressure tank. In this case, as no water can pass into 
 the lower end of the cylinder, the continued upward move- 
 ment of the piston causes it to leave the water, and thus 
 a vacuum is formed underneath it. 
 
 This vacuum together with the tank pressure on top of 
 the piston soon arrests the movement of the car, but the 
 stop is not so sudden. One objection to having the con- 
 nection from cylinder to pressure tank through the inlet 
 pipe I is, that if for any reason the pressure in the tank 
 should drop to zero, owing to the starting of a bad leak, 
 the water in the top end of the cylinder could immediately 
 
p^ 
 
 )58 
 
 Steam Engineering 
 
 
 Valr« Beafij 
 
 Fig. 395 
 
 .-. 
 
Hydraulic Elevators 959 
 
 run out with such freedom that if the car should happen 
 to be at, or near the top of the hatchway it would attain a 
 dangerous speed by the time it reached the bottom. But 
 by locating the pressure tank on the roof of the building 
 the danger from this source is obviated, for the reason that 
 the flow of the water from the cylinder would- then be 
 against a pressure due to the elevation of the tank, and to 
 this may be added the pressure of the atmosphere, for the 
 reason that the valve being closed, no water can pass into 
 the lower end of the cylinder, and as the piston moves up, 
 a vacuum is formed under it thus tending to retard its 
 motion. 
 
 The result is that the combined pressures are sufficient 
 to hold the car within safe speed limits. When the pressure 
 tank is located in the basement, the danger above referred 
 to is avoided by using a valve of the type shown in Figs. 
 395 and 396. Fig. 395 shows the casing, and Fig. 396 the 
 valve. 
 
 The difference between this valve and that of Fig. 394 
 is that it is provided with an additional piston V", see Fig. 
 396, which is called the throttle valve. When this valve 
 is used, the inlet pipe from the pressure tank is attached 
 to the port 12. When the elevator is stopped, the throttle 
 valve V" is directly opposite the port 12, and thus obstructs 
 the flow of water from the port 10. It will be seen that a 
 groove is turned in V" at the center line. In addition the 
 valve is not made a perfect fit in the casing, and the clear- 
 ance thus afforded is sufficient to permit water to pass by 
 in as large an amount as may be required to prevent a too 
 sudden stoppage of the car should the operator close the 
 valve too quickly. Another advantage is, that in case the 
 tank pressure should fail, the flow of water past this clear- 
 
960 
 
 Steam Engineering 
 
 Fig. 396 
 
 ance is retarded sufficiently to prevent a dangerous speed 
 in the descent of the car. 
 
 . 
 
Hydraulic Elevators 
 
 961 
 
 When the valve is moved in either direction to set the 
 car in motion, water passes from port 12 to port 10 through 
 side ports 14. A portion of this water passes directly from 
 12 to 14, and the other portion passes around the upper 
 lining 4, through circular passages 13, and thence down 
 
 J 
 
 Fig. 397 
 
 into 14, as indicated by the arrows. In this way sufficient 
 opening around the throttle valve is afforded even when 
 the port of the operating valve piston V is only slightly 
 open. The passages 13 and the connection between the 
 ports 14 and 10 are not easily made out from Fig. 395, but 
 
962 Steam Engineering 
 
 the arrows indicate the course of the water, and these make 
 the construction more easily understood. The lower cross 
 section through the passages 13, taken at right angles 
 to Fig. 395 will serve to illustrate more fully the construc- 
 tion. 
 
 The pistons used in vertical hydraulic elevators are made 
 in several designs, some being arranged so as to be packed 
 from the upper end, and others so as to be packed from the 
 lower end. Fig. 397 shows one of the latest designs of pis- 
 tons arranged to be packed from the lower end of the cylin- 
 der, which appears to be the favorite type now. The draw- 
 ing shows a section through the complete piston, with pack- 
 ing in place, also a section of the cylinder C. 
 
 Ordinary square packing is used, and this is held in 
 position by a follower secured by six bolts. Fig. 398 shows 
 the body of the piston only. The parts P and P" are made 
 to fit the cylinder, but the intervening section is cut away 
 on opposite sides, so as to afford space for the ends of the 
 piston-rods and their fastening nuts. The top and bottom 
 parts of the piston are connected by the pillars I and I. 
 
 In packing these pistons it is necessary to be careful not 
 to press the packing in too tight, as there is danger of burst- 
 ing the cjdinder by so doing, and even if this much damage 
 is not done, the friction caused by the excessive pressure 
 may be so great as to prevent the car from attaining its 
 full velocity. If a hard packing is used, and this is forced 
 into place dry and very tight, the chances are that when it 
 becomes well soaked it will expand enough to burst the 
 cylinder. Bursting hydraulic-elevator C3dinders is not a 
 very rare occurrence, and when it does occur it is due to 
 too great pressure of the piston packing against the sides 
 of the cylinder. 
 
Hydraulic Elevators 
 
 963 
 
 f i (U 
 
 
 ~ liFf 
 
 8P- 
 
 
 
 f ? J i 
 
 1 s. ' 
 
 
 
 p* 
 
 
 ^* 
 
 
 L -T 
 
 
 ' 
 
 I 
 
 
 
 J 
 
 
 
 
 _.- 
 
 
 
 
 P 
 
 
 p s 
 
 fee J 
 
 
 jg2 fg 
 
 
 
 
 
 
 
 Fig. 398 
 
964 Steam Engineering 
 
 Keferring to Fig. 389, it will be noticed that there are 
 two piston rods, E. 
 
 This construction was -adopted in the early days of hy- 
 draulic elevators partially to increase the safety of the 
 apparatus, but principally to prevent the traveling sheave 
 B from twisting around. The ropes tend to hold the sheave 
 from twisting, but they will not prevent slight movements, 
 while the double piston-rods will. Now and for several 
 years past, however, the frame of the traveling sheave has 
 been made in the form of a crosshead running in stationary 
 guides, thus effectually preventing any side movement of 
 the sheave. With* this construction 4he main benefit of the 
 double piston-rods is additional safety; while it is possible 
 for one rod to break or become loose, it is practically im- 
 possible for both to give way at the same time. 
 
 The arrangement of the cylinder C, the circulating pipe 
 K, and the valve V, in Fig. 389, is the same as in the dia- 
 gram Fig. 393, even the inlet I being similarly situated. 
 The small pipe c is for the purpose of carrying off the drip 
 from the upper side of the top cylinder head, ordinarily, 
 and also for the purpose of draining the water from the 
 upper end of the cylinder, in cases where it is necessary to 
 run the piston to the top of the cylinder to renew or adjust 
 the packing. Some cylinders are arranged to be packed 
 from the upper end and others from the lower end, the 
 latter design being the one generally used in modern ma- 
 chines. As will be noticed, the pipe c connects at the bot- 
 tom of the cylinder with other pipes that connect to the 
 valve chest and the lower end of the cylinder. All these 
 pipes are either to carry off the drip or to draw water from 
 the various parts of the cylinder and valve chest when 
 desired. Globe valves are placed in the drainage pipes so 
 as to keep them closed normally. 
 
Hydraulic Elevators 965 
 
 Counterbalance. — Generally a portion of the counter- 
 balance is placed on top of the piston, so that in such ma- 
 chines the counterbalance weight is divided into three parts, 
 one being within the cylinder, one in the traveling sheave 
 frame, and one constituting the independent counter- 
 balance. 
 
 Operating Devices. — In order if possible to avoid the 
 uncertainty of operation in connection with the hand rope 
 in high speed elevators, lever, and wheel operating devices 
 have been developed, and to make these devices operative 
 and reliable, the operating valves have been somewhat modi- 
 fied in design. The main valve, controlling the flow of water 
 into, and out of the cylinder, varies in diameter from 3 
 inches in small machines, to 7 or more inches in the large 
 sizes. Fig. 399 shows the lever device for operating, a 
 modern high speed hydraulic elevator. The lever L is 
 shown located in the car. The movement of this lever to 
 one side or the other rocks the horizontal lever M, and this 
 motion causes the sheave P mounted on the frame I to 
 rotate through a small angle. The rotation of P is trans- 
 mitted to P' through the rope k, and the rotation of P' 
 actuates the valves in a manner that will be presently ex- 
 plained. 
 
 Ropes m m, n n pass around sheaves NNNN located at 
 top and bottom of the elevator hatchway, as is clearly 
 shown. The ends m m are fastened to the ends of the 
 lever M but the sides n n are not connected with it, although 
 in the illustration they look as if they were. The side n 
 that runs up from the right-hand side N sheave at the bot- 
 tom passes over the N sheave at the left-hand side at the 
 top of the elevator hatchway. These two N sheaves at the 
 top are mounted upon a frame I which is arranged so as 
 to hold the sheaves firmly in the horizontal position, but 
 
966 
 
 Steam Engineering 
 
 Fig. 399 
 
Hydraulic Elevators 967 
 
 allows them to revolve freely around the studs upon which 
 they are mounted. The frame I is suspended from a rope 
 that passes over the two small sheaves resting on top of the 
 overhead beams. The end of this rope extends downward, 
 outside of the elevator hatchway, and has a weight sus- 
 pended from it so as to hold the ropes m m, n n, with the 
 proper tension. 
 
 Upon the larger sheave P are mounted the lower N N 
 sheaves. If the right-hand end of lever M is depressed, 
 the right-hand loop formed by the rope n m will be low- 
 ered, while the left side end will be raised, and as a conse- 
 quence the right side lower N sheave will swing downward 
 while the left side one will swing upward. Thus the rope 
 k will be pulled with the upper side moving from left to 
 right, and sheave P' will be rotated in the direction in 
 which the hands of a clock move. 
 
 This arrangement of ropes for transmitting the motion 
 of lever L to sheave P' is called the running rope system. 
 There is another way of accomplishing the result with sta- 
 tionary ropes, the upper ends of these being attached to 
 the upper frame I and the lower ends to the sides of sheave 
 P, or to the ends of a lever secured to this sheave. In this 
 arrangement the rope that is fastened to the right-hand 
 side of sheave P is secured to the left side of the upper 
 frame I. The sheaves NN NN are placed upon the ends 
 of lever M and each rope passes over one sheave art one end, 
 and under another sheave at the other end of M. This is 
 the standing rope system. For both systems there are sev- 
 eral modifications, but the results are the same in each 
 case, viz., to transmit the motion of lever L to sheave P'. 
 
 Valve v controls the flow of water into and out of the 
 hydraulic cylinder. This valve is actuated by a piston T 
 located in the enlarged portion of the valve chamber, and 
 
968 Steam Engineering 
 
 which is larger in diameter than valve v; consequently if 
 water under pressure is admitted to the space between T 
 and v, the pressure of the water upon the larger area of 
 piston T will cause it to move up, provided there is no 
 pressure on its top side. If water under pressure is ad- 
 mitted to both sides of piston T, it will be balanced and will 
 exert no force to move the valve in either direction. Valve v 
 will, however, have the pressure acting upon its upper side, 
 while the only pressure acting against its lower side will be 
 atmospheric pressure, or that of the tank into which the 
 water is discharged. Consequently the valve will move 
 downward. Water is admitted to the space above piston 
 T through a small pilot valve at h which is connected with 
 the pressure pipe through pipe g, while pipe f connects it 
 with the space above T. 
 
 When the car is at rest, pilot valve h is in a position to 
 close the ports connected with pipes g and f, and also pre- 
 vents the escape of water into the larger pipe connecting 
 the lower end of the pilot valve chamber with the main 
 discharge pipe. Under these conditions, the water in the 
 main valve chamber above piston T cannot escape unless 
 valve h leaks. When sheave P' is rotated in a clockwise 
 direction, the crank on the end of the shaft will draw down 
 the connecting rod j, and as valve h can move much easier 
 than main valve v and piston T the latter will remain 
 stationary, while h will be depressed. This movement of 
 h will uncover the ports connecting with pipes g and f , thus 
 establishing a through connection between the pressure pipe 
 and the space above T and the latter will be forced down- 
 ward, carrying with it throttle valve V which will uncover 
 the port connecting with pipe G, and also move the main 
 valve v far enough down to uncover the upper edge of the 
 port connecting with the lower end of the cylinder, thus 
 
Hydraulic Elevators 969 
 
 opening a communication between the two ends of the 
 main cylinder. Under these conditions the weight of the 
 elevator car which acts to pull piston F upward will set 
 the latter in motion, and the water in the upper end of the 
 cylinder E will be forced down through pipe G and 
 through the valve chamber, around valve V into the lower 
 end of the cylinder. The pipe G is called a circulating 
 pipe, as one of its objects is to provide a path through 
 which the water may circulate between the top and the 
 bottom of the cylinder E. 
 
 As the action just explained takes place when the ele- 
 vator car descends, it will be seen that, for the down trip, 
 no water is drawn from the pressure tank. To run the 
 car upward, the sheave P' is rotated counter clockwise by 
 swinging the car lever L in the opposite direction. When 
 P' is so rotated, the crank on the end of the shaft will push 
 connecting rod j upward, and thus pull on rod i and 
 thereby lift the pilot valve h. The upward movement of 
 h uncovers the port that connects with pipe f, bat keeps 
 that connecting with pipe g closed, so that the water con- 
 fined in the valve chamber above T can now escape through 
 pipe f, and the lower end of the pilot valve' chamber into 
 the discharge pipe. In this way the pressure acting on 
 the top side of T is removed, and the pressure acting 
 on the bottom side forces the valves up, owing, as has been 
 already explained, to the difference in area between T and 
 valve v. The upward movement of valve v opens communi- 
 cation between the port running to the lower end of the 
 hydraulic cylinder, and the discharge pipe, thus permitting 
 the water in the lower end of the cylinder to escape through 
 the discharge pipe. This upward movement of the valves 
 also raises throttle valve V and allows the water in the 
 pressure pipe free access to the port connecting with pipe 
 
970 Steam Engineering 
 
 G, thus admitting a new supply of water under pressure 
 to the space above the piston in the hydraulic cylinder. 
 Under these conditions the water acting upon the top side 
 of piston F in conjunction with the vacuum formed under 
 the piston by the escape of the water into the discharge 
 pipe, provides the force that depresses the piston and 
 thereby lifts the car. 
 
 Upon the rate of flow with which the water can enter, 
 or pass out of the cylinder will depend the velocity with 
 which the piston will move, and this rate of flow is evidently 
 dependent upon the extent to which the valves are opened. 
 If the operator in the car desires to run at a slow speed, 
 he moves lever L a short distance from the central posi- 
 tion; for a higher speed, he moves it further from the 
 center, and for the highest velocity, he moves it as far 
 as it will go. 
 
 Now suppose L is moved a short distance only, then 
 sheave P will* be rotated through a short angle, imparting 
 a correspondingly small movement to connecting rod j. 
 Suppose j is depressed, thus opening the connection be- 
 tween pipes g and f — water will begin to flow into the 
 space above T as soon as pilot valve h moves down far 
 enough to uncover the ports connecting with pipes g and 
 f and draw down the end S of lever Q. As j will now 
 be stationary, it will act as a fulcrum, and E will be 
 lifted. This movement will continue until pilot valve h 
 is raised sufficiently to cover the ports connecting with 
 pipes g and f, which will stop the flow of water into the 
 space above T. It will thus be seen that, after pilot valve 
 h has been moved by the rotation of the sheave P', main 
 valve v, and piston T also begin to move, and as they 
 move, the pilot valve is returned to stop position. If pilot 
 valve h is moved but a short distance from stop position, 
 
Hydraulic Elevators 971 
 
 piston T and valve v will have a correspondingly short 
 distance to move to return the pilot valve to stop position. 
 The amount of opening given to pilot valve h depends upon 
 the distance the car lever L is moved. If for a short dis- 
 tance, the opening will be but a small fraction of its travel, 
 and the main valve will open a correspondingly short dis- 
 tance, and vice versa. As water is practically incompres- 
 sible, it is apparent that if lever L be too quickly moved 
 to the central position when the car is moving at a high 
 rate of speed, the motion will be arrested with a violent 
 jerk. In order to prevent such action, means are provided 
 whereby the water may find an outlet, if the valve is closed 
 too suddenly. If the sudden stop occurs on the downward 
 trip of the car, which is the up-stroke of piston F, the 
 water will leak by the throttle valve V and flow back into 
 the pressure pipe, and will continue to flow until the car 
 has come to a stop. 
 
 If the throttle valve V were not provided, the water 
 would escape too freely, back into the pressure pipe, and 
 as a result the car could not be stopped in a very short 
 distance ; hence, the object of valve V is to provide means 
 to prevent a too sudden stop of the car on the down trip, 
 and at the same time not to permit the car to run farther 
 than is necessary to make a gradual stop. Valve V is 
 not water-tight, as has already been explained (see Fig. 
 396), and its throttling action begins gradually. 
 
 Should the car be stopped too suddenly on the up-trip, 
 the water in the lower end of cylinder E will be forced 
 through valve d at the bottom of pipe G, and the mo- 
 mentum of the moving parts will be expended in com- 
 pressing the spring that holds valve d to its seat. Fig. 399 
 has been reduced in length, but it shows in detail all of 
 the mechanism of a modern type vertical cylinder hy- 
 
972 
 
 Steam Engineering 
 
 Fig. 400 
 
Hydraulic Elevators 973 
 
 draulic elevator, with running rope or standing rope con- 
 trol. Other methods of control besides those already de- 
 scribed are in use, mainly in private dwellings and other 
 places where an operator is not employed. These consist 
 of magnetic controllers for operating the pilot valve by 
 means of push buttons, the magnets being operated by 
 current from the incandescent light circuit, or if such a 
 circuit is not available, the current is derived from pri- 
 mary, or storage batteries. 
 
 Horizontal Cylinder. — The principal difference between 
 the vertical, and the horizontal cylinder types of hydraulic 
 elevators lies in the fact that in the one type the cylinder 
 stands in a vertical position, while in the other it is placed 
 horizontally. The principles governing the operation of the 
 valve mechanism are practically the same in both cases, 
 outside of a few details which will be explained. Fig. 400 
 shows the general arrangement of a horizontal cylinder 
 hydraulic elevator, including pump and pressure tank. 
 The type here illustrated and described is the Crane push- 
 ing type elevator, there being two distinct classes of hori- 
 zontal hydraulic elevators, viz., the pushing and pulling 
 types. Referring to Fig. 400, the stationary sheaves and 
 rear end of the cylinder will be seen close to the hatch- 
 way. The main valve which controls the admission and 
 release of the water to and from the cylinder is located 
 at K, and is automatically operated by the movement of 
 the pilot valve L, the latter being actuated by the rocking 
 of shaft M, which is done by means of rods m m con- 
 nected with a running rope system operated by the lever 
 in the car. An automatic stop valve is located at R simi- 
 lar in design to that described in connection with vertical 
 cylinder machines. This valve is actuated by the mechan- 
 
974 
 
 Steam Engineering 
 
 ism at N, which is set in motion by the movement of the 
 crosshead. 
 
 Figs. 401, 402 and 403 show the apparatus in detail. 
 
 Fig. 401 
 
 In Fig. 401, which is a side elevation, it will be seen that 
 if lever S is moved in either direction, the rods m m will 
 
 Fig. 402 
 
 cause shaft M to rock, thus moving the pilot valve by 
 means of valve rod L'. Moving the pilot valve will either 
 
 Fig. 403 
 
 open or close main valve K, which will allow the water to 
 flow into, or out of the cylinder, depending upon what 
 direction lever S is moved. 
 
Hydraulic Elevators 975 
 
 If the operator fails to return lever S to stop position 
 when the car reaches the top of the hatchway, the frame 
 N will be carried to the right by the motion of the cross - 
 head, and the projecting arm D', Fig. 402, will strike 
 the stop mounted on rod D" connected to the end of the 
 frame. This movement of N will cause a roller at n' to 
 strike lever o', which will move to the right, and pull 
 rod Q with it, and this action will close stop-valve R, 
 which will stop the flow of water into the cylinder, and 
 the car will come to a stop. 
 
 Should the car be descending, the main piston will be 
 moving to the left, and if lever S is not returned to stop 
 position at the proper time, the automatic stop will act in 
 precisely the same way, except that frame N will be moved 
 to the left instead of to the right. 
 
 Referring to Fig. 403, which is a sectional elevation of 
 the cylinder, piston, sheaves and connecting parts, it will 
 be seen that there is a rubber ring around the piston end 
 of the plunger E, and a similar ring in the crosshead D. 
 A strong buffer frame I is attached to front cylinder head 
 G. The function of these parts is to act as cushions in 
 case the car travels past its normal position at either end. 
 These parts should be adjusted so as to prevent the car, or 
 counterbalance weight from striking the overhead beams 
 in case the automatic stop valve fails to act. 
 
 Pulling Type. — Fig. 404 shows a view of a pulling type 
 of horizontal cylinder hydraulic elevator. This machine is 
 made by the Whittier Machine Company, and its action 
 is as follows : G is the main operating valve, and the pilot 
 valve is located directly above it at J. The automatic stop 
 valve is at H, and is actuated by stop balls 1ST mounted on 
 rope L. These stop balls are moved by coming in contact 
 with an arm attached to the crosshead, which also carries 
 
976 
 
 Steam Engineering 
 
 Fig. 404 
 the whittier pulling machine 
 
Hydraulic Elevators 
 
 977 
 
 the traveling sheaves D, and shoes E on the crosshead 
 slide within the side guides. 
 
 The weight P suspended from the chain that travels 
 between two small guide sheaves located just below the 
 valve casing, is for the purpose of bringing the automatic 
 
 Fig. 405 
 stop valve to central position as soon as the piston moves 
 away from either end of the cylinder. The shackle bolts 
 for the ropes are shown at Q. 
 
 The main and the pilot valves of the Whittier machine 
 are shown in detail in Figs. 405 and 406, the first being a 
 
 To Cylinder From Cylinder 
 
 Fig. 406 
 plan view and the second a sectional side elevation. Ke- 
 f erring to Fig. 405, it will be seen that the operating lever 
 K is pivoted at the point F, so that when actuated by the 
 operating ropes AA' it imparts an end movement to the 
 pilot valve rod C. The ropes AA' are connected with the 
 
978 
 
 Steam Engineering 
 
 operating lever in the car by either a running, or a stand- 
 ing-rope arangement identical with those used for vertical- 
 cylinder elevators. 
 
 In Fig. 406 the pilot valve rod C is shown connected 
 with the top end of lever D, the latter being pivoted at G. 
 The part B, which holds the pivot G is actuated by the 
 lever K. The supply pipe is connected with the right-hand 
 end of the pilot-valve chamber through the pipe E. If the 
 rod C is moved to the left, high-pressure water will pass 
 through the pilot valve to the end I of the main valve and 
 force the latter to the left, thereby connecting the cylinder 
 with the discharge pipe, when the water will run out and 
 the elevator car descend. The forward movement of the 
 
 Fig. 407 
 
 main valve will carry the lower end of the lever I) to the 
 left and the upper end to the right, until the pilot valve 
 is returned to the closed position. If the pilot-valve rod 
 C is moved to the right, the end I of the main valve 
 will be connected with the discharge and the water will 
 escape, then the pressure acting on the piston L will force 
 the valves to the right and connect the supply pipe with 
 the cylinder, which will fill with water from the pressure 
 tank and the car will be forced upward. The movement 
 of the main valve to the right will carry the lower end of 
 the lever D in the same direction and the upper end to 
 the left, and return the pilot valve to the central position. 
 
Hydraulic Elevators 979 
 
 The pilot valve shown in Fig. 406 is provided with 
 stuffing-boxes at each end to insure tight joints with the 
 valve-rod, but this construction is not used in all the 
 Whittier elevators; in some of them the pilot valve is 
 made as shown in Fig. 407, where the escape of water at 
 the ends is prevented by the use of cup packings. The 
 pressure water enters through the port A, the discharge 
 being through the port B; consequently, the cups are set 
 so as to oppose the pressure which is exerted in both di- 
 rections from the port A. 
 
 Another design of the pulling-type elevator is presented 
 in Figs. 408, 409 and 410. This is called a "double-decked'" 
 machine, and is made by Morse, Williams & Co., of Phila- 
 delphia. Why it is called double-decked can be understood 
 from Fig. 408, which is a side elevation and shows two ma- 
 chines placed one over the other. In buildings where floor 
 space is limited, this construction is often adopted, in some 
 cases three and four machines being installed one over an- 
 other. Fig. 409 is a top view of Fig. 408, and Fig. 410 
 is an end view seen from the right side. In these machines 
 there is but one piston rod, as at B., Fig. 408. The 
 crosshead is similar to that in the Whittier machine, except 
 that the sides of the end bars are square with the side 
 frames, instead of in line with the traveling-sheave shaft, 
 as at J, Fig. 410. The guides F are set so that the 
 crosshead shoes a, slide on top of the upper flange, not 
 between the flanges. 
 
 At the stationary-sheave end of the guides there are 
 shorter guides U, which carry a shaft provided with small 
 rollers b, the function of which is to support the ropes 
 running over the upper sides of the sheaves. In Fig. 408 
 the upper machine is shown with the traveling sheaves 
 close to the stationary sheaves, caused by the car being at 
 
980 
 
 Steam Engineering 
 
 <jddn| 
 
 the lower floor of the building. In this machine the sup- 
 porting rollers b' are at the extreme right-hand end of 
 
Hydraulic Elevators 
 
 981 
 
 the guides IT. In the lower machine sheaves D are close 
 to the cylinder, as they will be when the elevator car is 
 at the top floor. In this case the supporting rollers b are 
 at the extreme left-hand end of guides U and midway be- 
 
 Fig. 410 
 
 tween the sheaves D and E, the better to support the ropes 
 at the central point. On the upper machine in Pig. 408 
 a hook 1 mounted on a shaft carried by the guide shoes c' 
 engages a piece e, secured to the part J', as shown in Fig. 
 510, at the center. At one end of the shaft which carries 
 
982 Steam Engineering 
 
 hook 1 there is a lever k. When the sheaves D' move to- 
 ward the cylinder, the hook 1 being engaged with lever e, 
 the supporting rollers b' are carried along with the hook ] 
 until lever k reaches an inclined plane m, up which the 
 rollers slide, causing the shaft to be rotated and hook 1 
 to be pulled up 1 out of the way of the lever e, the rollers 
 being left in the position of those shown on the lower 
 machine. The supporting roller shaft is kept in line, 
 notwithstanding that it is carried along by the part e 
 acting at the central point, by reason of the guide-shoes c 
 being provided with grooves that fit over the guides TJ, as 
 clearly shown in Fig. 410. When the traveling sheaves 
 move forward, the piece e engages hook 1 when the latter 
 is reached, and the roller shaft is carried forward to the 
 end of the guides, as shown at b. These supporting rollers 
 relieve the ropes of considerable strain when the stroke is 
 long, and the traveling sheaves are near the cylinder, but 
 they are of little service in short-stroke machines. The 
 movement of the roller shaft is equal to one-half the stroke 
 of the machine. 
 
 The Stop and Main Valves. — In a machine of the pull- 
 ing type the piston is forced toward the back end of the 
 cylinder on the upward motion of the car. If the auto- 
 matic stop-valve is properly adjusted, it will begin to close 
 at the right time to stop the car even with the upper floor ; 
 but if it is improperly adjusted, the car is likely to run 
 into the overhead beams, therefore buffers g g, faced with 
 rubber cushions h h, are provided. In the machine illus- 
 trated in Fig. 408 the automatic stop-valve does not fit 
 perfectly, and if the main valve is not closed when the 
 car reaches the upper floor, the car will not stop but will 
 slowly move upward until the crosshead brings up against 
 the buffer cushions h h. On the downward trip, if the 
 
Hydraulic Elevators 983 
 
 main valve is not closed when the car reaches the lower 
 floor, the car will settle gradually until it rests on the 
 bumpers, or the piston strikes the front cylinder head. 
 
 In Fig. 408 the main valve is located at G and is 
 actuated by a pinion at n which meshes with a rack in 
 the neck-bearing n'. The automatic stop-valve is con- 
 tained within the casing H and is actuated by a rod con- 
 necting with a crank-pin on a crank-disk mounted on the 
 shaft with the sprocket-wheel Q, Figs. 408 and 409. Tne 
 sprocket-wheel Q is rotated by means of a sprocket 
 mounted on the shaft with sprocket f, Fig. 409, which 
 latter is operated by a chain, the ends of which are affixed 
 to the ends of two square rods, the lower of which is shown 
 at L. Another chain around the sprocket P is connected 
 with the opposite ends of these two rods. To stop the 
 movement of the piston, the stop-valve is actuated to the 
 left. If the traveling sheave is moving toward the cylin- 
 der the actuating bar E attached to the crosshead will 
 strike the stop 1ST and move it to the left, which will set up 
 a counter-clockwise rotation of the sheaves and Q, and 
 this will move the crank-pin and the stop-valve to the 
 left. If the traveling sheave is moving away from the cylin- 
 der, the lower end of bar E will strike the stop 1ST on the 
 square rod L and, by carrying the latter to the right, ro- 
 tate sheaves and Q counter-clockwise in the same direc- 
 tion. The stops 1ST are hook-shaped; they slide over the 
 side projections on bar E, Fig. 410, and lock with it, 
 with the result that when the elevator is started on the 
 return trip the movement of the crosshead carries the stop 
 1ST with it, and the automatic stop-valve H is pulled open. 
 When the elevator is started it moves very slowly for a few 
 inches, as only the water that leaks by the automatic stop- 
 valve is available to move it, but as the movement of the 
 
984 
 
 Steam Engineering 
 
 Fig. 411 
 
Hydraulic Elevators 985 
 
 crosshead also operates the valve, the opening of the latter 
 is rapidly increased and the car speed correspondingly ac- 
 celerated. 
 
 When the bar E has carried the stop N as far as the 
 stop T the releasing lever S strikes the latter and the hook 
 on the stop N is raised so that the bar E may slide by and 
 leave the stop 1ST adjoining the stop T, ready to be struck 
 by the bar E on the next stroke. The actuating stops T 
 are not held on the rod L but on a rod directly in front 
 of it (see Fig, 410) , and this rod is secured, so it will 
 not move endwise, in the frame V. 
 
 Fig. 411 shows a double-deck arrangement of two sepa- 
 rate machines. This grouping of horizontal elevator en- 
 gines is often resorted to for the purpose of economizing 
 space, the machinery for operating two cars occupying the 
 same floor area as that ordinarily required for one. 
 
 High Pressure Elevators. — The types of elevators hither- 
 to discussed belong in the low pressure class, the water 
 pressures used in operating them not exceeding 200 lbs. per 
 square inch, the average being about 150 lbs. But the 
 increase in the height of modern office buildings, and the 
 demand for a high car speed have resulted in the develop- 
 ment of high pressure elevators, operating under pressures 
 as high as 700 lbs. per square inch, and even higher in 
 some cases. 
 
 The reduction in the size of the machine and piping 
 that can be effected by using this pressure is much greater 
 than would be supposed by those who have not investigated 
 the subject. To give a general idea of how great the re- 
 duction actually is, suppose a low-pressure elevator has 
 a cylinder 16 inches in diameter and works with a pres- 
 sure of 100 pounds. For such a machine the supply pipe 
 would probably be not less than 6 inches in diameter. Sub- 
 
986 Steam Engineering 
 
 stitute for this a high-pressure machine working with 800 
 pounds pressure per square inch; then, if everything else 
 remains unchanged, the area of the cylinder will be re- 
 duced to one-eighth, and this will make the diameter a 
 trifle under 5% inches, as compared with the low-pressure 
 cylinder of 16 inches diameter. This is not all the gain 
 that can be made; there can also be effected a great re- 
 duction in the size of the supply pipe, for as only one- 
 eighth of the quantity of water is required, the size of the 
 pipe can be reduced to the same degree as that of the cylin- 
 der, provided the water is to run through it at the same 
 velocity. This reduction would cut the pipe down from 
 6 inches to a trifle over 2 inches in diameter. 
 
 These reductions are not exactly what would be made in 
 actual practice, because the frictional loss in the small 
 high-pressure cylinder would not be as great as in the 
 large low-pressure cylinder, and the velocity of the water 
 through the supply pipe could be made greater for the 
 same percentage of loss; this would permit a farther re- 
 duction in the size of the pipe. In practice the gain in 
 this direction is utilized in part to reduce the size of the 
 apparatus, and in part to reduce the loss of energy in forc- 
 ing the water through the pipes. As a result, the loss of 
 energy due to the friction of the water passing through 
 the pipes, lifting cylinder and valves is reduced to about 
 5 or 6 per cent, whereas in low-pressure machines it runs 
 from, say, 10 to 30 per cent. The change of pressure 
 from 100 to 700 or 800 pounds brings about other changes 
 in the construction of the machine and apparatus and also 
 in the general arrangement of the system. 
 
 The arrangement of the various parts of a high-pressure 
 system is indicated by the diagram, Fig. 412. This dia- 
 gram shows a machine geared six to one. The cylinder is 
 
Hydraulic Elevators 
 
 987 
 
 shown at C, the plunger at P and the traveling sheaves 
 below it ; the cylinder is inverted, the plunger being forced 
 downward by the pressure of the water. This construc- 
 
 Pump to return Pilot Valve Discharge 
 to Mala Discharge Sjrtem 
 
 Fig. 412 
 
 tion is vised because the small size of the cylinder makes 
 it impracticable to use a piston and piston-rod, therefore 
 a solid plunger is provided and the pressure acts to push 
 it out of the cylinder. 
 
988 Steam Engineering 
 
 In Fig. 412 the pump forces water into the lower end 
 of the accumulator, from which a pipe runs to the main 
 valve, through which it passes to the pipe A and thence 
 to the lifting cylinder. On the return stroke the water 
 passes out of the cylinder through the pipe A and through 
 the upper end of the main valve to the discharge pipe, 
 which runs up to a tank placed on or near the roof of the 
 building. The object of this arrangement is to provide 
 a low pressure to operate the pilot valve, which is shown 
 in the diagram just above the main valve. In the first 
 high-pressure elevators made, the pilot valve was operated 
 with water at the same pressure that was used for the lift- 
 ing cylinder, but these valves were not successful, owing to 
 the fact that they had to be very small and the packings 
 would not withstand the wear due to the pinhead jets of 
 water striking them at terrific velocities; in addition, the 
 small holes through which the water passed were soon en- 
 larged so that the valve would not work satisfactorily. 
 With the low-pressure pilot valve there is no trouble. A 
 small tank is provided to receive the discharge from the 
 pilot valve and its actuating cylinder, and this water is 
 returned to the roof tank by means of a small pump as 
 shown in Fig. 412. 
 
 The Accumulator. — The accumulator takes the place of 
 the pressure tank of the low-pressure system. A pressure 
 tank cannot be used with the high-pressure system, owing 
 to the fact that it is troublesome and expensive to pump air 
 against a high pressure, and it is necessary to do this so 
 as to replenish the air that gradually leaks out of the pres- 
 sure tank. Even if there were no difficulty in pumping air 
 into a high-pressure tank, the accumulator would be pref- 
 erable, because with it the pressure depends upon the 
 weight on top of the plunger, not on the height of the 
 
Hydraulic Elevators 
 
 989 
 
 water in the cylinder. With a pressure tank the pressure 
 drops as soon as water is drawn out, and it runs up as 
 soon as the outflow stops, consequently the pressure is con- 
 tinually varying. 
 
 Fig. 413 
 
 The arrangement of the entire apparatus of an Otis high- 
 pressure vertical elevator is shown in Fig. 413. This il- 
 lustration shows several parts not represented in the ele- 
 mentary diagram, Fig. 412. The main pump is at A and 
 
990 Steam Engineering 
 
 at B is shown the prime mover, which in this case is an 
 electric motor, although in practice steam power is almost 
 always used. The accumulator is shown at C and the 
 main valve, and pilot valve are at D. From the main 
 valve the water passes to the lifting cylinder through pipe 
 E, passing first through an automatic stop-valve F, thence 
 through pipe G to cylinder H. The plunger is shown at 
 I, and the traveling sheaves at J. 
 
 The high-pressure water from the accumulator reaches 
 the main valve through pipe K and is discharged from the 
 valve through pipe L which runs up to the tank at the 
 top of the building. Through pipe M, the water returns 
 to the pump A. An air chamber is provided at Q to 
 smooth out any pulsations of the pump that its own air 
 chamber does not subdue. The small pump to return the 
 water discharged from the pilot valve to the roof tank is 
 also shown. 
 
 It will be noticed in Fig. 413 that the machine proper 
 of a vertical high-pressure elevator is not very elaborate. 
 
 Fig. 414 shows a sectional, and also a plan view of the 
 main and pilot valves. 
 
 The pilot valve is at A, and the main valve at C; B is 
 a motor cylinder, the piston of which moves the main 
 valve. In this construction, the pilot valve is not much 
 smaller in diameter than the main valve, and the motor 
 piston is very much larger than the main valve. The dif- 
 ference in the proportions of these parts as compared with 
 the valves described in connection with low-pressure ma- 
 chines is due to the fact that in the high-pressure system 
 the motor piston is actuated by low-pressure water, so as 
 to make it possible to use a pilot valve of large enough 
 size to be durable. As is shown in Fig. 413, the tank into 
 which the lifting cylinder discharges is placed high enough 
 
Hydraulic Elevators 
 
 991 
 
 to give enough pressure to operate the motor piston, and 
 from this tank water passes through the pilot valve A to 
 the cylinder B. If the motor piston were operated by 
 the high-pressure water, the pilot valve and its port holes 
 would have to be so small that the parts could not be made 
 sufficiently substantial. For this reason water at a pres- 
 
 Fig. 414 
 
 sure of about 80 pounds per square inch is used to operate 
 the motor piston. 
 
 It might be thought that having to discharge the water 
 in the lifting cylinder against a back pressure of 80 pounds 
 would cause considerable loss, and make the high-pressure 
 system objectionable on the score of low efficiency, but this 
 is not the case because the main pump draws water from 
 
992 Steam Engineering 
 
 this same discharge tank; therefore, the back pressure 
 against the lifting cylinder acts to help the pump, so that 
 in reality all the work the pump has to do is to force water 
 against a pressure equal to the difference between the pres- 
 sure of the accumulator and that of the discharge tank. 
 The net result is that if the accumulator pressure is 750 
 pounds, and that of the discharge tank is 80 pounds, the 
 actual pressure against which the pump acts is 750 — 80 
 =670 pounds, and the pressure that acts in the lifting 
 cylinder to raise the elevator car is 670 pounds, not taking 
 into account the losses due to friction of the water through 
 the pipes and valves on its way from the accumulator to 
 the cylinder. 
 
 Operation of Main and Pilot Valves. — The operation 
 of the main and pilot valve in Fig. 414 is as follows : If 
 the operator desires to run the car upward he moves the 
 car lever so as to pull up the rope W on the right side, 
 thus tilting the rock lever JST in a counter-clockwise direc- 
 tion. The levers N and L are secured to the shaft P; 
 hence, the end of L will move down and through the con- 
 necting rod L' will pull down the lever L" : and the latter, 
 through M, will depress the pilot valve. The center pipe 
 E is connected with the upper discharge tank : hence, water 
 will flow in and through the lower end of the pilot-valve 
 chamber, pass to the lower end of the motor-piston cylin- 
 der B, and raise the piston, the water above the latter pass- 
 ing out into the pilot-valve chamber above the valve, and 
 thence to the pipe D. As the motor-piston rod is connected 
 at both ends by arms J J with the ends of the main valve 
 C, the upward movement of the piston will lift the main 
 valve, and then the water from the accumulator coming 
 through the pipe I will pass into the center of the main 
 valve through the port S. The port Q will be above the 
 
Hydraulic Elevators 993 
 
 packing R, so that the water will pass out into the cen- 
 tral pipe H and thence to the lifting cylinder, and by 
 pushing the plunger out of the latter will lift the elevator 
 car. If the rock lever N" is tilted in the opposite direction, 
 the pilot valve will be raised, and then water will pass to 
 the upper end of the motor cylinder and depress the pis- 
 ton, thus moving the main valve down so that the water 
 in the lifting cylinder may escape through the ports Q' 
 into the upper end of the main valve and thence through 
 the ports S' to the upper discharge pipe G; from there it 
 passes to the discharge tank near the top of the building* 
 
 Cylinder and Plunger.. — Figs. 415 and 416 show the 
 construction of the plunger, cylinder, and sheaves of the 
 Otis high pressure vertical cylinder elevator. 
 
 Fig. 415 gives external and sectional views of the cylin- 
 der, the upper end of which is seen at A and the lower 
 end at B. To shorten up the drawing the cylinder is 
 broken at C C. The plunger is indicated by D. Above 
 the cylinder are shown the stationary sheaves held between 
 side frames made of channel iron G, to the lower end of 
 which the cylinder is bolted, as shown at G'. The channel 
 frames 6 are bolted to a rod H at the upper end, and 
 this is held between beams I that are secured to the wall 
 or floor framing of the building. The traveling sheaves 
 are carried in a crosshead attached to the lower end F of 
 the plunger. 
 
 The internal construction of the cylinder is shown in 
 the vertical section, which is taken at right angles to the 
 exterior view. The upper end of this drawing shows the 
 way in which the bearings of the stationary sheaves are 
 held between the side frame channel beams G G, and in 
 like manner the lower end shows the construction of the 
 cap F that forms the end of the plunger and the support 
 
994 
 
 Steam Engineering 
 
 Fig. 416 
 
 for the traveling-sheave frame. This cap is constructed 
 cup-shaped on its upper side to receive the drip from the 
 
Hydraulic Elevators 995 
 
 cylinder. The plunger, it will be noticed, does not fit the 
 cylinder throughout its entire length, but only for a short 
 distance at the lower end, where the stuffing-box is lo- 
 cated. The cylinder is held up by the rod H, and is sus- 
 tained against side displacement by means of one or more 
 rings K and the frame J, the construction of both of which 
 can be readily understood from the drawings. 
 
 The outlet M in Fig. 415 is the pipe connection through 
 which the actuating water enters and passes out of the 
 cylinder. T-bars I' I' to which the frame J is bolted 
 form the guides for the crosshead of the traveling sheaves, 
 and the cylinder is held true with these by means of the 
 frame J so as to keep the plunger and the crosshead guides 
 in line. 
 
 Fig. 416 shows side, and edge views of the crosshead, 
 the guides, and the traveling sheaves. 
 
 Fig. 417 shows the speed regulator used in connection 
 with the Otis high pressure type of elevator. This device 
 will not allow the car to attain- an excessively high speed 
 under any conditions, for the reason that it depends for 
 its action upon the velocity of the current of water passing 
 through it, and not upon the pressure. The device is con- 
 nected in the piping so that the water that flows into or 
 out of the lifting cylinder passes through it. If, when 
 the car is ascending, the water enters through port, C, and 
 passes out through D, then on the descending trip the 
 water will enter through D and pass out through C. In 
 either case, the water will have to pass through the open- 
 ings, E, in the valve piston, this passage causing a cer- 
 tain amount of loss in pressure dependent entirely upon 
 the velocity of the water through the holes, E. 
 
 Suppose that, when the car is running at 400 feet per 
 ninute, the loss of pressure suffered by the water in 
 
996 
 
 Steam Engineering 
 
 Fig. 417 
 
 passing through the piston holes, E, is 20 pounds; then, 
 if the car is running up, and the pressure of the water 
 when it reaches one side of B is 800 pounds, it will be, on 
 
Hydraulic Elevators 997 
 
 the other side, 780 pounds. If the car is running down 
 and the water is discharging into the delivery tank, a pres- 
 sure of 100 pounds on the cylinder side of B will corre- 
 spond to 80 pounds on the tank side of B; that is to .say, 
 in either case the difference in pressure between the two 
 sides of B will be 20 pounds. 
 
 From the construction of the device, it will be seen that 
 the force with which the piston rod, A, is moved endwise by 
 the difference in the pressure on the opposite sides of B 
 is resisted by the spring, K, so that by properly adjusting 
 this spring, the car can be made to run at any desired 
 speed with the main valve wide open, regardless of the 
 magnitude of the load or whether it is running up or 
 down. Thus it will be seen that, when this speed regulator 
 is provided, the car cannot attain an excessive velocity, 
 even if the operator becomes confused and opens the main 
 valve too wide. 
 
 In passing from either of the inlets, C or D, into the 
 interior of the cylinder, the water must flow through the 
 small holes in the casing, F. These holes are drilled on 
 spiral lines so that, when B moves in either direction, it 
 covers the holes one at a time, thus gradually closing the 
 outlet. The end movement of B is transmitted to one, or 
 the other of the levers, G, through rod, A, and the move- 
 ment of either lever will compress spring, K. 
 
 Direct Acting Plunger Type. — A direct acting plunger 
 elevator consists of a cylinder set vertically in the ground 
 directly under the car, and of length a few feet greater 
 than the travel of the elevator car. In this cylinder is a 
 plunger of the same length, carrying a car on its upper 
 end. The bottom of the plunger is supported by an in- 
 compressible body of water, and the car cannot descend 
 faster than the w^ater is forced out. 
 
998 
 
 Steam Engineering 
 
 Fig. 418 
 direct acting plunger elevator 
 
Hydraulic Elevators 999 
 
 The success of this elevator depends largely upon the 
 merits of the operating mechanism. In the installation of 
 this type of hydraulic elevator it is necessary to sink the 
 hole for the reception of the cylinder to a depth equal 
 to the height of the building. Fig. 418 shows the general 
 arrangement of the Otis direct acting plunger elevator. 
 This illustration is broken at a point between the elevator 
 car and the bottom of the elevator shaft in order to reduce 
 its length, but the part broken away would only show the 
 continuation of the guides, plunger, operating ropes, etc. ; 
 all the operating parts of the outfit are shown in the 
 illustration. 
 
 In plunger elevators, as the full pressure on the end of 
 the plunger acts to lift the car, the diameter of the plunger 
 is much smaller than in the geared types of elevators. The 
 pressure used varies from about 140, to 200 pounds per 
 square inch and the diameter of the plunger may be from 
 5 to 7 inches. The cylinder is made of steel pipe about 
 2 inches larger in diameter than the plunger, and the 
 hole in the ground is a couple of inches larger than the 
 cylinder. It will thus be seen that the hole in which the 
 cylinder is placed is not very large, so that it can be bored 
 in a manner similar to that employed for driving pipe 
 wells. If the subsoil is earth, a steel pipe lining is pro- 
 vided which is large enough to receive the cylinder. If 
 the hole is drilled in rock, no lining is required. 
 
 For the cylinder, a number of lengths of steel pipe are 
 turned true on the ends, threaded in a lathe, and joined 
 by sleeve couplings. The upper end of the cylinder is 
 screwed into a cast-iron section which is bored to fit the 
 plunger, and is provided with a stuffing-box and a pipe 
 connection through which the water enters and passes out 
 of the cylinder. The lower end of the cylinder is closed 
 
1000 Steam Engineering 
 
 by means of a suitable cap. The cylinder is coated with 
 a protecting paint and when in position, the space between 
 it and the sides of the hole is rilled with sand. 
 
 For the plunger, a number of lengths of steel pipe are 
 turned true and well polished. The sections are joined by 
 means of long internal sleeves which are so proportioned 
 that the transverse strength of the plunger at the joint is 
 as strong as at any other point. 
 
 As the elevator car can rise only as high as the plunger 
 travels, it follows that when the rise is 300 feet, the cylin- 
 der must extend down into the earth several feet more 
 than 300, because w^hen the car is at the top of the elevator 
 hatchway the bottom end of the plunger must be some dis- 
 tance below the top end of the cylinder. Furthermore, it 
 is necessary to provide sufficient length of plunger to carry 
 the car a short distance above the upper floor, say, two 
 feet, in order to avoid running the bottom of the plunger 
 too high up in the cylinder if the elevator should overrun 
 the upper limit of travel. 
 
 The plunger passes through a stuffing-box at the upper 
 end of the cylinder, and is provided with guide shoes at 
 the lower end to keep it in line and central. 
 
 Eeferring to Fig. 418, the car rests upon the upper end 
 of the plunger P, and the latter runs down into the cylin- 
 der C, the upper end of which projects above the ground 
 floor. From the top of the car a number of cables E ex- 
 tend upward and over a sheave S and thence down to a 
 counterbalance W. This counterbalance serves to reduce 
 the pressure required to raise the elevator, and also to 
 reduce the compression stress to which the plunger is 
 subjected. 
 
 The pipe of which the plunger is made weighs about 22 
 pounds per foot, so that a plunger 200 feet long will weigh 
 
Hydraulic Elevators 1001 
 
 about 4,400 pounds; this is more than the car is likely 
 to weigh, the latter ranging between 3,000 and 4,000 
 pounds. If the car weighs, say, 3,600 pounds, and the 
 plunger 4,400 pounds, the two combined will weigh 8,000 
 pounds, and with no counterbalance this weight would have 
 to be raised in addition to the load. Consequently the 
 plunger would be subjected to a compression stress of 3,600 
 pounds plus the load at the upper end, and 8,000 pounds 
 plus the load at the bottom, the stress increasing from top 
 downward at the rate of 22 pounds per foot. With a coun- 
 terbalance weighing 5,000 pounds, the weight raised will 
 be reduced to 3,000 pounds plus the load, and as the coun- 
 terbalance exceeds the weight of the car by 1,400 pounds, 
 it will actually hold up about one-third of the plunger,, 
 from the upper end downward, when the car is empty. 
 
 When the car is at the bottom of the shaft the plunger 
 is immersed in the water in the cylinder, consequently 
 a portion of its weight is balanced by the water it dis- 
 places. When the car is at the top of the shaft the 
 plunger is out in the air and its weight is not counter- 
 balanced to any extent by the water. This being the case, 
 the weight lifted will be less when the car is at the bottom 
 of its travel than when at the top, the difference being equal 
 to the weight of water displaced by the plunger. By prop- 
 erly proportioning the weight of the cables E, the load 
 lifted can be made equal at all points, for when the car is 
 at the bottom of the shaft these cables will hang above the 
 car, and thus will offset a portion of the counterbalance 
 W, while when the car is at the top of the shaft the cables 
 will hang above the counterbalance W and balance a por- 
 tion of the weight of the car. 
 
 The main valve for controlling the movement of the 
 car is shown at V, and the pilot valve at V. The two 
 
1002 Steam Engineering 
 
 valves A and B are the automatic stop or limit valves, A 
 being the top limit and B the bottom. The valve A is 
 actuated by the rope A" which pulls up the lever A' and 
 thereby closes the valve. This rope moves the lever A' 
 through the motion of the elevator car. Looking at the 
 illustration, it will be seen that the rope A" runs over 
 a sheave D mounted on top of the elevator car, and it can 
 also be seen that when the car approaches the upper limit 
 of travel, D begins to put a bend in A" and thereby draws 
 up the lever A'; by the time the car reaches the upper 
 floor, A' will be raised enough to close the valve A. By 
 this arrangement the valve is closed gradually and the 
 car is as gradually brought to a state of rest. 
 
 The valve B is actuated by the rope B" in precisely the 
 same manner that A is operated by the rope A". The rope 
 B" passes over the stationary sheave D' and under the 
 sheave D" located under the car, and when the latter de- 
 scends near enough to the lower floor, the bend put in the 
 rope B" by the sheave D" will raise the lever B' and grad- 
 ually close the valve B. 
 
 The pressure water enters through the valve A; hence, 
 at the top landing the automatic stop arrests the movement 
 of the car by shutting off the supply water. When the 
 elevator car descends, the discharge water passes out 
 through the valve B; hence, the bottom limit valve stops 
 the descent of the car by stopping the escape of water 
 from the cylinder. 
 
 Construction of Cylinder. — The construction of the upper 
 end of the cylinder is shown in Fig. 419. This drawing, 
 which is a vertical sectional elevation of the top of the 
 cylinder and plunger, also shows the way in which the 
 plunger is fastened to the under side of the car, as well 
 as the construction of the plunger. For the purpose of 
 
Hydraulic Elevators 
 
 1003 
 
 Fig. 419 
 
1004 Steam Engineering 
 
 reinforcing the plunger, a steel cable B is strung inside, 
 both of its ends fastened to a pin A, located some distance 
 below the center of the plunger, and the loop or bight, at 
 the top of the plunger, is passed around a tightening block 
 ; this block is arranged so as to be drawn up by the bolts 
 0' to put the desired tension on the rope B. The plunger 
 D is made of as many lengths of piping of the proper 
 size as may be necessary, these being connected by means 
 of long internal sleeves C. The plunger sections are turned 
 true and highly polished, and the screw threads at the 
 ends are made with great accuracy, so as to hold the sec- 
 tions in perfect alignment when connected. The threads 
 are also made extra long, so that the joints may be as 
 strong as the other parts of the pipe. For the purpose of 
 making the pipe sections come together perfectly central 
 when joined, the center portion of the sleeve is turned true, 
 and the ends of the pipe are bored to fit this portion ; when 
 the parts are screwed up, the turned central portion of 
 the sleeve slides into the bored-out ends of the pipes and 
 brings them into line, so that there is no point around 
 the joint where one part projects over the other. 
 
 The top of the cylinder is finished off with a casting F 
 screwed to the top of the upper section of the cylinder 
 barrel E. On top of the cylinder cap F is mounted a 
 stuffing-box casting G, containing the usual packing space 
 T and fitted with a gland G'. The latter is constructed 
 so as to form a space surrounding the plunger to hold oil 
 which is fed in from the oil cup K. Above this oil reser- 
 voir is a recess in which babbitt metal wiping rings I are 
 placed for the purpose of scraping the oil off the plunger 
 as it moves up, and retaining it in the space in gland G'. 
 In Fig. 418 it will be noticed that buffers F are provided 
 for the car to rest upon when at the lower floor. Similar 
 
Hydraulic Elevators 
 
 1005 
 
 buffers are also provided for the counterbalance W to rest 
 upon, this to prevent running the car up against the over- 
 head beams. The construction of the car buffers is shown 
 in Fig. 420, which is an external view of the upper end of 
 the cylinder taken at right angles to Fig. 419. The buffer 
 consists of a plunger P made of pipe, provided with a 
 
 Fig. 420 
 
 cast cap P' and a rubber cushion P". The plunger P 
 slides within a cylinder C, also made of pipe. Within this 
 cylinder there is a spring that is compressed by the plunger, 
 the lower end of the latter being provided with a tiat head 
 to press against the top of the spring. The cylinder C is 
 held in position by a side extension F, formed on the top 
 cylinder casting F. The nuts F' F" are screwed on the 
 
1006 Steam Engineering 
 
 cylinder C, the latter being threaded, and by this means 
 the height of the buffer is adjusted. To furnish additional 
 support, so that the buffer may not be pushed down, and 
 the thread of the nut F' stripped if the car should come 
 down unusually hard, a pipe extension E is provided, ex- 
 tending down to the floor, or some other firm support. 
 These buffers are set so as to be struck and compressed 
 every time the car comes down to the lower floor, acting 
 to stop the motion gradually. If the car descends at the 
 normal speed, the buffer is compressed slightly, just a 
 trifle more than is necessary to hold the unbalanced por- 
 tion of the weight of the car, but if the car speed in ap- 
 proaching the floor is excessive, the buffers will be com- 
 pressed farther, and the car will run a few inches below 
 the floor. 
 
 Boiler Power for Elevators. — The following very able 
 discussion of this subject is presented by Charles L. Hub- 
 bard in Power: 
 
 "The power necessary to operate an elevator depends 
 upon its size, the method of construction and counterbal- 
 ancing, the speed, and the efficiency. Placing these con- 
 ditions in the form of an equation : 
 
 eX33,000 
 in which 
 
 TF=weight of live load, 
 ^=unbalanced weight of car, 
 #=speed in feet per minute, 
 e=efnciency. 
 The elevators in most general use for passenger service 
 are of the hydraulic and electric types; for freight work, 
 some steam and belted elevators are in commission, the 
 
Boiler Power for Elevators 1007 
 
 latter being connected directly with the line shaft in shops 
 and factories. The general method of computing the power 
 is the same for both hydraulic and electric elevators, al- 
 though they differ to some extent in detail, making it ad- 
 visable to consider them separately. 
 
 The live load for a passenger elevator is usually figured 
 on a basis of from 60 to 80 pounds per square foot of floor 
 space, and the weight of the elevator itself from 100 to 
 125 pounds per square foot, which also includes the safety 
 device. These figures will be found ample for cars of or- 
 dinary construction, but may be exceeded somewhat in 
 the case of metal cars of especially massive design. 
 
 Hydraulic Elevators. — It is common practice with ele- 
 vators of this type to counterbalance up to about three- 
 fourths of the weight of the car. The speed varies from, 
 say 200, to 600 feet per minute, 400 feet being about the 
 average for office buildings of medium size. The efficiency- 
 is in the vicinity of 60 per cent. 
 
 In computing the boiler power, it is usually assumed 
 that probably all of the elevators will not be running at 
 one time at their maximum capacity; it must be remem- 
 bered also that power is required only on the upward trip, 
 as the weight of the car causes it to descend under the 
 control of a suitable braking device. When there is no 
 definite information at hand, it is customary to compute 
 the power necessary to operate all of the elevators at one 
 time under full load, and base the boiler power on two- 
 thirds of this result. 
 
 Example. — An office building has four hydraulic eleva- 
 tors, each having a floor space of 30 square feet. What 
 boiler power should be provided, using the following aver- 
 age data : Live load, 70 pounds per square foot of floor 
 space; weight of elevator, 100 pounds per square foot of 
 
1008 Steam Engineering 
 
 floor space; speed, 400 feet per minute; efficiency, 60 per 
 
 cent; steam consumption of pumps, 65 pounds per hour 
 
 per horse-power. 
 
 From the foregoing, 
 
 TF=30X70X3=6300; 
 
 14=30X100X3X0.25=2250. 
 
 Then for a continuous upward movement with a full load 
 
 the required horse-power would be : 
 
 (6300+2250) 400 
 
 =172 horse-power. 
 
 0.60X33,000 
 
 but, of course, under actual conditions one-half of the 
 time is occupied by the downward trips, and the power 
 required is therefore only one-half of this, or 86 horse- 
 power. Making allowance for stops at the various floors 
 and for the time that part of the elevators are idle, it 
 may be assumed that it will be sufficient to provide for 70 
 per cent of the full time, or 0.70X86=60 horse-power. 
 The steam consumption under the conditions stated would 
 be 60X65=3,900 pounds per hour. 
 
 Assuming 30 pounds of steam per boiler horse-power, 
 which may be taken with sufficient accuracy when the pres- 
 sure and feed-water temperature are not given, the re- 
 quired boiler horse-power will be 3,900-^30=130. The 
 boiler horse-power required for running a pump is com- 
 puted in a similar manner to that for an engine. 
 
 The rating, or capacity of a pump, however, is usually 
 expressed in gallons of water per minute raised to a given 
 height, instead of horse-power, as in the case of an en- 
 gine. 
 
 The weight of water in pounds per minute multiplied 
 by the height in feet to which it is raised, divided by 
 33,000, will give the useful, or delivered work of the pump 
 
Boiler Power for Elevators 1009 
 
 in horse-power. The friction of the water flowing through 
 the passages and valves is so great under ordinary working 
 conditions that not much more than 50 per cent of the 
 indicated horse-power of the steam cylinders is represented 
 by the net useful work. This calls for a large amount of 
 steam in proportion to the work done, as shown by the 
 table herewith, which gives the average steam consumption 
 of the ordinary duplex pump. 
 
 TABLE SHOWING AVERAGE STEAM CONSUMPTION" OF DUPLEX 
 
 PUMPS. 
 
 Pounds of Steam 
 per hour 
 Type of Pnmp per delivered 
 
 horse-power 
 
 Simple non-condensing 120 
 
 Compound non-condensing 65 
 
 Triple non-condensing 40 
 
 High-duty non-condensing . 30 
 
 The head against which a pump works is the vertical 
 distance between the surface of the water in the suction 
 reservoir and that in the discharge reservoir. If the 
 pump is delivering against a pressure, as in feeding a 
 boiler, the pressure may be reduced to "feet head," by 
 dividing the pressure per square inch by 0.43. 
 
 Electric Elevators. — The type of electric elevators most- 
 ly used is the drum. The speeds at which this type com- 
 monly runs may be taken as 300 and 500 feet per minute, 
 respectively, for single, and double-drum machines; for 
 regular work, speeds above 400 feet are not usually found 
 necessary for the average building. 
 
 So far as the necessary power is concerned, the single 
 drum and duplex machines may be considered together. 
 The efficiency of these is ordinarily from 50 to 70 per 
 
1010 Steam Engineering 
 
 cent, although theoretically the former is the more efficient 
 type. In practice it is not customary to count on much 
 more than 50 per cent, which gives results on the side of 
 safety. 
 
 The method of balancing the electric elevators of the 
 drum type differs from that applied to the hydraulic, in 
 that the entire weight of the car plus from 40 to 50 per 
 cent of the maximum live load is counterbalanced. From 
 this it is evident that with no load the power required to 
 pull the car down is that necessary to raise the excess 
 counter-weight, which may be taken as equal to one-half 
 the maximum live load, and to overcome the friction of 
 the machine. When the car is half loaded it is bal- 
 anced, and the power required is that to overcome friction 
 only. At full load the conditions are the same as for an 
 empty car, except the power is required during the up- 
 ward trip instead of the downward. It is evident that 
 power may be required for both the upward and downward 
 trips, depending upon the number of people in the car, 
 but it will never be as great at any one time as in the 
 case of the hydraulic elevator. 
 
 Example. — Taking the same conditions as in the pre- 
 ceding example, what boiler power will be required to 
 operate electric elevators of the drum type, having an 
 efficiency of 50 per cent and a speed of 300 feet per minute? 
 
 In this case u, the unbalanced weight of the car, disap- 
 pears, and the maximum live load is equal to only one- 
 half the weight of the people in the car, the other half 
 being counter-balanced, so that : 
 
 17=30X70X3X0.5=3150 pounds, 
 from which 
 
 3150X300 
 
 TT p rrv 
 
 ' ' 0.50X33,000 
 
Boiler Power for Elevators 1011 
 
 If the full load was carried on both upward and down- 
 ward trips, or sufficient of it on the downward trip to 
 overbalance the counter-weight and the friction of the car, 
 the conditions would be the same as in the case of the 
 hydraulic elevator, that is, power would only be required 
 on the upward trip. 
 
 This condition, however, does not hold, especially in the 
 case of office buildings, where during the morning hours 
 the maximum loads are on the upward trips, with empty 
 or nearly empty cars coming down. Under these con- 
 ditions the power is practically the same on both trips, 
 owing to the necessity of raising the counter-weight when 
 the car is descending. This makes it necessary to treat 
 the problem the same as though the machine were raising 
 a continuous load. 
 
 Assuming, as before, that a certain amount of time is 
 required for passengers to enter and leave the car, and 
 that all of the cars will not be running at one time, we 
 may take 70 per cent of the above, or 57X0.7=40, as the 
 maximum horse-power to be delivered continuously by the 
 motor. 
 
 Assuming efficiencies of 80, 90 and 85 per cent for the 
 
 motor, generator and engine, respectively, the required 
 
 indicated horse-power of the engine will be 
 
 40 
 
 ■ z=62 horse-power. 
 
 0.80X0.90X0.85 
 
 The boiler power will, of course, depend upon the water 
 rate of the engine. Assuming that a simple non-condens- 
 ing engine is employed, requiring 30 pounds of steam per 
 indicated horse-power per hour, the boiler power will be 
 practically the same as that of the engine, that is, .62 
 horse-power. The power required to operate duplex eleva- 
 
1012 Steam Engineering 
 
 tors is practically the same, except a higher speed may be 
 allowed." 
 
 The method of balancing a screw machine is practically 
 the same as for the hydraulic type. The efficiency of this 
 machine may be taken as about 70 per cent. The horse- 
 power for driving elevators of this type is calculated the 
 |same as for the hydraulic, except for the higher efficiency. 
 After the power of the motor has been computed, the 
 boiler power may be determined as in the preceding ex- 
 ample. 
 
 Freight elevators are computed in the same way, except 
 they are run at lower speeds, and are built especially to 
 carry the desired load in each particular case. When ap- 
 plying these methods of computation to any particular 
 case, the engineer should obtain all the data possible 
 regarding the type of machine to be used, the probable 
 speed, efficiency, etc., before proceeding; but if any of 
 the data are lacking, the average figures already given 
 may be used with approximate results. 
 
 QUESTIONS AND ANSWERS. 
 
 661. What are the essential parts of the Otis traction 
 elevator ? 
 
 Ans. A traction motor driving sheave, and a pair of 
 electrically released brake shoes. 
 
 662. What type of electric motor is used in the Otis 
 traction elevator? 
 
 Ans. A slow speed shunt- wound motor. 
 
 663. What is the principal function of the armature 
 shaft besides carrying the armature? 
 
 Ans. To support the load. 
 
 664. How, then, is the drum, or sheave driven? 
 Ans. By means of projecting arms from the armature, 
 
 that engage with similar arms projecting from the drum. 
 
Questions and Answers 1013 
 
 665. Describe the system of safety devices with which 
 this elevator is equipped ? 
 
 Ans. There are two groups of switches located respec- 
 tively at top and bottom of the shaft, each switch in series 
 being opened one after the other by the car as it passes. 
 This retards the speed and finally brings the car to stop, 
 applying the brake, independent of the operator in car. 
 
 666. Are there any other safeties besides this? 
 
 Ans. Yes — speed governors, wedge clamps for gripping 
 the guides, and potential switches. 
 
 667. Describe in general terms the construction of the 
 Otis geared traction elevator ? 
 
 Ans. A multi-grooved driving sheave around which the 
 cable works. The sheave is mounted upon a shaft driven 
 by geared wheels actuated by a right and left hand worm 
 cut on the armature shaft. 
 
 66S. What advantage is gained by the use of the double 
 screw, or worm? 
 
 Ans. The elimination of all end thrust. 
 
 669. With what kind of brake is this machine equipped ? 
 Ans. A mechanically applied, and electrically released 
 
 brake. 
 
 670. What type of motor is used? 
 
 Ans. Compound-wound — speed 800 E. P. M. 
 
 671. When is the series field of this motor used? 
 Ans. Only at starting. 
 
 672. Why? 
 
 Ans. To obtain a highly saturated field in the shortest 
 possible time. 
 
 673. How is a gradual slowing down of speed of car 
 obtained with this elevator? 
 
 Ans. By throwing a low resistance field across the ar- 
 mature, thus providing a dynamic brake action. 
 
1014 Steam Engineering 
 
 674. What kind of current is used for operating elec- 
 tric elevators? 
 
 Ans. Either alternating, or direct current. 
 
 675. How is the transmission of current to the motor 
 of an electric elevator controlled? 
 
 Ans. By means of an electric magnet controller op- 
 erated through the switch in the car. 
 
 676. How may considerable power be wasted in the 
 operation of electric elevators? 
 
 Ans. By careless handling — making unnecessary stops 
 and starts, or too sudden stops or starts. 
 
 677. Briefly, of what does the mechanism of a hydraulic 
 elevator consist? 
 
 Ans. A cylinder and piston with one or more rods con- 
 nected to a crosshead which carries the sheaves over which 
 run the lifting cables from which the car is suspended. 
 
 678. What moves this piston? 
 
 Ans. Water under pressure admitted by means of suit- 
 able valves causes the piston to move from one end of the 
 cylinder to the other, and back again. 
 
 679. How is this motion transmitted to the elevator 
 car? 
 
 Ans. By means of the sheaves mounted on the cross- 
 head which carry the lifting cables. 
 
 680. In what position is the cylinder placed? 
 
 Ans. Either vertical alongside the hatchway, or hori- 
 zontal in the basement of the building. 
 
 681. How are the valves of a hydraulic elevator op- 
 erated ? 
 
 Ans. In some cases by a hand rope passing through 
 the car and over small sheaves at the top and bottom of 
 the hatchway, and connected with the main valve in the 
 basement. By pulling this rope down the valve is opened. 
 
Questions and Answers 1015 
 
 and the car will ascend, while pulling the rope up will 
 cause the car to descend. 
 
 682. What safety devices are attached to this type of 
 elevator ? 
 
 Arts. Two balls are attached to the hand rope, one near 
 the bottom, and the other near the top. These balls come 
 in contact with the top, or bottom of the car, according 
 as it is going up or coming down, and being carried along 
 they, of course move the cable, thus actuating the valve, 
 bringing the car to a stop. 
 
 683. Is this device safe, and automatic? 
 Ans. It is. 
 
 684. Mention another safety device connected with 
 hydraulic elevators. 
 
 Ans. Safety clamps under the control of a speed limit 
 centrifugal governor which causes the clamps to grip the 
 guides and thus hold the car. 
 
 685. How is this safety governor operated? 
 
 Ans. By means of a small cable connected with the car 
 and moving with it, which passes over the sheave pulley 
 of the governor. 
 
 686. Why are some elevator pistons fitted with two pis- 
 ton rods? 
 
 Ans. To prevent the piston, and crosshead from turn- 
 ing or twisting, and also to strengthen the construction. 
 
 687. What other methods are used for manipulating 
 the water valve, besides the one already described? 
 
 Ans. Eunning ropes, and standing ropes, either of 
 which may be operated by means of a lever, or wheel in 
 the car. 
 
 688. Do these devices directly operate the main valve? 
 Ans. No. They operate a small valve called the pilot 
 
 valve. 
 
 689. What is the function of the pilot valve? 
 
1016 Steam Engineering 
 
 Ans. When opened it admits the pressure water to a 
 small cylinder with piston connected to the main valve 
 stem. This actuates the main valve, which in turn, by its 
 movement, closes the pilot valve. 
 
 690. Upon what does the amount of opening given the 
 pilot valve, and consequently the main valve depend? 
 
 Ans. Upon the distance the lever in the car is moved 
 from central position. 
 
 691. What is meant by central position of lever? 
 Ans. That position in which there is no flow of water 
 
 either into or out of the cylinder, and the car is moving 
 only by its momentum. 
 
 692. What is the result of moving the lever too quickly 
 to central position when the car is moving at a high 
 rate of speed? 
 
 Ans. The motion of the car will be arrested with a 
 sudden jerk. 
 
 693. How many kinds of horizontal hydraulic elevators 
 are in use ? 
 
 Ans. Two. One is the pushing, and the other the 
 pulling type. 
 
 694. Describe the action of the pushing type? 
 
 Ans. The car being at the bottom, the pressure water 
 is admitted behind the piston which then moves, pushing 
 the crosshead and cable sheave and lifting the car. 
 
 695. Describe the action of the pulling type? 
 Ans. It is the opposite of that just described. 
 
 696. Is there much difference in the valve mechanism 
 of the horizontal, and vertical types of hydraulic elevators? 
 
 Ans. Very little except a few minor details. 
 
 697. What is meant by a double-deck machine? 
 
 Ans. Where the floor space is restricted two, and some- 
 times three or four machines are mounted one above the 
 other- 
 
Questions and Answers 1017 
 
 698. What water pressure is usually carried in operat- 
 ing the types of hydraulic elevators that have hitherto 
 been described? 
 
 Arts. Pressures not exceeding 200 lbs., the average being 
 150 lbs. per square inch. 
 
 699. Are any higher pressures than this being used for 
 operating hydraulic elevators? 
 
 Ans. Yes. Pressures of 700 to 800 lbs. and higher. 
 
 700. Why are such high pressures used? 
 
 Ans. Owing to increased height of buildings, and the 
 demand for high car speed. 
 
 701. What advantage, other than high speed, is gained 
 by the use of high pressure elevators? 
 
 Ans. A reduction in the size of the valve mechanism, 
 piston areas and piping. 
 
 702. Mention another advantage in connection with 
 the high pressure system? 
 
 Ans. A reduction in the loss by friction of the water 
 passing through the pipes, owing to reduced areas. 
 
 703. What is the percentage of loss due to this cause? 
 Ans. In low pressure machines from 10 to 30 per 
 
 cent, and in high pressure machines from 5 to 6 per cent. 
 
 704. Describe in general terms the construction of the 
 cylinder and piston of a high pressure machine. 
 
 Ans. The cylinder area is reduced to about one-eighth 
 that of the low pressure type, and the piston is a solid 
 plunger. 
 
 705. How is the pressure maintained? 
 
 Ans. The pump forces water into the lower end of the 
 accumulator, an air-tight tank, which is also weighted. 
 From the accumulator a pipe runs to the main valve. 
 
 706. Describe in general terms the construction and 
 operation of the direct-acting plunger elevator. 
 
1018 Steam Engineering 
 
 Ans. A cylinder is set vertically in the ground under 
 the center of the car, and the length of it is slightly 
 greater than the travel of the car. In this cylinder is a 
 plunger of the same length, which carries the car. Water 
 under pressure is forced into the cylinder and thus lifts 
 the car, and allowed to run out at the top when the car 
 descends. The cylinder is about two inches larger in dia- 
 meter than the plunger, and is always full of water. 
 
 707. What is the usual diameter of the plunger? 
 Ans, 6I/2 to 7 inches. 
 
 708. How is it constructed? 
 
 Ans. Of lengths of highly polished steel pipe, joined 
 together with an internal sleeve, and having its lower end 
 closed. 
 
 709. What pressure is ordinarily used on this type of 
 elevator ? 
 
 Ans. 150 to 200 lbs. per square inch. 
 
 710. How is the top of the cylinder arranged? 
 
 Ans. With a packing gland through which the plunger 
 moves up and down. 
 
 711. What types of elevators are in general use for 
 passenger service? 
 
 Ans. Electric and hydraulic. 
 
 712. How is the capacity of a pump usually expressed? 
 Ans. In gallons of water per minute raised to a given 
 
 height. 
 
 713. What is meant by the head under which a pump 
 works ? 
 
 Ans. The vertical distance between the surface of the 
 water in the suction reservoir, and that in the discharge 
 reservoir. 
 
Electricity for Engineers 
 
 Electricity is an invisible agent, the exact nature of 
 which is not very well known, although the laws governing 
 its action, the methods of controlling it, and the effects 
 produced by it are becoming well known. It is necessary 
 to assume in the start that it is of such a nature as to 
 be susceptible of possessing quantity. We may, and do 
 use terms to designate definite and definable quantities 
 of electricity without being able to say just what is meant 
 by the word itself. For instance, referring to an electric 
 current, it is the transfer of definite quantities of elec- 
 tricity along a conductor, just as in a current of water, 
 gallons, or cubic feet are transferred through a pipe. But, 
 the idea of large quantities of electricity being stored up 
 in receptacles for future use, in a similar manner to water, 
 cannot be followed except in a limited sense, as for in- 
 stance, in the case of storage batteries. One of the most, 
 if not the most important generalizations ever made in 
 physical science is the doctrine of the conservation of 
 energy, or as it is sometimes called, the doctrine of the 
 indestructibility of energy. This doctrine teaches that the 
 total quantity of the energy in the universe is unalterable; 
 that is, if energy is expended or disappears in one form, 
 it must reappear in another form. A simple analogy will 
 serve to make this matter plain: Suppose a man, by means 
 of a rope passing over a pulley, raises a 100-pound weight 
 one foot above the surface of the earth, which means 100 
 foot pounds of work, or energy. Now, the man has ex- 
 erted, or put forth that amount of energy, and so far as 
 
 1019 
 
 *^i 
 
1020 Steam Engineering 
 
 he is concerned, he no longer possesses it. Apparently it 
 has been blotted out of existence — annihilated. But this 
 annihilation is only apparent for the reason that energy is 
 capable of existing in two forms, viz., kinetic, and potential 
 or stored energy. While the muscular force of the man is 
 being expended in actually doing work raising the 100- 
 pound weight, it is in a condition called kinetic energy. 
 While the weight is held in position at a distance of one 
 foot above the earth, it is producing a stress, or pull on the 
 rope, and is in the condition of stored or potential energy. 
 If the rope is suddenly loosed, the weight will descend, and 
 during this descent will put forth an amount of kinetic 
 energy exactly equal to the 100 pounds of work or energy 
 that was expended in raising it one foot from the ground. 
 
 Much of the mystery that exists in the minds of many 
 persons concerning electricity will be unraveled and made 
 clear when it is understood that, like all other natural 
 forces, electricity is only one of the many forms in which 
 energy manifests itself. Like all other forms of energy, 
 electric energy, or the power that electricity possesses of 
 doing work, is fixed and determinate. 
 
 An electric source, whether it be a voltaic cell, or a dyna- 
 mo, is capable, under given conditions, of producing a 
 certain quantity of electricity. In the case of the dynamo 
 being operated by the steam-engine, the heat energy stored 
 in the fuel by the sun's rays, is made to do a certain 
 amount of work, through the medium of the boiler, the 
 steam, and the engine, and this work or energy is simply 
 changed by the dynamo into the form of electric energy, 
 and passes on out through the circuit to do useful work in 
 the way of power, lighting, etc. 
 
 When electricity is caused to flow between any two 
 points in a circuit, the amount of work it can perform is 
 
Electricity for Engineers 1021 
 
 equal to the amount of electricity that passes, multiplied 
 by what is called the difference of potential through which 
 the electricity falls or moves. 
 
 When work is done on a quantity of water by forcing 
 it into a reservoir at a higher level than that from which 
 the water has been raised, the amount of work done can 
 be measured in foot-pounds by the quantity of water in 
 pounds so raised, multiplied by the difference in level 
 through which it is raised in feet. While it is not the 
 intention to suggest that electricity is a fluid, yet it pos- 
 sesses majry of the properties of a fluid, so that the amount 
 of work • electricity is capable of doing depends on the 
 quantity of electricity moved, as well as on the difference 
 of the electric level or potential through which it has been 
 raised. 
 
 The unit of quantity of a water current may be taken 
 as a cubic foot or a cubic inch. In electricity the practical 
 unit of quantity is a certain quantity of electricity called 
 a coulomb. In measuring this quantity of electricity, ref- 
 erence must be had to certain other electrical units, i. e., 
 the ampere, the volt and the ohm. 
 
 The ampere is the name given to a practical unit of 
 electric current, and is such a rate of electric flow as is 
 capable of transmitting a quantity of electricity equal to 
 one coulomb per second. A current of electricity equal 
 to one ampere will flow through a circuit whose resistance 
 is one ohm, when acted on by an electromotive force or 
 pressure of one volt. An ampere is approximately such a 
 current of electricity that is capable of depositing 1.118 
 milligrammes of silver per second from a specially pre- 
 pared solution of silver nitrate. 
 
 The volt or practical unit of electromotive force is an 
 electromotive force or pressure that is capable of causing 
 
1022 Steam Engineering 
 
 the flow of an electric current of one ampere through a 
 circuit, the electric resistance of which is equal to one ohm. 
 
 The ohm is the practical unit of electric resistance. It 
 is the resistance that would limit the flow of electricity 
 under an electromotive force of one volt to a current of 
 one ampere, or to a discharge of one coulomb per second. 
 It is equal to the resistance of a column of pure mercury 
 one square millimetre in area of cross section and 104.9 
 centimetres in length. 
 
 A coulomb is the practical unit of electric quantity. It 
 is the quantity of electricity that would pass in one second 
 through a circuit carrying a current of one ampere. 
 
 Electric energy can be measured in terms of electric 
 power or rate of doing work. A careful distinction should 
 be made between work, or the product of force by the dis- 
 tance through which the force acts, and power or rate of 
 doing work. As we have already seen, the unit of work 
 is called the foot-pound. The unit of power or rate of 
 doing work, or, as it is sometimes called, the unit of 
 activity is equal to the foot-pound per second, or foot- 
 pound second. 
 
 The amount of work electricity is capable of doing is 
 equal to the quantity of electricity that flows, multiplied 
 by the difference of level or potential through which it 
 flows. This is the volt-coulomb or joule. The amount of 
 electric activity or work per second is equal to the volt- 
 ampere or the watt. 
 
 THE WATT. 
 
 The volt-ampere or watt is equal to the power developed 
 when 44.25 foot-pounds of work are done per minute, or 
 0.7375 foot-pounds per second. 
 
Magnets 1023 
 
 If the ampere is replaced by the symbol I, the volt by 
 the symbol E, the watt by the symbol W, and resistance 
 by E, then, IXE=W, and I 2 XR=W. 
 
 The square of the current multiplied by the resistance 
 equals watts; and the square of the voltage divided by the 
 resistance equals watts, thus: E 2 -^K=W, expressed in 
 figures as follows: 
 
 First. An electromotive force or pressure of 10 volts 
 and a current of 20 amperes equals, 
 
 10X20=200 watts. 
 
 Second. A current of 10 amperes and a resistance of 
 30 ohms equals, 
 
 10X10X30=3000 watts 
 
 Third. An electromotive force of 10 volts, and a re- 
 sistance of 20 ohms equals, 
 
 10X10-4-20=5 watts 
 
 MAGNETS. 
 
 The natural magnet is a mineral consisting of a com- 
 bination of iron and oxygen, and its composition is indi- 
 cated by the chemical formula Fe 3 4 . The mineral is 
 called magnetite, and it is attracted by the magnet just 
 as iron is, only not so powerfully. 
 
 Some samples of magnetite attract iron. These are 
 natural magnets known to the ancients as the lodestone. 
 
 The permanent magnet is a piece of steel which has been 
 charged with magnetism, and retains it. It attracts iron, 
 its ends having the strongest attractive power, it tends to 
 point north and south, the same end always tending to- 
 wards the same pole. The poles of the magnet are thus 
 determined, and are designated the north pole, and the 
 south pole. 
 
1024 Steam Engineering 
 
 The north poles of two magnets tend to repel each 
 other, and the south poles influence each other in the same 
 manner. But the north pole of one magnet attracts the 
 south pole of another; like repels like, and unlike attracts 
 unlike. 
 
 There are various methods of charging magnets. One 
 process is as follows : Lay a bar of steel on a table, and 
 with one pole of a permanent magnet, stroke the steel 
 bar from center to end, always lifting the magnet clear of 
 the bar on the return stroke. This is repeated a number 
 of times, and then the same operation is applied with the' 
 other pole of the magnet to the other half of the bar. The 
 end of the bar stroked with the north pole of the magnet 
 will be a south pole, and vice versa. The stroking may be 
 done for both halves of the steel bar by using two mag- 
 nets at the same time. The north pole of one magnet 
 and the south pole of the other are brought almost to- 
 gether at the center of the bar, and simultaneously moved 
 out to the ends, always lifting them clear of the bar on 
 the return stroke, and the stroking is repeated. 
 
 The U-shaped Magnet, or as it is usually called, the 
 horseshoe magnet, may be charged or magnetized by strok- 
 ing with another horseshoe magnet from near the bend to 
 the ends, or from the ends to the bend. A piece of iron 
 should be laid across the ends during the process. 
 
 The Electro-Magnet. — If a bar of iron be surrounded 
 by a coil of wire through which an electric current is 
 passing, it will become charged magnetically, and will 
 attract iron. 
 
 LINES OF FORCE. 
 
 The passing of a current of electricity produces a con- 
 dition of more or less strain, or whirl in the ether, and 
 
Field of Force 1025 
 
 unless distorted in some way the locus or locality of the 
 condition is symmetrical with respect to the current. This 
 locality is called the field of force. It affects iron, and 
 is traced, and may be located by its effects upon the 
 needle of the compass, or upon iron filings. It is by virtue 
 of the field of force that every dynamo electric generator, 
 and every electric motor works. A needle held near a 
 magnet is attracted because of the field of force. In the 
 case of the mariner's compass, the needle is influenced by 
 the earth's field of force. A coil of wire rotated within 
 any artificial field of force, will generate electromotive 
 force, and it is due to this principle that the revolving 
 armature of a dynamo, or more properly speaking, a gen- 
 
 LINES OF FORCE SURROUNDING AN ACTIVE CONDUCTOR 
 
 erator, produces currents and potential capable of doing 
 work of various kinds. We can thus see that the electric 
 current in its effects is a very real and tangible thing, 
 although in theory it is somewhat imaginary. The mag- 
 net is the most familiar producer of lines of force, and the 
 polarity, or direction of these lines is fixed by assuming 
 that they pass through the steel of the magnet from its 
 south pole to its north pole, and issuing from the latter, 
 curve around through space and return to the south pole. 
 The direction taken by the electric current is fixed by 
 assuming that when produced by a galvanic battery, it 
 starts from the copper electrode, and passes through the 
 outer conductor, to the zinc plate, and the lines of force 
 
1026 Steam Engineering 
 
 surrounding the conductor will be in planes at right angles 
 to it, and will form closed lines around it. These lines 
 may be circular or otherwise, and their polarity, or in other 
 words, their direction of rotation, may be expressed by 
 saying that it is opposed to the motion of the hands of a 
 watch or clock, assuming that the current is coming toward 
 a person, and corresponds to the motion of the clock hands 
 when going away from the person. In the first case, the 
 polarity is anti-clockwise, and in the second case, it is 
 clockwise. Figs. 421 and 422 will serve to illustrate the 
 principle governing the action of these lines, the arrows 
 
 Fig. 422 
 lines of force surrounding an active conductor 
 
 in Fig. 421 indicating the direction of the current, while 
 Fig. 422 may be called an "end view/ 3 
 
 The smoke rings often produced from the smoker's pipe 
 are good representations of the whirling motion of these 
 lines of force. A conductor that is swept through a field 
 of force in such a direction as to cut the lines of force, has 
 electromotive force impressed upon it, and if the ends 
 of the conductor are connected so as to form a closed 
 circuit, a current of electricity will pass through it. The 
 electric current may therefore be considered as electricity 
 in motion, and the line of force with absolutely fixed di- 
 
Field of Force 
 
 1027 
 
 rection may be assumed to have a whirling motion around 
 its axis, which latter does not change, see Figs. 421 and 
 422. 
 
