THE MARINE STEAM ENGINE THE MARINE STEAM ENGINE A TREATISE FOR ENGINEERING STUDENTS YOUNG ENGINEERS, AND OFFICERS OF THE ROYAL NAVY AND MERCANTILE MARINE BY THE LATE KICHAKD SENNETT >\ E.VGINEER-IN-CHIEF OF THE NAVY \ FELLOW OF THE ROYAL SCHOOL OF NAVAL ARCHITECTURE AND MARINE ENQIN BERING ', MEMBER OF THE INSTITUTIONS OF CIVIL AND MECHANICAL ENGINEERS: VICE-PRESIDENT OF THE INSTITUTION OF NAVAL ARCHITECTS ; LATE INSTRUCTOR AND LECTURER IN MARINE ENGINEERING AT THE ROYAL NAVAL COLLEGE AND SIR HENRY J. ORAM, K.C.B. ENGINEER-IN-CHIEB- OF THE FLEET ; ENGINEER VICE-ADMIRAL ; VICB-PRESIDENT OF THE INSTITUTIONS OF NAVAL ARCHITECTS, AND OF METALS MEMBER OF COUNCIL INSTITUTION OF MECHANICAL ENGINKERS MEMBER AND WATT MEDALLIST OF THE INSTITUTION OF CIVIL ENGINEERS EXAMINER AND LATE LECTURER ON MARINE ENGINEERING AND ENGINE DESIGN AT THE ROYAL NAVAL COLLEGE; ETC. WITH NUMEROUS DIAGRAMS ELEVENTH ESMTrON !.! NEW IMPRESSION LONGMANS, GEEEN, AND CO. 39 PATERNOSTER ROW, LONDON NEW YORK, BOMBAY, AND CALCUTTA 1913 All rights reserved v- Bibliographical Note First, Edition, March 1882. Second Edition, with Additions and Corrections, October 1885. Third Edition, Revised and largely Rewritten by H. J. Oram, January 1898. Fourth to Tenth Editions, with Additions and Modifications, June 1899, September 1900, April 1902, January 1904, October 190G July 1908, and November 1909. Eleventh Edition. August 1911, reprinted April 1913. PEEFACB TO THE EIGHTH EDITION THE first two editions of this work were written by the late Mr. Eichard Sennett, but after his death, owing to great changes which had taken place in marine engineering, it required to be practically rewritten in order to modernise it. This task was undertaken by the writer in preference to preparing an independent new work, as there appeared to be advantageous features in its style and arrangement over others ; but on account of revisions and additions made in several new editions to keep the book as far as possible up to date, little now remains of Mr. Bennett's work. The printed matter and illustrations have been considerably increased from time to time as new editions were required, for it is generally agreed that ample illustration is essential to the proper understanding of written descriptions of engineering details. As showing the considerable changes which have taken place since the writer's first association with the book, the chapters on water-tube boilers, oil-fuel arrangements, internal combustion engines, and the marine steam-turbine may be mentioned. The importance of water-tube boilers has caused this subject to be dealt with at considerable length, while the chapter on the marine steam-turbine has in this edition been largely amplified 274251 Vi THE MARINE STEAM-ENGINE and the details of the Parsons type fully illustrated to keep pace with this departure in marine engineering, the rapidly in- creasing importance of which will be realised when it is stated that all new ships for the British Navy from battleships to torpedo-boat destroyers are being fitted with the Parsons' marine steam-turbine. As regards this chapter I acknowledge with many thanks assistance which has been given me by the Hon. C. A. Parsons and his staff. The chapter on internal combustion engines is inserted in this edition for the first time, as it appears desirable that a short account of oil and gas engines should be given owing to their advent for various purposes on ships and boats and their possibilities as regards the future. The care and management of marine engines and boilers have been dealt with in considerable detail, and it is hoped this will be of value to young engineers, although the duties of engineers in this respect cannot be adequately learnt from books, for actual experience in the engine rooms will alone completely supply the requisite instruction. What is given will, however, prepare young engineers for