STEAM BOILER ENGINEERING JIELIOS Y- ^ (^ K fy r • -ir^r^ ^ U^ '-—.?' HEINE SAFETY BOILER COMPANY >0^ ■'^> ,,^' #' ^ '' ^. •^c >>, ■'c. t/> ,^\' A^" -5 •^... v-^^ 'f -^^ HELIOS CORRECTIONS Page 51. line 13 and 14 from bottom. For "H. C. Meinholdt" read "H. C. Meinholtz" Page 57, line 10 from bottom. For "10 lb." read "21/2 lb." Page 83. line 6 from bottom. Cross out sentence beginning "Its specific heat" Page 118, caption. For "Sixteen" read "Twenty" Page 401, Fig 193 caption, or or read and Page 607, line 6 from bottom. For "Fig. 263" read 'Tig. 264" Page 608, line 16 from top. For "Fig. 258" read "Fig. 259" STEAM BOILER ENGINEERING A Treatise on Steam Boilers and the Design and Operation of Boiler Plants Published by HEINE SAFETY BOILER CO. W hAanufacturers of water tube boilers Saint Louis, Missouri 1920 ^2, ^<^^^'^ •^\^ ^ V^"^ TWENTY-SEVENTH EDITION COPYRIGHT 1920 HEINE SAFETY BOILER COMPANY SAINT LOUIS, MISSOURI It has been decided to follow the usual practice of giving new numbers to all new editions and of repeating the edition numbers on reprints only. In conformity uith this, the previous editions have been renumbered as follows: Old Dates of New Edition Publi- Edition Numbers cation Numbers 1 1893 1 1 1893 1 2 1893 2 2 1893 2 3 1894 3 3 1894 3 4 1895 4 5 1895 5 5 1895 5 6 1896 6 6 1896 6 6 1896 6 7 1897 7 7 1897 : 7 1897 7 8 1899 8 8 1899 8 8 1900 9 8 1900 10 Old Dates of New Edition Publi- Edition Numbers cation Numbers 9 1902 11 9 1902 11 9 1902 12 10 1904 13 10 1905 14 10 1906 15 10 1908 16 10 1909 17 10 1910 18 11 1912 19 11 1912 20 11 1914 21 11 1916 22 11 1917 23 11 1918 24 12 1919 25 12 1919 26 Present Edition. .1920 27 Gift Publisher MAY i iS£1 ai 5 s-^ Heine Safety Boiler Co. Qeneral Offices ST. LOUIS, MO. «Ba<:> Plants St. Louis, Mo. Phoenixville, Pa. Branch Offices NEW YORK BOSTON PHILADELPHIA 11 Broadway 50 Congress Street Pennsylvania Bldg. PITTSBURGH Park Bldg. CHICAGO First National Bank Bldg. CINCINNATI Union Trust Bldg. NEW ORLEANS Godchaux Bldg. DETROIT Dime Bank Bldg. CLEVELAND Schofield Bldg. DENVER Stearns-Roger Mfg. Co. 1718 California Street Representatives DALLAS Smith & Whitney Southwestern Life Bldg. HAVANA, CUBA Oscar B. Cintas SAN FRANCISCO Dorward Engineering Co. Cunard Bldg. CHARLOTTE, N. C. Alexander & Garsed YOKOHAMA, JAPAN Takata & Co. TORONTO Henry Engineering Co. :3 o 173 O c ^m -If ^ » — i * " ■a OS > o X ml o -3 C CO X C (L) o 03 CO c CO ■i-l CO (U .S 'C Preface to Twenty-seventh Edition THE present edition of Helios is entirely new. Since the book was first published, almost twenty-seven years ago, steam engineering practice has been completely revolutionized. Our knowledge of fuels, of their proper combus- tion, and of steam-power applications has been developed to a remarkable extent. This new Helios is intended to summarize the latest commercial developments in boiler-plant practice. It was written, compiled and edited by the Research Department of the Heine Safety Boiler Co. for the large number of engineers and men with engineering interests who have to deal with problems of boiler plant design and instal- lation. The preface to the first edition of Helios, which appeared in July, 1893, was written by Col. E. D. Meier, founder and first president of the Heine Safety Boiler Co. This preface, which is reprinted on the next two pages, carries a message that is as true today as when it was written by Colonel Meier. Helios — a Text Book on Steam Boiler Engi- neering — is respectfully dedicated to all those interested in increasing the efficiency, economy and capacity of steam power-plants. Heine Safety Boiler Co. St. Louis, December 11, 1920. 10 HELIOS Source of All Poiuer I Fountain of Light and Warvrith I Adored by the ancient husbandman as the God who blessed his labors with a harvest of golden grain ; revered by the early sage as the great visible means of the divine creative force ; pictured b}' the inspired artist as the tire- less charioteer who drives his four fiery steeds daily across the heavens, his head circled by a crowd of rays, his chariot wheel the disk of the sun itself. When primeval man began to think, the sun seemed to him the cause of all those wonders in nature which ministered to his simple wants, or taught his soul to hope. His crude feelings of awe and gratitude blossomed into worship, and we find the sun as central figure in all early religions. He was the Suraya of the Hindoos, the Baal of the Phoenicians, the Odin of the Norsemen, and his temples arose alike in ancient Mexico and Peru. As Mithras of the Parsees, he was adored as the symbol of the Supreme Deity, his mes- senger and agent for all good. As Osiris he received the worship and offerings of the Egyptians, whose priests, early adepts in the rudiments of science, saw in him the cause of the annual fructifying overflow of the Nile. Modern knowledge, with its vast array of facts and figures, can but verify and seal the faith of these ancient observers. What they dimly discerned as probable is now the central fact of physical science. From him are derived all the forces of nature which have been j-oked into the service of man. All animal and plant life draws its daily sustenance from the warmth and light of the sun, and it is but his transmuted energv^ we expend, when, with muscle of man or horse, we load our truck or roll it along the highway. Do we irrigate the soil from the pumps of a myriad of windmills? His rays, on plains far inland, supply the energy for the breeze which turns their vanes. Does a lumbering wheel drive a dozen stamps and a primitive arastra in some Alexican canj-on? Do might}" turbines whirl a million flying spindles and shake thousands of clattering looms on the banks of some Xew England stream? From the bosom of the ocean and the swamps of the tropics, Helios lifted those vapory Titans whose lifeblood courses in the mountain torrent and the river of the plain. Do a hundred cars rattle up the steep streets of the smiling city b}- the Golden Gate? Are massive ingots of steel forged to shape and size by the giant hammers of Bethlehem? The fuel which gives them mo- tion was stored for us, ages before man was evolved, by the rays which flash from his chariot wheels ! "The heat now radiating from our fire places has at some time previously been transmitted to the earth from the sun. If it be wood that we are burning, then we are using the sunbeams that have shone on the earth within a few decades. If it be coal, then we are transforming to heat the solar energy which arrived at the earth millions of years ago." Professor Langley remarks that "the great coal fields of Pennsylvania contain enough of the precious mineral to supply the wants of the United States for a thousand years. If all that tremendous accumulation of fuel were to be extracted and burned in one vast conflagration, the total quantity 11 of heat that would be produced would, no doubt, be stupendous, and yet," says this authority, who has taught us so much about the sun, "all the heat de- veloped by that terrific coal fire would not be equal to that which the sun pours forth in the thousandth part of each single second." The almost limitless stores of petroleum which are found in America and in Asia, and the smaller, though still vast supplies of natural gas which some favored localities are now exploiting, represent but so much sun-energy trans- muted through forests of prehistoric vegetation. Another authority tells us that the total amount of living force "which the sun pours out yearly upon every acre of the earth's surface, chiefly in the form of heat, is 800,000 horse-power." And he estimates that a flourishing crop utilizes only four-tenths of one per cent of this power. Remembering, then, that this sun-energy reaches us only one-half of each day, we ma}^ ivliencver ive learn hoiv, pick up on every acre an average of 175 horse-power during each hour of daylight, as a surplus which nature does not require for her work of food production. Attempts to utilize this daily waste have been made, and future inventors may fire their boilers directly with the radiant heat of the sun. But whether we depend on what he garnered for us ages ago, or quite recently, or on the stores he will lavish on us in the future, it is clear that man's continued existence on earth is directly dependent on HELIOS. In olden times the various trades or guilds chose as their patron saint some prominent person who was thought to have embodied in his life-work the special means and methods of their craft. By that token we claim Helios as our own. He has always carried the record for evaporative efficiency. He provides both the fuel and the water for our boilers. He teaches us perfect circulation, upward as mingled vapor and water by the action of heat, and down again by gravity as rain and river in solid water. It is therefore fit that the boiler in which this perfect and unobstructed circulation is made the leading feature of construction should have HELIOS as its emblem. In the following pages we have some account of the fuels used in the practical arts, of the water which becomes the vehicle for transmitting their energy into mechanical power, and of the limitations imposed by their varying conditions. These must all be taken into account in estimating how much we may expect of certain combinations of machinery. We trust that the tables and data may be found convenient for ready ref- erence alike by professional men, by manufacturers, and by that growing class of practical steam engineers who realize that true theory, consonant with collective experience, is within the reach of every thoughtful man who pulls the throttle. E. D. MEIER. This explanation of the choice of the word HELIOS, as the name of this book, appeared as the preface of the first edition in July, 1893, and the word has ever since been a prominent feature of our trade mark. 12 CONTENTS Preface 9 Helios, by E. D. Meier 10 ChaD. 1. Heine Practice 15 :: rir.g Facilities Operation of Heine Boilers : :' r r Characteristics Adaptability service Installation iinal Drum Boilers Facilities for Cleaning Superheaters Cross Dm:: Fii.ers Marine Boilers Standard Specifications Chap. 2, Boiler Rating and Design Boiler Horsepower Heating Surface Ratios Heating Surface Gas Passages Grate Surface Baffling Chap. 3. Superheaters 00 Capacin- and Economy Water Circulation Steadiness of Water Level 69 -"\ r ^ 1 . Stea: ..ll-i Hl.iill.c; Limit of Superiteat Control ci Superheat Types oi St:p err. eaters Superheating Surface Superheater ^Materials Industrial Uses Chap. 4, Furnaces and Settings -^ ~^^; Lias: Powdered Coal Oil Burning Tar Burning Gas Burning Refuse Burning Waste Heat Marine Settings Refractor}- Materials Firebrick Radiation and Leakage Chap. 5, Mechanical Stokers Overfeed Underfeed 159 Chain Grate Chap. 6, Chimneys and Flues 173 ^izes ::•' -.rrsepower r raft ana Capacity- Draft Required for Co^l Sizes bv Gas Oil, Gas and \Vood Chap. 7, Mechanica. Forced Draft Fan Drives Operating Difficulties Evase Chimneys Chimneys at Altitudes Chimney Construction Self- Supporting Steel Guyed Steel ^raft ."-m Characteristics iting Fans Pitot Tube Radial Brick Reinforced Concrete Remodeling Breech ings Dampers 223 Ducts and Dampers Induced Draft Stack Connections Chap. 8, Piping and Accessories V. ater Hantnter Weight of Pipe Fipin^ S: stents Bursting Pressure I lent in cation by Color Pipe Fittings iNI ate rials Ranges Temperature and Strength Valves Standard Pipe Sizes Blow-off Piping 243 Steam Pipe Smes Water Pipe Sizes £^q>ansion and Contraction Pipe Anchors Expansion Joints Steam Separators Chap. 9. Auxiliaries 297 ^team rumps Centrifugal Feed Pumps Power Pumps Automatic Regulation Feed Water Regulator: Injectors Feed Water Heating Open Feed Heaters Qosed Feed Heaters Economizers Air Heaters Engines and Turbines 13 CONTENTS Chap. 10, Heat Insulation 347 Surface Resistance Bare Surface Heat Loss "85 per cent Magnesia" Diatomaceous Earth Conductivities of Materials Heat Transmission Insulation Materials Asbestos Thickness of Insulation Economy of Insulation Boiler Drums Boiler Walls Outdoor Pipe Lines Underground Lines Cold Water Lines Chap. 11, Heat and Combustion Theory of Heat Thermometry Absolute Temperature Thermodynamic Scale Thermometers 369 Chap. 12, Steam Entropy Expansion Saturated Vapors Pyrometers Combustion Heat Units Ignition Temperatures Specific Heat of Solids Air for Combustion Heat Transfer Properties of Gases Temperature Drop, Boilers Specific Heat of Gases 407 Steam Flow, Nozzles Saturated Steam Tables Superheated Steam Tables Superheated Vapors Peabody Diagram Mollier Diagram Chap. 13, Fuel Classification of Coals Location of Coal Deposits Composition of U.S. Coals Commercial Sizes Sampling Coal Analyzing Coal Heat Value of Coal Mahler Coal Calorimeter Chap. 14, Feed Water Impurities in Water Analysis of Water Hardness Test Alkalinity Test Causticity Test Chap. 15, Boiler Testing. Personnel Duration Simple Test Data Weighing Feed Water Weighing Coal Quality of Steam Chap. 16, Operation. _. Boiler Fittings Hand Firing Cleaning Fires Firing Tools Banked Fires Quick Steaming from Bank Load Signals Smoke and Cinders Carbon Dioxide Ash Clinker Storage of Coal Deterioration in Storage Spontaneous Combustion Briquets Coke Tan Bark 435 Bagasse Liquid Fuels Tar Colloidal Fuel Gaseous Fuels Junker Gas Calorimeter High and Low Heat Values Specifications 499 Concentration Test Mechanical Treatment Thermal Treatment Chemical Treatment Zeolite Process Starting and Stopping Simple Test Report Simple Test Calculations Complete Test Data Flue Gas Analysis Complete Test Report Boiler Compounds Priming Foa i^ r Co on Sc . 513 jmplete Test Calculations Heat Balance Efficiency Accuracy Steam Used by Auxiliaries Liquid and Gaseous Fuels 551 Carbon Monoxide CO2 Recorders Draft Regulation Economical Operation Control Boards Measuring Water Metering Steam Weighing Coal Handling Coal Storing Coal Submerged Storage Conveyors Handling Oil Fuel Cleaning Boilers Renewing Tubes Care of Idle Boilers Boiler Inspection Steam Cost Accounts 14 Heine Standard Two Pass Boiler with Setting for Hand Firing. 15 CHAPTER 1 HEINE PRACTICE THE first Heine Boiler was designed by Colonel E. D. Meier and built in St. Louis in 1882. It is still in first-class working order, and is open to public inspection at the St. Louis Plant of the Heine Safety Boiler Company. Colonel Meier founded the Heine Safety Boiler Company in 1884 and was president of the company until his death in 1914. Heine Boilers have been built without interruption since the com- pany was founded ; the fact that many of those sold in the 'eighties are still in operation, testifies to the superiority that has always characterized them. This long period of operation, in conjunction with up-to-date factory methods and equipment, has enabled the Heine Company to build up an organization of experts in boiler design, manufacture, and operation. There are two plants — St. Louis, Mo., and Phoenixville, Pa. Each plant has complete manufacturing facilities, and consequently is an entirely independent source of supply. The general offices of the company are at St. Louis. Heine Boilers are of two general classes, longitudinal and cross drum. While the longitudinal drum type is the standard for land service, many Heine users prefer the cross drum on account of the low head room required. They are built in both types for marine service, though the cross drum is general practice for this work and the recognized standard. All Heine Boilers for land service are built to conform to the requirements of the Boiler Code formulated by the American Society of Mechanical Engineers, notwithstanding that weaker (and cheaper) construction is permitted in many states. In this code are incorporated the most rigid requirements for boiler construction and materials. Heine Boilers for marine service are built in accordance with the rules and regulations of the United States Board of Supervising Inspectors. They are approved by Lloyds' Register of Shipping and by the American Bureau of Shipping. 16 o ■*-> c CO V C g CO a; ■4-> CO < > o o o H E T N K P R A C T T C E 17 Heine Manufacturing Facilities THE two large plants owned and operated by the Heine Safety Boiler Company are shown on pages 6 and 7. Both are fully equipped with electric, hydraulic and pneumatic machinery, as well as with powerful cranes and hoists for handling the heavy weights involved in the manufacture of boilers. Steam is generated at each plant by a battery of Heine Boilers. At each plant the powder equipment — steam turbines, generators, condenser and cooling tower, engines, hydraulic pumps and accumulators, air-compressors — is installed almost entirely in dupli- cate, every precaution being taken to avoid a shutdown. Parts of the turbine-room and of the engine and pump rooms of the St. Louis plant are shown on pages 16 and 18. The power plant at Phoenix- ville is similar to that at St. Louis. The boiler-making tools found in the Heine plants include rolling and bending machines, flanging and forging presses, hydraulic riveters, punches, shears, steam hammers and forges, heating and annealing furnaces, for various purposes. Lathes, drill presses, boring mills, and other machine tools are used. Special machines and equipment, designed and built by the Heine Company, are employed for various purposes such as for accurately reaming rivet and tube holes. The larger electrically driven machines have individual motors, while the smaller machine-tools are belted to motor-driven line-shafts. Page 20 shows a heavy flanging press and one of the large steam hammers in the St. Louis plant. Portable hydraulic riveters are used for some operations, such as riveting waterlegs to the drums, shown on page 24. Hydraulic "bull"' riveters, page 26, are installed in towers equipped with high overhead cranes for handling boiler drums and other long parts. Page 22 shows part of the machine shop at Phoenixville. Page 30 shows the testing floor at St. Louis. In the sheet iron department, parts not subjected to pressure are fabricated, such as internal mud drums, deflection plates, boiler fronts and breechings. Ten Characteristics of Heine Boilers CERTAIN features of design and construction insure continuous, satisfactory service from all types of Heine Boilers. They can be summarized as follows : 1. Workmanship. Heine Boilers are built by expert workmen, in modern shops equipped particularly for the production of high- class water-tube boilers. The materials and the construction of every Heine Boiler conforms with the rules and regulations issued by the highest authorities. This means that Heine Boilers comply with the best standards as regards safety, economy and durability. 18 o c e o o G "So w PIEINEPRACTICE 19 2. Strength. The construction of the waterlegs or headers, flanged plates with ample staybolts, is approved and widely accepted practice. It has given the greatest satisfaction under such severe service as in the locomotive boiler and the Scotch marine boiler, and is highly commended by the foremost boiler authorities of all countries. It avoids welding, and permits better general design and accessibility, closer tube spacing, easier, freer circulation and less punishment of material during construction than do any of its sub- stitutes. The unusual strength of structure obtained by the direct connection of the drum and headers, virtually makes the Heine a ''one-piece" boiler, well qualified for prolonged hard service. The first Heine boiler built was used continuously for 35 years, after which period an inspection by The Fidelity and Casualty Company showed that it was still in proper working condition. 3. Overload Capacity. Heine Boilers are adapted for operation at high overloads, because of the unusual provision for rapid circulation, the large combustion space and the method of baffling. 4'. Water Purification. In the Heine Boilers a large proportion of the scale-forming impurities in the feed-water are deposited in the internal mud drum, and are thus prevented from accumulating on the heating surfaces. The ordinary mud drum is simply a recep- tacle for the collection by gravity (even this is hindered by the water circulation) of impurities precipitated within the boiler. With the Heine internal mud drum the new feed- water must be at least partly purified before it enters the water circulating in the boiler. The solids deposited are not hardened by heat, but remain in the form of a sludge, which can be easily blown oft'. 5. Free Circulation and Dry Steam. These are attained in the standard Heine Boiler by the use of spacious headers at each end of the tube nest, which are connected to the drum by large throat passages. The generated steam has ample room to escape without pulling water along. In the cross drum boiler, free steaming ability is promoted by a device in the upper part of the rear box header, which effects a primary separation of the steam and water. The return water circulation is along the upper tubes of the main bank The steam passes along the horizontal tubes and the final separation takes place in the cross drum. 6. Tube Design. Straight tubes, as used in the Heine Boiler, are the easiest to clean, install, examine, and renew ; they give max- imum efficiency and the best circulation. 7. Heating Surface. The gases flow parallel with the tubes in the Heine Boiler. After entering the nest of tubes, they do not leave it until they are discharged to the breeching. This method of gas passage has been proved to give the highest rate of heat trans- mission with the least draft loss. HEINE PRACTICE 21 8. Combustion Chamber. This is of ample size so that the gases are thoroughly mixed and burned before they strike the cool heating surface. The lower baffhng forms the roof of a reverbera- tory chamber, providing ideal conditions for perfect combustion. 9. Floor Space. The compact arrangement of heating surface due to the close tube spacing, lessens the floor space and head room required. Any number of Heine Boilers can be set in a single battery ; alleyways are unnecessary, so that the saving of space is large. Boilers set in a solid battery are immune from most of the losses by air infiltration and radiation. 10. Cleaning Facilities The outsides of the tubes are cleaned quickly and thoroughly by a soot blowing system operated from the front and back, and provided with every boiler. Side-wall dusting- doors are unnecessary, and their absence greatly reduces the air in- leakage, insuring a high percentage of CO2 with consequent fuel economy. Since straight tubes only are used, the inside surfaces are easily inspected and cleaned through the handholes in the water- legs. In the cross drum boiler, the tubes and nipples connectuig the drum with the box headers are quickly cleaned through the manholes provided. Section of Drum and Waterleg of Heine Standard Boiler. Note the Large Throat Area. o 4-1 c a a o CO a; C 'Xi u CO H E I N E P R A C T r C E 23 Heine Service THE Heine Safety Boiler Company maintains an Engineering De- partment for the assistance of its clients in the arrangement and improvement of new and existing boiler plants. Experience in the installation of boilers in plants of widely diversified size and type, qualifies us to recommend the best method of procedure to meet the conditions prevalent in any particular plant. This service covers not only boiler and furnace design for the various types of fuel and operating conditions, but includes recommendations as to building design, coal and ash handling equipment, piping, stacks, breech- ings, etc. The Research Department, besides being engaged upon new de- velopments in boiler engineering, is constantly rendering assistance in such problems as the efficient handling and combustion of all kinds of staple and refuse fuels, special furnace and boiler settings, baffling to meet unusual conditions, recovery of heat from waste gases, chimneys, draft, etc. The Library contains a copy of almost every domestic and foreign work on power plant engineering, besides a large collection of references on every conceivable phase of boiler practice. This information is at the disposal of our clients. The continuous satisfactory performance of every Heine boiler is our vital concern as well as that of the customer. Our interest in the boiler does not cease when it has left our shop. A Trouble De- partment is maintained, composed of technically and practically trained engineers whose principal duties are to assist our clients in overcoming any difficulties which may occur in boiler operation. This service includes such investigations as the study of firing methods, scale formation or priming due to poor water conditions, boiler inspection, boiler testing, etc., etc. There are sixteen branch offices and three distributing ware- houses for repair parts. The production of parts in large quantities by modern manufacturing methods, the storage of patterns, etc., results in the supply of renewals at small cost; and an eft'icient system of records of every ETeine boiler since the first, insures prompt shipment. Standard Longitudinal Drum Boilers THE standard ITeine Boiler, shown on pages 8 and 14, consists of a cylindrical shell or drum to which box-shaped headers (water- legs) are riveted at each end. These waterlegs are connected by the main nest of tubes. t Jifr - iH ^ 41^ ~~4P -' C? €> CI ^i^ > as u >> (S U O CO c > (2 HEINE PRACTICE 25 The drum consists of three sheets, riveted in accordance with the approved rules. It varies in diameter from 30 to 48 in. and in length from about 17 to 22 ft., according to the horsepower required. The longitudinal seams are of the double-strap butt-joint type, while girth or circumferential seams are of the lap-joint type, single or double riveted. The design of the riveting depends upon the pressure to be carried. The heads are dished to a radius equal to the diameter of the shell, and thus require no internal staying. A flanged manhole, pro- vided with a pressed steel cover, forms part of the rear head. The main steam outlet and the safety valve are attached to pressed steel saddles, riveted to the top of the drum near its front end. The material for both waterlegs and drums is the best firebox steel plate, made especially to Heine specifications and tested before shipment. Hollow Staybolts of Heavy Gauge Steel Tubing. The waterlegs are connected to the bottom of the drum near each end by a throat opening, page 21, braced by forged steel throat stays, page 46, which are riveted across when the waterlegs are attached. The waterlegs consist of two plates — the tube sheet and the hand- liole sheet. These plates are machine-flanged and are joined by a narrow plate similar to a butt-strap. The waterlegs are stayed by hollow staybolts made of carefully tested mild steel tubing ; these are screwed into tapped holes in the two plates, and the projecting ends upset from the outside. The tube holes and handholes are located accurately and bored to exact diameters. The waterlegs are built complete and then hydraulically riveted over the throat openings. The handholes are round, except a few at the top and bottom, which are oval and are used for the introduction of the round plates into the waterlegs. The handholes are closed in three different ways ; by strong cast iron plates ; by drop-forged steel plates ; or by the Key pressed steel handhole caps. All of these are inserted from the inside so that the steam pressure tends to tighten them, and does not loosen them as in the case of plates applied from o CO u CO C/3 m C •4-< a; > u O «4-l (U > 3 08 u >> u CO (U a a "5 cr (U V-i o H 13 HEINE PRACTICE 27 the outside. The plates are held in position by bolts and yokes, the latter bearing against the outside of the handhole sheet. Gaskets are required with the plates, but not with the Key caps which are rolled in slightly tapered holes so that the pressureVithin the boiler tends to hold them more tightly. Lap-welded steel tubes are supplied with the Heine Boiler, but charcoal iron or seamless steel tubes can be supplied as optional equipment. The tubes extend between the two waterlegs, and are (b) Handhole Closures, (a) Cast Iron; (b) Drop Forged Steel; (c) Key Pressed Steel Handhole Caps. expanded into the tube sheet by roller expanders. The tube ends are slightly flared to increase the holding power. The baffling on Heine boilers is varied somewhat according to the conditions of operation. Page 8 shows the single-pass, and page 12 the two-pass system. The simplest arrangement is to place the baffle tile on the lowest row of tubes, and a second baffle on the second row of tubes from the top, giving a single pass of the gases through the tube nest. The lower baffle may be placed on the third row of tubes from the bottom, thus giving a partial pass through the three lower rows, and a complete pass through the remainder of the nest of tubes. In still another arrangement one baffle is placed on either the first or third row of tubes from the m HEINEPRACTICE 29 bottom, and another baffle introduced a little more than half-way up the height of the tube nest, thus giving the products of combus- tion two full passes through the nest of tubes. The baffle tiles are designed to rest on or between the tube rows. The bottom row is formed of specially shaped fire-clay tile, while the upper and middle rows are either fire-clay or cast iron shapes, according to conditions. Heine Superheaters THE standard Heine Superheater, page 34, is placed at the side of the drum toward the front. It may be single — on one side, or in two parts — one on each side of the boiler. One or two units are used, according to the capacity and degree of superheat required. The superheater consists of a header box divided horizontally into three compartments, and with U-tubes inserted into one side and bridging the partitions. Steam from the boiler enters the lower compartment, passes through the lower nest of tubes into the middle compartment, then through the upper nest of tubes into the upper compartment, from which it issues. These passages effect a thor- ough mixture of the steam and ensure a uniform temperature. A small flue built in the side-wall carries part of the hot gases direct from the furnace into the rear of the superheater chamber. After making a first upward pass over the outermost ends of the tubes, the gases make a second downward pass over the rest of the tube surface ; and after leaving the superheater chamber pass along the boiler drum, thus giving up the remainder of their available heat. The header box is built with one seam and one row of rivets, the caulking edge being to the front. The two sheets of the box are braced by hollow staybolts. Access to the interior is gained by handholes closed by inside plates, which are placed opposite the tubes. The U tubes are Ij/^-in. diameter, of seamless steel. The superheater chamber is of brickwork, with a firebrick roof carried by T-bars. The front of the superheater is closed in by doors, which prevent radiation and give access to the header box. A damper in the outlet of the superheater chamber controls the flow of gases ; there is no danger of its becoming overheated, since the gases do not come in contact with it until they have been cooled by passing through the superheater. The damper is regulated by hand from the front of the boiler, or an automatic thermostatic control regulates the superheat to within 5 deg. above and below the temperature desired. A full and illustrated explanation of the temperature control, as well as a discussion of the dangers result- ing from uncontrolled and excessive superheats, is given in "Super- heater Logic," which also contains a complete description of the construction of the superheater. This Heine publication is mailed on request. o 2; c CO c H C ca C o u HEINE PRACTICE 31 No scale is deposited in the tubes because flooding of Heine superheaters is unnecessary. Closing the damper isolates the tubes from the hot gases, and then only saturated steam is delivered. The superheater is built complete and tested before shipment, so that it is ready for erection upon arrival. The arrangement is such that it can be cleaned easily and thor- oughly while in operation, insuring efficiency, close temperature regulation, and economy. The tubes are smooth and therefore accu- mulate very little soot ; this is easily removed by a steam lance passed through the hollow staybolts, or by a permanent soot blower similar to that on the boiler. Adaptability of Heine Boilers HEINE Boilers suit the conditions and plans of any power plant. There are no doors in the sidewalls and no aisles are required between boilers, because all cleaning, inspection and tube renewals are done from the front and back. Consequently, any number of boilers may be set in single battery and this materially reduces the cost of brickwork. With center-retort and side-feed stokers, hand firing, oil or gas firing, the space required is greatly reduced as is seen by comparing with layouts of other standard boilers ; and this lowers the cost of the boiler house. Such plants are generally simplified as there are no aisles to bridge, and this also applies to piping arrangements Operating efficiency is noticeably increased owing to the shorter flues, elimination of sidewall radiation and infiltration of air, and avoidance of air-leakage through sidewall cleaning and dusting doors and the numerous cracks inevitably starting from them. Heine boilers are running satisfactorily with stokers and mechan- ical furnaces of every standard type. All kinds of fuel are being successfully burned under them — fuel oil, gas, pulverized coal, tan bark, bagasse and sawdust. They are giving excellent service under the most varied conditions of power production, manufacture and process, where steam is required either steadily or in heavy and irregular drafts. The unusual adaptability of Heine Boilers for the utilization of waste heat from kilns, stills, metallurgical furnaces and other pro- cesses is discussed in Chapter 4. Installation of Heine Boilers HEINE Boilers of 500 H.P. or less are shipped completely assem- bled, page 36, while the larger sizes are knocked down for shipment, page 38. For export, they are shipped in separate parcels, containing the tubes, the central part of the drum, and the waterlegs with short section of drum attached. The cross drum boilers can be shipped entirely knocked down, page 40, the headers and drum o G a o CO ■M (/3 > o bO •i-i > HEINEPRACTICE 33 being complete in all respects so that assembling consists only of expanding the tubes. When set up ready for service, the Heine Boiler inclines upward from rear to front at a slope of one in twelve. The front end of the boiler is carried by heavy cast iron columns. For hand-firing, the waterleg rests directly on the columns ; while for stoker firing, brackets riveted to the waterlegs are supported on the columns, or the front of the boiler is carried on an overhead support. The rear end rests on rollers bearing on iron plates which are set in the top of the low brick wall forming part of the setting. These rollers permit expansion and contraction and avoid injurious strains. On each side of the boiler is a solid brick wall lined with fire- brick and carried to the height of the ornamental front. Returns are made at both front and rear, following the curvature of the drum and waterlegs, the weight of the brickwork being carried by metal supports. The space between these supports and the boiler is filled with asbestos fiber, w^hich prevents the ingress of air. The space prevents any displacement of brickwork due to expansion and contraction of the boiler, since the walls are supported independently and slightly away from the boiler. The brickwork is tied together by longitudinal and transverse anchor bolts secured at each end of the setting and at several places on the sides to substantial rolled steel buckstays. The top of the setting is closed on each side of the drum by cast iron plates, which rest on the sidewalls and on a tile- bar carried by brackets attached to the drum. Openings are left at the rear for the exit of the gases. A brick arch is built over *he drum to prevent radiation, and is of firebrick in the uptake. Over the uptake openings, and supported by the boiler walls, is placed a breeching hood of suitable shape to connect with the breeching. The cast iron fire fronts carrying the fire and ash door frames are bolted to the supporting columns, and a substantial firebrick w^all is built inside to prevent overheating. The fire fronts support the upper ornamental front, page 42. Large doors are provided at both front and back for access to the w^aterlegs. Stationary grates are ordinarily furnished, but shaking grates or any other form of furnace or stoker can be substituted. Stokers are frequently set directly under Heine Boilers owing to the large com- bustion space, and no more floor space is then occupied than with hand-firing; but it is often advantageous to use an extension furnace or Dutch oven. The Dutch oven is generally the best arrangement for burning sawdust, shavings, tan bark, bagasse and similar fuels, owing to the large furnace chamber desirable and the convenience of the top-feed. Methods of applying stokers and furnaces are shown in Chapters 4 and 5. 34 X \."^-"\-'S'T'X Heine Standard Superheater. HEINE PRACTICE 35 Operation of Heine Boilers THE water circulation and steam separation in the Heine Boiler are absolutely definite. The capacious headers and large throat openings allow a freedom of flow unattainable with sectional headers. The throat openings are from two to four times the area of the tubes which connect sectional headers to their drums. The resistance at the entrance of these tubes and of the zig-zag path along sectional headers is a further obstruction to circulation. Heine box-headers are common to all the tubes, and water enters the tubes round their whole circumference, whereas side-entry is cut off in sectional headers. The slope of the Heine drum provides deep water at the rear for the effective supply of the back header. The water rises through the large throat into the Heine drum at a suft'iciently low velocity to allow of efficient separation of the steam by the deflector plate ; while the steam and water is shot with considerable violence from the single tubes of sectional headers, making the drying of steam uncertain. The water surface in the drum is more than ample, for steam is not disengaged from it as in tank and fire-tube boilers. What little circulation there is in fire-tube boilers, is entirely haphazard, and the water surface must be large because the steam is disengaged at any point. In the Heine Boiler the circulation is vigorous and orderly, and the steam is separated from the water by a properly arranged deflector at a definitely established point over the front throat passages, page 46. The deflector plate throws down the water and allows the steam to pass quietly into the steam space above ; it then enters the dry pipe connected to the steam outlet. A salient feature of the Heine Boiler is the internal mud drum, in which the feed-water is partly purified and heated to the boiling point before it enters the water in circulation. The feed-water pipe enters through the top of the drum and passes down to the front end of the mud drum. The mud drum is entirely submerged ; and as the entering water is colder and therefore heavier than the water already inside, it travels along the bottom and becomes heated gradually. The mud drum is large enough to permit of such slow motion of the water that the dissolved impurities thrown down at steam temperatures have time to be deposited, together with mat- ter carried in suspension. As the water becomes heated, it rises and finally flows in a thin sheet, through the opening in the top of the front end of the drum, into the circulation system. It is therefore possible to drive the Heine Boiler at heavy loads with very cold feed- water. As the matter deposited is not subjected to fire tempera- tures, it does not tend to become baked and hard, but remains as a sludge easily blown out through the pipe at the rear of the drum. Q c o o (U u w o (4-1 CO 0) o PQ G o J3 HEINE PRACTICE 37 Because of the internal mud drum, the Heine Boiler works much more satisfactorily than any other boiler when only cold and dirty water are available. But it is always more economical to treat impure water before feeding it into the boiler, and to pre-heat it with waste steam or waste hot gases. The boiler is drained through a valve at the bottom of the rear waterleg. The steam connection of the water column is made at the top of the front head, and the water connection at the top of the waterleg. The pressure gage is attached to the middle of the orna- mental front and piped from the water column connection. The gases of combustion — whatever type of furnace or stoker is used — pass over the bridge wall into a large combustion chamber. The bridge wall is low enough to provide ample area between its top and the tubes. The large combined capacity of the furnace and combustion chambers is one of the outstanding merits of the Heine Boiler. Plenty of time and space is provided for the thorough mixture and complete combustion of the gases before they come in contact with the comparatively cool heating surfaces. This pro- vision for complete combustion, and the consequently improved efficiency and reduction of smoke has been proved so valuable that the Heine method has replaced the vertical baffling of many hori- zontal water-tube boilers and has even replaced the method of baffling of some types of vertical water-tube boilers. In Heine Boilers, the gases travel parallel to the tubes, except when entering and leaving the tube bank. This parallel flow is used whether the gases make one or more passes. With parallel flow, the gases completely encircle the tubes. When the gases flow across the tubes, as in cross- or vertically-baffled boilers, a dead pocket occurs on the ''down-stream" side of each tube. This effect can be seen by watching the almost stagnant water at the down-stream side of the piers of any bridge crossing a swiftly flowing river. Owing to the close tube spacing possible by the rational design of Heine header, the gases are broken up into smaller streams than is usual, so that the whole volume of gas is brought into intimate contact with the tube surface. That more efficient heat transmission is attained with parallel flow than with cross flow, has been frequently demonstrated in tests of cross-flow boilers that have been changed to parallel-flow. It is important that the gases should be kept in contact with the heating surface until all the available heat is absorbed. In all cross- or vertically-baffled boilers, however, the gases are twice taken entirely away from the tubes, where they waste heat by radiation. In addition to the evident waste of heat, the hot gases from the first pass flow along the bottom of the drum causing ebullition in the wrong place, the avoidance of which should be one of the main advantages of the water-tube boiler. Another advantage of the Q Xi (L> 4J O V U W c (U 3 6 D CO C o Q ID U o c o pq (U CO •-) a "a a CO (*-■ o o J3 HEINE PRACTICE 39 water tube boiler— that of keeping hot gases away from the drum and from riveted joints — is absent in cross baffled boilers. In the Heine Boiler, the gases are confined to the tube bank until they have parted with nearly all of their available heat. Not until then do they come in contact with the drum; consequently the last of their useful heat is given up without disturbing the quiet flow of solid water to the rear. The construction of the Heine Boiler combines sturdiness and resiliency. Water is boiled and steam generated in the bank of tubes and not in the drum or shell The gases are kept where they belong —among the tubes — until discarded to the uptake. The circulation path is farge and unrestricted, making the flow of water and steam slow enough for efficient separation— or for dry steam and a solid water stream. ^ Soot Blowing System, Side Elevation. HEINE PRACTI CE 41 Cleaning of Heine Boilers ALL cleaning — both inside and out — is performed from the front and rear. There are no openings in the sidewalls, or aisles between boilers. Soot and dust are blown from the tubes by a soot blower, which is provided with every Heine Boiler. It consists of a series of small nozzles which pass through the hollow stay-bolts, and which are supplied from permanent headers, so that the only manual labor required is to open and close the valves. The jets of steam issuing from the main nozzles create an intense momentary draft Rear View o O'-o^a'O'O'O'O'O o' I di'o°o«q£p<'0<>c>o°o»a- ' 0°OaO°0°OiP'0°OaO»Q-'^ imifMloP .o9^# ig9fg#oj'S ?J Soot Blowing System. Standard Fire Front of Heine Cross Drum Boiler. HEINEPRACTICE 43 which effectively dislodges the soot and dust and carries it to the uptake. The auxiliary jets are so located as to stir up accumula- tions on the baffling and in all corners. This work is done in a few minutes, generally during the noon rest, or just before or after closing down at night. It is so easy as to be entirely out of com- parison with the old-fashioned *'steam-lance," whose use is naturally neglected whenever possible. Thorough cleaning is immediately profitable as may be seen by the quick drop in temperature of the exit gases. Cleaning doors are provided on each side of the drum so that accumulations of dust and soot can be easily and quickly removed from the space over the upper baffle beneath the drum. The com- bustion chamber is cleaned through a door in the wall under the rear waterleg. The interior of the drum is thoroughly inspected through the manhole in the rear head, which also permits of attention to the mud-drum, deflection plate^ etc. The inside of the tubes is washed by a stream of water directed through some of the handholes. Only a few of the handholes need be opened for this purpose, since each gives sufficient access to four or five of the surrounding tubes. In scraping the tubes, however, each handhole must be opened to admit the scraper, although in both this and the washing process the handholes at one end only are opened. As only straight tubes are used, every part of the boiler can be reached, properly and quickly cleaned, and visually inspected, so that there is absolutely no uncertainty as to its condition. Renewing tubes is done from the outside as in cleaning tubes, the men standing erect and working comfortably and quickly. The inside of the box-waterleg is easily cleaned and inspected, because all the hand holes give light and access to one space. Heine Cross Drum Boiler— Land Service THE Heine Cross Drum Boiler for land service, page AA, consists of two box headers carrying a nest of inclined tubes and of a drum placed above and across, slightly to the rear of the front or lower header. The drum is connected to the top of each header by a row of tubes — short, nearly vertical, to the front header — and long, nearly horizontal, to the rear header. The main nest of tubes, with the headers, form a virtually closed or complete circulation system of remarkably low resistance owing to the capacious headers. The steam rises in the rear header, where its primary separation from the water is promoted by a device at the upper part. It then flows along the almost horizontal tubes, parting with most of the entrained water by gravity, to the final separator in the steam drum, where it is dried by centri- fugal action set up by a deflector. The water carried into the drum 44 Longitudinal Section of Heine Cross Drum Boiler with Chain Grate Stoker. HEINE PRACTICE 45 is returned, together with the new feed water, to the circulation system through the short tubes leading into the top of the front header. Steam is drawn from the ample storage space through a dry pipe extending nearly the whole length of the drum and pro- vided with small holes on the upper side. This closed circulating system and the means used in collecting and drying the steam while maintaining quiet water in the drum, is the outcome of exhaustive and prolonged research into the direction and velocity of flow in the different rows of tubes. As a result the tubes and baffling have been so proportioned and arranged that the overload performance of Heine Boilers of this type is acknowledged by users as a notable achievement. The mud-drum is constructed and operated on the same prin- ciple as that employed in the longitudinal drum boiler, described on pages 19 and 35. The movement of the feed-water therein is very slow, so that dissolved impurities which are thrown down at steam temperatures are deposited, as is matter carried in suspension. As the deposit is not hardened by exposure to fire temperatures, it remains as an easily blown-off sludge. Owing, also, to the slow movement of the feed water in the mud drum, it is heated to the boiling point before passing into the circulation system, so that Heine Boilers can be heavily driven with cold feed water. As the water issues from below the surface in the mud-druVn, any oil accu- mulated does not enter the boiler proper, but is discharged through the blow-off. Except in large boilers, the drum is made of a single sheet, with longitudinal double-strapped butt-joints. The heads are dished to a radius equal to their diameter, so that internal staying is not re- Cjuired. One head is generally provided with a flanged manhole with pressed steel cover and yoke ; but when more than two boilers are set in battery, the manholes of all but the end boilers are placed in the drum proper instead of in the head. A reinforcing plate is riveted to the drum, where each row of tubes enters. Forged steel pads are provided for the feed, blow-off, and water column connections, and pressed steel saddles, page 44, for safety valve and main steam outlet — all shaped to a snug fit on the drum, and either threaded or with stud-bolts to fasten the connections. The box headers consist of two heavy steel plates with long radius flanging at top and bottom and with flat parts formed at the proper angle to allow the drum tubes to enter squarely ; these plates are fully annealed before assembling. They are connected by a single-riveted lap joint, no butt straps being required. The resulting boxes are closecl by trough-shaped end-plates, flanged by hydraulic machinery at a single heat to a close fit, and riveted to the side plates. The holes in the tube and handhole sheets are accurately located and bored to exact diameters to secure proper angular relation between the drum tubes and those of the main bank. 46 o •a c C3 -4-1 w .s c o o CO .s •5 •4-> c o HEINE PRACTICE 47 These headers are stayed by hollow staybolts, page 25, of tested seamless tubing, which are screwed into tapped holes in both plates and the projecting ends neatly upset. The handholes are opposite the tube ends and are closed by one of several methods — cast iron or drop forged steel plates and gaskets making joints on the inside, or the Key handhole caps which are expanded in and require no gaskets, page 27. The tubes are the best quality lap-welded mild steel, made espe- cially to Heine specifications. They are 35^-in. diameter, secured by roller expanders and the ends flared for additional strength. The steam drum and the lower header are usually at the front end of the boiler, but to save head room this arrangement can be reversed. The front of the boiler is carried by columns which are secured to heavy lugs riveted to the header end plates. These columns are made of any length to give the desired height of furnace. Similar heavy lugs are riveted to the rear header, and these are connected to the rear columns by massive suspender bars. This provides a flexible support which allows for expansion and contraction due to temperature changes. The whole boiler is enclosed by brick side-walls, the rear wall being underneath the rear header. The top is closed by fire-brick and insulating covering, carried by T-bars resting on the side-walls. Casing doors at front and back give access to the headers for cleaning and inspection. Safety valves of proper size, a large high and low w^ater alarm column with quick acting shut-ofif device operated from the floor by chains, and three try cocks, are provided. A steam gage is attached to the boiler front, and feed, check and blow-of? valves are supplied and located so as to be easily accessible and conveniently manipu- lated. The required buck-stays, cleaning doors and anchor rods are supplied. The soot blower system applied to the cross-drum boiler consists of the nozzles inserted through the hollow staybolts of the rear header. The main jets create an intense momentary draft, which dislodges the accumulations from the tube surfaces and carries them to the uptake. Auxiliary nozzles are so located as to stir up and dispose of any accumulations on the baffle tiling. Heine Marine Boilers THE Heine Cross Drum Marine Boiler, page 50, is similar to the cross drum boiler for land service, the main difference being that it is shorter due to the lack of space. The standard marine boiler has 3^-in. tubes throughout ; but for oil-fuel, space is saved and sat- isfactory results obtained by the use of 2-in. tubes in the main bank. o a 73 u o m X 'a C/2 o J! HEINEPRACTICE 49 For low or medium superheat temperatures, superheaters of the type used for land installations are fitted. They are of the "waste- heat" kind, placed in the base of the uptake, as close as possible to the exit of the gases from the boiler. For higher superheat, the elements are passed through the middle of the main tube bank, where they are in contact with gases of high temperature. In ocean service the feed water cannot be kept entirely free from sea water, which sets up electrolytic action. Zinc plates are there- fore placed in the drum to act as the electro-negative agent and prevent corrosion. In the Heine Marine Boiler the United States Navy standard is used — ^ sq. ft. of exposed zinc for each 100 sq. ft. of heating surface — and the zinc plates are so secured as to ensure perfect electrical contact with the metal of the boiler. At the same time they are easily removable. A pressed steel basket is provided to catch the disintegrated zinc. The setting consists of a framework of rolled steel shapes so constructed that the four main columns — one on each side of each box header — are tied and securely braced against any motion. This framework carries a steel plate casing lined with firebrick, non- conducting material, or a combination of the two. The construction and operation of Heine Marine Boilers is explained more completely in another Heine publication — Marine Boiler Logic — which is sent upon request to those interested. Standard Boiler Specifications A NATIONAL and even an international standard of steam- boiler design is represented by the Boiler Code formulated in 1914 by the American Society of Mechanical Engineers, and since that time kept up to date by frequent revisions. The value of the Code is indicated by the fact that it has been adopted by more than tw'elve states in this country, by foreign countries, and by branches of the U^nited States Government. For many years the necessity of uniform boiler specifications has been recognized both by makers and users of boilers. In 1889, the American Boiler Manufacturers' Association adopted what were known as the Uniform American Boiler Specifications. These speci- fications, which were revised in later years, gave information relating to material, construction and calculation for all kinds of boilers. In this fundamental work Col. E. D. IMeier, founder and president of tlie Heine Safety Boiler Co., until his death in Decem- ber, 1914, took an important part. Colonel Meier was chairman of the committee which prepared the first specifications in 1898, was presi- dent of the American Boiler Manufacturers' Association from 1908 to 1914, and was its secretary for several years previous to 1908. 50 WATCRUINE GAUGE 6LAS CHECK VALVE DRAIN PAN COUNTERWEIGHT FIRE ASK DOOR FRONT COLUMN Longitudinal Section of Heine Cross Drum Marine Boiler. HEINE PRACTICE 51 In 1907 a board was appointed by the state of Massachusetts to prepare a set of boiler rules. The members of this board repre- sented different boiler interests, such as the users, makers, insur- ance companies, and operating engineers. The chairman of the board was the chief inspector of the Massachusetts Boiler Inspec- tion Department. The Massachusetts boiler rules were issued in 1909 and engineers considered that they represented a real advance in the art. From a national standpoint, however, the Massachusetts rules simply made one more set of conditions with which the boiler manufacturers and users had to comply. A boiler that is safe in Massachusetts certainly should be safe in any other state of the Union, but practically every state (at least in 1911) had special re- quirements for boiler construction, and these were rigidly enforced. The remedy for this condition was found by Colonel Meier; he had already noticed the beneficial working of the Steamboat and Locomotive Inspection Laws under Federal control. The best an- swer to the problem was to have the different states adopt uniform specifications for boilers, since a constitutional amendment would be required to put stationary boilers under Federal supervision. The different state legislatures and other authorities were willing to use such specifications, provided they could be assured of their value. In 1911 Colonel Meier, then president of the American Society of Mechanical Engineers, suggested that a committee of the Society "formulate standard specifications for the construction of steam boilers and other pressure vessels and for the care of same in service." This committee came into existence on Sept. 15, 1911, and was instructed to formulate a model engineers' and firemen's license law, a model boiler inspection law, and a standard code of boiler rules. Its first chairman was John A. Stevens, who had been a member of the Massachusetts Board of Boiler Rules. The boiler makers were represented by H. C. Meinholdt, vice-president of the Heine Safety Boiler Co. Upon Mr. Meinholdt's death in 1913, Colonel Meier was appointed a member of the committee. The other members represented different interests connected with boiler operation and construction. Three years were devoted to hearings and consultations. The Code was finally presented at the Annual Meeting of the American Society of Mechanical Engineers, in December, 1914, and on Febru- ary 13, 1915, it was approved by the Council of the Society. In preparing the Code every source of information was utilized, in order that the boiler situation should be thoroughly covered. Colonel Meier's original committee of seven members was assisted in the final preparation of the Code by eighteen notable boiler specialists in the design, installation and operation of boilers. The First Heine Boiler, Built in 1882. Still Good for High Pressure after Thirty-five Years of Continuous Service. Comparative Sizes of the First Heine Boiler and a Standard 500 H. P. Boiler. HETNE PRACTICE 53 Although in ill health, Colonel Meier was interested in the Code until his death. According to John A. Stevens, Chairman of the Code Committee : "Colonel Meier took a most active part in the formation of the A. S. M. E. Boiler Code, and up to within a few days of his death, had it constantly before him. It is one of the regrets of the Committee that he could not have lived to see the fruition of the work he so w^isely started." The Boiler Code is too long to give in full here, but can be obtained from the American Society of Alechanical Engineers, 29 West 39th Street, New York, by the payment of fifty cents. The Code is divided into two parts, the first applying to new installa- tions, and the second to existing installations. The Code as completed is much more far-reaching than the Massachusetts Rules. Quoting Mr. Stevens again, 'Tt specifies in detail the chemical and physical properties of all materials entering into the construction of boilers, and gives rules, formulas and tables that have been checked and rechecked by men of national reputa- tion, and in many cases verified by testing laboratories ; that is to say, in many cases, rules or formulas were withheld until actual tests in laboratories were made in order to prove the mathematics." The Committee formulating the Code has been made permanent, and holds regular meetings for the purpose of interpreting any points on which questions are raised. From time to time the Code is revised to include the latest knowledge of steam-boiler con- struction. The work of bringing the A. S. M. E. Boiler Code into use is being done by the American Uniform Boiler Law Society, which is carrying on an educational campaign in the states that have not yet adopted the Code. The Society is made up of representatives of the organizations interested in the construction or operation of steam boilers. In many states laws have been passed creating a board of boiler rules. Such boards are authorized to adopt the standard A. S. M. E. Code, and to amend it in accordance with the amend- ments made by the Society. State legislatures and authorities move slowly along engineering lines, but the use of the Code is increasing, and in time it undoubt- edly will be adopted in every state of the Union. At present "Code" boilers are required in certain states, but in others boilers built to less rigid rules can be installed. All Heine Boilers, no matter in what state they are used, comply with the requirements of the Code. The Heine Company is also assisting in its adoption through the work of its executives on the Code Committees of the American Society of Mechanical Engi- neers, the American Boiler Alanufacturers Association and the American Uniform Boiler Law Society. The Company believes that the Code should be adopted not only in every state in this country, but should also be made international in scope. 54 a OS U o c CO X >> V u V 'o •PQ J3 3 O Q CO CO w .5 55 CHAPTER 2 BOILER RATING AND DESIGN THE rating of a machine should naturally be expressed in terms of the useful work done by the machine. The useful work done by a boiler is represented by the heat transferred to the water in the boiler ; thereby causing evaporation, > In actual practice boiler pressures, initial steam conditions and feed water temperatures vary widely. If performances are to be compared, they must be reduced to an equal basis. The actual evaporation is therefore referred to an equivalent evaporation from a feed water temperature of 212 deg. into dry-saturated steam at the same temperature, or as it is com- monly expressed, "from and at 212 deg. Fahr." The heat added to each pound of water under these conditions will then be L at 212 deg. The 1915 A. S. M. E. Boiler Code stipulates that this quantity is 970.4 B. t. u. per pound. Goodenough gives a slightly higher value (971.7) which is probably more accurate. The heat actually absorbed by one pound of water while in the boiler will be H — q, where H is the heat content of the steam as it leaves the boiler — it may be wet-saturated, dry-saturated or superheated — and q is the heat of the liquid at the temperature of the feed water entering the boiler. gives, therefore, the pounds of water evaporated from and at 212 deg. and equivalent to the actual evaporation of one pound. This quantity F is called the "factor of evaporation." When multiplied by the pounds of water fed to the boiler for any given time, the product is the equivalent evaporation from and at 212 deg., expressed in pounds for thnt time. This equivalent evaporation is usually expressed, however, in pounds per pound of coal. Boiler Horse Power A boiler horsepower was originally defined as the actual evaporation of 30 lb. of water per hour from feed water at 100 deg. into dry-saturated steam at 70 lb. gage pressure. When the term "equivalent evaporation" came into use, however, it was applied to the boiler horsepower, which is now defined as the equivalent evaporation of 34.5 lb. per hour from and at 212 deg. A formula for finding this term would be expressed thus : , , p __ (H — q) (lb. H,0 fed per hr.) ^ F X lb. H.O fed per hr. (2) 971.7X34.5 ~ 34.5 The boiler horsepower and the engine horsepower are in no way related. When the original boiler horsepower unit was selected a one horsepower boiler would supply a one horsepower engine. Increase in the economy of engines, however, has changed that ratio until now a 100 horsepower boiler will supply 250 engine horsepower, at least. The term boiler horsepower has thus lost much of its significance. Almost any modern boiler will run continuously at from 150 to 200 per cent over its rating and for short periods 400 and even 500 per cent have been reached. Lowering Heine Standard Boiler into Hull of Dredge Boat "Texas" The Atlantic, Gulf & Pacific Company. of BOILERS 57 Heating Surface The better measure of boiler capacity is the heating surface. Heating surface is that surface which has hot gases on one side of it and water or steam on the other side. By the A. S. M. E. code, it is the surface "in con- tact with fire or hot gases." In all water-tube boilers and in most fire-tube boilers (the common vertical and Manning types are exceptions) the whole surface of the tubes is heating surface. Tube heating surface constitutes by far the greater part of the total, in any type of boiler. As boilers are built, it is usually the most effective part, except in internally-fired boilers. Additional heating surface is provided in horizontal tubular boilers, by the shell up to the line where the setting racks in, and by the heads up to the same level. The inner faces of the waterlegs, and part of the drum shell, in a Heine boiler are heating surface. Formerly 10 or 12 sq. ft. of heating surface was allowed per boiler horsepower. The corresponding rate of evaporation was usually around 3 lbs. of water per sq. ft. of heating surface per hour, for it was observed that if the rate of evaporation greatly exceeded 3 lbs. per sq. ft., the increase of coal consumption outran the gain in water evaporation, and the flue gas temperature became high. In good modern design, rates of evapora- tion much higher can be secured without serious sacrifice of efficiency. As high as 10 lb. is frequent in marine practice. From 4^ to 6 lb. is justified in power stations carrying highly variable loads, the slight loss in economy being more than offset by the reduced investment for boilers and power house space. The obtaining of these higher rates of evaporation is chiefly a matter of draft. Their attainment without a serious sacrifice of efficiency is a matter of boiler design. The proportions, tube sizes and spacing, baffling and general arrangement must all be properly worked out. The higher rates cannot be obtained at all with certain types, the common vertical boiler being an example. The cost of a given boiler, and also its size, varies almost directly with the amount of heatmg surface. Hence the desirability of high rates from an investment standpoint. Grate Surface The grate surface is important in determining the capacity of a boiler, although related only indirectly to its efficiency. The rate of combustion depends upon the kind of fuel and the draft. The latter may be determined by reference to the chart given in Chapter 5 on CHIMNEYS. For oil, there Is no grate, and capacity Is based upon furnace volume. In marine work a maximum oil consumption of 10 lb. per cu. ft. of furnace volume per hour Is permissible, but In land practice much less than this is allowed. The grate surface required for hand-fired boilers under normal opera- tion can be found bv : ^_ 33,480 H. P. (3) B K E G == Total grate surface, sq. ft. H.P.=^ Horsepower rating of boiler. B = Heat value of coal, B. t. u. per lb. K = Rate of combustion per sq. ft. of grate per hr., lb. E ^=: Combined efficiency of boiler and furnace, per cent. 58 BOILERS Heating Surface Ratios A ratio of 1 sq. ft. of grate area to 35 or 40 sq. ft. of heating surface is ■common for boilers that operate at rated capacity, when burning commercial sizes of anthracite. For overload capacity the ratio is taken at about 1 to 25, and for burning low grade coals a forced draft system is necessary. For bituminous coals, the ratio of grate area to the boiler heating surface runs as low as 1 to 30, and as high as 1 to 70 in different instances. L. S. Marks recommends the ratios, of grate proportions to operating economy and boiler capacity, given in Table 1. Table 1. Heating Surface Ratios — Bituminous Coals. Name of Coal Ratios of Grate Surface to Heating Surface For Economy For Capacity i Run of I Mine Slack Run of Mine Slack Grate Bar Openings, Inches Run of Mine Slack Va., W. Va., Neb., Pa. Ohio, Ky., Tenn., Ala. 111., Ind., Kan., Okla.. Colo., Wyoming 1 to 60 1 to 55 1 to 50 1 to 50 1 to 55 1 to 50 1 to 45 1 to 45 1 to 55 1 to 50 1 to 45 1 to 45 1 to 50 1 to 45 1 to 40 1 to 40 % Va Heat Transfer The rate of transmission of heat through the boiler surface depends chiefly upon the difference in temperature between the hot gases and water on the two sides of the heating surface, and upon the rate of movement of the two fluids across the surface. For those surfaces directly exposed to the fire, the transmission is due chiefly to radiation, which varies as some power of the temperature difference. A sustained high temperature in this region is therefore important. Other surfaces act more by convective transmission. The fluid flow then is of chief importance, the transmission varying about as the first power only of the temperature differences. As forced water circulation is not employed in large boilers, the water flow cannot be con- trolled at will. In general, the harder the boiler is driven, the better will be the water circulation, which is the condition desired. The heating surface directly exposed to the fire does most of the work. Gehhardt states that this would be true even if the furnace transmission varied as the first power only of the temperature. Here the last 20 per cent of the surface reduces the flue gas temperatures only 65 deg. This is of course an understatement. Allowing for the much greater effective- ness of that portion of the surface immediately adjacent to ths furnace, the last 20 per cent must necessarily reduce the flue temperature considerably less than 65 deg. Even at 65 deg., however, with ordinary operation, the omission of the last 20 per cent of the surface would cause a loss of only about 300 B. t. u. per pound of coal, or about 2 per cent. Hence where first costs are high or loads variable the ratio of heating surface to grate surface should be low. Hence also the slight loss of efficiency due to increasing rates of evaporation. In European practice, the heating surf&ce has been strictly limited and economizer surface employed to obtain low final stack tempera- tures. The fluid temperature difference is greater at the economizer, so that one square foot of economizer surface more than replaces a square foot of boiler surface. See Chapter 11 on HEAT. BOILERS 59 Gas Passages Gas circulation is subject to control both in design and operation. Since the effort is made to have all of the gas strike all of the heating surface (thus keeping down the flue temperature and stack loss), the gas velocity at a given rate of driving is determined solely by the nature and dimensions of the gas passages. Formerly certain proportions of the grate surface were allowed for the cross-sectional area through or around tubes, but the results were only accidentally correct. With proper operation, the kind and weight of coal to be burned per hour determines within reasonable limits the weight of gas produced per hour. The volume of this gas depends upon its tempera- ture, and the rate of decrease of temperature from furnace to stack has been determined by experiments for certain boilers. The velocity of this gas depends upon the draft (which is related to the rate of combustion) and upon frictional resistance, all of which can be valuated with fair accuracy. The volum.e and the velocity being known, the cross-sectional area necessary for gas passage can be calculated. With high draft, small area and high velocity, gases yield their heat at a rapid rate, but they are also moving to the stack at a rapid rate. The best rate of yield as compared with rate of movement determines the cross-sectional areas. For anthracite coal at low rates of combustion, the old rule was to use 1/7 of the grate surface for the area over the bridge wall, 1/8 for the flue area and 1/9 for the chimney area. Areas naturally decrease from passages near the furnace to those near the stack. Areas for gas passage can be correct, and operation nevertheless unsatis- factory, if the details of the baffling are wrong. The gas should as far as possible be compelled to strike the surfaces without indulging in short cuts or leaving dead spaces where the circulation is sluggish. A boiler is a machine, the moving parts being gas and water, and these motions must be correct if efficiency is to be good. Baffling PARTITIONS are placed among the tubes to direct the flow of the hot gases. These baffles can be vertical, causing the gases to flow across the tubes ; or horizontal, so that the gases travel the length of the tubes. In selecting the design of baffling for a given installation, its flexibility, ease and cost of upkeep, and influence on heating surface must all be considered. In- vestigations by the Bureau of Mines show : (1) A boiler whose heating surface is arranged to give long gas passages of small cross-section will be more efficient than a boiler in which the gas passages are short and of larger cross-section. (2) The efficiency of a water-tube boiler increases as the free area between individual tubes decreases and as the length of the gas pass increases. (3) By inserting baffles so that the heating surface is arranged in series with respect to the gas flow, the boiler efficiency will be increased. These results point to the desirability of horizontal baffles and the importance of the long, unchilled flame and the large furnace volume ob- tained by their use. The entire heating surface in a boiler is not active, because of the eddies peculiar to gas flow. With practical baffling, the inactive surface caused by dead gas pockets can be minimized. During tests by W. N. Polakov on the vertically baffled boiler, shown in Fig. 1, pyrometer measurements showed that only about 60 per cent of the surface was an active heat absorber, the remaining 40 per cent repre- senting the dead pockets. Horizontal baffles may not eliminate the dead regions, but they can reduce the inactive surface considerably by decreasing u a CO d C 5 -^ C ^ Q^ ^5 b5 Draff Gage to Draftin Furnace Draff Gage in Ashpit • .l<$^l\\V^s\\:^;^^^^x-^s^^^\^x^^ \r Fig. 1. Dead Regions in a Vertically Baffled Boiler. Shaded Parts show Inactive Surface. c lE (^ o c u E o o -f- 700 600 500 400 300 200 ^ 1 1 1 X PocahonfofS f^Clinchfield I 1 1 S ^ X ^- ,^-^ .^< > "^ O > u.--' r ,5 ^ ^* ^ ^ "o. .>^^ b ^ ■w^' t^- J.f< s^. ^H X " ..^ ^ \iorpP^ n^ji. 1 J «*" ^^ ^' vH "Steam Tzmperafure 363° F. \ 1 1 o «-o o o o Fig. 2. Boiler Capacity, Pcrcen+ Comparison of Stack Temperatures in Test Boiler when Baffled Vertically and Horizontally. 62 BOILERS the size of the dead comers. In Heine boilers, Fig. 5. a large percentage of the tube surface absorbs heat because of the battle construction. Horizontal baffles are recognized as standard for smokeless settings. Smokeless combustion usually cannot be obtained with verticalh^ baffled boilers unless the setting is ven,* high. With hand-firing and bituminous coal, vertically baffled boilers are not allowed where smoke ordinances are stringent. For this reason horizontal baffling has been applied to many boilers designed originally with vertical baffling. By substituting the hori- zontal for the vertical pass, a longer flame travel between the furnace and the tube region is obtained, without increasing the floor space. In tests by Henry Kreisinger and M. T. Ray, the draft through the verticalh' baffled boiler was 0.5 in. for an average load of 128 per cent. When the same boiler was baffled horizontally, the draft was only 0.375 in. K^t^TT, i^^^^^^^^^^^^p' Fig. 3. Original Vertical Baffling of Test Boiler. Fig. 4. Two-Pass Horizontal Baffling of Test Boiler. BOILERS 63 at 127 per cent load, with the same CO. percentage. These tests were con- ducted to determine whether horizontal passes gave good results when burning Pocahontas and CHnchfield (high-volatile) coals. Nineteen tests were run under actual plant operating conditions with the same boiler, baffled as shown in Figs. 3, 4, and 5- Table 2 summarizes these tests. The flue-gas temperatures at the different boiler loads are shown in Fig. 2. At 120 per cent capacity, the average temperature with the vertical baffles was 590 deg., and with the horizontal baffling only 500 deg. V///y,v.../.y//WMMW.v.'/ >^^^jyy/,>,y^//^^ ^^ ^ .v.yy/^v^w v. ^ ■>. '/ABsr/Ac///*^--.' - ■^-■- ---T^J^al|^>^ g'K^'-v^^^^^ Fig. 5. Three-Pass Horizontal Baffling of Test Boiler. Table 2. Results of Boiler Tests with Different Baffling. Original (Vertical) Two Horizontal Three Horizontal Baffling Passes Passes ''■ Name of Coal Poca- hontas Clinch- field Poca- hontas Clinch- field Poca- hontas CHnch- field Number of tests averaged. . . . 4 3 4 3 4 3 Water evaporated under actual conditions per lb. of coal as fired, lb 7.95 7.49 8.54 8.18 8.8:3 8.52 Equivalent evaporation per lb. of coal as fired, ■ b 9.42 8.90 9.92 9.61 10.33 9.97 Average hp. developed 320 285 335 357 303* 298* Maximum hp. developed. 341 297 355 365 317 311 B. t. u. per lb of dry coal 14,828 14,122 15,050 13,801 14,731 13,750 Ash, per cent 4.9 7.9 4.72 10.26 5.5 9.85 Approximate efficiency of boiler and furnace, per cent 61.3 60.9 63.6 67.2 67.7 69.9 *0n the test with three horizontal passes, higher capacity could have been developed, but the feed water was too hot and the injector would not feed it fast enough into the boiler BOILERS 65 When the boiler is baffled horizontally much better results can be obtained with high-volatile coal. There is also a marked improvement, when the horizontal baffling" is used, for Pocahontas coal. The horizontal three- pass baffling gave the highest evaporation and the horizontal two-pass developed the highest horsepower. With the two-pass horizontal baffling higher evaporation and horsepower can be obtained with Clinchfield coal, than with vertical baffling and the higher grade Pocahontas. The draft loss through the boiler is less for the horizontal two-pass than for the original vertical baffling. The number of turns taken by the gases is the same, but the resistance at the points of reversal is less with the horizontal two-pass baffling. Smoke records from a boiler baffled vertically and later changed over to horizontal baffling are shown in Fig. 6. The vertical baffles were re- sponsible for a high percentage of smoke, while with the horizontal baffles the boiler had a clean record. oz 3 I BZ 7 2 5 Z 5 2 Mill I I 9 1 3 1 1 r / 1 3 1 S 1 1 1 1 K « I 6 1 4 3 2 1 1 1T(\ - - - - - - - - - - - - - - - - - - - - ' ^ T,n - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - r> ^ „l„l„j „ „ ^1^ l„ ■ ^ /// ^ ^ Y/y VAc V^/jy ^d'Ki- ~-' ^ z/:^'/z',^:m:^4^'^ -^-i^^ 1 E10' ^--, ~^~-^~-^ -^ „ _(^^~ 1^ - — 4fll30 ~, - - — ,- „- ~ - — T, - r- -\~ W-<\v\ - - - , - 1 - - - - - — - - - , - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -\- - J 1 M) 59 58 57 56 55 54 53 52 51 50 49 4S 47 46 45 44 45 dZ 41 40 39 3 83 7l6~5'5l4 Blz"3l^30+'"' | Vert ical Ba ffle 02 9 2 8 27 2 6 2 5 2 U u 2 Z 20 19 1 1 3 1 7 1 3 1 5 1 1 13 12 1 1 ] ? I " e " i 8 -,7/1 1 - - - - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - " c;^0 - - - - - - - - - - - - - - - - - - - - - - - - - - - — - - - - - - - - - - - - - - - - - - - - - - - - - - - ^ ■^ ^n - - - - - - - - - - - — - - - - - - - - - — - - - - - - - - - - - - — - - - - - - - — - - - - - - - - - - - - - ~ — I" ~ -? - - - - - - - - - - - — — - - - - - - - - - - - - — — - - - — - - - - - - - - - - - - - - - - - — - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - — ^1030 - - - '- - - - - - - - - - - - - - - - - - - - - - — - - - - - - - - - - - - - - - - - - — - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - — - - — - - — — - - - - - - - - - - - - - - - - - - - - - - - ' t m 59 58 57 56 55 54 S3 52 51 50 49 48 47 46 45 44 43 4 Z~4J"40"3'9"58"J7"36'3S"34l3"j2~5l''30 ^'"^ | Horizontal Baffle. Fig. 6. Smoke Charts. Vertical baffles can be kept tight only with difficulty. Baffles that are not gas-tight allow the hot gases of combustion to short-circuit, resulting in high stack temperatures and a reduction in boiler efficiency. Because of the difficulty in installing the tiles, vertical baffles are often repaired with ordinary fire clay. With vertical baffling soot cleaning is difficult and the installation expensive. Frequently the cleaner is built in as a part of the baffles ; when the tile crumble away both the soot cleaner and the baffle must be renewed. According to the requirements, the horizontal baffles can be arranged for single, double, or triple gas-passes. Typical arrangements are shown in Chapter 4. The horizontal passes allow the gas to travel in series, in parallel, or for the two combined. The gases flow parallel to the tubes, as well as at right angles, when the pass is divided. The first baffle. Fig. 8, is then placed on the lowest row of tubes and extends to within 5 ft. of the rear waterleg. This baffle serves as a roof for the furnace and combustion chamber and permits of a simple stoker arrangement, with ample room for the gases to burn. The gases entering the boiler divide into two streams, one flowing beneath and the other above the middle baffle. 66 BOIL This rests upon the ninth row of tubes, with an opening at both front and rear. The top baffle extends from the rear waterlec to within several feet of the front waterleg, leaving an opening fir :' t iisrnarge of the gases from the boiler tnbes. Before passing tc zlt sir -it outlet, all the gases flow under the ':;i'-er i: i.s. rials, desizzzi ::r t^r :::5:i i: i: i :: :: f: : :_ t : ^ t : zrivrt^. Theshs:r5 fti :r. iirrtrt;: fr:: ::;5 i-.n sJ: :; r^ . 5 :-iron plates are sonie: iizi .iti :;r :::e ;r::tr ^t: ;: : :-:^r3 ' :r i :. £les. Capacity and Economy device has its own type of characteristic carve in tref £5 iri'/ites against onfpnt as abscissas. This r 2. E:t?.: - liler resembles the carve for a steam ■- e'e: :::: : ::;r :r generator, in being convex upward r.ri : :.-': ::; 1 peak. With all these devices, the a: . -:/: : if ifses absorbing the oatpat). Their ~ir r; :.: :..::::~.— !!?2ds and at heavy overloads. - :.; itr-ti : : :r.jni loads depending upon It 1 1: t : r^r T L :': for a short time. Over- t- : r : _ -t :::-tr is si milar in maintaining 5.::t: :r ::. :5 : : /.ry to carry overloads. It has _: ;::- :c ,ir.ve:- i: itfriTely by incre^?::^? the draft. : ':-.'.-: :i:\ :irr- yr::: im. load Every mechanical which efficiency is pic characteristic carve fc engine or turbine, or £i and having a wdl de£ efficiency falls to ztr: characteristic curve; ::: Electrical machiner ten^erature. A given loads do not reduce the efficiency, but is grea:! no definite time limit, : Except under extreir: indefinitely- With economical operaiicz sieam engines and tur^i^'ne? of the constant speed type have only moderate maximum overlrai ; ; . : The efficiency under overload drops off more rapidly than Lh^i oi a _:.ler. To obtain high overload capacity by admitting live steam to low presstire cylinders or stages leads to an abrupt drop of the effiaency, and even then there is a definite limit of capacity. The steam boiler, therefore, is almost tmiqne in its advantaeezus cer::r~ir.:e. iiuons Water Circulatioii In many heat-trar; as the fluid velocities i leads to rapid replace: the emission side, cc ; emitting fluid is other . difi^erence. In a stearr. points usually differ :: scarcely vary much wi: any mariced degree dej^ occurs by radiation, at marked degree depen i lion is sufficient to kee; by radiation, at surfaces gas circulation. Good drc^i' from difference 5 : : :. : mud in pockets 1 of adhesive bv. - : local overheat:::^ T -! :.:z : liberating surface and poor cir C • ' C -N -- — - r uiiivi. j \^ on : .- rlui if the heat- eace to augmec: zi t :: perature water tempera:, rt 5 .-: vzrious mtity of heat : : : r : t : : ; i can \ ' the efficier ; i t5 : : ::: ::. The hea: \::\,:z: \: ;i: ■.jie fire, does not in any : i^aing that the drcula- - T -insfer which occtu-s i-c ^re, ^i'-es not depend upon .: ever. It reduces stresses arising -: -:r^? the acctunulation of scale or z :ends to prevent the formation -z s-rc:?. Such unwetted spots may cause : apt to exist when boilers with insufficient culation are driven hard. BOILERS 67 Steadiness of Water Level This implies a large water surface "disengaging" or "liberating" surface, in proportion to the volume of water ; or perhaps more strictly, in proportion to the expected total evaporation. Priming may result from inadequate liberating surface and occurs, consequently, in many vertical boilers having the water level below the tops of the tubes. Drums should not be too small, else slight variations of water level may carry it rapidly below the danger line. B-Tile. T-Tile. L-Tile. Fig. 7. Forms of Tile Used with Heine Boilers. .... . ..r . ... . ...<..r ■■■■.. . ... . . . . . . . ■_■■■ ■■■ . . n . 1- \'o 'o '.'^. > ■ ■' •■ » J'" >■ .3 ;>■ • •..-.• Fig. 8. Divided Pass Baffle in Heine Boiler. Railway Exchange Building, St. Louis, Mo., operating 1052 H. P. of Heine Standard Boilers. 69 CHAPTER 3 SUPERHEATERS SUPERHEATED steam is steam whose temperature is higher than that corresponding to saturated steam at the same pressure ; steam which, when heat is removed, will not immediately begin the process of condensation. The properties of superheated steam approximate those of a perfect gas. Tables of these properties are given in Chapter 12 on STEAM. Advantages of Superheating. These are important because superheating reduces pipe and cylinder condensation. In a well-designed attached super- heater, the efficiency of the heating surface is at least as high as that of the boiler; and as the total heating surface is increased by that of the superheater the exit temperature of the gases will be decreased. This in- creases the overall efficiency of the boiler and superheater to a point which will, in general, make up for the increased heat required by the steam. With an independently fired superheater, more fuel will, of course, have to be burned. The measure of the extra fuel for superheating is the difference in the total heat of the steam when saturated, and when superheated ; this will depend upon the pressure and the superheat temperature, and also upon the temperature of the feed water. The following figures are based on a gage pressure of 165 pounds : Amount of Extra fuel, per cent, required when feed water enters at Superheat, Degrees 100° 150° 212° 50 100 150 200 2:73 5.13 7.40 9.61 2.85 5.38 7.74 10.05 3.03 5.70 8.21 10.66 The superheater does some of the work which the heating surface of the boiler would have to do if the same number of heat units were to be supplied in saturated steam, so that the boilers can be run at lower rating. The superheater may not increase the first cost of the boiler plant, for with the increased economy the number of units used may be decreased. The increased economy of the engines due to the use of superheated steam may naturally enable smaller condensers to be used, and may lessen the cost of pumping owing to less water being used. Superheated steam is used, almost without exception, in the largest and most economical plants. The pipe radiating surface can be reduced by the use of smaller pipes, owing to the fact that higher velocities (as high as 12,000 ft. per min.) are permitted with superheated steam. The theoretical gain is indicated in the temperature-entropy diagram, Fig. 9, in which areas represent heat quantities. The line (oa) starting at a temperature of 32 deg. is the liquid line and the area under (oa) represents the heat of the liquid, q, that is, the heat necessary to raise the temperature of one pound of water from 32 deg. to the temperature corresponding to 70 V o ■4-1 CO 3^ a; O o ^ ^2 1(3 o to c PQ u >* CO u cW w c C o ^ CO o o CO SUPERHEATERS n the pressure in the boiler where the vaporization takes place. The line (ab) represents this process of vaporization and the area under it is the heat, L, added during the process. At (b) the steam is in a dry-saturated condi- tion: (be) shows the superheating of the steam at constant pressure and the area below is the heat added during the process. The steep slope of the line (be) shows that the point (c), which is the final condition of super- heat, must be carried to a high temperature in order to have the area below \T 1 / h Ir i\\\\\\N\\\\\^\\\\^/////////^^^^^ '/A Fig. 9. Temperature — Entropy Diagram. of any size. A high degree of superheat, which means a high temperature, will add only a small number of heat units to the dry-saturated steam. For example, dry steam at 150 lb. abs. pressure has a heat content of 1195 B. t. u. per pound. If this steam is superheated 141.5 deg. to a tem- perature of 500 deg., the heat content will be 1274 B. t. u. or a gain of only 79 B. t. u. per pound for an increase in temperature of 141.5 deg. ; or 6.6 per cent increase in heat for 39.5 per cent gain in temperature. Effect on Reciprocating Engines. Steam, admitted to the cylinder of an engine, comes in contact with walls that have been cooled by contact with the low pressure steam exhausted during the previous stroke. Heat flows, therefore, from the steam to the cylinder walls, and if the steam is saturated part of it will be condensed ; sometimes this will be as much as 20 or 30 per cent. The loss due to surface condensation is one of the most serious occurring in the reciprocating steam engine. If the steam entering the cylinder is superheated, then the flow of heat caused by contact with the colder cylinder walls will cause a decrease in the amount of superheat, but no condensation until the temperature has been reduced to that of saturated steam. The many tests made on reciprocating engines using saturated and superheated steam have shown a smaller steam consumption for superheated steam. With moderate amounts of superheat, that is, up to 200 deg., the gains have been greater than for the higher temperatures. The extra invest- u SUPERHEATERS ment and cost of maintenance neutralize the gain from the higher temper- atures. The gain in steam economy due to superheat is most striking with small, simple engines, in which the cylinder condensation losses are the greatest. Tests on Buckej-e engines (simple 12 by 16 in., and compound 10 and V/Vz by 16 in.) with steam at 100 to 110 lb. pressure, show about what can be expected in this wav. Table 3 gives results of tests with superheats up to 200 de.g. Table 3. Pounds of Steam Per H. P. Per Hour for Different Superheats. ! _, . Rated load. Superheat temperature, degrees Engine Percent 50 100 150 200 Simple, non-condensing Simple, non-condensing Simple, non-condensing Com.pound, non-condensing. . . . Compound, condensing 30 50 100 100 100 -35.0 31.5 28.5 28.0 25.5 24.0 24.0 22.0 20.0 17.5 14.0 21.5 19.0 18.0 15.5 12.5 19.5 17.5 17.5 14.6 18.0 16.5 11.5 G. F. Gebhardt states that a fair estimate of the average percentage reduc- tion in steam consumption per horsepower hour with moderate superheating, that is from 100 to 125 deg.. based on continuous operation of existing plants, is : 1. Slow running, full stroke or throttling engines, including direct-acting pumps 40 2. Simple engines, non-condensing, with medium piston speed, including compound, direct-acting pumps .20 3. Compound condensing Corliss engines 10 4. Triple expansion engines 6 European builders guarantee steam consumption (in lb. per LH.P. per hr.) with highly superheated steam (total temperatures 750 to 850 deg.) as follows : Single cylinder condensing engines (uniflow) 8.5 Single cylinder non-condensing engines (uniflow)... 12.0 Compound condensing engines (locomobile) 8.0 Compound non-condensing engines (locomobile) 10.5 W. E. Dalby gives results on a small engine using superheated steam, taking the data from tests by Professor Ripper. Table 4 shows the differ- ence in the increase of the efficiency of theoretical and actual engines, both working under the same conditions : The steam is drj'-saturated in the first case. The theoretical efficiency increases from 14.2 to 15.9 per cent, or 11.6 per cent, while the actual efficienc}- gains 65.0 per cent, the increase being from 6.3 to 10.4 per cent. This shows, of course, that the superheat acts to decrease the losses in the actual engine. In comparing the performances of different engines, the heat consump- tion, rather than the steam consumption, should be used. The number of heat units required to develop one indicated horsepower in the actual engine takes into consideration the pressure, superheat and the steam consumption ihe avoidance of cylinder condensation by the use of superheat will affect both heat and steam consumption. So whatever the basis of comparison, the employment of superheated steam is an advantage. SUPERHEATERS 73 Table 4. Effect of Superheat on Actual and Theoretical Engines. Steam pressure, Lb./Sq. In. Superheat Degrees Steam Lb ./I. H.P./hr. Thermal efficiency, per cent I. H. p. Act. eng. Theor. eng. 13.33 13.33 13.47 13.49 101.7 98.5 98.6 99.5 0.0 98.3 254.2 319.6 39.62 33.80 23.36 20.08 6.3 7.1 9.5 10.4 14.2 14.6 15.2 15.9 Effect on Steam Turbines. The theoretical gain from the use of super- heated steam is the same in steam turbines and in reciprocating engines ; in either the available number of heat units are increased by the use of the superheating process. The actual gain, however, is less in the turbine than in the engine, for the action of the steam in the former is continuous while in the latter it is intermittent. Superheated steam is of little value in cor- recting surface condensation, because practically none occurs in the turbine. The water rate of the turbine is decreased by the superheating of the steam but to a less extent than in the reciprocating engine. Superheating is of importance in that erosion of the turbine blades caused by the presence of water in the saturated steam is almost entirely done away with. The effect of expansion on saturated steam is to increase its moisture content, so that even if the steam were dry at entrance, moisture would be present in the low pressure stages. If the steam is sufficiently superheated the heat reduction due to the expansion will not lower the temperature to that of saturated steam, which must be reached before condensation begins. Any moisture present in saturated steam has the effect of reducing the economy. The steam consumption of certain large turbines using superheated steam is decreased about 1 per cent for every 8 to 12 deg. of superheat up to 200 deg. ; the variation being from about 1% for 12 deg. at 50 deg. superheat to 8 deg. at 200 deg. superheat. In the same boiler plant the minimum saving in coal due to superheating is 4 to 5 per cent. This coal saving depends upon (1) the saving of steam resulting from the economy of the prime mover; and (2) the amount of coal necessary to obtain the superheat. Limit of Superheat. As far as material goes power plant apparatus might be designed to withstand temperatures of 800 or even 1000 deg. Other considerations, however, limit the amount of superheat, so that the most economical degree is determined by the operating conditions. In this country steam temperatures in power plants are seldom more than 600 deg. ; the superheat is from 200 to 250 deg., depending upon the boiler pressure. In Europe, however, where superheaters are almost invariably employed, 600 deg. is a common temperature and 400 deg. superheat, which would be a temperature of about 850 deg., is sometimes used. With these very high temperatures the first cost and maintenance are high, and the thermal gain is considerable. This would be advantageous when materials and labor costs are reasonable and fuel costs high. Such conditions were formerly found in Europe. In this country, however, labor and materials are expensive while fuel has been cheap. It is more economical, therefore, to use moderate degrees of superheat, even at the sacrifice of some gain in heat ; but as the cost of fuel increases, the tendency will be towards increased superheat. The engine design also determines to some extent the temperature to be used. The Corliss and slide-valve types of engines seem to reach their limit 74 SUPERHEATERS 75 at about 500 deg. Higher temperatures cause warping of the valves and interfere with lubrication. Very highly superheated steam, at temperatures of 600 deg. or more, is used in poppet-valve engines, since such valves do not warp and require no lubrication. Balanced piston and specially designed Corliss valves are also successful with high superheats. Steam-turbine construction and operation permit the use of steam tem- peratures as high as 800 deg. Nevertheless for reasons of economy of main- tenance, even the latest designed turbine plants are working with steam at temperatures not over 650 deg. Control of Superheat. Superheat temperatures may vary widely with the temperature of furnace, volume of air used, and rate of firing coal. Extreme variations should be avoided, as they may cause serious difficulties with the piping, valves and gaskets. Stoker firing and automatic feed and damper regulation will do much toward eliminating superheat fluctuations. Any variation in the boiler load will affect to a marked degree the tem- perature in superheaters placed inside the boiler setting, in the path of the hot gases. The truth of this last statement is shown by Fig. 10, and by the following quotation from "Superheater Logic," by the Heine Safety Boiler Company : "If the increase in load is sudden and there is a large momentary draft of steam with accompanying fall in boiler pressure, the superheat tempera- ture will fall because the rate of combustion is not increased. Conversely if a boiler is steaming at a heavy load and the load decreases suddenly, then the superheat, which is already very high due to the heavy load, will be further increased because of the smaller flow of steam through the tubes. In this way very excessive superheats are obtained from an equipment designed for only a moderate superheat at normal load. "Evidently the greatest economy is secured when a plant is designed and built for a certain fixed superheat and this temperature is maintained constant." Types of Superheaters. In general use are (1) the separately-fired, and (2) the attached type of superheater. The former is placed in its own setting and has a furnace of its own to supply heat; the latter is located within the setting of the boiler and receives heat from the hot gases as they pass on toward the stack. Both types receive steam containing perhaps 2 per cent moisture from the boiler and increase its temperature by the addi- tion of heat without changing the pressure. The steam elements are prac- tically the same in both types — a number of tubes or pipes arranged to contain a relatively small volume but to expose a large surface to the heat. The final temperature of steam in a superheater depends upon the tem- perature, volume and quality of the steam entering it, and upon the volume and temperature of the hot gases coming in contact with the tubes. The temperature and quality of the steam can be considered as constant while the load on the boiler determines the quantity of steam. Therefore the amount of superheat will be principally affected by the temperature and volume of the hot gases. If it is desired to maintain a constant degree of superheat, the flow of hot gases over the tubes must be controlled. Separately-fired superheaters are intended to give higher temperatures to the steam than can be obtained from attached superheaters. The super- heating coil is suspended over the furnace, protected from the direct heat of the furnace. Baffles are provided so that the hot gases make two or more passes around the tubes. Steam enters at the top and leaves at the bottom. The tube surface is increased by putting on cast iron rings outside the tubes. A flow of steam through the superheater must be provided to prevent burning, should the load be suddenly thrown off the boiler. All super- heaters should be equipped therefore with independent safety valves of the 76 SUPERHEATERS outside spring type, set at a slightly lower pressure than the boiler safety valves. There should be a drain for getting rid of any collected water before starting. The superheater should be so proportioned that the same quantity of steam will pass through all of the tubes in order that none of these can be by-passed, and consequently in danger of burning. Superheaters must be protected from exposure to hot gases with no steam flowing, as when firing up, cooling down or standing idle. With separately-fired superheaters the hot gases can be deflected so as to by-pass the superheating coil and flow directly from the furnace to the stack; or an outer cast iron covering with flanges may be provided to protect the steel tubes and store the heat. Also the superheater should be filled with water, or flooded whenever the flow of steam ceases. Flooding is objectionable in that scale-forming material can be deposited in the tubes, which cannot be cleaned. Any of the above methods may be applied to attached superheaters. When these are flooded the)^ generally are connected in parallel with the boiler heating or evaporating surface, so that they can be drained and connected in series with the boiler when superheat is desired. The attached or indirectly-fired superheater may be placed (1) at the rear of the furnace; (2) at the end of the heating surface just before the gases leave the boiler setting; and (3) at some intermediate point. The steam passing through the superheater will absorb heat, depending upon the temperature difference between the gases and the steam, and upon the amount of superheating surface. Therefore to obtain the same degree of superheat the amount of surface required in the furnace where the gases are hottest may be small as compared with the amount required when the superheater is placed at the end of the heating surface, where the gases are cooler. The usual location of the superheater in the boiler setting is such that the temperature of the hot gases reaching it seldom exceeds 1500 deg. In this position the attached superheater is subjected to the fluctuating tempera- tures of the hot gases. The amount of superheat will vary, therefore, with the load on the boiler and will increase as the boiler is forced. 1 U V 160 S 140 JZ L. §-120 to 1 '°° 1 80 g 60 o I 40 20 ^ ^ ^ ^ ,y ^ / / / so 100 ISO 200 250 ZOO Percen+ Looid Fig. 10. Effect of Load on Superheat with the Superheater in the Path of All the Boiler Gases. SUPERHEATERS n The more positive method of maintaining a constant superheat is by locating elements in a separate chamber, where a damper can be used to regulate the flow of gases, automatically if desired. The superheater can then be by-passed altogether in an emergency. Figs. 11 and 12 illustrate the details and location of the Heine super- heater. This consists of two parts, the superheater box and the tubes. Into this box are expanded the steel tubes arranged in four passes as shown. Two interior partitions separate the superheater box into three chambers. The steam enters at the bottom, passes through the lower tubes, returns to the central chamber through the second pass tubes and then flows through the third and fourth passes, returning to the upper chamber. 3 L 1 C Fig. 11. Details of Heine Superheater The location of the superheater is shown in Fig, 12. It can be installed on one or both sides of the boiler, according to the boiler size, and the superheat desired. The entire superheater is encased in brick work with a firebrick roof supported by special T-bars. This superheater chamber communicates with the furnace by a flue formed in the side wall, through which a small part of the furnace gas rises. This gas enters the rear of the chamber, makes two passes over the tubes and leaves at the front of the setting, passing over the surface of the boiler drum. A damper in the chamber outlet controls the flow of hot gas and is regulated from the front of the boiler, either by hand or by an automatic temperature control. 78 SUPERHEATERS Obvioush', the temperature of the superheated steam can be changed as desired by simplj- manipulating the damper in the outlet of the super- heater chamber, and the superheat can be maintained constant, regardless of the boiler load, the rate of combustion, the amount of air used for combus- tion, the furnace temperature, the opening of furnace doors or any other variable, such as the amount of soot on boiler and superheater surface. Fig. 12. The Heine Superheater. For automatic regulation of the superheat temperature, a complete regu- lator is installed as shown in Fig. 13. This regulator is quick acting and responds to small variations in steam temperature, as will be evident from its construction. The entire device consists of two main parts, the controller and the diaphragm-motor. The controller comprises a thermostat which con- trols a small supply of compressed air in accordance with the temperature of the superheated steam. The air is admitted to or released from the diaphragm-motor, connected by a link to the superheater damper handle. Provision for soot blowing is described on pages 31 and 41. SUPERHEATERS 79 Superhea-f-ed Steam Li'ne •■' Damper Pod'' Fig. 13. Arrangement of Automatic Temperature Regulator with Heine Superheater. The requirements of a successful superheater, as given by Gchhardt, are : 1. Security of operation or minimum danger of overheating. 2. Economical use of heat applied. 3. Provision for free expansion. 4. Disposition so that it may be cut out without interfering with the operation of the plant. 5. Provision for keeping the tubes free from soot and scale. Superheating Surface. The surface required is dependent upon the amount of heat to be transferred to the steam, and upon the rate of heat transfer per unit of surface. The operation is conveniently divided into three stages : Fig. 14. Superheat Chart from a Boiler Equipped with a Heine Superheater and Automatic Superheat Controller. o C & CO V c 'v X T3 V a o. '5 V 6^ "o U 1) > G V Q "o o u £ V j: U O SUPERHEATERS 81 1. Heat given up by the gases. 2. Heat transmitted through the metal walls of the elements. 3. Heat absorbed by the steam. The amount of heat involved in each of these stages is the same except for loss by radiation. The heat given up by the gases is : Wc (h—U) (4) the heat transferred is : SRd (5) and the heat absorbed bv the steam is : Wct {t,—h) (6) where : ^'^Superheating surface, sq. ft. per B.H.P. J'?=B.t.u. transferred per hour per sq. ft. of superheating surface per deg. F difference betw^een the mean temperatures of the gases and of the steam, and approximates : 1 to 3 for superheaters located at the end of the boiler heating surface, 3 to 5 when located between the first and second passes, 8 to 12 for separately fired superheaters and for superheaters located immediately over the furnace in stationary boilers or in the smoke box of locomotive boilers. rfrndifference between the mean temperatures of the gases and steam. W^=we\ght of gases passing through the superheater, lbs. per B.H.P. per hour, w^weight of steam passing through the superheater, lbs. per B.H.P. per hour. ci:=mean specific heat of the gases, c^nzmean specific heat of superheated steam. fi=rTemperature of gases entering superheater, deg. F. ^a^Temperature of gases leaving superheater, deg. F. ^3=Temperature of superheated steam, deg. F. ^4=Temperature of saturated steam, deg. F. Neglecting radiation, (1) is equal to (2) ; and neglecting the moisture in the incoming steam, (2) is equal to (3), therefore : and S: Rd (7) 'R^ (8) Instead of (3), the following may be preferred: w (H^—I-h) (9) where : FI^=Tota.\ heat of superheated steam above 32 deg. F. jF/2=Total heat of saturated steam above 32 deg. F., which may be easily corrected to allow for evaporating the moisture present. Instead of basing R on the difference in the temperatures of the gases and of the steam, it is more correct to divide the heat transfer into two stages— gas to metal and metal to steam. As this necessitates a knowledge of the metal temperatures it is generally confined to laboratory research. The precise value of R is dependent upon so many variable conditions, such as the velocity of the gases and of the steam, the condition of the surfaces as to soot and scale, the arrangement of the superheater tubes and the temperature differences involved, that refinements are out of place. I he SUPERHEATERS 83 amount of surface Is usually determined empirically on formulae derived from the results obtained in a large number of cases of the same general design, operating under similar conditions. This leaves the result in con- siderable doubt where the whole of the gases flow over the superheater with no possible control. With only a part of the gases flowing over the superheater under perfect control, the amount of surface can be simply related to the boiler heating surface, according to the degree of superheat required, and the resulting steam temperature will be kept constant within ±: 5 deg. F., as shown in Fig. 14. Superheater Materials. Heire superheaters are built of wrought steel, insuring ease of construction and durability. Superheater Piping and Fittings. Cast iron has been used for valves and fittings. Up to 600 deg., it is safe if the temperature is maintained constant. Under higher or fluctuating temperatures permanent increase in dimensions and numerous failures have resulted. Cast iron failures are undoubtedly due more to fluctuations in temperature than to constant high temperatures when it develops cracks and distortions. The advantage of cast steel for superheater material is that it is not damaged at high temperatures. This decreases the importance of protection and simplifies the installation. The construction, however, must be heavy and thick-walled. The strength of superheater materials drops off rapidly for temperatures above 600 deg., as shown by Gebhardt and others. Because of this rapid decrease in tensile strength, steam is seldom superheated to temperatures above 850 deg. Piping for superheated steam is usually made of mild steel. With the greater number of heat units in superheated steam, the pipe capacity is increased and relative conduction losses and leakage are reduced. Under superheated conditions much higher steam velocities can be used, 12,000 ft. per min. not being uncommon and 16,000 ft. per min. having been used. This, of course, increases the pipe line capacity. With the high tempera- tures resulting from superheat the problem of expansion must be carefully considered, especially when temperatures are likely to fluctuate widely. See chapter on piping. Industrial Uses. Superheated steam is used elsewhere than in engines and turbines. A Chicago gas company blows its water gas generators with superheated exhaust steam at about 2.5 lb. pressure, instead of using live steam. This results in a 20 per cent saving of boiler fuel. The capacity of the generators is increased because of the lengthening of the making period. The superheated steam relieves the generator of the work of re-evaporating the water, which is always present when saturated steam is used. Superheated steam is successfully used for process work, where both the latent heat and the heat of the superheat of the steam can be used, as for example, when the steam can be blown directly into the substance to be heated. When, however, only the heat of the superheat can be employed, the use of superheated steam does not pay. Its specific heat is only about one-half that of saturated steam and therefore, about twice as much super- heated steam would be required. Superheated steam may be justified when the heat of the superheat can be used in one operation and the latent heat or part of it in a connecting operation. The saturated steam left after the first operation must then contain enough heat for the second operation. 84 > (3 Ul 73 C3 ID « u u S = > . — r = 3 ^- = > 1< - ^ ,9 'Z Z> 2 - 3 v. — o 85 CHAPTER 4 FURNACES AND SETTINGS PROPER furnace design and adequate proportions are the essentials in securing high boiler efficiency. A single design of setting cannot be standardized to meet the various fuel, operation and space requirements. To obtain complete combustion, special designs are required for low and high volatile coals, gas, fuel oil, waste heat, and for hand or stoker firing. Furnace Design THE main problem in furnace design is to determine the volume of the furnace and the length of the flame travel. Furnaces with a small com- bustion space, in which the flame travel must be short, are not suited for the burning of high volatile coals at high rates of combustion. For reasonably complete combustion, the combustion chamber must be large enough to permit thorough mixing of the air and gases; sufficient time for combustion; and to maintain temperature sufficiently high to secure combustion. Mixing. To secure efficient combustion, the volatile distilled from coal, which in part is composed of tar vapor, gases and small solid particles of floating carbon, must be intimately mixed with an adequate supply of air. Fuel oil and gas must also be mixed thoroughly with air. If the right mixture is not maintained, the result is stratification, such as is common in hand-fired furnaces not operated properly. In stoker-fired installations the fuel is more evenly distributed over the grate. This prevents the inrush of large quantities of air in spots and the choking of air in other parts ; the products of com- bustion are, therefore, mixed more uniformly with oxygen-bearing air. Additional air is sometimes supplied above the fuel bed to obtain thor- ough burning. Arches, piers, wing walls and steam jets are sometimes added in hand-fired furnaces to give a thorough mixture of air and gas so that the higher volatile coals can be burned without smoke. The locations of these parts depend upon the kind of coal and the manner in which the boiler is to be operated. Such structures increase the draft loss through the boiler, so that the steaming capacity for a given draft is reduced. Generally, how- ever, they improve' combustion. Time. This is next in importance to the mixing requirement. The time available for combustion (before the gases are cooled by the boiler heating surface) depends upon the length of gas travel, or for the same grate area, upon the cubical contents of the furnace. The combustion space must be correctly related to the rate of combustion for a given fuel, otherwise economy will be sacrificed. Experiments by the Bureau of Mines with a Heine Boiler indicate the relation between boiler economy and furnace volume, as in Fig. 15. In these, semi-bituminous coal was burned on a Murphy stoker having a pro- jected grate area of 25 square feet. Pocahontas steaming coal was con- sumed at the rate of 65.4 lb. per sq. ft. of grate per hour. When the products of combustion had passed through 80 cu. ft. of combustion space, the gases contained fully 2).7 per cent of unconsumed combustible, but as the space traversed increased to 160 cu. ft. the combustible decreased to 1 per cent When a point corresponding to 260 cu. ft. of the furnace volume had been passed less than 0.5 per cent of combustible remained in the gases. This indicates that the larger the combustion space, the more nearly complete is combustion. 86 F I' R X A C E S A X D S E T T I X G S to 1 ' ' ' ^ ' 1 1 I 1 1 I 1 1 1 1 ' ' ! . ' 1 I 9 1 1 i , . , - : . ! I'll 8 \ 1 1 \ 1 1 t7 \ \ 26 1 ' \ 1 \ i o _ \ 1 c ' O £ 4 \ \ > 1 ^3 \ s. 1 o 1 s, i I ' s V ^ ' - n 1 ' ■ ■ . \~ 5: 100 153 200 Combustion Space Volume, Cubic Feet 250 300 Fig. 1 5. Relation between Furnace Volume and Completeness of Combustion. Temperature. The combustible gases in a boiler furnace must be kept at a temperature sufficiently high to permit complete combustion, economically and without smoke. The ignition temperature of hydrocarbon gases is between 1000 and 1500 degrees. However, this temperature varies with the amount of air, kind of fuel, and the quantity of neutral gases present. A high furnace temperature generally means rapid combustion and good efficienc}-. It is the result of higher CO2 and the absence of CO, so that the gases are more nearly burnt while traversing the furnace. The varia- tion of furnace temperature and boiler load is shown in Fig. 16. which represents tests by the U. S. Geological Sun-ey on a Heine boiler and underfeed stoker. 3000 2800 2600 52400 ^2200 I. o2000 II. • 1800 |l600 O1400 ^1200 £1000 I 800 H 60ot i 400 c = 200 1 _^ '-' ^ ^ ^.^-^^ 1 ^ > ^ / / 1 ! / / / 1 / 1 1 1 1 i 1 1 20 40 60 80 ;C0 120 140 Boiler Capacity, Percent 160 ISO 200 Fig. 16. Relation Between Boiler Capacity and Temperature of Combustion Chamber. FURNACES AND SETTINGS 87 The effect of temperature is also shown by tests of the University of Illinois on a Eleine boiler equipped with a Green chain grate, Fig. 17. An economizer and a large induced draft fan were used, so that the rates of combustion were high. Coals having a combustible volatile content of from 30 to 40 per cent were successfully burned. Fire clay tiles are placed on the boiler tubes directly over the fire, forming the roof of the furnace and preventing the hot gases, which are still not fully mixed, from coming in contact with the cooler tubes. ■»j/J"|*— J'-^^'-— >|/5"p Fig. 17. Heine Boiler Tested for Smokelessness. Tests were conducted on this boiler with C-tile on the bottom row of tubes, and then with 7'-tile. The C-tile encircle the tubes completely and present to the furnace a roof of solid firebrick. The T-tile rest upon the top of the tubes only, and therefore present to the furnace a roof of part brick and part water tubes. With T-tile, the smoke record varied from 9 to 17 per cent, which corresponds to Nos. ^ and 1 on the Ringelmann scale, respectively. The C-tile record showed zero smoke. The temperature of the gases entering the nest of tubes from the combustion chamber averaged 1384 deg. in the first test, and 1678 deg. in the second test. The corresponding temperatures over the bridge wall were about 1850 and 2150 degrees. Over 100 trials were made at loads varying from 60 to 150 per cent of rated boiler capacity, and from these L. P. Breckenridge concluded that it is almost impossible to make smoke with this setting under any condition and that it operates with economy. Furnace Volume. The Bureau of Mines shows that the furnace size is influenced mainly by the percentage of excess air, the rate of combustion and the kind of coal. FURNACES AND SETTINGS 89 A Heine boiler and a special Murphy side-feed stoker furnace were used in the tests. Table 5 gives the composition of the three grades of coal — Pocahontas, Pittsburgh and Illinois — ^burnt in these tests. The results, Fig. 18, represent a supply of 50 per cent excess air for two rates of com- bu'slion of the different coals, and give the combustion space necessary per square foot of grate area for various combustion conditions, which are expressed in terms of the ratio of undeveloped heat to the total heat in the coal. These figures can be used as a guide in proportioning almost any style of furnace. 1.6 2 2.5 3 3.5 Unconsumed Combustible, Percent. Fig. 18. Combustion Space Required per Square Foot of Grate Surface. Based on 50 Percent Excess Air for Coals Tested. 90 FURNACES AND SETTINGS Table 5. Analysis of Coals Used in the Tests. PROXIMATE ANALYSIS OF COAL AS RECEIVED Constituent Pocahontas Coal Pittsburgh Coal Illinois Coal Moisture Volatile matter Fixed carbon Ash per cent per cent per cent per cent 2.21 15.78 71.65 10.36 2.51 30.28 56.82 10.39 16.16 34.09 39.19 10.56 100.00 100.00 100.00 ULTIMATE ANALYSIS OF DRY COAL Hydrogen per cent Carbon per cent Nitrogen per cent Oxygen per cent Sulphur per cent Ash per cent Calorific value per pound, as received B. t. u. 3.92 80.90 1.06 2.97 .56 10.59 100.00 13,762 4.82 76.57 1.55 4.99 1.41 10.66 100.00 13,365 4.66 69.63 1.49 9.55 2.08 12.59 100.00 10,433 A long narrow combustion space is to be favored rather than a short wide one of the same cubical contents. For conditions other than Murphy type furnaces the secondary air supply should be thoroughly mixed with the gases arising from the fuel-bed. The secondary air should always be admitted near and over the fuel-bed, at high velocity, and in a large number of streams. A variation of 50 to 100 per cent in the excess of air makes no appre- ciable difference in the efficiency of the small furnace. In a furnace of large size, however, a small variation in the excess air will affect the oper- ating efficiency, so that close control of the air supply becomes necessary The minimum percentage of unconsumed combustible in the products of combustion is much larger in a furnace having a small combustion space than in a furnace having a large combustion space. The efficiency obtained with the large combustion space is therefore much higher. For boilers operated at heavy overloads, a large furnace volume is particularly essential. Efficient combustion is secured when the furnace volume permits ample time, adequate mixing and sufficient temperature for thorough burning of the gases. The boiler settings should be high and the baffles placed horizon- tally on the tubes. The horizontal baffling promotes the mixing of strat- ified layers of the gases, and gives the gases time to burn completely before the tubes cool them below the temperature of ignition. Head Room for Coal Burning Boilers. A definite height of boiler setting is required for complete fuel combustion. Investigations by O. Monnett on settings for the smokeless combustion of soft coal are summarized in Table 6, applying to water-tube boilers under average operation. FURNACES AND SETTINGS 91 Table 6. Headroom Requirements for Smokeless Settings Furnaces Horizontal Return Tubular Water Tube Hor. Vert. Hor. Vert. 54 60 66 72 Eaflf. Baff. Baff. Baff. 1-U' 1-14" 3i' 8i' Pitch Pitch Pitch Pitch Continental or Scotch Marine (All Dimensions in Inches) No. 6 -d No. 7 .