 When a current passes through a spiral conductor, as 
 shown in Fig. 423, in the direction indicated by the small 
 arrows, the direction of the lines of force produced will 
 be as indicated by the large arrow ; but if, instead of pass- 
 ing through the spiral conductor, the current should pass 
 through a conductor occupying the position of the large 
 arrow, then the lines of force would follow the direction 
 of the small arrows. 
 
 Fig. 423 
 
 DIRECTION OF LINES OF FORCE PRODUCED BY A CIRCULAR CURRENT 
 
 There are, then, surrounding a conductor carrying a 
 current of electricity, an infinite number of lines consti- 
 tuting in fact a volume of force, and the strength of this 
 volume, or field, varies with its nearness to, or distance 
 from the conductor. 
 
 In practice, the field near the conductor is the only 
 portion strong enough to play any part in useful work, and 
 this strength or density is estimated by the relative num- 
 ber of lines of force in a given cross-sectional area of the 
 field. 
 
1028 Steam Engineering 
 
 THE MAGNETIC CIRCUIT. 
 
 A fundamental difference exists between the electric, 
 and the magnetic circuit. By a constant electric current 
 passing upon its circuit, energy is developed, and energy 
 must be expended to maintain it; but the lines of force 
 are maintained in their circuit without the expenditure 
 of energy. The entire course taken by lines of force must 
 be a closed curve, either a circle, or an ellipse. In the 
 field of force maintained by the horseshoe magnet, or other 
 -shaped magnets, the lines of force pass through the mag- 
 net, and also through the space surrounding it, and their 
 path may approximate a circle, or an ellipse, or be a com- 
 bination of lines and curves, but this path must be con- 
 tinuous. A straight line of force, or a line of force ex- 
 tending into space without limit, is impossible. For the 
 passage of an electric current, a conductor forming a closed 
 circuit is required. This conductor may be any form of 
 matter, although a distinction is to be made between good 
 and bad conductors. For the passage of the magnetic cir- 
 cuit or lines of force no such arbitrary requirement exists, 
 although a distinction is also to be made, as, for instance, 
 air, or a vacuum are the worst conductors, while iron is 
 the best. There is in fact very little difference in sub- 
 stances as regards their ability to pass lines of force, with 
 the exception of iron which has over three hundred times 
 the power of passing lines of force that air has. The 
 electric current passes through a conductor in intensity 
 proportional to the electromotive force urging it. The 
 magnetic circuit passes through air or a vacuum in pro- 
 portion to the magneto-motive force urging it. 
 
 In order to create new lines of force, or in other words 
 to build up a field of force, new energy must be expended ; 
 
Field of Force 1029 
 
 but when the field of force is once built up, no energy is 
 required to maintain it, as the full current passing through 
 the circuit unopposed, except by resistance, maintains the 
 field of force without the expenditure of energy. This con- 
 dition is similar to the carrying of a weight up a flight 
 of stairs. Energy is expended in carrying the weight to 
 the top of the stairs, but when there it is maintained there 
 without requiring the expenditure of energy, and the 
 energy exerted in bringing the weight up-stairs would 
 seem to have disappeared, or to have been annihilated. 
 But this is not the case. On the contrary, the energy is 
 stored in the weight, and will be again expended when the 
 weight is taken down. So also the energy expended in 
 building up a field of force is stored there in the form of 
 electric potential, and may be expended in the production 
 of kinetic electric energy when the field goes out of ex- 
 istence. This disappearance of the field occurs when the 
 electric current ceases, the lines of force disappearing at a 
 more or less rapid rate, and in doing so they develop for- 
 ward electromotive force of the same polarity as the orig- 
 inal current, thus forcing additional current through the 
 line. 
 
 The leading characteristics of the field of force may be 
 summed up under the following general headings: 
 
 First. Energy is expended in building up a field of 
 force. 
 
 Second. No energy is expended in the maintenance of 
 a field of force. 
 
 Third. Energy is expended in the destruction of a field 
 of force. 
 
 Fourth. A field of force, then, must be, and is' the loca- 
 tion of potential energy. 
 
1030 
 
 Steam Engineering 
 
 Electro-Magnetic Induction. — If we take a coil of wire, 
 Fig. 424, and rapidly thrust a magnet into it, we shall 
 observe a certain deflection of the galvanometer needle 
 shown with it. This deflection continues only while the 
 magnet is in motion. After we have inserted the magnet 
 and it has come to rest the galvanometer needle will return 
 to its normal position. When we withdraw the magnet the 
 deflection of the needle will be in the opposite direction. 
 If the magnet is inserted or withdrawn with a very quick 
 
 Fig. 424 
 
 motion, the deflection will be considerable. If the magnet 
 is very slowly inserted, or withdrawn the deflection will 
 hardly be noticeable. The same phenomena w T ill occur if 
 instead of moving the magnet, we hold it stationary and 
 move the coil, or if both of them be moved towards or from 
 each other. The deflection of the compass needle indicates 
 that a current of electricity is passing along the wire, and 
 the experiments above described show exactly how currents 
 of electricity are produced in dynamos. 
 
Field of Force 
 
 1031 
 
 While a natural magnet will maintain a field of force in- 
 definitely without the expenditure of energy, it is necessary 
 that energy be indirectly expended in maintaining the field 
 of a dynamo, for the reason that an electro-magnet is pre- 
 ferred to a natural magnet in such a machine, because by 
 its use the dynamo may be made much smaller and lighter. 
 
 An electro-motive force is induced by rapidly cutting 
 lines of force, that is, by moving either a magnet over a 
 wire or a wire over, or near a magnet. The current in turn 
 is the result of this electro-motive force acting in a closed 
 circuit. A bar of iron becomes an electro-magnet if we 
 
 
 mi 
 
 
 
 t i i 
 
 \ 
 
 — ~»r 
 
 Fig. 425 
 
 wind about it a few turns of wire and cause a current of 
 electricity to flow along the wire, Fig. 425. The magnetism 
 is conceived to consist of lines of force, which leave the 
 bar at one end and enter it at the other, the direction of 
 these lines depending upon the direction in which the cur- 
 rent circulates about the bar of iron. The number of these 
 lines of force depends upon the number of ampere turns in 
 the iron bar and on the diameter, length, and quality of the 
 iron bar. 
 
 The meaning of the word ampere as used in electric 
 practice has already been defined. 
 
1032 Steam Engineering 
 
 Ampere turns is a term used to indicate the magnetizing 
 force ; it is the number of turns of wire on a magnet mul- 
 tiplied by the current in amperes flowing through these 
 turns of wire. 
 
 Haskins, in Electricity Made Simple, explains it in this 
 manner: "If, for instance, we have a current of one am- 
 pere flowing through a single turn of wire around a bar of 
 soft iron, and we have developed enough magnetism to lift 
 a keeper or other piece of iron, weighing one ounce, then 
 with one-half the amount of current and two coils around 
 the bar, we would obtain the same result, and with three 
 turns of wire we would require but one-third the current 
 to develop the same lifting power in the bar or magnet." 
 
 The law, of magnetic flow is very much the same as the 
 law of current flow. If the iron bar is of low magnetic re- 
 sistance, the flow will be quite great ; if of high resistance, 
 the flow will be small. 
 
 Lines of force can also be shunted just as a current of 
 electricity can ; that is, they will follow the path of lowest 
 resistance just as a stream of water or a current of elec- 
 tricity will. 
 
 Faraday's law of induction is as follows : "When a con- 
 ductor is moved in a magnetic field so as to cut the lines 
 of force, there is an electro-motive force impressed on the 
 conductor in a direction at right angles to the direction of 
 the motion, and at right angles also to the direction of the 
 lines of force." 
 
 Foucault or Eddy Currents. — If a conductor should be 
 so moved in a magnetic field that the number of lines of 
 force passing through it at an angle with its direction of 
 motion vary, a current will be produced within it. This 
 current will circle, or eddy around within the conductor, 
 and will absorb energy, and expend it in heating the me- 
 
The Dynamo 
 
 1033 
 
 tallic body of the conductor. These local currents are 
 called Foucault or eddy currents, and are a hindrance, 
 rather than a help to the generation of useful currents. 
 
 DYNAMO-ELECTRIC GENERATORS. 
 
 The dynamo is a machine for transforming mechanical 
 energy into electrical energy — mechanical energy is re- 
 
 1 
 
 Fig. 426 
 
 quired to operate the mechanism for changing field and 
 armature relations, and this energy is absorbed by the dy- 
 namo, and electric energy is produced in its stead. The 
 easiest way to comprehend the principles of the dynamo is 
 to follow up its construction from the most simple type, to 
 one of the more complicated forms. Dynamos are classi- 
 fied into two grand divisions, viz., alternating (A. C.) dy- 
 namos, and direct current (D. C.) dynamos. The A. C. 
 
1034 Steam Engineering 
 
 dynamo produces a current that reverses its direction of 
 flow periodically, in practice from twenty times and up- 
 ward per second. The D. C. dynamo produces a current of 
 unchanging direction. 
 
 The principal constituent parts of a dynamo are the ar- 
 mature, consisting of a core and windings, the field con- 
 sisting also of core and windings, the collecting rings, or 
 commutator, and brushes. The armature and field vary 
 in construction, their windings vary in system, and from 
 these variations, many different varieties of dynamos are 
 constructed. 
 
 Fig. 426 is an elementary sketch of a D. C. dynamo. 
 
 The wire a represents the armature, and we have also the 
 iron bar, and the coil of wire wound on it and, for the pres- 
 ent, we may consider the battery B as the source of the 
 current which produces the magnetism or lines of force in 
 the iron bar. The battery current magnetizes the iron bar 
 (which in dynamos is known as the field magnet) and pro- 
 duces the lines of force indicated by arrows. 
 
 These lines of force leave the field magnet of the dyna- 
 mo at the north pole marked 1ST, and pass through the air- 
 gap, and armature into the south pole marked S. As we be- 
 gin to move the wire or armature, it cuts through these 
 lines of force and begins to generate an electro-motive 
 force, which in turn will cause the current to flow if the 
 circuit is closed through a lamp or other device. 
 
 This current reverses in direction as the wire a passes 
 from the influence of the south pole into that of the north 
 pole, and the brushes B' and B", which transmit the current 
 to the outside wires, are so set that they change the con- 
 nection of the wire a at the time that it passes from one 
 pole to the other. By this means the current in the external 
 
The Dynamo 
 
 1035 
 
 circuit is kept constant in direction, although it alternates 
 in the armature. 
 
 The faster we turn the wire or armature, the greater 
 will be the electro-motive force generated. Instead of 
 using only one wire, as in Fig. 426, we may take many 
 turns before bringing the end out, and in so doing obtain 
 the well known drum armature, or, by a slightly different 
 method of winding, the gramme ring armature, Fig. 427. 
 
 Fig. 427 
 
 Here we have many wires cutting the lines of force at once 
 and the electro-motive force with the same number of rev- 
 olutions of the armature is correspondingly increased, and 
 the more turns of wire we arrange to cut those lines of force 
 per second the greater will be the E. M. F. Instead of pro- 
 viding more wire or increasing the speed of the armature 
 we can increase the magnetism, or number of lines of force, 
 by sending more current through the fields, that is increas- 
 ing the ampere turns. 
 
1036 
 
 Steam Engineering 
 
 If we wish to reverse the current flow we can do so by re- 
 volving the armature in the opposite direction, or by re- 
 versing the current through the fields. 
 
 Fig. 428 
 use of collecting or slip rings 
 
 Fig. 429 
 the simple alternating current dynamo, 
 positive 
 
 BRUSH M IS 
 
 Elementary Idea of an Alternating Current Dynamo. — 
 If instead of the brushes B' and B" as shown in Fig. 426, 
 we collect and transmit the current to the outside circuit 
 
 I 
 
The Dynamo 
 
 1037 
 
 by means of collector rings as shown in Fig. 428, we will 
 then have an alternating, instead of a direct, or constant 
 current as before mentioned. 
 
 In Figs. 429 and 430 are shown two positions of the 
 loop on the armature of an alternator. The collector rings 
 are insulated from the shaft and each other by mica. The 
 terminals of the loop are soldered or riveted (sometimes 
 
 Fig. 430 
 
 the simple alternator, shows coil at one-half a revolution 
 
 from Fig. 429. brush m is now negative 
 
 both) to the rings, and current is led to the external circuit 
 containing the lamps by stationary strips of copper which 
 form a sliding contact with the rings. 
 
 Eeferring to Fig. 429 it will be seen that during the 
 first half of the revolution of the loop ABCD, the direction 
 of the electro-motive force in AB is from B to A, and in 
 CD is from C to D. 
 
1038 
 
 Steam Engineering 
 
 The current flows from the brush M to the lamps so that 
 M is positive. 
 
 Keference to Fig. 430 shows that the wire in front of the 
 S-pole is still positive, but that it is now the wire CD in- 
 stead of AB, so P is the positive brush for the second half 
 of the revolution. There are two reversals of the current 
 per revolution. 
 
 Fig. 431 
 simple d. c. generator. at this instant the brush m is 
 
 POSITIVE 
 
 The number of alternations per minute is the speed in 
 revolutions per minute multiplied by the number of poles. 
 The number of cycles is found by multiplying the speed 
 in revolutions per second by the number of pairs of poles. 
 The number of cycles is usually spoken of as the frequency 
 of the alternator. 
 
The Dynamo 
 
 1039 
 
 The usual frequencies are for power 25, for motor cir- 
 cuits, and arc lamps 66, and for incandescent lighting 133. 
 
 The Direct Current Generator. — In Fig. 431 is shown 
 a loop and a two part commutator of a direct current gen- 
 erator. 
 
 Since the wire AB is moving down past a S-pole, the 
 current flows from B to A and out of the brush M, which 
 
 LAMPS 
 
 Fig. 432 
 
 simple d. c. generator. the armature has made half a 
 revolution, but brush m is still positive 
 
 is called the positive brush. In wire CD the current flows 
 from C to D, making P the negative brush. 
 
 After half a revolution the wire CD is over where AB 
 was, and is now delivering the current towards the external 
 circuit instead of away from it; but CD is now connected 
 through its commutator bar to brush M instead of to P so 
 that the brush M is still positive. (See Fig. 432.) 
 
1040 Steam Engineering 
 
 This arrangement of commutator bars and brushes per- 
 forms the duty of connecting the brush M to that part of 
 the winding, and only that part which is moving down in 
 front of a S-pole. As long as the wire AB moves up in 
 front of a N-pole the commutator connects it to brush P, 
 but as soon as it moves down in front of a S-pole it is im- 
 mediately disconnected from P, and a connection made 
 with M. 
 
 Fig. 433 
 
 an armature coil connected to a two-part commutator, so as 
 
 to deliver direct current 
 
 The two brushes are placed as shown in Fig. 434. In 
 this case the alternating electro-motive force will be re- 
 versed or commuted at the proper instant, and there will 
 be a one direction electro-motive force impressed on the 
 outside circuit. The split ring is called a commutator, and 
 is formed of alternate sections of conducting and non-con- 
 ducting material, running parallel with the shaft with 
 which it turns. It is placed on the shaft of the armature 
 so that it rotates with it, as shown in Fig. 437. The 
 brushes press upon its surface and collect the current from 
 
The Dynamo 1041 
 
 the bars. (See Fig. 438.) The function of the commu- 
 tator as before stated, is to change the connections of the 
 armature coils from the + or positive to the negative or — 
 side of the circuit at the time at which the coil connected 
 to the bar under the brush passes from the influence of one 
 pole piece into that of the other. This is the time at which 
 the current in the coil reverses in direction, and is called 
 the neutral point. If we consider, for the sake of simplic- 
 ity, an armature having only one turn of wire on it, as Fig. 
 426, there will be a time while the coil is in the position 
 indicated by dotted lines at c and d when no current is 
 being generated. The brushes on any dynamo should al- 
 
 Fig. 434 
 
 CROSS SECTION OF SIMPLE COMMUTATOR. BLACK REPRESENTS 
 COPPER ; WHITE SPACE IS MICA INSULATION 
 
 ways be set at this point, for this is the point of least spark- 
 ing. In actual practice all commutators have quite a num- 
 ber of bars and it is impossible to avoid, in passing under 
 the brushes, that at least two of them are in contact with a 
 brush at the same time. If a brush did leave one bar before 
 it touches another, the current would be entirely broken 
 for that length of time, and much sparking would result. 
 The nature of all armature windings is such that while the 
 brush is in contact with the commutator bars it short cir- 
 cuits that coil between them. This is the main reason why 
 the brushes must be kept at a point at which the coil which 
 is short circuited generates no current. 
 
1042 Steam Engineering 
 
 Although the electro-motive force generated in one coil 
 of a dynamo is very weak, the resistance of the "short cir- 
 cuit" formed by the dynamo brush is also very weak and 
 therefore the current may be quite strong. This current is 
 the main cause of sparking in dynamos. The number of 
 bars constituting a commutator depends upon the winding 
 of the armature, and the number of coils grouped thereon. 
 By increasing the number of coils and commutator sections 
 the tendency to spark at the brushes is decreased, and the 
 fluctuations of the current are also decreased. However, 
 
 Fig. 435 
 a single coil armature of many turns 
 
 there are many reasons against making the number of bars 
 on a commutator very great. Increasing the number of 
 bars in a commutator increases the cost of manufacture, 
 and in smaller dynamos, if the number of bars be increased 
 beyond a certain extent, each bar becomes so thin that a 
 brush of the proper thickness to collect the current from 
 the commutator would lap over too many bars of the com- 
 mutator at one time. Each commutator bar should be of 
 the size that will present sufficient metal for the carrying 
 capacity of the current generated in the coil to which it is 
 connected. Different builders of dynamos have different 
 ideas as to the number of amperes that may be carried per 
 
The Dynamo 
 
 1043 
 
 square inch in a commutator bar, but where a commutator 
 is. made of 95 per cent, copper it is usual to allow for each 
 100 amperes a commutator bar surface of IV2 sq. in. 
 The method of electrical connection between the com- 
 
 Fig. 436 
 
 an armature coil of many turns showing how the induced 
 
 e. m. f. of each turn adds itself to that of other turns 
 
 mutator bar and the coil of the armature varies in different 
 designs. Some builders solder the terminals of the coils 
 to the commutator bars; others bolt the terminals of the 
 coils to the bars; and some makers use hard drawn copper 
 
 Fig. 437 
 and "form" the armature coil in such a manner that both 
 ends of the coil become commutator bars, making the coil 
 continuous from one end of the commutator bar to the end 
 of the diametrically opposite commutator bar. 
 
 To increase the electro-motive force. The greater the 
 
1044 
 
 Steam Engineering 
 
 field strength, and the higher the speed the greater the 
 electro-motive force. 
 
 When the speed has been raised until the surface of the 
 armature is traveling at the rate of 3,000 ft. per minute* 
 no further increase is made, lest the bursting stresses be- 
 come too great. 
 
 \ 
 
 Fig. 438 
 separately and self-excited series dynamo. 
 
 In order to further increase the electro-motive force 
 more turns or loops of wire must be wound on the arma- 
 ture. A coil of 16 turns as in Pig. 435 will give an electro- 
 motive force 16 times as great as a coil like Fig. 426. Ref- 
 erence to Fig. 436 will serve to make this plain. 
 
 Suppose the direction of rotation to be the same as the 
 
 *This is called the Peripheral Speed of the armature 
 and is calculated by this rule : 
 
 P. S. equals 3.1416 x D x E. P. M. where D is the di- 
 ameter of armature in feet and R. P. M. is the revolution 
 of the armature per minute. 
 
The Dynamo 
 
 1045 
 
 hands of a watch when viewed from the commutator end of 
 the machine; then the electro-motive forces induced in the 
 successive portions of the wire will be as shown by the ar- 
 rows, and will add to each other impressing a high electro- 
 motive force on the brushes. These turns of wire are said 
 to be in series. 
 
 Fig. 439 
 
 drum winding on a drum core. four coils and four 
 commutator bars. for direct current 
 
 Fig. 440 
 diagram of fig. 439 
 
 Any betterment of the magnetic conductivity of the frame 
 of the machine will increase the electro-motive force; by 
 producing a greater flux per pound of copper on the field 
 magnets. Hence the winding of the armature inductors 
 
1046 Steam Engineering 
 
 (wires) on a core of very softest iron is an economic ne- 
 cessity, resulting in either a higher electro-motive force or 
 a reduction of the expense for copper in the field coils. 
 
 These cores are called Drum cores when the central hole 
 is just large enough for the shaft and the insulation around 
 it (Fig. 439) ; and are named Ring cores when the inter- 
 nal diameter of the ring is much larger than the shaft. 
 (Fig. 441.) The armature in Fig. 442 has a ring core, but 
 the end plates being in position, the large hole is concealed. 
 
 These cores are built up of a great many punchings of 
 soft iron from 15 to 40 mils thick, pickled so as to rust 
 them a little, Every tenth one is varnished or tissue paper 
 
 Fig. 441 
 
 SIMPLE GRAMME RING WINDING 
 
 pasted on. The rust, varnish and paper are all insulators 
 and when the punchings are assembled in a core, prevent 
 Eddy currents from flowing from one end of the armature 
 to the other and heating it. 
 
 These cores are sometimes smooth, but more frequently 
 are slotted with the wires laid in the slots. 
 
 About 10 to 15% of the length of the core is insulation, 
 and about 50% of the surface is slotted, containing the in- 
 ductors (wires.) 
 
 Continuous Electro-Motive Force. — While a single coil 
 of many turns produces a high electro-motive force, which 
 by a two part commutator is always applied to the exter- 
 
The Dynamo 1047 
 
 nal circuit in the same direction, yet this coil passes 
 through all the changes in voltage mentioned in connec- 
 tion with Fig. 426. Fig. 441 shows the construction of the 
 Gramme ring, so named from the inventor, Gramme. The 
 winding is on a ring coil made up of soft iron punchings 
 25 mils thick. The wires on the outer surface are active, 
 having electro-motive force induced in them, and called ar- 
 mature inductors. Fig. 443 shows the same winding with 
 eight coils, and eight commutator bars. In Fig. 442 the 
 armature as diagramed in Fig. 443 is shown completed 
 with its four bands. These bands are from 12 to £5 con- 
 
 
 Fig. 442 
 
 eight section eighty coil ring winding on a smooth ring 
 
 core, with eighty bar commutator. for direct current 
 
 volutions of phosphor-bronze wire in sizes varying from 
 ■No. 20 up to 14, laid on tightly over a mica insulation and 
 sweated with solder all the way round. 
 
 Eeferring to 443 it will be seen that the complete wind- 
 ing can be divided into two parts, one influenced by the N- 
 pole, the other by the S-pole standing at the commutator 
 end. The N-pole side moving upwards has its electro-mo- 
 tive force in direction from back to front of armature 
 through the inductors; the S-pole side has electro-motive 
 force in direction from back to front of armature through 
 the dead wire. 
 
1048 Steam Engineering 
 
 In winding the armature the wire is laid on in a con- 
 tinuous spiral as shown. This makes the electro-motive 
 force in each half of the armature in series, and allows the 
 current to flow from one coil to another, except at the 
 points where the N-half and S-half of the armature meet. 
 Here the electro-motive forces oppose and if wires were con- 
 nected for an instant to the winding, as shown in the cut. 
 the two opposing electro-motive forces would both force 
 electricity out into the wire at the top of the armature, and 
 
 Fig. 443 
 
 eight coil gramme ring winding, with eight part 
 
 commutator 
 
 draw it in at the bottom as shown by the arrows on these 
 wires. This will cause a current to flow in the external 
 circuit. 
 
 If the junctions of the coils are connected to eight com- 
 mutator bars, (one bar per coil), and connect the ends of 
 the external circuit by brushes to the commutator bars 
 which are midway between the N- and S-poles, then each 
 half of the armature separately generates an electro-motive 
 force, and delivers current to the external circuit. 
 
The Dynamo 1049 
 
 Suppose the armature to be revolving at the highest safe 
 speed. Each inductor will move past the magnet poles at 
 a speed of 3,000 feet a minute. With pole pieces 5x8 
 inches and a flux density of 90,000 lines per square inch, 
 the total flux will be 5 x 8 x 90,000 or 3.6 million lines. 
 
 The armature may be 9 inches in diameter which gives 
 it rotative speed 1,270 (nearly). 
 
 For E. P. M.*=P.S.t^(3.1416Xdiametsr). 
 
 3000X12 
 
 — =1270 nearly 
 
 3.1416X 9 
 and E.P.S.t=21 nearly. 
 An inductor therefore cuts 3.6 million lines of mag- 
 netism twenty-one times a second, which is equivalent to 
 cutting 75.6 millions once per second. 
 
 Since the cutting of 100 million lines per second by an 
 inductor induces 1 Volt pressure, each inductor on this 
 armature revolving in this field will produce 75.6-^-100 or 
 % of a volt approximately. 
 
 The 4 coils of 4 inductors each (Fig. 443) on the N"-half 
 of the armature being in series produce 3 volts per coil or 
 a total of 12 volts which is the electro-motive force of the 
 generator. 
 
 The S-half of the armature also generates a pressure of 
 12 volts, which is not added to the pressure of the N-half, 
 being in parallel with it. An inspection of Fig. 443 shows 
 that they oppose rather than add to each other ; but an out- 
 let being provided they turn aside through it, and send cur- 
 
 *Ee volutions per minute, 
 t Peripheral speed. 
 Revolutions per second. 
 §American Wire Gauge. 
 
1050 
 
 Steam Engineering 
 
 rents separately and independently towards the outside cir- 
 cuit. 
 
 If the armature is wound with No. 10 wire A.W.G.§ the 
 diameter of which is 0.102 inch or 102 mils, its area is 102 
 squared equal to 10,404 c. m. Allowing 700 c. m. per am- 
 pere, it will carry 15 amperes, without too much heating. 
 
 A ft 
 
 Two Pole, Two Clrcui; 
 
 Four r*oIe.Four Ch cuit.Four Brufttoes 
 la Multiple- 
 
 9$m> m& 
 
 Four Pole, Four Circult.Cross Connected 
 Two Brushes or Four Brushes, 
 in Multiple. 
 
 D > *p 
 
 Four Pole.Two Clrcirtt Ring 
 
 Two Brushes or Four Brushes, 
 
 in Multiple. 
 
 Fig. 444 
 
 SHOWING THE NUMBER AND POSITION OF BRUSHES ON DIFFERENT 
 ARMATURE WINDINGS 
 
 The black brushes are the ones actually used, the dotted ones 
 being dispensed with on account of the particular winding. 
 
 Since each side of the armature delivers its own current 
 to the brushes, the safe current output of this generator is 
 30 amperes. 
 
 Suppose there are 250 ft. of this No. 10 wire on this 
 armature. The resistance of the wire according to the wir- 
 ing table is 1.02 ohms per 1,000 ft. 
 
The Dynamo 
 
 1051 
 
 The resistance of all the wire on the armature is 0.255 
 ohm, and the resistance of the wire on each half of the ar- 
 mature is 0.128 ohm. 
 
 But the two halves are in parallel so the resistance of 
 the armature as measured from brush to brush will be one- 
 
 / k 
 
 
 Fig. 445 
 
 half of 0.128 or 0.064 ohm. The drop, or loss of pressure 
 in the armature will be I x E or 30 x 0.064=1.92 or say 2 
 volts. This machine being a shunt generator, the main 
 current does not pass through the fields, and there is no 
 further voltage lost. 
 
1052 
 
 Steam Engineering 
 
 The electro-motive force of this dynamo is 12 volts, and 
 its voltage is 10 volts. 
 
 Its output in watts will be 10X30=300 watts or 0.3 
 K.W. This is the rating of the machine, and it will carry 
 
 _ 
 
 Fig. 446 
 
 this load 22 hours a day without getting more than 90° 
 Fahr. hotter than the surrounding atmosphere. A prop- 
 erly proportioned machine will stand a 25 per cent over- 
 load for half an hour, rising an extra 30° in temperature, 
 
The Dynamo 1053 
 
 and it will stand a 50 per cent overload for one minute 
 without being damaged by the heat. 
 
 Drum Winding. — The extra labor involved in passing 
 the dead wire through the bore of a ring core is avoided 
 by going back to first principles again, and placing on the 
 core, (either drum or ring) a number of coils shaped as in 
 Fig. 435, producing a winding as shown in Fig. 439. It 
 is to be noted that the inductors lie entirely on the outer 
 surface of the core, and that the percentage of dead wire is 
 less than in Fig. 441. For a long, small diameter arma- 
 ture, drum winding uses the least wire, while for a short, 
 large diameter core, the ring winding will require fewer 
 pounds of copper. In order to make the diagram in Fig. 
 440 clear it has its proportions wrong. The dead part of 
 the wire is drawn very long and the active part very short. 
 The reverse is true of an actual winding. 
 
 Eef erring to Fig. 439, and using Fig. 440 as a guide, 
 the left side of the armature is the N-pole side and the 
 right the S-pole side; and the armature is revolving anti- 
 clockwise (otherwise the upper brush would be positive). 
 
 The electro-motive forces on the N-side and S-side of coil 
 T, as in Fig. 436, are in series and add up, producing a 
 current flow towards the lower (positive) brush. The cur- 
 rent passes through the inactive (dead) coil E in order to 
 get to the positive brush. 
 
 At the same time the electro-motive forces in coil B add 
 up and passing through the dead coil L, drive current out 
 of the lower brush. 
 
 The value of the electro-motive force is eight times that 
 which one inductor can produce. For the active coil T has 
 4 loops, i. e., 8 inductors in series, as also has the coil B. 
 Suppose T produces 8 volts, the two coils T and B are in 
 parallel and do not add their electro-motive forces. 
 
1054 
 
 Steam Engineering 
 
 The coils L and R are dead, L being in series with B and 
 E in series with T, but they produce no electro-motive force. 
 At the present instant they are but a wasteful resistance; 
 their value, however, will be soon seen. 
 
 When the armature has moved about % of a revolution, 
 T is cutting flux slantingly and R, which is in series with 
 
 Fig. 447 
 
 it, is beginning to cut flux also. T is only % active,, pro- 
 ducing say 6 volts, and R is not totally dead but ^4 active, 
 producing 2 volts. Hence the voltage of the machine is 
 still 8. 
 
 At 14 revolution R is doing full work and B is dead and 
 in series with it, while T is dead and L in series with it is 
 
<1 
 
 The Dynamo 1055 
 
 at full activity. Now E and L produce the electro-motive 
 force. 
 
 The current enters the armature through the upper 
 brush, splits and passes through the armature by two par- 
 allel circuits, one containing T and R in series and the 
 other containing L and B. During a revolution these coils 
 interchange places, but two coils are always in each circuit. 
 
 When 6 amperes flow in the external circuit the No. 16 
 wire of the armature is not overheated, as it has but 3 
 
 Fig. 448 
 
 amperes to carry. It has 2583 circular mils, which is more 
 than 3X700 CM. '.,' v ' VI v " v ' ' 
 
 Self -excitation of a Dynamo, — When a dynamo is stand- 
 ing idle the field magnets are weakly magnetic, due to 
 residual magnetism. 
 
 Let the armature revolve, and in a shunt, or compound 
 machine open, and in a series generator close the external 
 circuit. 
 
 A few volts will be generated and cause a current to 
 flow though the fields, hence the magnetism will increase 
 
1056 
 
 Steam Engineering 
 
 and more voltage will be induced. This voltage will send 
 increased current through the shunt field, and cause more 
 volts to be induced. 
 
 The machine is now "building up." 
 
 As more and more magnetism is put into the fields, it 
 becomes harder to get any more in as the iron is approach- 
 ing saturation and there is more and more leakage. 
 
 Hence at a certain point, depending on the design of the 
 machine, the difficulty of increasing the magnetism being 
 
 Fig. 449 
 
 added to the effect of the leakage just balances the tendency 
 of the voltage to be increased. If nothing else is done the 
 voltage of the dynamo will remain constant. 
 
 In the series field, is passing all the current drawn from 
 the machine, and the field strength and voltage tend to in- 
 crease. This increase is opposed by the I. R. loss in arma- 
 ture and field, and the effect of the increasing field density. 
 The net result is a. building up of the voltage and if the 
 load is not changed the voltage of the machine will remain 
 constant. 
 
The Dynamo 1057 
 
 Regulation. — If now in the shunt generator the external 
 circuit is closed, an extra current (very large in proportion 
 to the field current) is drawn from the armature and causes 
 an I. R. loss. 
 
 A lower voltage is thug impressed on the external cir- 
 cuit, also on the field. Hence the field weakens, and the 
 added results of I. R. loss and weaker field is a considerable 
 drop in voltage for each increase in load. 
 
 Resistance must be cut out of the field as load increases. 
 
 When in the series generator the load increases, a shunt 
 should be placed around the field to weaken it, if a con- 
 stant potential is desired. 
 
 Position of the Brushes, — In order that one set of 
 brushes may take away from, and the other set deliver cur- 
 rent to the generator in a bipolar machine these sets are on 
 opposite sides of the commutator. 
 
 In some d}^namos when the inductors come out of the 
 slots, one goes straight on to a commutator bar, and the 
 other is bent over to its proper bar. This puts the brushes 
 in line with part of the coil, and they will be found half 
 way between the pole tips. 
 
 It is usual to bend both inductors as they leave the slots 
 and connect to bars half way between the slots. Then the 
 brushes will be found opposite the middle of the pole piece. 
 
 In dynamos and non-reversing motors the brushes are a 
 little distance away from the points mentioned, but in re- 
 versing motors are exactly at these points. 
 
 The alternate brushes are of the same polarity, and there 
 is usually a set of brushes for each field magnet. 
 
 The placing of the brushes on the commutator with a 
 certain relation to the winding is necesary as a reference to 
 Fig. 444, or to the diagram of any winding will show that 
 
1058 
 
 Steam Engineering 
 
 the brush while collecting current is at the same time short 
 circuiting one of the coils. 
 
 In order that an excessive current may not be generated 
 in this short circuited coil it must be out in the interpolar 
 space at the time the brush touches the two bars belonging 
 to it. 
 
 Brushes and Commutators . — Figs. 445 to 449 show dif- 
 ferent arrangements of modern brushes and brush-holders. 
 These are used to take the current from the commutator 
 
 Fig. 450 
 
 and deliver it to the outside wires in the case of a dynamo, 
 and for the opposite in the case of a motor. 
 
 There are many different designs and constructions of 
 brushes and brush-holders, and these designs are brought 
 about by the various ideas of different builders in their at- 
 tempt to produce various advantageous results, but the 
 electrical connections and underlying principles remain the 
 same whether a copper or a carbon \>rush be used. 
 
 In any construction of brush holding device, if great care 
 is not exercised in keeping it thoroughly clean, trouble is 
 
Brushes and Commutators 1059 
 
 sure to be the result, and trouble of this nature increases 
 bo rapidly that unless the attendant immediately sets about 
 to right it, a burned out armature is almost sure to be the 
 consequence sooner or later. In alternating current dyna- 
 mos, where brushes rest on collector rings instead of com- 
 mutators, it is much easier to keep out of trouble, because 
 the brushes in this case merely collect the current from the 
 rings, and do not commutate or rectify it. 
 
 The brushes and commutator of a dynamo or motor are 
 probably the most important parts with which the engineer 
 
 / 
 
 Fig. 451 
 
 has to deal. Great care should be taken that the brushes set 
 squarely on the commutator, and that the surface of the 
 brushes and commutator are as smooth as possible. It is a 
 good plan, and in some cases the brush-holders are so 
 made, that the brushes set in a staggering position, that is 
 to say, in a position so that all the brushes will not wear in 
 the same place over the circumference of the commutator 
 and cause uneven wear across the length of the commutator 
 bars. In most machines the armature bearing is arranged 
 so that there is more or less side motion, which, when the 
 
1060 Steam Engineering 
 
 armature is running, causes a constant changing of the po- 
 sition of the brushes and commutator. 
 
 Whatever style of brush is used, the commutator should 
 be kept clean and allowed to polish or glaze itself while 
 running. Xo oil is necessary unless the brushes cut, and 
 then only at the point of cutting. A cloth (not cotton 
 waste) slightly greased with vaseline and applied to the 
 surface of the commutator while running is best for the 
 purpose of preventing the commutator from cutting. 
 Should the commutator become rough, it should be 
 
 / 
 
 /•- 
 
 Fig. 452 
 
 smoothed with sandpaper, never using emery cloth, because 
 emery is a conductor of electricity, and the particles of 
 emery are liable to lodge themselves between the commuta- 
 tor bars in the mica and short circuit the two bars, thereby 
 burning a small hole wherever such a particle of emery has 
 lodged itself. The emery will also work into the brushes 
 and copper bars and wear them down; it being almost im- 
 possible to remove all the emery. 
 
 In the end-on carbon brushes, Fig. 449, the contact sur- 
 face of the brushes should be occasionally cleaned by taking 
 a strip of sandpaper, with the smooth side of the paper to 
 
Brushes and Commutator 
 
 1061 
 
 the commutator, and the sanded side toward the contact 
 surface of the brush, and then by leaving the tension of the 
 brush down on the sandpaper, it is an easy matter to move 
 the sandpaper to and fro and thoroughly clean off the 
 glazed and dirty surface from the carbon, leaving it with a 
 concave that will exactly fit the commutator. 
 
 The advantages of carbon brushes are many. Among the 
 cardinal points are: The armature may run in either di- 
 rection without it being necessary to alter the brushes ; the 
 carbon can be manufactured with a quantiy of graphite in 
 its construction, thereby lowering the mechanical friction 
 
 
 M ^tl-i 3 
 
 
 
 
 
 
 
 * 
 
 
 
 — wwv- 
 
 o "•/ 
 
 YLn 
 
 
 
 WR 
 
 
 w \ 
 
 < \V^7 
 
 Fig. 453 
 
 of the brushes on the commutator ; they do not cut a com- 
 mutator so much by sparking ; the commutator has a longer 
 life, the wear being more evenly distributed. 
 
 Carbon brushes, due to their rather high resistance, will 
 often heat up considerably, but, although this heat is ob- 
 jectionable, their resistance tends to cut down the sparking. 
 The brushes are sometimes coated with copper to reduce 
 their resistance. Often a carbon brush will be found which 
 is very hard. As a rule such a brush should be thrown 
 away, as it will heat abnormally and at the same time wear 
 the commutator. 
 
1062 Steam Engineering 
 
 In Fig. 450 we have one of the various so-called old 
 styles of leaf brush-holders. The end-on brushes are more 
 generally used in modern practice, because their contact 
 surface area is not increased or decreased by wear. Conse- 
 quently the brushes always remain in a diametrically oppo- 
 site position. With the old style brush-holding device, 
 where the brushes rest on the commutator at a tangent, 
 great care should be exercised not to allow the brushes to 
 wear in a position so that their points will be out of dia- 
 metrical opposition. Fig. 450 shows the correct setting of 
 
 Fig. 454 
 
 this type of brush, and Figs. 451 and 452 show the incor- 
 rect setting. 
 
 By remembering that each one of the commutator bars 
 is the end of a coil, and then just mentally tracing the cur- 
 rent through the coils from one brush to the other, we can 
 readily understand what the results are when the brushes 
 are neglected and left in a relative position, as shown in 
 these figures. 
 
 Sparking is the usual result of brushes allowed to wear 
 to such an extent. Overloading of a dynamo or motor will 
 also cause serious sparking, and no amount of care can 
 
Brushes and Commutator 1063 
 
 prevent damage to armature, commutator or brushes, if a 
 machine is permitted to be overloaded. 
 
 Sometimes the commutator will contain one or more 
 bars which, as the commutator gets old and wears down, 
 will wear away either too fast or too slow, due to the metal 
 being harder or softer than the rest of the bars forming 
 the commutator. This causes a roughness of the commu- 
 tator, and results in the flashing of the brushes and heating 
 of both the commutator and brushes. About the only sat- 
 isfactory method of remedying this evil is to take out the 
 armature, and have the commutator turned down in a lathe. 
 
 A short-circuited coil in the armature, or a broken arma- 
 ture connection, will also cause considerable sparking. 
 Either of these conditions can be located by means of a 
 Wheatsone bridge, or by what is known as the fall of po- 
 tential method. To make a test with this latter method, 
 connect in series with the armature to be tested some re- 
 sistance capable of carrying the necessary current, also an 
 ammeter. Some apparatus for varying the current strength, 
 such as a water rheostat, or lamp rack, must be connected 
 in the circuit, a diagram of which is shown in Fig. 453. 
 
 In the diagram, WE is the water rheostat or lamp rack, 
 E the known resistance, A the ammeter and M the arma- 
 ture to be tested. By means of the water rheostat regulate 
 the current passing over the apparatus until it is of such 
 strength that a deflection can be obtained on a voltmeter 
 when it is connected to two adjacent bars on the commuta- 
 tor. Suppose the armature coil between bars 1 and 2 on 
 the commutator were broken. The voltmeter connected 
 across these two bars would give the same reading as when 
 connected across the two points 10 and 11. If the volt- 
 meter were connected between any other two points on the 
 commutator on the same side as the broken coil no deflec- 
 
1064 Steam Engineering 
 
 tion would be obtained, while connecting the voltmeter be- 
 tween any two adjacent bars on the other side of the com- 
 mutator would give practically the same reading irrespect- 
 ive of which bars were used. The resistance of one or more 
 sections of the armature winding could also be found by 
 using Ohm's law, K=E/I, or the resistance would be equal 
 to the voltage divided by the current as shown on the am- 
 meter. It must be remembered that this latter will be true 
 only when there is an open coil in one side of the armature, 
 for in this case only will the whole current flow through the 
 one side. If the coil between bars 1 and 2 were short cir- 
 
 Fig. 455 
 
 cuited, the voltmeter would show practically no reading 
 between these bars; while between any other bars some de- 
 flection would be obtained. An open circuit, or short cir- 
 cuit will nearly always be found by examination, as the 
 trouble usually happens very close to the commutator con- 
 nections in the case of an open circuit, and may very often 
 be found between the commutator bars themselves^ in the 
 case of a short circuit. If the trouble is not at these places 
 it will usually be in the windings, in which case the only 
 remedy is to have it re-wound. Temporary repairs may be 
 made in the case of an open circuit by short circuiting the 
 
Brushes and Commutator 
 
 106£ 
 
 commutator bars around the open circuit, but this method 
 should only be used in emergency, as the sparking will in 
 time destroy the commutator. 
 
 With many dynamos, especially of older types, it is nec- 
 essary to shift the brushes with every change of load. The 
 current produced by the armature makes a magnet out of 
 it, and the magnetism of the armature opposes that of the 
 fields. In Fig. 454 the. armature is working with a very 
 light load and the lines of force of the field magnets are 
 
 1 To* 1 
 
 ,*ve 
 
 Fig. 456 
 showing position of brush for sparklers. 
 
 CURRENT 
 
 COLLECTION OF 
 
 only slightly opposed by those of the armature. In Fig, 
 455 we assume a heavy load on the dynamo and conse j 
 quently the magnetism of the armature opposes that of the 
 fields. This changes the location of the neutral point 
 (when the coils under the brush generate no current) and 
 it becomes necessary to shift the brushes accordingly, or 
 great sparking would result. The amount of shifting nec- 
 essary with changes of load varies in different d3 r namos. 
 If the field is very strong compared to the armature, it will 
 be but little. If the armature (as in some arc dynamos) 
 
1066 
 
 Steam Engineering 
 
 is very strong compared to the field, it will be considerable. 
 
 In dynamos, with increasing load, the brushes should 
 be shifted in the direction of rotation, and in the opposite 
 direction when the load decreases. 
 
 Never allow a dynamo or motor to stand in a damp place 
 uncovered. Moisture is apt to soak into the windings and 
 cause a short circuit or ground when started. Great care 
 should also be used should it ever be found necessary to use 
 water on a heated bearing. If the water is allowed to reach 
 
 Fig. 457 
 circuits in a series dynamo or motor 
 
 the armature, or commutator, it is bound to cause trouble. 
 Water should only be used in case of emergency, and then 
 sparingly. 
 
 Sparking. — When a current is broken there is always a 
 spark, which is greater the more turns in the wire, and the 
 more iron within these turns. That is, the more inductive 
 the current the worse the spark. 
 
 The conditions are right for excessive sparking in a ma- 
 chine, for the circuit is inductive and, although the circuit 
 
Brushes and Commutator 1067 
 
 is not actually broken, the current being merely shifted, 
 yet the result is equivalent to it. 
 
 Looking at Fig. 456 and considering the line N" N to be 
 about midway between the pole pieces. The coil B is short 
 circuited but has no current in it because : 
 
 1. The field is very weak and the coil is moving paral- 
 lel to it, so no electro-motive force is generated in the coil. 
 
 2. The currents from the 1ST- and S-side of winding en- 
 ter the brush without going through the coil B. 
 
 Coil B has therefore no current in it, but being connected 
 to A and C whose potential is high, B is charged with elec- 
 tricity, and it is full of coulombs* which are at rest. 
 
 When the armature revolves as shown and the toe of a 
 copper brush leaves bar 3 the current from C must instantly 
 change over going through B to reach the brush. The 
 coulombs in B which are at rest should instantly move at 
 full speed becoming a part of the armature current. 
 
 It being impossible to set the coulombs in B into motion 
 instantaneously, it is evident that the current from C en- 
 counters more than the ohmic resistance of the coil B. This 
 extra opposition is called reactance. 
 
 The path through B being momentarily practically non- 
 conducting, the circuit is broken by the bar moving away 
 from the brush, and a spark or arc formed. 
 
 The circuit being inductive (having turns containing 
 iron), the spark is persistent and holds until the reactance 
 of coil B decreasing, it begins to conduct and diverts 
 enough current into the proper path, and the arc goes out 
 for lack of current to maintain it. 
 
 *A coulomb is a certain quantity of electricity. When 
 a coulomb passes a given point every second a current of 
 one ampere is said to flow. 
 
 ^ 
 
1068 Steam Engineering 
 
 This sparking is avoided in the following way: 
 
 1. Carbon brushes of high resistance are used which, 
 as the part of the brush touching a bar gets narrower, due 
 to the high resistance, throttle the current, gradually forc- 
 ing it over to the coil B. Hence B does not have to in- 
 stantly carry all the current. 
 
 2. Move the brushes of a dynamo in direction of rota- 
 tion until they are nearer the pole shoe, exactly as is shown 
 in Eig. 456. 
 
 The short cicuited coil B is now under the fringe from 
 the pole piece; and is moving obliquely through a stronger 
 field. A small electro-motive force is generated in it. 
 
 From the illustration it will be seen that a current in the 
 same, as in C (for B and C are under influence of same 
 pole piece) flows around through B, the bars 2 and 3 and 
 the brush. 
 
 By shifting the brushes a little to and fro the correct 
 strength of field can be selected, and the obliquity at which 
 it is cut adjusted, so that a current will be made to flow 
 in B not only of the same direction as that in C, but also 
 of exactly the same value. 
 
 Hence when the toe of the brush slips from bar 3 the 
 current in C instead of running against the impedance 
 (the sum of the resistance and reactance) of coil B, finds 
 itself merely falling in behind the flow already established, 
 and there is no tendency to spark. 
 
 In a motor the brushes are shifted in opposite direction 
 to the rotation to get the no sparking position. Hence the 
 positions for sparkless forward or backward running are 
 some distance apart. 
 
 It is a mere matter of first cost to produce a machine 
 with absolutely sparkless commutation under any condi- 
 tions. It is the skill of the designers which has (without 
 
 te_ 
 
Types of Dynamos 
 
 1069 
 
 prohibitive cost) so reduced the distance between these two 
 points that it may be spanned by a thick carbon brush. 
 
 TYPES OF DYNAMOS. 
 
 Dynamos are divided into different types with reference 
 to the manner in which their fields and armature are inter- 
 connected. 
 
 Ammeter 
 
 Resistance eox 
 
 ~Sffi 
 
 p= E; 
 
 Fig. 45S 
 
 CIRCUITS OF A SHUNT DYNAMO WITH INSTRUMENTS AND A LOAD OF 
 
 LAMPS 
 
 The series dynamo. — Pig. 457. The same current tra- 
 verses the field, armature and main or external circuits. 
 The conductors in these circuits are about the same size. 
 The circuits are all in series. 
 
 This dynamo is used for arc lighting and, as a booster 
 for increasing the pressure on a feeder carrying current 
 furnished by some other generator. 
 
 The characteristic of this type is to furnish power at an 
 increased voltage as the load increases. If sufficient current 
 is drawn to overload the machine, the voltage will drop. 
 
 ^ 
 
1070 Steam Engineering 
 
 The shunt dynamo. — Fig. 458. Here the field circuit is 
 arranged as a shunt circuit. The armature and external 
 circuits are in series. The armature current is the sum of 
 the external, and field currents. The conductors on the 
 field are very much smaller than those on the armature, as 
 they carry only 2 to 5 per cent as much current. The shunt 
 dynamo is used for incandescent lamp lighting, and mill 
 and factory power. 
 
 The leading characteristic of the shunt generator is to 
 allow the voltage to fall, as the load is increased. It is 
 evident that only by a combination of these two classes into 
 a compound dynamo, Fig. 459, can a generator be pro- 
 duced which will deliver any power within its rated capac- 
 ity, and still hold a steady voltage. 
 
 The armature is similar to the armature of the shunt dy- 
 namo, but the fields have two distinct windings, one shunt 
 and the other series. 
 
 The series dynamo is often called a constant current 
 generator because its tendency is that way, and with a reg- 
 ulator it will furnish a constant current. 
 
 The shunt dynamo is similarly termed a constant poten- 
 tial generator. For with a regulator it will keep to a con- 
 stant voltage. 
 
 If a compound wound dynamo is supplying a circuit at 
 a constant potential it may be almost self regulating. Sup- 
 pose that the resistance of the external circuit be dimin- 
 ished. This will send more current through the series coil, 
 thus increasing the intensity of the field. But the reduc- 
 tion of the resistance in the outer circuit reduces the cur- 
 rent in the shunt winding. This action tends to reduce the 
 intensity of the field. 
 
 If the two exciting coils, viz. shunt and series, are prop- 
 erly proportioned, the intensity of the field may be main- 
 
Types of Dynamos 
 
 1071 
 
 tained practically constant, even though the resistance of 
 the external circuit is increased or diminished. The arma- 
 ture being kept at a constant speed of rotation, in a con- 
 stant field of force, by the engine, or other source of power, 
 it will impress upon the circuit a constant voltage. This 
 applies of course to an accurately arranged winding. 
 
 Over compounding. — The result of such even action is 
 the maintenance of a constant voltage at the terminals of 
 the machine. In electrical work, all sorts of conditions 
 must be met. A very usual one is that on a circuit a con- 
 
 Fig. 459 
 
 CIRCUITS IN A COMPOUND DYNAMO 
 
 stant voltage is required, not at the generating plant, but 
 in the heart of the district several miles distant. In an 
 over-compounded dynamo the series coil is given a certain 
 number of turns in proportion to the turns in the high 
 resistance shunt coil, and the influence of the series coil 
 overbalances that of the shunt coil. The result of over- 
 compounding is to cause the voltage at the terminals of the 
 machine to rise with the increase of current. The propor- 
 tional increase of voltage with increase of current can be 
 accurately regulated by the relative sizes of the coils. It is 
 only necessary to follow what has been said regarding the 
 
1072 Steam Engineering 
 
 series dynamo, and to regard the compound wound ma- 
 chine as a series dynamo greatly reduced in its character- 
 istic action. Over-compounding makes it possible to main- 
 tain a constant voltage at any point within a district. The 
 resistance of the mains between the dynamo in the central 
 station, and the given point in the district is known. The 
 drop in voltage due to that resistance varies with the cur- 
 rent. The over-compounding of the machine can be reg- 
 ulated to give the same increase in voltage with the in- 
 crease in current, and thus the voltage at any desired point 
 in the district can be kept constant, following Ohm's law. 
 Suppose that the resistance of a single lead of the mains is 
 0.01 ohm. Then the resistance of the two leads is 0.02 ohm. 
 Assuming a maximum current of 500 amperes is needed, 
 the drop due to the specified resistance and current will be 
 EI=E, or 0.02X500=10 volts. This is an -extreme case, 
 but the dynamo by over-compounding can be made to vary 
 its voltage at the terminals in this, or in any other desired 
 proportion to the current. With the resistance given above, 
 and the variation in voltage for the current as calculated 
 above, which variation is at the terminals, a constant volt- 
 age would be maintained at the outer portion of the leads. 
 The series field coils of a dynamo can only be excited by 
 the working current, or by a portion of it. When the ma- 
 chine is compound wound, the series coils are taken care of 
 by the machine, but the shunt coils may receive their cur- 
 rent from other sources. But in order to make the dynamo 
 self regulating, the shunt coil should be fed from the ma- 
 chine proper. This practice also makes the dynamo self- 
 contained. In some cases the terminals of the shunt coils 
 are connected to the leads, or bus bars of the main circuit; 
 and if several dynamos are operated, and a constant poten- 
 tial maintained in the circuit at all times, a new element is 
 
 ^_ 
 
Types of Dynamos 
 
 KJ7S 
 
 introduced in the excitation of the field, for the reason that 
 the current in the shunt coil is independent of the speed 
 of the dynamo, and the shunt coils continue to excite the 
 field to a certain extent, and this excitation is never re- 
 duced to zero until the connection with the bus bar, or main 
 connection is broken. This is a case of under-compound- 
 ing, and the advantage of it is that it makes it possible to 
 excite the field before starting the dynamo. The field is 
 not only excited, but the correct polarity is established be- 
 
 
 
 -^^ 
 
 
 1- 
 
 
 
 ~^5r\r-\ 
 
 
 ) 
 
 / -\ 
 
 ill 
 
 ^S 
 
 
 I N 
 
 
 t 
 
 
 
 ) 
 
 
 
 
 
 Fig. 460 
 separate-circuit dynamo 
 
 fore the armature begins to revolve. The capacity of the 
 shunt coil is considerable, and it cannot with safety be dis- 
 connected by a simple opening of a switch. A bank of 
 lamps is generally mounted in series with it, and the field 
 break switch is placed between the lamps and the main cir- 
 cuit. When it is opened the resistance of the lamps pre- 
 vents undue sparking. The shunt coil may also be excited 
 by an entirely independent source of electric energy, as a 
 storage battery, or an exciting dynamo. The exciting ma- 
 
1074 
 
 Steam Engineering 
 
 chine may be run at a constant voltage, thus passing an 
 absolutely constant current through the excited shunt coils. 
 The separately excited dynamo resembles the magneto 
 in its action, as the field strength does not directly depend 
 upon the current generated. The separate circuit dynamo 
 has either two separate armatures in the field space, or it 
 may have two sets of coils. Whichever it is, one armature 
 or coil set is used to excite the field, and the other to sup- 
 ply the current to the circuit. Fig. 460 shows such a dyna- 
 mo with two commutators, one for supplying the main cir- 
 cuit, and the other the field magnet current. 
 
 OPERATION" OF DYNAMOS. 
 
 Constant Potential Dynamos. — In order to thoroughly 
 explain the operation of dynamos, let us assume that we 
 
 Fig. 461 
 
 have the task of starting a new shunt dynamo, one that 
 has never generated any current. Our first step is to open 
 
Operation of Dynamos 
 
 1075 
 
 the main switch and turn the rheostat or field resistance 
 box so that all the resistance is in circuit. A rheostat con- 
 sists of a number of resistances, Figs. 461 and 462, so ar- 
 ranged that they can be cut in or out of the circuit with- 
 out opening the circuit. By reference to Fig. 462, it will 
 be seen that the current enters at the handle, and from 
 there passes to the contact point upon which the handle 
 happens to rest. If the handle is at 1 the current must 
 pass through all the wire in the box; if it is at 2 it simply 
 passes through the handle and out. 
 
 Fig. 462 
 
 Rheostats for the shunt circuit of a dynamo should have 
 sufficient resistance, so that when it is all inserted, the 
 voltage of the dynamo will slowly sink to zero. This 
 method of stopping the action of a dynamo is perfectly 
 safe, and should be followed wherever possible. 
 
 We are now running our dynamo with all resistance in 
 the shunt circuit. This is simply as an extra precaution 
 because we know nothing about this particular dynamo. 
 When it is known that the dynamo is in good order, the 
 
1076 
 
 Steam Engineering 
 
 engineer or attendant usually cuts out all the resistance, 
 and as the generator builds up or, in other words, generates 
 current, he proceeds, by the aid of the resistance box, to cut 
 down or diminish the flow of electricity around the field 
 magnets of the dynamo, and thereby diminish the mag- 
 netic density of the field magnets, and the electro-motive 
 force of the dynamo. 
 
 ttoggg) 
 
 Fig. 463 
 
 We must now gradually turn our rheostat so as to cut 
 out resistance, and watch the voltmeter, which is connected 
 as shown' at V in Fig. 463, and receives current whenever 
 the dynamo is operating. Suppose that the voltmeter in- 
 dicates nothing, and we find that the dynamo will not gen- 
 
Operation of Dynamos 1077 
 
 erate. On examination of all the connections we find every- 
 thing correct, and we now discover that the dynamo field 
 magnets do not contain what is termed "residual magne- 
 tism" sufficient to start the process of generating current. 
 
 Before an armature can generate current it must cut 
 lines of force, that is, is must revolve in a magnetic field. 
 If the dynamo has been generating current it is likely that 
 the iron cores of the field magnets will retain sufficient 
 magnetism to start the generation of current again. This 
 magnetism which remains in the iron is known as residual 
 magnetism. It will make itself manifest by attracting the 
 needle of a compass, or if strong, a screw driver or a pair 
 of pliers. If we find no magnetism in the iron core of the 
 field magnets, we may take the ends of the shunt winding 
 on the field magnets and pass current over them from a 
 battery. This current will produce sufficient magnetism 
 to cause the generator to build up; in other words, if we 
 disconnect these batteries, and connect the wires back again 
 from where we got them, we will find that we can generate 
 current with the machine. 
 
 When the machine begins to generate, we watch the volt- 
 meter, and cut resistance in or out of the circuit according 
 whether we need to lower or raise the voltage. If we have 
 only one dynamo we may close the main switch before we 
 begin generating, or after we have attained full voltage. 
 
 Again referring to the pole pieces on the dynamo, it is 
 possible that there is a sufficient quantity of residual mag- 
 netism in the pole pieces, and that the polarity of both 
 field magnets, between which the armature is revolving, is 
 the same. This would also cause the dynamo to fail in 
 generating current. If sending battery current through the 
 coils does not make one field a north pole and the other a 
 
1078 Steam Engineering 
 
 south pole, one of the fields must be connected wrong and 
 we must make some changes in the connection. 
 
 Eef erring to Fig. 463, a and b are the terminals of the 
 shunt winding on the fields. If the winding of the fields 
 is correctly put on it will be as in the little sketch at lower 
 corner ; that is, if both field magnets were taken out of their 
 places and put together, the winding should run as one 
 continuous spool. But if the winding on one field is wrong, 
 we need simply change its connection, as, for instance, 
 transferring c to a and a to c. 
 
 In order that a dynamo may excite itself, it is necessary 
 that the current produced by the residual magnetism shall 
 flow in such a direction as to strengthen this residual mag- 
 netism. If the current poduced by the residual magnetism 
 flows through the field coils in the opposite direction, it 
 will tend to weaken the residual magnetism, and conse- 
 quently to reduce the current which flows. 
 
 For this reason if the first attempt to start a dynamo 
 with battery current fails, the battery should be applied 
 with the opposite poles so that the magnetism it produces 
 in the fields will be in the opposite direction. 
 
 The magnetism, the fields, and all parts of the dynamo 
 may be in perfect working order, and yet a short circuit in 
 any part of the wiring will prevent the dynamo from build- 
 ing up. This short circuit will furnish a path of such low 
 resistance that all current will flow through it and none 
 can flow through the fields to induce magnetism. Often 
 dynamos fail to generate because of broken wires in the 
 field coils, poor contacts at brushes, or loose connections. 
 Sometimes also part of the wiring may be grounded on the 
 metal parts of the dynamo frame. A faulty position of 
 the brushes may also be a cause for the machine not gen- 
 erating. In some machines the proper position for the 
 
Operation of Dynamos 
 
 1079 
 
 brushes is opposite the space between the pole pieces, while 
 in other machines their proper position is about opposite 
 the middle of the pole piece. If the exact position is not 
 known, a movement of the brushes will sometimes cause 
 the generator to build up. 
 
 If there are several dynamos to be started great care 
 must be taken to see that the second machine is operating 
 at full voltage before the switch is closed connecting it to 
 
 Fig. 464 
 
 the switch board. The voltage should be exactly the same 
 as that of the first machine and the rheostat worked to keep 
 it so. If it is less, it is possible that the first machine will 
 run the second as a motor; if it is more, the second ma- 
 chine may run the first as motor, the machine having the 
 higher voltage will always supply the most current. 
 
 It is also necessary before throwing in the second ma- 
 chine (connecting it to the switch board) to see that its 
 polarity is the same as that of the machine with which it 
 
1 080 Steam Engineering 
 
 is to be run. By reference to Fig. 464 it will be seen that 
 the + poles of both machines connect to the same bar, and 
 if one of these machines is running and we wish to connect 
 the other with it, we must first be sure that the wire of the 
 second machine which leads to the top bus-bar is of the 
 same polarity. That is, if the top bus-bar is positive, or 
 sends out current, the wire of all dynamos connected to it 
 must also be positive. The simplest way to find the posi- 
 tive pole of a dynamo is with a cup of water. Take two 
 small wires and connect one to each of the main wires of 
 the dynamo and then insert the bare ends of both wires 
 into the water, small bubbles will soon be seen to rise in 
 the water from one of the wires. That wire which gives 
 off the bubbles is the negative wire. Take care that in 
 making this test you do not get the ends of the small wires 
 together or against the metal of the cup or you will form 
 a short circuit. The polarity of both dynamos must be 
 tested and wires of same polarity connected to the same 
 bus-bar. 
 
 Where several machines are to be operated in parallel, 
 compound dynamos are generally used, because it is 
 troublesome to keep two shunt machines working in har- 
 mony. 
 
 The starting of a compound wound dynamo is the same 
 as that of a plain shunt dynamo, but in connecting a com- 
 pound wound dynamo to its circuit it is necessary to be 
 sure that the shunt coils and series coils tend to drive the 
 lines of force around the magnetic circuit in the same di- 
 rection. If the series coil is connected up in the opposite 
 direction to the shunt coil the dynamo will build up all 
 right, and will work satisfactorily on very light loads. 
 When, however, the load becomes even, five or ten per cent, 
 of full load, the voltage drops off very rapidly, and it is im- 
 
Operation of Dynamos 1081 
 
 possible to get full voltage with even half the load on. This 
 is because the ampere turns due to the series coils decrease 
 the total ampere turns acting on the magnetic circuit in- 
 stead of increasing them as the load comes on. This lowers 
 the magnetic flux and of course lowers the resulting volt- 
 age. In such a case it will be necesary to reverse either the 
 field or series coils. 
 
 Fig. 464 shows connections for two compound wound 
 dynamos run in parallel. When two or more compound 
 wound dynamos are to be run together, the series fields of 
 all the machines are connected together in parallel by 
 means of wire leads or bus-bars which connect together the 
 brushes from which the series fields are taken. This is 
 known as the equalizer, and is shown by the line running 
 to the middle pole of the dynamo switch. By tracing out 
 the series circuits it will be seen that the current from the 
 upper brush of either dynamo has two paths to its bus-bar. 
 One of these leads through its own fields, and the other, by 
 means of the equalizer bar, through the fields of the other 
 dynamo. So long as both machines are generating equally 
 there is no difference of potential between the brushes of 
 No. 1 and No. 2. Should, from any cause, the voltage of 
 one machine be lowered, current from the other machine 
 would begin to flow through its fields and thereby raise the 
 voltage, at the same time reducing its own until both arq 
 again equal. The equalizer may never be called upon to 
 carry much current, but to have the machines regulate 
 closely it should be of very low resistance. It may also be 
 run as shown by the dotted lines but this will leave all 
 the machines alive when any one is generating. The am- 
 meters should be connected as shown. If they were on the 
 other side they would come under the influence of the 
 equalizing current and would indicate wrong, either too 
 
1082 Steam Engineering 
 
 high or too low. The equalizer should be closed at the 
 same time, or preferably a little before the mains are closed. 
 In some cases the middle, or equalizer, blade of the dyna- 
 mo switch is made longer than the outside to accomplish 
 this. 
 
 The series fields are often regulated by a shunt of va- 
 riable resistance. 
 
 To insure the best results compound machines should 
 be run at just the proper speed, otherwise the proportions 
 between the shunt and series coils are disturbed. 
 
 GENERAL RULES. 
 
 1. Be sure that the speed of the dynamo is right. 
 
 2. Be sure that all the belts are sufficiently' tight. 
 
 3. Be sure that all connections are firm and make good 
 contact. 
 
 4. Keep every part of the machine and dynamo room 
 scrupulously clean. 
 
 5. Keep all the insulations free from metal dust or 
 gritty substances. 
 
 6. Do not allow the insulation of the circuit to become 
 impaired in any way. 
 
 7. Keep all bearings of the machine well oiled. 
 
 8. Keep the brushes properly set, and see to it that they 
 do not cut, or scratch the commutator. 
 
 9. If the brushes spark, locate the trouble and rectify 
 it at once. 
 
 10. The durability of the commutator and brushes de- 
 pends on the care exercised by the person in charge of the 
 dvnamos. 
 
Operation of Dynamos 1083 
 
 11. At intervals the dynamos must be disconnected 
 from the circuit and thoroughly tested for leakage and 
 grounds. 
 
 12. In stations running less than twenty-four hours 
 per day, the circuit should be thoroughly tested and 
 grounds removed (if any are found) before current is 
 turned on. 
 
 13. Before throwing dynamos in circuit with others 
 running in multiple, be sure the pressure is the same as 
 that of the circuit; then close the switch. 
 
 14. Be sure each dynamo in circuit is so regulated as 
 to have its full share of load, and keep it so by use of re- 
 sistance box. 
 
 15. Keep belting in good order; when several machines 
 are operating in parallel and a belt runs off from one, the 
 others will run this machine as a motor. 
 
 16. In the same way if you shut down an engine driv- 
 ing a generator, the other generators will run the genera- 
 tor and the engine. 
 
 Constant Potential Switchboard. — Fig. 465 illustrates 
 the usual type of switchboard employed to connect, or 
 switch various dynamos, and to feed various circuits from. 
 These types, sizes and arrangements of switchboards vary, 
 and depend entirely on the type and size of the plant, the 
 number of dynamos used and the number of circuits to be 
 controlled. The switchboard in this cut has three dynamo 
 panels, and one load panel. At the left of the board and 
 near the top is the voltmeter, while on the three left panels 
 are the dynamo main switches and their respective amme- 
 ters. On the lower part of these three machine panels will 
 be noticed the protruding hand wheels of the field resist- 
 ance boxes, which are hidden back of the board. The meter 
 
1084 Steam Engineering 
 
 at the top of the right hand panel is the load ammeter and 
 registers the total number of amperes that are being sup- 
 plied to the circuits whose several switches are just below 
 the meter. 
 
 Fig. 465 
 
 Fig. 466 shows diagrammatically the reverse side of a 
 similar switchboard. Below all of the switches there are 
 installed fuses in each wire. The object of these fuses is 
 to protect the wires and also the dynamos. These fuses 
 consist of an alloy which melts at a comparatively low 
 temperature. If, for instance, a short circuit occurs in 
 
Operation of Dynamos 
 
 1085 
 
 any line, the current will suddenly become very strong and 
 will generate considerable heat. This heat will cause the 
 fuse to melt and open the circuit. If the fuse did not 
 melt, the current would continue and overheat the wires, 
 causing considerable damage and perhaps fires. The fuses 
 
 6 6 6,.--' 
 
 6 6 6| 
 
 + 999 
 
 #1 
 
 -'Or-' 6 6 6 6 6 6 6 6 
 
 ss $% n n 
 
 y *>? 39 ^,9 + 
 
 I 
 
 o i 6| 6 6 61 
 
 + 9 9 9 
 
 +9 9 9 
 
 6 6 
 
 IS 3+ |8 1+ 
 
 9 9 * 9 
 
 llilil 
 Su/itches 
 
 Fig. 466 
 
 should always be chosen of such a size that they will melt 
 before the current rises enough to do any damage. 
 
 Operation of Constant Current Dynamos. — Constant cur- 
 rent dynamos differ from constant potential dynamos 
 mainly in the higher voltage for which they are usually 
 constructed. Such machines are always more or less dan- 
 
1086 Steam Engineering 
 
 gerous to life, and great care must be taken not to touch 
 any of the current-carrying parts with bare hands. 
 
 When such parts must be handled, rubber gloves are 
 very convenient and useful if kept dry. High voltage 
 machines should always be surrounded by insulating plat- 
 forms of dry wood, or rubber mats, so arranged that one 
 must stand on them in order to touch any part of the 
 machine. By reference to Fig. 467 it will be seen that 
 the constant current dynamo is not equipped either with 
 a voltmeter or a field rheostat; but an ammeter should 
 always be used. The troubles encountered with these dy- 
 namos are much the same as those of constant potential 
 dynamos. Most of them are referred to in the following 
 descriptions and instructions for different systems and to 
 avoid repetition need not be mentioned here. 
 
 The type of dynamo generally used with constant cur- 
 rents is shown in Fig. 467 and is series wound; that is, 
 the same current that passes through the lights and outer 
 circuit also passes through the fields and excites them. 
 The fields of this dynamo are connected with a short cir- 
 cuiting switch S, which is generally used when the ma- 
 chine is to be shut down. When this switch is closed it 
 forms a path of much lower resistance than do the fields 
 of the dynamo, and all current passing through it and the 
 dynamo loses its magnetism and stops generating. A 
 constant potential dynamo will not begin generating if 
 there is a short circuit anywhere in the wiring connected 
 with it, but with the constant current dynamo it is often 
 necessary to provide a short circuit in order to start it. 
 If there is very much resistance in the line, or if it is 
 entirely open the dynamo will fail to generate. 
 
 In order to start generation a small wire may be at- 
 tached to one of the terminals of the dynamo and the 
 
Operation of Dynamos 
 
 1087 
 
 other end brought in contact with the other terminal for 
 a fraction of a second or the shortest possible instant. If 
 the circuit happens to be arranged somewhat as shown in 
 Fig. 467, the plug may be inserted so that the dynamo 
 is started through only one lamp. When this lamp is 
 burning properly the plugs may be suddenly withdrawn 
 
 Fig. 467 
 
 and the current will now force itself through the other 
 lamps. This process is known as "jumping in" and should 
 be used only in an emergency, as much damage may be 
 caused, especially if a dynamo is already running a large 
 number of lamps and is then "jumped into" a bad circuit. 
 This is also often done, but is just as dangerous as it would 
 
1088 Steam Engineering 
 
 be to attempt to start a heavy steam engine by opening 
 up the throttle valve with a quick jerk. 
 
 Constant current dynamos are, or should be always equip- 
 ped with automatic regulators, and before the dynamo is 
 started special attention must be given the regulator to 
 see that it is in proper working order. 
 
 Often it may be desirable and even necessary to run two 
 dynamos in series, as, for instance, if a circuit has been 
 extended beyond the capacity of one machine. In such 
 a case the regulator of one machine is cut out, and that 
 
 Fig. 468 
 
 machine set to operate at about its highest electromotive 
 force, and the variations are taken care of by the other 
 dynamo. 
 
 The Brush System. — The brush arc dynamo is quite dis- 
 tinct from other constant current dynamos in general use. 
 The brush arc generator is of the open coil type, the funda- 
 mental principle of which is illustrated in Fig. 468. Two 
 pairs of coils, placed at right angles on an iron core, are 
 rotated in a magnetic field. The horizontal coils repre- 
 sented in the diagram are producing their maximum elec- 
 tromotive force, while the pair of coils at right angles to 
 
Operation of Dynamos 
 
 1089 
 
 them is generating practically no electromotive force. The 
 brushes are placed on the segments of the four-part com- 
 mutator, so as to collect only the current generated by the 
 two horizontal coils. The other coils are open circuited or 
 completely cut out of the circuit. 
 
 Such a machine will generate current, continuous in di- 
 rection, but fluctuating considerably in amount. These 
 
 
 
 Fig. 469 
 
 fluctuations will be diminished by the addition of more 
 coils to the armature. 
 
 Fig. 469 shows the connections of an eight-coil brush 
 arc generator. Each bobbin is connected in series with 
 the one diametrically opposite. The connection is not 
 shown on the diagram. It will be noticed that of those 
 coils connected to the outer ring on which the brushes A 
 
1090 Steam Engineering 
 
 and A 1 bear, only 3, 3 1 are in circuit, I, l 1 being entirely 
 cut out; while on the inside ring all coils 2, 2 1 and 4, 4 1 
 are in circuit, the two pairs being parallel ; 4, 4 1 are com- 
 ing into the field of best action ; in other words, they are 
 approaching that part of the field in which there is most 
 rapid change of magnetic flux, while 2, 2 1 are approaching 
 that part in which the flux is uniform. In 4, 4 1 there is 
 an increasing electro-motive force being generated, and 
 the current is rising; while in 2, 2 1 , the electromotive force 
 is decreasing and the current falling. Unless 2, 2 1 were cut 
 out of the circuit a point would soon be reached where the 
 
 Fig. 470 
 
 electromotive force in 2, 2 1 would be zero, and consequently 
 4, 4 1 would be short circuited through 2, 2 1 . Just before 
 this occurs, however, 2, 2 1 have passed from under the 
 brush, and the small current still flowing draws out the 
 spark seen on the commutator of all open coil machines. 
 Setting the Brushes. — A pressure brush should always 
 be used over the under brush in the same holder, as it 
 improves the running of the commutator and secures 
 better contact on the segment. The combination is re- 
 ferred to as the "brush." The brushes should be set 
 about 5y s in. from the front side of the brass brush- 
 holder. 
 
Operation of Dynamos 1091 
 
 In setting the brushes, commence with the inner pair 
 and set one brush about 5% in. from the holder to tip of 
 the brush, then rotate the rocker or armature until the 
 tip of the brush is exactly in line with the end of a copper 
 segment, as shown in Fig. 470. The other brush should 
 be set on the corresponding segment 90° removed (the 
 same relative position on the next forward segment) ; but 
 if the length of the brush from the holder is less than 5Vs 
 in., move both brushes forward until the length of the 
 shorter brush from the holder is 5% in. Now set the two 
 extreme outer brushes in the same manner, clamping 
 firmly in position, and by using a straight edge or steel 
 rule, all the brushes can be set in exactly the same line 
 
 i I 
 
 Fig. 471 Fig. 472 Fig. 473 
 
 and firmly secured. The spark on one of the six brushes 
 may be a trifle longer than on the others. In this case, move 
 the brush forward a trifle so as to make the sparks on the 
 six brushes about the same length. Equality in the spark 
 lengths is not essential, but it gives at a glance an in- 
 dication of the running condition of the machine. 
 
 Brushes should not bear on the commutator less than 
 % in. from the point of the brush, or, as illustrated in 
 Fig. 471, they will tend to drop into the commutator 
 slots and pound the copper tip of the wood block, causing 
 the fingers of the brushes to break off. If, on the other 
 hand, the bearing is too far from the end, or the brushes 
 are set too long, as in Fig. 472, the point of the brush will 
 not be in contact with the segment, thereby prolonging 
 
1092 Steam Engineering 
 
 the break, and allowing the spark to follow the tip with 
 consequent burning of the segments and brushes. 
 
 Fig. 473 shows correct setting with the tip of the brush 
 nearly tangential and stiff on the segment as it leaves. 
 
 Care of Commutator. — If the commutator needs lubri- 
 cation, oil it very sparingly. Once or twice during a run 
 is ample. If the oil has a tendency to blacken the com- 
 mutator instead of making it bright, wipe the commutator 
 with a dry cloth. Too much oil causes flashing. 
 
 The machine, of course, generates high potential, and 
 the cloth, or whatever is used to oil the commutator, 
 should therefore be placed on a stick so that the hand is not 
 in any way between the brushes. 
 
 A rubber mat should be provided for the attendant to 
 stand on when working around the commutator or brushes. 
 
 One hand only should be used, and great care exercised 
 not to touch two brush clamps or brushes at the same 
 time; never with switches closed. 
 
 As soon as current is shut off from the machine the com- 
 mutator should be cleaned. A piece of very fine sandpaper 
 held against the commutator under a strip of wood for 
 about a minute before the machine is stopped, will scour 
 the commutator sufficiently. The brushes need not be re- 
 moved. An effort should be made to have the machine 
 cleaned immediately after it is shut down. Five minutes 
 at that time will give better results than half an hour when 
 the machine is cold. Never use a file, emery cloth or cro- 
 cus, on the commutator. New blocks will sometimes cause 
 flashing, due to the presence of sap in the wood. The ma- 
 chine should be run for a few hours with a slightly longer 
 spark, say y 2 in., and the commutator then thoroughly 
 cleaned with fine sandpaper. 
 
Operation of Dynamos 
 
 1093 
 
 All constant current arc machines require an auto- 
 matic regulator to increase the voltage as more lamps are 
 cut into the circuit, and decrease it as lamps are cat out. 
 
 To Controller 
 
 Fig. 474 
 
 \ To Control fer 
 
 We will give only one of the several forms of regulators 
 used with this system. 
 
 The form 1 regulator is placed on the frame of the 
 machine beneath the commutator, and a constant motion is 
 imparted to its main shaft through a small belt running 
 
1094 
 
 Steam Engineering 
 
 around the armature shaft. (See Fig. 474.) By means 
 of magnetic clutches and bevel gears, a pinion shaft is 
 rotated, which moves the rack and the rocker arm and so 
 shifts the brushes on the commutator to maintain a spark 
 of about % in. on short circuit and % in. at full load; 
 at the same time the rheostat arm is moved over the con- 
 tacts to cut resistance in, or out of the shunt around the 
 field circuit. 
 
 CONNECTIONS OF BRUSH CONTROLLER 
 
 To Circuit or Ammeter 
 
 To Clutch at F for Clockwise. 
 
 To Clutch at E for Counter Clockwise. 
 
 To Clutch at E for Clockwise. 
 To Clutch at F for Counter Clockwise 
 Changed 6 June '98. 
 
 Fig. 475 
 
 The current for the magnetic clutches is regulated by 
 the controller. 
 
 The controller consists principally of two magnets which 
 are energized by the main current, and act when the current 
 is too high or too low by sending a small current to one 
 of the clutches. 
 
 A careful examination of the controller (see Fig. 475), 
 in connection with Fig. 474, will give a clear idea of its 
 
Operation of Dynamos 1095 
 
 regulating action. It is generally advantageous to make 
 the yoke which carries the brushes on the machines, and the ' 
 arm moving the rheostat, rather tight. As the magnetic 
 clutches act with considerable force, it is not necessary to 
 adjust these moving parts so loosely that they will move 
 without considerable pressure on the rocker handle. Less 
 difficulty will then be experienced in adjusting the con- 
 troller. 
 
 For shunt lamps, the controller may be adjusted to per- 
 mit a variation of .4 ampere above or below normal; for 
 differential lamps, the variation above and below normal 
 should not exceed .2 ampere. The limits given in the fol- 
 lowing instructions are for differential lamps, and may be 
 extended .2 ampere above or below for shunt lamps. 
 
 If the controller is out of adjustment and fails to keep 
 the current normal, do not try to adjust the tensions of 
 both armatures at the same time. For example, suppose 
 the current is too high, either one of the two spools 
 may be out of adjustment. The left-hand spool I may 
 not take hold quickly enough, or the spool F may take 
 hold too quickly. To make the adjustment, screw up the 
 adjusting button K on the right hand spool, increasing the 
 tension. This will have a tendency to let the current fall 
 much lower before the armature comes in contact with H, 
 to cause the current to increase. By simply tapping the 
 armature 6 quickly with a pencil or piece of wood, forcing 
 it down to its contact, and at the same time watching the 
 ammeter, the current may be brought up to 6.8 amperes if 
 6.6 amperes is normal, or to 9.8 if 9.6 amperes is normal. 
 "With the current at 6.8 amperes, which is .2 amperes high, 
 the adjusting button L should be turned to increase the 
 tension on this spring until the armature M comes in touch 
 with contact N, which will force current down through 0. 
 
1096 Steam Engineering 
 
 The clutch which pulls the brushes forward and rocks the 
 rheostat back for less current will thus be energized. Ee- 
 peat this adjustment two or three times, but do not touch 
 the adjusting button K ; adjust L until it is just right. 
 
 At the side of the armature M a little wedge is screwed 
 in by means of an adjusting button, and increases or 
 decreases the leverage on this armature. See that this 
 wedge is fairly well in between the core or frame of the 
 spool and the spring of the armature. The armature M 
 may have to be taken out and the spring slightly bent. 
 It is advisable to have the screw which passes through the 
 adjuster button L about half way in, to allow an equal 
 distance up and down for adjusting this lighter spring 
 after the wedge shaped piece is in the right position to 
 give the necessary tension on the spring which is fastened 
 to the armature M. 
 
 In the right-hand corner P, a small bent piece of wire 
 is placed for tightening up the screw which fastens the 
 spring to the frame of the spool. As the contact made 
 by the spring and the frame of the spool held together 
 by a screw and button is a part of the magnetic circuit, it 
 will be almost impossible to get this spring back to exactly 
 the same tension after once removing it. Therefore, the 
 adjusting buttons of the controller must be turned slightly 
 in order to bring it back to its proper adjustment. This, 
 however, is an after consideration, and care should be 
 taken to have the screw which holds the spring and frame 
 together always tight. 
 
 Having adjusted the spool I so that the current will 
 not rise above 6.8 amperes (or 9.8 amperes), move the ar- 
 mature M up to contact N with a pencil or piece of wood, 
 causing the current to be reduced to about 6.2 (or 9.2). 
 After the current settles at this point, decrease the tension 
 
Operation of Dynamos 1097 
 
 on the spring which is fastened to armature G, allowing 
 this armature to fall down to contact H. Current will 
 then flow through Q, which will rock the brushes back and 
 also move the rheostat arm for more current. As the 
 spool I has been adjusted for 6.8 (or 9.8) amperes, the 
 current cannot rise above that amount no matter how the 
 spool F is adjusted. 
 
 With very little practice in moving the armature of 
 one spool with a pencil, the othetf can be adjusted much 
 more readily than if an attempt is made to adjust the 
 screws K and L at the same time. 
 
 The two small shunt coils E and S, are connected 
 around the two contacts simply to decrease the spark be- 
 tween the silver and platinum contacts. If they should 
 become short circuited in any way, so that their resist- 
 ances become diminished, sufficient cuirent may pass 
 through eithei of them to operate the regulator. If unable 
 to locate the trouble disconnect these coils at points T and 
 U, when a thorough examination can be made. M and G 
 need not move more than just enough to open the con- 
 tact ; ^2 i n - is ample. 
 
 In starting the machine, the lower switch, which short 
 circuits the field, should be opened last. 
 
 The switch in the left-hand corner of the controller, 
 Fig. 475, cuts out the two resistance wires which are used 
 to force the current through wires and Q to the clutches. 
 Open this switch, which leaves the automatic device of the 
 controller in circuit, so that it will move the brush rocker. 
 Unclamp the brush rocker from the rheostat arm rocker. 
 Move the brushes by hand to give the proper spark, al- 
 lowing the rheostat arm, however, to be moved by the con- 
 troller. After the switches are opened, the rheostat arm 
 will go clear around to a full load position, and then, as 
 
1098 
 
 Steam Engineering 
 
 the current rises, the controller takes hold and brings the 
 arm back. In the meantime, rock the brushes forward or 
 backward and keep the sparK about the proper length, 
 say % in., at full load to % in., on short circuit. Gradu- 
 ally the rheostat arm will settle, the spark will become con- 
 stant, and the machine will give its proper current. Then 
 clamp the rocker and rheostat arm together and let the 
 machine regulate itself. 
 
 This method is much better than opening the switches 
 on the machine, and allowing the wall controller to take 
 
 PULLEY END COMMUTATOR END 
 
 Fig. 476 
 
 care of the machine from the start. By allowing the 
 controller to start the machine, a trifle longer spark is ob- 
 tained than by the other method, unless the machine is run 
 from the beginning on a very full load. 
 