such experience, and give- information on points which they are at first more or less unacquainted with. In the preparation of a work of this kind, one becomes indebted in various ways to many friends, and to these the writer tenders his thanks, especially to Engineer Commander P. Marrack, K.N., Engineer Inspector at the Admiralty. LONDON, 1906. H. J. OEAM. NOTE TO ELEVENTH EDITION. VARIOUS additions have been made in this edition, especially in those chapters dealing with the Steam Turbine, the Torsion Meter, and the Internal Combustion Engine, as required by their develop- ment and increasing importance in Marine Engineering. July, 1911. CONTENTS. INTRODUCTORY. CHAPTER PACK I. HISTORY AND PROGRESS OF MARINE ENGINEERING . 1 II. WORK AND EFFICIENCY . . 19 III. HEAT AND ITS EFFECT ON WATER .... 22 THE BOILEE. IV. COMBUSTION AND ECONOMY OF FUEL BOILER EF- FICIENCY 33 V. METHODS OF ACCELERATING THE RATE OF COMBUSTION OF FUEL 45 VI. PETROLEUM AS FUEL 58 VII. ARRANGEMENT AND EFFICIENCY OF BOILERS WATER TANK BOILERS 57 VIII. WATER-TUBE OR TUBULOUS BOILERS .... 74 IX. BOILER MOUNTINGS AND BOILER-ROOM FITTINGS . . 100 X. CORROSION AND PRESERVATION OF BOILERS . . .127 THE STEAM. XI. EFFICIENCY OF THE STEAM 134 XII. EXPANSION OF STEAM . . . . . , . 1386 XIII. METHODS OF INCREASING THE EXPANSIVE EFFICIENCY OF STEAM 155 XIV. COMPOUND OR STAGE EXPANSION ENGINES 162 yiii THE MAKINE STEAM-ENGINE THE MECHANISM. CHAPTER PA< XV. REGULATING AND EXPANSION VALVES AND GEAR . 166 XVI. SLIDE-VALVES AND FITTINGS 172 XVII. STARTING JSND REVERSING ARBANGFMENTS . . 197 XVIII. ARRANGEMENT OF THE CYLINDERS OF COMPOUND, TRIPLE, AND QUADRUPLE EXPANSION ENGINES 212 XIX. DETAILS OF CYLINDERS AND ENGINE-ROOM FITTINGS IN CONNECTION 225 XX. CONDENSERS, FEED-WATER FITTINGS, AND UNDER- WATER VALVES ,. 244 XXI. ROTARY MOTION 268 XXlA. THE MARINE STEAM-TURBINE .... 285b THE PROPELLER. XXII. PROPULSION ... . 2&7 XXIII. CO-EFFICIENTS AND CURVES OF PERFORMANCE . . 300 XXIV. PADDLE-WHEELS . .... 309 XXV. SCREW-PROPELLERS 315 GENERAL. XXVI. THE INDICATOR AND INDICATOR DIAGRAMS . . 334 XXVlA. THE TORSION METER 361a XXVII. PUMPING, WATERTIGHT, FIRE, DRAIN, AND FLOODING ARRANGEMENTS . . . . . .362 XXVIII. AUXILIARY MACHINERY AND FITTINGS . . . 372 XXVIIlA. INTERNAL COMBUSTION ENGINES . . . . 41 5a XXIX. RAISING STEAM AND GETTING UNDER WAY . . 416 XXX. MANAGEMENT OF ENGINES UNDER WAY ENGINE AND BOILER DEFECTS 428 XXXI. ENGINES DONE WITH EXAMINATIONS, ADJUST- MENTS, AND GENERAL INFORMATION . . . 444 CONTENTS CHAPTER XXXII. MATERIALS USED IN CONSTRUCTION . . . XXXIII. THEORETICAL INDICATOR DIAGRAMS OP STAGE EX- PANSION ENGINES PAGV 450 459 APPENDIX. (A) Application of the Indicator diagram to Determine the Stresses on Crank-Shafts. Curves of Twisting Moments 483 () Effect of the Inertia of the Reciprocating Parts of the Engines ......... 485 INDEX 491 THE MAEINE STEAM-ENGINE. CHAPTER 1. HISTORY AND PROGRESS. THE earliest steam-engines were simply reciprocating engines, and for many purposes such engines are still used even at the present day. Until, however, a suitable method of turning reciprocating into rota- tive motion had been discovered and utilised not any progress was made in adapting the steam-engine to the propulsion of vessels. The adoption of the crank effected this desirable object, enabled the power of the engine to be transmitted to the propeller smoothly and without shock, and was an indispensable step in the progress of steam navi- gation. The marine steam-engine may justly be considered as a production of the nineteenth century. In the latter part of the eighteenth century several attempts were made to adapt the steam-engine for the pro- pulsion of boats, but none of them were quite successful. The first practical steamboat was built on the Clyde, in 1801, by William Symington, for Lord Dundas. She was called the ' Charlotte Dundas,' and was worked for some time with success as