^No. 8 'O Down draft 03 McMillan •^ Twin fire Semi. ext. refuse burning •>^ Burke 2 rJi McMillan.... Chain grate c 73 Moore 2 oj Roney fe^ 20th Cent.... ^ Detroit ^-^ Model 17)^ McKenzie. . . . Murphy ol T3 American "§ oj Jones Taylor Westinghouse Shell to dead plate Front header to floor 32 34 34 36 72 * 78 * 36 40 40 42 t t t t 32 34 34 36 72 * 78 * Shell to floor 60 60 60 60 72 * 78 * 52 54 60 60 72 * 78 ♦ 58 60 62 64 72 * 78 * ft ft tt tt 84 * 90 * 48 48 50 54 60 * 66 * 48 48 50 54 60 * 66 * 72 72 78 78 84 114 96 120 48 54 60 60 72 102 78 108 60 60 60 72 84 108 90 120 54 60 66 72 84 108 90 120 66 72 78 84 90 * 96 * 66 72 78 84 90 * 96 * 66 70 70 70 90 * 96 * 66 72 78 84 90 * 96 * ** ** ** * * Full extension Full extension ** ** ** ** Full extension Full extension Full extension Full extension Shell to Dead Plate 42 42 42 42 78 96 84 102 36 38 40 42 78 96 84 102 ** ** ** ** 84 102 90 108 ** ** ** ** 84 102 90 108 Min. diam. of furnace 36 in. ** * Combinations not recommended as smokeless settings. ** Combinations not ordinarily met with in practice. t Not adapted to water-tube boilers, tt Applied only t j water-tube boilers. No. 8 better for H. R. T. boilers. t Exceptionally wide settings will need more head room to take care of extra spring of arch. 92 FURNACES AND SETTINGS Classification of Settings IN the burning of fuels economy is represented by completeness of com- bustion and smokelessness. As this depends upon the style of setting, air supply and method of feeding coal, it is used by H. Kreisinger as a basis for classifying furnaces, as shown in Fig. 19. At (A) is a hand-fired furnace into which the coal is fed intermittently on the top of the fire. The air Coa/ Distillation.^ . «s lone \ O Hand Fired Furnace Distillation ^^^<^ 1 1 U \^^^ B Side Feed Stoker K Distillation % f lone C Chain Grate Underfeed Stoker Fig. 19. Classification of Furnaces According to Method of Feeding Coal and Air. comes in a continuous stream through the grate, from the bottom. Some air should also be supplied over the fuel-bed. _ In the side-feed stoker (B) the coal is fed continuously from the side and the air from the bottom at right angles to the path of the coal. The coal moves down the grate by gravity and by the agitation of the grate bars. Air can also be admitted through special tuyeres placed imme- diately above the fuel-bed, at the entrance of the coal into the furnace. Some' air enters through the coal in the magazine. The diagram (C) shows a furnace equipped with traveling or chain grate. The feeding of the coal is accomplished by the motion of the grate. The air and coal are both fed continuously, the air being fed at right angles to the coal path. Additional air is supplied through the coal in the maga- zine, through the thin fuel-bed near the bridge wall, and through leaks along the side walls. In the underfeed stoker (D) the air and coal are fed uniformly and in the same direction. Air is also admitted through the damper in the front door of the furnace. These styles of furnaces are shown in the following illustrations with settings of Heine boilers as installed in modern plants under standard as well as special conditions, and for a variety of fuels. In practice each problem FURNACES AND SETTINGS 93 has to be studied to decide upon the proper furnace design and proportions. Generally a change in the location and in the type of tile used in the baffles will give furnaces for particular combustion requirements. In vertically-baffled boilers the extinguishing action of the tubes, with the short flame travel, produces an undesirable amount of smoke. If the combustion in these boilers is to be smokeless the furnace volume and there- fore the setting height must be increased considerably. Even then the mixing effect of the bridge wall and combustion chamber are absent. The horizontally-baffled boiler has the necessary furnace volume with the ordinary height of setting. Horizontal baft'les, in hand or stoker fired boilers, permit a long travel of unchilled flame and maximum time for com- pletion of combustion. The turn of the gases at the bridge-wall disrupts any tendency to stratify, and this mixing effect also promotes combustion. Settings for Hand Firing TN burning bituminous coal, it is not practicable, according to O. Monnett. ^ to combine a hand-fired furnace with a vertically baffled water-tube boiler. To prevent smoke the furnace must be arranged with a horizontal baffle, as in Fig. 20. In this design the lower part of the tubes over the fire is left bare by using T-tiles for the baffle. For the high temperature zone over the bridge wall and for some distance back of it, the tubes are entirely encased in C-tiles. This part of the baffle is extended from the T-tiles to the deflection arch provided to mix the air and gases thoroughly. pmmmmmmmmmM^ Fig. 20. Hand-fired Setting for Bituminous Coal (Areas of Passages are given in Percent of Grate Area.) o PQ CO c CO ■M CO /////M •■/<>-■' Fig. 26. Chain Grate Setting. With side-feed or double inclined stokers, the boiler can be set with an extended furnace or with a flush front. In the t>pical setting. Fig. 27, the bottom row of tubes is enclosed in baffle tiles to give a solid roof, and an auxiliary bridge wall breaks up the currents of gases and insures a thorough mixture. The side-feed stoker combined with a vertically baffled boiler will not gne smokeless combustion. With horizontal baffles a 7'_>-ft. clearance is sutticient between the bottom of the front header and the floor line. 1-^ U R N A C F. S A N l^) S K T T T X G S 101 The 07:cr-fccd type of stoker fits in at the front of the boiler and has a shaking or dumping grate at the foot of the bridge- wall. For boilers with horizontal baffles, a 6-ft. setting is required, while for vertical baffles the clearance should be aliout 9 feet. Fig. 28 shows a Heine boiler and a front- %W/MW///////////y *v >> VY S\^^ s^S^^?^ -N^ yy ^^^s^^ys-s^s>^>^'-^vs-y^V v.^T^ VM Fig. 27. Side Feed Stoker and Extension Furnace Setting. feed stoker. Tlie typical l)affle arrangement is used, but deflection arches or piers sometimes aid in mixing the gases. When the clear opening between the top of the bridge-wall and the bottom of the hrst row of tubes is not less than 40 per cent of the grate area, piers are not required. c "S u '0 o PQ o •0 4-J Wi d ns CS •0 E 4-1 CO W 15 H ■53 6 ffi U 14-1 N •S P4' 'C w K •-^ 10 • (M w o> W (U u A ;^ +J 2 o !§ ■« ■M J2 G ;3 cc C/3 S ta -M rt .« Oh fi "< ^ •d bD » c CO • »H a CO a (U U ■5 m T3H u cS OS (U ■*-> ^^ Xfl ■5 0) PQ .s 'O u CO •0 C Oh* cC ■M • CO K (U t^ .S 'C VO ffi (4-> ^ H Ph' W) , .S 1 K •M lU Ih in u 10 FURNACES A X D SETTINGS 103 Fig. 28. Setting for Overfeed Stoker. With the nnderfccd stoker, the rates of combustion are usually high, so that a great volume of combustible gas has to be burned in the furnace before being chilled by the boiler surface. For this reason, the standard Heine furnace design, Fig. 29, is generally retained. The settings can be lower for the horizontal types of underfeed stokers than for the in- clined types. Fig. 29. Setting for Horizontal Underfeed Stoker. 104 FURNACES AND SETTINGS Fig. 30 shows a Heine boiler and superheater set for mechanical draft, and an underfeed stoker of the inclined type. The headroom between the waterles- and the floor line is about 7 feet. The lower baffle is made to mm Fig. 30. Inclined Underfeed Stoker in Heine Boiler, Equipped with Superheater and Mechanical Draft. enclose the tubes. By changing the tile to the third row of tubes, the setting in Fig. 31 is obtained. In this, more heat is absorbed by direct radiation, and excessive furnace temperatures are avoided. F U R N A C E S A N D- S E T T I X G S 105 By installing double stokers, boiler capacity and efficiency can he in- creased for almost the same space. One stoker is placed at the front and one at the rear of the setting-, as in Fig. 32. By forcing a greater weight of --•ases through the boiler, the capacity is increased. The larger furnace Fig. 31, Modified Stoker Setting. volume gives better combustion ; also, a larger proportion ot heat V; » ^^l'; ^d to the boiler. At heavv loads the overall efficiency is highci than when one stoker is used. Anv variation in the efficiency is due to changes in the furnace operation, because the efficiency of the boiler, proper, as a heat absorber, is practically constant. 106 FURNACES AND SETTINGS Methods of handling coal and ash are discussed in Chapter 16 on OPERATION. Fig. 32. Double Stoker Setting for Heine Boiler with Superheater. FURNACES AND S K T T T N (-. S 107 Ashpits THE ashpit is made of concrete or brick. The design depends upon the boiler load, kind of coal, type of furnace, whether hand or stoker fired, and of setting. Ashpits satisfactory with a mechanical or pneumatic system may give trouble for hand removal, while pits for hand operation may also prove satisfactory with a conveyor. The ashpit should be large enough to accommodate the ashes from an 18 to 20-hr. run. Such pits elimmate the handling of ashes by the night shift. They also protect the grates or stokers against destruction by the action of accumulated ash and clinker. In practice, however, ashpits for hand-fired furnaces are seldom of more than an 8 or 10-hr. capacity. Pits having capac- ities of 12 to 14 hr. are generally provided for stoker installations. To proportion the pit for a given period, the maximum amount of fuel that can be burned on the grates must first be determined. The maximum percentage of ash or refuse should be figured on the basis of the lowest grade of fuel to be burned. The pounds of ash and refuse to be handled per hour is the product obtained by multiplying the percentage refuse and the hourly fuel consumption. The volume is determined by allowing 40 lb. of ash to the cubic foot. The total capacity required then depends upon the periods of ash removal. Ashpits should be so accessible that they can be easily cleaned ; otherwise the work may not be attended to regularly, and the grates or stoker mech- anism v/ill be damaged. Fairly small pits are easily cleaned and give better results than large pits, which involve heavy labor. Ample room must be provided for the use of a hoe or shovel. The pit should be not longer than 8 feet. Doors, gates or valves, as used on hoppers, should be arranged to open and close easily and should be accessible from the floor. Means of inspection should be provided to make sure that all the ash has been dis- charged. With reasonable care, the cost of ashpit repairs or relining can be kept low. Some typical designs of ashpits are given for different operating con- ditions. The simplest form is the usual pit for hand-fired furnaces, as shown in Fig. 33. ■J.TI- ft A-": Fig. 33. Common Ashpit for Hand Firing. A modification to obtain greater ash capacity without sacrificing ease of ash removal is shown in Fig. 34. Grand Central Terminal of the New York Central Railroad, New York City in course of construction. This building contains 8550 H P ^' of Heine Standard Boilers. F IT R N A C E S AND S R T T I N G S 109 Fig, 34. Large Capacity Ashpit for Hand Firing. A common form, particularly for side-feed stokers, is shown in Fig. 35. The cost of construction and maintenance is low ; Imt it is very difficult to remove ash from pits of this form unless a pneumatic or steam conveyor is used. Fig. 3 5. Rectangular Ashpit of Large Capacity. In modern stoker-fired plants it is the general practice to use hopper ashpits. The labor of handling the ash is greatly reduced and the installa- tion of ash conveyors is more convenient. The tunnel under the firing floor enables the ash to be easily hoed from the hopper ashpit into conveyors or ash cars without interfering with tbe work on the firing floor. Fig. 36 shows an example of such an arrangement. 110 FURNACES AXD SETTINGS This system is also frequently used in hand-fired furnaces burning very low grade fuels having a high ash content. Dumping grates or dumpmg dead plates are then generally used. O ii \^.^itt x^ m -M 1 # Wi^^■^yo-.■■.'?^-^^ ■*£3-.i a CO 4) V o CO CO o VO u CO 0. FURNACES AND SETTINGS 115 Powdered coal requires care in handling. In a well-designed and prop- erly operated plant there is but little danger from explosions, iriowever, where hoppers, conveyors, elevators and dust collectors are not tight, and the powdered coal is allowed to escape into the room, there is great liability of explosion due to the possibility of the ignition of the cloud of coal dust by an open flame. Pulverized coal when newly ground is practically a fluid, because of the entrained air, hence it is readily handled by conveyors and flows easily from hoppers. But, after standing from 36 to 48 hours, the entrained air escapes and the coal settles down and packs in the hoppers. The correct way to overcome the difficulty of packed hoppers is to provide compressed air lines in the hopper sides and thus agitate the packed coal with air, supplemented by hand poking. Hammering the hopper sides to make the coal flow only causes it to pack the tighter in the bin. The sides of powdered coal hoppers should have a slope of not less than sixty degrees. In order to handle the crushed coal in the pulverizers it is generally necessary to dry it down to fiom one to two per cent moisture content. The pulverizer is generally adjusted for grinding the coal down to a fineness of 85 per cent through the 200-mesh sieve, and 95 per cent through the 100- mesh sieve. The better combustion conditions obtained with coal of greater fineness than given above does not warrant the cost of the extra pulveriza- tion. Powdered Coal Burners II} URNER Installations usually include a feeder of the screw conveyor -*-^ type, such as Fig. 40. The capacity of the feeder depends upon the pitch and depth of the screw, while the amount of feed is controlled by its speed, which is adjusted by a variable speed motor drive. Air for feeding and mixing is supplied by a blov/er at 6 oz. pressure. The fuel, as it drops into this blast of air, is agitated by a paddle wheel so that the mixture of air Fig. 40. Lopulco Type Variable-speed Fuel Feeder. 116 FURNACES AND SETTINGS and coal remains practically of constant density nntil injected into the fur- nace. The type of burner recommended with this equipment is shown in Eior. 41. Fuel ariK Air Inlet Damper Fig. 41. Lopulco Type Pulverized Fuel Burner. In the burner shown in Fig. 42. a variable speed screw feeder at the bottom of the pulverized fuel bin delivers the coal, the amount being regu- lated by a hand wheel. A feeder of this type having a capacity of 500 lb. of fuel an hour can be regulated to deliver as little as 26 lb. an hour. There are tv/o air supplies, botli controlled by blast ga^es. The air for combustion is at 1^-oz. pressure, while the air conveying the fuel is at 6-oz. pressure, expanding down to ly4-oz. in the burner. The burner used is of cast iron pipe with a specially shaped elbow in which the fuel pipe is placed. Primary Air Q.oz Powdered " Fuel Bin Secondary Air l^oz- Blast Gate- Feeder -—^Jnand \ C '" Blast Gate Peep Hole- Furnace Wall -- ^ Burner- Fig. 42. Quigley Burner Arrangement for Powdered Coal. In another Inirner arrangement no mechanism whatever is used. The air in motion through a mass c>\ powdered fuel picks up sufficient fuel to make a combustible mixture. According to W . A. Ezaiis, the control of the fuel supply to the burners l)y air regulation rather than by varying the speed of a screw feed gives best results. The speed of the screw conveyor cannot be adjusted closely, but the air blast is subject to exact control. For any given feed adjustment, a burner arrangement should deliver the required fuel with not more than a 3 per cent variation in quantity for any number of 5-min. intervals. F U R N A C 1^. S AND SETTINGS 117 Settings for Oil Burning THE ii?e of petroleum as fuel for steam generation has increased remark- ably within the last decade. This has been brought about by the abun- dant supply resulting from the development of new oil fields, and by certain advantages of oil tiring over coal firing. But as the supply of petroleum suitable for fuel has not kept pace with the unusual demand, uncertain deliveries and increasing cost are now working to the disadvantage of those plants using oil. There is no doubt but that oil ranks second in importance to coal as fuel for steam generation, but with the present rapid depletion of oil resources it is evident that oil firing will never supercede the use of coal. In general the petroleum used for steam generation is of two types, the one commonly called fuel oil is the heavy oil resulting from a partial refin- ing of paraffin crude, and the other is the unrefined, asphaltum-base, crude oil. The oils found in the mid-continent and Eastern fields contain a paraf- fin base, while those produced in the Gulf and Western fields contain an asphaltum base. A discussion of petroleum with typical analysis is given in Chapter 13 on FUEL. The success of oil firing depends largely upon proper furnace design, and there are a number of important points which must be considered. First, a large amount of refractory radiating surface must be provided to assist in combustion. Good practice in this regard is to allow from 0.9 to 1.2 square feet of radiating surface per boiler horsepower developed. Second, the furnace volume must he so proportioned that the gases are given time for complete combustion before reaching the comparatively cool heating surface. A combustion space of about 2.0 cubic feet per developed boiler horsepower will satisfactorily meet the average volumetric requirements. Fig. 43. Typical Oil Burning Setting. FURNACES AND SETTINGS 119 In proportioning both radiating surface and combustion space, the proposed ratings at which the boilers are to be operated should be used in the calcu- lations rather than the manufacturers' nominal rated horsepower. The setting of the Heine boiler, with its large combustion space and ample refractory radiating surface, satisfactorily meets the requirements of oil firing. A typical setting is illustrated in Fig. 43. The location of the burners in oil-fired setting design, should be such that the flame action will not be localized on portions of the heating surface, so that trouble from blow-torch action with the resultant blistering of tubes will be obviated. The oil or flame should not impinge directly on any por- tion of the furnace brickwork, because when starting up a furnace the oil dripping down after impingement on such cold surfaces may collect on the floor of the combustion chamber in such quantities that a serious explosion may occur when this pool of oil becomes heated up to the ignition point. Certain features in chimney design for oil firing are discussed in Chapter 6 on CHIMNEYS. Oil Burners ONE advantage in the use of oil for fuel lies largely in the fact that it can be broken up into minute drops so that the air for combustion comes into intimate contact with every particle of the liquid with the combustible gases evolved. The requirements for efficient combustion are a chamber of the proper proportions with the correct air supply properly distributed, and the thorough atomization of the entering fuel, the term "burner" being applied to the atomizing device. The desired effect is secured either by the action of steam or compressed air, which atomizes the oil and carries it into the furnace, or by purely mechanical means. There are many types of oil burners and these are arranged differently because of tlie method of operation and the shape of the flame. Sometimes the oil is sprayed out in a fan-like flame between firebrick blocks, which form the approximate boundaries for the flame. The burner can be inserted through the firing door, with the grates cov- ered with checkerwork with ^-in. space between the bricks, but the "low setting" is preferred, in which the grates are removed, and the checkerwork laid on supporting brick in the ashpit and the bridge wall cut level with the top of the checkerwork. Steam atomizers include outside mixers, in which the steam impinges on the oil current just beyond the tip of the burner, and inside mixers in which the two come into contact within the burner. A combustible mixture of atom- ized liquid and volatile gases issues from the nozzle. In air atomizers, a jet of air under high or low pressure is used to break up the oil, part of the air for combustion entering in this manner. With mechanical atomizers the oil, preferably heated, is forced out under pressure through a distributing- tip, or by the whirling action of a revolving carrier. Burners utilizing steam for atomization are installed in many stationary oil-burning power plants. They produce thorough atomization, with a long- flame, but cannot be used where the steam would be liable to condensation, and great care must always be taken to keep the steam consumption down to a minimum. Air atomizers are desirable in marine work or in stationary plants where it is necessary to conserve the water supply, and they have the further advantage that the latent heat in the exhaust from the blowers or compressors is returned to the boiler, and no heat is carried away by the steam in the flue gases. They give a short, intense flame and the furnace brick- work must be proportioned accordingly. Under proper conditions, either steam or air atomizers can be operated with a stean-i consumption of 2 or 3 per cent of that produced by the boilers. Mechanical atomizers require 120 F U R X A C E S AND SETTINGS little .-team, and their exhaust can all be returned to the boilers. Tnej- are. in general, susceptible of ven.' nne adjustment to meet var\-ing load con- ditions. Illustrated below are several t>~pes of burners now on the market. In the Hammcl Burner, Fig. 44, the oil, either heated or cold, is fed into the upper pipe, is forced through the sloping passage in the burner to the mix- ing chamber C. Here it encounters the entering steam jet at an angle, the hea\->- hydrocarbons are atomized, and the lighter ones vaporized, and the mixture issues from the burner to the combustion chamber. Thin renewable plates forming the top and bottom of combustion chamber C receive any wear due to grit in the oil. while moisture carried in with the steam flows along the lower passage and is blown out under the steel plate. The Ham- mcl Oil Burning System is ordinarily installed without arches, bridge walls or target walls. a u u er -ead. Head Sfea' Fig. 44. The Hammel Oil Burner. T3 — ZT The Staf'lcs & Pjcifcr Burner, Fig. 45. operates with steam or air, which flows through the large pipe encasing the oil pipe, until it enters the mixer, which is set with the apex P slightly below the center of the tip. The flow of oil is regulated bj* the valve rod inside the steam pipe, operated bv the wheel shown. /?./ Fig. 45. The Staples and Pfeifer Oil Burner. 1-^ I' R X A C J-: S A X USE T T 1 X G S 121 Tn the focrst Fuel Oil Burner, Fig. 46, the oil under gravity or pres- sure feed flows in through the lower pipe, and the atomizing steam or air through the upper pipe. The illustration shows a fan-tail burner, although burners giving a cone-shaped flame are also furnished. Fig. 46. The Foerst Fan-tail Type Oil Burner. The ir X. Best Calorcx Burner. Fig. 47. is an cxiernal mixer, employ- ing a jet of the atomizing fluid issuing at right angles to the oil. Ihe atomizer lip is held tightlv, but can be raised for blowing out incrustations with the aid of the by-pass. Burners are made for throwing a long, narrow flame, or a fan-shaped one up to 9 feet wide. 3 Oh CO > V a u o O 1) a a "3 o CO CO V G FURNACES AND SETTINGS 123 By- Pass Valve- ^Orj Fig. 47. The W. N. Best "Calorex" Oil Burner. The Koerting Cyclone Oil Burner, Fig. 48, is designed for use where forced draft is required, or where it is desired to make use of a low pressure oil pump already installed. The oil issues from an atomizing nozzle, while the pipe through which it flows is surrounded by a passage carrying com- pressed air, which receives a gyratory motion, so that the mixture coming out of the cylinder forms a spreading cone, in which the flame remains close to the burner. Air atomizing burners are also supplied, and burners for use where the oil is under gravity, as in small plants. Ji'r Blast Connection Air Recjisfer Fireclay Cylinder Fig. 48. The Koerting Cyclone Oil Burner. Of more general application is the Koerting Mechanical Oil Burning Sys- tern, in which the fuel is pumped at high pressure to centrifugal spray nozzles, at a temperature of about 260 deg. F. The burner is surrounded by an ad- justable cylindrical air register, admitting air through rectangular openings, giving an intimate mixture of combustible material. The Cocn System, Fig. 49, utilizes a mechanical burner into which the oil is pumped under pressure and receives a whirling motion. The adjusting wheel shown in the sketch is used to regulate the flow; by turning it the small ball at the cone end can be lowered, reducing the flow to a minimum without shutting it of¥. ' OS FURXACES AXD SETTINGS Adfush'nq Wheel Shui-off Valve Y\a. 49. The Coen Oil Burner. The /?av Roiarx Burner, Fig. 50, atomizes the oil m an open cup. re- volving at hiVhspLd, while a^r under V. lb. pressure issues from a cylmdrical slot surrourdki-^e atomizer and directs the mixture into the furnace. The ;umpblo^^r and atomizer are driven by a 34 H. P. motor, and can be swung from the furnace front. Fig. 50. The Ray Rotarj^ Crude Oil Burner. Oil a^ fuel requires the use of certain auxiliarj- apparatus, most Important " t^'sf m^s^L^rTc^lin^ior oU pump and condensing ^e hea1.r set manufactured by the G. E. Witt Co. The oil, -^^^Xourh^^Vtraifer t^^ numo is delivered to the heater, after which it passes through a strainer to ?he oil burner line The heater consists of copper tubes, through which the exhauTsteam from the pump circulates, heating the oil m the cast iron chamber surrounding the copper coiU. FURNACES AND SETTINGS 125 Oiu Inlet ^-■ To Pump Oil iNLEj^^jTlll To Heater 0il5trainer / .Outlet To Burners 5ectionThru Heater Fig. 51. Witt Oil Pumping Set with Condensing Type Heater. Tar Burning "VV/ATER gas tar, which is a by-product from gas works using the water ^^ gas system, makes excellent fuel for use under steam boilers. An aver- age tar will have a calorific value of about 15,000 to 17,000 B. t, u. per 11). and will weigh about 9.5 lbs. per gallon. In general it may be said that a furnace suitable for burning crude oil will give satisfactory results when using water gas tar as fusl. Refer to remarks given elsewhere on oil burning furnace design. Crude oil burners can be satisfactorily used for burning tar, though provision should be made for straining the tar before it reaches the burner, and clean-out connections for blowing out tar lines and burners with steam or compressed air should be provided. Inasmuch as a low flash point is a characteristic of water gas tar, it should not be preheated beyond the tempera- ture at which it is sufficiently fluid to be handled. Coal gas tar may be used for boiler firing, but the present high value of coal tar derivatives, which are used as bases for dyes, explosives, etc., precludes its use as a fuel. CO Q bB PQ CO CO G O CO bO CO V X CO o g G u PQ CO O a a *3 o PQ V C CO c CO w o FURNACES AND SETTINGS 127 Gas Burning NATURAL gas, blast furnace gas, coke oven gas and producer gas are the four principal types of gaseous fuels which are available for use under steam boilers. NATURAL GAS : Natural gas is probably the most widely used of the four principle gases, although the depletion of the natural gas fields is now so rapid, that its utilization is being rapidly curtailed. Representative analyses of natural gas from various locations are given in Chapter 13 on FUEL. The design of a boiler furnace for burning natural gas involves several important points. First, the furnace volume or combustion space must be proportioned so that the gases will not come into contact with the cool heat absorbing surface until combustion is completed. A furnace volume of about 2 cu. ft. per rated horsepower will give sufficient combustion space to meet the above conditions. The standard Heine boiler, with its arrange- ment of horizontal baffling on the lower row of tubes, gives a furnace volume particularlv well adapted for the burning of natural gas. Dutch oven furnace construction is not necessary with Heine boilers burning natural gas. Second, in order to prevent laning action of the gases in their passage through the boiler it is more desirable to use a large number of small burners than a few large ones. One burner for 25 to 30 rated boiler horsepower will give satisfactory results. Third, where furnace widths are over 5'0" it is desirable to install checkerwork to act as an igniter for the gases. In some cases one checkerwall placed about three or four feet from the burner outlets is used as an igniter and a second checkerwall, sorne three or four feet behind the first, acts to break up the flame and mix the gases thoroughly after passing through the first. Fig. 52 shows a typical natural gas burning setting for a Heme boiler. ro fe, ^(^(';^^.^c^.^/.^:tf.d^-d<-:^\-^d g U V FURNACES AND SETTINGS 139 Fig. 62. Alternative Settings for Burning Bagasse. Waste Heat Settings CERTAIN manufacturing processes depending on the direct combustion of fuel are inherently inefficient when considered from a thermal stand- point The term efficiency, as applied to these various processes, has the same significance as it has when applied to the operation of a direct fired <;team boiler. In boiler practice the object is to utilize every available B. t. u for the generation of steam; but there are certain unavoidable heat losses ot which the greatest is the heat carried away by the stack gases. ^ In some industrial burning operations the thermal efficiency is not above 40 per cent. That is to say, the number of B. t. u. actually utilized in the melting smelting or treatment of the material involved, is only 40 per cent of the number of B. t. u. actually supplied to the furnace as fuel. In these operations, as in steam boiler practice, the largest thermal loss is the heat carried away by the waste or stack gases. In order to increase the efficiency of the primary furnace, waste heat boilers are installed, which generate steam for pknt use This steam is a direct saving. With the ever increasing price of fuel, the mstallation ot waste heat boilers is decidedly advisable wherever conditions permit. o in OS V X 08 V G 'C X o o "S ■« •4-) c: o (J 6 CO V O 1) a O 6 O c V e a O •O c csl O a & V O V a CO O FURNACES AND SETTINGS 141 The operation of the followmg types of furnaces with their relatively low thermal efficiencies, is in general such that waste heat boilers can be profitably installed. Open Hearth Steel Furnaces. Rotary Cement Kilns. Puddling Furnaces. Malleable Iron Melting Furnaces. Forge Heating Furnaces. Bee Hive Coke Ovens. Coal Gas Benches. Oil Stills. Zinc, Copper, Nickel, etc.. Refining Furnaces. Soda Ash Furnaces. Glass Melting Furnaces. Waste heat boilers cannot be conveniently installed with every such furnace, because raw materials, fuels and operating conditions differ so widely that each proposed installation requires individual study to determine the feasibility of a waste heat boiler installation, and the best method of its application. Inasmuch as the temperatures of waste gases available for waste heat boilers vary from below 1000° F. for long cement kilns up to 2200 for melting furnaces, it is obvious that there can be no set or standard proportion of boiler heating surface. With gases around 1000° F. the heat transferred to the boilers by radiation is almost negligible and the steam is generated principally by convected heat. Where the gases are at temperatures above 2000° F. the radiation is appreciable, approaching that of a direct-fired boiler. Hence a boiler for high temperature waste heat work varies but little in design from a standard direct-fired unit. The m.ajority of waste heat boilers in service are utilizing gases at temperatures ranging from 1100° to 1600° F. In this class steam is generated by convected heat and therefore the arrangement of heating surface and baffling departs materially from the standard for direct-fired work. The transfer of heat by convection follows certain laws, of which cog- nizance is taken in the design of Heine waste heat boilers for relatively low temperature work. As early as 1874 Professor Osborn Reynolds developed a law of convection, which has been later substantiated by such investigators as Nicholson, Jordan, Stanton and Fessenden. This law states that the rate of heat transfer bears a certain definite relation to the velocity with which the gases sweep over the heat absorbing surface. Or stated in different words — the B. t. u. transferred per square foot of heating surface per hour per degree difference in temperature between gas and water increase with increasing gas velocities. Therefore, in a waste heat boiler of the convected heat type, in order to obtain a satisfactory rate of heat transfer and to keep the heating surface within reasonable limits, the gas velocities employed are considerably higher than in direct-fired practice. The first modern high gas velocity waste heat boiler was a standard Heine boiler installed in 1910 by C. J. Bacon at the South Chicago Works of the Illinois Steel Co. The gas velocity in this boiler was equal to 5300 lbs. of gas per square foot of gas passage area per hour, and established the high limit up to the present time. High gas velocities, which generally run from 2500 to 4500 lbs. of gas per hour per square foot of average gas passage area, are obtained in the Heine waste heat boiler by various methods of baffling. In instances where the gases are comparatively free from dust, horizontal baffling is employed. This is easily installed and replaced, and readily rearranged, should it be desired to increase or decrease the gas velocity in order to alter the rate of heat transfer. 142 FURXACES AXD SETTINGS In instances where the gases are burdened with dust, which would accumulate on horizontal baffles, there are emploj-ed other methods of baffling which maintain a high gas velocit}- and allow the dust to fall clear of the tube bank. Several dift'erent types of baft'ling are used in Heine waste heat boilers, and these make such a varietj- of possible arrangements that no tA'pical illustration can be given. The dust falls into hoppers built integral with the setting and equipped with air tight cleanout doors. Due to the high gas velocity employed, there is an unusually high draft loss through the boiler, which is taken care of by induced draft fans. Fans have a steadying effect on the draft at the primary furnace, and when so desired the draft at the furnace may be increased wnth increased furnace output. It is desirable that the fans be driven b}" a variable speed motor or steam, turbine, so that any variation in the quantity' of gas may be satis- factorily handled. In plants where the temperature of the waste gases approaches that of direct-fired practice, or where the conditions do not warrant the expense of an induced draft fan installation, it is customary to use a single pass waste heat boiler and to employ- natural draft. The boiler is then verj- similar in design to a standard direct-fired unit. It is generalh- preferable to install waste heat boilers in connection with continuously operated furnaces. If the furnace is operated only part of the time, it is customar}- to install auxiliary grates under the boiler and to fire coal directly, when the boiler is not being supplied with waste heat from the furnace. The necessity of having tight settings is continuously brought to the at- tention of direct-fired boiler operators ; but in waste heat utilization this requirement is even more important, for there is a greater vacuum in w^aste heat settings, and hence a greater tendency for air leakage through crevices in the brickwork, around loose doors, etc. The waterleg construction of the Heine waste heat boiler is such that one continuous surface is presented at both the front and rear of the setting. There are no separate headers and therefore no crevices to caulk with asbestos rope, which quickly becomes brittle, often drops out, and thus increases the air leakage. The soot blower elements project through the hollow sta3-bolts of the front and rear waterlegs, so that it is not necessary to place dusting doors in the side walls. The fewer the openings in the setting brickwork the more durable it is and the less the tendency for air leakage. All cleanout or access doors should be provided with gaskets to insure tight closure. Steel casings for waste heat boiler settings are not altogether satisfactory, because cracks are likeh' to develop in the brickwork, and being inaccessible behind the casing are hard to detect and repair. Asphaltic compounds suitable for painting the exterior of the brickwork are satisfactorj- for reducing air leakage. One fact in the design of a complete waste heat boiler installation should be constantly borne in mind, — tlie operation of the boiler must in no way interfere with the operation of the primar}- furnace to which it is connected. Bj-pass flues and dampers must be arranged so that in case something un- foreseen happens the gases of combustion can either be passed up the stack or to another waste heat boiler. Where there are two or more boilers utilizing the waste gases from two or more furnaces, it is desirable, where space or operating conditions permit, to arrange one common fine into which the waste gases from all furnaces discharge, and from which branch flues lead to as many boilers as are necessar\- to handle the gases satisfactorily. With this arrangement the dampers can be placed so that any desired flexi- bilit>' of operation is obtained. FURNACES AND SETTINGS 143 Marine Settings IN shipping practice boilers of compact design and light weight are re- quired so that the cargo capacity will be a maximum. Only water-tube boilers fulhll these requirements. For cargo carriers and other steamships, boilers, Fig. 63, are supported by a steel structure secured to the framing in the vessel. On this structure is a steel-plate casing, which encloses the entire setting. Inside of the casing is insulating material, faced with firebrick. This construction insures pro- tection against high temperatures and minimizes the radiation and infiltration losses. Fig. 63. Heine Marine Cross Drum Boiler. For dredge boat service, the setting is bunt itij of lirel)rick, hollow tile, asbestos and sheet iron. All parts of the furnace interior exposed to high temperatures are lined with firebrick. Back of this is the tile, which is Front View of Marine Casings for a Battery of Two Heine Cross Drum Marine Boilers. Rear View of Marine Casings for a Battery of Two Heine Cross Drum Marine Boilers. FURNACES AND SETTINGS 145 covered with asbestos on the outside. The sheet iron encases the entire setting, as shown in Fig. 64. The boiler itself is carried on steel supports at the front and rear, while the breeching and stack are carried by structural framing. Separate Heine publications dealing with marine boiler practice are sent on request. Fig. 64. Heine Dredge Boat Boiler Setting. Boiler Setting Requirements THE essentials of a boiler setting are a firm foundation, proper distribu- tion of brickwork and steel supports, adequate furnace and ashpit space, and insulation against heat losses. The furnace proper and masonry parts included in the furnace should be made of materials that will stand severe service and high temperature with the least maintenance. The refractory material should be combinations of fire-clay, or else special firebrick. _ The boiler must be supported on a solid base to prevent settling and cracking of the walls. A weak base may impose severe strains upon the boiler piping, resulting in sprung and leaky joints and ruptured connections. The soil is the determining factor in proportioning the foundation. In soft ground under a large boiler, it may be necessary to drive piles or to lay a concrete base at least 2 ft. thick over the entire space occupied by the setting. The walls are started on this base or a concrete foundation with footings is laid to receive the brick and steel structure. The depth of foundations and width of footings then depend upon the size of boiler. The side and end walls of a boiler setting should not be less than 12 in. thick. In older designs, a 2-in. air space was generally provided. It was thought that the double wall preventied heat losses and also cracking due to expansion. Tests by the U. S. Geological Survey indicate that an air space is of little value in setting walls. The radiation losses appear to be greater for a wall with an air space than for a solid wall, especially if the air space is near the furnace side. FURNACES AND SETTINGS 147 While concrete has been used in several installations, the walls of the setting, as a rule, are made of well-burned red brick. These should be laid true and in high grade mortar, consisting of a thorough mixture of one part Portland cement, three parts unslaked lime and sixteen parts of clean sharp sand. Each brick should be solidly imbedded and the joint fully filled. Ordinarily, the furnace, ashpit, bridge wall, arches and floor of the combustion chamlier are built of red brick. All parts of the brickwork in contact with the hot gases or exposed to the flame, should be faced with or else built entirely of firebrick capable of withstanding the high tem- peratures. The firebrick should be highly refractory and should be mechanically strong and sound so that it will not spall, flake or crumble. Firebrick linings, walls and arches must be given reasonable care. They should be laid in fire-clay mortar having the same properties as the brick itself. Flux- ing material, such as lime, should not be used in making the joints. Fig. 65 can be used in estimating the number of brick required for standard water- tube boiler settings. o "l CD 15 q: o V) c (0 O X 100 200 300 400 500 Boiler Rating in Horsepower Fig 65. Approximate Number of Brick Required for Standard Heine Boiler Settings. GOO o L CD o 148 FURXACzs a::i szmxGS The lurriace construction can be ma if =:r:: rer :r ~:-r d'jrable by using special blocks in place of the star : i - r : : ^^ 7 T.t : :cks are ??.-rer irz therefore reduce the number : :- :t: :ti Z :he use :: : - .: refractorj, a one-piece, con: : . : :i. :.:..:...: .:: :: .r can f . . .: :...:5 eliminating all joints. 7 T 7 5 s i-dd be strengthened by steel channel buck-stays placed :.: 7 : tt 1 : : e -etting and at several points along :he siies These 5 7 e -e: T :: :Jie walls bv longitudinal and transerre i":h:- ri? Other structural members are rr :t_ - : e :ir number and distribution depending upon :-.e ^e of furnace. Refractory Materials T i : _ ^^ ^ T ;T':^rure5. acncn :: t : ^.ses : ;i ne inii. izrciics ^nc ;: me n : :r and adding :: : . :: : \e nre. Tne rein :: r t? for boiler furnaces :' bricks. r ; ecial forms, ani ; t. F:-e r'ay (a mixture :; sh ;i anf a!n~ in ::::? :ne ^asis of mos: ::: - : ' aterials. Ac: ' r :: _ .. - : -:: ;7; is used eittt: r : ; ; : - n: : - t : - : :: r n : : : Z: : her and r^i f: n !:^ : :t t: : :t: : _ :: : ii 7: : : : : : : :: is :.z^ : . 3ther re:: :: ::y n:a::er sirh as bauxite n i^ esia, to lend plasticity. Tire :7iy5 are divi t_ : : :■ classes: flint clay and plastic clay, the :' ri::Tr iT.ng the harder : :i i: re r.early chemically pure. Flint clays are :t - :r mottled n : ; n Plastic &re clays vary in colzr :r:n: It : i:.:. inchidnn ^ri r nd olive. The plastic is aiiei :: : e r : mj- to incre ne : e n generally at the cost oi its rrin i: r less. Commer : i. r.re i.:. i : - many impurities, and the color 7- n : . 5 -:e r^^ide to its quaiir. . T:er 7; srch as silica, baoxiie, chrome, ms.^::es :e and dolomite have r : ^ . "^ : ^her than fire clay, but have n;: ;r:ved satisfactory in : r r ;: :: T.rese materials do not withsrsni sniien heating, cooling. ; r T : r e : : n : : the gases and ash. T :e : _ : : n rain in a coal furnace, according to JVm. A. Heisel. are i: :i : r t t ' : r.z life and general use of silica brick. With an oil r ^if - 7 : T ^ T ~: re. as far as chemical action goes, but the e ne T : nr :rrr r : f re :: sadden starting or stopping cause r ; e ; ii T.-rr :i : : ^: f::..nig or the breaking off of large 7 : xite brick, according to A. D. Williams, cost two to three times as : --e clay or silica brick. They are hard and tough, cinder does r : :: them: and they last longer than silica brick when exposed to - . However, bauxite :enis :: s;s.7 and break off when suddenly At high pressures :. e ;er?.:rre5 ;/;''; 'rr 2nd magnesite brick cannot withstand the strain f . :_ i :r : r^ md cooling, so that they have not found favor except r sir.; i: z:_7r r^.-l operations. Fire Brick PLASTICITY, accordii^ to JL 5. Marks, is considered the mam factor m ^elertion of fire brick. It indicates the tendency of a bride to tHgoeMne temperature lower than its melting point and to become deformed ^ en load- Under a unit stress of 100 lb. per sq. in., the plastic point re than 2400 d^-, otherwise the brick is not suitable for boiler :r :_ ^.z:. FURNACES AND SETTINGS 149 Fusing point is the temperature at which fire brick will fuse. A high value ordinarily indicates that the critical temperature, or that of plasticity, is correspondingly high. Expansion represents the tendency of the brick to change in size with change in temperature. Lineal expansion of from 0.01 to 0.08 in. in a 9-in. brick is the permissible limit for furnace construction. Compression is measured by the strength or load necessary to cause crushing at the center of a A%-'m.. face, by a steel block 1-in. square. Hardness indicates the brittleness of brick and its tendency to crumble ; it is ordinarily estimated on an arbitrary scale of 10. Ratio of nodules expresses the percentage occupied by flint grains in a given volume. The scale is : high, 90 to 100 per cent ; medium, 50 to 90 per cent ; low, 10 to 50 per cent. These nodules are the average size flint grains found in a carefully crushed brick. Small nodules are the size of anthracite rice ; large nodules are the size of anthracite pea. These characteristics are summarized in Table 6, for the three classes of -first-grade or No. 1 brick. Class A brick are suitable for stoker settings operated at high overload or for other extremes of operation. Class B brick are used for furnaces of stoker-fired boilers operating at normal load, and for hand-fired boilers under overloads. Class C brick are recommended for standard boiler settings, for occasional short overloads. Table 6. Properties of Commercial Fire Brick FIRST GRADE (No. 1) No. 2 Characteristics Grade Class A Class B Class C Safe Fusion Point, deg.. 3,200-3,300 2,900-3,200 2,900-3,000 2,400-2,700 Compression, lb. per sq. m 6,500-7,500 7,500-11,000 8,500-15,000 14,200-32,000 Relative Hardness 1-2 2-A 4-6 6-10 Size of Nodules medium medium to medium to small to very medium large large small Ratio of Nodules high medium to medium low low to very high to medium low The figures in Table 6 indicate that the better the brick the softer it is. It should not be any harder, therefore, than is required for the necessary strength. The unequal expansion and localized stresses due to sudden temperature changes often cause failure when the fire brick is hard and brittle. The melting temperatures of refractory brick, as determined by C. W. Kanolt, are given in Table 7. The temperatures do not indicate the fit- ness of the material .for use in boilers, because the erosion, crushing strength, ability to withstand sudden load changes and to resist fluxion, must all be considered. In stoker-fired boilers temperatures of nearly 3200° F. have been obtained, although the melting point of chemically pure fire clay is only 3326 degrees. IdO F I' R X A C E S A X D S E T T I X G S Table 7. Meltinz Points of Fire Brick Brick Temp^ Deg. Fire Clay Silica Magnesia. Bauxite. Chromite. 2.732-3.1S2 3.092-3.182 3902 2.912-3.272 3.722 A simple quaiiiy test is niaue oy ureaKiing tiie uncK. in a low graae brick the fracture will be fine and uniform, like bread. In a better qualit>- brick the surface is open, clean, white and flinty. Fire brick 9-in. long are considered standard. ^lanufacturers carr>- a stock of the shapes and sizes shown in Fig. 66. Special sizes can sometimes be purchased from stock, but usually have t-:^ be made to order. Straight Brick. Small Brick. Split Brick. 2-inch Brick. Soap Brick. No. 2 Wedse. No.i Ke> No.l Neck. No. 4. Key. No. 2 Neck. Jamb. End Skew. Feather Edge. No. 3 Arch. Circle Brick. Fig. 66. Some Standard Fire Brick Shapes. FURNACES AND SETTINGS 151 Table 8 gives the weight of different refractories, as brick and as mortar. Table 8. Approximate Weights of Refractories Material Mortar or Cement, Lb. per Cu. Ft. Common Clay. Fire Clay Silica Chrome Magnesia Plastic 100 150 128 175 160 120 (Solid) 78 85 75 135 127 Influence of Ash. Refractory materials may deteriorate because of the chemical action of the fused ash and of the gases. Certain constituents of ash, according to E. G. Bailey, influence the fusibility of the fire brick. In one installation, where the furnace lining gave trouble, the fusing tempera- ture of the fire brick was 3100 deg., and that of the ash was 2600 cleg. ; the chemical action of the combination caused fusion at 2400 degrees. Ash from other coals would not have melted the fire brick used; other brick and the same ash might not have so materially affected the melting point. Mortar and Cements. Many arches and walls seem to have failed liecause the mortar used in making the joints melts and allows the brick or blocks to fall. The mortar used should be of practically the same composition as the brick itself. For fire clay brick, finely ground fire clay mortar should be used ; silica cement for silica brick ; and magnesia cement for magnesia brick. The fire clay mortar should be of the first quality, otherwise it will melt and run long before the brick. Common sand, salt, or lime, hasten fusion, and cement the brick thoroughh^ but at high temperatures this fusion destroys the brick prematurely. Tests by Raymond M. Howe show that the addition of only 5 per cent of Portland cement, asbestos or salt lowered the fusion point of fire clay almost 400 degrees. On the other hand, fire sand, which is calcined clay or fire brick in powder form, can be added to the mortar and prevents shrinkage of the raw clay and crumbling of the joints. This shrinkage can be prevented, and a firmer joint estab- lished, not by adding foreign materials to the fire clay, but by using the same material, taking the precaution, however, that a certain amount of clay has previoush^ been shrunk. Several commercial cements withstand temperatures as high as 3100 deg., and are recommended for use with high grade fire brick. The trend of opinion favors furnace walls of as few different materials as possible ; these must be selected carefully, even though solid fire brick are to be used. The use of two grades of brick, rather than one. may be preferable and economical, especially as the burden on side walls and on an arch is different. Side walls for coal fuel, states Heisel, generally require a refractory less porous and soft than would be used in an arch, to withstand the abrasion caused by the fire tools, and the cutting caused by breaking or removing the clinkers. Furnace walls are safeguarded and the lining preserved by devices which supplv air to the walls and thus prevent clinker from adhermg to them. This reduces the temperatures without reducing the furnace efficiency. Perforated refractory blocks. Fig. 67, are used for the lining in the lower parts of the side walls, bridge walls, and wherever the action is most severe. Air is admitted through holes in the wall blocks. The holes are connected by ducts to the fan draft system. With underfeed stokers, these blocks may materially increase the life of the hnmgs. 152 FURNACES A X D \* ,-^_ — ^ Air Dud Air Duct ^ wiih Samper r'/^^j Damper -+©' Rod Longitudinal Section. Fig. 67. Refracton.' Blocks for Ventilating Furnace Walls With standard brick the joints and parts to lay are so numerous that blocks are made for door arches, furnace walls, and bridge walls. The blocks are keyed or have a tongue and groove, and sometimes are machined to insure a good fit. It is said that one 24-in. block takes the place of 40 standard brick, and reduces by more than two-thirds the running inches in the joints in the face of the wall. In place of the blocks, so-called plastic fire brick is used for boiler settings. This is a moist plasric mass, compounded of fire clays mechan- ically treated so that expansion is practically eliminated. The plastic refractory is placed by hand and pounded so that the front arch, side and front walls, bridge wall, or combustion chamber lining is one continuous structure. This material, it is said, does not break or spall under varying furnace temperatures. FURNACES AND SETTINGS 153 Arch Construction. All brick in the same row should be of even shape and thickness, this applying, states Heiscl, to arches particularly. The vari- ation in size should not exceed /4-in. in a maximum length of 9 inches. The dry brick selected should be tried over the arch form, and those of uneven thickness should be cut and rubbed to avoid large mortar joints. Wedges should be used to keep the brick bottom in even contact with the arch form. The key course should be a true fit from top to bottom and should be driven from 1 to 1^ in., depending upon the hardness of the brick and the width of the arch. Suspended flat arches are sometimes used instead of tlie ordinary sprung arch. Fig. 68 shows a double suspension arch, about 3 in. deeper than the ordinary single arch. A so-called reserve arch is placed above, and supports the lower arch. An air space is provided between the two arches. If a burn-out occurs, the upper arch protects the supporting beams until the boiler can be shut down and the damaged blocks replaced. The new parts are slid into the grooves of the reserve arch. Fig. 68. Liptak Type of Suspended Flat Arch. Radiation and Leakage COMMON brick is somewhat unsatisfactory for boiler settings. As it is not a refractory material, it is always protected from high temperatures by a lining of firebrick. It is a poor heat insulator; it is porous and permits considerable infiltration of air, and it cracks easily, especially around openings such as dusting doors, and allows further air inleakage. Front View of 500 H. P. Heine Standard Boiler set over ^Westinghouse Underfeed Stoker. Fl^RNACKS AND SETTINGS 155 Insulating material will decrease heat loss to a consideral)le extent. Siliceous insulating material may be cut into blocks of standard firebrick size which have sufficient strength to be laid as a core wall between the fireback furnace lining and the outer red brick course. Such a wall is shown in Fig. 69. 2500^ Fire Sr/ck-'.^y ,Common ' Brick 2S000 Brick /nsu/afina Brick Common Brick Plain Wall Insulated Wall Fig. 69. Heat Flow Temperature Gradients in Brick Wall. The insulating brick should be at least 4^ in. thick. It should be laid with broken joints and in a mortar made of material having the same characteristics. The temperature drops through a standard boiler wall and an insulated wall are compared in Fig. 69, by A. L. Gossinaii. Metal wall ties are used in bonding or else firebrick, insulating l)rick and red brick are tied into a solid wall by brick headers staggered in at intervals. Fig. 70 shows the thermal conductivities of refractories and insulation, the measurements being made on slabs one inch thick and one square foot in area. 156 F U R X A C E S AND S E T T T X G S The insulation reduces the radiation loss, but on account of the joints in the brick setting the air leakage is not eliminated. To offset the infiltra- tion only, states /. Harrington, a glazed or vitrified brick, laid in cement mortar, gives a hard and durable wall, but the heat transmission is high. A boiler setting encased in sheet steel is practically air tight, but the steel has no insulation value. 12 10 r9 b7 c C X a u- 5 a. ■*^ 3 y y ^/ y 1 i y y y^ y / y y _^ ^ r ~p^^ ^ y f ,y^ A ^ *^ > k' ^ M >^ M / -tH ^ ^ y y ^ :::^ :^ >^ /^ c^ y y ,j > / ^ y ^ y 1 1 I 1 1 a = Silica Brick, 97.3»/cu. fi b 'Quarfzife,//9*f/ca.f-/- c -All Fire Clay,li9*/cu.ft cl= Insulafinci Brick, 27-3C L i 1 1 l^cu.ff. 1 1 1 1 i 1 1 1 1 1 1 1 1 1 L^ — { — 200 400 leoo GOO 800 1000 1200 1400 Temperature Difference, Degrees Fig. 70. Heat Conductivity of Brick, One Inch Thick 1800 2000 F IT R X A C E S AND SETTINGS 157 Radiation and infiltration losses are both eliminated by applying asbestos or magnesia on the outside of the setting walls, and then encasing the whole with sheet steel. This construction is expensive and carries the objection that cracks in the brickwork are difficult to detect or repair. A less costly construction, which also reduces both losses, is described by E. S. Hight. The details are shown in Fig, 71. The saving effected by this insulation is said to be sufficient to repay the first cost in less than six months, providing the boilers are operated at full load 50 per cent of the time. Wire loops are inserted into the red brick of the setting wall, so that they overhang at every fifth or sixth course. After the wall has been laid up, a Vi6 in- finish (two or three coats) of coal tar is applied. This should be boiled to a thin consistency and have asbestos wool stirred into it. After the mixture has dried a plastic asbestos paste or cement is applied to a thickness of about V/4 inches. Over this a ' wire mesh is stretched and fastened to the protruding loops by small wire clips. Then another ^-in. layer of asbestos cement is applied. When the plastic mass is dry, the surface is covered with 10-oz. duck or canvas. This is pasted down tightly and the edges are fastened by wires or metal strips to the steel work of the setting. The duck is finished with two coats of asphalt paint or varnish. \i^%— Asbestos Cement -Wire Loop 10 oz. Duck, with (2 coats aspha/fum **6W/'re~. Fig, 71. %-2"Chicken Wire ^.Coai Tar and Asbestos £ric/<- Scttinq Wire Loop inwlacc Inexpensive Method of Protecting Setting Against Radiation and Infiltration Losses. For the covering of boiler tops and drums, insulating brick have been found most desirable. This can be strengthened by a course of common brick and then a 2-in. topping of concrete. 159 CHAPTER 5 MECHANICAL STOKERS THE advantage of automatic stokers as compared with hand firing lies mainly in the more efficient combustion of the fuel, the elimination of smoke and dirt in the boiler room, and in the ability to drive boilers at high rating. In large plants where automatic coal and ash handling equip- ment can also be installed advantageously, the use of stokers reduces the labor cost and the labor difficulties. The emission of smoke, except for brief periods, is forbidden in many cities ; and when smoke is eliminated, the general efficiency of the boiler plant is usually increased. With stokers the fuel is fed and the air supplied uniformly; no fire doors need be opened to chill the boiler and dilute the stack gases ; thus combustion is most thorough even with poor fuel, at combustion rates that produce the highest steaming values. The grade of fuel influences the choice and design of a stoker, but when it is difficult to secure coal from the same source con- tinually, the load conditions are even more important. A plant that must be operated frequently at 300 or 400 per cent of rating must necessarily lie equipped with stokers that can be driven at corresponding rates, with forced draft, regardless of the fuel available. When the load conditions are more nearly uniform, the stokers can be of lower forcing ability, and those best suited to the coal available can be chosen. The following illustrations are given as examples of the types classified . Overfeed Stokers TN overfeed stokers the coal is generally burnt on sloping grates. The general ■'-position of these is fixed, but reciprocating grate sections gradually work the burning fuel down to the ash receiver. The coal is fed from hoppers adjoining the upper part of the grates and passes first over a coking section, where the volatile gases formed are burned by the aid of secondary air. Overfeed stokers are used with a wide variety of fuels, and boilers are operated up to 200 per cent of rating without overheating the grates. Cleveland Stoker, Fig. 72. The coal from the hopper is pushed in by feed plates and pokers, so arranged that by increasing the speed of the rectangular feed plates the depth of the fuel bed can be increased. The draft is adjustable for the particular coal used; the three dampers in the wind box below the grates distributing the required air. The entire unit is shipped assembled, and runs on tracks so that it can be removed to gain access to the setting. Detroit Automatic Furnace, Fig. 7Z. Coal is fed to the magazines by hand or from chutes, and is driven to the coking plate by pusher boxes, from which it slides down the grates to the clinker grinder, where a supply of exhaust steam softens the clinker. Air for combustion is supplied at a STOKERS ' >'. **".« .'-'*.-».'> ■ 3''^v^Vg;;;5-;; - ^VV"^^?;^:;^^;y^:-':;f:?;t^.i'f ;•;;•:;•/ ■-.^f-yi ^^V ^TI"!"?^^ r^ - i: kM Fig. 77. Universal Automatic Underfeed Stoker. 164 STOKERS Wesiinghouse Underfeed Stoker, Fig. 7S, is of the gravity.- underfeed t>-pe; the coal is fed to the lower zone, but its movement toward the dump plate is aided by the slope of the retorts. Between the retorts are semi- circular corrugated tuyeres D, which supplj- air under pressure. The coal is moved by the upper ram K, by the lower ram O in the bed of the retort, and by the moving "overfeed section"' G at the rear and bottom. The ash dtmips are in pairs, pivoted front and rear. Air enters through the tuAeres separat- ing the retorts, through the overfeed section, and through box J at the front. This stoker is recommended for plants where the load is subject to wide and sudden variations. Natural draft can be used at light loads, and 400 per cent of rating can be secured for peaks, at 6 to 7-in. pressure in the wind box. 11 i^^y^^^^a Fig. 78. Westinghouse Underfeed Stoker. Taylor Stoker. Fig. 79. The retorts are sloping, with periorared tuyeres in between; each step is V-shaped, the opening being toward the front. The coal is pushed into the retorts 1 by feeding rams 5, and is either crowded upward or pushed into the fire bj- short-stroke rams 6, 6, the final combus- tion taking place on the extension grates 7. The combustible gases are ignited in the incandescent zone at the front and top of the coal bed. The power dump plate 8 is rapidly oscillated to dislodge and dump the refuse and clinkers. In an alternative design the refuse is ground between crush- ers, at a speed which keeps the discharge ash-sealed, Bitmninous, semi- bituminous, and semi-anthracite, and even lignite coals can be bumei At normal ratings a forced draft of 1.5 to 2 in. is used, with 0.03-in. suction. A wind box pressure of 3 to 4 in. with 0.03-in. suction, will permit continuous operation at 200 to 300 per cent rating. During peaks, from 60 to 80 lb. of coal per sq. ft. per hr. can be burned. STOKERS 165 %y' ^\ ^y. Fig. 79. Taylor Underfeed Stoker. Riley Stoker, Fig. 80. The retort walls move and also agitate the "overfeed grate bars," v^hich supply air for combustion. Farther down the slope, at the moving overfeed bars, the unconsumed coke is burned with the aid of smaller quantities of air. The refuse finally passes to the rocker dump plates, which are in continuous operation ; here the refuse is crushed and ejected at a rate depending on the size of the opening. The stoker can burn lignite and all grades of bituminous coals. Forced draft is used, up to 5 in., with a slight suction. At peak loads 200 to 300 per cent rating and over is obtained. Fig. 80. Riley Underfeed Stoker. 166 L ^^. m^ im 2500 H. P. Installation of Heine Standard Boilers set over Westinghouse Underfeed Stokers in the Plant of Harrisons, Inc., Philadelphia, Pa. STOKERS 167 Chain or Traveling Grate Stokers IN THE chain grate stoker the coal is deposited on the grate in front, and is ignited by the aid of arches. It is then coked, gradually burned to ash without agitation or cleaning, and is automatically dumped at the rear. The gear-trains driving the pulley-shafts are actuated by a ratchet and pawl, an adjustable arm being reciprocated by an eccentric on a line shaft. Chain grates handle normal loads efficiently, and with a minimum of smoke, al- though the maximum rate of driving is only about 250 per cent. They work particularly well with low-grade, free-burning bituminous coals, such as those from Illinois and Iowa, containing 30 to 40 per cent volatile and 10 to 20 per cent ash. With coals of a lower ash-content, the stoker may over- heat. Continental Chain Grate Stoker consists of small units, with dove-tail and semi-circular recesses for locking each grate, and of rollers traveling on upper and lower tracks. The ignition arch over the front is made of ventilated tile. The depth of fuel bed is regulated by a tile-lined_ gate. A water-cooled chamber in front of the bridge wall prevents adhesion of clinker. The stoker is built for all grades of free-burning coal and lignite with ash content over 7 per cent, and for all sizes from slack to 2-in. nut. A suction of 0.2 in. over the fire is sufficient when burning Illinois and Indiana coal at a 30-lb. rate, or 0.5 in. at a 50-lb. rate. Fig. 81. Green Chain Grate Stoker — Type K. 168 STOKERS Coxe Traveling Grate. The pressure in the air compartments below the tire is varied according to the thicknesses of fuel bed. A combustion arch covers the greater part of the grate. This stoker is designed for small anthracite and coke breeze, but also operates with free-burning, high-ash coals. The former have been burnt at rates up to 50 lb. per sq. ft, per hour. Forced draft of 1 to 2 in. is used. Type K Green Chain Grate, Fig. 81, emplo^-s a large, flat, ventilated ignition arch. In some installations a stationary waterback is placed in the bridge wall. Natural draft is used ; about 0.1 in. is required for each 10 lb. of coal burned per square foot per hour, the usual rate being 30 to 40 lb- The Type K stoker is designed for free-burning coals. Type L Green Chain Grate is built for coking coals. The coal passes from the hopper to a stationary inclined plate, where it is coked before dropping onto the grate. Either natural or forced draft is used with this type, or induced draft when economizers are installed. Installations are operated up to 250 per cent of rating. Fig. 82. Harrington Chain Grate Stoker. Brady (Harrington) Grate, Fig. 82, is designed for forced draft, at combustion rates up to 75 lb., although natural draft can be used at normal rating. The grate is built of small interlocking bars, giving a continuous surface, no parts of which are exposed to excess heat in turning at the rear. The air supply at different points is controlled by adjustable dampers STOKERS 169 Illinois Chain Grate has a slight dip to the rear, and a long, flat com- bustion arch. Middle Western coals with over 20 per cent ash are burnt. At a 40-lb. rate the draft is 0.63 in. over the fire and 1 in. at the i>,''i>_'°'.o;'>.' y',» 'i'rf>^.'^-i'^! VV^io'.^; "o'V'' .'"'>'• ii'?''i':°. ■* ;oyo'-.'<3. .'o .'o ■/ i .'J^. ■>..','. ^. a' '>lS.-o:6'',:o''^y-i'-.'' riVo Fig. 83. Illinois Chain Grate Stoker. damper. With coals containing from 10 to 20 per cent ash, 0.4 in. over the fire is sufficient. Under forced draft, the draft over the fire can be less than 0.15 in., with 1 to 4-in. wind-box pressure. 170 STOKERS Laclede-Christy Chain Grate, Fig. 84. has a slightly inclined grate, in an air-tight setting, with long overhead arch. Air enters through small openings in the links, a swinging damper being used to reduce the supply at the rear. This stoker is designed for high-volatile, high-ash coals, espe- cially those from the West, and operates under natural draft. A chimney height of 200 ft. is sufficient for operation at more than 200 per cent rating. ■' "'^i^ ■■■ *■■' Fig 84. Laclede-Christy Chain Grate Stoker. Playford Chain Grate. The fiat ignition arch is air-cooled, a water- cooled fuel-gate preventing back-firing of coal in the hopper. The bridge wall is protected from clinker, and air inleakage prevented, by a fixed water- back. In some installations a movable back is cooled by either water or air; the material at the back of the grate can then be held back or dumped at will. The stoker is adapted for bituminous coals with 25 to 40 per cent volatile matter. Natural draft, 0.15 to 0.4 in., is used. STOKERS 171 National Stoker, Fig. 85. Rows of pushers in recesses in the middle and lower parts of the inchned grate are hand operated by levers in the boiler front. The fuel is fed, coked and burned as in mechanically operated stokers. This stoker is applied to small or medium-sized furnaces- Fig. 85. National Hand Operated Overfeed Stoker. o PQ u OS n a a +j Ui o d *C 0. vo bfi S c o o >^ o o u PCI c o G "a 6 0^ O O &/) (^ 173 CHAPTER 6 CHIMNEYS AND FLUES THE pressure of the draft is the difference in the weight of the column of hot gases within the chimney and of the corresponding column of air outside. It is measured by the difference in level of water in the legs of a "U" tube, of which one leg is connected to the base of the stack and the other is open to the atmosphere. The hotter the gases, the higher the chimney, or the cooler the atmosphere, the greater is the draft. The performance of chimneys is disturbed by many circumstances, particularly by the weather. Variations in the barometer affect the draft nearly 10 per cent. The draft may be nearly 50 per cent greater when the air temperature is zero than when it is 100 degrees. As the quantity of gas flowing up the chimney is increased, the pressure necessary to overcome the friction of the gas flow is increased, leaving a lower draft reading on the "U" gage. While there is a minimum height for any draft requirement, the height is generally influenced by local considerations. For satisfactory results, chimneys should be higher than surrounding buildings, hills, trees or other nearby obstructions, so that wind eddies will not interfere with the draft. The minimum chimney height necessary in any case depends upon the fuel used. Wood requires the least height, good bituminous coal requires a medium height, while fine sizes of anthracite need the greatest chimney height. The rate of combustion, boiler gas passages, flue design, and the number of boilers, also influence the stack height. Small plants burning bituminous coal or large anthracite may have stacks from 70 to 100 ft. high. If burning anthracite pea or buckwheat, they should be 125 to 150 ft. high. Plants of 800 H.P. or more should have stacks not less than 150 ft., whatever kind of coal is burned. To burn No. 3 buck- wheat at any practical rate, the chimney will have to be more than twice as high as would be required to burn pea coal. This height is generally prohibitive, and small anthracites are almost invariably burned with artificial draft. The tallest chimney in the world is the interior stack of the Equitable Building, New York, 596 ft. high, serving 3500 H.P. of Heine boilers. Chimneys over 200 ft. high are usually unnecessary. Unless conditions call for a taller stack, two or more shorter stacks should be erected, as the two will usually cost less than the taller stack. There is a diameter corres- ponding to the most economical construction for any stack height. Accord- ing to W. Deinlein, the smallest product of diameter and height represents the chimney of minimum cost. For any given conditions, this relation can be established graphically as shown in Fig. 86: Assuming a masonry chim- ney, we find from the "H = height" curve that this particular chimney could be i75 ft. high by 20 in. diameter, or 125 ft. by 23 in., or 100 ft. by 31 in., and so forth. These products are then plotted to form the curve "dH = Relative Cost" and we see that the lowest point of this curve occurs at 25 in., for which diameter the appropriate height is 115 feet. This is the lowest priced chimney that can be built to meet the conditions. 174 CHIMNEYS 3S0 300 250 = 200 :75 150 o 100 50 1 1 M .- ck _ ^+n„l C-t-^^L. : 1 [ 1 1 I ^' 1 / i J ,'-' U^ \ ..^i X ^^ ^P^ X i i 1 \ S ■---:; ';y^ \ v., ^<^ _^«^^«^^ ^^ H- = Heigh f ^>«; 1 1 1 "I E 3 4 5 6 7 Chimney Diameter in Feet Fig. 86. Relation of Height and Diameter to Minimum Cost of Chimney for a given Boiler Capacity. The gas temperature in the stack falls as the distance above the entering flue increases. This is shown in Fig. 87, based upon tests by Kilhorn and Alexander, on a tall masonry chimney. An analysis of numerous tests, by E. J. Miller, shows that the observed draft intensity usually does not vary more than 3 per cent from that calcu- lated when the temperature drop in the chimney is allowed for. Still, in general chimney calculations, uniform temperature is assumed, and the temperature of the entering gases is the temperature used. Hence, the great difference between the draft calculated and that actually observed. This difference is stated by different authorities as 10, 15, and 20 per cent, and they recommend that appropriate allowance be made. In the following treatment, the fall in temperature of the gases as they ascend the stack has been taken into consideration. The average temperature of the gases in stacks of different diameters and heights has been deduced from observation, and curves convenient for general use have been drawn. The logical method of treating the subject is to compute the character- istics of chimneys, as is done with fans. The minimum draft necessar}- at the base of the chimney' should first be found, and then chimney sizes to produce that draft at the required capacity can easih' be chosen. In the following discussion, reasonable values of air and gas temperatures, and operating efficiency, will be assumed and the effect of departures therefrom indicated. These assumed conditions must be lived up to in operation, or the calculated results will not be attained. CHIMNEYS 175 240 T 1 r- 1 220 1 1 200 ' 180 \ \ •160 \ \ •^140 Si. \ ^ 120 E X 100 o V \ 80 \ \ €0 \ \, 40 \, V \ 20 N N X 50 4 00 4 50 5 30 Gas Tempera+ure.degJahr: Fig. 87. Fall of Gas Temperature as Distance from Entering Flue Increases. Chimney Sizes by Horsepower T^HE chimney horsepower table of William Kent, modified to include the -L draft at the base of the chimney, is given in Table 9. The draft to be observed at the base of the stack as given in the table. is computed on the following assumptions : The horsepower given is the rated horsepower of the boilers. The boilers are run at 130 per cent of their rating. Five pounds of coal are burned per boiler horsepower hour. Each pound of coal produces 20 lb. of flue gases. Atmospheric temperature, 60 deg. Barometer, 30 inches. Humidity ignored as negligible. Temperature of gases entering stack, 500 deg. Allowance has been made for the drop of temperature of the gases as they ascend the stack. As an example, take five boilers, each rated at 160 H.P., making 800 H.P. in all. From the table, it is seen that this load is met by the following propor- tions 72 inches dia. 100 feet high 0.50 inch draft 66 inches dia. 150 feet high 0.65 inch draft 60 inches dia. 200 feet high 0.74 inch draft 76 C H I ^I X E Y S To decide which of these is appropriate, local conditions must be first considered. Then the necessary draft at the stack base must be determined from the draft resistances of the fuel bed, boiler setting and so forth, as explained later; and the sum of these will determine the draft necessary- at the stack base and consequently the minimum height of chimney. Then the most economical proportion of height to diameter should be found by apply- ing the principle illustrated in Fig. 86, so that the chimne}* of least cost, which will meet the various conditions, may be rjdopted. Table 9. Chimney Sizes by Horsepower. Dia. In. Area, (A) Sq. Ft. Effec- tive Area, Sq. Ft. E = A— 0.6 Va HEIGHT OF CHIMNEY, Ft. 60 70 80 ' 90 I 100' 110 125 150 175 200 i 225 i 250 Upper Fig\ire= Commercial Horsepower Rating Lower Figure= Draft at Base of Chimney at 130 i>er cent of Commercial Horsepower Rating Equiv- alent Square Chimney In. Side of Square Ve-I-4 24 3.14 27 3.98 30 4.91 2.08 3.58 54 58 0.35 78 0.35 100 0.35 62 0.38 83 0.38 107 0.38 66 0.41 88 0.42 113 0.42 ■ 0.31 72 0.31 92 0.31 * 119 <,, 0.45 22 24 27 33 36 39 5.94 7.07 8.30 4.48 A 5.47 6.57 115 125 133 141 149 0.31 0.35 0.38 0.42 0.46 141 152, 163 173 182 0.31 0.35 0.39 0.43 0.46 ....I 183| 196 208 219 ....|0.35l 0.391 0.43 0.47 156 0.48, 191 0.49; 229 0.50 2041 0.53 2451 0.54 1 268 0.58 30 32 35 42 9.62 48 12.57 54 15.90 7.76 10.44 13.51 216 0.35 231 0.39 311 0.39 245 258, 0.43 0.47| 330 3481 0.44 0.481 427i 449 0.45 0.49' 271 0.51 365 0.52 472 0.53 289 316 342 0.55 0.59 0.61 389 426 460 0.56 0.60 0.64 503 551 595 0.57 0.62 0.67 492 0.68 636 1 675 0.7l| 0.74 38 43 48 60 66 72 19.64 23.76 28.27 16.98/ 20.83; 25.08; 536 1 565 0.45 0.49 694 1 0.501 835| 0.50' 593 632 0.53 0.57 728 776 0.53 0.58 876 934 0.54 0.59 692 0.64 849 0.65 1,023 0.67 800, 848 0.74| 0.77 981 1,040 0.761 0.80 1,105 1,181 1,253 0.73| 0.781 0.83 748 0.70 918 0.72 894 0.78 1,097 0.82 1,320 0.851 54 59 64 78 84 90 33.18 38.48 44.18 29.73^ 34. 76 J 40.19, 1,038 1,107 1,212 1,310 1,400 1,485 1,565 I 0.54| 0.60| 0.671 0.751 0.80| 0.85| 0.88i 1,214 1,294 1,418 1,531 1,637 1,736 1,830 0.55 0.611 0.68 |1,496 1,639 0.611 0.69 0.76) 0.82 0.87| 0.91 1,770 1,893 2,008 2,116 0.77| 0.84| 0.89( 0.94 70 80 96 102 108 50.27 56.75 63.62 46.01j 52.23^ 58.83 1,712 1,876 0.62| 0.70 1,944 2,130 0.62| 0.70 2,090 2,399 I 0.631 0.71 2,027 2,167 0.18| 0.85 2,300 2,459 0.79| 0.86 2,592 2,771 0.801 0.881 2,298 0.91| 2,609 0.931 2,939 0.951 2,423 0.96 2,750 0.98 3,098 1.00 86 91 96 114 120 132 70.88 78.54 95.03 65.83' 73. 22 I 89.18/ 2,685 0.72 2,986 0.73 3,637 0.74 2,900 3,100 0.811 0.901 3,226 3,448 0.821 0.91 3,929 4,200 0.841 0.931 3,288 0.97 3,657 0.98 4,455 1.00 3,466 1.02 3,855 1.03 4,696] 1.06 101 107 117 144 156 168 113 . 10 132 . 73 153.94 106.72/ 125.82 f 146.51/ 4,352, 0.75 1 4,701,5,026 5,331 5,618 128 0.86 0.95| 1.03| 1.09 . 5,542 5,925 6,285 6,624 138 0.881 0.971 1.051 1.12i; 6,454 6,899 7,318 7,713 ^ 150 0.89, 0.981 1.071 1.15 CHIMNEYS 177 The assumptions on which the table is based meet all ordinary condi- tions. The effect of other conditions will now be discussed and compared. As stated above, the draft at the chimney base, as given in the table, was computed at 130 per cent of boiler rating. In the example just taken the drafts read from the table are those to be expected when the boilers are running at 130 per cent of rating or developing 800x130 per cent=1040 B.H.P. In the following discussion, the draft read from the table is considered as one hundred per cent. The first change considered will be that caused by adding or taking off boilers, the load on individual boilers remaining the same. Under these circumstances, the temperature of the gases entering the chimney remains the same, and the draft falls off as the addition of more boilers increases the load on the chimney. The rate at which the draft falls off depends upon the ratio of diameter to height (H/D) and curves have been drawn for different ratios in Fig. 88. These show very clearly that the draft diminishes much more rapidly in slender than in squat chimneys. (40 130 leo no ^100 <+- E90 "5 80 I TO c^60 50 40 30 20 J5 a..^ !^^^ -~J^ N 2 ^ ^^ 16^ ^ ^^ ^ ^ A \ r^ ^ B N^ ^ )D ^ v^ 16 ^ n" \; ^ k 25] 'D ^ N ^ ^ ^ -^ 14 "0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 l9 20 Coirbon Dioxide (C0^), Per Cent Fig. 91. Effect of Excessive Air. Increase in Weight of Gases as CO2 is Reduced. 180 -d V 03 .3 w V 03 — H CO ^ o«5 O 03 03 fj ^^ o "^ 03 •> U •»-> O cS G 03 O u (-H "d "J s O (u ^^ o 2 +j o tuBm CHIMNEYS 181 isi found from analysis of the flue gases as explained in Chapter 15 on BOILER TESTING, and is shown by the percentage of CO2. Fig. 91 is a representative example of the weight of gases per pound of fuel with different percentages of CO2. With the coal of analysis used in drawing the curve, 20 pounds of gas per pound of fuel is due to 11 per cent of CO2. If the CO2 is reduced to 7 per cent, then the weight of gas is increased to 30 pounds, or 50 per cent more. Under these conditions a given chimney could only care for two-thirds the load expressed in boiler horsepower. In many instances overloaded chimneys have been relieved by the addition of forced draft and otherwise improved operation so that the weight of gas per boiler horse- power has been sufficiently reduced to enable more power to be developed without alteration to the chimney. Draft and Capacity of Chimneys "T^HE curves, Fig. 92, are deduced from observations by Peabody and Miller ^ and by /. C. Smnllzvood. All are for temperatures above that of the atmosphere. Thus, taking gases entering at 500 deg., and atmos- pheric temperature of 60 deg., the difference is 440 deg. In a masonry stack 100 150 200 250 Height of Chimney, feet 350 Fig. 92. Average Temperature of Gases in Percent of Entering Temperature according to Height of Chimneys. 7 ft. diameter, 200 ft. high, the average temperature will be 80 per cent of the entering temperature, 440 X 0.80, or 350 -f 60 = 410 deg. as actual average temperature. At heavy loads the average temperature will probably be a larger proportion of the entering temperature, and at light loads a smaller proportion than those shown by the curves. Any such differences from the curves given are likely to be negligibly small. Fig. 93 gives the weight per cubic foot of the chimney gases under aver- age conditions, at different temperatures, and Fig. 94, that of air. The static draft appropriate to any chimney can be calculated by means of these three charts. Continuing with the last example and taking the temperature of the air at 60 deg. (the common assumption in designing chim- neys), the weight of air per cubic foot is seen to be 0.0764 pounds. A column of air of one square foot cross-section, 200 ft. high, will weigh 200 X 0.0764 = 15.28 pounds. The column of gas (at 410 deg.) of the same height will weigh 200 X 0.484 = 9.68 pounds. The difference, 15.28 — 9.68, or 5.6 lb., is the pressure per square foot of the resulting draft. Then the static draft is 5.6 X 0.192 = 1.08 in. of water. 182 CHIMNEYS ao7o 0.06: .if 0.05: o. 0.04C ■n 0.03C aozo . _ — »— ^' I ^ i_ '**»^ r>_ , ' ' — ^t]' > , i_ 100 200 ;:: -:: ::: e:: ":: soo 9oo looo Fig. 93. Weight of Flue Gases, 0090 C.085 Si u «> -SQ075 c 3 0.070 0.065 20 40 60 80 Temperodxirc, Degrees Fig. 94. Weight of Air. 100 120 140 In common practice, the entering temperature of 500 deg. would be taken, giving a static draft of 1.26 in,, which is wrong. This static draft of 1.08 in. cannot be read on a U-gage. because part of it is lost in overcoming the friction of the gases in the chimney. The draft loss by chimney and flue friction can be read from Fig. 95. The curves are drawn for a temperature of 440 degrees. The draft loss for any other temxperature can be obtained by multiplying that read from the curves b}' the multipliers given by the upper curve. For instance, take the dotted lines as an example ; if the temperature is 575 degrees, enter the upper scale with this temperature and proceed vertically downwards to intersection with the curve, then horizontally to the right hand scale and read the multi- plier as 0.87. If the upper scale be entered with 440 degrees, the multiplier is with similar proceedure found to be 1.00. For unlined steel stacks and flues multiply the final result by 0.94. C H I ]\I N E Y S 183 Temperature, Degrees. — C\J K3 oo c iii 0.70 "O.50 1 0.40 O.30 § 0.20 ^ 0.10 V \ ! \\ \ l\\' \ \ \\ \ > K K pe _ /^ i l\ ^ k V \ ra fares Multi- \\ \ \ \ \/ Draft Loss by is Figure-. IV \ \ K\ \ \ \ \, \ \\ \ \ \, ^^ \ vi ,v v\ \ \ s, \J ,.:] <^ ^/ ^ ^ \ ~^r— l\ \ \\ \ -^^ ■'a' S \ V Ov ^ --i^ '^ -^ "^\. \\ -^ ■"■^ -^ \\ ^ H ^ r^^ ^ 'A^Sec ond .. , ■ ^ ^ ■^E^ ^ i =^ 1 M— ■ — i.6o: 1.50 1.40- 1.30 1.10- 1.00' 0.90- 0.80 ; 0.70 0.60 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Area of Circular Chimney or Flue, Square Fee-V. Fig. 95. Frictional Draft Loss per 100 Ft. of Circular Flue or Stack (Based on 30 Inch Barometer and 440° Gas Temperature). The draft loss can be calculated from this formula, due to A. L. on which Fig. 95 is based: f LV^ h Menzin, (10) DT /i= Draft loss, inches of water. L^ Height of chimney, or length of flue, feet. D = Diameter of flue or chimney, feet. F = Velocity of gases, feet per second. T = Absolute temperature, degrees. f — onOR for circular masonry stacks or flues. = 0.0075 for unlined circular steel stacks or flues. Fig. 95 was drawn with / = 0.008. For square stacks or flues having the same area as round ones of diameter D, multiply h as found above by 1.06. For other shapes, the follow- ing multipliers can be used : Ratio of Sides Multiplier Itol lto2 lto3 lto4 lto5 lto6 1.06 1.09 1.14 1.19 1.23 1.27 Taking the last chimney example, 7 ft. diameter by 200 ft. high with an average temperature of the gases of 410 deg. and a velocity of 30 ft per second we enter Fig. 95 and find the draft loss for 38.5 sq. ft. to be 0.114 inch. As the curves are drawn for 440 deg. we enter the correction 184 C H I :^1 X E Y S portion with 410 de^. and find a multiplier of 1.035; applying this to tlie 0.114 we get 0.118. This is the draft loss per 100 ft., so doubling it we get 0.24. This result can be checked by the Mensin formula (10). Under the assumed conditions the static draft for this chimney is 1.08 inches. Deducting the friction draft loss of 0.24 in., we find that the avail- able draft at the base of the stack is 0.84 inch. This is the "draft" which is read on the U-gage. To convert this to horsepower, 30 ft. per second multiplied by the chim- ney area of 38.5 sq. ft., gives 1155 cu. ft. per second. From Fig. 93 we find the weight per cu. ft. of the gases to be 0.484, so that we have 56 lb. of gas per second or 201,600 lb. per hour. As we have been assuming 100 lb. of gas per hour per horsepower, the rate becomes 2016 horsepower. With Western coals, the sizes given in Kent's table should be increased 25 to 60 per cent. It is wiser, however, to determine the amount of coal to be burned per horsepower, either by Fig. 96 or independently of it, bearing in mind that the eiTiciency generally attained with poor coal is low, while a higher draft loss through the fuel-bed will be read from Fig. 97. Chimney proportions of existing stoker-fired plants in different parts of the country are given in Table 10. A comparison with the Kent table is included. Table 10. Chimney Installations in Typical Power Plants. COAL-BURNING STOKER-FIRED H. P. of No. of Units Chimney H/D H. P. per Sq. Ft. of Stack Area Chimney H. P. (Kent) Percent of Kent's H. P. Type of Boilers Height Diam. 1 Stoker 1,530 2,500 2,800 2 4 4 125 150 230 8 9 10 15.6 16.7 23.0 30 39 36 1,708 2,400 3,690 90 104 76 Taylor Roney Chain Grate 3,600 3,600 4,000 6 6 8 225 225 210 13 11 12 17.3 20.5 17.5 27 37 35 6,290 4,450 5,140 57 81 78 Murphy Roney M urphy 4,800 4,800 5,800 8 8 10 180 210 250 14 13 17 12.9 16.2 14.7 31 36 26 6,530 6,080 11,480 73 79 51 Chain Grate Taylor Chain Grate 9,600 9,760 10,400 16 8 20 275 250 300 16 19 18 17.2 13.2 16.7 48 34 41 11,640 14,400 14,100 82 68 74 Taylor Chain Grate Roney 12,000 15,600 12 24 250 250 20 21 12.5 11.9 38 45 16,000 17,600 j 75 89 Taylor Taylor Flue Sices. Formula (,10) is appropriate for flues as well as for chimneys. As an example, find the draft loss in a straight brick flue 8 ft. high, 4 ft. wide, 200 ft. long, with gases at 550 deg., traveling at 30 ft. per second? Entering the lower scale of Fig. 95 with 32 square feet and proceeding vertically upwards to the curve of velocity of 30 feet per second, and then horizontally to the left-hand scale, the draft loss of 0.125 is read. Entering the upper scale with a temperature of 550 degrees, and proceeding as directed on the previous page, a multiplier of 0.89 is obtained, and apply- ing this to 0.125, a draft loss of 0.111 is found. This is for 100 feet, so that for 200 feet the loss is 0.222. But this loss is for a circular flue. The ratio of sides is 4 : 8 or 1 : 2 for which the multiplier is 1.09, and applying this to 0.222, the draft loss for the conditions laid down is found to be 0.24 inch. CHIMNEYS 185 Draft Required for Coal THE draft required at the base of the chimney is the sum of the draft losses caused by the resistance of the fuel-bed, boiler setting, economizer (if there is one), flues and dampers, and the draft absorbed in setting the gases in motion. Fig. 96 will give the number of pounds of coal which will be burned per boiler-horsepower-hour. This should be confirmed by the expected evapora- tion per pound of fuel, by taking the appropriate point on the evaporation curve and then moving vertically to the coal curve, where, for example, an evaporation of 10 lb. of water is seen to necessitate burning 3.45 lb. of coal per boiler-horsepower per hour. 12 7 ^'- ri "^n 0^ / f^:^ 11 6 \ i ^ \ i i. 10 5 \ J' \ ^ \ )i 6> ^ G O 5 9t^4 \ 4' \ x\^o^^ y V \ 6 1 BH / lAnir 10US Sem iBit jmin DUS Ant nrac ite N Low Gro de Hiqih Qrads; Buckwheat Barley Rice n High Vo ■ Low Asfi I High .ow |Voloi Ash tile Fig. 96, Quantity of Coal Required for Given Quantity of Water Evaporated. Knowing the weight of coal to be burned per hour and dividing it by the total grate area, the number of pounds to be burned per square foot per hour is obtained. Fig. 97 shows the draft required through the fuel-bed. The curves have been plotted from a large number of boiler tests and represent good general practice. Reference should also be made to Chapter 2 on BOILERS. The draft loss through a regular Heine Boiler setting is given by Fig. 98, for both one and two passes. With poor management, allowing excess air, the draft required will be greater. Fig. 98 is based on the use of 12 cu. ft. of air per horsepower per minute. It can also be used to show the increase of draft necessitated by an increase of air due to poor firing or leaks. Suppose that 15 cu. ft. of air per horsepower per minute is used instead of 12. Then the air used is 15/12 or 125 per cent of that forming the basis of the chart. The actual proportion of rated horsepower developed is multiplied by 125 per cent to find the draft necessary. If the boilers are running at 120 per cent of rating, 120 X 125 = 150 per cent, and the draft required is read for a single pass boiler as 0.28 inch. For cross or vertically baffled boilers, a sufficiently close approximation is obtained by adding 10 to 20 per cent to the draft loss read from Fig. 98. 186 CHIMNEYS / // / P90 . ,,//// / i 1 i i IN//// / a - / i /X / / 1 t 1 t / //f/ / y c ■ r ; //> / / ^y ei ■'/ ■% / / / / y^ y" - '■"'/ ^ / ■'V / y^.-y^ s -/ -f -/ y .y^y^ yp^ _ .t// X / ^ y 3^- y^^y^ y^y^y^ z" \ 1 / ^ -"y^l^-'J-^^^^^^^ ^-^^ -' ' • /> y y y Jy^^^^yt^t:^^^'^'^ 'yy ^^ ^ i^it^glX^^^'^ ^<>^ ' 2 "^ Fig. 97 7c 4-0 Draft Required Through Fuel Bed for Different Grades of Coal. Fig. 98. Draft Loss Through a Regular Heine Boiler Setting, Compared for One and Two Passes. The draft loss through economizers 5 to S ft wide can var>- between 0.02 and 0.5 in. for each 10 ft. of length. They are generally built long and narrow with tubes 9 to 12 ft. high, because their efficiency is greater as the speed of the gases is increased, as is shown in discussing heat transfer in Chapter 11. The draft loss can be computed from CHIMNEYS 187 h= (^-^0^) ll^NT (11) 10" ^ ^ /i== Draft loss, inches of water W = Weight of gases, pounds per hour, divided by the number of lineal feet of pipe in each economizer section. i\r = number of economizer sections. T =: mean absolute temperature of gases, degrees. The draft loss through breechings and flues can be taken as 0.1 in. of water per 100 ft. length and 0.05 in. for each right angle turn, if the area is about 20 per cent greater than that of the stack. The loss due to altering the speed of the gases at each abrupt enlargement and change of shape is : /j= Draft loss, inches of water. Vi and F2=: Different velocities, feet per second. r= Absolute temperature of gases, degrees In long flues having several sudden enlargements, changes in form of cross- section and sharp turns, the loss may be considerable. The draft lost in accelerating the gases is: h = 0.125 J— T For a gas temperature of 500 deg., this becomes 7680 The following are values of draft lost in producing velocity for practical conditions : Velocity, feet per second 20 30 40 50 60 Draft loss, inches of water 0.05 0.12 0.21 0.33 0.47 The foregoing draft losses should be tabulated for any given case, showing the assumptions on which they are based, as in the following example : Fuel-Bed Resistance Boilers, 200 H.P. Grate area, 40 sq. ft. Good bituminous run of mine coal. Say 3.75 lb. of coal per hour per horsepower, as in Fig. 96. Boilers to operate at rated capacity 200 X 3.75 := 750 lb. of coal per hour per boiler. Divide by 40 sq. ft. of grate = 19 lb. per sq. ft. per hour. Read from Fig. 97 0.21 Boiler Resistance If single-pass Heine boilers, read from Fig. 98 as 0.12. If desired, allow 20 per cent for more air, reading draft at 120 instead of 100 per cent 0.18 Breechings and Flues Flue 80 ft. long at 0.10 per 100 ft. gives 0.08 and two bends at 0.05 each, 0.10. Tapers where required, no abrupt enlargements 0.18 Velocity of Gases Say 25 ft. per second so that - gives 0.08 Minimum draft at chimney base necessary to operate the plant 0.65 St. Joseph Lead Co., Rivermines, Mo., operating 7000 H. P. of Heine Standard Boilers. CHIMNEYS 189 Chimney Sizes as Determined by Gas IN departing from ordinary conditions, for which Kent's table was de- signed, it is well to make calculations on the basis of the quantity of gas to be dealt with, rather than on weight of fuel or horsepower. The quantity of gas can be based on the heat value of the coal, as recom- mended by V. J. Azhe. It has been shown that the weight of air required per 10,000 B. t. u. generated, varies with the available hydrogen in the fuel from 7.65 lb. for anthracite to 7.04 for oil. In solid fuel the maximum varia- tion from 7.6 is less than i 1 per cent. Therefore, while the weight of air per pound of coal will vary greatly with its heat value, the weight of air per horsepower for 100 per cent boiler and furnace efficiency will remain constant at 25.4 lb., and the weight of flue gases at about 31 pounds. Dividing this by the efficiency, we have the weight of gas per hour per horsepower developed. Following are the weights of gases for different fuels : Efificiency, Weight of Gases, percent lb. per hr. per H. P. Anthracite ; 65 48 Semi-Bituminous 60 52 High grade Bituminous 55 56 Illinois Bituminous, poor 50 62 Oil 70 42 The volume of the gases at any temperature is obtained by dividing the total weight by the weight per cubic foot as read from Fig. 93. Dividing this volume by 3600 times the chimney or flue area, will give the velocity in feet per second. The following have been recommended as economical velocities, consid- ering the total quantity of gases : Velocity, Gases, lb. per hr. feet per second 1,700 10 8,300 15 25,000 20 83,000 25 200,000 30 415,000 35 830,000 40 1,330,000 45 These velocities should be considered only as approximate. The draft losses should be determined for several velocities with different sizes of chimney so that the most economical can be chosen. Chimneys for Oil, Gas and Wood GENERALLY the sizes of chimneys calculated on a gas basis are much smaller than those found from Kent's table. Ample allowance should be made for driving boilers above their rated power, poor coal, poor firing, leakage of air through brickwork and from idle boilers. With oil burning excessive draft is more wasteful and more likely to occur than with coal. Undue chimney height and capacity must therefore be avoided. The loss of draft through the burners, boiler setting and flues is considerably lower than for coal, because the weight of gases per horse- power is less ; the weight per pound of fuel is greater, however, as shown in Fig. 91. The temperature of the gases is lower, so that oil- stacks produce less draft than coal stacks. The burners, however, give some- what of a forced draft effect. Defective draft is also to be avoided, since pressure within the boiler setting generally causes rapid deterioration of brickwork. Owing to the smaller quantity of gases, the chimney diameter should be smaller. 190 C H I ^1 N E Y S C. R. Weymouth observes that the necessary height for oil chimneys is much less than ordinarily supposed when boilers are operated at rating, and considerably greater at heavy overloads. The sizes of oil chimneys should be based on the maximum load and the draft resistance due thereto, rather than on the rated horsepower of the connected boilers. Table 11 is based on the horsepower developed (not on rated horsepower of boilers, as was Table 9 for coal) when the boilers are being operated at 150 per cent of rating. It is a modification of C. R. Wey- mouth's table for plants at sea-level, assuming temperature of air as 80 deg. and of gases as 500 deg. With properly designed connections and short flues, the sizes given will be found satisfactory. Table 11. Chimney Sizes for Oil-Burning Plants. HEIGHT ABOVE FLOOR LINE, FEET Dia. In. 80 90 100 110 120 130 140 150 160 30 33 36 206 356 312 249 310 379 280 349 427 304 381 466 324 405 497 340 426 523 354 444 545 366 459. 564 377 472 581 39 42 45 376 443 518 455 539 630 514 609 713 561 665 779 599 711 834 631 749 879 657 782 918 681 810 952 701 835 981 48 54 60 599 779 985 729 951 1.200 827 1,080 1,370 904 1,180 1,500 967 1,270 1,610 1.020 1,340 1,710 1,070 1,400 1,790 1,110 1,460 1,860 1,140 1,500 1,920 66 72 78 1,220 1,470 1,750 1,490 1.810 2,150 1,700 2.060 2,460 1,860 2,260 2,710 2,000 2,430 2,910 2,120 2,580 3,090 2,220 2,710 3,250 2,310 2,820 3.380 2,390 2,910 3,500 84 90 96 2,060 2,390 2.750 2,530 2.950 3,390 2,900 3,370 3,880 3,190 3,720 4.290 3,440 4,010 4.630 3,650 4,260 4,920 3,840 4,480 5,180 4,000 4,670 5,400 4,150 4,850 5,610 102 108 3,140 3,870 1 4,440 3,550 4,380 | 5,020 4,900 5,550 5,290 6,000 5,630 6,390 5,930 6,730 6.190 7.030 6,430 7,300 114 120 3,990 4,440 4,920 5,490 5,650 6,310 6,250 6,990 6.760 7,560 7,200 8,060 7,590 8,490 7,930 8,890 8,250 9,240 Analysis of figures on several oil chimneys shows the height to be be- tween 100 and 180 ft.; the diametjer 1/10 to 1/15 of the height, depending upon local conditions ; one square foot of chimney area serves 40 to 50 rated horsepower of boilers. The general practice of engineers on the Pacific Coast, states George Dorward, is to use 50 per cent of the area as stated in Kent's table for stacks for coal. For Heine boilers up to 200 H.P., stacks not in excess of 60 ft. in height from the boiler room floor line to the top of stack, are the general practice. Over 200 H.P. the same rule is used, i. e., 50 per cent of the area as stated by Kent, and not in excess of 80 ft. in height. This practice, it has been found, works very successfully. With blast furnace gas, the volume of chimney gases is greater and at a higher temperature than with coal, so that stack diameters are about the same. The draft loss through horizontally baffled boilers runs from 0.6 to 0.9 in. when operating at capacities up to about 175 per cent of rating, which are attained in practice with chimneys from 115 to 140 ft. high. As in oil-burning chimneys the height and capacity should be deter- mined by the draft requirement at maximum capacity. Excessive and defec- tive draft should be avoided as causing waste and setting deterioration re5pectivel3\ CHIMNEYS 191 When burning zvood, economy of operation is not easily realized ; large quantities of excess air and high stack temperatures are not uncommon. Compared with coal burners, wood burning chimneys can be much lower. Owing to the greater volume of gases, the diameter should be 10 per cent greater than for coal. Because of the variations in the properties of different kinds of wood, variations in size and wetness, and different methods of firing, draft losses through the fuel-bed and boiler setting can be approximated only. Wood burning chimneys are best located directly on top of the boiler, to avoid accumulations of unburned particles that might otherwise be deposited in the base of the stack. Such deposits have been ignited, thus destroying the stacks. If such accumulations cannot be avoided, the lower part of the stack should be lined with firebrick. Municipal refuse destructors and garbage incinerators should have chim- neys at least 200 ft. high to meet popular demand that the effects of odors be eliminated. High-temperature destructors operated under forced draft do not require such heights to take care of the draft; and with proper handling, no objectionable odors are emitted. Owing to variation in the proportion of combustible matter and water in the refuse of dift'erent cities, and the frequent use of coal or oil when only the garbage is burned, no general figures on draft requirements are possible. For any particular city, these proportions are usually known or ascertained sufficiently closely so that boiler and chimney sizes can be determined. Un- sorted municipal refuse as collected averages one-third carbon, one-third ash, and one-third water. Boilers and chimneys based on this proportion will give satisfactory results. Evasc or Venturi Chimneys are used to a limited extent in Europe and a few have been installed in this country. Fig. 99 is diagrammatic and explains the system, which is identical with that of jet-blowers and ex- hausters. -ivase Chim/t9if Fig. 99. Evase Chimney. 192 CHIMNEYS A fan supplies air for the motor jet, which creates a greater vacuum at the chimney base than the vacuum due to the natural draft of the chimney. Roughly speaking, the ratio between the vacuum at the chimney base and the air pressure at the motor jet equals the ratio between the area of the air nozzle and the area of the throat of the chimney. This ratio may be conveniently made from 1 : 6 to 1 : 10. Usually each stack is connected to one or two boilers. Therefore, since the throat diameter is kept small, such stacks may be made only 50 to 75 feet high without disturbing the proper proportions. With the low stack height and small throat diameter, only light loads are carried on natural draft, and the motor jet is used for the higher ratings. The draft may be controlled either by varying the area of the motor nozzle, or by var\ang the air pressure with a damper in the air pipe, or by using a variable speed motor to drive the fan. Chimneys at Altitudes AT high altitudes the specific gravity of the gases is B/30 of the specific gravity at sea level, where B is height of barometer in inches due to altitude, which may be read from Fig. 100; therefore their velocity through the fuel-bed, boiler setting and economizer must be increased by 30/5 in order to deal with the same weight of gases. Since the draft loss varies as the square of the velocity and as the specific gravity of the gases, it will be 30/5 or R times the draft loss at sea-level. This ratio is given in one of the curves of Fig. 100 or can be calculated. 30 60 29 ?8 50 27 26 40 25 24 30 23 22 21 f* ^ ^ 1 ! N ^~" ^, -^ecrr, . \ \ ^ ^^ f^ v^ / X <^ ^f A / "^ ^ P^c /^ r~ ~-^ "^ ^^ ■^ y / ^^ "^ U by* ^ ^ y (\ p.. ^ ^ e . ^ ^ ^, ^^ 2 3 -tfS '^.^■^^^ ■^ f^ ^ e^sl ^^ d -^ f. ^ ^ jt^lE .+«:] A eoij; u ^ ^ ^ fc^l \jr^ ^ ^ ^ r^ o GO ^ ^ ^ 1000 ^ooo 5000 4000 5000 6000 Altitude, Feet 7000 1.7 1.5 1.2 8000 9000 \0000 Fig. 100. Factors to be Used in Calculating Draft Losses in Chimneys at High Altitudes. The draft lost in giving velocity to the gases and at sudden enlarge- ments is 5/30 of that lost in giving the same velocity at sea-level. For the same draft loss with the same length of flues, their diameter (or equivalent diameter) must be increased i?°**. But it will simplify mat- CHIMNEYS 193 ters to make this increase the same as the increase of chimney diameter, the flue area continuing to be 20 per cent greater than that of the chimney. The draft loss through the flues will then be a little less than at sea-level. The draft power of the chimney is primarily 5/30 of that at sea-level. But the normal temperature, being less than at sea-level, reduces this ratio. The height necessary to give the same draft at the base would have to be increased as 30/5, nearly. But the increased height is accompanied by a lower average temperature within the chimney and by an increased friction loss due to the increased height. Also, the draft required at the chimney base is increased as 30/5 less the advantage derived from the larger flues men- tioned above. If the diameter of the chimney is not changed, the velocity is greater with still more friction loss. From a careful analysis of these changes, compared with results in actual practice, it is recommended that the height be increased as (/?i-3), and the diameter as (7?"-"). Curves are drawn in Fig. 100, giving both of these ratios. Take the example set forth in tabular form on page 187, resulting in a chimney say 150 ft. by 66 in. diameter at sea-level, and assume that the plant is to be at an altitude of 5000 feet. From Fig. 100, read R"-^ as 1.28 and 150 X 1.28 equals 192 feet. Read i?o.6 as 1.12 and 66 X 1.12 = 74 in. diameter. The figures for any given design should be checked as follows : A table like that on page 187 should be prepared, showing the draft necessary at the stack base, the barometer ratio R being considered. The static draft of the stack of the sizes derived as in the last paragraph should be calculated, taking the gas temperature average from Fig. 92. The weight of air and gas taken from Figs. 93 and 94 are divided by R from Fig. 100 and their dififer- ence, multiplied by the height of the stack and by 0.192, is the static draft in inches of water. The friction loss is now read from Fig. 95 or calculated from the formula (10) and corrected by dividing by R. It is then deducted from the static draft, giving the available draft at the base of the stack, which can be compared with that required. As the altitude is increased, the height of the chimney increases fasteir than its diameter ; consequently the proportion of diameter to height will sometimes become unmanageable. This can be overcome by increasing the grate area or by the use of induced or forced draft. Chimney Construction CHIMNEYS for modern power houses and industrial plants are made of steel plate, radial brick or reinforced concrete, either lined or unlined, and are usually of circular cross section. For the same area a round chimney has a greater capacity ; its shape requires the least weight for stability, and presents the least resistance to the wind. A maximum wind velocity of 100 m. p. h. is used in the design of such stacks, the equivalent pressure being taken at 50 lb. per sq. ft. for flat surfaces, and 30 lb. per sq. ft. of projected area of circular stacks. The following notes deal only with the practical features that must be considered in selecting the type of stacks. The structural design of a chim- ney, including calculations for foundation, stability and strength, is an intri- cate subject, which is a study for the chimney specialist. Chimney foundations are usually made of concrete in a mixture of 1 part cement, 2^ parts sand, and 5 parts broken stone or gravel, and poured in a '"wet" condition in layers 6 to 8 in. thick, which are thoroughly rammed into place. The safe bearing load for ordinary soil is 2 tons per square foot, because the chimney represents a concentrated weight on a small area. This is considerably lower than the loads permissible in building construction. 194 CHIMNEYS Foundations for brick chimneys are not as massive as the foundations used for steel and reinforced concrete stacks, because they function only as supports of the chimney column. In steel and concrete construction the foundation acts both as a support and anchor for the stack, the two forming practically one mass, giving the desired stabilit}". Reinforcing bars are frequently used. Table 12 indicates the proportions of foundations necessary for self-sup- porting steel and radial block stacks. The least depth and width of square or block foundations are considered. In steel stacks with a foundation hav- ing tapering sides, the widths at the top should not be reduced more than 3 or 4 ft. over those given in the table. For normal soil, the foundations sup- porting brick stacks can be battered or stepped off. using the widths given as the size of the bottom slab. The top slab should be at least a foot wider than the stack, all around, and the offsets made so that a line drawn along the edge of foundation will make an angle of 60 deg. with its base. Table 12. Dimensions of Concrete Foundations For Brick and Steel Stacks Stack Radial Brick Self-Supporting Steel Diameter, Feet Height, Feet Width, Feet Depth, Feet Width, Feet Depth, Feet 100 125 150 12 16; 20 '>2 4M 5 6 16 20 23 1 175 241. - 26 8,4 8 200 29 8 29 9H 9 200 30 8 31 10 10 200 31 9 32 lOH In poor soil, it may be necessan.- to sink piles. These are usually spaced 2 to 2y2 ft. on centers, and the tops cut off below the surface water line. A bed of concrete 2 or 3 ft. thick, into which the piles extend, is then formed as a base to receive the regular chimney foundation. Self- Supporting Steel Stacks SELF-SUSTAINING stacks as a rule are practically straight; that is, the walls above the flue openings are parallel. The base section can also be cyl- indrical. However, it is usually flared and includes the flue connection. The height of the bell-mouth base depends, therefore, upon the run of breeching and the location of the flue opening. \Vhen the flared part is one-quarter of the stack height, the sides take the slope of a cone having its apex on the center line along the top of the stack. This flared base has a diameter about one-third greater than the stack proper, permitting the connection of a larger flue, and the entr}- of the flue gases with the least interference. The flue opening in the plate of the chimney base weakens the structure, and requires reinforcing. Stiffening members across the top and bottom of the opening are sometimes used. More often the cut-away section is strength- ened by angle or T-shapes riveted to the sides and extended beyond the top and bottom of the opening, or a combination of these methods can be used to reinforce the flue opening all around. The flanged base plate riveted to the bottom of the base section is gen- eralh' made of two or more cast iron segments. More modern practice calls for a built-up steel base ring. Equally spaced around this are lugs drilled for the anchor bolts that hold the stack down to its foundation. CHIMNEYS 195 Above the base the stack is divided into several sections, each consist- ing of from five to twelve courses, 4 to 7 ft. high. Each course is made up of one or more sheets, depending upon the stack diameter. Lap joints are invariably used for vertical seams and often for girth seams ; the latter are also made with butt joints either inside or outside of the shell. Fre- quently intermediate courses have lap joints, but the sections are assembled with butt joints that reinforce the stack. In unlined stacks, an outside butt joint is preferred as it leaves the stack smooth on the inside. In lined stacks, the inside connections can be utilized to support the brickwork. Butt joints can be made either with the ordinary straps, or else flanged with angles riveted to the shell and bolted together. The riveting is generally figured on a factor of safety of four as a minimum. It is a moot question whether self-supporting steel stacks should be lined. The brick lining does not add to the strength of the chimney, although often the stack must carry it. Sometimes the lining is isolated and made self-supporting, acting as an inner core. Moisture may collect in the air space formed between the Hning and the shell, thus promoting corrosion. The lining reduces radiation and protects the steel from the corrosive action of the chimney gases. When a lining is used in a steel stack it should be carried up the full height. Radial firebrick, common brick, concrete and sometimes a filler of sand for the air space provided by independent linings are used for lining construction. Generally a 4-in. wall supported by an angle iron ring fastened to the stack every 15 to 20 ft. will serve. The lower section of stack can be lined with firebrick, and the upper section with common brick, using fire clay and cement mortar joints respectively. For an independent lining 8-in. brick will be required for the lower half of the stack and 4-in. brick for the upper half. The brick can be set close to the shell, or an air space of 1 to 2 in. left between the steel and the brickwork. To preserve the stack, the steel is usually given one coat of paint on both surfaces before erection. After the stack is in place, it is usually treated with two or three coats of heat-resisting paint. This is intended to protect the stack from the corrosive action of the atmosphere as well as to prevent air inleakage. To maintain the stack a painter's ring should be fitted near the top. This consists of a circular metal track with trolley and block to facilitate painting. In the base of the stack a cleanout door should be provided for access to the interior and for the removal of soot and cinder accumulation. Standard size cleanouts measure 24 1)y 36 in. and are made of either heavy cast iron or steel plate fitted with frames, hinges and clamps. The contact surfaces should be planed so that the door will be air-tight when closed. It is also advisable to install a steel ladder extending from the base to the top of the stack. This can be on the inside, although it is generally placed on the outside about 8 in. from the stack and fastened to the shell through riveted bracket connections. Ladders are frequently built with 3-in. side bars, ^ in. thick, with rungs or steps of ^-in. round iron, 15 to 18 in. long, and spaced 12 to 15 in. on centers. In fastening the ladder to the stack, care must be taken to prevent strains due to the unequal expansion and contraction of the steel shell and the ladder. Table 13 illustrates the size and sections and thickness of plate used in the construction of self-supporting stacks. Other instances of good practice are afforded by the stacks serving some of the large central stations. Four steel stacks in an electric light plant, each 297 ft. above the boiler grates and 21 ft. in diameter, are made of }i-m. and ^-in. steel plate in courses 7 ft. high. Ten vertical stiffening posts of 6 by 4 in. angle iron are riveted to the inside of each shell. At each 20 ft. of height two angle irons support a stack lining, which consists of 1-in. concrete and 4-in. red brick for the entire height. An 18-in. steel ladder on the outside gives access to 196 CHIMNEYS 197 Table 13. Plate Dimensions For Self- Supporting Steel Stacks Diameter, Inches Total Height, Feet Bottom Section, Including Flare 2nd Section 3rd Section 4th Section 5th Section Height Feet Plate Inches Height Feet Plate Inches Height Feet Plate Inches Height Feet Plate Inches Height Feet Plate Inches 54 100 165 185 40 30 65 5 16 30 50 60 H 5 16 5 16 30 45 60 3 16 M }4 66 40 3 16 78 120 200 225 250 50 85 80 H JL. 16 'A 60 20 30 5 16 Vs 7 16 90 25 30 5 16 H 132 95 1^ 144 30 5 16 80 14 each stack, and a gallery or grated walkway with hand railing is placetl around the top. The stacks rest on plate girders that are part of the build- ing construction, and are also braced against swaying and wind action. In a street railway plant the two steel stacks, each serving 16 boilers, are supported and braced by the framing of the building. The stacks are 132 ft. in height above the foundation and are made in three sections of 5^-in., >2-in. and ^-in. steel plate, each 44 ft. high. An 8-in. red brick lining, backed by 1-in. cement, is supported every 25 ft. on rings that stiffen the stacks. Another central station has three stacks, each 260 ft. high and 22 ft. diameter. The support and wind bracing is furnished by the building con- struction. Five sections varying in thickness from ^/ic to ^-in. plate make up the height. At each section an angle iron stififener and Z-bar ring support the lining, which is of 4-in. red brick backed with 1 in. of concrete. The details of a self-supporting steel stack for moderate size plants are shown in Fig. 101. This stack, which was designed and fabricated by the Chicago Bridge & Iron Works, is 13 ft. diameter and 185 ft. high. It is made up of 32 courses in five sections, including the base with the flue opening. Each course consists of three sheets and is about 5 ft. 9 in. high. The thick- ness of plate varies from ^-in. at the top to 3/^-in. at the bottom. The stack is anchored to a concrete foundation on top of which is a sectional cast iron base 2 in. thick, in 12 segments. Immediately above the base ring and riveted to the base of the stack are 24 built-up steel plate lugs that hold the anchor bolts. The base section is conical or tapered, 18 ft. high and 19 ft. diameter. The first parallel or cylindrical plate course above this is 13 ft. 1]4 in. while the last course at the top is only 1 in. less inside diameter. The individual courses 7 ft. high. Ten vertical stiffening posts of 6 by 4 in. angle iron are the different girth seams. In the base section a flue opening 7 by 20 ft. is rein- forced by plates and angles to strengthen the cut-away part of the stack. A steel ladder on the outside extends the full height. It is 14 in. wide with side bars 2 by }i in., and rungs of S/^ in. square iron. The ladder is strapped to the shell at the top of every second course, 8 in. from the stack. Guyed Steel Stacks nn HE guyed or supported steel stack is designed to simply carry its own ^ weight. Stability or resistance against wind pressure is cared for by fas- tenings to adjoining walls or by guy wires. Guyed or supported stacks do not require heavy foundations, because they are much lighter than self-supporting stacks. Usually they are riveted to the smoke breeching or else arc con- nected with the smoke up-take and with the boiler setting. 198 CHIMNEYS JW/^^'Z- 2-Bars2''xWx-- IS'-Tk" \ I ?-BenfBars 7V/8'xO-llii'- W^ ■V- m •iS'W Radius 't Plate Top V^ <-/" .'Splice <-6-6'WI?adius i. Plate Boft ■'A" Plate WP/vets I PART OF TOP SECTION ^i^ \<-9-6WPactia5 i Plate Sottom of dBase PART OF BASE SEaiON Bent Plate IO"xWW'-8W- Bent Plate , lOW'xWW-sA Bottom X of Plate-'' DETAIL OF ANCHOR BRACKH TxIO'Flue— Opening l2"xW- l2"x'/2" 4"x&'x%"L--\ 12 "xW-- k 19'-0--^ WlO-yClBase-^ Fig. 101. Construction Details of a Self- Supporting Steel Stack. CHIMNEYS 199 The thickness of plate used varies considerably and is largely governed by the degree of permanence required. Corrosive action by the elements and stack gases gradually reduce the thickness of the sheets until the stack is no longer safe. The thickness of plate is ordinarily kept within the limits given in Table 14. Table 14. Dimensions of Guyed Steel Stacks. Diameter Thickness of Plate Inches Maximum Minimum 30 36 42 No. 8 gage Vi6 in. yk in. No. 10 gage No. 10 gage No. 10 gage 48 54 60 Va in. Vio in. Vi6 in. No. 8 gage Via in. Vie in. The size of rivets used should be : y% in. diameter for No. 10 and No. 8 gage plate. Vi6 in. diameter for Vie in. plate. '/le or y2 in. diameter for ^ in. plate. Yz or Y^ in. diameter for Vie in. plate. The circumferential pitch is generally made equivalent to one rivet for each inch of diameter of the stack or 3^/7 in. pitch, and the longitudinal pitch is made 3 to 4 inches. Fig. 102. b c cl Styles of Joints for Guyed or Supported Steel Stacks. 200 C H I ]\I N E Y S Tt is common to make the plates thinner in the upper portion of the stack. As the corrosive action is more energetic at the top, many prefer to make the upper part thicker than the lower, or at least to keep the thickness the same for the full height. The plate courses may be assembled as shown in Fig. 102, in which the "shingle"' lap (a) is composed of tapered sections and is designed to shed water. In joints like (b) the larger sections slip over the ends of the smaller sections and all the sections are parallel or cylindrical.. With another method (c) the lower end of the upper course slips into the lower course. Sometimes a strap-joint (d) is used, in which the ends of sections are butted together and a steel band placed around the joint and riveted to each plate, making a very strong but much more expensive chimney. ■^ '> 5" Band, inside and outside J^-^ <-72"l.D.'-> t.