 The machine will require a trifle longer spark on light 
 load, or on bad circuits, than when running at full load. 
 This fact shuld be borne in mind in wet weather, when 
 trouble with grounds is experienced. 
 
 A reliable ammeter should always be connected in the 
 circuit of an arc generator, so that the exact current may 
 
Operation of Dynamos 
 
 1099 
 
 be read at a glance. It should be connected into the nega- 
 tive side of the line where the circuit leaves the regula- 
 tor. 
 
 The Thomson-Houston System. — The Thomson-Houston 
 dynamo differs from other arc dynamos principally in the 
 nature of its armature winding. This is shown in Fig. 476. 
 One end of each of the three coils is connected to a copper 
 ring common to all. The other end of each coil terminates 
 at one of the. three commutator segments. 
 
 Fig. 477 
 
 The following instructions regarding the management, 
 and operation of this machine may prove useful: 
 
 Setting the Cut-out. — After the brushes are in position 
 the cut-out must be set. This is done by turning the com- 
 muntator on the shaft in the direction of rotation (if the 
 commutator is set in position the whole armature must be 
 revolved) until any two segments are just touching the 
 primary brush on that side, as segments A' and A"' touch 
 brush B 4 in Fig. 477. 
 
1100 Steam Engineering 
 
 Under these conditions brush B 1 should be at the left- 
 hand edge of upper segment. Then turn commutator until 
 the same two segments are just touching brush B 2 , when 
 the end of Brush B 3 should just come to the right-hand 
 edge of the lower segment. If the secondary brush projects 
 beyond the edge of the segment the regulator arm should 
 be bent down; if it does not come to the edge of the seg- 
 ment, the arm should be bent up. 
 
 Care must be taken that the regulator armature is down 
 on the stop when the cut-out is being set. These adjust- 
 ments by bending regulatoi arm are always made in the 
 factory before testing the machine, and should never be 
 made on machines away from the factory, unless the regu- 
 lator arm has been bent by accident. If it becomes nec- 
 essary to make any adjustments they should be made by 
 means of the sliding connection attached to the inner yoke. 
 
 Always try the cut-out on both primary brushes. If it 
 does not come the same on both, turn one over. If the 
 brush-holders are correctly set by the guage, there should 
 be no trouble in getting the cut-out set properly after one 
 or two trials. 
 
 To set the commutator in the proper position on a right- 
 hand machine, with a ring armature, find the leading wire 
 of No. 1 coil, Fig. 476. It is the custom in the factory to 
 paint this lead red, also to paint a red mark on the center 
 band between two groups of coils, namely, the last half 
 of No. 1 coil and the first half of No. 3 coil. The first 
 half of a coil is that group from which the lead comes. The 
 last half is diametrically opposite the first half, and the 
 lead wire belonging to it is connected with the brass ring 
 on the outside of the connection disk on the commutator 
 end. 
 
Operation of Dynamos 
 
 1101 
 
 In Fig. 478, the first halves of the three coils are rep- 
 resented by 1, 2 and 3, and the last halves by 1', 2' and 3'. 
 
 A narrow piece of tin with sharply pointed ends is bent 
 up over the sides of the middle band at the center of the 
 red mark so that the points are opposite each other. 
 
 When the red mark and red lead have been found, turn 
 the armature until the last half of No. 1 coil has wholly 
 disappeared under the left field and until the left-hand 
 
 i^_Red marK pa.niea 
 on center fc>ar*c< 
 
 Fig. 478 
 
 edge of the first coil to the right of the red mark (No. 3 
 in Fig. 478) is just in line with the edge of the left field. 
 The red lead will then be in position shown in Fig. 478 and 
 the armature is in proper position to set the commutator. 
 In the case of the right-hand drum armature, the lead- 
 ing wire of the first coil should be found. This lead may 
 be recognized from the fact that it is more heavily insul- 
 ated than the rest, and is found in the center of the outer 
 
1102 
 
 Steam Engineering 
 
 coil, on the commutator end. With this wire turned under- 
 neath, rotate the armature forward, or counter-clockwise, 
 until the pegs on the right-hand side of this coil just dis- 
 appear under the left field. (See Fig. 479.) 
 
 The position of the red lead and the red mark on the 
 band are the same on all armatures, but their positions in 
 the fields of the machines called left-hand (clockwise ro- 
 
 Fig. 479 
 
 tation), should be as shown in Figs. 480 and 481 when set- 
 ting the commutator. 
 
 When the armature of a right-handed machine is in 
 position, the commutator is turned on the shaft until seg- 
 ment No. 1 is in the same relative position as the last half 
 of No. 1 coil; segment No. 2 should correspond with the 
 last half of No. 2 coil, and segment No. 3 with the last 
 half of No. 3 coil, as shown on Figs. 478 and 479. 
 
 For left-hand machines, see Figs. 480 and 481. 
 
Operation of Dynamos 
 
 1103 
 
 The distance from the tip of the brush, which is on 
 top, to the left-hand edge of No. 2 segment on a right- 
 hand machine, or to the right-hand edge of No. 3 segment 
 in a left-hand machine is called the lead, and should be 
 made to correspond with the following table. 
 
 Red mark pairvt-aci 
 on. cervLer oand. 
 
 Fig. 480 
 
 TABLE OF LEADS. 
 
 DRUM ARMATURES. 
 
 C 12 *4 inch positive 
 C 2 % inch positive 
 E 12 T 7 6 inch positive 
 E 2 % inch positive 
 H 12 14 inch positive 
 H 2 % inch positive 
 
 y 4 
 
 RING 
 K 12 
 
 K 2 
 
 M 12 
 
 M 2 % 
 LD 12 14 
 LD 2 % 
 MD 12 if 
 MD 2 if 
 
 ARMATURES. 
 
 inch positive 
 inch positive 
 inch negative 
 inch negative 
 inch positive 
 inch positive 
 inch positive 
 inch positive 
 
1104 
 
 Steam Engineering 
 
 Place the screws in the binding posts at the lower ends 
 of the sliding connections, and put on the dash pot con- 
 nections between the brushes, with the heads of the con- 
 necting screws outward. In every case the barrel part of 
 the dash pot is connected to the top brush-holder, and 
 plunger part to the bottom brush-holder. 
 
 See that the field and regulator wires are connected 
 and that all connections are securely made. 
 
 
 Fig. 481 
 
 When all connections have been made, make a careful 
 examination of screws, joints and all moving parts. They 
 must be free from stickiness, and bind in any position. 
 
 To determine when the machine is under full load, notice 
 the position of the regulator armature, which should be 
 within % in. of the stop. At full load the normal length 
 of the spark on the commutator should be about 3/16 in. 
 If it is less than this, shut down the machine and move 
 the commutator forward or in the direction of rotation 
 
Operation of Dynamos 
 
 1105 
 
 until the spark is of the desired length. If the spark is 
 too long, move the commutator back the proper amount. 
 
 A general view of the complete dynamo is given in Fig. 
 482, and will help explain the regulator used with this 
 system. 
 
 The regulator is fastened to the frame of the machine 
 by two short bolts. On the right-hand machine its posi- 
 
 Fig. 4S2 
 
 tion is on the left-hand side, as shown in Fig. 482. On 
 the left-hand machine, i. e., one which runs clockwise, its 
 position is on the opposite side. Before filling the dash 
 pot D with glycerine, see that the regulator lever and its 
 connections, brush yokes, etc., are free in every joint, and 
 that the lever L can move freely up and down. Then fill 
 the dash pot D with concentrated glycerine. The long wire 
 
1106 
 
 Steam Engineering 
 
 from the regulator magnet M is connected with the left- 
 hand binding post P of the machine, and the short wire 
 with the post P 2 on the side of the machine. The inside 
 wire of the field magnet, or that leaving the iron flange, 
 of the left-hand field should be connected into post P 2 
 also, as shown in Fig. 482. The electric circuit (see Fig. 
 483) should be complete from post P 1 , on the controller 
 magnet, through the lamps to the post N on the machine, 
 through the right-hand field magnet C, to the brushes 
 
 Fig. 483 
 
 B 1 B 1 , through the commutator and armature to the brushes 
 B B, through the left-hand field C, to posts P 2 and P, 
 thence to posts P 2 and P on the controller magnet, through 
 the controller magnet to P 1 . The current passes in the 
 direction indicated by the arrows. 
 
 When an arc machine is to be run frequently at a small 
 fraction of its normal capacity, the use of a light load 
 device is advisable to secure the best results in regula- 
 tion. 
 
Operation of Dynamos 
 
 1107 
 
 The rheostat for this purpose (see Fig. 484) is connected 
 in shunt with the right field of the generator. Facing 
 the rheostat with the right binding posts at the bottom, 
 the contact on the right side or No. 1 gives open circuit 
 and throws the rheostat out of use. Point No. 2 gives a 
 resistance of 44 to 46 ohms and Point No. 3 gives a re- 
 sistance of 20 to 22 ohms. 
 
 This rheostat with a 75-light machine allows the fol- 
 lowing variations : Point 1, 75 to 48 lights ; Point 2, 48 to 
 
 Fig. 484 
 
 25 lights; Point 3, 25 lights or less. For use with other 
 sizes of generators, the adjustment of the rheostat must be 
 made to suit the conditions. 
 
 When the rheostat is in use, the sparks at the commuta- 
 tor will be somewhat larger than normal, but will not be 
 detrimental. 
 
 The controller magnet (see Fig. 485) is to be fastened 
 securely by screws to the wall or some rigid upright sup- 
 port, taking care to have it perfectly plumb. It is con- 
 
1108 
 
 Steam Engineering 
 
 nee ted to the machine in the manner shown in Fig. 482, 
 i. e., the binding Post P 2 on the controller magnet is con- 
 nected to the binding post P 2 (see Fig. 482) on the end 
 of the machine/ and likewise the post P on the controller 
 to the post P on the leg of the machine ; the post P 1 forms 
 the positive terminal from which the circuit is run to the 
 lamps and beck to N*. 
 
 P» 
 
 Great care should be taken to see that the wires P P 
 and P 2 P 2 are fastened securely in place; for if connec- 
 tion between P and P should be impaired or broken, the 
 regulator magnet M would be thrown out of action, thus 
 throwing on the full power of the machine, and if the 
 
Operation of Dynamos 1109 
 
 wire P 2 P 2 should become loosened, the full power of tho 
 magnet M would be thrown on, and the regulator lever 
 L, rising in consequence, would greatly weaken or put out 
 the lights. 
 
 The wires leading from the controller magnet to the' ma- 
 chine should have an extra heavy insulation. 
 
 Care should be taken in putting up the controller mag- 
 net that the following directions are followed: 
 
 1. The cores B of the axial magnets C C must hang 
 exactly in the center, and be free to move up and down. 
 
 2. The screws fastening the yoke or tie pieces to the 
 two cores must not be loosened. 
 
 3. The contacts must be firmly closed when the cores 
 are not attracted by the coils C C, which is the case, of 
 course, when no current is being generated by the machine, 
 and when the cores are lifted, the contacts must open from 
 1/64 in. to 1/32 in. ; a greater opening than 1/32 in. has 
 the effect of lengthening the time of action of the regula- 
 tor magnet. This tends to render the current unsteady, 
 and in case of a very weak dash pot, or short circuit might 
 cause flashing. Adjustment must be made if necessary 
 by bending the lower contact up or down, taking care that 
 it is kept parallel with the upper contact, so that when they 
 are closed, contact will be made across its whole width. If 
 this adjustment is not properly made there will be destruc- 
 tive sparking on a small portion of the contact surfaces. 
 
 4. All connections must be perfectly secure. 
 
 5. The check nuts 1ST must be tight. 
 
 6. The carbons in the tubes L must be whole. These 
 carbons form a permanent shunt of high resistance around 
 the regulator magnet M, and if broken will cause destruc- 
 tive sparking at contacts 0, burning them and seriously 
 interfering with close regulation of the generator. In case 
 
1110 Steam Engineering 
 
 a carbon should become broken, temporary repairs may 
 be made by splicing the broken pieces with a fine copper 
 wire. 
 
 To keep the action of the controller perfect the contacts 
 should be occasionally cleaned by inserting a folded 
 piece of fine emery cloth and drawing it back and forth. 
 
 The amount of current generated by each machine de- 
 pends upon the adjustment of the spring S. If the 
 tension of this spring is increased, the current will be di- 
 minished, if the tension is diminished the current will be 
 increased. 
 
 In starting these dynamos when the armature has 
 reached its proper speed, the short circuiting switch on 
 the frame should be opened. This method allows the 
 generator to take up its load gradually, and is a vc^y im- 
 portant point in the handling of the machine. 
 
 ELECTRIC MOTORS. 
 
 The doctrine of the conservation of energy alreaciv re- 
 ferred to in this volume, may safely be regarded a* the 
 corner stone of engineering science, and in nothing W it 
 better illustrated than in the reversibility of the dynamo, 
 and motor. When the armature of a dynamo is caused 
 ta revolve within the field of force, by mechanical power, 
 resistance will be encountered if the circuit is closed, and 
 the result is that the mechanical energy is absorbed, and 
 converted into electrical energy, the presence of which is 
 easily detected by the heating the wires, and other means. 
 Energy is conserved. 
 
 In the electric motor, this action is exactly reversed. 
 Electrical energy is absorbed, and mechanical energy is 
 supplied by it. In engineering practice an electric ma- 
 
Electric Motors 1111 
 
 c!iine (dynamo or motor) , often automatically changes 
 from motor to dynamo, or the reverse, and in some cases 
 serious trouble results, if the change is not detected in 
 time. 
 
 Any dynamo may be used as a motor and consequently 
 we have as many types of motors as there types of dy- 
 namos. The pull of a motor depends upon the repulsion 
 and attraction between the lines of force, or magnetism of 
 the wire, and core of the armature, and that of the fields. 
 We have seen that in a dynamo, as we force a wire through 
 a magnetic field, current is generated. The more current 
 there is generated, or flowing in such a wire, the greater 
 will be the expenditure of power necessary to force such 
 a wire through a magnetic field; in other words, the cur- 
 rents flowing in the wires of a dynamo armature, always 
 tend to drive the armature in a direction opposite to that 
 in which it is being driven. 
 
 If, then, instead of revolving a dynamo armature by 
 machanical means, we connect it to a source of electricity 
 and allow a current to flow through it we must obtain 
 motion, and the direction of this motion will depend upon 
 the direction in which the current flows, so long as this 
 current does not alter the magnetism of the fields. 
 
 The electric motor is built exactly like a dynamo; con- 
 sequently, as its armature revolves it not only does useful 
 work, such as turning whatever machinery it is belted to, 
 but it also generates an electromotive force. For instance, 
 if a motor, running at full speed and receiving current 
 from a dynamo (Fig. 486), were suddenly disconnected by 
 opening the main switch, it would at once begin acting as 
 a generator and sending out current. This can be easily 
 seen with any motor equipped with a starting box, such as 
 
1112 
 
 Steam Engineering 
 
 shown; for the current from the motor will continue to 
 energize the fields, and the little magnet M so as to hold the 
 arm of the starting box until the motor has nearly come to 
 rest. If it were not for the current generated by the motor, 
 this arm would fly back the instant the switch is onened. 
 
 Fig. 486 
 
 The electromotive force set up by a motor always op- 
 poses that of the dynamo driving it; that is, the current 
 which the motor tends to send out would flow in the op- 
 posite direction to that which is driving it. 
 
 This may be compared, and is somewhat similar, to 
 the back pressure of the water which a pump is forcing into 
 a tank. If the check valves were removed and the steam 
 
Electric Motors 1113 
 
 pressure shut off, the water would tend to force the pump 
 backward. 
 
 This electromotive force is called the counter electro- 
 motive force of the motor. The counter electro-motive force 
 of the motor varies with the speed of the motor, and also 
 limits the speed of the motor, for it is obviously impossible 
 that a motor should develop higher counter E. M. F. than 
 the E. M. F. of the dynamo driving it. 
 
 The highest possible speed of a motor is, then, that 
 speed at which its counter E. M. F. becomes equal to the 
 E. M. F. of the dynamo supplying the current, and this is 
 the speed which would be obtained were the motor doing 
 no work and running without friction. This condition 
 is impossible in practice, and the counter E. M. F. of the 
 motor is always less than the E. M. F. of the dynamo. To 
 speed up a motor it must run faster in order to develop 
 an E. M. F. equal to that of the dynamo. This may be 
 done by lessening the number of turns of wire on the ar- 
 mature, or by lessening, the magnetism of the fields. In 
 doing so, however, the capacity of the motor for per- 
 forming work is also lessened. 
 
 The power that can be obtained from an electric motor 
 depends upon two things : the current flowing in its ar- 
 mature coils, and the strength of magnetism developed in 
 the fields. 
 
 Assuming the fields as remaining constant, the power 
 of the motor must then vary as the current flowing through 
 it. Suppose we have a motor being driven by an E. M. F. 
 of 110 volts and it is doing no work; it will be running at 
 full speed and its counter E. M. F. will therefore also be 
 very near 110 volts. If now a load be thrown on this mo- 
 tor, it must get more current in order to develop the nec- 
 essary power to carry the load. 
 
1114 Steam Engineering 
 
 Throwing on the load will decrease the speed of this 
 motor, and consequently its counter E. M. F. will fall, 
 say to 100 volts. The E. M. E. of the dynamo heing 110 
 and the counter E. M. E. of the motor 100, there will be 
 considerable current forced through the armature of the 
 motor, so that it can now handle the load. 
 
 The current in the armature at all times will equal 
 
 E — E' 
 
 w T here E is the electromotive force of the dy- 
 
 namo, E' the counter electromotive force of motor> and R 
 the resistance of the motor armature. In order that a 
 motor should keep a nearly uniform speed, for varying 
 loads, the resistance of its armature should be very low, 
 for then a slight drop in counter E. M. F. will allow con- 
 siderable current to flow through the armature. The above 
 applies particularly to the shunt motor shown in Fig. 486. 
 In this diagram C is a double pole fuse block, S the main 
 controlling switch, R the starting box, or rheostat, M the 
 magnet, which holds the arm of the starting box in place 
 when it is brought over against it, F the fields, and A 
 the armature of the motor. 
 
 The current enters, say at the right hand fuse, and 
 passes to the starting box and along the fine wires shown 
 in dotted lines through the fields of the motor and coil 
 M to the other fuse. The fields of the motor and the little 
 magnet M are now charged, but as yet there is no current 
 passing through the armature and no motion. We now 
 slowly move the arm on the starting box to the right; 
 this admits a little current, limited by the resistance in 
 the starting box, to the motor armature and it begins to 
 revolve, and as we continue to move the arm to the right, 
 the armature gains in speed because we admit more current 
 
Electric Motors 
 
 1115 
 
 to it by cutting out more and more resistance. When the 
 armature attains full speed, the arm comes in contact 
 with the little magnet M, and is held there by magnetism. 
 The whole object of the starting box is to check the inrush 
 of current, while the armature is developing its counter 
 E. M. F. or back pressure. 
 
 Fig. 487 
 
 When the armature has attained its normal speed, the 
 starting box is no longer in use. If for any reason the 
 current ceases to flow, the little magnet M loses its magnet- 
 ism and releases the arm, which (actuated by a spring) 
 flies back and opens the circuit so that, should the current 
 suddenly come on again, the sudden inrush will not damage 
 the armature. 
 
1116 
 
 Steam Engineering 
 
 In Fig. 487 are shown the connections of a series wound 
 motor with an automatic release spool on the starting box 
 of a sufficiently high resistance so that it can be connected 
 directly across the circuit. This becomes necessary since 
 the field windings are in series with the armature. 
 
 The speed of a series motor may be decreased by connect- 
 ing a resistance in series with the motor, and may be in- 
 
 Fig. 488 
 
 creased in speed by cutting out some of the field windings. 
 In electric railway work where two motors are used on one 
 car, they are usually connected in series with each other 
 in starting up, and then in parallel with each other while 
 running at full or nearly full speed. The series motor is 
 well adapted to such work as electric railway work, or for 
 
Electric Motors 1117 
 
 cranes and so forth, because it will automatically regulate 
 its speed to the load to be moved, exerting a powerful 
 torque at a low speed while pulling a heavy load. Such a 
 motor, however, requires constant attendance when the 
 load becomes light, as it will tend to "run away" unless 
 its speed is checked. 
 
 In Fig. 488 we have a diagram of a compound wound 
 motor connected with a type of starting box that cuts 
 out the armature when current has been, cut off the lines 
 supplying the motor, as before explained. In addition to 
 this there is another electro magnet which is traversed 
 by the main current on its path to the armature. Should 
 the motor be overloaded by some means, the current flow- 
 ing to the armature would exced the normal flow. The 
 magnetism thus produced would overcome the tension of 
 a spring* on the armature of the so-called "overload mag- 
 net" and cause it to short circuit the magnet which holds 
 the resistance lever, and allow it to fly back and open the 
 armature circuit. By so doing the liability of burning out 
 the armature due to overload is reduced to a minimum. 
 
 The compound motor may be made to run at a very 
 constant speed, if the current in the series winding of the 
 fields is arranged to act in opposition to that of the shunt 
 winding. In such a case an increase in the load of a 
 motor w T ill weaken the fields and allow more current to 
 flow through the armature without decreasing the speed 
 of the armature, as would be necesary in a shunt motor. 
 Such motors, however, are not very often used, since an 
 overload would weaken the fields too much and cause 
 trouble. 
 
 If the current in the series field acts in the same direc- 
 tion as that of the shunt fields, the motor will slow up 
 some when a heavy load comes on, but will take care of 
 
1118 
 
 Steam Engineering 
 
 the load without much trouble. Fig. 489 shows a start- 
 ing box arranged as a speed controller. It differs from 
 other starting boxes only in so far that the resistance wire 
 is much larger, and that the little magnet will hold the arm 
 at any place we desire, so that if we leave the arm at any 
 
 Fig. 4S9 
 
 intermediate point the motor will run at reduced speed. 
 This sort of speed regulation can be used only where the 
 load on the motor is quite constant. If the load varies, the 
 speed will vary. Another and a better way of varying 
 the speed of motors consists in cutting a variable resist- 
 
Electric Motors 1119 
 
 ance into the field circuit, because as more resistance is 
 cut into the circuit the fields become weaker and the motor 
 speeds up. If possible, motors should be so designed that 
 they can operate at their normal speed, and they will then 
 cause little trouble. 
 
 Motors have much the same faults as dynamos, but they 
 make themselves manifest in a different way. An open 
 field circuit will prevent the motor from starting, and will 
 cause the melting of fuses or burning out of an armature. 
 The direction of rotation can be altered by reversing the 
 current through either the armature or the fields. If the 
 current is reversed through both, the motor will continue 
 to run in the same direction. A short circuit in the fields, 
 if it cuts out only a part of the wiring, will cause the mo- 
 tor to run faster and very likely spark badly. If the 
 brushes are not set exactly opposite each other, there will 
 also be bad sparking. If they are not at the neutral point, 
 the motor will spark badly. Brushes should always be 
 set at the point of least sparking. If it becomes neces- 
 sary to open the field circuit, it should be done slowly, 
 letting the arc gradually die out. A quick break of a 
 circuit in connection with any dynamo, or motor is not 
 advisable, as it is very likely to break down the insulation 
 of the machine. 
 
 The ordinary starting box for motors is wound with 
 comparatively fine wire and will get very hot if left in cir- 
 cuit long. The movement of the arm from the first to 
 the last point should not occupy more than thirty seconds, 
 and if the armature does not begin to move at the first 
 point the arm should be thrown back and the trouble lo- 
 cated. 
 
 Alternating Current Motors. — By a proper combination 
 of two phase or three phase currents it is possible to pro- 
 
1120 
 
 Steam Engineering 
 
 duce a rotating magnetic pole. By placing inside of the 
 apparatus which produces this rotating magnetic pole, a 
 suitable short circuited armature, this armature will be 
 dragged around by the rotating pole in much the same 
 way that a short circuited armature in a direct current ma- 
 chine would be dragged around if the fields were revolved. 
 Such a machine is called an induction motor. The arma- 
 ture will revolve without any current entering it from the 
 external circuit. This does away with commutators, collec- 
 tor rings, brushes, brush-holders, and in fact many of the 
 parts which are so necessary in direct current machines. 
 
 B B 
 
 B B 
 Fig. 490 
 rotary field coils 
 
 The rapidity of the alternations in the external circuit de- 
 termines the speed of the motor. 
 
 Synchronous Motors. — Some alternating current motors 
 are known as "synchronous" motors. What is meant by 
 synchronous is, occurring at the same time, or in unison. 
 As an example, suppose two clocks are ticking just alike 
 so that the pendulums start and stop at the same time; 
 we would hear but one tick. These two clocks would then 
 be in synchronism. If an alternating current generator 
 has 32 field coils and revolves at the rate of 60 E. P. M., 
 then a synchronous motor with only 4 field coils would re- 
 volve at the rate of 480 E. P. M. This motor would op- 
 
Electric Motors 
 
 1121 
 
 erate in synchrony with the generator, and yet would make 
 480 E. P. M. while the generator made 60 E. P. M. 
 
 The production of the rotary field is the main reason 
 for the generation of polyphase currents. 
 
 Fig. 490 shows four coils of wire. Assume that the 
 coils B B receive an alternating current, and the coils A A 
 receive another current in quadrature with the first. Then 
 when the current in B B is at maximum, the current in 
 A A will be at minimum, and as the current in B B de- 
 creases, the current in A A will increase. 
 
 Fig. 491 
 two phase rotating field coil and armature 
 
 When the B current is at maximum, there will be es- 
 tablished N and S magnet poles on a horizontal axis pass- 
 ing through the center of the B coil. The A coils when 
 active will establish poles on an axis perpendicular thereto. 
 
 Poles at intermediate points will also be established 
 when current is passing through all four coils. The result 
 of this arrangement is that north and south poles are kept 
 traveling around the circle by the alternating currents 
 acting in quadrature with each other, meaning that the 
 angle of lag and lead between the two current waves is 
 90° or a quarter circle. 
 
1122 
 
 Steam Engineering 
 
 Currents of this kind constitute a two phase alternating 
 current and the changes occur about 100 times per second. 
 Fig. 491 shows a cylindrical laminated core wound with a 
 re-entrant coil, and mounted on bearings within the field. 
 This core will rotate because the alternating currents 
 passing through the field coils will induce currents in its 
 wires, owing to their rotary field of force. 
 
 In order to establish in the core the polarity above de- 
 scribed, the lines of force must be cut by its windings. 
 Consequently it lags behind, and its revolutions per minute 
 
 Fig. 492 
 three phase generator, and induction motor 
 
 are from 5 to 10 per cent slower than those of the rotary 
 field. If it were made to synchronize with the field it would 
 have no induced polarity, and no pull or torque would be 
 exerted upon it. Therefore, it constantly falls behind, 
 and the amount of this drop is termed its slip. Fig. 492 
 is a diagrammatic view of the generation of a three-phase 
 current, and the operation by it of an induction motor. 
 Following the lines and numbers will show that the stator 
 of the motor receives the same currents that are induced in 
 the stator of the generator. 
 
Electric Motors 
 
 1123 
 
 But the poles of the generator travel around it, the 
 result being that a rotary field is produced in the stator of 
 the generator. Fig. 493 represents a four-pole, three- 
 phase generator driving such a motor. 
 
 There are 12 armature coils, three sets marked A, B, C, 
 for each pole of the generator, thus giving a three-phase 
 current. They are connected in Y combination. The gen- 
 erator is shown on the left, the field being the rotor. 
 
 The motor is shown on the right of the diagram, and it 
 also has 12 coils marked as in the generator, and Y con- 
 
 Fig. 493 
 four-pole three-phase generator and induction motor 
 
 nected. The generator and motor are connected by the 
 three wires a, b, and c, the fourth wire being omitted, as 
 it would have no load to carry. The large letters on the 
 armature indicate the course of the windings. The three- 
 phase current produces a rotary field, on the same general 
 principle as does the two-phase current. The lag of the 
 currents behind each other acts to cause the poles resulting 
 from the combined action of the coils, to rotate around 
 the field. Motors constructed upon this principle are 
 termed induction motors, and the coils on the armature 
 (which is the rotor), are self-contained, having their ter- 
 
1124 
 
 Steam Engineering 
 
 minals connected so that the winding is re-entrant, and 
 has no outside connection whatever. Fig. 494 shows such a 
 
 Fig. 494 
 
 INDUCTION MOTOR WITH SQUIRREL CAGE ARMATURE 
 
 motor complete. The rotary field referred to in the fore- 
 going description should not be confounded with the re- 
 
 Fig. 495 
 squirrel cage armature 
 
 volving field. In the rotary field the rotary action is purely 
 electrical, the poles simply rotating around the circle, there 
 being no rotation of any part of the mechanism. But a re- 
 
Questions and Answers 1125 
 
 volving field is entirely different. It revolves on an axis 
 like a wheel. The student should remember this, as there 
 is danger of confusion in the use of the two terms. A 
 combined rotary, and revolving field may be obtained by 
 a simple modification of the mechanical structure, in which 
 the field is mounted on journals, and the armature is 
 stationary. Fig. 495 shows the squirrel-cage armature of 
 an induction motor, the core being laminated, and having 
 straight conductors of copper lying in the longitudinal 
 grooves close to its surface. The ends of these conductors 
 are connected to two rings of copper. 
 
 QUESTIONS AND ANSWERS. 
 
 714. What is electricity? 
 
 Ans. Electricity is an invisible agent. Its exact na- 
 ture is not very well known, although the laws govern- 
 ing its action, the methods of controlling it, and the ef- 
 fects produced by it are becoming well known. 
 
 715. Is it correct to use the term quantity with refer- 
 ence to electricity? 
 
 An^. It is. We may use terms to designate definite 
 quantities of electricity, passing through a conductor, in the 
 same way that we speak of gallons of water flowing through 
 a pipe. 
 
 716. Is it proper to assume that there are large quanti- 
 ties of electricity stored for future use, in a manner similar 
 to water? 
 
 Ans. It is not, except in a limited sense, as in storage 
 batteries. 
 
 718. Define the doctrine of the conservation of energy. 
 
1126 Steam Engineering 
 
 Ans. The total quantity of energy in the universe is 
 unalterable. When energy is expended, or disappears in 
 one form, it must reappear in another form. 
 
 719. In accordance with this doctrine, what would be 
 the proper term to apply to electricity w T ith reference to 
 the physical requirements of man? 
 
 Ans. It is a useful agent for the rapid transmission of 
 stored up energy in fuel, water falls, etc. 
 
 720. What is the practical unit of quantity used in 
 speaking of electricity? 
 
 Ans. The coulomb. It is that quantity of electricity 
 that would pass in one second through a circuit carrying a 
 current of one ampere. 
 
 721. What is an ampere? 
 
 Ans, It is the unit of volume, or rate of flow. A cur- 
 rent of one ampere will flow through a circuit whose re- 
 sistance equals one ohm, when the electro-motive force, or 
 pressure behind it equals one volt. 
 
 722. What is a volt? 
 
 Ans. The volt is the unit of electro-motive force, and 
 represents a pressure that will cause the flow of one am- 
 pere through a circuit in which the resistance equals 
 one ohm. 
 
 723. What is an ohm? 
 
 Ans. The ohm is the practical unit of electrical resist- 
 ance. It is that amount of resistance that would limit the 
 flow of electricity under an electromotive force of one 
 volt, to a current of one ampere, or to a discharge of 
 one coulomb per second. It equals the resistance of a 
 column of mercury one sq. millimetre in area of cross sec- 
 tion, and 104.9 centimetres in length. 
 
 724. What is the unit of work? 
 Ans. The foot pound. 
 
Questions and Answers 1127 
 
 725. What is the unit of power, or rate of doing work? 
 A ns. The foot pound, per second. 
 
 726. How is the amount of work that electricity is ca- 
 pable of doing, measured ? 
 
 Ans. By the volt-coulomb, or Joule. The amount of 
 electrical work per second is, equal to the volt ampere, or 
 watt. 
 
 727. What amount of power developed is represented 
 by the watt ? 
 
 Ans. 44.25 foot-lbs. of work per minute, or 0.7375 foot- 
 lbs, per second. 
 
 728. What is a magnet? 
 
 Ans. A mineral consisting of a combination of iron and 
 oxygen. 
 
 729. What is the chemical formula of a magnet? 
 Ans. Fe 3 4 . 
 
 730. What is a permanent magnet? 
 
 Ans. A piece of steel that has been charged with mag- 
 netism, and retains it. 
 
 731. What is meant by the poles of a magnet? 
 
 Ans. All magnets tend to point north and south, the 
 same end always pointing in the same direction ; hence the 
 end pointing north is called the north pole, and the end 
 pointing south is termed the south pole. 
 
 732. What peculiar characteristic attaches to the poles 
 of magnets ? 
 
 Ans. The north poles of two magnets tend to repel 
 each other, and the same is true of the south poles. But 
 the north pole of one magnet attracts the south pole of an- 
 other, like repels like, and unlike attracts unlike. 
 
 733. What is an electro magnet? 
 
 Ans. A bar of iron surrounded by a coil of wire through 
 which an electric current is passing. 
 
1128 Steam Engineering 
 
 734. What are lines of force? 
 
 A ns. They are certain imaginary lines passing through 
 the steel of the magnet from its south pole to its north pole, 
 and issuing from the latter they curve around through 
 space and return to the south pole. 
 
 735. What is the magnetic circuit? 
 
 Ans. It is the path of these lines of force, around and 
 through the magnet. It resembles a closed curve, either a 
 circle, or an ellipse. 
 
 736. Explain the difference between the magnetic cir- 
 cuit and the electric circuit. 
 
 A ns. The magnetic circuit, or field of force, that sur- 
 rounds a magnet is maintained without the expenditure of 
 energy, while on the other hand an electric current passing 
 upon its circuit develops energy, and energy must be ex- 
 pended to maintain it. 
 
 737. Are there any other points of difference between 
 the two circuits. 
 
 Ans. Yes, the electric current passes through a con- 
 ductor in intensity proportional to the electro-motive force 
 urging it, while the magnetic circuit passes through air, 
 or a vacuum in proportion to the magneto-motive force 
 urging it. 
 
 738. What is meant by the term potential as applied in 
 electric practice? 
 
 Ans. Voltage or pressure. 
 
 739. What is the law of induction? 
 
 Ans. When a conductor is moved in a magnetic field 
 of force so as to cut the lines of force, there is an electro- 
 motive force impressed on the conductor in a direction at 
 right angles to the direction of motion, and at right an- 
 gles to the direction of the lines of force. 
 
 740. What is a dvnamo? 
 
Questions and Answers 1129 
 
 Ans. A machine for transforming mechanical energy 
 into electrical energy. 
 
 741. How is the field of force maintained in a dynamo? 
 Ans. By means of electro-magnets. 
 
 742. Does not this require the expenditure of energy? 
 Ans. Yes; a certain amount of energy is indirectly ex- 
 pended. 
 
 743. How are dynamos classified? 
 
 Ans. Into two grand divisions, viz., direct current dy- 
 namos and alternating current dynamos. 
 
 744. What is direct electrical current? 
 Ans. A current of unchanging direction. 
 
 745. What is an alternating current? 
 
 Ans. A current that reverses its direction of flow, pe- 
 riodically, from 20 times and upward per second. 
 
 746. Name the principal constituent parts of a dy- 
 namo. 
 
 Ans. The armature, the field, the collecting rings, or 
 commutator, and the brushes. 
 
 747. How is electro motive force or current induced in 
 a dynamo? 
 
 Ans. By rapidly changing field and armature relations 
 by means of mechanical energy. 
 
 748. How is the output of a dynamo stated? 
 
 Ans. In Kilowatts equal to 1,000 X volts X amperes. 
 
 749. How is the output of a motor stated? 
 
 Ans. In horse power, equal to Watts intake-f-746Xef- 
 ficiency expressed decimally. (Not as a percentage.) 
 
 750. What is the voltage of a dynamo? of motor? 
 Ans. It is the pressure that the generator or alternator 
 
 delivers at its own terminals. The voltage of a motor is the 
 voltage which should be applied to its terminals in order 
 to develop full horse power. 
 
]130 Steam Engineering 
 
 751. What is full load current of dynamo? of motor? 
 Ans. Full load current of a dynamo is that current 
 
 which may be drawn steady for 24 hours without causing 
 any part of the machine to exceed a safe temperature, i. e.. 
 150° Fahr. This applies to factory motors. 
 
 752. What is meant by the rating of a dynamo? Of a 
 motor ? 
 
 Ans. The product of full load current multiplied by 
 the voltage expressed in Kilowatts is rating of a dynamo. 
 The actual mechanical horse power developed at the pinion 
 of the motor as tested in shop. 
 
 753. What is the armature core? 
 
 Ans. The sheet iron body which carries the armature 
 winding, and conducts the flux from pole piece to pole piece. 
 
 754. What is the armature spider? 
 
 Ans. The casting consisting of hub and arms which* 
 supports armature core. 
 
 755. What are binding wires? 
 
 Ans. They are narrow bands of phosphor bronze wire 
 placed around the armature every three or four inches to 
 help bind the winding to the core. They rest on strips of 
 mica, and are sweated with solder all around. 
 
 756. What are commutator segments? 
 
 Ans. The commutator segments or bars are the copper 
 pieces of which the commutator is built. 
 
 757. What are commutator leads? 
 
 Ans. They are the ends of the armature winding ex- 
 tending from the core to the lug of the commutator bar. 
 
 758. What are pole pieces? 
 
 Ans. The end of the magnet core nearest the armature. 
 Usually larger than the core. 
 
 759. What are magnet cores? 
 Ans. The iron inside the field coil. 
 
Questions and Answers 1131 
 
 760. What is the yoke? 
 
 Ans. The part of magnetic circuit connecting the mag- 
 net cores. 
 
 761. What is the pitch of an armature winding? 
 
 Ans. It is the number of teeth between the two sides of 
 a formed coil plus one tooth. 
 
 Example : The two sides of a coil are in slots number 
 3 and 17, then pitch is 14. 
 
 762. Is there insulation between winding and core? 
 Ans. Yes. Mica or fuller board ; there is also the tape 
 
 on coil. 
 
 763. What insulation is there between conductors of 
 winding ? 
 
 Ans. The double cotton covering of each wire makes 
 four thicknesses between conductors. 
 
 764. What is the air gap? 
 
 Ans. It is the air space between armature and pole 
 pieces. In dynamos it is made as small as possible for ef- 
 ficiency. 
 
 In motors it is not made too small because this tends to 
 make the machine spark due to the weak field. In D. C. 
 series motors it is from % to % of an inch, in A. C. series 
 motor it is smaller, say 1/10 to % inch. 
 
 The larger the air gap of a motor the more the bearings 
 may wear before there is danger of the armature rubbing 
 against the lower pole pieces. 
 
 765. What are field spools? 
 
 Ans. The brass shells on which the field coils are 
 wound. 
 
 766. What is the commutator? 
 
 Ans. It is a series of copper bars placed parallel to 
 the shaft, insulated from each other and from the frame of 
 the machine. Each is connected to the winding and cur- 
 
1132 Steam Engineering 
 
 rent flows from the winding through them to the brushes. 
 It at the same time reverses the connections between the 
 brushes and the winding at the proper times so that the 
 brush always collects current. 
 
 767. What is a collector or slip ring? 
 
 Ans. A collector consists of two or more rings of copper 
 placed around the shaft and insulated from it, and each 
 other. Each is connected to a part of the winding. The 
 brushes rest on the rings. 
 
 They are used to collect current from a revolving arma- 
 ture style of alternator, to feed current into armatures of 
 rotary converters, or the revolving fields of alternators. 
 
 The collector has no corrective influence and passes on 
 the A. C. or D. C. current exactly as it receives it. 
 
 Single phase machines have two rings; two, three, and 
 six phase machines have three rings. 
 
 768. Is there a difference between no load and full load 
 voltage of dynamos? 
 
 Ans. Yes. A shunt dynamo gives highest voltage at no 
 load and lowest at overloads ; the series dynamo gives lowest 
 at no load and highest at full load. The compound dy- 
 namo is a combination of series and shunt, and gives same 
 voltage at all loads. 
 
 An alternator acts like a shunt dynamo. 
 
 769. What is a field rheostat? 
 
 Ans. It is a resistance in the field circuit which can be 
 varied to change the current, and hence the field strength. 
 This alters the voltage of the dynamo. 
 
 770. What are commutated fields? 
 
 Ans. In some motors the field coils are arranged in sec- 
 tions so that they may be arranged in parallel, or series, or 
 in combinations. 
 
Questions and Answers 1133 
 
 All coils in parallel give the greatest current and hence 
 slowest speed of motor; all coils in series give the weakest 
 field and the fastest speed. 
 
 771. What relation has field strength to the speed ol 
 motor ? 
 
 Ans. The weaker the field the faster the speed, for the 
 motor must revolve fast to generate its proper counter 
 E. M. F. 
 
 772. What relation has armature strength to the speed 
 of motor ? 
 
 Ans. The greater the armature current the higher the 
 speed. 
 
 773. What effect on the power of motor does field, and 
 armature strength have? 
 
 Ans. The greater the field and armature current the 
 greater the power. 
 
 774. What is a ring winding? 
 
 Ans. One which passes over and under around the core, 
 a space being left between the shaft and core to accommo- 
 date the winding. 
 
 775. What is a drum winding? 
 
 Ans. One where all winding is on 1 the outer surface of 
 the core. 
 
 776. Upon what does sparkless commutation of current 
 depend ? 
 
 Ans. (1) The more commutator bars the better, there 
 being less voltage and therefore tendency to spark between 
 bars. The average railway motor has from 100 to 125 
 bars on commutator. 
 
 (2) The fewer the ampere turns on the armature in 
 comparison to the ampere turns on the field the less spark- 
 ing. 
 
1134 Steam Engineering 
 
 (3) The more turns short-circuited by the brush when 
 touching two or more bars at once, the greater the tendency 
 to spark. 
 
 777. What is a shunt field? 
 
 Ans. One whose coils are placed as a shunt across the 
 brushes. It carries a small current. 
 
 778. What is a series field? 
 
 Ans. One which carries the main, or nearly all the 
 main current, and is placed in series with the armature. 
 A small strip of resistance metal is used sometimes to di- 
 vert a portion of the main current from the series field. 
 
 779. What are Foucault, or eddy currents? 
 
 Ans. Local currents set up within the armature, and 
 acting as a hindrance to the generation of useful current. 
 
 780. How may the electro-motive force be increased ? 
 Ans. By increasing the speed, or by adding more turns 
 
 or loops of wire to the armature winding. 
 
 781. What is meant by self excitation of a dynamo? 
 
 Ans. When the dynamo is standing still, the field mag- 
 nets become weakly magnetic, but when the armature begins 
 to revolve a few volts of electric current will be sent through 
 the field coils, gradually increasing the magnetic strength 
 until full voltage is reached. 
 
 782. What is a series dynamo? 
 
 Ans. One in which the same current that travels the 
 main circuit also traverses the field. 
 
 783. Explain the action of the shu.nt dynamo. 
 
 Ans. The field circuit is a shunt, and only a portion of 
 the main current passes through it. 
 
 784. How are the fields of a compound dynamo ex- 
 cited? 
 
Questions and Answers 1135 
 
 Ans. The fields have two distinct windings ; one shunt, 
 and the other series. 
 
 785. What advantage pertains to the compound wound 
 dynamo ? 
 
 Ans. It is practically self-regulating. 
 
 786. What is the difference between the dynamo and 
 the electric motor? 
 
 Ans. Practically none in the principles governing the 
 design of the machines. Any dynamo may be used as a 
 motor, and vice versa. 
 
 787. State the difference in their functions. 
 
 Ans. The dynamo converts mechanical energy into elec- 
 trical energy, while the motor converts electrical energy 
 into mechanical energy. 
 
 788. Upon what does the power to be obtained from 
 a motor depend? 
 
 Ans. Two things, viz., the current flowing in its arma- 
 ture coils, and the strength of magnetism developed in its 
 fields. 
 
 789. How is the speed of motors controlled? 
 Ans. By a starting box or rheostat. 
 
 790. How may the direction of rotation of a motor 
 be reversed? 
 
 Ans. By reversing the current through either the ar- 
 mature or the fields. 
 
 791. Upon what principle does the alternating current 
 motor act ? 
 
 Ans. Upon the principle of induction, having for its 
 main accessory the rotary field. 
 
 792. How is a rotary field produced? 
 
1136 Steam Engineering 
 
 Ans. By the use of polyphase currents. 
 
 793. Explain the meaning of the term rotary field. 
 
 Ans. In a rotary field the rotary action is purely elec- 
 trical, the poles simply rotating around the circle. There 
 is no rotation of the mechanism of the field. 
 
 794. What then is a revolving field ? 
 
 Ans. A field that revolves around an axis like a wheel. 
 
 
Electric Currents 
 
 Keference having been frequently made in the foregoing 
 pages to different kinds of electric currents, such as direct, 
 alternating, two and three phase, etc., it is now in order to 
 give a short explanation of their leading characteristics. 
 The direct current is in a measure explained by its title 
 direct, meaning that it travels in the same pressure direc- 
 tion straight from the generator to the locality where it 
 does work, and then back again to the generator, over the 
 return wire. The natural tendency of the current gener- 
 ated in all dynamos is to alternate, that is it starts at a 
 value of zero, rises to a maximum of one polarity, de- 
 scends to a value of zero again, and changing in direction 
 of pressure, attains a maximum of opposite polarity, from 
 whence it returns to zero again, these alternations being 
 constantly repeated over and over again. In the direct 
 current generator the alternating electro-motive force pro- 
 ducing this current is reversed or commuted at the proper 
 instant by means of the commutator, and brushes, and the 
 result is that a one direction electro-motive force, having a 
 constant fixed potential or voltage, is impressed upon the 
 external circuit. 
 
 The alternating current. In order to get a clear concep- 
 tion of the true nature of the alternating current it is ab- 
 solutely necessary that the student should comprehend, and 
 bear in mind the meaning of the different terms used in 
 alternating current practice, such as volts, amperes, fre- 
 quency, phase, and power- factor. These will be taken up 
 and discussed in their logical order, with reference to their 
 
 1137 
 
1138 
 
 Steam Engineering 
 
 practical meaning, omitting as much as possible all theo- 
 retical, and mathematical deductions. The voltage, or 
 pressure in an alternating current does not have a constant 
 fixed value, as in the direct current system, but is contin- 
 ually changing in amount, and alternating in the direction 
 of pressure at equal, regular intervals of time. Eeference 
 to Fig. 496 will serve to explain the action of the alternat- 
 ing electro-motive force within the generator, and also the 
 action of the alternating current produced by it. The hori- 
 zontal line having degrees from to 360 marked upon it 
 represents the line of zero values or no voltage. The lengths 1 
 
 Fig. 496 
 sine curve of generating circle. 
 
 of the vertical lines correspond to the distance of points of 
 the curve from the horizontal or zero line. The left hand 
 quadrant of the generating circle is divided into angles of 
 22y 2 ° or one sixteenth of a circumference. For each angle 
 lines are drawn, such as M P. On the zero line, divisions 
 corresponding to the angles are laid off, and ordinates 
 erected upon them. Each sine determines the length of the 
 ordinate corresponding to its angle, as for instance the sine 
 M P of 45° determines the length of the ordinate M P 
 erected on the second (or 45°) of the sixteen divisions of 
 the zero line. 
 
Electric Currents 1139 
 
 The sines as drawn in Fig. 496 represent the values of 
 the E M F from zero to 90° or one quarter of the gener- 
 ating circle, and the length of the ordinate erected upon 
 the 90° point of the zero line corresponds to the highest 
 voltage value of the current wave above the zero line. The 
 portion of the wave above the line may be assumed to rep- 
 resent the positive pole, and the portion below the line the 
 negative pole. 
 
 It will easily be seen that if sines are drawn in each 
 quadrant of the circle, the lengths of the ordinates for the 
 remaining parts of the wave curve may be determined from 
 them, and thus a true representation of one complete wave, 
 or cycle, be obtained. 
 
 In the alternating current dynamo the current is sent to 
 the line exactly as it is generated in the armature, flowing 
 out one wire, and back on the other and then reversing, and 
 flowing out on the wire on which it has just flowed in, and 
 back on the wire on which it had formerly flowed out. An 
 illustration which will more fully explain this action can 
 be found by supposing the two ends of the cylinder 
 of a piston pump were connected by means of a pipe 
 and then, having done away with all the valves except 
 the suction valves, the pump was started. At the be- 
 ginning of the stroke, w^ater would be forced out one 
 side of the cylinder around the pipe into the other 
 side of the cylinder, and after the piston had reached 
 the end of the stroke and started back, the water 
 would then take a return course back to where it had 
 started. In this case the pump could be likened to the dy- 
 namo, and the pipe to the wires, and the current to the 
 water flowing back and forth. As the water pressure in the 
 pipe will fluctuate, reaching maximum at one point in the 
 stroke, and zero at another point, so also when the alter- 
 
 j 
 
1140 
 
 Steam Engineering 
 
 nating current wave reaches its point of highest voltage or 
 pressure the whole circuit is affected, and when it reaches 
 zero value, the whole circuit is at zero. The expression wave 
 should be clearly understood. It means that the whole cir- 
 cuit passes simultaneously through the values of the cycle 
 represented in the wave curve. The number of waves per 
 second is called the frequency of the current, therefore 
 when we speak of a frequency of 60 we mean that it re- 
 quires one-sixtieth of a second for the voltage to pass 
 through a complete cycle, or in other words 60 cycles are 
 
 
 
 
 B, 
 
 C 
 
 
 
 L 
 
 
 
 
 
 
 
 
 
 h- 
 
 
 
 
 
 
 
 
 •^. 
 
 
 
 
 
 
 
 
 *o 
 
 
 
 
 
 
 
 
 O 
 
 
 
 
 
 
 
 
 CL 
 
 
 
 
 
 
 
 
 A 
 
 
 8 
 
 C 
 
 \ D 
 
 
 
 E 
 
 Uj 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 "•■•» 
 
 
 
 
 
 
 
 
 K 
 
 
 
 
 
 
 
 
 <s 
 
 
 
 
 
 
 
 
 e> 
 
 
 
 
 
 
 
 
 U4 
 
 
 
 
 
 
 
 
 £ 
 
 
 
 
 
 
 
 
 Fig. 497 
 
 
 c 
 
 HANGES 
 
 IN 
 
 AMOUNT AN 
 
 D DIRECTION 
 
 OF 
 
 PKESSUB 
 
 E 
 
 completed in one second. By alternations is meant simply 
 the change in direction of pressure, or voltage, of the cur- 
 rent, and it will be seen by reference to Fig. 497 that two 
 alternations occur in each complete cycle, one at C, and 
 the other at E, (assuming that we start at zero value of A). 
 Alternations are usually expressed in terms of the number 
 per minute, as for instance 7,200 alternations means 60 
 cycles per second; for since there are two alternations per 
 cycle, the number of cycles per minute will be 7,200-4-2= 
 3,600, and the cycles per second, or frequency will be 
 
Electric Currents 1141 
 
 3,600-1-60=60. The following table gives the alternations 
 corresponding to the usual commercial frequencies : 
 
 Frequency. Alternations. 
 
 25 3,000 
 
 50 6,000 
 
 60 7,200 
 
 133 16,000 
 
 The action of the alternating current as represented in 
 Figs. 496-497 can be considered as continuing indef- 
 initely in the same regular order, and in the same inter- 
 vals of time. Eeferring to Fig. 497, the curved line AB', 
 CD' E represents the alternating voltage as it rises at A to 
 a positive maximum value at B', then falls to zero at C, 
 where the direction of pressure is reversed, and the same 
 maximum value of the voltage in the negative direction is 
 reached at D' when it again falls to zero at E. The word 
 "period" is sometimes used to designate the time in seconds 
 or fractions of a second required to pass through a complete 
 cycle, and the number of periods per second is termed the 
 frequency. We have so far considered only the voltage wave 
 but in actual practice the volt-meter does not indicate the 
 peak of the voltage wave, but rather that of the current 
 wave, which is usually about 0.707 or roughly speaking .7 
 of the maximum voltage. For instance, when the volt-meter 
 reading is 110 volts, the maximum value at the peak of the 
 wave will be 155 volts, nearly. The pressure indicated by 
 the volt-meter is the effective voltage, and it is with this 
 voltage value that the engineer is concerned in every-day 
 work. 
 
 The maximum voltage is important to the station man 
 only in testing insulating materials, and in the design of 
 line insulators on high tension transmission lines. As in 
 
1142 
 
 Steam Engineering 
 
 the case of the volt-meter, the ordinary alternating amme- 
 ter measures about 70.7 per cent of the maximum value of 
 the amperes at the peak of the current wave. The amme- 
 ter reading of effective current produces the same heating 
 effect, gives out the same available energy as a direct cur- 
 rent of the same amount. When there is no apparatus with 
 an iron magnetic circuit connected to an alternating cur- 
 rent system, such as induction motors, arc lamps, etc., the 
 current wave will begin to rise with the voltage wave, reach 
 its maximum value at the same instant as the voltage does, 
 
 Fig. 498 
 voltage and current waves 
 
 and complete the cycle in exact time relation with the 
 voltage. Fig. 498 shows both the voltage and the current 
 waves, the zero line being divided into 360° as in Fig. 496. 
 The full line represents the voltage wave, and the dotted 
 line the current wave. In commercial alternating current 
 work the choking action or "inductance" as it is called 
 which results from the presence of the iron magnetic cir- 
 cuit, caused by the connection of the electrical apparatus 
 with the main circuit, and in which apparatus there is more 
 or less iron surrounded by, or enclosing coils, causes the 
 
Electric Currents 
 
 1143 
 
 current wave to lag behind the voltage wave, that is the 
 zero, maximum, and all intermediate values of the current 
 will follow a certain interval of time, or a certain number 
 of electrical degrees, behind the corresponding values of the 
 voltage. 
 
 Phase, Lag, and Lead. — The term phase is employed to 
 denote the relative position of a current wave with respect 
 to the wave of electro-motive force producing it. Fig. 498 
 shows voltage and current in phase, that is the waves of 
 
 
 
 y 
 
 ,''" \-., 
 
 
 
 
 
 
 / / 
 
 
 \ 
 
 270° 
 
 
 360° 
 
 
 
 45° f 90° 
 
 t80° 
 
 V \ 
 
 
 
 * 
 / 
 / 
 
 
 
 •* — 
 
 
 \ \ 
 
 
 
 / 
 
 > 
 
 4S ° 
 
 < 
 
 
 \ 
 
 " x x ^ J 
 
 ' y 
 
 y 
 
 ANGLE 
 
 
 
 
 
 
 or 
 
 
 
 
 
 
 
 LAG 
 
 Fig. 499 
 current lagging 45 degrees behind the voltage 
 
 both are in unison, both starting at zero, and reaching their 
 maximum values at the same instant. If however the cur- 
 rent lags behind the voltage, as shown by Fig. 499, it is 
 said to be out of phase, and the amount of this lag in de- 
 grees is called the angle of lag, and depends upon the na- 
 ture of the load, being greatest for a load of induction mo- 
 tors, and series arc lamp. 
 
 In Fig. 499 the current wave (dotted line) is shown as 
 lagging 45 electrical degrees behind the voltage wave (full 
 line), and in this case the angle of lag is 45°. 
 
1144 
 
 Steam Engineering 
 
 In some cases, especially in the operation of rotary con- 
 verters, and synchronous motors, the current wave may be 
 ahead of, or lead the voltage wave. This is caused by an 
 action directly the opposite of inductance, called capacity, 
 and is illustrated in Fig. 500, where a current lead of 15 
 electrical degrees is shown, and in which the angle of lead 
 is 15°. In the alternating current-generator the field coils 
 occupy about 50% of the surface of the field bore, because 
 when their inner edges are tight together, their outer edges 
 are apart, due to the larger circumference at the pole pieces, 
 
 — /5 
 ANGLt 
 
 or 
 
 LCAD 
 
 Fig. 500 
 
 showing a current lead of 15 degrees 
 
 and because some interpolar space must be left to prevent 
 excessive leakage from pole to pole. 
 
 Only 50% of the armature bore is wound, for otherwise 
 the coils would be so wide that they would extend over into 
 the field of a wrong pole piece. If one side of a coil is un- 
 der a N-pole the other side should be under a S-pole. Then 
 the two electro-motive forces induced, add together. 
 Should the coil be so wide as to extend over to the next 
 N-pole any electro-motive force induced by that pole would 
 be subtracted. 
 
Electric Currents 1145 
 
 There is then on the ordinary alternator half of the ar- 
 mature empty. Such a machine is called a Single Phase 
 Alternator. 
 
 Two and Three Phase. — It occurred to some inventor 
 that an entirely separate winding could be put on between 
 the coils of the original winding, and be connected to its 
 own collector. The current was to be led to a different cir- 
 cuit, but it soon became evident that it was better to make 
 of the four wires from the alternator, a three-wire circuit 
 by joining two of them inside the armature and leading out 
 three wires to the switchboard. Such an alternator is a 
 Two Phase Alternator. 
 
 Fig. 501 
 
 3-PHASE Y CONNECTION 
 
 Of course the capacity of the machine is not doubled, be- 
 cause from a single phase alternator is drawn enough cur- 
 rent to heat it to the safe limit. From a two phase alter- 
 nator we do the same thing. The reason we gain in capac- 
 ity is because in a single phase machine the heating is con- 
 centrated, while in the two phase machine it is evenly dis- 
 tributed all over the armature. 
 
 Even in a two phase alternator there is a portion of the 
 armature not used for winding, and there was still a desire 
 to reduce the number of line wires. This led to the Three 
 Phase Alternator. 
 
1146 
 
 Steam Engineering 
 
 The three armature windings of the alternator are con- 
 nected together at one point, and the other ends to the 
 three collector rings, or the three windings are connected 
 in series and the three points where they are joined are 
 connected to the three collector rings. 
 
 The former winding is called a Y winding and is shown in 
 Fig. 501. The latter is a A (Delta) winding and is shown in 
 Fig. 502. The European names are respectively Star and 
 Mesh windings. 
 
 Fig. 502 
 3-phase delta connection 
 
 The three wires of a three phase system each act as a 
 main wire, and a return wire for one of the others at the 
 same time. The actual current in the wire is the difference 
 of the two currents : in and outgoing. 
 
 If the same three phase armature is connected first as a 
 Y and then as a A winding these differences will be noticed. 
 
 The Y armature will give the higher voltage and have 
 less current capacity. The A will give a lower voltage and 
 have greater current capacity. Power that can be drawn 
 from each is the same. 
 
 Transformers and other apparatus are wound two, and 
 three phase, and also Y and A, for use with the correspond- 
 ingly wound alternator. 
 
Electric Currents 
 
 1147 
 
 By a peculiar connection of coils, rotary converters are 
 wound for six phase currents; it having been discovered 
 that it is possible to do sg with the result of increased out- 
 put for a given sized machine. 
 
 Fig. 503 
 waves in quadrature 
 
 Two, three and six phase machinery is often grouped 
 under name of polyphase. 
 
 Waves in quadrature. — Fig. 498 shows waves in phase. 
 In Fig. 503 are shown waves in quadrature, that is the 
 
 Fig. 504 
 waves in opposition 
 
 angle of lead is 90° which is a quarter of a circle. When 
 the angle of lag, or lead is 180° the waves are said to be in 
 opposition. This is illustrated in Fig. 504. 
 
 J 
 
1148 Steam Engineering 
 
 QUESTIONS AND ANSWEBS. 
 
 795. What is the leading characteristic of the direct 
 current f 
 
 Ans. It travels in the same direction of pressure. 
 
 796. What is the tendency of the current generated in 
 all dynamos? 
 
 Ans. It is alternating in voltage or pressure. 
 
 797. Explain the meaning of the term alternating as 
 used in this connection. 
 
 Ans. The current starts at a value of zero, rises to a 
 maximum of polarity, descends to a value of zero again, and 
 changing in direction of pressure, rises to a maximum of 
 opposite polarity, from whence it drops to zero again. 
 
 798. How then is direct current produced from this al- 
 ternating current? 
 
 Ans. By means of the commutator and brushes on the 
 direct current generator. 
 
 799. What is the leading characteristic of the alternat- 
 ing current? 
 
 Ans. Its voltage is continually changing at regular in- 
 tervals from zero to maximum in the direction of opposite 
 polarity. 
 
 800. How is this action best represented? 
 
 Ans. By wave curves drawn above and below a horizon- 
 tal line representing zero. 
 
 801. In what manner does the action of the alternating 
 current affect the circuit through which it travels ? 
 
 Ans. The whole circuit passes simultaneously through 
 voltage values of the cycle represented by the wave curve. 
 
 802. What is meant by the frequency of an alternating 
 current ? 
 
 Ans. The number of waves or cycles per second. 
 
Questions and Answers 1149 
 
 803. What does a frequency of 60 mean? 
 
 Ans. It means that the voltage values pass through a 
 complete cycle in one sixtieth of a second, that is 60 cycles 
 per second. 
 
 804. What is meant by alternations? 
 
 Ans. The number of reversals per minute in the di- 
 rection of pressure. 
 
 805. How many alternations would there be in a cur- 
 rent having a frequency of 60 ? 
 
 Ans, 7,200. 
 
 806. What is meant by a "period?" 
 
 Ans. The time in seconds or fractions of a second re- 
 quired to pass through a complete cycle. 
 
 807. What is meant by current wave? 
 
 Ans. It means the actual values of the current as shown 
 by the volt-meter and ammeter. 
 
 808. Do these equal the values of the theoretical wave 
 curve ? 
 
 Ans. They do not, reaching about 70 per cent. 
 
 809. Why is this? 
 
 Ans. It is due to the influence of the iron magnetic 
 circuit caused by the connections of induction motors, arc 
 lamps, and other electrical apparatus. 
 
 810. What is meant by effective current? 
 
 Ans. The voltage and volume as shown by the volt- 
 meter and ammeter. 
 
 811. In what respect is the maximum voltage as shown 
 by the calculated wave curve useful? 
 
 Ans. It is useful in testing insulating materials. 
 
 812. What is meant by phase in electric practice? 
 Ans. It denotes the relative position of a current wave. 
 
 with respect to the wave of electro-motive force producing 
 it. 
 
 ^J 
 
1150 Steam Engineering 
 
 813. When is a current in phase? 
 
 Ans. When the two waves just mentioned start at zero 
 and reach their maximum values at the same instant. 
 
 814. What is meant by lag? 
 
 Ans. When the current wave lags behind the voltage 
 wave. 
 
 815. What is meant by lead? 
 
 Ans. When the current wave is ahead of, or leads the 
 voltage wave. 
 
 816. What is the meaning of two and three phase cur- 
 rents ? 
 
 Ans. When the winding of the armature is such that 
 two or three electro-motive forces in quadrature with each 
 other are simultaneously produced by the generator the cur- 
 rents thus produced may be distributed over four or six 
 conductors, a pair for each current. 
 
 817. Is it necessary to have a pair of conductors for 
 each current in two and three phase current work ? 
 
 Ans. No. By means of the Y winding it is possible to 
 distribute the current over three wires, each wire acting as 
 a main, and return wire for one of the others. 
 
Armature Design and Construction* 
 
 Economy of construction demands that an armature be 
 run at a high rate of speed. In any armature the output in 
 volts can be increased by simply increasing the speed; the 
 output in amperes cannot be so increased unless at the same 
 time larger wires are used. If, however, in any armature 
 we should increase the size of the wires, so that fewer turns 
 would be upon it, we can compensate for the consequent 
 loss in voltage by increasing the speed, and thus, with the 
 
 Fig. 505 
 
 same armature, also increase the output in amperes. It will 
 be seen that speed is an important item in the construction 
 of any armature. To operate at a high rate of speed re- 
 quires the very best workmanship and mechanical construc- 
 tion. 
 
 Whenever a high speed is to be used it is of the utmost 
 importance to see that the armature is well balanced. Any 
 
 *From "Armatures and Armature Winding," by Horst- 
 man and Tousley. — 
 
 1151 
 
1152 
 
 Steam Engineering 
 
 rotating piece of machinery is said to be out of balance 
 when one side is heavier than the other. This condition of 
 being out of balance will manifest itself by a more or less 
 severe jarring, and shaking, of the frame upon which it 
 rests when running. 
 
 Whether an armature is in balance while at rest can be 
 easily determined by placing it upon two knife edges, as 
 shown in Fig. 505. If these edges are perfectly level, 
 the armature will roll to one side or the other until the 
 heavier part is at the bottom. If the diameter of the ar- 
 mature is small compared to its length, this test will not 
 be very sensitive. If the diameter is great as compared to 
 
 /. 
 
 / 
 
 
 V g . ~E 
 
 1 
 
 ¥2. 
 
 Fig. 506 
 
 its length a small excess of weight on one side will cause it 
 to roll over. If a very good balance for high speed is to be 
 obtained this method must not be relied upon. In such a 
 case the armature should be placed in bearings and run at 
 its proper speed. If there is much jarring or shaking the 
 armature is out of balance, and this must be rectified. 
 
 It is obvious that this had best be done before any wire is 
 placed on the core. How it may come about that the arma- 
 ture may be perfectly balanced statically and yet almost 
 OHifit for the work while in operation at a high rate of speed 
 can be seen from Fig. 506. If there is an excess of 
 weight at 1 this may be perfectly balanced for a state ef 
 rest by the addition of a similar weight at 2. If, however, 
 
Armature Construction 1153 
 
 the armature is revolved at a high rate of speed there will 
 be a tendency to strain the shaft as indicated by the dotted 
 lines. 
 
 An armature out of balance is rectified by adding weights 
 at different places until the proper amount is found. This 
 will make itself evident by the smooth running. If possi- 
 ble, the weights should now be removed and an equal weight 
 of metal removed from the armature at the side opposite 
 to that at which it was found necessary to add weight. If. 
 for instance, it was found necessary to add one pound at 
 3, Fig. 506, the same result can be obtained by removing 
 one pound at 1. 
 
 In speaking of high speeds is must be understood that it 
 is not, necessarily, a great number of revolutions that are 
 required to produce a certain E. M. F. What is required 
 is that a certain number of conductors shall cut through 
 the lines of force passing between the pole-pieces in a given 
 length of time. As these conductors are always located on 
 the periphery of the armature, it is the speed of this part 
 that counts. The greater the diameter of the armature, 
 therefore, the lower the speed of the shaft. Other things 
 being equal, the capacity of an armature is directly propor- 
 tional to its length. We may therefore choose whether we 
 shall increase the capacity of a machine by increasing the 
 length of the armature, or the diameter. 
 
 If the length of the armature is too great there is some 
 danger that the shaft will bend, not only from centrifugal 
 force to which it is subject, but also from the magnetic at- 
 traction of the pole pieces if it is not well centered. 
 
 The centering of an armature is an important point. 
 It rests between two powerful magnets. If it is exactly in 
 the center, the attraction of one pole piece will neutralize 
 that of the other ; but if it is the least bit out of center, there 
 
L 
 
 1154 Steam Engineering 
 
 will be a strong attraction to one side and this will greatly 
 add to the friction. The bearings and pole pieces should 
 be in such relations to each other that they can be truly 
 centered, and that there will be no likelihood of their 
 becoming loosened. The bearings should have sufficient 
 surface so that the wear will be a minimum. Bearings 
 should, furthermore, not be of iron or steel. If the 
 shaft is constructed of the same material there may 
 be some magnetic attraction between the shaft and the 
 bearing which would increase the friction, and cause 
 heating. Bearings should also be out of line of the 
 magnetic circuit, as such magnetization will cause the 
 shaft to generate Foucault currents, which will heat it, and 
 in turn heat the bearings. The shaft should also be pro- 
 tected by shields, which will prevent oil from running along 
 it and getting into the wires on the armature. The lateral 
 play which is essential to the smooth running of the shaft 
 can be obtained by lining up the shaft after the belt is put 
 on. This lateral play also tends to distribute the wearing 
 surface of the brushes over the surface of the commutator, 
 thereby giving a more uniform contact surface. It is quite 
 evident that if the armature was made to run without this 
 lateral movement the brushes would always bear on the 
 same part of the commutator and a ridge would soon ap- 
 pear on it. 
 
 The inexperienced mechanic should be warned not to 
 skip lightly over any part of the work. While, of course, 
 there is no visible connection between the armature and 
 the pole pieces of the machine, and while it seems to be 
 turning free and easy, it must be borne in mind that the 
 force exerted upon the armature is, nevertheless, just as 
 great as though a friction clutch of the capacity of the ar- 
 mature were applied to the periphery of the armature. 
 
Armature Construction 1155 
 
 Furthermore, in the case of a sudden overload, or short 
 circuit, or too rapid starting in the case of a motor, the 
 force applied is almost as severe as the blow of a hammer. 
 
 MECHANICAL CONSTRUCTION OF THE ARMATURE. 
 
 All good armatures are made up of a number of punch- 
 ings similar to those shown in Figs. 507-508-509. These 
 punchings are made of soft iron or steel. The figures 
 illustrate the different forms of slots "used in connection 
 with armatures. Into these slots the wires are wound, as 
 will be hereafter explained. The punchings are usually 
 made of thin iron with some form of insulation provided 
 
 Fig. 507 Fig. 508 Fig. 509 
 
 between them to reduce the Foucault, or eddy, currents. 
 This insulation is obtained by inserting layers of thin paper 
 between the sheets of metal, or by coating the punchings 
 themselves. Paper, and similar materials used for this 
 purpose will in time char from the heat of the armature 
 and work out and tend to loosen the armature. Care 
 should also be exercised in the use of an insulating var- 
 nish, as some of these varnishes soften from the heat of the 
 armature, and are thrown out on the pole pieces. 
 
 As many of the punchings as are necessary are slipped 
 upon the shaft of the armature as indicated in Fig. 505, 
 and fastened together with clamps shrunk upon the shaft, 
 
1156 Steam Engineering 
 
 or with large nuts screwed on the shaft. Bolts extending 
 through the punchings are often used. These bolts must 
 be insulated from the punchings; otherwise there will be 
 a flow of current through the shaft, the body of the arma- 
 ture and the bolts. It is well to remember in laying out 
 the armature and the means of fastening it to the shaft 
 that the Foucault currents will flow according to the prin- 
 ciples of any other electrical circuit, so that to keep these 
 
 Fig. 510 
 
 currents to a minimum, no electrical paths should be pro- 
 vided through the armature core. 
 
 Where an armature is slotted as indicated in Fig. 505, 
 some of the punchings are often made of smaller diameter 
 than the rest, or are afterward turned down as indicated in 
 the figure. This is to allow room for the binding wires 
 which are put on after the winding is completed. Some- 
 times the punchings are not slotted, but are milled out, 
 and narrow bars of metal or wood inserted in the grooves 
 as shown in Fig. 510. These bars are for the purpose of 
 
Armature Construction 
 
 1157 
 
 keeping the wires from slipping. If of metal, they must 
 be insulated from the punchings for the same reason as was 
 explained with the use of bolts. 
 
 In some cases the slots are made partially closed as 
 shown. This makes it a little more difficult to insert the 
 wires, but they are then held securely in place. Often 
 these slots are made wedge shape, and the tops closed by 
 means of wood or fiber strips after the wires have been 
 put in place. In some cases the slots containing the wirea 
 are entirely closed. 
 
 Fig. 511 
 
 In slotted armatures, especially if the slots are deep, 
 when the punchings are forced together, that part of the 
 punchings which projects beyond the ring E, Fig. 505, is 
 likely to bulge out. In order to prevent this a few pieces 
 of extra heavy metal are obtained and used at the ends. 
 One punching of insulating material is also generally used 
 at each end. 
 
 For small armatures the punchings are generally left 
 solid. With diameters of 18 inches or so, openings are left. 
 These openings lighten the armature, and are also useful 
 
1158 Steam Engineering 
 
 in ventilating it to reduce the heating. With very large 
 armatures, opportunities for radial ventilation must also 
 be given. For this purpose some of the punchings are ' 
 corrugated, or otherwise arranged, so that they allow air 
 to pass from the center outward. When* such pieces (see 
 Fig. 511) are used in connection with the openings shown 
 in the punchings, the air drawn in at the sides escapes ra- 
 dially, and thus helps to keep the armature cool. 
 
 The punchings are preferably made of metal ranging 
 from 10 to 30 mils in thickness. The thinner the better, 
 so long as the metal can be easily handled. Punchings 
 should be made as accurate as possible. Where it is nec- 
 essary to turn down an armature to obtain perfect round- 
 ness, the Foucault current losses are greatly increased. 
 This is due to the fact that the cutting tool of a lathe has a 
 tendency to bend over the edges of the thin punchings, and 
 cause an electrical contact which allows current to flow. If 
 it is necessary to smooth down an armature this work is 
 best done with a sharp file. 
 
 ARMATURE WINDING. 
 
 Armature windings are divided into three general 
 classes, viz. : 
 
 1 — King wound armatures. 
 
 2 — Drum wound armatures. 
 
 3 — Disk wound armatures. 
 
 The winding of each of these classes is again subdivided 
 into what is known as open coil winding, where the wind- 
 ing is part of the time on open circuit; and closed coil 
 winding, where the winding forms a closed circuit. 
 
 The ring and drum windings are in most general use, 
 the disk winding not having had any extensive applica- 
 
Armature Winding 
 
 1159 
 
 tion in this country. On direct current machines, wind- 
 ings of the closed coil type are generally used, although 
 the open coil type of armature is employed on some con- 
 stant current arc light generators. This type of armature 
 is open to the serious objection that the sparking at the 
 brushes is excessive, and some special means must always 
 be provided to reduce it. 
 
 Gramme Ring. — The ring wound armature, or as it is 
 more commonly called, the Gramme ring armature, com- 
 prises an iron core made in the form of a ring around which 
 are wound the conductors which are to convey the current. 
 
 Fig. 512 
 
 The various coils are wound on separately, the wire being 
 carried over the outside of the iron core, then through the 
 center opening and again around the outside of the core, 
 this operation being repeated until all the wire for that 
 individual section is wound on. The adjacent coil is then 
 wound on in the same manner, the ends of each coil being 
 brought out to the commutator side of the armature. 
 
 There are various advantages, and disadvantages, to this 
 class of winding and, the conditions under which the ma- 
 chine is to be used must be taken into consideration in de- 
 termining whether it is the best form to use. 
 
1160 
 
 Steam Engineering 
 
 As only those conductors which cut lines of force are 
 active in the production of current, it is evident that those 
 conductors which lie on the inner side of the iron ring serve 
 no useful purpose so far as the generation of current is con- 
 cerned. Numerous attempts have been made to utilize this 
 part of the winding by making the pole pieces extend around 
 the ring in such a manner that lines of force will pass to 
 the inside of the ring ; also by arranging an additional pole 
 piece on the inside of the armature but mechanical consid- 
 erations have shown these methods to be impractical. 
 
 Fig. 513 
 
 The dead wire on the inside of the armature constitutes 
 one of the greatest disadvantages of this class of winding, 
 and this is especially the case where the armature carries 
 heavy currents. In arc lighting machines, where a compara- 
 tively small current is used, this loss is not of so great im- 
 portance, and is entirely outweighed by the several advan- 
 tages, as will appear after further consideration. In laying 
 out ring armatures it is well to remember, that, where the 
 armature coils consist of only a few turns of fairly heavy 
 conductor, the losses become proportionately less as com- 
 
Armature Winding 
 
 1161 
 
 pared with the drum armature, as the cross connectors on 
 drum armatures also form an inactive part of the circuit. 
 
 In Fig. 514 is shown a simple ring wound armature with 
 a bi-polar. field. The end of one coil is connected to the 
 beginning of the next, and the winding therefore forms a 
 continuous spiral, encircling the iron ring core. Taps taken 
 off at the point of connection of the various coils are carried 
 to segments of the commutator, brushes being provided, to 
 either conduct the current from, or convey it to the commu- 
 
 Fig. 514 
 
 tator as the case may be. It will be seen that with an arma- 
 ture of this kind each individual coil is generating an electro- 
 motive force which is proportional to the number of lines of 
 force being cut by the coil. Assuming for the present that 
 w r e have a uniform field, it is plain that the volt-meter con- 
 nected across the ends of coil 13,or 5 would indicate a certain 
 difference of potential, and the potential readings over the 
 other coils would show a gradually diminishing difference of 
 potential, until we reach the point of brush contact, where 
 
1162 Steam Engineering 
 
 the difference of potential would be practically nothing. It 
 is also evident that at no place in the winding is there any 
 great difference of potential between adjacent wires, or be- 
 tween adjacent commutator segments. By greatly increas- 
 ing the number of coils and, also the number of commutator 
 segments, the difference of potential between adjacent coils 
 and commutator segments can be still further reduced. 
 
 A further inspection of the drawing will show that there 
 are no crosses between wires of opposite polarity on the taps 
 extending to the commutator segments. Herein lies one of 
 the great advantages of this style of winding over the drum 
 winding. 
 
 Other advantages pertaining to this class of winding are 
 as follows : 
 
 (a) As it is possible to increase the diameter of the arma- 
 ture without greatly increasing its weight, a much higher 
 velocity can be obtained in the moving conductor, with a 
 corresponding increase in the induced E. M. F. 
 
 (b) A defective coil can be easily detected, and easily re- 
 placed without disturbing the balance of the winding. 
 
 (c) In case of emergency a defective coil can sometimes 
 be cut out, and the machine still operated. 
 
 (d) Better ventilation due to the open style of construc- 
 tion. 
 
 Its disadvantages in addition to those already mentioned 
 are: 
 
 (a) The resistance of the magnetic circuit is increased, 
 owing to the shape of the armature. 
 
 (b) A ring armature requires more work in the winding 
 as each coil has to be wound by hand, and is therefore more 
 expensive. 
 
 While ring armatures are all wound in practically the 
 same manner, i. e., each coil wound separately, a number of 
 
Armature Winding 
 
 1163 
 
 different connections between the coils, and the commutator 
 segments are employed. A development of the faces of the 
 pole pieces, together with the armature conductors, will 
 show in a plainer manner the relations existing between the 
 coils and their connections. The development of the arma- 
 ture in Fig. 514 is shown in Fig. 515, and is that view which 
 would be obtained were a person to take a position corre- 
 sponding to that occupied by the armature shaft and make 
 a complete revolution, thus bringing into view consecutively 
 all the pole piece faces, and the armature conductors. 
 
 mmmBEpGnHEEGpE 
 
 Fig. 515 
 
 In the figure the full lines denote the active conductors, 
 and the dotted lines the inactive conductors on the inside 
 of the armature ring. The small squares at the top repre- 
 sent the commutator segments, and the shaded cross sections 
 the pole pieces. The arrows indicate the direction of flow 
 of the induced current. 
 
 By an examination of the figure it will be seen that there 
 are two commutator segments, one at which the current in 
 both wires connected to it has a tendency to flow in a posi- 
 tive direction, or toward it, and the other where the current 
 tends to flow away from it, or in a negative direction. These 
 are obviously the proper locations for the brushes. It will 
 
1164 Steam Engineering 
 
 be seen further that the end of one coil connects to the be- 
 ginning of the coil next to it. 
 
 While the figure represents a simple armature of sixteen 
 coils, it is apparent that the number of coils could be greatly 
 increased or, instead of a coil having but one turn, it could 
 consist of a number of turns of wire. 
 
 Drum Windings. — The drum wound armature varies pri- 
 marily from the ring wound armature in the shape of +he 
 core. While with the latter the core is in the shape of a ring 
 or hollow cylinder, the conductors being wound spirally 
 around the ring, with a drum-wound armature the core ia> 
 in the shape of a solid cylinder, or drum, the conductors 
 being wound around the outside surface in a direction par- 
 allel to the shaft. It must not be understood that the shape 
 of the core alone determines the class of armature winding, 
 for in some machines a drum winding is placed on a ring 
 core. The distinguishing characteristic of the ring wind- 
 ing is, that the active conductors, which pass over the face 
 of the armature from the front to the back, have their re- 
 turn conductor pass through the opening in the center of 
 the ring from the back to the front, this part of the con- 
 ductor being inactive in the production of current. With a 
 drum winding the conductors, in returning from the back 
 to the front of the armature, also pass over the face of the 
 armature, where they can cut lines of force and are also 
 active in the production of current. It will thus be seen that 
 in the ring armature considerable of the wire is not only 
 inactive in the production of current, but at the same time 
 is the cause of a loss of energy, due to its resistance, with 
 a resultant heating of the armature. This objectionable fea- 
 ture is to a great extent overcome in the drum winding. 
 Less wire therefore has to be used on a drum-wound arma- 
 
Armature Winding 
 
 1165 
 
 ture, other conditions being equal, than on a ring-wound 
 armature of the same capacity, and the armature has a 
 lower resistance. 
 
 At first glance the winding of a drum armature appears 
 a quite difficult matter, but with a little study it will be 
 found that it is not very much unlike that of the ring arma- 
 
 Fig. 516 
 
 ture. A simple case of drum winding is shown in Fig. 516. 
 There are 12 conductors on the armature face, and 6 com- 
 mutator segments. Suppose we take a wire and connect it 
 to segment a of the commutator. Now start to wind around 
 the armature, passing along 1 to the rear and returning by 
 way of 6 to the front where we loop back to commutator seg- 
 

 1166 Steam Engineering 
 
 ment b. Now make another turn around the armature by 
 way of 3 and 8, returning to segment c of the commutator. 
 Eepeat this procedure, gradually turning the armature to 
 the left. When the last turn 11, 4 has been made, we come 
 back to commutator bar a, the one from which we started. 
 This operation can be considered as simply winding a wire 
 spirally around the drum, and bringing down loops to the 
 commutator segments, ending at the point from which we 
 start. 
 
 The first question which presents itself to the student is, 
 Why does not the wire which passes over 1 return in the 
 diametrically opposite position, or 7 ? Consider for a mo- 
 ment the armature shown in Fig. 516. Suppose we start 
 our wire at segment a of the commutator, pass to the rear 
 of the armature along 1, and return to the front end along 
 the diametrically opposite position 7. Now loop back to 
 segment b of the commutator and from there make another 
 turn around the armature by way of 3 and 9 and back to 
 segment c. From segment c make another loop around the 
 armature by way of 5 and 11 and return to segment d. It 
 will now be seen that we have made a complete revolution 
 of the armature, but have made connection to only half the 
 commutator segments. In order to keep up the winding in 
 a regular manner, the wire from commutator segment d 
 should pass to the rear of the armature along space 7, but 
 this space we find already occupied by the return of 1. If 
 we were to continue with our winding from this point, we 
 would have to carry the wire from segment d to position 6 
 or 8, but this would result in an unbalanced winding. 
 
 It is plain that, in order to keep the winding symmetrical, 
 the conductors in passing from the front to the rear of 
 the armature must occupy the positions 1, 3, 5; 7, 9, 11, and 
 
Armature Winding 
 
 1167 
 
 the even numbered positions will then serve as the returns 
 for these wires. 
 
 It will be noticed that in the example shown there are 
 6 coils, comprising 12 conductors and 6 commutator seg- 
 ments. If the armature was so designed that we had an 
 uneven number of coils, for instance 7 coils, in which case 
 there would be 14 conductors, and 7 commutator segments, 
 the rear connections could be made directly across a diameter 
 as shown in Fig. 517. This gives a perfectly symmetrical 
 
 Fig. 517 
 
 winding. Only one coil will be short-circuited at a time 
 for, with the brushes set across a diameter of the commuta- 
 tor when one brush is in such a position that it laps across 
 two segments, the. other brush is in the center of a segment. 
 Fig. 518 shows the connections of a drum-wound arma- 
 ture having 8 coils comprising 16 conductors and 8 commu- 
 tator segments. While in the example shown each coi] con- 
 sists of only a single loop with two conductors, a coil may 
 consist of a number of turns of wire, in which case the 
 
1168 
 
 Steam Engineering 
 
 drawing indicates merely the connections for the beginning 
 and end of each coil. 
 
 As has been previously explained, the conductor which 
 passes from the front to the rear of the armature along space 
 1 cannot be brought back to the front of the armature if 
 the winding is to be perfectly regular along the diametri- 
 cally opposite space, 9, but must return along one of the 
 
 Fig. 518 
 
 spaces to the right or left of 9. The expression for deter- 
 mining the proper spacing for the return conductor is: 
 
 m 
 
 where y= spacing or pitch, 
 
 n=number of poles, 
 
 z=number of conductors, 
 
 b=number of conductors to a coil. 
 The symbol + means simply, plus or minus, that it is op- 
 tional with us whether we add 1 to, or subtract 1 from the 
 number found by the operations indicated in the formula. 
 
Armature Winding 1169 
 
 In Fig. 518 n=2, z=16, b=2, therefore 
 
 Each conductor is connected at the rear of the arma- 
 ture to one 7 spaces in advance of it ; as 1 to 8, 3 to 10, 
 etc. 
 