a tug on the Forth and Clyde Canal, but was withdrawn from this service in consequence of an apprehension that the banks of the canal would suffer from the wash of the propeller. This boat was fitted with a single paddle-wheel placed near the stern, driven by a horizontal direct-acting engine, with connecting-rod and crank, and the general arrangement of her machinery would be considered creditable even at the present day. The first recorded instance of steam navigation proving commer- cially successful was in America, where, in 1807, Robert Fulton built a steam vessel called the * Clermont,' propelled by paddles driven by a Boulton & Watt engine. In 1812 Henry Bell built a vessel called the ' Comet,' which was successfully worked on the Clyde as a passenger steamer between Glasgow and Greenock. The ' Comet ' was propelled by two pairs of paddles, each paddle having four floats or blades, somewhat resembling a pair of canoe paddles, crossed at right angles. The paddles were driven by an engine of somewhat peculiar design, which, however, approximated to the side-lever engine of a later clay. This small boat was the first passenger steamer in Europe. 2 VlIK MARINE STEAM-ENGINE From this date the success of steam navigation may be said to have been secured, and the advancement that has been made since has not consisted so much in the discovery of new principles as in the exten- sion of old ones, and the introduction and development of improved mechanism and workmanship, with consequent economy of fuel. The result has been a progressive increase in the size, power, and speed of steamships and in the extent of their voyages ; this increase culminat- ing in the new fast steamships of the Cunard Steamship Company for the Atlantic voyage, which will displace over 35,000 tons, and be capable of being driven at a speed of 25 knots by engines of over 60,000 indicated horse-power. Side-lever engine. The propeller used in the earlier steainsnips was invariably the paddle-wheel, and the type of engine existing and giving satisfaction on land was naturally adapted at first to rotate Fm. 1. these paddle-wheels. Almost all these early engines were, therefore, of the beam type. In America the beam was generally placed over the crank, while in this country it was placed below the crank. The latter type of engine was known as the side-lever engine. The HISTORY AND PROGRESS 3 general arrangement of the side-lever engine is shown in outline in Fig. 1, and it represents the type usually fitted not only in the first steam vessels, but also for some years after. On the top of the piston-rod is fixed a crosshead with side-rods, s, attached at each end, which, passing down on either side of the cylinder, are connected to the ends, A, of a beam or side-lever, A B, oscillating on a fulcrum or gudgeon at its centre, C. The opposite ends, B, of these side-levers are fitted with journals carrying the crosstail, to the centre of which, one end of the connecting-rod B D is attached, the other end working on the crankpin D. The air-pump B is worked by side-rods from intermediate points in the side-levers, the upper ends of the air-pump side-rods being jointed to the opposite ends of the air- pump crosshead, to the centre of which the air-pump rod is secured. The piston-rod crosshead works in vertical guides to insure parallelism, and the parallel-motion rods used in land beam engines are dispensed with. Grasshopper engines. The arrangement of the side-levers was sometimes varied by making them levers of the third order, the gudgeon or fulcrum being at one end and the steam cylinder placed between the gudgeon and connecting-rod. These engines were com- monly known as grasshopper engines. The side-lever type of engine, though very heavy and occupying a large space for the power developed, was safe and reliable, securing a sufficient length of connecting-rod, and having its moving