^ — mm Note W Rivets to be driven hot and tight On vertical seams 2'/2" centers, on girth seams 2"centers. lS/i6"Diam. Drilled Hole ^''/4"Steel Plafe Gvy Lugs and Strap If 03 Details of &uy Strgip ■ Rivet to Breeching Fig. 103. Construction of a Guyed Steel Stack. C H I IVI N E Y S 201 While each of these methods have their advocates, the best practice ap- pears to be indicated by (c). With (a) the seams cannot be made tight, and water from the inside of the stack leaks through, and corrodes and discolors the outside. With (c) the joints are easily filled with paint and made perfectly tight, so that corrosion is reduced to a minimum, Guys should be of not less than ^2 in. wire rope. Each guy should have a turnbuckle to take up slack and equalize tautness. The anchorage, whether "dead men" or buildings, must be such that there is no possibility of failure in the highest wind. The guj^s are attached to the stack either by eyebolts, with reinforcing plates inside, or by a guy-ring, carried around the stack in sections whose ends are bent out to form lugs. While the guy ring is the strongest construction when new, corrosion appears to concentrate about it, and so weakens the stack that the eyebolt method is perhaps the strongest permanently. The number of guys and their arrangement depends upon the height of the stack. Low stacks up to 50 or 60 feet may have one set of three or four guys. Over 60 feet, there should be two sets of four guys each, and stacks over 125 feet usually have three sets of four guys each. The upper or single set is generally attached to the stack about 12 feet below the top. When there are two sets of guys, the lower set is attached about 2/3 of the height from the ground to the upper set. When there are three sets of guys, the upper set is attached about 12 feet from the top, the lower set at about half the height of the upper set, and the middle set about half way between the upper and lower sets. Guys are commonly anchored at a distance from the base equal to the height of the guy band, so that they are stretched at an angle of 45°. When two or three sets of guys are used, the upper set may be arranged to form an angle of only 60° with the vertical. In congested city sections, stacks are often fastened to building walls by brackets or strap-iron anchors. Stiff guys may be made of 2 in. pipe for stacks up to 75 feet high, and of 3 in. pipe for higher stacks. All stiff guys should be well braced against Ijending unless they are very short. A guyed stack of >^-in. steel plate, built by the' Neii* York Central Iron JVorks, is shown in Fig. 103, It is intended for direct connection to the smoke flue. This stack has an inside diameter of 72' in. and is 104 ft. high overall. Each course is 5 ft. high and is made with lap-joints single riveted. At about 40 ft. from the top a heavy ring is fastened to the stack, reinforcing it to receive the lugs for the guy wires. The top is finished with a steel band on the outside and reinforced with another band on the inside. Radial Brick Chimneys COMMON brick is seldom used for chimney walls except for small house- heating plants. Larger stacks have walls of vitrified hollow or perforated brick formed to occupy a certain position in the circular and radial lines of the chimney. It is said that the perforations in the brick form> a dead air space, which reduces the loss from radiation and pfevents sudden temperature changes within the stack. These radial blocks are larger than common brick and are made in sizes and shapes for all diameters. The method of laying and bonding as used in Hcinicke chimneys, and some of the shapes used in Custodis construction, are illustrated in Fig. 104. The brick are laid in cement lime mortar, with Yz in. joints, to give a straight batter or taper from top to bottom. The outside surface is invariably smooth while the inside surface sometimes has a series of steps, owing to the change in wall thickness of the different sections of the chimney wall. Starting with a thickness of one brick, or about 7 in., at the top, the wall thickness is increased about 2 in. for each section, which is generally 20 ft. high. A circular chimney 200 ft. high would have an actual thickness of 24 in. at the base. The wall thicknesses, m 202 CHIMNEYS Fig. 104. Brick Bond in Heinicke Chimney and Different Shapes of Custodis Radial Brick. Table 15. Outside Diameter Feet of Base of Brick Chimneys Height of Chimney Faet Internal Diameter at Top, Feet and Inches 3—0 a— 6 4—0 4—6 5—0 5—6 6—0 ICM) to 80 85 7.42 7.80 8.18 7.69 8.04 8,38 7.961 8.27 8.581 8.46 8.70 8-95 8.96 9.13 9-31 9.96, 10.02 10.08! 90 95 B.73 S.5S " 9.19 : 9.50 •9. IS 9.4:3 9.67 9.S.3 10.13 ::».i9 10. 11.25 11.75 12. 110 115 i;. 10.20 10.55 10.03 10.40 10.77 10.21 10 10.60 10. 10. 9S 11. 07 11.03 11. .50 11.95 12. h-' 120 125 130 10.79 11.16 10.55 10.90 11J21 11.25 11.65 11.14 11.50 ll.SS 11.37 11. 11.75 11. 12.1; 12. 41 11.45 11. 75 11.75 12, .50 12 .55 12. ,75 13. 13.50 13. 50 14.OOS14.50 14.22 14.69 15.00 15.15 135 140 145 12.05 12.45 12. S5 12.25 12.63 13.00 12.4: 1- 12.S:' 12. 13.15 13. 22 13.2S 13. 13.1 73 14.0S 14.43 14.87 15.30 i: 14. 5S 14.^- 1-.-3 15.45 ■ ---. '--..—. l^.^T 1'.;.; 15.60 150 155 100 13.25 13. 5S 13.92 13.3S 13.73 14. OS 13.5- 13. J 14.2: 15.19 15.43 15. OS 15.42 15.75 15.31^5.61115^)1 15.55115.8116.07 165 170 175 14.25 1-=.^; U.: ; :-;."3 14. S6 U 14.59 14. Tj U.— 15.11 15.26 1: 14.92 1-5.13 15.:i3 1.5..50 1-5.66 15 22 15.; 49 15.: 5S 15.-50 15.75.1':. 15.66 1 " C,"i 15.78116.00116.22 16.02'l6.20|l6.38 16-25 16.40fl6.54 ISO 1S5 190 15.S0 16. 16.50 16.65 16.80 16.75 16.91 17.06 17.00 17.16 17.31 195 200 205 :1 17..57 " 17.S3 : ::.16 210 215 220 22.=» 1 - . - 1 1:::: i ::;: i;::: • • 1 1 ' ! ii .50 J3 CHIMNEYS 203 9"-><^ "'^-Cement Head with W.I. Ring ^U7'/2" 4y4"Lining -I I F/ue Opening — WxZ"W.I.Ringat fooi of column and above and below the flue opening j Ur—l9'-6"-—^ k- 25'-e" -» Chimney on Octagonal Base ,-->'• Wafer Table of (Neat Cement ^ I Beams over Flue WrSpace--' % Opening sufficient ^^ '"^ "^ to carry weigh f-^^ il8'/A -i ^- V^OutDia.ie-Of'^ w--ie'-e" >J ?5'-6"— Li ->\ Chimney Round for Full Height Fig. 105. Example of Kellogg Radial Brick Chimneys. i Burnside Shops of the IlHnois Central Railroad, Chicago, 111. 2590 H. P. of Heine Standard Boilers. CHIMNEYS 205 two styles of Kellogg radial block chimneys, are shown in Fig. 105. The batter indicated is based upon the figures in Table 15, from which layouts can be made for stacks 3 to 10 ft. diameter and 75 to 225 ft. high. The design should be checked to see that tension does not occur on the windward side, with the maximum wind pressure allowed, as the chimney would then be unsafe. It is common practice to use regular hard building brick for the base of the chimney, when it is of a sciuare or octagonal form. If the base forms part of the building wall, the two should be bonded by a slip joint, shown in the lower left-hand view of Fig. 106. The radial brick above the breeching f Cement Cap, 1-3 mh '/4''x5"m Retaining .. I^ing set in fuilt^ed ^ of cement mortar Outside Fitter Wall to protect beams from., atmosptiere. 4'l. Concrete 2f- Flue Opening/ Head of Chimney Brick Lining,^ }>tinimum air space 2' t^etween lining . and main wall f^;Lining Inside yofStacl< I I Beams on ^Bearing Plates '^.fFi^eofArchfor each2'ofFtue Opening Widf- Builcting mil bonded mta base of chimney by means of slip Joint Plan of Octogonal Base Building Wall-. Section through Flue Opening Boiffle-Wall carried on I Beams 2' below opening, to at least S' above flue opening For flue dia- meters ofS' and under, use 4" watlOverS'use 8"walt Square Base Forming Part of Building Wall Chimney Having Two Flue Openings Diametrically Opposed Fig. 106. Typical Details of Radial Brick Chimney Construction. entrance, shown in the upper right-hand view of Fig. 106, is supported by heavy beams on bearing plates with air spaces at each end to permit ex- pansion. The steel is protected against the effects of the gases of combustion by a flat arch. To prevent cracking, radial brick chimneys are provided with rein- forcing bands that take up the stresses due to expansion. One company conceals three or four 3 by 5/16 in. bar steel bands in the brick work. These rings are placed below and above the flue opening, ai or near the top of the lining and in the chimney cap or cornice. Another method is to place these bands at every change in wall thickness, omitting some of them when the bricks have corrugated sides. When gas temperatures are high, additional expansion rings are placed on the outside, spaced about 6 ft. on centers. A lining inside the chimney is also necessary as a further safeguard against expansion strains. This lining is independent of the stack and is separated from it by an air space of at least 2 in., which prevents the gases from coming in contact with the chinmey brickwork. For steam 206 C H I ^I X E Y S boiler plants the lining is made 30 to 50 ft. high, or about one-fifth the stack height. For very high gas temperatures the lining should be carried up at least half way, preferably to the full height. Expansion linings are made of ordinary fire brick or of perforated blocks about 4 in. thick. They are started 2 ft. below the flue opening in the stack. Sometimes the space between the lining and stack is covered at the top. One method is to corbel or rack out the shell of the chimney. This protecting ledge prevents soot or dirt from filling the air space. Ladders are also a necessar}' adjunct to chimneys. These are located either inside or outside for the full height of the stack. The rungs should be of ^ in. round iron, preferably galvanized, of "U" shape, spaced on 15-in. centers and securely anchored to the masonry. Lightning rods should be provided to protect brick chimneys. A number of pointed rods, above the top of the stack, are connected to one or more con- ductors extending down to a ground connection beneath the grade line. Points extending 6 to 8 ft. above the top are subject to rapid deterioration owing to the action of the outflowing gases. It is advisable, therefore, to locate a greater number of points around the stack so they will not project more than 6 ft. above the top. Less than two points should not be used on any stack. On large chimneys the lightning rods can be spaced from 6 ft. to 3 ft. on centers, on the outside circumference of the stack. 23'-6'/4" — 23'-2'/4'' — Cross Section J S'-e"- > 9'-0"High Plan Fig, 107. Soot Collector System in a Large Chimney. CHIMNEYS 207 The lightning rods are usually made of %-in. copper, tipped with Yz-in. platinum thimble points. They are fastened to the masonry and are inter- connected by a copper cable placed completely around the top of the stack. To complete the circuit one or two bare copper cables, of ^ or 7/16-in. diameter, are connected to this ring. These conductors extend down the side of the chimney, where they are fastened at intervals, and terminate in a copper ground plate located in permanently moistened earth, in a charcoal bed, or in a pocket filled with crushed coke, and placed away from the chimney foundation. The grounding terminal can be of the coil, plate or cylinder t>'pe. For access to the interior of the stack and to facilitate cleaning, a cleanout door should be located in the base. Standard cast iron cleanouts measure 24 by 36 in. and are fitted with frames, hinges and latches. A tight fit is essential, so the contact surfaces should be planed. An effective method for the removal of soot and cinders from large chimneys is represented, according to Thos. S. Clark, by a collector system installed in a radial brick chimney 300 ft. high, 19 ft. diameter at the top, and about 23^ ft. at the base. Super-imposed hoppers. Fig. 107, are lo- cated below the flue opening in the base of the stack. These hoppers are de- signed to collect the soot and cinders dropped by the gases in passing up the chimney. The hopper floors are concrete lined with brick. Two are used so that the door in one is closed when the door in the other is open, to prevent the possibility of an open draft up the chimney through both hoppers. Access to each hopper is provided through a manhole, which is reached by a ladder on the outside of the chimney. Each hopper can be cleaned from a gallery built around the rim. In the chimney base are doors large enough to allow a cart to be backed in under the lower hopper to remove the soot and cinders. Reinforced Concrete Stacks THE advantages claimed for reinforced concrete chimne3^s are light weight, minimum space, strength, and rapidity of construction. All joints are eliminated, the stack and foundation being one monolithic structure. Patented steel forms are used rather than wood forms. The structural design is ordinarily based upon a maximum compression in the concrete of 350 lb. per sq. in. and a maximum tension in the steel of 16,000 lb. per sq. in. The details of a reinforced concrete stack 180 ft. high and 8 ft. in diameter, are shown in Fig. 109. The walls are considerably lighter than brick construction and are concentric with an even taper from top to bottom. The wall thickness is 5 in. at the top and 11 in. at the base. The concrete mix- ture is 1 part cement, 2 parts sand and 3 parts crushed stone or gravel. This is poured "wet" and then tamped in the steel forms and around the reinforc- ing bars to secure a thorough bond, as well as smooth inside and outside surfaces. Vertical reinforcing bars are placed about 3 in. from the outer surface and are distributed proportionately to the load. Around the circumference the stack is reinforced horizontally by heavy wire mesh, woven in triangular form. This is set close to the outside surface of the wall, as indicated in Fig. 108. The flue opening in the stack is also reinforced and the walls there are about 50 per cent thicker. Figs. 110 and 111 show the process of constructing a concrete stack. One view shows the steel forms and reinforcing rods in place, ready to receive the concrete mixture and the other the completed base section of the stack with the forms removed. The entire chimney is usually finished with a cement wash. 208 C H 1 -M X E Y S ^-Wire Mesh ^4 Layers of Bars Fig. 108. Base and Foundation of Heine Reinforced Concrete Stack. To protect the chimney column from the stresses due to expansion an isolated inner core or lining must be installed. This is built of firebrick or perforated blocks in the same manner as described for brick chimneys. Instead of the ladder steps used in brick construction, concrete stacks are equipped with tackle, consisting of a bronze pulley anchored to the top of the stack, and a 3 16-in, wire cable. A soot separator is an integral part of the reinforced concrete stack shown in Fig. 112. This stack serves a plant in which patent-leather is manu- factured. Soot and cinders issuing from the old chimne\- lodged upon and damaged the leather, which is dried in the open. The stack has an outside diameter of 8 ft. 8 in. at the top and 23 ft. 8 in. at the base. The unusual taper is due to the soot separator, which is built in at the base as part of the chimney. The soot separator, which consists of two concentric stacks 29 ft. high, is made of radial brick. The separating chamber is in the outside circular passage while the inside section is the chimney proper, the two being connected by three openings in the wall. These openings are of sufficient area to handle the volume of gases through the 8 ft. area, which corresponds to the inside diameter of the chimney at the top. The flue gas entering the chimney through the 5 by 11 ft. breeching connection has its velocity reduced and owing to the shape of the passage, it flows spirally. This combined action separates the soot and cinders from the gas. which then passes up and out of the chimney free from ash. The outside wall of the soot separator also serves as the expansion lining for the chimney. The top of the separating chamber is closed with a cast iron cap. In the base of the chimne}' proper are two cast iron cleanout doors for removal of soot. A 2-in. perforated steam pipe has been provided. Tile drains, as indicated in Fig. 112, have been installed, to keep the chimney free from water. CHIMNEYS 209 ■^8'-0'^-p\ Double layer of Wire Mesh 3'-0" below and above opening. Thickness I of waffs increa- sed 50%. Reinforcing at Smoke Opening Remforcing-- -25 '-P"- Fig. 109. Heine Reinforced Concrete Chimney. 210 Fig. 110. Steel Forms and Reinforcing Rods in Place to Receive Concrete. Fig. 111. Completed Base Section of a Concrete Stack. C H T ^t N E Y S 211 -Terra Coffa Drain ^-2" Perforated Iron Pipe Terra Coffa Draln"^'^''^" ^'''^^ Opening Section A-A Triangular Mesh Horizontal Reinforcement 3 Openings -5'-0"wide ty 15^6" high. Each placed as shown. Nofe:- Jy/o Cast Iron Clean-oof Doors where direcfec/ in base of stack flue Opening Radial Brick ' %<-2" i -Special Cast Irdh Cap w III ! !i !' Li 'illii'llr Over each open- ing in flue-l-6'x IZ25*IBeam 4'^" long. Bent to circle of 4'0"Rad ^<- \ i — I > — /5 T I Flue Opening ^^ i^'^>j\ IT-O"^ ^ 25'-0" >\ Original Brick Stack Fig. 113. Reinforcing an K 25'-0" H Stack Afier Concreting Old Brick Stack. 214 CHI M X E Y S Remodeling of Chimneys T^RICK chimneys are increased in height b\- adding a gu\-ed length of steel ^ stack. In some instances the added portion is built of radial brick. Where the old part is of square cross section, an octagonal adapting portion is worked in. Sometimes this work is done while the boilers are under fire. Bent brick chimneys can be straightened by sawing out mortar from the convex side. Chimneys that are dangerously defective ma}- be made safe by applying a casing of reinforced concrete. Fig. 113 illustrates an example. Steel chimneys that have become badly corroded may be renovated with a con- crete casing. Breechings I 'HE breechings or fmes should be so arranged as to offer a minimum -■- of resistance to the flow of gases. The area should be large enough so that a reasonable accumulation of flue dust will not cause any noticeable choking. The run should be as short and direct as possible. Connecting flues should be so designed that the entering gases tend to flow parallel with the gases alread}- in the main flue. Access doors should be placed conveniently to facilitate cleaning. Flues are frequently made 15 to 25 per cent larger in area than the stack, depending upon the amount of flue dust expected. Where fine fuel is burned with forced draft, the deposit of flue dust is relatively large and therefore liberal areas should be allowed. Builders of chimneys prefer to limit the area of fl.ue openings to 7 to 10 per cent greater than that of the stack. For structural reasons, the width of opening in the chimney should not be more than one-third the outside diameter of the chimney, the neces- sary area being obtained by increasing the height of flue opening. Sometimes the breeching area is proportioned to the total grate area served by allowing 22 per cent of the grate surface as the minimum' cross- sectional area of the flue. But this is not good practice, for the size of flue is entirely dependent upon the volume of gases to be dealt with, while the volume of gases due to any given grate surface varies with the intensity of the draft. A breeching suitable for a given grate area under natural draft may be far too small for the same size of grate imder forced draft The breeching area should be determined by gas velocity-. The draft loss depends upon the gas velocity in relation to the length, area and shape of the flue. The velocitj- may \a.ry from 15 feet per second for long rectangular flues of small area, to 35 or 40 feet per second for large short circular fl.ues. The draft loss maj^ be found by formula (10) on page 183. Whatever velocity is chosen, the resulting area should be increased sufficiently to allow for the deposit of flue dust. A breeching of circular cross-section causes less draft loss than a rectangular or square section, and the flatter the rectangle, the greater is the draft loss. This is clearly shown by the coefficients of formula (lO. Square or rectangular breechings with a semi-circular top are good designs. In practice, sharp bends and right angle turns are the most com^mon faults found in breechings and smoke connections. While it is not difficult to make or connect long-sweep turns and to install necessary- deflectors, these details may be neglected unless the work is carefully supers-ised. Space conditions often make the installation of some bends necessan.-. The designer must then use the least number of bends and make them as long and gradual as possible. The bends necessary for a change in direction should have an inside radius at least equal to lj'2 times the diameter or width of the breeching. CHIMNEYS 215 Fig. 114 will emphasize the bad effect of sharp gas turns. The entering gases tend to strike the opposite wall and leave eddies as at A, A, which are the equivalents of reduction in flue area. Rounded corners at X and near A would reduce the draft loss, but the gases from Boiler No. 1 would still interfere with the flow from Boiler No. 2. This figure also shows poor design in making the breeching parallel. The gases from Boiler No. 2 lose velocity in filling the larger area of the main flue, and as this velocity has been given to the gases by the effect of the chimney, velocity so lost is wasted chimney effort. As the gases from Boiler No. 1 crowd into the main flue, the gases from Boiler No. 2 have less space and their velocity is again increased, putting more work on the chimney. To Stack From Boiler No. I From Boiler No. 2 Fig. 114. Effects of Right-angle Turns in a Smoke Flue. Fig. 115 illustrates excellent practice in designing a breeching to serve several boilers. The bottom of the sides is made horizontal to agree with the boiler settings, and the increase in area as each boiler is connected is taken care of by the sloping top. The deflection plates forming the bottom are made parallel with the top, keeping the gas velocity uniform, and the steps between them provide ideal locations for the pampers. I r>^ t/ce Fig. 115. Breeching and Damper Arrangement for a Battery of Boilers. A good example of breeching design for several boilers is shown on page 218. The connection to the stack should be through an easy upward bend, so as to enter the chimney at about 45 degrees. Where breechings from boilers on both sides of a chimney meet before entering it, care should be taken to guide the two currents into fairly parallel streams before they meet. Fig. 116 is given to emphasize the bad effect of two opposing gas currents in a bull-headed or T-connection. To- gether with the area-reducing eddies at A, A, as in Fig. 116, this head-on collision of the two streams may cause sufficient draft loss to reduce the boiler capacity seriously. Equitable Building, New York City. 3500 H. P. of Heine Standard Boilers. Tallest Chimney in the World. CHIMNEYS 217 f^rom Boiler No. I A r From 'Boiler No. 2 Fig. 116. 7b Stack Effects of Bull-headed Connection on Gas Flow in Breeching. In such instances curved deflecting plates as at X, particularly when a dividing plate is carried from X to the entrance of the flue leading to the stack, have made a notable improvement. Rounding the corners as at A, A, is a still further advantage. Fig. 117 shows two flues connected to a central stack. To reduce the draft loss from the head-on collision of the gases, a baffle is placed in the base of the chimney, so that the gases are deflected into parallel directions. From _ Boiler No. I From Boiler No.? ''Stack Fig. 117. Baffle Wall in Chimney to Prevent Collision of Gases. Examples of good practice in breeching design where the chimney is carried by a symmetrical hood are illustrated by Figs. 118 and 119, which show breeching hoods for one and two boilers respectively. As most engineering problems are solved by compromise, so the power plant designer must frequently compromise between ideal flue design and increased height of stack. Flat rectangular breechings and sharp curves may become necessary to meet space restrictions, and the increased chimney height resulting therefrom must be accepted as imavoidable. Steel or iron plate is used in constructing breechings and smoke connec- tions. For main breechings of square section, metal 3/16 in. thick is required. The sides, bottom and top are braced or reinforced on the outside with 2^-in. angle iron. Individual smoke connections between boilers and breeching are usually made of No. 10 gage metal, although for longer runs and large size boilers No. 8 gage plate is sometimes used. When of square section, these are held at the corners by l-V4-in. angle iron, and are also reinforced or further stiffened with angle iron on the outside. For the removal of soot accumulation and for access to the breeching, cleanout doors should be provided at convenient points. It is good practice to install one cleanout at the far end of the breeching and at least one other cleanout along the run of flue, either in one side or at the bottom. Clean- out doors are made of heavy cast iron or steel plate, fitted with massive •d V CO Wi CO US u CO >— I >o t-i C0 O T) _r ■♦-' TJCO CO i; ^ o 3 G IS u (U PQ CHIMNEYS 210 Fig. 118. Ideal Breeching Arrangement for Single Boiler. D ampers Boi/er A/o. / *//>* 3 oiler No. 2 Fig. 119. Ideal Breeching Arrangement for Two Boilers. 220 CHIMNEYS hinges and one or two clamps to facilitate opening and closing of the door. iJoor frames are riveted to the breeching ; both the frames and doors should be planed so as to be air-tight. Sliding doors are sometimes used for cleanouts. Breechings and smoke flues should be covered with non-conducting material, such as asbestos or magnesia heat insulation, or else be protected with refractory brick or other vitrihed material. The coverings or linings are frequently placed inside the breeching to protect the metal against the possible corrosive action of the gases, although it is advisable to have the insulation or lining on the outside. The breeching, smooth on the inside, will then permit a straight uninterrupted liow of the gases into the >moke stack; there will be no loose pieces to fall into the breeching and obstruct the gas passage, and repairs can be made without interfering with plant operation. The insulation on smoke fines is important because it pre- vents lowering the gas temperature, by reducing heat losses. If this temper- ature is lowered while the gases are passing through the flue, the effective draft will be reduced. Overhead steel breechings are usually hung from the building construc- tion, although special supports are frequently required. Underground flues involve a high friction loss because of the large num- ber of turns in the gas path from the boilers to the stack. The brick or concrete used for these flues is porous, so that the flue is subject to leak- age. Being located below the boiler room floor the flues are difficult to keep clean and the soot gradually accumulates and obstructs the gas passage. Dampers T^AMPERS are used both to vary the gas flow in controlling the rate of '^ coml)ustion, and to close the flue entirely in isolating idle boilers. Dampers should move easily and when wide open offer the least possible resistance to gas flow. Dampers used for isolating idle boilers or flues should be reasonably gas-tight. Levers or handles to operate dampers should be located in par- ticularly convenient and easily accessible positions, and be so arranged that they definitely indicate how wide the dampers are open. Dampers should be made the full area of the breeching or uptake. If a rectangular damper is used, it will cause the least disturbance to orderl}- gas flow if swung about its longer axis. Fig. 120, for a rectangular damper turning about its shorter axis, illustrates faulty design by showing the area wasted in the formation of eddies. Fig. 121 illustrates good practice in damper arrangement. The dampers swing in unison about their longer axes ; and when wide open, the gas flow is virtually undisturbed. Each boiler must be provided with an independent damper. It should fit well, so that when the boiler is idle there will be very little leakage. Inleakage of cold air into the main flue through defective dampers of idle boilers reduces the draft very seriously. Individual boiler dampers are set by hand so as to divide the load equally between the boilers by correcting the unavoidable differences between the drafts at boilers near the stack and those at boilers more remote. Varia- tions in the general or total load are cared for by a main damper near the chimney, controlled either by hand or by an autoinatic regulator. Damper regulators are discussed in Chapter 16 on OPERATION. The main damper need not be tight unless there are more than one. such as when two or more flues enter the same chimney. Sometimes the main damper is prevented from forming a tight closure, either by providing a hole in it, by stops to limit its travel, or by adjustment of the operating mechanism. CHIMNEYS 221 Br««,chin3--> Fig. 120. Faulty Damper Installation. Operating -^ Lever Fig. 121. Proper Location of Dampers, 799 CHIMNEYS Dampers should be balanced and should move easily. Swivel or "butter- fly" dampers are generally used, since they swing freely and are not apt to get out of order. Sluice or slide dampers are sometimes necessary- to meet space requirements, but are avoided wherever possible, as they are difficult to move, especially when there is dust in the slides or the dampers are slightly warped. Dampers are operated by chain, wire rope or rods. Rods are preferable, because they give positive action, whereas if chain or rope is used, reliance must be placed on the overbalance for movement in one direction. If any of the bearings stick, the damper may remain in one position without the defect becoming immediately known ; whereas rods show such a trouble at once. For this reason, where rope or chain is used, the overbalance is made much heavier than is generally necessary, thus making movement more difficult. Unless the handles for operating the dampers are brought to a con- venient position, so that the attendant can work them, easily, they will not be adjusted as frequently as they should be, and waste of fuel will result from failure to relate the draft to the load and the fuel. The bad effects of controlling the draft by means of the ashdoors and tiredoors are fairly well known, but blame for this condition should usually be placed on those responsible for making damper operation difficult and awkward. The handles should be arranged so as to definitely indicate how much the damper is open. This indication is sufficiently important to warrant checking from time to time. Lost motion prevents correct indication and should be eliminated, either by overbalance or refitting. The damper shaft should be squared where the operating lever is attached to prevent any possibility of slipping. The same requirement applies also to any other shaft and lever of the operating mechanism. Fig. 122 shows the construction details and general proportions of a good damper design. .■S/8' Rivets SV 3 3 3 3| 3_ 35 -^ :5 D. O g % 80 g40 -o4 3:^ 60 it: 30 ^3 40 ZO"^? 20 10 1 Sf-Q f/'c A ^r. "^^ ^ »s.. \ \ H' )rsef. ■)owe r r\^-^^ y_^^ ■^ «Sfc ^ 7^ ^^ xO^ £ i>^ -^ \ ^v ^ X^ r \ \ yf y^ S\ i / N \ \ 1 N \ 10 20 30 40 50 60 70 80 90 100 110 120 130 WO Air Flow,Thousandsof Cu.Ft.perMin. Fig. 128. Pressure Characteristics of Backwardly Curved Blade Fans. types determines their applicability to meet the particular problem under consideration. The conditions imposed by hand firing and by each of the various types of stokers are different, and" the demands of each at different Mccormick Building. Chicago, 111., equipped with Heine Standard Boilers. MECHANICAL DRAFT 231 ?Z0 1?0 12 210 no II 200 100 10 180 90 9 IGO 80 8 4- S- 140 §70+^7 o o IizocSgoJg o -c o glOO §50^5 80 t 40 ^'4 GO 30 o3 40 20 2 20 10 I ° ° °0 10 20 30 40 50 GO 70 80 90 100 110 120 130 140 150 160 Air Flow .Thousands of Cu.Ft per Min. Fig. 129. Pressure Characteristics of Radial Type of Fans. y y y X ,«<■/ / 6fc 7 fie Press ^2, M< f\ y ■->< > A y "^ \ (A ■A ^ "^ \ s. ,vO y / s "^ s. I X r \ L i y) f \ ^ \ 1 \ ^ loads are different. The pressures required at different loads must therefore be compared with the fan characteristics to determine which type of fan will be appropriate. 240 120 12 220 110 II 200 100 10 180 90 9 160 80 8 1405 70 d7 |l20'j60'fe6 c* c ^ 12100 .5! 50 -g 5 80Ci40:t:"4- 60 30"^ 3 40 20 2 20 10 I / / / J / \ <^^ / \ i ^01 fie Press jre —/ y 7^ '^ ^. \^'f- P^ f*^ ^^ ^ \ V ,{> r y s \ \ s^ ■3- y \ s. \ / r p\ sN / \ \ / ^ 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Air Flow,Thou sands of Cu.Ft. per Min. Fig. 130. Pressure Characteristics of Forwardly Curved Blade Fans. 2Z2 ^I E C H A X I C A L D R A F T For use with stokers, there is a temptation to pick a small fan and accept a poorer efficiency for the peak loads, especially when they occur for only a short time each day. Whether this is good economics will depend upon the frequency and duration -A the peak loads. There is always danger that the tip speed of the fan so selected will be too high at the peak load. Fans are designed for a safe tip speed of 16,000 to 18,000 ft. per min. An excellent specification requirement is that the fans shall be run without showing any signs of permanent distortion for two hours at a speed 25 per cent above the highest operating speed. As stresses due to centrifugal force increase as the square of the speed, the stress during the two-hour run will be about 50 per cent greater than under the most severe specified condition. This test can be met by an}^ properly designed fan without causing harm to show up then or later. Tests at higher than 25 per cent overspeed should not be called for, as the stresses put upon the fan might be great enough to start ruptures, which might escape inspection after the test run. Pcrfoniiance of Fan. A test on a manufacturer's test plate with the fan blowing into a long straight duct is simple enough, although it requires extreme care, but to test a fan after installation is extremel}^ difficult. The only readily available instrument for measuring the volume of air in a duct is the double pitot tube. Fig. 131 shows this tube and its connections to the indicating gages. When the pitot tube is carefully used, volumes can be determined within 2 per cent accuracy. To secure this accuracy, measure- ments must be made in a straight run of pipe far enough away from the fan so that the turbulence it sets up in the air is dissipated, and a smooth steady parallel flow is insured. Usually the distance from the fan outlet to the pitot tube should equal 10 or 15 pipe diameters. In most forced draft installations there is no straight pipe of this length, so that the results must be regarded as indeterminate. The readings with a pitot tube are sometimes surprisingly accurate, even when it is placed close to the fan outlet, but never- theless one should always select as a place of measurement the longest run of straight pipe available. The volume delivered by the fan can be determined from the manufac- turer's pressure, volume and horsepower-volume curves, drawn for the speed at which the fan is tested. The pressure can be determined by taking five or six readings at different places in the main duct, allowing about Vio in. for the loss from the fan outlet to the main duct. The volume corre- sponding to this pressure can be determined from the pressure-volume curve. If the fan is driven b}^ a motor so that the horsepower can be determined for the same conditions an additional check can be secured from the horse- power-volume curve. The volumes determined by pressure and b}^ horse- power should check within 5 per cent. When the air velocities are measured by a pitot tube, the duct must be divided into at least 16 equal areas and a reading taken at the center of each. In obtaining the average of the 16 readings of velocity pressure, the veloci- ties can be calculated for each reading and the average then determined ; or the average velocit}' pressure can be calculated by squaring the mean of the square roots of the 16 readings. The pitot tube shown in Fig. 131 is double. The small inside tube is open onl}^ at the end, which must point directly and truly into the air stream. The pressure indicated on a U tube with one leg connected to this inner tube and the other leg open to the atmosphere, is the static pressure in the pipe plus the velocity pressure. The larger outside tube is plugged at the end and has four 0.02 in. holes drilled perpendicularh' through the sides. The pressure indicated on a U tube with one leg connected to this outer tube and the other leg open to the atmosphere is the static pressure in the pipe only, since because of the small perpendicular holes, the pressure is entirely independent of the air velocity. The difference between these readings is the velocity pressure. If, instead of connecting U gages as just described, the .AI E C H A X I C A L D R A F T 233r 4 Holes in Outer .'Tube only 0.02" Dia. \\\\\\\\\\\\\\\V.\\'\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\V\V' vyyy///y'yyy/^/yyyyyy^yyyyy/y>//y///yy^y///yy^y/yyyy/'yyyy/yy/yyy/^^^ wvwwvwwwvwvv x's^:^?^^ s^\V\\\V^VVV V\VVs\V\^\\W Fig. 131, -Not Less Than 2'^ ^-^/je"-^- 2^/6"- A Double Pitot Tube for Measuring the Volume of Air in a Duct. inner tube of the double pitot tube is connected to one leg of the U gage, and the outer tube to the other leg, the reading of the U gage will now be the velocity pressure, since the static pressure is applied to both legs of the U gage and is thus canceled. The velocity can be calculated from the velocity pressure by the follow- ing formula : C13) V= 1096 P \ zc V = velocity, feet per minute. p =z velocity pressure, inches of water. zv = density of air in pipe, pounds per cubic foot. At 65 deg. and standard barometric conditions, the density of air is 0.075 lb. per cubic foot. The above formula is readily derived from J'l=2gh (14) / 1= velocity, feet per second, o- 1= 32.2 =1 acceleration due to gravit}^ /i =: head, feet of air (equivalent to }> in inches of water). O u - O >.« >> ^^ S ci, c b CO -j; 3 ^ u u o •^ u CO u ^ C CO oco "—I u . c o o «^ CO a MECHANICAL DRAFT 235 The horsepower represented by the air leaving the fan, usually called air horsepower, is the fan output and can be calculated from //.P. = 0.000,158 Qp (15) Q 1= volume, cubic feet per minute. p := pressure, inches of water. If this fan output is used to determine the mechanical efficiency of the fan, p should be the total or impact pressure ; that is, the sum of the static and velocity pressures, which sum is given by the reading at the small open end tube. If the static efficiency is to be found, the fan is not credited with the energy due to the velocity of discharge, and p should be the static pressure, or the reading given by the large outside tube. The quantity of air handled per minute by forced draft fans is frequently a large percentage of the cubical contents of the room in which the fans are placed, so that not infrequently the static pressure in the room is 0.2 in. below atmosphere. This condition will automatically be taken care of by the readings of the U tubes themselves, provided they are always placed in the same room from which the fans are exhausting their air. Ducts and Dampers. The shape and arrangement of ducts and the plac- ing of dampers has an important effect upon the pressure of the fan as car- ried through to the stoker windbox. Bends should have an inner radius of from 1 J/2 to 3 diameters. Y's should be used in preference to T's, and if T's are necessary the "Poor Type" of Fig. 132 should be avoided, if possible, or the sharp corners changed to be like the dotted lines. The one marked "Good Type" v/ith rounded corners and deflecting plates is preferred ; and if the ducts are of rectangular cross-section, the deflecting plates are easily applied. t t t t / PoorTyp« Good Type Fig. 132. Good and Poor Forms of Tees. Dampers. When two or more fans blow into a common duct, outlet dampers for each fan must be provided; these can be closed when any fan is not in operation. These dampers frequently cause large reductions in fan pressure. An ordinary butterfly damper should have a small indi- cator placed parallel to the damper and fastened to the damper shaft outside the duct, whenever the damper handle itself will not serve as an indicator. When the handle can be placed in a position other than parallel to the damper itself no one can be sure when the damper is open. The butterfly damper should be placed as far from the fan as is convenient. Its shaft should lie in a plane perpendicular to the fan shaft; that is, the damper shaft should always be vertical rather than horizontal. Louver dampers are frequently placed in or close to the fan outlet. The shafts of these should also be provided with an indicating mechanism. They should be vertical, particularly with the small housing types of fans. The air in the fan outlet is in a highly turbulent condition due to the 236 M E C H A X T C A L D R A F T action of the wheel and does not come from the outlet in parallel lines and with even velocit}* distribution. When louver dampers are used in the fan outlet with horizontal shafts arranged parallel to the fan shaft, the pressure readings taken beyond the damper will invariably show that the best position of the damper is parth- closed and not wide open. If the shafts are vertical, the damper in its wide open position will always offer the least restriction, and the resistance will be less than in any position with the horizontal shafts. Screens for forced draft fan inlets should always be provided. Serious accidents have occurred in instances where the arms and legs of attendants have been drawn into contact with the impeller. These screens sometimes present a serious obstruction; but they need not be heavier than 5^-in. wire. nor closer than 2-in. mesh. There have been occasions when inlet screens made of ordinar>- expanded metal have offered a resistance sufficient to cause a 1-in. drop in pressure in the fan inlet. Air Leakage in Ducts. All ducts carr5-ing air under pressure must be tight. The leakage that can occur in ordinarj" ducts is seldom appre- ciated because the air cannot be seen. Air will leak through joints much more easily than water will. The pressure on a forced draft duct may be 6-in. of water, representing a head of air of 416 feet. In carrying water at a head of this magnitude the utmost precautions would be taken to keep the ducts tight, but with air the importance of this point is apt to be over- looked. The leakage loss in the average installation is always nearer 20 per cent than 10 per cent. Even concrete ducts do not prevent the leakage. In some large concrete ducts it is so great that pressure cannot be created in them. The inner surfaces of all air ducts, whether concrete or metal, should be liberally coated with a good paint. The larger duas of the sys- tem will have the most leakage, and should be painted while under pressure. Induced Draft TO decide upon satisfactory induced draft installation necessitates a great deal of experience and common sense. It is simple enough to figure the weight of the gases from the amount of air supplied to burn the fuel, and if the temperature is known, to figure the volume of those gases. The tem- perature, however, and consequently the volume, cannot be predetermined accurateh'. The inriltration through boiler settings, flue connections and economizer is an uncertain quantity'; it does not remain constant, but in time increases : the fan, however, must always be capable of overcoming an}' pressure set up in the fire-box. The infiltering air is cold and not only adds to the weight of the gases but reduces their temperature. An induced draft fan should be selected therefore with plentv* of reserve capacitN'. The driver for the fan should also be large, with at least 20 per cent excess power. Table 17 ma}' be used as an example of induced draft fan sizes : but the dim.ensions differ considerably with different manufacturers. The chief troubles with induced draft fans are mechanical ; high speed fans, particularly, becoming unbalanced. The cinders passing through the fan cause a certain amount of erosion. The scroll sheet or round- about of the fan housing suffers most, and the inlet edges of the fan blades sometimes show signs of wear. In all induced draft fans the scroll sheet should be at least Vie-iru thick. When oil leakage occurs, dust and cinders are deposited on the blades. They pack down tight and form with the oil a heavj' hard cake. The leakage oil runs along the shaft through the shaft opening in the housing, and from there is carried into the fan wheel, covering the blades. M ECU A X T C A T. D R A F T 237 Table 1 7. Sizes and Weights of Induced Draft Fans. INCHES Boiler Output, Fan Outlet Area, Weight Complete, H. P Sq. Ft. Lb. A B c 100 1.6 52 48 50 1,000 200 3.2 70 64 65 2,000 400 6.4 95 87 82 3,700 600 9.6 120 110 109 5,500 800 13.00 140 128 120 7,000 1,000 15.00 156 143 138 9,000 2,000 32.00 220 202 146 17,000 3.000 48.00 270 248 170 25,000 Most induced draft installations are of single inlet fans with overhung wheels. The two bearings are then outside of the flow of hot gases. This wheel is satisfactory, provided the shaft is large enough. The heat of the gases handled by the fan is conducted along the shaft to the bearings, and these bearings must be water-cooled. A short cast iron pedestal set in concrete is a satisfactory support. The concrete can often be brought up almost to the bearing bases ; the bearings are then mounted on I-beams securely embedded in the concrete. Built-up structural steel pedes- tals should be used only for very slow speeds and low powers. In the larger cities the nuisance caused by the discharge of solid matter from the stacks of power houses must be overcome. The under- feed stoker has to some degree eliminated the discharge of black clouds of smoke. But owing to the high draft pressures used at large boiler loads, the discharge of heavy cinders has been aggravated. In one type of draft fan, the dust and soot are separated from the gases, and are delivered into dust chambers, from which they fall by gravity into collecting hoppers. The cinder-separating induced draft fan has an efficienc}'- of dust removal of 75 per cent. It is substantially a paddle wheel fan of good propor- tions and takes about 10 per cent more power than the plain fan. The allowable speed on induced draft fans is considerably less than that on forced draft fans, even when the construction is identical. The temperatures of the gases handled by the induced draft fan range from Fifth Avenue Building, New York City, operating 1400 H. P. of Heine Standard Boilers. MECHANICAL DRAFT 239 300 to 750 deg. At lower boiler ratings with the gases passing through the economizer, temperatures may be as low as 300 deg. The flues are usually arranged so that the gases can be by-passed and do not pass through the economizer. With high boiler ratings and the economizer by-passed, temperatures will sometimes be as high as 750 deg. A high fan speed is then required, as the draft loss at these high ratings, even without the economizer, is considerable. In addition, owing to the high temperature, the fan must handle a large volume of gases. Somewhere between 500 and 700 deg., the elastic limit of iron and mild steel is only 50 per cent of the elastic limit at ordinary temperatures, say of 70 deg. The designers of rotating machinery have found that it is not safe to stress material above one-third the elastic limit. These con- siderations are borne out specifically by the behaviour of induced draft fans. The desire for high-speed direct-connected units resulted in many installa- tions of the backwardly curved blade fan for induced draft. This practice has been almost entirely discontinued, as the fans were installed for speeds 40,000 ^30,000 I Range of \ \ Induced Draft Jemperal-ures ] 20,000 "S 10,000 UJ 300 400 500 600 Temperature , Degrees. Fig. 133. Variation of Yield Point with Temperature. that produce stresses of_ 10,000 lb. per sq. in., and they failed when the elastic limit of the materials was reduced because of the high temperatures. Fig. 133 shows how the elastic limit, or more properly the yield point, varies with the temperature. The peripheral speed of induced draft fans should be limited to 11,000 ft. per min. It is true that most of the time when the gases are passing through the economizer a fan so limited w^ill be unnecessarily strong. But even though the high temperatures and large volumes occur only seldom the fan must always handle the necessary load. Load on Induced and Forced Draft Fans. The induced draft fan must take care of all the resistances, from the fire-box through the boiler and economizer. The resistance cannot be overcome by the forced draft fan, because positive pressures would be produced, blowing the gases of com- bustion out through the leaks. The forced draft fan has the advantage of working with gas of greater density, and should supply the pressure nec- essary to overcome the resistances as far as the top of the fuel bed. Suppose the density of the gases handled by the induced draft fan is half that of the air handled by the forced draft fan, a not unusual condi- tion ; then to overcome a given resistance the induced draft fan will require twice the power. Consider an installation in which 4 in. of water is required for the forced draft and a static suction of 2 in. of water is required 240 M ]•: C 1 1 A X I C A L J; R A F T at the stack end of the ccoiioinizer. The difference between these two pressures (one ]>ositivc and the other negative) is 6 in. of water. Tf the forced draft fan snjjplied the wliole i)ressurc drop of 6 in. the horsepower required would he ().0(J()158 X VoUunc X 6 Fan Efficiency If, however, tlie wliole pressure drop was taken care of by the induced draft fan the volume handled would be twice as great and with the same fan efficiency the hf)rsepc;vver will be 0.000158 X (2 X Forced Draft Volume) X 6 Fan Efficiency =r 2 X Forced Draft Horsepower. The fundamental formula for the work done by a fan shows this differ- ence more clearly. The work done by a fan can be expressed by J = iuXQXli (10) where / is the work, zv the density, Q the volume, and It the head in feet (jf gas of density w. For both forced and induced draft fans the ])r(Kluct (7c; X Q), which equals the weight of gases, is the same, ignoring very slight change in si)ccil"ic gravity due to the different chemical composition of the two gases. Ikit h for the forced draft is only half the h required to produce the same difference in the water colunni when the work is don2 by the in- duced draft fan. The 6-in. water pressure represents 415 ft. of the cold air and 830 ft. of the hot air. In view of this peculiarity the induced draft fan should do only that work which on account of the nature of the service cannot be done by the forced draft fan. Testing of Induced Draft I-aiis. The greatest difficulty in testing these fans as installed is to locate a straight run of pipe where a steady, imiform and straight gas flow can be obtained. The i)itot tube, Fig. 131, gives some indication of the fan i)erformance. The volume of gasjs is sometimes determined from the weight of coal burned and the CO^ readings. Theo- retically the results should be fairly accurate, but practically they are uncer- tain, owing partly to the fact that ai small difference in the percentage of COj corresponds to a great difference in volume of the air. The densities of tlic hot gases of combustion and of the cold infdtering air differ greatly, so that the mixture stratifies, and it is extremely difficult to secure a fair sami)lc. The leakage is through the walls of the passages; consequently the air almost entirely surrounds the moving mass of gas and the percentage of COa will be greatest near the center. Even after passing through the fail this stratification is still evident. The most satisfactory method of testing an induced draft fan is to divide the fan inlet duct into say 16 equal areas and take a reading of velocity with the pitot tube at the center of each of these areas. Knowing the tcm])eraturc and consequently the gas density, the volume of the gases can be calculated from these readings. The formulas for the testing of forced draft fans are applicaljJe. Tlie velocity sliould be measured on the inlet, ratlier than the outlet side. The llow to the inlet is almost invariably accom])anied by an increase in velocity, and is a maximmn at the fan inlet. The movement of the gases tends then to become steady and uniform, and the velocity can be measured accurately in a short run of straight Hue. On the outlet side the fan wheel causes local eddies in the air, so that any velocity determination is extremely difficult. The test must be made with the pitot tube or its close equivalent. Tn the smaller plants the induced draft fan may furnish all the neces- sary draft, the stack being only a short connection to discharge the hot gases above tlie r(M)f. This is good practice from the standpoint of cost but a plant of any si/c may create a nuisance, as the discharged soot and cinders settle thickly on nearby structures. Most of the larger plants use fair sized M I', (■ II A X I C.\ I ) K A I' 'V 241 stacks and when operating at low rating hy-i)ass iho indnccd drafl l;iii. Two dampers arc then rccpiircd ; one on the fan inlet and llie other in llie by-pa.ss ; the second damper separates the suction and discharge ol llic fan. Tlic fan damper shonhl be on the inlet rather than on the onllet side, because the dead pockets formed by a fan with an outlet damper shotdd he avoided in induced draft (lues. VVhen Ihe fan is by-passed and tlie outlet damper closed, there is no movement of gas in the whole fan housing. Such an arrangement has been known to result in an explosion. The damper in the by-j)ass shoidd be as tight as possible. The pressure difference between fan outlet and iidet is equal to the full static pressure developed Fig. 1.54. Ideal Connection ol Fan to Stack. by the fan and any leakage space around the by-pass damper will permit a recircidation of gas, which will reduce the capacity of the fan for liandliMg fresh products of conibuslion from the boiler. In laying out the connection from the fan ontlet to llie stack port all bends (sharp ones especially) should be avoided. The static pressure in this connecting duct is ])elow atmosphere only by the amount of suction produced by the stack. When air Hows around bends the pressure is greater on the outside of the cnrve. If a pressure around a bend becomes greater than tiie stack suction, some of the products of combustion leak into the I)oiIer roon). Iwcn a very small anionnt of this leakage is objec- tionable, as it makes the boiler honse unpleasant to woik in. JM'g. 134 shows an ideal connection between fan and stack. 243 CHAPTER 8 PIPING AND ACCESSORIES THE same care given to the design and installation of boilers and engines should be given to the piping system. The object of any system of boiler room piping is to conduct a fluid safely from one point to another. This must be done with economy, but no commercial consideration should be allowed to interfere with the fundamental requirement of safety. More accidents originate in defective piping than in defective boilers. The failure of pipe, fittings and valves is due not as a rule to excessive fluid pressure, but to the presence of water in steam lines, excessive and continued vibra- tion, changes of temperature, and faulty methods of support. Wafer in steam lines is a source of danger, and every precaution should be taken to avoid its presence. The chief danger from water in steam lines is water-hammer, which generally results from admitting high pressure steam into a cold pipe con- taining condensed water. In pipes nearly horizontal, Stromeyer has shown that under these conditions a slug of water may attain sufficient velocity to burst massive fittings. He cites an instance where a large boiler stop valve disk was turned inside out and driven into the boiler against the steam pressure. Piping systems should be designed either to avoid the possibility of water accumulating on top of closed valves or to provide ample and accessible drainage facilities. This requirement is of especial importance in connecting boilers into a main steam line. Where pipes are connected to safety valves to enable them to discharge above the roof, the connection to the safety valve casing should be by means of a Tee. A pipe — at least V/i in. — should be taken from a blank flange on the lower leg of the Tee to insure permanent drainage ; and this pipe should be without a valve or other obstruction, but should discharge into the atmosphere or blow-off tank. Piping should be erected so that water-collecting traps or pockets will not be formed. Large drain pipes should be provided wherever pockets cannot be avoided. Drains should be placed at the bases of risers and wher- ever water can accumulate because of the closing of a stop valve. If drain valves are not likely to be attended properly, drains should be trapped, so that the water will be removed automatically. Steam supply branches should be connected to the upper side of mains. Drains should be connected to the low- est point of reducing flanges, reducing tees, and taper reducers. Steam lines should be installed with a uniform grade of about 1 in. to 40 ft., so that they will drain to some predetermined point. Drainage is more complete if the water and steam flow in the same direction. Vibration In piping is a source of trouble and danger to the pipe itself, and to joints, valves, fittings, supports and anchors. It is often set up by water slugs delivered by ill-designed or carelessly operated boilers, or from accumulations of condensed water, Alodern power plant practice favors high steam velocities, which tend to diminish condensation. But slugs of water are then driven along at higher velocities, and as their kinetic energ\' increases as the square of their velocity, the vibration trouble is aggravated. Consequently, drainage facilities cannot be neglected because of high velocity alone. As a matter of fact, condensate is more apt to be carried past drip- pockets and separators by high, than by low velocity. Vibration is also caused by the intermittent flow of steam to reciprocating engines, unless separators or receivers are installed in the steam lines close to the engmes. 244 PIPING Expansion and Contraction. Pipes are bound to expand when heated by the entermg steam and hot water and to contract as the temperature falls with the shutting off of the steam or water. The increase in the circum- ference of a pipe because of an increase in its temperature is of little practical consequence. The lengthwise (linear) expansion of a pipe is great, how- ever, for pipes used in power plant practice. The force exerted by expand- ing and contracting pipe is practically irresistible. Therefore, piping moist be anchored, and then the direction in which it will expand and contract can be predetermined and the expansion and contraction absorbed, so that it will not damage the pipe itself, the fittings forming a part of the line, or the appara- tus to which the pipe is connected. Selection of System. The selection of the piping system should be based upon the factors of uninterrupted service, low cost of operation, and low cost of installation. The piping system, boiler and prime movers should be selected at the same time, and to form a single unit. If uninterrupted plant operation is of value, piping must be so designed that its failure in part will not shut down the whole plant. The point to which it is justifiable to carry refinements insuring continuous plant operation depends upon the commercial value of uninterrupted service. The layout of essential power plant piping should be consistent. If steam mains are well protected, feed mains, exhaust mains, oil lines, and other essential portions of the piping equipment should be protected in the same way. Heater, economizer or condenser connections need not be thus refined, because operation without them is possible, although it may be decidedly undesirable. This is especially true of plants containing more than one of each economic auxiliary. These should be connected so that they can be operated temporarily at an overload with reduced economy, should one unit or its connections fail. The feed-water temperature may be 150 deg. when two heaters are used instead of three, but even that is preferable to cold water. Overloaded condensers may mean a vacuum much less than normal, but this is preferable to exhausting to atmosphere. Ji '-Exhausf Marin • , Engim Engine --Condenser "T r Boilers Heater-' F ^■"- Sieam Main ^^Eeed Main Fig. 13 5. Diagram of End to End Single Header System. The single header system. Figs. 135 and 136, is simple and the first cost is low. For the end-to-end arrangement of boiler room and engine room. Fig. 135, this system is not reliable, as a break in one of the mains shuts down the entire plant. For the back-to-back arrangement of boiler room and engine room, Fig. 136, the feed-water header and exhaust header are still undesirable, although the steam header can be divided by valves and part of the plant operated if some one section fails. PIPING 245 Fig. 136. Diagram of Back to Back Single Header System. With the duplicate header system, Figs. 137 and 138, the plant is much more reliable, but the first cost of the system is high, and each piece of apparatus must be connected to two independent headers. Unless both headers are in continuous operation, or are located at a considerable distance from the apparatus, joints and connections are subjected to severe strains due to expansion and contraction. ■^ -rExhausf Main T Englnz Engim 3^ i^-'Condznser fnginz ■ — ■ y ^ S Heoit'er y Feed Pumps Boilzrs m. TT Feed Main^' ^^^ Ei £ :ii:| ^"'"-Sizaim Main Fig. 137. Diagram of Duplicate Header System. :r o vo (U CO >> G a 5 CO O i- u CO CO ^W (U -S -^^ o U *s ID (4 u «{ bO 'cO Ui (U T) (U (I4 PIPING 247 Ua- m & >feec^ Pumps Boilzrs iSfLd ^-fizatzr H Ed H Mains Engine ti: E£:f Engine \5feam Mains Enginz r'Conofenser ■r ^-Exhausf Mains Fig. 138. Diagram of Duplicate Header System. The ]oop or ring header system, Figs. 139 and 140, is more reliable than the single header system, but its first cost is high. It has advantages when the physical limitations of property or buildings prevent the installation of a unit system. ";^Exiiausf Loop -^ r^— I ri Engim T r Engine T- r Engine ^-Condenser Heater- ^Feeol Pumps Boilers ^^Z -i^ ~ i ^y-- steam Loop Feed Water Loop-^- Fig. 139. Diagram of Loop Header System. The unit system, Fig. 141, represents ihe l)est standard practice for large plants, but it can well be used in plants of moderate size. The complete plant is virtually composed of small independent units, any one of which can be shut down without affecting the others. The first cost of this sys- tem is high, but is more than justified when uninterrupted service must be had. The high first cost is due not alone to the piping system but also to the fact that each engine or turbine has its own separate boilers, condensers, feed pumps, circulating pumps, vacuum pumps, and feed-water heaters. Separate coal-and-ash handling equipment is also supplied for large units. 248 frf PIPING ._. rzsoi F'jrrps Boilers V 7l Heater^ is ^ ii jI Lj. i L-i 'zzy i',^~z' oreotm uoop^' h-l pi-| hI i^ i4 .^ Englm r]^ ^-f.'-rj-^r _::jc-x Condenser- -■** Fig. 140. Diagram of Loop Header System. Engine Condenser^ R r 4- t"4 I l-J Enginz I Engine bl 4i ,>>5r?:».?7 /" ."22:7 ',;'yrz: •R^ ^ _ .-reoTTsr ZWafer ;.- ^^ ^ "5 "H 3 c: -l- 4- U •^^ ^ ,^,-223 .-.yz' 1 Sir? -iJ Condenser ^ H ^ -ec/rer I "H ■^ Fig. 141. Diagram of Unit System. PIPING 249 In a modified unit system, Fig. 142, the complete plant is divided into distinct sections, each entirely independent of the others and operated as a complete plant. This system is not so reliable as the unit system because sections of the same mains must be used ; fewer auxiliaries however are required. It is not desirable for plants which operate at a high load factor, but is adapted to those whose daily light load period is long enough so that the mains can be repaired. The number of the sections into which the plant is divided depends upon the load characteristic. If a plant requires two- thirds of its capacity for its lightest load, three sections would be necessary. A plant operated at half load for the greater part of each day could be divided into two sections. Condenser ^^^ ~/iecif(zr Boilers Cono/enser—' Fig. 142. Diagram of Divided or Sectional System. The modified unit system, Fig. 142, actually requires but two auxiliaries of each kind ; each set of auxiliaries hov*^ever should be able to handle the light load for the entire plant. If the capacity of each set is sufficient_ for full load, even though it is overloaded, the danger of shutdown due to failure of mains or connections is greatly reduced. A complete set of auxiliaries for each section of the plant adds materially to its flexibility, economy, and reliability. In deciding upon the number of sections, the size and accessi- bility of the mains and the time required for their repairs should be con- sidered. Piping should always be accessible, for safety and economy. The ac- cessibility possible for any given set of physical conditions should be a factor in the selection of a piping system, because it affects the time required for repairs and therefore the reliability of plant operation. 2S0 A part of the 8550 H. P. installation of Heine Standard Boilers and Heine Superheaters in the New York Central Railroad Terminal, New York City. This company operates 18,000 H. P. of Heine Boilers. PIPING 251 The durability of boiler room piping has an important effect on the continuity of service. Irrespective of its first cost, the best pipe and pipe- fitting material, will be the cheapest in the long run, for any but the most temporary installations. A diagramatic layout of boiler room and engine room piping should be made for every plant, and a copy of this diagram posted in a conspicuous and accessible place in both boiler and engine room. The diagram should be large enough so that all the lines and captions can be quickly distin- guished. All valves should be numbered and the diagram accompanied by a tabulation of the lines or equipment controlled by each valve. The diagram can well be made as a tracing. Any requisite number of copies can then be made, and it can be easily corrected and kept up to date in the event of changes in, or additions to, the piping system. Identification of Piping A STANDARDIZED color scheme is a practical aid to the identification of -^*- piping. The report of the A. S. M. E. Committee on Identification of Power House Piping, suggests that color shall be used on flanges, valves and fittings only, the piping itself being painted to conform to the color scheme of the room. The colors recommended are as follows : Division Color Steam — High pressure White Exhaust system Buff Water — Fresh water, low pressure Blue Fresh water, high pressure in boiler feed lines Blue and White Salt water Green Oil, delivery and discharge Brass or Bronze Yellow Pneumatic Gray Gas — City lighting service Aluminum Gas engine service - Black, red flanges Fuel Oil Black Refrigerating — Pipe Gray Flanges and fittings White and Green Stripes Pipe and Piping Materials "Practically all boiler room piping is made of either mild steel or -*- wrought iron. Because of its lower price, steel pipe is more common than wrought iron, and for most purposes fulfills all requirements. Wrought Iron pipe is more durable than steel pipe, especially when buried under ground or subjected to extreme exposure. It is said not to corrode as easily as steel and therefore is to be preferred for blow-off pipes, drips and drains, and wherever corrosion may be severe. The term "wrought iron pipe" is often used loosely, for both steel and wrought iron pipe. In the trade steel pipe is furnished, unless genuine wrought iron pipe is specified. Cast iron pipe is used for low pressure work. Because of its low tensile strength and consequent great weight, it is seldom used for high pressure pipe. Cast iron is used however in the construction of headers, although it is not recommended for high temperatures. For complicated headers with a number of branch lines, a casting is cheaper than fittings, and the number of joints is considerably less. 252 P T P T X G Cast steel is used for headers, especially for highly superheated steam, and resists high temperatures much better than cast iron. The cost of cast steel is high, and it is difficult to secure uniform castings, free from hidden defects. Brass withstands the corrosive action of hot water better than iron or steel, and is sometimes used for feed-water lines and headers. Its high cost limits its use even for this service and practicalh^ prohibits its use in other parts of a piping system. It is weak and brittle at high temperatures. Copper is expensive, deteriorates rapidly under high temperatures, and weakens under recurrent stress variations. It was formerly popular in marine service because of its flexibility, although this is offset by its low tensile strength. The use of high pressures and high degrees of superheat is increasing, so that the total temperature of water and steam must be considered in se- lecting materials. Table 18 gives the average tensile strength of metals at different temperatures, as determined by the Crane Company. The table ypplies to the initial effect of high temperatures, but does not indicate the effect of continued high temperature, as the time each specimen was heated had to be limited. The results show however that cast iron undergoes a slow but constant loss of strength when subjected to temperatures over 400 deg., and that steel does not undergo any material decrease, other than its initial loss of strength, because of continued temperatures as high as 800 degrees. Table 18. Effect of Temperature on the Tensile Strength of Metals. Material AVERAGE TENSILE STRENGTH, LB. PER SQ. IN. AT TEMPERATURE NOTED 70 300 450 600 750 900 950 1000 1030 Steam metal 31,780 35,345 34,170 26,370 34,260 36,025 21,900 27,630 33,050 12,180 16,100 21,380 10,280 13,000 19,640 9,530 6,630 9,650 Special brass Navy "G" bronze. 6,400 Hard metal Cast Monel metal. 33,735 52,870 22.060 34,280 23,260 31,180 47,200 20,730 23,150 39,450 21.240 19,170 41,787 21.925 10,825 5,710 26,400 Soft cast iron . . . 19,820 Ferro steel Malleable iron Cast steel 32,692 37,625 73,325 33,290 33,505 76,570 33,400 33,280 81,167 33,110 34,000 67,366 32,860 34,055 41,388 25,780 ' 27,ii6 27,310 ■ 17,568 Commercial wrought iron and steel pipe is divided into four weight classifications; standard, extra heavy, double extra heavy and large O.D. A fifth classification, lighter than standard pipe and known as "merchants pipe," was formerly made but its use has generalh" been discontinued. Standard, extra heavy and double extra heavy commercial iron pipe is designated by its nominal internal diameter, in sizes from Jg to 12 inches. The external diameter of extra heavy and double extra heavy pipe is the same as that of standard pipe, and the internal diameter therefore is smaller. Above the 12-in. size, pipe is usually classed as "large O.D." and is desig- nated by its actual outside diameter, although some manufacturers list sizes with nominal internal diameters of 13, 14 and 15 inches. Commercial wrought iron and steel pipe is butt-welded in sizes 1^ in. or less for wrought iron, and 3 in. or smaller for steel. The larger sizes are lap-welded. The principal dimensions and the weight of standard wrought iron and steel pipe are given in Table 19. The same data for extra heavy and double extra heavy pipe are given in Table 20 and 21, respectively. PIPING 253 (L) ft CO m m A ^ cc a c CO ft a o U T) CO H n ,»^ m 6 S 4-1 CO 2 Water in. One Ln. Ft. of Pipe lO lO 05 (M>-iin CO CO t- i-H (N CO OOCO Ift i^OO lO «D 00 -^ CO in CO C-O 00 OC mOrH t-ooco 00 I-H CO CO(NC0 O-i^CD 00 00 OS OS rH rH t-05m CD(Nt- t-ot- 00(NO5 CO OOO rH I-H m CD 00 rHC- miN ^o' ■ tH (Ncotj* lOCDOO IN CO IN rHrHIN rH t- m (NINCO ■^ Tf rH CO CO -^ 05 CS OS T* -^m OS 05 05 cot- 00 o m OIN I-H rH U.S.Gals. in One Lin. Ft. of Pipe CO lOO •OO'-i rtOOO (X) 00 iC ooo OOCD -^ t- o t~ Oi-i 1-1 05^^ Tl<00 1-1 (N CO in rHOOOS CDINCO CD ooo rHINOO o rH m mocD (35 IN 00 O5CDC0 m(NiN IN cot- OS (OS CO rH005 '*meo CDt-CD OS OOrH m 05 CD 00 00 IN (N'*t- m(N '*rH OO Oo ■ ■ "rH rHININ (NC0t1< '*'*'* mmt- 00 050 (Mm 1— 1 I-H Length to Contain One Cu. Ft. . t-t-co CD -^ 00 OC0.-H 050CD mco CO t- CO I-l IN t>05 c-05in t> t~cO o -^ in cgOGO rHCOOS COOrH -.^t-m 00 rH I-H 05000 00 -^ m t-05CD OOlNt- m CD m OOIN rH t-00 m •^ CO '* m t- ■* (NINO cooot- 000 05 OSt-CD <-l 00 (NOS CD 't &j coco -^ "co x)io (N 1-1 COOCD t- t> ;d «DO(N 05 1:-^* OC5T)< CO 1-H rH 1-1 05t- rH -*COIN IN IN rH rH rH rH i-lj-ii-t o 1 1 0) P-i o o . h- 1 0) o H-l 3 O5C0 t- ,-1 LOl-l ,:j -^ t-cooo t- in CD in (NO 00 t- CD T}< -"^ in 05 00 OS CO CO (N-<*t- cD m ^ OOt-TT t-INt- Tf T* CO CD rH t- C- 00 -rj* CO CO CO moo 00 rH rH 00 CO CO IN ooo m CD m CO IN(N(N IN OS (NOS IN y-H 5£) -^CO COIN 1-1 rH 1-1 rH o 01 i-ieO 00 •COt-lrt ^coo lOCD 05 1-lOM Oi-iO coocn OOrHTt (N OS in ecocn 00 coco ^CDOO oot-co CDOIN OO'* m m-5j< IN com 'cftosm Tf CO CO mm m mmiN CO CO CO 0S05(N 05 05t- (N(MIN ^00 '* mco(N (N(N(N INO rH05 (NrH 0>t-U5 ■^COIN (NINr-l 1-H rHO 0) 1.1 < M b< > c oco'^ in CO 05 (MCOt)< OS 05 in «3 05C- tot-o ^OOO O(M00 IXMCD ^ ooo c-ooo rH CD CO rH CD m 00 IN CD mo5(N 05^*00 OS t- t- COOSrH (NOOrH t-oo O OS -^ CD OS IN t-t-m oomo OOOrf COOO iN'*m COCO ot- CDrH Co t/2 rH rHININ CO CO "^ mcot- 00 05 05 OrHCO rH rH rH IN-* CO r-ir-tr-i t-ooo rHrHIN (Nm IN IN t- -^ tH ^lOOOi ^Oi-Ht-h ■<:f CO ''^f OCO'^D coiooo in«5 in Oicoin ^ooo 00 CO CD 00 OS 00 c-cooo Ot~CD CO -^ o C-050 rH 00 rH 05C0 CD OOOrH t- com IN 00 00 oc-m osmco CO ooo O t-CD 005 00 OOOOO m '* CO oomt- '*CO'* CD CO COOO 00 05 I-H (N CO "* t- 05 iNino rHrHIN 00 00 rH IN CO m 0(NrH mcDoo ooom 00t-O5 '*C0 t- rH rH CO rH 1-H rH 05 (N CO mooo rHrHIN rHOO COOO (N(N (D-j X C 05 05 00 ^i-HINCO ttCO 00 in com loooco ■^ ino to CO CO I-H 00 Tj" (NrHCD 05INCD ^ CO in TjH inco ocoo 05CDC0 IN'* CO t-CO(N ■* CD •* cooco (NCOCO ^t-t- CO CO "^ CO CD CO t- 1--<* CO COOO t- t-co COCO t-05rH rH iN^in 05(Nm rH IN (N moo IN IN IN CO rH rH T* CO CO CO C~-t- rH CO CO "^ ^t-o -* '* m COO mcD (M^i-I t-05N 05 05>-l CO O5C0 in 05 T-H i-h;0 t£> (N05-<^ IN CD CD CO OS CD o OS in t-oot~ cooc- rH t- ^ CO m CD rH m OS 00 05O CO00(N O5C0t- OIN t- INlNTt" t- t- rH t-t-OS m m IN m m 00 0005 -* m c- (NCOO rH IN '* (3s IN rJ- M O lO ICOO in CO 00 00 i-l<£> i-H I-H 00 00 CO t- INt-O 05C0 00.-l«> IN t~IN C^ rH in IN t-«5 CO in 05 05t-0 t- in rH ooot- O5C0rH t> incD 1* '* CD t- -^ OS 05 m CO -<* t- rH moo mo5(N ocot- T* oom (N^m CO IN 00 t-co CO t- m m co OS Tji t-t-o m m t- ot- Tjtt- oom ,-?o r-t I-H (NINCO int-05 0(NTf rH rH rH OOCO'* rH(NIN 00 CO rH (N CO CO Ti* in i-HrH rH CO CD CD OrHIN (NININ t- t>00 CO '* in (N(N(N O rH t- OOOt- (NCO(N (NCg05 (N^t- COCOIN t- m m OCDt- CO CO CO omm cot-t- CO CO CO m mco t-t-C5 CO CO CO OS OS OO '* ■* o 6 ca 05 -i^J^ CO ooo oo t- OOi-HO co;do OS 00 00 CD CO Tf ■ 05C0 inoo t>oo ooino ooco OOCD mom mm m (N(N(N CO CD CO mm o (N(Nm CD CD t- OOO m m m c-t- t- ooo mmo t-t-o OOO ooo OOO OO OO OO ►-HO iH r-* rHrHIN (NCO-^ Tj mm CDt-00 00 050 I-H OOrH r-< T-< r-< ININ^ I-H rH rH mcDt- rH rH I-H ooo rH(N :^:^;^ I-H rH (N (NCOCO Tj< -rt" m CO t-00 00 050 OOrH 1-1 rl r-l (NINCO Q d T^m t- QQ do ooo rH(M Penn Mutual Life Insurance Building, Philadelphia, Pa., equipped with Heine Standard Boilers. PIPING 255 a; a >> > V CO ^ ■^ a\ W . O G . . rt a a o c d CO j_, Si CO o csi 43 CO H be -J o. o J= 3 h4S. 0) C/1 w S S c =" aiJS 04 a a>M ^ CO -C C Eh OO O On On On 00 fe SO O '^ On O O ro CN ■<— I O 00 O NO -rfi ro • t^ NO O 'l>- CS Ov •<— I PO 00 rO !>• lO ;^ O NO ON t^ lO . ro t— t^ COn lO T-H = 0-^ 0*0 C/3 On On 00 CO 72 lO On ON t^ -^ fN .NO ON ro CN NO ■«-i r^ ON CN jjCN NO '-H ■^ lO 00 . T-H ro fO J . . . o «0 On NO • On '-H (M C o '-^ '— I lO r^l ro T-H o rsi lO O ID O rtH^ Th LO vO >-i\i-i\«i t^ NO CO ^— I ^— I On O O T-^ lO CO O ^ CO O NO CO CN lO !>• '— I On rfi On On ■'-H On t^ t^ -rti ■^ CO O LO NO On '^ CO CN O CO 0\ CN CO CO CO T^l NO ^ CO On CO CO tH tJ< NO 00 lO NO LO lO 00 CO to '-H t^ •^ CO O t^ CO o On ON •>— I CO On CO NO r^l T-H r- 00 NO !>. 00 o -^ CO t^ CO 00 NO lO CN t^ ON •^ to o NO CO CO T-H CO •^ CN CN -^ lO CN CN T-H T-H On T* t:^ NO to On T-H T-H vO NO r<**-- to Ttl T-H CO NO CO T-H 00 T-H ^ CN On lO CO O On T-H T-H O ■^ NO 00 to T-H r^ CN O NO 00 to 00 CO O 00 C^^ NO 00 "* NO 00 CN T-H NO On CN NO ^ NO to NO On rs 00 T-H 00 On T-H NO CN T-H to t^ On O On O CN T-H CN to NO lo o NO CN to t^ O CN CO O "^ CN O NO CO ON CO lO O O r-~ O O 00 to O CN CO Tfi lO CN to CN NO T-H to On ON 00 O CO O On On On 00 1>- O • • 00 CO NO Th NO 00 00 t^ NO t^ O CN O 00 T-H ■^ T-H T-H rfi to NO t^ to -^ On »0 On Tt ^ ^ ■^ 00 ^ to NO O CO O On NO CO to On -^ Ot^ o CN t^ CN O ^ r-H t^ 00 1^ CO OJ>- T-H !>. -^ TtH tot— CO T-H 00 00 T-H t^ On NO t^ •<* t^ o T-H T-H CN X>- lO to CO ID f^ CO CO CO CO -rti T* O OCO O O NO lO o to T* 'tl to ■^ t^ T^l CN t^ to to T-H T-H to -^ CO CO NO O NOf^ O NO to to NO O CN t-- o ^ to lO T* lO CN CO OON NO ■^ T-H t-- t^ CN CO NO t^ NO O^ NO NO T* to r. NO C~^1 CO CN NO NO Tf NO t^ 00 Tt o to !>. On O CO ^ NO NO CO r^ i>- -^ CN O 00 t^ On O NO T-H CN On CO t^ O NO r- t^ O CO CN CO CO 00 CN -^ CO !>• T-H CN t^ On O CO NO CO CO CO 00 to to CN CO J:^ r-~ t^ C 00 T* O T^ to NO o o o o o o to to to to o o CN to to NO t^ t^ 00 On O to O O CN to to NO t^ t^ ON O 00 lO to to CN 00 CO ■^ CO O On 00 r-H T-H C lO CO CN T* CN 0> f^ to CO CN CN CN On CN •<* 00 On f^ to CO CN CN CN CN CN NO t— t^ ■^ O t^ Tfi CN CN t^ CO O^ T-H fS T^l T-H CN CN CN ■^ CN 00 »0 CO CO CO T-H rfH t^ On t^ OC' CN CO NO O CO to t^ NO 00 to C^l t^ CO T-H NO NO On 1>- O t^ CO NO T-H CN to t^ C T-H T-H T-H CN "tJ^ T-H CN •<* T-H rh 00 CN ON 00 On T-H NO O CO i^ CO Tt^ Ttl Tti to CN -^ to to 00 CN NO O On T-H CN O CO t^ O ^ '^ tJi to to ^H T-H •^H T-H On CO t^ lO CN t^ CN NO t^ r^ 00 OO 00 OO 00 O O O O o o o c lO to to to o c o o to o o o t^ o o o T-H CO T* to o c c o to o o o r- O O O CN rfi to NO c T3 c lO c be c "Z ^ 2 c ^ (D t. •— a: "^ Q..2 c On O T-H CN CO •^^ to 256 PIPING a > u X Si O Q o (S c at O. a o U V H "3 c o 2 •- 3 a> H (d l^"^3CC^OCN r—C^X^ -TTw-C^ O'TNC^ O O ^ lt~* c^ O Lc uc -^, i/^ O O I'T ^- t-». . — r^c^jtx^irj'.— — oc •— *^, — Of^oc t^^OOC'^^'— Xt-T X-^*— t--iOcc X c^ it; ;n »— I 3o I -c-r LCOr^ Oi^^ LCOO •— -Ott XLcio LCXO'^'^CN ^: — 1— C: x— 1-~ 2; ] :i; ■^ 23 LC o C> "^ o o 'T X O T+" lO o ; O — t^ -^ X lO : Lc t^ o ^ X o __ ^ ^ — X — — - x-^-O oor^i OC NO •^ I— c> CN O CS lO O O -^ 1~- ; >— LT, r-^ i/~. rj- •^ iC 3 O <-C ^ rf »OvO OC Cs '-1 lO X '-I ; i/~, TT X *^ Lc t~~ ;o ■^ CN , O C" r^ 3"0 CLC o to -^lO X <^ ■^«o o O j -^ C: rq CN> TT »o t^ o r^ X r^t:^ '— CN CO CM ••-H O hr Lc o O «N O O *^- o ^^t- O »0 I C" O "^ ^a Ti- o ir^ O r^ •~ o ■^ ^ T— ' y-^ y-^ CS "^ U-; X '^ -^ JTJ _.I^ re X iX '^ C'— •^r-jr'^'rr lOt^OC C^ — r^i '-rr- X X LT, C^ "^ T lO lO X »-| >— ^- rsj wCN'— CNC^TT OOLT- — x^-r- o *e I-O o >— LC C r^fCrj- iou-;t^ C^Oc^J •rri-cr^ ^^ J= X = I ■^" O CN ; c^ X '-C -r- *e ir; — — rN :^i -^ -^ O fC t^ r^ !>i r^i C: C> '^ O r-» r^ ^ CC CN U-: O t^ 73 a ^J; ^^\^- m, — — ^-,— OOOOOC XXX ■^3 s cCNOio r- ^-1 lO ■^ lO »o 00 CX) QC r^iTt O o ^ ^ ^_ ^ X ^] — ^ r^ LC LC • torrj Cn c^ o 3 r^ 3 -si tc X O ^ r^ J-^ ^ -^ ^ X o -e '-''-'CNr^rrs-^KJ'tou-j'or^x ■--^ ! ■^^ ^— I rN -\ -\i -.\ j PIPING 257 Table 22. ApF >roximate Weight Per Foot of Lar ge( D. D. Pipe. THICKNESS, INCHES Outside Diameter 1 1 1 of Pipe H Vl6 1 "/'l6 1 M I 16 H i Inches Pounds Pounds Pounds Pounds Pounds Pounds Pounds Pounds 14 36 71 45 68 54 56 63.37 72.09 80 72 89 27 106 00 15 39 38 49 02 58 57 68.04 77.43 86 73 95 95 114 00 16 42 05 52 35 62 57 72.71 82.77 92 74 102 62 122 00 17 44 72 55 69 66 58 77.38 88.11 98 74 109 30 130 00 18 47 39 59 03 70 58 82.06 93.45 104 75 115 97 138 00 20 57 00 65 70 78 59 91.40 104.13 116 77 129 33 154 00 21 59 20 69 04 82 60 96.07 109.47 122 78 136 00 162 00 22 62 60 72 38 86 60 100.75 114.81 128 78 142 68 170 00 24 68 00 85 00 94 61 110.09 125.49 140 80 156 03 186 00 26 74 00 93 00 102 62 119.44 136.17 152 81 169 38 202 00 28 80 00 100 00 120 00 128.78 146.85 164 83 182 73 218 00 30 85 00 107 00 128 00 138.13 157.53 176 84 196 07 234 00 Large O.D. pipe is generally made in outside diameters of from 14 to 30 in., and in thicknesses ranging from ^ to ^ inches. Table 22 gives the weight of large O.D. pipe of standard thicknesses. Cold drawn steel tubing can be obtained in regular pipe sizes from 5^ to 4 in. ; and in the standard, extra heavy and double extra heavy weights, as well as in special tubing dimensions and weights. The pipe weight should be selected to give durability and to maintain safety, rather than for initial safety. The standard hydrostatic test pres- sures, to which pipes are subjected at the mills, exceed even modern power plant pressures ; the initial ultimate strength of pipe is greater than any pressure stress likely to occur in ordinary practice. The following formula gives the approximate pressure at which pipe will burst : 2 T S P=^ (17) P = Bursting pressure, lb. per sq. in. T := Thickness of pipe wall, inches D =: Outside diameter of pipe, inches S = Tensile strength of material, lb. per sq. in. Machinery's Handbook gives the value of S, determined by actual bursting tests, as 40,000 for butt-welded steel pipe and 50,000 for lap-welded steel pipe. Table 23 of bursting pressures, is based on the above formula. Butt-welded pipe in sizes 3 in. and smaller and lap-welded pipes in sizes 3y2 in. and larger, are used in calculating the table. It is stated that the accuracy of the figures has been checked by exhaustive tests conducted by the National Tube Company. The pressures given in Table 23 are the approximate pressures at which new pipe will burst. In designing or selecting piping, a factor of safety is used ranging from six to fifteen, depending upon the severity of the service, the degree of exposure or corrosive action encountered, the dura- bility desired, and the probability of future operation at increased pressure. The second edition of the specifications issued by the Power Plant Piping Society recommends that all pipe (except boiler feed lines) be wrought steel with welded seams, butt-welded for the 2-in. and smaller sizes and lap- welded for the 2j^-in. and larger sizes. (General commercial steel pipe is butt-welded in the 3-in. and smaller sizes.) ?»-!--,-,_ ■Ill iiiiiiiiiiiijj II II II II 11 II 11 II nil II II II 11 11 II II 11 11 II II 5|IIIII!"ILW si II ffT^ ^4V \^_ Old National Bank Building, Spokane, Wash., equipped with Heine Standard Boilers, P I P I N Tx 259 Table 23. Approximate Bursting Pressures for Steel Pipe. Size of Pipe, Inches BURSTING PRESSURE, POUNDS PER SQUARE INCH Standard Extra Heavy Double Extra Heavy 13,032 10,784 10,384 17,624 14,928 14,000 28,000 1 i>i 8,608 8,088 6,744 11,728 10,888 9,200 23,464 21,776 18,408 2 2K 6,104 5,184 5,648 8,416 7,336 7,680 16,840 15,360 14,680 13,714 15,900 14,970 14,200 13,480 13,040 11,470 10,140 Size of Pipe, Inches BURSTING PRESSURE, POUNDS PER SQUARE INCH Large O. D., 3^-in. Thick Large O. D., J^-in. Thick 14 15 16 2,680 2,500 2,340 3,570 3,333 3,120 18 20 22 24 2,080 1,870 1,700 1,560 2,770 2,500 2,270 2,080 For pipe sizes up to and including 7 in., standard wrought steel pipe should be used for saturated or superheated steam lines with a working pres- sure not exceeding 250 lb. per sq. in. and a total temperature not exceeding 700 degrees. For saturated steam lines with a working pressure of not over 150 lb. per sq. in. the weight of pipe in pounds per foot should be 24.69 for 8 in., 34.24 for 10 in., 43.77 for 12 in., and O.D. sizes should be from Vio to Vio in. thick. For saturated or super- heated steam lines with a working pressure from 150 to 250 lb. per sq. in. and a total temperature of not over 700 deg. the weight of pipe in pounds per foot should be, 28.55 for 8 in., 40.48 for 10 in., 49.56 for 12 in., and O.D. sizes should be from ^U to '/lo in. thick. 260 PIPING For saturated or superheated steam lines with a working pressure of not over 350 lb. per sq. in. and a total temperature of not over 700 deg.. all pipe, up to and including 12 in., should be extra heavy, and O.D. sizes should be 5^-in. thick. For boiler feed lines with a working pressure of from 200 to 400 lb. per sq. in., extra heavy wrought steel pipe should be used up 10 and including 12 in., and O.D. sizes should be 3^ in. thick. If the water is extremely bad, the use of extra hea^y drawn brass pipe or extra heavy galvanized wrought steel pipe is recommended. For boiler feed lines with a working pressure of not over 200 lb. per sq. in. and with favorable water conditions, standard wrought steel pipe should be used for sizes to and including 7 in.; the weight of pipe in pounds per toot should be 28.55 for 8 in., 40.48 for 10 in., 49.56 for 12 in. Extra heav3' wrought steel pipe, standard weight galvanized wrought steel pipe or brass pipe should be used when there is considerable corrosion. Table 24. Standard Iron Pipe Sizes. Iron Pipe Size, Inches ACTUAL DIAMETERS, INCHES Outside Inside APPROXIMATE WEIGHT, POUNDS PER FOOT Brass Copper 1 134 2 0.405 0.540 0.675 0.840 1.050 1.315 i 1.660 1.900 2.375 1 0.281 0.375 0.484 0.625 0.822 1.062 1.368 1.600 2.062 0.25 0.43 0.62 0.90 1.25 1.70 2.50 3.00 4.00 8.30 10. PO 0.26 0.45 0.65 95 1 31 1 79 2.63 3.15 4.20 6. 04 8.72 11.45 4 4.500 4.000 12.70 13.33 4H 5.000 4.500 13.90 14.60 5 5 . 563 5.062 15.75 16.54 6 6.625 6.125 18.31 19.23 For blow-off lines for boilers operating with either superheated or sat- urated steam, extra heavy wrought steel pipe should be used. (Galvanized extra heavy steel pipe is preferable to black for this service.) For low pressure water lines, with a working pressure of not over 50 lb. per sq. in., and with favorable water conditions, standard wrought steel pipe should be used for sizes to and including 7 in.; the weight of pipe in pounds per foot should be 28.55 for 8 in., 40.48 for 10 in., 49.56 for 12 in., and O. D. sizes should be from Vs to Vic in. thick. When the corrosion due PIPING 261 to the water is extremely bad, or the pipe is laid in the ground, cast iron flanged pipe, built to American Water Works Standards, should be used exclusively. Seamless drawn brass and copper pipe can likewise be obtained in pipe sizes from ^ to 6 in., and in the standard and extra heavy weights. The actual inside diameter and the weights per foot of brass and copper pipe, Tables 24 and 25, differ from those of wrought iron. Table 25. Extra Heavy Iron Pipe Sizes. Iron Pipe Size, Inches ACTUAL DIAMETER, INCHES Outside Inside APPROXIMATE WEIGHT POUNDS PER FOOT Brass Copper H ^ 0.405 0.540 0.675 0.205 0.294 0.421 0.370 0.625 0.830 0.389 0.651 0.872 ^ 0.840 0.542 1.200 1.260 ^ 1.050 0.736 1.660 1.743 1 1.315 0.951 2.360 2.478 IH 1.660 1.272 3.300 3.465 m 1.900 1.494 4.250 4.462 2 2.375 1.933 5.460 5.733 2y2 2.875 2.315 8.300 8.715 3 3.500 2.892 11.200 11.760 3K 4.000 3.358 13 . 700 14.385 4 4.500 3.818 16.500 17.325 43^ 5.000 4.250 19.470 20.440 5 5.563 4.813 22.800 23 . 940 6 6.625 5.750 32.000 33.600 Pipe Fittings T) IPE fittings are made of cast iron, malleable iron, cast steel, brass, or ^ other alloys. Cast iron fittings are the most common, as they fulfill the usual service requirements. They are made in standard weight, for 125 lb. working steam pressure, and in extra heavy weight, for 250 lb. working steam pressure. . Malleable iron fittings are generally restricted to 2-in. or smaller sizes. In these they are used extensively on saturated steam lines and on boiler feed lines with working pressures of not over 250 lb. per sq. in. Malleable fittings are made in standard weight, for 125 lb. working steam pressure, and in extra heavy weight for 250 lb. working steam pressure. Cast steel fittings are now generally used on superheated steam lines, especially when the working pressure is over 200 lb. and the total tempera- ture is more than 500 degrees. They are made for superheated steam pres- sures as high as 350 lb. per sq. in. and for a total temperature of 800 degrees. Iron pipe-size brass fittings are made in two weights, — a standard weight for working steam pressures up to 125 lb. per sq. in. and an extra heavy weight for working steam pressures up to 250 lb. per sq. in. They are used onlv when brass piping is installed, which is rarely. o CS ID C CO w G "5 Pu o O u O V< ffl CO 0.C0 s ^ o o ^ > .2 ° C 3 • '• GO D. u 00 « c o spa Si PIPING 263 Pipe fittings are divided into two classes, screwed and flanged. Screwed fittings are used generally in the smaller sizes. The making, and more par- ticularly the breaking, of joints is much easier with flanged than with screwed fittings. No hard and fast rule governs the limits within which each type of fitting should be used. Some authorities specify flanged fittings on all lines 2^ in. or larger, while others state that all fittings 4 in. or larger should be flanged. The present tendency seems to be to use flanged fittings on all lines larger than 3 inches. Standard weight and extra heavy cast iron flanged fittings are listed in sizes from ^ to 24 inches. Screwed fittings in the same material are listed in sizes from yi to 12 in., in standard weight ; and from ^^ to 12 in., in the extra heavy. Extra heavy cast steel flanged fittings, for 350 lb. pressure, and 800 deg. total temperature, are listed in sizes from 1^4 to 24 inches. Similar screwed fittings are listed in a more limited range, from about 3 to 6 inches. Iron pipe-size brass flanged fittings are made in a limited range in standard weight (from about 2 to 6 in.), but extra heavy brass flanged fit- tings can be obtained in any of the extra heavy cast iron patterns. Iron pipe-size brass screwed fittings are listed for 125 lb. pressure in sizes varying from about % to 4 in., and in cast iron patterns, for steam pressures up to 250 lbs., in sizes varying from ^ to 6 inches. Malleable iron screwed fittings for 125 lb. pressure are listed in sizes from Ys to about 7 inches. Extra heavy malleable screwed fittings, for 250 lb. pressure, are listed in sizes from ^ to about 6 inches. Only the thread dimensions of screwed fittings are standardized. Un- fortunately the other principal dimensions have not been standardized, as have those for flanges and flanged fittings. Consequently the dimensions of screwed fittings vary widely with the different manufacturers. The American Standard dimensions of flanges and flanged fittings are accepted and used by nearly all manufacturers. The complete standard in- cludes sizes up to 100 in. diameter. The standards most used, from 1 to 48 in., are given in Tables 26 to 29, the first two being for 125 lb. and the other two for 250 lb. working pressure. The letters in the tables of fittings refer to the lettered dimensions in Fig. 143. The following explanatory notes apply to the tables of flanges and flange fittings : a — Standard and extra heavy reducing elbows carry same dimen- sions center to face as regular elbows of largest straight size. b — Standard and extra heavy tees, crosses and laterals, reducing on run only, carry same dimensions face to face as largest straight size. c — All extra heavy fittings and flanges to have a raised surface Vie in. high inside of bolt holes for gaskets. d — Standard weight fittings and flanges to be plain faced. e — Bolt holes to be % in. larger in diameter than bolts. f — Bolt holes to straddle center line. g — Face to face dimension of reducers, either straight or eccen- tric, for all pressures, shall be the same face to face as given in table of dimensions. h — Square head bolts with hexagonal nuts are recommended. i — For bolts, l->^-in. diameter and larger, studs with a nut on each end are satisfactory. j — Specifications of long radius fittings refer only to elbows made in two center to face dimensions. These are to be known as elbows and long radius elbows, the latter being used only when so specified. 264 PIPING The general methods of cofinccting pipe are by coupHngs, nut unions, or flange unions. The first two are screwed connections, and the last can be made with a gasket or with metal-to-metal seats. Couplings are made of cast iron, standard or extra heavy, from about ^2 to 3 in. ; of malleable iron, in standard weight from ^ to 6 in. ; of brass, in standard weight, from y% to 4 in. ; and in extra heavy weight, from ^ to 6 inches. They can be obtained in all three materials ; threaded right-hand, or right and left. Couplings should be used only for the smaller sizes of pipe. hAH w J 90* Ell Double BranchEH SidcOutleVEM LongRodiusEU 4-5-EII •-A-4-i-A-» "XlF] T^ 0) -P s fin & C IS 1 1 6 % 1 s 1 1^ 7 1/2 8 33^ 3^ 4 5 53/2 6 IM 2 23^ 73/^ 8 9 5M 63^ 7 IM IM 2 4 43/2 5 7 16 Yi 9 16 3 3^8 3^ 4 4 4 7 16 7 16 ¥1 7 T6 1% _7_ 16 2 3 9 10 11 43^ 5 53^ 63^ 7 7M 23/^ 3 3 103/2 12 13 8 93^ 10 23^ 23^ 3 (> 6 7 73^ 11 16 4M 53^ 6 4 4 4 7 16 7 16 7 16 33^ 4 4K 12 13 14 6 63^ 7 83^ 9 93^ 33^ 4 4 143^ 15 153^ 113^ 12 123^ 3 3 3 63/2 7 73/2 83^ 9 93^ 13 16 15 16 15 16 7 73^ 7M 4 8 8 'A % 7 16 3^ 3/2 5 6 7 15 16 17 73^ 8 83^ 103^ 113^ 12M 43^ 5 53^ 17 18 203^ 133^ 143^ 163^ 'SV2 33^ 4 8 9 10 10 11 123^2 15 T6 1 ll^ 83^ 93^ lOM 8 8 8 % % % 3^2 9 16 ^8 8 9 10 18 20 22 9 10 11 14 153i 16M 53^ 6 63^ 22 24 253^ 17H 193^ 203^ 43/^ 43^ 5 11 113^ 12 13 >2 15 16 13^ 13/8 ll^ 11% 133^ 143^ 8 12 12 % % y% 11 16 % 12 14 15 24 28 29 12 14 14M 19 213/^ 22M 73^ 8 30 33 343^ 243^ 27 283^ 6 6 14 16 17 19 21 223^ 44 83/2 9 9 22 24 26 293^ 32 343i IH 1>^ 2 273^ 293^ 31% 20 20 24 1% l3i ii% 13^ lA 28 30 32 48 50 52 24 25 26 39 413^ 44 14 15 16 56 59 463^ 49 93^ 10 28 30 32 363^ 38^ 41^ 9 J- ■^16 2>^ 2W 34 36 38 U 28 28 28 13^ IH IM 1^8 ii^ 134 34 54 56 58 27 28 29 463/^ 49 513^ 17 18 19 34 36 38 43 M 46 48 M 2l'6 23/8 2^/^ 403^ 42% 453^ 32 32 32 13^ 13^ 1 -^ 36 1^ 38 1 y 40 60 62 64 30 31 32 54 563^ 59 20 21 22 40 42 44 50M 53 553^ 23^ 2^ 25/^ 4734 493^ 51% 36 36 40 1^ 1^ 1^ 1% 1 11 42 44 v^% 46 66 68 33 34 613^ 64 23 24 46 48 573^ 593^ oil •^16 2M 53% 56 40 44 1^ 1^ 1 J-5 48 A'^Mf unions are made with malleable iron, steel or brass bodies, with gaskets or with brass or bronze seats. The commercial size range is from ]4, to 4 in., but they are not used in sizes larger than 2 inches. Nut unions are not intended primarily for high pressure work ; for low or medium pres- sures however the connection is satisfactory and easily broken. Their use permits desirable piping layouts and connections that would otherwise be im- practicable. Unions with brass or bronze seats are usually preferable to the all-iron gasket type. PIPING 267 Table 27. American Standard Dimensions for Pipe Flanges for 125 Pounds Working Pressure Diameter of Pipe, Inches Diameter of Flange, Inches Thickness of Flange, Inches Width of Flange Face, Inches Diameter of Bolt Circle, Inches No. of Bolts Diameter of Bolts, Inches Diameter of Bolt Holes, Inches 1 IM 4 43^ 5 1^ 16 1^ 1% 3 3^ 3K 4 h 4 1^ 4 3^ 1^ 9 16 2 2^ 3 6 7 73^ n 16 % 2 2K 2% 4% 4 5H 4 6 4 % % % 3M 4 43^ 83^ 9 9M 13 16 15 16 23^ 23^ 2% 7 73^ 7% 4 8 8 % % % % % % 5 6 7 10 11 123^ 15 16 1 1^ 23^ 2% 83^ 8 93^ 8 10% 8 % % % 8 9 10 133^ 15 16 13^ 2% 8 3 11% 8 13% 12 14% 12 % % Vs Vs 1 12 19 14 21 15 221^ 1% 1% 33^ 33^ 17 i 12 K 1 18% 12 1 IH 20 16 1 13^ 16 18 20 231^ ! l^ 25 1 1^ 27K 1 IH 33^ 3% 21% 22% 25 16 16 20 1 1^ 13^ 13^ 1% 22 24 26 293^ IH 32 IJ^ 341^ 2 3% 4 43^ 27% 293^ 31% 20 20 24 1% 1% 1% 1% 28 30 32 36M 38% 41% 2^ 23^ 2% 4% 4% 4J^ 34 1 28 36 28 383^ 28 1% 1% 13^ 1^^ 1^ 34 43M 2^ 4K 403^ 36 46 23^ 5 42% 38 48% 1 2% 53^ 45K 32 32 32 IK 13/2 1^ 1^/^ 1^ 1% 40 42 44 50% 53 55K 23^ 2^ 2^ 5% 5^ 5^ 47% 493^ 51% 36 36 40 1% 1% 1% 46 48 5734 593^ 9 li ^16 2% 5^ 5% 53% 56 40 44 1% 1% 1% Flange unions are of two general types, those with cast or malleable bodies and brass-to-brass or brass-to-iron seats, similar to those of nut unions ; and those in which a gasket is used. The first type is expensive and, although made in sizes from I/2 to 12 in., its use in practice is limited to the smaller sizes. It has an advantage for connections that must be often broken and remade. The second and more common type of flange union is that in which the pipe ends to be connected are secured in or by two metal flanges ; a gasket is inserted between the flanges and the flanges are drawn together by bolts. The most satisfactory forms of this type of union are the screwed joint, the peened joint, the lapped or Van Stone joint, and the welded joint. Fig. 144 gives examples of these four joints. 268 P I P I X G Table 28. American Standard Dimensions for Flanged Fittings for 250 Pounds Working Pressure. (See Fig. 143.) SIZE <— X OS o M t£ e> a ;:^ ^ S r=* = ,S X .^ u u . ^ ^** 9 eS r^ '"^ o ct :« 3 d ^ - S S3 m '^m fe„ C3 b o o O ■fca o P=4 o o o Li O S3 51 51 3^ O 3 1 c Ci O ^ 9 ^^ n^ C_3 §-1 ^- .2 .2^ 6 ea rC4 — ' ^ ^ &4 a ~ z: ^ • A-A A B C D E F G 1 11.^ 9 4 4M 4K 0>9 6 23^ 2^ 8H 11 6>2 8M 2K 23^ 4M 5 6 I 16 13 16 3^ 3^ 4H ^2 E a 1^ 1 ^ 2 3 10 11 12 53- 6 7H 3 113^2 3 3^1 13 3K!l4 9 103^ 11 2H 2M 3 6 63^ 814 3^ 1 o 6^ ^1 4 33^ 4 41.^ 13 14 15 6>2 7 71^ 9 91^ 4 43^ 414 16 17 18 83^11^ 9 il2M 53^ 6 iD}4\i2y2 iQYoii^yo 18 1 143^ 18^ 213^1 231^ 3 I 7 3;^' 71-^ 9 10 1034 734 7J^ 8H 741 15 I 339 . .. 17Ki 4 I 9 19 43^ 10 11 12J^ 14 1^8 llv 9^ 10^8 IJillJi 8 '-^i 12 ''A 12 's' 12 126 1 13 14 |30 15 15 31 1 151^ 19 21^ 22M 8 133391273^9 6 14 203^ 83^^1373^^131 i 63^116 |23 9 1393^133 I 63^^(17 \2A.Vo 2% 2^ 173^116 20Mi20 213^^120 Us 16 18 20 133 i36 139 163^ 18 24 263^ 191^29 93^^ 10 42 451/^ 10i^'49 3434 373^ 403^ 73^il8 8 19 83^!20 253/9 28 303^ 2^122^ 2^824M 23^'27 20 24 24 13^ 16 H 16 % 13 16 s 20 10 14 1 6 25^^!20i9, 5 ill 15 1% 13 12 s 16 y 21 103^ 15K! 61^ 273^^1223^9: 5 113^ IBK Wa. 14 12 1 1 \ % 10 2:3 iiVo 163^1 7 1293 9i24 ! 51/i 12 171^ VA 15M' 16 ! 1 ! 15 16 1 ^- ^ 16 114 1^-8 Wo 22 24 26 41 45 48 2Qy> 22 >| ■^,4 313^ 34 363^ 11 12 13 53 571^ 43 >^ 47^ 93^ 10 ■ 22 '24 26 33 36 38^ 2% 2H 2M 29M 32 341^ 24 24 ■^8 132 ll^ 1 i^ 28 52 55 58 26 271^ 29 39 41K 44 14 1 ■?8 40M 43 45H 2H 3 3H 37 39 H" 413 9 28 28 ■■»8 1?8 1^4 IJ'8 1 '^ 30 15 16 30 32 2 32 ■v; 34 61 65 68 301 9 461 9 17 34 47I/2 50 52 M 3M 43H 46 48 28 32 32 1^8 ?.H 36 323^ 34 49 513^ 18 19 36 38 23s 38 2i% 40 71 74 78 35>9 37 39 54 -^0 40 •5439 57 59 K ^16 3H bOH 52M DO 36 36 36 VA 2 •>_2_ 42 44 563^^ 59 21 22 •::J:::: 42 44 Oil - 16 13 - 16 46 4S 81 84 403^2|6U2i23 : 42 |64 ,24 j.... ,....,.... 46 48 6U2 6b 4 37 }4 603:r 40 40 2 2 2,^ 3 In the screwed joint, the flange is screwed on the pipe until the pipe projects about Vie in. bej-ond the face of the flange. A facing cut is then taken across the face of the flange and the end of the pipe. The face of the flange should then be square with the axis of the pipe and the gasket should bear on the end of the pipe. This joint is accepted for all sizes of pipe in saturated steam lines with working pressures not greater than 125 lb., on boiler feed lines with working pressures up to 150 lb., for blow-off lines, and for low pressure water lines. It is also used on medium and high pres- sure saturated and superheated steam lines and boiler feed lines in sizes up to about 8 inches. rrfil Ihn H^l IP 269 :iD o^EZi ^ Fig. 144. Typical Flange Joints. Table 29. American Standard Dimensions for Pipe Flanges for 250 Pounds Working Pressure Diameter of Pipe, Inches Diameter of Flange, Inches Thickness of Flange, Inches Width of Flange Face, Inches Diameter of Bolt C ircle. Inches No. of Bolts Diameter of Bolts, Inches Diameter of Bolt Holes, Inches 1 1^ 1^ 5 6 H iM ^ ! m 3^ 43^ 4 K 1 H 4 1 % 1 M 2 2M 3 6>^ !i : 2M 1 21^ iH 2^ 5 ! 4 5% 4 6^ 8 % i % K I K K :^ 3^ 4 4M 9 10 103^ 1^ 2M 7M IM 3 7K 1^ 3 8>^ 8 8 8 K J^ K K K ; K 5 6 7 11 iH 123^ li^ 14 1^ 3 1 9M 3^ UK 8 1^ Ji 12 1 ^ >^ 12 1 K 1 8 9 10 15 16M 173^ 1^/^ 33^ IM 3^ 13 14 15K 12 12 16 y% 1 1 1 13^ 1 iK 12 20M 14 23 15 243^ 2 4M 23^8 43^ 2^ 4M 17^ 20M 21 H 16 1 13^ 20 1^ 20 1 IK IK IK IK 16 18 20 25^ 1 2K 28 1 2% 303^ 1 23^ -t^ 1 223^ 5 24M 53^ 27 20 IK 24 , IK 24 , 13^ IK IK 22 24 26 33 36 383^ 2^ 5M 2H 6K 29M 24 IK 32 24 1^ 343^2 28 ]^ IK IK IK 28 30 32 40M 43 45 1< 2M 3 33-^ 63^ 6^ 37 28 39 K 28 413^ ! 28 1^8 IK IK IK 2 34 36 38 47^ 50 52i> u to u a U •^ 00 -oH c a . w£ C ffl* X3 o o_a c^ .25: 4-1 CO .s o o ,l^yl^^-^^^>\^#x PIPING 271 The peened joint is formed by shrinking a flange onto the end of the pipe, which is peened or expanded into a recess in the face of the flange. A light facing cut is then taken across the face of the flange and the end of the pipe. This joint is better than the simple screwed flange, especially for sizes larger than 6 in., but cannot be made up well at the place of erection. The lapped or Van Stone joint, one of the most flexible in use, is made by upsetting and flattening the heated end of the pipe so as to form a flare oi lap. The flared end is faced to insure uniform thickness and a tight joint. The lapped portion of the pipe is also finished on the edge. The flanges are loose on the pipe, their hubs being bored slightly larger than the outside diameter of the pipe, and simply serve to draw the lapped ends of the pipe against a gasket. In some forms, the lapped part of the pipe is not of uniform thickness but tapers toward the edge; the face of the flange inside the bolt holes are then faced to the angle of inclination of the back side of the lapped part of the pipe. The lapped joint is recommended for practically all kinds of service. It is especially valuable on high pressure superheated steam lines and high pressure boiler-feed lines. The ivclded joint is made by welding a flange on the end of the pipe. Theoretically this is the nearest perfect of all joints, because a welded flange becomes a part of the pipe itself. Its success depends upon the care with which the weld is made. In practice the welded joint is reliable and satis- factory and is considered to be the best for high pressures and high de- grees of superheat. There is little choice between a well-made lapped joint and a well-made welded joint. Both are more expensive than the simpler types, but in high pressure work their cost is more than justified. Flange materials. Cast iron, malleable iron, cast steel, wrought steel and brass are used for flanges. Cast iron flanges are extensively used on sat- urated steam lines, boiler feed lines, and low pressure water lines. Malleable iron flanges are not as common as cast iron flanges, but are applicable to the same service. Cast steel and wrought steel flanges are recommended for high pres- sure saturated and superheated steam lines, high pressure boiler feed lines, and blow-ofif lines. Brass flanges are used only with brass pipe and almost exclusively in the screwed type of joint. The following figures, due to the Crane Company, show the ultimate strength of pipe flange metals : Ultimate strength. Material lb. per sq. in. Cast iron, ordinary grade 14,000 Gray cast iron, high grade 22,500 Malleable iron 37,000 Forged steel 51,000 Cast steel 67,000 Valves VALVES control to a great extent the safety of a plant. Their location determines the flexibility of the piping system, either in normal opera- tion or in times of emergency. Safety valves for boilers generally must comply with the specifications of local or national codes. The A. S- M. E. Boiler Code requires that they shall be of the direct spring-loaded pop type, with seat and bearing surface of the disk either inclined at an angle of about 45 deg., or flat at an angle of about 90 de^. to the center of the spindle, 272 PIPING The safety valve charts. Figs. 145 and 146, may be used for determining the proper number and sizes of safety valves required. The charts are made up so that it is necessar\- to take only the rated horsepower of the boiler and run up the vertical line to the slanting line corresponding to the relieving pressure desired, and the proper size and number of safety valves are indi- cated at the left of the zone in which the vertical horsepower rating line crosses the relieving pressure line. If the intersection comes on a zone divi- sion line, the smaller valves are to be used. Exam pic. One 806 H.P. boiler to operate at 190 pounds gage pressure. The two-valve chart stops below 806 H.P. Therefore, wc must go to the three-valve chart. We hnd that the 806 H.P. vertical line does not inter- sect the 190 lb. pressure line. This indicates that more than three valves are necessary. We then take one-half the rated horsepower, and find that two 4 in. safety valves will relieve 403 H.P. The proper valve specifica- tion in this case is therefore four 4 in. safetv valves. \ 1 1 1 1 ; ill 1 1 1 — 1 1 1 1 1 1 i t 1 M'A/ y. ^/ 4A4^AZ^ ^ '^ Al 1 W^/TV-^ w^ym^^. 1 1 ' //y/v/y/yyA<^'<^^^ . i /I/ ///l/^/X/XVV'.^// ^ Ui 4 N J. /A// Y//A^^. <<^ ^y. ^\ -J / T/T/^ -y^ w i 1 0) 1 t//y//y %^^$^^ y \ 1 III ^ - >A////// 1 1 > u \LuML^/y/z//yyy ! H -i 7/////////: /ZA^Za 1 -j/=/'?U^/^AS^i4y0^M^^^ ' ~ — — //////// //y/Vy'Oy^ t 1 1 I ^ ////////y/ <^^ 1 1 1 \ 1 1 1 111 1 li. 3' < -* 1- _j //////v///y^ 1 1 1 1 t RELIEVING CAPACITIES OF ^^^^^P^^ 1 1 1 i 1 1 ,TWO _J_ 1 cn ,, ' ^ v/7/M^:^^^ 1 1 1 1 '^ zmnmiumir 1 1 5A si FETY VALVES j 1 2i' o iminiuif// FL>T .ATS 1 , 1 1 INT. LIFt. mm m ' - - A. S. M. E. STO'. 1 1 I % m 'Ml 'Ml IL _ _ 1 1 1 1 i 1 1 1 a/'/^o 1 60 lao MO 180 22U 260 300 340 380 420 460 500 540 580 620 660 700 740 780 820 B. H.P. BOILER HORSE POWER. Fig. 145. Relieving Capacities of Two Ashton Safety Valves. ) 4}' 1 z / / > . y . ^ y ^^^ ^1^ ^^ ^^ ^ ^ <-' K^ •~y X v^. [^.^ k3 yp^ ^•^ f\'=>$> [?^ r^ i^^ \^;y< i^ y ^ ^i^ ^k K y y. K'- ^l^ '^^ X^ ^ • 1 / /. y.' ^u ^ y iK A ^ ry y < 'y y^^ ^^ ^ 0) 4 / ^ /\/ y n^ y y 'y, y' \r -^A r^' ^ y^ y^ >;> N '. / / /[/ X ^.^ X. X ^ t^ -'P W. ^ '^y ' m'l \ ^.^ \/ A'' X X IK y. y ^ -^< y^ ■^y 1 1 1 1 Y f /J ^y ^^ X kM ^^^^ K^ K> ^^■i*^ 1 1 \ ^ T > \^ t/ y\/ //} V; yy ^iS>" 1 1 1 <3r X. yy^v^^A^/ y^^^.^^^i^i^j^ ^ 1 1 / ^/K y" Wyy^^^.^^ ,, V, ^/h ^ y'yyzz^.^:::^ 1 'c ■ >/P^;>;j^^>^;>::>:P::^;^^:;:> ^ \ 1 u 1 iZ 3' < z <;<^^^;^^^^;^ y< \ RE LIEV ING CAPACITIES OF j;^^^^ f$^^^^^ i \ 1 T 1-1 1— r- CO ■ '^ p^ '^1 1 1 HrM:. 1 1 ^1 > ■ -J f/ Y\ 1 SAFETY VALVES »• u 1 \ FLAT SEATS | | | | "NT L IFT. l| 1 ASM e:. 9td'. i 1 1 i ! 1 1 1 Y*. ao 7M3M 340 380 420 460 500 540 580 620 660 700 740 780 820 860 900 »40 980 1020 1060 0OILER HORSE POWER. ' "' Fig. 146. Relieving Capacities of Three Ashton Safety Valves, PIPING 273 Safety valves are also discussed in Chapter 16 on OPERATION. Globe valves, probably the most common type of stop valve, can be used simply as a stop valve, or also to partly throttle the flow of a fluid. These valves should be installed so as to close against the pressure, because if the pressure acts above the disk and the latter becomes detached from the stem, they cannot l)e opened. A further advantage in closing globe valves against the pressure is the ease of packing the spindle stuffing box when the valve is closed. These valves should not be placed in a horizontal return line, especially with the stem vertical, because the condensate must fill the pipe al)Out half full before it can flow through. The glol)e valve should be designed so that it can be packed under full line pressure and so that the disk or the scat can be quickly repaired. Valves with outside screws are preferable to those with inside screws, unless the screw must be protected because of the valve location. The out- side screw type indicates more quickly whether it is open or closed. This is especially true of the type having a rising stem or spindle and a stationary wheel. Globe valves are made in both screwed and flanged types, with brass, iron or steel bodies and with composition, babbitt, bronze, nickel and nickel alloy disks and seat rings. Standard pattern screwed brass globe valves, rated for about 150 lb. working steam pressure or 250 lb. working water pressure, are made in sizes from V^ to 3 inches. Extra heavy screwed brass valves, rated for about 300 lb. working steam pressure, or about 500 lb. working water pressure, are made in sizes from % to 3 inches. Flanged standard brass valve sizes range from 34 to 3 inches. Extra heavy flanged brass valves are made in sizes from ^4 to 3 inches. Brass globe valves are not commonly more than 2 in. diameter. Their use is limited to saturated steam lines, boiler feed lines and water lines of medium or low pressure. Standard pattern iron-body screwed globe valves, rated for about 150 lb. steam or 250 lb. water pressure, are made in sizes from 2 to 12 in., and the same type flange is made in sizes from 2 to 24 inches. Extra heavy iron-body globe valves, rated for about 250 lb. steam or 400 lb. water pressure, are made in either screwed or flanged types, and in sizes from 2 to 12 inches. Iron-body valves Avith disks, seat rings and spindles of other materials, are satisfactory for saturated steam lines, boiler feed lines and water lines with pressures up to their ratings, but are not so good as steel valves for pres- sures over 150 pounds. Valves 6 in. and larger should be equipped with by-passes, especially for the higher pressures. Steel valves should be used in superheated steam lines and high pres- sure feed lines. These are made in sizes from 2 to 12 in., in the extra heavy weight, and are rated for 350 lb. working steam pressure. Disks for globe valves are made of a wide variety of materials. Com- position disks are made in several grades ; soft for low pressure water, rubber for cold water up to 250 lb. pressure, semi-hard for hot water and boiler feed lines, hard for steam lines up to 150 lb. pressure. Babbitt metal disks are often used in low pressure hot water and steam lines. Brass or bronze disks are used in high pressure saturated steam lines and feed lines, the harder grades for the higher pressures. Nickel and alloys high in nickel are recommended for the highest pressures and for superheated steam. Valve seats, or at least seat rings, should be made of non-corrosive metal of characteristics similar to those required of metallic disks. Gate valves offer a minimum resistance to the flow of a fluid, but when throttled are hard to regulate and are likely to chatter. They are made of the same materials as globe valves and are applicable to the same types of service, except for throttling. For higli class installations, particularly in the larger sizes, gate valves represent the best standard practice. By-passes should be used with high pressure gate valves of 6-in. or larger diameter. 274 PIPING A stop valve should not be placed in a vertical steam line, unless it is possible to drain the condensate that collects above the valve seat when the valve is closed. Automatic non-return valves should be installed on each boiler when the plant contains more than one. These valves automatically equalize the pres- sures of the different boilers, tliereby tending to equalize the loads. They can be used to cut in or cut out boilers automatically, will automatically cut a boiler off the line in case of an internal rupture, and will prevent steam being accidentally turned into a cold boiler. These automatic valves are made in man}- forms, all essentially check valves, although they may be stop valves as well. The control can be re- mote non-automatic, as well as hand and automatic, so that their automatic action can be tested at any time. The non-return valve should be carefully made and should be extremely rugged, because it is subjected to great stresses. It is usualh' attached di- rectl}' to the boiler nozzle, so that the boiler must be shut down if the valve has to be repaired. Besides the non-return valve, a gate valve should be placed between each boiler and the header or main, beyond the non-return valve. Check valves. Among these, the ball check is uncommon. The weighted check is more popular, as it can be used as a combination relief valve and check. The disk check has much the same bod)- as a globe valve and offers about the same resistance to flow. The swing check, by far the most com- mon, is simple, effective and oft'ers the least resistance to flow. A check valve is subject to severe service and must be so designed that its disk and seat can be repaired. In essential lines, such as boiler feed lines, a check valve should be protected by a stop valve on each side, so that a defective disk can be repaired without taking the pressure off the line. For feed lines to boilers in continuous operation, or when regulating valves are subjected to severe usage, both the check valve and the regulating valve should be protected by a stop valve on each side of the two ; the stop valves are normally wide open and are closed only when either the check or the regulating valve must be repaired. Combination stop and check valves are used frequently in boiler feed lines and can be combined with regulating valves to reduce the number of valves required to obtain a fair protection. In blozi'-oit connections, three types of valve are commonly used; a specially designed blow-off valve, a blow-off cock, and a gate valve. In the best practice a special blow-off valve and either a cock or a gate valve are installed in each blow-off connection between the boiler and the blow-off main, the cock or gate valve being located next to the boiler. The cock or gate valves should be opened first and closed last, when blowing down, so as to reduce the wear on them, and so that they can be depended upon to hold pressure when the regular blow-off valve is being repaired. Plug cocks are satisfactory- for this service, especially on boilers operated at low or medium pressures, but a gate valve is better and can more easily be used as a wash-out valve. Plug cocks should be equipped with a spring or other compensating device, to automatically take up wear. Steel or iron blow-off valves, gate valves and cocks should be extra hea\->-, steel being preferable for the higher pressures and temperatures. Valve disks and seats should be so arranged that thej' can be repaired. Blow-off service is severe and is particularly harsh when scale and sediment is present in quantity. The manufacturers have proposed that blow-off valves for power boilers operating with pressures up to 250 lb. be made onl}- in the extra heavy pat- tern and in the 1, \]2, 2 and 2^ i-in. sizes; the 1-in. size to be screwed, the V/z and 2-in. sizes screwed or flanged, and the IVz-'m. size flanged. PIPING 275 Blow-Off Piping. Each boiler should have its own blow-off pipe. This should end in the boiler room, or where discharge on account of a leaky valve will be sure to attract attention. In most cities hot water is not per- mitted to be discharged into the sewer. A blow-off tank is then placed at a sufficient height that it will drain by gravity into the sewer. This tank should be provided with a man-hole, an open vent pipe, and with inlet and outlet pipes connected with the blow-off pipe and the sewer respectively. A valve should be placed in the outlet pipe. In horizontal return tubular boilers, the blow-off pipe should be covered with magnesia, asbestos or fire brick where it passes through the back con- nection. It can be protected by a connection from it to the boiler just below the water line. In this way, water is continually circulated, and the blow-off pipe will not burn. A valve should be placed in this connection, and closed before the blow-off cock is opened. Reference should also be made to Chapter 16 on OPERATION. Size of Steam Pipes ASIDE from the attraction of gravity, a fluid flows through a pipe only because the pressure at one end is greater than that at the other. The higher the velocity desired, the greater must be the difference between initial and final pressures. The problem of selecting a pipe to conduct a given quantity of steam or water in a given time therefore resolves itself into striking a balance between high velocity, which requires a high pressure drop but permits the use of a small pipe ; and low velocity, which requires a large pipe but can be obtained with a small drop in pressure. The drop In pressure caused by friction does not represent an equivalent loss of energy, because the energy reappears as heat. If the steam enter- ing the pipe line is wet, this heat tends to evaporate the moisture in the steam. If steam is dry when it enters the line, the heat tends to superheat it, or if it entered as superheated steam, to add to its superheat. The equip- ment to which the steam is delivered and in which it is used determines whether this heat, gained at the expense of a drop in pressure, is utilized or wasted. If it is utilized, the net loss due to friction is negligible; if not, the pressure consumed in overcoming friction becomes a loss. The use of a Iiigh velocity reduces the size of steam mains and thereby directly reduces the loss by radiation and the cost of the equipment. Steam velocities of from 3500 to 6000 ft. per min. have been common in the past, but in present practice velocities are from 12,000 to 20,000 ft. per min. This increase has occurred partly because superheated steam is being more com- monly used and also because prime movers utilize the superheat from pipe friction to reduce their steam consumption. Pipe friction represents an absolute loss if the steam consumption of an engine, pump or other apparatus, instead of being reduced because of the superheat, is increased because of the lower pressure. It has been determined analytically and experimentally that the pressure loss due to the steady flow of a fluid through a pipe of uniform diameter varies with the density of the fluid, is proportional to the length of the pipe, decreases as the diameter of the pipe increases, increases with the roughness of the interior surface, and increases nearly as the square of the velocity. The old method of basing steam pipe sizes on the velocity of the steam, has given place to the more correct method of determining the pipe diameter in accordance with the drop of pressure allowable. It is almost immaterial what the velocity may be so long as this pressure drop condition is met. 276 PIPING The formula srenerallv used i; jr' {■--f) P = 0.000131 X ^~ ^. from which Tv' a v: = s; p (f ^ .(..M) (18.) P =: Drop in pressure, lb. per sq. in. JV = Weight of steam flowing, lb. per min. Ji = Length of pipe, feet d = Internal diameter of pipe, inches ZL' = Mean density of steam, lb. per cu. ft. This formula, as simplified by Spitcglns (Armour Engineer. 1917). is where : If = Weight of steam in pounds per second P = Pressure drop in pounds zi' = Mean density of steam h =z Lenarth of pipe in feet. j^= 1100^ for 16 in. pipe 800 for 14 in. pipe 550 for 12 in. pipe 350 for 10 m. pipe 195 for 8 in. pipe 97 for 6 in. pipe 60 for 5 in. pipe 32.5 for 4 in, pipe 15.5 for 3 in. pipe 8.5 for Il'o in. pipe 5.1 for 2 in. pipe 2,5 for V/2 in. pipe 0.75 for 1 in. pipe GebJmrdt says that this formula (\9) gives results which accord closely with obser\-ation, and as it is more convenient to use than (18) it is to be preferred. To facilitate the determination of steam pipe sizes, the following charts: Figs. 147. 148, 149. 150 and 151. have been prepared in accordance with the above values of k as determined by S/'itcglas. Particular care has been taken to make them very easy to use. The following instructions will make this quite clear : Saturated Steam. 1. Enter the lower left-hand scale with the weight of steam to be carried in pounds per hour, 2. Proceed vertically to the proper curve of pressure, which is the initial pressure at the entrance of the pipe. 3. From this intersection, proceed horizontally to the right to the curve of pressure drop per 100 feet. 4. Proceed vertically downwards from this intersection to the lower right-hand scale and read the size of pipe required. PIPING 277 O (U e ID +-> C D O 0. o o o (U w 2n PIPING PIPING 279 u 3 O X a o c o £U o o o o o o o o (U a «4-l o N 280 PIPING _ _— - ^ „„....„... A.....A...A A - — Si^ i s ^ M.,..^..\...\ ^ \ \ it m__\,1 4j,_„.-. S{L-^-\-V-- 1 ..A--0\-V- . ^._^.^..\. . fg ""a^ PX& ^5r- ^^ 5 ^ § ^ ^ § +/(3i Li+-:iS '^ 5 '' »■ S * ^ 5 ? ' . Jr I'Z/.Vi^^''-';5^^^5^^'^'^"' -^ P^ii^^^"^' t^:^^^^'^^^^^^^'^ ■i--^ ^ ^ "^ " ^■^''^''^?.^''''^^^^ <■'' ^''.^x^ "^ v' ^ ■> Z' /" y* _ - " _ - -""--^Iq:^^^^::^^^ ^^^:<^^^^^ --=^" ^^^>^'^%^^:^^^/^^^ ^^ -^^^"^ ^■^Z^z^'y A^^ ^^"^ ^^^^OP' ^Zt^ ^^1^'^ /J7 ^^Z^^^t^^^ 2,^^ ^v^7 - - - -^^'^^'^- ^B^I.^^ZZ/^ /.t^Z ^-=^^ ^n>f\o%> / ' ,-^ ^^^ J;yfw^ ^^^^ ^ i^S^ ^^%^ 7 -.^ /^ ^ y^ -.Z ^ Z _ _,^ ^ _Z V / ^ ^2 y'^^ y 7 ^ ,' ' Z ^ ^ -.Z ^^^^ _ _ __ _ _ _z ^z_z z z 2 ' /^ / J y /J _ _ - _ - -^Z z / r 4- _j_ J 53 I ^^ lis 3 O \ \ k \ \ \ N s. \ \ I \ \ k \ \ \ \ \ s \ V \ V V V \ \ \ V k \ \ > V \ \ \ \ N V \ \ \ \ \ \ s s \ \ \ V \ \ \, \ \ k \ \ \ V s. \ \ ^\ V \^ \ ^ s \. \, \ \ \ N \ \ \ \, \ s V \ ^^ \ > \ \ V s. \ N \\ \ \ \ \ s. \ \\ \ \ \^ \ rs vV \ k' ^ \ ^ ^ \^ s; kV \ \ \ \J\ \ ^ \ \ \ > \N \ \ \ \ A k\ \C ^ \ V \ .V 1^ ^ S s. ^^ \^ ' oA <^ ^ s> V\\ ^. 1 f<^\ \ kN v\ hN "X \ N 'Sb^^ N^ ^ S vN\ S^ \ •^ fev \ \\ S^ \\\\ k •^ k \ S sm <" \ \ ^ \ \\\^m N kxsnw^ \\^ ^ iS^ ^ \ ^ ^ ^ J^ "^ > ^ o^ 10 CO N a '•3 c S CO u +J CO TJ +J CO u CO W s CO xn ■M CO A u a CO 4J t-i V > a o U ti .o u CO A u bfi PIPING 283 The losses due to obstructions can be determined by: ~2j (21) // = /.- ^' H = Friction head, feet k = Constant V ■= Velocity, ft. per sec. g = Acceleration due to gravity For the constant k, Gebhardt gives the following values : 45 deg. ell 0.182 90 deg. ell 0.98 Gate valve 0.182 Globe valve 1.91 Angle valve 2.94 The friction caused by valves and fittings can be expressed in terms of equivalent length of straight pipe ; the following values are used : Obstruction Pipe Diameters 45 deg. ell 6 90 deg. ell 30 90 deg. tee 60 Gate valve 6 Globe valve 60 Angle valve 90 Bend, with radius equal pipe diameter.... 20 Bend, with radius equal 2 to 8 diameters 10 Water velocities in power plant practice range from 50 to 400 ft. per minute. The velocities in suction lines, especially in those carrying hot water, should be from 75 to 150 ft. per minute. A velocity of from 300 to 400 ft. per min. is common in boiler feed lines. Expansion and Contraction THE expansion and contraction of piping because of temperature changes is large enough to demand careful consideration. Higher pressures and higher degrees of superheat emphasize the importance of the subject, as does also the increasing use of efficient insulating materials. Formerly it was assumed that radiation from the surface of a pipe reduces its expansion to about half the theoretical amount, but actual tests have shown that the expansion of well-insulated pipe closely approaches the theoretical value. The amount a pipe will expand depends upon its initial length, the rise in temperature to which it is subjected, and the coefficient of linear expansion of the material. This statement is expressed by the following formula : I = C h (h — t) (22) / = Expansion, inches C = Coefficient of linear expansion, per deg. F. h = Initial length, inches t = Initial temperature, deg. F. ti = Final temperature, deg. F. The coefficient of linear expansion is not constant at all temperatures. In calculating the expansion of piping, the mean coefficient must be used. The coefficients of expansion of cast iron at different temperatures have th6 following values : Deg. Coefficient 100 0.00000600 150 0.00000612 200 0.00000625 250 0.0O000642 300 0.00000660 400 0.00000700 500 0.00000740 i X G CO s i2cQ ft. u OJ o 05 •:3 ft. •I MM MiHa PIPING 285 The coefficient of linear expansion of other materials can be obtained by multiplying these values by 1.1 for wrought mild steel, 1.5 for wrought copper, and 1.6 for wrought brass. Table 30, due to Gebhardt, gives the mean coefficient of linear expansion of materials for different temperature ranges. Table 30. Coefficients of Linear Expansion of Piping Materials. Material Temperature Range Wrought iron and mild steel Wrought iron Cast iron Cast steel Hardened steel ^ . Nickel-steel, 36 per cent nickel Copper, cast Copper, wrought Cast brass Brass wire and sheets 32-212 32-572 32-212 32-212 32-212 32-572 32-212 32-572 32-212 32-212 Mean Coefficient C per Deg. Y. . 