 In winding an armature according to the plan shown 
 where each coil consists of a number of turns of wire, we 
 would start with the wire connected to commutator segment 
 a, and wind along space 1 to the back of the armature, thence 
 across the back of the armature to space 8, returning to the 
 front of the armature along space 8 and across the front to 
 space 1, continuing until all the wire of this coil is wound 
 on. The end of the wire would now be brought to segment 
 b of the commutator. The second coil is now wound on, 
 starting from segment b and winding to the back of the ar- 
 mature along space 3, across the back to space 10, to the 
 front along space 10 and across the front to space 3, con- 
 tinuing in this manner until this coil is also wound on. The 
 end of this coil is now brought to commutator segment c. 
 The remaining coils are wound on in the spaces indicated. 
 
 In the actual winding of an armature the commutator is 
 generally left off during the process of winding, the begin- 
 ning and end of each coil being brought out and connected 
 to the commutator after the armature is completely wound. 
 A winding table which shows the several steps just de- 
 scribed and which is very convenient both for winding and 
 connecting is given below: 
 
 a-l-8-b e-9-16-f 
 
 b-3-10-c f-ll-2-g 
 
 c-5-12-d g-13-4-h 
 
 d-7-14-e h-15-6-a 
 
1170 
 
 Steam Engineering 
 
 This table shows both the position of each coil and the 
 commutator connections; for instance, segment b is con- 
 nected to the end of coil 1-8 and to the beginning of coil 
 3-10. 
 
 The development of the armature winding, Fig. 519, will 
 show in a plainer manner the various connections made, also 
 the direction of flow of the induced current in the various 
 conductors. Following out the direction of current it will 
 be seen that at commutator segment f, the current in both 
 conductors flows toward the segment, while in segment b 
 
 Fig. 519. 
 
 the current flows away from the commutator. These two 
 positions are the proper points for the brush contacts. 
 
 With the armature connected, as shown, the brushes lie 
 in an almost direct line, between the pole pieces, and the 
 connections on the front of the armature are symmetrical. 
 It is quite evident that we could, without changing the or- 
 der of the winding, turn the commutator through an angle 
 of 90°, thus bringing the brushes in a line with the spaces 
 between the pole pieces. The front connections would not 
 then be symmetrical, one connection to each coil being short- 
 ened, and the other being lengthened. The design of some 
 
Armature Winding 
 
 1171 
 
 machines is such that locating the brushes in a line with 
 the pole pieces brings them in an inaccessible position, and 
 the commutator is therefore shifted as described. 
 
 There are two circuits through the armature from brush 
 to brush and in the position shown these circuits are as 
 follows : 
 
 b-3-10-c-5-12-d-7-14-e-9-16-f 
 
 + 
 
 b-8-l-a-6-15-h-4-13-g-2-ll-f 
 
 Fig. 520 
 
 As the armature revolves in the direction shown by the 
 arrows, the positive brush will short-circuit commutator seg- 
 ments e, and f, and the negative brush segments a, and b. 
 The two coils e-9-16-f and b-8-l-a will therefore be short- 
 circuited, and the full difference of potential of the machine 
 will exist between them. As these coils are adjacent with 
 each other, in a smooth face armature where the coils con- 
 sist of a number of turns of wire, they will be placed side 
 by side, and the question of insulation between them there- 
 fore becomes of considerable importance. 
 
1172 
 
 Steam Engineering 
 
 Following out the paths on the development of the wind- 
 ing, it will also be seen that there are numerous crosses be- 
 tween wires of greatly different potentials. Compare with 
 the ring armature winding shown in Fig. 514. 
 
 Fig. 522 
 
 To obviate some of the objectionable features of the wind- 
 ing just described, the method shown in Fig. 520 is used. 
 The value of y is in this case 5, each conductor at the re^r 
 of the armature being connected to another conductor 5 
 
Armature Winding 
 
 1173 
 
 spaces ahead of it. The coils short-circuited by the brushes 
 are now separated, and there are fewer crosses between con- 
 ductors at the ends of the armature. Tracing out the cir- 
 cuits it will be seen that the current induced in some of the 
 conductors is in opposition to that of the remainder of the 
 circuit. This has the effect of decreasing the demagnetizing 
 effect of the armature. 
 
 The armatures which have so far been considered have 
 had but one layer of wire. Fig. 522 shows an armature 
 
 Fig. 523 
 
 with 24 conductors and 12 commutator segments with the 
 wire placed on in two layers. The development of this wind- 
 ing is also shown in Fig. 523. The winding table is given 
 below : 
 
 a-l-7-b g-19-13-h 
 
 b-2-8-c h-20-14-i 
 
 c-3-9-d i-21-15-j 
 
 d-4-10-e j-22-16-k 
 
 e-5-ll-f k-23-17-1 
 
 f-6-12-g 1-24-18-a 
 
1174 Steam Engineering 
 
 One of the first points which will be noted is, that each 
 conductor in returning from the back of the armature to 
 the front passes through the diametrically opposite space; 
 coil 1-7, for instance. The rear connections are not shown, 
 as they would complicate the drawing. If we start to wind 
 this armature from commutator segment a, winding coil 
 1-7, returning to segment i and continuing our winding 
 from segment &, coil 2-8, segment c, to coil 3-9, segment d 
 to coil 4-10, segment e to coil 5-11 and segment / to coil 
 6-12 it will be seen that we have made a complete revolution 
 of the armature and have only made connection to half the 
 commutator segments. We can complete the winding by 
 continuing with the outer layers. It is evident that the 
 outer layer of coils will have a greater resistance due to 
 their increased length and will also travel at a greater speed 
 than the coils of the inside layer. 
 
 The two paths through the armature, from the positive 
 to the negative brush vary between the coils in the outer 
 layer, and those in the inner layer, and in one position of 
 the armature one of the paths from brush to brush is through 
 the coils of the inner layer exclusively, and the other path 
 through the coils of the outer. This results in a constant 
 variation between the electro-motive forces induced in the 
 two halves of the armature. 
 
 The two paths through the armature from brush to brush 
 are 
 
 b-2-8-c-3-9-d-4-10-e-5-ll-f-6-12-g-19-13-h ^| 
 
 b-7-l-a-18-24-l-17-23-k-16-22-j-15-21-i-14-20-hJ 
 As the armature moves forward from the position shown, 
 coil 1-7 is short-circuited by the negative brush and coil 
 13-19 by the positive brush. It will thus be seen that a 
 
Armature Winding 
 
 1175 
 
 considerable difference of potential exists between the inner 
 and outer layers of wire, and they will have to be well in- 
 sulated from each other. It will also be seen that no great 
 difference of potential exists between adjacent coils. The 
 two short-circuited coils lying as they do, one above the 
 
 Fig. 524 
 
 other, are both in the neutral point of the field at the point 
 of commutation. This can be considered as an advantage 
 over the previous type where the short-circuited coils are 
 somewhat separated, and are therefore not commutated at 
 the exact neutral point. 
 
1176 
 
 Steam Engineering 
 
 In the previous examples of drum windings we have con- 
 sidered only the methods of winding used with bi-polar 
 fields. As has been explained elsewhere there are many con- 
 ditions where the use of a bi-polar field is not advisable, and 
 numerous advantages are gained by using a multi-polar field, 
 or a field consisting of more than one pair of poles. 
 
 The same general principles apply to multi-polar wind- 
 ings as apply to bi-polar windings, and these various appli- 
 cations will be described. We will investigate only those 
 methods in general use, there being a number of other 
 
 Fig. 525 
 
 schemes of winding which are in the main only extensions 
 of the principles here shown. 
 
 Fig. 524 shows an armature winding, with its develop- 
 ment, Fig. 525, consisting of 18 conductors and a 4-pole 
 field. Following out the circuits from one commutator seg- 
 ment to the next or the developed winding, Fig. 525, it will 
 be seen that the winding after making a turn of the arma- 
 ture, laps back to the commutator segment next to the one 
 from which it started, and is therefore called a lap winding. 
 Tracing out the winding from commutator segment a, we 
 find it follows the path a-l-6-b, b-3-8-c, c-5-10-d, etc., until 
 
Armature Winding 1177 
 
 it arrives at coil i-17-4-a, where it returns to the starting 
 point. A complete revolution of the armature has been 
 made, and every conductor has been passed through, and 
 each one only once, forming what is termed a single re- 
 entrant winding. 
 
 Observing the end connections of coil a-l-6-b, for instance, 
 it will be seen that the value of y for the rear connection is 
 5, each conductor at the rear of the armature connecting to 
 one five spaces beyond. The value of y for the front con- 
 nection is — 3, each conductor being connected to a conduc- 
 tor three spaces back from it. The average spacing is there- 
 fore 4, and the difference between the front and rear spacing 
 is 2. 
 
 In connecting up the armature for a bi-polar field, in 
 order that the induced currents would flow in the same di- 
 rection in all conductors connected in series, we found it 
 necessary to connect together at the rear of the armature, 
 the conductors lying under a north pole with those lying al- 
 most directly opposite it under a south pole. So, in the case 
 of a four-pole field, each conductor at the rear of the arma- 
 ture is connected in series with a conductor which lies in 
 a field of opposite sign which, in this case, is not across a 
 diameter, but one-fourth the distance around the armature. 
 The value of y, the spacing, should therefore be nearly equal 
 to the total number of conductors divided by the number oi 
 poles, or z-hn where z=the number of conductors and n= 
 the number of poles. As explained under the section on 
 bi-polar armatures, this spacing may be either greater or 
 less than the value just given. If the spacing is greater 
 than z-^-n, the cross connections will be longer, with a re- 
 sulting increase in armature resistance. With the spacing 
 less than z-i-n the cross connections will be correspondingly 
 shortened, and the armature resistance lessened, and the 
 
1178 Steam Engineering 
 
 conductors lying between the pole pieces will then oppose 
 each other. 
 
 In Fig. 524 it will be noticed that there are an even num- 
 ber of conductors, and that the spacing at the rear is 5 and 
 at the front — 3. In all lap windings, with multi-polar 
 fields, there must be an even number of conductors, and the 
 spacings at the front and rear must be odd and must differ 
 by 2. 
 
 Fig. 526 
 
 A simple plan by means of which the student may inves- 
 tigate these several conditions, consists in drawing roughly 
 a circle, subdividing it with as many intersections as there 
 are conductors on the armature, and then drawing a series 
 of connecting lines through the various points. These lines 
 will then represent the armature conductors, and their con- 
 nections, the lines on the outside of the circle representing 
 the rear connections, and the lines on the inside of the circle 
 the front connections. 
 
Armature Winding 
 
 1179 
 
 Fig. 526 shows this scheme worked out for the armature 
 shown in Fig. 524. That the armature must have an even 
 number of conductors can be seen by figures similar to that 
 shown in Fig. 527. Here 17 conductors are shown with a 
 rear spacing of 5 and a front spacing of — 3. The line from 
 13 should connect to a conductor 5 spaces beyond, or con- 
 ductor 1, but this conductor is already connected. 
 
 i5J 
 
 J3\ 
 
 Fig. 527 
 
 With a bi-polar field, and a one-layer winding, it will be 
 remembered that adjacent commutator segments were con- 
 nected to every other conductor, the even numbered con- 
 ductors being taken as returns for the odd numbered con- 
 ductors. Similarly in a multi-polar armature, our spacing 
 must be such that only every other conductor is connected 
 
1180 Steam Engineering 
 
 to a commutator segment. The front and rear spacings 
 must therefore differ by 2. 
 
 That the front and back spacings must be odd can be 
 easily determined with the scheme previously described, Fig. 
 528 showing an armature with 18 conductors, and a spacing 
 at the rear of 6 and at the front 4. We see here that the 
 loops close on themselves and would form a short-circuited 
 winding. 
 
 te\ 
 
 
 
 
 "I 
 
 ~-t$ — K 
 
 Fig. 528 
 
 With a lap-wound armature there are as many paths 
 through the armature, and as many brushes as there are 
 poles. This can be seen from the development of Fig. 524, 
 the paths through the armature being 
 
 i-2-15-h-18-13-g 
 
 i-17-4-a-l-6-b 
 
 e-12-7-d-10-5-c 
 
 e-9-14-f-ll-16-g 
 These paths are unequal in length, as will be noticed from 
 the drawing, when the brush which bears on the commu- 
 
Armature Winding 1181 
 
 tator segments b, and c, has moved from this position. In 
 order to make all the paths of equal length, the number of 
 coils must be a multiple of the number of pairs of poles. 
 For example, 16 conductors (8 coils) with a four-pole field 
 (2 pairs of poles), would give uniform paths, each contain- 
 ing an equal number of coils. The objection to this arrange- 
 ment lies in the fact that four coils would be short-circuited 
 at the same time. An examination of Fig. 524 where the 
 number of coils is not a multiple of the number of pairs of 
 poles, will show that four coils are not short-circuited at 
 the same time. Where the number of coils is comparatively- 
 large the objection to the unequal length of the paths is not 
 of so great importance. Where slotted armatures are used, 
 the same conditions as just stated apply. It is quite evident 
 that instead of having the conductors placed around the 
 outside of the periphery of the armature, these conductors 
 could be arranged in suitable slots. For instance, in Fig. 
 528 each pair of conductors such as 1 and 2, 3 and 4, etc., 
 could be placed in separate slots, in which case the same 
 diagrams would apply, it being customary to consider the 
 even numbered conductors as lying in the lower layer, and 
 the odd numbered conductors as lying in the upper layer. 
 As the number of conductors must be even, it is plain that 
 there can be either an even or odd number of slots, but the 
 number of conductors per slot must be such that the total 
 number of slots, times the number of conductors per slot, 
 must be an even number. 
 
 In Fig. 529 is shown an armuture similar to the armature 
 previously shown in Fig. 524. There are exactly the same 
 number of conductors and commutator segments. The con- 
 ductors are placed on in the same positions, and the con- 
 nections on the back of the armature are identical with 
 those of the previous figure. The distinguishing feature of 
 
1182 
 
 Steam Engineering 
 
 this armature lies in the method of connecting the various 
 coils to each other, and to the commutator segments at the 
 front of the armature. Where, in the previously described 
 armature connection, each coil after making a turn of the 
 armature, was carried back to a commutator segment ad- 
 
 Fig. 529 
 
 jacent to the one from which it started; in the present case 
 the end of each armature coil is connected by means of a 
 commutator segment, to a coil some distance in advance 
 of it. 
 
 The developed winding clearly shows the manner in which 
 this connection is made. It will be seen that the conductors 
 
Armature Winding 
 
 1183 
 
 are so connected that the current induced in each is in the 
 same direction as that in the remaining conductors of the 
 series. It will also be noticed that the developed winding of 
 each element forms a sort of wave and this winding is there- 
 fore known as a "wave" winding. 
 
 The scheme previously described may be employed to get 
 a clearer understanding of this winding. This consists in 
 drawing a circle, and dividing it with as many intersections 
 as there are conductors on the armature, and then drawing 
 a series of connecting lines through the various points, as 
 
 Fig. 530 
 
 shown by the winding table. The lines on the outside of 
 the circle are to be considered as the rear connections of the 
 armature, and the lines inside the circle, the front connec- 
 tions, or those connections running to the commutator seg- 
 ments. Tracing out the winding (or its development, Fig. 
 530), it will be seen that, starting from any one point and 
 following out the winding circuit, every conductor is passed 
 over once, and the winding finally returns on itself. 
 
 The spacing or pitch for the rear is 5, being the same 
 as that used for the lap winding, the conductor passing to 
 the rear of the armature along 1, and returning along space 
 
1184 Steam Engineering 
 
 6. The spacing at the front of the armature differs from 
 that of the lap winding in that it is not carried back, but 
 advances 5 spaces forward. The formula previously used 
 for determining the number of conductors and the spacing 
 may be applied in the present case. 
 
 -(- ) 
 
 n\h +1 ) 
 
 7= 
 
 In Fig. 529. 
 
 n, the number of poles=4; 
 
 z, the number of conductors=18; 
 
 b, the number of conductors to a coil=2. 
 
 For four-pole machines this formula simplified is z= 
 4y + 2. In Fig. 529 z=4X5— 2=18. 
 
 While the front and back spacings in the drawing shown 
 are alike, i. e., 5 and 5, it is also possible to have these 
 spacings differ. It is evident that the average spacing must 
 be approximately equal to the total number of conductors 
 divided by the number of poles, as the winding in passing 
 around the armature from one commutator segment to the 
 one next to it, comes under each pole piece. In the ex- 
 
 z 
 ample shown in Fig. 529 — is equal to 4%, the average 
 
 n 
 
 spacing may, therefore be taken as 4, in which case the 
 front spacing could be 5, and the rear spacing 3. 
 
 The pitches at the front and rear of the armature must 
 be odd, for, as has already been explained, the even num- 
 bered conductors are considered as returns for the odd num- 
 bered conductors. 
 
Armature Winding 1185 
 
 The winding table for this armature is 
 
 a-l-6-f 
 
 f-ll-16-b 
 
 b-3-8-g 
 
 g-13-18-c 
 
 c-5-10-h 
 
 h-15-2-d 
 
 d-7-ia-i 
 
 i-17-4-e 
 
 e-9-14-a 
 The two paths from the — to the + brush are : 
 i-17-4-e-9-14-a-l-6-f-ll-16-b-3-8-g ) 
 
 + 
 
 i-12-7-d-2-15-h-10-5-c-18-13-g ) 
 
 It will be seen that one path contains one more coil than 
 the other and that, with narrow brashes, only one coil is 
 short circuited at a time. 
 
 We have thus far been studying armature winding from 
 a theoretical standpoint. 
 
 It is now in order to devote a space to the practical side. 
 In the applicaton of the wire, the first thing in order is 
 the proper insulation of the slots wherein the wire is to 
 rest. The most suitable materials for this purpose are 
 
 Shellaced paper, or cloth, 
 
 Shellaced cardboard, 
 
 Thin fibre, 
 
 Mica. 
 
 After the slot has been carefully insulated we may begin 
 to apply the wire. Figure 531 illustrates two methods of 
 doing this. In the first method shown at a the winding is 
 begun in one corner of the slot, and continued in regular 
 order, progressing first from left to right, until one layer is 
 finished, and then from right to left until the second layer 
 
1186 
 
 Steam Engineering 
 
 is complete. By this method we can see, by referring to the 
 figure, that the last turn of the second layer comes in very 
 close contact with the first turn of the first layer. The same 
 condition will exist with every other layer in the same coil. 
 The result of this is a great liability to abrasion in the first 
 place, further a great liability of the insulation being 
 pierced, should the coil be wound with a great number of 
 turns, so that a great difference of potential would exist 
 within it. We must bear in mind that the insulation of 
 
 Fig. 531 
 
 armature wires is very thin, economy of space being a great 
 consideration in all cases. 
 
 By the above method of winding another great disadvan- 
 tage is introduced. The lowest coil of wire being so tightly 
 hemmed in, and at the same time there being considerable 
 necessity for handling the wire, the end of which is pro- 
 jecting, there is much risk of breaking it off short. If this 
 occurs it becomes necessary to unwind the whole coil in 
 order to get at this wire for repairs. 
 
Armature Winding 1187 
 
 In order to avoid these elements of trouble, the method 
 now to be described is extensively used. Take of the wire 
 that is to be wound upon the armature, sufficient to make 
 one coil; the amount required can best be determined by- 
 winding one coil temporarily, and then unwinding it and 
 using it to measure the other coils with. Take one of the 
 wires so obtained and mark the center of it and place it 
 exactly in the center of the slot as shown in Figure 531. 
 Now begin winding from the center, to one side until that 
 side is filled, next begin winding the other side in the same 
 way and continue winding the second layer in the same way, 
 half from each side, until the slot is filled. By this method 
 if the number of layers is even, the two ends of the coil 
 will finish side by side in the center ; if there is an uneven 
 number of layers the two ends of the coil will be at opposite 
 sides. It will make no particular difference which is the 
 case. 
 
 The full difference of potential of the coil will exist 
 between the two wires of the last layer which lie side by side, 
 and a difference of potential of a lesser degree between the 
 two middle wires of each layer. It might, therefore, be 
 advisable, where the coil consists of a number of turns, to 
 provide an insulating layer between the two halves of the 
 coil. 
 
 When the last layer is placed on the armature great care 
 should be exercised to see that it finishes off smooth. If 
 possible avoid the condition of wires shown in Fig. 531. 
 The wire at the right is likely to work down in time, and 
 thus leave a loose wire above it that may work down and 
 cause trouble. 
 
 A wire in the position of the one shown in Fig. 531 
 exerts a leverage on the other wires, and will gradually force 
 its way down. 
 
1188 
 
 Steam Engineering 
 
 If the armature to be wound, has no slots, a few clamps 
 (Fig. 532) will serve to hold the wire in place while a coil 
 is being wound. 
 
 Before starting the winding, tape should be laid on the 
 armature, leaving it long enough so that it can be used to 
 tie the coils together when the clamps are removed. Each 
 wire should go to its proper place, and by no means cross 
 any other wire below it so as to form a bulge. The strain on 
 
 Fig. 532 
 
 the wires of an armature, whether dynamo or motor, is at 
 times very severe, and if there is any flaw it will surely 
 show itself. 
 
 In the case of fine windings, each layer as it is put in 
 place should be thoroughly soaked with shellac. No cur- 
 rent, except of a very low potential from a small battery, 
 should be used either for testing or any other purpose until 
 this shellac is dry. Shellac until dried is a conductor and 
 may be pierced by the current and thus leave a gap, through 
 which at a later time current may leak. An armature of 
 
Armature Winding 1189 
 
 this kind is usually baked at a high temperature for 24 
 hours. 
 
 As an illustration of the great care that is advisable in 
 the insulation of armature wires, we may state that some 
 manufacturers place the magnet windings into tanks from 
 which the air can be exhausted. After the air Is withdrawn 
 from the coils, the insulating compound is allowed to flow 
 into the tank until the coil is submerged. This allows the 
 insulating compound to enter into the most minute open- 
 ings that may exist between the wires. Air pressure is 
 afterward applied to make certain that the interior of the 
 coil is reached by the fluid. 
 
 As each coil is finished it may be tested for correctness 
 of winding by a battery of two or three cells, and a small 
 galvanometer. The battery if always applied in the same 
 way must always produce the same deflection on the gal- 
 vanometer (see Fig. 546) ; if it does not do this the coil 
 in question has been wound wrong. It is not always neces- 
 sary to unwind the coil to correct this ; frequently all that 
 will be necessary is to connect the terminals of the coil in 
 the opposite way from the rest. As this, however, often 
 necessitates a crossing of the wires it is sometimes objec- 
 tionable. 
 
 When all of the coils have been wound upon the armature 
 the end of each coil is to be fastened to the beginning of 
 the next. Both are then fastened to their respective commu- 
 tator bars. It is well to tape the two wires together; this 
 leaves them stronger to resist mechanical interference, and 
 also occupies less space. This latter is an important con- 
 sideration where there are many coils. 
 
 The commutator sections are sometimes provided with 
 screws to hold the wire, but oftener the wires are soldered 
 directly to the commutator segments. This latter is the 
 
1190 
 
 Steam Engineering 
 
 safest method but may cause some trouble should it be 
 desired to remove the commutator for repairs. 
 
 The next step is the placing of the binding wires. These 
 are to hold the wires of the armature in place and must 
 always be used, unless the slots on the armature are of the 
 
 Fig. 533 
 
 nearly enclosed type. The binding wires are wound upon 
 the finished armature as shown in Figure 533. After plac- 
 ing a band of insulating material, such as mica, where the 
 wires are to go, begin by taking one or two turns of wire 
 around the armature with the spool ; draw these as tight as 
 possible and solder as indicated by arrow in the drawing. 
 
Armature Winding 1191 
 
 Now proceed, and put the balance of the necessary turns in 
 place by revolving the armature and holding the spool with 
 the wire stationary. In this way the winding can be placed 
 very accurately and close together. After a sufficient num- 
 ber of turns have been placed they are all soldered together 
 over the whole circumference to avoid possibility of any of 
 the wires breaking loose and causing damage. 
 
 Where the winding begins and ends a thin piece of brass 
 should be laid under the wire before it is wound on. After 
 the winding is finished this is bent over and soldered. Iron 
 and steel should not be used for binding wires; although 
 the section may not be large, they would always increase the 
 magnetic leakage that would to some extent lessen the 
 E. M. P. of the machine. The size of the binding wires 
 used ranges from number 20 to number 10. The latter is 
 used for the larger machines and the first for the smaller. 
 Usually about one-third of the armature is covered by such 
 wires. 
 
 The student of drum armature winding will save him- 
 self considerable worry, and mental tribulation if he will, 
 at the beginning, construct for himself out of a large spool 
 or some similar circular object a little imitation armature, 
 upon which he can wind with strings such coils as are 
 herein described as being in use on armatures. These little 
 experiments will be more realistic if, for this purpose the ar- 
 mature of some old fan motor can be procured. Such an 
 armature should preferably be of the slotted kind; if the 
 wooden spool above referred to is used its periphery should 
 be divided off into the proper number of spaces by insert- 
 ing suitable nails thereon. Much can be learned in this 
 way regarding armature winding that can never be fully 
 grasped in any other way. 
 
1192 Steam Engineering 
 
 QUESTIONS AND ANSWERS. 
 
 818. Can the properties of a dynamo be accurately cal- 
 culated from any of the formulas given for that purpose? 
 
 Ans. No. The accurate design of a new type of dynamo, 
 and an armature as well, is as much a matter of experiment 
 as it is of calculation. 
 
 819. Why is this? 
 
 Ans. There are so many factors involved in the calcu- 
 lation that cannot be accurately determined until a ma- 
 chine of the exact dimensions of the one under considera- 
 tion has been built. 
 
 820. What are the principal factors that are so trouble- 
 some to determine? 
 
 Ans. The permeability of the iron, the resistance of 
 the magnetic circuit, the tendency to leakage of the lines 
 of force, the exact proportion of the dead wire, the reaction 
 of the armature, the losses due to Foucault currents. 
 
 821. Are not the causes of all these losses well under- 
 stood ? 
 
 Ans. They are, and it is easy enough to tell what must 
 be done to lessen any or all of them. It is merely their 
 exact value which is indeterminate until the machine in 
 question is in operation. 
 
 822. What is the chief precaution which must be taken 
 i this account. 
 
 Ans. It is necessary to leave some part of the controlling 
 influences so that they can be readily varied and thus adjust 
 the machine so that it will be exactly right when it is finally 
 finished. 
 
 823. How can this best bedone?^ 
 
 Ans. Since it is manifest Very troublesome to rewind 
 an armature, if perchance too gTeat or too small a number 
 
Questions and Answers 1193 
 
 of wires have been placed upon it, the proper factors to be 
 arranged to be variable are : the speed, and the strength of 
 the field. In some cases the speed, even, is not changeable, 
 and the whole duty of compensating for misjudgment in 
 the calculations falls upon variations of the field strength. 
 
 824. Can the whole regulation be accomplished in this 
 way? 
 
 Ans. It can, and in most cases this is the method relied 
 upon. It is very easily accomplished by this method if we 
 arrange to have the fields magnetized to only a low degree 
 of saturation. By doing this, however, we are led to provide 
 field magnets whose capacity is far in excess of what we 
 believe to be necessary and, therefore, more expensive. So 
 that again in the last consideration it behooves us to experi- 
 ment before we definitely determine the exact proportion 
 of our dynamo or motor. 
 
 825. Are there any formulae that can be used in deter- 
 mining the exact proportions? 
 
 Ans. There are, and they are given below. These will 
 materially assist the student in forming an idea how the 
 different parts can be adjusted to bring about the desired 
 final result. For the following formulae we shall adopt the 
 attached set of symbols : 
 
 Let F=the total number of lines of force, or flux, 
 V=the number of volts to be generated, 
 S=the number of slots in the armature, 
 E.P.S.=the number of revolutions per second, 
 W=the number of wires per slot. 
 Then, to find the number of wires necessary per slot where 
 the speed and flux are fixed: 
 
 10 8 XV 
 
 W=- 
 
 FXSXE.P.S. 
 
1194 Steam Engineering 
 
 To find the necessary speed where the number of wires, and 
 
 the flux, are fixed: 
 
 10 8 XV 
 E. P. S.= 
 
 FXSXW 
 
 To find the necessary strength of field, where the wires 
 and speed are fixed : 
 
 io 8 xv 
 
 F= ■ 
 
 SXE. P. S.XW 
 
 To find the volts generated : 
 
 FXSXWXRP.S. 
 
 V=- 
 
 10 8 
 
 826. Are these formulae used in actual practice to deter- 
 mine the size of wire, speed, etc. ? 
 
 A ns. These formulae are of value principally in check- 
 ing up the actual calculations made. 
 
 827. How is an armature actually designed? 
 
 Ans. In actual practice whenever a new dynamo or 
 motor is to be constructed it is, so to speak, built up around 
 the armature. That is to say, the armature must first be 
 designed, and the other parts made to fit around it. 
 
 828. What is the principal consideration to be taken 
 into account? 
 
 Ans. In order to deliver a certain current, the number 
 of poles, etc., being fixed, which is with rare exceptions the 
 case, we must use a certain size wire. 
 
 829. Is there no choice whatever in the size of wire 
 for a given current? 
 
 Ans. There is some choice. In most cases the heating 
 of the wire on the armature determines the size of wire to 
 be used; in other cases it is the drop in potential at the 
 terminals of the armature that governs. 
 
Questions and Answers 1195 
 
 830. How does the size of wire affect the heating, and 
 the loss of potential? 
 
 Ans. Both of these losses, and the troubles occurring 
 from them, are lessened by selecting wires of greater 
 diameter. 
 
 831. How do you proceed to calculate the necessary size 
 of wire ? 
 
 Ans. The number of wires, and the dimensions of the 
 armature for any given purpose can be found by trial cal- 
 culations only. By this we mean that, unless we are very 
 lucky, we shall have to make a number of calculations, 
 using, perhaps, different dimensions and wires before we 
 get the result that suits us best. 
 
 832. Give an example. 
 
 Ans. As an example let us take an armature 8 inches 
 in diameter and 8 inches in length and see what it will 
 do for us. Such an armature has a cross-section of 64 sq. 
 inches and, assuming a flux of 30,000 lines of force per 
 square inch, we have a total flux of 1,920,000 lines through 
 the armature. We first find how often one wire must cut 
 this number of lines of force to generate, say, 110 volts. 
 To do this we first divide 110X100,000,000 (which is the 
 total number of lines to be cut per second) by the total 
 flux, 1,920,000, and obtain as the result 5728. Next, to 
 get the necessary number of wires to be placed upon the 
 armature, we must divide this quotient (5728) by the 
 number of revolutions the armature makes per second. If 
 our armature revolves at the rate of twenty revolutions per 
 second (1,200 per minute) we shall need one-twentieth 
 of 5,728 wires placed upon it. This amounts to 286. As 
 our armature, 8 inches in diameter, has a circumference of 
 25.12 inches, this gives us a wire running about 11 per 
 inch. If there is to be but one layer, this gives a number 
 
1196 Steam Engineering 
 
 12 wire. As the two sides of the armature are in parallel 
 we have a capacity of 2 times 14.31 amperes according to 
 Table 50. If we decide to use two layers, we can take a 
 No. 6 wire, 5.5 per inch, and obtain a capacity of 56.55 
 amperes. It may be stated in explanation of the calcula- 
 tions here made that each wire in the course of one revolu- 
 tion of the armature cuts the total flux two times; but as 
 the two halves of the armature are in parallel, each side 
 must produce the full voltage by itself. 
 
 833. How much radiating surface is usually allowed per 
 watt of energy used up ? 
 
 Ans. That depends very much on the work for which 
 the armature is intended. If it is for a railway motor, 
 which is entirely enclosed, and almost constantly in use, it 
 is much more than, for instance, an elevator in a private 
 residence where there is but very little use, and only at long 
 intervals, so that the armature has time to cool off between 
 one run and another. Table 50 is based upon the require- 
 ment that there shall be three square inches of radiating 
 surface for each watt of energy expended in the coils. 
 
 834. What radiating surface is allowed for each watt 
 expended in the case of an armature ? 
 
 Ans. This amount varies in different machines, being 
 as low as 1 square inch per watt, and as high as three square 
 inches per watt. About 1.75 square inches per watt ex- 
 pended can be considered as a fair average for armatures 
 \nd about 3 inches per watt expended for field coils. 
 
 835. How is the table referred to (Table 50) made up? 
 Ans. This table is figured from the formula, 
 
 BS 
 
 I= J 3XR 
 
Questions and Answers 1197 
 
 E S being the radiating surface, and E the resistance of a 
 unit of length of the wire under consideration. This form- 
 ula gives the current allowed where the wire is wound in 
 one layer. As we add more layers we must, with each suc- 
 cessive layer, reduce the current, so that the square of the 
 current multiplied by the resistance (which equals the 
 watts) shall remain always the same, because increasing 
 the depth of the winding does not affect the radiating sur- 
 face of the coil. 
 
 836. The table gives the carrying capacity only to a 
 depth of six layers ; how is the carryng capacity of a greater 
 number of layers to be found? 
 
 Ans. To do this we refer to Table 50 and select from the 
 column headed I 2 the number pertaining to the wire in 
 question. This number represents the square of the cur- 
 rent permissible with one layer of wire. Divide this num- 
 ber by the number of layers it is intended to use, and extract 
 the square root of the number so found. The result will be 
 the carrying capacity of the wire in question, wound to a 
 depth of that number of layers. As a general guide we may 
 bear in mind that, as we multiply the number of layers by 
 4, 16, 64, 256, we, each time, decrease by one-half the 
 carrying capacity of the wire. From this we can see that 
 the capacity of the wires after a certain number of layers 
 have been considered, decreases very slowly, though very 
 fast with the first few layers. 
 
 837. Is there need of very great accuracy in these 
 calculations ? 
 
 Ans. Great accuracy is not necessary in these calcula- 
 tions. We can always lengthen our armature a little by 
 adding a few punchings, should the potential be insufficient, 
 and we can always vary the speed and strength of field con- 
 
1198 
 
 Steam Engineering 
 
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Questions and Answers 
 
 1199 
 
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1200 Steam Engineering 
 
 siderably. Adding to any of these would tend to increase 
 the E. M. P. of the armature, but not its capacity in 
 amperes. 
 
 838. If the capacity of the armature is not sufficient, 
 how do we proceed ? 
 
 Ans. Take the next larger wire, or such a wire as will 
 give the desired capacity, and from the diameter of this 
 wire figure out a new armature. By using the same num- 
 ber of wires of a larger diameter, a greater cross-section of 
 armature is obtained. 
 
 839. Do these considerations apply equally well, 
 whether an armature is slotted, or not? 
 
 Ans. The only difference is that with a slotted arma- 
 ture it is necessary to take into consideration the length of 
 the winding space in the slots only, not the total circum- 
 ference of the armature. There is also considerable loss of 
 flux through the teeth of the armature so that the flux must 
 be assumed less. A great flux is obtainable, however, with 
 the same field winding, as the magnetic circuit of a dynamo 
 with a slotted armature has less resistance. 
 
 840. How do you proceed in the case of a slotted arma- 
 ture? 
 
 Ans. If we have an armature provided with slots of a 
 fixed size we can but arrange to accommodate ourselves to 
 it as best we may. It may be that the slots are of such size 
 that the wire we have selected through our calculation will 
 not fill out the slot well, and we must, therefore, try some 
 other size wire. In this case it will be preferable to select 
 a larger size wire if practicable. This had best be tried by 
 actual experiment. As the wire often will not fill out the 
 slot quite fully, calculations are not exactly reliable. Any 
 deficiency can, of course, be made up by filling in with insu- 
 
Questions and Answers 1201 
 
 lation. The number of wires per slot is found by dividing 
 the total number of wires by the number of slots. 
 
 841. How can the size of a slot capable of holding a 
 certain number of wires be determined? 
 
 Arts. The approximate depth of the slot can be obtained 
 by multiplying the diameter of the wire to be used by .86 
 and this by the number of layers placed over each other. 
 The result will be exact if the wires lie as shown in Figure 
 512. The width of the slot can be found by multiplying the 
 diameter of the wire by the number of turns per layer. It 
 will be seen from the figure that each alternate layer will 
 contain one turn less than the first. 
 
 842. Can slots be proportioned so that they will accom- 
 modate any number of wires ? 
 
 Arts. The slots must be proportioned to the number 
 of wires to be used, and the number of wires per slot must- 
 be carefully considered. If the number of turns per slot 
 are few, the wires should be placed as shown in Figure 513. 
 If there are many, according to Figure 512. Which of these 
 two methods is to be used will have a bearing on the num- 
 ber of wires per slot. The total number must be a multiple 
 of the number of layers. 
 
 843. After we have selected our wire, and determined 
 the number of wires to be used, can we form some idea of 
 what the losses in the armature will be? 
 
 Arts. We can easily figure the approximate loss of volt- 
 age in the armature from the size of wire to be used. To 
 do this we first find from Table 50 the resistance per foot of 
 the wire in question, and then measure the length of wire 
 in one coil and multiply the resistance by the number of 
 feet. If we have a bi-polar armature we again multiply 
 this by half the number of coils (the two sides being in 
 parallel). Since the loss in voltage is equal to the amperes 
 
1202 Steam Engineering 
 
 multiplied by the resistance, we need but to multiply the 
 resistance so found by half the total current to find the 
 loss in voltage that will occur. This loss is, of course, in 
 direct proportion to the current. This loss is not of much 
 importance in ring armatures, or in drum armatures either, 
 when they are working with small currents, or on constant 
 current work such as arc lighting; but with heavy, and 
 variable currents it is a very important matter, and the 
 lower the losses can be kept, the better. 
 
 844. Are there any special considerations to be borne 
 in mind while winding the different coils ? 
 
 Ans. It is quite important to see that each coil contains 
 the same number of turns, and that these fill out the same 
 relative space. 
 
 845. Why is this so important? 
 
 Ans. We have already seen that the two halves of the 
 armature are generating in parallel, that is, the currents 
 from the two sides meet at the positive brush and flow out 
 to the line, and return by the negative side to the armature. 
 If now there are fewer turns of wire on one side than on 
 the other, or if there is one weak coil in the armature, one 
 side or the other will always be generating a greater E. M. F. 
 than the other and consequently current from the high pres- 
 sure side will flow through the winding of the low side. 
 To see this more clearly refer to Figure 514. On the arma- 
 ture there shown, there are 16 coils. If this armature is to 
 generate 40 volts, each coil will be called upon to produce 5 
 volts. Now suppose one of the coils to be cut out of the 
 circuit entirely. It is clear that at all times except when 
 the dead coil is at the neutral points, there are 8 coils gen- 
 eraing on one side against 7 on the other; i. e., 40 volts 
 against 35. In order to find the current that would flow in 
 such an armature while on open circuit, subtract the low 
 
Questions and Answers 1203 
 
 voltage from the high, which leaves an active voltage of 5. 
 If the resistance of the armature were .1 ohm a current of 
 50 amperes will be circulating a great part of the tiine. 
 
 846. Why would this not be a eonstant current ? 
 
 Ans. For the reason that this current would be con- 
 stantly changing in direction, because the strong side of the 
 armature would be first on one side, and then on the other, 
 of the fields. On open circuit a perfect armature would 
 generate no current whatever; with an armature as de- 
 scribed the current mentioned would always be flowing 
 toward the coil which is cut dead. 
 
 The current would be changing in strength, because dur- 
 ing the time the dead coil is short circuited by a brush it 
 would be balanced by another coil under the opposite brush 
 which for the moment is also dead. Consequently during 
 that time the armature would not be generating at all. 
 
 847. How would this inequality of generation manifest 
 itself if the dynamo were generating current ? 
 
 Ans. If the dynamo were generating current this con- 
 dition would greatly reduce its capacity. The current flows 
 only in obedience to the pressure, and as this would be 
 variable the current would of course also be variable. 
 
 848. Are differences in potential between different parts 
 of an armature caused by any other conditions in the ar- 
 mature ? 
 
 Ans. Such differences are sometimes caused by the loca- 
 tion of the wires of different coils. Other things being equal 
 the E. M. F. generated by any coil varies with its distance 
 from the center of the armature. It can readily be seen 
 that the farther a wire is from the center, the greater will 
 be the area enclosed and therefore the greater the number 
 of lines of force cut by it. 
 
1204 Steam Engineering 
 
 849. What other cause is there for inequality of genera- 
 tion? 
 
 Ans. Another cause for inequality of generation be- 
 tween different coils lies in a difference of resistance. 
 
 850. Does this affect the generation on open circuit? 
 Ans. It does not. We have already seen that the loss 
 
 in potential in any circuit is proportional to the current 
 flowing, multiplied by resistance of the circuit in which it 
 flows. Therefore the drop in potential in any coil is in 
 proportion to the current being taken from it. If one coil 
 therefore has a much higher resistance than the others its 
 potential will fall much more, and the side of the armature 
 on which it happens to be will be of lower E. M. F. than 
 the other, and there will be the same tendency to a vacillat- 
 ing current as in the case of coils of uneven number of 
 turns. The variations will, however, not be near so great, 
 for an excessive current flow from the strong side will re- 
 duce the pressure on that side, and the checking of the cur- 
 rent on the low side will raise the pressure there, so that a 
 balance will be obtained without any great current flow. 
 The main danger of introducing inequality in the resistance 
 of the winding lies in the winding of the inside of the coil 
 with Gramme ring armatures. The space for the winding 
 at this point is necessarily of a different shape than that 
 on the outside, and there are also the spokes of the arma- 
 ture to contend with. 
 
 851. How many methods of armature winding are in 
 general use ? 
 
 Ans. The methods of armature winding are very numer- 
 ous. For the present we shall confine ourselves to the 
 methods used with hand winding on cylinder armatures. 
 
 852. Which is the most simple of these windings? 
 
Questions and Answers 
 
 1205 
 
 Ans. The simplest one of these windings is that shown 
 in Figure 534, and we shall take this one for the purpose 
 of demonstration. It will be noticed that in this figure there 
 are 12 slots in the armature and 6 commutator sections, 
 indicated by the wires twisted together. 
 
 853. Is it necessary that this proportion of slots and 
 armature coils exist? 
 
 Fig. 534 
 
 Ans. It is not; in fact it is not at all desirable that this 
 proportion should exist, but this proportion is very con- 
 venient for winding, as we shall see. 
 
 Begin winding by selecting two of the slots located 
 opposite each other, as shown in the figure, and starting 
 at 1 wind into those slots as many turns of wire as has been 
 determined there should be and bring the last end of the 
 
1206 Steam Engineering 
 
 coil to the commutator section next the one from which we 
 started. 
 
 854. Should this be to the one in front of, or behind 
 the section from which the winding started ? 
 
 Ans. This is immaterial. In actual practice there 
 should not be any commutator sections in place while wind- 
 ing. They would be very much in the way. Instead, tie the 
 two ends of the coil together and properly mark the be- 
 ginning and end. 
 
 855. Are all coils wound in the same way? 
 
 Ans. They are; but in this case we must skip one slot 
 at each subsequent coil, in order to make them come out 
 right in the end. That is to say, if the first coil is wound 
 into 1, 1, the second must be wound into 2, 2, the third 
 into 3, 3, etc. 
 
 856. Why is this? 
 
 Ans. As each coil fills out two slots, we have with the 
 third coil finished half of the armature. If we were to wind 
 the slots in consecutive order, the connections for the com- 
 mutator would all come on one side, and we could do noth- 
 ing with the armature. As we now continue in the order 
 we have started we finally complete the entire winding and 
 have the beginning and end of one coil opposite each com- 
 mutator section. We can now fasten the beginning of the 
 first coil to its proper commutator section, and the end of 
 it to the next one. It will be immaterial whether this be to 
 the section ahead, or behind the starting section, but, which- 
 ever way we start, we must be sure to continue in the 
 same way. 
 
 857. This being the most simple method of armature 
 winding, why are not all armatures wound in this way? 
 
 Ans. The great objection to an armature wound in this 
 way is that the coils become too large. 
 
Questions and Answers 1207 
 
 858. Why are large coils objectionable? 
 
 Ans. In order to understand why large coils are objec- 
 tionable we refer to the commutator shown at the right of 
 Figure 534. Here a brush is shown bridging two commu- 
 tator sections and short circuiting the coil connected to 
 them. The coil indicated by the black line is the same one 
 shown in the slots 1, 1, and the connections are identical. 
 It can readily be seen that all of the coils will in turn 
 become short circuited in the same way in the course of 
 every revolution of the armature. 
 
 Now in the first place assume that the coil when thus 
 short circuited is in an entirely dead part of the field. 
 When a brush short circuits such a coil it takes all the 
 current away from it. When the brush leaves the forward 
 section of the commutator this short circuit must be broken, 
 and current must be again established through the coil. 
 As every coil possesses some inductance (which acts for an 
 instant like a very high resistance), there is a tendency for 
 the current in that half of the armature to jump across the 
 insulation between the commutator sections, rather than 
 pass through the coil. If this occurs there is destructive 
 sparking. The greater the number of turns of wire in any 
 coil, the greater will be the likelihood of this taking place. 
 
 859. Is this the main reason why the coils on an arma- 
 ture should be made up of few turns of wire ? 
 
 Ans. It is not. The most important reason for this is 
 the following : If the coil is not in an entirely "dead" part 
 of the field there is always some current generated in it 
 during the time the brush is in the position discussed above. 
 This current circulates in the coil during the time the 
 brush holds it on short circuit, without appearing in the 
 outer circuit, and is therefore a dead loss. It furthermore 
 
1208 
 
 Steam Engineering 
 
 tends to heat the coils. Because two of the coils are nearly 
 always on short circuit in this way, the loss and the heating 
 are considerable when the coils are large. When these cur- 
 rents are broken by the commutator section sliding from 
 under the brush, they also make themselves evident by 
 severe sparking, if the coils are large. 
 
 Fig. 535 
 
 860. Are there any more reasons why large coils are 
 objectionable? 
 
 Ans. Another reason why large coils in an armature 
 are objectionable can best be understood by reference to 
 Fig. 535. A simple dynamo such as is depicted in this 
 figure delivers a current graphically illustrated by Fig. 536. 
 It will be seen that this is really an intermittent current. 
 This is because the dynamo has but one coil, and while 
 
Questions and Answers 1209 
 
 this is at the neutral points, nothing is being generated. 
 The current therefore fluctuates from to its maximum. 
 If we add one more coil the current line becomes as shown 
 in Fig. 537, and the greater the number of coils the smaller 
 becomes the percentage of non-generating coils, and the 
 nearer does the current line approach a straight line show- 
 ing a steady value. 
 
 861. Why cannot small coils be wound in the manner 
 shown in Fig. 534. 
 
 Ans. It is desirable to make the coils as small as pos- 
 sible. The ideal coil would consist of only one turn. Now 
 
 Fig. 536 
 
 FiCx. 537 
 
 as long as we wind only one coil into one slot we shall 
 have the coils needlessly large. The number of coils is 
 limited by the number of commutator sections, and unless 
 we wind two coils into each slot (as we can see from Fig. 
 534) we can have but half as many commutator sections 
 as there are slots. In order to get a small coil it is there- 
 fore necessary to get two coils into each slot, 
 
 862. Can this be done in more than one way? 
 
 Ans. This can be done according to any of the plans 
 _ shown in Fig. 538. In this figure the black and white 
 circles respectively represent the wires of the two different 
 coils wound into the same slot. 
 
1210 Steam Engineering 
 
 We have already seen under ring armatures, that wires 
 of different coils should all be of the same distance from 
 the center of the armature, so as to cut the same number 
 of lines; it follows, therefore, that the plan showing one 
 coil wound over the other should not be used where it can 
 be avoided. 
 
 863. How do you manage to place two coils in one slot? 
 
 Ans. In order to understand exactly how this is done 
 let us consult Fig. 539. This figure is a duplicate of Fig. 
 534 with the exception that now we have as many com- 
 mutator sections as there are slots in the armature. The 
 
 
 Fig. 538 
 
 black circles represent the wires of one set of coils, and the 
 light those of the other. 
 
 The simplest method of winding two coils into one slot 
 is, first to wind one coil complete, filling half the slot, then 
 turn the armature half way round and wind the second 
 coil over the first. As this, however, gives two coils of dif- 
 ferent lengths and resistance, and also cutting a different 
 number of lines of force, such a winding is seldom used. 
 A better way is the following: Cut two wires of sufficient 
 length so that each will make one coil, place the armature 
 upon two crossbars of convenient height so that it can be 
 
Questions and Answers 
 
 1211 
 
 easily turned over when required. Mark all of the slots 
 with appropriate numbers according to the plan of wiring 
 selected, so there may be no confusion when the work is 
 started. A very good plan is shown in Fig. 534. This 
 plan gives the smallest head of any because there are al- 
 ways two coils running parallel to each other across the 
 ends of the armature. Thus we have three lavers of coils 
 
 Fig. 539 
 
 crossing over each other, while with any of the others 
 we should have six. But in order to get the advantage of 
 this smaller head, we cannot wind the coils in the order 
 given in the explanation of this winding. It becomes neces- 
 sary to wind completely, at the same time, the two coils 
 that are running parallel with each other across the ends. 
 To do this requires more experience and forethought, than 
 the way previously described. 
 
1212 Steam Engineering 
 
 Begin the winding with the coil marked 1, and make 
 one complete turn and fasten the two ends of the wire to- 
 gether temporarily if more turns are to follow, or fas- 
 ten each to its proper place on the commutator, if there 
 is to be but one turn. Now turn the armature half way 
 round and wind the other wire in the same way. If there 
 are to be more turns, continue to wind the second turn. 
 After this is finished turn the armature back to its original 
 position and wind the first wire again. Eepeat in this 
 manner until the desired number of turns in both coils have 
 been obtained. By reference to Fig. 539 we note that the 
 windings do not skip slots as in Fig. 534. This is easily 
 explained when it is noticed that each slot contains two 
 conductors and that at each step we skip one conductor as 
 before. 
 
 It is not necessary in actual practice to turn the arma- 
 ture around as above suggested. This was suggested merely 
 as a beginning to make the principle more plain. The 
 same result can readily be obtained if the armature is left 
 stationary. The windings need merely to be so arranged 
 that they will come right for connection to the commutator 
 as shown in the cut. 
 
 It is well enough to use care that all of the coils are wound 
 in the same direction, but it will not materially affect the 
 operation, if one part of the coils are wound left hand, and 
 the others right hand. The essential point is to see that 
 they are so connected that the magnetism resulting from a 
 current flow through the coil will be the same in all. If 
 it is different in one coil from the others it can easily be 
 rectified by simply changing the end connections of the 
 coil in question. 
 
 864. Are all armatures hand wound ? 
 
Questions and Answers 
 
 1213 
 
 Ans. Hand winding is customary with the smaller 
 drum, and ring armatures only. It is the only method 
 that can be used with ring armatures, and also with drum 
 armatures where the wire is to encircle the whole armature. 
 The larger dynamos are now made mostly multipolar, and 
 in these the coils do not return at nearly, or wholly, diam- 
 etrically opposite points as they do in those machines we 
 have so far had under consideration. With multipolar ma- 
 chines the armature is divided into as many sections as 
 there are poles. While it is possible to work any regularly 
 
 ^ w ^^'^ xsaigBo&;c ^^^ 
 
 Fig. 540 
 
 wound drum, or ring armature in connection with many 
 poles, it is not customary to do so. In general the coil 
 wound on a multipolar armature has its return winding 
 spaced about as far from the first turn, as it is from the 
 center of one pole piece to the center of the next one. 
 
 865. How does this affect the winding? 
 
 Ans. This gives us a winding of much lower resistance 
 than could otherwise be obtained, and the magnetic circuit 
 is also much better. Furthermore, it makes possible the 
 use of so-called "former coils." 
 
1214 
 
 Steam Engineering 
 
 866. What is a former coil? 
 
 Ans. A former coil is one that is wound upon a former, 
 i. e., one that is wound complete before it is placed upon the 
 armature. 
 
 867. How are such coils made up ? 
 
 Ans. Figs. 540 and 541 show two styles of former coils, 
 and the manner in which they are wound. In Fig. 540 the 
 black circles represent strong pins fastened into a piece of 
 
 Fig. 541 
 plank, or other suitable material. The wire is wound 
 around these pins as indicated in the figure, as many turns 
 being taken as it has been decided to allow for each coil. 
 When the coil is thus completely wound it is taken from 
 the pins, and the lower ends placed in a suitable clamp, as 
 indicated by the broken line in the lower center of the 
 figure. After this clamp is fastened onto the coil the two 
 halves of the coil are spread apart, one being pulled to- 
 ward the operator and the other pushed away from him at 
 
Questions and Answers 1215 
 
 right angles to the clamp. In this way the coil is made to 
 assume the shape illustrated in Fig. 542. Before winding 
 a coil in this manner it is of course necessary to know ex- 
 actly what length it must be, and a pattern coil must there- 
 fore first of all be prepared, from which the spacing of the 
 pins can be taken, so that the completed coil will fit into 
 the slots for which it is intended. 
 
 868. How are such coils placed upon the armature? 
 
 Ans. Begin placing the coils at any convenient slot, and 
 lay them in, as indicated in Fig. 542. It is necessary to 
 mark the beginning, and end of each coil, so that there 
 
 Fig. 542 
 
 may be no wrong connection when the wires are finally 
 connected to the commutator. 
 
 Before placing the coils the slots must of course be in- 
 sulated as explained previously. We now continue to lay 
 in coils until the whole armature is full, but when nearly 
 full, the forward ends of the coils we are placing require 
 to be brought under the first coils put in place. To do 
 this it is merely necessary to raise up the first six coils, 
 (in this case) and place the forward ends of the last six 
 under them in the regular order. , 
 
 869. By what name is this winding known? 
 
 Ans. This is known as the "evolute" winding. It will 
 be noticed that when this winding is completed, the wires 
 of the outer portion entirely conceal those of the inner, and 
 
1216 Steam Engineering 
 
 thus give this style of winding its characteristic appearance. 
 
 870. What other manner of winding multipolar arma- 
 tures is there? 
 
 Ans. Another method of forming coils is illustrated in 
 Fig. 541. In this case the coil is first wound around two 
 pins, as shown at the top of the figure. The ends are then 
 placed in clamps, as indicated by the dotted lines at the 
 top and shaded lines in the center of the figure. After 
 these clamps are fastened, the coil is turned one-fourth 
 around, and the wires spread over the four pins, as indi- 
 cated in the figure. 
 
 871. How is this coil placed upon the armature? 
 
 Fig. 543 
 
 Ans. The coil formed in the manner above assumes the 
 shape shown in side view in Fig. 543 and is placed upon 
 the armature as there indicated, the manner of placing 
 being the same as that of the previous coil. 
 
 872. What name is given to this style of winding? 
 Ans. This is termed a "barrel" winding and its charac- 
 teristic appearance can be seen from the figure. 
 
 873. Is it necessary to carry out the same kind of wind- 
 ing on both sides of an armature? 
 
 Ans. There is nothing to prevent one from using one 
 of these windings on one side of the armature, and the 
 other on the opposite side. They cannot, however, be com- 
 
Questions and Answers 
 
 1217 
 
 bined on the same side. The windings of large machines 
 very often are made up of bars of copper made of special 
 sizes to suit. These are often arranged as shown in Figs. 
 544 and 545. Sometimes such bars are bare and laid into 
 the slots with insulation loose on the sides and bottom and 
 between the different bars of a slot. Such winding is often 
 held in place by pieces of wood inserted into the slots as 
 indicated in Fig. 543, the slots being specially prepared to 
 admit of this. Where no such provision has been made the 
 wires are held in place by the usual binding wires. 
 
 £Z 
 
 w 
 
 Fig. 544 
 
 MOTOR ARMATURES. 
 
 874. Is there any difference between the armature of 
 motors and dynamos? 
 
 Ans. Theoretically there is no difference between the 
 armature of a dynamo and motor. In fact, many machines 
 are placed in conditions in which their functions change, 
 perhaps a hundred times per day, from that of generator 
 to that of motor. 
 
 875. Are there any special provisions necessary to make 
 them operate thus ? 
 
 Ans. No. This change takes place automatically, and 
 the operation is so smooth that the observer will have no 
 idea in which capacity the machine may be operating from 
 
1218 
 
 Steam Engineering 
 
 moment to moment. It is also no unusual thing for a 
 dynamo working in parallel with other generators to be- 
 come reversed, and instead of delivering current to the 
 line, it will be drawing from it and running as a motor. 
 
 876. What should one principally have in view in the 
 design of a motor armature ? 
 
 Ans. Motor armatures must be designed to produce a 
 certain counter E. M. F. just as dynamo armatures are 
 designed to produce E. M. F. In the case of a dynamo the 
 
 Fig. 545 
 
 power is measured by the product of the E. M. F. and the 
 current, so in the motor the power is proportional to the 
 product of the counter E. M. F. and the current. 
 
 877. How do you proceed to calculate the winding for 
 a motor armature? , 
 
 Ans. In the same way as with a dynamo except that 
 the E. M. F. should not be figured as high. The current 
 
 V-v 
 
 passing through a D. C. motor equals , where V is the 
 
 volume of the line that supplies it ; v the counter E. M. F. 
 of the armature, and E its resistance. It is apparent that 
 in order to get more power out of a given motor, its coun- 
 
Questions and Answers 1219 
 
 ter E. M. F. must be reduced in order that a greater cur- 
 rent can flow. 
 
 878. How is this brought about? 
 
 Ans. With a motor in operation this counter E. M. F. 
 is reduced when the speed reduces, on account of a heavier 
 load. More current is thus allowed to flow until the power 
 of the motor becomes equal to the work required of it, but 
 if the load exceeds the capacity of the motor it will take 
 too much current, and burn out the armature. If a motor 
 is to be designed to operate at a certain speed, all of these 
 facts must be taken into consideration, and the wires so 
 selected that when running at the required speed, the neces- 
 sary counter E. M. F. will be generated. 
 
 For illustration, take the same armature that was con- 
 sidered in the previous section. In this case a No. 12 wire 
 was required. This gave 11 turns per inch, and its car- 
 rying capacity was 14.3 amperes. The dimensions of the 
 armature were 8"x8", requiring about 770 feet of wire. 
 With this quantity of No. 12 the resistance is 1.39 ohms. 
 
 Only one-half of this, however, is on one side, and only 
 14.3 amperes pass on one side, so that the total E. M. F. 
 to drive this current through the armature is 14.3X-697, 
 which is 9.96. In order that this motor may allow the 14.3 
 amperes to pass, its counter E. M. F. must fall to 9.96 
 volts less than the E. M. F. of the line. If this is 110, the 
 speed must slack off about 9 per cent in order that the 
 motor may develop its full power. 
 
 It is easily seen from this that, in order that the motor 
 may operate at a fairly constant speed, the resistance of the 
 armature should be made as low as possible. In practice it 
 is generally made so low that a reduction of 1 per cent in 
 speed wll bring about the required lowering of counter 
 E. M. F. to cause the proper current to flow. 
 
1220 
 
 Steam Engineering 
 
 ARMATURE TROUBLES. 
 
 879. How do armature troubles manifest themselves? 
 Ans. Either by excessive sparking at the commutator, 
 
 or by abnormal heating of the armature. 
 
 880. What are the causes of such troubles? 
 
 Ans. They may result from any one of the following 
 causes: There may be a wrong connection of one, or more 
 of the coils. Some of the coils may be grounded. There 
 may be an open circuit. There may be a short circuit. 
 
 #r 
 
 
 Fig. 546 
 
 The brushes may be improperly set. The brushes may not 
 make sufficient contact with the commutator. The com- 
 mutator may be rough or worn. The fields may be of 
 uneven strength. 
 
 881. How can a wrong connection of the coils be tested 
 for? 
 
 Ans. In order to see how this test can be made let us 
 consider Fig. 546 for a moment. This figure shows the 
 wiring of an armature connected to the commutator seg- 
 ments exactly as it would be if it were taken off, and the 
 
Questions and Answers 1221 
 
 coils separated without detaching from the commutator, in- 
 stead of being placed in an orderly manner upon the core 
 of the armature. In other words, the connections are ex- 
 actly as in an armature. If we should now take the two 
 wires of some supply of current capable of delivering a 
 few amperes, and connect these two wires to two adjacent 
 commutator segments, as shown at a, and h, it is clear that 
 current would flow through the coil connected between 
 these two sections, and also through the other coils. The 
 current has two paths: one through the single coil, the 
 other through the remaining seven coils in series. 
 
 The current in the two coils flows in opposite directions, 
 with the result that a field of force is set up in the vicinity 
 of the single coil. A suitable galvanometer placed at this 
 point will be deflected in a certain direction. By revolving 
 the armature and applying the test to each succeeding pair 
 of commutator sections, a number of deflections of the 
 needle will be obtained. 
 
 If all the coils are correctly connected these deflections 
 will all be in the same direction. If one of the coils is con- 
 nected wrong, a different deflection will be obtained. If 
 one of the coils has been wound on in the wrong direction, 
 it is not necessary to rewind it ; the connections can simply 
 be reversed. 
 
 882. What is meant by a "ground" ? 
 
 Ans. An electrical connection between some current 
 carrying part of the armature, and the metal armature 
 frame. A "ground" is often caused by the insulating cov- 
 ering of the wire breaking down, thus allowing the wire to 
 come in contact with the iron core. 
 
 883. How do you test for this condition? 
 
 Ans. The simplest method of testing for a ground con- 
 sists in taking a lamp or voltmeter and connecting it as 
 
1222 Steam Engineering 
 
 shown in Fig. 546. Place one of the wires in contact with 
 the iron core, and the other in contact with the wire on 
 the armature. If the lamp lights, there is a connection be- 
 tween the wire and the core, and this should be removed. 
 
 884. How is an open circuit located? 
 
 Ans. Eeferring to Fig. 546, connect the commutator 
 as shown by the horizontal lines c. d. to some source of 
 supply. A rheostat is needed to adjust the current strength 
 until a suitable deflection of the needle is obtained between 
 adjacent commutator segments. Now, take two wires of 
 the voltmeter and test the voltage between the various ad- 
 jacent commutator segments. A reading will be obtained 
 between each two segments on one side of the commutator, 
 but on the side which contains the open coil no reading 
 will be obtained until connection is made between the two 
 segments to which the open coil is connected. At this 
 point the voltmeter will show practically the full voltage of 
 the supply current. 
 
 885. How do you locate a short circuit? 
 
 Ans. If the short circuit has come on while the arma- 
 ture was in use, it will locate itself by a burned out coil. 
 To test a new armature for short circuits we can proceed 
 in the same way as for open circuit, the only difference 
 being that, when we come to the short-circuited coil, we 
 shall obtain either none, or at least a reduced deflection. 
 
 886. What effect does an improper location of the 
 brushes have? 
 
 Ans. An improper location of the brushes will mani- 
 fest itself by a more or less severe sparking. If the brushes 
 are of the right dimensions the trouble can be remedied 
 by simply shifting them to the proper location, which is that 
 of least sparking. Brushes should be of such length, and 
 
Questions and Answers 1223 
 
 set at such an angle, that they come in contact with diamet- 
 rically opposite points on the commutator, with all bi-polar 
 machines. 
 
 887. How must the brushes be set in connection with 
 multipolar machines ? 
 
 Ans. This depends on the manner in which the armature 
 is wound. With a la> winding there are as many brushes 
 as there are pole pieces, and they must be equally spaced 
 around the periphery of the commutator. Provision must 
 also be made so that they can be shifted to the point of least 
 sparking. In wave wound armatures there may be only 
 two brushes, these being so spaced that they are separated 
 by an angle equal to the angle of separation of two ad- 
 jacent pole pieces ; for instance, with a four-pole field they 
 would be separated by an angle of 90°. 
 
 888. Is much shifting of the brushes necessary? 
 
 Ans. This depends very much on the design of the ma- 
 chine. With some of the older machines constant shifting 
 of the brushes is required with changes in the load, but with 
 the newer, and better machines this is reduced to a mini- 
 mum. 
 
 889. What is the ordinary size of a carbon brush? 
 Ans. It should be of such size that not more than 25 
 
 to 40 amperes per square inch of carbon are ever required 
 to flow through it. 
 
 890. How does inequality in field strength affect an ar- 
 mature ? 
 
 Ans. Wherever this exists there will be more lines of 
 force cut by the armature on one side than on the other, 
 thus causing a higher potential to be generated on one side 
 than on the other. The brushes will have to be set uneven 
 distances apart around the commutator, and useless cur- 
 
1224 Steam Engineering 
 
 rents will be set up in the armature windings, which will 
 not only cause a loss of power, but which will tend to over- 
 heat the armature. 
 
 SWITCHBOARDS. 
 
 Switchboards are made up of panels of slate on a frame 
 of angle iron. Each panel is designed for certain work so 
 that a description of the different kinds of panels is suffi- 
 cient. 
 
 The first board to consider is the D. C. outgoing line 
 board, served from D. C. generators. 
 
 D. C. Generator Panels. 
 
 Fig. 547 shows three generator panels, each of which is 
 regularly equipped, from a capacity of 250 to 6,500 am- 
 peres with 
 
 1 Carbon break or magnetic blow-out circuit breaker, 
 with telltale. 
 
 1 Illuminated dial ammeter with shunt. 
 
 1 Hand wheel and chain for operating rheostat. 
 
 1 Eeceptacle for voltmeter plug 
 
 1 S. P.-S. T. field switch.* 
 
 1 S. P.-S. T. main switch. 
 
 1 Eecording Watt-hour meter. 
 
 A rear view of these panels is shown in Fig. 552. 
 
 *S. T. means single throw. 
 
 D. T. means double throw, i. e., the switch has two sets 
 of clips and can be thrown into either of them. 
 
 S. P. means single pole. 
 
 D. P. means double pole, i. e., opens both sides of circuit 
 
 T. P. means triple pole, i. e., opens every conductor of 
 a 3-phase system. 
 
Switch Boards 
 
 1225 
 
 Fig. 547 
 d. c. generator panels 
 
1226 
 
 Steam Engineering 
 
 iSffiL 
 
 Fig. 548 
 
 BEAR VIEW OF FIG. 547 
 
Sivitch Boards 
 
 1227 
 
 The best practice puts a main switch at the machine, 
 so that the cables from machines to board may be cut off 
 from generator. It is also good practice to run the equal- 
 izer cable along in ducts from machine to machine without 
 carrying it to the board. 
 
 This equalizer connects the junctions of series field and 
 brush on all machines as shown in Fig. 549 ; the shunt coils 
 being omitted to simplify diagram. 
 
 It is best to place the main switch and equalizer switch 
 on a pedestal panel as shown in Fig. 550 for moderate ca- 
 
 Fig. 549 
 
 EQUALIZER 
 
 pacity and in Fig. 551 for 4,000 ampere (and larger) ma- 
 chines. The upper switch being the main switch. The 
 rear view of these large capacity pedestals is shown in Fig. 
 556. 
 
 A better view of the 4,000 ampere toggle operated main 
 switch is given in Fig. 553. The quick-break S. P.-S. T. 
 switch is illustrated in Fig. 554. 
 
 The field switch, Fig. 555, has a carbon break. Just 
 before the switch opens it makes contact with an extra clip 
 which puts a resistance on as a shunt around the field coils. 
 
1228 
 
 Steam Engineering 
 
 Fig. 
 
 Fig. 5 51 
 
 Fig. 550 
 
 pedestal panel for main and equalizer switches 
 
 small capacity 
 
 Fig. 551 
 
 main and equalizer switches for large capacity 
 
 If this were not done the fields would act like a kicking, 
 or spark coil and their insulation be damaged. 
 
 In Fig. 556 is seen the diagram of the panel shown in 
 Figs. 557 and 558 when capacity is 800 K. W. or under. 
 
 _ 
 
Switch Boards 
 
 1229 
 
 Fig. 552 
 bear view of fig. 551 
 
' 
 
 3230 
 
 Steam Engineering 
 
Switch Boards 
 
 1231 
 
 Fig. 557 shows the same panel when capacity is larger. 
 The panel at left is for 1,000 and 1,200 K. W., the next 
 for 1,500 K. W. and over. The cuts on right side show the 
 back and side view of the 1,500 K. W. panel. 
 
 U 
 
 Type C Form K 
 C/rcu/t Breaker 
 
 Mo/hBus Bat 
 
 - TID /4mmet er 
 Potent/a/ Bus Wire Support 
 
 ■ Pheostot r/onc/whee/ 
 
 F/e/d Stv/tch (on. 
 ~ Generator Porie/ on/yj 
 
 ■ Potent/a/ Peceptac/e 
 
 • Card r/o/der 
 Rheostat Cha/n \ 
 
 Operating Afechon/sm) 
 
 - Z /ght/n$ Switch 
 Type QB Forno^ Stv/tch 
 
 -Pecord/ng Wattmeter 
 Wot tmeter Pes is tone e 
 
 i*- - /e - -m 
 
 Fig. 556 
 
 CONSTRUCTION OF FIG. 547 FOR SMALL CAPACITY 
 
 The scheme of electrical connections for panel of Fig. 
 547 is shown in Fig. 558. 
 
 D. C. Feeder Panels. 
 
 A set of feeder panels for one feeder each is shown in 
 Figs. 559 and 560, a panel for two feeders with separate 
 switches and one ammeter reading sum of both currents is 
 
1232 
 
 Steam Engineering 
 
 O^SSpPSTTU^p 
 
 & 
 
 vl to 
 
 
 u — > a, ^ 4. — :$ — »i 
 
 Fig. 557 
 construction of fig. 547 for large capacity 
 
 
Switch Boards 
 
 1233 
 
 shown in Fig. 561, while Fig. 562 has an instrument and 
 switch for each circuit. 
 
 Fig. 563 gives the diagram of these feeder panels and 
 Fig. 564 gives the electrical connections. 
 
 BOCM l/?e 
 
 fuse |J ! 
 
 ritlZT 1 To A 'a rrr > &*tt 
 
 &es/s LoncQ ■ 
 
 t. /gr>L /ng S*> Cc ft 
 To Center Stud 
 
 Of~L/gr>ling Sw/LcrJ 
 onoc/jocent Pane/ j 
 
 7^, 
 CLO t ion f'gnts (J 6 
 
 1? 
 
 Positive Bus 
 Equalizer Bus 
 
 
 -Lightning Generator 
 'Arrester 
 
 Fig. 558 
 d. c. generator panels 
 
 With panels as described the way to throw a generator 
 in parallel with other generators already running, the fol- 
 lowing procedure should be followed : 
 
1234 
 
 Steam Engineering 
 
 Fig. 559 
 d. c. feeder panels 
 
Switch Boards 1235 
 
 First — Close main and equalizer switches (on pedestal 
 or panel near machine). 
 
 Second — Close field switch (on panel). 
 
 Third — Close circuit breaker. 
 
 Fourth — Insert potential plug in receptacle and regulate 
 voltage. 
 
 Fifth — When the proper voltage is obtained, close the 
 other main switch (on panel). 
 
 All the above applies to the distribution of the output of 
 rotary converters, but as they have some peculiarities they 
 will be considered later. 
 
 A. C. Generator Panel. 
 
 The panel in Fig. 565 contains: 
 
 1 Horizontal edgewise balanced three-phase indicating 
 wattmeter, arranged for reading both the kilowatts output 
 and the wattless component. 
 
 1 Horizontal edgewise ammeter. 
 
 1 Horizontal edgewise volt-meter. 
 
 1 Balanced three-phase induction recording wattmeter. 
 
 1 D. P. D. T. potential reversing switch for the indi- 
 cating wattmeter. 
 
 1 Four-point receptacle for synchronizing connections. 
 
 1 Hand-wheel and chain operating mechanism for field 
 rheostat. 
 
 1 S. P. S. T. carbon break field switch with discharge 
 clips. 
 
 1 D. P. D. T. engine governor control switch. 
 
 1 T. P. S. T. oil switch. 
 
 1 Current transformer for instruments. 
 
 2 Potential transformers for instruments. 
 
 The functions of the instruments are to indicate the 
 current, voltage and kilowatts output of the generator, and 
 the wattless component of the output. For indicating the 
 
1236 
 
 Steam Engineering 
 
 Fig. 560 
 rear view of fig. 559 
 
Switch Boards - 1237 
 
 wattless component, the potential coil of the indicating 
 wattmeter is wired to the potential reversing switch, which 
 is normally held by a spring so as to connect the instrument 
 up as a wattmeter. By throwing the switch against the 
 spring into the other position the potential coil is reversed, 
 and the instrument reads the wattless compotent, giving a 
 ready means of detecting any currents flowing between the 
 alternators which are operating in parallel. 
 
 The engine governor switch is to operate the motor which 
 temporarily controls the governor on engine, or turbine 
 when their speeds are being altered to bring two alternators 
 into synchronism, or adjusting the division of load when 
 operating in parallel. 
 
 The generator oil switch has no automatic overload re- 
 lease, as it is important to keep the generator in service dur- 
 ing heavy short circuits caused by trouble on the transmis- 
 sion lines. When such short circuits occur, the generators 
 are immediately relieved by the opening of the automatic 
 line switches. 
 
 The diagrams for connecting up generator panels accord- 
 ing as transformers are, or are not used will be found in 
 Figs. 566 and 567. 
 
 A. C. Outgoing Panel. — The panel on left of Fig. 568 
 contains : 
 
 3 Horizontal edgewise ammeters. 
 
 1 T. P. S. T. oil switch, with overload release. 
 
 3 Current transformers. 
 
 Three ammeters — one for each phase — are furnished for 
 each line, to facilitate the detection of unbalancing due to 
 open circuits or leakage. With balanced loads, the amme- 
 ter pointers should show equal deflections under normal 
 conditions. As the ammeters are arranged in a perpendicu- 
 
1238 . 
 
 Steam Engineering 
 
 
 Ei-. vte 
 
 Fig. 561 
 two feeder d. c. panel 
 
 Fig. 562 
 1,200 d. c. ampere, railway feeder panel for two circuits 
 
Switch Boards 
 
 1239 
 
 n 
 
 LL 
 
 «-€=3-esCT>Q Q 
 
 <a c& 
 
 4 
 
 N 
 
 Of 
 
 
 i, 
 
 So 
 
 } 
 
 ^ 
 
 3 
 
 S3 
 
 <T> 
 
 
 h 
 
 Ct 
 
 i 
 
 ± 
 
 c© 9*mmm<mm 
 
 ^mmmKEm 
 
 313 
 
 Fig. 563 
 
 CONSTRUCTION OF FIGS. 559 AND 562 
 
1240 
 
 Steam Engineering 
 
 ■vQ&Qflr^^r 
 
 
 L --Qi 5 
 
 '^'o 
 
 -<y 
 
 sQSiSJLQr* 
 
 ■N.-U 
 
 § 
 
 <* 
 
 * 
 
 S 
 
 
 'I 
 
 ¥|W" f 
 
 
 
 &5 
 
 -Oi 
 
 r<y 
 
 
 
 sSlQSlSlr^ So ~ 
 
 
 T3 
 
 4 
 
 Fig. 564 
 three styles of d. c. feeder panels 
 
1241 
 
 Fig. 565 
 a. c. generator panel 
 
 lar row' any variation in the deflection of the pointers is 
 readily detected. i 
 
 The current transformers serve to operate the ammeters 
 ^nd the automatic release on oil switches. 
 
 _^ 
 
1242 
 
 Steam Engineering 
 
 c***>r 
 
 Case JO "otnerwise as Case /f* 
 
 A TGBonefm'th Tyjoerfbrmh", Switch AT G /tone/ with TyjoeFfbrrrt /C3*/ /tch 
 
 ™^~ Main w ^~ mm ■— —^^— 
 
 ffesistona 
 | j 7ermina/ J&/oc/c 
 
 on OH Switch 
 
 ffesistonce 
 
 rb/t/neter. 
 Bo/ance 3Phase 
 'tfecortfino/yattmeter 
 
 8vxs 
 
 Synchron/x/np Suse9 
 
 Tbfrneroency 
 (Governor on 7urbine 
 
 Oi/ Switch Operating 
 //Buses on Pone/ 
 
 Ground 3us 
 
 Potentio/ 
 Transformer 
 
 indicating 
 
 'Wottmeter 
 
 » To/tss&rv FtC'ttr Bu4 
 \7ripCoii 
 
 '~+so Emergency 
 Gover/7oron T&r&ne 
 ■Ammeter 
 
 ^Current 
 Transform*? 
 
 g3 Start /no 
 pfo] Runninp 
 5ynchran/*.inp P/c/gs 
 
 Connections for 
 the Engine Governor Contro/ Afotor 
 and Syy/ 'ten when Su/>p/ied 
 
 Fig. 566 
 a. €. generator panel without step-up transformer* 
 
 k. 
 
Switch Boards 1243 
 
 The panel on right of Fig. 568 has but one ammeter and 
 merely has the handle for operating the oil switch. The 
 actual switch being in a brick compartment at rear of 
 panel. The overload relay (3-pole) which trips the oil 
 switch is at base of panel. 
 
 Fig. 569 gives the electrical connections of panels in 
 Fig. 568. 
 
 The swinging bracket of Fig. 570 contains a synchro- 
 nism indicator, two lamps for synchronizing (practically 
 a duplicate set of synchronizers) and a voltmeter for the 
 station exciter generator.* 
 
 To use the synchronism indicator put one plug in on 
 panel of a generator which is running, and the other plug 
 in the panel of the generator which is starting. 
 
 Fig. 571 shows a complete switchboard of one generator 
 panel in center, a panel for one outgoing line on the right, 
 an exciter panel on left, with the swinging bracket on ex- 
 treme left. 
 
 Such a switchboard would be extended towards the right 
 indefinitely, as more lines were put on the station, by the 
 addition of more outgoing line panels. 
 
 Exciter Panel. — Each exciter panel is equipped with : 
 
 1 Thomson feeder type ammeter. 
 
 1 Hand-wheel for operating rheostat. 
 
 1 Two-point potential receptacle connected to voltmeter. 
 
 1 S. P. S. T. positive lever switch, with fuse mounted 
 back of panel. 
 
 One Exciter Panel in every switchboard is furnished 
 with the following additional switches: (as in Fig. 572.) 
 
 *D. C. Generator furnishing current for field of alter- 
 nator. 
 
Case A 
 ATG r*a/tB/ with 7y/Def~fbrm //j Switch 
 
 ■" MaSn 
 
 nes/ 
 Suv/tch^ 2s 
 
 Mormo/iy in 
 \Lower C//ps 
 
 rfmmete/ 
 Yo/tnoeter 
 
 Res/stance 
 
 Green Lamp 
 (Open) 
 
 fbtentia/ 
 frons formers 
 fuse 
 
 Case j3 otherw/se as Case /?' 
 >9TG Pane/ with} 7ypef~fdrm KSwtcH 
 
 Coup//n(? 
 
 /25Vo/t DC. Buses 
 on (?// Switch 
 
 :± /ndicat/ng Wattmeter 
 
 J 7ermino/B/ocA 
 ' On O// Switch 
 
 Wattmeter^, 
 
 Synchron/z/ngP/ugs 
 Starting/ 
 
 IPoj 
 
 > 
 
 ffunn/ng 
 Synchronizing Buses 
 
 7d Emergency 
 Covernor on Turbine 
 
 — -v 
 
 Oi/Sw/tch Operot/na 
 3 uses on Panei^ 
 
 Ground Bus 
 fW^-^A^-VS^frunsformer 
 
 =6 
 
 ^ 
 
 7a/%s/t/Ve 
 £jrc/ter&us 
 
 im-i 
 
 in 
 
 B 
 
 (3 
 
 CxciterBu3 
 \1\7r,pCo,/ 
 Tbfnoergency 
 Governor on7i/rbtr* 
 
 £ 
 
 =B3 
 
 EB 
 
 1 wa^v I ***** I 555^ 
 
 rAA^pySA-fAAA^ 
 
 Current Transformer 
 
 To Positive 
 fxc/terBus 
 
 -X 
 
 [i 
 
 5*v/£c/? 
 
 Connections for thefng/ne 
 Governor Con troi Motor 
 and Sw/tch when Supp//ed 
 
 /fitematmg Current Generator 
 ^mmm-Bus 
 
 ALTERNATING CURRENT GENERATOR PANEL FOR GENERATOR WITH STEP-U* 
 TRANSFORMER 
 
 Fig. 567 
 
 a. c. generator panel for generator with step-up 
 
 transformer 
 
Switch Boards 
 
 1245 
 
 Fig. 568 
 a. c. outgoing line panels 
 
 2 S. P. S. T. lever switches, with fuses back of panel, 
 for the control of station lighting and auxiliary circuits. 
 
1246 
 
 Steam Engineering 
 
 Cose /fWrf/bne/ 
 with Type ffdrm'Hs Switch 
 
 Switches 
 
 Switch — »| 
 Ammeters 
 
 Case *3 'otherwise asCase'/?A Tfthnef 
 with Type FForm ft Switch 
 
 p— — — *^ — 
 
 Coup/mf' 
 
 Overioad 
 fie/ay 
 
 rledLannp- -j^fc — 
 
 SMtch^XX*^ 
 
 Greer? /.a/r?p 
 (C/osecO 
 
 TerminaJ Biock 
 on 0/7 Switch 
 
 ^Current 
 Transformer 
 
 
 # 
 
 32j !: 
 
 £>// Switch operating 
 ffuses on Pane/ 
 
 TripCoi/s 
 
 Outgoing line 
 
 I ? I ?l y^te&c Detectors 
 
 Cho/ret 
 Coi/s 
 
 Hi 
 
 S ? ! Lightning 
 %% Arresters 
 
 LJJ 
 
 Fig. 569 
 a. c. outgoing line panel 
 
Switch Boards 
 
 1247 
 
 On the frame of each exciter there are required the 
 following switches, mounted on a common slate base: 
 
 1 S. P. S. T. negative lever switch. 
 
 1 S. P. S. T. lever switch for equalizing. 
 
 The exciter panels are designed single pole, i. e., only 
 the positive leads of the generators are connected to the 
 switch-board panels and only the positive bus-bar is mounted 
 back of them. The negative and equalizer leads are con- 
 
 Fig. 570 
 
 SYNCHRONISM INDICATOR AND EXCITER VOLTMETER ON SWINGING 
 
 BRACKET 
 
 nected through their switches to the negative and equalizer 
 bus-bars, which are placed under the floor near the exciters. 
 With the bus-bars of opposite polarity so widely separated 
 there is practically no chance of short circuit of the ex- 
 citer connections. The positive field leads of the alternators 
 are carried to the panels, while the negative field leads are 
 permanently connected to the negative exciter bus-bar. 
 
 Fig. 573 will give the electrical connections of an exciter 
 panel. 
 
1248 
 
 Steam Engineering 
 
 Fig. 571 
 
 main station switchboard for one a. c. generator and one 
 outgoing line 
 
 The blower motors running the blowers which cool trans- 
 formers are of the 3-phase induction type, or D. C. shunt 
 motors. 
 
 k 
 
Switch Boards 
 
 1249 
 
 Fig. 572 
 
 EXCITER PANEL AUXILIARY LIGHTING SWITCHES ON SUB-BASE 
 
 The D. C. motors are started by the regular starting box, 
 Fig 574. 
 
 The current to an induction motor is controlled by a 
 switch like Fig. 575. if from auxiliary low voltage buses, 
 
r 
 
 1250 
 
 Steam Engineering 
 
 Buses 
 /feceptac/e 
 
 This fuse anct Switch 
 byCus tomer 
 
 ~Bu3e9 
 
 Fig. 573 
 
 EXCITER PANEL 
 
Switch Boards 
 
 1251 
 
 or from an oil switch on a panel like Fig. 576, if full sta- 
 tion voltage is used. 
 
 The actual starting is done by a switch as in Fig. 577, 
 which is between secondaries of transformers or reactance 
 coils and the induction motor. 
 
 Fig. 578 shows connections of an induction motor to 
 main buses, using an oil switch and a starting switch. 
 
 Fig. 5 74 
 
 Fig. 574 
 
 starting panel for d. c. blower set 
 
 Fig. 575 
 
 main switch panel for a. c. blower set 
 
 The operation of several sub-stations on a single line is 
 generally recognized as good practice. 
 
 To insure continuity of service in the event of line 
 trouble, it is expedient to sectionalize the line at every sub- 
 
 ^ 
 
1252 
 
 Steam Engineering 
 
 1 1 
 
 Fig. 576 Fig. 577 
 
 Fig. 576 
 
 oil switch a. c. panel for incoming line 
 
 motor driving exciter or a. c. side of rotary 
 
 Fig. 577 
 induction motor or rotary starting panel 
 
Switch Boards 1253 
 
 station that is located at an intermediate point of the line. 
 This sectionalizing is accomplished at each intermediate 
 station by carrying the incoming line to the bus-bars 
 through the air brake disconnecting switches which are in- 
 stalled in connection with the arresters, and by carrying the 
 outgoing line through an oil switch. In case of line trouble, 
 this arrangement allows all sections of the line between the 
 generating station, and any section on which the trouble 
 occurs to be operated continuously. The power is auto- 
 matically cut off from the section in trouble by an oil switch 
 in the outgoing line panel equipment of the sub-station at 
 the generating station end of the section, so that the air 
 brake disconnecting switches in the sub-station at the other 
 end of the section need never be opened under load. 
 