00000656 0.00000895 0.00000618 0.00000600 0.00000689 0.00000030 0.00000955 0.00001092 0.00001043 0.00001075 Table 31. Increase of Length, in Inches per 100 Feet, of Steam Pipes. Temperature Increase, Cast Iron Wrought Iron steel Brass and Copper Degrees i 50 1 0.36 0.40 0.38 0.57 100 0.72 0.79 0.76 1.14 125 0.88 0.97 0.92 1.40 150 1.10 1.21 1.15 1.75 175 1.28 1.41 1.34 2.04 200 1.50 1.65 1.57 2.38 225 1.70 1.87 1.78 2.70 250 1.90 2.09 1.99 3.02 275 2.15 2.36 2.26 3.42 300 2.35 2.58 2.47 3.74 325 2.60 2.86 2.73 4.13 350 2.80 3.08 2.94 4.45 375 3.15 3.46 3.31 5.01 400 3.30 3.63 3.46 5.24 425 3.68 L05 3.86 5.85 450 3.89 4.28 4.08 6.18 475 4.20 4.62 4.41 6.68 500 4.45 4.90 4.67 7.06 525 4.75 5.22 4.99 7.55 550 5.05 5.55 5.30 8.03 575 5.36 5.90 5.63 8.52 600 5.70 6.26 5.98 9.06 625 6.05 6.65 6.35 9.62 650 6.40 7.05 6.71 10.18 675 6.78 7.46 7.12 10.78 700 7.15 7.86 7.50 . 11.37 725 7.58 8.33 7.96 12.06 750 7.96 8.75 8.36 12.66 775 8.42 9.26 8.84 13.38 800 8.87 0.76 9.31 14.10 286 PIPING Approximate values for the linear expansion of steam pipes of cast iron, wrought iron, steel, brass and copper as given in Machinery's Handbook, will be found in Table 31. If the ends of a pipe were fixed and the pipe were heated, the tendency to expand would create a compressive stress. For the temperature changes common in power plants this stress would far exceed the compressive strength of the material. The axial force exerted by expanding or contracting pipe can be calculated as follows : P = C E A (h — t) (23) P z=z Axial force, pounds C = Coefficient linear expansion E = Modulus of elasticity A = Sectional area of pipe wall, sq. in. t = Initial temperature, deg. /j = Final temperature, deg. The moduh of elasticity of materials are as follows : Wrought iron 25,000,000 Steel 30,000,000 Cast iron 15,000,000 Copper 15,000,000 Brass 10,000,000 According to this formula, a 6-in. extra heavy wrought iron pipe 200 ft. long, if heated or cooled through a temperature range of 300 deg., exerts an axial force of 573,750 pounds. The sectional area of the metal of the pipe is 8.5 sq. in. so that the unit stress produced is much larger than the ultimate strength of the material. A temperature range of 300 deg. is by no means uncommon, so that for runs much shorter than the one assumed, piping must be free to expand or contract, and its expansion must be so controlled and directed that it will not strain connections, valves or fittings. Pipe Anchors THE expansion of piping cannot be limited, but its direction can be pre- determined by anchoring one end, both ends or the middle of a run. If one end is anchored, the expansion must be absorbed at the free end of the line. If both ends are anchored, the expansion will be from them toward the middle of the run and must be absorbed, preferably at some one place. With center anchorage the expansion is forced toward the free ends of the line, where it must be absorbed. Anchors must be firmly fastened to a rigid and heavy part of the power- plant structure, and must also be securely fastened to the pipe. If the pipe is not prevented from moving at the point at which the anchor is applied, the entire equipment for absorbing expansion is useless, and severe stresses will be thrown on all parts of the piping system. When both ends of a straight run are anchored with an expansion joint between, the end thrust is the steam pressure multiplied by the cross-sectional area of the pipe at its largest diameter. With sHp joints like Fig. 153, the area is that of the out- side diameter of the sleeve; and with corrugated joints as Fig. 154, or their equivalent, the largest inside diameter of the corrugations is to be taken. Thus, a 12-inch pipe with a slip-joint carrying steam at 250 lbs., will develop an end thrust of nearly 17 tons, and it may be greater than this with a corrugated joint. Expansion Joints "DlPE bends offer a satisfactory means of providing for expansion. The ■^ radius of a bend should not be less than five pipe diameters. The pipe should be straight on each end for a distance equal to twice its diameter. Pipe bends should be fitted with extra-heavy lapped or welded flanges, be- cause the joints are subjected to severe stresses. Expansion is absorbed by a bend only because it is sprung out of normal shape, thus permitting the line to expand. PIPING 287 Fig. 152. Typical Pipe Anchors. Table 32, due to the Crane Company, shows the linear expansion pos- sible with quarter bends. The expansion values can be multiplied by 2 for "U" bends, by 4 for single offset bends or "Expansion U" bends, and by 5 for double offset bends or circle bends. The values given do not take into consideration the springing of the bends when installing them. When a bend is sprung a distance equal to that in the table, twice the linear expansion given can be absorbed. Springing pipes when cold, so that they are then under tension, in- creases the linear expansion that can be cared for, and affords relief to lines used almost continuously at or near their maximum temperature. Table 32. Expansion (in Inches) Cared for by Quarter Bends. Size of Pipe, Inches MINIMUM RADIUS, IN. RADIUS OF BENDS, INCHES 20 30 40 50 60 70 80 90 100 110 Standard Pipe Extra Strong Pipe 120 214 10 12 14 7 8 10 3/8 Vs 5 T6 Vs 11 16 Vs 1 2M VA IH 3M 2M 2% 43^ 3^ 3M 5K 4^ 4^ 3 6 5K SH 4 16 18 20 12 14 15 'A 7 16 15 16 ii^ 1 -3- ^ 16 2^8 IK 23^ 2H 3% 3^ 3 4M 4K 3K 5M 5K 4^ 4H 5 53/i 6 7 26 30 34 20 24 28 y% 9 16 1 IK2 2 IK2 23/2 2M 2 3H 2K 2K 4 3K 3 4% 4K 3M 5K 8 4K 10 45 54 70 40 50 65 1 13/2 1^8 IK 2 IK IK 2K 2 3 2K 2K 3K 12 3 14 .... 2K Table Z2> gives data as to minimum allowable radius and length of tangent, useful in laying out expansion bends. The illustrations annexed to the table show different designs. Expansion joints are of two general types. Slip joints consist primarily of a brass sleeve, sliding in a stuffing box. They are made with and without a CO CO ^ .2 S "S 'C go; u- CN o c o '5 CO CO CO o PIPING 289 V a (L) -4-) 0) a OS O 0^ S u 3 2 .2 C a CO H :^ ^ CN -t 00 On l-H C^l 1 «S rn CN CN fO CO 00 ON O ■<-l CN 1 o c o o ^-H 1—1 00 00 00 1 ■«— 1 1-1 00 00 c o 00 O 00 CN 00 00 00 00 1— ( T-l ID 1— 1 O 00 00 t^ OO 00 O 1-H 1—1 tH 1—1 T— 1 c O to V0 1>- -^ 1—1 1-H o lOiO 1—1 •rH o ^—1 o lO o CN t^ C 1—1 1—1 On OO 1— 1 \0 Cn 1—1 c Tf 00 fO CN On ^O OO "in CO CN 00 ^ OO c CO CM \0 o CN CN t-^ vO l>- O to CN -H O to t^ CN CN 00 ^ 1—1 1—1 NO to NO re c T— 1 O CM ■r-l 1—1 to lO nC 1—1 T— 1 to to NO fC CN OO -+ to NO CN T. X. c 1— 1 "o ; 00 . '^ '. fii : a; • ^ ; C3 . c« . "> • -o • < : S : £ : 1 '^ ■»— 1 Size of Pipe Inches CD X u o HH 1— 1 c/2 CD O i, C C c T C c c c c: u - 22 ^ • 3 d. - "^ ^ r^ »S O CvJ i: c 4-1 c c3 C 0) :Q 4-1 1- 290 PIPING anchor bases, and with traverses up to about 10 inches. In the second ty^pe, expansion is cared for by the axial spring of a corrugated copper pipe. For high pressures, the copper is re-enforced by inner and outer iron equaliz- ing rings. Both t}'pes are useful when lack of space prevents the use of pipe bends. Fig. 153 illustrates the Ross expansion joint, showing the guide for maintaining the pipes in alignment. Fig. 153. Ross Crosshead Guided Expansion Joint. The piping between the anchors should be carefully lined up so that there will be no tendency for it to spring or buckle if the slip joint is too tightly packed. Bolts are necessary to prevent the sleeve being drawn out by such circumstances as the failure of an anchor. Fig. 154 is the Badger corrugated copper expansion joint, showing the reinforcing rings which lie in the corrugations and relieve the copper pipe of carrying the pressure. Fig. 154. Badger Self-Ekjualizing Expansion Joint. PIPING 291 The number of corrugations is dependent upon the amount of expansion to be absorbed. 2 corrugations take care of 1 in. expansion. 3 corrugations take care of 1>'2 in. expansion. 4 corrugations take care of 2 in. expansion. The advantage of this type of joint is that no packing is required. Double-swing fittings are satisfactory for small piping in short runs, but not for heavy pipes or long runs. For a really good expansion joint, the threads of the screwed connections should be carefully cut and then ground in. It is hardly to be expected that a screwed connection can be^ steam- tight, and at the same time permit easily any movement in fitting the pipe. Szvivel Joints are similar to the double-swing screwed fittings, without the disadvantage of the latter. They can be used for lines containing flanged fittings, or when pipe bends cannot be installed. (brt^ c^ Q^^dD^O JUL Fig. 155. Three Classes of Pipe Supports — Hangers, Standards, andBrackets. c (S a U u IS S •-* o — m ^1 ^ 3 Q PIPING 293 Flexible metallic iubiiig is excellent for absorbing expansion in small pipes. Care must be taken that it is not subjected to thrust or tension. It must be arranged in the same manner as Pipe bends just described. Supports and Hangers T)lPE supports and hangers vary of necessity with the plant layouts, but -^ their construction is fairly well standardized. Pipe supports, Fig. 155, can be divided roughly into three classes, — hangers, standards and brackets. Hangers are used for supporting piping from ceilings and overhead structural members ; standards for supporting piping on and from engine and boiler room floors ; and brackets for supporting piping on and from walls and vertical structural members. The plainer and lighter types of pipe hanger can be used for short runs, with steam or water lines up to about 6 in. diameter. On long runs they can be used if the connection between the hanger ring and the ceiling is long, and if its upper end is not rigidly attached to the ceiling. For large pipe, long runs or when the supporting strap must be short or rigid, the hanger should be equipped with one or more rollers. The support for high temperature lines should be equipped with a lower roller and also with a roller resting on the top of the pipe. The upper roller should be bolted by tie-rods to the support. Springs should be placed between the sup- port and the rods, so that the latter can move slightly. Supports for large or heavy mains should be adjustable to maintain alignment. Steam Separators I 'O protect plant equipment and obtain economical operation, all piping -'■ systems should be provided with separators to eliminate entrained mois- ture, condensate oil, grease or other foreign matter. Moisture carried into the steam cylinder lessens the economy in steam and lubricants, and may also cause damage. Oil in exhaust steam fouls the condensate, lodges in condensers, accumulates on turbine blades, and on the inner surfaces of radiators, and renders the condensate unsuitable for boiler feed. The function of a steam separator is to deliver clean, dry steam. Steam separators are used on live and superheated steam lines. The oil separator extracts the grease, leaving a condensate that is pure distilled water and therefore suitable for boiler feeding or for industrial processes. Oil separators are used on exhaust and vacuum steam lines, for low pressure turbines, feed water heaters, condensers and heating systems. Steam and oil separators operate either by intercepting the steam cur- rent, or by changing its direction. Cast iron bodies having various shaped grids in the form of single or multiple baffles are ordinarily used for separators. The accumulated matter is drawn off intermittently or is taken care of continuously by a trap. The separators. Figs. 156, 157 and 158, are practical designs intended for vertical, horizontal or angle pipe connection, A single, ribbed baffle has a steam port at each side ; below it is the collecting well with its water gage column. Steam entering from one end of the pipe line impinges on the baffle, where it leaves the water or oil, and continues on around either side of it, through the steam ports. The intercepted water or oil is directed, by the ribs' on the baffle, down to the well. A drain, to catch any con- densation, is also provided on the "dry" or steam outlet side. 294 PIPING Fig. 156. Horizontal and Vertical Steam Separators. m =] Fig. 15 7. Horizontal and Vertical Oil Separators. PIPING 295 The receiver type separators, Fig. 158, are usually made of plate and may have riveted or welded joints. This construction is used when long lines of piping might be subject to violent vibration. The large receiver serves as a reservoir for steam and is useful to supply the intermittent demand of a slow speed engine, and receives any inrush of water from the main. The water in the receiver is stored until a trap drains it away. The steady flow of steam resulting from the installation of a receiver separator often makes possible the use of smaller mains, which decrease the first cost, and reduce the loss of heat by radiation. Fig. 158. Horizontal and Vertical Receiver Separators. All separators should be selected on a basis of the steam supply required, and not by the size of the flange or pipe outlets. c 6 K T. ■"■ a: _ S -r 297 CHAPTER 9 AUXILIARIES Quantity of Feed Water THE quantity of feed water required per hour is the B.H.P. to be devel- oped, multiplied by 34.5, and divided by the factor of evaporation. To allows some margin, the division by the factor of evaporation is omitted. As there are 8.3 lb. of water to the gallon, the rate becomes 4.15 gallons per hour or 0,07 gal. per minute. This hgure, expressed as 7 g.p.m. per 100 E.H.P., is frequently used in determining pump sizes; but it is too small. Boilers are often run at considerable overloads for long periods. There- fore, the quantity of feed water required must be based on the probable B.H.P. to be developed, and not on the boiler rating. As the demand for feed water fluctuates with the load, the supply must be large enough to take care of peak loads. Pump makers allow from 7^ to 10 g.p.m. per 100 B.H.P. developed to take care of contingencies. The feed pump must not only overcom.e the steam pressure in the boiler, but must also develop a head sufficient to overcome pipe friction in the system, the resistance of the feed check valves, and some excess pressure besides. Therefore the feed pump must usually discharge at a pressure of 25 to 30 lb. in excess of the boiler pressure. Direct-Acting Steam Pumps TDUAIPS are divided into three general types: direct-acting steam pumps, ■^ centrifugal pumps, and positive displacement power-driven pumps. The popularity of the direct-acting steam pump as a boiler feeder is due in great part to the fact that it is the oldest and best known type. Often it is the only type of pump well understood by the operating engineer, and so represents the only good solution to the feed problem. For feed purposes the simple steam end is generally used. It is not so economical of steam as the compound or triple expansion steam end, but the latter cost so much more that only rarely are they selected. The greater number of parts with the complication and extra space are also against the compound and triple pumps. Tables 36 and Zl show the economies of steam-turbine-driven centrifugal pumps and the direct-acting steam pump. If the plant layout does not provide an excess of exhaust steam for feed heating, or other useful work, the exhaust steam from the pump can be thus used to increase the thermal efficiency of the plant. On the other hand, if the exhaust steam has to be wasted to the atmosphere, the economy of auxiliaries becomes important and the direct-acting feed pump is often displaced by a more efficient type. The pump that gives the average water horsepower for the least expenditure for coal is the one to be desired, therefore the great difference in the steam consumption of direct-acting pumps and centrifugals, in the larger sizes, eliminates the former from consideration. The centrifugal pump is not suited to the smaller capacities, so that the direct-acting steam pump finds one of its most useful fields in installations up to 2,000 boiler horsepower, in which a compact steam pump is desired. Its 298 AUXILIARIE S chief competitor in this capacity range is the motor-driven triplex pump, but owing to the lower cost and greater ease with which steam can be supplied, the steam pump is often preferred. Above 2000 boiler horsepower the cen- trifugal pump is usually favored. Direct-acting steam pumps can be classified as to the number of steam and water cylinders, that is, simplex or duplex, one steam and one water cylinder, or two of each side by side. Simplex pumps are often preferred for boiler feed service because the design always insures a full, complete stroke. When the pump cannot "short stroke," the piston rods, cylinder liners and plungers cannot wear down in the center, leaving a shoulder at each end. These shoulders may cause sticking of the pump or breakage of the cylinder or stuffing boxes due to the wedging effect of the "shouldered" portions, when the stroke is unex- pectedly long or full. Another advantage of the simplex pump is that it has only about half as many working parts as has a duplex pump. Consequently fewer parts wear out and fewer spare parts need to be carried. This applies particularly to the water valves. The simplex pump has but one water piston. Even if this is double act- ing, a steady and uniform flow of water from the pump is precluded. The steam valve-gear always reverses quickly at the end of the stroke, but there will still be some pause at this point. A break in the flow of the water results, sometimes developing a water hammer in the discharge lines. Sim- plex pumps should be equipped with a generous sized air chamber on the discharge line. The chamber must always be kept well filled with air to act as a cushion and to compensate for that absorbed by the water. Table 34. Ratings of Simplex Direct-Acting Steam Pumps. SIZE Single Strokes per Min. Double Strokes or R. P. M. Capacity, Gallons per Min. Boiler Hp. (34H lb. Water per Hr.) Piston Speed, Ft. per Min. 3x2x4 4^x33^x6 53^x31^x7 57 50 49 28.5 25 24.5 3 7.5 12.2 50 110 175 19 25 25 6x4x8 73^x5x10 9x6x12 48.6 48 42 24.3 21 300 24 40 580 21 j 61 870 32.5 40 42 10x7x12 14x8x12 42 21 42 21 84 109 1,220 42 1,570 42 Table 34 gives the usual commercial sizes of simplex pumps and their normal ratings for boiler feed service. Under the heading "size" the three figures indicate the diameter of the steam and water cylinders and the length of the stroke. The sizes and ratings are the average prevailing among sev- eral of the prominent pump manufacturers. Some pumps, by virtue of large valve areas and water passages, are rated for greater boiler horsepowers than others of the same dimensions. The factor of safety may differ, thus affecting the rating. The sizes given indicate the usual range for this type of pump. The simplex pump is most popular in the smaller sizes, as the pul- sating discharge effect is magnified in the larger sizes. The rated capacities, in Tables 34 and 35, are based upon a volumetric efficiency of from 85 to 90 per cent. The efficiency attained in the boiler room depends upon the care taken of the pumps, and probably will not ex- ceed 60 to 65 per cent. This is equivalent to realizing a capacity of about AUXILI ARTE S 299 70 per cent of the boiler horsepower given in Tables 34 and 35. The pump should then be of a size so that it can gain on the largest load likely to be carried, or so that the water level can be raised during a peak load if it has fallen too low, without racing the pump. When hot water is handled the piston speed is from one-half to one- third of what would be good practice for pumping cold water. This is to prevent vaporization of the water and keep the pump from becoming "steam bound." If the piston speed is too high, the water will not follow the piston or plunger during the suction stroke, and a partial vacuum is formed in the plunger chamber. When the plunger is reversed it travels quickly through the vacuous space created and meets the water with an impact suffi- cient to cause a serious knock. The pump then vibrates badly and the knock may even damage the water valves or other parts, as well as the pipe lines. The duplex pump (two water cylinders) discharges the water at a much more uniform rate of flow than the simplex type, as the steam valve gear of one side is actuated by the piston on the other side of the pump, and the steam valves are so designed that the two pistons are 90 deg. apart in the working cjxle. Generally both water pistons are moving. At the end of the stroke of one piston, during the slight pause, the other side is working, thus maintaining a more even water flow than is present in a simplex pump. In operating these pumps both sides should have a "full" stroke, or the cylin- ders or stuffing boxes may be broken through the shoulders formed when "short stroking." . Table 35 gives the prevailing sizes and ratings of duplex pumps. Table 35. Ratings of Duplex Direct- Acting Steam Pumps. EACH SIDE Capacity, Gal. per Min. Boiler H. P. (34 3^ lb. Water per Hr.) SIZE Single Strokes per Min. Double Strokes or R. P. M. Piston Speed, Ft. per Min. 3x2x3 43^x2^x4 5^x3^x5 72 36 57 ! 28.5 53 1 26.5 5.7 11.4 21.5 95 190 360 18 19 22 6x4x6 73^x5x6 73^x43^x10 50 50 49 25 25 24 32 50 65 535 840 1,080 25 25 40 9x534x10 10x6x10 10x7x10 48 48 48 24 24 24 87 116 156 1,450 1,940 2,600 40 40 40 12x7x12 12x81^x12 16xl0%xl2 42 42 42 21 21 21 164 243 370 2,750 4,050 6,200 42 42 42 Piston pumps, or those having water pistons operating inside the water cylinder, and packed to a good fit, are necessarily more subject to water slippage or leakage past the pistons than is the plunger type, in which the leakage is through a stuffing box to outside the pump. In the plunger type the packing in the stuffing box can easily be adjusted to care for any leakage that develops due to wear. In the piston type the adjustment of the pack- ing in the piston, if there is any, necessitates partly dismantling the pump. This is so troublesome as to be often neglected. The fact that the leakage cannot be easily detected renders this type unsuited to high pressure work, since the leakage increases with the pressure. s '^ ^ C (0 O 4J 4-. W n u o o o U Q c o tH ::^ O .Sm "5 ,5 CO u T3 as 5 " CO u a (/3 W 5 o CU CO w c ^ OS A U X T L I A R T E S 301 Although wear of the plunger can be easily detected, ihc plunger is easily scored from dust and grit. Also plunger pumps cost more than the piston t\-pe so that the}' are used principally for tlie higher pressures. Piston pumps are not used for water pressures over 150 to 200 pounds. The plunger type is preferred where the pressures are in excess of 150 pounds. Hot water has a corrosive effect upon iron, especially when it travels over the iron surface at velocities such as are present in a pump. It is well therefore to preserve the pump by making certain parts of brass or bronze. The water cylinder should have a brass liner, and the piston should be bronze or brass. The water valves can be of bronze or hard rubber, with bronze seats. The water piston, rod, or plunger, can be of iron or steel. Iron plungers are usually preferred, especially in the larger sizes, but unusual water conditions often dictate the use of bronze, even at a considerable in- crease in cost. The performance of simple direct-acting steam pumps can be calculated from the following formulas : I-LP.^^IL (24) 3960 ^ ^ d- G ^=^ (25) M.E.P.=/' (P—BF)=().7i) (P—BP) (26) M.E.P. d' Kl?) H =: Discharge head, feet H'=:Head, feet H" = Head, pounds G = Capacity, gal. per min., double acting pumps only, either simplex or duplex 5" = Piston speed of pump. ft. per min. (for one side only of duplex pump) d =z Diameter of plunger or water piston, inches D = Diameter steam cylinder, inches H.P. = Delivered or water horsepower k =z Constant =: 5 in. for simplex pumps = 3.55 for duplex pumps M.E.P. =z Mean effective pressure in steam cylinder P = Steam pressure at throttle, absolute BP:=: Back or exhaust pressure, absolute F =: Diagram factor = 0.70. Direct-acting pumps must be large enough to feed the boilers when operated at normal or slow speeds. A high speed direct-acting pump hand- ling hot water may ''knock" badly and cause damage to the discharge pipe lines. 302 AUXILIARIES Table 36. Steam Consumption — Simple Direct- Acting Steam Pumps. In pounds per water horsepower per hour. Stroke. Inches >teani Pressure at Pump, Pounds Gage 60 SO 90 100 110 120 130 140 150 4 230 210 204 200 195 190 188 187 186 6 200 170 165 162 158 , 156 154 153 152 8 160 145 142 139 1 137 1 135 134 133 132 10 140 130 126 122 120 ! 119 117 116 115 12 130 120 116 112 110 109 108 107 106 15 120 110 106 104 102 100 99 98 97 18 100 104 100 97 96 94 94 93 92 Table 36 gives the steam consumption of the simple pumps used for boiler sen'ice. Some designs will be more efiicient than others, so that the table will not apply to every simple direct-acting boiler feed pump. The values are for pumps in good condition, with a well lagged steam cylinder, receiving drj- saturated steam at the throttle, and exhausting to the atmos- phere. Centrifugal Pumps ^^^ENTRIFUGAL pumps are compact, practically noiseless, require small ^■^ foundations, and pump at practicalh' a uniform rate. They require little lubrication or adjustment of packing. Once started, they can be left without attention for a considerable time. These pumps are most in favor for the larger installations, in which the boiler capacity is 2000 horsepower or more. The running clearance inside the pump is small, at points where the water under discharge pressure is sep- arated from the suction side, so that slippage must be considered. Many ingenious devices are used to reduce this leakage and to ser\-e as a correc- tion when it does occur. The clearances cannot be reduced enough to elimi- nate slippage, so that the capacity and hence the loss in small pumps is proportionately greater than in the larger ones. The larger sizes therefore give the best results. Centrifugal feed pumps are usually of the multi-stage t\-pe, each stage doing its proportionate part of the work of increasing the water pressure. The maximum pressures are from 60 to 100 lb. per stage. Thus a 250-lb. discharge pressure would mean a three-stage pump. The water is received by the first-stage impeller, which picks it up and imparts to it a velocity head. This velocity is reduced, either in a channel of gradualh" increasing area, or in a diffusion ring having vanes and passages, while the water is conducted to the impeller of the next stage. The head developed depends upon the velocity- imparted to the water, and will therefore be governed by the peripheral velocity- of the impeller. Thus for a given head there can be used either a large diameter impeller with a slow rotative speed or a smaller diameter and proportionately in- creased R.P.M., to give the same rim speed. As the diameter of the ira- AUXILIARIES 303 peller governs the diameter of the pump it is desirable to have high speeds, with smaller impellers, to reduce the cost and the space required. For ordinary, or small changes, the capacity of a centrifugal pump varies directly as the speed, and the head as the square of the speed. This applies particularly for maximum efficiency at the different heads. The operating characteristics of a well designed feed pump are shown in Fig, 159. The curves are laid out so that heads, capacities and speeds are expressed in percentages. Thus if 500 g.p.m. is the normal capacity it will be shown as 100 per cent on the capacity scale ; 250 g.p.m. will be given as 50 per cent ; and 625 g.p.m. as 125 per cent of normal. 80 >- ) 10 20 30 Fig, 159. Operating Characteristics of Centrifugal Pumps. 40 50. 60 10 &0 90 100 110 120 130 140 150 160 Percent of Capacity at Maximum Efficiency Point The heavy lines show the head, capacity and characteristics for normal speed operation and the lighter lines the performance at fractional speeds. As boiler feeding takes place practically at constant pressure a change in capacity must be met by a change in speed or by throttling. Hence the head can be considered as fixed, and can be indicated as 100 per cent or the Line "A." The head-capacity lines for different speeds cut the line "A" at points indicating the percentage or normal speed for the capacities at this head. The brake horsepower capacity lines will then show the percentage of normal horsepower for different speeds. Maximum efficiency lines give the actual pump efficiency for any head and capacity. These also are based upon percentages. As an example, take a pump designed for 400 g.p.m., 200 lb. pressure, 2600 r.p.m., 62 per cent efficiency, and 75 brake horsepower required for driving. All these are represented by 100 per cent on the curve. Suppose it is desired to find the other conditions for a capacity of 300 g.p.m. Then say — Capacity = 300 g,p.m. /^given) = 75 per cent of normal Head = 200 lb. =: 100 per cent of normal (no change) Speed == 96 per cent of normal (from curve) =: 2500 r.p.m. Efficiency = 96 per cent of normal (from curve) = 58.5 per cent Brake horsepower = 80 per cent of normal (from curve) = 60 brake horsepower. Kimball Building, Chicago. 111., equipped with Heine Standard Boilers. AUXILIARIES 305 Fig. 159 shows the relations upon which depend the regulation of the pump to meet varying demands. The head-capacity curves give the best information as to the operation of centrifugal pumps. The efficiency curve should be flat, so that the efficiency is high over a wide capacity, thus main- taining good economy under speed regulation. The horsepower curve should rise to a maximum at the normal operating capacity and then fall off so that no overload vi^ill be thrown on the driver should the pressure be reduced. This is particularly important in motor driven pumps, since overloads can be serious. Table Z1 gives capacities and steam consumption for different sizes of centrifugal feed pumps. The calculation of capacity is explained elsewhere. Table 3 7. Performance of Three Stage Centrifugal Feed Pumps. (150 Lb. Steam Pressure — 175 Lb. Water Pressure — 13 5 Ft. Per Stage) Size, Inches R. P. M. G. P. M. B.H.P.* Pump Effic. Per cent H.P. Req. Turbine Water Rate, Lb. per Brake H.P per Hr. Steam, Lb. per Water H.P. per Hr. 3 4 5 2,500 to 3.000 2,600 to 3,000 2,200 to 2,730 300 500 750 4,000 6,700 10,000 56 64 67 53 78 110 140 210 42 42 42 39 38 75 66 63 6 8 1,500 to 2,000 1,500 to 2,000 1,000 1,500 13,200 20,000 70 71 56 54 * 0.075 gal. per B.H.P. used to provide a factor of safety. The turbine water rates represent commercial averages. The column at the right (steam per water H.P. per hour) is given so that the performance can be compared directly with that of direct-acting steam pumps. Performance data, due to /. Brcslav, are given in Table 38 for a boiler feed pump and for a compouna duplex direct-acting steam pump. Both pumps were designed for 250 g.p.m. and were operated nine hours a day at 160 lb. steam pressure and 2 lb. l^ack pressure. Table 38. Operating Cost Comparison of Boiler Feed Pumps. Turbo Comp. Centrifugal Duplex First cost $1,008 $980 Valves to be watched 14-18 Packing boxes 4 18 Oil used in 15 days, pints .A.bout 4 30 Grease, pounds 4 Maintenance, packing, etc.. per year $30 $120 Steam consumption, pounds per boiler horsepower per hour 38-40 40-55 A simple duplex steam pump would have cost here about $600 but the steam consumption would then be about ICX) lb. per B.H.P. per hour. The comparison shows that the compound steam end type of a direct-acting pump is required, if the economy of the turbine driven centrifugal pump is to be obtained. The direct-acting pump is more complicated however, and the maintenance and lubrication charges are much greater. The leading advantages of centrifugal pumps are compactness, silent running, durability and superior economy in cost of power, attendance and repairs, and the facility with which they may be adapted to any location 306 AUXILIARIES where they may be supplied with power by direct connection to an electric motor or steam turbine. As boiler feeders, they have the advantage over reciprocating pumps of continuous delivery without shock or hammering, and of producing no excessive pressure on feed mains for any adjustment of feed stop valves or other stoppage of pipe connections. The commercial forms of centrifugal pumps are usually of the multi- stage tv-pe, either with or without diffusion rings. Fig. 160. De Laval Turbine Driven Centrifugal Boiler Feeder. Fig. 160 shows a pump without diffusers. The water after being picked up by the impeller of one stage is discharged to the next stage through a return channel cast as a part of the pump casing. This channel is designed so as to reduce gradually the velocity- of the water leaving the impeller and trans- form this velocity' to pressure head. The advantages of this type of pump are said to be simplicity of construction and the absence of small water pas- sages that might become blocked by foreign matter. A single stage direct turbine-driven centrifugal feed pump has attained some favor in Europe and is also beginning to be recognized in this countrj-. This has a pump impeller and turbine wheel mounted on one short shaft. The pump and turbine housings are close to each other and as the machine runs at a high speed, 5C00 to 8000 r.p.m., it is a compact unit. These pumps are designed to produce sufficient pressure to feed any usual boiler, and can operate against a pressure of 250 lb. or greater. Owing to the high speed, this pump is not accepted for general boiler feed use in this country, in spite of its low cost and the small space required. When the water is fed through an economizer to the boiler a four-stage pump can be arranged so that one stage pumps to the economizer and through it lo the main feed pump, which has three stages and discharges into the boiler. Sometimes the pumping unit is made up of two separate pumps, each with its own driver; but two pumps on one base, and driven by one prime mover, are to be preferred. Thus each pump always works in harmonj- with the other. The two pumps can be arranged, with the econo- mizer stage uncoupled or by-passed, to feed directly to the boilers. These economizer sets are particularly well adapted to plants in which it is de- sired to decrease the water pressure in the economizer tubes, because the pressure in the economizer is usually one quarter of that with the ordinary feed pump. A U X T L T A R T 1^: S 307 Fig. 160a shows a multi-stage high-pressure centrifugal pump used for boiler feeding. It is really a volute pump so arranged that the volute of one stage is led into the suction of the next stage, and the high pressure is attained by putting in series as many stages as necessary. It is claimed that the advantage of the volute, besides the simplicity, is that the efficiency is maintained for a greater range than with the diffusion vane type of pump ; also the cost of the diffusion vanes, which are subject to wear, is eliminated. The force on the horizontal split of the case, due to the high pressure of the water, is taken care of by the bolts on the outside flange, and by through bolts nearer the center line. The hydraulic balancing mechanism, which per- forms the functions of a thrust bearing, is so arranged that both stuffing boxes are under a low pressure and sealed with water. Every part of the pump, except the case and shaft, is made of bronze. The two ring-oiled bearings are equipped with large oil reservoirs. Turbine-driven centrifugal boiler feed pumps have many advantages in addition to their compactness and reliability. Fig. 160a. Lea-Courtenay Multi-stage High-pressure Centrifugal Pump for Boiler Feeding. They give reliable and uninterrupted service with little, and often un- skilled, attention. There is an entire absence of pulsation, shock, vibration or over-pressure in pipe lines, thus making relief valves unnecessary and rendering the pump suitable for use with automatic boiler feed regulators acting inde- pendently at each boiler, or with feed-water meters. The cost of maintaining the piping system is reduced, because less strain is thrown upon it. Close governing is obtained, either at constant speed or at constant excess pressure. There is entire freedom from liability to injury by overloading. Troublesome parts, such as valves, packings, sliding surfaces, air chamber, etc., are eliminated. There is little expense for attendance and upkeep, due to the simplicity and few wearing parts. All parts are easily accessible. Cylinder lubricants are not required and little oil of any kind. The steam consumption is lower than that of direct-acting pumps, and superheated steam or low pressure steam can be used. The exhaust is entirely free of oil and can be used in open feed heaters, or introduced into an intermediate stage of the main turbine without danger of introducing oil into the boilers. 308 3 N > C OS u o V C V o U B 3 «> "o u as O o OS c CS CO .2 *S M » AUXILIARIES 309 Direct-Acting Power Pumps DIRECT-ACTING power pumps are rarely used for boiler feeding. These positive displacement pumps are selected usually where the available sources of motive power prevent the use of the direct-acting steam pump. These pumps are reliable, their maintenance cost is low and in small capacities their efficiency usually higher (lower brake horsepower required) than centrifugal pumps. In the larger sizes, 3000 boiler horsepower and over, they become ex- pensive and the centrifugal pump is more generally used. The triplex plunger pump gives a steady flow of water, the cost of power is less than the centrifugal pump when applied to boiler feeding, it can be automatically regulated, it is reliable and if given intelligent attention it will maintain its high efficiency for 15 to 20 years with, no cost for repairs ex- cept for packing and valves. The high efficiency of the triplex pump is attained not merely at its rated capacity, but is nearly constant throughout the full range of operation provided its capacity is regulated by changing the speed. The average effi- ciency is therefore greater than a mere comparison of catalog percentages would indicate. The triplex pump has a practically constant efficiency at different speeds. The capacity is proportional to the speed. The discharge head does not have to be throttled to regulate its capacity. The efficiency of the variable- speed direct-current motors used to drive triplex pumps is more nearly constant at variable load and speed than the efficiency of constant-speed motors is at the variable load used to drive centrifugal pumps. Small re- ciprocating engines have much better efficiencies at variable speeds than small turbines at variable loads. Comparing two types of boiler-feeding units, one a motor-driven cen- trifugal pump and the other a motor-driven triplex pump, taking into con- sideration the daily load curve of the plant and the efficiency curves of the two pumps, together with the efficiency curves of the two motors, it was found that the actual coal required by the triplex pump would be less than one-half that required by the centrifugal. A similar comparison covering steam driven units would show even greater difference in favor of the triplex pump. Against these advantages are, more space required, higher first cost, more complicated apparatus and more attendance. With stokers of the forced-draft type, states /. C. Hazvkins, the engine that drives the fan can be used to drive the triplex pump also. The feed pump is then operated at a speed in proportion to the amount of steam used and needs little other regulation. If automatic feed-water regulators are used a relief valve set at about 30 lb. in excess of the boiler pressure must be placed in the discharge line (probably by-passed back to the suction) to prevent overpressure. The triplex pump is simple, gives a nearly constant flow of water, and at all speeds has about equal efficiency, ranging from 70 to 85 per cent. The first cost of a pump and motor, however, is higher than that of a duplex pump. Methods of Driving Pumps \A OTORS are selected primarily because of plant conditions limiting the *-^'' use of steam from auxiliaries. Because of the difficulty of regulating its speed to meet the varying capacity demands the electric motor is not selected when steam power is permissible. If any of the power plant auxiliaries are steam-actuated, the boiler feed pump should be one. The alternating current motor must be run at constant speed, and the direct cur- rent machines equipped with complicated control devices if the speed is to be varied considerably. This speed variation is essential in feed pumps. 310 A r X : L : A R T ^ 5 For alternating current, the squirrel-cage induction motor is used. The starting current is high, hut a feed pump continues in operation for a considerable time, herce tre gre^T =:s.r::rr rirrtr.: lies not justify the use of a slip-ring motcr. On direct-cur -r": 5er-^::e i :::;:: i-l ::r ? usti T't series- wound is un5at:;:i:::r7 itri.Sf i: ..is i i :: f . :i .5 5. iir .y tiken o^ as when the Z-'-'-'-Z t; ::: rs 1; :r :: .: 1 : r ^: iii i 5 .::::::; Z'.\z shunt wound motor is Yaiiiaclr ::r r.iT 5tr its r. i:::.::.: :: ::5 : :r .:i: :-5: ee: characteristic. The co— ; . : 1- : . ii :.;::: ijtrii u: .ir.irr Asft.ei lii but not to E iir.reriu: ex:en:; it will slow down if overlziiei and thus furnish relief. Steam r. r::: e^ ire used principally with centrifugal pumps, as the high 5;eef: ;_55i A :.. :. is ;inip are n:e: ~i::: i e: : :r. of cost and floor 5;i:e. T.r les ire :.e:?ii^-!::!ica! £.: i: s:ee^r -A -600 r.pjn,>. The V i:tr r.:e.- :: Ae sreiri rrir.t :.:\i : e direct-acting purr, r are ::.:::- i Tr.e r.:r;Ae : = r :e rer.:'ated closely :: ~ee: - ir: A^ ^:— er le— ands. 1:5 srei in be chs-.-irei eiAer manually or au:::.:i:icallv, by thrirr'irr the rr.-.ee. ir. 1 rrrri r.-irir siioiU'_ _e :r. :r.e s.'.i::, ;r 1 ..erii-ic coupuny suouiQ Stea::: erri-es r :: 1: s : r r ::i:: e fite: A '1 to 600 r.pjn,; this is tee .:\v Ar lire:: 1 t : :t: r^^ii : :::: s :::: are too large and costly when dn • e:: a: T: fits ^Ti:-ir: e ::r irr.:: : ral pumps is not desired, as the 'e'.: is A is 1 s ir:t :i riiAe 11 re t 1' expense. Steam engines are si s:e:: .7 :: :ir si it sitti r^^iA: ::: res, and Automatic Regulation of Pumps T limp consists of riie ireiiure regn- r : : - trol device at the boilers. en punq) discharge pressure by 11; eing reduced so that with a sire 111 me feed- water lines is not boilers. In steam-acmaied pumps, uae pressiire regulator consists of a balanced valve, placed in the steam Ime to the pump, near the punq> valve chest. The balanced valve construction is used to render operation easier and prevent sticking. The cylinder of a piston on the throttle-valve stem conmonnicates with the feed-water hue so Uiat its pressure acts against the piston. When this pressure is increased, the stem is depressed, closing the v^e and throt- tling the steam to the prime mover so that the speed is reduced. A spring or loaded lever on the valve stem opposes the action of the piston, thus balancing the water force. The spring can be adjusted to maint aiii any desired pressure in the water lines. A diaphragm can be used instead of the piston and water cylinder for sio^lidty and to reduce the cost. The so-called constant excess-pressure regulator has the ;i~e ee e :? as a constant pressure regulating valve. The discharge v i:e- ;-is -f however, acts on one side of the piston or diaphragm and thr s e 11 pressure on the other. The spring or loaded lever is adjusir difference between boiler and water pressure is maintained ccrs:ir.: iz ex:e5= pressure is just sufficient to force the feed water ir.:: the boiler. AUXILI ARIE S 311 This regulator is used with widely varying steam pressures to prevent the pump from discharging against too great a head when the steam pres- sure in the boilers is low. With a constant pressure governor, the water pressure must be sufficiently high to feed the boiler under maximum steam pressure. When the boiler pressure drops, the water pressure will be much greater than actually required, and the pump will be consuming more steam than necessary. Positive displacement power pumps are regulated either by varying the speed of the prime mover, or by a by-pass control, which opens the discharge from the pump to the suction, allowing the water to circulate through the pump. A check valve prevents the water in the discharge line from flowing back into the pump. ("e-'/Po^^ ^'-Gu/c/e Wheel ,^ -Valve Sfew 5 'A" Long Old Valve ' Bonne-t ^. WBolf Toip <%^^,^^;; , , 1/4 "Pipe Tap ' It": VaWoles "r-l'/a" Close wifh To Service Wafer Pressure- Fig. 161, Details of a Motor-Driven Pump Regulator. SzcV\on A-A These machines are usually belted to a constant speed source of power, or are motor-driven ; the speed of the driver can be varied only when it is a direct-current or wound-rotor motor, and even then the control apparatus is likely to be unduly complicated. The essential elements of a constant excess-pressure governor for a wound rotor motor-driven feed pump are described by C. H. Sonntag as follows: The regulator, Fig. 161, works on the follow-up motion principle, such as is used on steam steering engines. The base casting is made from u o go, Co 3 O !/l O a o ::: a c a cQ a -Ho C C ^> •2 ^ = 2 Oh ^ ^K AUXILIARIES 313 an old motor rail. The diaphragm chamber and parts below it are from a V/i-'m. constant excess-pressure steam-pump governor. The motor used is of the wound-rotor type, and the three brush holders of the regulators, being in metallic contact with their supporting arm, short-circuit more or less of the resistance in the rotor circuit, according to their position on the face of the contact panel. The subdivisions of the rotor resistance are equal in the three phases, but corresponding sections of this resistance in the three phases are shunted successively instead of at the same time. This gives three times as many subdivisions of speed as there are contacts on the panel, and the result is smooth acceleration, with a speed for almost any rate of feed. The regulator does not open the primary circuit of the motor, nor stop it, but it will bring the motor down to a low speed. The pump is fitted with a spring-loaded relief valve set above the working pressure, which acts as a safety device when the discharge line is absolutely stopped. The panel is so connected to the resistance that the lowest position of the brushes shunts all the resistance. To start the pump and regulator, the valves leading to the upper and lower diaphragm surfaces are opened, also the one supplying service-water pressure to the follow-up. The drip valve should be open enough to let the plunger and the brush rigging down slowly when the follow-up valve is closed. The follow-up valve is then held open by raising the upper lever until the brushes are at the top of the panel and the primary switch is closed, when the motor will start slowly. The follow-up valve is released and the motor will accelerate up to the desired excess pressure. This is determined by the position of the 7-lb. weight on the lever arm, 15 lb. being about right for boiler feeding. When the plant is small and steaming is steady, the pumps are started and run until there is a good level of water in the gage glass. The pump is stopped when the level begins to rise too high, and started again when the glass begins to show that the water level is below normal. Centrifugal motor-driven pumps can be operated either with the by-pass or with the control described for the power pump. The capacity of centrifugal pumps drops off with an increase in head pressure ; consequently the pump speed tends to be regulated automatically, and pressures cannot become dan- gerous. This characteristic is not so pronounced that a centrifugal pump is independent of regulating devices. The control is usually of the by-pass type, consisting of a safety valve which under a predetermined pressure opens up and allows the discharge to flow back to the suction. This pressure is above normal, but is lower than the shut-off or zero capacity head of the pump. In steam-actuated pumps the control is simpler, since the speed can easily be changed by throttling the steam supply. With this method, power is not wasted by circulating water through the pump, and the pump is not constantly being stopped and started again. The supply is throttled by utilizing the rise and fall of water in the boilers, hot well, or open heater. Feed Water Regulators ' I 'HE feed-regulator throttle-valve in the feed lines is controlled by the ^ water level in the boiler steam-drum or in the hot well. The hot well level is used principally in marine service, and calls for operation on a closed circuit. The amount of water (in the form of liquid or steam) must be correct, therefore, in the entire system, — water lines, steam lines, and boiler. Regulators governed by the water level in the steam drum are of the continuous-feed type, in which the feed water flows at all times and the rate 314 AUXILIARIES of flow 15 regulated in accordance with the water level in the drum; or they are of the intermittent-feed type, and the water is fed or not fed, as the level falls below or exceeds a predetermined point in the steam drum. The continuous-feed regulator is designed to give even steaming and close regulation with slight danger of the water level dropping to a dan- gerous point. The water in the drum is not cooled off suddenly by the addition of large quantities of water, but feeding is continuous so that steam can be generated uniformh^ and most economically. One intermittent-feed regulator contains a vertical expansion pipe, the top of which is connected with the steam drum at the normal water level: the bottom of this pipe is connected with the steam drum below the normal water level. As the water level in the drmn falls, it also falls in the expansion pipe. Steam is then admitted to the pipe, thus increasing its temperature, since tlie water in the pipe is cooler than the steam. This increase in tem- perature expands the pipe and causes a motion that is transmitted to the feed- water valve-stem. The valve is thus opened and more water admitted. When water rises in the steam drum, the level also rises in the expansion pipe. The temperature of the expansion pipe is reduced, and the pipe contracts, closing the feed valve. Fig. 162 shows the design of this intermittent regu- lator. I ^Steam Connecfion tiorrr,al\ Wafer Level Fig. 162. Copes' Feed Water Regulator. In another t}-pe of intermittent regulator, a rise of water in the steam drum or water column above the normal is followed by the overflow of the water into a trap, thus opening it. Steam is then admitted to the pressure chamber of the feed valve, which is promptly closed. When the water level falls below the normal, the trap automatically closes. The pressure chamber of the feed valve exhausts into the hot well. Feed regulators of the continuous t>'pe take into account the rise and fall of water in the gage glass, due not only to the quantitj- in the drum, but also to the change in density of the water in the steam drum. When the boiler load is increased suddenly, steam is generated more rapidh- and the steam pressure drops. More steam bubbles will rise through the water in the drum, thus decreasing the density- of this water. The density in the gage glass remains unchanged. Hence the level in the gage glass rises more slowlv than does the water level in the drum, until the increased rate of AUXILI ARIE S 315 steam generation causes it to fall. The water level in the gage glass then falls, and the rate of feeding is increased in response, to maintain an even level in the glass. When the load falls off suddenly, the steam pressure is increased ; this is followed by a less rapid generation of steam and a reduction in the amount of steam bubbles rising through the water space. The density of the water in the drum is increased, while as before, the water level in the gage glass falls more slowly than does that of the level in the drum. When the evaporation is less rapid, the water level in both the steam drum and gage glass is ultimately raised; and the rate of feeding is reduced. Consequently rise and fall due to density changes and changes in level due to variation in the rate of evaporation, do not occur simultaneously. This lagging action is used in some continuous-feed regulators, which provide a strong feed during the decreasing load and lessen the feed rate in proportion to the evaporation rate when the load is increasing rapidly. Under decreasing load the furnace heat is thus stored, and is not wasted or discharged to the flues. When the load is increasing, the rate of feed is not increased greatly but Is kept as low as is consistent with safety. The furnace can then be used to generate steam instead of to heat large quantities of feed water. Fig. 163. Continuous Regulator of Float Type. In still another type. Fig. 163, a float normally rests upon the water in a chamber installed at the level of the water in the boiler drums. The rising and falling of the float is communicated to the throttle valve and thus regu- lates the feed continuously. The float can be partly filled with a volatile liquid, which expands because of the temperature changes in the float cham- ber. This expansion tends to equalize the external pressure on the float, due to the steam. The feed control valves used with the float are placed inside the regulating chamber, so that there are no outside stuffing boxes to be packed. o c M C 'C •a t> a o. o as c c 'o c O o c CO CO g CO 02 •d o o a A U X T T, T A R T R S 317 Location of Feed Pumps FOR cold water service, that is, water at 60 to 70 cleg., feed pumps give satisfaction with a suction lift as high as 15 feet. Generally, however, the suction lift of the feed pump is decreased by the temperature of the water. The atmospheric pressure which is equivalent to a head of 34 feet of water, forces the water into the pump. In practice, deductions must be made for the loss of head at the pipe entrance, pipe friction, valve friction, acceleration of water to its highest velocity, and pressure necessary to pre- vent vaporization of hot water. For example : Entrance loss, say - 2.0 feet Suction pipe friction 2 5 feet Acceleration, or velocity head 2.0 feet Pressure to prevent vaporization at 120°.... 3.9 feet Assumed lift 15.0 feet 25.4 feet Available head for lifting suction valves and as a factor of safety for contin- gencies 8.6 feet Total 34.0 feet The velocity head of 2 ft. is a typical figure for a centrifugal pump, in which the water velocity through the eye of the impeller will be about 12 ft. per second. Fig. 164 shows curves of suction lift or suction head for different water temperatures. The right-hand curve represents theoretical conditions as in the steam tables, or the pressure to prevent vaporization of the water. The curve in the middle represents the maximum suction lift or maximum suction head. For ordinary piping, the left-hand curve should be used. 200 Sl80 «> L. 1*160 «) ^140 c a E f^lOO 80 60 \ ^--., •C^eo. ^. \ \ X-o. \ \ \ >^ ^t \ \ \ 1 1 20 10 -0 Suction Pressure .Feet 20 30 Suction Lift, Feet 4-0 Fig. 164. Suction Lift or Suction Head at Different Temperatures. If the capacity is too high for a pump or suction pipe handling hot water the velocity head will be increased and the water handled will be vaporized. If the suction pressure is too low, or the lift is too high, the hot water will be vaporized. Vaporization causes knocking in the dis- charge lines and greatly reduces the capacity and efficiency of a direct-acting pump. The capacity will also be decreased with centrifugal pumps, since the water passages will be filled partly with vapor and partly with water. The effect of temperature on capacit}^ is shown by a test of a centrifugal boiler feed pump, due to John Howard. This was a 3-in. three-stage pump, designed for 150 gal. per min. against 195 lb. pressure, and was driven at 3000 r.p.m. by a steam turbine. The water was measured by a flow meter, which was afterward calibrated and found correct. 318 AUXILIARIES The capacity test (see Fig. 165 > gave the results for a constaiit head and for constant speed. The first cur\-e was obtained by the use of a pump governor, and the second when the govern ;r is cut out, the capacity being varied bv throttlinsr the discharg^e. 250. ,3100 ^^v,^ ^ - - "\.^ 1 • 1 ^^-. y^ 1 230 ^Sre f- . ^^^ ^vf^ . ->^ ! ! J^^^^"^ ^^.^-^ \ -"-^^ \ pr\/\ - \ i \ l = " \ c: 30005 in oj 2900-^ -»- _c o 2800.? ■¥• C Z700 o > « esoo 40 !60 -z Fig. 165. Capacity Test for Hot Feed Water at Constant Speed and Constant Head. In making the :er.:pera:ure-capacir>- test t,Fig. 165) the temperature of the water in the open heater from which the pump took its suction was varied by controlling the amount of steam passing into it. The great varia- tion was undoubtedly- due to the extremely smaU head (only about 30 in. above the center-line) on the suction side of the pmnp. Because of this small head, the guarantee was only for 180 deg., but by speeding up the pump water at 190 deg. could be safely handled. The suction lift should be kept low or the suction pressure high in ac- cordance with Fig. 164. The suction pipe should be as direct as possible with no imnecessary elbows or valves. The suction piping should be of generous size; a velocity- of 2 ft per second should not be exceeded for hot water. Suction pipes should be accessible for inspection and arranged so that valve spindles can be repacked easih-. Particular care should be taken to avoid leaks in the suction pipe. These do not show directly on the dis- charge side, although they are sometimes indicated by a ""jump"' of the pump at the start of everj- stroke. With long lines or deep lifts, the line and ptunp can be kept "primed" by a check or foot valve at the bottom. With long suction lines, more par- ticularly with single CA'linder pumps, an air vessel should be fitted on the line, to prevent knocking. AUXILI ARTE S 319 Injectors as Boiler Feeders INJECTORS are made in many forms, but Fig. 166 shows the typical ar- rangement and illustrates the method of operation. Steam is admitted through the valve M, by turning the handle K, and enters the expanding nozzles where the pressure is reduced and the velocity greatly increased. The steam jet is then guided to the contracting nozzle or lifting tube V. In passing from the first to the second nozzle it carries along the air in the chamber and creates a vacuum. The water to be pumped rises in the suc- tion pipe and fills the chamber. The steam and water thus enter the lifting tube, passing to the mixing nozzle C, and the steam is condensed. When the water and steam have reached the delivery nozzle D the steam has been condensed and the water is traveling at a high velocity imparted to it by the steam. The delivery nozzle is increased in cross-sectional area, reduc- ing the velocity and hence increasing the pressure of the water. Conse- quently its head is sufficient to overcome the resistance of the feed valve, and the water enters the boiler. The steam has thus imparted kinetic energy to the water ; this energy is converted from velocity to pressure in the de- livery nozzle. The water is heated through the condensation of the steam. The action of the injector depends not only upon the impact of the jet of steam, but also upon its efficient and complete condensation, which must occur during its passage through the combining tube. At 180 lb. boiler pres- sure the water must attain a terminal velocity of 163 ft. per sec. to balance the pressure, and something more to lift the check valve and enter the boiler. If the total length of the converging combining tube is 7^ in., the interval of time during which the steam can be condensed is only 0.008 of a second and the acceleration is 4 miles per second per second. Anything that tends to diminish rapid condensation operates against mechanical efficiency. An increase in the temperature of the water supply, moisture or superheat in the steam ; all tend to reduce the proper ratio be- tween the weight of the water delivered into the boiler and that of the motive steam. The steam must undergo instant and complete condensation, and its velocity must reach a maximum at the instant of impact with the water. -K i/'5team Fijg. 166. A Boiler Feed Injector. Lytton Building, Chicago, 111., containing 1500 H. P. of Heine Standard Boilers. A U X I L I A R I 1^: S 321 Experiments with saturated steam prove that the flow is in accord with the well-known formula based upon adiabatic expansion. The velocity of superheated steam is slightly higher as it follows the law of a perfect gas until condensation due to expansion begins; the velocity of the combined jet would consequently be increased, but this advantage is overbalanced by the shorter interval of contact and condensation, during which the additional heat in the steam must be abstracted. Consequently the mechanical efficiency is lowered. To obtain good results with superheated steam, the injector tubes and nozzles must be specially designed. The practical effect of superheated steam upon the action of an injector is to reduce the maximum capacity, increase the minimum capacity, and to lower the limiting temperature of the water supply with which the injector can operate. Further, with high pressure and superheat, an inefficiently de- signed instrument is inoperative. It is therefore advantageous and usually practicable to supply the injector with saturated steam through a special pipe. The steam pressure range over which an injector will work depends upon the distance between the steam nozzle and the lifting tube. With a fixed dis- tance between these two points the injector will operate only with a pressure range of about 75 pounds. If the injector is designed for 175 lb. maximum pressure the minimum steam pressure under which it will operate will be 100 pounds. After the maximum and minimum pressures are passed the ratio of steam velocity to quantity of water for complete condensation of the steam is not correct. The injector can be operated only by throttling or opening its suction line, or by varying the distance between the steam and lifting nozzles. Commercial devices are supplied to render the injector operative over a wider steam pressure range. In one type a half turn of the valve handle allows the nozzle to remain in one position so that the pressure range is 90 or 100 lb. maximum. A full turn of the handle changes the position of the nozzle, giving a higher range of steam pressures, 100 or 175 pounds. The action of this type is indicated in Table 39. Table 39. Steam Pressures at Lifting Nozzles of Injectors. Lift, Feed Water at 72 Deg. Feed Water at 100 Deg. Start Works up to Start 1 j Works Up to 1 Not lifting 1 20 160 25 150 30 130 25 26 33 125 2 8 i 120 i 100 14 20 42 80 110 85 55 80 Another injector has a double set of nozzles; the first lifts the water and delivers it to the second, which acts as a forcing nozzle to deliver the water to the boiler. The capacity of this type can be changed by varying the amount of steam admitted to the lifting nozzle. The quantity of water varies directly with the steam pressure at the lifting nozzle ; this reduction in water is desired for the proper functioning of the forcing nozzle. Any change in steam pressure or in quantity of water to condense the steam thus affects both nozzles, so that pressure changes require no hand adjustment. This type has operating characteristics as indicated in Table 40. 322 AUXILIARIES Table 40. Steam Pressures at Lifting Nozzles of Injector. Lift, Feet Feed Water Temperature 72 Deg. 100 Deg. 120 Deg. 140 Deg. Start Up to Start Up to I Start j Up to Start Up to Not lifting 25 25 35 350 300 270 25 30 40 265 265 235 35 35 45 230 230 205 35 140 2 8 45 110 14 20 45 65 240 185 50 70 210 155 55 65 140 120 Another type, commonly called an inspirator, Fig. 167, has two nozzles, but the steam pressure cannot be adjusted at the lifting nozzle. The lifting and forcing nozzles receive steam from separate openings, so that the steam pressures can be adjusted separately through valves in the steam lines. ^Si-eam Wafer- Fig. 167. An Inspirator Type Injector. In all injectors a check valve is placed in the mixing chamber, with openings into the mixing nozzle, so that in starting, before water is drawn into the mixing tube to condense the steam, the mixture of steam and air can escape to the atmosphere. When the steam is condensed a partial vacuum is formed in this chamber and the check valve automatically closes, opening only when condensation fails. AUXTLTARTES 323 The thermal efficiency of an injector, considered as a pump only, is about 2 per cent. As a combined pump and feed-water heater the thermal efficiency is nearly 100 per cent, the only heat of the steam not returned to the boiler being a small percentage lost by radiation. If the exhaust steam available for feed-water heating is not sufficient to heat the water above its limit possible with the injector, the latter is a good feeding apparatus. On the other hand the injector is not so economical if it interferes with the economic use of exhaust steam in the plant. It is rarely installed as the main feed unit, unless in small plants where a feed pump might not receive attention. The injector, however, is so reliable, compact and inexpensive that it almost always is placed in the boiler room as an auxiliary feed device, to be used should the main feed pumps become inoperative. Many plants operate at high over-all economy during the heating season when all the exhaust steam is utilized, but decrease their economy when the exhaust is wasted to the atmosphere. Extra exhaust, winter or summer, can be used to feed the boilers by means of an exhaust steam injector. The heat taken from the boiler in the form of steam is nearly all returned at once by the live-steam injector, but the exhaust-steam injector returns heat to the boiler that is about to escape through the engine exhaust pipe. The water so condensed is free from scale-forming matter, but all oil should be removed from the exhaust steam. Restarting an exhaust-steam injector is not difficult when the water flows to it under pressure or live steam is available. Air entering the injector will always cause a "break," so that unusual care should be taken to avoid leaks in the suction pipe. With some waters trouble is caused by scale in the lifting, mixing and discharge nozzles ; this is probably due to evaporation to dryness of water remaining after a stop. Economy of Feed Water Heating T^HE principal function of a feed water heater is to utilize the heat from -■- exhaust steam or flue gases, which would otherwise be wasted. The per cent of saving effected by heating the feed water may be expressed by the following formula : Per cent saving = 100 ^ ^ C28^ H—{t,—Z2) ^ ■' where h = the temperature of water entering the heater, t^ = the tempera- ture of water leaving the heater and H = the total heat above 32 degrees per pound of steam at the boiler pressure. Feed water heating results in the further advantages : first, of increasing the steaming capacity of the boiler by eliminating the heat required for heating the feed water ; second, by its action as a purifier certain scale- forming ingredients in the feed water are removed; and third, by feed- ing water into the boiler drum at or near the steam temperature the tendency of setting up temperature strains in the boiler metal is eliminated. Classification of Feed Water Heaters T-J EATERS may be classified into three main groups, viz: closed heaters, ■'■ -'■ open heaters and economizers. Open or cloged heaters may utilize ex- haust or live steam, while economizers utilize the waste heat in the exit flue gases. The selection of one or more of these types of heaters will depend largely upon conditions at the particular plant in question. Open heaters may be of three different types. In the one type, generally known as the live steam purifier, live steam is used to heat the feed water up to a temperature of approximately 300 degrees in order to precipitate out o a ■4-1 w 3 o in a C +j o CO O O o OS o '2 H AUXILIARIES 325 such scale-forming elements as the sulphates of lime and magnesia. The use of the live steam purifier should be confined to those plants where the feed water contains sulphates. A second type of open heater is designed for the use of exhaust steam at atmospheric pressure or less, while the third type is designed for the use of exhaust steam at back pressure up to 10 or 20 lbs., depending upon the back pressures on the auxiliary engines and pumps. In the open heater, Fig. 168, steam enters the opening of the shell on one side, pear the top, and passes through an oil separator into the mixing chamber. The cold feed water enters at the top of the shell, and passes over and through a set of perforated trays, where it is broken into fine Fig. 168. Cochrane Metering Open Feed Water Heater. particles, to insure thorough and intimate contact with the steam. The mix- ing of steam and water condenses the steam and the mixture, or hot water, falls to the bottom of the shell through a bed of filtering material. A float controls the amount of water entering the heater so that a constant water level is maintained at the bottom. An overflow provides against the water level rising too high in the shell and backing up into the exhaust steam lines, should the float control become inoperative. Since the heat given up by the steam, plus the losses due to radiation, must equal that gained by the water, the amount of steam to raise a given amount of water to a desired temperature, is easily calculated, as is also the resulting 326 AUXILIARIES feed-water temperature, when the amounts of steam and water are given. The radiation losses can be made negligible with proper insulation, so this factor is eliminated in the formula : (f,— fO JJ'= (H — 32 — t,) S — = — ^'~^' (29) JV H-i-32 — t, ^ tz =: Temperature of water to boilers (hot) fi = Temperature of water to heater (cold) H = Total heat of steam at back pressure conditions. B.t.u. S = Weight of steam, pounds W z= Weight of water, pounds. The heat of the liquid at the two temperatures should be used for exact calculations, but the foregoing is sufficiently accurate for commercial pur- poses. In selecting an open heater, the following features should be considered : 1. Skc. The heater must have sufficient steam space and tray area. 2. Oil Separator. This is necessary if exhaust steam contains oil, as when reciprocating-engines or pumps exhaust into the heater. Oil must be efficiently separated and drained off. 3. Filter Bed. This is frequently omitted. 4. Hot Well, or space at bottom must be ample so as to act as a settling basin and reservoir for the feed pump. Vapor vent should be pro- vided for escape of air and vapor. ( Hot well can also be used as a purifier space.) 5. Re^nlaiing J^alz'e Is necessary- to maintain proper water level in the shell. The design should also be considered in the light of its applicability to plant requirements. That part of the heat so used which is not converted into work is re- turned to the boiler instead of being rejected to the condenser circulating water, giving the maximum thermal efficiency. In one heater an indicating and recording mechanism is supplied to measure the feed water, so that the quantity- can be checked closely and the heat balance and performance easily calculated. These devices are valua- ble in order to maintain a running check on performance. When the exhaust steam pressure is above atmosphere, exhaust valves are used on the heater or exliaust steam lines. These allow the steam to be ex- hausted to the atmosphere or to the low pressure end of the main turbine. In one valve a nest of spring-loaded relief valves performs this function. These valves have individual dash pots. The action with them is smoother and less likely to stick than with one large valve. The tension of the valve springs can be regulated by a handwheel from outside the valve. The high back pressure that may be required in the morning to run the heating system can be decreased in the afternoon when the buildings have been warmed. A thermostat can be attached to a heater to control the drives of auxili- aries. These can be arranged for double drive, with motor on one side and turbine on the other. When too much steam is exhausted to the heater the pressure in the exhaust lines is raised, and the temperature is increased. The thermostat then operates to throttle the turbine, and more of the load is taken by the motor. Thus less exhaust steam is supplied, and the excess of steam is reduced in proportion. When the supply of steam in the heater is insufficient, the pressure in the exhaust line drops, the temperature is re- duced and the thermostat permits more steam to flow to the turbine. The turbine then picks up the load and furnishes more steam to the heater. AUXILIARIES 327 Relief valves can be used to bleed steam from one of the low pres- sure stages of the main turbine and lead it to the heater during periods of low pressure in the exhaust line. A high feed-water temperature is thus maintained. Closed feed water heaters may be grouped into two classes, steam tube and water tube. Those in which the steam passes through tubes and the water is contained in the heater shell are known as steam tube types, while those in which the water flows through the tubes and the steam is con- tained in the heater shell are classified as water tube types. Steam tube and water tube heaters may operate on the parallel current or counterflow principle, and they may be designed so that the steam or water makes one pass through the heater (single flow), or so that the steam and water may make several passes (multi-flow). Expansion End wi+h both Heads Removed £:?(haust\Ou+lei \ A \ Feed Inlef End wi+h Head Removed ^ Fetal Inkf Section Thru A-B Fig. 169. Closed Feed-Water Heater. Fig. 169 illustrates a typical closed water tube feed-water heater of the multi-flow type. Water is circulated in six passes to insure maximum heat transfer from steam to water. The number of passes varies, but two is the usual practice. Tubes are secured to tube sheets by screwing, welding or ex- panding. In some designs each tube is packed with ferrule glands, to simplify replacements. The floating head construction provides for expansion and contraction of the tubes under varying temperatures. This feature is important when straight tubes are secured rigidly at each end to the tube sheet. Most closed heaters are arranged so that they can be installed either vertically or horizontally, as best suits the space and piping. The Patterson-Berryman closed feed-water heater, illustrated in Fig. 170, is of the water tube type. The water makes a double pass through inverted U-tubes, while the steam passes through the body of the heater. A chamber at the bottom, provided with a blow-off connection, serves as a receptacle for the collection of scale, sediment, etc. In one heater, Fig. 171, coiled water tubes are connected to the top and bottom water headers with special leakproof unions. The coils allow for ex- pansion and contraction of the tubes and present maximum heatmg surface This type is of the one-pass design, water entering at the bottom header and leaving from the top. Tubes are examined or repaired through a door in the front of the shell. AUXILIARIES 329 Fig. 170. U-Tube Feedwater Heater. Open or Closed Heaters "T^HE general construction of the power plant usually determines the type of ■'- heater. In marine service, for instance, because of space limitations and the rolling of the ship, closed heaters are usually installed. Open heaters adapted to this service are in general use, how^ever, by the English mercantile marine. In ice plants the closed heater might be preferable, since the con- densed steam would be available for ice-making ; on the other hand, much better ice is made with the open heater, because it acts as a reboiler, driving off the air and other gases, which purge off through the vent. With closed heaters this air passes through the heater into the boiler an-d engine. A greater amount of boiling is then required in the reboiler, with greater waste of steam. Vacuum reboilers are sometimes found inadequate, and the capacity must be increased by the use of atmospheric reboilers. 330 AUXILIARIES ---.-- / Fig. 1,1. Mill ti- tubular Feedwater Heater. The two types are compared in the following tabulation: Open Heater Closed Heater Lfficiency With sufficient exhaust steam for heating, the feed water can reach the same temperature as the enter- ing steam. Scale and oil do not affect the heat transmission. The maximimi temperature of the feed water will always be several degrees lower than the temperature of the steam. If the scale or oil are deposited upon the tubes, heat transmission is lowered. Pressures It is not ordinarily subjected to The water pressure is slightly much more than the atmospheric greater than that in the boiler, when pressure. the heater is placed on the pressure Can be made, however, for back side of the feed pump, as is ens- pressures of 15 lb. or more. tomar\-. A U X T L T \ R T K S 331 Safety If the heater is to be used with It will safely withstand any ordi- a back pressure, a good valve, pre- nary pressure. However, any shut- ferabl}^ with more than one disk. off valve in the feed line should be should be fitted. Otherwise, the placed between the feed pump and back pressure valve might stick and the heater, with a check valve be- blow up the heater. tween the heater and the boiler. Purification Since the exhaust steam and feed The oil does not come in con- water mingle, provision must be tact with the feed water. made to remove the oil from the Scale is removed only with diffi- steam. culty. Scale and other impurities pre- cipitated in the heater are easily removed and do no harm. Corrosion The open heater prevents cor- With the closed heater the oxy- rosion by driving out oxygen orig- gen is not discharged and corrosion inally dissolved in the water. of piping and boilers occurs. Location Must always be placed higher May be placed anywhere on the than the pump on the suction side. pressure side of the pump. The greater the vertical distance between the pump and heater, the better. Feed Pumps With supply under suction two Only one cold-water feed pump pumps are necessary and one must is necessary. handle hot water. Adaptahility Particularly adaptable for heat- Adapted to use in small space, ing systems and wherever the re- and when condensate of exhaust turns are piped directly to the steam can be used in process work, heater. Economizers THE economizer is a closed feed-water heater utilizing the hot waste gases of combustion. As a piece of apparatus for the promotion of boiler room economy, the economizer is rapidly gaining favor, due to increasing prices of fuel, and to the large stack losses inherent with the present prac- tice of forcing boilers to high ratings. Two types of economizer may be met in practice, one in which the economizer is an integral part of the boiler and the other in which it is an independent unit. When an economizer forms an integral of a boiler its design is generally such that steel tubes, headers and drums have to be used. Inasmuch as there is extreme liability for corrosion due to the con- densation of moisture or sweating of the outside of economizer tubes, cast iron should be used rather than steel, due to its lesser tendency to fail by corrosion, unless there is some special method taken to prevent the cor- rosion of the steel. Fig. 172 illustrates one widely used type of independent economizer. It consists of vertical cast iron tubes, which are arranged in sections in the flue leading from boiler uptake to stack. When in position the sections are com- posed of bottom and top headers into which the tubes are pressed, a metal-to- metal joint being formed. The top and bottom headers of the sections are connected to branch pipes, one extending lengthwise at the top of the economizer and the other extending lengthwise at the l)ottom. Both top and Hotel St. Regis, New York City, operating 1450 H. P. of Heine Standard Boilers. AUXILIARIES 333 !*w r Wtt«tOttU«( Fig. 172. Green Fuel Economizer. bottom branch pipes are located accessibly outside of the economizer setting or casing. The feed water enters the economizer through the lower branch pipe nearest the gas outlet of the economizer and leaves through the upper branch pipe nearest the point where the flue gases enter the economizer from the boiler. Either mechanical soot blowers or mechanically operated scrapers may be used for cleaning the external tube surfaces. If scrapers are used, their operating mechanism is generally placed on the top of the economizer. The motive power for scraper operation may be supplied from some convenient line shaft or by individual motor or engine. Blow off valves and safety valves must be provided with economizers. For flexibility and continuity of boiler operation it is desirable to have a by-pass flue from boiler uptake directly to the stack. Inasmuch as gas explosions sometimes occur within economizer settings, it is desirable to provide quick opening explosion doors therein. Economizer Performance THE stack gases in a boiler indicate the amount of heat available for feed- water heating. Table 41 gives roughly the heat content of the gases of combustion in the flues and uptakes. If the fuel has a heat value of 10,000 B.t.u. per pound, the stack gases are at 500 deg., and the stoker is of the overfeed type, then Table 41 shows that the heat in the stack gases will be about 18.2 per cent, or 1820 B.t.u., for every pound of fuel consumed in the furnace. The difference between the heat in the gases entering and leaving the economizer represents the saving. In the example just mentioned, if the gases leave at 350 deg., they contain 12 per cent of the heat in the fuel ; the economizer then saves 6.2 per cent. The economizer is most useful, therefore, when the heat of the stack gases is greatest in proportion to the heat of the fuel or when the losses would ordinarily be the greatest ; as with an overloaded boiler, hand-fired or having an overfeed stoker and draft. The overload on the boiler will be indicated by high stack temperature. As is shown by Table 41 with normal load and efficient firing, the stack losses may not be sufficient to warrant the expense of an economizer. The stack gases will not heat the feed water appreciably, unless the economizer is large and costly. 334 A U X T L T A R T E S Table 41. Heat of Fuel in Percent Present in Flue Gases. Flue-Gas Underfeed Stoker. Oveneed or Narural Hand Firing, Temperarure, Degrees Forced Draft Draft Stoker Natural Draft Air per lb. of combust- ^ ..^ ' .^, ible, lb i ^^ I ^ 30 300 .... .... 12.4 350 .... 12.0 14.9 400 .... ' 14.0 17.4 450 , 12.2 16.1 i 20.0 500 13. S ' 18.2 ' 22.6 550 15.4 20.3 25.2 600 17 22.4 1 24.4 26.5 27.8 650 700 18.5 1 20.1 30.4 750 800 21.7 23.2 The method of calculating economizer performance is given by A. B. Clark as follows : Assume that the economizer is to be so proportioned that the combined efficiency of both boiler and economizer will be 80 per cent the coal containing 10.000 B.t.u. per pound. The steam has a pressure of 250 lb. gage, and 250 deg, of superheat, the feed water entering the economizer at 100 deg. The heat contained will then be 1340 B.t.u. per pound of steam. The feed water contains 68 B.t.u., so that the heat given up by boiler and economizer is 1272 B.t.u. per pound of steam. As the efficiency is 80 per cent, 8000 B.t.u, of the 10.000 B.t.u. in each pound of coal is used, and the evaporation is 8000 -^ 1272, or 6.Z lb. of water per po'ind of coal. Allowing for excess air and infiltration of air, about \22S lb. of flue gases will be produced per pound of coal burned. If the radiation loss is neglected, the heat given up by the flue gases must equal the heat absorbed by the water ; that is. the product of the specific heat, weight and drop of temperature of the flue gases must equal the product of the specific heat, weight and rise of temperature of the water. Let tg represent the drop of temperature of the flue gases and tw repre- sent the rise of temperature of the water. Then 0.24 X 1225 X f^ = 1 X 6.3 X ^«' ig _ IX 6.3 ^ 14 tii- ~ 024 X 1225 This means that for even.- degree of temperature increase of the 62 lb. of water, the 1225 lb, of flue gases will drop 2.14 deg. in temperature. The water passing through the economizer is taken as 100.000 lb. per hour, which the boiler, it is assumed, can evaporate. The temperature of the gases leaving the boiler is taken as 600 degrees. The average temperature difference between the water and gases in the case assumed above is 4S4.3 degrees. Tests on economizers show that the rate of heat transfer from gas to water is about 5.5 B.t.u. per square foot of surface per hour per degree temperature ditterence between the gases and the water, when the economizer is proportioned for a gas flow of B.OOO lb. per hour per square foot of area. It will be 4 B.t.u. per square foot if the flow is reduced to 3,000 lb. per hour and in proportion between these two points. The water usualh- flows through all of the sections in parallel. With long, narrow economizers and where the gases have a large drop in temperature the economizer is .sometimes subdivided into groups, through which the water is passed in series, progressing in a direction counter to that of the AUXILIARIES 335 gases, thus obtaining- a greater total transmission of heat according to the counter-flow principle. The individual sections can also be connected in series, but this complicates cleaning and blowing down. The transmission coefficient varies with the mean gas temperature as shown in Fig. 173, due to Geo. II. Gibson. The rate of heat recovery by the 6.0 5.0 4.0 cci w c cy O 61 3.0 .!2 i- ^ r\ 2.0 / / y ^^' y y y ,.^ ^ 7\ r \ p X |00° f^ ^ J / y ^ ^ j> 3001 h , / / / y x- H / f /. / y ^' / / /. y / // /> / / y/ / 3G0 1?0 1080 1440 1800 2160 2520 Gas Flow, Lb. per. Hr. per Ft of Pipe in Sec+ion Z880 3240 3600 Fig. 173. Variation of Coefficient of Transmission with Mean Gas Temperatures. 1800 1700 IGOO 1500 cl400 L 1300 ^1200 o-llUU to biooo S'900 CO nnn Z 700 8 wo o ^ 500 -t- ^ 400 300 200 100 1 — f"™" Ti, y y^ A \ \ / y / y .A ^fy / ^ ^ •4 j^/ /A y y .^^ \^. Z A V t« ^ f 4 /y 4^^. [ ? ^0^^'f' .f t y :^ 'y ^(i-^ L A •i' A <^ 4 ,r 4 K / ** A '^ /^ yu ^y / ^ ^y /^ 4 V ^ y ^ f/ r ^ y f// > ^ /^ i y^ A I Z 3 4 5 6 7 8 9 10 II 12 13 14 15 ' 16 17 18 19 20 l\ 11 Th Water. Flow, Lb. per 5q. Ft. per Hour Fig. 174. Variation of Rate of Heat Recovery by the Economizer. 1400 H. P. of Heine Standard Boilers equipped with Murphy Stokers, in the Fifth Avenue Building, New York City. AUXILIARIES 337 economizer increases directly as the load on the boiler to which it is con- nected. This is shown by Fig. 174, also due to Geo. H. Gibson. The heat recovery while the load is increasing appears to be somewhat less than while it is decreasing, owing to the fact that the rate of heat recovery can be determined only by measuring the temperature of the water as it leaves the economizer. Using the higher value for calculation, the heat transfer per square foot per hour is 5.5 X 484.3, or 2663 B.t.u. Therefore the surface required to raise 100,000 lb. of water through 10 deg. is 100,000 X 10 -i- 2663 = 376 sq, ft. The next step is to assume new values for gas and water temper- atures and calculate the surface required. Table 42. General Dimensions of Economizers. 12 12 No. of Tubes Length of Tubes, Feet Weight of Section Full of Water, Pounds External Heating Surface, Square Feet per Section Number of Sections in Economizer Length Over Economizer Wide Ft.— In. 4 4 4 9 ' 1,636 10 1,756 11 1 877 51.0 55.8 60.7 i 4 2—5 8 4—10 12 7— 3 4 1 12 1 2,005 65.4 ! 16 6 19! 2,388 | 76.5 i 20 6 i 10 ' 2,570 1 83.8 j 24 7— 8 12— 1 14— 6 6 11 2,751 91.0 28 16—11 6 12 2,942 98.3 32 19— 4 8 9 3,096 102.0 36 22—113/^ 8 10 3,337 111.7 40 25— 43^ 8 11 3,578 121.4 44 27— 93^ 8 12 3,885 1 131.0 48 31— 5 10 9 3,760 127.5 52 33—10 10 10 4,061 : 139 . 6 56 36— 3 10 11 4,363 1 151.7 60 38— 8 10 12 4,684 ; 163.8 64 42— 33^ 12 9 4,380 153.9 68 44— sy2 12 10 4,742 167.5 72 47- 13/2 49— 63^ 53— 2 As the temperatures of the water and gas approach, the surface must be increased for a given rise of the water temperature. The ashpit loss will be about 3 per cent and the unaccounted-for losses and radiation are about 3.5 per cent. As the efficiency of boiler and economizer is 80 per cent, the flue-gas loss will be 13.5 per cent, or 1350 B.t.u. per pound of coal. Flue gases from the coal will contain about 0.5 lb. of water in the form of superheated steam ; therefore, as the total weight of the gases is 12.25 lb. per pound of coal, the gases will weigh 11.75 lb. and the water vapor 0.50 pound. Assuming that the air entering the boiler is at a temperature of 70 deg. the temperature of the escaping gases can be found from the equation, 11.75X0.24 (^ — 70) -f 0.5x0.48(f — 212) 4-0.5 X 970.4 H- 0.5 (212 — 70) = 1350 t = 340 deg. If the final gas temperature is 340 deg. the surface required is 8,000 square feet. The feed-water temperature will be 220 deg., a rise of 120 Cook County Court House, Chicago 111. containing 1830 H. P. of Heine Standard Boilers. AUXILIARIES 339 deg. from the assumed initial temperature. The return in heat units per pound of coal is fired is 6.3 X 120 = 756 B.t.u., or a return of 7.56 per cent on a heat value of 10,000 B.t.u. Having determined the surface area of the economizer, the space require- ments can be checked with fair accuracy from Table 42, which gives the dimensions of the economizer made by a prominent manufacturer. Tliis table will apply as a general guide in determining the room required. Air Heaters HEATING the air supply to furnaces by abstracting heat from the exit gases is just as logical a method of saving fuel as is heating the feed water in the same way. The saving effected can be directly measured by the drop in temperature of the flue gases in passing through the air heater, or by the rise in temperature of the air, when the weights of air and gas per pound of fuel are known. Usually the gases are passed through vertical pipes of about 3-in. bore, around which the air flows horizontally. In a system recently described by /. Van Brunt, the heater consists of a nest of semi-circular plates ar- ranged in pairs so that the air flows in a path curved circumferentially from inlet to outlet, while the gases flow between the plates in straight chordal paths. This design makes a very compact and convenient arrangement. The rate of heat transmission varies with the cleanliness of the surface, with the gas and air velocities, and with the difference in temperature be- tween the gas and the air. Consequently, the areas of the passages and of the heating surface are directly related. In Table 43 the symbols have the following meanings : IV =: Weight of air or gas, pounds per hour. A ■= Area of passages, square feet. R = B.t.u. transmitted from flue gas to air per square foot of surface per hour per degree difference between average temperatures of gas and air. Table 43 can be entered with IV/A, and the value of R found. The heat (in B.t.u.) to be transmitted per hour divided by R times the average temperature difference between the gas and air is the heating surface required. Table 43. Heat Transmitted Between Flue Gases and Air. W A Values of R at Temperature Differences 100 I 200 I 300 1,000 2,000. 3,000, 4,000 1.6 1.7 i 1.8 1.9 2.3 ! 2.7 2.2 2.9 t 3.7 2.5 I 3.5 ; 4.6 This table has been prepared on the assumption that the values of JV/A for gas and air will not vary more than 10 to 15 per cent. The area through the tubes is commonly from 30 to 50 per cent greater than that of the equiva- lent breeching. The air passages can be proportioned in the same manner as directed in Chapter 6 on CHIMNEYS, allowing for the temperature of air desired, and making the area between the tubes the mean of the hot and cold air ducts. The loss of draft through a well-designed heater will be about 0.1 in. of water column. The loss of air pressure will be from 0.1 to 0.2 in.; and to this must be added the resistance of the air ducts, making allowance for bends that cannot be avoided. o PQ C CB ■4-1 m .S o o C *G 'S +j t: o u o" 'a O c c 'G O 00 o 4-) Wi o O c O U o a CO AUXILIARIES 341 Heating the air for combustion is practiced to a considerable extent in marine work, with mechanical draft. In the Howden system the air is forced through the heater, while in the Ellis and Eaves system it is drawn through by the induced draft fan. Most of the applications in land service have been confined to municipal refuse destructors wherein forced draft fans or steam-jet blowers draw the air through the heater and discharge it into a closed ashpit, the tempera- ture rise being from 300 to 500 deg. When the air for combustion is heated 300 deg. or more, trouble might be expected from grate bars burning out more rapidly, and from excessive clinkering ; but this does not appear to be the case. When heat that would otherwise be wasted in industrial processes can be used to heat the air for combustion, the thermal efficiency of the whole plant is increased. In electric power plants it is becoming general so to utilize the heated air resulting from ventilating the generators, the air ducts being piped from the generators to the forced draft fan inlets. The forced draft air can be drawn from parts of the boiler room or from the space near industrial processes, space that otherwise might become unpleasantly hot, making for more comfortable operation and increased thermal efficiency. Auxiliary Engines and Turbines IN certain definite fields, according to /. S. Barstow, the small turbine is of conceded superiority, and in other fields the engine must hold sway. The following factors determine the adaptability, cost and economy of the equip- ment to be installed for any given service : A. — Maximum or minimum permissible speed, and whether the ap- paratus is driven at constant or variable speed. B. — Steam pressure (Initial and final) and superheat temperature, if any. C. — Power capacity of apparatus. D. — Space requirements of turbine and engine units, available room, power house construction, and cost of foundation or other sup- porting structure. E. — Use or application, if any, of exhaust for feed water heating, steam heating or process. F. — Available cooling water supply; If the turbine or engine Is to be run condensing, the temperature of the water and whether it must be artificially cooled and re-circulated. G. — Operating conditions, attendance, oiling, starting and stopping, vibration and noise. H. — Cost of complete installations. Including foundations, piping and condenser equipment, if any. Not until about 20 years ago was a practicable small turbine developed, and even up to ten years ago the turbine was looked upon mainly as an experiment. In the last few years, however, this type of prime mover has been built not only in small sizes, but also in 50,000 H.P. units for large cen- tral stations. The turbine therefore is as well developed as is the steam engine after more than one hundred years of improvement. Speed Limitation is of first importance in selecting the type of prime mover. Peripheral velocities must be high to utilize efficiently the energy of a steam jet in the turbine. Its water rate is lowest, therefore, when run- ning at a constant high speed. When speed variation or reversal is required, or when the speed is necessarily low, the engine is much better adapted to the service. 342 Erecting Two Heine Standard Boilers for the Caribbean Petroleum Co., San Lorenzo, Venezuela. AUXILIARIES 343 If an engine is run at very high speeds, operating troubles are sure to be numerous, the upkeep is excessive, and the service unsatisfactory. The lack of driven apparatus designed to run efficiently at speeds consistent with high turbine economy has, in the past, frequently dictated the use of engines as prime movers. Speed reduction gears have been used with the turbine almost from the beginning of its commercial development. Recent improvements in high speed gearing, as well as in the manufacture of high speed direct-connected generators, blowers and pumps, running at 3000 r.p.m. and above, have greatly increased the possibilities for turbine installations. Direct-current generators as small as 10 KAV. capacity, and 60 cycle alternators of capacities as low as 150 KAV., designed for gear drive, are now obtainable. It is said that the increased efficiency of the higher speed turbine, and the saving effected in the generator construction by reason of the slower speed per- missible in the driven end, justify the expense and complication that the gears introduce. For power station work, where some of the auxiliaries are usually motor driven, the exhaust steam can be entirely condensed in the feed-water heater, and the water rate of the steam driven auxiliaries is not a limiting factor. Reliability, accessibility, low maintenance and labor costs are of more vital importance. Power station designers have always preferred, therefore, the turbo-auxiliary units, and there is now a decided tendency toward geared installations. Small engine units are run at high speeds, so that it is exceedingly difficult to keep them in continuous service, and almost impossible to secure smooth, quiet operation. The reciprocating units require close attention, and must be shut down, overhauled, and adjusted at frequent intervals; the cost of maintenance is high and breakdowns are by no means rare. An accident to a circulating or hot-well pump, for example, usually necessitates a shut- down of the main generator, with consequent loss of production, and in a public utilities plant, loss of prestige and the incurrence of public ill-will. In central stations, therefore, where the main units are few in number and of large size, the circulating, hot-well and boiler feed pumps are usually turbine-driven. For driving fans of large capacity at low pressures, say less than 1^ in. of water, for induced draft, hot air heating and ventilating systems, engines seem well suited. Fans built for this service run at less than 200 r.p.m., and are of the paddle-wheel type. In induced draft work, load fluctuation may require frequent changes in speed ; the engine is under the control of a throttling regulator, which is automatically actuated by a change of steam pressure. These conditions are unfavorable to turbine economy. The furnaces of underfeed stokers often carry air-duct pressures as high as 6 or 8 in. of water; the high speed multi-blade fan then makes the better in- stallatio», particularly when one fan serves several boilers. The size of the blower units would be excessive at speeds below 400 r.p.m., and the engine drive is uncertain and exi)ensive at this speed. Underfeed stokers at best can develop only from one-quarter to one-third their maximum capacity with natural draft, so that a blower breakdown under peak load is a serious matter. The ability of the turbine to stand up under the conditions justly entitles it to preference. Owing to the freedom from reciprocating motion, the foundations re- quired for turbines are small and light, there being little vibration to be absorbed when the machines are well aligned and balanced. The small sizes can be safely operated on floors designed for the ordinary loads. No diffi- culty is experienced with the transmission of vibration to the structural mem- bers of the building or to the piping" system. 344 d CO a CO IS V w 'o C as ^ G S CO (h-i o o oc . rr- O •^ CS C 'm C w CJ '^ .— ■*-' u •" " e c V CO . "^ u CO CO a o AUXILIARIES 345 The turbine is often used for boiler feed-pumps (centrifugal type) of more than 250 gal. per min. capacity, or about 3,000 boiler horsepower developed, and on account of its small size the layout is usually neater and more compact. When regulation by throttling is unnecessary, and the pumps run at or near capacity, the economy is better than that of the direct acting type. Valve renewal and packing troubles are avoided. The overload capa- city of the centrifugal type is small, so that the pump must be proportioned to meet the maximum demand, not the average boiler horsepower require- ments. In the smaller sizes, the cost of turbine units is high ; when the load fluctuates widely and the speed must vary, the economy is poor and it is better to install reciprocating pumps. The turbine possesses a great advantage in the simplicity of its con- struction, which tends toward increased reliability and lower cost of main- tenance. It can be started and loaded more quickly. In operation, it re- quires much less attention than an engine of corresponding capacity. The lubrication devices are few in number and of simple design. Applicability of Turbines. Summarizing the foregoing, the held of use- fulness of the turbine can be stated to be : 1. — 'Direct-connected units, operating condensing. 60 cycle generators in all sizes. Direct-current generators up to 1000 K.W. capacit}', including exciter units of all sizes. Centrifugal pumps operating under substantially constant head and quan- tity conditions, and at heads say from 100 ft. up, depending upon the size of the unit. (This includes boiler feed pumps of more than 250 g.p.m. capacity, or 3,000 boiler horsepower developed.) Fans and blowers for delivering air at pressure from 1^ in. water col- umn to 30 lb. per sq. in. 2. — Direct connected units, operating non-condensing for all the above pur- poses, when steam economy is not the prime factor, or when the ex- haust steam can be completely utilized, particularly if exhaust steam must be oil-free. 3. — 'Geared units, operating either condensing or non-condensing, for all the above applications ; and for others where a steam engine is required on account of the slow speed of the driven apparatus. Applicability of Engines. The fields of usefulness of the engine are given as follows : 1, — Non-condensing units, direct-connected, or belted and used for driving electric generators of all classes except exciter sets of small capacity, unless belted from the main engine. Centrifugal pumps, operating under variable head and quantity conditions and at low heads, say up to 100 ft., depending on the capacity of the unit. Pumps and compressors for delivering water or gases in small quantities and at high pressures ; pumps at pressures above 100 lb. per sq. in. and compressors at pressures from 1 lb. per sq. in. and above. Fans and blowers (including induced draft fans) for handling air in variable quantities and at low pressures, say not over 5-in. water column. All apparatus requiring reversal in direction or rotation, as in hoisting and traction engines. 2. — Condensing units directly connected or belted, for all the above purposes, particularly when the condensing water supply is limited, and the water must be re-cooled and recirculated. Adflpina Hotel, Philadrfphia. Pa., cootaming four 255 H. P. 347 CHAPTER 10 HEAT INSULATION THE function of a heat insulating material is to retard heat flow. It is heat insulation whether used to keep heat where it is wanted, as in a steam pipe ; or to keep heat away from where it is not wanted, as from the cold water in a drinking water line. Surface Resistance. The heat lost per degree temperature difference between steam and air from metal 1-in. thick, heated by steam on one side, and exposed to air on the other, is much less than the value of k shown for the metal because the temperature difference between surfaces, ti — tz, is much less than the temperature difference between steam and air, ^s — ^a. (See Fig. 175.) The air cannot take up the heat as rapidly as it can be trans- mitted by the metal; therefore, the temperature drop from the outside surface of the metal to the surrounding air is almost all of the total temperature difference between the steam and air. The drop through the metal, ti — 12, is only a small part of the total. The amount of heat transmitted per hour through unit thickness of material on flat surface \s k {f^ — t^). This hold- ing back of the heat due to the inability of air to take it up as quickly as it can be transmitted is called "surface resistance." Afefcr/- Fig. 175. Comparison of Heat Transmission from a Metal Plate, 1 inch Thick, when Insulated and Not Insulated. In good conductors of heat the greater part of the resistance offered to heat flow is surface resistance. In insulating material, however, most of the MS INSULATION resistance is in the insulation, and the surface resistance hs.? !e55 effect on the amount of heat transmitted. The surface resistance of a surface su: : tr^f pared with that of one exposed to air. A p:^e s:: fore transmit a vastly greater amount of hei: rounded by air, even though the ir.terr.al ccriu same for each pipe. Losses from Bare Heated 5 7: ;: 7 r r 1. Fig, 176, shows the rate of heat loss at various tempera: ure iifitre .;ti r:ween hot surface and sur- rounding air. Curve 2 shows the total heat loss at any particular tempera- ture difference. Ordinates for curve 1 are on the left, and for curve 2 on the right of the chart. . water is small as com- rred in water will there- ir. :he same pipe sur- ::v of the metal is the iOO 200 ^ 500 Tzmp.Diff. b>ctween Hot Surface and Surrouroiro 500 '.^^z-zzs Fig. 176. Comparison of Rate of Heat Loss at Various Temperatrire Differences and at a Constant Temperature Difference. INSULATION 349 Table 44, for different steam pressures and temperatures, shows the heat lost per year from a square foot of heated surface, the amount of coal re- quired to replace these losses and the square feet required to waste a ton of co^l per year. Table 44. Heat Losses from Uninsulated Hot Surfaces. Steam Pressure (Gage), Lb. Steam Temperature, Degrees Temp. Difif., Steam and Surrounding Air, Degrees Heat Loss per Sq. Ft. per Hr., B.t.u. Pounds of Coal Wasted per Year per Sq. Ft. of Uninsulated Surface Sq. Ft. of Surface Wasting 1 Ton of Coal per Year 10 25 212 240 267 142 170 197 334 425 522.5 293 372 458 6.82 5.38 4.37 50 75 ' 100 298 320 338 228 250 268 644 737.5 820 564 646 718 3.55 3.10 2.79 150 200 250 366 388 406 296 318 336 960 1,079 1,184 840 945 1,036 2.38 2.12 1.93 Temperatures Below 212 Degrees. Surface Temperature, Degrees Temp. DiflF., Surface and Surrounding Air, Degrees Heat Loss per Sq. Ft. per Hr., B.t.u. Pounds of Coal Wasted per Year per Sq. Foot of Uninsulated Surface Sq. Ft. of Surface Wasting 1 Ton of Coal per Year 100 120 140 30 50 70 56.6 97.5 142.0 49.6 85.4 124.3 40.3 23.4 16.1 160 180 200 90 110 130 190.0 242.0 298.5 166.3 212.0 261.5 12.03 9.44 7.65 Above figures based upon 10,000 B.t.u. available per pound of coal, which is equivalent to a boiler efficiency of 70 per cent, the heat value of the coal being assumed as 14,000 B.t.u. per pound. The temperature of the "surrounding air" is 70 degrees in both parts of the table. At 100 lb. pressure, less than 3 sq. ft. of bare surface are required to waste a ton of coal in a year. An area greater than this is exposed when a pair of 10-in, flanges is left uninsulated. Also, many surfaces at low temperatures are left uninsulated on the ground that the temperature is not high enough to justify insulation. Table 44 shows, however, that only 12 sq. ft. of surface at 160 deg. are required to waste a ton of coal per year. Surfaces too hot to be touched with comfort represent a loss of heat. Fig. 177 shows the saving by the use of a good insulation. Value of Heat Insulation. Heat insulation saves fuel directly or in- directly; in addition, insulated equipment renders better service, working con- ditions near heated surfaces are more comfortable, and the safety from fire and accident is greater. Insulation cannot prevent the flow of heat completely, as it does the flow of electricity. All substances conduct heat to some extent. Table 45 350 V O CO il U 7 'c vT o s ^ X V OH 1- (X, o INSULA TI ON 351 shows how much lower the conductivities of some materials are than those of others and therefore indicates wliich should he good insulators. 50 100 150 200 e50 300 350 400 450 Difference between Pipe oind Room Temperatures, Degrees Fig, 177. Heat Loss from Bare Steam Pipe and Saving Effected by Good Insulation Covering. Lines A and B show Saving per Degree Difference is Much Greater at High Steam Temperatures. Couduclivitics of Materials. Tiihh 45 shows the conductivities of com- mon materials. The conductivity, k, is expressed in B.t.u. per square fool per degree temperature difference hetween surfaces per inch thickness per hour. Requirements of Good Insulation. In order to he satisfactory, an insula- tion must withstand the temperature and the wear and tear imposed upon it. The mechanical form must permit its application in workmanlike manner to the surfaces to he insulated. The insulation must he durahle and must he efficient in preventing heat flow. Insulating materials of laminated fihrous structure arc considered more durahle than molded forms of insulation. 352 c O O d O K 3 2 CO D "I O >> ^^ O O J3 O •M t-i U. r" D :;: G o -^ PQ CO CO O CD C/3 .s CO 0) H INSULATION 353 Table 45. Conductivities of Materials. Material Temperature, Degrees Conductivity, (k) Silver Silver Copper Copper Aluminum Aluminum Pure Iron Wrought Iron Steel (Soft) Cast Iron Coal* Granite •. Ice Marble Limestone Sandstone Soil (Wet) Soil (Dry) Firebrick Concrete (Stone) Concrete (Stone) Concrete (Cinder) Glass Brickwork Water Sand (White, Dry) Wood— Maple Wood— Oak Wood — Yellow Pine Wood — White Pine Diatomaceous Earth Blocks Air Cell Asbestos 85 percent Magnesia Asbesto-Sponge, Felted Cork Hair Felt . . Air (True Conductivity, Radiation and Convection eliminated) ** 64 212 64 212 64 212 212 212 212 ,800 1,000 300 300 300 50 50 2,920 2,880 2,667 2,638 1,393 1,428 439 412 322 314 23.2 20.0 16.5 15.0 15.0 14.5 10.7 2.55 9.0 0.50 7.8 6.38 2.35 7.0 5.0 4.35 2.7 1.17 1.04 1.0 0.83 0.85 0.72 to 0.55 0.468 0.35 0.30 0.18 In the materials from Diatomaceous Earth to Hair Felt, inclusive, the temperatures are the differences between surfaces. When the temperature is not stated in the table, it is understood to be at or near that of the ordinary room. *Carbon, in its various forms, h,a3 conductivities varying between extremely wide limits. Some forms of graphite have conductivities from 10 to 20 times as great as that given above for coal, while powdered charcoal has a conductivity only about l/30th that of coal. **Radiation and convection are the largest factors in the transmission of heat through open air, conduction being comparatively insignificant. The true conductivity is approached only when the air is confined in minute cells, and the effects of radiation and convection are minimized. Practically all commercial insulations depend upon entrapped air for their insulating value. Air has a low heat conducting power (see Table 45) and if confined in small spaces to minimize the effect of convection within the spaces, and of radiation of heat across them, the resistance to heat flow is high. Even perfect vacuum would be ineffective in preventing heat flow unless the bounding surfaces were mirrored to prevent radiation. 354 lATION La Fig. 178 the heat losses tliFcmg^ diflFerent commercial m s i ^PafiTig mate- rials are compared. Table 46 shows the tibi<^nesses and weights per lineal foot of the materials referred to in Fig. 178. The nses for which materials ~e"fed by mannfacttirers ire also grren. re: O-S-I t- 0.8C a45 a4€ p.-zn III / ! t 1 1 ^^ / <. ^ ^ / / / / / ^ ^-^ ,/ y .^ ^ ^ -X v^ X >X^ \ 1 y \ <'^ A. y ^^""^ >• ^ V 'yi''^ ^ ^ ^ ^ y ^ ^ — -— 5-^^^^^ - - ■^ ^ ^ > ^^^-^ ,- -^ -s=* ^ ^ -f^r ^ ^ iic: -.- < " ' ' '^^ 1 * ^' " f i^ti==^ -r"^^,^ -" . -.- '^..-^^^ - ■ ' ' ' ' ^^ — " . ^^_ -■^ ^- fe -^ ^ ^ === — - '< ''" ■^^ ^-■^ •^^ -:; ::^ ^^ ■ ^ -f'-- i i! [ 1 1 ; i 500 ( PipeTempe' - - . 'f - - : - ~ - .e ' Fig. 1 78. Comparison of Heat Loss Through Different Insulation Materials. Materials for Insvlaticms. Asbestos, Fig. 179. is the most important of all materials nsed as insulations at steam temperatures. Many insulations con- sist almost oitirely of asbestos^ and on account of its fibrous form asbestos is used as a binding material in almost every insulation manufactured for high temperatures. INSULATION 355 Table 46. Thickness and Weight of Insulating Materials, Test No. Material Thickness, , Inches L, ^ ' Lb. per Actual Appar- Lin. ent Ft. Recommended for I II III IV V VI VII VIII IX X XI XII XIII XIV XV XVI XVII XX XXIV 0.9S 1.25 J-M 85 per cent Magnesia. . 1 . 11 J-M Indented J-M Vitribestos J-M Eureka J-M Molded Asbestos J-M Wool Felt Sal-mo Expanded Carey Carocel Carey Serrated Carey Duplex Carey 85 per cent Magnesia. Sal-mo Wool Felt I Nonpareil High Pressure ' 1 . 16 J-M Asbestos Fire Felt . 99 J-M Asbesto-Sponge Felted.. J-M Asbestocel 0.99 1.00 .96 1.10 J-M Air Cell Plastic 85 per cent Magnesia. Sal-mo Air Cell 00 05 1.18 1.12 1.11 1.04 1.26 1.10 1.07 1.06 1.13 1.01 1.19 1.01 1.23 1.09 1.16 1.10 1.11 1.05 0.95 2.73 3.46 4.05 4.60 5.53 2.59 3.47 3.06 5.66 1.79 2.74 3.73 2.96 3.75 4.04 1.94 1.55 3.33 1.57 High pressure steam. High pressure steam. Stack and breeching linings. Low pressure steam and hot water. Low and medium pressure steam. Low pressure steam and hot water. High pressure steam. Medium and low pressure steam. High pressure steam. Low pressure steam and hot water. High pressure steam. Low pressure steam and hot water. Highpressure&superheated steam. Highpressure&superheatedsteam. High pressure & superheated steam. Medium and low pressure steam and hot water. Low pressure steam andhot water. Fittings and irregular surfaces. Low pressure steam and hot water. *Apparent thickness is distance from pipe surface to outer surface of insulation. Chemicall}', asbestos is a hydrated silicate of magnesia. A typical analysis is given below : Per cent. Silica (SiOJ 41.0 Magnesium oxide (MgO) 41.5 Ferric oxide (FejOa) 3.0 Aluminum oxide (AlaO:;) 0.9 Water (H,0) 12 to 14 Asbestos, although highly heat resisting, has little insulating value in its natural rock form (see Fig. 179). Not until the hbers are separated and manufactured into felts, in w^hich they entrap a large number of finely divided air spaces, does asbestos become an efficient insulating material. Fig. 179. Rock Asbestos. ^ c ^ ■r^ WO 4-) - o ■*j i^ 2 Q o f^ u > U o *■ CJ U K •T. CO ^ — ffl o m ^ -a ^ w o 0) ^ CS "— > •^ ^ m a o V INSULATION 357 Asbestos will withstand temperatures up to about 1500 deg,, but the fibers become brittle when subjected continuously to temperatures above 1200 degrees. The limit for the fire-felt type of asbestos insulation, which consists principally of asbestos fiber and a binding material, is about 1200 de- grees. The limiting temperature for laminated forms of asbestos insula- tion is about 700 degrees. The limit for the cellular types of asbestos insula- tion is about 300 deg., on account of the organic matter used in the asbestos felt from which they are built. Carbonate of Magnesia. Next in importance to asbestos is hydrated magnesium carbonate [4MgC03. Mg(0H)2. 5H2O]. This material in the form manufactured for insulating purposes is light and porous and has good insulating value. The necessary mechanical strength and durabiliiv are secured by mixing about 15 per cent of asbestos fiber and 85 per cent of hydrated magnesium carbonate ; from this the name "'85 per cent magnesia'' is derived. The natural rock from which the magnesium carbonate is obtained is hard and dense, resembling marble. In this original form the material has practically no insulating value. The high insulating value of 85 per cent magnesia is due to the process of manufacturing. The magnesium carbon- ate is separated from the other ingredients in the original stone, the finished product having one-tenth of the density and less than one-twentieth of the conductivity of the natural rock. The 85 per cent magnesia is not adapted to temperatures above 500 degrees. At higher temperatures the material is calcined, loses CO2, shrinks and loses strength rapidly. Diatomaceoiis Earth (Kieselgiihr) is a naturally occurring mineral of high heat resistance. It consists of practically pure silica (Si02), which is finely divided, owing to the manner in which the deposits were built up under water in prehistoric times from the skeletons of microscopic organisms known as diatoms. The insulating value is less than that of asbestos or magnesia, but it will withstand higher temperatures than either of these materials. In molded forms it is usually strengthened by being mixed with asbestos fiber. Blocks manufactured from diatomaceous earth will withstand temperatures up to 2000 degrees. Cork. For the insulation of larger surfaces at low temperatures, as in refrigeration work, cork is the most desirable material. The source of cork is the bark of the cork oak tree. The cork is ground and molded into sheets by the application of heat and pressure. No binding material is re- quired as the natural gum of the cork cements the particles firmly, and serves as a moisture proof coating as well. The use of cork is confined almost exclusively to refrigeration and cold storage work. Flair Felt. This has the highest insulating value of any commercial insulating material. It is widely used for the insulation of brine and cold water pipes, and is then sealed in with waterproof membranes to prevent access of moisture from the air. On outdoor steam lines, hair felt is also used outside of other insula- tions. The inner layer of asbestos or magnesia protects the hair felt from the high temperatures, while the high insulating value of the hair felt in- creases the efficiency of the combination. The maximum temperature to which hair felt can be subjected is about 250 degrees. Miscellaneous Materials. Wool, silk, and cotton have insulating value, but this is principally used in clothing. Wood and paper are of value as insulations, and are used in building construction. o *j 03 u ■4-) OS u o c "5 Ud 6 s •So •c.S "SCQ a '1 5 -a c GO 09 v C "C (U 00 o INSULATION 359 Heat Transmission Through Insulation. The factors in determining the rate at which heat will be transmitted through miit area of an insulating material are : (13 The conductivity of the material, (2) The temperature difference between its two surfaces, (3) The thickness of the insulation, (4) The form of insulated surface. Of lesser importance are the finish of the surface and the velocity of air currents over the surfaces. Table 45 shows how greatly the conductivities of materials vary. The figures in the table are surface-to-surface conductivities. Fig. 178, however, compares approximately equal thicknesses of insulating materials, the ordi- nates being actual rates of heat transmission per square foot per hour per degree temperature difference between hot surface and surrounding air. 1-2 I I ! \ np Diff 'SOODe 9- \ i \ 300 L eg. \ \ ^ \ >g. ^V ^ ^ --_. 2 3 1 hickness, Inches Fig. 180. Effect on Heat Transmission from a Flat Surface of Various Thicknesses of Insulating Material. 360 HEAT Effect of Temperature on Heat Transmission. Fig. 180 shows that the rate of heat transmission per degree is not the same at all temperatures. However, the loss at any temperature can be found by muhiplying the transmission factor given in the chart for any temperature difference between hot surface and surrounding air, by that temperature difference. Efficiency. Insulations are often compared in terms of their "insulating efficiencies." As thus used, the term "efticiency" is the percentage of the uninsulated surface loss saved by a given insulation. It is bare surface loss minus loss from insulated surface, divided by bare surface loss ; both losses apply to the same area and are for the same temperature difference. Thickness and Heat Transmission. Fig, 180 shows the variation of heat transmission from different thicknesses of material on flat surfaces. The loss through material 2-in. thick is greater than one-half of that through material 1-in. thick, even though the figures are for flat surfaces, for which the re- sistance of the 2-in. material is exactly double that of the 1-in. material. The "surface resistance" is practically the same for the 1-in. as for the 2-in. thickness. Consequently, the resistance of 2 in. of material plus one surface resistance is not double that of the 1 in. of material plus one surface re- sistance, and heat transmission is inversely proportional to total resistance. ■ D 1 j < ! CO 5\ Q cL ^ 1 1 «s0.4 - \ V XV V I- CI N n:^ <^ ^:::;^ \ ■v & to 1 ^^^"**~«^^/~'~" : I^ 300 \ Ter np. Di'ff grees V) or C Thickness, Inches Fig, 181. Effect on Heat Transmission from a Pipe Surface of Various Thicknesses of Insulating Material. Fig, 181 shows the effect of the thickness on heat transmission for pipe surfaces. The loss through material 2-in. thick is even more above one-half of that through the 1-in. thickness, than it was for the flat surfaces. In addition to the surface resistance effect, the second inch of insulation is applied over a larger area than the first inch, so that it does not offer as much resistance to heat flow. Pipe Size and Heat Transmission. Fig. 182 shows how the rate of heat transmission through a given thickness of insulation varies with pipe size. By comparing this chart with Fig. 180. the losses through different thicknesses on pipes are found to be greater than through the same thickness of the same insulation on flat surfaces ; also, as shown in Fig. 183. the losses are greater on small than on large pipes, other factors being the same. INSULATION 361 08 0.7 0.6 g-05 '0.4 S0.3 hQ2 \ \ \\ \\ \ \\ \; \, ^ ^\ s \ k^, V \ -V, ■^ ^ ^ ^ A 9DWlol ' \ ^> N .^ \'ll£5 5 /" \^ <^ .^^ " ■ ~~~~ /'/2 ' \ C::- ■-^ , . \ ^ "~~~ ^- — =^ iS- ■ ■ •— -^ 4" )123456789 10 II Nominal Diameter of Pipe, Inches Fig. 182. Comparison of Heat Loss from Various Sizes of Pipe. 12 In flat surface insulation all the heat flows straight through in parallel lines, but in pipe insulation the heat has a continually widening path into which to spread as it flows outward. Consequently more heat will flow from a given area of pipe surface than from the same area of flat surface. The smaller the pipe the more rapidly the path for heat flow spreads out ; there- fore the greater is the rate of heat loss for a given pipe area and thickness of insulation. Fig. 183. Relative Heat Loss Through Flat and Curved Surfaces. Air Currcn\s and Surface Finisli. Air currents greatly decrease the sur- face resistance. With bare surfaces the losses can be increased by the efi^ect of wind to several times the values in still air. When efficient insulations are applied so that they are sealed against the effect of air blowing through the joints, the maximum increase in heat transmission due to wind velocity varies from about 10 per cent for an insulation 3-in. thick to about 30 per cent for a 1-in. thick insulation. These figures are only approximate, because the more efficient the insulation, the less affected it is by wind velocity. If the insulation is loosely applied so that air can circulate through the joints and crevices or between the insulation and the pipe, wind can in- crease the loss upward of 100 per cent. Painting the surface of insulation usually decreases the loss of heat slightly and is desirable because the sur- face is thus sealed against circulation of air. Z61 o T3 . 'Z ^ ■^ o 1^ w r o U i.i: C u C. O ."^ V ffl *- V C *C X Cm O o o o INSULATION 363 Thickness of Insulation. The thickness it will pay to use depends upon: (1) The temperature difference between hot surface and air, (2) The value of the heat units to be saved by insulation. (3) The size of pipe, (4) The kind of insulation used, (5) The cost of insulation. The last increment of insulation put on should save enough to pay a good return on its cost. The minimum allowable return is usually taken at about 14 per cent, which covers interest and depreciation. 5/4" -= ^ ^ S^ ^ 1^ — (^4 i?3 Sfec •ma '40 Cent s per 1,000,000 B.TM. ^ f ^ "^ , ^ ^ ^ l^ <^ -^ / ^ ^' ^ / /' ,^ ,^ ^ ^ II ^ / ^^ ^^ ^ ""^f^ -y. ^ >: ^ -^ ^^ 100 200 300 400 500 600 100 200 300 Temperature Difference, Degrees 400 500 600 5(f3 steam at 60 Cen not- innnnnh r t fs ^ '^ pe^ ' ^y ^ ^ ^ r\ ^ ^^ / / > ^ ^ '^ ^ y / ^ \ ^ "^ ^ ^ / 'a ^ ^ > ^ '/ A ^ y ^% f>- -^ ^ /> :; y' ,^ -^ ^^ i\^ ^ ^^ 'y ^ ^ ^ C94 10 7 f^2 ^ ^ ^- steam af 80 C Lnor- in/vinm R enfs Til y y per ' 'i \ y ^ y ^ ^ Oy A y y" ^ / A ^ _.^-- ^ / / A / 1 w y [y ^ ^^ 9 \/ ApA ^ ^ y y y y\ ■^1 / 'A 215 ^ >^ > A .>' 100 200 300 400 500 600 100 200 300 Temperature Difference, Degrees 400 500 600 Fig. 184. Chart for Determining Most Economical Thickness of 85 Per cent Magnesia. V 'C u INSULATION 365 Fig. 184 is a chart for determining the most economical thickness of 85 per cent magnesia. It can also be used in selecting the thickness of other materials. However, the actual saving should be checked to determine whether the return on the investment is satisfactory. The data given in Figs. 178 to 184 can be used to determine the most economical thickness of insulation, as follows : Required to find whether 2 or 2^<2 in. thickness of asbestos sponge felted insulation should be used on a boiler drum. Steam pressure is 150 lb. gage; cost of coal, $5 per ton; cost of insulation, 30 cents per sq. ft. 1 in. thick; boiler room temperature, 80 degrees. (All heat losses and savings are expressed in B.t.u. per de- gree of temperature difference.) Steam temperature at 150 lb. gage pressure 366 Room temperature 80 Temperature difference 286 Heat loss per sq. ft. per hour through 2-in. thick asbestos sponge felted (Fig. 180) 0.21 Heat loss per sq. ft. per hour through 2^ in. thick asbestos sponge felted 0.17 Saving per sq. ft. per hour per deg. temp. diff. by use of 2f-2-in. thick- ness - 0.O4 Saving per sq. ft. per hour = 286 X 0.04 = 11.44 Saving per sq. ft. per year = 8760 X 11-44 = 100.300 Saving in lb. of coal per sq. ft. 100.300 i^n-2 per year =: 10.03 10,000 Saving in dollars per sq. ft. per year _10^y $5.00 = 0.025 20000 ' Cost of 2y2 in. insulation per sq. ft. = lYz X 0.30 = 0.75 Cost of 2 in. insulation per sq. ft. = 2 X 0.30 ^ 0.60 Cost of additional ^ in. of insulation ^=- .._. 0.15 Above saving expressed as percentage return on additional cost lOOX^^ = 16.7 0.15 This is a satisfactory return so that the use of 2>2 in. thick insulation is a paying investment. (On such surfaces as boiler drums and heaters, the >4 in. of insulation is usualh" applied in the form of a plastic insulating cement.) In like manner, Figs. 182 and 184 can be used to check the most economical thicknesses of pipe insulations. Insulation of Boiler Drums and Piping. In insulating steam and hot water pipes and boiler drums, the correct thickness (see Fig. 184) should be applied so that there are no crevices or open joints. Asbestos cement can be used to seal openings, and a layer of asbestos cement can be applied over the outside of sheet or block insulation, to give a smooth hard finish. 366 u , o , m CO •a V CO T5 o C CO ■♦J C C/3 (U 1 o CO CO S o U 4-> n ^ H <4-l C CO . CO Oh u • ^ o o ^ 4-1 «^ CO a) CO P:JU (U c x: (U +j (L> U 'o' e u V o > o o ;^ ■M (U u CO U o ^:^ oPQ ol u a PU c o •4-< c CO 369 CHAPTER 11 HEAT AND COMBUSTION Theory of Heat HEAT is a form of energy convertible in exact quantitative relations into other forms of energy. When two bodies at different temperatures are placed in communication, the temperature of the warmer body falls while that of the colder rises until the two bodies attain the same temperature. To account for this phenomenon, we say that heat flows from the hotter to the colder body. The fall of temperature of the one is due to a loss of heat, while the rise in temperature of the other is due to a gain in heat. In the caloric theory, heat or caloric was assumed to be a fluid which could flow from one body to another and thus cause changes of temperature. But the experiments of Rum ford, Dav\', and Joule invalidated the old caloric theory and established the modern mechanical theory. Heat may be generated by the expenditure of mechanical work, by chemical reaction, or by the electric current. Familiar examples are the heating of bearings due to friction, the heat generated by the combustion of coal, and the heat produced in an electric lamp filament. Useful work can be done by the expenditure of heat, as in the steam engine. The law of definite relationship between work done and heat ex- pended has been firmly established by the experiments of Joule. According to Joule, heat is not a fluid substance like caloric, but is a form of energy due to the motion or configuration of the molecules in a body or system. Thermometry T~'HE measurement of the quantity of heat abstracted from or added to ^ a body depends primarily upon the measurement of temperatures ; that is, upon thermometry. The temperature of a body is a measure of the intensity of its heat, or its ability to impart heat to cooler bodies or to abstract heat from warmer ones. Temperature is expressed in units called degrees, whicJi are subdivisions of the temperature range between the temperature of melting ice and that of boiling water. There are three temperature scales in use ; the scale of Fahrenheit, which is used in nearly all engineering work ; that of CelsiiiG, called the Centigrade scale, which is used generally in scientific laboratory work; and that of Reaumur, which is used to some extent in Europe. The Fahrenheit scale is practically the only one used in American power p]ant practice. When no scale is mentioned in this book, the temperatures are given in degrees Fahrenheit. Conversions of temperature readings from one scale to another are quite simple, as may be seen from the following table : 370 HEAT Table 47. Temperature Scales. Explanation Degrees Fahrenheit Degrees Centigrade Degrees Reaumur Freezing Point Boiling Point 32° 212° 180° 9 0° 100° 100'' 5 0° 80° Difference 80° Ratio of Difference 4 Conversions are made as follows : (CX 4- )+^2 = F (RX 4- )-T^2 = F 4 (F-32) X -g- =^ RX -^ =^C 4 {F-3Z)X -^ =R CX 4- =R (30) (31) (32) {33) (34) (35) Absolute Temperature INVESTIGATIONS with gases show that as they are cooled the pressure they exert is diminished uniformly. The temperature at which the pressure would vanish is called "absolute zero." This point, which has been closely approached in practice, is expressed as — 460 deg. Fahr. The "absolute temperature" of a body is therefore its temperature above absolute zero, that is, the regular scale reading plus 460, and is often used in calculations relating to expansion and radiation. Thermodynamic Temperature Scale "T^HE only standard of temperature which depends solely upon the nature ■^ of heat and is independent of the nature of any measuring substance is the "Thermodynamic Temperature Scale." By this scale, the ratio of any two temperatures is equal to the ratio between heat absorbed and emitted liy a reversible thermodynamic engine working between the same tempera- tures. Again, these temperatures are numerically equal to those that would be indicated b}' an ideal gas thermometer, obeying exactly Boyle's law, PV = RT. Constant-volume gas thermometers, employing gases whose devia- tions from the properties of perfect gases are known, are used, therefore, to calibrate instruments for actual temperature measurement. Hydrogen is used for calibrating when the temperatures do not exceed 600 degrees. From 6(K) to 2800 deg. nitrogen is preferable, as it has less tendency to diffuse through the walls at the higher temperatures. The temperatures are observed as functions of the pressure increment, and a calibration thus determined for simpler forms of thermometer exposed to the same temperature. Thermometers and Pyrometers FIXED points have been determined by comparison with standard gas thermometers, and are used in calibrating instruments for high tempera- ture readings. These are expressed in degrees Fahrenheit as follows : HEAT 371 Table 48. Fixed Points. Substance Naphthalene boils at 760 mm. (29.92 in. of mercury) pressure Benzophenone boils at 760 mm. pressure Cadmium melts or soHdifies in air Zinc melts or solidifies in air Sulphur boils at 760 mm. pressure Antimony melts or solidifies in CO. , Aluminum solidifies in CO2 - Silver melts or solidifies in CO2 Gold melts or solidiljes in CO2 Copper melts or solidifies in CO2 Lithium metasilicate melts in air Diopside, pure, melts in air Nickel melts or solidifies in H and N Cobalt melts or solidifies in H and N Palladium melts or solidifies in air Anorthite melts in air Platinum melts in air Deg. F. 424.4 582.5 609.4 786.7 832.0 1165.6 1217.3 1760.0 1944.3 1980.7 2193.8 2526.2 2645.6 2713.6 2820.6 2821.1 3186.0 Instruments for measuring temperature are classified by /. A. Moyer in Table 49, which also gives the temperature range and degree of accuracy usually obtainable. Table 49. Thermometers. Type Range Deg. F. Accuracy Deg. F, 1. Mercury Thermometers. (a) Ordinary Type — 38 to + 575 From 1.0 deg. in common instruments up to 0.01 deg. (b) Jena Glass, cap- — 38 to + 1000 Higher ranges accurate to illary tube filled with 1 deg. nitrogen. (c) Quartz Glass, — 37 to + 1500 Higher ranges accurate to capillary tube filled 1 deg. with nitrogen. 2. Alcohol or Petrol-ether — 325 to + 100 Accurate to 1 deg. 3. Electrical Resistance — 400 to + 2200 Accurate to 0.01 deg. for range of to 500 deg. 4. Thermo-electric — 400 to + 3500 Reliable to nearest 5 deg. b. Metallic-expansion, mechanical + 300 to + 1000 Uncertain 6. Vapor + 95 to + 1350 Reliable to nearest 2 to 10 7. Radiation deg. (a) Thermo-couple + 300 to + 4000 Reliable to about nearest in focus of mirror. 20 deg. (b) Bolometer — 400 to temper- Reliable to about nearest ature of sun 20 deg. 8. Optical + 1100 to temper- Reliable to about nearest ature of sun 20 deg. 9. Seger Cones + 1100 to + 3600 Reliable to about nearest 20 deg. 372 o PQ i) G v X c o OS CO 04 CO X >> ■i-> u HEAT 373 Mercury Thermometers. Becniise of the uniform expansion of mercury, and its sensitiveness to heat, it is commonly used as the fluid for thermometric measurement within the ranges given in Table 49. Up -to temperatures of about 575°, the ordinary type of thermometer has a vacuum in the capillary tube above the mercury, while for higher temperature ranges the capillary tube is filled with nitrogen or carbonic acid gas under high pressure. Re- searches carried on at Jena have resulted in the production of a special glass for thermometers, known as the Jena normal glass ; this glass has practically the same coefficient of expansion as mercury, and hence is particularly suit- able for thermometers. Correction for Stem Exposure. Thermometers are usually graduated to read correctly for total immersion ; that is, with the bulb and stem at the same temperature. However, in general power plant measurement work it is seldom that the bulb and stem are at the same temperature: therefore, in order to obtain the correct temperature a "stem correction" must be applied. The stem correction (K) may be calculated from the formula: 7^ = 0.000088 n (t—t) (36) in which ;; is the number of degrees of the scale reading not immersed, t^ the indicated temperature, and t the mean temperature of the air surrounding the stem as shown by a second thermometer. Calibration of a Thermometer. When a thermometer Is intended for exact work, its two fixed points, viz : the freezing point and boiling point, should be verified, and the graduations calibrated. To test for the accuracy of the graduations, a short column of the mercury in the stem, say 15 or 20 degrees in length, is detached by jarring, and its length measured in suc- cessive positions through the entire length of the stem by means of the scale marked thereon. Where the capillary tube is relatively narrow, the thread of mercury will be correspondingly long, and thus b}^ its changes in length the irregularities in the thermometer tube can be determined and a calibra- tion curve deduced. Thermometer Wells. A thermometer well is used in measuring the temperature of steam or water when it is impossible to immerse the ther- mometer bulb directly. A well generally consists of a hollow plug, threaded at the upper end. It is screwed into a threaded hole in the top of the hori- zontal pipe through which the steam or water flows, the lower part of the well extending vertically into the interior of the pipe as far as the center. if practicable. The inside diameter of the well should be slightly larger than the outside diameter of the thermometer tube. The well should be filled with mercury or high grade mineral oil for temperatures below 500°, and with soft solder for higher temperatures. For superheated steam, the immersed portion of the well should preferably be fluted so as to increase the area of absorbing surface. Alcohol Thermometers. The low limit for mercury thermometers is about — 33 degrees Fahr. Hence, when it is necessary to measure lower tem- peratures, the alcohol thermometer is employed, in which alcohol or petrol ether is substituted for mercury as the expanding fluid. Electrical Resistance Thermometers are based on the variation of the electrical resistance of certain metals with the temperature. Platinum has a uniform resistance, and withstands high temperatures, hence is often used for this work. The resistance thermometer is made of a coil of pure annealed platinum wire wound upon a mica framework. The variation in resistance is measured by a Wheatstone bridge. Inasmuch as small currents are used with this device, delicate galvanometers are required. Thermo-electric Pyrometers, Fig. 185, are based upon the fact that when wires of two different metals are joined at one end and heated, an electro- motive force will be set up between the free or cold ends of the wires. The combination of two such wires is known as a thermo-couple. The voltage 374 HEAT so set up. when the '"hot" end is at a higher temperature than the "cold"' end, usually increases as the temperature difference increases and may be measured by a sensitive galvanometer or voltmeter. ~P Fig. 185. Thermo-electric Pyrometer, There are two general types of thermo-couples, viz : high resistance and low resistance. The high resistance couple is formed of platinum and platinum-rhodium wires of small diameter and is often called a rare metal couple. Base metal or low resistance couples are made of iron versus con- stantan, chromel versus alumel and various other special patented alloys that are obtainable in sizes of Xo. 6 or 8 B. W. G. Platinum and platinum- rhodium couples ma}^ be used up to a temperature of 3500° F., while base metal couples are not suitable above 2000° F.. though their safe working temperature depends on the character of the alloys used. Thermo-couples, whether of the rare metal or base metal types, should preferably be housed in protecting tubes. Iron pipe will satisfactorily serve as a protecting tube up to 1500° F., but above this temperature, special alloy, quartz or porcelain tubes should be used. Mechanical Pyrometers, Fig. 186. depend for their action upon the dif- ferent rates of expansion of two different substances, that are generally in the form of iron and brass, or graphite and iron rods. The movement of the rods resulting from expansion is multiplied by gears and levers and com- municated to an indicating dial graduated in degrees. These pyrometers sometimes find application in the determination of boiler flue gas tempera- tures. They should be frequently calibrated, although at best they give unreliable results. A peculiarity of these mechanical pyrometers is apt to be disconcerting if the inexperienced observer is not warned. On placing in a flue, the outer element expands first and causes the pointer to indicate a very low tempera- ture, after which it rises to the proper temperature as the- inner element becomes heated. On withdrawing the instrument, the outer element cools first and causes the pointer to indicate a very high temperature until the inner element cools. Owing to this peculiarit}-. they are obviously unreliable where there are wide temperature fluctuations. HEAT 375 Fig, 186. Mechanical Pyrometer. Fig. 187. Recording Vapor Thermometer. 376 V x: ■ij U-. O ■M c C8 a V X. ■M +J CO , c >^ o '^ ^ r/) u -»-• u -M 3 u > r; U Pu u CO , 7 (for heat transfer between two black bodies) can then be multiplied by this average, the result being the ai'crage net heat radiated by the hot surfaces to the boiler. The higher the fuel bed temperature the more heat passes to the boiler surface as radiant energ>- instead of being carried by the gases as sensible heat. Fig. 189 shows the extremely rapid increase at high temperatures, the radiation being four to five times as great at 3500 deg. as at 2500 deg. abso- lute. Each curve is plotted for a constant temperature (as indicated) of the soot coating on the water-heating plates. 7000r l&OO 2000 2S00 3090 3500 _ Temperature of Fuel Bed and Furnace, Abs Deg F "" Fig. 189. Relation Between Furnace Temperature and Radiated Heat for Constant Temperatures ^800, 1200, etc.j of the Soot Coating. Tests by the University of Illinois on Heine boilers, with and without a baffle protecting the lower row of tubes, showed a much lower flue-gas temperature, and 3 to 5 per cent higher efficiency when the tubes were ex- posed to radiation. Little smoke was produced in this case, although if the amount of heat transferred by radiation is too great the tire is cooled, and combustion is incomplete. A fuel bed under the boiler gives greater transmission by radiation than does a Dutch oven. Up to the point where the products of combustion are cooled below the ignition temperature, any heat transmitted by radiation, instead of being carried by the gases, is clear gain. High transmission by radiation requires a large fuel surface exposed at a wide angle to the heating surfaces, and high temperature of the fuel bed surfaces. The latter, however, must not be so high as to damage the furnace lining or fuse the ash. li ]<: A T 383 Conduction CONDUCTION through a homogeneous solid is measured by the •f/-^lll-l\xr1n^-in. thick tubes was 41.5 deg. below the temperature of the gas surface. The heat conducted was, therefore, —^ X 41.5 = 136,000 B.t.u. per sq. ft. per hr, corresponding to 4.05 boiler horsepower per square foot, or 0.247 sq. ft. per boiler horsepower. Thermal resistance is the reciprocal of thermal conductivity, and the total resistance of several bodies through which the heat must pass, one after the other, is the sum of the individual resistances. A break in a substance creates a surface resistance, so that boiler seams in contact with the fire should be eliminated. Convection TN most boilers, the bulk of the heat is carried by the gases and by contact -^ with the heating surface delivered to the boiler. This process is called convection. While considerable work has been done to elucidate the subject of con- vection, it must be admitted that much research is still necessary, Rankine's convection formula is based on the assumption that the rate of heat transfer is dependent simply upon the square of the difference in the temperatures of the gases and of the heating surface, and is independent of the velocity of the gases. This assumption is now generally rejected. Many prominent scientists and engineers have made investigations that have provided interesting information. In 1874, Professor Osborne Reynolds formulated a law of heat transfer which may be expressed as : R = a+ b^y (39) where R ^ B.t,u, transferred per sq, ft. of heating surface per hour per degree difference between the temperatures of gas and metal W = Weight of gas per hour A = Area of gas passage a and b = Constants. This law is based fundamentally on the rate of flow of the gas over the heating surface ; it has been frequently and conclusively confirmed by Stanton, Nicolson, Jordan and others. Jordan summarized the convection law of heat transfer as follows : 1. For a constant rate of mass-flow, the rate of heat transfer is pro- portional to the temperature difference between gas and metal. 2. For a given temperature difference, the rate of heat transfer in- creases with increasing gas velocity according to a linear law. 3. For a given gas velocity and a given temperature difference, the rate of heat transfer increases with the absolute value of the temperature. 4. The rate of heat transfer depends upon the condition of the heating surface. 5. The rate of heat transfer depends on the size of the channel through which the gas is flowing, the smaller the ratio of the area of the channel to the perimeter of the channel, that is, the smaller the hydraulic depth, the greater the ratio of heat transfer. 386 HEAT The value of^a is influenced by the condition of the heating surface. It varies between 1.75 and 225. With reasonably clean surfaces, it is generally very close to 2.0, and this remains the case no matter what the circumstances may be. The value of b is of the most importance. It is influenced by the hydrau- lic depth of the channel, and by the temperature. All ordinarv conditions are met by writing b = 0.001. The effect of this, at say 2,000 and 4,000 pounds of gas per sq. ft. of gas passage area per hour, is : / 2.000 \ (™) 2.0 + 0.001 I -^ — \^4=zR / 4.000 \ and 2.0 + 0.001 I — ]=6 — R Some take a much higher value of b with a consequent!}- higher value of 7? ; but as these higher values of R are not realized in practice when the radiation eftect is eliminated, it is customary to make an arbitrary addition to the amount of heating surface so deduced. Investigations now in progress by the Research Department of the Heine Cotnpany have yielded some surprising information. Under certain circumstances the value of b may be increased very considerably, — in some instances to as much as 0.004. To show the effect of this, the same gas rates as above are taken, namely. 2.000 and 4,000 pounds. / 2.000 \ 2.0 + 0.004 I ^ — \ = 10 = R / 4.000 \ 2.0 + 0.0O4 I — 1 = 18 = 7? The amount of heating surface required is, of course, inversely pro- portional to R when radiant heat is not considered. So that when \V/A = say 4.000 pounds, a boiler with i? = 18 would have a heating surface only one-third of that of a boiler with i? = 6, the capacity and efficiency being the same for both. Lawford H. Fry has made a broad investigation of the work of experi- menters in this line and has devised a formula which harmonizes the results of a large number of tests. This formula does not directly express the rate of heat transfer, but rather gives an expression for the rise or fall of tem- perature of a gas in its passage through a flue, the wall of which is at a higher or lower temperature than the gas. When the gas is hotter than the flue, lolog^^—lolog^^ =Mx (40) where .*" = Distance along the flue from entrance Ti = Initial gas temperature, deg. absolute Tz := Exit gas temperature, deg. absolute Tz =: Mean flue wall temperature, deg. absolute .V = Coefficient lolog = Logarithm of the logarithm Coefficient J./ depends on the flue dimensions and the rate of gas flow. HEAT 387 Fig. 190 is drawn from Fry's formula, and shows the relation of gas temperatures to proportion of heating surface passed over, with 2,500° initial and 450° exit temperatures in conjunction with a water temperature of 360°. The application of the law of high gas velocity to waste heat boilers has been mentioned in Chapter 4 on FURNACES AND SETTINGS. 2600 240O 220O 2000 1800 k " i600 ^ 1400 I ^|'200 1000 800 60 400 200 n \ \ T I \ \ ^ \ \ > y \ ^ y \ ^ \ \ V • \ V ^':t \^ \r^ \ C-- V- \. — S ^•=>>^ \, '- ^.^ 3 s \h ^ s. s. s, ■ v ">, •^ >-^ "*■ ->..^___ Tef VPf mtuh ? f ?/ ,m w 77 '4 f^ D r- a i \Q 20 30 40 50 60 70 80 90 100 Percentage of Heafing Surface Fassec^ Fig. 190. Relation Between Temperature of Gases and Heating Surface Passed Over. Three Heine Standard Boilers, in the American Express Co. Building, New York City, set over Detroit Stokers. HEAT 38Q Temperature Drop in Boilers FIG 191 shows the results of tests by the Bureau of Mines on a Heine Boiler, operating at 4.4 lb. per square foot per hour, in which temperatures of both sides of the tube were taken. These tests also show the large tem- perature drop between hot gas and metal, and the small drop through the metal to the water; the temperatures at the l^^-hour point bemg as follows: Gases Gas-side Surface Wate^r-side Water At beginning of path 2552 400 358 347 At end of plith - 688 352 349 347 Fig. 191. Temperature Readings in Conductivity Test. The transfer of heat from metal to water, if the circulation is sufficient. is rapid, because of the high specific heat of water. The high rate of heat transfer m condensers, which may be more than 1000 B.t.u. per sq. fl. per hour per deg. difference, ilhistrates this. Combustion COMBUSTION is the process of oxidation or the chemical union of an element with oxygen, and takes place with such rapidity that considerable light and heat are produced. The principal combustible elements ni fuel are carbon, hydrogen and sulphur. The oxygen necessary for the combustion of fuel is provided by the air, which is a' mechanical mixture, not a chemical compound. Air consists principally of oxygen and nitrogen and contains small amounts of carbon- 390 HEAT dioxide, water vapor, argon and other rare and inert gases. These inert gases are ordinarily included with the nitrogen, so that the composition of air is generally given as : Per Cent by Volume PerC ;ent by Weight 0.. 20.91 23.15 N, 79.09 76.85 The chemical combination of oxygen with the combustible elements of fuels occurs in definite and invariable proportions — a law which may be better understood by the following brief references to elementary chemistry. All substances, whether gaseous, liquid, or solid, are either elements, compounds or mixtures. An element is a substance which cannot be reduced to a simpler form. Carbon, sulphur, oxygen, hydrogen, etc., are elements. A compound is a substance which can be reduced into simpler forms or elements by chemical process. Water, carbon-dioxide, iron sulphide, etc., are chemical compounds. A mechanical mixture contains one or more substances not held in chemical combination. Air, as mentioned above, is a mixture of the elements, oxygen and nitrogen, and the compounds carbon-dioxide, water vapor, etc. Molecules. If an element or compound be divided and redivided into particles, until the limit is eventually reached where the substance can not exist by itself without losing its characteristics, that particle is known as a molecule. If such a molecule be dissociated into its component elements, these elements are known as atoms. The elements are represented in chemical nomenclature by letters, such as H for hj^drogen, C for carbon, Fe for iron, etc., etc. Compounds are represented by groups of letters with subscripts which indicate the numbers and kinds of atoms contained in the molecule. For example, the symbol H2O for water indicates that two atoms of hydrogen and one atom of oxygen comprise one molecule of water. Atoms seldom exist uncombined, hence the symbols for oxygen, nitrogen, etc., are written O2 and No, which indicate that there are two atoms in the molecules. Carbon exists in a number of dififerent forms and hence there are many carbon molecules, each containing a different number of atoms. The latest investigations seem to indicate that the least number of atoms in any carbon molecule is twelve. Atomic Weights. The atoms of different elements have different relative masses or weights. As hydrogen is the lightest, its atomic weight is generally given as 1 and the weights of other atoms referred thereto, but sometimes oxygen is given as 16 and used as the basis. Table 54 gives the atomic weights of those elements most frequently met with in the combustion of fuels. Table 54. Atomic Weights. Element Hydrogen. Carbon Sulphur Oxygen Nitrogen... Symbol H C S o N Approx. Atomic Wts. 1 12 32 16 14 Accurate Atomic Wts. 1.008 12.005 32.07 16.00 14.01 HEAT 391 Molecular J V eights. When two or more elements combine to form a compound, the relative weight of the molecule formed will equal the com- l)ined weight of the atoms which comprise it. For example, the water mole- cule. H2O consists of one atom of oxj-gen (atomic wt. 16), and two atoms of hydrogen (atomic wt. 1). 16 + 2=18, the molecular weight of water. Significance of Atomic and Molecular Weights. When expressing any- chemical reaction by an equation, the relative weights concerned in the re- action are obtained directly by using the atomic or molecular weights. For example : C + O, =^ CO. 12 + 32 =44 These relative weights may l)e expressed in kilograms, tons, pounds or in any other unit of weight. Where gases are Involved^ the relative number of molecules of the gaseous substance occurring in the reaction stand for the relative volume of that gas. Roman numerals are generall}^ used to designate these relative volumes, which may be expressed in cubic meters, cubic feet, etc. For example, in the combustion of methane, one volume of methane unites with two volumes of oxygen to form one volume of carbon-dioxide and two volumes of water vapor. I IT I II r/i4 + 20. =C0^ + 2H^0 Heat of Combustion is usually expressed as the B.t.u. generated b}' the complete combustion of one pound of fuel. When elements or compounds enter into chemical combination with one another, heat Is either evolved or absorbed ; that is, the reaction Is either exothermal or endothermal. The reactions In combustion practice are exothermal. When one pound of pure carbon burns completely to carbon-dioxide, 14,544 B.t.u. are generated. When carbon Is not supplied with sufficient air for complete combustion, carbon monoxide Is formed and only 4,351 B.t.u. are liberated. The presence of even a small amount of carbon monoxide In boiler flue gases indicates a waste of fuel since each pound of carbon In this CO has yielded less than one-third of its available heat. The effect of the presence of carbon monoxide in the flue gases on boiler and furnace efflclencv Is explained In Chapter 15 on TESTING and Chapter 16 on OPERATION." Table 55 gives the weight and volumetric reactions and the heat evolved in the combustion of those elements or substances occurring in fuels. Ignition Temperature. As defined above, combustion Is characterized by the rapid chemical union of oxygen with the combustible substance. The rapidity or speed of the chemical reaction depends definiteh' on temperature. It is a well known fact that a lump of coal, even though surrounded by the requisite amount of oxygen for combustion, will not burn, imless it Is at a relatively high temperature. So also for every combustible substance there is a definite temperature below which the substance will not oxidize or burn. This temperature, which is known as the ignition temperature, is given in Table 56 for various components of coal and for CO. It is to be noted that the fixed carbon In coal ignites at a lower tempera- ture than the volatile hydrocarbons. Carbon monoxide will Ignite at about 1210 degrees F. Therefore, with poor firing, delayed or secondary combustion may take place If oxygen is mixed with the CO In the proper proportions at a temperature of 1210° or above. 392 HEAT 393 _3 A Q c o 3 a o U in I in I Si CO H IT) ^^-^^ --V.-V ^ (N ro T*H v_^^_^ ^^ — '^ — ' -* ro Oi \0 (M o o lo O O Th ON CO rs On o rt< u^ o fN lO ■^ CO O 00 o ON lO o »o -* O Ti< O-H Tj^ lO ••— 1 d" •«—( vOiO rx 4- + I + O ! tl X u ^ I s o X i '-' " o o o - *- ^ — 0) 0) o o 394 HEAT Table 56. Ignition Temperatures. Combustible Ignition Substance Temperature Deg. F. Fixed Carbon — Bituminous Coal _ 766 Fixed Carbon — Anthracite Coal — .. 925 Carbon Monoxide .._ 1210 Hvdrocarbon? 900-1200 Hvdrogen - 1130 Sulphur --. 470 Theoretical Furnace Temperatures may be calculated on tlie basis of the following formula : where t = Temperature of combustion /, = Temperature of air r{ =^ B.t.u. developed b}' combustion rr' = Weight of products of combustion l' =: Mean specific heat of products of combustion between fi and t. The use of this formula involves a trial and error method in the deter- mination of the mean specific heat of the products of combustion. The theoretical furnace temperatures calculated by the above formula or modifi- cations of it have but little value to the engineer, as the actual furnace tem- perature is affected by variations in the rate of air supply, by the complete- ness of combustion, and by radiation from the fuel bed and flame to the cold surrounding surfaces. Actual furnace temperature will therefore always be lower than theoretical temperatures. Air Theoretically Required for Combustion. Table 55 gives the combus- tion reactions which occur in the burning of fuel. From these, the amount of ox3"gen necessar\" and consequently the weight of air theoreticalh* re- quired can be readily calculated by means of tlie atomic weights of the substances involved. The method of computing the air required for the combustion of carbon to CO2 will be given in the following example, which is tj-pical of the manner in which the results given in Table 57 are calculated. From Table 55 it is obser\-ed that one atom of carbon unites with two atoms of oxygen to form carbon dioxide. C 4- O, = CO... From Table 54 it is noted that the atomic weight of carbon i*; 12 and of oxvsren is 16. hence 12 4- (2x16) =44. or twelve parts of carbon by weight unite with thirty-two part? of oxygen by weight to form fort}-four parts of carbon dioxide b}- weight. Xow, if we consider one pound of carbon as being burned, the weight of ox>gen necessar\^ for combustion will be ^/^ or 2.667 lbs. Since air contains 23.15 per cent oxAgen by weight, there will be re- quired 4.32 lbs. of air to supply 1 lb. of oxygen. Then, 2.667 V 4.32 = 11.52 lbs. air required. HEAT 395 Table 57. Theoretical Air Requirements per lb. of Combustible. Combustible element or Compound Oxygen Required Pounds Air Required Pounds Air Required cu. ft. at 80° F Carbon to CO Carbon to CO.. CO to CO, Hydrogen Sulphur to SO.,... Sulphur to SOa... 1.33 2.67 0.57 5.76 11.52 2.47 78.4 156.5 33.5 8.00 1.00 1.50 34.56 4.32 6.48 469.5 58.6 88.2 Methane 4.00 Acetylene 3.08 17.28 13.29 234.8 180.9 Ethylene 1 3.43 14.81 201.6 Ethane 3 73 16.13 6.10 219.5 Hydrogen Sulphide ' 1.41 83.0 The theoretical air requirements given in Table 58 are calculated on the basis of the approximate atomic weights. The Bureau of Mines gives the following formula for calculating theoretical air requirements, based upon the accurate atomic weights. [F r= 0.1158 C + 0.3448// — 0.04336 {OS) (41a) where : W = \h. of air per lb. of fuel C = Percentage of carbon, ultimate analysis H = Percentage of hydrogen, ultimate analysis ^ Percentage of oxygen, ultimate analysis S = Percentage of sulphur, ultimate analysis The weight of air will be per pound of coal, per pound of dr}- coal, or per pound of combustible, according to the basis on which the analysis is reported. Air requirements of typical coals were calculated by the Bureau of Mines formula as follows : Table 58. Air Required per lb. of Coal. COAL B.t.u. per lb. Coal by Analysis, Per cent Pounds Air per lb. of fuel Air per 10,000 C H S B.t.u., Lb. Lignite, poor. Lignite, good Sub. bit., poor Sub. bit., good Bituminous, poor Bituminous, good Semi-bituminous, poor Semi-bituminous, good Semi-anthracite Anthracite, poor.. . . . . Anthracite, good 10,560 10,960 14,130 14,120| 14,700 13,700| 60.1 60.1 78.0 80.7 84.6 80.3 5.9 5.4 5.3 27.0 17.9 11.5 0.6 4.9 0.6 4.6 4.8 3.6 4.6 5.1 3.6 1.0 0.5 1.7 8.2 10.3 10.7 11.2 10.4 6,350 37.5 7.1 45.6 1.0 4.8 7,190 41.3 6.8 40.8 0.9 5.4 9,210 52.5 6.1 34.1 0.3 6.7 7.52 7.38 7.30 7.49 7.29 7.60 7.64 7.62 12,5801 13,350' 79.2 81.4 2.2 3.1 4.6 5.1 0.5 0.6 9.7 10.2 7.74 7 . 65 396 n (U V) C u V (L) +J X CC Lw ^ o V a Oi 3 in ffi V c o 4) o ffi lO '0 00 c G CC c CO CC l-l ■iJ c o o o - IL) c u OJ c ffi (U «+-. o o o ^ cu CC X () o O b 1— ( < (N (U 0) 4J CC («-< Wi o > ^ ii CC a (U fi u (U o U Ih ^ CO CC j: JH < HEAT 397 Table 58 shows that while the weight of air required per pound of fuel varies greatly with the composition of the coal, it is nearly proportional to the heat value. The weight may run from 7 to 12 lb. per pound of coal, and averages about 7.5 lb. per 10,000 B.t.u. Air Actually Required for Combustion IN practice it is necessary to supply more air than that theoretically re- quired, owing to the products of combustion getting in the way when combustion is nearly complete. At the beginning of combustion in a theoretically perfect mixture of CO and air, CO and Os molecules will come together more frequently than when they are impeded by CO2 molecules formed as combustion progresses. The last free molecules of CO and O2 will probably not come together until the temperature has fallen below their combining or ignition point. Combustion, therefore, is always more intense in the earlier part of a flame and is languid at the tip. Mixing, agitation, or eddying of the gases will hasten combustion, but an excess of the O2 mole- cules is still necessary to ensure complete combustion in a reasonable time ; the more thoroughly the air is distributed and mixed with the combustible gases, the less excess will be required. Even in gas-burning installations, where the air is intimately mixed with the fuel, some excess air must be used, and appreciable time is required to complete combustion. This is shown by the CO present in the flue gases, if the comparatively cool heating surface is too close to the burner so that the flame reaches it and its tip is extinguished. The combustion space between the fire and the heating surface should, therefore, be ample, and should be so arranged that the gas stream is diverted and broken up. In coal burning furnaces an excess of at least 40 per cent, or 1.4 times the amount of air theoretically required, is usually necessary. Products of complete combustion of fuels containing only carbon and hydrogen are carbon dioxide and water, as will be noted by reference to the reaction equation given in Table 55. The weights of these products may be readily calculated by the use of atomic weights, and the relative volumes will be noted in the volumetric equations in Table 55. The volume of CO2 resulting from the complete combustion of carbon is the same as that of the oxygen consumed, because each molecule of oxygen, O2, takes up an atom of carbon to form a molecule of CO2. Therefore, the CO2 and the unused oxygen in the flue gases cannot possibly exceed the 20.9 per cent of the oxygen in the atmosphere. But the volume of CO resulting from incomplete combustion is twice that of the oxj'gen con- sumed, because each atom of the oxygen molecule takes up an atom of carbon to form a CO molecule, thus making two molecules of CO for each molecule of O2. Therefore, if CO is present, the (CO2 + O2 + CO) in the flue gases can exceed 20.9 per cent. The steam which results from burning the hydrogen in the fuel condenses and does not show in the analysis, conse- quently the oxygen consumed disappears, and the highest possible propor- tion of CO2 and O2 in the flue gases is less than 20.9, — being about 19 per cent with bituminous coals. The analvsis of the products of combustion is discussed in Chapter 15 on TESTING. Combustion Losses. In the combustion of fuel, certain losses occur which vitally affect boiler efficiency. These losses are (1) the loss due to the in- complete combustion of carbon, (2) the loss due to latent heat of moisture formed in the burning of hydrogen, (3) the loss due to unconsumed carbon in the refuse, and (4) the loss due to incomplete combustion of the volatile hydrocarbons. The determination of these losses, together with certain other losses, inherent in methods of boiler operation, such as heat carried away by chimney gases, heat lost by radiation, etc., is discussed under the subject of the heat balance in Chapter 15 on TESTING. 398 HEAT Properties of Gases I 'HE general law for the effects of temperature and pressure on gases is -*- represented by the following equation : I'P = RT (.42) V = \'olume. cu. ft. per lb. P = Pressure, lb. per sq. in. absolute = gage pressure -|- 14.696 R =: Constant, differing with the gas T ^ Temperature absolute =:: deg. Fahr. -}- 460. Equation 42 shows that the volume increases with rise in temperature and decreases with rise in pressure. With pressure unchanged, at temperature t. the volume is VJt,-\-460) fi4-460 For constant temperaiure, at Po the volume = ViPJPa, where P^ and P, can be expressed in pounds per square inch absolute, or in inches or millimeters of mercury. When the desired value is to be derived from the volume under 'standard conditions." ['i is the volume at 32 deg. and atmospheric pressure, which corresponds to 492 deg. absolute and 14.696 lb. per sq. in. pressure (760 mm. or 29.921 in. of mercury). Table 59. Physical Characteristics of Gases Involved in Furnace Work At 32 " F. and atmospheric pressure — =:lb. per V cu. ft. At 80 " F . Lb. per cu. ft. Hvdrogen, Ho 5.3140 ^lethane, CH, , 0.6682 Carbon Monoxide, CO! 0.3826 177.900 22.372 12.809 0.00562 0.04470 0.07807 0.00512 0.04083 0.07113 Nitrogen, X2 0. 3824 , 12. 801 Air 0.3701 ' 12.390 Average flue gas 0.3555 11. 920 0.07812 08071 0.08400 0.07127 0.07353 0.07650 Oxvgen, O2 0.3348 Carbon Dioxide. CO. . . 2420 Sulphur Dioxide. SO-.. 0.1635 11.208 s.ias 5 . 473 0.08922 0.12341 0.18271 0.08129 0.11244 0.16646 The densit}', which is the reciprocal of the volume, decreases with rise in temperature and increases with higher pressure. The changes in volume and density of the gases referred to in Table 59 are shown in Fig. 192. Air containing the maximum amount of vapor for the existing tem- perature is said to be "saturated." Fig. 193 shows the weight of pure dry air for temperatures from to 212 deg. at standard atmospheric pressure 04.696 lb. per sq. in.), also the weight of air and vapor in a saturated mixture under the same pressure. HEAT 399 0.20 ,0.15 bo.io 'l>, 0.05 0.00 80 eo 40 I 20 , ..,,,.,. _ I \ \ V \ ' \ \ \ \ \ ' \ ' N^ i\ ^v >^V^ \ '"sj^ ^S^ "^^ ^^ ^«v ^'^^^v^^^ "^^"^ \ -^-^ ^ ^^t '^ ?• •«. ^ ' ^ '^^i^ ^v^ ^^ ■'^ ^ ^ ^ "~" ' """""■"■ — r""~T--+-.ZT^'*'™*=^SSE:~II^ Hydroqen(H2) =-Z^"" , L -1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 1.. 1 1 / / ^^ / r ^^^-^ / if^^V^ rW (^^i<#^'^/''fO^'' "M 'fW^^'^^W csV A^^jk'%^ ^^' W i^^'^ ^^ \/ ^ ^^^^fiC^' ^'^ / (^'!^'^^^'th -^'" / /,a«^^^.rt(?«a,[cOii^' / ..<^.^'^^'W4^\,.Q^ ^^^ / „oi^^''VbomTnL,-^«i^^" > C^^^ ^f^UMrfY ^'0' ^^ .---^ ^^L^'l^ — " i--'^ -4(00 500 iOOO 1500 2000 2500 Degrees Fahrenheit Fig. 192, Temperature in Relation to Volume and Density of Gases. Table 60 gives the weight and volume of air at temperatures to 1000 deg., and pressures up to 100 lb. gage. Intervening values can be interpolated by the use of the general laws explained above. Specific Heat of Gases. There is frequent necessity for the use of the specific heat of gases in the computation of combustion data. As defined in the units of measurements used in power plant work, the specific heat of a substance is the B.t.u. required to raise tlie temperature of one pound one degree. The specific heats of all substances, whether gaseous, liquid, or solid, vary with temperature. In the case of liquids or solids, there is little differ- ence between the specific heats at constant pressure and those at constant volume. However, for gases there is considerable difference in the specific heats under these two conditions. The gases in combustion practice may be assumed to be at constant pressure. Specific heats may be still further classified as being instantaneous or mean. The instantaneous specific heat of a substance is defined as the amount of heat required at a definite temperature to raise the temperature of a unit weight 1 degree. The mean specific heat of a substance for a given temperature interval, is the specific heat l)y whicli tlie temperature dift'erence nmst be multiplied to determine the amount of heat necessary to raise a imit weight through the given temperature interval. The mean specific heat is generally used in the calculation of combustion data. 400 KEAT Table 60. Weight and Volume of Pure Air at Different Pressures- ^ Gase pr€ss-.ir6S 25 ill lira. re'i- E. — O-Ib. 5-Ib. KMb. 2D4b- 504b. KMMbL f- ~ W V W T W T W V W T W T :: :^^^ ^- ::^ ^ : soo' 3.6:: ": 1.49 SI I4i:.5 7.0i:.i9^5 -5. 01 .5720^ 3.6f .do8 1.50 9q\ . 1395 7.16. 19551 5 . 12 . 3645 2 . 75 . 645 1 . 55 30 32 40 .0811 .0S09 0795 12.34 12.38 12.59 1366 1360 13:3S 7.3c 7.47 18761 50 60 70 078012.84 076413.10 075013.35 7.6i 7.79 7.94 1839 1803 1770 5.44:1.34321 2.92L6 ' 5.55 .3362 2.98^.5; 5.65 .3302 3.03 .5S4 I ^ 71 80 90 100 0736113.60 072313.83 071014.10 .0988110.13 .097010.32 .0954 10.50 1239 1218 119 8. OS 8.21 8.36 17381 1707 1676 D. to 5.86 5.97 .3242 .3182 3122 3.09 3.14 3.21 .5*2 561 .551 1.75 1.78 1.83 110 IPO 130 .0698114.35 .068614.58 .0674 0937 0921 14.861.0905 10.69 10.87 11.07 1176 1155 1135 8.51 8.66 8.82 1615 1618 1590 6.08 6.18 6.29 .3070 .3018 .2966 3.26 3.32 3-38 .512 .533 .524 1.85 1.88 1.91 140 150 160 .0663115.09 .0652 15.36 .064215.601 .0889 .0874 .0669 11.27 11.47 11.53 1115 1096 1078 8.97 9.13 9.281 1565 1541 1517 6.39 6.49 6.60 .2915 .2865 .2820 3.43[.516 3.49-508 3.55-499 1.94 1.97 2.01 170 180 190 .063] .0622 .0612 15.86 16.10 16.3 0846111.831 0833^ 0820 n-" 10621 9.431 o '*?' .1493) 6.691 .2775 2"30 -:?0 3-61 3.67 -491 .484 .476 2.t"i4 2.07 2.10 200 SO 240 .0603 0585 a5681 16.60 17.12 -62 .080 .07S: .0700 '.-^,\ I .021. :3S:3' 7.24 . 2ooo 2675 2605 3.77 3.81 3.85 .470 .457 .444 2.13 2.19 2.20 260 280 300 118- 101 18.61 19.13 ,07^ .07i:i . 07K :^ ii.os 130. 1273 1237 7.62 7.85 8.09 .2435 .2370 .2300 4.11 4.22 4.35 -431 -420 -407 2-32 2.38 2.45 350 400 450 .04911 .0463121.65! .043: 8.62 9.18 ■?.68 .2160 .2035 .1925 4.64 4.92 5.20 .382 .360 .340 2.62 2-78 2.95 500 550 600 .0il4 039^ 0370 ^ :j.23| oOiiO.76 -n' 11.31 1820 1730 1650 5.50 5.78 6.06 .322 .306 -292 3.11 3.27 3.4^3 700 800 900 aM2 0316 0293 29-25 31.70 .34.18 0460t21 . 75 .042^: - 039 - oo m 1509 1390 1287 6.64 7-20 7.76 267 .246 .227 4.06 4-41 1000 1.0273 36.68 .036 - ^ :5.56[.1199 8.34 .212 4.72 Yaliaes in above table based upon pare air a: a:- -zi^.: : -^^jrre (14.69€ lb. per sq. in- or 29.92 in. vaescarj). w=Weig|it in pounds per cubic foot. T=l/w=Valiiine in cobic feet per poond. There is considerable disagreement between the specific heats of gases as determined bv many investigators. Prof. G. B. Upton collaborated the work of Mallard, LeChatelicr, Holbom and Henning, Langen, Pier and others, and derived the formulas of Table 61, which are sufficiently accurate for engineer- ing calculations. 0.09 HEAT 4 / / ^ ^.^ / TV5; fe^ f 0.08 ^< =5^ ^ ^ fe^ ^ ^ -«^ raj. "^ c>^ ^*«N», 0.07 •v ^"^^ l/t-^ ■ "S ^«r<7/>/^^ ^ -r^""H-^c^^/;-/i._. X. >^ /^^yi: — ki^'r^^^//?!. . v> SsTv ^^^;,^p- =^-T-^ 'A cUUb <^ ^ .£y^ <^^^ / \rr<^ r^/i?">;r L^o / ^1. -v^.-^ S^-^^. o0.05 / V-^ 1 ^> ^ ■Q-^ / ^ ^f^. rs / ^ > <^ :? --S- 1- A^ L*5>o ^ ^^- ° 004 ' ^v) \V" N: ._ =="0.02 AV Cyvr- ^ (Vv^ Vo \ \^ l/ ^^1 \^ ' \ ^^V ■r^ C^£ \ J•^^'^ \\fy > 0.01 irits (^r^ /■ Mi>i>^ \ ■y I. if cn^^^- 401 i 100 Tempera+ure, Degrees. Fahrenheit Fig. 193. Weights of Air or Water Vapor. 200 212 Table 61. Mean Specific Heat Formulas (Const. Press.) Range o° C to f° C Gas Formula 0. 0.216 4- 0.000014^ A^ and CO 0.243 + 0.000019/ CO, 0.200 + 75 X 10-"/— 21 X 10-«/- + 2.2 X lO-^^^^ H, 3.369 4- 0.00055/' Air 0.237 + 0.00O019f Water Vapor 0.452 + 7.4 X 10-"/ + 92.6 X 10-»/2_ 20.6 X 10-^2/3 The curves, Figs. 194, 195 and 196, showing the mean specific heats at constant pressure of those gases most commonly met with in combustion practice, are based upon the formulas given in Table 61. Above a tempera- ture of about 2000° F., the values are somewhat uncertain and the results are dependable only to the first two significant figures after the decimal point. HEAT 403 \ -r \ -\- 1- ■■ ] \ \ \ l \ \ \ \ \ \ 1 \ \ \ \ \ \ \ \ \ \ I \\ \ * V \ [ \ \ \ V ' 1 ^_ 1 \ \ \ ] \ \ \ \\ \ \ '\ 1 h \ 1 1 \ \ \ \ \ \ \ I \ r \ \ \ r 4. 1 ^ i T \ 1 1 n I I ^\ \ \ >\ \ \ ^i 1 1 ^ I ^ i V. \ pi \\ \ : h ' . \ ^ r >V v.\ \ 1 T \ \ ■"' "<.■ , N, \ \ ' ^v ^ ^ ,^' >, ^L i N \ t \ ^V \ -c \ ^ A \ ^ < a ^ ^ M . ,0)1 i \ \ ^i \ < £>^ k \ ^ J ^N L_ \ ^-T r-N 1 '^\ I s 1 [ \ V ^ ^ V 1 -^ lT ^v\ \ SJ \ s \ \ \ \ S, \ \ Sj \ 1 s, i V. \ \ > s. \ 1 > s ^ > ^. \ > ^, L_ \ . a. c o U k % (L) Qj O ^^ ^ CJ «M (U a CO ^ c CO ^ ^ (^ * CM CM Cvj eg 04 Cvj CM oa (h 4if9fi o/^/09ds 404 HEAT -^^^H ^.'J-'.^^^S HEAT 405 \ ^ \ ^ \ >s \ ^ ^ :s ^ ^ N ^ V V V r ^ \ \ \ V 5^ -^ i ^ ^v t^ l<^ > v\ ^\ i ^T . ^. 1 \ V ^ V ^ _ „ r 3 T" 5 i Y 1 r V j L V \ L I "f CI* CVJ c CO ^ k O on ^i a J' CO > Q>) -$ u i) V>) S'^ 4-1 ^ Jk CO 5^ ^ ^ <+4 ^ k^ o ^ ■M CO X v:> Jji U iVj (U a ^ CO Si ^ o o o o O o o o o o o o 00 "^ CM o oo CO ^ «M o oo vo "^ UJ to «4) K> m "0 in »o »f) ^ ''^ ^ /^// ^VP^'^S 406 (4-1 Ui (U T3 C , ^>. CO ^* C o •— V ^ > o ^ u +-> >^ ^ (U (U "o z ffl - a -d u u CO C M CO ^ +-I >««i CO ^ (]) n ^ U (U ffi>^ ^ OJ C z ■^^> CO +-» CO tw ■M c ■M »-H C , CO OU cu K in •<4- (U J3 CO 4(17 Chapter 12 STEAM Properties of Water Vapor THE water used in the generation of steam may be present in the boiler plant in a number of different forms. It undergoes various transforma- tions in the boiler or in the auxiliary apparatus used in the boiler plant. In this chapter the nature of water vapor is explained, and tables of the properties of steam are given, accompanied by a demonstration of their application to practical problems. Entropy. In solving thermodynamic problems a mathematical ratio, considered as a property of substances and known by the name entropy, is of value. Most, if not all of such problems, can be solved without the use of entropy, but engineers are now generally convinced of its advantage. It should be thought of, however, simply as a mathematical expression. It is difficult to give a comprehensive definition of this property. One that will answer the purpose here is that for any reversible operation an infinitesimal change of entropy is ecjual to an infinitesimal change in the quantity of heat divided by the absolute temperature at wdiich that change takes place, the transformation being so small that no change of tempera- tL're can occur. Thus changes only, of entropy, can be measured. Expressed as an equation, d

is the symbol for entropy, // for quantity of heat, and T lor absolute temperature. Any finite change can therefore be found by integrat- ing this expression between the proper limits. Rewriting it in the form, dH = Td4>, gives a simple expression for heat in terms of the temperature, an easily measured quantity, and of the change of entropy. Tables are calcu- lated or charts constructed, giving changes of entropy. A measurement of the temperature and a knowledge of one other property, as the quality or ^■olume, in order to determine the change of entropy, are all that are required to find the quantit}^ of heat. Isothermal Expansion. If a substance, while expanding, has sufficient heat added to it to keep the temperature constant, the process is termed "isothermal." The pressure and temperature of saturated steam will vary or remain constant together, while if an ideal gas expands with the temperature constant, the pressure varies inversely with the volume. Adiabatic Expansion. This is an imaginary change supposed to take place in a substance placed inside of some vessel, as a cylinder, all the walls of which are of non-conducting material ; consequently, no heat passes through the w^alls to the substance or away from it. It is isolated from all outside heat. Work can be done, however, by drawing on the energy already stored in the substance. A reversible adiabatic is an imaginary change taking place without friction or other actual losses. When the direction of such a change is reversed, all the accompanying heat changes are reversed. Upon completion, everything affected by the heat changes in the original direction will be returned to its initial condition as far as heat is concerned. This applies to the working fluid and to substances outside as well. An expansion or compression of this nature takes place at constant entropy. A part of the 3500 H. P. installation of Heine Boilers in the Equitable Office Building, New York City. STEAM 409 Characteristics of Vapors. When a substance changes from a liquid to a gaseous state it passes through an intermediate condition in which neither the laws of liquids nor those of gases are applicable. While in this interme- diate stage, the substance is known as a vapor. A saturated vapor is one that can exist in contact with its liquid ; withdrawal of heat, however small the amount, will cause some of the vapor to return to its liquid form. The saturated condition extends therefore from the time when this vapor first begins to form from the liquid to the time when a state of complete vaporization is reached. The vapor is dry-saturated just at the instant of complete evaporation. During the process of vaporization it is known as wet-saturated vapor. When a dry-saturated vapor is further subjected to heat, its charac- teristics gradually approach those of a gas and it is then said to be in a superheated state. ^^^^^^ Fig. 197. Perfect Vacuum surrounding Cylinder containing Free Piston and Liquid. If a closed vessel, provided with the means of measuring pressure and temperature, is filled with saturated vapor it will be noticed that for any given pressure only one temperature of the vapor can exist. Any change in pressure will cause a corresponding change in temperature. Therefore, only one of those quantities need be known to locate the others. This condition applies only to saturated vapor. Formation of Vapors. Imagine a free piston, of known weight, in a cylinder, containing a pound of liquid (Fig. 197), the whole apparatus being surrounded by a perfect vacuum. Imagine the temperature of this liquid to be that of melting ice, 32 deg. (This is universally recognized as the datum temperature from which such measurements as heat and entropy are taken). The weight of the piston will impose a certain pressure {p) upon the liquid. If heat is added to the liquid the temperature will have to increase to that corresponding- to this pressure (p) before the process of vaporization can begin. A rise in temperature will be the only effect of this heat addition, until this temperature is reached. (Any increase of volume is small enough to be negligible and the pressure (p) will, of course, remain unchanged.) If more heat is applied at this point vapor will be formed. During this process the temperature will not change ; the weight of the piston re- maining the same, the pressure will be constant. The volume occupied by the substance will increase and in so doing the piston will be gradually raised. 410 S T E A ^r If a sufficient quantity oi heat be added, complete vaporization will result and the cylinder will contain dry saturated vapor, the liquid having disappeared. Beyond this point the temperature will increase, the piston con- tinuing its upward motion. The process has now reached the superheating stage and can be continued indefinite!}'. At first, as the vapor leaves the condition of saturation, its characteristics will continue to show a marked dift'erence from those of gases; as higher temperatures are reached this difference lessens and finally the superheated vapor takes on all the attri- butes of and becomes a gas. The pressure remains constant during all three processes — ^the heating of the liquid, the vaporization, and the superheating of the vapor. Saturated Vapors. The heat necessary to raise the temperature of one pound of liquid from 32 deg. to any higher temperature is known as the heat of the liquid. It can be calculated by the equation r J 32 q= / Cedt (44) J 32 hi which q is the heat of the liquid, and Ce is the specific heat of the liquid. The entropy of the liquid above that at 32 deg. can be found by integrating T -f J 492 »= = / ^ (45) in which cte is the entropy of the liquid above that at 32° F. (492 deg. abs.), Ce is the specific heat of the liquid as before, and T is the absolute tempera- ture. The specific volume of a liquid (cubic feet per pound) is considered to be a constant quantity for all temperatures and pressures and is represented by 8. The density (pounds per cubic foot) is the reciprocal of the specific volume. Tables giving the properties of saturated vapors for different pressures and temperatures contain those of the above quantities that are not constant. If a pound of liquid is complete!}' vaporized at constant pressure and temperature, the heat necessarily added is known as the "latent heat of vaporization.'' and is expressed as L. This was first found by experiment. From such experiments empirical formulas have been derived, l^y means of which tlie values in the tables have been calculated. The increase in entropy during vaporization, known as tlie ''entropy of vaporization," is found by dividing the heat of vaporization by the absolute temperature. Its expression in symbols is 4>s or L/T. The sum of the lieat of the liquid q and the lieat of vaporization L, is known as the total heat of drv saturated vapor and is represented by H. H = q^L (46) Similarly the total entropy is = =: 1.6045. Tliis must equal the total entropy of dry-saturated steam at some lower pressure. In Table 62 the last column is examined until the same figure 1.6045 is found. Opposite this in column 2 the pressure is given as 100 lb. absolute. (b) When the expansion is carried to 50 lb. abs., the final quality (x) can be found by equating the total entropy of this wet saturated steam to that of the steam in the initial superheated condition. Then 4>e [50-lbs.] + .t-~ [50-llx] = 1.6045 In Table 62 opposite 50 lb. pressure, columns 8 and 9 respectively, we have L T 4>e = 0.4108, -f:^ = 1.2501 0.4108 -^ 1.25014- = 1.6(H5 X = 0.955 414 S T E A M When extreme accuracy is not necessarj-, graphical charts can be used in place of the tables. The use of two of these charts. Figs. 198 and 199, is ex- plained below. Temperature-Entropy Diagrams T^HE diagram, Fig. 198, is given by Prof. C. H. Peahody to solve problems -■- in saturated and superheated steam. The abscissas are units of entropy and the ordinates are degrees Fahrenheit. At the left is a scale of pressures by aid of which the nearest degree can be chosen for use in the saturated region ; in the superheated region constant pressure lines are drawn and are numbered near the saturated line, as 100-lb. (pounds). The saturation line (which separates the saturated and superheated regions) gives the entropy of drs'-saturated steam, 4>e + L/T. The dotted lines give the quality x; the values are numbered at the bottom. In the superheated region the dotted lines give the superheat or excess temperature over that of saturated steam at the same pressure. The heat contents q -J- xL are given hy full lines lettered '"B-tu."" which slope toward the right downward. The specific volumes are given b}^ full lines lettered '"Cu. Ft," which have a moderate inclination from the horizontal. In the superheated region the lines can be distinguished b}^ sighting along them. The use of the diagram given in Fig. 198 is illustrated b}' the following examples : Example 1. Given the absolute pressure 160 lb. and the wetness 2 per cent (> = 0.98) : Find the entropy, heat content and specific volume. The nearest temperature is 362 deg.. and this line intersects the quality line X = 0.98 at entropy = 1-54. The B.t.u. line intersecting this point is 1175 B.t.u. z= q -\- xL and the specific volume line for 2.7 cu. ft. also crosses this point. These figures are of course obtained by interpolation. Example 2. Given the absolute pressure 160 lb. and 100 deg. superheat: Find the entropy, heat content and specific volume. The pressure curve 160 lb. in the superheat region cuts the 100 deg. superheat line at entropy 1.63. The intersection of tlie heat and volume lines give H = 1250 and specific volume ^ 33 cu. ft. (Adiabatic changes during which the entropy is constant are represented b\' vertical lines, while isothermal or constant temperature changes are hori- zontal lines.) Example 3. Steam at 120 lb. absolute pressure and 100 deg. superheat expands adiabatically to a temperature of 142 deg. Find the final quality and the final specific volume. Tlie 120-lb. line crosses the 100-dcg. superheat line at entropy 1.65. This property" is constant during the change, therefore following down the vertical entropy line 1.65 until the horizontal temperature line 142 deg. is reached, we read the quality as 0.86 and the specific volume as 100 cu. ft. MoUier Diagram for Steam THE Mollier diagram for steam, as found in Goodenough's tables, is shown in Fig. 199. In this diagram lines parallel to the coordinate axes give values of heat content and entropy, as read on the scales along the margin. Constant pressure curves slope downward and to the left. In the region of superheat constant temperature lines curve gradually toward the left downward. These are replaced in the saturated region bj* constant quality lines. Any point on the diagram represents a definite state of the fluid. If the point lies in the region of superheat the heat content, entropy, pressure and temperature are read directly. In the saturated region the quality is given, but the temperature must be obtained from the pressure. £ UJ (^ ^ pM (£< £ ^ pM 6 3 3 3 3' 3 3 3 3 1.5 1.6/ f f /1.7/ / / 1/8 y 1 .9 2.0 2.1 2.2 '-""" /Wr-^W^ *(] -h' -fk' St^-fr-h'^h' ' . __ _ -- 1 - 57^ 1 X'/ 11/ TW^ ^ 7 J 1\ 1 s 1 Al Jl_ l' ^ Ui l/v '\/ n^ir* /h / / V /'/ \' /\ // »J5J " ^, l*L'\ ,.)L./ a "''R^l T WF T ITI fK" " J '^/'5?//v ,:5y5/^ l^^L'^iih i ■ i ITKr ------ _ _- -- _ — ::-650 1/ f '/ I'S^i n^I i)^ Tt^ i ^ T ur i^ 1 l\ > M«^V / / l^r I/ClP l^^l ^T "nTl V^ J. 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'."v r\,^.. . 53 ^ X iii.1// ^ ^ '';>nrtiiritUKt-^r-- - - tu\ :5 Sm^.^^S^,;,--:-:":: ^ 5 -s^^^jjL^ Sw->^^v •^-/^^c*♦^. 1.6 1.6 1.7 1.8 1 9 2.0 2.1 2.2 ^ Fig. 198. Peabody's Temperature Entropy Diagram for Steam, AdOUlN3 STEAM 417 To prevent confusion, the volume curves are not given. This property can, however, be easily obtained. If tlie point lies in tlie superheat region, read the pressure and temperature from the diagram and look up the corre- sponding value of volume in Table 63. If it lies in the saturated region, read the pressure and quaHty from the diagram, look up the specific volume of dry- saturated steam at the same pressure in Table 62 and multiply this by the quality. The following illustrations of the use of this diagram are given by Professor Goodenough. Example 1. Find the properties of steam at a pressure of 120 lb. abso- lute and a temperature of 412 deg. From the diagrams the point that represents the state of the steam is found at the intersection of the curves p = 120 and t = 412. From the scales are read H = 1231 B.t.u., * = 1.637. From Table 63 the specific volume is found to be 4.16 cu. ft. (These particular values could be found as easily and more accurately from Table 63.) Example 2. Steam at a pressure of 120 lb. absolute and a temperature of 412 deg. expands adiabatically. At what pressure does it become dry- saturated ? During this change the entropy remains constant ; hence the final state is given by the intersection of the line

Fig. 201. Simple Convergent Nozzle. The use of the formulas can be explained by an example. Steam at a pressure of 140 lb. abs. and a temperature of 400 deg. flows through a standard convergent nozzle, 1-in. diameter, into a pipe line where the pressure is 60 lb. abs. How many pounds will pass through the nozzle per second? 420 S T E A ^I ' 1 T- M ' ! -TT"! T MM ! , , ' ■ ' I 1 ■ 1 1 1 IM 1 i 1 1 1 1 1 \ ■ \ _^ \ i ; ' \ \ ' 1 , \ 1 \ ' \ \ 1 ' , 1 ■' 1 : \ \ 1 1 : \ \ 1 i { i A \ I 1 i 1 ' 1 1 ! \ \ \ \ \ ; 1 1 ! \ \ 1 ! \ \ 1 ! \ \ 1. \ \ \ , , I 1 N \ : , 1 ; 1 1 ' 1 ! V A ■ 7- V \ 1 \ \ A \ ^ \ . . 1 1 , \\ \ V - > \ 1 ; ^, . i . ^ £i L , . , , 1 t^v ■ ■ 1 \ ; 1 • s^ 1 ' N« ; ! ' ' > i 1 i i O --3 ^. 1 A r\ *A , i ' . - :v V. r iN. ! ^N <. 1 i 1 ^\ 1 ^^ t \ 1 *cK I \ 1 j \ 4 *N k_ \ 1 1 _ ; ^ -J Vn 1 s ' ' 1 |-^ ^c i s ■ \ ! 1 V s \ 1 1 ^ ««-i ^ '^*N L I 'V V % k k s V, •n ^ S V •^ ^ K k N, —i ^ _j L u u □ d ^ -J 1 '^ »<> Ci 5 %j T. ^ ■j: ^o X n ci ^ •«* ^^ <; — •>> T. 1? S QN z K 'u Ci 5 ^ ^ •rJ ^ s Xfl ^ !_ «ti «0 1 E < o ^ r^ Ci: is: On Ci o 9> OOh^^in ^K>C^4— . O ci d d o q' o' c» d o o STEAM 421 Using the Mollier chart we find that steam Pi at 140 lb. abs. and 400 deg. has a heat content of 1221 B.t.u., and an entropy of 1.61. The pressure in the throat of the nozzle, Pt will be 0.58 of 140 lb. or 81 lb. abs. As the change between these two pressures is adiabatic we follow the 1.61 entropy line on the chart until it intersects the 81-lb. pressure curve. Here we read the heat content as 1173 and the quality, x = 0.987. The specific volume at this pres- sure and quality is 0.987 X 5.42 = 5.v35 cu. ft. The velocity in the throat of the nozzle will be : Ft = 224v' Hi — Ht = 224 i/ 1221 —1173 = 1552 ft. per sec. The area of a 1-in. orifice = 0.00545 sq. ft., so that the weight per second will be : W= 4^= 0.00545 X 1552 _T^i^ w 5.35 In solving this problem the final heat content in the velocity formula is taken at 0.58 of the initial pressure, which is the pressure at the throat of the nozzle, and not the final pressure in the pipe line. These formulas can be applied to either superheated or saturated steam. As a result of experiments, empirical formulas have been derived for the flow of steam ; these are sufficiently accurate for engineering purposes. Two sets are in common use, one by Napier and the other by Grashof. Napier's experiments were made on dry-saturated steam and his formulas apply only to steam in approximately that condition. He found that : W = '^£^ when P. = or < 0.6Pi (52) JV = O.O292.IP2 (Pi — P2) when P, > O.6P1 (53) W = Amount of steam, pounds per second A = Area of orifice, square inches Pi = Absolute pressure before orifice, pounds per square inch P2 1= Absolute pressure after orifice, pounds per square inch. The first of these gives results accurate within 2 per cent. The second formula is not to be recommended as accurate within 8 per cent when Pn/P^ is 0.85 or higher. Grashof's formula for dry-saturated steam when P2 ^ or <^ 0.58 Pi is : A p,n.97 W = ^^ (54) For a given nozzle, the weight discharged is greater for wet-saturated than for dry steam. The flow then is inversely proportional to the square root of Xx, and Grashof's formula becomes A P,0.97 ^=^nA— (55) 60 V^i To find the weight of steam discharged when P^ is greater than 0.58Pi, the curves in Fig. 202 are convenient. They are plotted from the results of Rateau's experiments on convergent nozzles and thin plate orifices. The discharge for the nozzle is first found for the condition when P^ is less than 0,58Pi. This is done either by formula (52) or by formula (54). Then the P . ratio ^ IS found, and the lower (abscissa) scale of Fig. 202 entered with this ratio. Proceed vertically to the point of intersection with curve for Everett Building, New York City, equipped with Heine Boilers. STEAM 423 convergent nozzles, and then horizontally to the left (ordinate) scale and read the coe.fficient of discharge. Multiply by this coefficient the discharge as just found, and the result is the actual discharge under the conditions given. To find the weight of steam discharged through an orifice in a thin plate, proceed as above, except that intersection is made w^ith the curve for thin plate orifice. Example : By the use of a thin diaphragm inserted between the flanges of a joint in the steam pipe supplying an auxiliary engine, it is desired to find the weight of steam consumed by the engine. The pressures observed are 152 and 143 pounds ; and the hole in the diaphragm is Vis inch. The area of the orifice is 0.0767 sq. in., and the absolute pressure Pi is 166.7 lb. Then by formula (52) ^^^ .076 X 166.7 W = ■ =Tr = 0.18088 lb. per sec. per sq. in. discharge when P2 is less than 0.58Pi Now Pi = 166.7 and P2 = 157.7 and 157.7/166.7 = 0.946. Entering the lower scale of Fig. 202 with 0.946, proceeding vertically to intersection with orifice curve and horizontally to the left-hand scale, read as coefficient 0.31. Mu1':i':!ying by the coefficient 0.31 the maximum discharge 0.18088 as found above, the discharge through the thin plate is found to be 5.6 pounds per sec; multiplying by 3,600, the discharge is 202 pounds of steam per hour. The pipe on the supply side of the diaphragm should be straight for at least 10 times its bore. The diameter of the hole in the diaphragm should not be larger than one quarter of the pipe bore. If necessary, a larger pipe must be put in on the supply side with a straight length of not less than 10 times its bore. If the diaphragm is thicker than Vg4 inch, it should be countersunk at an angle of 45° on the downstream side, so that the parallel part of the hole is not more than ^64 inch long. On the inlet side of the diaphragm, burrs should be removed and great care taken not to round away the entrance corner which must be left sharp. Owing to the difficulty of removing the burrs while keeping the corner sharp, it is sometimes easier to use a much thicker diaphragm and form a convergent nozzle in it. The thickness of the diaphragm should then be about twice the diameter of the hole. There should be a parallel portion whose length is about half the diameter of the hole, and a curved portion formed to a radius of about 1^2 diameters, making a smooth, rounded or bell-mouthed entrance similar to Fig. 201. While the diaphragm method is a simple one for finding the steam con- sumption of auxiliaries, and so forth, it is essential that great care be used in getting the exact diameter of the hole and the exact pressures obtaining. The pressure gages used should be connected within about 12 inches on each side of the diaphragm. To insure accuracy, they should be tested be- fore and after taking the readings, and, as a further check, the readings should be repeated with the positions of the gages reversed. Experimental data for the flow of superheated steam through nozzles and orifices are lacking. One of the latest formulas, in the form of that of Grashof, is worked out from experiments by Lewicke and checked from data in possession of the General Electric (Ilompany. This formula is as follows : W = ^^^ C56^ 60(1 +0.0065 P») ^^ in which D is the superheat in degrees Fahrenheit, and the other symbols are as before. 424 .^:.i Table 62. Prooerties c: 5 = rv:r=ted Steara. IK per quid per; H 29.72 29.62 29.52 29. i2 29.32 29 29 29 28 2S ,22 li ,02 ,92 ,S2 28.72 25.62 25.52 25. i2 0. ^4.55 2992 44.97 .1965 52.67 .2456 5883 .2947 63 981056 0.3438] -3929' 4:421 .491^ .5403 0.589 .639 .688 .737 28.32 .786 1 28.22 0835 28.12 .884 1 28.as .933 ! 27.92 .982 27.SS4 27.82 27.72 27.62 27.52 27.42 27.32 27.22 27.12 27.02 26.92 26.82 26.72 2-6.62 26.52 26.42 68.43 72-35 75. S7 79.06 81.98 84.68 87.19 89-54 91.75 ^.83 95.80 97-67 99.46 101.17 ! 101.76 1.031 1102.80 1.081 104.37 1.130 105.88 1.179 107.33 1-22S 10S.73 2086 1550 1255 1.326 1.375 1.424- 1.474 1.523 1.572 1.621 1.670 1.719 110.08 111.39 112.66 113.89 115.08 116.24 117.37^ 118.471 119.54i 120.58^ 913 805 720 632 596 0.000334 .000491 .000645 .000797 .000947 0.001096 .001243 .001389 .001534 .001679 549 ^0.0018^ 508.71 .001966 474.3i .002108 444.^ 418.2 .002391 395.00 374.^ 355.7 33&9 333.31 323.7 309^ 297.1 283.5 274.7 .002250 .002532 .002672 .002811 .002950 0.00300 0.00309 .00323 .00337 -00350 .00364 264.7 0. ^3.3 246.9! 238.9 231.4J 1 224.410 217.8 211.6 205.7 . 200.2^ . .00378 00391 00405 00419 00432 .00446 00459 00473 00486 00500 2^361074.2 13.04 1079.2 20731062^ 26.91 32.06 106&1 36.301090.1 4a42 1091.9 ^.93 47.11 3aQ8 52.72 1097 33.23 57.57 59.77 1100.8 61.84 1101.8 63.81 7a79 72y36 7386 73.30 78.05 79.36 80621 1083.7 1093.3 1095.0 1096.4 1071.7 0.00522.1687 2.1739 1066.1 .0262^2.113021392 1062.0 .0413 2.0732 2.1146 1058.8 .(^5 2.0423 2.0956 1056.01 .0632112.0169 2.0801 1053.6 0.0717 1.9956^2.0672 1051.3 .0790 1.9768"2.0558 1049.6 .0856 1.96G:. ^ :M38 1(H7.9 .09151.943512.0370 10I6.4J .09691.93202.0290 .6 1044.9l0.1019ll.9198l2.Q217 1098.8 1099.8 1102.7 65l68 1103.3 67.46 11(^.3 69.16 1103.1 69.76 1103.4 11(».9 110&6 1107.2 1107.9 76.70 1108.3 1109.1 1109.7 1110L3 81.8311110.8 83.01 1111.4 84.19 1111.9 85.32!lll2.4 86.41 1112.^ 87.481113.3 88-52 1113.8 1043.3 .10631.90852.0150 1(H23 1041.1 i(Mao 1088.9 1037.9 1036.9 1086.0 1033.1 1034.2 1033.4 1082.6 1031.8 1031.1 1080.4 1029.7 1029.0 1028.3 0.1221 1316 .11061.89802.0087 .1148 1.8882 2.0080 .1183 1.8791 1.9976 1.87051 .9926 .125411.862411.9878 1.9833 ?790 12861.8547 c>o^ i. 50 11 1425 1.8213 .1450 1.8135 1.9603 .1519 1.8274 1.9674 0.1474 1.8099 1497 1.8045 1.9341 1.9639 1.9573 1.9311 1.7992? .1540 1.7942^1.9482 .1561 1.789311.9454 1027.710.1381 .1601 1.9427 1.9401 1027.01 1026.4 .16201.77561.9376 1025.8 .1638 1.7713 1.9351 1025.3 .1656 1.7671 1.9327 STEAM 425 Table 62. Properties of Saturated Steam — Cont. Pressure In. of mer- cury Lb. per sq. in. (Abs.) Temp., Vol- ume, cu. ft. per lb. Weight, lb. per cu. ft. Heat content in B.t.u. of liquid of vapor Latent Heat of vapori- zation in B.t.u. Entropy of liquid of va- poriza- tion of vapor H 26.32 26.22 26.12 26.02 25.92 1.768 1.817 1.866 1.916 1.965 121.60 122.59 123.57 124.52 125.44 195.0 190.0 185.3 180.8 176.5 0.00513 .00526 .00540 .00553 .00566 89.53 90.52 91.49 92.44 93.37 1114.2 1114.7 1115.1 1115.5 1115.9 25.848 2 126.10 173.6 0.00576 94.02 1116.2 25.82 25.72 25.62 25.52 2.014 2.063 2.112 2.161 126.35 127.25 128.12 128.97 172.5 168.7 165.0 161.5 0.00580 .00593 .00606 .00619 94.28 95.16 96.03 96.89 1116.3 1116.7 1117.1 1117.5 25.12 25.32 25.22 25.12 25.02 2.211 2.260 2.309 2.358 2.407 129.81 130.64 131.44 132.24 133.02 158.1 154.8 151.7 148.8 145.9 0.00633 .00646 .00659 .00672 .00685 97.73 98.55 99.35 100.14 100.92 1117.8 1118.2 1118.6 1118.9 1119.2 21.92 23.92 2.456 2.947 133.78 140.80 143.2 120.7 0.00698 .00829 110.68 108.69 1119.6 1122.6 23.812 3 141.49 118.7 0.00843 109.38 1122.9 22.92 21.92 3.438 3.929 146.88 152.26 110.4 92.1 0.00958 .01085 114.8 120.2 1125.2 1127.5 21.776 4 152.99 90.6 0.01104 120.9 1127.9 20.92 19.92 4.421 4.912 157.10 161.50 82.5 74.8 0.01212 .01338 125.0 129.4 1129.6 1131.4 19.74 5 162.25 73.5 0.01360 130.1 1131.7 18.92 17.92 5.403 5.894 165.55 169.30 68.4 63.0 0.01463 .01587 133.4 137.2 1133.1 1134.7 17.704 6 170.07 62.0 0.01614 137.9 1135.0 16.92 15.92 6.39 6.88 172.79 176.06 58.5 54.6 0.01710 .01833 140.7 143.9 1136.1 1137.5 15.67 7 176.85 53.7 0.01864 144.7 1137.8 1024.7 1024.2 1023.6 1023.1 1022.5 1022.2 1022.0 1021.5 1021.1 1020.6 1020.1 1019.7 1019.2 1018.8 1018.3 1017.9 1013.9 1013.5 1010.5 1007.4 1007.0 1004.6 1002.1 1001.6 999.7 997.5 997.1 995.5 993.6 993.1 0.1673 .1690 .1707 .1723 .1739 0.1750 0.1755 .1770 .1785 .1799 0.1813 .1827 .1841 .1854 .1867 0.1880 .1998 0.2009 0.2098 .2187 0.2199 0.2265 .2336 0.2348 0.2401 2461 0.2473 0.2516 2568 0.2581 1.7631 1.7591 1.7553 1.7515 1.7478 1.7452 1.7442 1.7407 1.7373 1.7340 1.7307 1.7275 1.7244 1.7214 1.7184 1.7154 1.6888 1.6862 1.6661 1.6464 1.6438 1.6290 1.6134 1.6107 1.5992 1.5862 1.5835 .15742 1.5630 1.5603 1.9304 1.9281 1.9260 1.9238 1.9217 1.9203 1.9197 1.9177 1.9158 1.9139 1.9121 1.9103 1.9085 1.9068 1.9051 1.9034 1.8886 1.8871 1.8760 1.8651 1.8637 1.8556 1.8470 1.8456 1.8393 1.8323 1.8308 1.8258 1.8198 1.8184 426 STEAM Table 62. Properties of Saturated Steam. — Cont. Pressure Temp., Vol- ume, cu. ft. per lb. Weight, lb. per cu. ft. ; Heat content in B.t.u. Latent Entropy 1 In. of mer- cury Lb, per sq. in. (Abs.) of liquid of vapor heatof vapori- zation o{ B.Tu. , ^^"^^ 1 of va- poriza- tdon of vapor p ! t V 1 V q H 1 ! ^ 14.92 7.37 179.14 51.14 0.01955 147.0 1138.8 991.7 0.2617 1.5526 1.8143 13.92 7.86 182.06 48.14 .02077 149.9 1140.0 990.0 .26621.5429 1 1.8091 13.63 8 182.87 47.35 0.02112 150.8 1140.3 989.5 0.26751.5402 1 1.8077 12.92 8.35 184.83 45.49 0.02198 152.7 1141.1 988.3 0.2705 1.5337 1.80i2 11.92 8.84 187.46 43.12 .02319 155.4 1142.1 986.7 .2746 1.5250 1.7996 11.60 9 188.28 42.41 0.02358 156.2 1142.5 986.3 0.2759 1.5223 1.7982 10.92 9.33 189.97 40.99 0.02439 157.9 1143.1 985.2 0.2785 1.5168 1.7953 9.92 9.82 192.38 39.08 .02559 160.3 1144.1 983.8 .2822 1.5089 1.7912 9.56 10 193.21 38.43 0.02602 161.1 1144.4 983.3 0.2835 1.5062 1.7897 8.92 10.31 194.68 37.34 0.02678 162.6 1145.0 982.4 0.2858 1.5015 1.7873 7.92 10.81 196.89 35.75 .02797 164.8 1145.9 981.1 .2892 1.4944 1.7835 7.52 11 197.75 35.16 0.02844 165.7 1146.2 980.5 0.2905 1.4916 1.7821 6.92 11.30 199.03 34.29 0.02916 167.0 1146.7 979.8 0.2924 1.4876 1.7800 5.92 11.79 201.09 32.95 .03035 169.0 1147.5 978.5 .2955 1.4810 1.7766 5.49 12 201.96 32.41 0.03086 169.9 1147.9 978.0 0.2969 1.4783 1.7752 4.92 12.28 203.08 31.71 0.03153 170.1 1148.3 977.3 0.2986 1.4747 1.7733 3.92 12.77 205.00 30.57 .03271 173.0 1149.1 976.1 .3015 1.4687 1.7702 3.45 13 205.88 30.07 0.03326 173.8 1149.4 975.6 0.3028 1.4659 1.7687 2.92 13.26 206.87 29.51 0.03388 174.8 1149.8 974.9 0.3Oi3 1.4629 1.7671 1.92 13.75 208.67 28.53 .03505 176.6 1150.5 973.8 .3070 1.4572 1.7642 1.42 14 209.56 28.06 0.03564 177.5 1150.8 973.3 0.3083i 1.4545 1.7628 0.92 14.24 210.43' 27.61 0.03622 178.4 1151.2 972.7 0.3096 1.4518 1.7614 0.0 14.697 212 26.81 0.03730 180.0 1151.7 971.7 0.3120 1.4469 1.7589 — 14.74 212.13 26.75 0.03739 180.1 1151.8 971.7 0.3122 1.4465 1.7587 STEAM 427 Table 62. Properties of Saturated Steam. — Cont. Pressure Lb. per sq. in. Vol- Weight, Heat content in B.t.u. Latent heat of Entropy 1 Temp., ume, lb. per vapori- Absol- ute °F. cu. ft. cu. ft. of of zation of of va- of Gage per lb. liquid vapor in B.t.u. liquid poriza- tion vapor P t V 1 V q H L Cjjg L T 45 0.3 15 213.0 26.30 0.03802 181.0 1152.2 971.2 0.3135 1.4438 1.7573 5.3 20 228.0 20.10 0.0498 196.0 1157.7 961.7 0.3356 1.3987 1.7343 10.3 25 240.1 16.32 0.0613 208.2 1162.1 953.8 0.3531 1.3633 1.7164 15.3 30 250.3 13.76 0.0727 218.6 1165.7 947.1 0.3679 1.3340 1.7019 20.3 35 259.3 11.91 0.0840 227.7 1168.7 941.0 0.3805 1.3090 1.6895 25.3 40 267.2 10.51 0.0951 235.8 1171.3 935.5 0.3917 1.2871 1.6788 30.3 45 274.4 9.41 0.1062 243.1 1173.6 930.5 0.4017 1.2677 1.6694 35.3 50 281.0 8.53 0.1173 249.8 1175.6 925.9 0.4108 1.2501 1.6609 40.3 55 287.1 7.80 0.1283 255.9 1177.5 921.5 0.4190 1.2342 1.6532 45.3 60 292.7 7.18 0.1392 261.7 1179.1 917.4 0.4267 1.2195 1.6462 50.3 65 298.0 6.66 0.1501 267.1 1180.6 913.5 0.4338 1.2058 1.6397 55.3 70 302.9 6.22 0.1609 272.2 1182.0 909.8 0.4405 1.1931 1.6336 60.3 75 307.6 5.82 0.1717 277.0 1183.3 906.2 0.4468 1.1812 1.6280 65.3 80 312.0 5.48 0.1824 281.6 1184.4 902.8 0.4527 1.1700 1.6227 70.3 85 316.3 5.18 0.1932 286.0 1185.5 899.6 0.4583 1.1595 1.6178 75.3 90 320.3 4.905 0.2039 290.1 1186.5 896.4 0.4636 1.1495 1.6131 80.3 95 324.1 4.663 0.2145 294.1 1187.5 893.4 0.4687 1.1400 1.6087 85.3 100 327.8 4.442 0.2251 297.9 1188.4 890.5 0.4736 1.1309 1.6045 90.3 105 331.4 4.240 0.2358 301.6 1189.2 887.6 0.4782 1.1222 1.6004 95.3 110 334.8 4.057 0.2465 305.1 1190.0 884.8 0.4827 1.1138 1.5965 100.3 115 338.1 3.889 0.2572 308.6 1190.7 882.1 0.4870 1.1058 1.5928 105.3 120 341.3 3.735 0.2678 311.9 1191.4 879.5 0.4911 1.0982 1.5893 110.3 125 344.4 3.593 0.2783 315.1 1192.0 876.9 0.4950 1.0908 1.5858 115.3 130 347.4 3.461 0.2889 318.2 1192.6 874.4 0.4989 1.0836 1.5825 120.3 135 350.3 3.340 0.2994 321.2 1193.2 872.0 0.5026 1.0767 1.5793 125.3 140 353.1 3.226 0.3100 324.2 1193.7 869.6 0.5062 1.0700 1.5762 130.3 145 355.8 3.120 0.3206 327.0 1194.2 867.2 0.5097 1.0636 1.5733 135.3 150 358.5 3.020 0.3311 329.8 1194.7 864.9 0.5131 1.0573 1.5704 140.3 155 361.1 2.927 0.3417 332.5 1195.2 862.7 0.5164 1.0512 1.5676 145.3 160 363.6 2.839 0.3522 335.2 1195.7 860.5 0.5196 1.0453 1.5649 150.3 165 366.1 2.757 0.3627 337.8 1196.1 858.3 0.5227 1.0395 1.5622 155.3 170 368.5 2.679 0.3733 340.3 1196.5 856.2 0.5258 1.0339 1.5597 160.3 175 370.8 2.605 0.3838 342.8 1196.9 854.1 0.5287 1.0284 1.5572 165.3 180 373.1 2.536 0.3943 345.2 1197.2 852.0 0.5316 1.0231 1.5547 170.3 185 375.4 2.470 0.4048 347.6 1197.6 849.9 0.5344 1.0179 1.5523 428 STEAM Table 62. Properties of Saturated Steam. — Cont. Pressiire Heat content Lb. per s ,q. in. Temp., Vol- ume, Weight, lb. per inB t.u. Latent heat of vapori- Entropy Gage Also- late =F. cu. ft. per lb. cu. ft. of liquid of vapor zation in B.t.u. of liquid of va- poriza- tion of vapor P t V 1 q H L T 175.3 190 377.6 2.408 0.4154 350 1197.9 847.9 0.5372 1.0128 1.5500 180.3 195 379.7 2.348 0.4259 352.2 1198.2 846.0 0.5399 1.0079 1.5478 185.3 200 381.9 2.292 04304 354.5 1198.5 S44.0 05426 1.0030 1.5456 1&0.3 205 383.9 2.238 0.4469 356.7 1198.7 &42.1 05451 0.9983 1.5434 195.3 210 386.0 2.186 0.457 358.8 1199.0 8402 0.5477 09936 1.5413 200.3 215 388.0 2.137 0.468 361.0 1199.2 S38.3 0.5502 0.9890 1.5392 205.3 220 390.0 2.090 0.478 363.0 1199.5 836.5 0.5526 0.9846 1.5372 210.3 225 391.9 2.045 0.489 365.1 1199.7 834.6 O5550 0.9802 1.5352 215.3 230 393.8 2.002 0.499 367.1 1199.9 832.8 0.5573 0.9760 1.5333 220.3 235 395.6 1.961 O510 369.1 1200.1831.0 0.5597 09717 1.5314 225.3 240 397.5 1.921 0.521 371.0 1200.3 829.3 05619 0.9676 1.5295 230.3 245 399.3 1.883 0531 373.0 1200.5 827.5 05041 09635 1.5276 235.3 250 •iOl.l 1.846 0542 374.9 1200.6 825.8 05663 0.9595 1.5258 240.3 255 402.9 1.811 0.552 376.7 1200.8 824.1 0.5685 0.9556 1.5241 245.3 260 404.5 1.777 0.56.3 378.6 1201.0 822.4 0.5706 09517 1.5223 250.3 265 406.2 1.745 0.573 380.4 1201.1 8207 0.5727 0.O479 1.5206 255.3 270 407.9 1.713 0.584 382.2 1201.2 819.1 0.5747 0.9442 1.5189 260.3 275 409.6 1.683 0.594 383.9 1201.4 817.4 0.5(6. 0.9405 1.5172 265.3 280 411.2 1.654 0.605 3S5.7 1201.5 815.8 0.5787 09369 1.5156 270.3 285 412.8 1.625 0.615 387.4 1201.6 814.2 O5806 09333 1.5139 275.3 290 414.4 1.598 0.626 .389.1 1201.7 812.6 0.5826 09298 1.5123 280.3 295 415.9 1.571 0636 .390.8 1201.8 811.0 05845 09263 1.5108 285.3 300 417.5 1.545 0047 392.4 1201.9 809.4 05863 0.9229 1.5092 290.3 305 419.0 1.520 0.658 394.1 1202.0 807.9 0.5882 09195 1.5077 295.3 310 420.5 1.496 0668 395.7 1202.0 806.4 0.5900 0.91&2 1.5062 300.3 315 421.0 1.473 0.679 397.3 1202.1 804.8 0.5918 09129 1.5047 305.3 320 423.4 1.450 0.690 398.9 1202.2 803.3 0.5935 O9097 1.5032 310.3 325 424.9 1.428 O700 400.4 1202.2 801.8 05953 0.9065 1.5018 315.3 330 426.3 1.407 0711 402.0 1202.3 800.3 O5970 O9034 1.50O4 320.3 335 427.7 1.386 0721 403.5 1202.3 798.9 0.5987 O9003 1.4990 325.3 340 429.1 1.366 0732 405.0 1202.4 797.4 O6004 0.8972 1.4976 330.3 345 430.5 1.346 0.743 406.5 1202.4 795.9 0.6020 0.8942 1.4962 335.3 350 431.9 1.327 0.753 408.0 1202.5 794.5 06036 08912 1.4949 360.3 375 438.5 1.239 0.807 415.1 1202.6 787.5 0.6115 0.8768 1.48^ 385.3 400 444.8 1.162 0.860 422.0 1202.5 7806 O6190 0.8631 1.4821 Table 63. Properties of Superheated Steam. 429 p* 100 [327.8] 105 [331.4] 110 [334.8] 115 [338.1] °F. V 4) H V * H V H V 4) H Sat. 4.44 1.6045 1188.4 4.24 1.6004 1189.2 4.06 1.5965 1190.0 3.89 1.5928 1190.7 340 4.53 1.6130 1195.2 4.30 1.6065 1194.1 4.09 1.6002 1192.9 3.90 1.5941 1191.8 350 360 370 380 390 4.60 4.67 4.74 4.81 4.88 1.6199 1.6267 1.6333 1.6398 1.6461 1200.8 1206.3 1211.7 1217.1 1222.5 4.37 4.44 4.50 4.57 4.64 1.6135 1.6203 1.6270 1.6335 1.6399 1199.7 1205.3 1210.8 1216.2 1221.6 4.16 4.22 4.29 4.35 4.42 1.6073 1.6142 1.6209 1.6275 1.6339 1198.6 1204.2 1209.8 1215.3 1220.7 3.97 4.03 4.09 4.15 4.21 1.6012 1.6082 1.6150 1.6217 1.6282 1197.5 1203.2 1208.8 1214.3 1219.8 4eo 410 420 430 440 4.95 5.02 5.08 5.15 5.22 1.6523 1.6585 1.6645 1.6704 1.6762 1227.8 1233.1 1238.4 1243.6 1248.8 4.70 4.77 4.83 4.90 4.96 1.6462 1.6523 1.6584 1.6644 1.6702 1227.0 1232.3 1237.6 1242.9 1248.1 4.48 4.54 4.60 4.67 4.73 1.6403 1.6465 1.6526 1.6586 1.6645 1226.1 1231.5 1236.9 1242.2 1247.4 4.27 4.34 4.40 4.46 4.52 1.6346 1.6408 1.6470 1.6530 1.6589 1225.3 1230.7 1236.1 1241.4 1246.7 450 460 470 480 490 5.28 5.35 5.41 5.48 5.54 1.6820 1.6876 1.6932 1.6986 1.7040 1254.0 1259.2 1264.3 1269.4 1274.5 5.02 5.09 5.15 5.21 5.27 1.6760 1.6817 1.6872 1.6927 1.6981 1253.3 1258.5 1263.7 1268.8 1273.9 4.79 4.85 4.91 4.97 5.03 1.6703 1.6760 1.6816 1.6871 1.6925 1252.7 1257.9 1263.1 1268.2 1273.4 4.57 4.63 4.69 4.75 4.80 1.6647 1.6704 1.6761 1.6817 1.6871 1252.0 1257.2 1262.4 1267.6 1272.8 500 550 600 650 700 5.61 5.93 6.24 6.55 6.86 1.7093 1.7349 1.7592 1.7822 1.8042 1279.6 1304.8 1329.8 1354.8 1379.7 5.33 5.64 5.94 6.24 6.53 1.7035 1.7292 1.7535 1.7766 1.7986 1279.0 1304.4 1329.5 1354.5 1379.5 5.09 5.38 5.67 5.95 6.23 1.6979 1.7237 1.7481 1.7712 1.7933 1278.5 1303.9 1329.1 1354.2 1379.2 4.86 5.14 5.42 5.69 5.96 1.6925 1.7184 1.7429 1.7661 1.7882 1278.0 1303.5 1328.8 1353.9 1379.0 750 7.17 1.8253 1404.7 6.82 1.8197 1404.5 6.51 1.8145 1404.3 6.23 1.8094 1404.1 P* 120 [341.3] 125 [344.4] 130 [347.4] 135 [350.3] "F. V H V * H V 43 H V 4> H Sat. 3.74 1.5893 1191.4 3.59 1.5858 1192.0 3.46 1.5825 1192.6 3.34 1.5793 1193.2 350 3.79 1.5955 1196.4 3.63 1.5899 1195.3 3.48 1.5844 1194.2 3.39 1.5863 1198.9 360 3.85 1.6025 1202.1 3.69 1.5970 1201.1 3.54 1.5916 1200.0 3.45 1.5934 1204.8 370 3.91 1.6094 1207.8 3.75 1.6039 1206.8 3.59 1.5986 1205.8 3.50 1.6003 1210.5 380 3.97 1.6161 1213.4 3.80 1.6106 1212.4 3.65 1.6054 1211.5 3.56 1.6070 1216.2 390 4.03 1.6226 1218.9 3.86 1.6172 1218.0 3.70 1.6121 1217.1 3.61 1.6136 1221.8 400 4.09 1.6291 1224.4 3.92 1.6237 1223.6 3.76 1.6186 1222.7 3.66 1.6200 1227.4 410 4.15 1.6354 1229.9 3.97 1.6301 1229.1 3.81 1.6250 1228.2 3.72 1.6263 1232.9 420 4.21 1.6415 1235.3 4.03 1.6363 1234.5 3.87 1.6313 1233.7 3.77 1.6325 1238.4 430 4.26 1.6476 1240.7 4.08 1.6424 1239.9 3.92 1.6374 1239.1 3.82 1.6386 1243.8 440 4.32 1.6536 1246.0 4.14 1.6484 1245.3 3.97 1.6434 1244.5 3.87 1.6446 1249.2 450 4.38 1.6594 1251.3 4.19 1.6543 1250.6 4.03 1.6494 1249.9 3.92 1.6505 1254.6 460 4.43 1.6652 1256.6 4.25 1.6601 1255.9 4.08 1.6552 1255.2 3.97 1.6562 1259.9 470 4.49 1.6709 1261.8 4.30 1.6658 1261.2 4.13 1.6610 1260.5 4.02 1.6619 1265.2 480 4.54 1.6765 1267.0 4.35 1.6714 1266.4 4.18 1.6666 1265.8 4.07 1.6675 1270.5 490 4.60 1.6820 1272.2 4.41 1.6770 1271.7 4.23 1.6721 1271.1 4.12 1.6730 1275.7 500 4.65 1.6874 1277.4 4.46 1.6824 1276.9 4.28 1.6776 1276.3 4.17 1.6784 1280.9 510 4.71 1.6927 1282.6 4.51 1.6878 1282.0 4.34 1.6830 1281.5 4.22 1.6837 1286.2 520 4.76 1.6980 1287.7 4.56 1.6931 1287.2 4.39 1.6883 1286.7 4.27 1.6890 1291.4 530 4.82 1.7032 1292.8 4.62 1.6983 1292.4 4.44 1.6936 1291.9 4.32 1.6942 1296.6 540 4.87 1.7083 1297.9 4.67 1.7034 1297.5 4.49 1.6987 1297.0 4.37 1.6993 1301.7 550 4.92 1.7134 1303.0 4.72 1.7085 1302.6 4.54 1.7039 1302.1 4.60 1.7241 1327.3 600 5.19 1.7379 1328.4 4.98 1.7332 1328.0 4.78 1.7285 1327.7 4.84 1.7475 1352.7 650 5.45 1.7612 1353.6 5.23 1.7565 1353.3 5.03 1.7519 1353.0 5.07 1.7698 1378.0 700 5.71 1.7833 1378.7 5.48 1.7787 1378.5 5.27 1.7742 1378.2 5.30 1.7912 1403.3 750 5.97 1.8046 1403.9 5.73 1.8000 1403.7 5.51 1.7955 1403.5 5.53 1.8117 1428.7 * To the right of (P) appear steam pressures and corresponding saturated steam temperatures; the latter are in bracltets. P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and 4> and H are the entropy and total heat of superheated steam measured from 32 deg. 430 Table 63. Properties of Superheated Steam — -Cont. p* 140 :353 1] 145 [355 •S] 1 50 [358 ■5] 1 55 [361 11 ^F. cS H V O H V O H V e> H Sat. 3.23| 1.5762 ii;^3.7 3.12 1.5733 1194.2. 3.02 1.5704 1194.7 2.93 1.5676 1195.2 360 3.26 1.5S13 3.32 1.5SS4 1197.9 1203.7 3.14 3.19 1.5763 1.5S35 1196.S 1202.7 3.03 3. OS 1.5715 1.57S7 1195.7 1201.6 370 2.97 1.5741 1200.6 3.S0 3.37 1.5953 1209.5 3.25 1.5905 120S.5 3.13 1.5S5S 1207.5 3.02 1.5812 1206.5 390 3.42 1.6021 1215.2 3.30 1.59.3 1214.3j 3. IS 1.5927 1213.3 3.07 1.5881 1212.4 400 3.4S 1.60S7 1220.9 3.35 1.6040 1220.0 3.23 1.5994 1219.1 3.12 1.5949 1218.2 410 3.53 1.6152 1226.5 3.40 1.6106 1225.7 3.2S 1.6060 1224.8 3.16 1.6016 1223.9 420 3.5S 1.6216 1232.1 3.45 1.6170 1231.3 3.33 1.6124 1230.4 3.21 1.60S1 1229.6 430 3.63 1.627S 1237.6 3.50 1.6232 1236. S 3.37 1.61SS 1236.0 3.26 1.6144 1235.3 440 3.6S 1.6339 1243.1 3.54 1.6294 1242.3 3.42 1.6250 1241.6 1 3.30 1.6207 1240.8 450 3.73 1.6400 124S.5 3.59 1.6354 1247.8 3.4711.6310 1247.1 3.35 1.626S 1246.3 460 3.7S 1.645S 1253.9 3.64 1.6414 1253.2 3.51 1.6370 1252.5 3.40 1.632S 1251.8 470 3. S3 1.6517 1259.3 3.69 1.6472 125S.6 3.56 1.6429 1257.9 3.44 1.63S7 1257.3 4S0 3.S7 1.6573 1264.6 3.73 1.6529 1264.0 3.61 1.64S6 1263.3 3.4S 1.6445 1262.7 490 3.92 1.6629 1269.9 1 3.7S 1.65S6 1269.3, 3.65 1.6543 126S.7 3.53 1.6502 1 1268.1 500 3.97 1.66S5 1275.2 3.S3 1.6641 1274.6 3.69 1.6599 1274.0 1 3.57 1.655S 1273.4 510 4.02 1.6739 12S0.4 3.S7 1.6696 1279.9 3.74 1.6654 1279.3 3.62 1.6613 1278.8 520 4.06 1.6793 12S5.6 3.92 1.6750 12S5.1 3.7S 1.670S 12S4.6: 3.66 1.6667 1284.1 530 4.11 1.6S46 1290.9 3.97 1.6S03 1290.4 3. S3 1.6761 12S9.9 3.7011.6721 12S9.3 540 4.16 1.6S9S 1296.0 1 1 4.01 1.6S55 1295.6 3.S7 1.6S14 1295.1 3.75:1.6774 1294.6 550 4.21 1.6949 1301.2 4.06 1.6907 1300.S 3.92 1.6S66 1300.3 3.79' 1.6826 1299.8 600 4.44 1.719S 1326.9 4.2S 1.7156 1326.5 4.13 1 7116 1326.1 4.00 1.7077 1325.8 650 4.66 1.7433 1352.4 4.50 1.7392 1352.1 4.35 1.7352 1351.7 4.20 1.7313 1351.4 700 4.89 1.7656 137/ .7 4.72 1.7616 1377.5 4.56 1.7576 1377.2 4.41 1.753S 1377.0 750 5.11 1.7S70 1403.1 1 4.93 1.7S30 1 1402.9 4.77 1.7791 1402.6 4.61 1.7753 1 1402.4 P* 160 :S63.6: 165 [366.1] 170 :36S.5: 175 [370.8] =F. * H n e> H V rt H Sat. 2.84 1.5040 j 1195.7 2.7C 1.5622 1196.1 1 j 2.6S 1.5597 1 1106.5 1 2.61 1.5572 1196.9 370 2.87 1.5696 1199.5 2.7S 1.5651 119S.5 2.69 1.560S 1197.4' 1 1 380 9 qo 1.5767 1205.5 2.S2 1.5723 1204.5 2.73 1.5681 1203.5 2.65 1.56391 1202.5 390 2.97 1.583S 1211.4 2.S7 1.5794 j 1210.5 2.78 1.5752 1209.5: 2.69 1.5711 1208.5 400 3.01 1.5906 1217.3 2.92 1.5863 I2I6.4' 2.82 1.5821 1215.4 -^ 1.5781 1214.5 410 3.06 1.5973 1223.1 2.96 1.5931 1222 2 2.87 1.5889 1221.3 2.7S 1.5849 1220.4 420 3.11 1.603S 12-^S S 3.00 1.5997 122s. 2.91 1.5956 1227.11 2.82 1.5916 1226.3 430 3.15 1.6102 1234.5 3.05 1.6061 1233.7 2.95 1.6021 1232.8! 2.86 1.5981 1232.0 4^0 3.20 1.6165 1240.1 1 3.09 1.6124 1239.3 3.00 1.6084 1238.5. 2.91jl.6045 1237.7 450 3.24 1.6226 1245.6 1 3.14 1.6186 1244.9 3.04 1.6146 1244.2' 2.95 1.6108 1243.4 460 3.2s 1.62S7 1251.1 3.1s 1.6247 1250.5 3.0s 1.6207 1249.8 2.99 1.6169 1249.0 470 3.33 1.6346 1256.6 3.22 1.6306 1256.0 3.12 1.6267 1255.3 3.03 1.6230 1254.6 480 3.37 1.6404 1262.1 3.26 1.6365 1261.4 3.16 1.6326 1260.8 3.07 1.6289 1260.1 490 3.41 1.6461 1267.5 1 3.31 1.6422 1 1266.9 3.20 1.6384 1266.3 3.11 1.6347 1265.6 500 3.46 1.6518 1272.9 3.35 1.6479 1272.3 3.24 1.6441 1271.7 3.15 1.6404 1271.1 510 3.50 1.6573 127S.2; 3.39 1.6535 1277.6 3.29 1.6497 1277.1 3.19 1.6460 1276.5 520 3.54 1.662S 12S3.5' 3.43 1.65S9 1283. 3.33 1.6552 12S2.5 3.23 1.6515 1281.9 530 3.5S 1.66S2 12SS.S 3.47 1.6643 1288.3 3.37 1.6606 1287.8 3.27 1.6570 1287.3 540 3.62 1.6735 1294.1 1 1 3.51 1.6697 1293.6 3.41 1.6660 1293.1 3.30 1.6624 1292.6 550 3.67 1.6787 1299.3 3.55 1.6749 1298.9 3.45 1.6712 1298.4 3.34 1.6676 1297.9 600 3.87 1.7039 1325.4 3.75 1.7002 1325.0 3.64 1.6966 1324.6 3.53 1.6931 1324.2 650 4.07 1.7276 1351.1 3.95 1.7240 1350.8 3.83 1.7204 1350.5 3.72 1.7170 1350.1 700 4.27 1.7501 1376.7 4.14 1.7466 1376.4 4.02 1.7431 1376.2: 3.90 1.7397 1375.9 750 4.47 1.7717 1402.2 4.33 1.76i2 1402.0 4.20 1.7647 1401.8 4.08 1.7613 1401.5 800 4.66 1.7924 1427.7 4.52 1.7^x9 1427.6 4.3S 1.7854 1427.4 4.26 1.7821 1427.2 850 4.85 1.8123 1453.4 4.70,1.S0SS 1453.2, 4.56 1.S054 1453.1 4.43 1.S021 1452.9 * To the right of vP; appear steam pressures and corresponding saturated steam temperatures ; the latter are in brackets. P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and and H are the entropy and total heat of superheated steam measured from 32 deg. Tabl e 63. Properties of Superheated Steam — Cont. 431 p* 180 [373.1] 185 [375.4] 190 [377.6] 195 [379.7] °F. V H V

H Sat. 2.54 1.5547 1197.2 2.47 1.5523 1197.6 2.41 1.5500 1197.9 2.35 1.5478 1198.2 380 2.57 2.61 1.5598 1.5670 1201.4 1207.6 2.49 2.53 1.5558 1.5631 1200.4 1206.6 2.42 2.46 1.5518 1.5592 1199.4 1205.6 390 2.39 1.5554 1204.6 400 410 420 430 440 2.65 2.70 2.74 2.78 2.82 1.5741 1.5810 1.5877 1.5943 1.6007 1213.6 1219.5 1225.4 1231.2 1237.0 2.57 2.62 2.66 2.70 2.74 1.5702 1.5771 1.5839 1.5905 1.5970 1212.6 1218.6 1224.5 1230.4 1236.2 2.50 2.54 2.58 2.62 2.66 1.5663 1.5733 1.5801 1.5868 1.5933 1211.7 1217.7 1223.7 1229.6 1235.4 2.43 2.47 2.51 2.55 2.59 1.5626 1.5696 1.5765 1.5832 1.5897 1210.7 1216.8 1222.8 1228.7 1234.6 450 460 470 480 490 2.86 2.90 2.94 2.98 3.02 1.6070 1.6132 1.6192 1.6252 1.6310 1242.7 1248.3 1253.9 1259.5 1265.0 2.78 2.82 2.86 2.90 2.93 1.6033 1.6095 1.6156 1.6216 1.6275 1241.9 1247.6 1253.3 1258.9 1264.4 2.70 2.74 2.78 2.81 2.85 1.5997 1.6059 1.6121 1.6181 1.6240 1241.2 1246.9 1252.6 1258.2 1263.8 2.63 2.66 2.70 2.74 2.77 1.5961 1.6024 1.6086 1.6146 1.6206 1240.4 1246.2 1251.9 1257.5 1263.1 500 510 520 530 540 3.06 3.10 3.13 3.17 3.21 1.6368 1.6424 1.6480 1.6534 1.6588 1270.5 1275.9 1281.4 1286.8 1292.1 2.97 3.01 3.04 3.08 3.12 1.6332 1.6389 1.6445 1.6500 1.6554 1269.9 1275.4 1280.8 1286.2 1291.6 2.89 2.93 2.96 3.00 3.03 1.6298 1.6355 1.6411 1.6466 1.6520 1269.3 1274.8 1280.3 1285.7 1291.1 2.81 2.85 2.88 2.92 2.95 1.6264 1.6321 1.6377 1.6433 1.6487 1268.7 1274.2 1279.7 1285.2 1290.6 550 600 650 700 750 3.25 3.43 3.61 3.79 3.96 1.6641 1.6896 1.7136 1.7364 1.7581 1297.4 1323.8 1349.8 1375.6 1401.3 3.16 3.34 3.51 3.68 3.85 1.6607 1.6863 1.7104 1.7331 1.7549 1297.0 1323.4 1349.5 1375.4 1401.1 3.07 3.25 3.42 3.59 3.75 1.6574 1.6830 1.7072 1.7300 1.7518 1296.5 1323.0 1349.1 1375.1 1400.9 2.99 3.02 3.06 3.09 3.13 1.6541 1.6594 1.6646 1.6698 1.6749 1296.0 1301.4 1306.7 1312.0 1317.3 800 850 900 4.14 4.31 4.49 1.7789 1.7989 1.8183 1427.0 1452.7 1478.6 4.02 4.19 4.36 1.7757 1.7958 1.8152 1426.8 1452.6 1478.5 3.92 4.08 4.25 1.7727 1.7927 1.8121 1426.6 1452.4 1478.3 3.16 3.33 3.49 1.6799 1.7041 1.7269 1322.6 1348.8 1374.8 P* 200 [381.9] 205 [383.9] 210 [386.0] 215 [388.0] °F. V * H V * H V * H V 2.14 4> H Sat. 2.29 1.5456 1198.5 2.24 1.5434 1198.7 2.19 1.5413 1199.0 1.5392 1199.2 390 2.32 1.5516 1203.6 2.26 1.5479 1202.6 2.20 1.5443 1201.6 2.15 1.5407 1200.5 400 2.36 1.5589 1209.8 2.30 1.5552 1208.8 2.24 1.5517 1207.9 2.18 1.5482 1206.9 410 2.40 1.5660 1215.9 2.34 1.5624 1215.0 2.28 1.5589 1214.1 2.22 1.5554 1213.1 420 2.44 1.5729 1221.9 2.38 1.5693 1221.1 2.32 1.5659 1220.2 2.26 1.5625 1219.3 430 2.48 1.5796 1227.9 2.42 1.5761 1227.1 2.35 1.5727 1226.2 2.29 1.5694 1225.4 440 2.52 1.5862 1233.8 2.45 1.5828 1233.0 2.39 1.5794 1232.2 2.33 1.5761 1231.4 450 2.56 1.5927 1239.7 2.49 1.5893 1238.9 2.43 1.5859 1238.1 2.36 1.5827 1237.4 460 2.59 1.5990 1245.5 2.53 1.5956 1244.7 2.46 1.5923 1244.0 2.40 1.5891 1243.3 470 2.63 1.6052 1251.2 2.56 1.6019 1250.5 2.50 1.5986 1249.8 2.43 1.5954 1249.1 480 2.67 1.6113 1256.9 2.60 1.6080 1256.2 2.53 1.6047 1255.5 2.47 1.6015 1254.8 490 2.70 1.6172 1262.5 2.63 1.6140 1261.8 2.57 1.6108 1261.2 2.50 1.6076 1260.5 500 2.74 1.6231 1268.1 2.67 1.6199 1267.4 2.60 1.6167 1266.9 2.54 1.6136 1266.2 510 2.77 1.6288 1273.6 2.70 1.6256 1273.0 2.63 1.6225 1272.5 2.57 1.6194 1271.9 520 2.81 1.6345 1279.1 2.74 1.6313 1278.6 2.67 1.6282 1278.0 2.60 1.6251 1277.4 530 2.84 1.6400 1284.6 2.77 1.6369 1284.1 2.70 1.6338 1283.5 2.64 1.6307 1283.0 640 2.88 1.6455 1290.1 2.80 1.6424 1289.6 2.73 1.6393 1289.0 2.67 1.6363 1288.5 550 2.91 1.6509 1295.5 2.84 1.6478 1295.0 2.77 1.6447 1294.5 2.70 1.6417 1294.0 560 2.95 1.6562 1300.9 2.87 1.6531 1300.4 2.80 1.6501 1299.9 2.73 1.6471 1299.4 570 2.98 1.6614 1306.2 2.90 1.6584 1305.8 2.83 1.6553 1305.3 2.76 1.6524 1304.9 580 3.01 1.6666 1311.6 2.94 1.6636 1311.1 2.86 1.6605 1310.7 2.80 1.6576 1310.3 590 3.05 1.6717 1316.9 2.97 1.6687 1316.5 2.90 1.6657 1316.1 2.83 1.6628 1315.6 600 3.08 1.6768 1322.2 3.00 1.6737 1321.8 2.93 1.6707 1321.4 2.86 1.6678 1321.0 650 3.24 1.7010 1348.5 3.16 1.6981 1348.2 3.09 1.6951 1347.8 3.01 1.6923 1347.5 700 3.40 1.7239 1374.5 3.32 1.7211 1374.3 3.24 1.7182 1374.0 3.16 1.7154 1373.7 750 3.56 1.7458 1400.4 3.48 1.7429 1400.2 3.39 1.7401 1399.9 3.31 1.7374 1399.7 * To the right of (P) appear steam pressures and corresponding saturated steam temperatures; the latter are in brackets. P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and and H are the entropy and total heat of superheated steam measured from 32 deg. 432 Table 63. Properties of Superheated Steam — Cont. p* 220 [390.0] ' 225 [391.9] 230 [393.8] ' 235 [395.6] °F. V (t> H 1 ^' H V H 1 V n Sat. 2.09 1.5372 1199.5 2.05 1.5352 1199.7 2.00 1.5333 1199.9 1.96 1.5314 1200.1 400 2.13 1.5447 1205.9 2.08 1.5413 1204.9 2.02 1.5379 1204.0 1.98 1.5346 1202.9 410 2.17 1.5520 1212.2 2.11 1.54S() 1211.3 2.06 1.5453 1210.3 2.01 1.5421 1209.4 420 2.20 1.5591 1218.41 2.15 1.555S 1217.5 2.10 1.5526 1216.6 2.05 1.5494 1215.7 430 2.24 1.5660 1224. o 2.18 1.5628 1223.7 2.13 1.5596 1222.8 2.08 1.5564 1222.0 440 2.27 1.5728 1230.6 2.22 1.5696 1229.8 2.16 1.5664 1229.0 2.11 1.5633 1228.2 450 2.31 1.5794 1236.6 2.25 1.5762 1235.8 2.20 1.573l' 1235.0 2.15 1.5700 1234.3 4G0 2.34 1.5859 1242.5, 2.28 1.5827 1241.8 2.23 1.5797 1241.0 2.18 1.5766 1240.3 470 2.38 1.5922 1248.4 2.32 1.5891 1247.7 2.26 1..5861 1246.9 2.21 1..5831 1246.2 480 3.41 1.5984 1254.2 2.35 1.5953 1253.5 2.30 1.5923! 1252.8 2.24 1.5894 1252.1 490 2.44 1.6045 1259.9 2.38 1.6014 1259.3 2.33 1.5985 1258.6 2.28 1.5955 1257.9 500 2.47 1.6105 1265.6 2.42 1.6074 1265.0 2.36 1.6045 1264.4 2.31 1.6016 1263.7 510 2.51 1.6163 1271.3 2.45 1.6133 1270.7 2.39 1.6104 1270.1 2.34 1.6075 1269.5 520 2.54 1.6221 1276.9 2.48 1.6191 1276.3 2.42 1.6162i 1275.7 2.37 1.6134 1275.1 530 2.57 1.6277 1282.51 2.51 1.6248 1281.9 2.45 1.62191 1281.3 2.40 1.6191 1280.8 540 2.60 1.6333 1288.0 2.54 1.6304 1287.5 2.49 1.6275 1286.9 2.43 1.6247 1286.4 550 2.64 1.6388 1293.5 2.57 1.6359 1293.0 2.52 1.6331 1292.5 2.46 1.6303 1292.0 560 2.67 1.6442 1299.0 2.60 1.6413 1298.5 2.55 1.6385i 1298.0 2.49 1.6357 1297.5 570 2.70 1.6495 1304.4 2.64 1.6466 1303.9 2.58 1.64381 1303.5 2.52 1.6411 1303.0 580 2.73 1.6547 1309.8 2.67 1.6519 1309.4 2.61 1.649l| 1308.9 2.55 1.6464 1308.5 590 2.76 1.659i; 1315.2 2.70 1.6571 1314.8 2.64 1.6543 1314.3 2.58 1.6516 1313.9 600 2.79 1.6650 1320.6 2.73 1.6622 1320.2 2.67 1.6594 1319.7 2.61 1.6567 1319.3 650 2.94 1.6895 1347.1 2.88; 1.68GS 1346. s; 2.81 1.6841 1346.5 2.75 1.6815 1346.1 700 3.09 1.7126 1373.4, 3.02 1.7100 1373.11 2.95 1.7073 1372.8 2.89 1.7047 1372.5 750 3.24 1.7346 1399.5' 3.16 1.7320 1399.2 3.09 1. 72941 1399.0 3.03 1.7269 1398.8 800 3.38 1.7557 1425.5! 3.30 1.7531 1425.3 3.23 1.7505 1425.1 3.16 1.7480 1424.9 P*l 240 [397 5] 245 [399.3] , i 2 50 [401.1] 2 55 [402.9] °F. V O n V H V n V H Sat. 1.92 1.5295 1200.3 1.88 1.5276 1200.5 1.846 1.5258 1200.6! 1.811 1.5241 1200.8 400 1.93 1.5314 1202.0 1 410 1.96 1.5389 1208.4 1.92 1.5357 1207.5 !l.877 1.5326 1206.5 1.835 1.5295 1205.6 420 2.00 1.5462 1214.8 1.95 1.5430 1213.91 1.910 1.5400 1213.0 1.868 1.5369 1212.1 430 2.03 1.5533 1221.1 1.99 1.5502 1220.2 1.942 1.5472 1219.4 1.900 1.5442 1218.5 440 2.07 1.5602 1227.3 2.02 1.5572 1226.5 1.974 1 1.5542 1225.7 1.932 1.5513 1224.8 450 2.10 1.567o!l233.5 2.05 1.5640 1232.7 2.006 1.5611 1231.91 1.963 1.5582 1231.1 460 2.13 1.5736 1239.5 2.08 1.5707 1238.8 j2.038 1.5678 1238.0 '1.994 1.5649 1237.2 470 2.16 1.5801 1245.5 2.11 1.5772 1244.8 2.069 1.5743 1244.0 2.02.-) 1.5715 1243.3 480 2.19 1.5864 1251.4 2.15 1.5836 1250.7 12.099 1.5807 1250.0 2.055 1.5779 1249.3 490 2.23 1.5926 1257.3 2.18 1.5898 1256.6 2.129 1.5870 1255.9 2.085 1.5842 1255.3 500 2.26 1.5987 1263.1 2.21 1.5959 1262.5 2.159 1.5931 1261.8 2.114 1.5904 1261.2 510 2.29 1.6047 1268.8 2.24 1.6019 1268.2 2.189 1.5991 1267.61 2.143 1.5964 1267.0 520 2.32 1.6105 1274.5 2.27 1.6078 1274.0 2.218 1.6050 1273.4' 2.172 1.6024 1272.8 530 2.35 1.6163 1280.2 2.30 1.6135 1279.7 '2.247 1.6108 1279.1 2.201 1.6082 1278.5 540 2.38 1.6220 1285.9 2.33 1.6192 1285.3 2.276 1.6166 1284.8 2.229 1.6139 1284.2 550 2.41 1.6275 1291.4 2.36 1.6248 1290.9 2.305 1.6222 1290.4 2.257 1.6196 1289.8 560 2.44 1.6330 1297.0 2.38 1.6303 1296.5 2.333 1.6277 1296.0 2.285 1.6251 1295.5 570 2.46 1.6384 1302.5 2.41 1.6357 1302.0 2.361 1.6331 1301.6 2.313 1.6305 1301.1 580 2.49 1.6437 1308.0 2.44 1.6410 1307.5 2.389 1.6384 1307.1 2.340 1.6359 1306.6 590 2.52 1.6489 1313.5 2.47 1.6463 1313.0; 2.417 1.6437 1312.6, 2.368 1.6412 1312.1 600 2.55 1.6541 1318.9 2.50 1.6514 1318.5 2.444 1.6489 1318.1 2.395 1.6464 1317.6 650 2.69 1.6789 1345.8 2.63 1.6763 1345.4 2.579 1.6738 1345.1 2.527 1.6714 1344.7 700 2.83 1.7022 1372.3 2.77 1.6997 1372.0; 2.711 1.6973 1371.7 2.657 1.6949 1371.4 750 2.96 1.7244 1398.5 2.90 1.7219 1398.3! 2.840 1.7195 1398.0 2.784 1.7172 1397.8 800 3.09 1.7456 1424.7 3.03 1.7431 1424.5 .2.968 1.7408 1424.3, 2.909 1.7385 1424.1 • To the right of (P) appear steam pressures and corresponding saturated steam temperatures; the laiter are in brackets. P and V are respectively the absolute pressure and the volume in cb. ft. per lb.; and 4> and H are the entropy and total heat of superheated steam measiured from 32 deg. Table 63. Properties of Superheated Steam — Cont. 433 260 [404.5] 1.777 1.795 1.828 1.860 1.891 1.922 1.952 1.982 2.012 2.042 2.071 2.099 2.128 2.156 2.184 2.212 2.239 2.266 2.293 2.320 2.347 2.477 2.605 2.730 2.853 2.974 O 1.5223 1.5264 1.5339 1.5413 1.5484 1.5553 1.5621 1.5687 1.5752 1.5815 1.5877 1.5938 1.5998 1.6056 1.6113 1.6170 1.6225 1.6280 1.6334 1.6387 1.6439 1.6690 1.6925 1.7149 1.7362 1.7566 H 1201.0 1204.6 1211.2 1217.6 1224.0 1230.3 1236.5 1242.6 1248.6 1254.6 1260.5 1266.4 1272.2 1278.0 1283.7 1289.4 1295.0 1300.6 1306.2 1311.7 1317.2 1344.4 1371.1 1397.6 1423.8 1450.1 265 [406.2] 1.745 1.757 1.789 1 820 1.851 1.882 1.912 1.942 1.971 2.000 2.029 2.057 2.085 2.113 2.140 2.168 2.195 2.221 2.248 2.274 2.301 2.429 2.555 2.678 2.798 2.917 H 1.5206 1.5234 1.5309 1.5383 1.5455 1.5525 1.5593 1.5659 1.5724 1.5788 1.5850 1.5911 1.5971 1.6030 1.6088 1.6145 1.6200 1.6255 1.6309 1.6362 1.6415 1.6666 1.6902 1.7126 1.7339 1.7544 1201.1 1203.6 1210.2 1216.7 1223.1 1229.5 1235.7 1241.8 1247.9 1253.9 1259.9 1256.8 1271.6 1277.4 1283.1 1288.8 1294.5 1300.1 1305.7 1311.2 1316.7 1344.0 1370.8 1397.3 1423.6 1449.9 270 [407.9] 1.713 1.751 1.782 1.813 1.843 1.873 1.902 1.931 1.960 1.988 2.016 2.044 2.071 2.098 2.125 2.152 2.178 2.204 2.230 2.256 2.382 2.506 2.627 2.746 2.863 1.5189 1.5281 1.5355 1.5427 1.5497 1.5565 1.5632 1.5698 1.5762 1.5824 1.5885 1.5946 1.6005 1.6063 1.6120 1.6176 1.6231 1.6285 1.6338 1.6391 1.6643 1.6879 1.7104 1.7317 1.7522 H 1201.2 1209.3 1215.8 1222.3 1228.6 1234.9 1241.1 1247.2 1253.2 1259.2 1265.1 1271.0 1276.8 1282.6 1288.3 1294.0 1299.6 1305.2 1310.8 1316.3 1343.7 1370.5 1397.1 1423.4 1449.7 275 [409.6] 1.683 1.715 1.746 1.776 1.806 1.835 1.864 1.893 1.921 1.949 1.977 2.004 2.031 2.058 2.084 2.110 2.136 2.162 2.1: 2.213 2.338 2.459 2.578 2.695 2.810 1.5172 H 1201.4 1.5252 1.5326 1.5399 1.5469 1.5538 1.5605 1.5671 1.5735 1.5798 1.5860 1.5920 1.5980 1.6038 1.6095 1.6151 1.6206 1.6261 1.6314 1.6367 1.6620 1.6857 1.7082 1.7296 1.7501 1208.4 1215.0 1221.4 1227.8 1234.1 1240.3 1246.5 1252.6 1258.6 1264.5 1270.4 1276.2 1282.0 1287.8 1293.5 1299.1 1304.7 1310.3 1315.9 1343.3 1370.2 1396.8 1423.2 1449.6 280 [411.2] 1.654 1.680 1.711 1.741 1.770 1.799 1.828 1.856 1.884 1.911 1.939 1.966 1.992 2.019 2.045 2.070 2.096 2.122 2.147 2.172 2.295 2.414 2.531 2.646 2.759 2.872 1.5156 1.5223 1.5298 1.5371 1.5442 1.5511 1.5579 1.5645 1.5710 1.5773 1.5835 1.5895 1.5955 1.6013 1.6071 1.6127 1.6182 1.6237 1.6291 1.6344 1.6597 1.6835 1.7060 1.7274 1.7480 1.7677 H 1201.5 1207.4 1214.1 1220.6 1227.0 1233.3 1239.6 1245.8 1251.9 1257.9 1263.9 1269.8 1275.7 1281.5 1287.2 1292.9 1298.6 1304.3 1309.9 1315.5 1342.9 1369.9 1396.6 1423.0 1449.4 1475.7 285 [412.8] 1.625 1.647 1.677 1.707 1.736 1.764 1.792 1.820 1.848 1.875 1.902 1.929 1.955 1.981 2.007 2.032 2.057 2.082 2.107 2.132 2.253 2.371 2.486 2.599 2.710 2.821 1.5139 1.5195 1.5270 1.5344 1.5415 1.5485 1.5553 1.5619 1.5684 1.5748 1.5810 1.5871 1.5931 1.5989 1.6047 1.6103 1.6159 1.6214 1.6268 1.6321 1.6575 1.6813 1.7039 1.7253 1.7459 1.7657 H 1201.6 1206.5 1213.2 1219.7 1226.2 1232.6 1238.8 1245.0 1251.2 1257.3 1263.3 1269.2 1275.1 1280.9 1286.7 1292.5 1298.2 1303.8 1309.4 1315.0 1342.6 1369.6 1396.3 1422.8 1449.2 1475.6 290 [414.4] 1.598 1.614 1.644 1.673 702 730 758 786 813 1.840 1.866 1.893 1.919 1.944 1.970 1.995 2.020 2.045 2.069 2.093 2.213 2.329 2.442 2.553 2.663 2.772 1.5123 1.5167 1.5243 1.5317 1.5389 1.5459 1.5527 1.5594 1.5659 1 5723 1.5785 1.5846 1.5906 i;5965 1.6023 1.6080 1.6136 1.6191 1.6245 1.6298 1.6553 1.6792 1.7018 1.7233 1.7439 1.7637 H 1201.7 1205.5 1212.3 1218.9 1225.4 1231.8 1238.1 1244.3 1250.5 1256.6 1262.6 1268.6 1274.5 1280.4 1286.2 1291.9 1297.6 1303.3 1309.0 1314.6 1342.2 1369.3 1396.1 1422.6 1449.0 1475.4 295 [415.9] 1.571 1.583 1.612 1.641 1.670 1.698 1.725 1.753 1.780 1.806 1.832 1.858 1.884 1.909 1.934 1.959 1.984 2.008 2.032 2.056 2.174 2.288 2.400 2.509 2.617 2.724 1.5108 1.5139 1.5216 1.5290 1.5362 1.5432 1.5501 1.5568 1.5634 1.5698 1.5761 1.5823 1.5883 1.5942 1.6000 1.6057 1.6113 1.6168 1.6222 1.6276 1.6532 1.6771 1.6997 1.7213 1.7419 1.7617 H 1201.8 1204.6 1211.4 1218.0 1224.5 1231.0 1237.3 1243.6 1249.8 1255.9 1262.0 1268.0 1273.9 1279.8 1285.6 1291.4 1297.1 1302.8 1308.5 1314.1 1341.8 1369.0 1395.8 1422.4 1448.9 1475.3 * To the right of (P) appear steam pressures and corresponding saturated steam temperatures; the latter are in brackets. P and V are respectively tlie absolute pressure and the volume in cb. ft. per lb. ; and 4> and H are the entropy and total heat of superheated steam measured from 32 deg. 434 Table 63. ProDerties of Suoerheated Steam — Coni^, p* 300 '417.5; 310 ;420.5; 320 :423.4; 330 :426.3: 'Y . V c H T c H V - H - o H Sat. 1.545 1.5092 1201.9 1.496 1.5062 1202.0J jl.4o0 1.5032 1202.2 1.407 1.50Q4 1202.3 430 1.5S2 1.51S9 1210.4 1.523 1.5136 120S.6 1.469 1.50S4 1206. S 1.417 1.5033 1204.9 440 1.610 1.5263 1217.1 1.551 1.5211 1215.4 1.496 1.51 60 1213.6 !l.444 1 1.5110 1211.8 450 1.63S 1.5336 1223.7 1.57:- , r^v^ 1222.0' 1.523 1.5235 1220.3" 1.471 1.51S6 1218.6 460 1.666 1.54:07 1230.2 1.60-; = - -- -1 -)o<; 5 1.550 1.5307 1227.0 1.497 1.5259 1225.3 470 1.693 1..5476 1236.6 l.oi-; 1 :^-: 1235.0 ,1.576 1.537S 1233.5 1.522 1.53:^ 1231.9 -Ivfl 1.720 1.5544 1242 : ■ '- .-. ■.< 1 54^5 1241.4 1.602 1.5447 1239.9 1.547 1.5400 123S.4 4yO 1.747 1.5610 124.^ 1 - •: >o 1.5561 1247.7 1.627 1.5514 1246.3 1.572 1.546S 1244.9 500 1.773 1.5674 1255.2 1.711 1.5626 1253.9; ; 1.652 1.55S0 1252.6 ,1-597 1.5534 1251.2 510 1.799 1.5737 1261.3 1.736 1.5690 1260.0 1.677 1.5644 125S.8 1.621 1.5599 1257.4 520 1.S25 1.5799 1267.4 1.761 1.5752 1266.1 1.701 1.5707 1264.9 1.6*5 1.5662 1263.6 530 1.V.50 1.5S.59 1273 3 1.7S6 1 5S13 1272.1 1.725 1.5. 6S 1271.0 1.669 1.5724 1269.7 540 1.S75 1.591V ::-;■ : - >- - : '>"! 127S.1 1.749 1.5S29 1277.0 1.692 1.5785 1275.8 550 -.-■:: 1.5977 12S.: L ' -i : _ - - :.; _ 12^4 ' ; - - V V ^ 12S2 ':' 1 715 1.5S45 12S1.S 560 : -^ 1 60:34 12v; ! ^ - V • -:.-,."'" V :. V 1 " ;■ -; ' - --:- l-^- > 1 73S 1.5903 12S7.7 5. l.c-^- 1.6090 12.;-: ^^_ " -,,\4.n 1295.'! i . ^l f 1 . OVJO 1294.';' i. 1 61 1.5961 1293.6 ovO 1.973 1.6146 130- ^ • ■ L ';.102 1301.4 l.■^42 1.6059 1300.4 1.7S3 1.6017 1299.5 590 1.997 1.6200 130^1 1.-2- 1.6157 1307.1 1.S65 1.6114 1306.2 1.S05 1.6073 1305.2 600 2.020 1.6254 1313.7' 1 1.952 1.6211 1312 S 1.SS7 1.6169 1311.9 1.S27 1.612S 1311.0 650 2.136 1.6510 134: ^ - ■T'O 1.64r69 1340.7 1 997 1.642S 1340.0 1.934 1.63SS 1339.3 700 2.249 1.6750 13— ' - :"4 1.6710 136S.1 2.104 1.6670 1367.5 2.03S 1.6632 1366.9 7-"' ' 2.359 1.6977 13vo : -._>i 1.6937 1395.0 2.20S ]^ t^xQx 1394. ." ■"' T sr, 1 Ai.Ai 1394.0 S !>' J 2.467 1.7193 1422.2 2.3S6 1.7153 1421.7 2.310 1.7115 1421 1 _ _ ; ■ ^ 1420.9 2 573 1.7399 144 _ '57S 1.7597 147 .7 2.4S9 1.736C> 144S.3 2.410 1.7323 1447.9 .1 2.591 1.7559 1474. S 2.509 1.7522 1474. 5 2.336 1.72 So 1447.6 2.443 1.74S6 1474.2 P* 341:1 360 434. 3S0 '439. 400 :444.S" - ^ I * I ^ i( ^ j * I ^ |j ^ ! * I Sat. 1.366 1.4976 1202.4 1.291 1.4922 430 440 450 460 470 4S0 490 5M 510 520 530 540 539 560 570 580 590 6§0 650 700 750 2 8«0 2 850 2 900 2 36S 1.49S3 1203.0 395 1.5061 1210.0j 421 1.5137 12I6.9I 447 1.5211 1223. 7I 472 1.52-S3 1230.4; 497 1.. 53.54 123- 1.355 1.379 403 1202.5 1.223 1.4S71 1202.6, 1.5119 1220.4 1.5193 1227.2 1.526.5 1233.9 1.162 1.4821 1202.0 521:1.5422 12^ : ^27 1.5335 1240. 5 1.272 1.5030 1217.0 1.296 1.5105 1224.0 1.319 1.517S 1230.S 1.342 1.5249 1237.5 545 569 592 615 638 661 683 705 727 7491 770 1 875 976 1..54> 1-^ 1.555 : - - ' 1.5619 12o2. 1.56^1 126S. 1.5743 1274 1.5803 12 f 1.5S62 1- 1.450 1.5403 1 1.473 1.5469 1 1.495 1.5534 1 1.51. 1.559S 1 1 ?39 1.5660 1 I 1 -:1 1.5721 1 247.0 2.53.4 2-59. S 266.1 272.3 1.592: - 1.5977 1_ 1.6033 13 1.364 1.3S6 1.40S 1.429 1.451 1.472 1.492 1.5319 1.5:3S7 1.5453 1.551> 1.55S1 1^5" ^4 1.5"^^ 1.533 1.553 1.5>-- 1.5SS0 1244.2 1250.7 1257.2 126:3.6 1269.9 1276.1 i:-2.3 l_->.4 i2i'4.4 1:300.4 1 . : ' . ; ; 1.65.^4 lo: 075 1.6S24 13: 172 1.7042 14: . _>010'130>.2 1 6275 1337.0 3 1.6522 1365.0 7 1.6754 1392.4 :9 1.6974 1419.5 1.572 1.5936 1306.4 1.669 1.6204 1335.4 1.761 1.6453 1363.7 1.S51 1.66S7 1391.4 1.939 1.690S 141S.6 1.198 1.4943 1213.6 1.221 1.5020 1220.7 1.243 1.5094 1227.7 1.265 1.5167 1234.6 1.2S7'l.523S 1241.3 1.309 1.5307 124S.0 1.330 1.5374 1254.6 1.350 1.5440 1261.1 1.371 1.5505 1267.5 1.391 1.556S 1273. S 1.411 1.56- ::> 1.430 1.56:- :_^ 2 1.450 1.574;- i-r-_.4 1.469 1.5S07 129S.5 1.4S.S 1.5S64 1304.5 1.5S1 1.6136 1333.9 1.669 1.63S7 1362.4 1.755 1.6622 1390.3 1x3'^ 1 6S45 1417.7 267 1.7251 1447 360 1.7451 1473 2.139 1.71S3 1446.5 2.024 1.711S 1445.7 1 : - 1 1 .J-b. 1444.9 2 22^ 1.73S4 1473.3 2.109 1.7320 1472.6 2.002 1.7259 1472.0 * To the right of P appear steam pressures and corresponding saturated steaxn temperatures: the latter are in brackets. P and V are respectivelv the absolute pressure and the volume in cb. ft. i>er lb. : and 4> and H are the entropy and total heat of superheated steam measured from 32 deg. 435 Chapter 13 FUEL COAL in its different forms is the principal fuel used in boilers. Its appli- cation, anal3^sis and purchase have been most highly developed. The use of oil is increasing rapidly, and other fuels are employed when factors of economy or delivery warrant. Natural gas and crude oil or petroleum have the highest heat value of the commercial gaseous and liquid fuels ; and because of their ease of operation, gas and oil are highly regarded as fuels. Classification of Coals COAL is a dark brown or black mineral substance, found in the carbonif- erous geological formation. All coals are formed from vegetable growth fossilized by moisture, heat, pressure and time, and can be individually dis- tinguished by the physical structure as well as by the chemical peculiarities. A broad classification includes wood fiber or cellulose, which is the lowest of the group, followed in order by peat, lignite, bituminous coal, semi-bituminous. K) Oxygen- Percent 15 20 25 30 35 40 45 95 90 85 80 75 70 65 60' 55 50 Carbon - Percent Fig. 203. Grouping Coals according to Chemical Constituents. 45 semi-anthracite, anthracite coal and graphite. The differences in composition are shown in Fig. 203, based on data prepared by the Bureau of Mines. Start- ing from the lowest in the group, each succeeding variety of coal is distin- guished by an increase in carbon and a decrease in oxygen. The hydrogen remains practically constant for the lower part of the group but decreases rapidly in the higher part. The curve is plotted from analyses computed on a basis of coal free from moisture, ash, nitrogen and sulphur. Therefore, the sum of the carbon, hydrogen and oxygen content as given equals 100 per cent. Wood is the representative of the organic substance from which coal is derived. The extreme variations of its properties explain the differences found in coal. The term wood includes trees, small plants, and mosses, which are com- posed chemically of cellulose, or of fiber and sap or sap deposits between the fibers. Actual wood has a higher carbon content than cellulose or moss. It contains from 15 to 25 per cent of moisture even when air dried. The ash content may be from 2 to 3 per cent. Dry wood has a heat value of 8000 to 9000 B.t.u., and ordinary fire wood of 5000 to 6000 B.t.u. per pound. Peat is organic matter in the first stages of conversion to coal. It is found in swamps and bogs and consists of roots and fibers in every stage of decomposition, these containing 70 to 85 per cent of moisture. Its color varies from yellow, through brown, to black. Its percentage of nitrogen and oxygen is large and its volatile matter poorly combustible. Peat is valuable 436 FUEL as a fuel only after having been thoroughly dried. Air-dried peat has a heat value of 9000 B.t.u., and when completely dry the value may be over 10,000 B.t.u. per pound. Lignite, sometimes called brown coal, is the next step from peat in the formation of coal. It contains from 30 to 50 per cent of water, this being reduced by air-drying to from 10 to 20 per cent. Lignite is of a woody texture and does not coke on being carbonized. Its heat value is between 7000 and 8000 B.t.u. per pound, while the ash content varies from 5 to 10 per cent. As it disintegrates rapidly on exposure, lignite cannot be shipped any distance except in cold weather when frozen. Sub-bituminous coal is next to lignite in order of age. The chemical difference between it and lignite is not clearly defined and so it is sometimes called black lignite. However, the physical difference is marked. The sub- bituminous coal is black and shiny, has only a small trace of woody structure, contains less water and has a higher heat value than lignite. It differs from bituminous coals by the slacking it undergoes when exposed to the weather. Bituminous coal includes the so-called soft coals, which vary in color from dark brown to pitch black. The important divisions of this group are the caking and the non-caking coals ; both burn with a yellowish flame, and give off smoke. Caking coal has a tendency to fuse and swell in size during heating. lis high volatile content and richness in hydrocarbons make it valu- able in the manufacture of coal gas. Non-caking coal burns freely without fusing, is therefore well adapted to burning on grates without interfering with the air supply required for combustion, and is used extensively under steam boilers. The heat value is between 14,000 and 15,000 B.t.u. per pound. Semi-bituminous coal is brighter in appearance, and somewhat harder than bituminous coal, more nearly resembling anthracite. It is generally free burning, without smoke. It burns with a short flame and has a high heat value. Semi-anthracite coal is harder than semi-bituminous. It burns freely with a short flame, yielding great heat with little clinker and ash. It swells considerably in size but does not cake, and tends to split up on burning. Semi-anthracite when newly fractured will soil or soot the hand, while pure anthracite will not. There is only a small amount of this coal in the United States. Anthracite, commonly called hard coal, is practically all fixed carbon. It generally occurs with slate streaks, has a deep black color, and a shiny semi-metallic luster. It contains little hydrocarbon, is slow to ignite, and burns with a short yellowish flame which changes to a faint blue, but with little or no smoke. Anthracite does not sotten or swell, but breaks into small pieces when rapidly heated. Because the price of the coal decreases with the size, anthracite of less than V^-m. diameter is generally used for steam purposes. The smaller sizes often contain slate which cannot be dis- tinguished, so that the ash content is high. Anthracite has a specific gravity varying from 1.3 to 1.8. Graphite is the highest of the coal group but is not available for fuel because of the high temperature required for its ignition. While practically pure carbon it can be burned only with difficulty in the hottest fire and when mixed with other coals. The classification of coals by name, as above, is only a convenience. The different coals overlap to some extent and a technical description is necessary. For this purpose the chemical properties of the coals have generally been used, as shown in Table 64, by C. E. Lnckc. Campbell proposes a classification on the ratio of the total carbon (C) to the total hydrogen (H) FUEL 437 of the ultimate analysis. The coals are divided into twelve groups, but sufficient data to fix the values marked (?) are not available. Frazer sug- gests the fixed carbon (f. c.) divided by the volatile combustible matter (v. m.) of the proximate analysis, while Muck recommends the total carbon content of dry and ash free coal, as a standard. Another classification is based on the fixed carbon in the combustible, as in the last column of the tabulation. Table 64. Classification of Coal by Composition. Coal 1 Campbell Frazer Muck General Class. C H - f. c. v.m. %c in Combustible % f. c. in Combustible A Graphite and graphite coal 00 to ? Anthracite 100 to 12 Anthracite 95 B Anthracite ?to30 Anthracite 97 to 92.5 c Anthracite 30 to 26 D Semi-anthracite 26 to 23 12 to 8 92.5 to 87.5 E Semi-bituminous 23 to 20 8 to 5 Common Coal 82 87.5 to 75 F Bituminous 20 to 17 Bituminous 5 to Bituminous, Eastern 75 to 60 G Bituminous.. . . 17 to 14.4 H Bituminous 14.4 to 12.5 Bituminous, Western 65 to 50 I Bituminous 12.5 to 11.2 J Lignite 11.2 to 9.3 70 Under 50 K Peat 9.3 to? 59 L Wood or Cellulose. . . 7.2 50 Cannel coal differs from the general group of coals and is therefore not included in the previous classification. It lies somewhere between bituminous and sub-bituminous but is considerably higher in hydrogen than either. It is said that the name is derived from the fact that this coal burns like a candle. Cannel coal is hard, dull black, easily broken, and gives a large amount of gas when heated. It is valuable, therefore, as an "enricher" in gas making. Location of Coal Deposits in the United States I 'HE map. Fig. 204, shows the areas in which coals are mined, the older de- ^ posits being grouped into seven fields. Some graphite coal is found in Rhode Island ; most of the anthracite comes from Eastern Pennsylvania ; semi-bituminous comes mainly from the northeast section of the Appalachian field ; bituminous coals are found in the remaining larger fields ; sub-bitumi- FUEL 439 I Graph/ fe Vm-A Bifuminous \Anthracife lii!illllllill '5t/i? -bifuminous \Semi-bifummous ^^^^LJgnife 1-R I- Graphite 5- Eastern Inferior 2-Pa Anfhracife 6-Wesfern Inferior ^-Appalachian 7-Soufhwesf Inferior ■4-Norfhern Inferior Fig. 204. Coal Fields of the United States. nous is found mostly in the western states, and lignite comes from the South and Northwest. The coals from all these localities have been analyzed by the Bureau of Mines, the compositions being listed in Table 65. Composition of Coals T N burning coal, first the moisture is driven off. next the volatile matter, and ■*■ then the remaining fixed carbon ignites, leaving a residue of ash. These four constituents of coal are ordinarily determined by the "proximate analysis," which gives information sufficient for all practical purposes. The chemical elements are accurately determined by the ''ultimate analysis" which gives the percentage of carbon, hydrogen, nitrogen, sulphur and ash. The per- centage of oxygen is taken as the difference between 100 and the sum of the other five constituents because there is no simple direct method of deter- mining it. The results for both analyses. Table 65, are for coal "as received," which means that the weight of moisture in the actual sample, as received at the laboratory or in the coal at the point of sampling in the mine, is included in the test samples. However, both proximate and ultimate analyses can be made or computed to a dry or "moisture free" condition or to a basis of "moisture-and-ash-free" coal. The moisture-free analysis gives the compo- sition and heat value of dry coal while the moisture-and-ash-free analysis gives the approxiniate composition and heat value of the dry combustible matter. Table 68, for a typical coal sample, indicates the three values. Commercial Sizes of Coals ThOR commercial purposes, coals are classified by trade names that desig- -*- nate the size, but the names and sizes vary in different localities. In bituminous fields this variation is marked, while in the anthracite trade a fair standard exists, as indicated in Table 66. 440 FUEL Table 65. Composition and Heat Value of United States Coals. County, Bed or Local Name Proximate Analysis "A5 Received" 11 -bI Llriinate Analysis "As Received" >> O d o u Alabama Bibb, Belle Ellen Jefferson, Dolomite Jefferson, Littleton St. Clair,Da%-is Tillman Sta.) Shelby, Straven Tuscaloosa, Avernant Alaska Alaska Peninsula, Ciiignik Bay, Thompson Valley. . . . Bering River, Hartline Cook Inlet, Port Graham . . . . Matanuska.Matanuska River Seward Peninsula, Chicago Creek Arizona Navajo, Oraibi Arkansas Logan, Paris Pope, Russell%-ille Sebastian, Greenwood California Monterey, Stone Canyon. . . . Colorado Boulder, Lafayerte El Paso, Pikeview Garfield, Newcastle Montezuma, Cortez Weld, Platte%-ille Georgia Chattooga, Menlo Idaho Fremont, Hayden Illinois Clinton, *Germantown Franklin, Zeigler La SaUe, '=^La SaUe Macoupin, '^Staunton Madison, C ollins\-ille Marion, *CentraIia Montgomery, Panama St. Clair, *Shiloh Saline, Harrisburg Sangamon, =^Auburn Williamson, Carter^-ille Williamson, Herrin Indiana Clay, ^Brazil Greene, ^^Linton Knox, *Bicknell 3.16 3.16 2.53 3.39 3.83 2.62 31.05 25.40 26.94 30.69 32.03 24.18 59.56 67.75 59.48 57.08 58.66 64.11 6.23 3.69 11.05 8.84 5.48 9.09 10.77 30.37 43.99 14.87 4.75 19.96 1.72 13.72 3S.73 24.36 63.31 32.46 58.97 18.22 8.85 14.95 37j82 26.14 32.16 3.88 9.88 32.64 46.86 10.62 2.77 2.07 3.21 14.69 9.81 14.84 73.47 78.82 72.66 9.07 9.30 9.29 6.95 46.69 40.13 6.23 19.15 26.20 4.45 3.89 28.90 30.82 29.67 42.05 37.01 28.83 44.27 37.67 49.56 46.58 37.25 5.76 6.46 3.94 12.52 5.02 3.80 15.88 65.83 14.49 11.45 37.24 47.01 4.30 11.35 11.S2 12.39 13.54 12.70 9.95 13.31 11.69 6.01 16.00 9.18 8.80 34.62 27.66 36.89 35.69 36.36 34.76 33.62 35.70 32.37 32.41 27.30 29.85 40.63 55.10 41.80 40.03 41.47 42.06 41.34 39.42 54.32 37.82 55.40 53.83 13.40 5.42 8.92 10.74 9.47 13.23 1L73 13.19 7.30 13.77 8.12 7.52 Parke, *Rosedale Pike, *Lirtles Sullivan, Dugger Vigo, *Macks%ille Warrick, Elberfeld Iowa Appanoose, *Centerville. Lucas, '^'Chariton Polk, =^Altoona Wapello, *Laddsdale. . . . Kansas Cherokee, *Scamnion Crawford, Fuller Leavenworth, Lansing. . . Linn, 'Jewett 16.91 26.85 3S.S7 17-37! 