 When duplicate transmission lines are used, two incom- 
 ing line panels and two outgoing line panels are recom- 
 mended for each intermediate sub-station. The installa- 
 tion of these individual panels facilitates the disconnection 
 of either line of any section and the continuance of the 
 service over the other line of the section without any in- 
 terruption. 
 
 Arc Switchboards. — Fig. 579 shows a general view of the 
 Thomson-Houston plug switchboard. A rear view of the 
 same board is given in Pig. 580. 
 
 In a standard panel the number of horizontal rows of 
 holes equals one more than the number of generators. The 
 vertical holes are always twice the number of generators. 
 The positive leads of the generators are attached to the 
 binding posts on the left-hand ends of the horizontal con- 
 ductors. The negative leads are connected to the corre- 
 sponding binding posts at the right-hand end of the board. 
 
 The positive line wires are connected to the vertical straps 
 
1254 
 
 Steam Engineering 
 
 Case s9 ' Cose 3 othermse <rs Cose 'A* 
 
 ATI terr>e/w/t/i7yjoerrorm HjSwitch /?TI fane/ with Type f form ft 'Switch 
 
 fases^ 
 
 
 
 
 
 Trip 
 . So*' 
 
 [C~ 
 
 l >AAAr"L^vV I *tf*J 
 
 Current Transformer 
 
 fled lamp 
 (C/osecfJ 
 
 • Green lamp 
 
 (OpenJ O// Switch 
 
 BBS t Opera t/no Buses 
 on/Zone/ 
 
 1 
 
 uy 
 
 Main Transformer 
 
 Switch 
 
 /nofuction Motor 
 
 Fig. 578 
 induction motor panel 
 
Switch Boards 
 
 1255 
 
 on the left, and the negative wires to the similar straps on 
 the right of the center panel. 
 
 If a switchboard plug be inserted in any of the holes of 
 the board, it puts the corresponding generator lead and the 
 line wire in electrical connection, but as the positive line 
 wires are back of the positive generator leads only, it is 
 
 Fig. 579 
 
 not possible to reverse the connection of the line and the 
 generator accidentally, though any other combinations of 
 lines and generators can be made readily and quickly. 
 
 The holes of the lower horizontal rows have bushings 
 connected with the vertical straps only. Plugs connected 
 in pairs by flexible cable and inserted in the holes put the 
 corresponding vertical straps in connection as needed, and 
 
1256 
 
 Steam Engineering 
 
 normally independent lines may be connected when one 
 generator is required to supply several circuits. 
 
 Lines and generator leads may be transferred, while run- 
 ning, by the use of these cables, without shutting down ma- 
 chines or extinguishing lamps. 
 
 The standard boards are arranged for an equal number 
 of generators and circuits, but special boards for any ratio 
 of circuits to generators can be built, 
 
 
 * B*)B vB • 191 
 
 I|| H H 
 
 
 
 
 IliBiwfl 
 
 - 
 
 
 
 JK 
 
 Fig. 580 
 
 As it is sometimes convenient, even in small plants, to 
 interchange lines and generators without shutting down 
 machines, a special transfer cable with plugs has been de- 
 vised. This serves the same purpose as the regular trans- 
 fer cable, but the plugs may be used in any of the holes of 
 the switchboard, as they are insulated, except at the tip, 
 and when inserted connect with the line strips only. 
 
 The transfer of circuits from one generator to another 
 gives trouble to dynamo tenders who are not familiar with 
 the operation of these plug switchboards. Fig. 581 illus- 
 
Switch Boards 
 
 1251 
 
 e- 
 
 o 
 o o 
 
 C) o o 
 
 • o o 
 
 o o o 
 
 o o 
 
 _2 3_ 
 
 Tt- 
 
 -e — © 
 
 -© — © 
 
 o o o o 
 o o o o 
 
 
 
 
 E> 
 
 
 
 
 
 
 
 1 Ik 4 
 
 > o 
 
 r\ 4 
 
 
 
 
 I , ' 
 
 4h -4 
 
 
 w 
 
 /^-\ 
 
 w 
 
 o 
 
 1 1 
 
 1 * 
 
 3 
 
 W V \J , 
 
 o o o 
 
 o o o 
 
 o 
 
 o 
 
 3 
 
 
 O o 
 
 o o o 
 
 o 
 
 o 
 
 
 Fig. 581 
 
1258 
 
 Steam Engineering 
 
 trates the successive steps for transferring the lamps of 
 two independent circuits from two generators to one with- 
 out extinguishing the lamps on either circuit. 
 
 This process is a very simple example of switchboard 
 manipulation, but illustrates the method used for all com- 
 binations. 
 
 Fig. 582 
 
 The location of plugs is shown by the black circles, which 
 indicate that the corresponding bars of the horizontal and 
 vertical rows are connected. 
 
 Circuits No. 1 and No. 2, running independently from 
 generators No. 1 and No. 2, respectively, are to be trans- 
 ferred to run in series on generator No. 2. 
 
 In A, Fig. 581, are two circuits running independently. 
 In B the positive sides of both generators and circuits are 
 connected by the insertion of additional plugs. 
 
 At C both generators and circuits are in series. 
 
Switch Boards 1259 
 
 Next insert plugs and cables as shown in D. Then 
 withdraw plugs on row corresponding to generator No. 1, 
 and the circuits No. 1 and No. 2 are in series on machine 
 No. 2, and machine No. 1 is disconnected as at E. 
 
 Similar transfers can be made between any two circuits 
 or machines/ and by a continuation of the process additional 
 circuits can be thrown in the same machine. The transfer 
 of the two circuits to independent generators is accom- 
 plished by reversing the process illustrated. 
 
 Fig. 582 shows the wiring and connections of the West- 
 ern Electric Co/s series arc switchboard. At the top of 
 the board are mounted six ammeters, one being connected 
 in the circuit of each machine. On the lower part of the 
 board are a number of holes, under which, on the back of 
 the board, are mounted spring jacks to which the circuit 
 and machine terminals are connected. For making con- 
 nections between dynamos and circuits, flexible cables ter- 
 minating at each end in a plug, are used; these are com- 
 monly called "jumpers." The board shown has a capacity 
 of six machines and nine circuits, and with the connec- 
 tions as shown, machine 1 is furnishing current to circuit 1, 
 machine 2 is furnishing current to circuits 2 and 3, and 
 machine 4 is furnishing current to circuits 4, 5 and 7. In 
 connecting together arc dynamos and circuits the positive 
 of the machine (or that terminal from which the current 
 is flowing) is connected to the positive of the circuit (the 
 terminal into which the current is flowing). Likewise the 
 negative of the machine is connected to the negative of the 
 circuit. Where more than one circuit is to be operated from 
 one dynamo, the negative of the first circuit is connected 
 to the positive of the second. At each side of the name plate 
 (at 3, for instance) there are three holes. The large hole 
 is used for the permanent connection, while the smaller 
 
1260 Steam Engineering 
 
 holes are used for transferring circuits, without shutting 
 down the dynamo. Smaller cables and plugs are used for 
 transferring. If it is desired to cut off circuit 5 from 
 machine 4, a plug is inserted in one of the small holes at 
 the right of 4, the other plug being inserted in one of the 
 holes at the left of 7. Circuit 5 would now be short-cir- 
 cuited, and the plug in the + of 5 can now be transferred 
 to the permanent connection in the + of 7, and the cords 
 running to 5 removed. If it is desired to cut in a circuit, 
 say circuit 6 onto machine 2, insert a cord between the — of 
 circuit 2 and the + °f 6 and another between the — of 6 
 and the + of 3. Now pull the plug on the cord connect- 
 ing the — of 2 and the + of 3 and insert the permanent 
 connections. In cutting in circuits, if they contain a great 
 number of lights, a long arc may be drawn when the plug 
 between 2 and 3 is pulled, and it is sometimes advisable to 
 shut down the machine when making a change of this kind. 
 
 TRANSFORMERS. 
 
 When a current passes through a conductor it creates 
 around it a field of force. If a second wire, or conductor 
 lies parallel to the first during the time that the field of 
 force is being built up, electromotive force will be impressed 
 upon it, and will be of such polarity that the current pro- 
 duced by it will be in a direction opposite to the direction 
 of the original current. The transformer contains two 
 coils of wire insulated from each other. 
 
 In Fig. 583 is shown the principle upon which the trans- 
 former used in alternating current work operates. Two 
 separate coils of wire are wound on a ring of laminated 
 iron. One of the coils contains a number of turns of fine 
 wire, while the other contains only a few turns of large 
 
 fis&^ 
 
Transformers 
 
 1261 
 
 wire. When an alternating current is sent around the coils 
 of fine wire, generally called the primary, a current will be 
 induced in the coil of heavy wire, or secondary. The amount 
 of current induced in the larger wire will be relatively 
 greater in amperes, and less in potential than that of the 
 fine wire circuit. This ratio is almost entirely dependent 
 upon the relative number of turns existing between the 
 large and the small wires. To illustrate, suppose we had 
 a current of 10 amperes at a pressure of 1,000 volts in the 
 
 Fig. 583 
 
 primary, and there were ten times as many turns of wire 
 in the primary coil as in the secondary, then we would get 
 a current of 100 amperes at a pressure of 100 volts in the 
 secondary coil. This same relation would hold true what- 
 ever the ratio between the number of turns on the two 
 coils might be. In Fig. 584 is shown a core of iron hav- 
 ing on one end a primary coil connected to a battery. On 
 the other end of the core is another coil connected to the 
 ends of which is an incandescent lamp. By making and 
 breaking the battery circuit the lamp may be made to flash 
 
1262 
 
 Steam Engineering 
 
 up, due to the great voltage induced in the secondary coil. 
 This is a good thing to remember when working with a 
 dynamo or motor. Do not quickly break the shunt field 
 connection, as the increased voltage due to the current in- 
 
 Fig. 584 
 
 duced by the field magnet when the circuit is broken is 
 liable to puncture the insulation and necessitate the re- 
 winding of the field coil. 
 
 Eeferring to Fig. 585, A Tepresents the alternator, B its 
 brushes and D and E the mains to the transformer H. This 
 
 Fig. 585 
 
 DIAGRAM OF ALTERNATOR, LINE, TRANSFORMER, AND SECONDARY 
 
 CIRCUIT 
 
 transformer consists of a core of iron C on which are two 
 windings. The coil P is called the primary, and is con- 
 nected to the main from alternator. The other coil S is 
 called the secondary, and to it the load is connected. 
 
Transformers 
 
 1263 
 
 Fig. 586 
 transformer coils in wound, bound and taped stages of 
 completion 
 
1264 
 
 Steam Engineering 
 
 Whatever the voltage of alternator A., that of the sec- 
 ondary circuit F. L. G. will be three-eighths of it because 
 there are eight turns on the primary and three turns on the 
 secondary. The power in the secondary circuit is practi- 
 cally the same (minus the losses) as is given out by the al- 
 ternator,, hence the primary current is low and wire is small. 
 The secondary current is large and the wire is large. 
 
 Since one kilowatt can be a combination of a large cur- 
 rent and small pressure, or small current and large pres- 
 
 Fig. 587 
 
 COILS, AIR DUCTS AND SEPARATORS FOR TRANSFORMER 
 
 sure, it is evident that the transformer simply transfers the 
 power, and transforms the voltage, and indirectly the cur- 
 rent. 
 
 This transformer (Fig. 585) lowers the voltage and is 
 called a step down transformer. 
 
 When the secondary is connected to the alternator, the 
 transformer raises the voltage and is called a step up trans- 
 former. 
 
 The coils of a transformer must be very well insulated. 
 After winding they are bound, to keep them in shape, and 
 
Transformers 1265 
 
 then wound with linen tape, or varnished cambric cloth. 
 Fig. 586 shows a coil in the three stages of completion. 
 
 In Fig. 587 is shown a set of completed coils, together 
 with the ventilating ducts and mica barriers sufficient for 
 one leg of a transformer. 
 
 Fig. 588 shows the two legs of a transformer, which form 
 its iron core, each over half filled with coils. The coil is 
 made of sheets of soft iron. 
 
 Fig. 589 shows the manner in which the coils are some- 
 times bound up to be placed in transformer as one coil. 
 
 Exciting Current. — The Exciting Current, being also 
 called by various other names, such as leakage current, open 
 circuit current, and magnetizing current, is a very impor- 
 tant factor. 
 
 In order that a transformer may be ready to do its work 
 it is always connected to the line. This means that the 
 primary coil is always magnetizing the core, if no current 
 is drawn from the secondary. 
 
 This steady flow of current to excite the primary is the 
 price we have to pay for having the transformer continually 
 ready for service. 
 
 A transformer should therefore never be left on a line 
 unless it is needed. 
 
 Efficiency of Transformers. — The losses in transformers 
 are less than any other piece of electrical machinery or ap- 
 paratus; 98 per cent of the intake being delivered in the 
 larger sizes as used in railroad sub-stations or power houses, 
 when fully loaded. Unfortunately they lose about the same 
 amount of power at all loads. 
 
 A. 100 K. W. transformer loses 2 K. W. at full load, its 
 efficiency is then 98-^100=0.98. At half load it loses 
 2 K. W., but is only carrying 50 K. W., so (its losses are 
 
Fig. 5S8 
 
 INTERIOR CONSTRUCTION OF AN AIR BLAST TRANSFORMER 
 
 
 
 1 
 1 ,s 
 
 1 • ? 
 
 Fig. 589 
 set of coils made up ready to be placed in transformer 
 
Transformers 
 
 1267 
 
 now equivalent to 4 K. W. on a 100 K. W.) its efficiency 
 is 48-7-50=0.96. 
 
 Fig. 590 
 air blast transformer 
 
 At quarter load it takes in 25 K. W., loses 2 K. W., so 
 its efficiency is 23-^25=0.92. 
 
 By clever designing transformers are built to be most 
 efficient at three-quarters load. They are a little less effi- 
 
 ^ 
 
1268 Steam Engineering 
 
 cient at half, and full loads, and still less at quarter load, 
 and quarter overload, but never fall below 95 per cent. 
 
 Cooling Transformers. — Small transformers hung up on 
 poles are cooled by surface radiation only. 
 
 Medium sized ones are filled with oil. This conducts the 
 heat to the iron case, and also acts as an insulator. 
 
 The oil will also flow in and fill .a break in the cloth, or 
 mica after a puncture. 
 
 Air blast avoids the danger of oil in case of fire or flame 
 due to short circuits. They are cheap as a transformer may 
 be much more heavily loaded when cooled by the air blast, 
 and the blower only consumes 1-10 of 1 per cent of the full 
 load output of transformer. 
 
 Fig. 590 shows the interior construction of an air blast 
 transformer and Fig. 591 shows how they are installed. 
 
 Water cooled. These are the smallest and cheapest trans- 
 formers to build, but not so cheap to run as is the air blast. 
 
 The cases are filled with oil which absorbs heat from coils. 
 Pipes are run through the oil, in which cold water is cir- 
 culated. 
 
 In a water power plant where the head of water would 
 render pumps unnecessary the water cooled type would cer- 
 tainly be the best. 
 
 Auto-Transformers. — These are only applicable to cer- 
 tain cases. 
 
 The idea is shown in Fig. 592. The same coil of wire 
 A to B is used as primary and secondary, the whole being 
 the primary, and portions as C to D, D to E, or C to E 
 being used as secondary. 
 
 They are only used where the primary voltage is fairly 
 low and the secondary voltage is not less than one-fifth of 
 the primary voltage. 
 
OQ 
 M 
 W 
 3 
 05 
 O 
 
 OQ 
 
 « 
 
 H 
 H 
 
 - 
 * 
 
 <j 
 
 fa 
 
 o 
 
 fc 
 
 o 
 
 t-t 
 H 
 "3 
 
 H 
 GO 
 
1270 Steam Engineering 
 
 They are used instead of resistances to start A. C. motors. 
 
 Allis-Chalmers Power Transformers. — Transformers for 
 use on power transmission lines are made by Allis-Chalmers 
 Company in three different types, depending on the method 
 used for cooling. These types are as follows : oil- filled self- 
 cooled (0. F. S. C.) ; oil-filled water-cooled (0. F. W. C.) 
 and air-blast. In the first the heat is carried off by radia- 
 tion, and conduction from the case; in the second by the 
 circulation of water through coiled pipes immersed in the 
 oil; and in the third by currents of air forced through the 
 
 B E 
 
 Fig. 592 
 diagram of auto-transformer or compensator 
 
 transformer. Oil-insulated transformers are used in the 
 great majority of cases, and the question as to whether they 
 shall be self-cooled or water-cooled is determined largely by 
 the size of the units, and the available supply of cooling 
 water. 
 
 Self-cooled transformers are built in sizes up to 250 K. 
 V. A. (kilo volt- amperes). Above this size the external 
 surface of the case is not sufficient for the effective radia- 
 tion of the heat unless the case is made abnormally large. 
 Fig. 593 shows a standard transformer of this type. 
 
 Water-cooled transformers, Fig. 594, are made in sizes 
 from 100 K. V. A. up. Water is circulated through a coil 
 of seamless copper tubing immersed in the oil in the upper 
 
Transformers 
 
 1271 
 
 part of the tank, and the heat is effectively carried off. 
 Wherever water is available and not expensive this method 
 is preferable to air cooling, even for comparatively small 
 
 9 Fig. 593 
 
 allis-chalmers oil-filled self-cooled transformer, 60 cycle, 
 170 k. w., 20,000 to 2,300 volts 
 
 transformers, as it permits operation at lower temperatures, 
 and allows more margin for overloads. 
 
 Air-blast transformers are made in sizes from 75 K. V. 
 A. up. Cooling is effected by placing the transformer over 
 
 ^ 
 
Fig. 594 
 
 ALLIS-CHALMERS OIL-FILLED WATER-COOLED TRANSFORMER, 25 CYCLE, 
 
 500 k. w., 20,000 to 375 volts 
 
 _ 
 
Transformers 1273 
 
 an air chamber in which a pressure of air is maintained 
 by motor driven fans ; currents of air passing up around the 
 transformer carry off the heat. In this type oil cannot be 
 used for insulating purposes, and 25,000 volts is the high- 
 est pressure for which it is advisable to build them. 
 
 Much has been written about the relative fire risks of 
 air-blast and oil-filled transformers, but this is a matter 
 that depends as much on surrounding conditions, and the 
 location of the transformers as upon the construction. The 
 air-blast transformer contains a small quantity of inflam- 
 mable matter as compared with the oil-filled transformer, 
 but this material is much more easily ignited. A break- 
 down in an air-blast transformer is usually followed by 
 an electric arc that sets fire to the insulating materials, and 
 the flame soon spreads under the action of the forced cir- 
 culation of air. Although the fire is of comparatively short 
 duration, it is quite capable of ignitng the building unless 
 everything near the transformers is of fire-proof construc- 
 tion. 
 
 The chance of an oil-filled transformer catching fire on 
 account of any short circuit in the windings is extremely 
 small, because oil will burn only in the presence of oxygen, 
 and, since the transformer is completely submerged in oil, 
 no air can get at it. Moreover, the oil used in transfor- 
 mers is not easily ignited ; it will not burn in open air un- 
 less its temperature is first raised to about 400° P. In 
 fact, the chief danger of fire is not that the oil may be 
 ignited by any defect or arc within the transformer, but 
 that a fire in the building in which the transformers are 
 installed may so heat the oil as to cause it to take fire. 
 
 General construction. — The general construction of the 
 coils and core is much the same in all three types, regard- 
 less of the method of cooling. All transformer coils are 
 
1274 
 
 Steam Engineering 
 
 Fig. 595 
 
 PARTLY ASSEMBLED 25 CYCLE, 500 K. W., 20,000 TO 375 VOLT 
 TRANSFORMER 
 
Transformers 
 
 1275 
 
 Fig. 596 
 
 CORE AND COILS, 500 K. W., 20,000 TO 375 VOLT TRANSFORMERS 
 
r 
 
 1276 
 
 Steam Engineering 
 
 wound with double cotton covered strip copper, one turn 
 per layer, with fullerboard insulation, in addition to the 
 cotton covering, between turns. Exceptions to this con- 
 
 Fig. 597 
 struction are made only when the size of the conductor is 
 such as to render the use of copper strip impracticable, and 
 in such cases the coils are wound with round, double-cotton 
 
 fi£tt« 
 
Transformers 1277 
 
 covered wire with few turns per layer, so that the voltage 
 between the layers is kept within safe limit j. The core is 
 built up of steel sheets 0.0014 inch thick. In the larger 
 sizes, space blocks are placed every few inches in the core, 
 thus providing ducts through which oil can circulate and 
 carry off the heat. Also, in assembling the coils, spaces are 
 formed between the coil sections, and between the coils and 
 core, so that all parts are in contact with a free circulation 
 of oil. Fig. 595 shows a core partly built up and Fig. 596 
 core and coils completely assembled. Fig. 597 shows the 
 windings and core for a transformer of smaller output. 
 
 ROTARY CONVERTERS. 
 
 Perhaps one of the greatest objections to the use of direct 
 current is the inability to change its voltage without the 
 use of moving machinery. 
 
 There is but one way to transform direct current and that 
 is by a motor and generator. 
 
 This motor-generator set usually consists of a direct cur- 
 rent motor driven by current at the pressure of the incom- 
 ing line. This motor drives a direct current generator 
 which furnishes current at the desired pressure. 
 
 By altering the strength of the field of the generator we 
 regulate the outgoing pressure to suit the requirements. 
 
 The motor and generator are built on the same shaft, 
 and set on a long cast iron base, making them mechanically 
 one machine. 
 
 When the incoming and outgoing voltages can have the 
 same ratio to each other always, a cheaper form of ma- 
 chine can be used called a Dynamotor. 
 
 This is a direct current- motor running on the incoming 
 voltages. On the same armature core is a separate winding 
 connected to its own commutator at the other end of arma- 
 
1278 
 
 Steam Engineering 
 
 ture. The one set of field magnets serves for the motor 
 winding and the generator or dynamo winding. 
 
 The Rotary Converter. — Combines in a single machine 
 the functions of the two machines just described. In one 
 sense it may be regarded as an alternating-current syn- 
 chronous motor driving a direct-current generator, or if 
 
 Fig. 598 
 westinghouse 1,500 k. w. rotary converter 
 
 the machine be inverted, it may be considered a direct-cur- 
 rent motor, driving an alternating-current generator. 
 
 As direct current cannot readily be generated at, or trans- 
 formed to a high voltage, which economical distribution dic- 
 tates, alternating current is almost invariably used for all 
 except very small electrical power transmissions. Wherever 
 
Rotary Converters 
 
 1279 
 
 direct current is used, as in direct current railway lines, the 
 alternating current must be transformed into direct cur- 
 rent. While, of course, this can be accomplished by means 
 of a motor-generator set, consisting of an alternating cur- 
 rent motor connected to a direct current generator, the 
 
 Fig. 599 
 
 westinghouse 300 k. w. rotary converter, 600 d. c. volts, 500 
 
 d. c. amperes, three-phase, 60 cycles 
 
 higher efficiency and lower cost of the rotary converter ac- 
 counts for the almost universal practice of using it in pref- 
 erence to the motor-generator on low frequencies. 
 
 Eotary converters have many of the features which dis- 
 tinguish the most modern direct-current machines; the 
 
1280 
 
 Steam Engineering 
 
 only material difference being the addition of collector 
 rings connected to certain points of the armature winding. 
 The number of such connections depends upon the number 
 of poles and phases. 
 
 The machine is built for single-phase, two-phase, three- 
 phase or six-phase circuits, although single-phase and six- 
 phase converters are seldom desired. A two phase con- 
 verter is provided with four collecting rings, and a three- 
 
 Fig. 600 
 
 westinghouse rotary converter armature from the collectob 
 
 side, 300 k. w., 550 volts, three-phase 
 
 phase converter is provided wth three collecting rings. As 
 it is usually found expedient to transmit the alternating 
 current at high pressure, transformers must be employed 
 for lowering the potential to secure the proper direct volt- 
 age. Where the converter is operated from direct, to alter- 
 nating current, transformers are usually employed to raise 
 the voltage for transmission. 
 
 A rotary converter may be separately excited, but it is 
 usually shunt wound, or compound wound, depending upon 
 
Rotary Converters 1281 
 
 the nature of the service. When the load is variable, as in 
 railway service, the machine is compound wound, which 
 tends to maintain the direct current voltage constant, by 
 compensating for the drop in the supply circuit as the load 
 comes on. The ratio between the alternating and direct 
 current voltages of a rotary converter depends upon the 
 number of phases, upon the wave form of its alternating 
 current, upon the lead given to the direct current brushes, 
 and to a slight extent upon the field excitation. In any 
 given converter, therefore, the direct current voltage de- 
 pends practically upon the voltage of the alternating cur- 
 rent applied. To a smaller extent it depends upon the 
 armature drop, which diminishes the voltage ratio in slight 
 proportion with the load when running A. C. to D. C. and 
 increases the ratio when running D. C. to A. C. This will 
 be easily seen by referring to a saturation curve. 
 
 With a sine wave the ratios of conversion are approxi- 
 mately as follows : 
 Single Phase, Two Phase, Three Phase, Six Phase, 
 
 .71 .71 .61 .71 or .61 
 
 Thus if the D. C. voltage be 550 volts, the A. C, if two- 
 phase, will be .71X550=390 volts, and if three-phase, it 
 will be .61X550=335 volts. The ratio of conversion in 
 the six-phase is .71 with the star connection, or .61 with 
 the double delta connection. 
 
 The variations from these figures with wave forms in 
 commercial use are taken into account in the ratios of the 
 transformers used in connection with the rotary converters. 
 
 The rotary converter built by the Westinghouse Com- 
 pany presents in its frame the same mechanical features as 
 are found in its well-known line of direct current machines. 
 The machine is of the multipolar type, havng laminated 
 steel poles, cast, or bolted to its iron yoke, and carrying 
 
1282 Steam Engineering 
 
 easily removable field coils. If the windings are compound, 
 the series, and shunt coils are insulated separately. The 
 armature is of the slotted drum type, with either a two cir- 
 cuit, or multiple type of winding. The number of poles in 
 a rotary converter is dependent upon the speed of the ar- 
 mature and the frequency, as is the case with all alternating 
 current machinery. 
 
 This feature accounts for the difficulty in designing ro- 
 tary converters for high frequencies, as the maximum arma- 
 
 Fig. 601 
 
 WESTINGHOUSE COMPLETE ROTARY CONVERTER ARMATURE FROM THE 
 COMMUTATOR SIDE, 300 K. W., 550 VOLTS, THREE-PHASE 
 
 ture speed is limited by the maximum safe speed of the 
 periphery of armature and commutator. With a given 
 speed, however, the number of poles is proportional to the 
 frequency, and with a given maximum speed of armature 
 and commutator periphery, the distance between adjacent 
 poles, and therefore adjacent brush holders, is inversely 
 proportional to the frequency. With high voltage 60-cycle 
 converters, these facts necessitate high commutator speeds, 
 short distances between poles, and between brush holders. 
 
Rotary Converters 1283 
 
 narrow commutator segments, and a high voltage between 
 adjacent segments; resulting in a tendency to flashing over 
 between brushes at sudden overload. 
 
 This should always be borne in mind when choosing the 
 frequency of a system on which rotary converters are to be 
 used, and it applies particularly to 500 and 600 volt rail- 
 way rotary converters, which are required to withstand 
 much more severe service than is ever experienced on light- 
 ing systems. 
 
 In the erection of a rotary converter the following con- 
 siderations should, as far as possible, be observed: 
 
 First. It should not be located in a position where it 
 would be exposed to moisture, as drippings from pipes, or 
 escaping steam. 
 
 Second. It should not be exposed to dirt or dust, espe- 
 cially from coal. 
 
 Third. It should be located in as cool and well venti- 
 lated a place as possible. The temperature of the machine 
 depends upon the temperature of the air surrounding it. 
 
 Fourth. It should be so located as to allow easy access 
 to the alternating current brushes, and also to the com- 
 mutator. These are the parts requiring special attention. 
 Eotary converters should be set on substantial foundations 
 in order to prevent vibration w T hen running. 
 
 The following list of instructions refer more particularly 
 to Westinghouse machines, but much of it will apply to 
 others. 
 
 Insulation of Frame. — Whether the frame should be in- 
 sulated from the ground is a matter to be determined by the 
 engineer in charge of the plant, but rotary converters are 
 usually not insulated. However, the following remarks 
 which apply to alternating practice, may not be amiss : Gen- 
 erally speaking, the strain on the insulation of the windings 
 
1284 Steam Engineering 
 
 will be decreased, and the danger to the attendant increased 
 by insulating the frame. When, however, it is considered 
 advisable to insulate the frame, the foundation should be 
 capped with a strong wooden frame bolted down. The bolts 
 which hold this frame to the masonry should not come in 
 contact with those which hold the machine to the frame, 
 nor should any metal, or electrical conductor unite the two 
 sets of bolts. 
 
 The wooden insulating frame under the machine may 
 also be covered with some insulating waterproof paint or 
 compound. 
 
 Erection of Machine. — When placing the parts of a ma- 
 chine in position the following points should be observed: 
 
 (1) Set the lower half of the field in position and place 
 the armature in its bearings, having first carefully examined 
 the bearings and oil wells to be sure that they are clean and 
 free from dirt. Be sure that the oil rings are in place and 
 in good running order. 
 
 (2) Clean the contact surfaces of both halves of the 
 field and file off the burs, if any exist, to secure perfect 
 magnetic joints at the division of the yoke. 
 
 (3) Set the upper half of the field in position and 
 secure it to the lower half by means of the field bolts and 
 feather keys. 
 
 (4) Note that the machine is to be perfectly level along 
 the axis of the shaft, except that when an oscillator is at- 
 tached the machine is placed slightly out of level, as will 
 be pointed out later. 
 
 Armature. — Never try to support any of the weight of 
 an armature by the commutator or collector rings. Do not 
 allow these parts to rest on any blocking, and do not pass 
 a rope around them for the purpose of lifting. When hand- 
 ling the armature always support it with a rope slung 
 
Rotary Converters 1285 
 
 about the shaft, and be careful not to mar or scratch the 
 shaft, as any roughness would cause it to cut the bearings 
 and so produce heating when the machine is running. 
 
 In putting the armature in the field be careful not to 
 scratch the bearings, nor to bend the oil rings. 
 
 Coils. Assembly or field coils. — The field coils of the 
 larger machines are shipped separately. The coils are held 
 on the poles by the dampers, which should be bolted to the 
 pole pieces. The coils on each of the separate halves of the 
 field should be properly connected before the machine is 
 set up. 
 
 Each pole piece has a number stamped with steel stencil 
 and also painted in red, and a red line is drawn parallel 
 and near to one edge of the pole. This line and number 
 correspond to similar marks inside the coil. In erecting, 
 place the coils on the poles so that the marks coincide. 
 
 If a rotary converter has been exposed to dampness it 
 may be dried out by employing one of the following meth- 
 ods: 
 
 (1) Short-circuit the field and apply to the collecting 
 rings about 10 per cent of normal alternating current volt- 
 age, which may usually be obtained from the lowering 
 transformers. During this application the D. C. brushes 
 must be raised and the rotary must be at a standstill. The 
 standard Westinghouse transformers are usually provided 
 with taps, between which a low voltage may be obtained. 
 
 (2) Eun the rotary converter, driving it by a suitable 
 motor, and short-circuit the armature on the direct cur- 
 rent side with very weak field excitation. If shunt wound, 
 separate excitation at very low voltage must be used. If 
 the converter be compound wound, the armature may be 
 short-circuited through the series field coils. As rotary con- 
 verters are usually very sensitive as series machines this 
 
1286 Steam Engineering 
 
 method should be undertaken only by those who are thor- 
 oughly experienced, as there is danger of excessive current. 
 
 (3) Dry the field coils from a source of separate excita- 
 tion, with about two-thirds of the normal D. C. voltage. 
 This will also dry the armature somewhat. While drying 
 out, the temperature of the accessible parts should be 
 watched closely, and not be allowed to exceed 75° C. 
 
 In drying out with current there is always danger of 
 overheating the windings, as the inner parts may get in- 
 jurously hot because they cannot quickly dissipate the heat 
 generated in them. Coils containing moisture are more 
 easily injured by overheating than those which are already 
 dry. Several hours, or even days, may be required for 
 thoroughly drying out. 
 
 Repairs to Armatures. — The instructions pertaining to 
 armature troubles, and repairs to commutators and other 
 parts of electric generators, will also apply in the case of 
 rotary converters. 
 
 Bucking. — Bucking is the expressive name given to the 
 action of the rotary converter when arcing occurs between 
 two adjacent brush holder arms, thereby short-circuiting 
 the machine. Bucking is, in general, due to abnormally 
 high voltage, or a path of low resistance over the commu- 
 tator surface, or to abnormal commutation conditions. The 
 poorer the commutation, the more liable will the machine 
 be to buck whenever these abnormal operating conditions 
 occur. Some of the particular causes for bucking are the 
 following : 
 
 a) Eough or dirty commutator. A drop of water fall- 
 ing on the commutator has been known to cause the ma- 
 chine to buck. 
 
 (b) Excessive voltage due to increase in A. C. voltage. 
 
Rotary Converters 1287 
 
 (c) Excessive voltage due to static disturbances from 
 lightning arrester short-circuits. 
 
 (d) Excessive voltage due to static discharge from or 
 through lowering transformers. When bucking is due to 
 this cause, it will usually occur when switching is done in 
 the high tension circuits. 
 
 (e) Bucking may be caused by fluctuations in the volt- 
 age, due to the removal of a short-circuit. 
 
 In multiple wound rotary converters, balancing rings or 
 cross-connections are employed as in direct current gener- 
 ators. These rings connect together points of equal poten- 
 tial around the commutator. 
 
 By this means the same field strength is obtained under 
 each pole. 
 
 Oscillators. — The armature of a rotary converter re- 
 volving with its horizontal shaft will take up normally a 
 fixed position relative to its bearings, and the frame of 
 the machine, and revolve without any tendency to move 
 or oscillate in the direction of its length. This is detri- 
 mental to its best operation as the brushes are liable to wear 
 grooves in the commutator, and collector. It therefore be- 
 comes necessary to provide a means of producing a periodic 
 movement of the armature in the direction of its length, and 
 this function is performed by the oscillator. 
 
 There are two -classes of oscillators, viz.: mechanical and 
 magnetic. The mechanical oscillator employed by the West- 
 inghouse Co. is described as follows: 
 
 This device is self-contained and is carried over one end 
 of the shaft. The operating part consists of a steel plate 
 grooved by a circular ball race in which travels a hardened 
 steel ball. The steel plate is not quite parallel to the face 
 of the end of the shaft. The normal position of the ball is 
 
1288 
 
 Steam, Engineering 
 
 at the lowest point of the circular race. The steel plate is 
 backed by a spring. 
 
 The machine is leveled so that the armature is slightly 
 inclined toward the oscillator. The steel plate is then ad- 
 justed so that when the ball is at its bottom position it just 
 comes in contact with the shaft end. As the armature re- 
 volves the ball is carried up the race, and owing to the 
 
 Magnetic Oscillators 
 No.2 
 
 D.C.Voltago 
 I 
 
 W 
 
 Interrupter 
 
 Fig. 602 
 diagram of connections for magnetic oscillator 
 
 inclination of this race, compresses the spring. The reaction 
 of the spring drives the shaft away. Thus the armature re- 
 ceives an impulse, which moves it toward the other limit 
 of its travel, and it continues to move until the opposing 
 forces bring it to rest and start it back to its normal posi- 
 tion, where it again comes in contact with the ball, and the 
 operation begins over again. Fig. 602 shows a diagram- 
 matic view of the Westinghouse magnetic oscillator, of which 
 
Rotary Converters 1289 
 
 the following is a description. A magnet is mounted upon 
 one of the bearing housings of the rotary converter in such 
 a manner as to attract the end of the shaft. When the cir- 
 cuit is closed the magnet draws the shaft toward it and 
 when the circuit opens, the armature tends to resume its 
 normal position which is determined by the leveling of the 
 converter. The magnet has in series with it a make and 
 break device called an interrupter which is controlled by a 
 dash-pot to secure the proper frequency of action. 
 
 As the dash-pot offers an adjustable resistance, the fre- 
 quency of the impulses is adjustible. When there are a num- 
 ber of rotary converters in the same sub-station, the magnetic 
 oscillators are connected in series, and controlled by a single 
 interrupter. 
 
 Under certain conditions the commutator, and collector 
 surfaces of machines provided with oscillators may be worn 
 in irregular wavy grooves. 
 
 When this occurs it will then be necessary to turn down 
 the commutator and collector. 
 
 QUESTIONS AND ANSWERS. 
 
 891. What is the function of a transformer? 
 
 Ans. To transform the current from a higher, to a lower 
 voltage, or vice-versa. 
 
 892. What principles govern the action of a trans- 
 former? 
 
 Ans. The principles of electro-magnetic induction. 
 
 893. What is a step up transformer? 
 Ans. A transformer that raises the voltage. 
 
 894. What is a step down transformer? 
 Ans. One that lowers the voltage. 
 
 895. How are transformers cooled? 
 
1290 Steam Engineering 
 
 Ans. Small sizes by surface radiation. Larger sizes by 
 oil ; also by air blast. Some of the smaller sizes are cooled 
 by water circulating through surrounding coils. 
 
 896. How is direct current transformed from one volt- 
 age to another ? 
 
 Ans. By means of a machine called a motor-generator. 
 
 897. Describe in brief a motor-generator. 
 
 Ans. It consists usually of a D. C. motor driven by 
 current at the voltage of the incoming line. This motor in 
 turn drives a D.- C. generator that furnishes current at the 
 desired voltage. 
 
 898. How is the outgoing voltage regulated? 
 
 Ans. By altering the field strength of the generator. 
 
 899. In case the incoming and outgoing current can bear 
 the same ratio to each other constantly, what kind of an 
 apparatus is used ? 
 
 Ans. A machine called a dynamotor. 
 
 900. Describe the operation of a dynamotor. 
 
 Ans. It is a D. C. motor running on the incoming volt- 
 ages. On the same armature core is a separate winding 
 connected to its own commutator at the other end of the 
 armature. One set of field magnets serves for the motor 
 winding and the generator or dynamo winding. 
 
 901. Describe in general terms a rotary converter. 
 
 Ans. It combines in a single machine the functions of 
 a motor-generator, and a dynamotor. 
 
 902. Why are rotary converters and transformers neces- 
 sary? 
 
 Ans. Because it is more economical to transmit alter- 
 nating current at high voltages and transform, or convert 
 it to the lower voltage at which it is used. 
 
 903. Give another reason for using rotary converters. 
 
Questions and Answers 1291 
 
 Ans. For the purpose of transforming alternating cur- 
 rent into direct current when direct current is used. 
 
 904. What is the chief point of difference between a 
 rotary converter and a direct current generator ? 
 
 Ans. The rotary has collector rings connected to certain 
 points of the armature winding. 
 
 905. What governs the number of such connections? 
 Ans. The number of poles and phases. 
 
 906. Describe the different types of rotaries. 
 
 Ans. They are built for single-phase, two-phase, three- 
 phase or six-phase. 
 
 907. How many collecting rings has a two-phase con- 
 verter ? 
 
 Ans. Four collecting rings. 
 
 908. How many collecting rings has a three-phase con- 
 verter ? 
 
 Ans. Three collecting rings. 
 
 909. When alternating current is transmitted at high 
 pressure, what means are employed for lowering the po- 
 tential ? 
 
 Ans. Transformers. 
 
 910. When the incoming current is direct and the out- 
 going current alternating, how is the voltage raised ? 
 
 Ans. By step up transformers. 
 
 911. Describe the winding of a rotary converter. 
 
 Ans. It is usually shunt wound, or compound wound, 
 although sometimes separately excited. 
 
 912. How are rotaries in railway service usually wound ? 
 Ans. Compound, owing to variations in the load. 
 
 913. What advantage is gained by this method of wind- 
 ing? 
 
 Ans. It tends to maintain the D. C. voltage constant. 
 
1292 Steam Engineering 
 
 914. Upon what does the ratio between the A. C. and 
 D. C. voltages of a rotary depend? 
 
 Ans. Upon the number of phases, the lead given the 
 D. C. brushes, the wave form of its alternating current, 
 and upon the field excitation. 
 
 915. Does the armature drop affect this ratio to any 
 extent ? 
 
 Ans. It does by decreasing it slightly when running 
 A. C. to D. C. and increasing it when running D. C. to 
 A. C. 
 
 916. What are the ratios of conversion approximately? 
 Ans. Single-phase 71 
 
 Two-phase 71 
 
 Three-phase 61 
 
 Six-phase 71 or .61 
 
 917. Give an example illustrating above. 
 
 Ans. If D. C. voltage is 550 volts, the A. C, if two- 
 phase will be 500X-71=390 volts, or if three-phase it will 
 be 550X-61=335 volts. 
 
 918. What precautions should be observed in the erec- 
 tion of a rotary converter ? 
 
 Ans. First — It should be protected from moisture. Sec- 
 ond — It should be protected from dust or dirt. Third — It 
 should be in a well ventilated room and kept as cool as 
 possible. 
 
 919. Should the frame of the machine be insulated? 
 
 Ans. Generally speaking the strain on the winding in- 
 sulation will be decreased, and danger to attendant increased 
 by insulating the frame. 
 
 920. If a rotary has been exposed to dampness how may 
 it be dried out ? 
 
 Ans. By running it with about 10 per cent of the nor- 
 mal A. C. voltage, while at same time observing certain 
 
Questions and Answers 1293 
 
 precautions noted in the text of this book under head of 
 rotary converters. 
 
 921. What method should be pursued in caring for the 
 commutator ? 
 
 Ans. Wipe it off with a piece of canvas — never use waste. 
 Lubricate it with a very small quantity of vaseline, or oil 
 applied with a piece of cloth. See that none of the segments 
 is at all loose. 
 
 If it gets out of true turn it down. 
 
 922. If a commutator gets hot while carrying only a 
 normal load what should be done ? 
 
 Ans. Heating under such conditions is an indication 
 that the commutator is worn out, and should be replaced 
 by a new one. 
 
 923. Give some of the causes of sparking at the brushes. 
 Ans. Brushes may not have proper lead. 
 
 Brushes may not fit commutator. 
 Brushes may be burned on end. 
 Commutator surface may be rough. 
 
 924. What is meant by a rotary bucking ? 
 
 Ans. When arcing occurs between two adjacent brush 
 holder arms, thus short circuiting the machine. 
 
 925. Name a few of the principal causes of bucking. 
 Ans. Eough or dirty commutator. 
 
 Excessive voltage. 
 Fluctuations in the voltage. 
 
 926. What is an oscillator, and what is its function? 
 
 Ans. An oscillator is a device operated either magnet- 
 ically, or by mechanical means, and its function is to pro- 
 duce a slight, periodic movement of the armature shaft 
 endwise. 
 
 927. Why is this endwise movement of the shaft neces- 
 sary? 
 
1294 Steam Engineering 
 
 Ans. In order to prevent the wearing of grooves in the 
 commutator. 
 
 928. What is meant by the hunting of a rotary con- 
 verter ? 
 
 Ans. It is a slight change of the speed of the armature. 
 
 929. What is the cause of hunting? 
 
 Ans. Irregularities in the speed of the generator deliv- 
 ering current to the rotary, thus causing a slight difference 
 in the relative positions of the armature of the two machines, 
 resulting in a change in the phase positions of the generator 
 ft. M. F. and the counter E. M. F. of the converter. 
 
 930. What are the usual methods of starting rotary con- 
 verters ? 
 
 Ans. First — By a separate A. C. starting motor. 
 
 Second — By applying direct current to the commutator. 
 This starts the converter as a shunt motor. 
 
 Third — By applying alternating current directly to the 
 collector rings. This starts the converter as an induction 
 motor. 
 
 931. What is meant by synchronizing a rotary converter ? 
 Ans. Bringing it to the same frequency, the same phase, 
 
 and the same voltage as the generator from which it is 
 receiving current. 
 
 932. What method is employed to determine when the 
 machines are in synchronism ? 
 
 Ans. There are several methods, the most common one 
 being by means of incandescent lamps connected in series 
 with the two machines. 
 
 933. What is a synchroscope? 
 
 Ans. It is an instrument for determining when electrical 
 machines are in synchronism. 
 \ 934. What is an automatic synchronizer? 
 
Questions and Answers 1295 
 
 Ans. It is a device that will automatically synchronize 
 two electrical machines; also connect a synchronized ma- 
 chine with the main by means of an electrically operated 
 switch, 
 
 935. Name two important points to be looked after be- 
 fore starting a rotary converter. 
 
 Ans. First — See that both the A. C. and D. C. brashes 
 are properly adjusted and that every thing is clear about 
 the converter. Second — See that the switches on board are 
 open on both the A. C. and D. C. sides, and that the resist- 
 ance of the rheostat is all cut in the field circuit. 
 

Oil Switches 
 
 As considerable space has been devoted to oil switches, 
 the subject will be continued still further by a brief expla- 
 nation of the construction and operation of this type of 
 switches, and also of oil circuit breakers. The principle of 
 construction is shown in Fig. 603. On the right and left 
 hand are two metallic rods which descend through insulating 
 
 £FL-~ 
 
 is 
 
 t 
 
 Fig. 603 
 
 blocks, and carry springs at their lower end projecting there- 
 from. Another metallic rod descends between these two, 
 and carries a cross-piece at its lower end, having beveled 
 carbon contacts C. C. facing upward. This rod moves up 
 and down through an insulating block, and it is connected 
 to one lead of the circuit, while both side rods are connected 
 
 1297 
 
1298 Steam Engineering 
 
 to the other. When the central rod is raised the carbon 
 blocks C. C. enter between the springs and make the contact, 
 closing the circuit. When lowered it opens the circuit. Thus 
 far the action of the switch is similar to the ordinary switch, 
 but in order to prevent the formation of arcs, and to insure 
 definite action in the opening or closing of the circuit, the 
 lower portion of the mechanism is immersed in oil con- 
 tained in a tank which is shown in section in the diagram 
 
 Fig. 604 
 type i westinghouse oil switch 
 
 Pig. 603. Oil switches are made in many different styles, 
 but the one feature of the complete submersion of all live 
 parts in oil, governs all. They are also as a rule held in the 
 open position, either by gravity or by special locking mechan- 
 ism consisting of a safety catch that holds the switch open 
 until released by pressure of a button in the end of the 
 operating handle. 
 
 The development of the oil switch, and circuit-breaker has 
 produced what is probably the most valuable addition to 
 
Oil Switches 1299 
 
 high-potential line apparatus made during the last ten 
 years. It is indeed likely that the development of high-ten- 
 sion transmission of power would have been very seriously 
 hampered but for the invention of the oil switch. 
 
 This use of oil has made it possible to rupture easily and 
 safely, circuits carrying heavy currents at high voltage and, 
 further, to open these circuits under conditions of short 
 circuit. The possibility of opening high-tension circuits 
 under conditions of heavy overload has made possible the 
 development and application of the present system of relays. 
 
 Fig. 605 
 type d westinghouse oil switch 
 
 By means of these relays, used in connection with oil circuit- 
 breakers, perfect protection can be secured for the apparatus 
 to which they are applied. 
 
 The term "switch" is given to those pieces of apparatus 
 in which the contacts are similar to the ordinary switch, 
 and are opened and closed by hand. Devices in which the 
 contacts tend to separate, and are only held in a closed posi- 
 tion by means of triggers and toggles are called "circuit- 
 breakers." 
 
1300 Steam Engineering 
 
 The Westinghouse oil switches are essentially knife 
 switches immersed in oil, the blades being connected to a 
 common operating lever by specially treated wooden rods. 
 The knife-blade contacts are used, as they give the most 
 perfect contact and therefore the lowest temperature rise. 
 
 Fig. 604 shows a Westinghouse type I oil-switch for 
 switchboard use only. Fig. 605 shows the type D Westing- 
 house oil-switch for outdoor service, the casing being mois- 
 ture proof, and the leads brought out underneath through 
 
 Fig. 606 
 
 sealed bushings as shown. Fig. 606 shows the same switch 
 with the oil tank removed. Fig. 607 shows the Westing- 
 house type B oil circuit-breaker, designed for potentials 
 from 3,300 to 22,000 volts, and currents from 300 to 1,200 
 amperes. This device is a double-break, oil circuit-breaker. 
 It may be automatic or non-automatic, and may be placed 
 on the back of the switchboard, or arranged for distant con- 
 trol through rods and levers. 
 
 Through a very simple system of levers, the operating 
 handle is connected to a cast-iron cross bar, to which are 
 
Oil Switches 
 
 1301 
 
 fastened the movable contact arms. To the lower end of 
 the wooden arm is fastened a metal yoke with a conical 
 contact on either end. When the circuit is closed these 
 contacts engage with two stationary contacts, forming one 
 
 # 
 
 Fig. 607 
 type b westinghouse oil circuit breaker 
 
 pole of the breaker. Each stationary contact is supported 
 by a porcelain insulator, rigidly secured to the frame. The 
 leads are brought to the terminals of the stationary contact 
 within the insulator, forming an unbroken and continuous 
 
1302 
 
 Steam Engineering 
 
 insulated conductor between the circuit-breaker, and the 
 bus-bar or line. Each pole of the circuit-breaker has a tank 
 in which its live metal parts are immersed in oil, each tank 
 being entirely independent of the adjacent one. 
 
 These tanks have a lining so formed as to reduce the 
 quantity of oil required and which serves as a barrier be- 
 
 
 Fig. 608 
 
 TYPE E WESTINGHOUSE OIL CIRCUIT BREAKER 
 
 tween the two stationary contacts, yet allowing ample space 
 for the movement of the wooden arm and its contacts. The 
 lining serves as an insulation, and reduces to a minimum all 
 danger of the arc communicating through the oil. Any one 
 of the tanks may be removed without interfering in any 
 particular with the others. Fig. 608 shows the type E 
 
Oil Switches 1303 
 
 Westinghouse oil circuit-breaker, electrically operated. This 
 circuit-breaker is also designed for high potentials, and 
 heavy currents. 
 
 A simple system of toggles and levers is mounted on the 
 top of the breaker, and a powerful electro-magnet is arranged 
 with its movable core attached to the lever system, so that 
 when it is drawn into the coil, the circuit-breaker will be 
 closed. A small single-pole, double-throw switch is mount- 
 ed on the breaker, and is operated by the motion of the 
 levers in opening or closing the circuit; it controls the 
 tell-tale indicator, and lamp which are mounted in view of 
 the operator. These circuit-breakers are operated by 125 
 volts direct-current, and are calibrated for 3,000 alterna- 
 tions. 
 
 ELECTRO-METERS. 
 
 Galvanometers. — An electric current passing near a mag- 
 netic needle deflects the needle, and if the current is passed 
 first over the needle and then back under it in an opposite 
 direction, the needle will be still further deflected. 
 
 An instrument consisting of a coil of wire carrying the 
 current to be tested, and a magnet; the two being so ar- 
 ranged that one can be deflected, is called a galvanometer. 
 
 There are two types, the Thompson and the D'Arsonval. 
 . The Thompson type has the coil of wire stationary, and 
 the light magnetic needle suspended by a silk thread. These 
 can be made more sensitive than the other type, but are not 
 portable, and external fields have a great influence on them, 
 causing them to give false indications. This is prevented 
 by thick soft iron cases, much too heavy to be carried 
 around. 
 
 The silk suspension makes the needle sensitive to vibra- 
 tion. 
 
1304 Steam Engineering 
 
 It is a fine laboratory instrument, and with modified con- 
 struction has been used in the workshop and field, but for 
 this work the D'Arsonval is much better. 
 
 The D'Arsonval type has a very small, light coil of wire 
 suspended by a fine bronze wire between the poles of a sta- 
 tionary magnet. Since the movable part is not a magnet 
 except during the actual instant of the test, outside mag- 
 netic fields have no influence on its motion. To shield it 
 during test, a thin soft iron or steel case is put on the in- 
 strument which does not affect its portability. These covers 
 are usually copper, brass or nickel plated for appearance 
 sake, but the actual material is iron for the purpose of 
 shielding the instrument. 
 
 These D'Arsonval galvanometers are not so sensitive as 
 the other type, which for ordinary work is a great advan- 
 tage. 
 
 Both of these types have the needle swinging over a 
 circular scale divided into degrees, or may have a small 
 mirror attached so that the deflection may be read by the 
 motion of a spot of light moving along a long ruler sup- 
 ported about a yard away from galvanometer. 
 
 As mentioned before, twice the current does not give 
 twice the deflection, but by sending known currents through 
 a galvanometer, and marking a scale with pen and ink we 
 could make an ampere meter. This is called Calibration. 
 
 Ammeters and Voltmeters. — The ammeters and volt- 
 meters of commercial work are all special adaptations of 
 the D'Arsonval galvanometer or, for the least accurate work 
 such as on switchboards ; they are of the magnetic vane type. 
 
 The Weston instruments are D'Arsonval galvanometers. 
 
 Fig. 609 shows an instrument with the cover removed. 
 A large permanent magnet of U shape is supported by a 
 gun-metal casting screwed to the ends of the limbs, and 
 
Electro Meters 
 
 1305 
 
 jsnmnm 
 
 WM ZL 
 
 unmmm 
 
 mmm* 
 
 Fig. 609 
 interior of weston instrument 
 
1306 Steam Engineering 
 
 the whole of the working part is built up on this mag- 
 net independent of the case, so that the movement can 
 be removed bodily from the case by simply taking out 
 one screw which holds the gun-metal casting in place. 
 The inside polar faces of the magnet are surfaced up so 
 as to come closely into contact with wrought-iron pole 
 pieces which are bored out to about 1 in. diameter, and 
 fixed rigidly in their place with screws passing through 
 the limbs of the magnet. To these pole pieces a second 
 gun-metal casting is screwed, which forms a support for a 
 soft iron cylinder % in. diameter inside the bored out pole 
 pieces, and also a support for the scale. The soft iron 
 cylinder fills up most of the space between the pole pieces, 
 allowing an air space at either side of % in-,, and in this 
 space a fairly strong, uniform, magnetic field exists. A coil 
 of fine insulated copper wire of about twelve turns is 
 wound on a thin brass frame, large enough to embrace the 
 soft iron cylinder, with freedom to move in the space be- 
 tween it and the pole pieces. This is pivoted in jeweled 
 bearings which are screwed to the pole pieces, but insulated 
 from them, forming little bridges across, and the ends of 
 the coil are connected to these bridge pieces by spiral springs, 
 one at the top and the other at the bottom of the coil, the 
 springs being wound in opposite directions, so that when 
 one is wound up by a movement of the coil the other is 
 unwound. This arrangement corrects for any variation in 
 temperature, for the effect on one spring would be counter- 
 acted by the opposite effect on the other. The coil normally 
 lies at 45° to the line joining the poles of the magnet, and 
 consequently the magnetic field created by a current in the 
 coil will be displaced relatively to the field of the horseshoe 
 magnet as shown in Fig. 610, and the lines twist the coil 
 through a certain angle against the action of the spiral 
 
Electro Meters 
 
 1307 
 
 Fig. 610 
 
 diagram of magnets, flux, coil and inner core of weston 
 
 instrument 
 
 Fig. 611 
 view of movement of weston instruments 
 
1308 Steam Engineering 
 
 springs, the angular movement of the coil depending on 
 the strength of the current in the coil and the strength of 
 the field in which it is placed. 
 
 To the coil is attached a pointer of aluminum, the whole 
 being balanced so that the instrument can be read in any 
 position, and the pointer and scale are bent up so as to come 
 near the front of the case. 
 
 A perspective view of the movement is shown in Fig. 611. 
 
 In this instrument the whole current does not go through 
 the coil, but only a small fraction of it. The main part of 
 the current crosses from one terminal to the other by a 
 broad strip of metal under the base of the instrument, 
 while the coil is placed as a shunt across the terminals, or 
 as a conductor in parallel with the metal strip (Fig. 612), 
 and consequently the ratio of the currents in the strip and 
 in the coil will be inversely proportioned to their resistances. 
 Now with a given strength magnetic field due to the magnet 
 and a given elasticity of the spiral springs, it will require 
 a certain number of ampere turns in the coil to produce 
 the full deflection on the scale. This can be secured by 
 adjusting the resistance of the strip connecting the term- 
 inals so that the same movement will do for any instrument. 
 Thus, suppose the instrument were required to read to 
 a maximum of 10 amperes, and we required 1 ampere in 
 the coil to give the maximum deflection, then the resist- 
 ance of the coil must be 9 times that of the strip, so that 
 the current will divide at the terminals, 9/10 going through 
 the metal strip and 1/10 through the coil. If the instru- 
 ment is required to read to a maximum of 100 amperes, 
 then the metal strip must have 99 times less resistance 
 than the coil, and the current will then divide at the term- 
 inals, 99/100 going through the strip and 1/100 going 
 through the coil, which will give a reading to the full range 
 
Electro Meters 
 
 1309 
 
 of the scale as before. By the arrangement of the pole 
 pieces, and wrought iron cylinder the field due to the per- 
 manent magnet is practically uniform over the range of 
 movement of the coil, and so the scale readings are the 
 same size throughout. Should the permanent magnet 
 
 Fig. 612 
 magnet and shunt of weston ammeter 
 
 vary in strength, the instrument would not read correctly, 
 but the magnets are so treated that the falling off in strength 
 over a number of years is inappreciable. 
 
 The strip or shunt for portable instruments is always 
 inside the case, while for switchboard instruments the shunt 
 
1310 
 
 Steam Engineering 
 
 is too large (Fig. 613) and is placed separately on the back 
 of the board. Leads are run along the board to the meter 
 terminals which project through holes in the board from 
 the meter which is in front. 
 
 Fig. 613 
 external shunts for ammeters. 1000 and 5000 ampere sizes 
 
 Such a switchboard instrument is shown in Fig. 614 and 
 Fig. 615. 
 
 A Voltmeter is made by removing the metal strip or shunt 
 connecting the terminals and placing a resistance coil in 
 series with the moving coil. 
 
Electro Meters 
 
 1311 
 
 As it takes 1/100 amperes to swing the pointer over full 
 scale for every volt the instrument reads, it must have 100 
 ohms in the resistance coil. 
 
 A 500 volt instrument will have 500,000 ohms resistance, 
 and hence 1/100 amperes w T ill flow through the moving coil. 
 
 The moving coil is wound on a copper, or aluminum 
 frame, which when it swings has current induced in it by 
 the magnets and stops vibrating very quickly; in fact, you 
 cannot detect any vibration. The needle seems to move to 
 
 Fig. 614 
 switch board instrument 
 
 a certain spot and stop dead. This is called a "dead beat" 
 needle. 
 
 Some instruments have electro-magnets instead of per- 
 manent magnets. The Thomson Astatic instruments are 
 of this type. Two of these instruments are shown in Figs. 
 615 and 616. This latter has a scale or dial of opal glass 
 with an electric light behnd it. This makes the instrument 
 easily read from a distance or at night. These are called 
 "illuminated dial instruments." 
 
1312 
 
 Steam Engineering 
 
 Fig. 615 
 switch board ammeter 
 
 Fig. 616 
 
 ILLUMINATED DIAL INSTRUMENT 
 
 _ 
 
 The instrument shown in Fig. 614 has an extra hand 
 ending in a ring. This can be set at the voltage it is 
 desired to maintain. The most hasty glance will then show 
 whether the voltage is too high or too low. 
 
Electro Meters 
 
 1313 
 
 In order to save space on switchboards some instruments 
 are made thin and broad and are set horizontally or ver- 
 tically. 
 
 Fig. 617 shows the exterior and interior of a Thomson 
 Edgewise Ammeter. 
 
 The Thomson Inclined Coil instruments as shown in 
 
 Fig. 617 
 thomson horizontal ammeter 
 
 Fig. 618 are portable instruments used for alternating cur- 
 rent only. In an emergency they can be used to measure 
 direct current by reading, then reversing current, reading 
 again, and averaging results. 
 
 The action of the magnetism of the inclined coil is to 
 twist the inclined sheet iron vane "a" around to the dotted 
 line position. 
 
1314 
 
 Steam Engineering 
 
 The Weston instruments described are for direct current 
 only. The company makes an alternating current volt- 
 meter but no ammeter. Thomson Astatic instruments are 
 for direct current. The Thomson Inclined Coil in portable, 
 or edgewise switchboard form is for alternating current. 
 
 Wattmeters. — By combining two coils, one movable, the 
 other stationary, one attached as a voltmeter with series 
 resistance, the other attached as an ammeter, with a shunt, 
 we get an instrument whose needle indicates power or watts. 
 These are called indicating wattmeters. 
 
 sQU) 
 
 Fig. 618 
 thomson inclined coil instrument 
 
 The recording wattmeter records watt-hours. A watt- 
 hour is one watt of power used for an hour, or any combina- 
 tion like one-quarter of a watt for four hours, etc. 
 
 The Thomson Eecording Watt-Hour Meter is used for 
 direct, or alternating current. It is shown with dust-proof 
 case removed in Fig. 619. The connections made to it are 
 shown in Fig. 620. By "lights" in the figure must be 
 understood any load at all. 
 
 The meter consists of an electric motor whose armature 
 A, Fig. 620, is supplied with current from the mains 
 through a high resistance P in the back of the instrument, 
 and a small field coil on right-hand side. 
 
Electro Meters 
 
 1315 
 
 This armature is in shunt across the circuit, hence its 
 current is proportional to the voltage. 
 
 The main current passes through the field F, hence the 
 strength of the field is proportional to the current. 
 
 The speed of the motor is therefore proportional to both 
 current and voltage, that is to the power, or watts. 
 
 Fig. 619 
 thomson recording watt-hour meter 
 
 The armature shaft goes on past the commutator, to a 
 cyclometer with dials like a gas meter. The revolutions are 
 here recorded as watt-hours. 
 
 The auxiliary field is just strong enough to nearly over- 
 come the friction in the bearings and cyclometer, so that the 
 smallest current through the mains will produce rotation. 
 
 At the bottom of the armature shaft is an aluminum 
 disc revolving between the poles of permanent magnets. 
 
1316 
 
 Steam Engineering 
 
 This devide prevents the meter from running at too great a 
 speed and gives an adjustment for accuracy. 
 
 The further out the magnets are swung the faster is the 
 motion of the metal passing between their poles, and the 
 greater a retarding effect they produce. 
 
 Fig. 620 
 diagram of connections. thomson recording watt-hour meter 
 
 A meter running too slow from age, or dirty bearings 
 could be brought up to proper speed by swinging the mag- 
 nets in a little. 
 
 For heavy currents the appearance of the meter is quite 
 different, as is shown in Fig. 621. The retarding device is 
 
Electro Meters 
 
 1317 
 
 enclosed in a case, and the whole instrument is enclosed 
 in a dust-proof glass case. 
 
 Switchboard Maintenance. — The increasing relative cost 
 of switchboard apparatus in power plants justifies more 
 thorough inspection on the part of attendants than at 
 present obtains in many installations. There is a feeling 
 
 Fig. 621 
 large capacity thomson recording watt-hour meter 
 
 in some quarters that if a switchboard is blown out every 
 day with compressed air, and the instruments wiped with a 
 dust cloth, nothing further in the way of inspection need 
 be done until something goes wrong. 
 
 There are more moving parts on a modern switchboard 
 than one would at first suppose, and a certain amount of 
 
1318 Steam Engineering 
 
 attention is an essential of continuous reliable service. In 
 addition to the indicating and recording instruments there 
 are time limit relays, circuit-breaker controls, oil switch 
 mechanisms and other contacts to look after, while the 
 possibility of overheated parts of switches and coils is always 
 present. Oil switches in operation should be inspected for 
 overheating at least three times a day during the heaviest 
 part of the load, and the binding posts of potential trans- 
 formers, regulators and instruments should be looked after 
 every two or three weeks with an eye to their becoming loose. 
 
 The oil tanks on oil switches ought to be dropped cer- 
 tainly once in three months, and the contacts carefully ex- 
 amined to locate any broken or bent springs, burned con- 
 tacts or loose connections. When these contacts are cleaned 
 with a file or in any way where there is a chance of per- 
 sonal connection with the wiring system, the utmost care is 
 essential that current should be cut off, and high-potential 
 contacts avoided. Knife switches for simple disconnect- 
 ing work are worth many times their cost. 
 
 The solenoid equipment of time-limit relays are often 
 neglected for long periods. The adjustment of these de- 
 vices should be tested every two or three months and the 
 contacts cleaned with the finest sandpaper or emery cloth. 
 There is a tendency sometimes to forget that these relays 
 are delicate apparatus. The adjustment of spring tension 
 to hold contact pieces in place and the varnishing of 
 solenoid plungers need to be carefully done. No little 
 trouble can arise by careless varnishing of plungers so 
 that they stick in one position and do 'not respond to the 
 load variations above normal. Another point likely to be 
 neglected is the care of the leather diaphragm on the relay 
 bellows. This should be dressed with neatsfoot oil every 
 two or three months to prevent it from becoming stiff and 
 
Electro Meters 1319 
 
 hard. Lightning arresters should always be examined and 
 placed in condition after a storm; rheostat contact points, 
 fixed and movable, carbon brakes and copper feeder and 
 switch jaws all need regular inspection just as much as 
 commutators, brushes and bearings. 
 
 LIGHTNING ARRESTERS. 
 
 Ordinarily a lightning discharge, which is an equaliza- 
 tion of potential between the earth, and either clouds or 
 saturated atmosphere above the earth, will take place 
 through the path of least resistance, but, as pointed out by 
 Eowland, there is a certain factor somewhat resembling 
 inertia which causes the lightning, once started, to follow 
 sometimes an irregular path, similarly, for instance, as 
 when a piece of paper is suddenly torn. Transmission lines 
 and buildings of ordinary height surrounded by trees are 
 not peculiarly subject to damage from lightning, because 
 they cover a comparatively small portion of the earth, and 
 are surrounded by objects of greater height, which offer a 
 better path for the lightning discharge to the earth. They 
 do, however, receive some discharge, and the damage which 
 might be done can be very great. It is therefore, necessary 
 to provide ample protection. 
 
 Generally speaking, the severe manifestations of light- 
 ning are confined to a relatively small area, which rarely 
 exceeds in extent an area of about one square mile. It may 
 be concluded from this that protective apparatus situated at 
 certain points along the line will afford no protection to 
 remote points. 
 
 Generally speaking, the broad requirements for light- 
 ning protection consist in supplying paths to ground for any 
 charge which might accumulate on lines, or machinery from 
 
1320 Steam Engineering 
 
 any cause whatever. The ideal arrester will cause excessive 
 potential differences to be relieved instantaneously, and stop 
 the flow of current, as soon as the potential has fallen to 
 safe limits for the line. No one type of lightning arrester 
 fulfills all requirements, and accordingly it is found expe- 
 dient to use different types and combinations, in different 
 situations, and under different conditions. 
 
 For the protection of electric circuits, grounded guard 
 wires are best, and when the cost over the whole system 
 would prove prohibitive, they should be confined to such 
 localities as are peculiarly liable to suffer destructive dis- 
 charges. Three ground wires are required for the best 
 practicable protection. One of these should be placed on 
 top, and in the middle of the line, and should be a heavy 
 galvanized steel cable, and the other two, which should be 
 heavy telegraph wires, are placed outside, and above the 
 top side conductors. The ground wires should be earthed 
 at every pole for the first 10 or 12 poles from the building, 
 and at every second pole on the rest of the line. Graded 
 resistance, or aluminum type lightning arresters should be 
 installed on every feeder issuing from the station, and on 
 the primary and secondary of every transformer, and a 
 surge protector in the station, but choke coils having a 
 large number of turns should not be used in the station, 
 as they represent a possible source of danger. 
 
 Where from internal causes, such as flashing over a 
 bushing or insulator, the arcing ground sends a series of 
 oscillations through the circuit, it is necessary to provide an 
 arrester which will continue to discharge the abnormal volt- 
 age for a sufficient period to permit the operator to locate 
 and isolate the trouble. Half an hour is generally found 
 to suffice for the period of an arrester, as this will give time 
 
Lightning Arresters 1321 
 
 to discover the point of trouble, where this is remote from 
 the station. 
 
 Horn arresters placed along the line at various places 
 will do much to protect insulators from puncturing or arc- 
 ing across. These horn arresters should be adjusted to arc 
 at something below the wet arc-over voltage of the insu- 
 lators, and should be connected to earth direct. Only one 
 phase per pole should be protected by a horn arrester, so 
 that in the event of two horns arcing simultaneously, the 
 earth resistance can be utilized to limit the discharge. 
 Ground wires should not be grounded at poles carrying horn 
 arresters. 
 
 Lightning rods above wooden poles are an advantage. 
 Graded resistance multigap, or aluminum arresters should 
 be used on outgoing and incoming lines. Choke coils 
 should be in the circuit just back of the arresters, which, in 
 turn, are placed quite near the passages and are provided 
 with disconnecting switches. 
 
 Multigap Arresters. — The general theory of the multigap 
 arrester is as follows: When voltage is applied across a 
 series of multigap cylinders, the voltage distribution is not 
 uniform. The voltage distributes according to the capacity 
 of the cylinders, both between themselves and also to ground, 
 and the capacity of the cylinders to ground, results in the 
 concentration of voltage across the gaps nearest the line. 
 Fig. 622 shows the theoretical voltage gradient along an 
 arrester. The voltage across the end gaps reaches a certain 
 value. They arc across, passing the strain back to the other 
 gaps, which in turn arc over until the spark has passed en- 
 tirely across. The arrester in this manner arcs over at 
 voltage much lower than would be required if the voltage 
 distributed evenly. When the arrester has arced over, and 
 current is flowing the voltage then does distribute evenly 
 
1322 
 
 Steam Engineering 
 
 between the gaps, and is for this reason too low to maintain 
 an alternating current arc. The arc, therefore, lasts only 
 to the end of a half cycle, and then goes out. The maxi- 
 mum voltage per gap at which the arc will extinguish at 
 the end of the half cycle depends to a great extent upon the 
 metal of the cylinders. Thus some metals are more efficient 
 than others in extinguishing the arc. 
 
 u v ** ' 
 
 -i v i 
 
 V 
 
 ^ 
 
 u 
 
 ^J(o^- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 V 
 
 
 ^i<2 
 
 fe 
 
 f& 
 
 ^i 
 
 
 
 
 
 
 
 
 
 
 
 y 
 
 
 \ 
 
 
 
 
 
 ^ 
 
 pA 
 
 fM 
 
 
 
 
 
 
 
 
 * 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 ^^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 "*~ 
 
 ^^ 
 
 ^ 
 
 
 
 
 
 
 
 
 
 o Gape 
 
 Fig. 622 
 lightning arrester 
 
 When the voltage of an alternating current passes through 
 zero, of course no current flows. Before the current flows 
 in the reverse direction the voltage must again break 
 through the dielectric. The voltage required to do this 
 depends upon how much the dielectric has been 
 weakened by the passage of the arc. The cooler the arc, 
 the less the dielectric is weakened, and the higher will 
 be the voltage required to reverse the arc. As the temper- 
 ature of the arc depends upon the boiling point of the 
 cathode metal, in very much the same way as the temper- 
 
Lightning Arresters 
 
 1323 
 
 ature of steam depends upon the boiling point of the water, 
 metals with low boiling points are used for the lightning 
 arrester cylinders, in order to keep down the arc tem- 
 perature. 
 
 The use of resistance in a lightning arrester needs very 
 careful consideration. Lightning does not readily pass 
 
 L//v e 
 
 Fig. 623 
 
 STATION ARRESTER 
 
 through resistance, especially when in series with multigaps, 
 and therefore series resistance should not be used. At the 
 same time it is very desirable in some way to limit the cur- 
 rent. This problem has at last been solved by use of a low 
 shunt resistance, shunting a part of the gaps and so propor- 
 tioned to divert the current from the gaps, after the dis- 
 charge has passed the ground. Shunt resistance has been 
 
1324 Steam Engineering 
 
 used before, but never for this purpose, and was never made 
 low enough to divert the arc in this way. 
 
 It is obvious, of course, that a discharge taking place 
 through a high resistance will not relieve the line except in a 
 case of the static. What happens, however, is something 
 like this: When a surge of dangerous voltage rises, and 
 before it reaches a danger point, the series gaps arc over. 
 The series gaps then being practically short-circuited by the 
 arc the voltage concentrates across the lowest division of the 
 shunted gaps, and these at once also break down. The cur- 
 rent is then limited by the medium resistance, and the volt- 
 age is concentrated across the second division of the arrester. 
 If these gaps break down, the discharge is limited only by 
 the low resistance, which should take care of most cases. 
 If necessary, however, the voltage can "break back" in this 
 way, and cut out all resistance. The number of gaps to 
 rectify depends largely on the current that flows. In this 
 arrester the number of gaps discharging increases as the 
 limiting resistance decreases. The arrester will, therefore, 
 operate and extingush the arc at the end of the half-cycle 
 no matter which path the current takes. 
 
 Instructions for Installing 600 Volt D. C. Aluminum 
 Lightning Arresters. — The principal elements of this ar- 
 rester are two cells, each consisting of two concentric alum- 
 inum plates immersed in an electrolyte contained in a 
 glass jar. 
 
 The outside plate of each cell should be the positive, and 
 the inner one the negative, as indicated by the marking of 
 the four studs on the porcelain cover, two studs supporting 
 each plate. 
 
 In addition, station arresters are fitted with a balancing 
 resistance in shunt with each cell and a series fuse; car 
 arresters, with a series fuse as connecting link between the 
 
Lightning Arresters 
 
 1325 
 
 two cells. A diagram of connections is shown in Fig. 624. 
 
 To Fill the Arrester. — Unscrew the metal rings at the 
 top of the jars and lift off the porcelain covers, with the 
 aluminum plates attached, without removing the connec- 
 tion between the two units. Pour enough electrolyte into 
 the jars to bring the level to about one inch from cover. 
 Add % pint of oil to each jar. 
 
 In transferring the electrolyte, or oil from the carboy, 
 or other container used for shipping, employ nothing but 
 
 LlN£ 
 
 Fig. 624 
 car arrester 
 
 clean aluminum, or glass vessels and funnels. Take every 
 precaution to prevent any dust or other material from get- 
 ting into the electrolyte. 
 
 Before connecting permanently to the circuit it is ad- 
 visable to connect the arrester in series with five 120 volt 
 incandescent lamps across the 600 volt circuit. The lamps 
 will burn brightly for an instant and then rapidly diminish 
 to darkness, thus indicating that the film is all right. If the 
 lamps are dark at first, the circuit should be opened and 
 
1326 Steam Engineering 
 
 closed, and a small snappy spark at the contact point will 
 show that the circuit is complete and the film in proper 
 condition. The lamps should then be removed and the cells 
 connected directly to the circuit. 
 
 Connections. — These should be as short as possible be- 
 tween line and ground, and only to those points on which 
 the terminals are placed when shipped. Use only the style 
 of terminal furnished, as they afford no chance for a short 
 circuit by swinging against the opposite terminal. In the 
 case of pole arresters the test with series lamps, as de- 
 scribed above, should be made before making the last con- 
 nection, otherwise there may be a considerable flash due to 
 an instantaneous current rush. The ground connection of 
 these line arresters should be made directly to the ground 
 bus, and driven pipe ground. 
 
 Operation. — If the arrester has stood assembled in its 
 electrolyte for a month or more, when reconnected there will 
 be a momentary rush of current which may amount to sev- 
 eral hundred amperes. To avoid this current rush, use 
 lamps in series as explained above. 
 
 It is preferable, however, when an arrester is to be left 
 out of service for some time, to pour out the electrolyte and 
 oil, wash the plates and jars with clean water and put the 
 plates back in the jar. When replacing in service, make the 
 usual test with lamps. 
 
 After operating for some time, arresters without balanc- 
 ing resistance, may divide the voltage unequally between 
 cells, which is indicated by sparkling of the plates in one 
 cell. In such cases the arrester should be removed from the 
 circuit, and connected to a test circuit with a bank of five 
 lamps in shunt with each jar; that is ten lamps from line to 
 line with the middle point connected between cells. After 
 operating this way for several hours remove the lamps. If 
 
Lightning Arresters 1327 
 
 sparkling has ceased, the arrester is ready to be placed in 
 service. 
 
 After the arrester has been in operation for a short time, 
 the electrolyte may become dark in appearance, but this 
 condition is normal. 
 
 Inspection should cover answers to the following ques- 
 tions : 
 
 1. Are there any loose connections? 
 
 2. Is the level of the electrolyte at the proper height? 
 
 3. Are the positive plates worn off at the surface of 
 the electrolyte? 
 
 4. Are the connecting leads as short as possible? 
 
 5. Does either cell sparkle? 
 
 Multigap Lightning Arresters for Alternating Currents. 
 — These arresters, designed upon an elaboration of Prof. 
 Elihu Thomson's fundamental patents, consist of a series 
 of spark gaps shunted by graded resistances, but without 
 series resistance. The advantages possessed by them are: 
 
 1. Uniform voltage discharge over a wide range of 
 frequency due to graded resistance. 
 
 2. Shunting the dynamic current through resistance. 
 
 3. The "breaking back" action on low frequency surges. 
 
 4. Fuse in ground leg of non-grounded neutral systems. 
 
 5. Adjustable gap in each leg shunted by a fuse. 
 
 6. Metallic resistance rods of improved composition. 
 
 7. Durable knurled cylinders of special alloy. 
 
 8. General Electric standard multiplex connection. 
 When properly installed they will perform the following 
 
 functions : 
 
 First. Prevent excessive rise of potential of a transi- 
 tory nature between lines, as well as between lines and 
 ground. 
 
r 
 
 1328 Steam Engineering 
 
 Second. Bestrain the flow of electric current across 
 the gaps, and extinguish the arc when normal potential is 
 restored. 
 
 Third. Discharge high potentials covering a wide range 
 of frequency. 
 
 The essential elements of the arrester are, a number of 
 cylinders • spaced with a small air gap between them and, 
 placed between line and ground, and between line and line. 
 In operation the multigap arrester discharges at a much 
 lower voltage than would a single gap having a length 
 equal to the sum of the small gaps. 
 
 In explaining the action of multigaps, there are three 
 things to consider: 
 
 1. The transmission of the static stress along the line 
 of cylinders. 
 
 2. The sparking of the gaps. 
 
 3. The action and duration of the dynamic current 
 which follows the spark, and the extinguishment of the 
 arc. 
 
 A spark may be defined as conduction of electricty by 
 the air, and an arc as conduction of electricity by vapor of 
 the electrode. 
 
 Distribution of Static Stress Along Cylinders. — The cyl- 
 inders of the multigap arrester act like plates of condensers 
 in series. This condenser function is the essential feature 
 of its operation. When a static stress is applied to a series 
 of cylinders between line and ground (Fig. 625), the stress 
 is instantly carried from end to end. If the top cylinder 
 is positive it will attract a negative charge on the face of the 
 adjacent cylinder, and repel an equal positive charge to the 
 opposite face, and so on down the entire row. The second 
 cvlinder has a definite capacity relative to the third cylinder 
 and also to the ground; consequently the charge induced on 
 
Lightning Arresters 
 
 1329 
 
 the third cylinder will be less than on the second cylinder, 
 due to the fact that only part of the positive charge on the 
 second cylinder induces negative electricity on the third, 
 while the rest of the charge induces negative electricity to 
 the ground. Each successive cylinder, counting from the 
 top of the arrester, will have a slightly smaller charge of 
 
 5" 
 o 
 o 
 o 
 o 
 
 X l0iV 
 
 O 
 O 
 
 o 
 
 o 
 
 >< /ffed/i/m 
 \J/fasistonce 
 
 o 
 
 a 
 
 \J/?&S/>stonce 
 
 o 
 o 
 
 2 
 
 Fig. 625 
 
 ARRANGEMENT OF RESISTANCES 
 
 electricity than the preceding one. This condition has been 
 expressed as a "steeper potential gradient near the line." 
 
 Sparking of the Gaps. — The quantity of electricity in- 
 duced on the second cylinder is greater than on any lower 
 cylinder, and its gap has a greater potential strain across it 
 as shown by Fig. 626. When the potential across the first 
 
1330 
 
 Steam Engineering 
 
 gap is sufficient to spark, the second cylinder is charged to 
 line potential, and the second gap receives the static strain 
 and breaks down. The successive action is similar to over- 
 turning a row of nine-pins by pushing the first pin against 
 the second. This phenomenon explains why a given length 
 of air gap concentrated in one gap requires more potential 
 to spark across it, than the same total length made up of a 
 row of multigaps. As the spark crosses each successive 
 
 u v ^ 
 
 ^"OWOO'TOOflN 
 
 TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT 
 
 V 
 
 F 
 
 ^r~ 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 = 
 
 F 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 S, 
 
 
 *<<£ 
 
 
 feo 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 v 
 
 
 
 
 fe& 
 
 
 ^J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 r^ 
 
 r^ 
 
 p>* 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 K 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 *«-a 
 
 
 
 
 
 .5 
 
 f^ 
 
 :*>. 
 
 
 Gaps 
 
 9 
 
 Fig. 626 
 
 DIAGRAM SHOWING CONDENSER ACTION OF CYLINDERS AND 
 
 
 
 
 
 
 POT] 
 
 snt: 
 
 [AL 
 
 GRi< 
 
 lDIE 
 
 NT 
 
 FOB 
 
 ST 
 
 ATK 
 
 3 SI 
 
 DRES 
 
 S 
 
 
 
 
 gap, the potential gradient along the remainder readjusts 
 itself. 
 
 How the Dynamic Arc is Extinguished. — When the 
 sparks extend across all the gaps the dynamic current will 
 follow if, at that instant, the dynamic potential is sufficient. 
 On account of the relatively greater current of the dynamic 
 flow, the distribution of potential along the gaps becomes 
 equal, and has the value necessary to maintain the dynamic 
 
Lightning Arresters 
 
 1331 
 
 current arc on a gap. The dynamic current continues to 
 flow until the potential of the generator passes through 
 zero to the next half cycle, when the arc-extinguishing 
 quality of the metal cylinders comes into action. The alloy 
 contains a metal of low boiling point which prevents the 
 reversal of the dynamic current. It is a rectifying effect, 
 and before the potential again reverses, the arc vapor in the 
 gaps has cooled to a non-conducting state. 
 
 SportiGQ 
 
 £=j EJ 
 
 Fig. 627 
 connections for 33,000-volt y system with grounded neutral 
 
 The Cumulative or Breaking Back Effect. — The graded 
 shunt resistances (Figs. 627 and 628) give a valuable effect 
 not brought out in the previous description, where the 
 arrester is considered as four separate arresters. This is the 
 cumulative or breaking back action. 
 
 When a lightning strain between line and ground takes 
 place, the potential is carried down the high resistance, H, 
 to the series gaps, GS, and the series gaps spark over. Al- 
 
1332 
 
 Steam Engineering 
 
 though it may require several thousand volts to spark across 
 an air gap, it requires relatively only a few volts to main- 
 tain the arc which follows the spark. In consequence, when 
 the gaps GS spark over, the lower end of the high resistance 
 
 Fig. 628 
 connections fob 33,000-volt delta or ungrounded y systems 
 
 is reduced practically to ground potential. If the high 
 resistance can carry the discharge current without giving 
 an ohmic drop sufficient to break down the shunted gaps 
 GH, nothing further occurs — the arc goes out. If, on the 
 
 ^ 
 
Lightning Arresters 
 
 1333 
 
 contrary, the lightning stroke is too heavy for this, the 
 potential strain is thrown across the shunted gaps, GH, 
 equal in number to the previous set. In other words, the 
 same voltage breaks down both of the groups of gaps, GS 
 and GH, in succession. The lightning discharge current is 
 now limited only by the medium resistance, M, and the 
 potential is concentrated across the gaps, GM. If the 
 medium resistance cannot discharge the lightning, the gaps 
 GM spark, and the discharge is limited only by the low 
 resistance. The low resistance should take care of most 
 
 Fig. 629 
 
 "V" UNIT OF MULTIGAP LIGHTNING ARRESTERS 
 
 cases, but with extraordinarily heavy strokes and high fre- 
 quencies, the discharge can break back far enough to cut 
 out all resistance. In the last step the resistance is rela- 
 tively low in proportion to the number of shunt gaps, GL, 
 and is designed to cut out the dynamic current instantly 
 from the gap, GL. The illustration (Fig. 631) of the 2,200 
 volt arrester shows that the low resistance actually performs 
 this function. This breaking back effect is valuable in 
 discharging lightning of low frequency, in a manner better 
 than has been obtained before. 
 