13.58 32.07 46.20 8.15 12.08 32.48 44.42 11.02 10.72 11.12 13.48 12.82 9.69 39.29 36.98 32.51 34.80 38.59 41.42 42.55 48.38 42.08 41.04 8.5 < 9.35 5.63 10.30 10.68 14.08 35.59 39.37 10.96 1 15.39 30.49 41.49 12.63 13.88 36.94 35.17 14.01 8.24 30.74 45.02 16.00 2.50 33.80 51J25 12.451 4.85 33.53 52.52 9.10 11.10 35.51 40.69 12.70 9.04 29.69 45.55 15.72 1.20 0.56 0.79 2.34 0.97 0.64 5.33 5.05 4.80 5.18 5.29 4.72 78.28 S2.28 74.44 73. SI 77.26 77.52 1.37 1.36 1.59 1.53 1.25 1.48 7.59 7.06 7.33; 8.30; 9.75 6.55 0.70 4.98 55.27 0.62 3.14 65.93 0.52 5.S1 49.53 0.46 4.46 70.78 0.65 6.12 41.79 0.67 45.89 1.12 5.42 62.00 1.13 19.71 2.79 4.02 78.71 1.74 3.62 80.28 3.12 3.75 78.37 1.46 1.47 1.52 3.95 3.59 3.95 4.17 6.28 66.01 1.17 16.14 0.25 0.30 0.44 7.04 0.46 5.93 6.13 5.43 4.96 6.64 56.38 49.36 72.57 66.19 48.36 1.08 0.66 L72 1.16 0.93 30.60 37.09 15.90 8.13 38.59 1.27 4.32 70.59 1.09 8.24 0.54 5.94 68.09 1.40 19.73 4.76 0.46 3.92 4.03 3.67 3.87 3.75 4.38 1.66 4.05 0.90 1.13 5.41 5.44 5.S5 5.71 5.81 5.25 5.19 5.46 5.27 5.55 5.10 5.08 57.36 67.87 61.29 58.69 60.91 59.64 59.07 57.15 71.63 53.89 68.45 68.70 1.05 1.34 1.00 0.95 0.99 1.04 0.95 0.94 1.34 0.91 1.14 1.33 18.02 19.47 19.02 19.88 19.15 16.97 19.31 18.88 12.80 21.83 16.29 16.24 14,141 14,616 13,286 13,363 13,799 13,729 0.61 23.57 i 9,641 1.32 10.77 10,820 0.92 34.37 8,793 1.42 7.93 12,585 1.89 5.48 52,97 1.01 21.28 0.91 5.65 63.53 1.42 20.34 3.65 5.34 60.45 0.89 18.651 3.83 3.78 L09 3.27 4.79 5.86 5.63 5.94 5.66 5.39 63.48 63.01 66.01 61.16 62.36 1.16 1.13 1.49 1.03 1.28 4.26 5.57 58.49 0.90 3.19 5.74 55.81 1.14 6.15 5.52 54.68 0.84 5.03 4.81 59.82 0.94 17.10 17.10 19.84 18.58 15.50 19.82 21.49 18.80 13.40 10,800 13,774 13,702 13,588 12,477 9,616 8,352 13,129 12,341 8,465 12,791 12,094 10,733 11,961 11,399 10,807 10,989 10,960 10,548 10,999 12,793 9,940 12,015 12,222 9,524 11,419 11,011 11,767 11,549 11,788 11,119 11,412 10,723 10,242 10,244 11,027 5.68 4.91 69.07 1.20 6.69 12,900 4.95 5.08 71.20 1.24 8.43 12,942 3.99 5.30 60.72 1.13 16.16 11,065 3.72 5.01 60.99 1.06 13.50 11,142 "^Indicates samples from car deliveries; all others are mine samples. FUEL 441 Table 65. Composition and Heat Value of United States Coals — Cont. County, Bed or Local Name Proximate Analysis "As Received" Ultimate Analysis "As Received" 3 Of m c o C4 u X O 0)1-] > CS « S t> ft 2 fc,^ Ultimate Analysis "As Received" 3 ^ c 3 J -J Pennsyl vania — C ontinue d Cambria, Nanty Glo Cambria, Portage Cambria, St. Benedict Cambria, Van Ormer Cambria, Vintondale Cambria, Windber Center, Osceola Mills Clarion, Blue Ball Station Clearfield, Boardman Clearfield, Philipsburg Clearfield, Smoke Run. . Fayette, Connellsville. . . Indiana, Cl>Tner Indiana, Glen Campbell. Jefferson, Sykesville Lackawanna, Diinmore. Luzerne, Pittston SchuvDdll, Miners\alle. . Schuylkill, Tower City. Somerset, Jerome Somerset, MacDonaldton. . . Somerset, "Windber Sullivan, Lopez Washington, Marianna Westmoreland, Greensburg. Rhode Island Newport, Portsmouth Providence, Cranston South Dakota Perkins, Lodgepole Tennessee Anderson, Brice\ille Campbell, LafoUette Rhea, Da>-ton Texas Houston, Crockett Wood, Hoj-t Utah Carbon, Sunnyside Emery, Emery Iron, Cedar City Summit, Coahille Virginia Henrico, Ga\ton Lee, Darb>'\-ille Russell, Dante Tazewell, Pocahontas Wise, Georgel Washington King, Black Diamond King, Cumberland Elittitas, Roslyn Pierce, Carbonado Thurston, Centralia West Virginia Fayette, Carlisle Fayette, Fayette Fayette, Hawks Nest Fayette, Kay Moor Fayette, MacDonald 2.84 3.52 2.94 2.73 3.63 3.30 2.08 1.90 2.95 0.90 3.73 3.24 2.06 3.08 2.44 3.43 2.19 2.76 3.33 1.44 1.03 2.40 3.16 1.44 2.14 22.92 4.54 19.78 17.32 19.52 24.98 18.63 12.50 21.46 22.00 21.29 21.59 20.29 27.13 24.46 27.32 28.44 6.79 5.67 2.48 3.27 15.21 16.03 13.50 8.59 34.61 30.02 2.78 3.01 70.89 73.27 70.87 63.64 71.20 77.90 69.87 66.30 66.92 68.49 68.41 62.52 66.09 61.16 60.68 78.25 86.24 82.07 84.28 73.38 72.57 77.80 78.08 57.77 58.81 58.37 78.69 6.49 5.89 6.67 8.65 6.54 6.33 6.59 9.80 8.84 9.02 1-0 I 7.11 7.39 8.44 8.44 11.53 5.90 12.69 9.12 9.97 10.37 6.31 10.17 6.18 9.03 15.93 13.76 1.85 1.06 1.76 0.81 1.98 1.04 1.99 1.95 1.35 1.99 1.33 0.95 2.19 1.29 1.32 0.46 0.57 0.54 0.60 0.90 2.22 1.26 0.67 0.78 1.17 4.87 4.78 5.04 4.89 4.90 4.46 4.92 4.66 4.74 4.57 4.86 5.24 5.08 4.99 5.07 2.52 2.70 2.23 3.08 4.17 4.29 4.44 3.47 5.23 5.03 80.83 82.06 79.78 78.24 80.59 81.65 80.58 78.05 78.51 79.49 78.92 78.00 79.39 76.71 76.91 78.85 86.37 79.22 81.35 79.43 79.17 82.62 79.49 78.76 76.33 1.32 1.23 1.26 1.22 1.23 1.27 1.29 1.14 1.19 1.31 1.22 1.23 1.19 1.27 1.31 0.77 0.91 0.68 0.79 1.34 1.24 1.31 1.10 1.44 1.56 4.64 4.98 5.49 6.19 4.76 5.25 4.63 4.40 5.37 3.62 6.10 7.47 4.76 7.30 6.95 5.87 3.55 4.64 5.06 4.19 2.71 4.06 5.10 7.61 6.88 14,285 14,278 14,143 13,860 14,119 14,340 14,274 13,760 13,901 14,060 13,970 13,919 14,170 13,772 13,732 12,782 13,828 12,577 13,351 13,799 13,700 14,370 13,376 14,242 13,662 0.10 2.84 58.46 0.18 22.49 8,528 0.87 0.46 82.39 0.12 1.75i 11,624 39.16 24.68 27.81 8.35 2.22 6.60 38.02 0.53 44.2? 1.70 35.02 53.14 10.14 2.92 32.04 58.23 6.81 1.76 27.86 49.57 20.81 34.70 32.23 21.87 33.71 29.25 29.76 5.96 38.68 48.77 3.93 40.92 49.22 10.35 36.33 43.70 14.20 36.00 44.80 2.81 3.42 2.76 3.50 2.48 7.98 5.84 3.89 3.81 25.08 4.95 3.22 5.00 3.17 3.22 25.70 34.36 34.96 15.50 31.71 37.69 31.32 37.00 26.60 32.25 lg.l6 22.28 24.50 25.11 17.53 62.47 58.83 56.51 76.80 60.30 45.95 36.46 46.49 49.33 34.02 73.75 71.68 67.20 68.81 76.46 11.201 7.28 I 6.59 5.93, 9.62 5.00 9.02 3.39 5.77 4.20 5.51 8.38 26.38 12.62 20.26 8.65 3.14 2.82 3.30 2.91 2.79 1.06 4.97 75.32 1.80 6.71 1.14 5.19 74.95 1.62 10.29 0.49 4.51 66.24 1.19 6.76 0.79 6.93 39.25 0.72 41.11 0.53 6.79 42.52 0.79 42.09 1.73 5.43 71.28 0.39 5.52 73.02 5.82 5.13 61.24 1.41 5.79 61.40 6,307 13,462 13,514 11,666 7,056 7,348 1.52 13.45 12,841 1.25 13.891 12,965 0.95 17.241 10,874 1.09 25.311 10,630 1.43 0.58 0.59 0.73 0.52 0.45 0.47 0.37 0.39 0.82 0.82 0.55 0.55 0.52 0.64 4.90 5.25 5.32 4.77 5.59 5.60 4.80 5.58 5.01 6.37 5.09 5.11 5.12 5.09 5.01 76.55 77.98 80.13 83.36 79.69 64.79 52.77 68.55 63.85 47.26 82.15 83.07 80.06 82.59 84.11 1.81 1.29 1.43 1.08 1.56 1.69 1.30 1.31 1.93 .91 1.48 1.56 1.38 1.63 1.56 6.29 11.51 6.76 5.86 7.13 19.09 14.28 11.57 8.56 35.99 7.32 6.89 9.59 7.26 5.89 13,493 14,134 14,148 14,630 14,252 11,732 9,529 12,434 11,518 8,170 14,434 14,702 14,280 14,584 14,760 *Indicates samples from car deliveries; all others are mine samples. FUEL 443 Table 65. Composition and Heat Value of United States Coals — Cont. Proximate Analysis "As Received" Ultimate Analysis "As Received" ,4k County, Bed or Local Name Moisture Volatile Matter Fixed Carbon Ash Sulphur Hydrogen Carbon Nitrogen Oxygen Heat Value B.t.u. per L "As Receiv West Virginia — Continued Fayette, Page 3.32 28.88 62.72 5.08 2.94 19.69 68.67 8.70 1.66 32.89 59.94 5.51 2.80 14.50 77.40 5.33 2.30 16.98 76.21 4.51 2.19 13.91 75.25 8.65 3.32 16.22 76.35 4.11 3.25 14.46 78.05 4.24 2.55 13.44 78.57 5.44 2.32 16.76 69.80 11.12 3.00 13.00 78.80 5.23 2.95 35.01 56.44 5.60 3.43 14.58 77.89 4.10 3.58 13.17 79.10 4.15 1.63 28.42 62.01 7.94 1.40 26.40 62.92 9.28 3.30 14.00 77.60 5.14 3.02 16.06 78.75 2.17 1.12 20.74 70.38 7.76 17.29 31.33 45.89 5.49 11.45 42.58 39.33 6.64 21.27 32.83 42.75 3.15 15.86 33.01 47.39 3.74 16.02 33.63 47.60 2.75 23.88 34.33 38.44 3.35 0.80 5.29 79.73 1.37 7.73 1.86 4.70 77.66 1.45 5.63 0.93 5.16 78.97 1.26 8.17 0.64 4.56 83.39 1.03 5.05 0.66 4.36 85.00 1.20 4.27 0.57 4.45 80.69 1.19 4.45 0.55 4.67 83.05 1.16 6.46 0.48 4.65 84.05 1.12 5.46 0.57 4.58 83.60 1.01 4,80 1.78 4.35 77.46 1.27 4.02 0.48 4.46 82.84 1.05 5.94 0.67 5.33 77.89 1.38 9.13 0.67 4.79 83.79 1.06 5.59 0.56 4.90 83.59 1.07 5.73 0.96 5.00 78.24 1.28 6.58 1.50 4.83 77.92 1.43 5.04 0.63 4.60 82.94 1.41 5.28 0.80 5.02 85.02 1.40 5.59 1.05 4.52 81.22 1.59 3.86 0.35 5.64 59.15 0.85 28.52 0.38 5.27 59.66 0.94 27.11 0.89 6.13 55.91 0.75 33.17 0.59 6.06 62.03 1.29 26.29 0.94 6.11 62.29 1.08 26.83 0.38 6.29 54.07 1.14 34.77 14,209 Fayette, Sun 13,786 Logan, Holden 14,126 M'Dowell, Ashland 14,550 M'Dowell, Big Four 14,636 13,995 14,587 M'Dowell, Coalwood M'Dowell, Eckman M'Dowell, Ennis 14,571 14,569 13,514 14,500 13,862 14,602 14,598 13,937 13,808 14,490 M'Dowell, Powhatan M'Dowell, Roderfield M'Dowell, Worth Marion, Monongah Mercer, Coaldale Mercer, Wenonah Monongalia, Richard Preston, Masontown Raleigh, Sophia Raleigh, Stonewall 15,001 Tucker, Thomas Wyoming Bighorn, Cody Carbon, Hanna 13,800 10,055 10,890 Fremont, Hudson 9,779 Hot Springs, Kirby Sweetwater, Superior Sheridan, Monarch 10,984 10,849 9,335 ♦Indicates samples from car deliveries; all others are mine samples. Prepared with square- mesh screens Prepared with round- mesh screens Sizes Through mesh opening, inches Over mesh opening, inches Through mesh diameter, inches Over mesh diameter, inches Broken (furnace) Egg Stove 4 2 2M 2 2^ Nut (chestnut) 'A Va Va 1K2 Vie 1 y% Pea Buckwheat No. 1 Vie Vie Buckwheat No. 2 (rice) Buckwheat No. 3 (barley) M y% Vie 1 Vie 1 Vie Vie In some instances a No. 4 Buckwheat has been marketed ; and some mines supply "Birdseye" which is practically a mixture of Nos. 2 and 3 Buck- wheats, or "through Vie and over Vie." Hotel Claridge, New York City, equipped with Heine BoUers. FUEL 445 For the sizing of bituminous coals the American Society of Mechanical Engineers has recommended the following: EASTERN BITUMINOUS Lump coal must pass over a 1^-in. mesh bar screen. Nut coal must pass through a V/i-'m. mesh, and over a %-in. screen. Slack coal must pass through a ^-in. bar screen. WESTERN BITUMINOUS Lump coal comes in 6-in., 3-in. and V/s.-m. sizes, and the respective lumps must pass over circular openings of corresponding size. Where the lump coal is sized as 6 by 3 in. and 3 by 1^ in., the coal must pass through the larger opening and over the smaller. Steam nut of 3-in. size must pass through a 3-in. circular opening and over a \%-m. mesh. Nut of 1^-in. size must pass through a 1^-in. and over a ^-in. opening, and %-in. coal must pass through a ^-in, mesh and over a 5^-in. opening. Coal screenings must pass through a 1^-in. round mesh. In the coal fields "run-of-mine" is the name given to the unscreened coal taken from the mine, and "culm" is the residue from screenings, in- cluding "silt" and other anthracite dust. Sampling Coal SAMPLES taken at the mine, says G. S. Pope, are generally of higher grade than those obtained from the average commercial shipments. The former contain a lower percentage of ash and have a higher heat value. Persons without experience generally select a sample better than the average run of the coal delivered. However, an experienced collector, by using good judgment, can obtain samples so fairly representative that the results of the analyses are reasonably accurate.. The value of laboratory analysis has been questioned largely because of ignorance or carelessness in taking the samples. The laboratory test makes use of one gram — about V28 of an ounce — of coal. The particles of coal in this sample should have been a considerable and equal distance apart in the original bulk shipment. A representative sample can be obtained only by repeated and systematic crushing, dividing and discarding — such as is described below. The sample should contain about the same proportions of fine and coarse coal as well as foreign matter, such as slate and bone, in order to show the quality of the coal delivered as a whole. To this end portions of coal are selected from all parts of the wagon, car, or ship, then mixed and systematically reduced to the quantity required for analysis. The original or gross sample should weigh 500 lb. or more, preferably 1000 to 2000 pounds. The Bureau of Mines has established a 1000-lb. sample as sufficient to give reliable results for coal comparatively free from impurities. For other coals a larger sample is required. Increasing the size of the gross sample tends toward accuracy, but the possible increase is limited by the cost of collection and reduction. A separate sample should be taken from each 500 tons or less of coal delivered. The gross sample is usually reduced to quantities varying between 2 to 5 lb. and then sent to the laboratory. Representative sam.ples can best be taken during the time when the coal is being loaded or unloaded. Portions of 10 to 30 lb., depending upon the size and weight of the largest pieces of coal, should be systematically taken with a shovel or a specially designed tool. The mechanical method is pre- ferred to shovel sampling, as it eliminates the personal equation. Care should be exercised to secure equal amounts of coal from near the top, the middle and bottom of the load. Clean boxes, buckets or ash cans may 446 FUEL be used for holding the portions of coal that make up the gross sample. The receptacles should have tight-fitting lids which can be locked, to prevent gain or loss in moisture and to preserve the integrity of the sample. The next step is to prepare the 1000 lb. gross sample for shipment to the laboratory. Three operations are involved : crushing, mixing and reduc- tion in quantity. These can be done by mechanical means, using a so-called sample grinder, or else by the hand method described by the Bureau of Mines, which involves six stages, Fig. 205, to obtain the final 5 lb. sample. In this procedure the coal must be broken down to the sizes given in Table 67, before division into equal parts. The lumps can be crushed with a tamper, maul or sledge, on a hard, clean, dry floor free from cracks. Other tools required are a shovel, broom and rake ; also a blanket measuring about 6 by 8 ft. The coal is raked while being crushed, so that all lumps will be broken. The floor or blanket is swept clean of discarded coal after each sample has been divided into equal parts. The space where this is done should be protected from rain, snow, wind and direct sunlight. The alternate-shovel method of reducing the gross sample, as shown in the first and second stages in Fig. 205, is repeated until the sample is reduced Table 67. Largest Sizes of Coal Allowable in Samples. Stage of Preparation Weight of Sample, Lb. Size of Coal, inches 1 2 3 1,000 500 250 1 4 5 6 125 60 30 16 to about 250 pounds. Before each reduction in quantity the sample should be crushed to the fineness prescribed in Table 67. The crushed coal is shoveled into a conical pile as in diagrams 2 and 7, by depositing each shovelful of coal on top of the preceding one, and then formed into a long pile as follows ; The sampler takes a shovelful of coal from the conical pile and spreads it out in a straight line as in diagrams 3 at A and 8 at A, the width being that of the shovel and the length, from 5 to 10 feet. His next shovelful is spread directly over the top of the first shovelful, but in the opposite direc- tion, and so on back and forth, the pile being occasionally flattened until all the coal has been formed into one long pile, as shown in diagrams 3 and 8 at B. The sampler then discards half of his pile, and beginning at one side of the pile, at either end, and shoveling from the bottom of the pile, takes one shovelful (No. 1, in diagrams 4 and 9) and sets it aside; advanc- ing along the side of the pile a distance equal to the width of the shovel, he takes a second shovelful (No. 2) and discards it; again advancing in the same direction one shovel v.idth. he takes a third shovelful (No. 3), and adds it to the first. Shovelful No. 4 is taken in a like manner and discarded, the fifth shovelful (No. 5) is retained, and so on, the sampler advanc- ing always in the same direction around the pile, so that its size will be reduced uniformly. When the pile is removed, about half the original FUEL 447 coal should be contained in the new pile formed by the alternate shovelfuls which have been retained. The retained halves are shown at A and the rejected halves are shown at B, in diagrams 5 and 10, Fig. 205. After the gross sample has been decreased by the above method to about 250 lb., the quantity is further reduced by the quartering method. Before each quartering, the sample should be crushed to the fineness de- scribed in Table 67. Quantities of 125 to 250 lb. should be thoroughly mixed by coning and reconing, as in diagrams 12 and 13 ; quantities less than 125 lb. should be placed on a cloth or blanket, measuring about 6 by 8 ft. ; mixed by raising first one end of the cloth and then the other, as in diagrams 18, 24 and 30, so as to roll the coal back and forth ; and after being thoroughly mixed, formed into a conical pile by gathering the four corners of the cloth, as in diagrams 19, 25 and 31. The conical pile is quartered by flattening the cone, its apex being pressed vertically down with a shovel or board. The flattened mass, which must be of uniform thickness and diameter, is then marked into quarters, as in diagrams 14, 20, 26 and 32, by two lines that intersect at right angles directly under a point corresponding to the apex of the original cone. The diagonally *s in. diameter and 7 in. long, has a capacity of 5 to 7 lb. of coal. The shipping box is made of well-seasoned basswood with lock-jointed comers, fulh- reinforced. Two suit-case catches are placed near opposite comers, inside the box, to operate in either of the two possible ways of assembh'. Small holes are drilled through opposite sides of the box, as at g. and through a small part of the catch lug. By releasing the catches with a nail inserted in the two holes, the box is easily opened. In using this container, the sample of coal is placed in the paper case and the edge of the cap is sealed tight with adhesive tape. With each container sent to the laboratory- for analysis, there should be a ticket bearing the name and address of the plant, the date, the kind and size of coal, the number of tons represented by the sample, and other similar information. This form, properly tilled in, can be placed inside the container or preferably around the container on the outside, before wrapping for mailing. A copy should be retained for reference or checking. Fuel Analysis HP HE term moisture, as used in fuel analyses, represents the loss in weight -■- of a coal sample when dried for a given time at a given temperature. This is taken as the total moisture in the coal received at the laboratory*. Volatile matter is the gaseous combustible matter of the coal and represents the hydrocarbons and other gaseous compounds which distill off on application of heat, as well as some incombustible gases. Fixed carbon is the solid combustible matter represented by the uncom- bined carbon in the coal or the carbon remaining after distillation. It is not pure carbon nor is it the total carbon in the coal, for a part of the carbon is expelled as volatile matter. Ash is the incombustible remaining after the moisture and volatile matter have been driven from the coal and the fixed carbon burned; it is the residue left from complete combustion of the coal. These four items are set forth in the proximate analysis, which may show them in either of three different ways. The whole four items may be given in one statement, as in the second column of Table 68. known as '"as received." The moisture may be stated separate!}- or ignored, and the other three items given as in the third column ; and this is known as ■'moisture free" or '"dr}- coal."" The ash also may be stated separately, and the other two items given as in the fourth column, known as ■"combustible" or "moisture and ash free.'"' Table 68. Proximate Coal Analvsis Statements. Constituent As received, Per cent Moisture-free, Per cent Moisture and ash-free, Per cent Moisture Volatile matter Fixed Carbon 10 30 50 '33.'33 'ST.'SO ho .56 62 . 50 Ash 10 100 11.11 Total 100.00 100.00 The foUov.-ing instructions for the proximate and ultimate analyses of coal, and for the analyses of liquid fuels are taken from the 1915 Code of the American Societ}- of Mechanical Engineers. FUEL 451 Proximate Analysis of Coal. The apparatus required for proximate analysis consists of a mill for grinding coal, chemical scales sensitive to Viooo of the amount weighed, drj'ing apparatus, a platinum crucible, a Bun- sen burner and blast lamp, a supply of oxygen gas, and such chemicals and chemical apparatus as may be required. The elements to be determined are moisture, volatile matter, fixed carbon, ash and sulphur. Determine the loss from air-drying and the total moisture in the ash as received, as explained elsewhere. To determine volatile matter, place about one gram of the air-dried powdered coal in the crucible and heat in a drying oven to 220° F. for one hour (or longer if necessary to obtain minimum weight), cool in a desic- cator and weigh. Cover the crucible with a loose platinum plate. Heat 7 minutes with a Bunsen burner giving a 6 to 8 in. flame, the crucible being supported 3 in. above the top of the burner tube and protected from outside air currents by a cylindrical asbestos chimney 3 in. diameter. Cool in a desiccator, remove the cover, and weigh. The loss in weight represents the volatile matter. In the U. S. Bureau of Mines practice a 1-gram sample of fine (60- mesh) air-dried coal is heated to a temperature of 1750° F. in a plat- inum crucible with a close-fitting cover for seven minutes over a No. 3 Meker burner giving a flame 16 to 18 cm. high. The crucible is placed so that its bottom is 2 cm. above the top of the burner. To protect the crucible from the efi^ects of drafts it is surrounded by a sheet iron chimney of special design. The loss in weight minus the weight of moisture determined at 220° F. represents the volatile matter. To ascertain the ash, expose the residue in the crucible to the blast lamp until it is completely burned, using a stream of oxygen if desired to hasten the process. The residue left is the ash. The Bureau of Mines determines the ash in the residue from the mois- ture determination. The moisture is determined by heating 1 gram of the 60-mesh air-dried coal in a porcelain crucible for one hour at 220° F. in a constant temperature heating-oven. To determine the ash, the crucible is heated slowly in a muffle furnace until the volatile matter is driven off. Ignition in the muffle is continued at a tempera- ture of 1380° F., with occasional stirring of the ash until all the par- ticles of carbon have disappeared. The crucible is cooled in a desic- cator, weighed, heated again for half an hour, and weighed again. The process is repeated until the variation in weight between two successive ignitions is 0.0005 gram or less. The difference between the residue left after the expulsion of the volatile matter and the ash is the fixed carbon. To determine sulphur by Eschka's method, which is the one com- monly used, a sample of 60-mesh coal weighing 1.3736 grams is mixed in a 30 cc. platinum crucible with about 2 grams of Eschka mixture (2 parts light calcined magnesium oxide, 1 part anhydrous sodium carbonate) and about 1 gram of the Eschka mixture is spread over it as a cover. The mixture is carefully burned out over a gradually increasing alcohol or natural gas flame. When all black particles are burned out the crucible is cooled, the con- tents digested with hot water, filtered, washed, and the solution treated with saturated bromine water and hydrochloric acid, boiled, and the sulphur pre- cipitated as barium sulphate by adding a solution of barium chloride. Ultimate Analysis of Coal. The apparatus required for ultimate analj^sis consists of a mill and other apparatus for grinding and pulverizing the coal ; chemical scales sensitive to Viooo of the amount weighed; drying apparatus; combustion apparatus, embracing a combustion furnace, a glass combustion tube one end of which is filled with copper oxide and chromate of lead and the other end with a roll of oxidized copper gauze, a porcelain boat, a set of o CD V G 'v a a "5 v O CO (Z4 CO x: O d U CQ PQ V) B CO < V Xi H V U ]'. T. 453 l)ull)S containing hydrate of potassium, a U-tul)e filled with chloride of calcium, and a sui)ply of pure oxygen and pure air; together with .suita1)lc chemicals and chemical apparatus required for the various processes. The elements to l)e determined are moisture, carhon, hydrogen, oxygen, sulphur, nitrogen, and ash. The moisture is determined in the manner as pointed out above. The carhon and hydrogen are obtained by the use of the combustion apparatus. One-half gram of the pulverized oven-dried coal is placed in the porcelain boat, which is introduced between the copper roll and the copper oxide within the combustion tulje. After the contents within have been thor- oughly dried out by a sufficient preliminary heating aided Ijy a current of dry air, the furnace is set to work and the coal burned by first passing air through the tube and finally oxygen, conducting the products of comlmstion through the potash bulbs and the chloride of calcium tube. The carbon dioxide produced by the combustion of the carl)on is absorbed by the ])()tash, and the water formed by the coml)Ustion of hydrogen is taken up by the chloride of calcium. The quantity of carbon is determined by weighing the bulbs before and after, thereby obtaining the weight of the carbon dioxide produced, and then calculating the weight of carbon from the known compo- sition of the dioxide. Likewise, the quantity of hydrogen is determined by weighing the calcium tube l)efore and after, which gives the amount of water produced, and, dividing by 9, the amount of hydrogen. Sulphur is found by the method described above under the heading Proximate Analysis. To determine nitrogen, a certain weight of coal is mixed with strong sulphuric acid and permanganate of potash and heated until nearly colorless. This process converts the nitrogen into ammonia and then into sul])hate of ammonia, and the amount of sulphate is determined l)y making the solution alkaline and then distilling it. The nitrogen is found by calculation from the known composition of ammonia. The ash is found by weighing the refuse left in the combustion boat after the coal is completely burned. The oxygen is the difference between the sum of the elements previously determined and the original weight of coal. The ultimate analysis of coal, as will be seen from the above descrip- tion, requires the use of so much chemical apparatus, and at best it is so com- plicated that it is not likely to be done except in a fully equipped chemical la])oratory. It should not be undertaken by one who is not entirely familiar with all the details of the work. Analysis of Liquid Fuels. The determination of carbon and hydrogen in liquid fuels is made in the same manner as that concerning the solid fuels above descril)ed, using special means for preventing loss in the various processes on account of the volatile characteristics of the fuel. To determine the sulphur, the oil or other liquid is heated with nitric acid and barium chloride. The quantity of sulphate of Ijarium thus ])ro(luced is ascertained by filtering and weighing, and the sulphur calculated from the known composition of the compound. The ultimate analysis of liquid fuel, like that of coal, should be under- taken only by a person familiar with all the necessary details. Heat Value of Coal The heal value of coal is represented by the heat unit.<; liberated by -*• perfect combustion and is usually expressed in British thermal units per pound of fuel. This value can be approximated from either tiie proxi- mate or ultimate analysis. From its proximate analysis the B.t.u. value of one pound of coal is given by Lucke as : 454 FUEL B.tu. = 14,544 c + 27,000 "\ 4 + 0-5 ) (57) in which c and v are the fractional weights of fixed carbon and volatile, respectively, in the coal. From its ultimate analysis the B.tu. value of coal can be approximated by the Dulong formula B.t.u. = 14.544 C + 62,028 (h— -^\ -f 4050 6" (58) in which C is carbon, H is hydrogen. O is oxygen and S is sulphur, expressed as the fractional part of one pound of coal. K>.000 !IS^ 'BlOOC l X X : 1 ^\ ! i ' \ : X ' 1 \ 1 1 N^ ' I 1 \ \ \ 1 ' 1 ^i 1 III i 1 >»J \ 1 i \ 1 N 1 , i , 1 5 10 15 20 25 /fsA //r Dry Coa/^ Per cert Fig. 210. Relation between Heat and Ash Content. FUEL 459 The evaporation is related to ash content as shown in Fig. 211, due to W. N. Polakov. With an increase of ash the evaporation falls, rapidly at first and more slowly when the percentage is high. Large excess of air and additional losses due to frequent cleaning accompany the use of coal of high ash content. 9.0 m o o I- 8.6 8.4 8.? 8.0 2 7. o Q. <0 1^ 7.6 « 74 7.2 ZO ■ O ■ 3 \ ^ n \ \ o ^ \ \ o s I o o \ A 1 1 ' 1 V 1 i \ < 5 n \ \ \ \ o o \ 3 ^ O <^r \ i ^ \ S^ V. ^ 1^ 16 IS 20 22 24 26 28 Ash in Dry Coal, per cent. Fig. 211. Relation between Evaporation and Ash Content of Coal. 30 Clinker CLINKER is formed bv the mechanical adhesion of the particles of ash, or by the fusion of the ash to form slag. Some of the constituents of ash act as alloys and form a fused mass of clinker known as "'running ashes." Clinker can be classified as "hard" and "soft" by these character- istics : Hard clinker is the result of the direct melting of the ash or some of its components. When due to the fusing of the ash, the clinker will form a large, hard cake. When due to the melting of some of the ash constit- uents the clinker will be distributed throughout the ash in the form of small c8 a S u V H 1 4J V l-H V ^ u o 00 C3 u >> t> 2 ^ u ^ d V U (-■ •4-1 T) OS c o • ^* u c "3 .2 (^ "•2 CO o "ffl 2 O _c c3 u o u o "5 a n '-Ij u Qt c PQ V V ffi CU K o o o FUEL 461 hard chunks. Hard clinker hardens while in the ash on the grates. It is usually the direct result of bad firing methods. Soft clinker is not directly chargeable to poor firing, but poor firing may start the formation and hasten the spread of clinker. Soft clinker is caused by the slagging of the ash, that is, the silica of the ash combines with the base having the lowest fusing temperature. After having formed, the clinker continues to grow until the whole grate is covered. In appearance it is not unlike hard clinker, having a crust on top although fluid beneath the surface. Soft clinker varies in consistency from a thick paste to a heavy oil ; the more fluid it is, the faster it spreads, remaining molten while on the grate but hardening when the temperature is lowered. Fusion of Ash. For the constituents of ash, the fusing temperatures (in degrees Fahrenheit) are as follows : Sulphur (S) 239 Alumina (AI2O3) 3416 Silica (SiOa) 3227 Calcium oxide (CaO) 3452 Iron (Fe) 2840 Magnesium oxide (MgO)....3882 All the fusing temperatures (except sulphur) are higher than those found in a boiler furnace. The efifect of clinker is shown in Fig. 212, due to /. P. Sparrow. The tests were made on boilers equipped with standard stokers. The efficiency remained constant up to 2335 degrees. Above this the efficiency increased rapidly with a small rise in temperature, but beyond 2475 deg., the efficiency remained constant up to 2900 degrees. The critical point of ash-fusion is between 2400 and 2500 degrees. If the ash-fusion temperatures are below 2400 deg., the coals are classed as clinkering, and if above 2500 deg., as non-clinkering. The standard ash-fusion temperature is taken as 2450 deg., with a variation of 50 deg. plus or minus. 80 79 78 a: 77 T3 c. E 76 o O 75, f i / / J 7 2200 2500 2400 2500 2600 2700 2800 Ash Fusion Tempera+ure, de3. Fahr. Fig. 212. Effect of Clinker on Efficiency. 2900 The clinkering behavior of coal is indicated in Table 70, due to L. J. J off ray, which gives results from burning tests. The coals with non-clinkering ash listed in the table were low in sulphur and in lime, and did not clinker at 2900 deg. in a dazzling white fire. The ash in the clinkering coals fused at a temperature of 2200 deg., because the sulphur and lime content were 462 FUEL high in proportion to the silica, alumina, and the iron oxide. Sulphur content alone does not indicate that the coal may clinker, although with normal ash content and 4 per cent or more sulphur, the coals listed have such a tendency. Table 70. Ash Behavior of Coal from Illinois and Indiana Mines. Test No. Ash in r. 1 1. Heat Value, Drj- Coal, Sulphur, g t_u, CUnker Color of Ash per cent. P^'' cent. pgj. u^ 1 9.63 0.64 12.325 Xo White 2 10.30 1.30 12.1.36 Xo White 3 10.00 1.19 12.368 Xo Light Gray 4 12.73 2.96 12.389 Yes Reddish Grav 5 11.80 4.43 11.768 Slightlv Reddish Gray 6 13.85 4.02 ll.&i2 Yes Reddish Gray 7 12.80 4.52 11.693 Yes Reddish Grav 8 17.96 4.58 11.124 Yes Reddish Gray 9 8.48 1.47 12,251 Xo White 10 12.49 4.50 11,921 Yes Dark Gray Investigations of the Bureau- of Mines on the fusibility of ash have been compiled in Table 71. The softening temperatures represent the average point of fusion. In making the tests, the ash samples were molded into solid triangular pj-ramids -^-d-in. high and ^:;-in. along the base. These were mounted in a vertical position and fused down to a spherical lump. The values thus obtained in the laboratory are said to be comparable with those obtained in the actual boiler furnace. The softening temperatures in Table 71 vary from 1900 to 3100 degrees. Above 2400 deg., little trouble should be experienced from clinkering. The temiperatures have been grouped into three classes, as follows: (1) Refrac- tor\- ashes softening above 2600 deg. (2) Ashes of medium fusibility, soft- ening between 2200 and 2600 deg. (3) Easily fusible ash, softening below 2200 deg. The coals of high softening temperatures are from the lower or older beds. The bituminous fields of Penns3'lvania, however, give a more refractory ash than similar beds in West Virginia. The ash from the anthra- cite districts is very refractory and the softening temperatures are usually above 3000 degrees. The softening or fusing temperature of ash is a measure of its clink- ering qualities, although seldom included in coal specifications. This is undoubtedly due to the many difficulties surrounding the temperature deter- mination, and to the fact that no definition of melting temperature has been accepted as standard. Clinkering in boiler furnaces is due to thick or heavy fires, excessive stirring of fuel beds, live coals in ashpit, too much slack in the coal, closed ashpit doors, or to the admission of pre-heated air under grates. With thick fires the air supply is decreased, so that the ash becomes heated. In an atmosphere furnishing oxj-gen, the melting point of ash is higher than if it is heated in a reducing atmosphere. A considerable thick- ness of ash is mixed with the burning coal in the thick fuel bed, and on account of the lower air velocitj-. a reducing zone exists near the grate. In the thin fire the reducing zone is confined to the last inch or two, at the top, where the few ash particles are separated and cannot fuse into clinker. FUEL 463 Table 71. Fusibility of Ash from the Coals of the United States. ALABAMA Location and Bed Black Creek. Clark.. Coal City. . . Gholson. . . . Harkness. . . Helena Jagger Jefferson . . . . Mary Lee. . . Percent in Soften- ing Dry Coal Temp. of of Deg. Ash Sulphur 2,530 3.31 0.83 2,350 8.68 1.06 2,250 4.35 1.10 2,240 6.64 0.73 2,460 11.51 1.57 2,430 8.91 0.46 2,690 9.81 0.67 2,120 7.45 2.80 2,830 9.90 0.74 Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal of Ash of Sulphur Maylene Montevallo. . . Nickel Plate. . . Pratt Thompson. . . . Upper Straven Yellow Creek. . Youngblood . . . 2,350 3,330 2,620 2,430 2,230 2,340 2,370 3,130 8.29 7.24 4.73 5.49 8.85 7.45 13 . 90 8.62 0.45 0.76 0.75 1.59 0.52 0.88 2.91 1.08 ARKANSAS Denning. . . Hartshorne. 2,200 2,120 7.38 11.59 2.45 1.40 Paris Sluin Basin 2,140 2,180 3.38 2.23 10.12 10.36 ILLINOIS No. 1 Bed 2,110 11 74 4 86 No. 6 Bed 2,160 10 27 2 30 No. 2 Bed 2,010 9 97 3 58 No. 7 Bed 2,050 10 62 2 69 No. 5 Bed 1,990 10 84 3 28 INDIANA No. 3 Bed No. 4 Bed No. 5 Bed 2,090 10.61 4.34 2,390 8.17 1.62 2,130 10.23 3.54 No. 6 Bed, Minshall. . 2,040 2,120 9.91 9.80 KANSAS 2.65 2.99 Bevier . . . Cherokee . 1,980 2,110 14.83 9.42 Leavenworth . . . . Weir-Pittsburgh. 2,020 2,010 18.26 11.68 5.46 5.31 KENTUCKY No. 6 Bed No. 9 Bed No. 10 Bed No. 11 Bed No. 12 Bed Alum Elkhorn. . . Fire Clay . . Flag Harlan. . . . Hazard .... Hickory. . . 2,130 8.81 2.97 2,030 10.53 3.67 1,990 11.99 4.18 2,030 9.57 4.08 2,150 10.20 2.30 2,940 4.37 0.61 2,470 3.83 0.68 2,790 5.35 0.82 2,880 7.52 0.83 2,700 3.94 0.85 2,460 8.56 0.79 2,340 5.37 1.07 Jellico Kellioka Lower Boiling. . . Lower H ignite. . . LowerStandiford Mason Miller Creek. . . . Poplar Lick , . . . Rawl Straight Creek . . Thacker Upper Hance. . . 2,460 6.92 2,830 2.21 2,880 11.65 2,440 4.57 2,260 5.24 2,320 3.93 2,160 4.33 2,670 5.30 2,680 7.53 2,110 3.40 2,430 4.42| 2,330 4.74 1.56 0.49 1.01 1.10 1.81 1.14 1.90 1.05 1.90 1.17 1.39 1.61 464 FUEL Table 71. Fusibility of Ash from the Coals of the United States — Cont. MARYLAND Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal of Ash of Sulphur Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal of Ash of Sulphur Bakerstown Bluebaugh Brush Creek. . . . Clarion Franklin Gallitzen Grantsville Little Pittsburgh Lower Freeport. . 3,560 10.26 1.70 2,770 12.99 1.63 2,470 9.61 1.26 2,280 9.61 2.42 2,410 8.48 1.36 2,140 12.15 3.33 2,490 8.23 1.22 3,010 7.95 1.18 2,150 20.51 4.11 Lower Kittaning. Mercer Pittsburgh Quakertown Split-Six Lpper Freeport. . L'pper Kittaning. L'pper Sewickley. Waynesburg . . . . 2,440 10.76 2.620 18.14 2,930 7.67 3,010 17.03 2,220 12.42 2,500 10.72 3,010 9.50 2,840 6.65 2.410 13.75 2.26 3.28 1.03 2.92 2.55 2.03 0.86 1.09 2.58 MLSSOURI Bevier Bowen Cainsville Cherokee Jordan Lexington Lower Richhill 1,960 13.47 4.90 1,940 13.18 4.61 1.980 12.71 5.78 2,150 7.51 1.97 2,010 12.74 4.42 2,000 13.48 4.04 1,940 15.39 5.43 Lower- Weir- Pittsburgh Mulberry. . . . Milk\' Richhill Tebo Waverly 1,940 10.78 1,990 14.58 1,940 11.28 1,970 15.47 2.040 11. &1 2,020 17.43 4.45 3.18 5.25 6.12 4.66 8.29 omo Anderson 2,120 10.86 3.92 Pittsburgh 2,210 8.47 3.58 Lower Freeport. . 2,280 9.55 2.95 L'niontown 2,230 16.10 3.58 Lower Kittaning. 2,120 9.24 5.72 Upper Freeport.. 2,280 8.48 3.09 Mahoning 2,OiO 6.59 3.67 Washington 2,520 21.90 2.98 Meigs Creek. . . . 2,330 13.02 4.23 Waynesburg 2,400 15.92 3.15 Middle Kittaning 2,450 8.00 1.86 OKLAHOMA Dawson. . . . Henryetta. . Lehigh Coal. Lower Hart- shorne .... McAllister . . 1,920 1,980 2,150 2,020 2,180 8.95 8.03 11.46 6.03 6.94 3.91 1.59 4.17 1.43 1.67 McCurtain. Panama. . . . Stigler L^pper Hart- shorne. . . 2,110 2,160 2,050 6.92 6.81 5.13 2,170 6.15 0.84 1.46 1.91 1.51 PENNSYLVANIA i^Bituminous Region^ Bloss Brook\'ille Fulton Little Pittsburgh Lower Freeport. . 2,630 11.96 2.25 2,809 12.98 1.86 2,940 7.36 1.18 2,390 8.13 1.70 2,390 8.52 2.06: Lower Kittaning. Middle Kittaning Pittsburgh Upper Freeport. . Upper Kittaning. 2,550 7.86 2,380 11.06 2,360 7.17 2,350 9.35 2,350 8.67 2.03 2.98 1.43 2.13 2.16 FUEL 465 Table 71. Fusibility of Ash from the Coals of the United States — Cont. PENNSYLVANIA — Continued — (Districts in Anthracite Region) Soften- ing Temp. Deg. Percent in Dry Coal Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal Location and Bed of Ash of Sulphur of Ash of Sulphur East Schuylkill . . Hazelton Pittston Plymouth 2,990 2,960 3,010 3,010 11.19 14.50 6.03 12.52 0.78 0.61 0.58 0.84 Scranton Shamokin West Schuylkill.. Wilkesbarre 3,010 2,960 2,730 3,010 12.39 16.59 18.07 13.17 0.79 0.90 0.82 0.78 TENNESSEE No. 4 Bed ... . No. 10 Bed. .. Angel Battle Creek. . Billygpat Blue Gem. ... Bon Air No. 2 Castle Rock. . Catoosa Coal Creek. . . . Frozen Head . . Grassy Ridge . Hooper Jellico Jordan Kelly Lower Dean . . . Mingo 2,220 9.08 3.62 2,150 11.42 3.14 2,160 5.80 1.94 2,520 9.68 1.52 2,600 3.26 1.12 2,100 3.32 1.34 2,180 10.27 3.24 2,260 10.78 2.68 2,250 7.11 2.59 2,260 6.30 2.37 2,680 6.92 0.92 2,470 3.75 1.87 2,330 2.58 0.69 2,350 4.95 1.87 2,320 3.33 0.90 2,530 7.63 1.33 2,340 3.69 0.72 2,390 4.25 1.27 1 Monarch Morgan Spring. Mud Slip Nelson Old Eagle Old Etna Paint Rock. . . . Poplar Lick. . . . Red Ash Rex Bed Richland Rich Mountain Sandstone Part- ing Sewanee Soddy Upper Dean. . . . Waldon Ridge. . 2,320 11.29 2,260 11.05 2,640 4.21 2,340 18.73 2,290 3.57 2,140 2.63 2,420 6.03 2,610 8.36 2,570 6.13 2,230 5.59 2,590 10.53 2,370 3.03 2,380 10.34 2,460 10.02 2,580 16.38 2,290 12.02 2,580 8.17 2.77 3.46 0.92 1.11 1.39 0.76 1.74 1.84 1.13 1.07 0.92 1.29 1.26 1.20 1.16 2.29 0.92 TEXAS Santa Tomas. 2,580 19.21 1.98 VIRGINIA No. 4 Bed "B" Bed Big Bed Big A., No. 2. . Big Townhill. . "C" Bed Clintwood Duncan Glamorgan Imboden Jawbone Kennedy Large Bed .... Little Townhill 2,180 6.58 0.49 2,420 17.73 2.21 2,420 19.89 0.57 2,320 6.34 0.60 2,240 11.84 0.48 2,210 10.26 1.40 2,670 3.26 0.87 2,160 6.65 0.88 2,160 5.86 1.22 2,420 11.47 1.56 2,240 19.86 1.03 2,190 7.95 1.09 2,880 20.19 0.62 2,440 8.40 0.56 Little Bed Lower Banner. . . Lower Boiling. . . Meadow Milner Mohawk Pardee Pocahontas No.3 Pocahontas No. 5 Red Ash Small Splash Dam Upper Upper Banner. . . 3,010 21.29 2,280 6.37 2,720 8.74 2,480 12.92 2,120 5.89 2,160 3.49 2,460 8.04 2,420 4.26 2,090 5.19 2,240 5.96 3,010 42.98 2,720 5.77 3,010 29.72 2,420 6.43 0.49 0.72 1.12 0.62 1.69 1.32 1.59 0.54 0.82 0.64 0.34 0.65 0.38 0.67 466 FUEL Table 71. Fusibility of Ash from the Coals of the United States — Cont. WEST VIRGINIA Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal of Ash of Sulphur Location and Bed Soften- ing Temp. Deg. Percent in Dry Coal of of Ash Sulphur No. 2 Gas Beckley Cedar Grove .... Coalburg Eagle Fire Creek Lower Freeport. . Lower Kittaning. Mahoning Middle Kittaning Pittsburgh 2,750 5.86 0.88 2,800 4.76 0.65 2,610 5.83 1.07 2,960 8.80 0.76 2,940 4.40 0.77 2,540 6.60 0.84 2,090 9.84 3.14 2,660 7.64 1.76 2,160 5.62 1.89 2,110 10.93 4.06 2,170 7.20 2.24 Pocahontas No. 3 Pocahontas No. 4 Pocahontas No. 5 Pocahontas No. 6 Redstone Sewell Sewickley Upper Freeport.. Welch Winif rede 2,440 4.70 2,480 6.31 2,700 6.23 2,400 2.88 2,120 6.96 2,560 3.93 2,080 9.51 2,190 6.17 2,840 7.41 2,970 8.44 0.59 0.64 0.62 0.70 1.92 0.72 3.99 1.97 0.62 0.83 Avoiding Clinker. The following suggestions are offered by the Bureau of Mines: Use thin fires and keep the fuel bed level by placing fresh coal on thin spots. Do not level fire with rake or stir it with splice bar. Fire coal in small charges, especially if it contains much slack. This will prevent crust formation and the need of breaking it. Do not burn coal in the ashpit. Keep water in tight ashpits, otherwise blow in steam. In heating and decomposing, the steam will absorb heat as it passes through the grate, ash and fuel bed. Keep the ashpit doors open and regulate the draft by dampers. When the coal contains clinkering ash, an increase of the draft, states L. /. J affray, gives better combustion and reduces the slag. The air added through the fire keeps the temperature of the ash below the fusing point. Should clinkering continue, relief can be had, according to L. Rankin, by spreading over the grate a few shovelfuls of limestone crushed to the size of a walnut ; this should be done when the fire is banked or after it is cleaned. More heat may be lost by the frequent cleaning of the fire than because of its clinkering, especially with coals that fuse into large masses. Frequently the combustion is almost entirely stopped while the clinker is being removed. Storage of Coal COAL in a compact or solid mass, has the following approximate weights per cubic foot of space occupied : Anthracite, 85 to 95 lb. ; bituminous, 70 to 80 lb. ; lignite, 65 to 75 lb. Peat weighs between 25 and 35 lb., while briquetted fuel weighs 40 to 45 lb. per cubic foot. Table 72 gives the approxi- mate weights of coals in storage. The variation in weight of different grades of coal is not due solely to the specific gravity of the solid coal. The quantity of surface moisture, the proportions of coarse and fine coal, and the amount of shaking or settling also influence its weight as delivered or as stored. Coals of high fixed carbon are relatively heavy, while increased ash content lowers the weight per cubic foot. The younger coals and those of high moisture content are relatively of low weight. FUEL 467 Table 72. Approximate Weights of Coals. Anthracite Name Bituminous Name Lb./cu. ft. Cu. ft./ton Lb./cu. ft. Cu. ft./ton Broken Stove Pea Buckwheat 70 65 60 55 28 31 33 36 Lump Nut Slack Run of mine. . . 60 55 50 45 33 36 40 45 Deterioration in Storage COAL undergoes a change in heat value and weight due to weathering when stored in the open, indoors or under water. Usually the volume and sometimes the weight is increased. Coal stored under fresh or salt water may retain from 2 to 12 per cent moisture, but its heat value is practically unchanged. Exposure of coal to the air, either in the open or under cover, reduces its heat value. The quantity of carbon and disposable hydrogen is diminished, while the quantity of oxygen and indisposable hydrogen is increased. Extensive experiments by S. W. Parr on Illinois coal showed that the most rapid loss in heat value occurred during the first ten days. After this the rate of loss diminished, although the loss continued indefinitely. The total loss in the open was substantially the same as in covered bins, ranging from 1 to 3 per cent after exposure for one year. Fine coal suffers a greater loss in heat value than do the larger sizes. The loss of volatile matter is negligible in its effect on heat value. After being exposed to air for one year, West Virginia slack lost less than 1 per cent in heat value ; run-of-mine only 0.5 per cent ; Pittsburgh run-of-mine 0.4 per cent ; and Wyoming sub-bituminous about 3.5 per cent. This last coal deteriorated 5.3 per cent in heat value after an exposure to air for 2^ years. Coal in transit will lose in heat value because of oxidation of its new surface after mining. The loss increases with the hydrogen content, ranging from 0.1 per cent for semi-bituminous to 1.3 per cent for sub-bituminous and lignite. Spontaneous Combustion of Coal TN the storage of coal, spontaneous combustion must be provided against. ■^ Anthracite coal is not subject to spontaneous combustion and can be safely stored in any quantity. Soft coal may ignite and disintegrate unless stored under water. Spontaneous combustion of coal is due to slow oxidation in an air supply sufficient to support the oxidation, but insufficient to carry away all the heat formed. The friability of the coal, or its tendency to break up into fine particles and dust, as well as its chemical nature, are the major causes of spontaneous combustion. Dust and small sizes of coal are dangerous in a coal pile containing larger-sized coal, because the resultant openings permit the flow of a mod- erate amount of air to the interior. The amount of volatile matter in the coal does not of itself increase the liability to spontaneous heating, and there is no assurance of safety in the storage of low volatile or smokeless coals. Pittsburgh run-of-mine has shown a greater tendency to spontaneous Finance Building, Philadelphia, Pa., equipped with Heine Boilers. FUEL 469 combustion than have high volatile gas coals. Western coals with a high amount of volatile are usually liable, but this is due particularly to the high oxygen content. Such coals become heated readily by oxidation faster than the heat can be dissipated. The influence of moisture and sulphur on spontaneous combustion has not been definitely determined. The Bureau of Mines has not found a single instance of moisture causing heating, although laboratory tests by Richter show that moist coal oxidizes rapidly. While there are no conclusive data on the action of sulphur, experiments indicate that it is only a minor factor. According to the Bureau of Mines, the following precautions should be observed in storing coal : 1. Do not pile in cones ; pile evenly not over 12 ft, and so that any point in the interior will not be over 10 ft. from an air cooled surface. 2. If possible, store only screened nut coal. 3. Keep out the dust as much as possible by reducing the handling to a minimum. 4. Pile so that lump and fine sizes are distributed evenly, not allowing lumps to roll to the bottom and form air passages. 5. Rehandle and screen after two months. 6. Do not store near outside heat sources, even though moderate in degree. 7. After mining, allow six weeks' seasoning before storing. 8. Avoid alternate wetting and drying. 9. Prevent air reaching the interior of the pile by avoiding inter- stices around timbers and brick work, or through porous bottoms, such as coarse cinders. 10. Do not attempt to ventilate with pipes as they may do more harm than good. In practice coal that has been stored six to eight weeks and has even become heated will seldom again heat spontaneously if rehandled and thor- oughly cooled by the air. The drenching of the coal pile will not extinguish a fire, because the crust that forms over the fire prevents the water from reaching it. It is necessary to remove the coal from around the burning part and to spread out the coal before water can be used with effect. Briquets COAL dust, culm, slack and similar waste due to mining of the coals and low grade fuels unsuitable for transportation can be used as fuel by briquetting or pressing into solid blocks. Domestic experiments and the experience of foreign manufacturers indicate that briquetting increases the commercial value of low grade coals sufficiently to more than cover the cost of production. Undoubtedly on account of the low cost, briquetted fuel is used in European countries. In the United States, the difference in cost between steam sizes and slack is small and the cost of manufacturing the briquetted fuel is high, so that its use is limited to locomotive furnaces and to house heaters or stoves. However, tests by the U. S. Geological Survey with briquetted coal in hand-fired furnaces of Heine Boilers have repeatedly shown satisfactory economy, with no smoke. Briquets are generally machine made. Coal dust and small pieces of coal are mixed with a binding substance to hold the particles together, are heated, and are subjected to heavy pressure in molds. The fuel material is sometimes mixed with clay, rolled into balls by hand, and then air-dried. They are made in shapes and sizes. Fig. 213, weighing from 1 oz. to sev- eral pounds. Rectangular briquets measuring 6^4 by 5^2 by 4^ in. and having rounded corners, weigh about 7 pounds. Smaller briquets, of 6^^ by 4J4 by lYz in. weigh about 4 lb. each. 470 FUEL ,-^S Fig. 213. Different Styles, -A - -i '. . . • ■&s;--v'-" I 23456789 10 APP>RO)aMATE SCALE &(YHS SIZES IN INCHES Shapes and Sizes of Coal Briquets. A? the coal resources of the countn- diminish, the economic importance of briquetted fuel will be better realized. Further development should also lead to methods for the recovery of valuable by-products from the coals used in making briquets. The size and shape of a briquet determine the extent of its use. Hea\y rectangular blocks are convenient for storage. According to /. E. Mills, the French Xa\'>- estimates the weight of briquets that can be stored in a given space as 10 per cent more than that of lump coal. The British Admiralty- reports a gain as high as 20 per cent. To hasten combustion large briquets are broken up when fed into the furnace. Stored briquets are not subject to spontaneous combustion or to notice- able weathering due to exposure. Briquets not over 2 lb. in weight are favored abroad. The most common forms are prismatic with round edges or ovoid shapes. These briquets are easily handled, cause little dust and minimum breakage. The rounded edges permit good air circulation and therefore thorough combustion. The properties of briquetted fuel depend largeh' upon the grade and amount of binder used with the coal mixture. The most common binder used, states C. L. Wright, is a pitch made either from coal tar or water-gas tar, although starch, lime and sulphite liquor are sometimes used. With the correct binder smokeless combustion can be expected. Other advantages of this fuel are regularity" in size, uniform condition of fuel-bed, no clinker, minimum, attention to fires, high heating value, high rates of combustion, small loss from breakage, and little weathering. Anthracite briquets have been made from coal dust mixed with drj- pitch. According to E. F. Loiscau, the pitch represents 10 per cent of the bulk of the briquet and is prepared from tar at h72 deg. by separating the volatile matter it contains. The fuel mixture is continuouslv heated by steam so FUEL 471 as to maintain a temperature of 212 deg,, at which the pitch acts as a binder. It is then passed between rollers made of semi-oval molds, in which the briquets are formed. The pressed fuel, about the size of an egg, drops on to a belt conveyor ; this carries it to a screen in eight minutes, the briquets then being cool enough for handling and delivery. Carhocoal briquets are made in sizes ranging from 1 to 5 oz. and repre- sent about 72 per cent of the raw coal. As described by C. T. Malcolmson, the raw coal is first crushed and then distilled at a temperature of about 900 deg., yielding gas, tar and "semi-carbocoal," which is rich m carbon. Pitch obtained from the tar is then mixed with the semi-carbocoal and formed into briquets. These are in turn distilled at a temperature of about 1800 deg., resulting in the recovery of additional coal-tar products and the production of the carbocoal fuel. The fuel is dense, uniform in size and quality, and of grayish black color. Anal3^sis shows from 1 to 3 per cent moisture ; 0.75 to 3.5 per cent volatile matter ; 82 to 90 per cent fixed carbon and 7 to 12 per cent ash. It is said that carbocoal requires no greater draft than bituminous coal. Lignite briquets can be made without a binding material, according to the Bureau of Mines. Lignite briquets burnt in furnaces of steam boilers have proved equal to good Middle West bituminous coal. They will endure handling and resist weathering better than raw lignite, and manual labor is not required from the time the lignite is loaded into the mine car until the briquets are delivered to the consumer. The lignite after mining is crushed and screened and then dried to re- duce the high moisture content. Closed conveyors carry the powdered lignite to hoppers that feed the molds, where it is subjected to a pressure of about 20,000 lb. per sq. in. The heat developed during compression liberates the tarry matter from the material and cements the fuel. Lignite yields gas, ammonia, oils and tar on carbonizing. The residue can be made into briquets by the addition of a binding material. In one plant, states /. B. C. Kershaw, the ovens or retorts take a 10-ton charge of lignite and heat it for two hours at about 900 deg. The yield of by-products at this temperature include 10,000 cu. ft. of gas, 13 gal. of tar oil, and 2.5 lb. of ammonium sulphate per ton of lignite. After the distillation is completed the residue is mixed with pitch and other binders to form the briquets. Analysis of these lignite briquets shows 1.34 per cent moisture ; 7.6 per cent volatile matter ; 84.04 per cent fixed carbon ; 7.02 per cent ash, and a heat value of 14,000 B.t.u. per pound. Peat briquets are possible commercial fuel for steam boilers. The peat used abroad as a domestic fuel is not as rich in combined nitrogen as the peat of the United States. By gasification the latter will yield ammonia, tar and other chemical compounds of value. Peat produces a large amount of gas of good quality when consumed in a gas producer. The gas can be used in engines or for the firing of boil- ers. With by-product gas producers, sufficient ammonia can be recovered to pay for most of the operating costs, so that the gas and power it furnishes are practically free. Technical success, says F. P. Coffin, has been attained by several pro- cesses but commercial success in peat manufacture has not yet been demon- strated. Of the several plants that have at times operated in the United States, one uses a centrifugal pump for removing the peat from its bed. According to Win. Kent, the pump discharges into storage bins, and after some of the water in the peat has drained away, the material is further dried by exhaust steam and stack gases. When dry, the peat is reduced to powder, and conveyed to a press where it is compressed into regularly shaped blocks. The briquetted peat is clean and withstands handling as well as transportation. o <4-l CO U o a u U , o V u u V CU V j: <4-l Ui o *J . c CO u CO a; u o cj B ^ u O G ^ u CO 6J3 K C U-i u a , w PU -0 Dd C3 CO o in 4> VO X, tn •4J CO fi 4^ .1-1 & 03 U 0) a o o n >> c u ta c a V a ffi o CO ji a o H ■*-> a a 4J CO C 04 K 00 00 CO CO (m o ■M u CO a FUEL 473 Solid Fueis Other Than Coal yjH^ ODD fuel consists of sawdust, shavings or other refuse produced in ^^ quantity, as in wood-working plants and saw mills. Cord wood is used to a limited extent, when timber is plentiful and other fuels expensive. Wood, of course, is used in starting coal fires. Table 73. Weights and Compositions of Air-Dried Woods. Wood Lb. per cu. ft. Lb. in 1 cord H. N Ash Heat Value, B.t.u. per lb. Ash... Beech . Birch . . Elm... Oak... Pine . . . Poplar. Willow 46 43 45 35 3,520 3,250 2,880 2,350 49.18 49.36 50.20 48.99 6.27 43.91 0.07 6.01 42.69 0.91 6.20 41.62 1.15 6.20 44.25 0.06 0.57 1.06 0.81 0.50 5,420 5,400 5,580 5,400 52 3,850 49.64 5.92 41.16 1.29 30 2,000 50.31 6.20 43.08 0.04 36 2,130 49.37 6.21 41.60 0.96 25 1,920 49.96 5.96 39.56 0.96 1.97 0.37 1.86 3.37 5,460 6,700 6,660 6,830 Freshly cut wood contains about 45 per cent of water by weight. After air-drying the moisture content is 15 to 25 per cent. The average heat value of dry wood is about 7700 B.t.u. per pound. The weights and com- positions of air-dried wood are given in Table I'i. As fuel, 1 lb. of wood is assumed to equal 0.40 lb, of coal, or 1 lb. of coal equals 2^ lb, of wood. Measuring in bulk, 2 cords of wood are considered the equal of 1 ton of coal. Sometimes 1 lb. of wood is said to give an evaporation of 6 lb. of water from and at 212 deg., which represents a heat value of 5794 B.t.u. per pound. By weight, shavings, sawdust and refuse lumber have the same heat value as the original wood. Charcoal is made by heating wood in a closed vessel. Distillation begins at about 400 deg., leaving a residue of common black charcoal. Other grades of charcoal are obtained at higher carbonizing temperatures. The wood melts, and at about 620 deg. yields a mass similar to soft coal coke. At temperatures over 2000 deg. a black dense solid charcoal is formed. Wood will yield about 18 per cent charcoal and 82 per cent volatile matter by weight at high temperature, and 68 per cent charcoal and 32 per cent volatile at low temperature. The carbon content varies then from 85 to 55 per cent. The heat value is generally about 11,000 B.t.u. per pound. Char- coal absorbs moisture rapidly up to 15 per cent. It is seldom used in boiler practice except when it is a by-product, as in the manufacture of wood alcohol or turpentine. Coke is the solid substance remaining after coals are distilled in retorts or partly burned in ovens. The bituminous coals are used extensively, al- though lignite and peat offer commercial possibilities. In gas retorts, a large yield of gas of high illuminating value is desired, so that the coke is a by- product. In beehive coke ovens high-grade coke is produced for use in metallurgical processes. In by-product coke-ovens, good coke, a large coke yield or else gas and chemical by-products may be desired. The coke yield varies between 35 to 90 per cent of the weight of coal. Cokes are generally rough and may be dense and soft, or porous and hard. The color varies from silvery, light gray to dark gray and black. They readily attract and retain moisture and if not properly protected may contain 20 474 UEL per cent by weight. Coke bums without flame or smoke and makes an in- tense tire when forced. The heat value is between 12,000 and 14,000 B.t.u. per pound. Analysis gives an average of 1.3 per cent volatile matter ; 88 per cent fixed carbon ; 0,8 per cent sulphur ; 1.5 per cent moisture ; and 8.4 per cent ash. The average weight of solid coke is about 45 lb. per cubic foot. Heaped coke weighs about 30 lb. per cubic foot, or 75 cubic feet to the long ton. Coke generally costs as much as coal, so that it is not used to anj' extent as a boiler fuel. Coke breeze consists of the line particles left when the coke is drawn from the ovens, or of the screenings from coke prepared for blast furnaces. It represents about 2 to 2^2 per cent of the coal originally used in the coking process. Generally, it is considered as waste, but by burning coke breeze under boilers, its fuel value can be utilized. Com has been used as fuel when the crop was plentiful and the price low. At 15 cents a bushel corn would be as cheap a fuel as coal at about S8 per ton. It is sometimes used as an emergency fuel in grain-growing localities. Boiler tests by C. R. Richards showed that bituminous coal gave 1.9 times as much heat per pound as corn on account of the difference in heat value of the fuels. Calorimeter tests place the heat value of corn and cob at about 8000 B.t.u. per pound, the cob alone at 7500 B.t.u., and dry corn at 9000 B.Lu. Corn weighs about 56 lb. per bushel. Strazv, used in som.e localities as fuel, consists of the stems or stalks of grain. Its composition is about 36 per cent carbon ; 5 per cent hydrogen ; 38 per cent oxygen; 0.5 per cent nitrogen; 15.75 per cent moisture; and 4.75 per cent ash, which gives a heat value of 5411 B.t.u. per pound. Dr>- straw will average from 5600 to 6700 B.t.u. per pound. Straw when compressed weighs about 7 lb. per cubic foot. Tan bark is the fibrous portion, known as spent tan, which is left from ground bark emploj-ed as a leather tanning agent. The raw bark is usually air-dried oak or hemlock but in the process it absorbs sufficient moisture to make the spent tan weigh more than twice the raw material, two-thirds of this weight being water. The waste heat of the chimney gases can be used for dr\-ing the fuel. Fig. 214 gives heat values of tan bark for different moisture contents, derived from Table 74. The net heat value cannot be measured directly, so that the total calorific value should be determined by combustion in a fuel calorimeter. At best, the useful heat of a liquid, gaseous or wet fuel, can be determined only approximately, for it involves the ultimate analysis and assumptions depending upon operating conditions. Table 74. Calorific Value of Tan Bark with various Percentages of Moisture, B.t.u. per Lb. Wet Tan. Losses of Heat due Net Heat Value, B.t-u. Efficiency, Per cent Lb. Evap. per Lb. Moisture Moisture H 1 in Fuel Heating Air Wet Tan. 0.20 0.30 0.40 6,336 5,544 4,752 261 392 ^ T 1 564 493 423 1,446 1,266 1.085 4,065 3,393 2.772 64.2 61.2 57.3 4.19 3.50 2.81 0.50 0.60 0.70 O.SO 3,960 3,168 2,376 1,584 653 784 914 1,045 352 282 211 141 904 723 542 362 2,051 1,379 709 36 51.8 43.5 29.8 2 5 2.11 1.42 0.73 . 03 Composition of dry tan bark a^umed to be C, 0.50; H, 0.06; O, 0.40; N and Ash, 0.04. Heating value bf Dulong's formula 7,920 B.t.u. per pound. Exit gases are assumed to be at 600 deg. Fabr. FUEL 475 6000' -^ ^ '* " ~ ■" ■ n ■ ■ ■■ .. ■■ >» >»^ ^ ■«« "ic OS ■^ " V ^ ■> ^ l^ ' ». ■> "«? •^ > •^ jLM) " ■^ •> >? >., ">>. "^ •»-. "■«, ^. t^ ■■»^ "^ r^. b h. , ■>« ^ ^, S ^ 9nn/) . 1000'. 20 3C 40 50 60 Moisture in Fuel, Percent Fig. 214. Heat Value of Tan Bark. 70 80 Dry tan bark consists of about 50 per cent carbon; 6 per cent hydrogen; 40 per cent nitrogen ; and 4 per cent ash, giving a heat value of 8000 B.t.u. per pound. Dry tan bark with 15 per cent ash has a heat value of about 6100 B.t.u. ; and with 1.5 per cent ash, about 9000 B.t.u. per pound. Wet tan bark, as used for boiler firing, has a heat value of about 5500 B.t.u. per pound with 30 per cent moisture; and 3500 B.t.u. with 60 per cent moisture. An evaporation from and at 212 deg. of 2 to 3 lb. of water per pound of wet fuel can be expected in specially designed furnaces. Bagasse, or megass, that part of the sugar cane remaining after the ex- traction of the juice, is widely used as fuel for boilers on sugar plantations. The refuse resulting from the treatment of the raw cane by the sugar mill rolls is known as "mill bagasse," while the product remaining after a series of soaking processes of the raw chopped cane is known as "diffusion bagasse," The fuel value of bagasse depends upon the amount of woody fiber it contains and upon the amount of combustible matter, such as sucrose, glucose and gum, retained in the liquid. Louisiana bagasse, according to E. C Freeland, consists of about 40 per cent fibre, 7 per cent sucrose and other constituents, the remaining 53 per cent being water. Bagasse obtained from tropical cane, according to L. A. Be cud, contains Z7 to 45 per cent woody fiber ; 9 to 10 per cent combustible ; and 46 to 53 per cent water. The composition of dry bagasse ranges between 43 and 47 per cent carbon ; 5.4 and 6.6 per cent hydrogen ; 45 and 49 per cent oxygen ; and 5 and 3 per cent ash. Its average heat value as determined by test is 8300 B.t.u. per pound. Owing to the usual moisture content of the fuel as fired, its heat value then is only 400O B.t.u. or less. One pound of the fuel will evaporate about 2 to 3 lb. of water from and at 212 deg. By utilizing waste gases and drying the bagasse before firing, better results can be ob- tained. The fuel yield from sugar cane can be taken as 25 per cent. One ton of cane as ground will therefore give 500 lb. or more of wet bagasse. Table 75 gives the calorific values of diffusion bagasse of varying per- centages of moisture. Table 76 gives the calorific value of one pound of mill bagasse at dif- ferent extractions, based upon a cane of 10 per cent fiber and juice of 15 per cent total solids. 476 FUEL o O OS O CO c8 at a CO OJ OJ ^ c E-" .2 0) 52 CO CO 0. Is Is 4J O 3 "o 0) K be a m .2 c 0) ;> . c4 m c c 1 CS tc m .s 3 I > Q a 0) -Si a; < CO CO • ca 3 O bO w a t> — 3 V -H 3 u — 3 "eS 3' -e '3< 3 ■e 3 «r?2 ^- c« fe pq H fq W pq 6^ 90 0.00 100.00 8,325 8,325 8,325 1.68 119 85 28.33 66.67 5,550 3.33 240 1.67 116 5,900 339 5,561 2.52 119 80 42.50 50.00 4,162 5.00 361 2.50 174 4,697 509 4,188 3.34 120 75 51.00 40.00 3,330 6.00 433 3.00 209 3,972 611 3,361 4.17 120 70 56.67 33.33 2,775 6.67 482 3.33 232 3,489 679 2,810 4.98 120 65 60.71 28.57 2,378 7.15 516 3.57 248 3,142 727 2,415 5.80 121 60 63.75 25.00 2,081 7.50 541 3.75 261 2,883 764 2,119 6.61 121 55 66.12 22.22 1,850 7.78 562 3.88 270 2,682 792 1,890 7.40 121 50 68.00 20.00 1,665 8.00 578 4.00 278 2,521 815 1,706 8.21 122 45 69.55 18.18 1,513 8.18 591 4.09 284 2,388 833 1,555 9.00 122 40 70.83 16.67 1,388 8.33 601 4.17 290 2,279 849 1,430 9.79 123 25 73.67 13.33 1,110 8.67 626 4.33 301 2,037 883 1,154 12.13 124 15 75.00 11.77 980 8.82 637 4.41 307 1,924 899 1,025 13.66 124 76.50 10.00 832 9.00 650 4.50 313 1,795 916 879 15.93 126 Fig. 215 gives the heat value of both "diffusion" and "mill" bagasse, cor- responding to Column 2 of Table 75 and Column 9 of Table 76. Heat Value of Wet Fuels "T^HE useful heat liberated by fuels fired wet is lower than the total heat -'- value determined by calorimeter tests. The calorific power, as fired, of green wood, tan bark and bagasse, is termed the gross heat value. By de- ducting from this gross value the heat required to evaporate the moisture and raise it to the temperature of the gases leaving the boiler, the net heat 478 FUEL 30 4C so Moisture in Fue/, Percenf Fig. 215. Heat Value of Bagasse. value absorbed by the boiler water is obtained. Therefore, a dr>' sample having a total of 7000 B.t.u. per pound by calorimeter test will have a gross heat value of 5600 B.tu. per pound, if it contains 20 per cent moisture. To compute the net heat value of wet fuels, the following formula can be used : h. L=(9H+ JV) X [ (212 - -f 972] - [0.48 (h - 212) ] (59) ill which h. 1. is the B.t.u. lost per pound; H is the hydrogen content; 17 the water; t and fi are the temperatures of the air supply and the chimney gases. The result is the heat lost in the superheated steam_ formed by the combustion of the hydrogen and from the water in the wet fuel. If green wood contains 6 per cent hydrogen and 24 per cent water as fired, and the air supplied for combustion is at 72 deg., resulting in a stack temperature of 462 deg., the loss is: (9 X 0.06 + 0.24) X [ (212 - 72) H- 972] ^ [0.48 (462 - 212) ] = 987 B.t.u. Assume that this wood sample has a heat value of 6987 B.t.u. by calorimeter test. The net heat value is found by deducting the loss due to hydrogen and water, which gives 6000 B.t.u. per pound for steaming purposes. Liquid Fuels FUEL oil consists practically of petroleum or of its residue after the rnore volatile oils have been removed. The petroleum or crude oil is a viscous mineral oil varying in color from light brown through shades of green to black. The specific gravity is generally between 0.80 and 0.98. corresponding to 45 and 12 deg. Baume. respectively. Fuel oil at 10 deg. Baume has a specific gravit}- of 1.00. the same as that of water. The gravit>- of oil is usually measured on the Baume scale. This can be converted by the following Bureau of Standards formula, for liquids lighter than water : . ^ . 140 (60) Specific Gravity = 130 - deg. Be Deg. Baume = 140 Spec. Grav, — 130 (61) FUEL 479 Crude oil is a mixture of hydrocarbons that often contain a small per- centage of sulphur, oxygen and nitrogen. It can be distilled into gasoline. benzine, kerosene and other oils, which differ considerably physically and chemically, depending upon the locality, the source of supply, and upon the treatment or distillation process. After the kerosene has been run off, the oils remaining, of from 12 to 25 deg. Baume, are available as fuel for steam boilers. Gasoline is a petroleum product of about 74 to 64 deg. Baume. Benzine is a distillate of about 55 deg. Baume, while kerosene ranges from about 48 to v35 deg. Baume. However, the high price of these lighter distillates prevents their use as a boiler fuel. Oils are classified by their flash point, the temperature at which they give off inflammable vapors ; viscosity, the tendency of the oil particles to hold together, thus retarding the flow ; moisture, in the form of an emulsion in the heavier oils ; sulphur, which produces obnoxious gases and has a cor- roding effect if condensed on boiler tubes and stack; density; and heat value. The properties of fuel oils from different localities are given in Table 77, by C. E. Lucke. Table 77. Composition land Heat Value of Oil Fuels. Deg. Baume Ultimate analysis, per cent Heat value. Kind C. H. O+N. s. B.t.u. per )b. California fuel oil California crude Kansas crude 14.93 16.24 31.67 38.89 23.18 21.25 21.56 36.47 81.52 86.30 85.40 85.00 86.10 83.26 84.60 84.30 11.61 16.70 13.07 13.80 13.90 12.41 10.90 14.10 6.92 0.55 0.80 18,926 21,723 20,345 Ohio crude 0.60 '"3;83" 2.87 1.60 0.60 0.60 0.50 1.63 20,752 Pennsylvania crude. . . Texas fuel oil Texas crude West Virginia crude. . . 20,949 19,654 18,977 20,809 The heat value of oil can be determined accurately by calorimeter test. An approximate method proposed by /. N. LeConte gives the value, free from moisture, as 17,680 + (60 X deg. Be) B.t.u. per pound. Another method utilizes the Dillon" formula: B.t.u. ^ 14,544 C + 62,028 /'i/ ^ ) + ^050 .S" (62) in which C is carbon, H is hydrogen, is oxygen and S is sulphur, as ob- tained from the ultimate analysis. This formula gives a heat value of about 5 per cent higher than that of California oils, as determined by calo- rimeter. Fig. 216 shows other heat values. These indicate that per pound the lighter oils have a higher calorific value than the heavier fuels, but a lower value per gallon. A barrel of heavy petroleum will therefore have a higher heat value than a barrel of lighter oil. The average California oil has a specific gravity of about 0.96, which corresponds to 15.16 deg. Baume at a temperature of 60 deg. The average weight of a gallon of oil is 8.03 pounds. As it usually comes in barrels of 42 gal., the average weight of a barrel of fuel oil is ZZ7 pounds. The heat value is about 18,700 B.t.u. per pound, which should easily give an equivalent evaporation from and at 212 deg. of about 14.5 lb. of water per pound of fuel. Peoples Gas, Light 8b Coke Co., Chicago, Ills., operating Heine Boilers, FUEL 481 'iBZOO ^'^ *°° 18500 ^°° ^°° ^'^ ®°° 19000 "'^ ^°° '""^ ''°° 19500 B.t.u. per Pgund Fig. 216. Heating Value of Fuel Oil. Coal tar is a by-product of coking processes. Its commercial value usually prevents its use as a fuel. This black, viscous liquid must be heated and strained before it can be used. The coal tar yield is from 4^ to 6j/4 per cent of the weight of the coal used in gas or coke manufacture. The specific gravity is about 1.25, so that a gallon weighs 10.4 pounds. It is lower in hydrogen and higher in carbon than petroleum, an ultimate analysis showing 89.21 per cent carbon; 4.95 per cent hydrogen; 1.05 per cent nitrogen; 4.23 per cent oxygen ; 0.56 per cent sulphur ; and a trace of ash. Coal tar has a heat value of about 15,800 B.t.u. per pound. Tar oils include pitch, creosote, anthracene and other residuum from distillation. Oil tar produced in gas apparatus has a specific gravity of 1.15, is less viscous than coal tar, and can be handled much like other fuels. Its composition is 92.7 per cent carbon; 6.13 per cent hydrogen; 0.11 per cent nitrogen; 0.69 per cent oxygen; 0.37 per cent sulphur; and a trace of ash. giving a heat value of 17,100 B.t.u. per pound. Colloidal fuel was developed by the Submarine Defense Association to meet war conditions. It is an emulsion of powdered solid fuel and oil fuel. A so-called fixateur is used to stabilize the elements of the mixture 482 FUEL that have different specific gravities, and thus maintain a homogeneous product. Most oils in their natural state can be mixed with pulverized solids to make the smokeless colloidal fuel. Dried and pulverized bituminous and anthracite coals can be used, as can lignite, peat coke, charcoal or wood, so long as two-thirds of the dn.- solid fuel is combustible. The colloidal fuel is fired with the same equipment used for oil burning. A marine boiler test gave an equivalent evaporation of 13.6 lb. of water per pound of colloidal fuel at an efficiency of 76.8 per cent, while straight Mexican oil gave an equivalent evaporation of 13.97 lb. of water per pound of oil fuel at an efficiency of 73.32 per cent. With coal of 13.500 B.tu. per pound and crude oil of 18,200 B.t.u. per pound, the colloidal fuel has a heat value of 17.000 B.t.u. per pound, with 25 per cent solid fuel in suspension ; and 16.300 B.t.u. per pound with 40 per cent of solids in the mixture. It is possible to combine 45 per cent oil. 20 per cent tar and 30 per cent powdered coal and still obtain a stable colloidal fuel that can be stored for a month or more without the solids settling. With such mixture it is said at least 50 per cent of the oil fuel now used can be saved, and equal if not greater heat value per barrel obtained at a lower cost. Gaseous Fuels IX ga? fuels each constituent has a known heating power. The total heat value of a cubic foot of gas can be determined by multiphnng the fractional constituents and the corresponding heating powers per cubic foot, and by adding the products. The low heat values are given by C. E. Lucke as follows : Gas B.t.u. per cu. ft. Hydrogen _ _ 292 Methane -_ - _ - _.. 959 Ethjlene — - 1595 Benzine (or illuminants contained) „ 3795 Carbon monoxide„ — 341 Natural gas is often held at high pressure in huge natural, underground reser\-oirs that are tapped by sinking wells. The gas is piped and distributed over long distances, and delivered at working pressures of 2 to 8 ounces. The principal combustible components of natural gas are methane (marsh gas) and hydrogen. The incombustible gases are carbon dioxide, nitrogen and ox\gen. Table 78. compiled bj* G. A. Burrell, gives the average heat value and the composition for different samples. Arti/ia'ul gases are made principally from coal or oil. Natural gas costs 10 to 30 cents per 1000 cu. ft., while coal and water gases cost $1 or more. With coal at S5 per ton, producer gas will deliver 35,000 B.t.u. for one cent, while natural gas at 20 cents gives 50.000 B.t.u. for one cent. The compositions and heating values of gas fuels are compared in Table 79. Owing to the variations in heat values, different quantities of gas are required to generate one boiler horsepower. Junker Gas Calorimeter THE heat value of gaseous fuels is generally determined with the Junker Gas Calorimeter illustrated in Fig. 217. This instrument consists of a vertical cylindrical water chamber contain- ing vertical tubes, ^rhich is heated bj* the gas burned in a Bunsen lamp beneath. The products of com.bustion pass upward through a combustion chamber and downward through the tubes, while the water passes in at the bottom and out at the top in a continuous current. The quantity of gas is measured by a gas meter, and the quantity of water by collecting the overflow FUEL 483 Table 78. Properties of Natural Gas. (G. A. Burrell, Nat. Gas A.ssn. of America, May, 1914) Volumetric Composition, Per cent Higher Heating Value B.t.u. per Cu. Ft. 32° F and 29.92 in. Specific Location of Wells Carbon Dioxide, CO2 Oxygen O2 Nitrogen N2 Methane CH4 Ethane C2H2 Gravity, Airz=l Armstrong Co., Pa. Osage Co., Okla. . . Kiefer, Okla 0.05| 0.0 1.10: 0.0 2.40I 0.0 1.45 4.6 1.8 81.6 94.3 64.1 16.9 0.0 31.7 1,184 1,004 1,272 0.64 0.58 0.74 Barron Co., Ky. .. . Barron Co., Ky Moab, Utah 2.5 2.6 3.6 0.0 0.0 0.0 1.3 5.1 5.6 23.6 44.1 90.8 69.7 48.2 0.0 1,548 1,367 967 0.91 0.84 0.61 Moab, Utah Northwestern Ore . Crawford Co., Pa. . 3.5 3.0 0.0 0.0 0.0 0.0 6.5 0.9 2.3 90.0 96.1 6.6 0.0 0.0 91.1 959 1,023 1,766 0.62 0.58 1.01 Northwestern Ore . Tillamook, Ore. . . . Stillwater, Nev. . . . 0.5 0.1 1.3 0.0 0.0 0.0 12.5 97.9 3.1 87.0 2.0 95.6 0.0 0.0 0.0 927 21 1,018 0.60 0.96 0.58 Clarion Co., Pa.. . . Forest Co., Pa Clarion Co., Pa.. . . 0.0 0.0 0.0 0.0 0.0 0.0 1.1 1.0 1.7 96.4 70.8 80.5 2.5 28.2 17.8 1,073 1,279 1,189 0.57 0.70 0.65 Butler Co., Pa Kings Co., Cal .... Greybull Field, Wyo 0.0 30.4 0.2 0.0 0.0 0.0 0.9 2.4 0.8 53.3 66.2 81.7 45.8 1.0 17.3 1,420 724 1,192 0.78 0.85 0.64 Casing head gas. . . McKean Co., Pa. . 0.0 0.5 0.0 0.0 0.0 0.0 1.3 3.1 1.0 51.5 64.1 86.0 47.2 32.3 13.0 1,427 1,282 1,159 0.77 0.68 0.59 Caddo Parish Field, La Park County, Okla. 0.9 0.0 0.0 0.0 1.5 1.8 97.6 94.4 0.0 3.8 1,039 1,076 0.57 0.59 Bradford, Pa Nortonville, N. D.. Schulto Field, Okla. 0.0 1.3 0.5 0.0 0.0 0.0 8.9 13.6 1.5 18.9 85.1 76.4 72.2 0.0 21.6 1,534 1.00 907 0.62 1,215 0.67 Casing head gas used for produc- tion of gasoline. . 0.0 0.0 3.3 78.7 18.0 2,424 1.38 From Pittsburg gas supply From Columbus gas supply 0.0 0.0 0.0 0.0 1.2 1.6 79.2 80.3 19.6 18.1 1,208 1,193 0.65 0.64 Table 79. Composition of Gas Fuels, by Percentages. Fuel Combustible — by Volume Incombustible-by Volume Heat Value, B.t.u. Hydrogen Methane Ethylene Carbon Monoxide Carbon Dioxide Oxygen Nitrogen per cu. ft. Natural gas Coal gas Water gas 1.7 39.78 21.8 94.16 45.16 30.7 0.30 6.38 12.9 0.55 7.04 28.1 0.29 1.08 3.8 0.30 0.06 0.5 2.80 0.50 2.2 1,000 730 700 Coke oven gas.. . Blast furnace gas Producer gas. . . . Oil gas 53.2 3.0 2.81 32.0 35.0 2.0 6.0 27.5 14.34 2.0 10.0 10.5 ' 'o!r 0.5 2.0 59.4 66.7 3.0 620 100 5.56 48.0 "l6"5' 110 850 u Q c o ■i-t C o o x: o c V U o CO c C3 u c o 3 O FUEL 485 Fig. 217. The Junker Gas Calorimeter. discharged from the apparatus. Thermometers are inserted at the points of entrance and exit. The heat of combustion of a cu. ft. of gas is determined by multiplying the rise of temperature in deg. F. by the weight of water in lb., and dividing the product by the volume of gas in cu. ft. The result thus found after being corrected for moisture and reduced to the equivalent at 32 deg. and 14,696 lbs. per sq. in., is what is termed the "higher value," and this is the value, unless otherwise stated, which is generally employed. The ''low value" is obtained by multiplying the weight of the con- densed vapor resulting from the combustion, expressed in lb., by the total heat of atmospheric steam above the temperature of the condensed vapor, dividing the product by the volume of the gas in cu. ft., and subtracting the quotient from the higher value. Heat Value of Liquid and Gaseous Fuels THE heating power of a fuel, as used in calculating boiler trials, is the value determined by calorimeter test. Some fuels contain hydrogen, and others moisture, thus reducing the heat available for steam. Most liquid fuels and some gases contain a high percentage of hydrogen. Their calorific power as determined by calorimeter test is called the "high" heat value, while the available heat is known as the "low" heat value. The difference between the two is equal to the latent heat of steam formed 486 FUEL by the burning of the hydrogen, which cannc: be absorbed by the wa:er in the boiler. As hydrogen combines with eight times its weight of oxygen, the result is 9 lb. of water for the combustion of 1 lb. of hydrogen. ' The latent heat of steam being 97U B.t.u. per pound, this combustion represents a total of 8745 B.t-u. per pound of hydrogen. Deducting this from 60,626 B.Lu., the high heat value of hydrogen, gives 51,1^ B.Lu. as the low heat value per pound of hydrogen. On a volumetric basis the high heat value of hjdrogen can be taken as 340 B.t-u. per cubic foot and the low heat value as 290 B.t.u., leaving 50 B.t.u. per cubic foot that is not absorbed by the boiler water. If a calorimeter test gives the high heat value of oil as IS ': B.tu. per pound and the fuel contains 10 per cent hvdrogen, the:. :'.'.- ! ei: value is 18,500 — (0.10 X 8745) = 17,625 B.t.u. per pound ap;:-::-i.:-:: . If a sample of gas fuel containing 20 per cent hydrogen by volume has a high heat value of 710 B.t-u. per cubic foot as determined by calorimeter, then the low heat value is 710 — (02 X 50) =700 B.t.u. per cubic foot Buying Fuels Under Contract ' I HE purchase of fuels under contract and specification involves expense in -»• sampling and analysis, but many engineers believe the advantages gained are worth the cost. Large consumers of coal and oil have adopted the con- tract and specification method, because it guarantees economy when quaUty and price are considered. Power reports a saving of S20.000 in the coal bills of 18 plants, the fuel having been tested at a central laboratory at a cost of $1,500 for the year. Specifications insure a more uniform grade of fuel than can be other- wise obtained. Boiler plant operation can be studied more carefully and adjustments made to secure the highest efficiency with the grade of fuel delivered. However, sampling and analyzing are expensive. Fuel contractors hold that many specifications are unreasonable, and sometimes add 5 to 10 per cent to the price to cover contingencies. Specifications for Coal THE following specification for the purchase of coal on a heat value basis is given by /. E. Woodwell, as typical of central power station practice : A. The company agrees to furnish and deliver to the consumer. , at such times and in such quantities as ordered by the consumer for consumption at said premises during the term hereof, at the consumer's option, either or all of the kinds of coal described below; said coals to average the following assays: Coal of size passing through screen having circular perforation in diam. . in. in. in. Coal of size passing over screen having circular perforation in diam in. in. „ in. Moisture in coal as de- livered 9c % - % Ash in coal as deUvered % % % Heat value per pound of dr\- coaL B.Lu. B.t.ii- B.tu. From following count}* From following state FUEL 487 Coal of the above respective descriptions and specified assays, not aver- age assays, to be hereinafter known as the contract grade of the respective kinds. B. The consumer agrees to purchase from the company all of the coal required for consumption at said premises during the term of this contract, except as set forth in paragraph C below, and to pay the company for each ton of 2000 lb. avoirdupois of coal delivered and accepted in accordance with all of the terms of this contract at the following contract rate per ton of each respective contract grade, at which rates the company will deliver the following respective numbers of B.t.u. for one cent, the contract guarantee : Kind of Coal Contract Rate per Ton Contract Guarantee $ Equal to net B.t.u. for 1 cent <}• >( <( (I d» << a << Said B.t.u. for one cent being in each case determined as follows : Multiply the B.t.u. per lb. of dry coal by the per cent moisture, expressed in decimals, and subtract the product so found from the B.t.u, Then multiply the remainder by 2000 and divide this product by the contract rate per ton plus one-half the ash percentage, both expressed as cents. C. It is provided that the consumer may purchase for con- sumption at said premises coal other than herein contracted for test purposes, it being understood that the total of such coal so purchased, shall not exceed 5 per cent of the total consumption during the term of this contract. D. It is understood that the company may deliver coal hereunder con- taining as high as 3 per cent more ash and as high as 3 per cent more mois- ture and as low as 500 fewer B.t.u. per pound dry than specified above for contract grades. E. Should any coal delivered hereunder contain more than the per cent of ash or moisture or fewer than the number of B.t.u. per pound dry allowed under paragraph D hereof, the consumer may, at its option, either accept or reject the same. F. All coal accepted hereunder shall be paid for monthly at a price per ton determined by taking the average of the delivered values obtained from the analysis of all the samples taken during the month, said delivered value in each case being obtained as follows : Multiply the number of B.t.u. delivered per pound of dry coal by the per cent of moisture delivered, expressed in decimals, and subtract the product so found from the B.t.u. delivered per pound of dry coal. Then multiply the remainder by 2000 and divide this product by the contract guarantee. From the quotient, expressed as dollars and cents, subtract one-half of the ash per- centage delivered, expressed as cents. How such a rule works is illustrated in the diagram. Fig. 218, in which the standard is 9 per cent moisture, 8 per cent ash and 13,500 .B.t.u. per pound of dry coal at $3 per ton. Coal of 500 B.t.u. and 3 per cent each of moisture and ash, either below or above the specification base, is the minimum acceptable and the maximum practicable, respectively, as shown in the diagram. On this basis the average premium or penalty is a little over 5 cents for each 100 B.t.u. above or below the standard. An Ohio street railway company has specifications drawn on a basis of a graded scale of premiums and penalties. The established standard for heat value ranges from 12,610 to 12,759 B.t.u. per pound of dry coal. The standard for ash is from to 15 per cent and for sulphur from to 3.5 per cent. The premiums on heat value are graded to a maximum of 21 cents per ton, above the basic price, for 13,960 B.t.u. and over. The penalties o c U 6 U u O 'a B CO u o n .S X vo CO l-l O CO FUEL 489 ^ N \ \ S X \s 3^0 \ ^ 'fix ■§ V, X \ ^t ^ N ■o \ ^ N, 1 1 ■s N V i , "x k. X N ^ .§ \ ^ X s. ,^ 'g "N^ X ^ ^ ^ S; y^ ^ s. V \ ^ ^ y \ 3.00 Con fra zt P r'Ice ^ ^ V X y ^ '> ,y ^ 0^^ '\ ^ X y 200 300 400 liBOO 600 B.+.u. per Pound Dry Coal Fig. 218. Comparison of Base Price and Price to be Paid for Coal Bought on Specifications. are also graded to as high as 50 cents per ton for heating powers of 10,660 to 10,809 B.t.u. There is no premium for the minimum ash content, but there is a penalty for excess ash, amounting to 50 cents per ton when the ash is 29.1 per cent and higher. The penalty for sulphur above the standard is graded to 45 cents per ton when the content is 10 per cent or more. This contract provides that should the coal company or contractor fail at any time to supply the quality and quantity of coal specified, the consumer may purchase a supply in the open market, at prevailing rates, and collect from the contractor any difference in cost. The company reserves the right to cancel and relet the contract should the coal company fail to meet all the terms specified. The contract of a New York transit company gives an average premium and exacts an average penalty of about 2 cents for every 100 B.t.u. above or below the standard. Its standard is 14,201 to 14.250 B.t.u., 20 per cent or less volatile matter; 9 per cent or less ash, and VA per cent or less sulphur. For heat values above the standard the premium reaches 26 cents per ton for 15,505 B.t.u. per pound of dry coal. For values below it the penalty is a maximum of 45 cents per ton at 12,000 B.t.u. or lower. The other penal- ties are highest at 18 cents a ton for 24 per cent or more of volatile matter ; 23 cents for 13>4 per cent or more of ash, and 12 cents for a maximum of 2^ per cent sulphur. The IJ. S. Government, a large user of coal for power and heating pur- poses, buys fuel under specifications that merge the heat value, ash, moisture and price, into a single unit of cost per 1,000.000 B.t.u. Provisions are made for penalties and premiums with respect to the contract standard. 490 FUEL The intent of the specifications is to insure a coal deliven- similar within reasonable limits to the standard of the contract and not continually to make corrections in price for slight variations in heat value. A 2 per cent variation from the standard is allowed before the price is corrected, as it is recognized that the quality- of the coal cannot be controlled within narrow limits. Orders of 50 tons or less are sampled only at the discretion of the Government, because the collecting and preparing of a representative sample, and the cost of analysis, would considerably increase the cost. Under these specifications it is possible to utilize the output from a group of coal mines. Anthracite for power and heating purposes includes the pea and buckwheat sizes from the mines in the counties of Susquehanna, Lackawanna. Luzerne, Carbon. Schuylkill. Columbia. Sullivan. Northumber- land and Dauphin, in the state of Pennsylvania. Coal accepted as bitumi- nous includes the usual bituminous grades, as well as semi-bituminous, sub- bituminous, and lignite. All the coals are analyzed and tested by the Bureau of Mines, on the basis of its specifications. The main provisions for bituminous and anthra- cite coal are : Proposals. Sealed proposals, in duplicate, on blank forms supplied by the — , to furnish such quantities of coal as specified herein as may be required for use of the for the fiscal year ending — , will be received until 2 o'clock p. m., _ , at the office of the , and then opened. Each bidder shall have the right to be present either in person or by attorney, when the bids are opened. Proposals, in duplicate, must be forwarded to the . postage prepaid. Proposals must be made in duplicate on the form provided, and must be signed by the individual, partnership, or corporation making the same. When made by a partnership, the name of each partner must be signed. If made by a corporation, proposals must be signed by the oflficer thereof authorized to bind it by contract, and be accompanied by a copy, under seal, of his authority to sign. The proposals must be accompanied by cash or by certified check drawn payable to the order of the , in the amount equal to 2 per cent of the estimated amount involved for the fuel for which bids are submitted, the minimum amount in any case to be $10. This requirement is solely to guarantee, if the award is made on the proposal, that within 10 da^'s after notice is given that an award has been made, the bidder will enter into a contract in accordance with the terms of the proposal and execute a bond for the faithful performance thereof, with good and sufficient sure- ties as hereinafter required. In the event of the failure of the bidder to enter into contract or execute bond, the cash or check guarantee will be forfeited. Bond. Each contractor shall be required to give a bond, with two or more individual sureties or one corporate surety duly qualified under the act of Congress approved Aug. 13. 1894. in which the contractor and the sureties shall covenant and agree that, in case the said contractor shall fail to do or perform any or all of the covenants, stipulations, and agreements of said contract on the part of the said contractor to be performed as therein set forth, the said contractor and his sureties shall forfeit and pay to the L'nited States of America any and all damages sustained by the L'nited States b)^ reason of any failure of the contractor fully and faithfully to keep and perform the terms and conditions of his contract, to be recovered in an action at law in the name of the United States in any proper court of FUEL 491 competent jurisdiction. Such sureties (except corporate sureties) shall justify their responsibility by affidavit showing that they severally own and possess property of the clear value in the aggregate of double the amount of the above-mentioned forfeiture over and above all debts and liabilities and all property by law exempt from execution. The affidavit shall be sworn to before a judge or a clerk of a court of record or a United States attorney, who must certify of his own personal knowledge that the sureties are suffi- cient to pay the full penalty of the bond. If the estimated amount involved in the contract does not exceed the sum of $200, then the bond may be waived with the consent of the depart- ment involved. Reservations. The right is reserved by the Government to reject any and all bids and to waive technical defects. Bidders are cautioned against guaranteeing higher standards of quality than can be maintained in delivered coal, as the Government reserves the right to reject any and all bids, if the Government has information regarding analyses and test results that indicate that higher standards have been offered than probably can be maintained. The right shall be reserved by the Government to purchase for the purpose of making boiler tests, other coal than that herein contracted for, pro- vided the amount so purchased shall not exceed 10 per cent of the estimated consumption during the period covered by this agreement. If it should appear to be to the best interests of the Government to do so, the right is reserved to award the contract for supplying coal at a price higher than that named in a lower bid, or in lower bids. If the bidder to whom the award is made shall fail to enter into a contract as herein provided, then the award may be annulled and the con- tract let to the next most desirable bidder without further advertisement, and such bidder shall be required to fulfill every stipulation expressed therein, as if he were the original party to whom the contract was awarded ; pro- vided, however, that such bidder is notified of said award within 60 days after the date on which the bids on this contract were opened. If such notice should not be given within said 60 days, then the acceptance of the award will be optional with the said bidder. No contract can be lawfully transferred or assigned. No proposal will be considered from any person, firm, or corporation in default of the performance of any contract or agreement made with the United States, or conclusively shown to have failed to perform satisfactorily such contract or agreement. Quantity. The estimated quantity of coal in tons of 2,000 lb. to be purchased is based upon the previous annual consumption, but the right will be reserved to order a greater or less quantity, subject to the actual requirements of the service. Delivery. The coal shall be delivered in such quantities at such times as the Government may direct. (Place of delivery to be stated.) All the available storage capacity of the Government coal bunkers shall be placed at the disposal of the contractor to facilitate delivery of coal under favorable conditions. When an order is issued for coal, the contractor upon commencing a delivery on that order shall continue the delivery with such rapidity as not to waste unduly the services of the Government inspector. After verbal or written notice shall have been given to deliver coal under this contract a second notice may be served in writing upon the contractor to make delivery of the coal so ordered within a reasonable time, to be determined by the Government official in charge, after receipt of said second notice. Should the contractor for any reason fail to comply 492 FUEL o DQ C 73 a a "5 6 o U > c Q o o CO O. c o FUEL 493 with the second request, the Government shall be at liberty to buy coal inde- pendent of this contract, and for coal so purchased to charge against the con- tractor and his sureties any excess in price over the price which would have l)een paid to the contractor had the coal been delivered by him. The contractor shall be allowed to deliver coal during the usual hours of teaming — that is, between 8 a. m. and 5 p. m. Weighing. (To be stated, by whom and where the coal shall be weighed.) Sampling. The contractor shall have the privilege of having a repre- sentative present to witness the collection and preparation of the samples to be forwarded to the laboratory. The samples shall be collected and prepared in accordance with the method given in the appendix, attached hereto as a part of these specifica- tions and proposals. Analyses. The samples shall be immediately forwarded to the Bureau of Mines, Department of the Interior, Washington, D. C, and they shall be analyzed and tested in accordance with the method recommended by the American Chemical Society and by the use of a bomb calorimeter. Such analyses and tests shall be made at no cost to the contractor. The results shall be reported by the Bureau of Amines in not more than fifteen days after the receipt of the sample. If more than one sample is received from the same delivery, the fifteen days shall date from the receipt of the last sample taken. Description of Coal Desired. The coal must be a good coal (kind and size to be specified), and must be adapted for successful use in the particular furnace and boiler equipment. Bidders are required to specify the coal offered in terms of moisture in the coal "as received," and of ash, volatile matter, sulphur, and B.t.u. in "dry coal," such values to become the standards for the coal of the successful bidder. In addition, the bidders are required to give the trade name of the coal offered, and other designation ; this information shall be furnished in spaces provided hereinafter. Coal of the description and analysis specified is herein known as coal of the contract grade. Bidders are cautioned against specifying higher stand- ards than can be maintained, for to do so will result in deductions in price and may result in the rejection of the delivered coal or the cancellation of the contract. In this connection it should be recognized that the small "mine samples" usually indicate a coal of higher economic value than that actually delivered in carload lots, because of the care taken to separate extraneous matter from the coal in the "mine samples." Award. In determining the award of this contract consideration will be given to the quality of the coal (expressed in terms of moisture in coal "as received," of ash in "dry coal," and B.t.u. in "dry coal"), offered by the respective bidders and to the operating results obtained with the same and with similar coals on previous contracts or by test, as well as to the price per ton. Bids may be rejected from further consideration if they offer coals regarding which the Government has information that they possess unsatis- factory physical characteristics or volatile matter or sulphur or ash con- tents, or that they are unsatisfactory because of clinkering or excessive refuse, or because of having failed to meet the requirements of city smoke ordinances, or for other cause that would indicate that they are of a character or quality that the Government considers unsuited for the storage space or the furnace equipment of the particular contract. Methods of Comparing Bids. In order to compare bids as to the quality of the coal offered, all proposals shall be adjusted to a connnon basis. 494 FUEL The method used shall be to merge the four variables — moisture, con- tent, ash content, heating value, and price bid per ton — into one figure, the cost of 1,000,000 B.t.u. The procedure under this method shall be as follows : (a) All bids shall be reduced to a common basis with respect to moisture, by dividing the price quoted in each bid by the difference between 100 per cent and the percentage of moisture guaranteed in the bid. The adjusted bids shall be figured to the nearest tenth of a cent. (b) The bids shall be adjusted to the same ash percentage by selecting as the standard the proposal that offers coal containing the lowest percentage of ash. The difference in ash content between any given bid and this standard shall be divided by two and the price in such bid, adjusted in accordance with the above, multiplied by the quotient. The result shall be added to the above adjusted price. The adjusted bids shall be figured to the nearest tenth of a cent. (c) On the basis of the adjusted price, allowance shall then be made for the varying heat values by computing the cost of 1,000.000 B.t.u. for each coal oft'ered. This determination shall be made by multiph'ing the price per ton adjusted for ash and moisture content by 1,000,000, and dividing the result by the product of 2.000 multiplied by the number of B.t.u. guar- anteed. If the coal is purchased on the basis of 2,240 lb. to the ton, the factor of 2,240 should be used instead of 2.000. After the elimination of undesirable bids, the selection of the lowest bid of those remaining on the basis of the cost per 1,000,000 B.t.u. may be considered by the Government as a tentative award only, the Government reserving the right to have practical service test or tests made under the direction of the Bureau of Mines, the results to determine the final award of contract. The interested bidder or his authorized representative may be present at such test. Coal Subject to Rejection. It Is understood that coal containing 3 per cent more moisture, or 4 per cent more ash, or 3 per cent more volatile matter, or 1 per cent more sulphur, or 4 per cent fewer B.t.u. than the specified guaranties as to the standards for the coal hereunder contracted for, or coal furnished from a mine or from mines other than herein speci- fied by the contractor, unless upon written permission of the Government, shall be considered subject to rejection, and the Government may, at its option, either accept or reject the same. Should the Government have con- sumed a part of such coal subject to rejection, such consumption shall not impair the Government's right to cause the contractor to remove the remain- der of the delivered coal subject to rejection. It is agreed that if the contractor shall furnish coal in three consecu- tive deliveries, or in case more than 20 per cent of the coal delivered to an}' date during the life of this contract shall contain 3 per cent more mois- ture, or 2 per cent more ash, or 3 per cent more volatile matter, or 1 per cent more sulphur, or 2 per cent fewer B.t.u. than the specified guaranties as to the standards for the coal hereunder contracted for, or if the coal is furnished from a mine or from mines other than herein specified, unless upon written permission of the Government, then this contract maj', at the option of the Government, be terminated, or the Government may, at its option, purchase coal in the open market until it may become satisfied that the contractor can furnish coal equal to the standards guaranteed, and the Government shall have the right to charge against the contractor any excess in price of coal so purchased over the corrected price that would have been paid to the contractor had the coal been delivered by him. Removal of Rejected Coal. The contractor shall be required to re- move, without cost to the Government, within 48 hours after notifica- tion, coal that has been rejected by the Government. Should the contractor not remove rejected coal within the said 48 hours, the Government shall then FUEL 495 be at liberty to have the said coal removed from its premises and to dispose of such coal by sale, as the Government shall elect. The proceeds from such sale, less all costs incidental to its removal and to the sale, shall be paid over to the contractor. Determination of Price. The Government hereby agrees to pay the contractor within thirty days after the completion of an order or delivery for each ton of 2,000 lb. of coal delivered and accepted in accordance with all the terms of this contract, the price per ton determined by taking the analysis of the sample, or the average of the analyses of the samples if more than one sample is analyzed, collected from the coal delivered upon the basis of the price herein named, adjusted as follows for variations in heat value, ash content, and moisture content from the standards guaran- teed herein by the contractor. Heat Unit Adjustment. Considering the coal on a "dry coal" basis, no adjustment in price shall be made for variations of 2 per cent or less in the number of B.t.u. from the guaranteed standard. When the variation in heat units exceeds 2 per cent of the guaranteed standard, the adjusted price shall be proportioned and shall be obtained as follows : B.t.u. delivered coal ("dry-coal" basis) ^ ■• . , • B.t.u. ("dry-coal" basis) specified m contract The adjusted price shall be figured to the nearest tenth of a cent. As an example, for coal delivered on a contract guaranteeing 14,000 B.t.u. on a "dry-coal" basis at a bid price of $3 per ton, showing by calo- rific test results varying between 13,720 and 14,280 B.t.u., there would be no price adjustment. If, however, by way of further example the delivered coal shows by calorific test 14,350 B.t.u. on a "dry-coal" basis, the price for this variation from the contract guaranty would be, by substitution in the formula : 14,350 _ 14000 ^ ?*^ — $0,075 Ash Adjustment. No adjustment in price shall be made for varia- tions of 2 per cent or less below or above the guaranteed percentage of ash on the "dry-coal" basis. When the variation exceeds 2 per cent, the adjust- ment in price shall be determined as follows : The difference between the ash content by analysis and the ash content guaranteed shall be divided by two and the quotient shall be multiplied by the bid price, and the result shall be added to or deducted from the B.t.u. adjusted price or the bid price, if there is no B.t.u. adjustment, according to whether the ash content by analysis is below or above the percentage guaranteed. The adjustment for ash content shall be figured to the nearest tenth of a cent. As an example of the method of determining the adjustment in cents per ton for coal containing an ash content varying by more than 2 per cent from the standard, consider that coal for which the above-mentioned heat unit adjustment is to be made has been delivered on a contract guaranteeing 10 per cent ash, and shows by analysis an ash content of 7.5 per cent. The adjustment in price would be determined as follows : The difference between 10 and 7.5 which is 2.5 would be divided by 2, and the quotient of 1.25 multiplied by $3, resulting in an adjustment of 3.7 cents per ton, which in this case would be an addition. The price after adjustment for the variations in heating value and ash content would be $3,075 plus $0,037, or $3,112. Moisture Adjustment. The price shall be further adjusted for mois- ture content in excess of the amount guaranteed by the contractor, the deduction being determined by multiplying the price bid by the percent- 496 FUEL age of moisture in excess of the amount guaranteed. The deduction shall be figured to the nearest tenth of a cent. As an example, consider that coal for which the above-mentioned heat unit and ash adjustments are to be made, and as having been delivered on a contract guaranteeing 3 per cent moisture, and that the coal shows by analysis 4.5 per cent moisture; then the bid price would be multiplied by 1.5 (repre- senting excess moisture), giving 4.5 cents as the deduction per ton. The price to be paid per ton for the coal would then be $3,112, less $0,045, or $3,067. Partial Payment. If the coal on visual inspection by the Govern- ment inspector appears to be acceptable coal, the Government shall have the right, immediateh' on the completion of an order, to make payment on 90 per cent of the amount of the bill, based on the tonnage delivered and the bid price per ton. The 10 per cent withheld is to cover an}' deduction on account of the delivery of coal that on analysis and test is subject to an adjustment in price. If the 10 per cent withheld should not be sufficient to cover the deduction, then the amount due the Government may be taken from any mone}- thereafter to become due to the contractor, or may be collected from the sureties. Because of the distance of the point of delivery from the laboratory, requiring several days for the transmittal of samples and the return of analytical report, because of loss of the original sample, necessitating the forwarding of the reserve sample, or for any other reason that would result in delayed pa3'ment, should such be withheld until receipt of analytical report, the Government may, as circumstances in its opinion warrant, exercise the foregoing right. Information to he Supplied. The following spaces should be filled in by the bidder for each bid, for if the information called for is not sup- plied, the proposal may be regarded as informal and rejected: The undersigned agrees to furnish to the the coal described below, in tons of 2.000 lb. each, and in quantity as may be required during the !iscal 3'ear ending, in accordance with the foregoing specifications; the coal to be delivered in such quantities and at such times as the Government may direct. (a) Kind and size of coal (b) Commercial name of coal (c) Xame of mine or mines (d) Location of mine or mines (town, county, and State) (e) Xame or other designation of coal bed or beds (f) Railroad on which mine or mines are located (g) Xame of operator of mine or mines (h) Percentage of moisture in coal "as received" (i) Percentage of ash in "dry coal" --. (j) Percentage of volatile matter in ''dry coal" (k) Percentage of sulphur in "dry coal'' (1) British thermal units per pound of "dry coal" (m) Additional description of coal deemed of importance by the bidder (n) Bid price per ton of 2,000 pounds. FUEL 497 Specifications for Oil FUEL OILS are commonly specified according to their density. While this is accepted trade practice, it is not an accurate gage of the fuel. The heavy oils are of an asphalt base, viscous, sluggish, and of relatively low heating power. The light oils are fluid at ordinary temperatures, are volatile, rich in hydrocarbons and high in heating power. The heating power, however, de- pends mainly upon the hydrogen and carbon content, and when reduced to ultimate analysis these values are about the same for both heavy and light oils. The commercial value of fuel oil depends upon how easily it can be handled, or how completely it can be atomized by the burner equip- ment, and these features are controlled by the viscosity of the fuel. Viscosity can be defined as molecular friction or the resistance to inter- nal movement of a liquid. It is generally measured by the scale of a visco- meter, such as the Saybolt, Redwood or Engler, which indicates the time required for an amount of oil to flow through a standard orifice or short tube under fixed conditions of head and temperature. The result, some- times expressed in "degrees," is simply a time ratio. The type of viscometer should always be named in specifying viscosity, because the standards vary in different instruments. As the viscosity is materially lessened as the temperature Increases, the fuel oil in power-plant practice is heated to about 160 deg. before being fed to the burners. At this temperature, California oils have a vis- cosity between 3.5 and 8.5 deg. Engler. Many of the lighter oils are sufficiently mobile at ordinary temperatures and do not require pre-heating. In general, oil fuel is heated to within 50 deg. of the flash point for boiler operation with mechanical burners. The flash point of the fuel indicates the temperature at which inflammable gases or vapors are given off. For oil fuels, it ranges from 220 to 280 deg. For safety in handling this should not be below 150 deg. When stored in tanks and at ordinary temperatures, there is practically no danger as the oil does not form any appreciable amount of gas at temperatures below the flash point. The flash point is determined by heating the oil fuel, usually in a closed container, and testing with a spark or flame. The vapor or gas is driven off and flashes or ignites. The temperature at which ignition takes place is called the flash point. In the so-called open test an open vessel prolongs the flash point, the temperature being higher than with the closed instruments of Abel, Pensky or Marten, which are considered standard. By continuing the heating beyond the flash point until the flash becomes permanent and the fuel continues to burn a temperature known as the burning point is reached. As a free supply of air is required in this test, the open-cup method is used. For Kern River oil, the burning point can be taken as between 260 and 270 degrees. The properties of oil, as outlined, are of prime importance in the pur- chase of the fuel, and are therefore included in commercial specifications. Naval Specifications for Oil. The British Navy specifies a flash point not lower than 175 deg., closed-cup test. The water content must not exceed 0.5 per cent ; sulphur not over 3. per cent ; and acidity expressed as oleic acid, a maximum of 0.05 per cent. The U. S. Navy requires a hydrocarbon oil of best quality, free from grit, acid and other foreign matter. A barrel of 42 gal,, each gallon of 231 cu. in. at 60 deg., is the standard. For a variation of 10 deg. from the standard temperature, 0.4 per cent is added or deducted to correct the meas- ured quantity. The oil must not contain more than 1 per cent water and sediment. If over 1 per cent, the excess is either deducted from the volume or else the fuel is rejected. 498 FUEL Viscosity at 100 deg. must not be higher than 200 Engler or 7000 seconds Saybolt. The flash point must not be below 150 deg. as the minimum by the Abel or Pensky-Marten closed-cup test, or 175 deg. by the Tagliabue open-cup method. For acceptance it should not be lower than the temper- ature at which the viscosity is 8 deg. Engler. /\s water is unity on the Engler scale, an oil having a viscosity of 8 deg. Engler at a temperature of 180 deg. will have a flash point of 180 deg. The equivalent of 8 deg. Engler is taken as 280 sec. Saybolt. Railroad Fuel Oil. The contract form of a large railroad system using oil as fuel, calls for the following : Fuel oil should have a density ranging between 13 and 29 deg. Baume at 60 deg. It should contain no sand or other foreign matter, such as sticks, waste and stone. The moisture content should be a minimum. Oil containing over 2 per cent water and other impurities will be rejected. Viscosity to be so low that the fuel oil will flow readily through a 4-in, pipe at 70 deg. temperature. Oil will not be accepted when the flash point is less than 110 deg. as tested by the Tagliabue open-cup method. The fuel is to be heated at the rate of 5 deg. per minute and the test flame applied at one-minute intervals after 90 deg. has been reached. Goz'enijncnt Oil Fuel. For the purchase of oil fuel for the different departments of the U. S. Government, the Bureau of Mines has outlined the main features controlling the efficient utilization of fuel oil under steam boilers, as follows : Fuel oil should be either a natural homogeneous oil or a homogeneous residue from a natural oil ; if the latter, all constituents having a low flash point should have been removed by distillation ; it should not be composed of a light oil and a heavy residue mixed in such proportions as to give the density desired. It should not have been distilled at a temperature high enough to burn it, nor at a temperature so high that flecks of carbonaceous matter began to separate. It should not flash below 140 deg. in a closed Abel-Pensky or Fensky- Marten test. Its specific gravity should range from 0.85 to 0.96 at 59 deg. ; the oil should be rejected if its specific gravity is above 0.97 at that temperature. It should be mobile, free from solid or semi-solid bodies, and should flow readily, at ordinary atmospheric temperature and under a head of 1 ft. of oil, through a 4-in. pipe 10 ft. in length. It should not congeal or become too sluggish to flow at 32 degrees. It should have a heating value of not less than 18,0(X) B.t.u. per pound; 18.450 B.t.u. to be the standard. A bonus is to be paid or a penalty deducted according as the fuel oil delivered is above or below this standard. It should be rejected if it contains more than 2 per cent water or more than 1 per cent sulphur. It should not contain more than a trace of sand, clay, or dirt. 499 CHAPTER 14 FEED W^ATER WATER, the most widely distributed liquid in nature, is the fluid gen- erally employed for converting heat energy into work by its expansion in the form of steam. Properties of Water CHEMICALLY pure water is a chemical combination of the two elements, hydrogen and oxygen, in the proportion of two parts hydrogen by volume to one part oxygen (H2O), or one part hydrogen by weight to eight parts of oxygen. Distilled water may be generally regarded as chemically pure. Water reaches its maximum density, 62.425 lb. per cu. ft. at 39.1 deg., and expands if this temperature is either raised or lowered. Fig. 219 shows its variation in weight and volume at temperatures from 20 to 250 deg. The values given are those at saturation pressure; that is, the pres- 63 62 o i£ o x> D- «n T5 c 1 60 32 212 59. 1 1 / 1 1 t 1 1 / '^ ' 1 "*- 1 / 1 1 N l/ / 1 S s. \ 1 N s % / 1 1 ^ / 1 1 1 \ / / 1 1 1 \ / 1 1 \ / 1 1 1 / \ 1 1 / \ 1 1 ^^> '/ \ 1 1 loV \, 1 1 1 / V 1.. 1 Y l^ 1 *^ y 1 \ \ 1 ^ X 1 \ >•, 1 _ ^ 1 s 20 50 100 150 200 Temperature, Degrees Fahrenheit 250 ,0170 .0169 .0168 0167 ,0166 8 0165 ^ ex .0164 S U- .0163 5 .0162 .0161 ,0160 Fig. 219. Variation of Weight and Volume of Water with Temperature. sure at which liquid and vapor in contact at the same temperature will remain in equilibrium. For temperatures between 32 and 212 deg., the weights and volumes at atmospheric pressure are practically indistinguishable from those at saturation pressure, as water is almost incompressible. The dotted lines beyond these ranges represent the volume and weight of water in contact with steam at the pressures (above or below ordinary atmospheric) corre- sponding to the temperatiires given. The specific heat of water at 63 deg. is taken as unity, that is, it requires 1 B.t.u. to raise a pound of water from 63 to 64 deg. The specific heat varies slightly at other temperatures, being 1.02 at 20 deg.; reaching its 500 FEED WATER minimum, 0.995, at 100 deg. ; and rising to 1.18 at 600 deg. The term, "mean specific heat" is applied to the difference in heat capacity per pound at two different temperatures, divided by the temperature difference. The mean specific heat of water from 32 to 175 deg. is 0.999, and for greater ranges it gradually rises, reaching 1.062 for the range from 32 to 600 deg. For many engineering purposes, the specific heat of water can be regarded as constant, and the heat liberated or absorbed taken as 1 B.t.u. per pound per degree of temperature change. 25 20 s_ s: o. in O E 15 E > O in JZ o c u 4- o 10 400 350 u 300- t_ C5 D O" 250 fc D- w 15 C D 200 a i_ D if) 150 f Q. C5 CD 50 -400 -350 300 ■§ i_ C5 ^ 250^ i_ D- U) T5 C 200 p 6) u D (/) to u D. O _5 o 100 < -150 Fig. 220. 