1334 
 
 Steam Engineering 
 
 After the spark passes, the dynamic arcs are extinguished 
 in the reversed order. The low resistance, L, is propor- 
 tioned so as to draw the dynamic arcs instantly from the 
 gaps, GL. The dynamic current continues in the next 
 
 Fig. 630 
 installation of a 12,000-volt, three-phase, multigap light- 
 ning arrester in the garfield park sub-station of the 
 west chicago park commission 
 
 group of gaps, GM, until the end of the half cycle of the 
 generator wave. At this instant the medium resistance, M, 
 aids the rectifying quality of the gaps, GM, by shunting 
 
 _. 
 
Lightning Arresters 1335 
 
 out the low frequency dynamic current of the generator. 
 On account of this shunting effect the current dies out 
 sooner in the gaps, GM, than it otherwise would. In the 
 same manner, but to a less degree, the high resistance, H, 
 draws the dynamic current from the gaps, GH. This cur- 
 rent now being limited by the high resistance, the arc is 
 easily extinguished at the end of the first one-half cycle of 
 the generator wave. 
 
 "Y" Unit for Muttigap Arresters. — The High-voltage 
 Multigap Arrester is made up of "V" units (see Fig. 629), 
 each unit consisting of gaps between knurled cylinders, 
 and connected together at their ends by short metal strips. 
 The base is of porcelain, which thoroughly insulates each 
 cylinder, and insures the proper functioning of the multi- 
 
 Cylinders. — The cylinders are made of an improved alloy 
 that contains metal of low boiling point which gives the 
 rectifying effect, and metals of high boiling point which 
 cannot vaporize in the presence of the one of low boiling 
 point. The cylinders are heavily knurled. As the arc plays 
 on the point of a knurl it gradually burns back and when 
 the metal of low boiling temperature is used up, the gap 
 is increased at that particular point. The knurling there- 
 fore, insures longer life to the cylinder, by forcing succes- 
 sive arcs to shift to a new point. When worn along the 
 entire face, the cylinder should be slightly turned. 
 
 Resistance Bods. — The low resistance section of the 
 graded shunt is composed of rods of a new metallic alloy. 
 These rods have large current-carrying capacity, and prac- 
 tically zero temperature coefficient up to red heat. 
 
 The medium and high resistance rods are of the same 
 standard composition previously used. The contacts are 
 
1336 Steam Engineering 
 
 metal caps shrunk on the ends; the resistances are perma- 
 nent in value and the inductance is reduced to a minimum. 
 The rods are designed with a large factor of safety, and 
 have sufficient heat absorbing capacity to take the dynamic 
 energy following transitory lightning discharges. They are 
 gktzed to prevent absorption of moisture, and surface arcing. 
 
Lightning Arresters 1337 
 
 DIFFERENCE BETWEEN ARRESTER FOR GROUNDED Y AND NON- 
 GROUNDED NEUTRAL SYSTEMS. 
 
 The connection for a three-phase arrester, 33,000 volts 
 between lines, are shown in the illustrations (Figs. 627 atfd 
 628). One illustration (Fig. 627) shows the design for a 
 thoroughly grounded Y system and the other for a non- 
 grounded neutral system. The latter (Fig. 628) includes 
 delta, ungrounded Y, and 1 Y systems grounded through a 
 high resistance. 
 
 The difference in design lies in the use of a fourth 
 arrester leg between the multiplex connection and ground, 
 on ungrounded systems. The reason for introducing the 
 fourth leg is evident. The arrester is designed to have two 
 legs between line and line. If one line became accidentally 
 grounded, the full line potential would be thrown across 
 one leg, if the fourth or ground leg were not present. On 
 a Y system with a grounded neutral, the accidentally 
 grounded phase causes a short circuit of the phase, and the 
 arrester is relieved of the strain by the tripping of the cir- 
 cuit breaker. Briefly stated, the fourth or ground leg of the 
 arrester is used when, for any reason, the system could 
 be operated, even for a short time, with one phase grounded. 
 
 Multiplex Connection. — The multiplex connection con- 
 sists of a common connection between the phase legs of the 
 arrester above the earth connection, and provides an arrester 
 better adapted to relieve high potential surges between lines 
 than would otherwise be possible. Its use also economizes 
 greatly in space and material for delta and partially ground- 
 ed or non-grounded Y systems. 
 
 Fuse Auxiliaries. — The practice of introducing an auxil- 
 iary adjustable gap between each line wire and its corres- 
 ponding leg of the arrester has been discarded in the new 
 
1338 Steam Engineering 
 
 design, with marked increase in the sensitiveness of the ar- 
 rester. As the gap is necessary, under certain abnormal 
 conditions, it is left on the arrester, but short circuited by 
 a fuse so that it comes into service only when the fuse blows 
 on account of an arc between phase and ground, or some 
 similar extremely severe continued strain. The sensitive- 
 ness is also greatly increased by the addition of a similar 
 shunting fuse around the adjustable gap in the ground leg 
 of the arrester. The ground leg is necessary only when 
 there is an accidental ground of a phase and, ordinarily the 
 increased sensitiveness is maintained continually. 
 
 Location. — Ample wall space should be provided and 
 plenty of room in front should be left for the operator. The 
 arresters should be placed as near as possible to where the 
 lines enter the buildng. The following minimum separa- 
 tion distances have proved entirely satisfactory. 
 
 TABLE GIVING PROPER SPACE BETWEEN LIGHTNING ARREST- 
 ERS AND SETTING OF ADJUSTABLE GAP. 
 
 Distance in Minimum 
 
 Inches Between Distance 
 
 Max. Live Parts of Between Inches of 
 
 Volts Adjacent Centers Gap 
 
 Phases (See Note) 
 
 7,600 
 
 8" 
 
 28" 
 
 %■■ 
 
 12,250 
 
 8" 
 
 28" 
 
 % 
 
 13,500 
 
 8" 
 
 33" 
 
 % 
 
 17,000 
 
 10" 
 
 35" 
 
 % 
 
 22,000 
 
 12" 
 
 37" 
 
 Yz 
 
 27,000 
 
 18" 
 
 48" 
 
 y 2 
 
 32,000 
 
 22" 
 
 52" 
 
 % 
 
 37,000 
 
 26" 
 
 56" 
 
 % 
 
 Note — If barriers are used the width of barriers should 
 be added to distances given. 
 
Lightning Arresters 1339 
 
 It is advisable to locate arresters in a dry place, and 
 before assembling them the wooden supports, insulators, 
 etc., should be thoroughly dried of all moisture which may 
 have collected during transportation. 
 
 The adjustable spark gap on these arresters is shunted 
 by a fuse. This fuse blows under certain conditions and 
 cuts in the added protection of the gap. The settings of 
 this gap for the various arresters should be as already ex- 
 plained. 
 
 Voltage Range of Arresters. — Lightning arresters of the 
 form described have been designed for voltages from 5,700 
 to 37,000. For lower voltages, down to 300 volts, alter- 
 nating current, the arresters are of slightly different design, 
 havng only two resistance rods. For 300 volts and less no 
 resistance is necessary, as the voltage is so low that the arc 
 cannot hold. These arresters, therefore, consist simply of 
 spark gaps. 
 
 LOW VOLTAGE ARRESTERS — FORMS Fl AND F2. 
 
 300 to 5,700 volts. 
 
 The 2,200-volt (Figs. 631 and 634) arrester consists of 
 one unit having fourteen cylinders, nine of which are 
 shunted by a low resistance and eleven by a high resistance. 
 As in the case of the high voltage arresters, the grading of 
 resistance provides selective paths for discharges. Its action 
 and advantages are therefore similar to those of the high- 
 voltage arrester. Accumulated static charges pass off across 
 the high resistance, and two gaps. High frequency dis- 
 charges pass across all the gaps; discharges of moderate 
 frequency across the low resistance, and four gaps. The 
 low resistance is so proportioned to the number of shunted 
 gaps that the high frequency discharge across these gaps 
 is not followed by the dynamic current; the dynamic shunt- 
 
1340 
 
 Steam Engineering 
 
 ing at once to the low resistance. The discharge takes place 
 over all the gaps, but the arcs between the gaps shunted 
 by the low resistances are very small compared with the 
 bright arcs between the last four gaps. The static dis- 
 charge passes through all the gaps, while the half wave of 
 dynamic current following the static is shunted part of the 
 way by the resistance. 
 
 LINE 
 
 GROUND 
 
 Fig. 631 
 form fl, 2,200-volt multigap arrester for stations 
 
 An oscillogram of this phenomenon is shown in Fig. 632. 
 The only current in the shunted gaps is the current of static 
 discharge. It should be noted, however, that the current 
 shown is not a measure of the true current, as the oscillo- 
 graph cannot respond to currents of such high frequency. 
 
 It should be here explained that the oscillograph is a 
 device consisting of a galvanometer of strong field and high 
 
Lightning Arresters 1341 
 
 frequency of vibration, and is used for recording waves of 
 alternating current. 
 
 This arrester is designed to operate across 2,200 volts. 
 It is used, however, from each line to ground, giving, thus 
 connected, sufficient protection, and being always able to 
 handle a discharge when one line is grounded. It is built 
 to be used single-pole, but by placing two or three in the 
 same box, becomes double-pole or triple-pole. 
 
 33 Amperes 
 
 A/c7AV>77£//77 
 
 Ct/rrGnt /n >Snunt /?<ss/ stance 
 
 ^<Stc?t/c D/scn&rj$<s 
 -4* 
 
 Cu/-/~en£ /n *Snu/ite& Oc?/ds 
 ^-S200 Vo/£± 
 
 Fig. 632 
 oscillograph curves showing lightning arrester action 
 
 The 1,000-volt arrester is the same in design, but has 
 only one gap between the high resistance rod and line. 
 
 The 3,000-volt arrester (see Fig. 633) is based on the 
 same general principle as the 2,200-volt arrester, differing 
 from it mainly in having two additional gaps to take care 
 of the higher voltage. 
 
1342 
 
 Steam Engineering 
 
 The 2,200-volt arrester (Fig. 634) is used in various 
 combinations to form arresters of higher voltage. 
 
 Low-Voltage Lightning Arresters. — For low-voltage, 
 alternating-current circuits up to 300 volts the lightning 
 arrester shown in Fig. 635 is used. This type meets the 
 requirements for the protection of low voltage circuits such 
 
 LINE 
 
 GROUND 
 
 Fig. 633 
 form f2, 3,000-volt multigap arrester for stations 
 
 as transformer secondaries, motors, series arc lamps, etc. 
 These arresters are made in single, double and triple-pole 
 units. 
 
 Protection of Cable Systems. — It is frequently necessary, 
 and desirable for circuits to dip underground when passing 
 through cities, under rivers, etc., and in these cases some 
 
Lightning Arresters 
 
 1343 
 
 form of metal covered cable is generally used. Eesonance 
 invariably produces high potentials at the junction of over- 
 head, and underground lines, and these potentials are often 
 of sufficient value to break down the insulation of the 
 cables, and also the insulation of apparatus installed on 
 the system. 
 
 Fig. 634 
 
 2,200-volt, form fl, lightning arrester, discharging and 
 
 shunting the dynamic current 
 
 Fig. 635 
 single-pole arrester 
 
 Whenever lines contain both inductance, and capacity 
 in appreciable quantities, high voltages, which endanger 
 the insulation of the whole system, and which it is impossi- 
 ble to detect on ordinary switchboard instruments may 
 exist. Abnormal voltages are therefore often found in cir- 
 
1344 
 
 .Steam Engineering 
 
 cuits containing a combination of underground, and over- 
 head circuits and in underground transmission lines. 
 
 Constant Current Arresters. — For constant current 
 lighting circuits, horn arresters with resistances are recom- 
 mended. It is advisable to place these arresters in the 
 
 Fig. 636 
 double-pole and triple-pole 300-volt arresters 
 
 station on each outgoing line. When cables are used, the 
 arrester should be placed on the pole where the cable joins 
 the overhead wires. Fig. 637 shows the appearance of a 
 horn lightning arrester. 
 
 Disconnecting Switches. — Lightning arresters with dis- 
 connecting switches are desirable in order that they may be 
 
Lightning . Arresters 1345 
 
 disconnected from the line for proper inspection, adjust- 
 ment, cleaning, etc., without opening the line circuit. 
 
 The disconnecting switches, except the 2,500-volt 
 switches, are of the post insulator type. The 2,500-volt 
 switches are single-blade, front connected, and are mounted 
 directly on marble bases. The post insulator switches are 
 arranged for mounting on flat surfaces. 
 
 Fig. 637 
 horn arrester for constant current circuits 
 
 Choke Coils. — The proper selection of choke coils is an 
 important feature of lightning protection. Choke coils 
 should be used with lightning arresters except, when the 
 arresters are used to protect cable systems. 
 
 Three types of choke coils are shown in Figs. 639 and 
 640. The 4,600-volt coil is made of insulated wire, wound 
 on wooden core supported by iron feet. The 6,000-volt 
 coil is made of insulated wire and is mounted on marble 
 
1346 
 
 Steam Engineering 
 
 base. For voltages above 6,000 the "hour glass" type with 
 air insulated turns is used. With this type the coil is 
 mounted on a wooden, slate or marble base. 
 
 Fig. 638 
 post type insulator disconnecting switch 
 
 Fig. 639 
 
 HOUR GLASS TYPE — CHOKE COIL 15,000-35,000 VOLTS 
 
 6,000 volts 4,600 volts 
 
 Fig. 640 
 
 low voltage choke coils 
 
 The "hour glass" type has the following advantages on 
 high voltages. 
 
Lightning Arresters 1347 
 
 1. Should there be any arcing between adjacent turns, 
 the coils will reinsulate themselves after the discharge. 
 
 2. They are mechanically strong, and sagging is pre- 
 vented by tapering the coils toward the center turns. 
 
 3. The insulating supports can best be designed for the 
 strains that they have to withstand. 
 
 In providing lightning arresters the following points 
 should be considered: 
 
 1. What is the normal line to line voltage? 
 
 2. How many sets of transmission lines are there? 
 
 3. Is the system single-phase, two-phase, or three- phase; 
 or three-phase, four wire? 
 
 4. Is the system delta connected; Y connected, neutral 
 non-grounded; or Y connected, neutral grounded? 
 
 5. If single-phase, is the neutral grounded? 
 
 6. Are switches to be furnished with the arrester? 
 
 7. If so, are they to be double-blade or single-blade? 
 
 8. If double-blade switches are required, state the cur- 
 rent-carrying capacity of the line switch. 
 
 9. Are choke coils to be furnished? If so, state their am- 
 pere capacities and the number desired. 
 
 10. The number of switch hooks to be furnished. 
 
 11. If the line is partly overhead, and partly under- 
 ground, submit a rough sketch that shows where the un- 
 derground portion is located with reference to the stations 
 and the remainder of the line. 
 
 DIRECT CURRENT LIGHTNING ARRESTERS. 
 
 The Type M Form D-2 arrester (Fig. 641) has been 
 the standard for direct current circuits for several years, 
 and is furnished for lighting and power circuits of from 
 60 to 375 volts, and for railway and power circuits of from 
 250 to 1,800 volts. 
 
1348 Steam Engineering 
 
 The present form of arrester is somewhat longer and 
 narrower than the earlier types, and the spark gap, and 
 non-inductive resistance are in a straight line, thus form- 
 ing a direct path for the discharge, and reducing to a mini- 
 mum the possibility of short circuit in the box in case of 
 excessively heavy lightning discharges. One of the valuable 
 features of the MD-2 arrester is the fact that all parts can 
 be readily inspected on removing the cover of the porcelain 
 enclosing box (Fig. 642) and a glance will show if the 
 arrester is in proper condition for the next storm. The 
 
 L 
 
 Fig. 641 
 direct current arrester, type m, form d-2 
 
 gap is surrounded by a strong electro-magnet, which im- 
 mediately blows out the dynamic arc through the chute after 
 the lightning discharge has passed. 
 
 The gaps on arresters up to 850 volts are adjusted to 
 .025 inch, and on higher voltages to .094 inch. These ar- 
 rangements have been found to afford excellent protection 
 to the insulation of the equipments, due to the low break- 
 down points. 
 
 The spark gap terminals are threaded, and attached to 
 the lid of the box, thus affording a ready method of ad- 
 
Lightning Arresters 
 
 1349 
 
 justment, positive grip on the terminals, and easy access 
 for examination. 
 
 Ground Connections. — In all lightning arrester installa- 
 tions it is of utmost importance to make perfect ground 
 connections, as a large majority of lightning arrester troubles 
 can be traced to the lack of this precaution. It has been 
 customary to ground a lightning arrester by means of a 
 
 Fig. 642 
 direct current lightning arrester- 
 
 -INTERIOR 
 
 large metal plate buried in a bed of charcoal, at a depth 
 of six or eight feet in the earth. 
 
 A more satisfactory method of making a ground is to 
 drive a number of 1-inch iron pipes six or eight feet into 
 the earth at several points about the "station, connecting 
 all these pipes together by means of copper yriie or pref - 
 erably copper strip. A quantity of salt should be placed 
 
1350 
 
 Steam Engineering 
 
 around each pipe at the surface of the ground and the 
 ground thoroughly moistened with water. It is advisable 
 to connect the pipes to the iron frame work of the station, 
 
 Fig. 643 
 
 HORN GAP INSTALLATION FOR 35,000 VOLT ALUMINUM LIGHTNING 
 ARRESTERS, SCHENECTADY POWER CO., SHOWING ROOF EN- 
 TRANCES TO STATION AND WALL ENTRANCES TO LIGHTNING 
 ARRESTER TOWER. ONE SET OF ARRESTERS 
 DISCONNECTED 
 
Lightning Arresters 1351 
 
 and also to any water mains, metal flumes, or trolley rails 
 that are available. 
 
 For the station of ordinary size the following recommen- 
 dation is made. Place three earth-pipes equally spaced near 
 each outside wall, making twelve altogether, and place 
 three extra pipes spaced about six feet apart at a point 
 nearest the arrester. 
 
 When plates are placed in streams of running water, it 
 is much better for them to be buried in the mud along the 
 bank, than to lie in the stream. Streams with rocky bot- 
 toms are to be avoided except as a last resort. 
 
 Whenever plates are placed at any distance from the 
 arrester it is advisable to drive a pipe in the earth directly 
 beneath the arrester, thus making the ground connections 
 as short as possible. Earth plates at a distance cannot be 
 depended upon. Long ground wires in a station cannot be 
 depended upon, unless a lead is carried to the multiple pipe- 
 earths described above. 
 
 In view of the fact that it is advisable to occasionally 
 examine the ground connections to see that they are in 
 proper condition, it is desirable to lay out the exact plans 
 of the location of the ground plates, ground wires, or pipes, 
 with a brief description of them, so that at any time the 
 data may be referred to. 
 
 From time to time the resistance of the ground connec- 
 tions should be measured to determine their condition. This 
 is very easily done when pipe grounds are installed, as the 
 resistance of one pipe can be accurately determined, when 
 three or more pipes are used. The resistance of a single 
 pipe ground in good condition has an average value of 
 about 15 ohms. A simple and satisfactory method of keep- 
 ing account of the condition of the earth connections is to 
 divide the pipe-earths into two groups, and connect each 
 
L 
 
 1352 Steam Engineering 
 
 group to the 110- volt lighting circuit, with an ammeter in 
 series. If there is a flow of about 20 amperes the condi- 
 tions are satisfactory, provided the pipe-earths are properly 
 distributed around the station. 
 
 ALUMINUM LIGHTNING ARRESTERS. 
 
 The design of the aluminum arrester is based on the 
 characteristics of a cell consisting of two aluminum plates 
 on which has been formed a film of hydroxide of aluminum, 
 immersed in a suitable electrolyte. This film is formed on 
 the aluminum plates by a series of chemical and electro- 
 chemical treatments at the factory. 
 
 Valve Action.— Uj) to a certain critical voltage this hy- 
 droxide film has the property of insulating, or rather op- 
 posing /the flow of current and is, therefore, closely analo- 
 gous to a counter-electromotive force. Up to this critical 
 voltage only a small leakage and charging current can 
 flow, but during any : rise above this voltage the current 
 flow through the cell is limited only by the actual resistance 
 of the electrolyte, which is very low. The action is com- 
 parable to that of the well-known . safety valve of a steam 
 boiler by which the steam is confined until the pressure 
 •rises to a given value, at which point the valve opens and 
 releases the excess pressure. This action of the aluminum 
 cell is also closely analogous to that of a storage battery on 
 direct currant. Up to about two volts per cell, impressed, 
 the storage battery, when charged, opposes an equal counter- 
 electro-motive force, shutting off the flow of current; but 
 for voltage above this value the current is limited only by 
 the internal resistance of the cell. This characteristic 
 makes the aluminum cell ideal as a means of discharging 
 abnormal potentials, or surges in electric circuits. It prae- 
 
Lightning Arresters 
 
 1353 
 
 tically prevents the flow of current at operating voltages, 
 but instantly short circuits such abnormal portions of a 
 potential wave, or surge, as would be dangerous to the in- 
 sulation of the system. 
 
 
 
 ^"^•^Jg 
 
 ^^Jj, 
 
 ^^ ^ 
 
 ^ ^ 
 
 ^ . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 t" — — — — — 
 
 
 JL 
 
 ^ 
 
 1 it — - 
 
 s 
 
 3 
 
 § - - 
 
 
 
 
 
 
 
 
 
 
 
 
 
 *. - 
 
 
 
 
 
 
 
 
 <» — 1 — -J 
 
 Fig. 644 
 volt- ampere characteristic curve of aluminum cell 
 
 A volt-ampere-characteristic-curve of the aluminum cell 
 on alternating current is shown in Fig. 644. The data for 
 this curve was taken with an oscillograph. It should be 
 
 J 
 
1354 Steam Engineering 
 
 noted that the critical voltage, alternating current, is slight- 
 ly above 340 volts. This cut gives the discharge rate only 
 up to 5 amperes, in order to better illustrate the normal and 
 critical voltage points. Above this value the discharge rate 
 depends almost entirely upon the internal resistance of the 
 electrolyte. This resistance is such that at double the nor- 
 mal operating voltage, or 600 volts per cell, the current 
 discharge is six hundred, to one thousand amperes for a 
 brief time. This rate of discharge represents a quantity of 
 electricity several times greater than the quantity liberated 
 by an ordinary induced lightning stroke. 
 
 Condenser Action. — Besides the valve action described 
 above there is another characteristic of the cell of great im- 
 portance. The thin insulating film of aluminum hydroxide 
 between the conducting aluminum and the conducting elec- 
 trolyte acts as a dielectric and the cell, therefore, is an 
 elecstatic condenser. A condenser of this type makes an 
 ideal path for high frequency lightning discharges. With 
 these arresters, for instance, 10,000 cycles, which is not an 
 unusual frequency for lightning disturbances, would dis- 
 charge almost 100 amperes without any rise in voltage. 
 
 Due to this capacity, these aluminum arresters cannot 
 be connected permanently across alternating voltage. The 
 charging current at normal frequency (about .5 amp.) 
 would in time heat the electrolyte. In every case, there- 
 fore, spark gaps set to arc over at slight increase of voltage, 
 insulate the arrester from the line. 
 
 Film Dissolution. — Another characteristic of the alumi- 
 num cell is the dissolution of a part of the film when the 
 plates stand in the electrolyte, and the cell is disconnected 
 from the circuit. The film is presumably composed of two 
 parts; one part is hard and insoluble, and apparently acts 
 as a skeleton to hold the more soluble part. When a cell, 
 
Lightning Arresters 
 
 1355 
 
 which has stood for some time disconnected, is reconnected 
 to the circuit, there is a momentary rush of current, which 
 replaces the part of the film which has dissolved. AH elec- 
 
 Elecirolyie 
 Cones in 
 Cross- ■ 
 Section I 
 
 Aluminum 
 
 Cones 
 
 Complete 
 
 Metal. 
 
 Base 
 
 Fig. 645 
 cross section of aluminum lightning arrester 
 
 trolytes dissolve the film, the extent of the dissolution de- 
 pending upon the length of time the film is in the electro- 
 lyte, the electrolyte used, and its temperature. It is neces- 
 
1356 
 
 Steam Engineering 
 
 sary to charge the cells from time to time to prevent the 
 initial rush of dynamic current causing trouble. By keep- 
 ing the films formed at all times, the initial rush of cur- 
 rent is prevented, and the ultimate temperature rise in case 
 of continued discharge of the arrester is minimized. The 
 ability of the arrester to take care of discharges lasting for 
 any considerable length of time, therefore, depends upon 
 the conditon of the arrester film. When the cells, in com- 
 mercial use, are allowed to stand for not more than a day 
 
 Fig. 646 
 parts of 15000 volt aluminum lightning arrester 
 
 or two, the film dissolution, and initial current rush is 
 negligible. Suitable means are provided with the arresters 
 for connecting them directly across the line. This is a 
 very simple operation, and thus the film is kept in good 
 condition. 
 
 In very warm climates it is sometimes advisable to take 
 special precaution to keep the cells normally cool. 
 
 Design. — The aluminum lightning arresters for alter- 
 
Lightning Arresters 
 
 1351 
 
 nating current circuits from 1,000 to 110,000 volts con- 
 sist essentially of inverted aluminum cones, placed one 
 above the other in stacks> and insulated with a vertical spac- 
 ing of about .3 inch. An electrolyte partially fills the 
 
 Fig. 647 
 parts of 4600 volt three-phase aluminum lightning arrester 
 
 space between adjacent cones, so forming aluminum cells 
 connected in series. The stack of cones with the electrolyte 
 between them is then immersed in a tank of oil. The elec- 
 trolyte being heavier than the oil remains between the 
 
r 
 
 1358 Steam Engineering 
 
 aluminum cones. The oil improves the insulation between 
 cones, prevents evaporation of the solution and, due to its 
 heat absorbing capacity, enables the arresters to discharge 
 continuously for long periods, a very valuable feature of 
 these arresters. The tanks are of steel with welded seams. 
 The general arrangement of the cells is shown in Figs. 
 645, 646 and 647. 
 
 QUESTIONS AND ANSWERS. 
 
 935. How are switchboards made up? 
 
 Ans. They are built up of panels of slate or marble sup- 
 ported by frames of angle iron. 
 
 936. How are the different panels designated? 
 
 Ans. Some are for motor control, others for dynamo 
 running, others for operating the outer circuit, and others 
 for charging storage batteries. 
 
 937. Is a knowledge of switchboards an important mat- 
 ter? 
 
 Ans. It is, and every engineer should especially study 
 those in his own station. 
 
 938. "What is the regular equipment of a D. C. switch- 
 board having a capacity of from 250 to 6,500 amperes? 
 
 A ws. One carbon-break or magnetic blow-out circuit 
 breaker with telltale. 
 
 One illuminated dial ammeter with shunt. 
 
 One hand wheel and chain for operating rheostat. - 
 
 One receptacle for voltmeter plug. 
 
 One S. P. S. T. field switch. ' 
 
 One S. P. S. T. main switch. 
 
 One recording watt-hour meter. 
 
 939. What is meant by the abbreviations S. P. S. T.? 
 Ans. Single Pole Single Throw. 
 
 ^_ 
 
Questions and Answers 1359 
 
 940. What does D. P. D. T. mean in speaking of switch- 
 boards ? 
 
 Ans. Double Pole Double Throw. 
 
 941. What is meant by T. P. ? 
 
 Ans. Triple pole. It opens every circuit of a three- 
 phase system. 
 
 942. Is it good practice to place a main switch at the 
 machine ? 
 
 Ans. It is best. 
 
 943. Why? 
 
 Ans. So that the cables from generator to board may 
 be cut off at the generator. 
 
 944. What is an equalizer? 
 
 Ans. It is a cable running along from machine to ma- 
 chine, and connecting the functions of series field and 
 brush on all the machines, but does not connect with switch- 
 board. 
 
 945. What kind of a break has the field switch? 
 Ans. A carbon break. 
 
 946. Describe the action of a field switch. 
 
 Ans. Just before it opens it makes contact with an extra 
 clip, and puts a resistance on as a shunt around the field 
 coils. 
 
 947. If this were not done what would be the conse- 
 quences ? 
 
 Ans. The fields would act as a spark-coil and the in- 
 sulation be damaged. 
 
 948. When it is desired to throw a generator in par- 
 allel with other generators already running what is the 
 proper method of procedure? 
 
 Ans. First. Close main and equalizer switches near the 
 machine. 
 
1360 Steam Engineering 
 
 Second. Close field switch on panel. 
 
 Third. Close circuit breaker. 
 
 Fourth. Insert potential plug in receptacle and regulate 
 voltage. 
 
 Fifth. When proper voltage is obtained close the other 
 main switch on panel. 
 
 949. What is meant by voltage? 
 Ans. Electric pressure, or potential. 
 
 950. What is a volt? 
 Ans. The unit of pressure. 
 
 951. What is a voltmeter? 
 
 Ans. An instrument that indicates the voltage. 
 
 952. What is an ohm? 
 Ans. The unit of resistance. 
 
 953. Give a brief definition of Ohm's law? 
 
 Ans. The electromotive force equals the resistance mul- 
 tiplied by current intensity. 
 
 954. What is an ampere? 
 
 Ans. It is the unit of volume, or quantity-time unit for 
 measuring the rate of flow of an electric current. 
 
 955. What is a coulomb? 
 
 Ans. It is an ampere-second. A coulomb equals the 
 flow of an ampere of current past a given point each second 
 of time. 
 
 956. What is an ammeter? 
 
 Ans. An apparatus ior measuring current rate. 
 
 957. What is the meaning of the word watt as used 
 in electrical work? 
 
 Ans. A watt is the unit of work. It equals volts X am- 
 peres. 
 
 '958. What is the function of the wattmeter? 
 
 Ans. To record the watt-hours of work. 
 
Questions and Answers 13S1 
 
 959. What is a kilo watt (K. W.) ? 
 Ans. 1,000 watts. 
 
 960. Expressed in mechanical horse-power, what is one 
 K. W. equal to? 
 
 Ans. 1000-^746=1 1/3 H. P. 
 
 961. What is a field rheostat? 
 
 Ans. An apparatus for controlling the current output. 
 
 962. What is the function of a transformer ? 
 
 Ans. To transform the current from a higher to a lower 
 voltage, or from A. C. to D. C. 
 
 963. W r hat is meant by synchronism of electric ma- 
 chines? 
 
 Ans, When the maximum value of the E. M. F. in 
 each machine occurs at exactly the same instant of time, 
 the machines are in sjmchronism. 
 
 964. What is meant by the exciter panel of a switch- 
 board ? 
 
 Ans. It is the panel that is equipped with the necessary 
 switches, etc., for connecting the small exciter dynamo with 
 the other generators in the station. 
 
 965. What is a sub-station? 
 
 Ans. It is the connecting link between the transmission 
 line, and the trolley wire or third rail. 
 
 966. When A. C. is generated at the power station, and 
 D. C. is used on the line, how is it accomplished ? 
 
 Ans. The A. C. is changed to D. C. by rotary converters 
 at the sub-station. 
 
 967. What is meant by frequency? 
 
 Ans. The number of times the current reverses per sec- 
 ond. 
 
 968. What is the usual frequency for railway motors? 
 Ans. 25 is the standard. 
 
 969. What is a frequency changer? 
 
1362 Steam Engineering 
 
 Ans. A machine which receives current at one frequency 
 and delivers it at another frequency. 
 
 970. What apparatus is used in an A. C. to D. C. sub- 
 station ? 
 
 Ans. Step down transformers, rotary converters, and 
 A. C. incoming and D. C. outgoing switchboards. 
 
 971. What is the proper procedure for placing rotary 
 converters in service ? 
 
 Ans. After the machine has been started from the A. 
 C. ends, and builds up with the proper polarity, first close 
 the equalizer switch (on machine) — second, close circuit 
 breaker on panel — third, insert potential plug in receptacle 
 and regulate voltage — fourth, when the proper voltage is 
 obtained, close positive switch (on panel). 
 
 972. What will be the result if the rotary builds up with 
 polarity reversed ? 
 
 Ans. The voltmeter will swing back of zero. 
 
 973. How may the polarity be corrected? 
 
 Ans. By means of the four-pole, double-throw field 
 break-up reversing switch mounted on the converter. 
 
 974. Describe an oil switch. 
 
 Ans. It is a switch similar in its action to other 
 switches, with the exception that its mechanism is im- 
 mersed in a small tank of oil. 
 
 975. What advantage is gained thereby? 
 
 Ans. Reliability of action in opening or closing a cir- 
 cuit. 
 
 976. Mention another advantage gained by the use of 
 the oil switch and oil circuit breaker. 
 
 Ans. It has made safely possible the transmission and 
 use of high-tension currents of electricity. 
 
 977. What is a circuit breaker? 
 
 Ans. It is a switch so designed as to be capable of fre- 
 
Questions and Answers 1363 
 
 quently opening the circuit carrying its full current with- 
 out any damage to itself. 
 
 978. What is a galvanometer? 
 
 Ans. An instrument consisting of a coil of wire car- 
 rying the current to be tested, and a magnet, the two be- 
 ing arranged so that one can be deflected. 
 
 979. Describe the Thompson type of galvanometer. 
 Ans. The coil of wire is stationary, and the light mag- 
 netic needle is suspended by a silk thread. 
 
 967. Describe the D'Arsonval galvanometer. 
 
 Ans. In this type the small light coil of wire is sus- 
 pended by a fine bronze wire between the poles of a station- 
 ary magnet. 
 
 968. How are the readings taken from these instru- 
 ments ? 
 
 Ans. From a circular scale, over which the needle of 
 the instrument swings. 
 
 980. What is a lightning discharge? 
 
 Ans. An equalization of potential between the earth, 
 and either clouds, or saturated atmosphere. 
 
 981. What path does the discharge generally follow? 
 Ans. The path of least resistance. 
 
 982. What are the general requirements for protection 
 of electric stations from lightning? 
 
 Ans. The supplying of paths to ground for any charge 
 which might accumulate on lines or machinery. 
 
 983. What is the general theory of the multi-gap light- 
 ning arrester? 
 
 Ans. When voltage is applied across a series of multi- 
 gap cylinders, the voltage distribution is not uniform, but 
 is governed by the capacity of the cylinders, both between 
 themselves, and also to ground, which results in the con- 
 centration of voltage across those gaps nearest the line. 
 
1364 Steam Engineering 
 
 984. What are the principal elements of a 600 volt 
 D. C. aluminum lightning arrester? 
 
 Ans. Two concentric aluminum plates immersed in an 
 electrolyte contained in a glass jar, the outside plate of 
 each cell being positive, and the inner one negative. 
 
 985. Describe the multigap lightning arrester for A. C. 
 Ans. It consists of a series of spark gaps shunted by 
 
 graded resistances, but without series resistance. 
 
 986. Describe briefly the aluminum lightning arrester. 
 Ans. It consists of two aluminum plates on which has 
 
 been formed a film of hydroxide of aluminum, immersed 
 in a suitable electrolyte. 
 
Current Distribution 
 
 Divided Circuits. — Currents of electricity, although they 
 have no such material existence as water or steam, still 
 obey the same general law ; that is, they flow and act along 
 the lines of least resistance. If a pipe extending to the 
 top of a ten-story building had a very large opening at the 
 first floor, it would be impossible to force water to the 
 top floor. All the water would run out at the first floor. 
 If the opening at the first floor were small only a part of 
 the water would escape through it, some would reach the 
 top of the building. The flow of water in each case is in- 
 
 Fig. 648 
 
 versely proportional to the resistance offered to it by the 
 different openings. 
 
 The same thing is true of currents of electricity. Where 
 several paths are open to a current of electricity the flow 
 through them will be in proportion to their conductivities, 
 which is the inverse ratio of their resistances. As an illus- 
 tration, the current flow through all of the lamps, Fig. 
 
 648, is the same, because each lamp offers the same re- 
 sistance. But if we arrange a number of lamps as in Fig. 
 
 649, the lampsi in series will offer twice as much resistance 
 as the single lamps, and will receive but half the current 
 of the single lamp. In Fig. 650 we have still another 
 
 1365 
 
1366 
 
 Steam Engineering 
 
 arrangement. The lamp A limits the current which can 
 flow through B and C, and that current which does flow 
 divides between B and C in proportion to their conductivi- 
 ties. If B has a resistance of 110 ohms and C 220 ohms, 
 then B will carry two parts of the current and, C only one. 
 The combined resistance of all lamps, Fig. 648, equals the 
 resistance of one lamp divided by the number of lamps. 
 The combined resistance, Fig. 649, equals the sum of the 
 resistances of the two lamps at A multiplied by the resist- 
 
 A, 
 
 OB 
 
 Fig. 649 
 
 Fig. 650 
 
 ance of B and divided by the sum of all the resistances. If 
 the resistance of each of the lamps were 110 ohms, the 
 problem would work out thus : 
 
 110+110X110 
 
 iio+iio+iio =73 1/3 ' 
 
 In Fig. 650 the total resistance is 
 
 110X220 
 ■ 1-110=183 1/3. 
 
 110+220 
 
 One practical illustration of the above law may be found 
 in the method of switching series arc lamps, Fig. 651. As 
 
Current Distribution 
 
 1367 
 
 long as the switch S is open the arc lamp burns, but as soon 
 as the switch is closed the lamp is extinguished because 
 the resistance of the short wire and the switch S is so 
 much less than that of the arc lamp that practically all 
 the current flows through S. 
 
 Wiring Systems. — The system of wiring which is most 
 generally used for incandescent lighting and ordinary pow- 
 er purposes is called the two-wire parallel system. In this 
 system of wiring the two wires run side by side, one of 
 them being the positive and one the negative. The lamps, 
 motors and other devices are then connected from one wire 
 to the other. A constant pressure of electricity is main- 
 
 Fig. 651 
 
 tained between the two wires, and the number and size of 
 lamps, or other apparatus, connected to these two wires, 
 determine how many amperes are required. Each lamp or 
 motor is independent of the others and may be turned 
 on or off without disturbing the others. 
 
 A diagram of such a system is shown in Fig. 652. 
 
 In this system the quantity of current varies in propor- 
 tion to the number of devices connected to it. Suppose 
 that we are maintaining a pressure or potential or electro- 
 motive force of 110 volts on such a system, and that we 
 have connected to the system ten 16 candle power incan- 
 descent lamps, consuming one-half ampere each. The total 
 
1368 
 
 Steam Engineering 
 
 quantity of current to supply these lamps would be 5 am- 
 peres. If we should now switch on ten more lamps the 
 quantity of current would be 10 amperes, and the pressure 
 would remain 110 volts. This system is also known as the 
 "constant potential system," or multiple arc system, and 
 among the numerous devices used in connection with it are 
 
 jl U U Hi 
 
 Fig. 652 
 
 TWO-WIRE PARALLEL SYSTEM 
 
 the constant potential arc lamp, the shunt motor, the com- 
 pound wound motor, the series motor, incandescent lamps, 
 etc. Electric street railways are also operated on this sys- 
 tem. The current supplied through this system of wiring 
 may be either direct or alternating current. 
 
 The series arc system, Fig. 653, is a loop; the greatest 
 electrical pressure being at the terminal, or terminal ends 
 
 -x- 
 
 -*- 
 
 Fig. 653 
 series arc system 
 
 of the loop. The current in such a system of wiring is 
 constant, and the pressure varies as the lamps or other 
 apparatus are inserted in or cut out of the circuit. This 
 system is also called the constant current system. The same 
 current passes through all of the lamps, and the different 
 lamps are also independent of each other. 
 
Current Distribution 
 
 1369 
 
 At the present time the series system is used mostly for 
 operating high tension series arc lamps. The use of motors 
 with it has been almost entirely abandoned. 
 
 The series multiple system, Fig. 654, is simply a number 
 of multiple systems placed in series. This method of wiring 
 
 Fig. 654 
 series multiple system 
 
 was at one time employed to run incandescent lights from 
 a high tension series arc light circuit, but on account of the 
 danger connected with the use of incandescent lamps, op- 
 erated from a high tension arc lamp circuit, the system has 
 been abandoned. It is not approved by insurance compa- 
 nies, and consequently is not often used. 
 
 Fig. 655 
 multiple series system 
 
 The multiple series system consists of a number of small 
 series circuits, connected in multiple, as shown in Fig. 655. 
 This system of wiring is used on constant potential sys- 
 tems, where the voltage is much greater than is required by 
 the apparatus to be used, as, for instance, connecting eleven 
 
r 
 
 1370 
 
 Steam Engineering 
 
 miniature lamps, whose individual pressure required is 10 
 volts, into a series, and then connecting the extreme ends of 
 such a series to a multiple circuit whose pressure is 110 
 volts. 
 
 The three wire system, Fig. 656, is a system of multiple 
 series. In this system, as its name implies, three wires are 
 used, connected up to the machines in the manner shown 
 in the diagram. Both machines are in series when all 
 lights are turned on, but should all lights on one side of 
 the neutral or center wire be turned off the machine on 
 the other side alone would run the other lights. 
 
 One of these wires is positive, the other is negative, and 
 the remaining one or center wire is neutral. In ordinary 
 
 Jf *A 6 6 6 6 6 
 
 F_A 9 9 9 9 9 
 
 Fig. 656 
 three wire system 
 
 practice from positive to negative wire, a potential of 220 
 volts is maintained, while from the neutral wire to either 
 of the outside wires a potential of 110 volts exists. The 
 advantages of such a system are many, principally among 
 them is the use of double the voltage of the two wire sys- 
 tem; this reduces the current one-half and allows the use 
 of smaller wires. This system* only requires three wires 
 for the same amount of current that would require four in 
 the other system. Motors are supplied at 220 volts, while 
 lights operate at 110. Incandescent lighting circuits can 
 be maintained from either outside wire to the neutral wire. 
 The saving in copper by dispensing with the fourth wire 
 
Current Distribution 1371 
 
 is not the only advantage in the saving of conductors. The 
 neutral wire may be much smaller than the outside wires 
 because it will seldom be called upon to carry much cur- 
 rent. 
 
 Inside of buildings, however, where overheating of a 
 wire is always dangerous, the neutral wire should be of 
 the same size as the others. By tracing out the circuits in 
 Fig. 656, it will readily be seen that, so long as all lamps 
 are burning, the current passes out of dynamo 1 into the 
 positive wire and from there through the lamps (always 
 two in series) to the negative or — wire, returning over it 
 to the — pole of dynamo 2. So long as an equal number 
 of lamps is burning on each side of the neutral, no current 
 passes over the neutral wire in either direction. But if the 
 positive or + w i re should be broken, say at a, dynamo 1 
 will no longer send current and the lamps between the posi- 
 tive and neutral wire will be out. 
 
 Dynamo 2 will now supply the lamps between the neutral 
 and the negative wire and for the time being the neutral 
 wire will become positive. Should the negative wire break 
 at b, the lamps connected to it would be out and dynamo 1 
 would supply the lights on its side, the neutral wire be- 
 coming negative. When motors of one or more horse-power 
 are used on this system, it is usual to connect them to the 
 outside wires using 220 volts. It is important also to ar- 
 range the wiring so that an equal number of lights are in- 
 stalled on each side of the neutral. When the lights and 
 motors are so arranged, the system is said to be "balanced." 
 It is also very important to arrange so that the neutral 
 wire cannot readily be broken. Should the neutral wire be 
 opened while, for instance, fifty lamps were burning on one 
 side and say ten or twenty on the other, the ten or twenty 
 would be broken by the excess voltage. Grounded wires 
 
1372 
 
 Steam Engineering 
 
 ordinarily cause more trouble than anything else on elec- 
 tric light or power circuits, but with the three wire system, 
 the neutral wire is often grounded. Grounds on this wire 
 are less objectionable than on other wires, because it car- 
 ries very little current, and that current is constantly vary- 
 ing in direction, so that no great amount of electrolysis 
 can occur at any one place. 
 
 Feeders. — (See Fig. 657) , as the name implies, is a 
 term used to designate wires which convey the current to 
 
 Serulce 
 
 
 ^f^^^^^^^^^^^^ 
 
 Branch 
 
 ■X Circuits^ 
 
 m 
 
 Fig. 657 
 
 any number of other wires, and the feeders become a part 
 of the multiple series, multiple and three wire systems. 
 
 Distributing mains are the wires from which the wires 
 entering buildings receive their supply. 
 
 Service wires are the wires that enter the buildings. 
 
 The center of distribution is a term used for that part 
 of the wiring system from which a number of branch cir- 
 cuits are fed by feeder wires. In most buildings the tap 
 lines are all brought to one point, and terminate in cut-out 
 boxes. These cut-out boxes are supplied by the main. Each 
 floor of the building may have a cut-out box, or each floor 
 
Current Distribution 
 
 1373 
 
 of the building may have several cut-out boxes of the above 
 description. 
 
 Calculation of Wires. — If we desire to transmit or deliver 
 a certain quantity of liquid through a pipe, we estimate the 
 size of the pipe and the comparison of sizes in the pipes by 
 squaring the diameter, in inches, and multiplying the re- 
 sult by the standard fraction .7854. By way of explanation 
 we will dwell upon the above method for a short time. In 
 Fig. 658 we have a surface which measures one* inch on all 
 four sides, and which has an area of one square inch. 
 
 Now in a circle which is contained in this figure, and 
 which touches all four sides of the square, we would only 
 
 Fig. 658 
 
 have .7854 of a square inch. If the diameter of this circle 
 is 2 inches instead of 1, you can readily see by Fig. 659 
 that its area is four times as great or 2X2=4. We then 
 multiply by the standard number .7854 in order to find the 
 area contained in the two-inch circle ; and if the diameter 
 were 3 inches, then 3X3=9, and 9X-7854 would be the 
 area in square inches contained in the three-inch circle. 
 
 Again, if we had a square one inch in area, like Fig. 660, 
 and we took one leg of a carpenter's compass and placed it 
 on one corner of this square, striking a quarter-circle from 
 one adjacent corner to the other adjacent corner, the area 
 inscribed by the compass would again be .7854 of a square 
 inch. 
 
1374 
 
 Steam Engineering 
 
 The above will explain to the reader the relation between 
 the circular and square mil. The circular mil is a circle 
 
 1 
 
 one mil ( of an inch) in diameter. The square mil 
 
 1,000 
 
 is a square, one mil long on each side. In the calculation 
 
 of wires for electrical purposes, the circular mil is generally 
 
 used, because we need only multiply the diameter of a wire 
 
 Fig. 659 
 
 by itself to obtain its area in circular mils. If we used 
 square mils we should have to multiply by .7854. 
 
 The resistance of a conductor (wire) increases directly 
 as its length, and decreases directly as its diameter is in- 
 creased. A wire having a diameter of one mil and being 
 one foot long has a resistance at ordinary temperature of 
 10.7 to 10.8 ohms. 10.8 ohms is the resistance usually 
 taken. If this wire were two feet long, it would have 
 a resistance of 21.4 ohms, but if it were two mils in diam- 
 eter and one foot long, it would have a resistance one- 
 fourth of 10.7, or about 2.67. 
 
Current Distribution 
 
 1375 
 
 Every transmission of electrical energy is accompanied 
 by a certain loss. We can never entirely prevent this loss 
 any more than we can entirely avoid friction. But we can 
 reduce our loss to a very small quantity simply by selecting 
 a very large wire to carry the current. This would be the 
 proper thing to do if it were not for the cost of copper, 
 which would make such an installation very expensive. As 
 it is, wires are usually figured at a loss of from 2 to 5 
 per cent. 
 
 The greater the loss of energy we allow in the wires, 
 the smaller will be the cost of wire, since we can use smaller 
 wires with the greater loss. 
 
 Fig. 660 
 
 In long distance transmission and where the quality of 
 light is not very important, a loss of 10 or 20 per cent is 
 sometimes allowed, but in stores, residences, etc., the loss 
 should not exceed 2 or 3 per cent, otherwise the candle 
 power of the lamps will vary too much. 
 
 Where the cost of fuel is high the saving in first cost of 
 copper is soon offset by the continuous extra cost of fuel 
 to make up for the losses in the wires. 
 
 To determine the size of wire necessary to carry a certain 
 current at a given number of volts loss, we may proceed in 
 the following manner : Multiply the number of feet of wire 
 in the circuit by the constant 10.7, and it will give the 
 circular mils necessary for one ohm of resistance. Multiply 
 
1376 Steam Engineering 
 
 this by the amperes, and this will give the circular mils- 
 
 for a loss of one volt. Divide this last result by the volts 
 
 to be lost, and the answer will be the number of circular 
 
 mils diameter that a copper wire must have to carry the 
 
 current with such a loss. After obtaining the number of 
 
 circular mils required, refer to table 53 and select the wire 
 
 having such a number of circular mils. 
 
 The formula is as follows : 
 
 Feet of wire X 10- ?X amperes 
 
 = circular mils. 
 
 Volts lost 
 
 By simply transposing the above terms we obtain an- 
 other formula, which can be used to determine the volts 
 lost in a given length of wire of a certain size, carrying a 
 certain number of amperes. 
 
 The formula is as follows : 
 
 Feet of wireX 10.7 X amperes 
 
 = Volts lost. 
 
 Circular mils 
 
 And again, by another change in the terms we obtain a 
 
 formula which shows the number of amperes that a wire 
 
 of given size and length will carry at a given number of 
 
 volts lost : 
 
 Circular mils X volts lost 
 
 ■ = Amperes. 
 
 Feet of wireX10.7 
 
 In computing the necessary size of a service or main 
 
 wire, to supply current for either lamps or motors, it is 
 
 necessary to know the exact number of feet from the 
 
 source of supply to the center of distribution. When the 
 
 distance of center of distribution is given it is well to 
 
 ascertain whether it is the true center or not. It may be 
 
 only the distance from a cut-out box that has been given, 
 
 when it should have been the distance from the point at 
 
 which the service enters the building or, perhaps from the 
 
Current Distribution 1377 
 
 point at which the service is connected to the street mains. 
 For when the size is determined it is for a certain loss 
 which is distributed over the entire length of the wire to 
 be installed. The transmission of additional current on 
 the mains in the building increases the drop in volts in 
 the main, and likewise in the service. Most buildings are 
 wired for a certain per cent loss in voltage, estimated from 
 the point where the service enters the building. All addi- 
 tions should be estimated from that point. 
 
 In using the formula for rinding the proper size wire 
 to carry current, the first thing to be determined is the 
 length of the wire; remember that the two wires are in 
 parallel, and therefore the total length of the wire is twice 
 the total distance from the commencement to the end of 
 the circuit. If the proposed load on this circuit is given 
 in lamps, you may reduce it to amperes, and if the pro- 
 posed load is given in horse-power, you may reduce it to 
 amperes. The voltage on the circuit is known in either 
 case. You take the loss of the voltage and divide the pro- 
 duct of amperes, multiplied by the length, as found, and 
 10.7 by it; this answer will be the size in circular mils of 
 a wire necessary to carry the amperes. 
 
 Example. — What is the size of wire required for a 50- 
 volt system, having 100 lamps at a distance of 100 ft., with 
 a 4 per cent loss? 
 
 Answer. — The load of 100 lamps on a 50-volt system is 
 100 amperes, and a 4 per cent loss of 50 volts is 2 volts. 
 Multiply the total length of the wire, which is twice the 
 distance, or 200 feet, by the 100 amperes of current; this 
 gives us 20,000. Then multiply this by the constant, which 
 is 10.7 ; this gives us 214,000. Divide this by 2, which is 
 the loss in volts, and you have 107,000 circular mils diam- 
 eter of wire required. 
 
1378 Steam Engineering 
 
 When determining the size of wire to be used it is al- 
 ways necessary to consult the table of carrying capacities, 
 and this will very often indicate a wire much larger than 
 that determined by the wiring formula, especially if a some- 
 what high loss is figured on. 
 
 When estimating the distance it is not always correct to 
 take the total distance. 
 
 To illustrate: Suppose one lamp is 100 feet from the 
 point at which the distance is determined, and the farthest 
 lamp is 400 feet, the remaining lamps being distributed 
 evenly between these two points, we would average the 
 distances between the first and last lamp, which would be 
 200 feet. It is necessary to use judgment in estimating the 
 mean or average distance, as the lamps or motors are 
 bunched differently in each case. 
 
 In a series system the loss in voltage makes considerable 
 difference to the power, but does not affect the quality of 
 the light as much as in a multiple arc or parallel system. 
 In a parallel system the lamps require a uniform pressure, 
 and this can only be had by keeping the loss low. In a 
 series system the lamps depend upon the constant current 
 and the voltage varies with the resistance, in order to keep 
 the current constant. This is accomplished by a regulator 
 on the dynamo, which is designed to compensate for the 
 changes of resistance in the circuit and to increase or de- 
 crease the pressure as required. 
 
 In estimating the size of wire for a series system you 
 consider the total length of the loop. There is no average 
 distance as the total current travels over the entire circuit. 
 We will assume that you have an arc light circuit of a 
 No. 6 Brown & Sharp gauge wire, and want to find what 
 loss there is in this circuit. You have the area of a No. 6 
 wire, which is 26,250 circular mils, and the length of the 
 
Current Distribution 1379 
 
 circuit, and from this we will figure the loss in this manner : 
 Assuming the circuit to be 10,000 feet long, and the cur- 
 rent 10 amperes, we will multiply 10,000 feet by 10 am- 
 peres, and this by 10.7, which gives us 1,070,000, and divide 
 this by 26,250. The answer is 40 volts, lost in the circuit. 
 
 Such a circuit would operate at perhaps 2,000 or 3,000 
 volts, and a loss of 40 volts would not be excessive. It 
 would be wasting a little less energy than is required to 
 burn one large arc lamp. 
 
 The multiple series system is a number of small wires 
 connected in multiple, and is the same as the multiple are 
 or parallel system. The wire is figured in the same way as 
 for the multiple arc system. 
 
 The series multiple system is a number of small parallel 
 systems, and these are connected in series by the main wire. 
 The wire is figured the same as for the series system. 
 
 The Edison three-wire system, is a double multiple, and 
 the two outside wires are the ones considered when carrying 
 capacity is figured. When this system is under full load 
 or balanced, the neutral wire does not carry any current, 
 but the blowing of a fuse in one of the outside wires may 
 force the neutral wire to carry as much current as the out- 
 side wire and it should, therefore, be of the same size. The 
 amount of copper needed with this system is only three- 
 eighths of that required for a two-wire system. 
 
 Wiring Tables. — On the following pages are presented 
 wiring tables 55, 56 and 57 for 110,220 and 500 volt work. 
 These tables are used in the following manner : Suppose we 
 wish to transmit 60 amperes a distance of 1,800 feet at 110 
 volts and at a loss of 5 per cent. We take the column 
 headed by 60 in the top row and follow it downward until 
 we come to 1,800, or the number nearest to it. From 
 this number we now follow horizontally to the left, and 
 
1380 Steam Engineering 
 
 under the column headed by 5 we find the proper size of 
 wire, which is 500,000 c. m. The same current, at a loss 
 of 10, would require only a 0000 wire, as indicated under 
 the column at the left, headed by 10. 
 
 Before making selection of wire, always consult table 53 
 of carrying capacities. This table is taken from the rules 
 of the National Board of Fire Underwriters, and is in gen- 
 eral use. 
 
 The first three of the following tables are wiring tables 
 for the three standard voltages, 110, 220, 500. From these 
 tables can be found the sizes of wire required to carry va- 
 rious amounts of current (in amperes) different distances 
 (in feet) at several percentages of loss, or the distance the 
 different sizes of wire will carry various amounts of cur- 
 rent at several percentages of loss can be found. 
 
 These tables are figured on safe carrying capacity for the 
 different sizes of wire. The distances in feet are to the 
 center of distribution. 
 
Current Distribution 1381 
 
 Table 53 
 carrying capacity of pure copper 
 
 (Underwriters' Rules.) 
 
 WIRES. 
 
 B. & S. G. 
 
 18 
 
 Table A. 
 
 Rubber 
 Insulation. 
 
 Amperes. 
 
 3 
 
 6 
 
 12 
 
 17 
 
 24 
 
 33 
 
 Table B. 
 
 Other 
 
 Insulations. 
 
 Amperes. 
 .... 5 
 
 Circular 
 Mils. 
 1,624 
 
 16 
 
 14 
 
 12 
 
 10 
 
 8 
 
 8 
 
 16 
 
 .... 23 
 
 32 
 
 .... 46 
 
 .... 65 
 
 .... 77 
 
 .... 92 
 
 .... 110 
 
 .... 131 
 
 156 
 
 185 
 
 220 
 
 262 
 
 .... 312 
 
 300 
 
 .... 400 
 
 .... 500 
 
 .... 590 
 
 680 
 
 760 
 
 840 
 
 920 
 
 1,000 
 
 1,080 
 
 1,150 
 
 1,220 
 
 1,290 
 
 1,360 
 
 1,430 
 
 1,490 
 
 1,550 
 
 1,610 
 
 2,583 
 
 4,107 
 
 6,530 
 
 10,380 
 
 16,510 
 
 6 
 
 46 
 
 26,250 
 
 5 
 
 54 
 
 33,100 
 
 4 
 
 65 
 
 41,740 
 
 3 
 
 76 
 
 52,630 
 
 2 
 
 90 
 
 66,370 
 
 1 
 
 107 
 
 83,690 
 
 
 
 127 
 
 105,500 
 
 00 
 
 000 
 
 150 
 
 177 
 
 133,100 
 
 167,800 
 
 0000 
 
 210 
 
 211,600 
 
 Circular Mils. 
 200,000 
 
 200 
 
 
 300,000 
 
 270 
 
 
 400,000 
 
 330 
 
 
 500,000 
 
 390 
 
 
 600,000 
 
 450 
 
 
 700,000 
 
 
 
 800,000 
 
 550 
 
 
 900,000 
 
 
 
 1,000,000 
 
 650 
 
 
 1,100,000 
 
 
 
 1,200,000 
 
 730 
 
 
 1,300,000 
 
 770 
 
 
 1,400,000 
 
 810 
 
 
 1,500,000 
 
 
 
 1,600,000 
 
 890 
 
 
 1,700,000 
 
 
 
 1,800,000 
 
 970 
 
 
 1,900,000 
 
 
 
 2,000,000 
 
 1,050 
 
 1,670 
 
 
 The lower limit is specified for rubber-covered wires to 
 prevent gradual deterioration of the high insulations by 
 the heat of the wires, but not from fear of igniting the 
 insulation. The question of drop is not taken into consid- 
 eration in the above tables. 
 
1382 
 
 Steam Engineering 
 
 Table 54 
 dimensions of pure copper wire. 
 
 
 
 Area. 
 
 Weight and Length. 
 
 
 
 
 
 
 Sp. Gr. 8.9 
 
 
 xA 
 
 Efl 
 
 i/5 
 
 
 
 
 c3 
 
 1 
 
 1 
 
 u 
 
 J3 
 
 <u 
 
 u % 
 
 u 
 V 
 
 u 
 
 p. 
 
 6 
 
 6 
 
 2 
 
 3 
 
 u 
 
 a 1 
 
 
 
 
 £ 
 
 5 
 
 U 
 
 in 
 
 jS 
 
 J S 
 
 ft a 
 
 0000 
 
 460.000 
 
 211600.0 
 
 166190.2 
 
 640.73 
 
 3383.04 
 
 1.56 
 
 000 
 
 409.640 
 
 167805.0 
 
 131793.7 
 
 508.12 
 
 2682.85 
 
 1.97 
 
 00 
 
 364.800 
 
 133079.0 
 
 104520.0 
 
 402.97 
 
 2127.66 
 
 2.48 
 
 
 
 324.950 
 
 105592.5 
 
 82932.2 
 
 319.74 
 
 1688.20 
 
 3.13 
 
 1 
 
 289.300 
 
 83694.5 
 
 65733.5 
 
 253.43 
 
 1338.10 
 
 3.95 
 
 2 
 
 257.630 
 
 66373.2 
 
 52129.4 
 
 200.98 
 
 1061.17 
 
 4.98 
 
 3 
 
 229.420 
 
 52633.5 
 
 41338.3 
 
 159.38 
 
 841.50 
 
 6.28 
 
 4 
 
 204.310 
 
 41742.6 
 
 32784.5 
 
 126.40 
 
 667.38 
 
 7.91 
 
 5 
 
 181.940 
 
 33102.2 
 
 25998.4 
 
 100.23 
 
 529.23 
 
 9.98 
 
 6 
 
 162.020 
 
 26250.5 
 
 20617.1 
 
 79.49 
 
 419.69 
 
 12.58 
 
 7 
 
 144.280 
 
 20816.7 
 
 16349.4 
 
 63.03 
 
 332.82 
 
 15.86 
 
 8 
 
 128.490 
 
 16509.7 
 
 12966.7 
 
 49.99 
 
 263.96 
 
 20.00 
 
 9 
 
 114.430 
 
 13094.2 
 
 10284.2 
 
 39.65 
 
 209.35 
 
 25.22 
 
 10 
 
 101.890 
 
 10381.6 
 
 8153.67 
 
 31.44 
 
 165.98 
 
 31.81 
 
 11 
 
 90.742 
 
 8234.11 
 
 6467.06 
 
 24.93 
 
 137.65 
 
 40.11 
 
 12 
 
 80.808 
 
 6529.94 
 
 5128.60 
 
 19.77 
 
 104.40 
 
 50.58 
 
 13 
 
 71.961 
 
 5178.39 
 
 4067.07 
 
 15.68 
 
 82.792 
 
 63.78 
 
 14 
 
 64.084 
 
 4106.76 
 
 3225.44 
 
 12.44 
 
 65.658 
 
 80.42 
 
 15 
 
 57.068 
 
 3256.76 
 
 2557.85 
 
 9.86 
 
 52.069 
 
 101.40 
 
 16 
 
 50.820 
 
 2582.67 
 
 2028.43 
 
 7.82 
 
 41.292 
 
 127.87 
 
 17 
 
 45.257 
 
 2048.20 
 
 1608.65 
 
 6.20 
 
 32.746 
 
 161.24 
 
 18 
 
 40.303 
 
 1624.33 
 
 1275.75 
 
 4.92 
 
 25.970 
 
 203.31 
 
 19 
 
 35.890 
 
 1288.09 
 
 1011.66 
 
 3.90 
 
 20.594 
 
 256.39 
 
 20 
 
 31.961 
 
 1021.44 
 
 802.24 
 
 3.09 
 
 16.331 
 
 323.32 
 
 21 
 
 28.462 
 
 810.09 
 
 636.24 
 
 2.45 
 
 12.952 
 
 407.67 
 
 22 
 
 25.347 
 
 642.47 
 
 504.60 
 
 1.95 
 
 10.272 
 
 514.03 
 
 23 
 
 22.571 
 
 509.45 
 
 400.12 
 
 1.54 
 
 8.1450 
 
 648.25 
 
 24 
 
 20.100 
 
 404.01 
 
 317.31 
 
 1.22 
 
 6.4593 
 
 817.43 
 
 25 
 
 17.900 
 
 320.41 
 
 251.65 
 
 .97 
 
 5.1227 
 
 1030.71 
 
 26 
 
 15.940 
 
 254.08 
 
 199.56 
 
 .77 
 
 4.0623 
 
 1299.77 
 
 27 
 
 14.195 
 
 201.50 
 
 158.26 
 
 .61 
 
 3.2215 
 
 1638.97 
 
 28 
 
 12.641 
 
 159.80 
 
 125.50 
 
 .48 
 
 2.5548 
 
 2066.71 
 
 29 
 
 11.257 
 
 126.72 
 
 99.526 
 
 .38 
 
 2.0260 
 
 2606.13 
 
 30 
 
 10.025 
 
 100.50 
 
 78.933 
 
 .30 
 
 1.6068 
 
 3286.04 
 
 31 
 
 8,928 
 
 79.71 
 
 62.603 
 
 .24 
 
 1.2744 
 
 4143.18 
 
 32 
 
 7.950 
 
 63.20 
 
 49.639 
 
 .19 
 
 1.0105 
 
 5225.26 
 
 33 
 
 7.080 
 
 50.13 
 
 39.360 
 
 .15 
 
 .8015 
 
 6588.33 
 
 34 
 
 6.304 
 
 39.74 
 
 31.212 
 
 .12 
 
 .6354 
 
 8310.17 
 
 35 
 
 5.614 
 
 31.52 
 
 24.753 
 
 .10 
 
 .5039 
 
 10478.46 
 
 36 
 
 5.000 
 
 25.00 
 
 19.635 
 
 .08 
 
 .3997 
 
 13209.98 
 
 37 
 
 4.453 
 
 19.83 
 
 15.574 
 
 .06 
 
 .3170 | 
 
 16654.70 
 
 38 
 
 3.965 
 
 15.72 
 
 12.347 
 
 .05 
 
 .2513 | 
 
 21006.60 
 
 39 
 
 3.531 
 
 12.47 
 
 9.7923 
 
 .04 1 
 
 .1993 | 
 
 26487.84 
 
 40 
 
 3.144 
 
 9.88 
 
 7.7635 
 
 .03 1 
 
 .1580 \ 
 
 33410.05 
 
 1 mile pure copper wire T V in. diam.=13.59 ohmns at 15.5° C. or 59.9° F. 
 1 circular mil. is .7854 square mil. 
 
Current Distribution 
 
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Dynamo Troubles 1387 
 
 Correcting Dynamo Troubles. — Inasmuch as the use of 
 small direct current electric dynamos is becoming very gen- 
 eral, and since they are frequently in operation under the 
 supervision of users who are not as a rule familiar with 
 electrical machinery, a few simple pointers relative to the 
 care and maintenance of an electric dynamo may help some 
 user to avoid considerable annoyance. 
 
 Electrical machinery, even though it has been largely 
 shrouded in mystery, is, nevertheless, comparatively simple 
 apparatus in its operation and maintenance. To a con- 
 siderable degree it is a delicate piece of mechanism, by 
 which is meant that it cannot be handled with the same 
 treatment as one would expect to give a clumsy, crude, or 
 inexpensive device. However, there are a few underlying 
 principles which govern such dynamos as are ordinarily 
 used in small isolated plants, which, if they are observed, 
 will enable practically any operator to maintain and keep 
 in perfect running condition any well constructed machine. 
 When the dynamo is received from the factory it should 
 be carefully examined to see if it is in apparently good con- 
 dition, or whether it shows evidence of having been in- 
 jured by rough handling in transit. If this inspection 
 points to its having arrived in good condition, its installa- 
 tion should be considered in a general way along the lines 
 similar to those which would be observed for the installa- 
 tion of any piece of machinery. Care should be taken to 
 see that the bearings are properly supplied with oil; that 
 the dynamo stands perfectly level on its foundation; that 
 the belt is of good quality and free from bumps or improper 
 lacing. It may be noted that the dynamo does not neces- 
 sarily require an independent foundation, which is de- 
 manded by some classes of apparatus. Because of the fact 
 
1388 Steam Engineering 
 
 that its vibration is very slight, any rigid or substantial floor 
 will answer for this purpose. 
 
 In starting up a dynamo, only two things which might be 
 termed "electrical" need be specially considered. The first 
 is the direction of rotation, because each dynamo as shipped 
 from the factory is so connected as to run in only one di- 
 rection and will not generate current if the direction of 
 rotation is reversed. It is an easy matter to change the 
 connections on a machine so that a reversed direction is 
 possible, and a sheet of instructions furnished with the 
 dynamo usually covers instructions for this modification, 
 but it should be remembered that each dynamo as received 
 by the user is so connected as to operate in only one direc- 
 tion. 
 
 The second matter for consideration is the speed of the 
 dynamo, which should not be less than, the speed given on 
 the name plate nor greater than ten per cent above the 
 speed. A slower speed would interfere with the building 
 up of the voltage, while a higher speed would deliver an ex- 
 cessive current from the machine. It is needless to add that 
 the directions for wiring connections furnished with the 
 dynamo should be followed carefully. 
 
 If, after a dynamo has once been running satisfactorily, 
 there occurs some difficulty in its operation, the probabilty 
 is that, unless the occasion of the trouble is due to some 
 mechanical injury or to the dynamo having become sat- 
 urated with water or oil, the nature of the trouble will most 
 frequently manifest itself in one or two ways. The first 
 is that the dynamo will refuse to generate current, and the 
 second is that sparking will show itself between the com- 
 mutator and the brushes. Under this latter head it is 
 worth remembering that the heating of a dynamo is gener- 
 ally due to some cause which, if it existed to a greater de- 
 
Dynamo Troubles 1389 
 
 gree, would manifest itself in sparking, so that many times 
 the heating of the machine means that trouble exists to 
 a limited extent, which, if it occurred in a greater degree, 
 would manifest itself in sparking. A common exception, 
 however, to this statement is that the brushes, if pressing 
 too firmly on the commutator, will from their friction pro- 
 duce heat. With the above explanation, the more frequent 
 difficulties can be classified under the two heads, "Failure of 
 the dynamo to generate" and "Sparking at the commuta- 
 tor." 
 
 If, on starting a dynamo, after its use has been discon- 
 tinued for a time, it refuses to generate, which means that 
 the operator is unable to secure electricity from it, he 
 should first assure himself that the machine is operating at 
 its proper speed and that there has been no speed reduc- 
 tion, due either to a slowing up of the motive power or to 
 a slippage of the belt. If no such difficulty appears, the 
 next investigation should determine as to whether or not the 
 resistance of the rheostat remains in the field circuit. In 
 many instances dynamos can frequently be made to 
 generate by simply moving the handle of the rheostat to 
 the point marked "highest voltage." The third and possi- 
 bly most common cause of failure of a dynamo to generate 
 is due to a defective contact between the commutator and 
 the brushes. This may be caused by a lack of proper ten- 
 sion on the brushes, due either to their being too weak or 
 their need of readjustment. Again the brushes and holders 
 may have become dirty and gummy, preventing their proper 
 action. An excessive amount of grease or dirt on the com- 
 mutator occasionally (especially in cold weather) forms a 
 scum over its surface which intervenes between it and the 
 brushes, retarding the flow of the current. It is possible 
 that the obstacle in the path of the current may lie else- 
 
1390 Steam Engineering 
 
 where than between the brushes and the commutator; as, 
 for instance, loose connection may exist in the wire leading 
 from the brushes to the head post. However, the operator 
 can look intelligently for the trouble when he realizes that 
 the early current generated when the dynamo begins to 
 operate is of slight intensity, and obstacles which would no't 
 interfere with the flow of the current of ordinary propor- 
 tions will retard the flow of this initial current, conse- 
 quently a very slight resistance or hindrance may prevent 
 the dynamo from generating. 
 
 To these statements may be added the facts that the 
 brushes may have become moved from their proper position 
 or the dynamo may have lost its magnetism. The latter 
 condition, however, is rare; and the former will not exist 
 unless the machine has been tampered with. In a later 
 paragraph is given information relative to the adjustment 
 of the brushes. 
 
 This brings us up to the general manifestation of trouble, 
 namely, sparking at the commutator, which is probably the 
 most frequent difficulty 'encountered in a dynamo. A 
 small red spark, which can be easily recognized as occa- 
 sioned by dirt, is not seriously injurious, and a cleaning of 
 the commutator and brushes will overcome it. However, a 
 vicious, spitting spark will, in the course of a comparatively 
 brief time, materially injure the dynamo, and when first 
 detected, steps should be taken to overcome it without de- 
 lay. 
 
 Briefly indicating the causes of sparking which do not 
 permit of ready classification, it may be possibly occasioned 
 by an excessive overload on the machine, due to a leakage in 
 the wiring or to the use of too many lights. If this is re- 
 sponsible for the sparking, the machine will heat materially 
 in all its parts. It may be true that an open circuit or a 
 
Dynamo Troubles 1391 
 
 break in the wiring of the armature may exist. In this 
 instance the spark will be very vicious, and an examination 
 of the commutator will show that it has been burned on 
 one of the mica lines across its surface. An open circuit 
 in one of the fields may also result in sparking, but this 
 can be determined by an unequal heating of the fields. 
 
 Coming, however, to the two most common causes of 
 sparking : the first lies in the fact that the contact between 
 the commutator and the brushes may not be firm and uni- 
 form. The commutator itself may be rough, or the bearing 
 surface of the brushes may be irregular; roughness of the 
 commutator resulting occasionally by its having been 
 burned down or worn. Occasionally the copper wears more 
 rapidly than the mica, leaving the mica projecting upon 
 the surface of the commutator. If the commutator is 
 rough, a piece of No. 2 sandpaper held firmly on its sur- 
 face while it is in operation will overcome minor irregulari- 
 ties. If this does not correct the trouble, the armature 
 should be taken to a first-class machine shop and the com- 
 mutator turned off in a lathe. 
 
 If the brushes are so worn that they do not fit snugly on 
 the commutator, fasten a strip of No. 2 sandpaper around 
 the face of the commutator, the sand side out ; then revolve 
 the commutator with this strip of sandpaper attached to it 
 until the bearing surface of the brushes will be trued up, 
 insuring a perfect contact. Strange as it may seem, the 
 most common cause of sparking, occasioned by an improper 
 contact, lies in the fact that the user does not recognize that 
 carbon brushes wear out and occasionally need to be re- 
 placed. Frequently machines are sent back to the manu- 
 facturer for repairs when the only occasion of the trouble 
 is that the carbon brushes have been worn until they can- 
 not rest firmly on the commutator. When the brushes be- 
 
1392 Steam Engineering 
 
 come so worn that it is difficult with the mechanism of the 
 holder to secure a firm pressure against the commutator, 
 they should be renewed with new and longer brushes. 
 
 The last occasion for sparking which will be mentioned 
 is that the brushes may have been shifted out of their proper 
 position in reference to each other and to the commutator. 
 On machines which have two-field coils the brushes should 
 rest on the commutator at points which are exactly opposite 
 to each other. On machines which have four-field coils 
 these points should be exactly 90° apart. If the brushes are 
 properly spaced in reference to each other, then their cor- 
 rect position on the commutator becomes a matter of locat- 
 ing what is known as the "neutral point." In order to 
 locate this neutral point, move the rocker arm which carries 
 all the brushes around with the direction of rotation, while 
 the machine is in operation, and carrying a comparatively 
 light load. Do this until a slight spark appears, then move 
 the rocker arm back in the opposite direction just enough to 
 stop the sparking; this will be the neutral point. 
 
 PRACTICAL POINTS. 
 
 Brushes and Commutators. — Brush holders and commu- 
 tators will sometimes show excessive temperatures because 
 of the heat which may come from a bearing in which the 
 armature shaft revolves. The failure of a bearing upon a 
 dynamo or a motor to run cool may be due to any one of 
 a great variety of causes, some of which are mechanical and 
 others electrical. 
 
 A common cause, and one which is not infrequently over- 
 looked is that of lack of sufficient oil in the bearing for the 
 purposes of lubrication. When renewing the supply of oil 
 to a bearing care should be exercised in the choice of oil, 
 
Dynamo Troubles 1393 
 
 making certain that it is free from dirt or grit, and that it 
 is an oil of good quality for the purpose in hand. The pas- 
 sages or oil ducts should be carefully examined and kept per- 
 fectly clear for the free running of the lubricant. A bear- 
 ing may be leaking at some point, causing the oil to run 
 off much sooner than an attendant would think, and this 
 kind of a defect should be carefully guarded against. 
 
 The modern dynamos and motors have their bearings so 
 designed that they are self-oiling, i. e., the oil is carried by 
 means of chains or rings from the oil chamber beneath the 
 bearing proper, up and over the shaft and through grooves 
 provided for the purpose, returning to the well to be used 
 over and over again. Gauge glasses are nearly always pro- 
 vided by means of which it is possible to observe at any 
 and all times the quantity of oil remaining in the well. 
 Oil used over and over again in this manner is quite likely 
 to gather foreign impurities. It is good practice to remove 
 the oil from bearings at least once a month, clean out the 
 bearing thoroughly with gasoline, filter carefully the oil 
 that is left and return the same to the bearing, adding a 
 sufficient quantity of fresh oil to make up for any loss which 
 has been the result of operation. 
 
 Gritty substances are very likely to work into bearings at 
 different times, depending upon the use which is made of a 
 motor or a generator. If electrical apparatus is to be placed 
 in a space that is dirty, and cannot well be kept clean, then 
 it is a good precaution to have the machine suitably en- 
 closed, or else to have the bearings completely enclosed with 
 tight-fitting plates about the shaft so as to exclude foreign 
 substances. Whenever it is found necessary to wash out a 
 bearing in order to remove any dirt, care should be exer- 
 cised not to get any water or kerosene upon the commutator 
 or windings of the machine. 
 
1394 Steam Engineering 
 
 A roughened shaft or a tight fit between the shaft and 
 the sleeve of the bearing may cause heating. These diffi- 
 culties are purely mechanical and are easily remedied, once 
 that the source of the trouble is ascertained. 
 
 Sudden and excessive strains sometimes spring the shaft 
 of a generator or a motor, and it not infrequently happens 
 that with some types of bearings they are thrown out of 
 line. Either of these causes will bring about a heating of 
 the bearing. A bent or crooked shaft can rarely ever be 
 straightened, the only remedy being a new one. Bearings 
 that can be thrown out of line for the reasons mentioned 
 are also susceptible of being properly aligned by means of 
 the caps and screws for holding them in position. 
 
 The end thrust of a collar on the armature shaft, upon 
 one side or the other of the machine, may cause a heated 
 bearing. When machines are driven by belting, or when 
 motors are connected with shafting by belting, it is an easy 
 matter to ascertain whether the armature is running freely 
 with respect to the belt connection. A stick placed against 
 the end of the shaft would enable one to move the armature 
 back and forth with ver)^ little effort. In fact, every arma- 
 ture should have free end play, and if a test with a stick as 
 mentioned does not show that such a free end play does 
 exist, then the machine should be lined up with respect 
 to its belt, so that such end play is secured. 
 
 The bearings may wear down sufficiently in time to per- 
 mit of the armature bands rubbing against the pole pieces, 
 or stationary iron of the machine. This can often be de- 
 tected by placing the ear near the frame of the machine 
 opposite the pole piece where it is thought that the arma- 
 ture might come in contact. It might also be detected by 
 turning the armature over slowly with the belt removed and 
 with the field current turned on. It might also happen, 
 
Dynamo Troubles 1395 
 
 however, that the armature will not touch any of the field 
 poles, except when running under load with the belt on. 
 The positive evidence of rubbing lies in an examination of 
 the circumference of the armature itself when the bands 
 around the armature will show whether there has been any- 
 rubbing or not. This kind of an examination can usually 
 be made without removing the armature from the machine. 
 If there should be positive evidences of rubbing, it must 
 not be allowed to continue. 
 
 The pulley, the belt or other parts of the revolving arma- 
 ture shaft may rub against adjacent surfaces, and bring 
 about a scraping or a rattling noise. The movement of the 
 shaft back and forth in its bearings in one direction or an- 
 other may stop the noise, in which case it will be a simple 
 matter to locate the cause, after which it will be an equally 
 simple matter to remedy the trouble. 
 
 Generally, in starting up a new generator or motor, the 
 new and unused carbon brushes upon a new, and previously 
 unused commutator will cause an unpleasant squeaking or 
 a hissing. The sound is usually of a high pitch and is easily 
 located. Sometimes, it may be due to but one or two new 
 brushes. These can be located by removing one brush at a 
 time until the noisy ones are found. Then by moistening 
 them slightly with a light oil, the noise from that particular 
 brush will be stopped. There should not, however, be so 
 much oil used for this purpose so that any of it will adhere 
 to the brush in the form of drops. It sometimes happens 
 that the commutator has not been finished off as 
 smoothly as it should have been and this, of course, 
 would cause a considerable humming until the commutator 
 surface had been worn over sufficiently to take on a polished 
 appearance. If the commutator is rough enough to cause a 
 hissing of the brushes, it should be polished off by hand be- 
 
1396 Steam Engineering 
 
 fore it is put into operation. This can be done in the 
 manner already described, and would insure a much bet- 
 ter commutator in service than if allowed to run along in 
 the rough state, trusting to luck that it will assume a pol- 
 ished appearance as a result of operating conditions alone. 
 
 A squeak due to the slipping of a belt upon the pulley 
 is easily located, and not confounded with any other noise 
 which may result from operating any class of machinery. 
 Whenever such slipping of a belt occurs, it means a loss 
 of power, and that means expensive operation. A care for 
 the details of operating costs will not permit of a squeaking 
 belt at any point. 
 
 Another kind of humming is often present in motors and 
 in some kinds of generators. This is the humming which 
 is something of a musical sound, and is likely to be con- 
 fined to the armature teeth as they pass the pole faces at 
 high speed. It is a molecular vibration due to the magnetic 
 reversals in the iron. If it is an objectionable feature in 
 the operation, it may be remedied by trimming off the ends 
 of the pole faces so that the full length of an armature tooth 
 would not be likely to leave the pole face throughout its 
 entire length at the same instant of time, but would shade 
 off instead. The testing of generators and motors in the 
 shops of the builders, however, is supposed to reveal exces- 
 sive humming, and the trimming of pole faces should be 
 done before the machine is sent to the shipping room. In 
 general, it is always well to be certain that the noises of 
 operation come from the electrical apparatus, and not from 
 some other equipment which might be close by. 
 
 Transformer Oil. — Transformer oil, its proper character, 
 treatment and use, has been much neglected by central sta- 
 tion engineers. It forms one of the weak links in the chain 
 of a high-tension electric-transmission system. In its dual 
 
Transformer Oil 1397 
 
 function as insulator and cooler, it requires high dielectric 
 strength, and high flash point, combined with great fluidity. 
 It should be neutral so as to not dissolve the insulation of 
 the core and coils immersed in it. 
 
 Of these qualities, the dielectric strength is the most va- 
 riable, for it depends largely upon the amount of moisture 
 present. The popular axiom that oil and water do not mix 
 is not scientifically correct, for oil does absorb a small 
 amount of moisture that materially lessens its dielectric 
 strength. Instances have been known of transformer oil 
 having broken down under 16,000 volts when wet, but 
 which stood the test of 40,000 volts after being dried. 
 
 While oil and water do not chemically mix, they may 
 mingle so closely as to require steam, or rheostat heating to 
 remove the water. Every precaution should be taken to 
 keep oil dry during shipment and in use, for it abhors dehy- 
 dration even more than nature abhors a vacuum. 
 
 It should have a high fire or flash test to eliminate dan- 
 ger of fire. Crude oil is refined by frictional distillation, 
 the most volatile products passing off first. These are low 
 in gravity and in burning temperature, as is exemplified by 
 gasoline. Kerosene for use in lamps is one of the next 
 products, soon followed by an oil suitable for transformer 
 purposes. This usually has a gravity of 30° Baume or 
 less, and burns at about 300° Fahrenheit. The higher the 
 temperature at which the product is distilled, the greater is 
 its viscosity. Consequently, what is gained in flashing tem- 
 perature is lost in fluidity. Acid introduced into the refin- 
 ing must be removed by adding just enough alkali to ren- 
 der the oil neutral. Disastrous fires have been known to 
 result from the volatilization of the oil by an arc. 
 
 Another frequent trouble is the deposition of a thick, 
 carbonaceous, jelly-like sludge on the cooling coils, and in 
 
1398 Steam Engineering 
 
 the circulating ducts. The former are covered so thick that 
 cooling is not effected, and the latter are so clogged that 
 circulation is difficult. Such deterioration generally occurs 
 when the oil has been overheated. The deposit is easily 
 washed off when hot, but becomes hard and brittle upon 
 exposure to the air, resembling bitumen in this respect. The 
 deposits around the points of high potential allow creepage, 
 so that a medium of high resistance may become a con- 
 ductor. 
 
 But careful examinations of these troubles show that 
 they are usually due to no inherent fault of the oil, but 
 to the transformer design, or more particularly to the at- 
 tendant's carelessness. 
 
 6 6 6-6 666666 
 
 6666666666 
 
 Fig. 661 
 
 Careful breakdown tests should be made not only when 
 the oil is furnished, but at frequent intervals thereafter, 
 once a month not being too often for main stations. Tests 
 for acidity will avoid the destruction of the insulation by dis- 
 solving, and flash tests will often prevent fires. The carbon 
 may be removed by occasional filtering. In case of leaky 
 cooling coils, the water should be drawn off from the bot- 
 tom until such time as the transformer can be taken out of 
 service and properly repaired. 
 
 All this trouble occurs with both water, and self-cooling 
 transformers. Where water is plentiful, it has been sug- 
 gested that outside circulation of the oil would cause bet- 
 ter cooling, and larger ventilating ducts would not become 
 
Transformer Oil 1399 
 
 clogged. We attain success only by the most careful at- 
 tention to the details of our work. , Look after the oil, and 
 transformer troubles will take care of themselves. 
 
 Three Wire System with One Dynamo. — When the load 
 on one side of the middle or neutral wire exactly equals the 
 load on the other side, as in Fig. 661, the circuit is bal- 
 anced, but it is very seldom that such load conditions exist, 
 at least for any length of time, and when there is a differ- 
 ence between the loads carried by the two sides, the circuit 
 is unbalanced. 
 
 In order therefore to successfully operate a three wire 
 system with one dynamo, it becomes necessary to provide 
 some method of taking care of the surplus current on the 
 
 4 Amperes _L f 5 Amperes I 
 
 1L 
 
 1E7^ 2 Amperes j M~^ | ^ j~ 
 
 ^T 3 Amperes I T J 1 j ? 
 
 4 Am per es. 
 
 Fig. 662 
 
 lightly loaded side, and transferring it to the heavily loaded 
 side ; in other words, to balance the circuit. There are two 
 methods by which this may be accomplished. 
 
 The first and most simple method of compensating for 
 unbalancing is to connect a storage battery between the 
 two main wires, and then connect the neutral wire to the 
 middle point of the battery, as shown in Fig. 662. Here 
 are shown connected 10 lamps on one side, and 6 on the 
 other. The direction of flow of the current is indicated 
 by the arrows. Assuming that the resistance of each lamp 
 is 220 ohms, which is the ordinary value for 110 volt lamps, 
 the joint resistance of the group of 10 lamps would be 
 
1400 Steam Engineering 
 
 220-^10=22 ohms. The joint resistance of the 6 lamps 
 on the other side would be 220-f-6=36.66 ohms. 
 
 The total resistance of both groups of lamps would be 
 22-J-36. 66=58. 66 ohms, and the volume of current flowing 
 through both groups would be 220-^58.66=3.75 amperes. 
 Assuming that each lamp requires % ampere of current, 
 the group of 10 will require 5 amperes, and the group of 
 6 requires 3 amperes. As the volume of current equals 3.75 
 amperes, it is evident that the 10 lamps will not get enough 
 current, while the group of 6 will get too much, unless, as 
 before mentioned, a balancer be provided, and right here 
 is where the storage battery enacts its role. Under the con- 
 ditions shown in Fig. 662, the A half of the battery will 
 deliver just enough current, provided the voltages are suit- 
 ably proportioned, to supply one-half of the excess or un- 
 balanced load on the heavy side of the system. The dynamo 
 supplies the other half of the excess current which comes in 
 on the neutral wire, with the current supplied by the A 
 section of the storage battery, and returns to the dynamo 
 through the B half of the battery charging that section. 
 
 This proportion holds good for any degree of unbalanc- 
 ing; that is, that part of the battery on the heavily loaded 
 side will send out one-half of the current in the neutral 
 wire, and the other half will go through the part of the bat- 
 tery that is on the light load side of the neutral. 
 
 This arrangement, though apparently ideal in simplicity 
 on paper, is not so attractive in practice, for the reason that 
 a regulator is needed in conjunction with the battery in 
 order to prevent it from exhausting itself when the load is 
 heavy, or drawing too heavily from the line when it is 
 light. Moreover, the two halves of the battery cannot be 
 kept in equal condition, because one side would do more 
 work than the other, unless the circuit could be unbalanced 
 
Three Wire System — One Dynamo 1401 
 
 alternately, and equally on, first one side and then the other. 
 This difficulty can be met, however, by exchanging the two 
 sections at regular intervals, say once a week. 
 
 A more practical method of compensation is by means 
 of what is commonly termed a "motor-balancer," but is 
 more correctly a motor-compensator. This consists of two 
 small motors exactly alike in all respects, their shafts rigidly 
 coupled together and their armatures connected, one on 
 each side of the neutral wire, as indicated in Fig. 663, where 
 120 lamps are represented on each side of the neutral wire. 
 Here it is assumed that the motor armatures require one 
 ampere to drive them, or 220 w^atts (110 watts each), and 
 for simplicity the current required by their field windings 
 is ignored. So long as the load is balanced, the tw r o arma- 
 tures will take current from the main wires only, and will 
 revolve idly. If more load is added to one side, however, 
 or some load taken off the other side, the equilibrium be- 
 tween the voltages of the two sides will be upset ; the volt- 
 age at the brushes of the motor on the lightly loaded side 
 will be higher than that at the brushes of its mate, and it 
 will drive the latter at a speed beyond that due to the cir- 
 cuit voltage, making a dynamo of it, and forcing it to carry 
 the unbalanced part of the heavier load on the circuit. This 
 is illustrated in Fig. 664, where 120 lamps are shown on one 
 side and 60 on the other, each of the circles representing 10 
 lamps, taking y 2 ampere each. What causes the distri- 
 bution of current shown is this : When the load in the B 
 division is reduced the voltage rises, because the losses in 
 the dynamo and circuit wires are reduced; the voltage be- 
 tween the neutral and the negative wires rises more than 
 that between the positive and neutral, because the resist- 
 ance there is higher — all the reduction of load has occurred 
 in that division of the circuit. The armature B, therefore, 
 
1402 
 
 Steam Engineering 
 
 jojosnadtuoo 
 
 
 eSnipntM ppij 
 jojcsngdtuoo 
 
 Saipai^ Piaij oujoqAq 
 
Three Wire System — One Dynamo 1403 
 
 speeds up, dragging the armature A with it until the volt- 
 age of the latter increases above that of its side of the cir- 
 cuit sufficiently to carry half of the ex-cess load on that side, 
 minus the power required to drive the two machines. This 
 power was assumed to be 220 watts; the current taken by 
 the two armatures in series in Fig. 663 being one ampere 
 and the total voltage 220. Here, one of the armatures does 
 all the work, so that the whole 220 watts must be applied 
 to it, in addition to an amount of power equal to that being 
 delivered by the armature A working as a dynamo. As the 
 armature B takes its current now from the unbalanced cur- 
 rent coming in on the neutral wire, it works at 110 volts 
 and therefore requires 2 amperes to overcome the losses in 
 the two machines (the losses in the windings are ignored 
 to simplify the problem) ; the neutral wire must carry 30 
 amperes because the 60 lamps in the negative division will 
 pass only 30 amperes. Deducting the 2 amperes for motor 
 losses leaves 28 amperes, which divides between the two 
 machines, 14 amperes supplying the motor with the energy 
 necessary to produce 14 amperes from the armature now 
 driven as a dynamo. 
 
 Another way to arrive at the division of current is as 
 follows: The main dynamo must supply all of the energy 
 represented in the circuit ; all that the compensator does is 
 to transfer the surplus energy from one side of the circuit 
 to the other — it cannot supply any additional energy be- 
 cause it is driven by energy taken from the main circuit. 
 Now the lamps take each % ampere at 110 volts, or 55 
 watts; there are 180 lamps, requiring 180X55=9900 watts. 
 The compensator requires 220 watts to overcome its no- 
 load losses, the extra losses at load being ignored for the 
 present. The lamps and compensator together, therefore, 
 require 9900+220=10,120 watts. Ignoring line losses, 
 
1404 
 
 Steam Engineering 
 
 the generator works at 220 volts, and in order to deliver 
 10,120 watts it must deliver 10,120-^-220=46 amperes. 
 Since the lamps in the positive division (A) require 60 am- 
 peres, the armature A working as a dynamo must supply 
 60 — 46=14 amperes. Consequently, of the, 30 amperes 
 in the neutral wire, 14 must have been generated in the 
 little machine; the other 16 pass through the motor arma- 
 ture B to the main dynamo, as prevously explained. 
 
 Fig. 665 
 
 The exact figures in practice would not be those here 
 stated because the line losses, the current in the field wind- 
 ings of the compensator, and the losses in their armature 
 windings affect the current distribution. The principle, 
 of course, is not affected ; the machine on the lightly loaded 
 side of the system always runs as a motor, and drives its 
 mate as a dynamo, the latter supplying about one-half of the 
 difference between the two divisions of the load, minus the 
 power required to drive the machine. The losses do affect 
 
Three Wire System — One Dynamo 1405 
 
 the voltage regulation, however. If the armature windings 
 of the compensator are of very low resistance, the voltages 
 on each side of the neutral will be kept almost exactly 
 equal; if the armature resistances are high, the voltage be- 
 tween the neutral and the main wire which carries the 
 heavier load will be appreciably lower than that on the 
 other side of the system. 
 
 The regulation obtained with motor compensators can be 
 much improved by cross-connecting the field windings, as 
 shown in Fig. 665. The result of this is that when the 
 load on the side A, for example, is less than that on the 
 other side, the voltage of the side A being higher than 
 that of the side B, the field strength of the machine A 
 will be weaker than that of the machine B, and its 
 speed will be higher than it would be with a steady 
 field. The machine B, on the other hand driven 
 as a dynamo, will have its field strengthened, and 
 will deliver a higher voltage than it would otherwise. In 
 other words the machine that runs as a motor runs at a 
 higher speed, thus giving its mate a higher voltage, and the 
 latter will also have a stronger field, increasing its voltage 
 still more, with the connections as shown, in Fig. 665, than 
 with the arrangement shown in Figs. 663 and 664. The 
 armature capacity of a motor balancer in amperes, must be 
 equal to one-half of the current that will flow in the neutral 
 wire when the system is out of balance by the maximum 
 amount possible under operating conditions, plus the cur- 
 rent required to overcome all losses in the two armatures 
 at full load. The losses in small armatures range from 
 5 to 10 per cent at full load; therefore if the armatures of 
 the balancer can carry 55 per cent of the maximum cur- 
 rent that is likely to ever flow through the neutral wire 
 they will be large enough. 
 
1406 Steam Engineering 
 
 ARC LAMPS. 
 
 When two rods of carbon are connected to a source of 
 current, and their ends brought into contact with each other, 
 and then separated a slight distance, the current will con- 
 tinue to pass across the interval, but an intense heat is 
 generated, and the space between the ends of the carbon 
 rods is filled with carbon vapor, and minute particles. The 
 current passes over this space in a bow-shape path or arc, 
 
 Fig. 666 
 
 and it is from this fact that the lamp gets its name. The 
 arc is constantly moving, and generally revolves around 
 the carbon points. This can be easily seen by looking closely 
 at a burning lamp through a smoked glass. After a lamp 
 has been burning for some time on direct current the car- 
 bons assume the shape shown in Fig. 666, the upper or 
 positive carbon assuming a cup shape, while the lower car- 
 bon generally burns to a point. This cup shape formation 
 
Arc Lamps 
 
 1407 
 
 on the upper or positive carbon acts as a reflector to throw 
 the light downward. The positive carbon burns away 
 about twice as fast as the negative carbon, and lamps must 
 be trimmed accordingly. Sometimes the current feeding 
 arc lamps (on direct current systems) becomes reversed, 
 either through the dynamo reversing its polarity or through 
 
 STARTING 
 RESISTANCE 
 
 Fig. 667 
 diagram of constant-current series arc lamp mechanism. 
 
 wrong plugging of the switchboard. The lamps will now 
 burn "upside down/' or, in other words, the bottom carbon 
 will be the positive one. In such a case, if let go, the 
 carbon holders of the lamp will be burned and the lamp 
 will burn for only half the time for which it was intended, 
 owing to the fact that the lower or negative carbon is only 
 
1408 Steam Engineering 
 
 one-half as long as the upper or positive carbon. Such a 
 condition can be determined by either of the following 
 ways: See if the light is being thrown downwards. See 
 which carbon is burning away the faster. Eaise the car- 
 bons and notice the formation of the carbon tips. When 
 the carbons are separated it will be noticed that the tip of 
 one 'carbon is considerably hotter than the other, and is 
 heated a longer distance from the point ; this is the positive 
 carbon. 
 
 The heat of the arc is very intense, that of the positive 
 pole being 7200° Fahr. and the negative 5400° Fahr. Fig. 
 667 illustrates the action of a constant current or series are 
 lamp. It shows the lamp inactive, the carbons in contact, 
 and the cut-out closed. If current is turned on, it goes 
 through the cut-out. In series with the cut-out is a coil 
 which provides the starting resistance. Its resistance shunts 
 sufficient current through the series magnet to cause it to 
 attract its armature and raise the clutch. This separates 
 the carbons, the arc strikes, and the current is shunted 
 through the shunt magnet. This at once begins to regu- 
 late the length of the arc. 
 
 The armatures of the shunt and series magnets operate 
 a rocker arm which is pivoted between the magnets, so that 
 the series and shunt magnet have reverse effects on the 
 movable upper carbon. As the shunt-magnet armature is 
 drawn up, the clutch descends, owing to the action of the 
 rocker arms, and the reverse action takes place when the 
 shunt-magnet armature descends. In this way the increase 
 of arc length, shunting more current through the shunt 
 magnet, causes the clutch to descend and the arc shortens. 
 The dash-pot is shown to the left of the central tube above 
 the rocker arm. Immediately below the clutch is the trip- 
 ping platform, seen extending over the top of the globe. 
 
Arc Lamps 1409 
 
 Adjusting Weight. — This slides back and forth upon the 
 rocker arm attached to the two armature rods. This is 
 fastened in any desired position by a setscrew. For varia- 
 tions in current exceeding 0.2 ampere above or below the 
 rated current of the lamp, the weight must be shifted. By 
 moving the weight toward the clutch rod the voltage is 
 reduced, and moving at away from the clutch rod increases 
 the voltage. 
 
 Fig. 668 shows a diagram of connections for the improved 
 Brush arc lamp. These lamps are used on constant current, 
 or series systems, and their action is as follows : 
 
 The carbons should rest in contact when the lamp is cut 
 out. When the switch is opened, part of the current from 
 the positive terminal hook P goes through the adjuster to 
 the yoke, and thence through the carbon rod and carbons 
 to the negative terminal hook N. The remainder of the cur- 
 rent goes to the cut-out block, but, as the cut-out block is 
 closed at first, the current crosses over through the cut-out 
 bar to the starting resistance, and so to the negative side of 
 the lamp. A part of it, however, is shunted at the cut-out 
 block through the coarse wire of the magnets, and so to the 
 upper carbon rod and carbons and out. This shunted cur- 
 rent energizes the magnet, and so raises the armature which 
 opens the cut-out, and at the same time establishes the arc 
 by separating the carbons. 
 
 The fine wire winding is connected in the opposite direc- 
 tion from the coarse wire winding, and its attraction is 
 therefore opposite. When the arc increases in length, its 
 resistance increases, and consequently the current in the 
 fine wire is increased. The attraction of the coarse wire 
 winding is therefore partly overcome, and the armature 
 begins to fall. As it falls, the arc is shortened and the 
 current in the fine wire decreases. The mechanism feeds 
 
1410 
 
 Steam Engineering 
 
 r\ 
 
 Fig. 668 
 
 the carbons, and regulates the arc so gradually that a perfect, 
 steady arc is maintained. 
 
 The fine wire of the magnets is connected in series with 
 
 _ 
 
Arc Lamps 1411 
 
 the winding of a small auxiliary cut-out magnet at the top 
 of the mechanism. 
 
 This magnet, which also has a supplementary coarse 
 winding, does not raise its armature unless the voltage at 
 the arc increases to 70 volts. The two windings connect 
 at the inside terminal on the lower side of the auxiliary cut- 
 out magnet, and the current from the fine wire of the main 
 magnets passes through both windings and then to the cut- 
 out block, and so to the starting resistance and out. 
 
 If the main current through the carbon is interrupted 
 (as by breaking of the carbons) the whole current of the 
 lamp passes through the fine wire circuit. Before this 
 excessive current has time to overheat the fine wire circuit, 
 it energizes the auxiliary cut-out magnet, and closes a cir- 
 cuit directly across the lamp through the coarse wire on 
 the auxiliary cut-out to the main cut-out block, and thence 
 to the negative terminal. 
 
 The auxiliary cut-out operates instantly, and prevents 
 any danger to the magnets during the short period required 
 for the main armature to drop and throw in the main cut- 
 out. When the main cut-out operates, the armature of the 
 auxiliary cut-out falls, because there is not sufficient cur- 
 rent in that circuit to energize the magnet. 
 
 The voltage at which the auxiliary cut-out magnet oper- 
 ates depends on the position of its armature, which is reg- 
 ulated by the screw securing the armature in position. It 
 should be adjusted to operate at not less than 70 volts. 
 
 One of the three methods of suspension may be used for 
 Brush lamps. If chimney suspension, which is the most 
 common, is adopted, the wire, cable or rope used to sus- 
 pend the lamp must be carefully insulated from the chim- 
 ney. For this purpose a porcelain insulator should be in- 
 
1412 
 
 Steam Engineering 
 
 serted between the support and the lamp, as shown in 
 Fig. 669. 
 
 Hook suspension may be used to advantage in some 
 places, but great care must be taken to insulate the support- 
 
 ■ $ i ' 
 
 1 ; i 1 
 
 ! IB ■ IB ■ ■* 
 } ^ JjR jjjl 1 
 
 1 -W 
 
 
 
 If 11 
 
 Fig. 669 
 
 ing wires from any conductors, as the hooks form the ter- 
 minals of the lamps. 
 
 The most convenient arrangement for indoor use is to 
 suspend the lamp from a hanger board. The porcelain 
 base of the hanger board prevents short circuits or grounds. 
 
Arc Lamps 1413 
 
 A protecting hood is not necessary for outdoor use, as 
 the lamp chimney and its base are one casting and effect- 
 ually exclude rain or snow. 
 
 The lamps run on circuits of 6.6 amperes for 1,200 and 
 9.6 amperes for 2,000 nominal candlepower. In case it is 
 necessary to run a lamp on a circuit differing from the 
 standard, the lamp may be adjusted by moving the contact 
 on the adjuster. About one ampere either above, or below 
 the normal may be compensated for by this means. 
 
 Permanent adjustment for special circuits of variation 
 greater than one ampere is made by filing the soft iron arma- 
 ture. The clutch should be so adjusted that the center of 
 the armature is -Jf in. above the plate when the trip on the 
 first rod is touching the bushing, and {^ in. when the trip 
 on the second rod is in a similar position. A small gauge 
 is convenient for adjusting the clutch. The position of the 
 trip of the clutch determines the feeding point of the lamp. 
 
 After thoroughly repairing and cleaning the lamp, it 
 should be run a short time before installing. Lamps should 
 not be tested in an exposed place, as a strong draft of air 
 will cause unpleasant hissing which may be mistaken for 
 some internal trouble. 
 
 Lamps should not hiss or flame if good carbons are used. 
 A voltmeter should always be used when adjusting or 
 testing. 
 
 The lamp terminals are marked P (positive) and N 
 (negative) and should be connected into circuit accord- 
 ingly. 
 
 The carbons should be solid and of uniform quality. For 
 the best results, the upper carbon should be 12 in.XiV i n -> 
 and the lower 7 in.XiV i n - The stub of the upper carbon 
 may then be used in the lower holder when retrimming. 
 
1414 
 
 Steam Engineering 
 
 At each trimming the rod should be carefully wiped with 
 clean cotton waste. If any sticky or dirty spots appear, 
 
 Fig. 670 
 
 which cannot be readily removed with waste, use a piece 
 of well-worn crocus cloth, always being careful to use a 
 piece of clean waste before pushing the rod into the lamp. 
 
 . 
 
Arc Lamps 1415 
 
 It should never be pushed up into the lamp in a dirty con- 
 dition. 
 
 The carbon rod may be unscrewed and removed with a 
 small screw driver, or small strip of metal inserted in the 
 slot cut in the rod cap. The cap will remain in the hole 
 through the yoke when the rod is taken out. 
 
 In Fig. 670 an interior view of the Thomson-Houston 
 arc lamp is shown. This lamp is also used on constant 
 current systems. 
 
 The lamps should be hung from the hanger boards pro- 
 vided with each lamp, or from suitable supports of wire or 
 chain. 
 
 As the hooks on the lamp form also its terminals, they 
 should be insulated, where a hanger board is not used, from 
 the chains or wires used to support the lamp. 
 
 When the lamps are hung where they are exposed to the 
 weather, they should be covered with a metal hood, to pre- 
 vent injury from rain and snow. 
 
 In such cases, care should be taken that the circuit wires 
 do not form a contact on the metal hood and short circuit 
 the lamp. 
 
 Before the lamps are 'hung up they should be carefully 
 examined to see that the joints are free to move, and that 
 all connections are perfect. 
 
 Xo lamp should be allowed to remain in circuit, with the 
 covers removed and the mechanism exposed. Such practice 
 is dangerous, and in violation of insurance rules. 
 
 The object of testing the lamps in the station is to find 
 any defects, if such exist, and to test all the conditions of 
 running, before delivering them to customers. The lamps 
 should not be hung up in their respective places in the ex- 
 ternal circuit, until everything is running with perfect 
 satisfaction. 
 
1416 
 
 Steam Engineering 
 
 The tension of the clamp which holds the rod is adjusted 
 by raising or lowering the arm at the top of the guide rod. 
 (See Fig. 671.) If the tension is too great the rod and 
 clutch will wear badly, and the feeling will be uneven, 
 
 t / 1 * / j j ; ■f z ftv> 2 v Z ' s s ~n 
 
 "w"~ 
 
 Fig. 671 
 
 causing unsteadiness in the lights. Too little tension will 
 not allow the clutch to hold up the rod, and any sudden 
 jar to the lamp will cause the rod to fall and the light to go 
 out. 
 
Arc Lamps 1417 
 
 The double carbon, or M lamp, should have the tension 
 of the second carbon a trifle lighter than the first one. 
 
 When adjusting the tension, be sure to keep the guide rod 
 perpendicular and in perfect line with the carbon rod; it 
 should be free to move up and down without sticking. 
 
 The tension of the clutch in the D lamp should be the 
 same as that of the K lamp. It is adjusted by tightening 
 or loosening the small coil spring from the arm of the 
 clutch to the bottom of the clamp stop. 
 
 To adjust the feeding point in the K lamp, press down 
 the main armature as far as it will go, then push up the 
 rod about one-half its length, let go the armature and then 
 press it down slowly and note the distance of the bottom 
 side of the armature above the base of the curved part of the 
 pole. When the rod just feeds, this distance should be % in. 
 If it is not, raise or lower the small stop which slides on the 
 guide rod passing through the arm of the clutch, until the 
 carbon rod will feed when the armature is *4 in- from the 
 rocker frame at base of pole. 
 
 To adjust the feeding point of the M lamp, adjust the 
 first rod as in the K lamp. Then let the first rod down 
 until the cap at the top rests on the transfer lever. The 
 second rod should feed with the armature at a point iV in- 
 higher than it was while feeding the first rod, that is, it 
 should be fV in. from rocker frame at base of pole. 
 
 The feeding point of the D lamp is adjusted by sliding 
 the clamp stop up or down, so that the rod will feed when 
 the relative distances of the armatures of the lifting magnet, 
 and the armature of the shunt magnet from rocker arm 
 frame arc in the ratio of 1 to 2. There should be a slight 
 lateral play in the rocker, between the lugs of the rocker 
 frame. 
 
1418 Steam Engineering 
 
 The armatures of all the magnets should be central with 
 cores, and come down squarely and evenly. There should 
 be a separation of £% in. between the silver contact points, 
 when the armature of the starting magnet is down. This 
 contact should be perfect when the armature is up. The 
 arm for adjusting the tension should not touch the wire or 
 frame of the lamp when at the highest point. There should 
 be a space of 3 3 2 in - o r Vs m - between the body of the clutch 
 and the arm of the clutch, to allow for wear on the bearing 
 surfaces. 
 
 Always trim the lamp with carbons of proper length to 
 cut out automatically, that is, have twice as much carbon 
 projecting from the top as from the bottom holder. Al- 
 ways allow a space of y± in., when the lamp is trimmed, 
 from the round head screw in the rod, near the carbon 
 holder, to the edge of the upper bushing, so that there will 
 be sufficient space to start the arc. 
 
 The arcs of the 1,200 candlepower lamps should be ad- 
 justed to 3/6 ± in., with full length of carbon. Arcs of 2,000 
 candlepower lamps should be adjusted from ■£% to ^ in. 
 when good carbons are used. 
 
 The action of a lamp that feeds badly may often be con- 
 founded with a badly flaming carbon. The distinction can 
 readily be made after a short observation. The arc of a 
 lamp that feeds badly will gradually grow long until it 
 flames, the clutch will let go suddenly, the upper carbon 
 will fall until it touches the lower carbon, and then pick 
 up. A bad carbon may burn nicely and feed evenly until a 
 bad spot in the carbon is reached, when the arc will sud- 
 denly become long and flame and smoke, due to impurities 
 in the carbon. Instead of dropping, as in the former case, 
 the upper carbon will feed to its correct position without 
 touching the lower carbon. 
 
Arc Lamps 
 
 1419 
 
 In a series arc lamp the shunt coil is used to regulate the 
 voltage over the arc. With constant potential arc lamps 
 this shunt coil is not needed, owing to the fact that the 
 voltage over the lamp is practically constant. Fig. 672 
 shows a diagram of an arc lamp for use on constant poten- 
 tial circuits. The upper carbon is supported by means of 
 an iron yoke which forms a core to the two solenoids M M. 
 Current entering binding posts T passes through the wind- 
 ings of these two solenoids and then through the carbons 
 
 Fig. 672 
 
 and through the resistance coil R to the other terminal of 
 the lamp. The action of the lamp is as follows : Current 
 passing over the solenoids M M is regulated by the resist- 
 ance across the arc. This current produces an electromag- 
 netic pull on the iron core and floats, magnetically, the core 
 and upper carbon. When the carbons burn away at the 
 crater the distance from point to point of the carbons is 
 increased, and a corresponding increase in resistance to the 
 flow of the current takes place. This reduces the flow of 
 
1420 Steam Engineering 
 
 current around the solenoids and correspondingly reduces 
 the electromagnetic pull on the core ; the iron core and car- 
 bon fall a slight distance by gravity. In so doing the dis- 
 tance at the crater is decreased and the flow of current 
 increased, and a corresponding increase in resistance to the 
 solenoids and drawing up the core and carbons. In this 
 way a very nice equilibrium between gravity and magnetic 
 pull is maintained. It will be noticed that this lamp has 
 no automatic cut-out as has the constant current arc lamp. 
 In a series arc lamp when the carbons are all consumed, the 
 automatic cut-out closes the circuit from the positive and 
 negative binding posts of the individual arc lamp, thereby 
 maintaining a path through the arc lamp over which the 
 current can continue to flow to supply the remaining arc 
 lamps in the series circuit. 
 
 The series arc, as its name would indicate, is the most 
 simple of all lighting circuits. The lamps are arranged so 
 that all the current from the positive pole of the dynamo 
 goes through each, and from the last on the conductor 
 leads back to the dynamo. The series system is more gen- 
 erally used where it is desired to illuminate a large district, 
 as in street lighting. It is also used to some extent in store 
 lighting, although the series arc is fast being replaced with 
 the constant potential arc for this purpose. 
 
 In the low tension or constant potential arc lamp the 
 use of a cut-out mechanism is not necessary, because these 
 lamps burn singly across the system of wiring, where a con- 
 stant potential is maintained, and hence when the carbons 
 are all consumed, current simply ceases to flow across them. 
 In the open arc lamp the potential across the crater is 
 usually from 45 to 50 volts, while in the inclosed arc lamp 
 the potential across the crater is from 68 to 75 volts. This 
 is due to the increased resistance through the crater, because 
 
Arc Lamps 
 
 1421 
 
 of the peculiar nature of the gases emitted from the crater 
 burning in a condition with practically no atmosphere. 
 When such an arc lamp is connected across a 110 volt cir- 
 cuit, the lamp contains a resistance coil in the mechanism 
 box over which the current must flow before producing the 
 
 Fig. 673 
 
 arc, see R. Fig. 672. This resistance coil assists to reduce 
 the pressure from 110 volts to the pressure required by the 
 arc or crater. If, for instance, the electromotive force across 
 the wires supplying current to a low tension arc lamp is 
 110 volts, and the pressure required to maintain the arc or 
 
1422 Steam Engineering 
 
 crater is 70 volts, then the resistance coil chokes down the 
 electromotive force from 110 to 70, or 40 volts. If the arc 
 consumes 4 amperes of current then the loss is 4 (amperes) 
 times 40 (volts), or 160 watts. This 160 watts is lost by 
 heat radiating to the atmosphere from the wire of the resist- 
 ance coil. The constant potential lamp is usually referred 
 to as the low tension arc lamp. The high tension arc lamp 
 generally burns with the arc in the open air, while the low 
 tension lamp burns with the arc encased in a small glass 
 bulb so arranged as to permit the upper carbon to slide into 
 the bulb in a manner that will maintain, as near as possible, 
 a condition whereby the arc burns in a gas containing no 
 oxygen. The enclosed arc lamp has the advantage of burn- 
 ing a considerable number of hours without being recar- 
 boned or trimmed ; but it also has the disadvantage that the 
 bulb enclosing the arc turns black after burning for some 
 time, caused by the gases emitted from the arc. This ren- 
 ders the bulb partially opaque, consequently imprisoning a 
 considerable quantity of useful light. Enclosed arc lamps 
 are also operated in series systems, and where they are so 
 used the objection of loss due to the cutting down of the 
 voltage (as in constant potential lamps) is overcome. En- 
 closed lamps are also operated on alternating current sys- 
 tems. 
 
 The operation of the alternating current arc lamp, and 
 the mechanism in the lamp is very similar to that of the di- 
 rect current arc lamp, but the magnets instead of being con- 
 structed of solid iron are laminated in a manner similar to 
 the system of lamination explained in the construction of 
 armatures. These laminated cores, and other parts forming 
 the magnetic circuit in the arc lamp are necessary to avoid 
 eddy currents. The crater has neither a cup shape on the 
 upper carbon, nor a point on the lower carbon, because cur- 
 
Arc Lamps 
 
 14213 
 
 rent flows through the crater alternately positive, and nega- 
 tive with each alternation. In the alternating arc lamp the 
 upper and lower carbons burn away with almost equal 
 rapidity, and the same quantity of light is projected upward 
 as downward. 
 
 Fig. 674 
 
 Fig. 675 
 
 Fig. 676 
 
 In Fig. 673 is shown an arc lamp with the case removed. 
 The two upper coils are the coarsely wound series coils, 
 while the two lower coils are the finely wound shunt coils. 
 This lamp is adapted for an enclosed arc bulb. The mag- 
 netically attracted cores are U shaped, and both cores are 
 connected together mechanically by non-magnetic metal, 
 
1424 Steam Engineering 
 
 such as brass or zinc, so that the magnetism set up in the 
 shunt coils will not be affected by the magnetism set up by 
 the series coils. This scheme is used in alternating current 
 lamps, while in direct current lamps the cores are made of 
 H shaped iron not laminated. 
 
 In Figs. 674 to 676 are shown three views of series en- 
 closed, alternating current arc lamps of the Western Elec- 
 tric Compam^. 
 
 Fig. 674. Side view of lamp, showing one series and one 
 shunt spool, lever movement and adjusting weight. This 
 weight is fastened upon a threaded rod, and the finest ad- 
 justment can be obtained by screwing the weight backward 
 or forward. Threads can be clamped in position when the 
 correct adjustment is obtained. 
 
 Fig. 675. Front view of lamp, showing shunt spools, 
 supporting resistance and cut-out. Note that lever carries 
 no current when in normal working position, but that in- 
 sulated bridge forms connection across two contacts, com- 
 pleting cut-out circuit when in position shown in cut. 
 
 Fig. 676. Eear view of lamp, showing series spool, short 
 circuiting switch, and manner of suspending dash-pot. Note 
 that the dash-pot is inverted, allowing such dirt as may 
 accumulate therein to fall out, rather than in the dash-pot. 
 
 The three cuts show the manner of suspending the spools 
 and their accessibility, it being possible to remove any 
 spool by simply taking out the two screws which fasten it 
 to the frame, and lifting it off the lower support. 
 
 The carbons used in arc lamps are extremely hard and 
 dense. They are made from a mixture of powdered gas 
 house coke, ground very fine, and a liquid like molasses, coal 
 tar, or some similar hydro-carbon, forming a stiff, homo- 
 geneous paste. This is molded into rods or pencils of the 
 required size and length, or other shapes, being solidified 
 
Arc Lamps 1425 
 
 under powerful hydrostatic pressure. The carbons are now 
 allowed to dry, after which they are placed in crucibles or 
 ovens, thoroughly covered with powdered carbon, either 
 lampblack or plumbago, and baked for several hours at a 
 high temperature. After cooling, they are sometimes re- 
 peatedly treated to a soaking bath of some fluid hydro- 
 carbon, alternated with baking, until the product is dense 
 as possible, all pores and openings having been filled solid. 
 Arc carbons are often plated with copper by electrolysis, 
 to insure better conductivity. 
 
 It is said that one 2,000 candlepower arc lamp will light 
 in open yards 20,000 sq. ft. ; in railroad stations, 14,000 
 sq. ft. ; in foundries and machine shops, 5,000 to 2,000 
 sq. ft. Where good, even illumination is desired, it is ad- 
 visable to use a greater number of smaller lamps evenly 
 distributed. 
 
 THE INCANDESCENT LAMP. 
 
 One of the fundamental laws of electric supply is, that 
 the resistance in an electric circuit should be concentrated 
 at the point where energy is to be developed, and the incan- 
 descent lamp is a good expression of this law, as the useful 
 resistance is that which is afforded by the filaments of the 
 lamp. The incandescent lamp comprises a carbon filament 
 enclosed in a glass bulb from which the air has, as far as 
 possible, been withdrawn, the carbon filament being sol- 
 dered to the ends of small platinum wires entering the glass 
 shell. Incandescent lamps can be burned either in series 
 or in multiple; the multiple system being the most used. 
 Series incandescent lamps are used to a considerable extent 
 in the smaller towns for street lighting and also for the 
 small miniature lamps burned in series on a constant po- 
 
1426 Steam Engineering 
 
 tential system, and used for decorative purposes. They are 
 also used in street car lighting. 
 
 When incandescent lamps are to be used in series, they 
 should be carefully selected; there is quite a difference in 
 the current consumed by different lamps, even of the same 
 make, and when they are all limited to the same current 
 quite a difference in candlepower may be noticeable. Some 
 will be above their rated candlepower and others below. 
 
 The resistance of an incandescent lamp when cold is 
 very high, varying in the ordinary 16 candlepower 110 volt 
 lamp from 600 to 1,000 ohms. When the lamp becomes 
 heated, as when current is passing through it, the resist- 
 ance reduces considerably, being in. the 16 candlepower 110 
 volt lamp about 220 ohms. 
 
 The current required by the various incandescent lamps 
 varies considerably for lamps of the same voltage and 
 candlepower, but a good average which can be used in figur- 
 ing currents is % ampere for a 16 candlepower 110 volt 
 lamp and ^ ampere for the 220 volt 16 candlepower lamp. 
 The amount of power, in watts, consumed by a lamp is 
 equal to the voltage multiplied by the current, or W=CXE. 
 A 16 candlepower 110 volt lamp taking % ampere would 
 consume 110X 1 / 4=55 watts, while a 220 volt lamp taking 
 % ampere would consume 220X"!?4— 55 watts. It will thus 
 be seen that while the current and voltage may vary, the 
 amount of power consumed will be approximately the same 
 for all 16 candlepower lamps. Lamps are rated at a certain 
 number of watts per candle, the amount varying from 3 to 4 
 watts for 16 candlepower 110 volt lamps. The proper lamp 
 to be used varies according to the conditions. While less 
 power is consumed in a 3.1 watt lamp, the life of the lamp 
 is comparatively shorter, so that the lamps will have to be 
 renewed oftener. With a 4 watt lamp a greater amount of 
 
Incandescent Lamps 1427 
 
 current is consumed, but the life of the lamp is longer. 
 Another point of great importance in burning incandescent 
 lamps is the voltage. The table below shows what effect 
 variation in voltage has on the candlepower and efficiency. 
 
 An increase in voltage increases the candlepower. This 
 increases the efficiency and shortens the life as follows : 
 
 A lamp burning at — 
 
 Normal voltage gives 100 per cent. C. P. and consumes 3.1 Watts per C. P. 
 
 1% above normal gives 106% C. P. and consumes 3. Watts per C. P. 
 
 2% above normal gives 112% C. P. and consumes 2.9 Watts per C. P. 
 
 3% above normal gives 118% C. P. and consumes 2.8 Watts per C. P. 
 
 4% above normal gives 125% C. P. and consumes 2.7 Watts per C. P. 
 
 5% above normal gives 132% C. P. and consumes 2.6 Watts per C. P. 
 
 6% above normal gives 140% C. P. and consumes 2.5 Watts per C. P. 
 
 A lamp burning at normal voltage should give its full 
 candlepower at its rated efficiency. A 3.1 watt lamp burn- 
 ing below its voltage loses its efficiency and candlepower as 
 follows : 
 
 If burned — 
 
 1% below normal it gives 95% C. P. and consumes 3.2 Watts per C. P. 
 
 2% below normal it gives 90% C. P. and consumes 3.35 Watts per C. P. 
 
 3% below normal it gives 85% C. P. and consumes 3.5 Watts per C. P. 
 
 4% below normal it gives 80% C. P. and consumes 3.6 Watts per C. P. 
 
 5% below normal it gives 75% C. P. and consumes 3.75 Watts per C. P. 
 
 6% below normal it gives 70% C. P. and consumes 4. Watts per C. P. 
 
 10% below normal it gives 50% C. P. and consumes 4.6 Watts per C. P. 
 
 By referring to the table it will be seen that with the 
 voltage raised 3 per cent (on a 110 volt system to a little 
 over 113 volts) the candlepower will increase 18 per cent, 
 or in other words, a 16 candlepower lamp would be raised 
 to nearly 19 candlepower. At the same time raising the 
 voltage will decrease the life of the lamp. This is shown 
 in the following table where, with an increase of 6 per cent 
 in the voltage, the life of the lamp is reduced 70 per cent. 
 A lamp at normal voltage has 100 per cent life. 
 
 The same lamp 1% above normal loses 18% life. 
 
 The same lamp 2% above normal loses 30% life. 
 
 The same lamp 3% above normal loses 44% life. 
 
 The same lamp 4% above normal loses 55% life. 
 
 The same lamp 5% above normal loses 62% life. 
 
 The same lamp 6% above normal loses 70% life. 
 
 ■M 
 
1428 
 
 Steam Engineering 
 
 To obtain satisfactory results, the voltage should be 
 kept constant at just the proper value. 
 
 Considerable heat is generated in an incandescent lamp, 
 so that as a general rule it is a bad plan to use paper shades 
 which come very close to the bulb. Where lamps are hung 
 so that there is a liability of their coming in contact with 
 surrounding inflammable material, such as in warehouses 
 and store-rooms, it is a good plan to enclose the lamp in a 
 wire guard. 
 
 Table 59 will prove a handy reference for estimating the 
 number of lamps (8 to 50 C. P.) that can be run per horse- 
 power or kilowatt. The table is figured for theoretical 
 values, so that the actual horsepower or kilowatts delivered 
 must be used, or else values less than those given must be 
 used to allow for loss in the lines. 
 
 Table 59 
 
 efficiency of incandescent lamps. 
 
 Candlepower. 
 
 Efficiency. 
 
 Total Watts. 
 
 Per 
 
 Horsepower. 
 
 Per Kilowatt. 
 
 8 1 
 
 3.5 
 
 28 | 
 
 26.6 
 
 35.7 
 
 8 
 
 4 
 
 32 
 
 23.3 
 
 31.2 
 
 16 
 
 3 
 
 48 
 
 15.5 
 
 20.8 
 
 16 
 
 3.1 
 
 50 
 
 14.9 
 
 20 
 
 16 
 
 3.5 
 
 56 
 
 13.3 
 
 17.8 
 
 16 
 
 4 
 
 64 
 
 11.6 
 
 15.6 
 
 20 
 
 3 
 
 60 
 
 12.4 
 
 16.6 
 
 20 
 
 3.1 
 
 62 
 
 12 
 
 16.1 
 
 20 
 
 3.5 
 
 70 
 
 10.6 
 
 14.2 
 
 25 
 
 3 
 
 75 
 
 9.9 
 
 13.3 
 
 25 
 
 3.1 
 
 77.5 
 
 9.6 
 
 12 9 
 
 25 
 
 3.5 
 
 87.5 
 
 8.5 
 
 11.4 
 
 25 
 
 4 
 
 100 
 
 7.4 
 
 10 
 
 32 
 
 3 
 
 96 
 
 7 
 
 10.4 
 
 32 
 
 3.1 
 
 99.2 
 
 7.5 
 
 10 
 
 32 
 
 3.5 
 
 112 
 
 6.6 
 
 8.9 
 
 50 
 
 3 
 
 150 
 
 4.9 
 
 6.6 
 
 50 
 
 3.1 
 
 155 
 
 4.8 
 
 6.4 
 
 50 
 
 3.5 
 
 175 
 
 4.2 
 
 5.7 
 
 The first column gives the candlepower. The second 
 column gives the number of watts consumed for each single 
 candlepower obtained, and is called the efficiency of the 
 
Incandescent Lamps 1429 
 
 lamp. Multiply the total candlepower by the efficiency and 
 you get the total number of watts consumed by the lamp. 
 The fourth column shows the number of lamps per 746 
 watts, and the last column the number of lamps per 1,000 
 watts. 
 
 The current and watts consumed by 110 volt lamps of 
 the different candlepowers are approximately given below. 
 
 4 candlepower 0.18 amperes, 20 watts. 
 
 8 candlepower 0.29 amperes, 32 watts. 
 
 16 candlepower 0.5 amperes, 55 watts. 
 
 32 candlepower 1.0 amperes, 110 watts. 
 
 The light given off by an incandescent lamp varies ac- 
 cording to the position from which it is viewed. In some 
 makes of lamps most of the light is given off directly down- 
 ward, while in other lamps the maximum light is given off 
 in a horizontal direction. The best lamp to use must be 
 determined by the location of the lamp and the place where 
 the light is required. By the use of suitable reflectors or 
 shades the light can be thrown in any direction desired. 
 A 16 candlepower lamp if placed seven feet above the floor 
 will light up a floor space of 100 sq. ft., providing the walls 
 are of a light color. If the walls are of a dull color, or if 
 a bright illumination is desired more lamps should be used. 
 Glass globes placed over the lamps reduce the light to a 
 considerable extent, as is shown in the following table: 
 
 Clear glass 10 per cent. 
 
 Holophane 12 per cent. 
 
 Opaline 20 to 40 per cent. 
 
 Ground 25 to 30 per cent. 
 
 Opal 25 to 60 per cent. 
 
 PRIMARY BATTERIES. 
 
 There are many places where a small amount of electri- 
 cal power is needed, but the amount is so small, that running 
 a line to the point would not pay. In such cases primary 
 batteries may be used to good advantage. 
 
1430 
 
 Steam Engineering 
 
 Construction. — If a piece of zinc, and a piece of copper 
 be placed in a jar containing dilute sulphuric acid, and 
 not allowed to touch each other below the surface of the 
 liquid, but are connected above it, by a wire, a current of 
 electricity will flow through the wire, and the wire will show 
 magnetic qualities. This is one of the most simple forms 
 of primary battery. The current flows from the copper 
 to the zinc outside of the cell, and from the zinc to the 
 copper in the liquid. 
 
 7>OS)TJVE 
 
 Pole or 
 
 ELECTJtODE 
 
 NEGATIVE 
 PLATE 
 
 NBGATiVB 
 
 P01£ OR 
 ELECTRODE. 
 
 PGSI7IVU 
 PLATE 
 
 Fig. 677 
 
 NAMES OF PARTS OF CELL 
 
 Tig. 677 shows a cell such as described above giving 
 names of the different parts. The zinc plate slowly dissolves, 
 and more or less hydrogen gas is thereby set free, which 
 arises in the form of bubbles. Carbon has been found 
 to be a good substitute for copper, in the makeup of battery 
 cells. The different types of cells are classified as follows : 
 
 Open circuit : A cell designed for intermittent work. 
 Periods of work short, intervals of rest long. Usually de- 
 
Primary Batteries 
 
 1431 
 
 signed for small currents. When not in use these cells must 
 be left on open circuit. 
 
 Semi-closed: A cell designed for fairly steady work. 
 Periods of work long, intervals of rest short. Often de- 
 signed to produce heavy currents. When not in use these 
 cells must be left on open circuit. 
 
 Closed circuit: A cell designed for continuous work. 
 Periods of work long, intervals of rest very short. Usually 
 designed for very small currents. Almost impossible to 
 design so as to produce much current. When not in use 
 they must be left on closed circuit. 
 
 
 Fig. 678 
 carbon cylinder cell 
 
 Polarization prevented : Cell so designed that no hydro- 
 gen gas is produced by chemical action of cell. 
 
 Polarization cured: Cell produces hydrogen, but a 
 chemical placed in the cell turns the hydrogen to water 
 which is harmless. 
 
 Polarization delayed : Cell has very large and absorbent 
 negative plate. 
 
 The Carl on Cylinder Cell. — These are sold under the 
 name of Law, Samson, Hercules, etc. It is an open cir- 
 
1432 
 
 Steam Engineering 
 
 cuit, polarization delayed type. They give a pressure of 
 1.5 volts and have a resistance of 1 to 2 ohms. Two of 
 them are shown in Fig. 678. 
 
 The carbon element is made with as large a surface as 
 possible. Carbon and charcoal have a remarkable power 
 of absorbing gases. A cubic inch of charcoal will condense 
 and absorb 20 to 30 cubic inches of gas. 
 
 The zinc element is a rod and the fluid a strong solution 
 of sal ammoniac in water. The scientific name of this 
 chemical is ammonium chloride. 
 
 Fig. 679 
 carbon cylinder cell with depolarizer 
 
 The action of the cell dissolves the zinc, forming zinc 
 chloride, which dissolves in the water. A little ammonia 
 and hydrogen gases are set free. The ammonia is dis- 
 solved by the water and the hydrogen absorbed by the 
 carbon. 
 
 In time the carbon gets soaked full of hydrogen, and 
 to restore the cell it should be taken out and boiled in water 
 for an hour. 
 
 These should only be used for call bells in offices or such 
 unimportant work. 
 
 Leclanche Cell. — This is an open-circuit, polarization 
 cured type. They are made in several forms. Voltage 1.5 
 
Primary Batteries 
 
 1433 
 
 and resistance 1 to 4 ohms. Uses sal ammoniac, zinc and 
 carbon. 
 
 The carbon cylinder cell is sometimes modified to the 
 Leclanche type by making the carbon element with a bot- 
 tom and no opening in the sides. This carbon can, or 
 bucket is filled with lumps of black oxide of manganese 
 
 Fig. 680 
 ordinary leclanche cell 
 
 Fig. 681 
 elements of the 
 gonda-leclanche cell 
 
 (manganese dioxide). The zinc is made in a cylindrical 
 form, surrounding the carbon. This cell is shown in Fig. 
 679. 
 
 The hydrogen is absorbed by the carbon but the man- 
 ganese dioxide, being in contact with the carbon, gives up 
 half of its oxygen to the hydrogen forming water, while it 
 is reduced to manganese monoxide. 
 
1434 Steam Engineering 
 
 This cell Is useful for call bell work, operating magnets 
 on interlocking machines, running tell-tales on interlock- 
 ing boards, and such other intermittent light work. 
 
 There is an older form of Leclanche cell shown in Fig. 
 680, where the carbon is placed in a cup of unglazed earthen 
 ware (like a yellow flower pot) called a porous cup. The 
 manganese is packed around the carbon slab. This form 
 does not give such a large current as the cell in Fig. 679 
 because its resistance is high, often as much as four or five 
 ohms. 
 
 A much used form of the Leclanche cell is the Gonda 
 cell. The elements are shown in Fig. 681. 
 
 Here the manganese is powdered, mixed with cheap mo- 
 lasses, then by heat and pressure formed into slabs. These 
 are attached to the carbon plates by rubber bands. 
 
 The bother and resistance of the porous cup is avoided. 
 
 The usual charge of a Leclanche type cell is a generous 
 quarter pound of sal ammoniac dissolved in sufficient water 
 to fill the jar two-thirds full after elements are in place. 
 
 The Gravity Cell. — This is a closed circuit cell with 
 polarization prevented. It is very much used for telegraph 
 circuits, operating the electrical devices in the lock and 
 block signals, the motors in automatic signals and generally 
 around interlocking plants. Its pressure is 1 volt and its 
 current capacity rather low for its resistance is 3 or 4 ohms. 
 
 This cell is made in many forms called Bluestone cell, 
 crow-foot battery, Lockwood cell, etc. 
 
 The parts of a gravity cell are shown in Fig. 682, and 
 the assembled cell in Fig. 683. 
 
 The glass jars should be about 7 inches high and 6 inches 
 in diameter. The zinc is cast in a shape so as to be easily 
 suspended from the edge of the jar. The form shown is 
 called a crow-foot zinc. It weighs about 3 pounds. 
 
Primary Batteries 
 
 1435 
 
 The copper element shown on left of Fig. 682 is made 
 of three sheets riveted together at center and then spread 
 out as shown. The rubber covered wire must be at- 
 tached to the copper element by riveting. If soldered the 
 joint would be eaten away by electrical action. 
 
 To set up a cell of ordinary size which holds about 0.8 
 
 Fig. 682 
 elements of gravity cell and jar 
 
 gallons of liquid, make two solutions, one of copper, the 
 other of zinc. 
 
 Zinc solution : Pint and a half of pure soft water and 
 10 oz. of crystallized sulphate of zinc (white vitriol). Mix 
 until dissolved and let it stand half a day in a glass jar. 
 
 Copper solution: Two and a half pints of soft water, 
 4 ozs. of crystallized sulphate of zinc, 8 ozs. crystallized 
 
1436 
 
 Steam Engineering 
 
 Mix and let stand a 
 
 sulphate of copper (blue vitriol), 
 few hours in a glass jar. 
 
 Dip edge of battery jar for an inch in melted paraffin 
 and let it cool. 
 
 Place the parts in jar as in Fig. 683 and pour jar nearly 
 ihree-fourths full of the zinc solution. Place it at once 
 
 Fig. 683 
 gravity cell ready for use 
 
 in the spot where it is to be used and pour in the copper 
 solution. 
 
 Insert a glass funnel in the top of a piece of %-inch 
 rubber tubing. Hold funnel so that lower end of the tube 
 will be in the middle of the jar and just a little above the 
 bottom. 
 
Primary Batteries 
 
 1437 
 
 Pour in the copper solution slowly until the copper ele- 
 ment is completely covered. Place the cell into service im- 
 mediately. 
 
 This cell will show a sharply defined line between the 
 blue copper solution and the colorless zinc solution. This 
 separation of solutions is essential to the celPs health. 
 Leaving the circuit open for any length of time will allow 
 the solutions to mix and spoil the cell. 
 
 The action of the cell is such that no hydrogen is per- 
 manently formed. The zinc is steadily dissolved into the 
 
 r\ 
 
 Fig. 684 
 long service copper element for gravity cell 
 
 zinc solution, setting free some hydrogen. This forms with 
 the 'copper sulphate, sulphuric acid and metallic copper. 
 The sulphuric acid dissolves more zinc, while the copper 
 plates itself on the copper element at the bottom of jar. 
 
 The zinc is consumed and the copper plate grows larger. 
 
 The effect of continued action is to increase the strength 
 of the zinc solution so that it tends to settle to bottom of jar. 
 
 The copper being taken out, bit by bit, from the copper 
 solution this latter gets lighter in weight and tends to rise 
 being pushed up by the zinc solution. 
 
1438 
 
 Steam Engineering 
 
 If the blue solution of copper sulphate ever touches the 
 zinc it will copper plate it at once. The cell will then have 
 two copper elements and stop working. 
 
 Cells should be given some attention, and clever manage- 
 ment will keep a gravity cell working continuously for an 
 almost indefinite time. 
 
 As helps in the maintenance of cells two improvements 
 have been made. 
 
 The form of copper element shown in Fig. 684 is better 
 when heavy currents are not needed. It is a copper ribbon 
 
 Fig. 685 
 d'infrevilles wasteless zinc 
 
 4 feet long and !/2 an mcn wide, coiled like a clock spring. 
 Zincs shaped like Fig. 685 are used until the prongs are all 
 eaten off. A new one is then put in service and the old 
 one jammed into the bottom of the new one as shown in 
 Fig. 686. 
 
 These zincs are hung from a spring clip shown in Fig. 
 687, which lays across the top of the jar. The stud on 
 the zinc makes a tight friction fit with the hole in the 
 hanger, due to the springiness of the metal. 
 
Primary Batteries 
 
 1439 
 
 To keep cells in order a hard rubber syringe with the 
 nozzle at right angles to barrel, holding about a pint, and a 
 hydrometer should be obtained. 
 
 The hydrometer (Fig. 688) is a hollow glass float loaded 
 with shot so as to- float upright. The heavier a liquid the 
 more of the stem sticks up above the surface. 
 
 These hydrometers are graduated on stem in actual spe- 
 cific gravities or in degrees Baume (pronounced Bomay). 
 One with a stem about two inches long graduated from 15° 
 to 40° Baume, or from 1.11 to 1.40 specific gravity, is best 
 for battery work. 
 
 Fig. 6S6 
 
 USING UP OLD ZINCS 
 
 The first signs of exhaustion in the cell will be a fading 
 of the deep blue color of the copper solution and a lowering 
 of the line of separation between blue and white liquids. 
 
 When this occurs drop in about an ounce of copper sul- 
 phate in lumps. Be sure the lumps fall to the bottom. 
 There will always be a lot of fine powder at the bottom 
 of the copper sulphate barrel. Use this for making up new 
 cells when possible. If too much accumulates for this pur- 
 pose, make a saturated solution of it in water. 
 
 A saturated solution is one where the water has dis- 
 solved all it possibly can of the chemical, and leaves some 
 
1440 Steam Engineering 
 
 yet undissolved on bottom of jar after repeated stirring. 
 
 Place this in cells showing signs of exhaustion in same 
 way as the copper solution was placed in a newly set up 
 cell. 
 
 The zinc solution should be tested as frequently as possi- 
 ble. Once in two weeks is not too often. Drop the hydrom- 
 eter gently in. Should it read i.15 draw some out with 
 syringe and replace by fresh water. 
 
 Do not let it go below 1.10. If you have a Baume scale 
 these numbers are 20 and 15 degrees. Throw all the re- 
 moved zinc in a wooden tub., whether from working cells or 
 from old cells, to be renewed. 
 
 Fig. 687 
 
 Keep half a dozen pieces of metallic zinc in this tub. 
 Any copper in this solution, mixed by cell's action, will 
 turn to a reddish brown curd which can be filtered out. 
 Eeduce the clear liquid to 1.10 and use in making up new 
 cells. 
 
 "Watch your zinc. Should any brown hangers develop 
 on it, detach them with a bent wire and let them fall to 
 bottom of cell. 
 
 In time, in spite of all care, the zinc in a cell gets red- 
 dish brown all over. It is now time to give a complete 
 overhauling. 
 
 Take the cell out of service. Syphon off zinc solution into 
 the tub. Lift zinc out carefully and at once scrub clean 
 with a wire brush. Wash and replace in another cell at 
 once or dry thoroughly and keep dry until needed. 
 
Primary Batteries 
 
 1441 
 
 Syphon off the rest of the liquid into another wooden tub 
 and use after filtering as copper solution to make up new 
 cells. 
 
 Any lumps of copper sulphate in the bottom take out, 
 rinse, and put in other cells. 
 
 Fig. 688 
 hydrometer with baume scale 
 
 The mud in bottom of cells and in the zinc solution tub 
 should be dried and sold to brass founders as "battery mud." 
 
 The copper plates taken from cells should be kept com- 
 pletely covered with water, wire and all, until needed again. 
 
1442 
 
 Steam Engineering 
 
 When they get too heavy and cumbersome sell them, as 
 they are an especially pure form of copper. 
 
 Xever leave gravity cell on open circuit; the liquids will 
 mix. 
 
 The Fuller Cell. — Semi-closed circuit type, for heavy 
 duty. Long periods of work with little rest. 
 
 Polarization cured. Pressure 2 volts, resistance 0.5 ohms. 
 Cell shown in Fig. 689. 
 
 These cells are carbon and zinc, and since the chemical 
 
 Fig. 689 
 fuller cell 
 
 which converts the hydrogen to water will attack the zinc, 
 a porous cup is used. 
 
 The carbon or the zinc can be placed in the porous cup, 
 but the zinc usually is. A tablespoonful of mercury is 
 placed in bottom of porous cup, the zinc set in and the cup 
 filled with very dilute sulphuric acid (1 acid, 50 w T ater). 
 The carbon is then placed in the outer jar, the porous cup 
 being also in, and the outer jar filled three-quarters full 
 of battery fluid or electropoin. 
 
 This is composed of 4 ozs. of bichromate of soda, l 1 /^ 
 pints of boiling water, mixed and cooled ; then while slowly 
 
Primary Batteries 
 
 1443 
 
 stirring add little by little 3 ozs. sulphuric acid taken out 
 of a carbon (not diluted). Never pour water into acid. 
 
 The bichromate of soda has so much oxygen in it that 
 it will turn the hydrogen to water, changing itself to chro- 
 mate of soda. 
 
 When the interior of the porous cup gets dark green 
 colored a cup should be soaked in 1 to 50 acid for an hour 
 
 Fig. 690 
 oxide plate of edison-lalande cell 
 
 and then mercury placed in bottom and zinc set in. Sim- 
 ply take out old cup and insert new one in its place. 
 
 The old zinc should be cleaned, porous cup washed and 
 then boiled in water and both placed in stock. 
 
 These cells should be left on open circuit when not in use. 
 They are very powerful, but nasty to handle and not as 
 cheap as the gravity cell. When the electropoin gets green- 
 ish it soon becomes exhausted, then throw it awav. Cold 
 
1444 Steam Engineering 
 
 battery rooms, or pits affect this cell less than the gravity 
 cell. 
 
 Edison-Lalande Cell. — This is a semi-closed type with 
 polarization cured. It has a resistance of 0.2 ohms and a 
 very low voltage, 0.7, but is a bull dog for holding on. 
 It will, when set up, start in to deliver a heavy current and 
 keep at it until all its chemicals are used up. It needs no 
 attention and is built so that you can not give any. 
 
 When it stops take out the copper and sell it, throwing 
 everything else out. Clean up the jar and fit out again. 
 
 The cell uses zinc and oxide of copper plates immersed in 
 a solution of caustic potash. The oxide plate is shown in 
 Fig. 690 and the complete cell with a glass jar in Fig. 691. 
 Porcelain jars are usually furnished. 
 
 The caustic potash comes in sticks sealed up in a tin 
 can. 
 
 Place the elements in jar and fill with water to about 
 one inch of the top. Take out the elements and put in the 
 sticks of potash. 
 
 Stir constantly while dissolving, for it gets very hot and 
 might- crack the jar. Be very careful not to get caustic 
 potash on your flesh. It not only burns terribly, but makes 
 a wound which is very hard to heal. 
 
 If you buy potash by bulk, make the solution up to 1.33 
 on specific gravity scale or 38° on the Baume scale. 
 
 Place the zinc and copper oxide elements in the jar, see- 
 ing that they are properly separated by the hard rubber 
 buffers. Pour the bottle of oil over the top of solution and 
 place cover on. 
 
 If buying oil by bulk, get a heavy paraffin oil which 
 will read 1.46 specific gravity or 48° Baume and pour a *4 
 inch layer on each cell 
 
Primary Batteries 
 
 1445 
 
 These are good cells, but any sulphuric acid or caustic 
 potash cell is a nasty thing to handle. 
 
 The action of the cell dissolves the zinc, setting free 
 hydrogen, which is changed to water by the copper oxide, 
 which is reduced to pure copper by giving up the oxygen 
 in it. 
 
 Fig. 691 
 edison-lalande cell 
 
 Dry Batteries. — A dry battery is one which has its elec- 
 trolyte disseminated through some solid material through 
 which it can diffuse itself. Plaster of Paris and gelatinous 
 compounds have been used for the solid part. The usual 
 construction is on the basis of the plaster of Paris combin- 
 nation. 
 
1446 
 
 Steam Engineering 
 
 The outer cup is made of zinc, and acts as the positive 
 electrode. Over it is slipped a strawboard tube. The object 
 is to prevent the zinc of two batteries from touching each 
 other so as to establish a wrong connection. The negative 
 electrode is a plate of carbon. This is placed in the center 
 of the zinc, and is so supported as not to touch it in any 
 place. Carbon and zinc both carry binding posts. The fill- 
 ing varies. The following is used in the Burnley cell : 
 
 A wooden plunger or template, somewhat larger than the 
 carbon, is inserted, and the following mixture introduced : 
 
 Fig. 692 
 
 DRY CELL 
 
 Ammonium chloride, zinc chloride, 1 part of each, plaster 
 of Paris, 3 parts, flour 0.87 part, water 2 parts. After this 
 has set a little, the wooden template is withdrawn, the car- 
 bon is inserted in the cavity left by its withdrawal, and the 
 space left unfilled is filled with the following mixture. 
 Ammonium chloride, zinc chloride, manganese binoxide, 
 granulated carbon, flour, 1 part of each, plaster 3 parts, 
 water 2 parts. The electromotive force of this cell is 1.4 
 volts, its resistance 0.3 ohm. 
 
 The Gassner dry cell has as negative a cylinder made of 
 a mixture of carbon and manganese dioxide. The filling 
 
Storage Batteries 1447 
 
 composition is as follows : Zinc oxide, ammonium chloride, 
 and zinc chloride, 1 part each, plaster of Paris 3 parts, 
 water 2 parts. 
 
 For the Meserole dry battery, there are mixed the fol- 
 lowing : Graphite, slacked lime, arsenious acid, and glucose 
 or dextrine, 1 part each, carbon and manganese binoxide, 
 3 parts each. The mixture is finely pulverized and rubbed 
 up in a saturated solution of ammonium chloride and sodium 
 chloride (common salt) with one-tenth its volume of a 
 solution of mercuric chloride and an equal volume of hydro- 
 chloric acid. These constituents are intimately mixed and 
 poured into the zinc cup, 
 
 Dry batteries are sealed with pitch. A hole is sometimes 
 left for the escape of gas. 
 
 STORAGE BATTERIES. 
 
 The storage cell is rapidly pushing the primary battery 
 aside in signal and fire alarm work on account of: 
 
 (1) Its high voltage. 
 
 (2) Its great current capacity. 
 
 (3) The lowering of total battery expense if used for 
 several years. 
 
 (4) Its steadiness of action. 
 
 Storage cells are used in train lighting to furnish light 
 when train is not in motion, and to steady the supply of 
 current. 
 
 They are used in some cases to furnish the power to 
 operate switches on locomotives and motor cars. 
 
 In power houses they offer a reserve supply of power, 
 and act as a steadier of the load on the generators. 
 
 The simplest storage cell would be two strips of lead 
 immersed in dilute sulphuric acid. When current is sent 
 
1448 
 
 Steam Engineering 
 
 through them one plate turns a dark brown color, md the 
 other a grey color. After an hour's passage of current 
 reverse the connection and charge the other way. The 
 plates will change color — the grey one becoming brown 
 and the other one grey. 
 
 If this charging first in one direction, and then in the 
 other be kept up, you will notice that after each reversal 
 of the current through the cell the acid is quiet but soon 
 
 begins to gas or boil. This is the signal to reverse the cur- 
 rent as the cell is charged. 
 
 When the cell takes several hours to gas it is in condi- 
 tion to use. 
 
 After one of the reversals continue to charge until cell 
 has gassed about fifteen minutes. Remove the charging 
 wires and connect to anything you wish to run. About 
 70% of the power you put into the cell can now be taken 
 out. 
 
 You may now use this as a storage cell, charging it up 
 
Storage Batteries 
 
 1449 
 
 till it gasses, and then using the accumulated electricity as 
 you please. 
 
 You always lose 30% but you have the advantages of 
 portability, and ability to work when engines are shut down. 
 
 In time you will notice that the lead plates become 
 spongy and should the cell be used long enough the plates 
 will finally crumble and break. You will notice that the 
 more spongy the plates become the greater a charge they are 
 capable of holding. 
 
 In fact, just before your battery goes to pieces its ca- 
 pacity is the greatest. 
 
 To make a commercially practical cell we would proceed 
 thus: 
 
 The lead plates would be replaced by grids as shown in 
 Fig. 693 or by grooved plates as in Fig. 694. 
 
 Litharge and sulphuric acid is mixed to a stiff paste 
 and the grids or grooved plates plastered with the paste and 
 stood up to dry. This makes a negative plate. 
 
 Using a paste of red lead and sulphuric acid the positive 
 plates are formed in the same way. 
 
 The objection to a storage cell using these plates is that 
 after very little use they go to pieces. The changing of the 
 red lead to the brown oxide, and the changing of the 
 litharge to spongy lead is accompanied by a swelling and 
 shrinking of the material. This loosens up the pasted mass 
 and it begins to fall out. 
 
 Most of the ingenuity of inventors has been concentrated 
 on making plates which would hold the active materials 
 firmly and continually. 
 
 Perhaps one of the best lead-lead (i. e. lead for both 
 plates) is the Electric Storage Battery Company's Chlor- 
 ide Cell 
 
1450 
 
 Steam Engineering 
 
 This cell is shown in Fig. 695. Its method of manufac- 
 ture is interesting and is practically as follows : 
 
 The first thing is to get finely divided lead which is 
 made by directing a blast of air against a stream of the 
 molten metal, producing a spray of lead which upon cool- 
 ing falls as a powder. This powder is dissolved in nitric 
 
 ^ 
 
 Fig. 694 
 grooved lead plates 
 
 acid and precipitated* as lead chloride on the addi- 
 tion of hydrochloric acid. This chloride washed and dried 
 forms the basis of the material which afterwards becomes 
 active in the negative plate. The lead chloride is mixed 
 with zinc chloride, and melted in crucibles, then cast into 
 
 *Turned back to a solid. 
 
Storage Batteries 
 
 1451 
 
 small blocks or tablets about % inch square and of the 
 thickness of the negative plate, which according to the size 
 of the battery varies from *4 inch to -^ inch. These tablets 
 are then put in molds and held in place by pins, so that 
 they clear each other 0.2 inch and are at the same distance 
 from the edges of the mold. Molten lead is then forced 
 into the mold under about seventy-five pounds pressure, 
 completely filling the space between the tablets. The result 
 
 Fig. 695 
 chloride accumulator 
 
 is a solid lead grid holding small squares of active material. 
 The lead chloride is then reduced by stacking the plates in 
 a tank containing a dilute solution 'of zinc chloride, slabs 
 of zinc being alternated with them. The assemblage of 
 plates constitutes a short-circuited cell, the lead chloride 
 being reduced to metallic lead. The plates are then thor- 
 oughly washed to remove all traces of zinc chloride. 
 
1452 Steam Engineering 
 
 A later form of negative plate consists of a "pocketed" 
 grid, the opening being filled with a litharge paste; this is 
 then covered with perforated lead sheets, which are soldered 
 to the grid. The positive plate is a firm grid, composed of 
 lead alloyed with about 5% of antimony, about ■£■$ inch 
 thick, with circular holes |f inch in diameter, staggered so 
 that the nearest points are .2 inch apart. Corrugated lead 
 ribbons §§ inch wide are then rolled into close spirals of §f 
 inch in diameter, which are forced into the circular holes of 
 the plate. By electro-chemical action these spirals are 
 formed into active material, the process requiring about 
 thirty hours; at the same time the spirals expand so that 
 they fit still more closely in the grids. This form of posi- 
 tive is known as the Manchester Plate. 
 
 In setting up the cells the plates are separated from each 
 other by special cherry wood partitions, the perforations 
 being connected by vertical grooves to facilitate the rising 
 of the gases. Sometimes glass rods are used as separators. 
 
 There are ten sizes of cell, the smallest containing three 
 plates 3 by 3 inches, and the largest having seventy-five 
 plates 15% by 30% inches, ranging in capacity from 5 to 
 12,000 ampere-hours, and in weight from 5% to 5,800 lbs. 
 The smaller sizes are provided with either rubber or glass 
 jars, and the larger one with lead-lined tanks. 
 
 In the lead-lead cells the negative plates deteriorate in 
 capacity, while the positive plates increase in capacity with 
 continued use. 
 
 To even things up, the two end plates are made negative 
 and they then alternate, thus giving one more negative plate 
 per cell. 
 
 A lead-zinc cell is made by the United States Battery Co. 
 It is shown in Fig. 696. 
 
Storage Batteries 
 
 1453 
 
 The positive plate is of perforated lead sheets riveted 
 together with lead rivets, and formed by the slow process 
 of charging and reversal as previously described. The nega- 
 tive element is a zinc amalgam which swells up when 
 charged. 
 
 This amalgam lies on bottom of jar, while the lead ele- 
 ment hangs over it. 
 
 The pressure given by these cells is a little higher than 
 a lead-lead cell, and they weigh less for the same capacity. 
 For signal work they are excellent, while for reserve power 
 
 Fig. 696 
 lead-zinc storage battery 
 
 use, the lead-lead cell is preierred as being better under 
 such severe conditions. 
 
 The Edison Cell uses grids of nickel plated iron, the grids 
 being filled with small nickel plated steel boxes which are 
 perforated with very small holes. 
 
 The boxes in positive plate are filled with oxide of nickel 
 and pulverized carbon, the negative boxes being filled with 
 oxide of iron and pulverized carbon. 
 
 The carbon in each case is merely to render material a 
 better conductor. 
 
1454 Steam Engineering 
 
 A 20% solution of caustic potash is used in a nickel plated 
 steel vessel. 
 
 The advantage of this cell is its lightness and ability to 
 stand the most reckless abuse. For railway work it is no 
 better than any other cell and its price puts it out of con- 
 sideration. 
 
 UNDERWRITER'S RULES 
 
 1. Generators. 
 
 a. Must be located in a dry place. 
 
 It is recommended that water-proof covers be provided, 
 which may be used in case of emergency. 
 
 If generators are allowed to become wet, there is likely 
 to be more or less charring or burning of the cotton insula- 
 tion of the wires, due 'to the fact that shellaced cotton will 
 conduct electricity when wet. The current leaking over this 
 moist conducting path, the resistance of which is being con- 
 stantly decreased by the formation of copper salts by elec- 
 trolytic action, may eventually develop excessive heat or 
 even fusion of some of the metallic parts. 
 
 b. Must never be placed in a room where any hazardous 
 process is carried on, nor in places where they would be 
 exposed to inflammable gases or flyings of combustible 
 materials. 
 
 Any generator, if badly designed, improperly handled, 
 poorly cared for or overloaded, is liable to produce sparks, 
 which may be of sufficient intensity to set fire to readily in- 
 flammable gases, dust, lint, oils and the like. 
 
 c. Must, when operating at a potential in excess of 550 
 volts, have their base frames permanently and effectively 
 grounded. 
 
 Must, when operating at a potential of 550 volts or less, 
 be thoroughly insulated from the ground wherever feasible. 
 
Underwriters' Rules 1455 
 
 Wooden base frames used for this purpose, and wooden 
 floors which are depended upon for insulation where, for 
 any reason it is necessary to omit the base frames, must be 
 kept filled to prevent absorption of moisture, and must be 
 kept clean and dry. 
 
 Where frame insulation is impracticable, the Inspection 
 Department having jurisdiction may, in writing, permit its 
 omission in which case the frame must be permanently and 
 effectively grounded. 
 
 A high potential machine should be surrounded by an in- 
 sulated platform. This may be made of wood, mounted on 
 insulating supports, and so arranged that a man must al- 
 ways .stand upon it in order to touch any part of the 
 machine. 
 
 In case of a machine having an insulated frame, if there 
 is trouble from static electricity due to belt friction, it 
 should be overcome by placing near the belt a metallic comb 
 connected with the earth, or by grounding the frame 
 through a resistance of not less than 300,000 ohms. 
 
 By "ground" is to be understood the earth, walls or floors 
 of masonry, pipes of any kind, iron beams, and the like. 
 
 If frame insulation is not provided, a slight fault in the 
 insulation of the magnet or armature coils is likely to 
 ground the electric system, and a short-circuit will then oc- 
 cur the instant another ground occurs at any point on the 
 system. 
 
 The reason for requiring a positive ground wherever 
 frame insulation is impracticable, is to provide a definite 
 path for leak currents, and thus prevent them from escap- 
 ing at points where they might do harm. A good ground 
 can be made by firmly attaching a wire to the dynamo 
 frame and to any main water pipe that is thoroughly con- 
 nected with underground pipes. The wire should not be 
 
1456 Steam Engineering 
 
 smaller than No. 6 B. & S. gage and should be securely 
 attached to the pipe by soldering it to a brass plug screwed 
 into a fitting, or by binding it under a heavy split clamp, or 
 by any other equally thorough method. With direct- con- 
 nected units, the engine or water-wheel would generally 
 furnish a sufficiently good ground. 
 
 It is best to provide a solid timber base-frame, even with 
 a wooden floor, for it is difficult to be sure that even a dry 
 floor will furnish perfect insulation, by reason of the many 
 nails driven through it, the pipe hangers likely to be screwed 
 into its under side and the many other possibilities of me- 
 tallic connection to the ground. For the same reason, care 
 should be taken that the bolts which hold the generator in 
 place do not pass way through the base-frame, so as to come 
 in contact with the floor. 
 
 The base-frame should raise the generator several inches 
 above the floor level, as a raised frame is more easily kept 
 free from metal dust, dampness, etc., which may afford an 
 opportunity for the escape of current to the ground. A 
 hard and durable finish for the timber can be made by sev- 
 eral coats of linseed oil, and a finish coat of shellac or hard 
 varnish. 
 
 When generators are direct-connected to engines or water- 
 wheels, it is necessary to use an insulating coupling if the 
 frames are to be insulated from the ground. The insulation 
 of such couplings is not entirely reliable, as the vibrations, 
 shocks and constant strain of driving, together with oil and 
 dirt, are very liable to destroy the insulating material. 
 
 d. Constant potential generators, except alternating 
 current machines and their exciters, must be protected from 
 excessive current by safety fuses or equivalent devices of 
 approved design. 
 
Underwriters Rules 1457 
 
 For two-wire, direct-current generators, single pole pro- 
 tection will be considered as satisfying the above rule, pro- 
 vided the safety device is located in the lead not connected 
 to the series winding. When supplying three-wire systems, 
 the generators should be so arranged that these protective 
 devices will come in the outside leads. 
 
 For three-wire, direct-current generators, a safety device 
 must be placed in each armature, direct-current lead, or a 
 double pole, double trip circuit breaker in each outside gen- 
 erator lead, and corresponding equalizer connection. 
 
 In general, generators should preferably have no exposed 
 live parts, and the leads should be well insulated and thor- 
 oughly protected against mechanical injury. This protec- 
 tion of the bare live parts against accidental contact would 
 apply also to any exposed, uninsulated conductors outside 
 of the generator, and not on the switchboard unless their 
 potential is practically that of the ground. 
 
 Where the needs of the service make the above require- 
 ments impracticable, the Inspection Department having 
 jurisdiction may, in writing, modify them. 
 
 If this protection is not provided, an accidental short- 
 circuit across the bus-bars, or the exposed metal parts of 
 the main switch on the switchboard is liable to result in the 
 burning out of the armature. 
 
 Owing to inherent qualities possessed by the alternating 
 current generator it is not considered necessary to protect 
 it, especially as the quick opening of a protective device 
 would be liable to give rise to momentary high voltage on 
 the system. 
 
 e. Must each be provided with a nameplate, giving the 
 maker's <name, the capacity in volts and amperes, and the 
 Jiormal speed in revolutions per minute. 
 
1458 Steam Engineering 
 
 The name-plate shows exactly what the machine was de- 
 signed for. Such information is often of great convenience, 
 and also tends to prevent overrating, either from ignorance, 
 or from a desire to magnify the merits of a machine in 
 order to help a sale. 
 
 /. Terminal blocks when used on generators must be 
 made of approved non-combustible, non-absorptive, insu- 
 lating material, siioh as slate, marble or porcelain. 
 
 A reliable voltmeter should be provided on the switch- 
 board, and it is best to have it so arranged as to show the 
 voltage not only between the wires of opposite polarity, 
 but also between each wire and the earth, thus serving as 
 a very sensitive ground detector. 
 
 It is also advised that a reliable ammeter be provided with 
 every constant-potential generator, and that it be clearly 
 marked to indicate the full load of the machine. This in- 
 strument measures the amount of current given out by the 
 generator and shows instantly if there is any undue load, 
 such as would be produced if too many lamps were put in 
 circuit, or if there were serious leakage of current at any 
 point on the system. It is always desirable to have all 
 generator ammeters on a switchboard so graduated that a 
 full scale deflection corresponds to the same degree of over- 
 load on each, so that when several machines of different 
 sizes are running in parallel, each machine will be doing its 
 share of the work when the ammeter pointers are in similar 
 positions. 
 
 2. Conductors. 
 
 From generators to switchboards, rheostats or other in- 
 struments, and then to outside lines : 
 
 a. Must be in plain sight or readily accessible. 
 
 Wires from generator to switchboard may, however, be 
 placed in a conduit in the brick or cement pier on which the 
 
Underwriters' Rules 1459 
 
 generator stands, provided that proper precautions are taken 
 to protect them against moisture and to thoroughly insulate 
 them from the pier. If lead-covered cable is used, no fur- 
 ther protection will be required, but it should not be al- 
 lowed to rest upon sharp edges which in time might cut 
 into the lead sheath, especially if the cables were liable to 
 vibration. A smooth runway is desired. If iron conduit is 
 provided, double braided rubber-covered wire will be satis- 
 factory. 
 
 Main conductors in immediate connection with the source 
 of power must be treated as especially dangerous, because 
 the whole capacity of the system would be concentrated in 
 them should an arc start, or an accidental short-circuit be 
 made between them. 
 
 b. Must have an approved insulating covering as called 
 for by rules in Class "C" for similar work, except that 
 in central stations, on exposed circuits, the wire which is 
 used must have a heavy braided, non-combustible outer cov- 
 ering. 
 
 Bus-bars may be made of bare metal. 
 
 Eubber insulations ignite easily and burn freely. Where 
 a number of wires are brought close together, as is generally 
 the case in dynamo rooms, especially about the switchboard, 
 it is therefore necessary to surround this inflammable ma- 
 terial with a tight, non-combustible outer cover. If this is 
 not done, a fire once started at this point would spread 
 along the wires, producing intense heat and a dense smoke. 
 Where the wires have such a covering and are well insu- 
 lated and supported, using only non-combustible materials, 
 it is believed that no appreciable fire hazard exists, even 
 with a large group of wires. 
 
 Flame proofing should be stripped back on all cables a 
 sufficient amount to give the necessary insulation distances 
 
 /A 
 
1460 Steam Engineering 
 
 for the voltage of the circuit on which the cable is used. The 
 stripping back of the flame proofing is necessary on account 
 of the poor insulating qualities of the flame proofing mate- 
 rial now available. Flame proofing may be omitted where 
 satisfactory fire proofing is accomplished by other means, 
 such as compartments, etc. 
 
 It is also recommended that all live parts of the switch- 
 board, such as bus-bars and other conductors, be protected 
 against accidental contact as far as practicable by suitable 
 insulation, which shall be "flame proof" or "slow-burning" 
 and designed to withstand a reasonable amount of abrasion. 
 The chances of accidental short-circuits may thereby be 
 greatly reduced. Insulated cable for bus-bars and connec- 
 tions is excellent for this purpose. However, the conduc- 
 tors could be wrapped or taped if this should be found 
 more convenient, but this method should never be used 
 unless it can be done well. Due to the possibly rather low 
 insulating properties of most fireproofing compounds as 
 used, special precautions would be necessary on high-voltage 
 circuits to prevent current leakage over the outer fireproofed 
 covering. 
 
 c. Must be kept so rigidly in place that they cannot 
 come in contact. 
 
 It is necessary, also, to protect the wires against acci- 
 dental blows from belt, or from ladders, etc., in the hands 
 of careless workmen. 
 
 d. Must in all other respects be installed with the same 
 precautions as required by rules in Class "C" for wires car- 
 rying a current of the same volume and potential. 
 
 e. In wiring switchboards the ground detector, volt- 
 meter, pilot lights and potential transformers must be con- 
 nected to a circuit of not less than No. 14 B. & S. gauge 
 
Underwriters' Rules 1461 
 
 wire that is protected by an approved fuse, this circuit is 
 not to carry over 660 watts. 
 
 For the protection of instruments and pilot lights on 
 switchboards, approved N. E. Code Standard Enclosed 
 Fuses are preferred, but approved enclosed fuses of other 
 designs of not over two (2) amperes capacity, may be used. 
 
 Voltmeter switches having concealed connections must 
 be plainly marked, showing connections made. 
 
 3. Switchboards. 
 
 a. Must be so placed as to reduce to a minimum the 
 danger of communicating fire to adjacent combustible ma- 
 terial. 
 
 It is often necessary, also, to protect the wires against 
 accidental blows from belt, or from ladders, etc., in the 
 hands of careless workmen. This may be done in about 
 the same manner as is recommended for wires on side walls. 
 
 Special attention is called to the fact that switchboards 
 should not be built down to the floor, nor up to the ceiling. 
 A space of at least ten or twelve inches should be left be- 
 tween the floor and the board, except when the floor about 
 the switchboard is of concrete or other fireproof construc- 
 tion, and a space of three feet, if possible, between the ceil- 
 ing and the board, in order to prevent fire from communi- 
 cating from the switchboard to the floor or ceiling, and also 
 to prevent the forming of a partially concealed space very 
 liable to be used for storage of rubbish and oily waste. 
 
 Great care in designing and locating a switchboard is 
 necessary for several reasons; the rheostats, measuring in- 
 struments, fuses, etc., are possible sources of fire; there is 
 a considerable number of bare live parts on the ordinary 
 board which afford good opportunity for accidental short- 
 circuits; and there is frequently a large amount of power 
 
1462 Steam Engineering 
 
 available at the board to quickly follow up any trouble at 
 this point. 
 
 b. Must be made of non-combustible material or of 
 hardwood in skeleton form, filled to prevent absorption of 
 moisture. 
 
 If wood is used all wires, and all current carrying parts 
 of the apparatus on the switchboard must be separated 
 therefrom by non-combustible, non-absorptive insulating 
 material. 
 
 Switchboards of slate or marble are now mostly used. A 
 slate board complete is but little more expensive than a 
 properly wired and equipped wooden board in skeleton 
 form. The non-combustible board is undoubtedly prefer- 
 able, and is therefore strongly recommended, especially for. 
 the larger equipments. 
 
 c. Must be accessible from all sides when the connec- 
 tions are on the back, but may be placed against a brick 
 or stone wall when the wiring is entirely on the face. 
 
 If the wiring is on the back, there should be a clear space 
 of at least eighteen inches between the wall and the ap- 
 paratus on the board, and even if the wiring is entirely on 
 the face, it is much better to have the board set out from the 
 wall. The space back of the board should not be closed in, 
 except by grating or netting either at the sides, top or bot- 
 tom, as such an enclosure is almost sure to be used as a 
 closet for clothing or for the storage of oil cans, rubbish, 
 etc. An open space is much more likely to be kept clean, 
 and is more convenient for making repairs, examinations, 
 etc. 
 
 d. Must be kept free from moisture. 
 
 Water on a switchboard is liable to produce serious 
 trouble, as it is almost certain to start leaks over the sur- 
 face of the insulating coverings on the wires and over the 
 
Underwriters 9 Rules 1463 
 
 board itself ; for water-soaked insulators, or a film of water 
 on a non-absorptive insulator, like glass, porcelain or hard 
 rubber, will conduct electricity to some extent. By elec- 
 trolytic action this leakage current will form salts of copper 
 over the surface of the insulating parts, and as these salts 
 are good conductors, the leakage current will be increased, 
 resulting in the inevitable destruction of the weakest part, 
 be it insulation, wire or dynamo. Under such conditions 
 there would also be great danger of the attendant receiving 
 severe shocks. 
 
 e. On switchboards the distances between bare live parts 
 of opposite polarity must be made as great as practicable, 
 and must not be less than those given for tablet-boards. 
 
 4. Resistance Boxes and Equalizers. 
 
 a. Must be placed on switchboard, or if not thereon, at 
 a distance of at least one foot from combustible material, 
 or separated therefrom by non-combustible, non-absorptive 
 insulating material such as slate or marble. 
 
 This will require the use of a slab or panel of non-com- 
 bustible, non-absorptive insulating material such as slate 
 or marble, somewhat larger than the rheostat, which shall 
 be secured in position independently of the rheostat sup- 
 ports. Bolts for supporting the rheostat shall be counter- 
 sunk at least % inch below the surface at the back of the 
 slab and filled. For proper mechanical strength, slab 
 should be of a thickness consistent with the size and weight 
 of the rheostat, and in no case to be less than % inch. * 
 
 If resistance devices are installed in rooms where dust 
 or combustible flyings would be liable to accumulate on 
 them, they should be equipped with a dustproof face-plate. 
 
 Kesistance boxes should be considered as stoves, which 
 under some conditions may become red hot, and from which 
 
1464 Steam Engineering 
 
 drops of heated metal may fall, or even be thrown some 
 distance. 
 