100 150 200 250 300 350 Boiling Point, Degrees Fahrenheit Variation of Boiling Point of Water with Pressure. Vapor rises from water at all temperatures, unless the vapor pressure in the space in contact with the water exceeds the saturation pressure. The boiling point for any particular pressure is the highest temperature which F E E D W A T E R 501 can be reached with the water and vapor in contact with it at that pressure, any heat added to the water resulting only in the formation of additional vapor. In the generation of steam for practical purposes, the ebullition is of course much more pronounced than is the formation of vapor at low temperatures, but the phenomenon is similar in its nature. The boiling point rises and falls with the pressure, so that daily changes in the barometer have a slight effect on the boiling point; these must be allowed for in calibrating thermometers. The boiling point is reduced at points of high elevation and consequent low average barometric pressure. As long as heat is supplied to a boiler producing steam, the temperature remains at the boiling point corresponding to the momentary pressure, so that the temperature of boiler water in contact with saturated steam can be judged from the pressure. Fig. 220 indicates the boiling point for pressures up to 400 lb. gage. The divisions to the right indicate the corresponding pressures in absolute units, equal to 14.696 plus the gage pressure in pounds per square inch. Absolute pressures in pounds per square inch are converted into "standard atmospheres" by dividing by standard or normal atmospheric pressure (14.696 lb. per sq. in.), which is the pressure that will support a column of mercury 760 mm. (29.921 in.) in height. Roughly, 2 in. of mercury correspond to each pound of pressure. Pure water boils at 212 deg. under standard atmospheric pressure. For boiling points lower than 212 deg., the pressures are less than atmospheric. They are expressed as absolute pressures, in pounds per square inch or in head of mercury; or by the amount of "vacuum," that is, the difference between the absolute head of mercury and the standard atmospheric head of 29.921 inches. For engineering purposes, the barometer is arranged so that the reading is subtracted from 30 instead of from 29.921, so that stand- ard atmospheric pressure when "referred to a 30-in. barometer" would be recorded as 0.08 in. of vacuum. Impurities in Water A LL known substances are more or less soluble in water, so that natural '^*' water supplies other than rain water are always contaminated, and contain in solution organic matter or traces of the solids with which they have come in contact. In a boiler, the solids remain behind when steam is produced, and the impurities are precipitated when their maximum con- centration is reached, that is, when the volume of water is sufficiently reduced to become saturated with the particular substance. These precipi- tates cause scale and accompanying troubles, the seriousness of which depends upon the nature and amount of the original impurities. The characteristics of a boiler feed water may be described by one or more of the following terms : temporary hardness, permanent hardness, alkalinity, causticity, acidity, and dissolved gases — the quantities of the im- purities being generally expressed in grains per U. S. gallon (231 cubic inches). Temporary hardness is the term applied to water containing the bicar- bonates of calcium, Ca(HC03)2, and magnesium, Mg(HC03)2, which are held in solution by an excess of carbon dioxide. Boiling at 212 degrees expells the carbon dioxide. In the one case, calcium carbonate, CaCO:!, pre- cipitates out directly. In the other, magnesium monocarbonate is formed. This is soluble and requires further treatment with calcium hydroxide. Ca(0H)2, to reduce to the precipitate Mg(0H)2. Sodium bicarbonate, NaHCOs, and sodium carbonate, NaaCOa, are found in the water in some localities. The former can be converted to the car- bonate by the use of calcium hydroxide, Ca(0H)3. Permanent hardness refers to those waters which contain sulphates, the most common of which is calcium sulphate, CaSO*. X o o o (U CO u CO > C „ CO OJ a a o « o S ^ CO O U 2 (u o >PQ Q S dffi S CO CO o > G Q v?if^^"- --:^'s:Mi. F E E D W A T E R 503 Solid calcium sulphate, CaS04, is known as plaster of Paris, or as gypsum when containing a larger amount of water of crystallization. It is highly soluble in water, 138 grains per gallon at 60 deg., and over 30 grains at 300 deg., but when concentrated, deposits a hard scale on the boiler tubes. It can be converted by the use of soda ash (sodium carbonate, NaaCOs), forming calcium carbonate, CaCOs, and sodium sulphate, Na2S04. The CaCOs can be precipitated before the water enters the boiler, but the Na2S04 remains in solution, and does not interfere with boiler operation unless it becomes highly concentrated. Magnesium sulphate, MgSO*, is decidedly soluble, but tends to react with any calcium salts present, forming hard calcium sulphate scale. Water containing MgS04 can be treated by introducing calcium hydroxide, Ca(OH)j, forming insoluble magnesium hydroxide, Mg(OH)j, and calcium sulphate, CaSO^, which can be corrected by soda ash. Iron oxides, FeO, Fe203 and Fe304; aluminum oxide or alumina, AI2O3 ; and silicon oxide or silica, SizOa, are scale-forming substances sometimes found in solution. Alkalinity, a term often used confusedly with temporary hardness, refers more particularly to waters containing impurities which will neutralize acids. Causticity describes waters that contain hydrates which react to the phenolphthalein indicator. This test is important in connection with waters which may give caustic embrittlement trouble. Acidity, as the term implies, refers to waters containing free acid. In mining districts the water often contains sulphuric and sulphurous acids. Organic acids are found in swamp water and in water contaminated with sewage. Chlorides and acids present in boiler feed water are neutralized bj^ the reagents used to correct sulphates and carbonates. Calcium chloride, CaCl2, and magnesium chloride, MgCU, are found in boiler feed water. The latter is troublesome, as at boiler temperatures it tends to form hydrochloric acid, which causes corrosion. Solid matter such as mud and silt are often present in boiler water, par- ticularly if the feed water is obtained from rivers and streams. Dissolved gases, or air entrained or in solution, in boiler feed water is recognized as a source of corrosion. Water Analysis "T^ABLE 80 gives some representative analyses of water from various locali- -*■ ties. Methods of Water Analysis. Where it is proposed to prescribe a method of feed water treatment for a boiler plant, it is obvious that water analyses should be carried out in a laboratory equipped especially for the purpose. However, there are a number of simple tests which can be performed in the boiler room with a minimum outlay for apparatus, and which will indicate to the plant engineer the advisability of installing feed water treatment. Test for Hardness. A 100 cubic centimeter sample of the water for analysis, together with a standard soap solution, is shaken in a flask; the soap solution being added a little at a time until a permanent lather is formed. The number of cubic centimeters of the standard soap solution required to form the permanent foam will be equivalent to the hardness in parts per 100,000, or in degrees "U. S." hardness depending upon the standard to which the soap solution is made up. One degree "U. S." hardness is equiva- lent to 1 grain of calcium carbonate per U. S. gallon (1 part in 58.349). Standard soap solutions may be obtained from chemical dealers. If this soap test is made on unboiled water, the total hardness will be determined, and if on boiled water, the permanent hardness will be obtained, the difference between the two being the temporary hardness. 504 FEED A\' A T E R Table 80. Water Analyses. ("Boiler Waters" by W. W. Christie) Grains per U. S. Gallon of 231 Cubic Inches. Where From u -^ » »-j X •c s-S s ^ ^ ■^^ ^. d IN E3 =11 V«)latile Organic Matter O 01 Buffalo, X. v., Lake Erie Pittsburgh, Allegheny River.. . . Pittsburgh, Monongahela River 5.66 0.37 1.06 3.32 0.58 3.781 0.58, 5.12' 0.64 0.37 0.78' 0.18 1.50 3.20 9.74 6.60 10.80 Pittsburgh, Pa., artesian well . . 23.45 Milwaukee, Wisconsin River. . .| 6.23 Galveston, Texas, 1 ' 13 . 68 5. 71, 18.41 4.67! 1-76 13.52326.64 1.04 20.14 Trace 0.821 49.43 6.50| 39.30 Trace Z^i . 84 Galveston, Texas, 2 I 21 . 79 Columbus, Ohio 20. 76 Washington, D. C, city supply.' 2.87 29.15 11.74 3.27 398.99 4.00 453.95 7.021 0.58| 6.501 46.60 Trace' 0.36' 2.10 8.60 Baltimore, Md., city supply.. .. ! 2.77 0.65 Sioux Citv, Iowa, city supplv . . 19 . 76j 1 . 24 Los Angeles, Cal., 1 '. . . 10.12| 5.84 Trace 0.10 3.80 1.17| 1.031 4.40 3.51 2.631 4.10 7.30 27.60 26.20 Los Angeles, Cal., 2. . . . Bay City, Mich., Bay. . Bay City, ]Mich., River. 3.72 8.47 4.84 12.59 10.36 20.48 33.66 126.78 0.76 1.15 3.00 6.00 8.74 23.07 49.20 10.92 179.20 Cincinnati, Ohio, River 3 . 88| . 78 Watertown, Conn 1.47| 4.51 Fort Wayne, Ind 8.78 6.22 1.79 1 . 761 Trace 3.511 1.59 Trace 1.78 10.98 6.73 9.52 31.08 Wilmington, Del , 10 . 04 Wichita, Kan 14.14 Springfield, 111., 1 ' 12.99 6.02 25.91 7.40 4.291 8.48 24.34 1.971 2.19 6.17f 35.00 2.00: 66.39 8.62' 33.17 Springfield, 111., 2 5.47 4.31; 1.56| 4.28 Hillsboro, 111 14.56; 2.97 2.391 1.63 Pueblo, Colo 4.32' 16.15 1.20 1.97 5.83| 21.45 Trace! 21.55 5.12 28.76 Long Island City, L. I.. . . . 4.0 28.0 16.0 Mississippi River above Missouri River 8.24 1.02 0.50 1 25 39.0 15.01 Mississippi River below mouth of Missouri River Mississippi River at St. Louis Water Works 10.641 7.41 1.36 1.22 9.64' 6.94, 1.54 1.57 15 9 86 36.49 85 29.54 Hudson River above Pough- keepsie, N. Y 1 . 06 Croton River above Crotoni Dam, N. Y I 4.571 0.16 0.11 10.76 ! 0.4o| 1.92 771 12.70 67^ 7.72 Croton River water from service' I pipes in New York City ', 2.36 Schuvlkill River above Phila- ! delphia, Pa 2.16| 0.29 0.49 1.36 1.30 3.72 4.24 Inasmuch as it is the custom to specify the hardness in terms of calcium carbonate per U. S. gallon, the following factors may be used to reduce the quantities of other salts present in a water to a calcium carbonate basis. Magnesium carbonate X L19 "I Magnesium sulphate X 0.833 Hardness as calcium X 1-05 >-= carbonate per X 0.735 I U. S. gallon X 0.901 Magnesium chloride Calcium sulphate Calcium chloride FEED WATER 505 A water containing more than 20 grains of calcium carbonate, magnesium carbonate or magnesium chloride per U. S. gallon, or more than 5 grains of calcium or magnesium sulphate per U. S. gallon, is considered undesirable for boiler feed. Table 81 roughly classifies the desirability of hard waters for boiler use. Table 81. Classification of Boiler Feed Waters. CaCO. MgCO:, MgCl2 CaS04 MgS04 Classification to 10 gr. 10 to 15 gr. 15 to 20 gr. 20 to 30 gr. Over 30 gr. to 2.5 gr. 2.5 to 4.0 gr. 4 to 5.0 gr. 5 to 7.5 gr. Over 7.5 gr. Very Good Good. Fair. Bad. Very Bad. Alkalinity Test. A 50 cubic centimeter sample of the water to be tested is titrated with a standard solution of sulphuric acid, using methyl orange as an indicator. The degree of alkalinity will be represented by the number of cubic centimeters of acid used to neutralize the solution, as will be indicated when the color of the solution just turns from pink to pale Aellow. The required standard sulphuric acid solution can be obtained from chemical dealers. Causticity Test. A 50 cubic centimeter sample of the water is titrated with a standard solution of sulphuric acid, using phenolphthalein as an indi- cator. The degree of causticity will be represented by the number of cubic centimeters of acid used to satisfy the reaction, as will be indicated when the solution turns from red to colorless. The alkalinity, hardness and causticity of a properly treated boiler water, as expressed in grains per U. S. gallon by analysis, should stand in the approximate relation of 6, 5 and 4. Concentration Test THE total concentration of soluble salts in a boiler fed with softened water can be estimated from the amount of sodium chloride or common salt (NaCl) in solution, which can be determined as follows: After blowing down the boiler, a sample is drawn from the water column, allowed to cool and settle, and 100 cc. of the clear liquid measured ofif. A drop of phenol- phthalein solution is added to the latter, turning it pink; then just sufficient N/20 sulphuric acid (about ^ per cent strong) from a burette to destroy the pink; and four drops potassium chromate indicator (containing 20 grains per 100 cc). Silver nitrate solution is then added slowly from another burette, while stirring the sample, until a permanent reddish precipitate is formed. If the silver nitrate solution is of a strength of 4.976 grains AgNOs per liter, each cubic centimeter of the solution consumed represents 1 grain of sodium chloride per gallon in the boiler water. Water Treatment \YyATER treatmefit may be roughly classified into three separate divisions, '^ viz : mechanical treatment, thermal treatment and chemical treatment. Mechanical Treatment. Raw water from rivers very often contains mud and silt in suspension, and if used directly in boilers will cause the deposi- c a Q u ^- — O c — 3 u .t: « ^ G3 o m '0 O cu F E E D W A T E R 50/ tion of mud on the heating surfaces, resulting in lowered heat transmission, burned tubes and bagged plates. Such solid matter may be removed by- settling, filtering or by a combination of these two methods. Heavy mud and sand can be eliminated by allowing the water to stand in settling basins, but suspended matter which will not gravitate must be removed by filtration. Settling basins are generally constructed of concrete. They should be ar- ranged in duplicate so that while one basin is settling the other may be drawn upon as the supply. The size of such basins will depend upon the characteristics of the particular water as regards sedimentation, which may be roughly determined by experimental tests conducted on not less than barrel samples. Filter beds may be constructed of coke, excelsior, crushed stone or sand, and they should be arranged in duplicate to allow for clean- ing. Thermal Treatment. As stated above, the carbonates of lime and mag- nesia are precipitated by boiling, hence it is obvious that any type of feed water heater will act to a certain extent as a purifier or softener. A descrip- tion of the various types of heaters and of economizers is given in Chapter 9 on AUXILIARIES. Chemical Treatment "T^HE chemical methods used for softening boiler feed water have been -*• practically unchanged for more than 50 years, except for special methods devised to obtain softened cold water. Hydrate of lime in the form of lime water, or of milk of lime, is still the most economic means for neutralizing acids, absorbing carbon dioxide, and converting bicarbonates to carbonates or hydrates. Likewise, soda ash is preferred for transforming sulphates, chlorides and nitrates to carbonates. While the chemical methods have not been changed, the engineering appliances for performing the softening process have undergone a radical evolution. The improvements have consisted prin- cipally in the proper use of heat for accelerating the chemical reaction, the more accurate feeding of chemical reagents, and the reduction in the labor required in handling chemicals and in removing precipitates. Two general types of lime-soda processes are used in power plants. In all essential respects, these two, the hot continuous and the cold continuous, processes, are similar. The treatment consists of adding to the raw water softening agents in carefully controlled amounts (which must agree with the composition of the water), mixing these thoroughly within the water, and permitting sufficient time to elapse for the separation of the "sludge" before the water is fed into the boiler. In the first process, the heat increases the rapidity of the chemical reactions, so that the storage space required is less than with the cold continuous process. The hot process expels the air from the water and so reduces corrosion. The cold process is used mainly when cold water is required for some special purpose, such as process work. Most softeners are of the continuous type. In intermittent softeners, two or more tanks are intermittently filled with raw water and chemicals. The treated water is then drawn off from one tank, while the other is filled and agitated by a revolving paddle so as to insure mixing and to stir up old sludge, which assists in settling out the new precipitate. The water softening apparatus usually includes some method of mixing the raw water with the chemical reagents ; the chemical reactions occur and the impurities are precipitated in a sedimentation tank. Sometimes the raw water is then passed through a filter tank. Chemical Feed. Chemicals must be fed to a softener accurately in pro- portion to the amount of water and to the impurities in the water. Other- wise the water will deposit scale, or will contain an excess of unused reagents. In some softeners the raw water flowing to the softener turns a water wheel or operates a tilting bucket. This in turn operates dippers in which the re- 508 F E E D W A T E R agents are ladled out to be mixed with the raw water. In one design part of the water is separated from the main supply by oritices or weirs, and flows through chambers containing the reagents. In another type, the water displaces the reagent from the tank, at tlie same time diluting that w^hich remains in the tank. The raw water is sometimes passed through a hydraulic motor, which drives a small chemical pump. The feed can also be controlled by hand, an operator adjusting the chemical pump to deliver the required amount of solution each hour. Results are more satisfacton.', however with the automatic feed. Sedimentation Tanks usually have a conical base, into which the precipi- tates settle. The hot water and softening reagents are delivered at the top, and settle to the bottom, where the clarified water is withdrawn. In some designs (see Fig. 221) an open feed water heater is placed above the sedimen- tation tank. The heating chamber of the softener can be divided into two compartments, one for heating the raw water, and the other the pure water supply, the latter passing directly to the boiler feed pump. Filters. In some installations a separate filter is often dispensed with, the sedimentation tank removing the impurities. Under other conditions a low-pressure sand filter is placed between the sedimentation tank and the boiler feed pump or meter, the water flowing through bj' gravity. The water delivered should be crystal clear, containing no solids except those in solu- tion, and practically no mud-forming properties. This clarified water will leave no troublesome deposit in the feed lines, pumps or meters, and is especially suitable for boilers operated at high ratings. In the hot process water softener, Fig. 221, the raw water flows over heating trays, where it is heated bj* exhaust steam purified of oil to a tem- perature within a few degrees of the steam itself. The water falls from the trays into the sedimentation tank. Immediateh- after the water is heated to the boiling point or near it, the softening chemicals are added. In certain waters, they may be added above the heating trays. A precipitate is formed, which settles toward the bottom of the sedimentation tank, traveling much faster than the water. Due to the lower viscosity of hot water, the precipi- tation is much more rapid than in cold water. As a result the precipitate passes to the conical bottom, from which it is removed by opening the blow- off valve. A chemical proportioner is used to regulate tlie proportion of lime and soda ash to the raw water. A thin plate with a restricting orifice, is placed in the raw water line between the regulating valve and heater. A differential pressure is set up on the two sides of the plate, proportional to the square of the flow. This pressure is continually translated to an effective direct pres- sure on the chemical orifice. The chemical solutions and the raw water each pass through their respective orifices at exactly the same effective pres- sure, so that the chemical? are always accurate!}' proportioned to the raw water. The chemical treatment is controlled by drawing a sample of the treated water from time to time and titrating with standardized solutions, the whole operation requiring about ten minutes. The titration readings are obtained and then located upon a chart supplied with the softener, from which the correct chemical treatment is immediately read. Thus the operator sees at a glance what change, if any, is required in the amounts of the chemicals. Zeolite Process. This process gives a water of zero hardness. The softening agent is an artificial material (permutit) composed largely of sodium compounds, which are exchanged for the incrusting (scale-forming) material of the water. The hard water flows over the permutit which is packed in a cylinder, or is forced through and flows from it with all scale-forming material removed. The softener must be regenerated from time to time by allowing a solution of salt to flow over it, thus restoring its original com- FEED WATER 509 510 FEED WATER position and actlvit}'. If the water is of a high degree of temporary or carbonate hardness, the zeolite process introduces a large amount of sodium salt, and foaming may occur. With such waters the zeolite process is modified, an intermittent or continuous equipment being connected through* a filter to a zeolite softener. Only lime is used in the tank, the soda compound being secured from the zeolite. The filter is placed between the tank and the zeolite softener to avoid any sludge coating the permutit particles, and thus impairing its efficiency. Boiler Compounds. Boiler compounds for scale prevention are ex- tensively used in sm^all isolated plants where the expense of a water-soften- ing plant would not be warranted. While it is to be admitted that all chemical reactions necessarj^ to prepare a feed water should preferably take place outside of the boiler itself, there is no doubt but that a compound suit- able for particularly bad conditions and correctly used is to be preferred to no treatment at all. Results of Poor Water on Boiler Operation IDRIMIXG describes that phenomenon occurring in steam boiler operation, in ■*- which water is delivered in belches with the steam. Foaming of boilers is the production of large quantities of bubbles in the steam space. If this water is carried out of the boiler, it erodes turbine blades, increases the steam consumption and causes waste of lubricating oil in reciprocating engines, while if the steam passes to a superheater, the water may carry solids to accumulate there as scale. Foaming and priming is encouraged by the presence of finely divided suspended matter, such as carbonate of lime, or of oil or soluble salts, such as sodium sulphate, either originally present or produced by the action of water-softening chemicals. At maximum capacity, water-tube boilers will stand a concentration of 200 to 300 grains of sodium sulphate per gallon; when foaming begins, the impurities can be removed by the use of the surface and bottom blow-offs. Even though some heat is lost, the removal of sediment and the stopping of foaming increases the efficiency. Foaming is also encouraged when oil is contained in the feed water introduced into boilers. The oil tends to collect on the tubes, to interfere with heat transmission, and to break down into corrosive acids. Oil carried in the exhaust steam from reciprocating engines or auxiliaries is removed by passing the steam through a separator rather than by skimming or filtering the condensate. The latter method is ineffective when the conden- sate contains oil in an emulsified or finely-divided state. Corrosion of boiler plates, tubes and rivets may be almost uniform in effect, in which case the action is difficult to detect, or it may be manifested by visible grooving and pitting. Corrosion of boiler metal is an electrolytic phenomenon by which a neutral iron atom, in contact with two positive hydrogen ions in the water, takes up their positive charges and becomes subject to oxidation. The hydrogen film formed tends to reduce the speed of the reaction almost to zero unless oxygen from the air or from acid-forming compounds is present in the water. The removal of carbon dioxide or other acids by chemical treatment, and the de-aeration of the water by pre-heating will prevent corrosion. Electrolysis or galvanic action with its resultant corrosion of the boiler metal, occurs frequently in marine practice, due principally to the presence of salt (NaCl) and air in the feed water. Zinc plates are therefore placed in the drum to act as the electro-negative element, thus hindering corrosion. See the description of the Heine Marine Boiler in Chapter 1. FEED WATER 511 Caustic Emhrittlcmcnt is a phenomenon which has lately received con- siderable study, but as yet its action is not definitely established. In certain localities in which boiler waters are of an alkaline character the development of cracks around seams and rivet holes below the water line have caused failures which can not be attributed to faulty materials or design. In- vestigation of the subject seems to disclose the fact that these failures are due \o an embrittlement of the boiler metal. This embrittlement is pre- sumably caused by the metal absorbing nascent hydrogen in such a way as to impair its physical properties. This effect has been decidedly pronounced in boilers using water containing a considerable amount of caustic soda, which has been present either due to over-treatment of the water, or as the result of the decomposition of the sodium bicarbonate NaHC03 occurring in the raw water. Scale Formation SOLUBLE carbonates and sulphates when concentrated in the boiler are precipitated as solids, which tend to accumulate and become baked into hard layers known as "scale," which has a high heat insulating value. As a result, fuel is wasted, and the metal becomes overheated. Expansion and con- traction strains follow and may greatly shorten the life of the tubes. _ Reports from boiler insurance companies show that the majority of boilers inspected are damaged from impure feed water by scale or by corrosion and pitting. Q_ o> 1 Cs! Q c^ ~ ■n: 01 o CS) cu 1_ D r +- CSi o rsf L. ^ C9 E -Q Ci) 1- f^) O 1_ L. -+- t) n 1- ^ T5 C O o 1500 [400 1300 1200 IIOO 1000 900 800 700 600 50^ 400 300 ZOO 100 / / y / / / / A^ / J- ^ AO^ "^ ¥ v\< A/ ^A / ^> ^ c f y fA > r \o^ ^. ^ c ?/ y ^ C .■^i)' / / q c^ p^ i f/ / / ?h ^f-e = - _ _ [^ / ^ " Cfe^ ^ ^ —" o o o — rg O O Heat Transmitte^d pe-p sq. ft. of Boiler Surface per Hour,B.TU. Fig. 2 22. Effect of Scale on Heat Transmission. Fig. 222, by E. RcuiVmgcr , shows the high temperature difference neces- sary in operating bolters with variation of heat transmission and of scale thickness. For the clean heating surface, the rate of transmission was 166 B.t.u. per sq. ft. per hour per degree difference between the metal and the water; for the plate coated with Scale No. 2, which was 0.217 in. thick, of conductivitv 23.85, the rate was reduced to Q B.t.u. ; and for the plate coated with Scale No. 3, of the same thickness, but of conductivity 8.06, the transmission raJ;e was only 31 B.t.u. For a plate with a heavy grease 512 FEED ^^' A T E R coating the rate was 13.5 B.t.u. The necessary temperature differences can be read on the scale to the left, which shows that with scale the metal must be maintained at a temperature several hundred degrees above that of the water, when the boiler is driven at the rates now common. The heat losses, which may be as great as 10 per cent, the damage to the boilers themselves, the cost of repairs and cleaning ; all these emphasize the importance of preventing the formation of scale. Distilled water if used exclusively is prohibitive in cost. The onl}' practical method, when scale-forming matter is present in the water, is to form soluble salts or non-scale producing precipitates. Sodium carbonate (soda ash) can be used for transforming sulphates, chlorides and nitrates to carbonates, while calcium hydroxide (lime water or milk of lime) will correct acids and bicarbonates. Two 200 H. P. Heine Cross-Drum Marine Boilers on the Dredge-boat "Dixie". Board of Port Commissioners, New Orleans, La. 513 CHAPTER 15 BOILER TESTING BOILER testing should not be lightly undertaken by anyone who has not had some training under an experienced testing engineer if reliable results are to be expected. The whole matter should be thoroughly understood both theoretically and practically. Accurate tests depend very largely upon the care and faithfulness of the observers. It is much easier to make mistakes than is realized by those who are not familiar with practical testing. Boiler tests are run to compare different boilers, stokers, etc. ; different kinds of fuel; different methods of operation, and so forth; but the object of the trial in every instance is to determine capacity, or efficiency in relation to capacity. To more definitely check the results, and to find the cause of unusually low or high efficiency by investigating the losses, the performance of the test and the analysis of the observations become more elaborate. The Rules for Conducting Evaporative Tests of Boilers, formulated by the American Society of Mechanical Engineers, 29 West 39th Street, New York, should be obtained and studied. All boiler tests should be made and re- ported in conformity with these rules, so that intelligent comparison with other boiler tests may be made. A new edition of the A. S, M. E. Code will be available about the time this book is published. If the following directions for conducting boiler tests conflict with the new Rules, the Rules must be followed in preference; but it is not expected that any serious differences will occur. In several instances where it was considered appropriate, parts of the A. S. M. E. Code of 1915 have been copied. To facilitate understanding the preparations for and making of boiler trials and computing the results, the subject will be treated in two parts. In the first part, the simpler tests will be considered where the capacit}^ only, or the efficiency and capacity, are wanted. In such instances, only the useful work done is measured, and the observations may be restricted to those necessary to attain this end. In the second part, the further observations and calculations necessary to prepare heat balances will be discussed. This work includes finding the amount and cause of the losses as well as the amount of useful work done. Personnel HTHE person conducting the test should have sufficient assistance to enable -*- him to oversee at all times everything connected with the test. He should satisfy himself from time to time that the weighing scales, instru- ments, etc., are giving correct indications and that all readings are being correctly and punctually recorded. He should continually be on the alert for any change in conditions, such as an unusual demand for steam, stoppage of stokers, fans, feed pumps, and so forth. His assistants should be chosen for their enthusiasm no less than for their ability ; and it may prove wiser to abandon and repeat the test rather than continue with an assistant who shows contempt for, or lack of interest in, the proceedings. o t- ^ :S T. TESTING 515 Condition of Boiler 'T~'HE condition of the boiler and furnace should first be ascertained, and -^ described in the report of the test. If it is desired to demonstrate the value of improved operating conditions, then a test should be run without any change whatever, followed by another before which defective brickwork, baffles, etc., should be repaired, soot and scale removed and the boiler put in generally clean and first-class working condition. If the expected capacity or efficiency is not realized, the heat balance will probably show the cause ; and if the necessary observations for calculating a heat balance have not been made, then another test must be run for this purpose. Changes can then be made in whatever direction the losses in the heat balance point, and other tests run until the results expected are realized. Sometimes several tests are run to enable an efficiency curve to be drawn at different loads or to enable comparison to be made of operating under different working conditions. Duration 'T'HE duration of the test must be sufficient to insure accuracy, and this ^ is governed by the closeness with which the amount of fuel and water involved at start and stop can be ascertained. With oil, gas, etc., there is no store of fuel in the furnace, and four or five hours is generally sufficient. With coal, the amount of fuel in the furnace must be judged at start and stop; and as this is often little better than guesswork, a much longer period is necessary because the error in this judgment may be a noticeable per- centage of the total fuel burned. With mechanical stokers carrying a steady load, 10 hours may be suf- ficient, but if there is much variation in load this should be greatly increased. With hand firing, the duration should not be less than 8 hours for anthracite or 10 hours for bituminous coal. The trial should be long enough for at least 250 pounds of coal to be burned on each square foot of grate area. If an accurate efficiency test is desired, it should be continued for 24 hours ; but for capacity only, 3 or 4 hours is sufficient. Simple Test Data TF the capacity only is wanted, the coal need not be weighed or analyzed; -^ but such tests are unusual since they give so little information. There- fore, only those tests will be discussed in which both capacity and efficiency are to be ascertained. Observations are necessary to obtain the following quantities: Weight of Feed Water Weight of Coal Heat Value of Coal Temperature of Feed Water Pressure of Steam Quality of Steam Particular accuracy is essential in determining the first three items. If any of these are incorrect, the test is useless. Weighing Feed Water I 'HE usual plan for weighing feed water is to have one or more tanks ■'■ on scales at a high level, discharging by gravity to a single tank below. The lower tank should be larger than either of the others, and have no pipe connections except the suction line to the feed pump. The level of the water in the lower tank should l)e noted at the connncnccmcnt of the test 516 TESTING and be brought back to this level at the end. The upper tanks may have overflows, but care must be taken that the overflow water cannot fall into the lower tank. The upper tanks must be large enough so that there is ample time for operating the filling and dumping valves, weighing the water and recording it. A simple rule will prevent mistakes — record immediately the time of dumping each tank: and if there are more than one tank, number them and record the time of dumping in separate columns. Water Meters are not considered sufficiently accurate or reliable for boiler testing; but in some instances it is almost impossible to avoid using them. They should be carefully calibrated before and after the test by weighing water metered into suitable tanks. When calibrating meters, care must be taken that all readings are from the same part of the cycle of motions operating the counter. As water meters measure volume, the temperature of the water during calibration must be taken, and the weight of water at that temperature used in the calculations. Water meters of the Venturi t>-pe, or weirs, are reliable ; but should be calibrated. Automatic water-weighers are installed in many large plants, and their readings may be used after calibration and examination as to reliability. Water Gage. A scale should be mounted close to the boiler gage glass so that the height of the water can be easib' read. Note should be made of the position of the scale and then it can be replaced accurately if the glass breaks during the trial. The position of the scale relative to the boiler must be definitely determined, so that the volume of water in the boiler cor- responding to any distance on the scale can be computed if necessary, as explained below. Water gages should not be blown down for at least one hour before starting and stopping, as this changes the water level in the glass, because the tem.perature and consequently the density- of the water in the gage and connecting pipe, is changed. The feed should be so managed that the water will be at the same level in the boiler at the end of the test as it was at the start. If this is not done, the difference in level must be allowed for b\' calculating the volume of water in the boiler between the two levels. The weight of water, calculated at the temperature in the boiler, must then be added or deducted as required. The correction for difference in level must always be made in this manner. Pumping in more water or blowing down are not permissible. Leakage. Care must be taken that all valves and fittings are tight. Blow- off pipes should be blanked off, or disconnected so that anj^ leakage can be s,Q.tn and measured. Where the feed pipe connects with other boilers, it ma}^ not be necessary to blank off these branches if they are provided with two valves with a drain cock or plug between, which may be kept open dur- ing the test to insure that no water is passing through leak>- valves. Un- avoidable leakage from pump stuffing boxes and so forth, must be weighed and deducted. Boiler leakage may be ascertained by closing all valves, maintaining pressure by means of a very slow fire, and noting the fall of water in the gage glass. Readings of this description should be taken even,- ten minutes and continued until they show a constant rate. Leakage from tubes in the feed water heater must be looked for. and any such leakage either measured or cured. Where drainage from heating s3'stems is automatically returned to the boiler, arrangements must be made to disconnect the system and discharge the condensate elsewhere during the test. The fundamental condition to keep in mind is that no water shall enter the boiler during the test except that w^hich is being weighed ; and that all the water which is weighed enters the boiler and leaves by way of the steam space only. TESTING 517 Weighing Coal COAL should be weighed only about as fast as required, but the supply must always be ample. In this way the amount on the firing floor can easily be estimated at any time, such as hourly. The same simple rule recom- mended for feed is desirable here — record immediately the time of dumping each wiieelbarrow load. Never trust to marks or tallies for weighing coal or (cod water. IVeighing Scales for coal and water should be examined carefully to see that they swing freely, and should be tested to see that they balance at zero and with standard weights of aljout the amount at which they will be used. Platform scales arc generally most convenient for weighing feed water tanks and wheelbarrows of coal and ash. , Heat Value of Coal X-J EAT value of coal is fully treated in Chapter 13 on FUEL, where ■*■ ■*■ methods of working down samples and of analysis are described, and representative analyses of fuels are given, A small sample should be taken from each wheelbarrow of coal be- fore weighing. The amount taken should be about 1 per cent with small anthracite and 2 per cent with bituminous coal. The bulk sample thus obtained should be worked down to about 10 lbs. as described in Chapter 13. Half of this is to be sent to the laboratory in an airtight fruit jar or similar airtight package, and the remainder kept for reference or to replace loss. The moisture in the coal is an important item and is difficult to get with accuracy. The moisture in the sample as received at the laboratory can be deter- mined with fair accuracy. But since coal readily absorl)s or gives ofif moisture according to the humidity of the atmosphere, different analysts will often obtain different results from the same sample. Unless the bulk sample while being collected during the test and while being worked down to a laboratory sample is kept in a cool place, it will not be representative as to moisture. If the sample is collected and worked down in a warm and drafty place, it may possibly lose as much as 2 per cent of water or even more. Therefore, it is often preferable to determine the moisture during the test, and for this purpose a small pair of scales is required, sensitive to about ^4 oz. when weighing about 20 pounds. A sample of about 20 lbs. (separate from the main bulk sample) is carefully selected to be representative as to moisture, shortly after commencement of the test ; and after weighing, it is spread out on a sheet iron tray and exposed to a temperature of about 250° F. for several hours. Care must be taken to protect the sample from strong drafts which might blow away some of the dry dust; and it is advisable to cover the tray with a perforated sheet iron cover, leaving a space of an inch or two between it and the coal. The tray may l)c placed on a flue or 1)reech- ing ; but it must not be allowed to get too hot or some of the volatile matter will be distilled off, thus giving an erroneous result. It may be necessary to support the tray on bricks or the like to prevent the sample getting too hot. For this determination, the coal should be crushed down so that the largest pieces are not over Yx inch. The sample is carefully weighed before and after drying for about four hours and then weighed every hour after- wards until two consecutive weighings agree. The loss in weight divided 1)y the weight before drying, multiplied by 100 is the percentage of moisture referred to coal "as fired." Feed Water Temperature pEED water temperature must be taken with a thermometer having the "*■ scale graduated on the glass stem. There sliould be several spare ther- mometers so that breakage will not cause stoppage of the test. 518 T E S T I X G The thermometer is placed in a thermometer-well screwed in the feed pipe. The well should be deep enough to reach to the center of the pipe, or at least well into the flowing water. It should not be in a pocket where the flow is sluggish. The well may be filled with mercun.- or oil. Response to changes of temperature is not as quick with oil as with mercurj- ; but unless there are unusually rapid changes of temperature, oil is quite good enough. Recording thermometers are desirable when there is much fluctuation, but they should be checked against the regular indicating thermometer readings. Thermometers and thermometer-wells are described in Chapter 11 on HEAT, to which reference should be made as to care and methods of use. Steam Pressure TD RES SURE gages should be tested with a dead-weight tester with both ^ rising and falling pressure, and the case should be tapped gently to see that the mechanism is free. Allowance must be made for head of water in the connecting pipe if there is any. Recording gages are useful for boiler testing, but their accuracy must be established. The pen or other recording device must be quite free to move with slight pressure fluctuations. The clock error — fast or slow — in relation to the clock or watch used for the test, must be ascertained and recorded. Ample s^'phons must be provided to prevent steam reaching the gages. Care of gaees and methods of use are described in Chapter 16 on OPERATION. ^ Quality of Steam IF the steam is not superheated, it m.ust be tested for the amount of moisture or entrained water present. For this purpose the throttling calorimeter is used when the moisture does not exceed 4 per cent, and the separating calo- rimeter for wetter steam. The Throttling Calorimeter was invented by Prof. C. H. Peabody, and has long been used with complete satisfaction. It is dependent upon the adiabatic expansion of steam through a nozzle. The heat converted into work as velocity* of the steam, is returned to the steam as sensible heat when the steam loses its velocity in the expansion chamber. As the total heat in the steam is the same after expansion to atmospheric pressure as it was at boiler pressure, it is obvious that some or all of the moisture present in the high pressure steam will be evaporated. If too much moisture is pres- ent, the resulting mixture will have a temperature of 212° F., while with drv* steam the temperature will be much higher, showing considerable superheat. From tlie amount of superheat of the expanded steam, the amount of moisture present in the steam before expansion can be readily calculated. Taking dr\- saturated steam of 150 lbs. gage pressure, the total heat per pound is 1196.1 B.t.u. The total heat per pound at atmospheric pressure is 1151.7, and the difference or 44.4 B.t.u. is used in superheating the steam at atmospheric pressure. If the steam contains 2 per cent of moisture the total heat is, for the steam : 0.9S X 1196.1 =-- 1172.18 for the water : 0.02 X 337.8 =z 6.77 1178.95 B.t.u. The total heat in one pound of dry steam at atmospheric pressure and 212° F. is 1151.7, and the difference. 1178.95 — 1151.7 = 2725 B.t.u.. is available to superheat the steam after the moisture has been evaporated. TESTING 519 As the specific heat of steam is 0.46, the amount of superheat will be : 27 25 ±i^ _ ego -p 0.46 ~^^ • The temperature of the expanded steam will be shown by the thermom- eter as : 212 + 59 = 271° F. If a regular or standard instrument is not available for making the test, one may be made up of pipe-fittings as illustrated in Fig. 223. Fig. 223. Throttling Calorimeter. 520 CO a 03 ;i I- o w C O CO U( M 5 gffiO o s o (U Bui o o (U TESTING 521 A piece of 4-in. pipe, 10 to 12 in. long, and screwed caps on each end make up the body of the calorimeter. Openings in the end are provided as shown — steam inlet at A usually >4-in. pipe, thermometer and gage con- nections at T, exhaust outlet at N of at least 1-in. pipe. Care must be taken to offset the pipes A and N. The whole calorimeter is heavily lagged to prevent radiation. The nipple A, through which the steam enters the calorimeter, is made of composition, cut with pipe thread and provided with an orifice for reducing the pressure and gaging the flow of steam. It is shown in detail at (b). The orifice may be made Ve* inch. Steam passes from the main through the orifice in A, in which it expands and enters the chamber K at atmospheric pressure. If the calorimeter is properly lagged so that no heat is lost by radiation, the heat content of one pound of steam at the lower pressure in the calorimeter will be the same as that at the boiler pressure. Kent's formula for reducing the observations of the throttling calo- rimeter is : M= 100 X H ^ nSl.7- 0.46 (/s- 212) ^^3^ where : M = Percentage of moisture in the steam H = Total heat of the high pressure steam, P^ ts= Temperature of the steam in the expansion chamber of the calorimeter L = Latent heat of the high pressure steam. Pi With low pressure steam, the outlet N of the calorimeter may be con- nected to the condenser. In that case the latent heat 1151.7 and the specific heat 0.46 in formula (63) are replaced by those due to the lower pressure in the expansion chamber K. The Mollier diagram given on page 416 is particularly applicable to the solution of this problem. Its use is illustrated below : Example 1. Boiler pressure, 100 lb. abs. ; calorimeter pressure, 20 lb. abs. ; calorimeter temperature, 250 deg. Find the percentage of wetness in the steam. Locating on the diagram the intersection of the 20-lb. line, and that for the temperature 250 deg., we find the heat content to be 1173 B.t.u. Follow- ing this B.t.u. line until it intersects the 100 lb. pressure line, we read the quality as 0.98. The priming will be (1 — 0.98) 100 = 2 per cent. The range of use of the calorimeter depends upon the heat available to superheat the steam. This in turn depends upon the boiler pressure and the drop in pressure. To get sufficient accuracy, not less than 10 deg. super- heat in the calorimeter is necessary. The following is taken from the "Description of Steam Calorimeters" in the A. S. M. E. 1915 Code. "The percentage of moisture is determined by observing the number of degrees of cooling that the thermometer in the low-pressure steam shows below the 'normal' reading for dry steam, and dividing that number by the 'constant' number of degrees representing 1 per cent of moisture. "To determine the 'normal' reading of the low-pressure thermometer corresponding to dry steam, the instrument should be attached to a horizon- tal steam pipe in such a way that the sampling nozzle projects upwards to near the top of the pipe, there being no perforations and the steam entering through the open top of the nozzle. The test should be made when the steam in the pipe is in a quiescent state, and when the steam pressure is maintained constantly at the poi;it observed on the main trial. If the steam pressure falls during the time when the observations are being made, the test should be con- tinued long enough to obtain the effect of an equivalent rise of pressure. 522 TESTING To find the 'constant' for 1 per cent of moisture divide the latent heat of the steam supplied to the calorimeter at the observed pressure or temperature by the specific heat of superheated steam at atmospheric pres- sure (0.46) and divide the quotient by 100. "Frnallj- ascertain the percentage of moisture by dividing the number of degrees of cooling by the constant, as above noted. "To determine the quantity of steam used by the calorimeter it is usually sufficient to calculate the quantity from the area of the orifice and the absolute pressure, using Xapier's formula for the number of lb. which passes through per second; that is, absolute pressure in lb. per sq. in. divided by 70 and multiplied by the area of orifice in sq. in. To determine the quantity by actual test, a steam hose may be attached to the outlet of the adorimeter, and carried to a barrel of water on platform scales. The amount of steam condensed in a certain time is determined, and thereby the quantity dis- charged per hour." Separating Calorimeter. When the percentage of moisture is too large for the throttling calorimeter, the separating calorimeter, Fig. 224, is used. In this the moisture is mechanically separated, just as it is in the ordinary power-plant separator. Steam enters as indicated, passes down into the perforated basin from which dry steam escapes through small openings near the top, while the moisture is deposited in the bottom of the calorimeter. The dn^- steam passes through the jacket surrounding the water, from which Gradoased Scale Gaxige- Steam Jacket Water Discharge Oriice Fig. 224. Carpenter Separating Calorimeter. TESTING 523 it is discharged through an orifice. This orifice can be used to measure the dry steam, or the discharge can be led to a condenser and the condensed steam weighed. The quantity of water separated in the reservoir can be determined by reading the special scale provided on the gage glass. The weight of water collected divided by the sum of the weights of this water and of the dry steam for the same period of time, gives a result which is the percentage of wetness. In practice the results obtained with the separating calorimeter are only approximately correct, because of the difficulty of draw- ing a representative sample from the pipe line. The calorimeter connection with the steam main, from which the sample of steam to be tested is taken, should be made according to A. S. M. E. recommendations. The ^-in. pipe should extend across the main to within >2-in. of the opposite side, the end being plugged. Around the circumference of this sample pipe should be drilled not less than twenty ]^-in. holes, spaced irregularly. The nearest hole should be at least ^-in. from the side of the main. Superheated Steam. Use a gas filled thermometer with enlarged bore at the upper end. The thermometer well should contain mercury or soft solder, and the immersed portion of the well should be fluted to cause quicker response to fluctuations of temperature. Where extreme accuracy is essential, make the stem correction as described on p, 373. Steam Tables 'T'HE report of the test should state which steam tables the calculations -'- were based on. Goodenough's tables are given on page 424 and are used throughout this book. If Marks and Davis's or Peabody's tables are used, care must be taken to adopt their values as constants in the formulas where they occur, such as in finding the factor of evaporation. Starting and Stopping SPECIAL consideration of the methods to be used in starting and stopping the test is necessary. These must be well thought out beforehand, and be suitable for the particular conditions to be encountered. Sufficient error to render the test useless is easily introduced, unless the proper observations are made quickly and simultaneously and immediately recorded. With hand fired boilers, in order that the fire may be as nearly as pos- sible in the same condition at start and at stop, the fire must be burned low and cleaned both before the beginning and before the end of the test, so that a clean fire is left on the grate in each instance. Thin fires are more easily judged than thick ones. Bituminous coal fires should be 2 to 4 in. thick at start and stop, and small anthracite fires may be 1 to 2 inches. Colored spectacles should be used in examining fires, particularly so with forced draft and soft coal, for little is to be seen, much less judged with any accuracy, without them. To start the test, note quickly the condition of the fire, the water level in the gage glass, the water level in the lower or suction tank of the feed water tanks, and the time. Record these observations with the time as the start of the test. Record the first steam pressure reading and the first feed water temperature reading immediately afterwards. To end the test, watch the fire when and after being cleaned, and as soon as it is in the same condition as at the start, note the water level in the gage glass, the water level in the lower feed water tank (preferably stopping the feed pump) and the time, and record these as the end of the test. o CO O--- ^ i£ u clc JJ" D u *. 0' T3 eg J2 O u ^ (S -,1 X •o V ^M a CO a 4J 3 C cr o CO 9i u u "o "T; c m s "o o u ^ C3 ■«-• •o & Cm o 09 a o o r^ Xfl 'C X !2 "o 'S c: u c 3 o n '^ OS OS •»-> 00 C o TESTING 525 If there is any difference in the gage glass level at start and stop, allowance is to be made later by calculation. If the water level is low in the lower feed water tank, weigh the amount necessary to make up the de- ficiency and add it to the total water fed ; and if the water level is high, bale out and weigh the excess and deduct it from the total. When a water meter is used, the procedure at both start and stop is to note the condition of the fire, the water level in the gage glass, the reading of the meter, and the time. Record these observations with the time as the starting and stopping times respectively. Weigh back any excess coal left on the firing floor and deduct it from the total. In a plant containing several boilers where it is not practicable to clean them simultaneously, the fires should be cleaned one after the other as rapidly as may be, and each one after cleaning charged with enough coal to maintain a thin fire in good working condition. After the last fire is cleaned and in working condition, burn all the fires low (say 4 to 6 in.), note quickly the thickness of each, also the water levels, steam pressure, and time, which last is taken as the starting time. Likewise when the time arrives for closing the test, the fires should be quickly cleaned one by one, and when this work is completed they should all be burned low the same as at the start, and the various final observations made as noted. In the case of a large boiler having several furnace doors requiring the fire to be cleaned in sections one after the other, the above directions per- taining to starting and stopping in a plant of several boilers may be followed. Mechanical Stokers. To obtain the desired equality of condition of the fire when a mechanical stoker other than a chain grate is used, the procedure should be modified where practicable as follows : Regulate the coal feed so as to burn the fire to the low condition re- quired for cleaning. Shut off the coal-feeding mechanism and fill the hoppers level full. Clean the ash or dump plate, note quickly the depth and condition of the coal on the grate, the water level, the steam pressure, and the tim.e, and record the latter as the starting time. Then start the coal- feeding mechanism, clean the ashpit, and proceed with the regular work of the test. When the time arrives for the close of the test, shut off the coal-feeding mechanism, fill the hoppers and burn the fire to the same low point as at the beginning. When this condition is reached, note the water level, the steam pressure, and the time, and record the latter as the stopping time. Finally clean the ash plate and haul the ashes. In the case of chain grate stokers, the desired operating conditions should be maintained for half an hour before starting a test and for a like period before its close, the height of stoker gate or throat plate and the speed of the grate being the same during both of these periods. Report of Simple Test Observations should be made punctually and immediately recorded. When it is essential that a number of instruments be read simultaneously, there should be an observer at each one. A signal should be given, such as by a bell or whistle, when the readings are to be taken. The frequency of taking the readings of steam pressure and feed water temperature depends upon the extent and rapidity of the fluctuations. Usually, half hourly observations are sufficient ; but if there is considerable variation, readings should be taken every 15 minutes. Records. The observations should be recorded on separate sheets so that different observers are not hampered by having to write in the same book. The plan of the test must be arranged beforehand and the duties of each 526 TESTING observer clearly defined. In important and complicated tests, one or more preliminary runs as rehearsals are very desirable. Make a note of every incident connected with the test together with the time of its occurrence, however unimportant or unnecessary it may appear at the time. The record sheets should either be printed or made up by hand before the test, and the original sheets should be kept, no matter how dirty they may be. Each record sheet should be dated and signed by the observer. As soon as possible after completing the test or even during its progress, the whole of the observations and remarks should be written up in a log book having pages not less than letter paper size — 11 in. by 8^4 inch. It is desirable that the records show the coal and water consumption each hour. This is easily done by allowing for the coal on the firing floor and for the height of the water in the gage glass at the end of each hour. But this is only incidental and the orderly procedure of weighing full tanks of water and of the regular quantity of coal must not be disturbed. Chart. Where there are fluctuations of load, steam pressure and so forth, it is advisable to plot a chart of the test. This may well be done while the test is in progress. Unlooked for conditions are shown at a glance. Fig. 225 is a chart reproduced from the A. S. M. E. 1915 Code. The form of report shown in Table 82 is suitable for the simpler kind of test which has been described. Items may be added to record other observations if desired, such as draft in uptake and at other points, weight of water actually evaporated per hour, smoke, etc. Sketches, photographs and descriptions should be attached, giving any particular information such as condition of boiler and furnace, arrangement of baffles and so forth. Table 82. Evaporative Test. Description of Boiler Rated H. P Located at Date of Test Duration Conducted by Coal, Kind size cost per lb., $... Grate, Type area draft Heating surface, boiler superheater economizer. (1 (2 (3 (4 (5 (6 (7 (8 (9 (10 (11 (12 (13 (14 Steam pressure, lb. per sq. in Percentage of moisture in steam or superheat, °F. Factor of correction for quality of steam Feed water temperature, °F Factor of evaporation Equivalent evaporation per hour, from and at 212° F., lb Equivalent evaporation per hour, from and at 212° F. per sq. It. of heating surface, lb Percentage of rated capacity developed Percentage of moisture in coal Dry coal per hour, lb Dry coal per sq. ft. of grate surface per hour, lb Equivalent evaporation from and at 212° F. per lb. of dry coal, lb Heating value per lb. of dry coal, B.t.u Efficiency, per cent TESTING ItJoo JO oit?os 527 ^§1 oa *® 3 £5 2 °° — — ■~~ ■n _ K / / 1 ^ _ c V ~ ^ ^ V h If ::§< — o. \ l\- ~- ^ ^ -^ i T f S L . --■ \ r — "^ S 1 — \ y T^ 1 '-v s \f _\ / l- ^ \ \ V Y > \ S^ \ \ i "t ^ ^ ^ ^ ''n\ C-8 j' pai iduitiK 7 L_ ^ X v E bqc nj m\ ijtjjfl Ijo ait 'OS Z\ f \ N s. .. y. ■rj- C3 < \ ^ \ ^ 1 > I ^- \ \ ^ i \ \ \\ \ V ^ c3' < ^ >- ' N 1 \ / b ^ \ \ \, \^ ■^ 1\ -- ^ ^ K ^ N s 1 7 rt ^^ \ \ 5 c2 X ^ \ \ <^. v^ ■y a \ r-\ . \ S 1, ^A N \ %\ Y i c \ ^ \ -^ k \ > F N y \\ \ < W \ \ .co_ m -I "^ ■<^ ^ \ ~T / y (aSnx o nB ks JO 9{t 3S / p V V y o o CD in - o o CO A Y \ ) i >:^ \ \ ) \ < \ ^ i ) i / 5 N \, \ j^ \ / / ^ fk ^ 4 c \ i Oc J ^ ^ \ ^ S ( \ \ \ ^ ■V H \ \ / \ ^ " •^ 3 1 N / \ f / t:< / f 1 \ J '^ Y~~ 1 \ s' ■d as t^ 533 Al s |T30 s den; >X 9"L I JPO nop / \ \ ^ . Ill o o ^S o o o G o o o m 1° / \ -\ \ !- o / O < t— \ V S \ " L ^> V v^ k k ■»«,^ \ V > ^ I — ^"C ^ \ s ^ ^'^ i o- ' ^ *-> J — 1 __ __ ^ ^^ __ __ H ^-4 8 S 8 § 8 §* 8 O O H o pq O bD d o J3 O (to a9;c^ JO ai^og 528 TESTING Calculation of Simple Test THE heading of the report should be filled in first. Xo explanation of this part is necessary, except to mention that the grate area is the horizontal area between furnace walls, so that the grate area is the same whether the grate is horizontal or sloping. In the following discussion, the numbers at the commencement of paragraohs are those of the items in Table 82. (1) This is the average of the observations. (2) ^lethods of finding the percentage of moisture in saturated steam have been discussed. With superheated steam, the temperature of saturated steam due to the pressure is found from the Steam Tables in Chapter 12 on STEAM, and deducted from the temperature of the superheated steam, giving the number of degrees of superheat. (3) When the percentage of moisture is less than 2, it is suiticient merely to deduct the percentage from the weight of water fed, in which case the factor of correction for quality is : per cent moisture ,,, ^-- wo '"> When the percentage is greater than 2, or if extreme accuracy is required, the factor of correction is : 1-.U|=^' C65) in which M is the proportion of moisture, H the total heat of 1 lb. of saturated steam, g^ the heat in w^ater at the temperature of saturated steam, and q the heat in water at the feed temperature. When the steam is superheated, there is no factor of correction. (4) This is the average of the observations. If there is an economizer and the test is of the boiler and economizer together, then this ^tem is the temperature of the feed water entering the economizer. If the test is of the boiler only, this item is the temperature of the feed water entering the boiler, whether there is an economizer or not. (5) The factor of evaporation may be described as the amount of heat transferred to each pound of feed water passed through the boiler, divided by the heat necessary to evaporate a pound of water from and at 212°. Therefore : ^=w' (^> where : F ^ Factor of evaporation H = Total heat of steam at boiler pressure or at pressure and tem- perature of superheated steam q = Total heat in water at feed temperature. Xo allowance is to be made for moisture in the steam, as this is taken care of in item 6. (6) The total weight of feed water is first corrected for differences in level of boiler water gage and in feed suction tank if necessary. If there is no superheater, this total weight is multiplied by item 3 to find the total water actually evaporated. This is multiplied by item 5 to find the total equivalent evaporation from and at 212^ F., and divided by the duration of the test in hours. (7) This is item 6 divided bv the actual water heating surface. (8) Item 6 divided by 34.5 gives the B.H.P. developed. The B.H.P. developed, divided by the rated H.P. of the boiler gives the percentage of the rated H.P. developed. TESTING 529 (9) This does not require further explanation. (10) The total coal weighed out is first corrected for differences in quantity in furnace at start and stop if necessary, and for any coal re- maining unused at end of test. The total weight of moisture as found by item 9 is deducted, leaving the total weight of dry coal. Dividing this by the duration of the test in hours gives the dry coal per hour. (11) This is item 10 divided by the grate area. (12) This is item 6 divided by item 10. (13) This is entered from the laboratory report. (14) This is item 12 multiplied by 971.7 and by 100, and divided by item 13. Complete Test Data A COMPLETE evaporative test includes several other observations in ad- ■^^ dition to those already described. These observations are directed mainly to finding the parasitic losses by means of a heat balance. To begin with, an ultimate analysis of the coal will be required, and this will be stated as in item 25 of Table 86. Temperature of Exit Gases may be taken with a gas filled thermometer. To get the average in a large flue, specially long thermometers are made to reach to the center or at least well into the gas current. An oil pot, or large thermometer-well may be arranged to hang into the flue, and the thermometer will then have to be lifted out of the oil each time it is read. Fig. 226. Portable Indicating Instrument of Wm. H. Bristol Electric Pyrometer. Electric pyrometers of the thermo-couple type are the handiest instru- ments for the purpose. The portable instrument shown in Fig. 226 is most convenient, for it may be connected to several "hot ends." Various thermometers and pyrometers arc described in Chapter 11 on HEAT. CI 09 V C TESTING 531 The temperature of the air entering the ashpit, item 16 of Table 86, may be taken as that of the boiler room in natural draft plants. With forced draft, the temperature should be taken near the fan inlet. Inexperienced observers should be zvarned against the danger of accident unless the fan inlet is screened. If air heaters are installed, the temperature should be taken both entering the heater and entering the ashpit, and so reported. Particular care must be taken that the thermometer is not exposed to radiation from nearby hot surfaces. Flue Gas Analysis. The average composition should be represented in the samples collected. For use in computing heat balances, the sample should be taken so as to include air leakage into the setting, and the sampling tube should be placed in the uptake. Even in good commercial settings, the CO2 may drop as much as 3 or 4 per cent between the combustion chamber and the stack. This inleakage may not be excessive, but nevertheless the conditions should be known. The efficiency of firing operations can be studied by analyzing '"grab" samples taken from the furnace or from among the tubes, and plotting the results as shown on page 575. Perforated sampling tubes are sometimes used, but a plain, open-end pipe, drawing from the center of the flue, is generally favored. A radial "spider" is also recommended by the Bureau of Mines. Fig. 227 shows a sampling tube inserted in a Heine boiler. The tube should be placed at least 3 ft. below the damper and 1 ft. above the steam drum, through a Gas Sampling Pipe,, Plan of Uptake W^ Collector Fig. 227. Method of Inserting Sampling Tube. 532 T E S T : X c hole drilled in the brick wall and closed with asbestos packing. By con- necting an ejector to the ;:;e a 5: ?-ll stream of gas is constantly drawn ont with the steam or water, and are: ref er.tstive sample can be drawn at any time fro:.- :. e current moving tc in :/e ejector. A continuous or average sair.ne r^; resenting one to six hcurs iteration can be secured by the arra: ne: -e::: shown in Fig. 228w The :.:-er 2-gal. bottle, initial^ full of ' ''e.-'—arUbfer Piressure Gauge Gas Fig. 2 28. Arrangement for obtaining Continuous or Average Sample of Flue Gas. water, is slowly emptied, drawing in the due gas. Such a sample produces an average upon the basis of time, rather than load, and is reasonably repre- sentative if the difference between the two water levels is 2 ft. or more, so as to maintain the effective head nearly uniform. If the sample is to stand over the water for more than two hours, or if it is subject to much variation in COs content, it should be collected over a saturated brine solution (one-fourth salt by weight) to minimize absorption by the liquid- All joints in the pipe connections should be tight and coated with asphaltum painL The Hne can be cleaned more easily if crosses having removable plugs are used instead of elbows, but the liability of leakage is increased. A water-cooled or quartz tube is desirable for the part of the sampler extending into the gas current, although a H to }^-rn. metal tube is satis- factory. For securing "grab" samples for combustion control, a ^ in. bore copper tube is preferable. It has less capacity for the same nominal size, and two or three rapid fillings of the burette suffice to clear it of air. It can be easily inserted through cleaning holes, so that samples can be taken from different points in the boiler. Gas Analysis Apparatus. For determining the composition of nue gases in ordinary- boiler work one of the simplest and most convenient instru- ments is the Orsat apparatus. This instrument can easily be used by the person conducting a test, or b\- some assistant whom he directs. Orsat Apparatus. The principal constituents of flue gas {CO^ O, and (Z0^ can be measured in the Orsat apparatus by passing a sample of the gas successively into three solutions, each having a high absorptive capacity for one of the constituent gases. The apparatus. Fig. 229. consists of a .reii :'^"?' bure::e. leveling bottle, three absorption pipettes and the connecti: :-. 71 r :rr::r 5 nlled with water by raising the leveling bottle. The flue gas :s ilien ad::-:::ed to the header, TESTING ;33 Pinch Cocks - Absorpiion Pipettes Rubber dags--- -^S7 ^27 ^S7- Levelinq Bottle Measuring Burette -Water Jaclxef Fig. 229. Orsat Apparatus for Analyzing Flue Gas. drawn into the burette, and rejected to the atmosphere. This is repeated several times until the water is saturated with CO2 and the system is hlled with gas. A 100 cc. sample is then taken into the burette by lowering the bottle until the surface of the water in the burette reaches the lowest graduation when it is at the same level as the water in the bottle, thus subjecting the sample to atmospheric pressure. Next comes the actual measuring. The gas supply is shut off, and the sample forced into the right-hand pipette, where the CO2 is absorbed by a solution of KOH, caustic potash. The sample is passed back and forth several times until its volume ceases to decrease, when the solution is drawn to its original level in the upper neck of the pipette and isolated again. The residual gas is then measured under atmospheric pressure, that is, with the water in the bottle and in the burette at the same level, and the loss in volume represents the percentage of CO2 in the original sample. The connection is now opened into the second pipette, which contains an alkaline solution of pyrogallic acid. The oxygen in the remainder of the sample is absorbed and the percentage determined in the same manner as was that of the CO2. The third pipette contains an ammoniacal solution of cuprous chlo- ride, CU2CI2, which absorbs the CO, and the loss in volume in this third opera- tion gives the percentage of CO. The cuprous chloride absorbs both CO and oxygen, and would thus give an erroneous indication if all free oxygen was not first removed. The oxygen is determined primarily in order to ascertain the CO content. The analysis for O2 and CO is not ordinarily made unless the presence of CO is suspected, as when the CO2 percentage is high and the supply of air may be deficient. To prevent sudden temperature changes while the sample is being exam- ined, the measuring burette is encased in a water jacket. The front legs of the pipettes are filled with small glass tubing, to afford large contact surface between the solutions and the gas, while the rear legs of the O2 and CO pipettes are closed to prevent contact of the solution with the air. 534 v: V 'J r. n c 3 O U c u €ii;ii^^^ TESTING 535 This is not necessary with the KOH solution used for the CO2 measurements. Orsat connections consist either of rubber tubings closed by pinch cocks, or of glass tubing with ground-glass cocks. The latter system is considered more reliable and operates satisfactorily when the cocks are clean and well lubricated. If momentary samples are obtained, the analyses should be made as frequently as possible, say every 15 to 30 minutes, depending on the skill of the operator, noting the furnace and firing conditions at the time the sample is drawn. If the sample drawn is a continuous one, the intervals may be made longer. For determining the hydrogen and other unburned combustible matter in the flue gases, and for general gas analysis, the Hempel apparatus, or some modification thereof, is required. Work of this kind should be entrusted to a person who is familiar with all phases of the subject. The Hempel Apparatus works on the same principle as the simple form of Orsat apparatus described, so far as the latter is applicable, except that the absorption may be hastened by shaking the pipettes bodily, bringing the chemical into most intimate contact with the gas. It is less portable and in some particulars it requires more careful manipulation than the Orsat, while for general analysis it is not adapted unless used in a well equipped chemical laboratory. The absorption pipettes are made in sets which are shaped in the form of glol)es, and a number of independent sets are required for the treatment of the different constituent gases. A simple pipette of the Hempel type is shown in Fig. 230. Hempel Pipette. The method of carrying on an analysis with the Hempel apparatus is as follows : A sample of gas measuring 100 cc. is drawn into the burette, and then transferred to the first pipette, wliich contains potassium hydrate dissolved in twice its weight of water. This solution absorbs carbon dioxide (CO2). The gas is then passed into the second pipette, containing saturated bromine water, which absorbs the heavy hydrocarbons (C2H4) ; then into the third pipette, containing a solution of pyrogallic acid and potassium hydrate in the 536 TESTING proportion of 5 grams of acid to 100 cc. of h\-drate, which absorbs ox\-gen (O) ; then into the fourth pipette, containing ammoniacal cuprous chloride, which absorbs carbon monoxide (CO), and finally into the fifth pipette, which is of large size and provided with exploding wires and galvanic batter}-, for the determination of marsh gas (CH4) and hydrogen (H). A measured quantity of oxygen gas is added to this pipette and the contents exploded by an electric spark from the batten.-, resulting in a mixture of carbon dioxide, nitrogen and free oxygen. The quantity.- of carbon dioxide is determined by passing the gas into the pipette containing potassium hydrate, and the quantity- of oxygen b}- subsequent!}- passing it into the pipette con- taining potassium pyrogallate, finally determining the quantity of marsh gas and hydrogen from the known reactions which occur during this process, and the composition of the resulting gases. For each of these processes the pipettes are shaken to hasten the absorp- tion, and the quantity absorbed is determined by returning the gas into the measuring burette and observing the successive differences. The ashes and refuse withdrawn from the furnace and ashpit during the progress of the test and at its close should be weighed, so far as possible, in a drj^ state. If wet, the amount of moisture should be ascertained and allowed for, a sample being taken and dried for this purpose. This sample may ser^-e also for analysis for the determination of unburned carbon and for fusing tests. When the ashes and refuse are to be reported, the ashpit and combustion chamber must be cleaned at the beginning and end of the test, and the amount found at the end of the test weighed. The dust and ash from the combustion chamber, tubes and flues, should be weighed separately. With hea^-^- forced draft there maj- be a considerable amount. In some instances endeavor is made to determine the amount carried up the stack. But it is practically impossible to ascertain these quantities with any precision. The temperatures in the furnace and combustion chambers may be taken by means of electrical or optical pyrometers. These instruments are described in Chapter 11 on HEAT. Draff gages should be connected between each boiler and its hand- damper, and as near the damper as practicable. In the case of a plant con- taining a number of boilers, a gage should also be connected to the main flue between the regulating damper and the boilers. It is desirable also to have gages connected to different points of the gas passage through the boiler ; to the furnace or furnaces, and in the case of forced draft, to the ashpits and blower ducts. If there is an economizer, a gage should be con- nected to the flue at each end of it. The same draft gage may be used for all tlie points mentioned, provided suitable pipes are run from the gage to each, arranged so as to be readily connected to either point at will. Draft gages are discussed in Chapter 16 on OPERATIOX. The height of the barometer should be obser^-ed during important tests and the average given in item 15. It is common to add 14.7 lb. to the gage pressure to find the absolute pressure : but the actual atmospheric pres- sure as read from the barometer should be added instead if extrem.e accuracy is desired. The humidity of the atmosphere should be observed for particularly accurate work. The usual wet and dry bulb thermometer, preferably of the sling type, is suitable for this purpose. Table S3 gives the relative humidit}^ from the wet and dry bulb thermometers. Table 84 gives the weight of moisture present and Table 85 gives the weight of saturated air. The relative humidity- is entered as item 16. TESTING 537 Table 83. Relative Humidity, in per cent (Total Saturation = 100%). Barometer 29.92 in. Dry Thermometer op Difference between Dry and Wet Thermometers, Deg. Fahr. 1 2 3 4 5 6 7 8 9 66.8 78.1 84.9 34.0 56.6 70.0 1.5 35.3 55.2 10 14.3 41.0 20 26.9 12.9 30 40 50 89.1 91.6 93.5 78.3 83.4 87.0 67.5 75.3 80.6 56.8 67.5 74.3 46.5 59.9 68.0 36.4 52.4 61.9 26.3 45.0 55.8 16.5 37.7 50.0 6.8 30.5 44.3 60 70 80 94.5 95.3 95.8 89.0 90.6 91.7 83.6 86.0 87.7 78.3 81.6 83.7 73.1 77.2 79.9 68.1 72.9 76.1 63.1 68.6 72.3 58.3 64.4 68.6 53.6 60.4 65.0 90 100 110 96.1 96.5 96.7 92.3 93.0 93.5 88.7 89.7 90.3 85.1 86.4 87.2 81.7 83.2 84.2 78.3 80.0 81.2 75.0 77.0 78.3 71.7 74.0 75.6 68.5 71.0 72.9 120 130 97.0 97.1 94.0 94.2 91.0 91.3 88.0 88.5 85.1 85.7 82.3 83.1 79.6 80.6 76.9 78.1 74.3 75.7 10 11 12 13 14 15 16 17 18 40 50 60 23.5 38.7 49.1 16.5 33.2 44.6 9.7 27.8 40.1 3.0 22.4 35.7 17.2 31.4 12.1 27.1 7.0 22.8 2.0 18.6 14.5 70 80 90 56.4 61.5 65.3 52.5 58.1 62.1 48.7 54.8 59.1 44.9 51.5 56.1 41.1 48.2 53.2 37.4 44.9 50.2 33.8 41.7 47.4 30.3 38.6 44.7 26.9 35.6 42.0 100 no 120 130 68.0 65.1 62.3 59.5 56.8 54.2 51.6 70.2 67.5 65.0 62.5 60.0 57.5 55.1 71.8 69.4 67.0 64.6 62.3 60.1 57.9 73.4 71.1 68.8 66.6 64.5 62.4 60.3 49.1 52.8 55.7 58.3 46.7 50.5 53.6 56.3 19 20 21 22 23 24 25 26 27 60 10.5 23.5 32.6 6.5 20.2 29.8 2.6 17.0 27.0 70 80 14.0 24.3 11.0 21.6 8.0 19.0 5.0 16.4 2.1 13.9 'ii.*4* 90 100 110 39.4 44.4 48.3 36.8 42.1 46.1 34.3 39.8 44.0 31.9 37.6 42.0 29.5 35.5 40.0 27.2 33.4 38.0 24.9 31.3 36.1 22.6 29.3 34.2 20.5 27.4 32.4 120 130 51.6 54.4 49.6 52.5 47.6 50.6 45.6 48.7 43.7 46.9 41.8 45.1 40.0 43.4 38.2 41.7 36.4 40.0 28 29 30 1 1 80 90 100 9.0 18.3 25.5 6.7 16.2 23.6 4.4 14.1 21.7 i 110 120 130 30.6 34.7 38.3 28.9 33.0 36.7 27.2 31.4 35.2 o C3 c a ■i-i V a 'C X T3 a a. '5 cr o OS y U "3 c H CO O o 15 O (0 H TESTING 539 Table 84. Weight of Moisture per 1,000 Lb, of Dry Air, in Pounds. Barometer 29.92 In. Dry Thermometer op Vapor Pressure, Inches of Mercury Difference between Dry and Wet Thermometers, Deg. Fahr. 1 2 3 4 5 6 7 0383 8 0.5 1.0 1.8 0.3 0.8 1.5 0.0 0.5 1.2 10 0.0631 0.1026 1.3 2.1 0.2 0.9 20 0.6 0.3 30 40 50 0.1640 0.2477 0.3625 3.4 5.2 7.7 3.0 4.8 7.2 2.7 4.4 6.7 2.3 3.9 6.2 1.9 3.5 5.7 1.6 3.1 5.2 1.2 2.7 4.7 0.9 2.3 4.3 60 70 80 0.5220 0.7390 1 . 0290 11.0 15.8 22.2 10.4 15.0 21.2 9.8 14.2 20.2 9.2 13.5 19.3 8.7 12.8 18.4 8.1 12.1 17.5 7.5 11.4 16.7 7.0 10.7 15.8 90 100 110 1.4170 1.9260 2.5890 30.9 43.3 59.6 29.7 41.6 57.5 28.5 40.0 55.4 27.3 38.4 53.4 26.1 36.8 51.5 25.0 35.4 49.6 23.9 34.0 47.8 22.8 32.6 45.9 120 130 3.4380 4.5200 82.5 112.5 79.7 108.9 76.8 105.3 74.1 101.7 71.4 98.2 68.8 94.9 66.3 91.7 63.9 88.6 8 9 10 11 12 13 14 15 16 30 0.6 1.9 3.8 0.3 1.6 3.4 40 1.2 2.9 0.8 2.5 0.5 2.1 0.2 1.7 1.3 3.4 50 0.9 0.5 60 70 80 6.4 10.1 15.0 5.9 9.4 14.2 5.4 8.8 13.5 4.9 8.2 12.7 4.4 7.6 11.9 3.9 7.0 11.2 6.4 10.4 16.0 2.9 5.8 9.7 2.5 5.2 9.0 90 100 110 21.8 31.2 44.1 20.8 29.9 42.4 19.8 28.6 40.7 18.8 27.3 39.1 17.9 26.2 37.6 16.9 25.0 36.0 23.9 34.5 49.0 15.2 22.8 33.0 14.3 21.7 31.6 120 130 61.5 85.7 59.3 82.8 57.1 79.9 55.1 77.1 53.0 74.3 51.0 71.5 68.9 95.3 47.0 66.2 45.1 63.6 17 18 19 20 21 22 23 24 25 50 0.1 2.0 4.7 60 1.6 4.1 1.1 3.6 0.7 3.1 0.3 2.6 70 2.1 1.6 1.1 0.7 80 90 100 8.4 13.5 20.7 7.7 12.7 19.7 7.1 11.8 18.7 6.5 11.1 17.7 5.9 10.3 16.8 5.3 9.6 15.8 4.7 8.9 14.9 4.1 8.1 13.9 3.5 7.4 13.0 110 120 130 30.1 43.2 61.1 28.8 41.4 58.6 27.5 39.7 56.3 26.3 38.0 54.1 25.0 36.5 52.0 23.8 35.0 50.0 22.6 33.5 48.0 21.5 32.0 46.2 20.3 30.5 44.4 26 27 28 29 30 70 0.2 2.9 6.7 80 90 2.4 6.1 1.9 5.4 1.3 4.8 0.8 4.2 — 100 110 120 130 12.1 19.2 29.1 42.6 11.3 18.1 27.7 40.9 10.5 17.0 26.3 39.2 9.7 16.0 25.1 37.5 8.9 15.0 23.8 35.9 540 TESTING Table 85. Weight in Pounds of One Cubic Foot of Saturated Air. Dry Barometric Pressure — -Inches Thermometer = F 26 27 28 29 30 10 20 0.0750 0.07338 0.071S0 0.07788 0.07620 0.07456 0.0S077 0.07903 0.07733 0.0S365 0.08185 0.08009 0.08654 0.08468 0.08286 30 40 50 0.07027 0.06879 0.06732 0.07297 0.07143 0.06992 0.07569 0.07409 0.07252 0.078.39 0.07675 0.07512 0.08110 0.07942 0.07773 60 70 80 0.0658S 0.06442 0.06297 0.06^43 0.06692 0.06542 0.07098 0.06943 0.06789 0.07.353 0.07193 0.07a34 0.07609 0.07440 0.07280 90 100 110 0.06146 0.05991 0.05828 0.06388 0.06228 0.06060 0.06629 0.06465 0.06293 0.06870 0.067a3 0.06526 0.07112 0.06939 0.06759 120 130 0.05653 0.05467 0.05882 0.05692 0.06111 0.05917 0.06339 0.06142 0.06569 0.06367 Report of Complete Test TABLE 86 contains the items necessary for recording a complete evap- orative test. The sequence of the items has been chosen so as to keep the same numbers as were used in the short report, and so avoid confusion in explaining the different items. The actual form of report used should be that prescribed in the A. S. M. E. Code. Table 86. Complete Evaporative Test. Description of Boiler Rated H.P Located at Date of Test Duration Conducted by Coal, Kind size cost per lb., S. Grate, t)-pe area draft... Heating surface, boiler superheater economizer. (1 (2 (8 (9 (10 (11 (12 (13 (14 Steami pressure, lb. per sq. in Percentage of moisture in steam or superheat. Factor of correction for quality- of steam Feed water temperature ""F Factor of evaporation Equivalent evaporation per hour, from and at 212'' F,, Ib... Equivalent evaporation per hour, from and at 212" F. per sq. ft. of heating surface, lb Percentage of rated capacit}- developed Percentage of moisture in coal Dry coal per hour, lb „ Dry coal per sq. ft. of grate surface per hour, lb Equivalent evaporation from and at 212° F. per lb. of dr}- coal, lb „.. Heating value per lb. of dry coal, B.t.u Efficiency per cent TESTING 541 (15 (16 (17 (18 (19 (20 (21 (22 (23 (24 (25 (26) (27) (28) Barometer, in. of mercury Relative humidity of air for combustion, per cent- Temperature of air for combustion, °F Furnace temperature, °F Temperature of gases leaving boiler, °F Draft pressure in ashpit, in. of water Draft in furnace, in. of water Draft, leaving boiler, in. of water Refuse, per cent of dry coal Combustible in refuse, per cent Ultimate analysis of dry coal : (a) Carbon, per cent (b) Hydrogen, per cent (c) Oxygen, per cent (d) Nitrogen, per cent (e) Sulphur, per cent (f) Ash, per cent Fusion temperature of ash Analysis of flue gases by volume : (a) Carbon dioxide (b) Oxygen (c) Carbon monoxide (d) Nitrogen Heat balance based on dry fuel : Description B.t.u. Per cent (a) Heat absorbed by the boiler (b) Loss due to evaporation of moisture in coal (c) Loss due to heat carried away by steam formed by the burning of hydrogen (d) Loss due to heat carried away in the dry flue gases (e) Loss due to carbon monoxide (f) Loss due to combustible in ash and refuse (g) Loss due to heating moisture in air (h) Loss due to unconsumed hydrogen and hydrocarbons, to radiation, and un- accounted for (i) Total heating value of 1 lb. of dry coal. Item 13 100.0 Calculation of Complete Test In the following explanation, the item numbers are given at the com- mencement of the paragraphs : (1 to 14) These are the same as in the short report. (15) This is the average of the observations. It is to be converted into lb. per sq. in., and added to the gage pressure, item 1, to find the absolute pressure with which to enter the steam tables. (16) This item will be used in computing item g of the heat balance. 542 TESTING (17) This is the average of the observations. It is used as the basic temperature in finding the losses set forth in items b, c, d and g of the heal balance. (18) This item is not used in the calculation of any of the results. It is necessary in researches into the transfer of heat by radiation and convection. It may also have some value in investigations as to any unusual formation of clinker in conjunction with item 26. ''IP") This item is used as the higher temperature in finding the losses set forth in items b, c, d and g of the heat balance. (20, 21 and 22) These items are recorded for comparison with other tests. (23) This item is used to compute the weight of air required and the weight of gases, in computing items d and g of the heat balance. (24) This Item is used in the calculation of item f of the heat balance. (25) This is the laboratory report. (26) This Is the laboratory' report, and Is of service in investigating instances of unusual clinker formation. See also the remarks on item 18. {T^^ This is the average of the obser\-ations. and Is used In the calcu- lation of items d and e of the heat balance. The value of this analysis In promoting economv is discussed in Chapter 16 on OPERATION. Heat Balance T— TAVING given attention to the rest of the items, the construction of the -*- ■'' heat balance can now be proceeded with. The heat balance may be made on the basis of coal as fired or of dr\* coal. The usual basis is dn,- coal, and the calculations will be studied In this manner. When the general method is understood, it is eas}' to make the heat balance in either of the waj-s mentioned. The letters at the commencement of the paragraphs are those of the items in the heat balance 28. (a) Heat absorbed by the boiler. Item 12 X 971.7. (b) Loss due to evaporation of moisture in coal. This moisture Is heated from the fire-room temperature, item 17, to 212 deg.. evaporated, and super- heated to the flue gas temperature, item 19. The latent heat of evaporation is 971.7, and the specific heat of the superheated steam is 0.47. The percentage of moisture. Item 9, is always reported on the weight of coal as fired. As the heat balance is based on dry coal, the moisture should be converted to this basis, though if the amount is small, the error is negligible. Thus 2 per cent of moisture becomes 2 X 100 98 ^ 2.04 per cent; and 10 per cent becomes 10 X 100 90 ^ 11.11 per cent. If coal containing 2 per cent of moisture Is fired at 60 deg., and the gases leave the boiler at 500 deg., then each pound of water takes up: 212 — 60= 152.0 (Heating to 212 deg.) 971.7 (Latent heat of evaporation) 500 — 212 = 288, and 288 X 0.47 = 136.0 ( For superheating) Total = 1259.7 B.t.u. per pound. Each pound of dry coal is accompanied by 0.0204 lb. of water and this, multiplied by 1259.7, gives 26 B.t.u. TESTING 543 (c) Loss due to heat earned away by steam formed by the bnrniwj, of hydrogen. This is dealt with similarly to the moisture loss^ except that the steam resulting is 9 times the weight of the hydrogen. Assuming the same fire-room and flue gas temperatures as before, the loss will again be 1259.7 B.t.u. per pound of steam formed. With dry coal containing 4 per cent of hydrogen, there will be 0.04 X 9 = 0.36 lb. of steam formed per pound of dry coal ; this multiplied by 1259.7 gives 453 B.t.u. {d) Loss due to heat earried aivay in the dry flue gases. This is nearly always the largest single item of loss. The temperature of the gas is raised from that of the fire-room, item 17, to the exit temperature, item 19. This rise of temperature multiplied by 0.24 (the assumed specific heat) is the B.t.u. loss for each pound of gas. From a fire-room temperature of 60 deg. to a flue-gas temperature of 500 deg., the loss is 440 X 0.24 = 105.6 B.t.u. per pound of flue gas. The weight of gas is computed from the flue gas analysis. An example is worked out in Table 87 to facilitate understanding the method. Table 87. Analysis of a Sample of Flue Gas. Volumetric j Molecular Analysis ! Weight Weights Per cent by Weights Carbon Oxygen Gas Per cent C=12 0=16 N=14 100 X Items (II X III) under IV-^Total i of IV 12/44ofC02 and 12/28 of CO 32/44ofC02 and 16/28 of CO Nitrogen I II III IV V VI VII VIII CO2 CO N 14.0 1.0 3.0 82.0 12+ (16X2) =44 12+16 =28 16X2 =32 14X2 =28 616 28 96 2,296 20.29 0.92 3.16 75.63 5.53 0.39 14.76 0.53 3.16 75.63 Total 100.0 3,036 100.00 5.92 18.45 75.63 The total amount of carbon in the gases (column VI) Is 5.92 per cent. Therefore the weight of dry gases is 100/5.92 = 16.89 lb. per pound of carbon. If the dry coal contains 80 per cent of carbon and the carbon lost to the ashpit is 2 per cent of the dry coal, then the carbon burned is 78 per cent of the dry coal, and the weight of dry gas is 16.89 X 0.78 = 13.17 lb. per pound of dry coal. As shown above, 105.6 B.t.u. are used to heat one pound of dry gas from 60 to 500 deg., and 13.17 X 105.6 = 1390 B.t.u. Study of Table 87 will show that the molecular weights may be can- celed and the following formula derived for the weight of dry flue gas PV = 1 1 CO, + 80, + 7 ( CO + iV,) 3 {CO, + CO) X \^^ 1.833 j (67) where : W = Weight of dry gas per pound of dry fuel CO2, CO, O2, N2 ^ Percentages by volume in flue gas analysis C, S = Percentages by weight from ultimate analysis of dry fuel. C is the carbon actually burned, that lost in ashes and refuse being deducted. (U CO fl CO Wi (U o CO a> 4-) a o ji O (U bfi 'O CO (U o CO &>> E. ^ o CO CO (U C o (U (U u H TESTING 545 (e) Loss due to carbon monoxide. When carbon is burned to COz, 14,540 B.t.u. are evolved per pound, as against 4,350 B.t.ii. when burned to CO. The difference — 10,190 B.t.u. — is the loss due to each pound of carbon burned to CO. Table 87, column VI, shows that 0.39 lb. of carbon are burned to CO out of 5.92 lb. of carbon present in the gases. The proportion of carbon burned to CO is 0.39 X 100/5.92 -= 6.59 per cent; the carbon present in the gases is 78 per cent of the dry coal, so that 0.0659 X 0.78 = 0.0514 lb. of carbon are burned to CO per pound of dry coal. The loss per pound of dry coal is 0.0514 X 10,190 = 524 B.t.u. Without proceeding according to Table 87, the CO loss may be found from : (^+w) ^ = cof+co '-^ • '^ + "T^^^ • ^ '"'^^ <^^ diere L := Loss in B.t.u. due to unburned CO 10,190= Difference between the heat generated by burning 1 pound of carbon to CO2 and CO respectively, and the rest of the symbols are as in equation (67). With bituminous coals the presence of CO generally indicates the presence of unbnrned hydrocarbons also, so that the whole loss due to combustible in the gases may be assumed to be about double that due to the CO loss. With the anthracites, the CO loss will be the whole loss under this head. (/) Loss due to combustible in ash and refuse. The combustible in the ash is the main part of this loss. Sometimes the amount is assumed as the difference between the percentage of ash as weighed up during the boiler test and that found by the coal analysis. Or a representative sample of the ash can be analyzed; if it contains 20 per cent of combustible, and the ash is 10 per cent of the dry coal, then 0.2 X 0.1 = 0.02 lb. of combustible in the ash per pound of dry coal. This can be considered as coke and valued at 14,540 B.t.u. per pound. The loss will be 14,540 X 0.02 = 291 B.t.u. per pound of dry coal. (g) Loss due to heating moisture in air. With the readings of the wet and dry bull) thermometers the weight of moisture per pound of air may be found from Table 84. The weight of air per pound of dry fuel is : A = W + LhO — C (69) where : A = Weight of air per pound of dry fuel W = Weight of dry gas per pound of dry fuel H2O := Weight of water vapor in Item 28c, or 9 X Item 25^* C =: Weight of fuel per pound of dry coal in products of corn- Item 23 bustion, 1 Yru\ — ■ Take the weight of gas per pound of dry coal as 13.17 as in item (/. Then tile weight of air will be : 13.17 + 0.36 — 0.78= 12.751b. The weight of saturated vapor per pound of dry air at 60 deg. is found from the hygrometric tables to be 0.011 ; if the humidity is 75 per cent, the weight of vapor will be 0.011 X 0.75 = 0.008 lb. per pound of dry air. As the weight of air per pound of dry coal is 12.75 lb., the weight of -vapor in the air is 12.75 X 0.008 = 0.102 lb. per pound of dry coal. The rise in tempera- ture by the specific heat of the vapor is 440 X 0.47 = 207 B.t.u. per pound of vapor, and 207 X 0.102 = 21 B.t.u. per pound of dry coal. 546 TESTING The loss due to humidity of the air is very small and is usually included in item h without separate determination. (h) Loss due to unconsumed hydrogen and hydroearhons, to radiation, and unaccounted for. The flue gas analysis rarely includes a determination of the unconsumed hydrogen and hydrocarbons, and the losses due thereto are usually included in this general item. The loss due to radiation is from 3 to 8 per cent of the heat value of the fueL When the boiler is driven hard and the temperature within the setting is high, the actual radiation loss is larger but is a smaller percentage of the heat generated ; whereas at ver>- low rates the actual loss is less, but is a larger percentage. Accurate measurement is impracticable : the radiation and '"unaccounted-for'" losses are usually lumped in one item, which is simply the difference between the sum of the rest of the items, and the heat value of the dr\- coal, item i. • A heat balance may now be made up as an example with the figures assumed, and Table 88 will illustrate the method. Table 88. Heat Balance. Destination B.t.a. i Per cent Heat absorbed by boiler = equivalent evaporation from and at 212 deg. per pound of dry- coal x 971.7(a) .... Loss due to evaporation of moisture in the coal (b) Loss due to heat carried away in the steam formed by combustion of hydrogen in the coal (c) Loss due to heat carried away in the dr\' flue gases (d) . . . Loss by incomplete combustion of carbon to CO (e) Loss due to combustible in ash and refuse (0 Loss due to heating moisture in air (g) Loss due to radiation, unconsumed hydrogen and hydro- carbons, and unaccounted for (h) Total calorific ^-alue of one pound of dn.- coal, item 13 (i 13.850 100 10,390 26 75.0 0.2 453 1.390 524 291 21 3.3 10.0 3.8 2.1 0.2 755 5.4 The second column is filled in first, and by dividing the different numbers of B.Lu. by their total, the percentages to be written in the third column are found. Efficiency THE efficiency shown by item a of the heat balance is the same as item 14. It is the combined efficiency- of the whole — ^boiler, superheater, furnace, grate — and is frequently called the overall efficiency. The consensus of opinion is that this is the only efficiency which should be reported. Attempts have been made to separate the overall efficiency into boiler efficiency and furnace cfficiencj-, and have resulted in much confusion. At present, it is absolutely impossible to decide what proportion of the losses due to unburned combustible gases and to radiat-on should be charged to the boiler and furnace respectively; and this proportion would verj- properly var>- according to the relative poorness of design of the boiler and stoker. While it would be valuable to know the furnace and boiler efficiencies sep- arately, it must be admitted that up to the present no method of finding them has been proposed which is not highly contentious. TESTING 547 Accuracy THE absolute accuracy of the results of a boiler test even when conducted with the greatest care is doubtful, but there is as yet no common agree- ment as to what the probable limits might be. It is generally conceded, however, that there are several sources of indeterminate error, the more im- portant of which are discussed below. The limits of accuracy of a test might very reasonably be taken to be within plus or minus 3 per cent. One of the sources of probable error is the sampling of coal. Even when the greatest care is taken to obtain a representative sample, there may be an indeterminate error in ascertaining the heat value of the coal, even though the laboratory analysis is most reliable. With modern apparatus these laboratory determinations should be substantially correct as regards the sample tested ; but the question as to how truly the sample represents the whole, is always present and cannot be answered indubitably. Another is the moisture contained in the coal. As explained in the pre- ceding paragraph, the sampling is more or less uncertain. It is contended by some that if the attempt is made to determine the moisture during the test, the methods of drying and weighing are unreliable ; while others con- tend that though the moisture as determined in the laboratory is accurate so far as the sample delivered to the laboratory is concerned, this sample probably does not represent the bulk of the coal actually burned since there must inevitably have been more or less loss of moisture during the collec- tion, preparation and handling of the sample. Similarly, it is problematical whether the samples collected for the determination of the moisture in steam and for gas analysis are representative of the bulk, although the testing of the samples obtained may be quite accurate. It is not unusual for heat balances to be reported to the nearest B.t.u. and to the nearest one-tenth of 1 per cent. But the present state of the art of boiler testing does not provide means for attaining anything like this ac- curacy. In general, results should be reported only to the nearest significant figure. Reporting results of any kind in small units is likely to convey an erroneous idea as to the real accuracy of the figures. It is therefore quite logical in the case of guarantee tests, that a sub- stantial compliance with the guarantee be accepted as full compliance there- with, although preferably a limit of tolerance should be agreed upon before- hand l)y the parties to the test. The amount of this tolerance might well bear some relation to the care exercised in arranging the details of the test. Steam Consumption by Auxiliaries THE steam or power used in generating forced or induced draft, reducing smoke by means of steam jets, driving stokers, atomizing liquid fuel, oil heaters, oil pumps, and so forth, should be determined and specifically reported. No deductions on this account are to be made ; but they may conveniently be reduced to a percentage of the steam generated. The method of finding the steam consumption of auxiliaries by means of the rate of fiow of steam through a nozzle or an orifice in a thin plate is described on page 421. Soot OOOT accumulations are seldom accounted for, as the quantity is small ^ during an ordinary trial. The quantity of combustible carried off in the gases as smoke is determined only rarely. A prepared surface of 21 sq. in. in area suspended in a stack has l^een found to collect 9 to 184 milligrams per hour. 548 TESTING Smoke NO wholly satisfactory methods for either quantitative or qualitative smoke determinations have yet come into use, nor have any reliable methods been established for definitely tixing even the relative density of the smoke issuing from chimneys at different times. One method commonly employed, which answers the purpose fairly well, is that of making frequent visual ob- servations of the chimney at intervals of one minute or less for a period of one hour and recording the observed characteristics according to the degree of blackness and density, and giving to the various degrees of smoke an arbitrarv percentage value rated in some such manner as that expressed in Table 89. Table 89. Smoke Percentages. Dense black 100 Medium black 80 Dense gray 60 Medium gray 40 Light gray 20 Very light - - 5 Trace - .- 1 Clear chimnev The color and density of smoke depend somewhat on the character of the sky or other background, and on the air and weather conditions obtaining when the observation is made, and these should be given due consideration in making comparisons. Observations of this kind are also subject to errors of judgment. Nevertheless, these methods are useful, especially when the results are plotted according to the percentage scale determined on so that a graphic representation of the changes can be shown. Various forms of charts and clouded glass arrangements for comparing and fixing smoke densities have been proposed and to some extent used : but these have proved more or less unsatisfactory and they are subject to personal errors, and to sky, wnnd, and weather conditions, the same as the simpler method above described. Among the chart methods referred to, the use of the Ringelmann smoke chart is perhaps the most familiar. This is shown in Fig. 231. To use this chart, four cards are ruled like those shown, though covering a much larger area, and placed in a horizontal row about 50 ft. from the observer, and in line between him and the chimney, together with two other cards, one of which is white and the other solid black. The observer glances rapidly from the chimney to the cards and judges which one corresponds with the color and density of the smoke. He makes these observations every minute, or oftener if desired, recording the number of the card representing the character of the smoke at the instant of observation. The results are then plotted on a chart, and the variations shown graphically. The lines in cards 1 to 4 are respectively 1, 2.3, 2).7, and 5.5 mm. thick, and the spaces 9, 7.7, 6.2), and 4.5 mm. The lines should be made with black India ink. A convenient method of recording and presenting smoke reports is illustrated on page 65. Another method of smoke determination consists in the use of a nar- row flat metal plate suspended in the flue, the character of the smoke being indicated by the amount and qualit}' of the soot and dust deposited upon the plate in a given time. This method, like others, is useful in furnishing a means of comparison in different cases rather than a means of exact de- termination. TESTING 549 • ■ No. 1. " — " "" No. 2. No. 3. No.4- Fig. 231. Ringelmann Smoke Chart. 550 TESTING Among tlie latest methods brought out for indicating and recording the density of smoke is one depending on the variations in the electrical conductivity of the metal selenium due to variations in the intensity- of light shining upon it. Openings are provided on eitlier side of the tiue directly opposite each other. The selenium is located at one opening and a strong light at the other. The intensity of the light ra^'s falling on the selenium varies with the densit>' of the smoke. A milliampere meter in circuit with the selenium cell registers the variations. Liquid and Gaseous Fuels Tests v.-ith liquid and gaseous fuels follow the same general lines as those with solid fuels. Liquid fuel tests are reported on weight of fuel as in solid fuel tests, while gas tests are commonly reported on a volumetric basis. West Side Station, Denver Gas & Electric Co., Denver, Colo. Part of 10,000 H. P. of Heine Standard Boilers and Heine Superheaters. 551 CHAPTER 16 OPERATION THE methods and apparatus concerned in the operation of boiler plants may be divided into two classes — necessities and money savers. The necessities, v^ithout which the plant either cannot be operated at all or cannot be operated with safety, will generally be considered first. Discussion of the money savers, which either reduce the cost of operation or assist in reducing it, will follow. The latter might be divided further into two classes — those which directly save money such as feed water heaters and coal conveyors, and those which show where waste occurs such as CO2 recorders and coal weighers. Boiler Fittings ' I 'HERE are several necessary items of equipment which must be attached -'■ to a steam boiler before it is placed in service, among which are a water column, safety valves, steam gage and blow-ofif valves. Water Column. The water column usually consists of a cast iron body connected at the bottom with a pipe to the boiler below the water level and at the top to the steam space of the boiler. It is provided with three or more trycocks, one placed at about the mean or normal v/ater line, and the others above and below. The gage glass is connected through gage cocks at its top and bottom to the water column ; and if both gage cocks are open, the water will stand in the glass at the same height as it is in the column and in the boiler. Both gage glass and water column should be provided with drain cocks, so that they may be blown out. If valves are placed in the pipes connecting the water column with the boiler, particular care must be taken to lock them or otherwise prevent absolutely their closure by unauthorized persons. Long pipe connections from the boiler to the water column should be avoided, as there is always the possibility of such long runs of pipe be- coming clogged with sediment or scale, thus causing the water' column to become inoperative. In these pipes crosses are preferable to elbows, for when the plugs are removed, the pipes can easily be cleaned and looked through. Fig. 231 shows the type of water column used as standard equipment on all Heine boilers. This column is provided with copper floats which operate a whistle when the water level is too high or too low. Safety Valves. The function of a safety valve is to prevent the pressure in the boiler to which it is attached from rising above a definite point called the working pressure. The working pressure of a new boiler is, of course, dependent upon the design and thickness of materials used in its construction. The working pressure of a boiler which has been in service for some time is dependent upon its age and physical condition, and is usually governed by the report of a municipal or insurance boiler inspector. The A. S. M. E. Boiler Code (1918) requires that the safety valve capac- ity for a boiler shall be such that the safety valve or valves will discharge all the steam that can be generated by the boiler without allowing the pres- sure to rise more than 6 per cent ajjove the maximum allowable working pressure, or more than 6 per cent above the highest pressure to which any valve may be set. The total relieving capacity of the safety valve or valves 552 1000 H. P. Heine Standard Boiler in course of erection at the Walter Reed Hospital, Washington, D. C. OPERATION 553 required on a boiler shall be determined on the basis of 6 lb. of steam per hour per sq. ft, of heating surface for water tube boilers. Charts for de- termining safety valve sizes are given in Chapter 8 on PIPING. 'Steam Fig. 231. Wafer Reliance Water Column equipped with Self-Closing Gage. When two or more safety valves are used on a boiler, they may be either separate or twin valves, which are made by mounting individual valves on a Y base, j- uplex, triplex or multiplex valves are those which have two or more valves in the same body or casing. The blow down, or dih'erence between opening and closing pressure of the safety valve shall not be more than 4 lb. on boilers carrying less than 100 lb. gage pressure, not more than 6 lb. on boilers carrying between 100 lb. and 200 lb. pressure, and not more than 8 lb. on boilers carrying over 200 lb. pressure. The use of weight lever safety valves or dead weight valves is not per- mitted under the A. S. M. E. Code, hence only spring loaded pop safety valves will be described Here. Fig. 232 illustrates a typical pop safety valve for use with saturated steam, in which the boiler pressure acting upon the under side of the valve is resisted by the helical spring. When the boiler pressure exceeds the spring resistance, the valve lifts from its seat and the steam escapes into the atmosphere. 554 OPERATION The valve is provided with a skirt which becomes rilled with steam when the valve is open, so that the efiFective area of the valve is increased. As soon as the valve lifts, this increased area immediately takes effect ; and the greater load on the spring compresses it more than would be the case with a plain valve, and the valve opens wider. Once open, the valve will remain open while the pressure drops below that which opened it, because of the effect of the increased area. The pressure per sq. in. on the added area is less than the boiler pressure, and is dependent upon the freedom with which the steam can escape from under the skirt. Passages connect this part with an annular space called the ' huddling chamber." and this chamber is pro- vided with an adjustable outlet. If the huddling chamber outlet is closed, the pressure under the skirt will be greater, and the boiler pressure will drop ver>- low before the spring can close the valve. If the huddling chamber outlet is wide open, the pressure in it and under the skirt will be small, and the valve will close with ver>' little drop of boiler pressure. The difference of pressure between that necessar>^ to open the valve and that at which the spring can close it, is called the ''blow down,"' and is adjusted by con- trolling the huddling chamber outlet. Fig. 232. Ashton Pop Safety Valve for Saturated Steam. It has been explained how the effect of the skirt is to cause the valve to open wide immediately upon opening at all. In closing, this action is reversed, for when tlie boiler pressure drops sufficiently to allow the spring to begin closing the valve, the pressure under the skirt drops and allows the spring to close the valve further, so that the action is cumulative and the valve closes quickly. Owing to the rapidity with which these valves open and close, they are called "pop" valves. The valve may be opened to discharge at any pressure less than the relieving pressure by operating the hand lever, OPERATION SS5 Every superheater should be equipped with a safety valve at its outlet, set to blow at a lower pressure than the boiler safety valves, in order that a flow of steam may be maintained through the superheater if fo*" any reason the main steam flow is stopped ; and this will avoid damage to the superheater tubes by burning. Fig. 233 shows a type of valve designed for superheated steam service. The spring is exposed to the air, so that high temperature steam does not affect its elasticity by coming in contact with it. Fig, 233. Consolidated Pop Safety Valve for Superheated Steam. Steam Pressure Gages. Every boiler must be equipped with a steam gage, which may be connected directly to the boiler steam space or to the water column or its steam connection. These gages are generally of the round-pattern, indicating type. They consist mainly of a pressure element in the form of a tube spring or a dia- phragm, and of a movement to operate the indicating mechanism. The styles differ chiefly in the details of construction, such as material, mountings, trimmings and finish. The Bourdon pressure element is an oval metal tube, closed at one end and bent in an arcuate form to give the single or double spring, as in Fig. 234. The free end of the tube is connected by one or more levers to a toothed sector or segmental rack, which actuates a small pinion on the pointer shaft. Lost motion is taken up by a hair spring attached to this shaft. 556 OPERATION For marine and portable work or in stationar3- installations where vibrations would jar the sensitive mechanism, the double-tube gage is recom- mended. This gage is not so easily affected by rapid fluctuations of pres- sure. The r«-o free ends of the pressure tubes are connected to a multi- plying mechanism similar to that in the single-tube gage, but the needle movement is much greater. Indicating Single Tube. Dial. " Double Tube Fig. 234. Bourdon Tube Steam Gages. When measuring pressure, gages snow the dinerence c^tween the inside pressure actuating the device, and the pressure on its outside. Therefore. when the gage indicates zero, the pressures inside and outside of the spring are the same; when it indicates 50 lb., then the pressure inside the spring is 50 lb. greater than the pressure on its outside. The absolute pressure is the sum of the atmospheric pressure (14.7 lb.) and the gage reading; thus 50 lb. gage is equivalent to 64^J lb. absolute. Pressure is usualh* expressed in pounds per square inch. In selecting a gage, the size and imit of the scale required should be specified, and the scale selected should not exceed one and one-half times the working pressure. Roimd pattern gages used on the steam plant, range from 3 to 12-in. diameter. The dials of indicating gages are usually silver finished brass, having figures and graduations filled with black enamel; or they may be black with silver figures. The casings are iron, brass or nickel- plated. Gages should be located so that they are accessible, can be easily read. and so connected as to insure correct readings. Standard gages have a J4 in, pipe-thread male connection and are generally provided with a stop cock. For dark or obscure places, illuminated dial gages should be usei Gage tubes may become softened when subjected to temperatures of more than 150 deg.. so that steam or ver>- hot water should not come in direct contact with the tube. A goose-neck siphon or loop. Fig. 235. is used to maintain a protective water seal between the gage and the steam supply. ^^'hen the gage is exposed and subject to freezing, a pet cock. Fig. 235d, should be provided for draining the water from the siphon. Freezing might burst the connection or damage the gage spring. This pet cock should not be opened when tke pressure gage is in ser\-ice. as then the water seal would be lost and the gage tube be liable to be damaged by contact with the steam. If a gage is placed below a pipe line. Fig. 235e, allowance must be made for the head of water in the seal to obtain correct readings. Such a correction can be made by multiplying the head of water in feet by .433. thus reducing it to lbs. pressure per sq. in., which should be deducted from the gage readings. OPERATION 557 Gages should be attached securely to minhnize the effects of vibration. Repeated jarring will cause wear of the rack and pinion, resulting in in- accurate pressure indications. Gages subject to vibration, or placed high up and in hot boiler rooms, should be frequently tested. As the spring of the gage has only a slight motion, the least interference with it will produce a noticeable error because of the greater movement of the needle or pointer. b. c. d. Fig. 235. Siphons for Steam Gages A gage can be calibrated by comparison with a standard test gage, or by trial on a dead weight tester, or on a mercury column tester. Where testing devices are not available, as in the small plant, gages should be sent to the factory. A typical dead weight tester, Fig. 236, consists of a Fig. 236. Dead Weight Gage Tester. stand on which is mounted an oil reservoir, plunger pump and cylinder fitted with a piston to receive the weights. The gage to be tested is attached to a three-way cock. Each test weight is marked with the pressure in pounds per square inch that it will show on the gage. The weights are placed on the disk, one at a time ; and they should be whirled while taking the reading, so as to eliminate the error caused by the friction of the plunger. If the gage is at variance with the dead weight applied, it may be corrected by removing the pointer with a gage-jack and pressing it back on the spindle at the proper indication. ; ;■ IB 13 1] 9 5! ia Eg in I 11 Bl 11 II i QS II II ]} i 11 10 II i] i Union Central Life Insurance Building, Cincinnati, Ohio, equipped with Heine Standard Boilers. 559 Fig. 237. Everlasting Blow-off Valve. Fig. 238. Yarway Seatless Blow-off Valve, 560 OPERATION Blow-off J^alvcs. All boilers should be equipped with one or more blow- ofiF pipes, with one or more cocks or valves on each pipe. The A. S. M. E. Code (1918.1 provides that blow-off piping shall not be less than 1 inch or larger than lYz inches, and that globe valves should not be used. The re- quirements of a good blow-off valve are that it shall provide a clear passage for water, mud and scale, and that it shall open easily and close tightly. Fig. 237 illustrates the Everlasting Blow-off Valve, which consists of a top and bottom bonnet and a disc which swings between seats on the faces of the bonnets. The disc is actuated hy a lever. Fig. 238 illustrates the Yarway Seatless Blov,-:f \'alve. A plunger V is operated by a hand wheel and screw. In closing the valve, the shoulder S on the plunger V engages the loose follower gland F. compressing the packing P above and below the port, thus making a tight closure. Fusible Plugs, see Tig. 239, are intended to protect a boiler in case of low water. At best, these plugs are unreliable, but the law in some states requires their use, even in water tube boilers. TiHiiVi Typ^" Oatsde^ ypo *- Fig. 239. Fusible Plug: The fusible plug consists of a brass or bronze fitting which may be screwed into the shell, furnace crown sheet, or waterleg of a boiler. The fit- ting is bored out and filled with pure tin or some composition metal which has a melting point but little above the temperature of the steam in the boiler. The metal of the plug transmits the heat to the water so rapidly that its temperature does not rise if it is covered with water; but if the water level falls below the plug, the fusible metal in the core will melt out, allowing the steam to escape. If heard or noticed, this will serve as an indication of low water. Methods of Hand Firing Coal HAXD-FIRIXG is not onl\- hard work, but requires considerable judg- ment and skill if waste of coal is to be avoided. The method of firing depends upon the kind and quality of coaL Bituininous Coal. Inasmuch as bituminous coals varj- widely in compo- sition, it is difficult to state definite rules for handling which will fit all cases. The most suitable method of firing a particular coal is best determined by experimenting with it, and a careful fireman soon learns how to p/oduce the best results. There are three general 53-5tcm5 of f.ri::^. k:.c ..:: as alternate, spread- ing and coking. In the alternate system, fresh coal is fired nrs: f r : - vr ' - ?. :e then on the other, or through alternate doors rrr ire . :rr : .::: two, so that the entire fire is not blanketed with green coaL This sj'stem is used where the grates are wide or when two or more furnaces have a common combustion chamber. OPERATION 561 The spreading system consists in charging a small amount of coal, spreading it in a thin layer over the entire grate at each firing ; usually it is spread from the bridge wall toward the door. Although it means more work for the fireman because the furnace must be fired frequently, the use of this system is increasing. It gives an air supply which is always more nearly proportional to the fuel supply. In the coking system, the fresh coal is piled up on the dead plate or on the front of the grate, so that the mass can become nearly or wholly coked. It is then pushed back toward the bridge wall, and spread evenly over the grate to make room for the new charge. When no dead plate is provided, about one-third of the grate at the front is left bare and receives fresh coal at each firing. This system is adapted to furnaces in which the gases pass horizontally over the fire. The spreading and alternate methods, as compared with the coking system, give higher efficiency, higher CO2 and lower temperature of exit gases. Because of the greater uniformity in furnace temperatures, steam is generated more uniformly. In the coking method less of the refuse appears as clinker and more as ash, but the combustible lost through the grate is about the same in the three methods of firing. The amount of slicing and raking is equal with all three, but the coking method also requires time and labor for leveling. The spreading and alternate methods of firing are widely used in hand firing non-caking and high volatile bituminous coals. In the alternate method the volatile matter given off by a fresh change of green coal on the one side of the grate, is mixed with some air which has been heated by passing through the fuel bed on the other side; but care must be taken to make provision for thoroughly mixing the gases from the two sides of the fire, and there is the difficulty of getting one side of the fire heavier than the other. Spreading over the complete fuel bed is perhaps more extensively used than even the alternate method, and has the advantage over the alternate method that the whole fuel bed can be kept of more uniform thickness, thus minimizing the possibility of holes occurring in the fire. The coking method is most applicable to those bituminous coals which cake or melt and run together upon heating. With this method the hydro- carbons must pass over the hottest part of the fire which is near the bridge wall, on their way to the boiler heating surface. The back part of the fire should be kept thicker, as the character of the coke bed is much more open here than at the front. Two disadvantages of the coking method of firing are that the fire doors must be kept open relatively long in order to work the fire, which results in large quantities of excess air; and the fire is being continually disturbed, a fact which will result in excessive clinkering with coals containing fusible ash. Following are a few general rules which have been formulated by the Coal Stoking and Anti-Smoke Committee of the Illinois Coal Operators' Association for the hand-firing of Illinois and Indiana coals. (1) Break all lumps, and do not fire coal into the furnace of a size larger than the fist. Large pieces do not ignite quickly and their presence results in the formation of holes in the fire, with consequent losses due to excess air. (2) Keep the ash pits bright at all times. If they become dark it is an indication that the grates are becoming covered with clinkers and that the fire needs cleaning. (3) Do not fire the coal in heaps on the grate unless filling up a hole. Spread the coal as it leaves the lip of the shovel. 562 OPERATION (4) When firing, spread the coal from the bridge wall forward. (5) Do not allow the fire to burn dull before charging. (6) Do not allow holes to form in the fire. Should one form, it should be filled by leveling. (7) Regulate the draft bj- the ash pit doors rather than b}- the manipu- lation of the stack dam.per. When the stack damper is closed the intensity of the draft is diminished, but by closing the ash pit doors the air supply is reduced. Referring to rule (7), general opinion is against regulating the draft by the ashpit doors. The air supph- is reduced, whether it is the damper or the ashpit doors that are partly closed. Closing the ashpit doors is generally believed to result in undul}^ heating the grate bars ; and it reduces the boiler efficiency by causing an increase in the leakage of air through defects in the setting. Anthracite. Anthracite should be fired by the spreading method, in small quantities and at frequent intervals. For large sizes of anthracite such as "stove" or "egg," almost any type of hand-fired furnace is suitable. However, the larger sizes of anthracite are now almost exclusively used for domestic purposes, and because of their high cost are but little used under steam boilers. The smaller grades of anthracite do, however, find extensive use as boiler-fuel, and their successful burning depends upon several factors. The small sizes of anthracite pack closely together on the grates, which makes the employment of a strong draft necessarj^ to secure the proper amount of air for combustion. Mechanical draft is usuall}^ employed, which is obtained by the use of steam jet blowers or by fans. As the fine grades of anthracite run higher in ash than the larger grades, there is considerable tendency toward clinker formation; and the employment of steam jet blowers for forced draft is desirable, as the introduction of steam into the ash pit decreases formation of clinker. It is desirable to disturb the fuel bed as little as possible with the firing tools. With a little practice, the fuel can be spread very thinh*. The fire should be kept of even thickness, and if necessary it may be levelled occa- sionally with a tee-bar. This can be a light tool made of a length of ^ or 1 in. pipe screwed into the branch of a tee, with pieces of pipe about 6 in. long screwed into the "runs." The fire is simply to be leveled with this tool, and not stirred up. Some firemen get good results by leveling the fire with a tee-bar between each firing. There is a limit to the forced draft pressure when small anthracites are burned, owing to the liability of lifting the fuel off the grate. This makes holes in the fire and carries some of the fuel into the combustion chamber and flues. Owing to the necessarily slower rate of combustion, the grate area for small sized anthracite is made larger than for bituminous coal in order to develop the same horsepower. The relation of grate area to boiler heating surface to develop the rated capacity of a boiler is given in Table 89. Table 89. Relation of Grate Area to Boiler Heating Surface. Size of Coal Ratio Xo. 1 Buckwheat 1 to 40 Xo. 2 1 to 35 Xo. 3 1 to 30 Xo. 4 1 to 25 OPERATION 563 On account of the large amount of ash in small hard coal, there will be a considerable depth of ash on the grate just before cleaning. The ashpit pressure is small just after cleaning, but as the ash thickens on the grate, the pressure must be greatly increased to maintain an even combustion rate. Therefore, forced draft blowers should be chosen which have characteristics showing that their efficiency is maintained over a wide pressure range. The "free burning" varieties of anthracite are burned satisfactorily when the above directions are followed. But with the harder coals — those con- taining very little volatile matter — it is usually necessary to mix from 10 to 15 per cent of bituminous coal. The bituminous coal should be fine "slack," not lumpy. Tools for Hand Firing. The hoe, slice bar, rake and shovel are the necessary hand tiring tools, and Fig. 240 illustrates those designed for a 6 ft. grate. 1 Standard pipe HOE 1 'round bar welded to end of pipe and blade riveted to It -p--tr-N\ /Welded -6'6- ->y 2'6 Welded ^ IV4 Standard pipe SLICE BAR -^^ ■X* "iW' ^i elded I Standard pipe RAKE Fig. 240. Tools for Hand Firing. For best results in hand-firing, the equipment must be so arranged that the shovel and other firing tools can be handled freely without hitting bumps and rivets. This implies sufficient firing space, a smooth floor to receive the coal, or still better, a hand or industrial coal car similar to the type shown in Fig. 241. In the firing procedure recommended by the Bureau of Mines, the fireman takes the position indicated in Fig. 242, in which he can see the thin spots in the fire and can throw the coal on without exertion. He stands 4>^ to 5 ft. in front of the furnace at about 12 to 18 in. from the center line of the firing door. The coal pile is about 2 ft. away. If the coal is less than 6 to 7 ft. from the boiler front, the fireman is crowded. To avoid the intense heat, he stands to one side of the door, and throws the coal in by guess. The room for handling the scoop is not suffi- cient, so it travels in the arc of a circle, scattering some coal in its path, and dumping the remainder in a heap on the dead plate or on the grate just inside of the firing doer. The result is an uneven lire that requires raking and spreading over the grate. ■i-i P3 c '" -0 m u u CO u TJ rz» C CO CQ 4-1 «J C3 c cu u jz K &£ (m u ^ 7S CU 4-1 4-) ffi ,o d o t" T/ J3 J= t: o o " 2 o "■*-> ■*-• 4-' C o .- "-J c £ S a. o 3 u CQ OPERATION 566 For economy, coal should be burned rapidly and at high temperatures. This means light firing or the frequent charging of small amounts of coal to prevent the thin places from burning through and admitting too much excess air. The amount of coal and time of firing depend upon the grate surface for the available draft. A draft of 1 in. in the uptake v^ill give good results with 2 to 2^ lb. of coal to a square foot of grate at each firing. A boiler with a grate 6 by 8. ft. would then require six to nine shovelfuls of coal at each firing period, about every 5 minutes. For a higher draft the interval might be 3 minutes, and for a lower draft the firing time might be 8 minutes. The facilities for handling, care in charging and cleaning fires, and the suitability of the type of grate to the fuel burned — all may cause loss or waste of coal. With poor facilities or management the total may run as high as 10 per cent of the coal consumed, while under fair operation the loss will average from 2 to 3 per cent. Fig. 241. Steel Coal Cars. \-Z'-\ •---4' to 5'-—^ Fig. 242. Proper Position for Hand-firing. 566 OPERATION The^ thickness of fuel-bed required depends to a large extent upon the grade of coal, available draft, firing periods and the experience of the fire- man. For a given operating condition and boiler setting, the thickness giving maximum efficiency can be determined by test. If the fuel-bed is too thin excess air will result. If it is too thick the air supply will be insufficient for proper combustion. In either case the boiler efficiency will be decreased. Generally a thin fire is to be favored, but with coarse coal the fire bed should be thicker. For the larger sizes of anthracite a fuel-bed of 6 to 10 in. can easily be carried ; a 2-in. bed will give good results with barley and rice coals. The free-burning bituminous coals can be easily handled with a 6 to lO-in. bed ; the poorer grades give good results with a fuel-bed 4 to 6 in. thick. Lignite. Lower grades of lignite disintegrate and crumble readily when heated. The packing of this finely divided fuel on the grate increases the resistance of the fuel bed to the flow of air, hence a high draft pressure is required for even moderate rates of combustion. This crumbling causes intense combustion near the grate where the air enters, and the high tem- perature at this point, coupled with the low fusion point of the ash, results in the formation of clinkers. The fuel bed should be disturbed as little as possible during firing, because of this tendency to form clinker. Special types of overlapping grates with small air spaces should be used to prevent the disintegrated lignite from sifting into the ash pit. The thickness of the fuel bed may vary from 4 to 8 inches with natural draft, and up to 20 inches with forced draft in the semi-producer tx-pe of furnace. Either the alternate or spreading type of firing may be used with lignite. Wood. Cord wood or slabs may be successfully burned on herring-bone grates with natural draft. When stacked in a furnace they form an open fire through which the friction draft loss is slight, and hence the fuel bed may be as much as from 2^4 to 3 feet in depth. Double-deck fire doors on the fire-fronts are convenient for feeding slab wood. Hog wood, or the refuse resulting from the maceration of logs and mill ends in a hogging machine, may be fed to the grates through chutes or by hand. It is generally burned in a Dutch oven on herring-bone or Tupper grates. The fuel bed may. be from two to four feet deep. Care should be taken to avoid too much excess air coming in through fuel chutes or by parts of the grates being uncovered. The bed of fuel should not be disturbed with firing tools of any kind ; but even then a large amount of unconsumed wood particles are carried away. Forced draft under the grates is not desirable, because of increasing the amount of "fly ash" and unconsumed particles of wood carried up into the breechings, etc., where secondary- combustion may cause damage. Excellent results are being obtained in burning this fuel on Laclede- Christ\- Chain Grate Stokers under Heine standard boilers. Compared with hand operation, these stokers give much higher boiler efficiency and entirely eliminate smoke and the carriage of unburned particles out of the furnace and combustion chambers. Wet or green sazidust is satisfactorily burned on hollow blast grate bars with forced draft. Inasmuch as the character of the sawdust as regards its resinous properties, moisture content and size of particles, vary in different localities, no general thickness of fire can be recommended, but usually it will be less than twelve inches. It is preferable to fire the sawdust over the grate surface evenly by hand. Heaps or cones formed when the sawdust is fed into the furnace through chutes should be constantly leveled. Shavings and fine dust from polishing machines are not usually available in sufficient quantities to burn alone. They are generally used in conjunction with coal fired grates, often set in an extension furnace. As this material OPERATION 567 is generally very dry, care must be taken that there is a vacuum in the fur- nace, for if not, the furnace brick work and cast iron fronts will be damaged by the intense heat. Tan Bark. Tan bark may be satisfactorily burned in a Dutch oven or extension type furnace equipped with horizontal or inclined stationary grates. The grates usually have from 20 to 30 per cent air space, with the actual opening between bars not more than '/le to ^A inch, thus preventing the tan bark from falling into the ash pit. The ratio of grate surface to boiler heating surface is generally about 1 to 30. The thickness of fuel bed varies with the character of the bark, furnace design and available draft. In the usual practice, the tan bark feed chutes are located in the top of the extension furnace arch, and the material builds up on the grates in the form of cones. These cones will vary in depth, and where they meet will be from 6 to 18 inches. Tan bark is sometimes fired with bituminous coal in a Dutch oven fur- nace equipped with dumping or shaking grates. The grate surface in such a case will range between 1 to 35 and 1 to 50. Cleaning Fires CLEANING a fire is made necessary by the accumulation of clinker and ash. which impede the air for combustion. The intervals between cleaning depend upon the proportion of ash in the coal and its fusibility, and upon the type of grate. If the coal contains much ash, or ash that is fusible, the fires must be cleaned frequently. Less clinker forms with light fires, which can often be run through a 12-hour shift without cleaning. Fires should be cleaned thoroughly, all clinker and ash being removed so that they cannot fuse and adhere to the side and bridge walls. Accumulations of clinker melted onto the furnace walls reduce the grate area ; and the brick- work is damaged when they are eventually broken ofif. The more quickly fires are cleaned, the less coal is wasted. The damper should be partly closed while it is being done. There are two general methods of cleaning fires, the side and the front to rear methods. In the side method, one side of the fire is cleaned at a time. The good coal on the top of the fuel bed is scraped and pushed to one side, large clinkers are broken up with a slice bar, and the refuse drawn out of the furnace. After one side is cleaned, all the burning coal from the other side is moved back and spread evenly over the cleaned part of the grate, after which a few shovels of green coal are added. This adding of fresh coal is necessary in order to have enough live coal to cover all the grate when the cleaning is completed. The refuse is then removed from the other half of the grate and the burning coal spread over the whole grate. In the front to rear method, the burning coal is pushed back with a hoe against the bridge wall and the exposed clinker removed. The burning coal is then pulled forward and formed into a narrow ridge across the bare grate. The clinker from the back of the fire is ''jumped" across the ridge with the hoe, and pulled out through the fire door. The ridge of live coal is then spread evenly over the grate. With this method it is difficult to get a really clean fire without wasting a lot of unburned coal. An improvemeiit on the front to rear method is to form the front of the bridge wall into a shelf or cleaning table. The live coal is pushed onto the cleaning table, giving every facility for thorough cleaning without waste of unburned coal. After the ash and clinker have been removed, the live coal is drawn forward from the cleaning table and spread over the grate. The height of the cleaning table above the grate should be such that it is about level with the top of the layer of ash. This will naturally vary with the quality of coal and with the length of time between cleanings, but about 6 in. will meet general conditions. 568 OPERATION With anthracite, dumping grates are frequently used. The tire is burned very low on one section by not feeding coal to it. and that section is then dumped. Burning fuel is pushed onto the clean grate and fresh fuel added. Other sections are similarly treated until the whole tire is cleaned. Stand-by Boilers and Banked Fires TDOWER plants which operate under changeable load conditions must always -*- be ready to carry the maximum or peak load, and in order to meet these sudden demands, steam pressure must be maintained on the boilers held in reserve. The length of time that stand-by boilers are held in reserve depends entirely upon the service. Boilers are held in reserve in public utility plants to meet the peak load demands of morning and evening rush hours which come on at detinite times ; and are also held for long periods to meet un- expected demands, such as are due to thunderstorms, tire protection serv- ice, etc. The quantity of fuel used in banking tires does not contribute directly to the power output of a station, but rather represents the losses due to radia- tion, leakage, etc., called the stand-by losses. Stand-by losses var>- widely in different plants and under different operating conditions, as is indicated in Table 90 which shows the fuel required for banking tires. Table 90. Fuel Consumed by Banked Fires. T f 1.1 . Method of Kind of Rated V^^^ ri?%o. lype oi Plant t:- - /- i tj xr t^ of Bank, Coal fer ■'*' I Finng Coal B.H.P. ^^ ^ Public Utility | Chain Grate Stoker 111. Bituminous 508 Public Utility [Chain Grate Stoker 111. Bituminous 508 Public Utilitv! Underfeed Stoker .Bituminous 600 2 130 24 450 24 ^ 330 Industrial Hand Fired |\V. Va. Bituminou. 640 72 192 Industrial Hand Fired IXo. 3 Anthracite 600 24 200 Industrial Side Feed Stoker 'ill. Bituminous 400 8 260 It is obvious that the coal required per hour for a short bank will not be as high as that required for a long bank, due to the fact that the setting remains hot from the previous operating period. When burning oil, about 2 per cent of the fuel used when operating the boiler at rating, will maintain the full steam pressure for a long banking period. Quick Steaming From Banked Fires Ti OILERS which may be called upon to carry sudden heavy loads must ^ have free and detinite circulation, as the water must get in motion quickly. Boiler circulation is not positive, but is induced by "bubble pump" action, w^herein the upward travel of the steam bubbles due to their buoyancy, sets the water in motion in the same direction. The unrestricted water passage offered by the spacious Heine waterleg is particularly favorable to starting circulation quickly. The curve of Fig. 243 by G. H. Perkins, of a quick steaming test on a 950 H.P. Heine boiler, demonstrates rapid response to sudden heavy loads by attaining 300 per cent of rating in 4 minutes and 23 seconds, or 3000 H.P. in 5 minutes, from a banked tire. Forced draft fires, oil or powdered coal, can handle these unexpected loads more rapidly than natural draft. The curve in Fig. 243 is of a trial with a Sanford Riley Underfeed Forced Draft Stoker. OPERATION 569 950 ■ . 300 «-^ > y • y y 250 / / y / ^ y / $ / <3'200 / / ^ / 1 v y y r "^ 150 t / / ^ k / «t J f 100 / J / J f 50 J r / f / / V Time, Minutes Fig. 243. * Quick Steaming from Banked Fires. 3850 2375 900 U35 950 475 Load Signals TT is often convenient for the firemen to know what load is being carried -■' in the engine room, especially in stations where the load is variable. This may be readily accomplished by the use of a simple signal system. A box with three rows of numbers painted on its glass front, each row from to 9 with a small lamp back of each number, may be placed prominently in the boiler room. The upper row of figures will represent the load in tens of thousands of kilowatts, the middle row thousands, and the lower row hun- dreds. A bank of twenty-nine switches, each switch corresponding to a num- ber on the signal box in the boiler room, will be placed in the engine room. The lamps in the signal box will light and inform the boiler room operators of the load being carried, as the switches are turned on. In very long boiler rooms the signal may be composed of a number of lamps arranged as in outdoor electric signs. Quite elaborate systems of load dispatching have been worked out in large inter-connected power stations. Prevention of Smoke SMOKE consists of small particles of unconsumed carbon which give to the gases a color ranging from light grey to dense black. It is caused by the lack of sufficient air at the proper temperature at the point where the volatile gases from the coal should be burned, with the result that the gases are only partly burned and carbon is set free. United Gas Improvement Company's Building, Philadelphia, Pa., equipped with Hein Standard BoUers. This company has installed 6200 H. P. of Heine Standard Boilers Operation 571 The density of smoke may be measured in several ways and the most popular method is by means of the Ringelmann charts, which are described in Chapter 15 on BOILER TESTING. Many cities enforce ordinances providing penalties to be inflicted upon those plants which are consistent smoke producers. Hence it is the engineer's concern to know of the possible methods for eliminating smoke. Smoke may be caused by (1) character of fuel, (2) improper method of firing, (3) poor furnace design, (4) lack of sufficient draft, and (5) insufficient furnace capacity. In general it may be stated that bituminous coals of high volatile content are more difficult to burn smokelessly than those of a low volatile content. When the various methods of firing were discussed earlier in this chap- ter, it was mentioned that the particular method selected would depend upon the type of fuel. In general, smokeless combustion will be more completely attained by firing the coal in small quantities and at frequent intervals. It is due principally to this fact that mechanical stokers usually accomplish smoke- less combustion. Much depends upon proper furnace design. The problem of attaining efficient and smokeless combustion resolves itself into three requirements, viz. : the mixing of the unburned gases with the proper amount of air for combustion, the allowance of time for combustion, and the maintenance of high furnace temperatures, all of which depend upon correct furnace design. The converse of proper mixing is stratification or laneing, which occurs commonly in hand-fired furnaces, and is the more objectionable where the gases rise directly from the fuel bed into the tubes as in the case of vertically baffled boilers. The installation of wingwalls, mixing" piers, arches, and steam jets is often necessary to effect smokeless combustion. But it is diffi- cult to construct such arches and piers to stand up satisfactorily under the intense furnace heat, and some of these mixing devices take up room, diminish the combustion space in the furnace and also reduce the available draft. The preferable way to reduce smoke and still obtain the proper mixing effect in the furnace is to employ horizontal baffles, with a curtain wall added for high volatile coals. Fig. 20 on page 93 shows such an arrangement which is highly successful. Time is also an important element in smokeless combustion and depends upon the length of gas travel and the volume of the combustion chamber. Horizontal baffling meets this requirement, as has been shown in experiments by the- U. S. Bureau of Mines with a Heine boiler in which, with a combustion rate of 64.5 lbs. of coal per square foot of grate area per hour, only 1 per cent of the total unconsumed combustible was present when the products of combustion had traversed 160 cubic feet of combustion space. The higher the furnace temperature the more rapid and complete is the combustion with absence of smoke, as is shown by tests made on a Heine boiler at the University of Illinois. This boiler was equipped with a bottom horizontal baffle of C tile which completely encircled the tubes of the lower row over the furnace. It was "almost impossible to make smoke with this setting under any condition of operation." Inasmuch as part of the air for the complete combustion of bituminous coal must be drawn through the fuel bed and the rest admitted above the fire, it is obvious that smoke will result if there is a lack of sufficient draft. The largest quantity of secondary air is required just after firing, and much less is needed for the rest of the cycle until the next firing. A well designed and operated furnace will burn a given fuel without smoke up to a certain critical combustion rate. Beyond this rate the eft'iciency will decrease and smoke will result, owing to the lack of air and of furnace 572 OPERATION capacity in which to mix the gases. This is the reason why hand-fired furnaces usually smoke when they are being forced to carr}- much overload. When fires are being kindled or when banked fires are being forced, smoke is almost unavoidable, and most cit>' ordinances provide exceptions to their rules to cover these circumstances. Cinders. In large central stations operating boilers at high ratings with stokers and forced and induced draft, there is often a nuisance caused by cinders discharged from the stacks. Attempts have been made to reduce this by installing cinder catchers in the stack, but these have not been par- ticularlj^ effective. A cinder-separating induced draft fan which is claimed to be successful, has recently been placed on the market. Meaning of Carbon Dioxide THE proportion of CO2 in fine gas is a gage of the success realized in pre- venting inleakage, and in securing combustion of the fuel with the minimum amount of air. The more nearly the maximum value is approached, the greater the success in keeping down the excess air and the consequent heat losses up the chimney. This maximum value runs from about 18.5 with high volatile bituminous coals to about 20.0 with anthracite. Assuming an all- carbon fuel, the percentage of excess air used can be calculated directly from the CO2 percentage, and equals : m '^-JL (70) in which D is the percentage of CO2 by volume in the exit fine gases. As each volume of CO2 present is produced by the consumption of an equal volume of cxy-gen, the numerator in the fraction represents the unconsumed or excess oxj-gen remaining in the gas. and the denominator the oxygen actually consumed; that is, the amount theoretically required for combustion. Fig. 244 indicates the amount of excess air, and the preventable fuel loss corresponding to obsers'ed percentages of CO2 based upon average coals. Good practice is represented by 15 per cent CO2, which corresponds to 40 per cent excess air, with practically no preventable loss up the stack. In the absence of effort to maintain high values of CO2, a usual average in a great man}' power plants is as low as 5 per cent. Of course, the exact amount of excess air and the preventable fuel loss will depend upon several circumstances. The chart, Fig. 245. by Haylctt O'Xeill, shows the effect of the flue gas temperature on the efficiency with different proportions of C0». These curves are topical, although they were drawn for the following specific conditions : Coal. B. t. u. per lb 14.500 Comxbustible. per cent — 90 Volatile hydrogen, per cent 5 Moisture, per cent 2 Relative humidity of air, per cent 65 Temperature of air, deg 80 CO in flue gases, per cent 0.1 Steam pressure, lb. per sq. in 150 Combustible in ash, per cent. —.. 30 The overall efficiency decreases as the CO2 content is reduced, and as the exit temperatures are increased, except with low flue temperatures. These correspond to lov/ rates of driving, with high radiation losses and low efficiency. OPERATION 573 700 600 cSOO o ;>• I4OO C < w S300 200 100 ■ ^ (is-l 60- 55- ' 50- -»- I «45- \ u I ^ \ in 40- \ o _1 ' JZ5- t) \ -^30- \ \ c \ ^25- \ i \ \ IQ^ \ \ \ 15- \ \ \ 10- \ \ \ \ s. S- V S, ^ \ "^ *>s ^^ « ^. 6 8 10 12 14 Carbon Dioxide, Percent 18 20 Fig. 244. Chart for Estimating Excess Air from Per cent of Carbon Dioxide. A high value of CO2 Is constantly sought in boiler operation. Few boilers are operated with an air supply even approaching the minimum, and the amount of CO in the flue gas becomes objectionable only when the air is so reduced that the CO2 is above 15 per cent. The CO2 is generally low when surplus air is introduced, and is increased by adjusting the draft and fuel-bed resistance, by closing holes in the setting, and by avoiding holes in the fire. With complete CO2 records the work of different firemen can be checked. When these records cannot be kept, special tests can be made and the conditions under which they were produced studied, so as to fix a standard of operation. Samples of such studies are given in Fig. 246. A comparison, of samples from different passes indicates leakage through the setting. 574 OPERATION "400 500 &:o ::o boo 900 1000 1100 Flue Gas Temperature, Deg. F. Fig. 245. Boiler Efficiency as affected by Flue-Gas Temperatures. Effects of Firing on Carbon Dioxide A COMPARISON of firing conditions with CO, records, either from an '^*- automatic chart or from one made bj- plotting the analysis of grab samples against time, indicates the effect of different operations on furnace efficiency. Fig. 246 illustrates the method. In A. which is hand-firing, the fire was dirt\- and the COj was down to 5 per cent ; but after cleaning, it rose to 13 per cent. Record B was made with a sloping grate stoker, and shows how the CO2 fell as the fire was cleaned, and rose as soon as the dump grate was closed. It was customary- to poke coal down from the hopper soon after each cleaning, and this was accompanied by a big drop in CO;, which indicated the entrance of much excess air due to the upper part of the grate being cov- ered with unignited coal. As this new coal became ignited, the COi again rose. The latter part of C shows good hand-firing; the COi rises after each firing and falls slowly. The first firing was uneven, and quickly burned into holes, which reduced the COj to 3 per cent. The effect of leveling a fire which was full of holes is shown in D. OPERATION 575 20 18 O 6 20 18 J 6 Oh U 8 6 n 1 c p c «3 1 ^>1 i ^ / ( - 1 '^ ^ 1 S, / V I ? 5 4 5 6 7 6 9 10 11 I? 15 14 15 16 Time in Minutes ■Dirty vs. clean fire, hand firing /— /— / ^N, / •>> / '\ ^ / N \, / "s sy / \, / N . / .5; '^g. L l.. 5 10 15 20 25 30 35 40 45 50 55 60 Time m Minu+es PoJ-.^ C — Good band firing I 3 I 2 ~1 1 o OlO 1 /-^ i 1 § <- <— ' — 1 \ / \ / / \ / \ / / / / > / y I L 12 3 4 5 Time in Mmu+es B — Sloping grate stoker 1 ■ ■ ■ k- ' ■ ' ' r V "V N, N, J 1 [-~^ ^1 •^1 I 1 J 2 3 4 5-678 Time in Minutes 9 10 It \12 D — Effect of leveling fire Fig. 246. Variation of CO2 with Different^Methods of Firing. Fig. 247, by M. GenscJi, shows the general effect of excess air. The fuels for which results were plotted are typical high-grade and low-grade coals, so that values for other coals would lie in the bands between the different pairs of curves. The combustion temperature and the efficiency 100 90 £ u 80 1 4500 ^ "^ I- •^ 1 4000 V \ >«. ■«. f^ C-/6 A>. \ \ v, ■>«. '^ S^ ^ o3500 \ \^ h «» . *V "«s \ \ \ "^ '^K ^ ^ ^ £^•3000 \ s [<: c^ "^ s. •^ > V N &^ / /< D2500 +- V s ^ h / / / ' N s h' y i_ ■Coal No. 1 ^, ^y-. > y g.2000 Loa/ no. / t . > / "-^ -^ ^^ ,^ 1-1500 A /> > ^ «, •■^ d 0', y k^ 1000 fw;^ u y ^ .^ ^ ^ f ' 1 1 1 1 -i.ip <^ni<; Temper afure^ Rno ^ ^ ^ / j=j =- "T "-■ •■" — — n 3000 2500 2000 1500 1000 ^60^ 50 Co WW a; « '^ o )r{ CO "o +j CO "^ *-■ CO *" C ■5 gw o .^ O 4J ^ w 5- o p O CO o g 13 o ^ r 4J . o Uu ► .tfh. t\-i ai 00 4J "O O CO c Pli CO - 4; O CO 4J C/3 -pes of flow meters are described imder "Metering Steam." OPERATION 595 Metering Steam \/fOST practical steam meters are based upon one or the other of two ^^ ^ principles, both depending on the velocity of flow. Either there is a constriction inserted in the steam pipe so as to cause a small pressure differ- ence, which will vary with the amount of steam passing, or the velocity of the flowing steam is measured by a pitot tube, or else the steam in flowing through an orifice impinges against a movable part which assumes different positions for different rates of flow. The actual measuring instrument can be placed at any convenient dis- tance from the steam pipe and is connected to it by two small copper tubes filled with water of condensation. These tubes transmit the differential pres- sure to the instrument. The latter can either indicate on a dial or scale the rate of flow of the steam at any instant, or record the rate of flow graphically on a chart, or integrate numerically by means of a counting mechanism the quantity which has passed in any given time. All these functions can be combined in one instrument. In instruments using the constricted-pipe principle, the quantity of steam passing per unit time is taken as being directly proportional to the square root of the difference of pressure on the two sides of the constriction. This proportion holds, however, only if the pressure and the superheat of the steam are constant. In the simplest form of pitot apparatus, two tubes are inserted through the side of the steam pipe, one being cut off flush with the inner wall of the pipe and the other bent so that its open end faces the flowing steam. Both tubes are submitted to the static pressure of the steam, but the bent one measures also the dynamic pressure due to the velocity. The difference in pressure in the two tubes is therefore a measure of the rate of flow and can be employed to operate an instrument. The disturbance of the flow due to the presence of the pitot tube itself must be reckoned with. An alternative to the fixed orifice consists of a variable orifice designed to create a constant pressure drop. The steam passes upward through the seat of an automatically lifting valve, which is held in a higher or lower position according to the rate of flow. A lever mechanism connects the valve Vv^ith the pointer of the instrument. At low velocities the forces acting are so small that the readings are unreliable. In Instruments depending upon the drop of pressure across an orifice, this difficulty can be overcome either by inserting a smaller orifice, or by using a butterfly valve which can be locked in one of several positions according to the rate of flow. Thus the range of the Instrument can be altered without Interfering with the steam pipe. In every type of instrument referred to, however, accurate metering is difficult when the density of the steam varies. The best steam meters working under commercial conditions are correct within plus or minus 2 per cent at loads ranging from three-quarters to full load. At half load the accuracy will be within 2^ per cent, and from one- quarter to one-sixth load it will be within 4 per cent. Such accuracy can be obtained only by calibrating each instrument under conditions similar to those under which it will have to work. In the simplest instruments, namely, those that merely Indicate the rate of flow at an instant, the dift'erential pressure acts upon liquid in a U-tube, the liquid rises in one limb and Indicates by Its height the rate of flow. This is read off a graduated scale placed alongside the liquid column. Water is sometimes used as the indicating liquid, partly on account of the ease with which it is automatically supplied by condensation, and partly because of the open scale obtained with small pressures. Mercury, however, is fre- quently adopted. 1.2" - R o > - o u t5% — — 2. - = £ — i o :: 3". y o o irj OPERATION 597 The instniinent shown m Fig. 261 uses the orifice principle at a constant difference of pressure, the size of orifice being- varied to allow different amounts of steam to pass. This is accomplished by a float set in the orifice, so shaped that its motion changes the effective area of the orifice. The float movement is transmitted to an arm carried by a horizontal shaft projecting through the casmg, and carrying, at its outer extremity, the recording pencil and indicator pointer. Inlet Fig. 261. Mechanism of Variable Orifice Type of Steam Flow Meter. Some of the instruments used to measure water (see Fig. 257) can also be used to measure steam. In the latter service, however, a condenser must be used so that the steam does not come directly into contact with the internal mechanism of the instrument. In some designs the steam flow meter is combined with other instruments. Fig. 262 consists of a steam flow meter, to record the amount of steam generated ; an air flow meter, to record the amount of air supplied to the furnace ; and a recording thermometer, to record the temperature of the uptake or the escaping chimney gases. All these readings are shown on a single chart. The steam flow is measured by the use of a special orifice, placed between two flanges in the pipe line, and corrugated to form its own gasket. Holes are drilled on either side of the flange in which the orifice is inserted, and are connected with the pressure recording device in the instrument. The air flow part of 5» OPERATION Fig. 262. EKag: rtrlonal View <^ Bailey Boiler Meter showing tz-j-ons and operation of Meter. OPERATION 599 the meter is operated by the difference between pressures in fire box and in smoke box. The flue gas temperature is obtained by the aid of a nitrogen- filled bulb, extending across the path of the gases where they leave the boiler heating surface. The average temperature of all gases is thus obtained, and the condition of the boiler heating surface and baffles can be checked. The record of steam flow is made in red ink, and that of air flow in blue ink. The latter is calibrated so that under ideal conditions the blue and red records coincide on the chart. When the air flow pen reads more than the steam flow, there is an excess of air passing, and when it reads less, the air supply is insufficient ; thus improper conditions can be easily rectified. Weighing Coal T~'HE equipment for this work may be divided into three classes — that for ■*■ weighing the coal received, that for weighing the total amount of coal consumed, and that for weighing the coal consumed by each boiler unit. For checking the amount of coal received at a plant, there are several types of equipment, — track scales, wagon scales, weighing hoppers with hand- operated or automatic scales, conveyor weighers, and coal meters. For de- termining the quantity of coal used each day in a boiler room the same types of weighing or measuring devices can be used, and also the movable weigh- ing hopper or traveling larry equipped with scale. Track scales are set in the car track so that a section of the rails is carried by the scale platform, and the railroad cars can be run upon the plat- form and weighed. The wagon scale is similar. The coal may be handled in small hand-operated industrial cars, automatic railway cars, or cars operated by electricity or a cable system. Track scales can be provided to weigh the coal handled by such cars, and if the amount handled justifies the expense, the scales can automatically record the weight as the car passes over the scale platform without stopping. The recording device of one of these scales consists of a wheel having the numbers in t\'pe on its periphery, and when a lever is moved by the attendant or is tripped automatically as the car passes over the platform, the wheel revolves a distance depending on the weight, and then prints the amount on a tape which is fed irom one roller and wound up on another. The weights of the different loads are thus recorded on the tape, which can be taken off whenever desired. Track scales are also used for overhead tracks, usually of the monorail type. A separate section of rail or rails is supported on the scale beam so that the larries or trolleys carrying the loads can be stopped and weighed, or if an automatic recording scale is installed, the loads can be weighed as they pass over this section of track. Fig. 258 illustrates an automatic receiving scale of 75 tons hourly capac- ity. This type of scale is very satisfactorily adapted to use in those plants where track scales cannot be installed. It operates by the gravity of the coal which must be delivered from some point above the scale, and thus can take its charges from a hopper, bunker, elevator or conveyor and dis- charge into a hopper, chute, conveyor or elevator boot, depending upon the service required and the local conditions of handling. A crusher is necessary to reduce run of mine coal to reasonably uniform sizes for the successful operation of an automatic hopper scale. Where this is not done, or where coal is handled on a belt, bucket or pan conveyor, a conveyor scale is applicable, and is recommended where head room will not admit of a hopper scale. In one type of conveyor scale a section of the conveyor is suspended on a floating platform balanced through a compound leverage system by an iron float in a cylinder of mercury. For varying weights, the float takes up different positions, and its movement offers a direct measure of the actual weight on the floating platform. An integrat- ing device is used to multiply the weight by the speed of the conveyor. 600 Installation of 2500 H. P. of Heine Standard Boilers in the Ridgewood Pumping Station, Brooklyn. X. Y. OPERATION 601 Fig. 258. Richardson Automatic Receiving Scale. Fig. 259. Traveling Weigh Hopper. 6G> TION For keepir.^ i 't devices ordiiiEr'.v e~ The automatic 5:i'e r the boiler fron:; :r " ihe coal after weiffhir.^- :dual from pper ar. ^ . XQ-J, ^ w consist? of s four-wheeled T The truck tz\ reared .:: iz L ;- read -r t: : r --rd. :. r; ?re usually driren by an electr izi'.t'i. 7 t : perator ride? ir. ^ cire :;i- It!: trti :o each boiler. Thes;: :5 ^tiding fr: : t : tr a helical vi: t ?:g. 260. v / ;; f of the amiun: :: iur! uiti ly t^:!; — i_ cica c-i tae :t 1 with ^ guide vane is . „' — V_ U I Fig. 260. Coal Meter of the Heucal Vane Type. When stoker fifed, the amo"".: -f coal used by each boiler nuty be roughly determined by installine rt : ution counters on the stoker shaft With chain grate stolrers the r.p.: I'r.e stoker sprocket must be used in conjunction with the depth :: f.rt : _ L:h of grate to get a rough check on the coal consumption. I: : rir : kers of the Riley, Taylor or Westinghouse type, about 17 t: 1 : f : : :.! : er retort is fed to the furnace with each revolution of the crank sna.il. OPERATION 603 Handling Coal THE handling of coal and ashes resolves itself into the following stages: (1) Unloading of coal as received, either by land or water; (2) Its transfer to bunkers or other storage; (3) Its movement to boilers ready for firing; and (4) Removal and final disposal of ashes. Unloading of Coal. When the plant Is not large enough to warrant a railroad siding the coal is delivered by truck and unloaded by hand. If bottom-dumping cars are available, the coal can be discharged directly into hoppers or into the storage space provided. With water delivery a clam- shell bucket, operated by a locomotive crane or from a tower, can be used to move the fuel from the barge. Methods of Storing Coal. In small plants the coal may be stored in bins, bunkers or piles inside the boiler room ; but in larger plants the quan- tities of coal used each day are so large that the inside bunkers hold only a few days' supply and outside storage is necessary. A convenient storage system often employed is that in which the storage space is adjacent to the boiler room and the whole served by a continuous bucket conveyor. This bucket conveyor runs horizontally in a tunnel beneath the coal storage space and boiler room floor, rises vertically at the far end of the boiler room, returns horizontally on a bridge over the boiler coal bunkers and outside storage space and finally descends at the outer end of the storage pile to the tunnel, thus completely encircling the boiler room and storage, Chutes below the coal storage bin deliver the coal to the Fig. 263. Circular Coal Storage System. o ■rJ CO V C5 O - s -< :/: :z X OPERATE O N 605 buckets, which then carry it up above the boiler bunkers where a tripping device overturns the buckets and discharges the coal to the bunkers. A con- tinuous bucket conveyor installation of this type usually handles ashes as well as coal. The Circular Storage System, Fig. 263, is often used for storing coal for power plant use and is suitable for capacities ranging from 5000 tons up. It consists of a long radius locomotive crane equipped with self-filling bucket, running on a circular track around a central track hopper into which coal is dumped from railroad cars. The coal to be stored is taken from this central pit or hopper by the bucket and delivered to the pile. This system has a handling capacity of from 40 to 250 tons per hour, according to the size of the bucket and crane employed. Rectangular Storage. A few large plants store their coal in a pile spanned by a traveling bridge. The coal is received in hopper bottom railroad cars which discharge into a pit running lengthwise of the pile, from which it is removed b}'^ a grab bucket operated from the bridge and placed on the storage pile. The capacity of a storage of this type is determined by the span of the bridge and length and height of pile. Economical handling capacities of storage systems of this type are from 100 to 300 tons per hour. Submerged Storage. Bituminous coal which is subject to spontaneous combustion is sometimes stored under water. Storage bins for this purpose may be constructed of concrete, the inside surfaces being treated with a waterproofing compound. A 6000 tons submerged storage pit has been con- structed by the Omaha Electric Light and Power Company. The pit is built of concrete with walls 22 ft. high on three sides. The fourth wall is 16 ft. higher and serves as the support for one rail of the crane runway. The other rail is carried by a girder along the side of the power house. Two 50-ton receiving hoppers, also of concrete, are located at the power house end of the submerged storage. The storage and spontaneous combustion of bituminous coal are dis- cussed on page 466. Transfer of Coal from Storage to Boiler Room. Where mechanical storage systems are in use, the transfer of the coal from storage pile to car is accomplished by means of grab buckets operated from locomotive cranes or bridges as described above. However, where mechanical storage systems arc not used, and where storage piles are at some distance from the boiler room, portable loaders are used to transfer the coal from pile to car or wagon. These loaders may be either of the bucket or belt type and may be driven by electric motor or gasoline engine. Coal can be transferred to the boiler bunkers by small hand or power- operated cars, or by a conveyor system. Conveyors may be of several dif- ferent types, the selection depending upon the conditions. Screw Conveyors may be used for horizontally conveying coal of ^/i inch or less, a distance of 100 or 150 ft. The conveyor or screw consists of sections of a stamped or rolled steel helix mounted on hollow steel shafting, carried by hangers. The screw, which is driven by gears or sprockets at one end, revolves in a steel box through which the fuel is conveyed. Scraper or Flight Conveyors may be used for conveying fine sizes of coal horizontally or on inclines up to about 45 degrees. Single strand conveyors of this type consist of a single chain to which are bolted steel flights or plates. Double strand conveyors have the flights suspended from two chains, and are used when the conveyors are long and subjected to heavy service. Either type may be equipped with sliding blocks or rollers. The troughs through which the coal is conveyed are made of steel plate or of wood lined with plates. 606 OPERATION OPERATION 607 Apron Conveyors are often used for conveying coal horizontally or on inclines up to about 30 degrees. Larger sizes of coal may be handled with this type than with screw or flight conveyors. The apron conveyor consists of two strands of roller chain separated by overlapping apron plates with sides from 2 to 6 inches high. These apron plates carry the coal ; and as the coal is carried instead of being dragged, less power is required and m.am- tenance costs are less than with scraper or screw conveyors. Pivoted Bucket Conveyors. Fig. 264, are frequently used in power plants. Their use in handling coal from storage to bunkers is discussed in a previous paragraph. This type of conveyor will handle comparatively large sizes of coal at capacities ranging from 15 to 200 tons per hour. Belt Conveyors will handle coal satisfactorily on horizontal runs or on inclines up to 20 degrees at capacities up to 500 tons per hour. This type of conveyor. Fig, 265, consists of an endless belt driven by suitable pulleys and carried upon idler pulleys so arranged that the "carrying" side of the belt becomes trough-shaped in cross-section. The loaded or carrying side may ua RETUnN lOLCftS Fig. 265. Belt Conveypr. be supported by three or five troughing idlers as may be required, while the empty side is carried on straight return idlers. The idlers are carried bv iron or wooden stands, spaced from 3 to 6 ft. centers on the troughing side, and from 6 to 12 ft. on the return side. The belts generally used consist of plies of cotton duck cemented together with a rubber compound and protected from moisture and abrasion by a rubber cover. Tripping devices placed at the required points discharge the coal from the belt. These trippers are mounted on a carriage and consist essentially of two pulleys, one above and slightly in advance of the other, so that the belt runs over the upper one and under the lower one, thus throwing the coal into a chute on the first down- ward turn of the belt. The trippers may be fixed so that the coal will always discharge at one point, or movable when it is desired to discharge the coal into different bunkers. ]\Iovable trippers may be propelled by a hand-crank or automatically propelled by gearing. Coal Crushers. When coal is handled by screw or scraper conveyors it is necessary to crush the coal down to about ^ inch size. Belt or Inicket conveyors will satisfactorily handle larger sizes. Coal crushers are generally installed beneath or adjacent to the receiving hoppers, see Fig. 263. A type of crusher satisfactory for reducing run of mine bituminous coal to a size suitable for stoker use, consists of two rolls provided with solid cast steel or renewable steel teeth. The rolls are mounted in a heavy frame and are gear driven. Relief spring bearings are provided for one of the rolls, so that they may separate in case tramp iron enters the crusher. 608 OPERATION Coal Bunkers are generally overhead when mechanical coal handling systems and stokers are installed. Usually, overhead bunkers should hold not less than one day's supply of coal. In large stations where there are no facilities for outside storage, the overhead bunkers may hold as much as a ten days' supply. Coal bunkers ma}'- be arranged so that each boiler or each batter> has its individual bunker, or there may be one continuous bunker for all the boilers. Catenary, parabolic and V-shaped bunkers are generally of the con- tinuous type. The angle of repose of coal varies from 35 to 40 degrees ; but due to convenience in fabricating, the 45 degrees slope is generally used for hopper bottoms. Overhead bunkers may be constructed of unlined steel plate, of structural steel lined with concrete or of reinforced concrete- Down spouts with a shut-off gate convey the coal from the bunkers to the firing floor or the stoker hoppers. Where overhead bunkers are not installed immediately over the boiler, traveling larries, Fig. 258, or traveling buckets, carry the coal from the distributing bunker or coal storage to the boiler fronts. Ash Handling Systems IN all boilers the ashes are either raked out onto the firing floors or are dropped into ash pits. The design and construction of ash pits of different types of boiler settings is discussed in Chapter 4 on FURNACES AND SET- TINGS. The pits often discharge into small push or electric cars, which carry the ashes to a conveyor or elevator system, from which they are carried to the ash bunkers. The coal handling system is used sometimes for carrying ashes, although it is considered that the two should be separated, because of the abrasive action of the ashes. When the systems are combined, the pivoted-bucket conveyor has the advantage that the parts can be replaced easily as they wear or corrode. The bucket and chain elevator, with rigid buckets, is a common method of elevating ashes. The ashes are fed into a boot forming the bottom part of the elevator, arc scooped up by the buckets and carried inside a casing to the top of the elevator, where they are discharged into a spout leading to the point of disposal. This may be an ash bunker, a truck or a railroad car. The skip hoist is another well known method of ash removal ; it con- sists of a bucket running on inclined or vertical tracks, and hoisted by a steel cable attached to a motor-driven winding machine. The bucket and chain elevator is recommended for small plants, where the lift is 40 ft. or less. For larger plants the skip hoist is said to have the advantages of simplicity, low power consumption, and ability to handle the large clinkers often produced by forced draft stokers at high overloads. Pneumatic Ash Conveyors. These consist primarily of a pipe through which a current of rapidly moving air carries the ashes to any desired point. Inlets to receive the ashes, consist of tees which are plugged when net in use ; and are provided wherever convenient, such as in front of the ashpits. The conveyor may discharge onto the ground or into a hopper from which cars and wagons may be filled. The commencement of the pipe should have an open end, so that there is an ample flow of air along the pipe at the first ash inlet. In vacuum conveyors, a vacuum is produced in a closed tank, either by means of a motor-driven or a steam jet exhauster. When steam-jets are used, they may either be arranged to exhaust from a hopper as just described, or may be introduced at some point or points after the last inlet, generally at a bend in the conveyor pipe. Steam-jet conveyors may either discharge into the open or into vented tanks. OPERATION 609 Since the ash travels at a high velocity, the abrasive action is considerable, especially at changes of direction. Therefore, bends are provided with easily replaceable "wearing-backs,'" and the ash is generally discharged against some form of target to protect the hopper wall. Fig. 266 shows one end of the boiler room of No. 2 plant of the Heine Company. The inlets of the ash conveyor are flush with the firing Hoor, and offer no impediment when closed. The ashes are removed very rapidly and the boiler room is kept free from dust and dirt. Fig. 266. Detrick-Hagan Steam- Jet Ash Conveyor. With hopper ashpits, the conveyor pipe may be laid on the basement floor or hung from the underside of the firing floor as is most convenient. Connections may also be made to the combustion chambers. Clinkers should be broken up and ashes and dust should be dry when fed to the conveyor to avoid clogging, particularly at bends. Water sprays are frequently placed in the conveyor pipe near the discharge end, or in the ash tank. Steam-jet conveyors are less noisy than vacuum systems with a steam- jet exhauster drawing from the ash tank. It is difficult to muffle these latter, owing to the abrasive or "sandblast" action of the fine dust quickly perforating metal baffles. Flumes. In some plants where there is a plentiful supply of water, flumes are constructed beneath the boiler setting, into which the stokers discharge their refuse. A stream of water flowing through the flume washes the ashes into a pit from which an elevator discharges them to a railroad car or wagon. 610 OPERATION The ash bins used with mechanical conveying sj^stems may be made of steel, concrete-lined, or of concrete on a steel skeleton. On account of the corrosive action of the wet ashes, concrete or brick bins are often used. They should be ventilated to prevent gas explosions. The discharge is from the bottom to wagons or railroad cars. Handling of Fuel Oil HPHE use of fuel oil requires special provisions for storage. While a -^ gravity sj^stem of boiler feed is sometimes permissible in small plants or in places where large outdoor areas are available for the location of distant tanks, the usual practice is to place properly vented cylindrical steel tanks under ground or at least below the level of the furnace. The arrangement adopted is governed in most instances by local and insurance regulations. The use of a continuous circulating system, that is, with the surplus oil returned to the tank by means of a release valve or by the use of a stand- pipe, prevents choking, and is especially important with highly viscous oils. The pumps, which are preferably installed in duplicate to protect against in- terruption of service, can be either rotary or reciprocating, although the former insures a more even pressure. Live or exhaust steam heaters are ordinarily used in the pressure line, with additional coils in the storage tank if very heavy oils are used. Some satisfactory systems for handling fuel oil are the Rogers-Higgins, Staples and Pfeifcr, Koerting, Coeii and Moore. Fig. 267, illustrating a Rogers-Higgins Oil System, shows the general principles involved. One of two duplex oil pumps, mounted on an exhaust steam heater, serves to draw the fuel from the storage tank and to force it through the heater and strainer to the burners in front of the furnace, where it is atomized by steam. The relief valve above the heater carries back the excess oil to the tank by a separate line. Venfl/ne-,^ ---Spiral Heater Coil Oil Suction-' Fig. 267. Diagram of Typical Oil Handling Installation. A detailed illustration of the oil pump and heater is shown in Fig. 51, on page 125. Cleaning Boilers THE successful and efficient operation of a boiler demands that the heat- ing surface be clean both externally and internally. External cleaning of the Heine boiler by means of an efficient mechanical soot blowing system has been discussed in Chapter 1 on HEINE PRACTICE. In water tube OPERATION 611 boilers, the waterlegs of which are not equipped with hollow staybolts, or in vertically baffled boilers, the external heating surface is cleaned with a hand lance, or the "rotating element" type of mechanical soot blower. If boilers are to be stored out in the weather for even short periods, the exterior surfaces should be protected with a good grade of red lead or black paint. To remove the grease and oil which remain from the operation of manu- facture, new boilers should be boiled out twice over, with a charge of 2 to 5 lb. of soda ash each time. The effect of scale on heat transmission has been discussed in Chapter 14 on FEED WATER. It is obvious that the preferable way to keep internal heating surfaces clean is to avoid scale formation by proper treat- ment of the water before it is fed to the boiler. However, all boiler plants are not equipped with water treating systems ; and often, under bad water conditions, it is not possible to purge the water of scale-forming materials entirely even with chemical treatment. Hence all boilers are subject in a greater or lesser degree to scale formation. When scale has once formed on the heating surface, it is usual to remove it by washing out or by turbining. If chemical compounds are used, care must be taken to see that the resulting mud or sludge is blown off, as otherwise there is a tendency for it to lodge again on the heating surface and cause bagged or blistered tubes. Where the scale is of a very soft nature, or where mud deposits on the tubes without baking, the heating surface may be effectively cleaned by washing out with water. But where the scale is hard, turbining is necessary. There are several types of turbine tube cleaners on the market, the most satisfactory of which is the water turbine. This, as Fig. 268, usually con- sists of a cylindrical casing containing a small hydraulic turbine, with the necessary guide plate and turbine wheel. On an extension of the turbine Fig. 268. Roto Tube Cleaner. shaft arms are mounted to which cutters are attached. These arms revolve at high speed and the cutters bearing upon the scale, chip it off the tube in small pieces. The stream of water flowing from the turbine envelopes the cutters, keeps their edges cool, and washes away the scale as it is loosened. It is not advisable to operate turbine tube cleaners by steam, because the hot steam exhausting through the tube heats it and causes it to expand to a greater length than its cool companions, and this tends to loosen the tube expansion in the waterleg, resultmg in leaks. Hammer type mechanical tube cleaners, in which the scale is loosened by a series of rapid hammer blows, are applicable to either water tube or fire tube boilers, but are more generally used for the latter. Care must be taken that they are not kept at work in one spot for any length of time, as this tends to weaken the tubes by peening bags on them. Both hammer and turbine types may be operated by water, steam or com- pressed air. 612 (U o • ^H o o «) OQ -a CO u u OS fe G C 05 CO 4-1 xn w CO *v u OJ TJ (U .S c •^ JO 13 > pq (U -d j:: Ui +-> CO ■$ CO -d c tu a CO +-> C/2 a '9 CO 2 .s G "5 o" »-H ^ o C :3 CO -d (U a .s ■4-* .9" *o fH 3 c a* iT CO O a. 6 tj .» c ^ >> CO t-c o o ^ CO CO ffi c CO S 4-» W o CO +J -o CO CO c 3 (U CO U CO O CO ffi ■M CO g m o 'O CO (U 3 _-M u 'H D OPERATION 613 Renewing Tubes OLD tubes can be removed readily by collapsing the ends of the tube with a cold chisel and hammer; but care must be taken not to injure the seat in the tube hole. When the new tube is in position for expanding, the ends should not pro- ject through the tube sheet more than "Ae nor less than ^Ae inch. There are two types of tube expanders in use, known as the Prosser and the Dudgeon. The Prosser type, which finds favor in locomotive practice, consists of a number of steel segments held together by a rubber or spring steel ring. These segments are of such a size that when the expander is collapsed, it is of smaller size than the bore of the tube, so that it may be inserted easily. The segments surround a tapered steel mandrel, by driving which the seg- ments are separated and bear against the tube. By gradually driving in the mandrel, slacking and turning the tool and driving again, the tube is expanded into its seat in the tube sheet. The Dudgeon expander, which is widely used in stationary water tube practice, expands the tube by the continuous pressure of steel rollers turning inside the tube. This type of expander, Fig. 269, consists of a hollow cylin- der, with three or more slots in which are steel rollers. A tapered steel mandrel is inserted through a central hole in the cylinder and l3ears upon the rolls. By revolving the expander and driving the mandrel, the rolls are forced outward as they rotate, thus expanding the tube. This expander can be either hand or power operated. Fig. 269. Henderer-Ferguson Self-Feed Roller Tube Expander. After expanding the tube into its seat in the tube sheet, the tube is slightly flared. Flaring can be done with a so-called "'belling" tool or by using the Dudgeon expander with one steeply tapered roll substituted for a straight roll. The tubes in water-tube boilers are seldom beaded. When desired this may be done with a beading tool or "boot." Care of Idle Boilers IF a boiler is to be out of service for three or four months it should be cleaned thoroughly both internally and externally, by washing out, turbin- ing and soot blowing. It should then be filled up with water, to which 100 or 150 lbs. of soda ash have been added. A slow fire should then be maintained until all air has been expelled from the boiler, after which the boiler should be pumped full and closed up tightly. If the stack is located directly above the boiler, the stack top should be covered, or the lioiler surface so protected that rain cannot reach it. If the boiler is to be idle for longer than three or four months, it should be emptied, turbined, waslied out, left open to dry, and brushed witli a scraper or stiff wire brush. A tray of quicklime should then be placed inside the drum and the boiler closed up tightly. 614 OPERATION Some engineers, before empt}-ing a boiler that is to be laid up. place several gallons of crude oil in the shell, so that when the blow-off or drain is opened and the water let out. the oil will form a protecting film on the internal heating surface. If this method is used, the boiler must be thor- oughly boiled out with soda ash before again being placed in service, so that all traces of oil may be removed. "Cutting-In" Boilers TO "cut-in" a boiler or to put it ■'"on the hne" after it has been out of service, is to place it in free communication with other boilers that are under steam. In cutting in a boiler that has been idle, the stop-valve should be kept closed until the steam pressure in the boiler has risen to the exact value that is prevailing at the time in the steam main to which the boiler is to be connected. It is not sufficient to bring the pressure to within a few pounds of that in the main. Practice of this kind should not be tolerated, for it is exceedingly important that the equality- should be as exact as the engineer can make it b}' the aid of his pressure gages. Then, when the equality' is apparently exact, the main stop-valve should be opened very slowly and carefully. It should be opened by a mere crack at first, because it will be impossible by means of commercial steam-gages to judge the equalitv- of the pressure so closely that there will be no flow of steam in either direction. The object of opening the valve slowly is to permit the small outstanding difference of pressure to become equalized ver>' g^adnall^^ If there is an}- evidence of disturbance in the boiler or the piping, as indicated by snapping or pounding, or by abnormal vibration of the boiler, the stop- valve should be immediately closed again. It is safer to have tlie pressure in the boiler that is to be cut in. a little higher than that in the steam main, rather than to have it a little lower, because steam will then flow from the boiler out into the main instead of in the opposite direction. Having the pressure in the boiler exceed that in the main, however, is not recommended. It is far better to have the two exactly equal. Boiler Inspection THERE are many engineers who believe that boiler inspection is solely the concern of the state or insurance boiler inspector. This attitude is not even justified from the consideration of safety only; and it is certainly not justified when successful and efficient operation is considered. The engineer should not only go over the boiler with the inspector at the time of his rather infrequent visits, but should also make it a point to inspect the boiler at intervals of a month or two. The inspection of the Heine water tube boiler will be discussed here, although the methods of procedure in the case of other types will be somewhat the same. Before making the actual inspection, the engineer will find it to his ad- vantage to have a blue print of the boiler and setting so that he may check an}' unusual condition by reference to the print. He will find it necessary' to have with him a six-foot rule, a pair of calipers, a stick of chalk, and a pencil and note book. An electric light in a guard on an extension cord is a desirable part of his equipment, though in lieu of this, a pocket flashlight, kerosene torch or candle may be used to furnish light. A mason's hammer is a desirable tool to carry, as it can be used for tapping tubes, rivets, etc., and also for chipping scale from the heating surface, clinker from the out- side of the tubes, etc. Inspection of the boiler must be both external and internal. External inspection covers the outside of the setting, the inside of the furnace, and the exterior of the tubes, waterlegs and shells, while interior inspection refers to the examination of the interior side of the boiler heating surface. OPERATION 615 In general, it Is most convenient to make the external examination first, for during this part of the work'i a helper may be knocking in man hole covers, removing hand hole plates and making ready for internal inspection. External Inspection. When examining the exterior of the setting, the condition of the brick work should be noted. Cracks and loose bricks should be pointed up to prevent air leakage. Inspection doors, fire doors, and ash doors should fit tightly. Buckstays should be close to the brick v^ork or they are not properly supporting the walls, which is their only function. Entering the furnace, the grates or stoker parts should be examined. Warped or burned grate bars or defective stoker parts should be renewed. That part of the furnace brick work subjected to the highest furnace tem- peratures should be carefully examined, particularly with reference to erosion or to excessive building up of clinker accumulations. Note whether or not the brickwork protecting the bottoms of the front and rear waterlegs is intact, as these parts should not be exposed to the direct action of flame. Scrape the soot and clinker down from the lower baffle and renew such tile as are faulty. By holding the light between the rows of tubes near each waterleg, look for evidence of leaky tube expansions or leaky staybolts. If any are evident, make note of the location by counting the row up from the bottom and over from one side, and record the same in the note book. Enter the setting above the tubes, and drop the light down between the rows of tubes near the waterleg and look for evidences of leaky expansions as was done from below. Note also the condition of the soot blower ele- ments, which should extend at least ^4 J"- and preferably >^ in. through the waterleg. If any are burned off flush with the waterleg they should be replaced, as the effectiveness of the blast is lessened and erosion of the staybolt is liable to result. Look for any soot accumulations which seem to indicate that the soot blowers are not effective in cleaning certain portions of the heating surface. Examine the upper baffle and make note of any tile replacements needed. Inspect the riveted throat connections and shell joints, looking for incrustations which may be evidence of leaks. Look carefully for external corrosion, such as thinning of tubes, and for commencement of cracks near joints in the sheets. Have the helper work the damper rigging and note the operation of the damper. This completes the external inspec- tion of the boiler. Internal Inshection. Before making the internal inspection of the boiler BE SURE that : (1) The main stop valve is tightly closed. (2) The automatic non-return valve is screwed down. (3) The blow-off valves are closed. (4) The feed water valves are closed. (5) The water tender or firemen know you are in the boiler. Upon entering the drum, note the thickness or character of the scale deposits, and look for evidences of oil along the water line. Chip away the scale at every seam, note the condition of the rivet heads and look for evidences of corrosion or grooving. Examine the throat stays, and by holding the light down into the waterleg, note the condition of the staybolts. In- spect the dry pipe, deflection plate and mud drum, and see that they are held securely in position. Examine the connections to the water column and see that the pipes are clear. Examine the staybolts in the waterleg. Tap them with the hammer to see if they are tight. Examine the hand hole cap seats, noting whether any are cut or grooved, or whether gaskets are sticking. Have a helper hold a light at one end of each tube while you examine the tube from the other end. Look for piles of loose scale, which, unless removed, may lodge in the tube and cause a bag or blister. Note character and thickness of scale. 616 OPERATION After the boiler and furnace have been inspected, the steam gage should be calibrated and the water column, blow-off piping and valves should be examined. If the safety valves have been repaired or reground, they will have to be reset by a responsible operator after the boiler is fired up. A report should be made after each inspection and filed for future reference. The report will make possible a comparison of the condition of the boiler at any time with its condition at former inspections ; and wiU also indicate any repairs that are liable to be needed at the next shut-down, so that the material may be ordered and be on hand when wanted, thus prevent- ing unnecessary delay. Cost of Generating Steam "pVERY power plant is a business in itself, whether it be a large central -^ station or a small isolated plant ; and as a business, its records should be kept in such a manner that the cost of producing power is known. The object of keeping records is not only to allocate charges for deter- mining a fair cost or selling price of the power ; but also to enable the plant manager to compare station performance from time to time, and the engineer to analyze the various records with a view of reducing all losses to a mini- mum. Different methods of cost accounting are applicable to dift"erent types of power plants. A public utilit}* corporation, which not only generates power, but distributes its product over a wide area, will of necessity employ a differ- ent cost keeping method than a manufacturing plant which uses its steam for power, lighting, industrial cooking, etc. Many states require that pubhc utility corporations submit annual statements on printed forms provided by the state, and this governs the method of cost accounting to be followed in such instances. But the owner of a private plant is free to use his own method of cost keeping, and the following general methods of accounting the cost of generating steam have been outlined for such cases. Power plant costs usually include the total cost of power production, with no subdivision of cost into boiler room and engine room expense. For example, the labor item is seldom subdivided so as to cover the various duties it performs ; yet the necessity of these operations being performed creates the expense, and unless it is known how much labor is required to perform them, the magnitude and cause of the expense is only approximate. The cost of generating steam is the largest factor in power cost, and hence it is essential for intelligent management that this cost be kept separate from engine room and distribution expenses. Costs can be divided into three general classes: (1) overhead or fixed charges, (2) operating costs and (3) maintenance costs. Overhead Charges Overhead or fixed charges may include : Interest on Investment Taxes Depreciation Insurance Rent Management Interest on Investment. Expert accountants are not in agreement as to the propriety of including this item. It is contended that interest forms part of profit, and if included in overhead cost it is virtually charged twice over. But in comparing competing equipment, interest on the cost at prevailing rates for borrowing money should be considered, so as to make the compari- son a fair one. Depreciation may be classified as: (1) physical depreciation and (2) functional depreciation or obsolescence. OPERATION 617 Physical depreciation is defined as the decrease in value of equipment due to age or wear and tear in service, while functional depreciation means the decrease in value of equipment due to its becoming unsuitable for use or out of date before the end of its estimated life. It is obvious that the rate of physical depreciation can be lessened by increasing the life of apparatus by repairs and proper maintenance. There is considerable disagreement between engineers and between ac- countants as to the proper method of computing depreciation charges. Probably the most commonly used is the straight-line method which is based upon the assumption that if the investment, less the salvage value, is divided by the life of the equipment, the resulting quotient expresses the amount which should be allowed each year to cover the accrued depreciation. Fre- quently the salvage value is not taken into consideration, as being more conservative. Rental. A proportion of the rent paid for land and buildings should be included in overhead charges, unless these are owned by the concern. Taxes. The location of the plant governs this item, which may range from 0.1 per cent to 2.5 per cent on the assessed valuation of the equipment. Insurance may include fire, employers' liability and boiler insurance ; the amount being charged to the cost of steam generation, being pro rated to suit the particular plant conditions. Management Cost is very frequently included in the overhead charges, and as such may include a proportion of the following : Manager's Time Office Maintenance Chief Engineer's Time Restaurant Drafting Room Care of Grounds Ofifice Help Miscellaneous Operating Costs Boiler room operating" costs include botli labor and material, wliich may be enumerated as follows : Fuel Water Lubricants Materials ( Miscellaneous Tools Water Softening Chemicals or Boiler Compounds Rags and Waste Miscellaneous Coal Unloading and Ilandling Feeding Stokers or Furnaces Tending Water Cleaning Fire Side of Boilers Cleaning Water Side of Boilers Labor < Cleaning Economizer Cleaning Feed Water Heaters Cleaning Boiler Room Ash Handling and Disposal Testing Boilers Miscellaneous 618 OPERATION Fuel is the largest single item of expense in boiler room operation, and therefore any saving effected in its use is readily noted on the cost sheet. Labor is the next highest cost of operation. By keeping careful record of the distribution of labor in the boiler room, operating costs in this regard can be kept down to the minimum necessar}^ for the efficient handling of the equipment. An}* undue labor cost in the items enumerated above wUl also serve to indicate the advisability of installing more efficient apparatus or labor saving machinery. Maintenance Costs Boiler room maintenance costs also include both labor and material. In some respects the line drawn between maintenance costs and operating costs is a line one ; though, in general, maintenance is understood to refer to the labor and material cost on repairs to : Superheaters Feed Water Heaters Water Softeners Pumps and Injectors Buildings Stacks and Breechings Coal Handling Machinery Ash Handling ^^lachinery Stokers and Furnaces Fans and Ducts Motors and Stoker Engines Boilers and Settings Economizers Piping, Valves, Traps, Pipe Covering Tools Instruments Miscellaneous Maintenance costs tend to increase with the age of equipment. While operating costs are low^ered by the installation of labor saving machinery, maintenance costs are slightlv increased. Four 315 H. P. Heine Standard Boilers set over Jones Underfeed Stokers in the Hamilton County Court House, Cincinnati, Ohio. 619 INDEX A.S.M.E., boiler construction code, 49 A.S.M.E., boiler testing rules, 513 Absolute temperature, 370 zero of temperature, 370 Accounts of steam generation cost, 616 Acidity of water, see Water Adiabatic expansion, 407 Peahody's diagram, 415 Air admission of secondary, 90 carbon dioxide excess and, 572 inleakage of, and, 573 combustion actual required, 397 theoretical required, 394 composition of, 390 cooled furnace blocks, 151 cooling firebrick walls, 151 currents and insulation, 361 excess, and weight of gases, 179 gas weight and excess, 179 heaters, 339 air pressure loss in, 339 humidity, 537 leakage, draft ducts, 236 settings, 153, 577 moisture in, 539 removal in feed water heaters, 329 required per pound of coal, 395 per 10,000 B.t.u., 189 with forced draft, 227 space, grates, 58, 97 setting walls, 145 specific heat, 403 water vapor and, weight of, 401 weight, 182 saturated, 540 volume and, 400 Alberger water meter, 589 Alcohol thermometers, 373 Analyses, coal, 440 Analysis. ash, 457 coal, 450 fuel, 450 gas, 532 conversion of volumetric, 543 Analysis — Continued gas — Continued weight of flue gases and, 179 Anthracite, 436 briquets, 470 cleaning fires, 568 firing low volatile, 563 forced draft and small, 562 free burning, 563 fuel bed thickness, 566 furnace for hand firing, 95 grate bars, 97 hand firing, 562 heating surface ratios, 562 high setting, 96 setting for hand firing, 95 sizes, 443 specific gravity, 436 Arches construction, 153 flat, 153 smoke and deflection, 93 Asbestos, 355 cement for boiler walls, 367 coating for settings, 157 conductivity, 353 heat resistance, 357 Ash, 457 analysis, 457 bins, 610 boiler testing, 536 coal, in evaporation and, 459 heat value and, 458 reducing, 458 combustible in, loss, 545 composition, 457 conveyors, 608 flume, 609 pneumatic, 608 steam jet, 608 vacuum, 608 determination, coal analysis, 451 effect on firebrick, 151 elevators, 608 fusibility in U. S. coals, 463 fusion, 461 Illinois coal, 462 Indiana coal, 462 handling, 608 hoists, 608 Ashpits, 107 capacity, 107 620 I X D E X Ashpits — Continued combustion in, 111 doors, 111 hand firing. 107, 109 hopper, 109 large capacit}', 109 leaky doors. 111 Hning of hopper, 111 side feed stokers, 109 valves, HI Atmosphere, composition of, 390 Atomic weights, 350 Atomizing oil fuel, 119 Auxiliaries exhaust to feed heaters, 326 regulation of exhaust to feed heater, 326 steam used by, 423, 547 Auxiliary engines, 341 fuel bed for blast furnace gas, 129 turbines, 341 B Badger expansion joint, 290 Baffles, deflecting, in flues, 217 divided pass, 65 flues, in, 217 forming furnace roof, 65 soot blowers and, 65 tight, keeping, 65 tiles, 66 Baffling, 59 boiler efficienc}- and, 63 chimney temperature and. 63 draft loss and, 62 exit gas temperature and, 63 extinguishing action with vertical, 93 flue gas temperature and, 63 furnace temperature and. 87 head room for vertical, 91 Heine boilers, 27 smoke and horizontal. S7 stack temperature and, 61 vertical, and head room, 91 waste heat boilers, 141 Bagasse burning, 137 composition, 477 grate bars for, 99 grates. 137 heat value, 475 Bailey boiler meter, 598 Balanced draft, 584 Banked fires, 568 fuel consumption by, 568 quick steaming from, 568 Bark, see Tan bark Barometer boiler testing and. 536 chimneys and height of, 173, 192 Bends, expansion pipe, 287 Best Calorex oil burner, 121 Birkholz-Terheck gas burner, 130 Bituminous coal, see Coal, bituminous Blast furnace gas, 128 boiler setting, 128 burners, 130 burning. 128 comoosition, 483 dust; 129 explosions, 129 heat valucj 483 igniting grate, 129 Blow down of safetv valves, 554 Blowins: soot, 39. 4L 610 Blow-off piping, 275 valves, 274, 560 Boiler, capacity and economy, 66 circulation. 66, 568 Heine, 35, 43 quick steaming and. 568 compounds, 510 construction, A. S. M. E. code. 49 drums, heat insulation of, 157 efficiency-, 546 baffling and, 63 carbon dioxide and. 572 characteristics, 66 clinker and, 461 superheating and, 69 with two stokers, 105 feeding, see Centrifugal boiler feed pumps Feed pumps Feed water heaters In lectors Water fittings. 551 Heine cross drum, 43 horsepower, 55 inspection. 614 precautions, 615 report, 616 operation, economical, 584 under *"test conditions."' 585 waste heat, 142 plant depreciation, 616 rating. 5S room basement, 110 settings. 85 air leakage. 153 air leakage and CO2. 573 air leakage, curing. 577 air leakage, prevention, 157 air leakage, testing for, 577 INDEX 621 Boiler — Continued settings — Continued air space in walls. 145 air-tight, for waste heat, 142 anchor rods, 148 anthracite, 95 arches in, 153 asbestos coating, 157 bagasse, 137 blast furnace gas, 128 brick required for, 147 brickwork, 145 buckstays, 148 cargo boats, 143 chain grate stokers, 100 classification, 92 concrete, 147 down draft, 95, 100 draft loss. 186 dredge boat, 143 fireclay mortar, 147 foundations, 145 front feed stokers, 101 gas burning, 127 glazed brick, 156 high smokeless, 91 insulating, 155 insulating brick, 155 magnesia coating, 157 marine, 143 oil burning, 117 over feed stokers, 101 powdered coal. 111 radiation, 153 refuse burning, 133 shavings, 134 side feed stokers, 100 smokeless, 93 steel casing, 156 stokers, 100 stokers, two, 105 tie rods, 148 underfeed stokers, 103 walls, 145 wall ties, 155 waste heat, 139 wood chips, 134 wood chips and coal, 134 specifications, standard, 49 testing, 513 accuracy, 515, 547 air temperature, 531 ashes and refuse, 536 ashes, combustible in, 545 barometer, 536 calculating heat balance, 542 calculating simple test, 528 calorimeter, Carpenter, 522 calorimeter, coal, 455 calorimeter, gas, 482 calorimeter, Junker, 482 calorimeter, Mahler, 455 Boiler — Continued testing — Continued calorimeter, Peabody, 518 calorimeter, separatmg, 522 calorimeter, throttling, 518 carbon monoxide loss, 545 Carpenter calorimeter, 522 chart, 526 coal sampling, 517 coal weighing, 517 condition of boiler, 515 data required, 515 draft gages, 536, 579 efficiency, boiler, 546 efficiency, furnace, 546 efficiency, overall, 546 errors, 547 exit gas temperature, 529 factor for moisture in steam, 528 factor of evaporation, 528 feed water temperature, 517 feed water weighing, 515 flue gas analysis, 531 flue gas heat loss, 543 flue gas temperature, 529 furnace temperature, 536 gas analysis, 532 gas analysis apparatus, 532 gas analysis, conversion, 543 gas sampling continuous, 532 gas sampling tubes, 531 gaseous fuel, 550 guarantee tolerance, 547 hand firing, 523 heat balance example, 546 heat balance form, 541 heat losses, 542 Hempel apparatus, 535 humidity of air, 536 humidity tables, 537 hydrocarbon loss, 546 hydrogen loss, 543, 546 leakage of water, 516 liquid fuel, 550 log book. 526 losses unaccounted for, 546 mechanical stokers, 525 moisture in air, 536, 539 moisture in air, loss by, 545 moisture in coal, loss by, 542 moisture in steam, 518 observations, 525 Orsat apparatus, 532 Orsat operation, 533 Peabody calorimeter, 518 personnel, 513 radiation loss, 546 records, 525 report of complete test. 540 report of simple test, 526 sampling" coal, 517 sampling gas, 531 622 INDEX Boiler — Continued testing — Continued sampling steam, 323 separating calorimeter, 522 starting and stopping, 523 steam pressure, 518 steam quality, 518 steam tables, 523 superheated steam, 523 temperature of air, 531 temperature of feed water, 517 temperature of flue gases. 529 temperature of furnace, 536 throttling calorimeter, 518 unaccounted for losses, 546 water gages, 516 water meters, 516, 587 weighing coal. 517 weighing feed water, 515 weighing scales, 517 weight of gases. 543 the first Heine, 52 tubes, conductivity. 383 wall insulation. 367 water gages. 516, 551 with two stokers, 105 Boilers, air-tight settings for waste heat, 142 baftling, 59 waste heat, 141 blowing soot. 610 Heine, 39, 41 cleaning, 610 Heine, 21, 39, 41, 43 convection and heat transfer. 385 in waste heat, 141 corrosion in marine, 49 "cutting in." 614 dead gas pockets. 59 draft loss, 62, 186 waste heat, 142 dusting. 610 dust in waste heat, 142 fans for waste heat. 142 feed water heating in Heine, 35, 45 gas pockets in, 59 heat transfer, 389 waste heat, 141 Heine cross dnim, 43 longitudinal drum. 23 marine, 47 high draft loss, 142 high eas velocit>', 141 idle, 613 stand-by. 568 _ _ steam separation in Heine, 35, 43 temperature drop in, 389 waste heat. 139 water purification in Heine, 19, 35, 45 zinc plates in marine, 49 Boiling point of water at different pres- sures, 500 Bomb calorimeter, 455 Bonnot powdered coal system, 112 Bourdon pressure gage, hhh BradshaiL'-Fraser gas burner, 131 Brady {Harrington) stoker, 168 Breechings, 214 arrangement, 219 baffles in, 217 cleaning doors, 217 construction, 217 design, 215 draft loss through, 187 example of, 218 insulation, 220, 367 size of, 214 Brick arches, 153 boiler settings, glazed, 156 insulating, 155 vitritied, 156 chimnevs, 201 hre. 148 plastic fire, 152 Bricks, number of, for settings. 147 Brickwork boiler settings, 145 smokeless combustion, 85 Bridgewall " cleaning table, 567 gas passage area over, 93 British thermal unit, 378 Briquets, 469 anthracite 470 carbocoal, 471 lignite, 471 peat, 471 weight of. 466 Buckstays, 148 Bunkers, coal, 608 Burners. gas, 128 oil, 119 powdered coal, 116 tar, 125 Burning superheaters. 76, 555 Buying fuels under contract, 486 C Calibrating p3Tometers, 370 thermometers, 370. 373 water meters. 516 California oil. heat value. 479 Calorex oil burner, 121 • Calorimeter. bomb. 455 Carpenter separating, 522 coal. 455 formula for throttling, 521 INDEX 623 Calorimeter — Continued gas, 482 Junker gas, 482 Mahler bomb, 455 Peahody steam, 518 separating, 522 steam connection, 523 throttling, 518 Campbell's coal classification, 437 Cannel coal, 437 Carbocoal briquets, 471 Carbon combustion data, 393 determination in coal, 451, 453 Carbon dioxide boiler efficiency and, 572 careless firing and, 572 excess air and, 572 desirable percentage, 572 dirty fires and, 575 leaky settings and, 573 recorders, 577 specific heat of, 403 weight of flue gases and, 179, 543 Carbon monoxide combustion data, 393 heat loss due to, 545, 577 recorders, 578 specific heat, 403 Carpenter calorimeter, 522 Cast iron, effect of heat on, 97, 252 for grates, 96 strength of, 97, 271 superheated steam and, 83 Cast steel and superheated steam, 83 Caustic embrittlement, 511 Causticity of feed water, 503. 505 Celsius temperature scale, 369 Cement, plastic fireclay, 152 settings coated with asbestos, 157 Centigrade temperature scale, 370 Centrifugal boiler feed pumps, 302 capacity, 305 characteristics, 303 DeLaval, 306 efficiency, 305 horsepower, 305 hot water capacity. 318 Lea-Court enay, 307 motor-driven, 313 regulating. 313 single-stage, 306 turbine driven, 305, 345 with low-pressure economizer, 306 Check valves, 274 Chimneys, 173 anthracite, 173 . at altitudes, 192 Chimneys — Continued B.H.P. and draft table, 176 baffles in, 217 brick, ladders on, 206 lining for, 205 radial, 201 capacity table, 176 characteristics, 177 cinders, discharging, 207, 208, 240, 572 cleaning doors, 195, 207 coal burned, weight of, 185 coal burning, anthracite, 173 western, 184 concrete, 207 design of, 209 erection of, 210 connections for flues, 214 induced draft fans, 241 cost by height, 173 defective, strengthening. 214 deflectors in, 217 draft capacity and. 181 H.P. and, table, 176 losses tabulated, 187 loss in, 182 required. 187 evase, 191 examples, 184 flue openings in, 214, 241 foundations, 193 sizes, 194 gas basis, design on, 189 gas burning. 190 gases, heat of fuel in, 334, 543 weight of. 182, 543 guyed steel. 197 H.P. and draft table, 176 height, anthracite, 173 cost and, 173 economical, 173 highest, 173, 216 concrete, 211 joints in steel, 200 ladders, brick, 206 _ steel, 195 lightning rods, 206 lining, brick, 205 steel, 195 municipal refuse, 191 oil burning. 189 power plant typical, 184 pressure of wind, 193 624 INDEX Chimneys — Continued radial brick, 201 refuse, municipal, 191 reinforced concrete, 207 reinforcing old brick, 213 remodeling, 214 self-supporting steel. 194 soot collectors in, 207 steel, guyed, 197 joints in, 200 ladders on, 195 lining for, 195 self-supporting, 194 strengthening defective, 214 stoker firing. 1S4 table, draft and H.P., 176 temperature, drop in, 174 gases, average. 181 topical power plant, 184 velocity- of gases in, 189 venturi. 191 wind pressure on, 193 wood burning, 191 Cinder separating fans, 237, 572 Cinders from chimnej-s. 572 Circulation, see Boiler circulation Cleaning boilers, see Boilers, cleaning coal, 458 fires, 567 anthracite. 568 COs and. 575 table, 567 Cleveland stoker, 159 Clinker, 459 adherence, 151 avoiding, 466 boiler efficiencv and, 461 hard, 459 Illinois coal. 462 Indiana coal. 462 soft. 461 sticking, 151 U. S, coals, 463 Coal, air required, 395 per 10,000 B.t.u., 189 analyses, 440 analysis, 450 statements, 450 anthracite, 436 ash, and heat value of, 458 fusibilitj.-. 463 reduction in. 458 bituminous, 436 fuel bed thickness, 566 hand firing, 560 briquets. 469 Coal — ^Continued bunkers, 608 burners for powdered, 115 burning powdered, 111 bu3-ing under contract 486 calorimeter, Mahler, 455 cannel, 437 carbon in, 453 classification, composition, 437 geological, 435 clinker, 459, 562 composition, 435, 440 consumption, banked fires, 568 stand-by boilers, 568 conveyors, 605 apron. 607 belt 607 flight, 605 pivoted bucket, 607 scraper, 605 screw, 605 crushers, 607 draft for, 185 evaporation and ash in. 459 composition, 483 heat value of, 483 gases, weight of flue, 543 geological classification, 435 hand firing, anthracite. 562 bituminous. 560 handling, 603 see Coal conveyors heat value by analysis, 453 calorimeter, 455 hydrogen in. 453. 543 location of deposits, 437 meter, helical vane, 602 moisture in. analysis, 450 errors. 547 loss due to. 542 sampling, 517 nitrogen in, 453 oxygen in, 453 powdered, burners, 115 burning. 111 proximate analysis. 451 sampling, 445 boiler testing. 517 errors. 547 semi-anthracite. 436 semi-bituminous, 436 sizes of anthracite. 443 bituminous. 445 I N IJ E X 625 Coal — Continued specifications, 486 spontaneous combustion of, 467 spouts, 60S storage, 603 circular, 605 deterioration, 467 rectangular, 605 submerged, 605 sub-bituminous, 436 sulphur in, 451, 463 -tar, see Tar ultimate analysis, 451 unloading, 603 volatile matter, 451 volume, 467 washing, 458 weighing, see Boiler testing- continuous, 599 conveyor scales, 599 helical vane, 602 hopper scale, 601 hopper, traveling, 601 stoker speed, 602 track scales, 599 traveling hopper, 601 traveling larry, 602 weight of, 466 Cochrane feed water heater. 325 Cochrane water softener, 509 Cocn oil burner, 123 Coke, breeze, 474 composition, 473 heat value, 473 -oven gas, burning, 131 composition, 483 heat value, 483 weight of, 474 Colloidal fuel, 481 Combustion, 389 air required, actual, 397 theoretical, 394 ashpit, 111 liaffle furnace roof and, 65 chamber, 85 blast furnace gas, 128 gas passage arens. ^3 Heine boilers, 21, 37 natural gas, 127 oil, 117 shape of. 90 size of. 85 surface, oil Imrning, 117 temperature, 86 chemistrv of, 390 data, 393 furnace temperature and, 86 Combustion — Continued furnace — Continued volume and, 87 heat of, 394 losses, 397 rate, 57 requirements, 85 space, grate area and, 89 required, 85, 89 spontaneous, of coal, 467 Combustion Eng. Co., Type "E" stoker. 161 Concrete boiler settings, 147 chimneys, 207 Condensers, heat transfer in. 389 Conduction of heat, 379, 383 Conductivity, boiler tubes, 383 insulation, 155 materials, 351 table of, 353 refractories. 155 Cones, Seger, ?)77 Continental stoker, 167 Control boards, 584 Convection, 379. 385 waste heat boilers, 141 Convevors, wood refuse and pneumatic, 133 see Coal conve}ors. Copes' feed water regulator, 314 Cork heat insulation, 357 Corn, heat value, 474 Corrosion, feed pumps, 301 feed water and, 510 .gases in feed water and, 503, 510 marine boilers, 49 Cost accounts of generating steam. 616 boilers 1)y lieating surface, 57 comparison of lioiler feed pumps, 305 reducing", of generating steam. 5S7 reduction, Polakov method of power, 585 Co.ve stoker, 168 Crushers, coal, 607 Culm, grate bars for. 97 "Cutting-in" boilers, 614 D Danu^^ers, 220 l)alancing. 222 design, 221 details, 222 forced draft, 235 induced draft, 241 o]ieration of. 222 regulators, 584 626 INDEX DtLaial centrifugal feed pump, 306 Depreciation of boiler plant. 616 Destructor chimneys, refuse. 191 Detrick-Hagan ash conveyor, 609 Detroit stoker, 159 Diatomaceous earth, 2>^7 Differential draft gages, 580 Disengaging surface, steam, 67 Down draft furnace, 95, 100 Draft anthracite, small, 173, 562 balanced, 584 chimney capacity and, 181 coal burning, 185 diagrams, 22?) ducts, forced, 235 air leakage, 236 forced, 227 sras^ss boiler testing, 536 choked passes. 581 compound. 580 connections, 580 diaphragm. 580 differential. 580 flow meter, 581 liquid for, 580 multiple. 580 poor fires. 581 simple. 579 slanting tube. 580 small pressure differences. 580 gas burning. 190 induced. 236 instruments, 579 lignite. 566 loss. accelerating gases. 187 air heaters, 339 altering gas velocity, 187 baffling and, 62 boiler setting, 186 chimneys. 182 economizers, 186 flues. 182. 187 fuel bed 185 waste heat boilers. 142 losses tabulated. 187 mechanical, 223 oil burning. 189 pressures, forced. 227. 231 regulators, 584 table, chimneys. 176 wood burning, 191 Ducts, forced draft. 235 air leakage in. 236 Dudgeon tube expander. 613 Dulotig formula. 454. 479 Dumping srrates. 97. 568 Dust blast furnace gas. 129 Dust — Continued blowers baffles and, 65 boilers, 39.' 41, 610 economizers. 333 superheaters. 31 doors, leaking, 153 separating fans. 237 waste heat boilers, 141 Earth, diatomaceous, 357 Economizers. 331 counter flow. 334 dimensions, 337 draft diagram. 225 loss through, 186 Green, 333 heating surface, 337 heat recovery- by, 335 transfer rate. 335 integral, 331 low pressure, 306 performance, 333 saving effected by, 333 scrapers. 333 soot blowers. 333 steel tube. 331 surface. 337 Electrical pyrometers. 373 Electrohsis and corrosion. 510 Embrittlement. caustic, 511 Engines. auxiliary. 341 fan. 343 pump. 309 stoker, 343 superheated steam. 69 Entropy. 407 diagrams. 414 Peabody, 415 MolUer, 416 superheated steam. 69 Equivalent evaporation. 55. 528 mechanical, of heat. 378 Erosion of turbine blades. 73 Eschka's method for sulphur, 451 Evaporation ash in coal and, 459 equivalent. BS. 528 factor of. 55, 528 rate. 57 rate and circulation. 66 Evase chimneys, 191 Everlasting blow-off valve. 560 Excess air. carbon dioxide and. 572 general etTect. 575 INDEX 627 Excess air — Continued weight of gases and, 179 Exit gases, see Flue gases Expansion, adiabatic, 407, 414 firebrick, 149 force of, piping, 286 isothermal, 407, 414 joints, 286 metals, coefficients, 283 nozzles, 417 pipe bends, 287 piping, 283 steam, 407 Explosion doors, 129 Explosions with blast furnace gas. 129 Extinguishing action with vertical baf- fling, 93 F Factor for moisture in steam, 528 of evaporation, 55. 528 Fahrenheit scale, 370 Fans, characteristics, 229 chimney connections for induced draft, 241 cinder separating, 237, 572 dampers for forced draft, 235 induced draft, 241 densitv of gases with induced draft, 239 dirt unbalancing, 229, 236 drives, 228 ducts, 235 efficiency, induced draft. 240 engine and feed pump, 309 engines, 343 erosion, induced draft, 236 forced draft, 227 ducts, 235 H.P. output, 235 inlet screens, 236 load on induced draft, 239 operating difficulties, 229 output. 235 performance, 232 pitot tube, testing. 232 safe tip speed, 232 screens, 236 sizes forced draft, 228 induced draft, 237 speed, induced draft, 237 safe, 232 test, 232 testing, 232 induced draft, 240 pitot tube, 232 Fans — Continued turbine driven, 227, 343 types of, 229 waste heat boilers, 142 water-cooled bearings, 237 weakened by heat, 239 weight, forced draft, 228 induced draft, 237 Feed pumps, 297 air chambers, 298 automatic regulation, 310 bronze fittings, 301 capacity, duplex, 299 hot water, 299, 317 simplex, 298 single cylinder, 298 centrifugal, see Centrifugal boiler feed pumps corrosion, 301 cost comparison, 305 direct acting power, 309 steam, 297 duplex, 299 excess pressure, 297 regulator, 310 knocking, 299 motor driven, 311 regulator, 311 performance, 301 piston speed, 299 power driven, 309 pressure regulator, 310 regulation, 313 "short stroking," 298, 299 simplex, 298 single cylinder, 298 "steam bound," 299 steam consumption, 302, 305 suction lift, 317 hot water, 317 suction piping, 318 triplex. 309 volumetric efficiency, 298 Feed water, see Water constant excess pressure, 310 economy of heating, 323 heaters, 323 closed, 327 Cochrane, 325 filter, 326 metering, 325 oil separating, 326 open, 323 Patterson-Berry man, 327 regulation of exhaust steam to. 326 removal of air in, 329 selection of, 330 628 INDEX Fee! :er — Continued ! ei: :::^ in Heine boilers, 35, 45 ice plants. 329 purification in Heine boilers. 19 quantity required. 297 regulators. 310 5:e:-m required to heat 325 7elr. jiair. 357 Ferguson tube expander, 613 Fery pjTometer, 377 Filters. feed water heater. 326 wster treatment. 50S ?;rr r :■: 148 a r-: :ed blocks. 151 blocKs, air-cooled. 151 -e-f: rated. 151 c : :: errial. 149 -ion of. 149 e T : : ash on. 151 n of. 149 f . I'int 149 h r e 5. 149 -:::;:e."r;.::r:f 149 plastic. 152 plasticity of. 14S special blocks. 148 standard shapes. 150 surface, oil burning. 117 weight of. 151 Fireclay. 148 cements, plastic. 151 mortar. 151 plastic cement. 151 Fire ashpit, in. Ill cleaning. 567 protection and stand-b^- boilers, 568 sand. 151 Fires, banked, 568 Firing carbon dioxide and. 574 tools. 563 Flexible metallic pipe. 293 Flooding superheaters. 76 Flow meter draft gage as. 581 Repuhlie, 594 steam. 595 variable orifice. 597 water. 594 Flow of steam. Grashof, 421 Xal*ier, 421 nozzles. 417 P,>0.58P,. 421 Rateau, 420 Flue gases, air heaters. 339 analysis. 531 apparatus. 532 conversion to weight. 543 Orsat. 532 heat of fuel in. 334 loss due to CO in. S45 loss due to heat in. 543 sampling, -'■ 531 : rure. 178. 529 -g and. 61. 63 e- e:-cy and. 574 - : tr vr Tine and. 69 -^:: f. 182. 543 Dairies in. 217 cleaning doors. 217 f : - -tion of. 217 r : rs in. 217 design of. 215 ex-T^nle of. 218 :: ?s. 182. 187 ir^UiaLion, 220 size. 184. 214 V e-r-und. 220 r!. ; rr _ nreclaj- mortar, 151 Foaming and bad water. 510 Foersi oil burner, 121 Forced draft, air required. 227 ducts, 235 fans, see Fans pressures. 227 Foundations. boiler settings. 145 chimney^s. 193 Fraser's coal classification, 437 Fuel. 435 air required. 395 analysis. 450 bed thickness, see fuel in question buying under contract. 4S6 classification of solid, 435 coUoidal. 481 consumption, banked fires. 568 errors in moisture in, 547 gaseous. 4S2 heat value, see fuel in question high. 485 low. 485 wet, 477 hydrogen loss. 543 liquid. 478 loss due to hxdrogen in, 543 moisture in. 542 INDEX 629 Fuel — Continued moisture in, errors, 547 tinding, 450, 517 loss by, 542 oil, see Oil sampling, 445 boiler testing, 517 errors, 547 suDerheating, extra for, 69 weight of gases, 543 wet, heat value of, 477 Furnaces, air-cooled lining, 151 arches, 153 l)affle roof, 65 boiler settings and, 85 chamber, gas passage areas, 93 design of, 85 down draft, 95, 100 gases from industrial, temperature of, 141 industrial, temperature of gases from, 141 linings, air-cooled, 151 oil burning, 119 smoke and down draft, 95, 100 smokeless, 93 temperature, complete combustion and, 86 observing. 536 theoretical, 394 tile roof and, 87 volume, see fuel in question Fusible plugs, 560 Fusion of ash, 461 firebrick, 149 G Gage, boiler water, 516, 551 piping, boiler water, 551 Gages, see Draft gages Pressure gages Gas, see Blast furnace gas Coal gas Coke-oven gas Flue gases Natural gas Oil gas Producer gas Water gas analysis, 532 CO recorders, 578 CO2 recorders, 577 Hempcl apparatus, 535 Orsat apparatus, 532 Gas — Continued burners, 128 burning, 127 settings. 127 calorimeter, 482 passage area, 59, 93 pockets, dead, 59 producer and superheated steam, 83 sampling, errors, 547 flue, 531 temperature drop, chimneys, 174 over heating surface, 3S>7 velocity, heat transfer, 385 waste heat boilers. 141 Gaseous fuels, 482 Gases, density of. 399 in feed water and corrosion. 503. 510 pressure effect, 398 properties, 398 specific heat of, 399. 401 temperature effect, 398 volume, 398 weight, 398 Gate valves, 273 Globe valves, 273 GoodcnougJi's steam taldes, 424 Graphite. 436 Grashof, flow of steam, 421 Grate, air space, 58, 97 bar openings, 58. 97 bars, anthracite. 97 bagasse, 137 cast iron for, 96 culm, 97 heat effect on cast iron, 97 lierringbone, 97 hollow, 99 slotted, 97 Tupper, 97 hand firing, 96 inclination 100 length, 99 slope. 100 surface, 57 anthracite, 562 ratio, 58. 562. 567 water. 95, 100 Green economizer, 333 Green stoker, 168 Gu\-s for steel chinmeys. 201 H Uas:aii ash convcvor, 609 Mair felt, 357 Ilnnniiel oil burner, 120 630 I X D E X Hammond water meter, 589 Hand firing, 560 anthracite, 562 low volatile, 563 setting, 95 ashpit, 107 large, 109 CO2 and, 574 coal cars, 563 depth of grate. 99 frequency, 565 grates, 96 losses, 565 methods, 560 rules, 561 space for, 563 thickness of fire, 566 tools. 563 Handhole caps, Key, 27, 47, 54 Hard coal, see Anthracite Harrington stoker, 16S Hays draft gage, 580 Head room, furnace for soft coal. 90 smokeless settings. 91 stoker settings, 100 vertical baffling, 91, 93 Heat balance, calculating. 542 example, 546 form of, 541 combustion, of, 391 conduction, 383 convection. 385 effect on strength of materials. 97. 239. 252 insulation. 347 air currents. 361 breechings, 220. 367 boiler drums, 157. v365 boiler settings, 155, 367 cold water pipes. 367 commercial, 354 conductivity, 156. 353 cork, 357 econom}-. 349 efficiencv. 360 flues. 220, 367 hair felt, 357 loose, 361 ''magnesia. 85%,"' 357 painting, 361 pipe size and, 360 piping, 360 piping, outdoor, 367 piping in trenches, 367 piping in tunnels, 367 piping, underground, 367 settings, 155 surface finish. 361 surface resistance, 347 Heat — Continued insulation — Continued thickness, 360 uses of, 355 walls, 2)67 waste without, 349 weight of, 355 loss, bare surfaces, 348 CO in flue gases. 545, 577 combustible in ash, 545 commercial insulators, 354 hydrocarbons, 546 hydrogen, 543 moisture in air, 545 moisture in coal, 542 radiation, 546 soot formation, 547 unaccounted for, 546 losses, see Heat balance mechanical equivalent of, 378 radiation, 379 resistance, 385 asbestos. 357 specific, 378 gases, 399 theorv, 369 transfer, 58, 378 air heaters, 339 boilers, 389 condensers, 389 convection, 385 economizers, 335 gas velocity and, 385 insulation, 359 scale and, 511 superheaters, 81 surface resistance, 347 waste heat boilers, 141 treatment, feed water, 507 units, 378 values, see fuel in question Diilong formula, 454, 479 Heaters, air, 339 feed water, see Feed water heaters Heating surface, 57 cost of boilers b}', 57 economizer, 337 evaporation rate, 57 gas temperature drop over, 387 ratios, 58 anthracite, 562 tan bark. 567 Height of furnace chamber and smoke, 90 stoker settings, 100 vertical baffling, 93 Heine baffle tile, 66 boiler, the first, 52 INDEX 631 Heine — Continued boilers, baffling, 27 circulation, 19, 568 cleanmg, 21 cross drum, 43 longitudinal drum, 23 marine, 47 overload capacity, 19, 568 small space required, 31 water purification in, 19 by-pass superheater, 78 marine superheater, 49 service, 23 soot blowers, 31, 41 superheat control, 29, 78 superheaters, 29, 78 Heine reinforced concrete chimney, 209 Hetnpel gas analysis apparatus, 535 Henderer tube expander, 613 High draft loss, waste heat boilers, 142 gas velocity heat transfer, 385 heat value of fuels, 485 pressure feed pumps, 301 setting anthracite, 96 smokelessness, 91 vertical baffling, 91 water signal, 551 Hog wood firing, 566 fuel bed thickness, 566 Hopper ashpits, 109 Horizontal baffling, 61 flame travel and, 93 furnace temperature and, 87 smoke and, 87, 93 Horsepower, boiler, 55 Hot water and feed pump capacity, 299, 317 corrosion, 301 suction lift. 317 Huddling chamber, safety valves, 554 Humidity of air, heat loss due to, 545 observing. 536 tables, 537 Hydrocarbons, heat loss due to, 546 Hydrogen, combustion data, 393 in fuels, 453 heat loss due to, 543 specific heat, 404 Ice plants, feed water heaters for, 329 Idle boilers, care of, 613 Ignition temperatures, 391, 394 Illinois stoker, 169 Impact pressure, pitot tube, 233 Induced draft, 236 chimney connection, 241 cinder separating fan, 237, 572 dampers, 241 density of gases, 239 diagram, 225 dirt unbalancing fans, 236 erosion of fans, 236 fan speeds, 237 sizes of fans, 237 weights of fans, 237 Infusorial earth (Kieselguhr), 357 Injectors, 319 '"breaking," 323 exhaust steam, 323 inspirators, 322 live steam, 319 scale in, 2)2?) steam pressure range, 321 suction lift. 321 suction piping, 323 superheated steam, 321 thermal efficiency, 323 Inleakage of air, see Air, leakage in settings, Inspection of boilers, 614 precautions, 615 report, 616 Inspirators, 322 Instrument boards, 584 Insulating brick, 155 Isothermal expansion, 407, 414 Jet blowers. 227 Jones stoker, 162 Junker gas calorimeter, 482 K Kellog chimneys, 203 Kent chimney table, 176 Ivey handhole caps, 27, 47, 54 Kieselguhr, 357 Kirkivood gas burner, 128 Kling-Weidlein gas burner, 130 Koerting oil burner, 123 oil burning system, 123 Laclede-Christy stoker, 170, 566 Ladders, brick chimneys, 206 steel chimneys, 195 Lance, steam, 43 Laning, or stratification, 93 Larry, coal weighing. 602 Lea-'Courtenay centrifugal feed pump, 307 Liberating surface, steam, 67 Lightning rods, 206 632 INDEX Lignite. 436 briquets, 471 composition, 436 tiring. 566 forced draft. 566 fuel bed thickness. 566 heat value, 436 moisture in. 436 weight of. 466 Lining, air-cooled furnace. 151 brick chimneys, 205 steel chimneys, 195 Liptak flat arch, 153 Liquid fuels. 478 boiler tests. 550 Load dispatching. 569 signals, 569 Lopulco powdered coal burner. 116 feeder, 115 Low heat value of fuels, 4S5 water signal 551 Lubrication and superheat, 75 M Marine boilers corrosion. 49 Heine, 47 settings. 143 zinc plates in. 49 superheaters. 49 Masoti damper regulator, 5S3 Mechanical draft. 223 equivalent of heat, 378 stokers. 159 chain grate. 167 front feed. 159 hand operated, 171 overfeed, 159 settings. 100 side feed, 1 59 underfeed, 161 treatment of water, 505 Megass. see Bagasse Mercurv thermometers. 373 Meters.' Bailey boiler. 598 coal, helical vane, 602 steam flow. 595 variable orifice. 597 water. SS7 boiler testing. 516 classification. SS7 gravimetric. 589 Venturi cppacities, 593 Venturi diagram. 590 ^^enturi formula. 591 V-notch. 589 Meters — Continued water — Continued V-notch formula. 591 volumetric. 589 Model stoker, 161 ^Moisture in air, 536, 545 coal. 450. 517 errors. 547 fuels, see fuel in question loss due to, 477, 542 steam. 518 factor for. ^28 Molecular weights. 391 MoUier diagram. 416 Moloch stoker. 162 Mono COo recorder. 578 Mortar, firebrick, 147 fluxes in, 151 fusion of. 151 weight of fireclay. 151 Muck's coal classification, 437 Mud drum, internal. 35. 45 N Xapicr, flow of steam, 421 Xational stoker, 171 Natural gas burners. 128 burning. 127 composition. 483 heat value, 483 working pressure, 482 Xa^"A- oil specifi.cations. 497 Nitrogen in coal. 453 specific heat. 403 Nozzles, steam, 417 convergent. 419 expansion. 417 P,>0.58P,. 421 Rateau, 420 O Oil. atomizing. 119 burners. 119 location, 119 burning. 117 boiler tests, 550 chimney table. 190 chimnevs. 189 combustion chamber. 117 nre brick surface. 117 furnace design. 119 consumption, stand-by boilers. 568 crude. 479 fuel. 478 composition. 479 handling. 610 INDEX 633 Oil — Continued fuel — Continued heat value, 479 settings, 117 specifications, 497 specific gravity, 479 composition, 483 heat value. 483 heater, 124 and pump, 124 separation in feed water heaters, 326 Heine boilers, 45 separators, 293 tar. composition. 481 heat value, 481 -tar, 481 Operating- cost of feed pumps, 305 cost of steam generation, 617 economical boiler. 584 under ''test conditions," 585 waste heat boilers, 142 Optical pyrometer, 2)77 Orifice, steam flow. 421 Orsat apparatus, 532 operation. 533 solutions, 533 Oxygen in coal, 453 specific heat, 403 P Pattersoii-Berrxman feed water heater, 327 Peabody calorimeter, 518 entropy diagram, 415 Peat, 435 briquets, ^71 lieat value. 436 weight, 466 Peck pivoted bucket conveyor, 606 Pipe ancliors. 286 ])rass, 252, 260 bursting pressure, 257 capacity, double extra heavy. 256 extra heavy, 255 standard, 253 cast iron, 251 condensation and superheating. 69 copper. 252. 260 extra heavy brass, 261 copper. 261 iron, 255 lieat efi^ect on strength of, 252 fittings, brass, 263 Pipe — Continued fittings — Continued cast iron, 261 cast steel, 261 flange, 263 flange unions, 267 flanged, 125 lb., 265 flanged, 250 lb., 268 general, 261 malleable iron, 261 names of, 264 nut unions, 265 flanges, 125 lb., 267 250 lb., 269 materials, 271 hangers, 293 headers, cast steel, 252 insulation, 360 sizes, double extra heavy, 256 extra heavv, 255 large O. D.. 257 standard, 253 steam, saturated, 276 steam, superheated, 281 water, 281 strength of, 257 supports, 293 water, 260 weight, brass, 260 copper, 260 double extra heavy, 256 extra heavy, 255 large O. D., 257 standard, 253 Pipes, flow of steam in, 275 water in, 281 friction pressure drop, 275 steam, size charts. 277 velocity-, 275 velocit}', steam, 275 water, 283 Piping, blow-off, 275 boiler water gage, 551 color identification, 251 design. 243 diagram. 251 drainage of steam, 243 expansion and contraction, 283 l)ends. 287 force, 286 joints, 286 of materials, 285 634 INDEX Piping — Continued feed pump suction, 318 flange joints, 267 identification. 251 insulation, 360 materials. expansion of, 285 moduli of elasticity, ^^6 saturated steam, 259 screwed flanges. 268 slope of steam, 243 steam, draining, 243 superheated steam, 69, 83, 259 system. duplicate header. 245 loop header, 247 ring header. 247 selection. 244 single header. 244 unit, 247 unit, modified. 249 Van Stone joint, 271 vibration in steam. 243 water in steam, 243 water hammer in steam, 243 welded flanges, 271 wrought iron, 251 Pitot tube. 232 double, 233 water meter. 591 Plastic rirebrick, 152 fireclaj- cements. 151 Plasticity- of firebrick, IAS Playford stoker. 170 Folakoz' control board, 585 Powdered coal burners, 116 burning. Ill control of air, 116 equipment 113 feeders, 115 settings. 111 Power feed pumps. 309 Pneumatic convevors, ash, 608 wood refuse, 133 Precision Instrument Co., draft gage. 581 Pressure, effect on boiling point of water, 500 effect on gases. 398 excess feed water, 297 gages, boiler testing, 518 correcting, 557 description, 555 head of water in pipes, 556 location, 556 siphons, 556 Pressure — Continued gages — Continued tester, 557 vibration. S57 water seal, 5S6 regulators, excess feed, 310 feed pump. 310 Priming, 67 bad feed water and, 510 Processes, industrial air heated by, 341 superheated steam for, S3 waste heat from, 139 Producer gas, burning. 131 composition of, 483 heat value, 483 Properties of gases, 398 saturated steam, 424 superheated steam, 429 water, 499 Prosser tube expander, 613 Proximate analysis of coal, 451 Ps3-chrometric tables. 537 Pulverized coal, see Powdered coal Pumps, see Feed pumps P\Tometers, accuracy-, 371 calibrating, 370 electrical resistance. 373 mechanical, 374 optical, 377 radiation, 377 range of, 371 thermo-electric. 373 Quick steaming from banked fires, 568 Quiglcy powdered coal burner, 116 R Radial brick chimneys, 201 Radiation. 379 boiler settings, 153 heat loss. 546 oil burning, surface. 117 pyrometers. 377 Stefan's formula, 379 surface for oil burning, 117 Rankine's convection formula, 385 Rateau, flow of steam, 420 Rated H.P. of boilers, 55 Ray rotar>- oil burner, 124 Reaumur temperature scale, 370 Reboilers for ice plants, 329 Receiver steam separators, 295 Recorders, CO,, 577 INDEX 635 Recorders — Continued smoke, 550 Refuse burning settings, 133 composition of municipal, 191 destructor chimneys, 191 Refractories, 148 perforated blocks, 151 thermal conductivity, 155 weights of, 151 Regulators, draft, 584 excess feed pressure, 310 feed pump pressure, 310 feed water, 313 superheat temperature, 78 Reinforced concrete chimneys, 207 Reinforcing old brick chimneys, 213 Renewing boiler tubes, 43, 613 Republic flow meter, 594 Resistance, heat, 385 surface, to heat flow, 347 Richardson coal scale, 601 Riley stoker, 165 Ringelmann smoke chart, 549 Roach stoker, 162 Roney stoker, 161 Ross expansion joint, 290 Rust concrete chimney, 211 S Safety valves, A.S.M.E. Code, 551 blow down allowed, 553 control, 554 discharge piping from, 243 huddling chamber, 554 operation of pop, 554 pressure rise allowed, 551 size chart, 272 specifications, 271 superheaters, 75, 555 Sampling- coal, 445 boiler testing, 517 errors, 547 flue gases, 531 tubes, for, 531 Sand, fire, 151 Sanford Riley stoker, 165 Sawdust burning, 566 fuel bed thickness, 566 grate bars, 99 heat value, 473 Scale, boiler formation, 511 heat transfer, 511 Scale, boiler — Continued injector, 323 removal, 611 superheaters, 76 Scales, temperature, 370 conversion, 370 thermodynamic, 370 weighing, boiler testing, 517 continuous, 599 conveyor, 599 track, 599 Secondary air admission, 90 Sedimentation tanks, 508 Seger cones, 377 Semi-anthracite coal, 436 Semi-bituminous coal, 436 Separating calorimeter, 522 Separator, feed water oil, 326 Settings, see Boiler settings Shavings, burning, 133, 566 burning dry, 134 grate bars, 99 heat value, 473 Signals, high water, 551 load, 569 low water, 551 Smoke, baffling, 65, 93 causes, 571 combustion space, 571 curtain walls, 93 deflection arch, 93 down draft furnace, 95, 100 furnace design, 571 temperature, 571 volume, 85 gas passage areas, 93 height of furnace chamber, 90 horizontal baffling, 62, 87, 93 indicators, 550 observations, 548 ordinances, 571 overloads, 571 prevention, 569 recorders, 550 records, 65 reports, 548 RingeUnann chart, 549 tile furnace roof, 87 vertical baffling, 93 Soft coal, see Coal, bituminous Soot blowers, 610 baffles and, 65 boilers, 39, 41 636 IXDEX Soot — Continoed blowers — Continued eccHioniizer, 333 superheater, 31 collectors in chimneys, 207. 208 heat loss by formation of, 547 Sorge-Cochrane water softener. 509 Specific heat, 378 r : -;» r :t _ ; ations. j>oiler, standard, 49 coat 486 oil fueL 497 Xavy, 497 railroad, 498 Spontaneous combustion of coal, 467 Stadcs, see Chimnejrs Staples and Pfeifer oil burner, 120 Stand-by boilers, 568 fire protection, 568 oil consunqytion, 568 quick steaming, 568 Static pressure, pitot tube, 232 Steam calorimeters. Carpenter, 522 connections, 523 fommla, 521 Pcabody. 518 separating. 522 throttling, 518 consumption, auxiliaries, 423, 547 feed pumps, 302, 305 cost accounts, 616 Polakoz' method of reducing. 585 diagram M oilier, 416 Peabody, 415 disengaging surface, 67 entropy, 407 diagrams. 415. 416 factor for moisture in, 528 .-. -21 meters. 595 meters, %-ariable orifice, 597 Xapier. 421 nozzles, 421 pipes, 275 Ratcau. 420 generation, maintenance costs. 618 operating costs, 617 reducing cost of. 587 Str ~ — rs. 608 erers. 595 --t» ^^ram, 415 re drop. 275 275 see Piping systems '" =^^c^^. see Pressure gages 5 ol410 r -ated, 424 - t ^ ;triieated, 429 quilir*. 51S receiver; 2^' 35,43 i*^ steam SQiar; separ^.i.r, _- superheated, -t superheater?, ^t tables, saturated, 424 superiieated. 429 Steel chimneys, see Chimneys, steel Stefan's radiation formula, 379 Stevens stoker, 163 Stokers. 159 see ^'Tecnanica! stokers. ; ~ " ' \ _ - ^ • - ' " — ; oaL see Coal storage - i or laning, 93 5!tion, 474 t. 474 lerials and heat 97. 239. Sub-bituminous coal. 436 ^ : ; lift izr.Ds. 317 -. ::. 317 s. 318 I N D E X 637 Sudden loads from banked fires, 568 Sulphur combustion data, 393 in coal, 451 in U. S. coal, 463 Superheat, accurate control, ll boiler load and, 75 control of, 75 damage by tiuctuation of, 75 fluctuations, 75 regulation, 75 regulator, 78 variation with furnace temperature, 76 gas flow, 76 load, 76 steam flow, 76 weakening materials. 83 Superheated steam, 69 advantages, 69 automatic temperature control, 78 lioiler eff^iciency, 69 constant temperature. 11 , 1'^ Corliss engines and. IZ cylinder condensation and, 69, 72 danger of temperature fluctuations, 75 economy, 69 engines using, tests of, 72 erosion of turbine blades. 73 European practice, IZ extra fuel for, 69 fittings, 83 flue gas temperature and, 69 industrial uses of, 83 injectors and, 321 limit of economy with engines, 71 lubrication and, 75 pipe condensation and, 69 pipe sizes, 281 piping, 259 poppet-valve engines and, 75 reciprocating engines and, 71 slide-valve engines and, IZ tables, 429 taking temperature, 523 temperature-entropy diagram, 69 tests of engines using, 11 theoretical engine and, 1'}) turbines and, IZ blade erosion of, 12) variation of temperature, 75 velocities in piping, 69, 83 water gas producers and, 83 Superheated vapors, 411 Superheaters, 69 attached, 75 burning, 76 liy-pass, 77 Superheaters — Continued cleaning, 31 details, 11 drains, l(i flooding, l(i heat transfer rate. 81 Heme, 29. 34. 11 marine, 49 materials, 83 weakness of, 83 position of, 76 protecting, 76 requirements, 79 safety valves, 75, 555 scale in, 16 separately fired, 75 soot blower. 31 surface efticienc3\ 69 required. 79 types of, 75 Surface, grate, 57 heating, boilers, 57, 562, 567 cost of boilers by. 57 economizer, 337 efficiency of superheater. 69 gas temperature drop and. 387 superheater. 79 resistance of insulation. 360 to heat flow, 347 steam disengaging, 67 waste of coal with bare hot, 349 T Tan bark Ixirning, 133 composition, 475 firing, 567 fuel bed thickness. 567 grate bars, 99 heating surface ratio with. 567 heat value, 474 moisture in, 474 settings for burning. 133 Tar burners, 125 burning, 125 composition coal, 481 oil, 481 heat value coal, 481 oil, 481 -oil. 481 specific gravity, 481 weight of coal, 481 Taylor stoker. 164 638 I X D E X Temperature absolute, 370 absolute zero of. 370 color schedule. 377 -entropy diagram, 415, 416 fixed points, 371 scales, 370 conversion, 370 thermodjTiamic. 370 Testing boilers, see Boiler testing Thermal units, 378 Thermod3-namic temperature scale, 370 Thermo-electric pyrometers, 373 Thermometers. accuracy. 371 alcohol, 373 calibration. 370, 373 mercur\-. 373 range of, 371 stem correction, 373 vapor, 377 wells, 373 Thermometn-. 369 Tile baffles. 66 furnace roof and smoke. 87 roof and furnace temperature, S7 Tolerance in guarantee tests. 547 Treatment of water, see Water Trenches, insulating piping in. 367 Trials of boilers, see Boiler testing Triplex feed pumps. 309 Tubes beading. 613 cleaning boiler, 43 cleaners. hammer type. 611 turbine t\-pe. 611 conductivity of boiler, 383 expanders. 613 flaring. 613 pitot, 232 renewing boiler, 43, 613 rolling. 613 Tunnels, insulating piping in, 367 Tupper grate bars, 97 Turbines, auxilian.-. 341 blades, erosion, 73 boiler feed pumps and. 345 fans and. 227. 343 feed pumps and, 345 superheated steam and. 73 tube cleaners, 611 U Ultimate analysis of coal, 451 Underfeed stokers. 161 Units, British thermal, 378 Units — Continued heat, 378 work, 378 Universal stoker. 163 Vacuum reboilers. 329 Valves, ashpit. 111 automatic non-return. 274 blow-off. 274. 560 check, 274 gate, 273 globe, 273 safety-, 271, 551 safet}-, superheater, 75, 555 Vapor thermometers, 377 water specific heat, 405 weight of air and, 401 Vapors, characteristics of, 409 \'elocit3', era 5 chimneys, 189 draft loss altering. 187 draft loss generating. 187 heat transfer and. 385 waste heat boilers, 141 pressure, pitot tube, 233 steam, nozzles. 417 pipes. 275 superheated. 69, S3 water, pipes, 283 Venturi chimneys, 191 meter, capacities. 593 diagram, 590 formula. 591 Vertical baffling, 61 extinguishing action. 93 head room for, 91 smoke and. 93 Vibration in piping. 243 Vitrified brick, 156 V-notch meter, 589 formula, 591 Volatile matter in coal. 451 W Walls, air space in boiler, 145 boiler setting, 145 insulation of boiler. 153, 367 leakage through setting, 157, 577 smoke and curtain. 93 ties for setting. 155 INDEX 639 Washing coal, 458 Waste heat boilers, 139 airtight settings, 142 baffling, 141 dust in, 142 heat transfer, 141 high draft loss, 142 high gas velocity, 141 industrial furnaces, 141 operation, 142 Waste of coal with bare hot surfaces, 349 Water acidity, 503 air in, removal of, 329 alkalinit}', 503 test, 505 analyses, table of, 504 analysis, 503 boiling point and pressure, 500 causticity, 503 test, 505 characteristics of boiler feed, 501 chemical treatment, 507 classification of feed, 505 concentration test of feed, 505 corrosion, 510 gases in, 503 foaming with bad, 510 -gas, composition, 483 generators and superheated steam. 83 heat value of, 483 tar burning, 125 gases in feed, 503 grate, 95, 100 hardness,. factors, 504 permanent, 501 temporary, 501 test, 503 heaters, see Feed water heaters heat treatment of, 507 impurities in, 501 meters, see Meters, water permanent hardness, 501 piping, 260 flow in, 281 insulating cold, 367 sizes of, 281 velocity in, 283 priming and bad. 510 properties of, 499 purification in Heine boilers, 19. 35, 45 softening, see Water treatment solid matter in, 503 Water — Continued specific heat of, 499 temporary hardness, 501 thermal treatment, 507 treatment, boiler compounds, 510 chemical feed, 507 chemical proportioners, 50S filters, 508 hot process, 508 Heine mud drum and, 35, 45 mechanical, 505 sedimentation tanks, 508 Sorge-Cochrane, 509 Zeolite, 508 vapor, characteristics, 409 specific heat, 405 • ^yeight of air and, 401 weight, maximum density, 499 volume and, 499 Weir, formula for V-notch, 591 Westinghoiisc-Roney stoker, 161 underfeed stoker, 164 Wet fuels, heat value of, 477 JVetsel stoker, 161 JVeiderholt chimneys, 211 Wind, heat insulation and, 361 pressure on chimneys, 193 IVitt oil heater and pump, 124 Wood fuel, 435, 473 chimneys, 191 chips, 134 coal and, 134 composition, 473 cord, 566 fuel bed thickness, 566 grate bars, 99 heat value, 435, 473 hog, 566 refuse settings, 133 sawdust, 566 slab, 566 Work, unit of, 378 WorthiiigtO}i water weigher, 589 Yarzvay blow-off valve, 560 Zeolite water treatment, 508 Zero of temperature, absolute, 370 Zinc plates in marine boilers. 49 T^lBUHC ,/«). new- ^ PRESS OF KUTTERER-JANSEN PRINTING CO. 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