 Motor-starting rheostats, arc lamp compensators, elec- 
 tric heaters and the like would all come under this rule 
 unless so designed as to make these precautions unneces- 
 sary for the desired safety. 
 
 b. Where protective resistances are necessary in con- 
 nection with automatic rheostats, incandescent lamps may 
 be used, provided that they do not carry or control the 
 main current nor constitute the regulating resistance of 
 the device. 
 
 When so used, lamps must be mounted in porcelain re- 
 ceptacles upon non-combustible supports, and must be so 
 arranged that they cannot have impressed upon them a 
 voltage greater than that for which they are rated. They 
 must in all cases be provided with a name-plate, which shall 
 be permanently attached beside the porcelain receptacle or 
 receptacles, and stamped with the candle-power and voltage 
 of the lamp or lamps to be used in each receptacle. 
 
 c. Wherever insulated wire is used for connection be- 
 tween resistances and the contact plate of a rheostat, the 
 insulation must be slow burning. For large field rheostats 
 and similar resistances, where the contact plates are not 
 mounted upon them, the connecting wires may be run to- 
 gether in groups so arranged that the maximum difference 
 of potential between any two wires in a group shall not 
 exceed 75 volts. Each group of wires must either be 
 mounted on non-combustible, non-absorptive insulators giv- 
 ing at least half-inch separation from surface wired over or, 
 where it is necessary to protect the wires from mechanical 
 injury or moisture, be run in approved lined conduit or 
 equivalent. 
 
Underwriters Rules 1465 
 
 5. Lightning Arresters. 
 
 a. Must be attached to each wire of every overhead cir- 
 cuit connected with the station. 
 
 It is recommended to all electric light and power com- 
 panies that arresters be connected at intervals over systems 
 in such numbers and so located as to prevent ordinary dis^ 
 charges entering (over the wires) buildings connected to 
 the lines. 
 
 The kind and degree of protection necessary depend 
 largely on circumstances. A short outdoor line from one 
 mill building to another will often require nothing, while 
 a long overhead line through an open 'exposed country will 
 generally need the most careful engineering to secure rea- 
 sonable freedom from lightning disturbances. 
 
 b. Must be located in readily accessible places away 
 from combustible materials, and as near as practicable to 
 the point where the wires enter the building. 
 
 In all cases, kinks, coils and sharp bends in the wires 
 between the arresters and the outdoor lines must be avoided 
 as far as possible. 
 
 The switchboard does not necessarily afford the only loca- 
 tion meeting these requirements. In fact, if the arresters 
 can be located in a safe and accessible place away from the 
 board, this should be done, for, in case the arrester should 
 fail or be seriously damaged there would then be less chance 
 of starting arcs on the board. 
 
 The arresters should be accessibly located, so that they 
 may be easily examined from time to time, and should al- 
 ways be isolated from combustible materials, as sparks are 
 sometimes produced when lightning is discharged through 
 them. 
 
 Kinks, coils, sharp bends, etc., may offer enormous re- 
 sistance to a lightning current, possibly preventing its dis- 
 
.. 
 
 1466 Steam Engineering 
 
 charge to ground through the arrester and causing it to 
 leave the wires at some other point, where it might do con- 
 siderable damage. 
 
 c. Must be connected with a thoroughly good and per- 
 manent ground connection by metallic strips or wires hav- 
 ing a conductivity not less than that of a No. 6 B. & S. 
 gauge copper wire, which must be run as nearly in a 
 straight line as possible from the arresters to the ground 
 connection. 
 
 Ground wires for lightning arresters must not be attached 
 to gas pipes within the buildings. 
 
 It is often desirable to introduce a choke coil in circuit 
 between the arresters and the dynamo. In no case should 
 the ground wires from lightning arresters be put into iron 
 pipes, as these would tend to impede the discharge. 
 
 d. All choke coils or other attachments, inherent to the 
 lightning protection equipment, shall have an insulation 
 from the ground or other conductors equal at least to the 
 insulation demanded at other points of the circuit in the 
 station. 
 
 6. Care and Attendance. 
 
 a. A competent man must be kept on duty where gen- 
 erators are operating. 
 
 b. Oily waste must be kept in approved metal cans 
 and removed daily. 
 
 Approved waste cans shall be made of metal with legs 
 raising can three inches from the floor, and with self-closing 
 covers. 
 
 7. Testing of Insulation Resistance. 
 
 a. All circuits except such as are permanently grounded 
 must be provided with reliable ground detectors. Detec- 
 tors which indicate continuously, and give an instant and 
 permanent indication of a ground are preferable. Ground 
 
Underwriters' Rules 1467 
 
 wires from detectors must not be attached to gas pipes 
 within the building. 
 
 b. Where continuously indicating detectors are not feas- 
 ible, the circuits should be tested at least once per day, and 
 preferably of tener. 
 
 c. Data obtained from all tests must be preserved for 
 examination by the Inspection Departmen£ having juris- 
 diction. 
 
 These rules on testing to be applied at such places as 
 may be designated by the Inspection Department having 
 jurisdiction. 
 
 8. Motors. 
 
 The use of motors operating at a potential in excess of 
 550 volts will only be approved when every practicable safe- 
 guard has been provided. Plans for such installations 
 should be submitted to the Inspection Department having 
 jurisdiction before any work is begun. 
 
 a. Must, when operating at a potential in excess of 550 
 volts, have no exposed live metal parts, and have their base 
 frames permanently and effectively grounded. 
 
 Motors operating at a potential of 550 volts or less must 
 be thoroughly insulated from the ground where feasible. 
 Wooden base frames used for this purpose, and wooden 
 floors, which are depended upon for insulation where, for 
 any reason, it is necessary to omit the base frames, must 
 be kept filled to prevent absorption of moisture, and must 
 be kept clean and dry. Where frame insulation is im- 
 practicable, the Inspection Department having jurisdic- 
 tion may, in writing, permit its omission, in which case the 
 frame must be permanently and effectively grounded. 
 
 A high-potential machine should be surrounded with an 
 insulated platform. This may be made of wood, mounted 
 on insulating supports, and so arranged that a man must 
 
1468 Steam Engineering 
 
 stand upon it in order to touch any part of the machine. 
 
 In case of a machine having an insulated frame, if there 
 is trouble from static electrcity due to belt friction, it 
 should be overcome by placing near the belt a metallic 
 comb connected to the earth, or by grounding the frame 
 through a resistance of not less than 300,000 ohms. 
 
 fr. Motors operating at a potential of 550 volts or less 
 must be wired with the same precautions as required for 
 wires carrying a current of the same volume. 
 
 Motors operating at a potential between 550 and 3,500 
 volts must be wired with approved multiple conductor, 
 metal sheathed cable in approved unlined metal conduit 
 firmly secured in place. The metal sheath must be perma- 
 nently and effectively grounded, and the installation of the 
 conduit must conform to rules for interior conduits, ex- 
 cept that at outlets approved outlet bushings shall be used. 
 
 The motor leads or branch circuits must be designed to 
 carry a current at least 25 per cent greater than that for 
 which the motor is rated, in order to provide for the in- 
 evitable occasional overloading of the motor and the in- 
 creased current required in starting, without overfusing the 
 wires; but where the wires under this rule would be over- 
 fused, in order to provide for the starting current, as in 
 the case of many of the alternating current motors, the 
 wires must be of such size as to be properly protected by 
 these larger fuses. 
 
 The insulation of the several conductors for high poten- 
 tial motors, where leaving the metal sheath at outlets must 
 be thoroughly protected from moisture and mechanical in- 
 jury. This may be accomplished by means of a pot head or 
 some equivalent method. The conduit must be substantially 
 bonded to the metal casings of all fittings and apparatus 
 connected to the inside high tension circuit. It would be 
 
Underwriters' Rules 1469 
 
 much preferable to make the conduit system continuous 
 throughout by connecting the conduit to fittings and motors 
 by means of screw joints, and this construction is strongly 
 recommended wherever practicable. 
 
 High potential motors should preferably be so located 
 that the amount of inside wiring will be reduced to a mini- 
 mum. 
 
 Inspection Departments having jurisdiction may permit 
 the wire for high potential motors to be installed accord- 
 ing to the general rules for high potential systems when 
 the outside wires directly enter a motor room. Under these 
 conditions there would generally be but a few feet of wire 
 inside the building and none outside the motor room. 
 
 c. Each motor and resistance box must be protected by 
 cut-out and controlled by a switch, said switch plainly indi- 
 cating whether "on" or "off." With motors of one-fourth 
 horse-power or less on circuits where the voltage does not 
 exceed 330, single pole switches may be used. The switch 
 and rheostat must be located within sight of the motor, ex- 
 cept in cases where special permission to locate them else- 
 where is given, in writing, by the inspection department 
 having jurisdiction. 
 
 The use of circuit-breakers with motors is recommended, 
 and may be required by the Inspection Department having 
 jurisdiction. 
 
 Where the circuit-breaking device on the motor-starting 
 rheostat disconnects all wires of the circuit, the switch called 
 for in this section may be omitted. 
 
 Overload-release devices on motor-starting rheostats will 
 not be considered to take the place of the cut-out required 
 by this section if they are inoperative during the starting 
 of the motor. 
 
1470 Steam Engineering 
 
 The switch is necessary for entirely disconnecting the 
 motor when not in use, and the cut-out to protect the motor 
 from excessive currents due to accidents or careless handling 
 when starting. An automatic circuit-breaker disconnecting 
 all wires of the circuit may, however, serve as both switch 
 and cut-out. 
 
 In general, motors should preferably have no exposed live 
 parts. 
 
 d. Eheostats must be so installed as to comply with 
 all the requirements of No. 4. Auto starters must comply 
 with requirements of No. 4c. 
 
 Starting rheostats and auto starters, unless equipped with 
 tight casings enclosing all current-carrying parts, should 
 be treated about the same as knife switches, and in all wet, 
 dusty or linty places, should be enclosed in dust-tight, fire- 
 proof cabinets. If a special motor room is provided, the 
 starting apparatus and safety devices should be included 
 within it. Where there is any liability of short circuits 
 across their exposed live parts being caused by accidental 
 contacts, they should either be enclosed in cabinets, or else 
 a railing should be erected around them to keep unauthor- 
 ized persons away from their immediate vicinity. 
 
 e. Must not be run in series-multiple, or multiple-series, 
 except on constant-potential systems, and then only by 
 special permission of the Inspection Department having 
 jurisdiction. 
 
 The objection to combinations of this character is that 
 the cutting-out of one motor, by accident or carelessness, 
 may subject the others to a current or voltage greater than 
 that for which they are designed; and if this occurs, and 
 the protecting devices fail, as sometimes happens, there is 
 very likely to be severe arcing, or a burn-out. 
 
Underwriters' Rules 1471 
 
 m 
 
 f. Must be covered with a waterproof cover when not 
 in use, and if deemed necessary by the Inspection Depart- 
 ment having jurisdiction, must be enclosed in an approved 
 case. 
 
 When it is necessary to locate a motor in the vicinity of 
 combustibles or in wet or very dusty or dirty places, it is 
 generally advisable to enclose it as above. 
 
 Such enclosures should be readily accessible, dust proof 
 and sufficiently ventilated to prevent an excessive rise of 
 temperature. The sides should preferably be made largely 
 of glass, so that the motor may be always plainly visible. 
 This lessens the chance of its being neglected, and allows 
 any derangement to be at once noticed. 
 
 The use of enclosed type motor is recommended in dusty 
 places, being preferable to wooden boxing. 
 
 From the nature of the question the decision as to de- 
 tails of constructon must be left to the Inspection Depart- 
 ment having jurisdiction to determine in each instance. 
 
 If possible, the enclosure should be large enough to per- 
 mit the attendant to enter it and easily get at any part of 
 the apparatus, and this would generally mean a small room. 
 If the motor is suspended from the ceiling, a floor could 
 generally be constructed below it and the four sides of this 
 elevated motor room could be built mainly of windows, 
 Eeady access to the room could be secured by means of a 
 short flight of stairs or a ladder. This can also be done 
 where the motor is supported on an elevated platform. 
 
 With alternating-current motors having no brushes, the 
 enclosure would generally be unnecessary. When located 
 on the floor, it would often be advisable to surround the 
 machine by a substantial pipe rail to keep people from 
 passing near it. 
 
1472 Steam Engineering 
 
 g. Must, when combined with ceiling fans, be hung 
 from insulated hooks, or else there must be an insulator in- 
 terposed between the motor and its support. 
 
 h. Must each be provided with a name-piate, giving 
 maker's name, the capacity in volts and amperes, and the 
 normal speed in revolutions per minute. 
 
 i. Terminal blocks when used on motors must be made 
 of approved non-combustible, non-absorptive, insulating 
 material such as slate, marble or porcelain. 
 
 /. Variable speed motors, unless of special and appro- 
 priate design, if controlled by means of field regulation, 
 must be so arranged and connected that they cannot be 
 started under weakened field. 
 
 9. Railway Power Plants. 
 
 a. Each feed wire before it leaves the station must be 
 equipped with an approved automatic circuit-breaker or 
 other device, which will immediately cut off the current 
 in case of an accidental ground. This device must be 
 mounted on a fireproof base, and in full view and reach of 
 the attendant. 
 
 An automatic circuit-breaker is preferable to a fuse, as 
 it acts more quickly, is more reliable, and can be more 
 quickly and safely replaced. 
 
 10. Storage or Primary Batteries. 
 
 a. When the current for light and power is taken from 
 primary or secondary batteries, the same general regula- 
 tions must be observed as apply to similar apparatus fed 
 from dynamo generators developing the same difference of 
 potential. 
 
 Charged storage batteries have in them at all times a 
 large amount of stored energy, and should therefore be 
 treated as carefully as generators of similar output. 
 
Underwriters' Rules 1473 
 
 1). Storage battery rooms must be thoroughly venti- 
 lated. 
 
 The action of the current in charging the battery liberates 
 at times large quantities of hydrogen and oxygen, and if 
 these should accumulate in the right proportions they would 
 form an explosive mixture which might be exploded by any 
 accidental spark. 
 
 c. Special attention is directed to the rules for wiring 
 in rooms where acid fumes exist. 
 
 d. All secondary batteries must be mounted on non-ab- 
 sorptive, non-combustible insulators, such as glass or thor- 
 oughly vitrified and glazed porcelain. 
 
 The battery needs to be insulated and nothing but glass, 
 porcelain and similar materials will retain their insulating 
 properties when exposed to the action of the water and 
 acid freely used about storage batteries. 
 
 e. The use of any metal liable to corrosion must be 
 avoided in cell connections of secondary batteries. 
 
 Eeduction of the cross-section of the connections by cor- 
 rosion would probably cause them to be burned out by the 
 normal current of the battery. 
 
 11. Transformers. 
 
 a. In central or sub-stations, the transformers must be 
 so placed that smoke from the burning out of the coil or 
 the boiling over of the oil (where oil filled cases are used) 
 could do no harm. 
 
 If the insulation in a transformer breaks down, consid- 
 erable heat is likely to be developed. This would cause a 
 dense smoke, which might be mistaken for a fire and result 
 in water being thrown into the building, and a heavy loss 
 thereby entailed. Moreover, with oil-cooled transformers, 
 
1474 Steam Engineering 
 
 especially if the cases are filled too full, the oil may become 
 ignited and boil over, producing a very stubborn fire. 
 
 b. In central or sub-stations casings of all transformers 
 must be permanently and effectively grounded. 
 
 Transformers used exclusively to supply current to 
 switchboard instruments need not be grounded, provided 
 they are thoroughly insulated. 
 
 While from a fire standpoint it is not considered neces- 
 sary to ground the casings of instrument transformers above 
 mentioned, it is believed advisable to ground them in order 
 to guard against danger from shock. It is evident that all 
 other metal work such as switchboard frames, instrument 
 cases, etc., which are liable to come in contact with a live 
 circuit should also be grounded to protect against this dan- 
 ger. 
 
Definitions 
 
 A 
 
 A. C. — Alternating Current. 
 
 Absorption. — The act of one form of matter sucking, or 
 draining in some other form of matter, as in the case 
 of a sponge taking up water. 
 
 Acceleration. — The increase of motion. 
 
 Accumulated Electricity. — Electricity confined or stored, 
 
 as in a condenser. 
 
 Accumulator. — Sometimes used to designate a condenser, a 
 Leyden jar, or a storage battery. 
 
 Active Coil. — A coil or conductor conveying a current of 
 electricity. 
 
 Active Current. — The active constituent of an alternating 
 current, in contradistinction from the wattless compo- 
 nent. 
 
 Active Wire. — The section of wire on the armature of a 
 dynamo which goes through the field of force, in con- 
 tradistinction from the remaining wire, which does not 
 pass through the flux. 
 
 Aerial Circuit. — An elevated circuit. 
 
 Air Blast. — A blast of air acting upon the surface of a 
 commutator to prevent damaging flashes. Also used to 
 cool transformers in some cases. 
 
 Air Gap. — Any gap or aperture in a circuit which con- 
 tains air only. 
 
 Air Insulation. — Insulation produced by the action of air. 
 
 1475 
 
1476 Steam Engineering 
 
 American Wire Gauge. — The name by which the Brown & 
 Sharpe wire gauge is known, in which the diameter of 
 the largest wire, No. 0000, is 0.46 inches, and wire No. 36, 
 0.005 inches, and all other diameters progress in geomet- 
 rical order. 
 
 Ammeter. — An abbreviation for ampere meter. Used for 
 measuring current rate, or volume. Any calibrated gal- 
 vanometer having its scale marked to read amperes is 
 an ammeter. 
 
 Ampere. — The unit of electric current flow. An ampere is 
 that volume of current which would pass through a cir- 
 cuit that offered a resistance of one ohm under an electro- 
 motive force of one volt. 
 
 Ampere Hour. — A unit of quantity equal to the amount of 
 electricity transmitted by one ampere flowing during one 
 hour. 
 
 Ampere Turn. — A unit of magneto-motive force equal to 
 the force resulting from the passing of one ampere over a 
 single turn of wire. 
 
 Anode. — The positive pole a battery. 
 
 Arc. — A segment of a circle. A voltaic arc. 
 
 Armature Eeaction. — The reactive magnetic effect result- 
 ing from the action of the current in the armature of a 
 dynamo on the magnetic circuit of the machine. 
 
 B 
 
 B. S. G. — British standard gauge. 
 
 B. & S. W. G. — Brown & Sharpe wire gauge. 
 
 B. W. G. — Birmingham wire gauge. 
 
 Balanced Load. — A load uniformly apportioned to two or 
 
 more generators. 
 Balanced Eesistance. — A resistance arranged in a bridge, 
 
 and balanced by the residuary resistance in the bridge. 
 
Definitions 1477 
 
 Bar Windings. — Armature windings constructed of copper 
 bars. 
 
 Bipolar. — Possessing two poles. 
 
 Birmingham Wire Gauge. — A wire gauge used in England. 
 
 Booster. — An auxiliary dynamo used to increase the volt- 
 age of a feeder, or a set of feeders beyond the voltage of 
 the rest of the system. 
 
 Bridge, Electric. — A contrivance used to measure unknown 
 resistances by comparison with adjustable ones. 
 
 Bunched Cable. — A cable having more than one wire, or 
 conductor. 
 
 Bus-bars. — Bars composed of heavy conducting metal, and 
 connected directly with the poles of generators. 
 
 C 
 
 C. G. S. — Centimetre, Gramme, second. 
 
 C. P. — Candle power. 
 
 Calibrate. — To ascertain the complete or relative values of 
 the indications of electrical measuring instruments. 
 
 Candle. — The unit of photometric energy. Equals the light 
 produced by a standard candle burning at the rate of two 
 grains per minute. 
 
 Cathode. — Opposed to anode. 
 
 Condenser. — A device for augmenting the capacity of an 
 insulated conductor by placing it in contiguity to another 
 earth-connected conductor, but from which it is sep- 
 arated by an intervening body which will permit electro- 
 static induction to occur through it. 
 
 Constant Current. — A current, the strength of which does 
 not vary. 
 
 Continuous Current. — A current flowing in the same di- 
 rection only. 
 
 Cycle of Alternations. — Alternations of the current per 
 
 second. 
 
1478 Steam Engineering 
 
 Coulomb. — The unit of electric quantity accepted for prac- 
 tice. That quantity of electricity that would pass in one 
 second through a circuit conveying one ampere. That 
 quantity of electricity contained in a condenser of one 
 Farad capacity when subjected to an E. M. F. of one 
 volt. 
 
 D. 
 
 D. C. — Direct current. 
 
 D. P. S. — Double pole switch. 
 
 Differential Winding. — Double winding of magnet coils 
 resulting in the opposition of the two poles to each other. 
 
 Dynamic Electricity. — Current electricity as distinguished 
 from static electricity. 
 
 Dyne.— The C. G. S. unit of force. 
 
 E 
 
 E. H. P. — Electrical horse-power. 
 E. M. F. — Electromotive force. 
 
 Electrolysis. — Chemical decomposition by the action of an 
 electric current. 
 
 F 
 
 Farad. — The practical unit of electrical capacity. That 
 capacity of a conductor that is capable of holding one 
 coulomb at one volt potential. 
 
 Feeders. — Wires furnishing the main conductors with cur- 
 rents at different points, thus serving to equalize the po- 
 tential under load. 
 
 Five-wire System. — A system wherein four series connected 
 dynamos are connected to five conductors. 
 
 Flux. — Magnetic induction; the number of lines of force 
 which pass through a magnetic circuit. 
 
 Frequency. — Number of cycles per unit of time by an al- 
 ternating current. 
 
Definitions 1479 
 
 G 
 
 Gramme. — A unit of weight equal to the weight of one cubic 
 centimetre of pure water at its maximum density, at a 
 temperature of 39.2° Fahr. in a vacuum. A weight 
 equal to 15.44 grains troy. 
 
 H 
 
 H. P. — Horse-power. 
 
 Hard-drawn Copper Wire. — Copper wire hardened without 
 annealing, by being drawn several times. 
 
 Henry. — The practical unit of electro-magnetic, or mag- 
 netic inductance. 
 
 Horse-power, Electric. — A rate of electrical work equal to 
 746 watts, or 746 volt-coulombs per second. 
 
 Hysteresis. — Slowness of magnetization in respect to mag- 
 netizing force. 
 
 I 
 
 Induction. — The influence exerted without contact, by a 
 
 magnetic field, or a charged mass upon neighboring 
 
 bodies. 
 Inverted Arc Lamp. — An arc lamp wherein the positive 
 
 carbon is below instead of above, as in the regular arc 
 
 lamp. 
 
 J 
 
 Jump Spark. — A disruptive spark excited between two con- 
 ductors, in distinction from a spark excited by a rubbing 
 contact. 
 
 K 
 K. W.— Kilowatt. 
 Kilowatt. — One thousand watts. 
 
 Kilowatt-Hour. — Work equal to the expenditure of one K. 
 W. in one hour. 
 
1480 Steam Engineering 
 
 L 
 
 Lag. — -Dropping behind. 
 
 Lagging of Current. — The retarding in phase of an al- 
 ternating current behind the pressure which produces it. 
 
 M 
 
 Megohm. — One million ohms. 
 
 Metre. — A measure of length equal to 39.368 inches. 
 "Micro-Fard. — The millionth of a Farad. 
 
 Mil. — One thousandth of an inch. 
 
 Multiphase." — Containing more than one phase. 
 
 Multiple Circuit. — A circuit in which the positive poles of 
 a number of separate sources, and receptive devices are 
 connected to a single positive lead or' conductor; their 
 negative poles being connected ' to a single negative lead 
 or conductor. 
 
 Multiple Series. — Series groups connected in multiple. 
 
 
 
 Ohm. — The practical unit of resistance. A resistance that 
 would confine the electric flow under an electromotive 
 force of one volt to a current of one ampere, or one cou- 
 lomb per second. 
 
 Ohm's Law. — The basic law, expressing the relation be- 
 tween current, E. M. F v and resistance in active cir- 
 
 . E 
 
 cuits. Expressed algebraically 1= — , in which I equals 
 
 E 
 current intensity, E equals E. M. F., and E equals resist- 
 ance. Other forms of expressing ohms law are as follows : 
 
 E 
 B=— . E=KI, 
 
 I ' 
 
Definitions 1481 
 
 Over Compounded. — Compound winding of such a charac- 
 ter on a dynamo that its voltage at its terminals is caused 
 to increase under a greater load. 
 
 P 
 
 Parallel Circuit. — A term signifying multiple circuit. 
 
 Parallel Series. — Signifies a multiple series connection. 
 
 Periodicity of Alternation. — The rate of succession of al- 
 ternations per second, or per minute. The frequency. 
 
 Polyphase Current. — Currents that constantly differ from 
 each other, due to their proportion of periods of alter- 
 nation, and adapted to polyphase motors. 
 
 Proposed Definition for 2,000 Candle Power. — An arc 
 whose maintenance will require 450 watts. 
 
 R 
 
 Rheostat. — Will adjust the resistance without opening the 
 circuit. 
 
 S 
 
 Standard Ohm. — A piece of pure copper wire one circular 
 mil in diameter, and one foot long at a certain tempera- 
 ture. 
 
 Static Electricity. — Electricity generated by friction. 
 
 V 
 
 Volt, — The practical unit of electromotive force. An E. 
 M. F. that would cause a current of one ampere to flow 
 through a resistance of one ohm. 
 
 W 
 
 Water Horse-Power. — The power developed by 15 cubic feet 
 of water falling through a distance of one foot per second. 
 
 Watt. — The practical unit of electric activity, rate of work, 
 or energy. A watt equals 44.25 foot pounds of work done 
 per minute, or 0.7375 foot-pounds of work done per sec- 
 ond. 
 
 Watt-Hour. — Unit of electric work. One watt exerted or 
 expended for one hour. 
 
1482 Steam Engineering 
 
 ELECTRIC AND MAGNETIC UNITS 
 
 The fundamental units ou which all the various standards are based are: — 
 The centimetre (length) =0.3937 in. The gramme (mass) = 15.432 grains and the second 
 (time). 
 
 A dyne is the unit of force in absolute C.G.S. and is that force which, acting upon a mass 
 of one gramme, produces an acceleration of one centimetre per second. 
 63.568 dynes = 1 grain. 
 981 dynes=l gramme. 
 The erg is the C.G.S. unit of work, and is the work expended to move a body through a 
 distance of one centimetre with a force of one dyne. 
 
 1 erg = 1 dyne centimetre, 
 1 erg =.000,000,1 joule, or joule 10~ 7 
 981 ergs = l gramme centimetre, 
 13,562,600 ergs = l foot-pound. 
 On the following page are given the relations existing between the practical units which 
 have been adopted and the C.G.S. units on which they are founded. 
 
 DERIVED UNITS 
 
 1 megohm =1 million ohms; 
 
 1 microhm = 1 millionth of an ohm; 
 
 1 milliampere =1 thousandth of an ampere; 
 
 1 micro-farad = 1 millionth of a farad; 
 
 1 millivolt = 1 thousandth of a volt; 
 
 1 kilowatt = 1000 watts=44,240 foot pounds per minute= 1.34 horse-power; 
 
 1 electrical horse- 
 power = 746 Watt hours =33,000 foot pounds per minute; 
 
 1 Joule = 1 Watt second =0.7373 foot pound; 
 
 1 foot pound =1.356 Joules; 
 
 1 B. T. U. =3,600,000 Watt seconds; 
 
 1 kilogramme metre= 7.233 foot pounds; 
 
 1 kilowatt hour = 1.34 horse-power hours; 
 
 1 French or metric 
 
 horse-power =75 kilogramme metres per second = 32,549 foot pounds per minute 
 = 736 Watts=0.9863 English horse-power; 
 
 1 English horse- 
 power = 1.01385 French horse-power (" force de cheval."). 
 
 MAGNETIC UNITS 
 
 The British Association proposed the adoption of a unit of magnetic flux under the name 
 of the Weber, equal to 10 8 magnetic lines of the C.G.S. system. The multiples kiloline for 
 1000 lines, and megaline for 1,000,000 lines have been found convenient for dynamo designers. 
 One Weber is equal to 100 megalines per square centimetre. A wire cutting one Weber per 
 second will have induced in it an electro-motive force of one volt. The Gauss is the C.G.S. 
 
 10 
 
 unit of magnetic potential, being equal to of an ampere turn. To convert ampere turns 
 
 4tt 4tt 
 
 into Gausses one must multiply by , or by 1.257. 
 
 10 
 
Electrical Units 
 
 1483 
 
 g 
 5 
 
 O 
 
 s 
 
 < 
 
 B 
 
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 Q 
 
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 K 
 
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 00 
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 w OS 
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 Multi 
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 Numb 
 
 C.G 
 
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 ingU 
 
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 "3 
 
 03 
 
 1 
 
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 T3 
 T3 03 
 
 a » 
 
 S 
 
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 £ 
 
 
 
 Ji no 
 
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 1 
 
 ll 
 
 w- 09 
 
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 031 
 
 
 Xi 
 
 
 
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 gQ 
 
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 CO 
 
 
 
 
 
 
 
 t^ 
 
 
 
 
 
 -h-O 
 
 
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 A J: 
 
 r x 
 
 8 h T' 
 
 11 w 
 
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 w 1 
 
 X 
 
 Ph 
 
 3 II 
 
 03 " 
 
 JL ^> 
 
 II 
 
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 W 
 
 
 Eh 
 
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 c? 
 
 hh* 
 
 ^ 
 
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 <M 
 
 CO 
 
 
 
 C<l 
 
 ormula 
 f Stand 
 rd Unit 
 Absolu 
 System 
 C.G.S.) 
 
 1 
 
 1 
 
 -" i 
 
 Hfw ^ 
 
 
 1 
 
 ^ 
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 1 H 
 
 M CM 
 
 
 HH 
 
 CM 
 
 mh o es a 
 
 hH 
 
 Ml 
 
 hH 
 
 
 HH 
 
 | 
 
 eg 
 
 & 
 
 The Ampere is the constant electric current which, when 
 ssed through a particular solution of nitrate of silver in water, 
 posits 0.001118 gramme per second. Or the flow of one 
 ulomb per second. 
 
 The Volt is the electrical pressure, which, if applied to a con- 
 ctor where resistance is 1 Ohm, will produce a current of 
 ampere, and which is represented by 0.6974 of the pressure 
 tween the poles of a Clark's voltaic cell at 15 deg. Centigrade. 
 
 The Ohm is the resistance offered by a column of mercury at 
 e temperature of melting ice 14.4521 grammes in mass of 
 nstant cross-section, and 106.3 centimetres long. 
 Is the rate of doing work when a current of 1 ampere flows 
 tween two points, having a difference of potential of 1 volt. 
 
 The quantity of electricity that flows per second past a given 
 int in a conductor which is carrying a current of 1 ampere, 
 [s capacity of condenser which would require a charge of one 
 ulomb to produce difference of potential of 1 volt between 
 e two conductors forming the condenser. 
 
 Is the inductance in a circuit when current is changing at 
 e rate of 1 ampere per second, and producing in that circuit 
 difference of potential of 1 volt. It corresponds to a rate of 
 ange of magnetic field strength through the circuit. 
 
 ■23 
 
 00 rt 
 03 ^ 
 
 s| 
 
 «s 
 
 c.2 
 
 §a 
 .sg 
 
 ll 
 
 03 O^ 
 
 "^ 3 > 
 oo"0 ^_i 
 
 
 eva « 
 
 X5— cjD 
 
 jd 9 
 
 a 33 
 
 £«-% 
 
 8*3 
 
 S« 
 
 *o 
 
 o-p 03 
 
 ® t i > 
 
 03 
 00 
 
 _>> >> 
 
 « 2*^.2 
 
 Ills 
 
 
 .3 § 
 
 O 2 03 
 
 S 
 
 ct O, 03 • rt 03 
 
 '43 O *H « 
 
 g'S ° a & 
 
 2.2 3£ 
 
 a> eg o> 
 
 rt u ci 
 
 03 Cj 03 Q. 
 
 u bfi 
 
 joquiiCg 
 
 - 
 
 w 
 
 P4 Ph 
 
 a 
 
 HH 
 
 ^ 
 
 *o 
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 03 
 8 
 0. 
 
 "0 
 
 a t 
 
 a ^ 
 g 
 
 a 
 
 3 
 
 a 
 < 
 
 > 
 
 £ 
 
 3 08 
 
 w 
 
 !-3 
 
Ind 
 
 ex 
 
 A 
 
 Page 
 
 Table — Areas and circumferences of circles 361-363 
 
 Table — Areas of segments of circles 1 13-1 14 
 
 Table — Areas of segments for boiler bracing 86 
 
 B 
 Table — Boiling point of water at various altitudes 302 
 
 C 
 
 Table — Carrying capacity of armature wires at various depths 
 
 of winding, and 3 sq. in. of radiating surface per watt 1198 
 
 Table — Carrying capacity of armature wires at various depths 
 
 of winding, and 1 sq. in. of radiating surface per watt 1199 
 
 Table — Carrying capacity of pure copper wire 1381 
 
 Table — Columns and I-beams for boiler setting , .64-65 
 
 Table — Commercial power gases — general properties 716 
 
 Table — Comparison of thermometer scales 290 
 
 Table — Composition of various coals 284 
 
 Table — Constituents of power gases 717 
 
 Table — Contents of cylinder in cu. ft. for each lineal foot in 
 
 length 825 
 
 Table — Cubic feet of ammonia gas required per minute per ton 
 
 of refrigeration 899 
 
 D 
 
 Table — Diameters of boiler rivets 89 
 
 Table — Diameter and pitch of rivets — double riveting 9° 
 
 Table — Dimensions of pure copper wire 1382 
 
to Index 
 
 Table — Efficiency of incandescent lamps 1428 
 
 Table — Efficiencies of air compressors at various altitudes. . . . 826 
 
 Table — Factors of evaporation < . . 343 
 
 Table — Flow of air through openings of various diameters.827-828 
 
 Table — Flow of steam through pipes 3 11 
 
 Table — Friction tests 559 
 
 H 
 
 Table — Horse-power required to compress air 825 
 
 Table — Hyperbolic logarithms 454 
 
 j 
 
 Table — Joint efficiencies (boiler) 91 
 
 K 
 
 Table — Kindling temperatures 283 
 
 Table — Lap and lead of Corliss valves 402 
 
 Table — Lloyd's rules 90 
 
 Table — Loss of heat from steam pipes 309 
 
 Table — Loss of pressure through friction of air in pipes 829 
 
 M 
 
 Table — Mean effective pressures 830 
 
 N 
 
 Table — Number of expansions 367 
 
 Table — Numbers : their square roots and cube roots 366 
 
 O 
 
 Table — Otis electric elevator data 942 
 
Index 
 
 P 
 
 Table- -Packing tests 558 
 
 Table — Physical properties of saturated steam 278-282 
 
 Table — Pressure of water 181-182 
 
 Table — Properties of saturated ammonia 918-919 
 
 Table — Proportions and efficiencies of riveted joints 90 
 
 Table — Proportions of single and double riveted joints 91 
 
 Table — Proportions of single riveted lap joints 92 
 
 Table — Proportions of double riveted lap and butt joints 93 
 
 Table — Proportions of triple riveted butt joints 94 
 
 Q 
 
 Table — Quantity of injection water required for jet condenser 363 
 
 R 
 
 Table — Relative value of non-conducting materials 307 
 
 Table — Requirements of pneumatic drills at various altitudes. . 831 
 
 S 
 
 Table — Sizes of air pumps — single acting 364 
 
 Table — Sizes of chimneys with appropriate horse power of 
 
 boilers 22,7 
 
 Table — Sizes, weight and resistance of pure copper wire 1386 
 
 Table — Spacing multi-gap lightning arresters \ 1338 
 
 Table — Specific heat of various substances 295 
 
 T 
 
 Table — Theoretical draft pressure in inches of water, in a 
 chimney 100 feet high 236 
 
 Table — Volume of air required for rock drills at sea level. . . . 831 
 Table — Volume and weight of air at various temperatures, and 
 at atmospheric pressure 240 
 
Index 
 
 W 
 
 Table — Weight of one cubic foot of water 301 
 
 Table — Wiring table for no volts 1383 
 
 Table — Wiring table for 220 volts 1384 
 
 Table — Wiring table for 500 volts 1385 
 
 A 
 
 Absolute zero 448 
 
 Adiabatic curve .' 449, 536-538 
 
 Air, composition of 238-239 
 
 Weight and volume of 239-240 
 
 Air compression 811-853 
 
 Adiabatic 812 
 
 At high altitudes 826 
 
 Catechism on 849-853 
 
 Compound compression 816-824 
 
 Conditions necessary for 811 
 
 Flow of free air through an orifice 827-828 
 
 Inter-cooling 816 
 
 Isothermal 812 
 
 Jacket cooling 816 
 
 Loss of pressure through friction 829-830 
 
 Mean effective pressures 830 
 
 Methods of removing heat of compression 814-819 
 
 Multi-stage .816-820 
 
 Sources of loss in 811 
 
 Volumetric efficiency .821-822 
 
 Air Compressors 811-853 
 
 Allis-Chalmers ^ 845-849 
 
 Dallett ; 843-845 
 
 Ingersoll-Rand 833-842 
 
 Compound 816 
 
 Cylinder lubrication 823-824 
 
 Drier air 822-823 
 
 Installation 831-833 
 
 Multi-stage 816-824 
 
 Pipe connections 832-833 
 
Index \ 
 
 Reduced strains 819-820 
 
 Single stage 822-823 
 
 Steam economy 820 
 
 Three stage 819 
 
 Two stage 819 
 
 Usefulness of 812 
 
 Allis-Chalmers Air Compressors : 845-849 
 
 Discharge valves 845 
 
 Rotary inlet valves 845 
 
 Valve gear 846-849 
 
 Allis-Chalmers Gas Engine 764-770 
 
 Design and construction of 766-767 
 
 Igniters 769 
 
 Lubrication . 769-770 
 
 Valve gear of 768 
 
 Allis-Chalmers Steam Turbine. 649-662 
 
 Action of steam in 652-653 
 
 Balance pistons 652-653 
 
 Bearings 655 
 
 Blades 653, 654-656 
 
 Description of 649-651 
 
 General view of 650 
 
 Governor . 655 
 
 Starting and operating 658-662 
 
 Thrust bearing 653 
 
 Aluminum Lightning Arrester 1352-1358 
 
 600 volt D. C 1324 
 
 Condenser action ; 1354 
 
 Design 1356-1358 
 
 Film dissolution 1354 
 
 For 1 10,000 volts 1356 
 
 Valve action 1352 
 
 American Stoker 214-216 
 
 American-Thompson Indicator 468-470 
 
 Ammonia 916-920 
 
 Anhydrous, composition of. 859 
 
 Composition of 916 
 
 Danger in fumes .911-912 
 
 How obtained 917 
 
Index 
 
 Hydrometer 920 
 
 Properties of 918-919 
 
 Specific gravity 917 
 
 Testing 919-920 
 
 Ammonia Condenser — Double Pipe 890-896 
 
 Brine system 892-895 
 
 Direct expansion system : 895-896 
 
 Angular Advance 456-457 
 
 Arc Lamps 1406 
 
 Action explained 1406 
 
 Adjusting weight I4°9 
 
 Brush lamp 1409-1414 
 
 Burning upside down 1407-1408 
 
 Carbons 1413-1414, 1424 
 
 Heat of arc 1408 
 
 Mechanism 1408 
 
 Method of suspension 141 1 
 
 Armature 1 151-1 191 
 
 Balancing 1151-1153 
 
 Bearings and pole pieces 1154-1155 
 
 Centering 1153-1154 
 
 Compensation for losses 1151 
 
 Materials to be used 1155-1156 
 
 Mechanical construction 11 55-1 159 
 
 Punched discs 1155-1158 
 
 Slotted 1156-1158 
 
 Armature Winding 1 158-1224 
 
 Advantages of drum style 1161-1162 
 
 Catechism on 1 192-1224 
 
 Compared with ring winding 1164 
 
 Connections for 8 coils 1167-1168 
 
 Connections for 12 coils M173-1175 
 
 Dead wire in 1 160 
 
 Development of \ 1 170-1 173 
 
 Drum windings 1 164-1 191 
 
 Formulae for spacing 1 168-1 169 
 
 Gramme ring .- 1159-1164 
 
 Insulating materials 1185-1186 
 
 Lap winding 1180-1181 
 
Index 
 
 Multipolar windings 1 176-1 185 
 
 Simplicity of 1 165-1 168 
 
 Wave winding 1181-1185 
 
 Winding table 1 169-1 170, 1 173, 1 185 
 
 Various methods of applying the wire 1185-1191 
 
 Armington and Sims Shaft Governor 435-438 
 
 Atlas Shaft Governor 433-435 
 
 Atlas Water Tube Boiler 38-48 
 
 Design and construction 38-42 
 
 Method of feeding 43-46 
 
 Safe working pressure 40 
 
 Automatic Furnaces — Murphy 207-209 
 
 Automatic Furnaces — Burke 220-223 
 
 B 
 
 Babcock & Wilcox Boiler 16-21 
 
 Construction of steam drums 18 
 
 End connections for tubes 16-18 
 
 Erection 18 
 
 Method of connecting 16-18 
 
 Operation 18-21 
 
 Back Arches 124-127 
 
 Barnes Draft Gauge 332-334 
 
 Batteries — Primary 1429-1454 
 
 Batteries — Storage 1447-1454 
 
 Belpaire Boiler 106-107 
 
 Calculating strength of stayed surfaces 111-116 
 
 Dished heads 117 
 
 Strength of unstayed surfaces 1 16-1 17 
 
 Through stay rods 108-1 1 1 
 
 Welded seams 118 
 
 Bigelow-Hornsby Boiler 30-34 
 
 Admission of feed water 32-33 
 
 Largeness of units 32 
 
 Section through setting 31 
 
 Blow-off Pipes 144-145 
 
 Boilers, care and operation of 262-277 
 
 Blisters and cracks 262 
 
Index 
 
 Blowing off 264 
 
 Catechism on 270-277 
 
 Feed pump or injector 262 
 
 Fusible plugs 263 
 
 Gauge cocks and water glasses 262 
 
 Loss in handling coal 269-270 
 
 Miscellaneous matters 265-270 
 
 Boiler Construction 77-122 
 
 Bursting pressure illustrated 83 
 
 Bursting pressure, formulae for finding 84-85 
 
 Bracing, rules and tables for 85-88 
 
 Catechism on 1 18-122 
 
 Crowfoot brace 103-104 
 
 Gusset stays and stay bolts 104-108 
 
 Importance of safe construction 77-78 
 
 Materials for 78-79 
 
 Punched and drilled plates 79-8o 
 
 Riveting, rules for 81-83 
 
 Rivets, diameters of 89 
 
 Riveted joints, proportions and efficiencies 90-93 
 
 Single riveted lap 94-95 
 
 Double riveted butt 95-97 
 
 Triple riveted butt 97-98 
 
 Quadruple riveted butt 98-102 
 
 Weakest parts of 90-102 
 
 Safe working pressure 85 
 
 Staying flat surfaces 102-1 16 
 
 Boiler Horse Power 345 
 
 Boiler Setting and Equipment 123-244 
 
 Back arches 124-127 
 
 Blow-off Pipes 144-145 
 
 Catechism on 182-188 
 
 Domes and mud drums 143 
 
 Feed pipes 145-147 
 
 Feed pumps 148-158 
 
 Selection of 148-149 
 
 Feed pumps, the Prescott 152-154 
 
 The Worthington 155-156 
 
 Care and operation 157-159 
 
Index 
 
 Fusible plugs 142, 143, 263 
 
 Grate surface 128 
 
 Insulation 129 
 
 Methods of support 123-124 
 
 Provisions for testing 159-162 
 
 Safety valves 135-142 
 
 Rules for 140-142 
 
 Setting steam valves of duplex pumps 150-152 
 
 Steam headers and connections 170-173 
 
 Steam gauges 132-134 
 
 Steam superheaters 173-176 
 
 The injector 163-170 
 
 Principles governing its actions 163-168 
 
 Sellers improved 168-170 
 
 Water columns 130-132 
 
 British Thermal Unit (B. T. U.) 293, 294, 298 
 
 Brush Arc Dynartio 1087-1098 
 
 Automatic regulation 1092-1093 
 
 Care of commutator 1091 
 
 Connections of . 1088-1089 
 
 Controller 1093-1096 
 
 Setting the brushes 1089-1091 
 
 Starting 1096-1098 
 
 C 
 
 Catechism on Air Compressors 849-853 
 
 Armature troubles 1220-1225 
 
 Armature winding 1 192-1224 
 
 Boilers 66-75 
 
 Boiler construction 1 18-122 
 
 Care and operation of boilers 270-277 
 
 Combustion, heat and water 313-316 
 
 Definitions 458-461 
 
 Electricity 1124-1135 
 
 Electric currents 1 148-1 151 
 
 Elevators 1012-1018 
 
 Evaporation tests 346-349 
 
 Gas engines 803-810 
 
Index 
 
 Indicator work 548-550 
 
 Lubrication and friction 577-579 
 
 Mechanical draft 241-243 
 
 Refrigeration 921-928 
 
 Rotary converters 1291-1295 
 
 Steam engines 368-371 
 
 Steam turbines 703-710 
 
 Switchboards 1358-1364 
 
 Transformers 1289-1291 
 
 Valve setting 438-444 
 
 Cahall Water Tube Boiler 3-8 
 
 Construction of 4-7 
 
 Swinging man-head 4-5 
 
 Tubes 7 
 
 Calculation of Wires 1373 
 
 Calorimeter 323-324, 329 
 
 Calorific value of fuel 286-287 
 
 Carbon 284 
 
 Care and Operation of Boilers 245-270 
 
 Ash conveyor 247-250 
 
 Cleaning fires 245-246 
 
 Duties of engineer 245 
 
 Feed water 259, 264 
 
 Fire tools 246-247 
 
 Firing — rules for 253-255, 263 
 
 Foaming and priming 260-261, 264 
 
 Pressure gauge 261-262 
 
 Renewing tubes 257-259 
 
 Safety valves 261 
 
 Washing out and cleaning 256-257, 263 
 
 Water level 262 
 
 Chimneys 231-240 
 
 Dimensions of 233-236 
 
 Functions of 231 
 
 Iron 237-238 
 
 Rules and Formulae for 233-238 
 
 Types of 232-233 
 
 Clearance . . . . , 448 
 
Index 
 
 Combustion 282, 288-336 
 
 Calorific value of fuel 286-287 
 
 Carbon 284 
 
 Coal — Analysis of 284-285 
 
 Hydrogen — Heating value of 284 
 
 Kindling point 283 
 
 Nitrogen 286 
 
 Oxygen, necessary for 283, 335-336 
 
 Temperature of the furnace 287 
 
 Compound Engines 351-352 
 
 Condensers 352-364 
 
 Jet 352-356 
 
 Siphon 358 
 
 Surface 357-3°4 
 
 Condensers for Steam Turbines 697 
 
 Consolidated Ice Machine 880-890 
 
 Construction of piston 883 
 
 Copper water jacket 882-883 
 
 Detailed description of 880-881 
 
 Stuffing boxes 883-884, 888-890 
 
 Suction and discharge valves 882-886 
 
 Coxe Mechanical Stoker 203 
 
 Crosby Indicator 465, 471-476 
 
 Current Distribution 1365-1373 
 
 Center of distribution 1372 
 
 Divided circuits 1365-1367 
 
 Feeders 1372 
 
 Multiple series 1369-1379 
 
 Service wires 1372 
 
 Series multiple 1369-1379 
 
 Three wire system 1370-1373, 1379 
 
 With two dynamos 1399-1405 
 
 Three wire parallel system 1368-1369 
 
 Wiring systems 1367 
 
 Curtis Steam Turbine 611-632 
 
 Action of steam in 617-618 
 
 Admission valves 617 
 
 Baffler 632 
 
 Clearance 629-630 
 
t Index 
 
 Governor 622-626 
 
 Initial nozzles and buckets 612-616 
 
 Shaft 613 
 
 Speed regulation 618-622 
 
 Step bearing 629 
 
 Wheels and stages 614-617 
 
 Cylindrical Flue Boiler . . I 
 
 D 
 
 Dallett Air Compressor 843-845 
 
 General description of 843 
 
 Governor and safety stop 843-844 
 
 Inlet and discharge valves 845 
 
 Definitions — Electric 1475-1481 
 
 Definitions 445-458 
 
 Of absolute zero 448 
 
 Angular advance — lap and lead 456-457 
 
 Clearance 448 
 
 Efficiency of plant 450-452 
 
 Expansions 446-447 
 
 Horse-power 448 
 
 Logarithms 452-454 
 
 Motion, force, work 449-450 
 
 Pressures 445-446 
 
 Vacuum 447-448 
 
 Catechism on 458-461 
 
 Deitz High Pressure Lubricator 574-576 
 
 De Lavergne Refrigerator 872 
 
 Action of machine explained 874-878 
 
 Characteristic features of 872-873 
 
 Sealed stuffing box 873 
 
 De Laval Steam Turbine 633-634 
 
 Action of steam in 640-642 
 
 Description of parts 636-640 
 
 Efficiency tests of 646-647 
 
 Gear — Flexible shaft 642-643 
 
 Governor 644-645 
 
 High speed of 633-636 
 
Index 
 
 Nozzles 634 
 
 Wheel 647 
 
 Detroit Lubricator 566-570 
 
 Diagram Analysis 485-550 
 
 Adiabatic curve 449, 536-538 
 
 Catechism on indicator work 543-550 
 
 Criticism of various diagrams 486-490 
 
 Explanation of a diagram 485-486 
 
 Isothermal curve 449 
 
 M. E. P., how to ascertain 490-493, 510-512, 516-520, 545 
 
 Ordinates, how to draw 539-543 
 
 Power calculations 539~548 
 
 Power test diagrams 506-510 
 
 Rule for strength of spring 497 
 
 Showing spring to be too strong 494-495 
 
 Steam consumption from 521-527 
 
 Theoretical clearance 527-531 
 
 Theoretical expansion curve 449, 531-536 
 
 Unequal cutoff 495-498 
 
 Wire drawing of steam 499 
 
 Diagrams from Gas Engines 744-749 
 
 Disposal of Exhaust of Steam Turbines 697-703 
 
 Condensers for steam turbines 697 
 
 Catechism on steam turbines 703-710 
 
 Dry air pump 698-699 
 
 Efficiency of turbine or reciprocating engine 699-701 
 
 Surface condenser, action of 701-703 
 
 Domes and Mud Drums 143 
 
 Dry Air Pump 698-699 
 
 Duplex Steam Pumps : 150-152 
 
 Duplex Water Tube Boiler 51-56 
 
 Method of Support 54 
 
 Sectional view of 52 
 
 Strong features of 51 
 
 Water circulation in 55 
 
 D. Slide Valve 373S77 
 
 Action of 375-379 
 
 Du Bois Tandem Gas Engine 779-788 
 
 Characteristic features of 779-782 
 
 Ignition 785-786 
 
Index 
 
 Lubrication . . . 7&7 
 
 Mixing valve 784-785 
 
 Starting ,., ....787-788 
 
 Valves, valve gear and governor 782-785 
 
 Dynamo , 1084-1 123 
 
 Brush arc 1087-1098 
 
 Constant current, operation of 1084-1087 
 
 Thomson-Houston 1098-1 1C9 
 
 Dynamo — Electric Generators : 1033-1072 
 
 Alternator 1036-1139 
 
 Brush holders 1061 
 
 Brushes and commutators 1058-1065 
 
 Carbon brushes < 1059-1060 
 
 Classification of > 1033-1034 
 
 Commutator 1041-1043, 1058 
 
 Compound dynamo 1069-1070 
 
 Constant potential dynamos 1073 
 
 D. C. generator ' 1039-1046 
 
 Drum windings 1046, 1053-1055 
 
 Function of 1033 
 
 Generation of current 1034-1036 
 
 General rules for starting 1081-1082 
 
 Gramme ring 1047-1052 
 
 Operation of 1073 
 
 Over-compounding 1070-1072 
 
 Principal parts of 1034 
 
 Regulation 1057-1058 
 
 Rheostat i 074-1075 
 
 Self-excitation 1055-1056 
 
 Series dynamo 1068-1069 
 
 Shunt dynamo 1069 
 
 Short circuit 1077 
 
 Starting machines 1078-1082 
 
 Under-compounding 1072-1073 
 
 Dynamo Troubles 1387-1396 
 
 Bearings, wear of 1394 
 
 Brushes and commutator 1392-1396- 
 
 Care in operation 1387-13891 
 
 Motor compensator for three wire 1401-1405, 
 
Index 
 
 Lubricators 1393-1395 
 
 Sources of trouble 1388-1391 
 
 Sparking^ causes of 1391-1392 
 
 Starting a new generator 1401-1405 
 
 E 
 
 Efficiency of Plant 339, 450-452 
 
 Electricity 1019-1481 
 
 Ampere turns 1032 
 
 Conservation of energy 1019-1020 
 
 Coulomb 1022 
 
 Current may be measured 1019 
 
 Electro-motive force 1031-1033 
 
 Extent of knowledge regarding it 1019 
 
 Foucault currents 1032 
 
 How measured 1021-1023 
 
 Induction — Faraday's law of 1032 
 
 Ohm 1022 
 
 One form of energy 1020-1021 
 
 Volt 1021-1022 
 
 Volt-Coulomb or Joule 1022 
 
 Watt 1022-1023 
 
 Electric Currents 1137-1147 
 
 Alternating current (A. C.) 1137-1143 
 
 Catechism on 1148-1150 
 
 Current waves 1 140-1 142 
 
 Delta winding 1 146 
 
 Direct Current (D. C.) 1137-1143 
 
 Frequency — Alternations 1141 
 
 Maximum voltage 1141-1142 
 
 Phase, lag and lead 1143-1145 
 
 Polyphase 1 147 
 
 Two and three phase 1 145-1 146 
 
 Waves in quadrature 1 147 
 
 Waves in opposition 1 147 
 
 Y. Winding 1 146-1 147 
 
 Electric Elevators 1009-1018 
 
 Boiler power required for 1009-1012 
 
Index 
 
 Catechism on 1012-1018 
 
 Electric Motors 1 109-1 124 
 
 Action explained 1 109-1 1 1 1 
 
 Alternating current motors 1 1 18-1 1 19 
 
 Catechism on 1 124- 1 135 
 
 Compound wound 1 1 16-1 1 17 
 
 Construction of 1 1 10 
 
 Course of current in 1 1 13 
 
 Electro-motive force of 1 1 1 1-1 1 12 
 
 Faults of 11 18 
 
 Highest speed of 11 12-1 1 14 
 
 Induction motor 1 121-1 123 
 
 Series wound 1115-1116 
 
 Starting box 1 1 17-1 1 18 
 
 Synchronous motors 1121-1123 
 
 Electro-Meters 1303-1319 
 
 Ammeters and volt-meters 1304 
 
 Galvanometers 1303-1304 
 
 Volt meter 1310-1314 
 
 Watt meters 1314-1317 
 
 Weston instrument 1304-1310 
 
 Electro-magnetic induction 1030-1031 
 
 Elevators 929-1018 
 
 Morse- Williams 979-985 
 
 Otis traction — electric 929-931 
 
 Otis hydraulic 944-971 
 
 Whittier hydraulic 975-979 
 
 Ellison's Draft Gauge 334-335 
 
 Erie City Water Tube Boiler 56-60 
 
 Side elevation of 58 
 
 Spacing of tubes 57~58 
 
 Steam separation 59-60 
 
 Evaporation Tests 3^7-345 
 
 Apparatus necessary 318-320 
 
 Barrus draft gauge 332-334 
 
 Boiler horse-power 345 
 
 Calorimeter 323, 324-329 
 
 Catechism on 346-349 
 
 Conducting a test 318-325 
 
Index 
 
 Determining quality of the steam 322-331 
 
 Ellison's draft gauge 334-335 
 
 Efficiency of plant — calculation of 339-340 
 
 Efficiency of boiler — calculation of 340-341 
 
 Equivalent evaporation explained 342-343 
 
 Factors of evaporation 343 
 
 Flue gas analysis 335-339 
 
 Measuring chimney draft 332-335 
 
 Object of 317 
 
 Orsat apparatus 33^>-339 
 
 Preparing for 317-318 
 
 Expansion 446-447 
 
 F 
 
 Factors of Evaporation 343 
 
 Feed Pipes 145-147 
 
 Feed Pumps 148-158 
 
 Feed Water for Boilers 259-264 
 
 Feed Water Heaters 189-197 
 
 Hoppes, class R 1 93-197 
 
 Kinds of 190 
 
 Open, or closed 190-195 
 
 Saving effected by 190-193 
 
 Field of Force 1028-1029 
 
 Fitchburg Engine 419-428 
 
 Adjusting valves of 425-428 
 
 Type of valves 420-423 
 
 Flow of Steam Through Pipes 310-313 
 
 Flue Gas Analysis 335-339 
 
 Foot Pound 293-294 
 
 Force 449-450 
 
 Friction — Laws of 551-555 
 
 Co-efficient of 553-555 
 
 Kinds of in mechanics 553 
 
 Of piston rod packing 557"56o 
 
 Second law of, illustrated 553-554 
 
 Fusible Plugs 142-143, 263 
 
Index 
 
 G 
 
 Gas Engine vi 711-810 
 
 Advantages of 750-751 
 
 Back pressure in 747 
 
 Batteries for ignition spark 722-724 
 
 Catechism on 803-810 
 
 Combustion for 718-746 
 
 Compared to steam engine 71 1-712 
 
 Compression in 719-720, 748 
 
 Cylinder lubrication 803 
 
 Diagrams from 744-749 
 
 Efficiency of power gases 736 
 
 Economy of 749-750 
 
 Exhaust of 730-733 
 
 Explosion and expansion 730 
 
 Explosive mixture 728-730 
 
 Finding centers 733~734 
 
 Fuel for 714-717 
 
 Indicator — Crosby, new 738-739 
 
 Crosby with detent 739-741 
 
 Tabor outside spring 742-743 
 
 Ignition — Magnetic 726 
 
 Timing of 727 
 
 Various methods of 719-728 
 
 I. H. P., calculations of 748-749 
 
 Induction of charge 718 
 
 Lubrication of 802-803 
 
 Producer gas 751-753 
 
 Spark coils 726-728 
 
 Valve setting 733~736 
 
 Valve timing 733 
 
 Allis-Chalmers 764-770 
 
 Du Bois 779-788 
 
 Reeves 792-795 
 
 Snow 776-779 
 
 Tower 788-792 
 
 Westinghouse 770-776 
 
 Gasoline Engine 795-801 
 
 Carbureter 797-798 
 
Index i 
 
 Constant level overflow 797 
 
 Gasoline pump 796 
 
 Generator or mixer 800-801 
 
 Principles governing action 795~798 
 
 Gas Producer 753-764 
 
 Efficiency of 763-764 
 
 Hydrogen content 764 
 
 Induced down draft : 762-763 
 
 Regulation of 764 
 
 Steam pressure type 761-763 
 
 Suction type 753-762 
 
 Gramme ring 1047-1052 
 
 Grate surface 128 
 
 Greene-Wheelock engine 411-420 
 
 Description of valves 412-414 
 
 Setting valves of 415-419 
 
 H 
 
 Hamilton Holzwarth Steam Turbine 663-679 
 
 Action of steam in 673-674 
 
 Catechism on . . 703-710 
 
 Clearance of blades 666-668 
 
 Comparison with other types 665-666 
 
 Construction of blades 668-669 
 
 Governor — Regulation 675-677 
 
 Running wheels 669-673 
 
 Stationary discs 674-675 
 
 Stuffing box . . 677-679 
 
 Heat 288-298 
 
 Absolute zero 290-291 
 
 British thermal unit (B. T. U.) 293, 294-298 
 
 Dr. Joule's discovery 292-293 
 
 Effects of 290 
 
 Foot pound 293-294. 
 
 Nature of 288-291 
 
 Sensible and latent heat 295-297 
 
 Specific heat 294-295 
 
 Thermo-Dynamics — First law of 292 
 
Index 
 
 Total heat of evaporation 298 
 
 Work done by 297-298 
 
 Heating Surface 266-269 
 
 Horse-power Explained 518-520 
 
 Hoppes Feed Water Heater 193-197 
 
 Hydraulics for Engineers 176-180 
 
 Hydraulic Elevators 944-1012 
 
 Action explained 944-946 
 
 Boiler power required for 1006-1009 
 
 Construction of 946-947 
 
 Counterbalance 965 
 
 Cylinders — Arrangement of 964 
 
 Horizontal cylinder 973-985 
 
 Operating devices 965-973 
 
 Operating valve 954-959 
 
 Piston and piston packing 962-963 
 
 Pressure tank 957-958 
 
 Safety governor, Otis 951-954 
 
 Speed limit devices 947-951 
 
 Throttle valve 959, 962-971 
 
 Vertical cylinder 960-973 
 
 Hydrogen 284 
 
 I 
 
 Ice Making 896-899 
 
 Requirements for pure ice 897 
 
 Process explained 997-998 
 
 Incandescent Lamp 1425-1429 
 
 Action explained 1425 
 
 Current required for 1426-1427 
 
 Efficiency of 1427-1429 
 
 Resistance 1426 
 
 Selection of 1426 
 
 Incrustation in Boilers 299-300 
 
 Indicator, the 463-485 
 
 Adjustment of valves with 499-502, 503-506 
 
 American-Thompson 468-470 
 
 Attaching to cylinder 481-482 
 
Index 
 
 Care of 482-483 
 
 Causes of error 512-516 
 
 Crosby 465, 471-476 
 
 How to take diagrams 483-485 
 
 Invention of 463 
 
 Principles of its action 463-465 
 
 Reducing mechanism 470, 476-480 
 
 Tabor 467-468 
 
 Indicators for Gas Engines 736-749 
 
 Crosby, new 73&~739 
 
 Crosby with detent 739-741 
 
 Monagraph for high speed 743-744 
 
 Tabor outside spring 742 
 
 Tabor parallel motion 742-743 
 
 Ingersoll-Rand Air Compressor 833-842 
 
 Air ball governor 838-839 
 
 Internal construction 833 
 
 Mason governor 840-842 
 
 Meyer cut-off valve 834-840 
 
 To remove inlet valves ^3^-^37 
 
 To set cut-off eccentric 837-838 
 
 To start 842 
 
 Unloader and regulator 834-836 
 
 Injector, the 163-170 
 
 Isothermal Curve 449 
 
 j 
 
 Jones underfeed Stoker 216-219 
 
 K 
 Kindling Point 283 
 
 L 
 
 Lap — Inside 374 
 
 Lap— Outside 374-375, 3^8 
 
 Latent Heat 295-297 
 
 Lead 374 
 
Index 
 
 Lightning Arresters 1319-1364 
 
 Aluminum — 600 volt D. C 1324, 1352-1358 
 
 Catechism on 1358-1364 
 
 Choke coils 1345-1347 
 
 Connections 1326 
 
 Constant current arresters 1344 
 
 D. C. arresters 1347-1349 
 
 Discharge of lightning 1319 
 
 Disconnecting switches 1344-1345 
 
 Distribution of stress 1328 
 
 Fuse auxiliaries 1337-1338 
 
 Ground connections 1349-1352 
 
 Horn gap installation 1350 
 
 Inspection 1326-1328 
 
 Low voltage arresters 1339-1342 
 
 Multigap arresters 1321-1322 
 
 Oscilliograph curves 1341 
 
 Protection of cable systems 1342-1344 
 
 Protection of electric circuits 1320 
 
 Resistance in arrester 1322-1324 
 
 Sparking of gaps 1329-1330 
 
 Voltage range 1339 
 
 Linde Ice Machine 863-872 
 
 Action of 863-868 
 
 Indicator diagrams from 865-866 
 
 Stuffing box 869-871 
 
 Logarithms 452-454 
 
 Lubrication 550-579 
 
 Catechism on 577-579 
 
 Cost of 561 
 
 Graphite as a lubricant 562-564 
 
 Of interior surfaces 564-565 
 
 Requirements of a good lubricant 560-561 
 
 Lubricating Appliances 565-577 
 
 Detroit lubricator 566-570 
 
 Dietz high pressure device 574-576 
 
 Manzel oil pump 574 
 
 Powell lubricator 570-574 
 
 Rochester force feed 576-577 
 
Judex 
 
 M 
 
 Magnets 1023-1031 
 
 Charging — various methods of 1024 
 
 Direction of current 1026-1027 
 
 Electro-magnet 1024 
 
 Electro-magnetic induction 1030-1031 
 
 Field of force 1 028-1029 
 
 Lines of force 1024, 1027-1031 
 
 Natural magnet 1023 
 
 Permanent magnet 1023-1024 
 
 U-shaped magnet 1024 
 
 Mansfield Chain Grate Stoker 201-202 
 
 Marzolf Boiler 48-51 
 
 Admission of feed water 51 
 
 Baffle and path of gases 50-51 
 
 Sectional view of 49 
 
 Maxim Boiler 28-30 
 
 Arrangement of heating surface 30 
 
 Front elevation 28 
 
 Mechanical Draft 223-243 
 
 Catechism on 241-243 
 
 General forms of apparatus 227-231 
 
 Mechanical Stokers 197-223 
 
 American under-feed 214-216 
 
 Classes of 200-201 
 
 Coxe 203 
 
 Jones under-feed 216-219 
 
 Mansfield chain grate 201-202 
 
 Playf ord 202-204 
 
 Roney 209-213 
 
 Vicars 204 
 
 Wilkinson 205-207 
 
 M. E. P. — How to Ascertain 490, 510, 545 
 
 Mil — Circular and Square 1373-1379 
 
 Monahan Gas Producer 756-758 
 
 Morse- Williams Hydraulic Elevator 979-985 
 
 Double-decked machine 979-981 
 
 Operation 983-985 
 
* Index 
 
 Motion 449-450 
 
 Murphy Furnace 207-209 
 
 N 
 Nitrogen 286 
 
 O 
 
 Oil Engines 8ioa-8ioi 
 
 Switches 1297-1303 
 
 Principles of construction 1297-1298 
 
 Safety of 1299 
 
 Westinghouse — types B and E 1300-1303 
 
 Westinghouse — type I 1298, 1300-1301 
 
 Ordinates — How to Draw Them 539-543 
 
 Orsat draft Gauge 336-339 
 
 Oscilliograph Curves 1341 
 
 Otis Direct Acting Hydraulic Elevators 997-1006 
 
 Construction of cylinder 1002-1006 
 
 Installation 999-1000 
 
 Stuffing box 1005 
 
 Otis High Pressure Elevators — Hydraulic 985-997 
 
 Accumulator 988-989 
 
 Advantages of 985-986 
 
 Arrangement of parts 986-989 
 
 Cylinder and plunger 993-995 
 
 Main and pilot valves 992-993 
 
 Movement of water in 989-992 
 
 Otis Traction Elevator — Electric 929-944 
 
 A. C. Machines 936-937 
 
 Arrangement of cables 93<>93i 
 
 Brake 936 
 
 Controller 931-932 
 
 Geared traction machines ; 933-938 
 
 Lever car switch 939 
 
 Magnet controller 938 
 
 Motor — description of 929-930 
 
 Oil cushion buffer 932-933 
 
 Operating — suggestions for 940-944 
 
 Oxygen 283, 335~33^ 
 
Index 
 
 P 
 
 Pressure-bursting 83-85 
 
 Safe working 85 
 
 Pressure gauge 261-262 
 
 Pressures 445-446 
 
 Primary batteries 1429-1454 
 
 Action of 1430-1431 
 
 Carbon cylinder cell 1431-1432 
 
 Care of 1437-1442 
 
 Closed circuit 1431 
 
 Dry batteries 1445-1447 
 
 Edison-Lalande cell 1^/1-1445 
 
 Fuller cell 1442-1444 
 
 Gravity 1434-1442 
 
 Hydrometer 1439 
 
 Ingredients 1435-1436 
 
 Leclanche cell 1432-1434 
 
 Open circuit 1430 
 
 Planimeter 545-547 
 
 Playford stoker 202-204 
 
 Power test diagrams 506-510 
 
 Calculations 539-548 
 
 Powell lubricator 570-574 
 
 Prescott steam pump 152-154 
 
 Producer gas 751-753 
 
 Properties of saturated steam 278-282 
 
 Q 
 
 Quadruple riveted butt joints 98-102 
 
 R 
 
 Rateau Steam Turbine 681-691 
 
 Action of steam in 681-685 
 
 Principles of 681 
 
 Regenerator for low pressures 685-691 
 
 Reeves Gas Engine 792-795 
 
 Governor 794 
 
Index 
 
 Jump spark for ignition 794-795 
 
 Lubrication of 795 
 
 Methods of construction 792-794 
 
 Water jacket for cylinder 794 
 
 Refrigeration 854-928 
 
 Absorption process 899-918 
 
 Brine — composition of 911 
 
 Catechism on 921-928 
 
 Compression system 859-899 
 
 Consolidated ice machine 880-886 
 
 Charging new system 913-914 
 
 De Lavergne refrigerator 872-878 
 
 Generator 907-909 
 
 Linde ice machine 863-872 
 
 Reece's improved apparatus 903-905 
 
 Systems of refrigeration 858 
 
 Thermo-dynamics — two first laws 854 
 
 Wet and dry refrigeration 860-862 
 
 Work of a refrigerating machine 857 
 
 Reidler-Stumpf Steam Turbine '. 693-696 
 
 Action of steam in 696 
 
 Blades — stationary and moving 693-696 
 
 Method of construction 693 
 
 Reynolds Long Range Cut-off Engine 403-411 
 
 Setting valves of 410-41 1 
 
 Riveted Joints — Boiler 90-116 
 
 Rochester Force Feed Lubricator 576-577 
 
 Roney Stoker 209-213 
 
 Rotary Converters 1277-1289 
 
 Bucking — causes of 1286-1287 
 
 Functions of 1277-1279 
 
 Insulation of frame 1283-1284 
 
 Oscillators for 1287-1289 
 
 Principles of action 1280-1283 
 
 Repairs to armatures 1286 
 
 Rules for erection 1283-1286 
 
 Russell Shaft Governor 431-433 
 
 Safety Valves 135-142 
 
 Sensible Heat 295-297 
 
Index 
 
 Series Wound Dynamo 1068-1069 
 
 Shaft Governors 428-438, 457 
 
 Armington and Sims 435-438 
 
 Atlas 433-435 
 
 General principles of 428-433 
 
 Russell 431-433 
 
 Shunt Wound Dynamo 1069 
 
 Smith Gas Producer 759-762 
 
 Snow Gas Engine 766-779 
 
 Inlet, and cut-off mechanism 778-779 
 
 Mixing chamber 776-777 
 
 Speed regulation 776 
 
 Sparking at Brushes — Causes of 1061, 1065-1068 
 
 Specific Heat 294-295 
 
 Stationary Boilers — Types of 1-75 
 
 Steam 302-316 
 
 Catechism on 313-316 
 
 Density of 305 
 
 Dry 304, 305-306 
 
 Flow of — through pipes 310-312 
 
 — from a given orfice 312-313 
 
 Generation of 303 
 
 In its relation to the engine 306 
 
 Nature of 302-303 
 
 Radiation of heat from 306-309 
 
 Relative volume of 305-306 
 
 Total heat of 304 
 
 Wet 304 
 
 Steam Consumption 521-527 
 
 Steam Gauges 132-134 
 
 Steam Engines 351-580 
 
 Catechism on 368-371 
 
 Classes of 351-352 
 
 Condensing engines 351-364 
 
 Cross compound 365-366 
 
 Multiple cylinder engines 364 
 
 Number of expansions 367 
 
 Steam jacket 367-368 
 
 Triple expansion 366-367 
 
Index 
 
 Water required for condenser 356,360-363 
 
 Steam Turbine 581-710 
 
 Blade — form of 586-587 
 
 Catechism on 703-710 
 
 Development of 583-585 
 
 Disposal of exhaust 697-703 
 
 Principles explained 581-585, 663-664 
 
 Stuffing boxes 587-592 
 
 Parsons 585-589 
 
 Rateau 589-591 
 
 Schulz 588 
 
 Speed regulation 591-592 
 
 Steam Turbines — Allis-Chalmers 649-662 
 
 Curtis 61 1-632 
 
 De Laval 633-634 
 
 Hamilton-Holzwarth 663-679 
 
 Rateau 681-691 
 
 Reidler-Stumpf 693-696 
 
 Westinghouse-Parsons 593-6io 
 
 Stirling Water Tube Boilers 21-28 
 
 Circulation of water in 25-26 
 
 How supported 21 
 
 Operation of 27-28 
 
 Steam and mud drums 21-22 
 
 Tubes — method of connecting 22-23 
 
 Storage Batteries 1447-1454 
 
 Action of 1449-1450 
 
 Advantages of 1447 
 
 Chloride accumulator 1451 
 
 Charging 1448-1449 
 
 Construction of 1447, 1449-1452 
 
 Edison cell 1453-1454 
 
 Superheater — Steam 173-176 
 
 Switchboard 1224-1364 
 
 A. C. generator panel 1235-1237 
 
 A. C. outgoing panel 1237-1241 
 
 Arc switchboards 1253 
 
 Catechism on 1358-1364 
 
 D. C. feeder panels 1231-1233 
 
Index 
 
 D. C. generator panels 1224-1235 
 
 Equalizer connections .- 1227 
 
 Exciter panels 1247-1251 
 
 Functions of instruments 1235-1237 
 
 Horizontal rows of holes 1253 
 
 Induction motor panel 1254 
 
 Maintenance of 1317-1319 
 
 Positive line wires 1253-1255 
 
 Step-up transformers 1244 
 
 Throwing in a generator 1233-1235 
 
 Transferring currents 1255-1259 
 
 Vertical rows of holes 1253 
 
 Switchboards — Thomson-Houston Series Arc 1253-1259 
 
 Western Electric Co.'s Series Arc 1259-1260 
 
 T 
 
 Tabor Indicator 467-468 
 
 Thermometers — Comparison of 289 290 
 
 Thermo-Dynamics — First Law of 292 
 
 Theoretical Clearance 527-531 
 
 Theoretical Expansion Curve 449, 531-536 
 
 Thomson-Houston Dynamo 1098-1 109 
 
 Operation of 1101-1105 
 
 Regulator 1 104 
 
 Rheostat 1 106-1 109 
 
 Setting the cut-out 1 098-1 103 
 
 Starting — rules of 1 109 
 
 Table of leads 1 102 
 
 Thomson-Houston Arc Lamp 1415 
 
 Adjustments of 1417-1418 
 
 Alternating current arc 1422 
 
 Directions for trimming 1418 
 
 Operation of 1415-1417 
 
 Series arc — action of 1419-1422 
 
 Total Heat of Evaporation 298 
 
 Tower Gas Engine 788-792 
 
 Construction of 789-790 
 
 For heavy duty 788 
 
 L 
 
Index 
 
 Governor 79^ 
 
 Governor valve 79 1 
 
 Ignition 791-792 
 
 Rating and weight of 789 
 
 Valve — how operated 790-791 
 
 Transformers 1260-1277 
 
 Allis-Chalmers transformers 1270-1277 
 
 Auto transformers 1268-1270 
 
 Catechism on 1289-1291 
 
 Cooling 1268-1271 
 
 Efficiency of 1265-1268 
 
 Exciting current 1265 
 
 Principles of 1260-1264 
 
 Step-up or step-down transformers 1264 
 
 Transformer Oil 1396-1399 
 
 Triumph Ice Machine 878-880 
 
 Description of parts 878-879 
 
 Piston rod packing 879-880 
 
 Tubular Boiler 1-3 
 
 Setting of 61-65 
 
 U 
 
 Underwriters' Rules 1454-1474 
 
 Conductors 1458-146 1 
 
 Generators 1454-1458 
 
 Lightning arresters 1465-1466 
 
 Motors 1467-1472 
 
 Railway power plants 1472-1473 
 
 Resistance boxes — equalizers 1463-1465 
 
 Switchboards 1461-1463 
 
 Transformers 1473-1474 
 
 Unequal cut-off 495-498 
 
 V 
 
 Vacuum 447-448 
 
 Valve Adjustment 373-403 
 
 Valve Gear of Corliss Engines 396-398 
 
Index 
 
 Valves, and Valve Setting 373-403 
 
 Action of D valve explained 375-389 
 
 Adjustment of Corliss valves 399*403 
 
 Angular advance — changes in 384-385 
 
 Catechism on 438-444 
 
 D slide valve — functions of 373S77 
 
 Eccentric rod — length of 391-395, 409 
 
 Inside lap — obj ect of 374 
 
 Lap — effect of changes in 374-375, 388 
 
 Lead — obj ect of 374 
 
 Placing engine on the center 389-392 
 
 Travel of valve 376 
 
 Zeuner valve diagrams , . .378-387 
 
 Vicars' Mechanical Stoker 204 
 
 Water Columns 130-132 
 
 Water 299-305 
 
 Action of heat upon 304-305 
 
 Boiling point and weight 301-302 
 
 Causes of incrustation in boilers 299-300 
 
 Composition of 299 
 
 Nature of 300 
 
 Westinghouse Gas Engine 770-776 
 
 Catechism on 803-810 
 
 Governor 773~774 
 
 Igniter plug 775 
 
 Inlet and exhaust valves 770-773 
 
 Mixing valve 774-775 
 
 Starting 77S~77^ 
 
 Vertical type 770-771 
 
 Westinghouse-Parsons Steam Turbine 593-610 
 
 Admission nozzles 607-609 
 
 Balancing pistons 598-599 
 
 Blade material 603-604 
 
 Capacity of 610 
 
 Catechism on 703-710 
 
 Direction of steam through 598 
 
 Double flow type 604-610 
 
 Efficiency of 603 
 
 Governor 601-602 
 
Index 
 
 Principles of action 594-597 
 
 Rotor 603 
 
 Shaft bearings 599-601 
 
 Speed of 593 
 
 Whittier — Pulling Type Elevators 975 
 
 Main and pilot valves 977-979 
 
 Wicks Vertical Water Tube Boiler 34-38 
 
 Drums or cylinders 34 
 
 Steam room ..'. . . 37 
 
 Tubes ?nd manholes 34-36 
 
 Wilkinson Stoker 205-207 
 
 Wire Drawing of Steam 499 
 
 Wiring Tables 1379-1386 
 
 Work 449-450 
 
 Work Done by Heat 297-298 
 
 Worthington Steam Pump 155-156 
 
 Y 
 Y Winding 1146-1147 
 
 Z 
 
 Zero — Absolute 448 
 
 Zeuner Valve Diagrams 37^-3^7 
 
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 son. Illustrated 1.00 ... 
 
 Horse Shoeing, Correct — Holmstrom. Il- 
 lustrated 1.00 ... 
 
 Hot Water Heating, Steam and Gas Fit- 
 ting — Donaldson. Illustrated 1.50 . . . 
 
 Heating and Lighting Railway Passen- 
 ger Cars — Prior 1.25 . . . 
 
 Locomotive Breakdowns, with Questions 
 
 and Answers — Wallace. Illustrated 1.51 
 
 Locomotive Fireman's Boiler Instructor- 
 Swingle 1.60 
 
 Locomotive Engineering — Swingle. Illus- 
 trated. Pocket Book Style 3.00 
 
 Machine Shop Practice — Brookes. Illus- 
 trated 2.00 . . . 
 
 Mechanical Drawing and Machine Design 
 
 — Westinghouse. Illustrated 2.00 ... 
 
 Motorman, How to Become a Successful. 
 
 Aylmer-Small. Illustrated 1.50 
 
 Motorman's Practical Air Brake Instruc- 
 tor — Denehie 1.50 
 
 Modern Electric Illumination, Theory 
 and Practice — Horstmann & Tousley. 
 Illustrated 2.00 
 
 Millwright's Practical Hand Book — Swin- 
 gle. Illustrated fc.00 ... 
 
 Modern American Telephony In All Its 
 
 Branches — Smith. Illustrated - «* 0* 
 
Price. 
 Titles. Cloth. Lea* 
 
 Operation of Trains and Station Work — 
 Prior. Illustrated 1.60 
 
 Painting:, Cyclopedia of — Maire. Illus- 
 trated 1.50 . . . 
 
 Pattern Making: and Foundry Practice — 
 Hand. Illustrated 1.50 
 
 Picture Making for Pleasure and Profit — 
 
 Baldwin. Illustrated 1.25 ... 
 
 Plumbing-, Practical, Up-to-Date — Clow. 
 
 Illustrated 1.50 . . . 
 
 Railway Roadbed and Track, Construc- 
 tion and Maintenance of — Prior. Illus- 
 trated 2.00 
 
 Railway Shop Up-to-Date — Haig. Illus- 
 trated 2.00 . 
 
 Sheet Metal Workers' Instructor — Rose. 
 
 Illustrated 2.00 . 
 
 Signist's Book of Modern Alphabets — Del- 
 
 amotte 1.50 . 
 
 Sign Painting, The Art of — Atkinson... 3.00 . 
 
 Stair Building and Hand Railing — Hodg- 
 son. Illustrated 1.00 . 
 
 Steam Boilers — Swingle. Illustrated 1. 
 
 Steel Square, A Key to — Woods 1.50 . 
 
 Steel Square, Vol. I — Hodgson. Illus- 
 trated 1.00 . 
 
 Steel Square, Vol. II — Hodgson. Illus- 
 trated 1.00 . 
 
 Steel Square, A B C — Hodgson 50 . 
 
 Steel Construction, Practical — Hodgson. 
 
 Illustrated 50 . 
 
 Storage Batteries — Niblett 50 . 
 
 Sho' Cards, A Show At — Atkinson and 
 
 Atkinson 3.00 . 
 
 Stonemasonry, Practical, Self-Taught — 
 
 Hodgson. Illustrated 1.00 . 
 
 Telegraphy Salf-Taught — Edison. Illus- 
 trated ._. 1.00 . 
 
 Telephone Hand-Book— Illus- 
 trated 1.00 . 
 
 Timber Framing, Light and Heavy — 
 
 Hodgson 2.00 . 
 
 Toolsmith and Steel Worker — Holford. 
 
 Illustrated 1.50 . 
 
 Turbine, The Steam — Swingle. Illustrated 1.00 . 
 
 Walschaert Valve Gear Breakdowns and 
 How to Adjust Them — Swingle. Illus- 
 trated 1.00 . 
 
 Wiring Diagrams, Modern — Horstmann 
 
 & Tousley. Illustrated 1.50 
 
 Wireless Telegraphy and Telephony — 
 
 V. H. Laughter 1.00 
 
 Wood Carving, Practical — Hodgson. Illus- 
 trated 1.50 
 
 THE BED BOOK SEBIES OF TBADE SCHOOL 
 
 MANUALS 
 
 By F. Maire 
 
 16 mo., Cloth, Illustrated. Price, each, $0.60 
 
 Exterior Painting, Wood, Iron and Brick. 
 Interior Painting, Water and Oil Colors. 
 Colors, What They Are and What to Expect 
 
 from Them. 
 
 Graining and Marbling. 
 Carriage Painting. 
 The Wood Finisher. 
 
STANDARD BOOKS for 
 
 ELECTRICAL 
 
 WORKERS 
 
 Wrtiten by Practical Men For 
 Practical Men 
 
 HENRY C. HORSTMANN 
 
 and 
 
 VICTOR H. TOUSLEY 
 
 expert electricians, have prepared 
 this entire set of Electrical, Books 
 to meet the needs of the beginner, 
 the practical workman, ancj all who 
 have to do with electricity. 
 
 Seven Wonderful 
 Books 
 
 MODERN ELECTRICAL CON- 
 STRUCTION. 425 pages, 
 200 diagrams, pocket size, full 
 leather limp, price $1.50 
 
 MODERN WIRING DIAGRAMS 
 AND DESCRIPTIONS. 
 
 300 pages, 225 illustrations, 
 pocket size, full leather limp, 
 price $1.50 
 
 ELECTRICAL WIRING AND CONSTRUCTION 
 TABLES. 112 pages, fully illustrated, pocket size, full 
 leather limp, price $1.50 
 
 PRACTICAL ARMATURE AND MAGNET WINDING 
 252 pages, 128 illustrations, and tables, pocket size, full 
 leather limp, price $1.50 
 
 ELECTRICIANS' OPERATING AND TESTING 
 MANUAL. 346 pages, 211 illustrations and tables, 
 pocket size, full leather limp, price ..$1.50 
 
 MODERN ELECTRIC ILLUMINATION-THEORY and 
 PRACTICE. 275 pages, fully illustrated, pocket size, full 
 leather limp, price $2.00 
 
 DYNAMO TENDING FOR ENGINEERS or Electricity 
 for Steam Engineers. 203 pages, 110 illustrations, and 
 tables, 12mo, cloth, price $1.50 
 
 Sent postpaid upon receipt of price 
 
 FREDERICK J. DRAKE & CO. 
 
 PUBLISHERS 
 
 CHICAGO, ILLINOIS 
 
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