parts practically in equilibrium. It consequently continued in general use for a great number of years, but was at length superseded by the direct-acting type, which was lighter and more compact. Introduction of steam war vessels. Steam vessels were introduced into the Eoyal Navy in the year 1820, when the * Monkey,' a vessel of 210 tons, was built at Rotherhithe and fitted by Messrs. Boulton * M x X ^ 7-4 per cent. At Three-quarter = 81 Power 100 At Half Power = _80 100 16-4 100 15-9 100 _90 100 70 x = 8 ' per cent ' Consequently we see that for naval machinery of the most modern type, the efficiency of the propelling machinery rarely exceeds 1\ to 8J per cent. Example from mercantile machinery. As an instructive compari- son let us take the special case of a vessel in the mercantile marine, where elaborate fittings were provided with a view to reducing coal consumption. In this case the coal consumption per I.H.P. per hour was found to vary from 1O7 Ibs. on trial to an average of 1-27 Ibs. on actual service. The calorific value of the coal was not determined, neither were the mechanical or propeller efficiencies, but assuming that the respective figures were : 12,000 British thermal units per Ib. for WORK AND EFFICIENCY 216 calorific value of the fuel, 90 per cent, for the mechanical efficiency, and 70 per cent, for the propeller efficiency, we see that on trial the resultant efficiency was about : 33000 x 60 , *" nt * 90 x 70 P07 x 12000-XT78 X 1001TT60 = which on service was reduced to about 9 '85 per cent. Graphical representation. Figure 12A represents graphically by the shaded areas the respective losses etc. in the four stages of the conversion of heat into useful work, for a case where : Boiler efficiency is taken = 75 per cent. Steam efficiency =15 Mechanical efficiency =90 ., Propeller efficiency = 70 Area A (= 100) = Work equivalent to heat value of 1 Ib. of fuel. B ( _ 7 5\ _ / Work equivalent to heat added to feed water in boiler I P er pound of fuel burnt. C ( = 11^) = Work done on pistons by steam generated by 1 Ib. of fuel. , D ( = 10|) = Work available at propeller per Ib. of fuel burnt. , E ( = 7-1) = Work expended in propelling ship per Ib. of fuel burnt. , B' ( = 25) = Work equivalent to boiler heat losses per Ib. of fuel burnt. , C' ( = 63|) = engine , D' ( = 1) = Work lost in bearing friction per Ib. of fuel burnt. , E' ( = 3'0) = Work wasted by the propeller FIG. 12A. Graphic Representation of Efficiencies. THE MARINE STEAM-ENGINE CHAPTER III. HEAT AND ITS EFFECT ON WATER. IN order to comprehend the principles on which the construction and performance of the steam-engine depend, and the object of the various improvements that have from time to time been introduced, it is necessary that the true nature and properties of heat should be known. Ws will, therefore, as concisely as possible, state the principal points relative to this subject, in order that the succeeding chapters may be clearly understood. Temperature. The temperature of a body may be defined as the extent to which it may be capable of communicating sensible heat, or heat that may be felt, to other adjacent bodies. When two bodies of different temperatures are placed in contact with each other, it is a well-known fact that the hotter body becomes cooler and the colder body hotter, till at length the two bodies become of the same temperature, after which no change in the temperature takes place. This is caused by the passage of heat from the hotter to the colder body, and shows clearly that heat is something that can be transferred from one body to another, so as to diminish the amount of heat in the former body and increase it in the latter. Effect of and nature of heat. When heat is added to or abstracted from a body, one of the two following effects is produced : either the temperature of the body is altered, or its state is changed. For example, if heat be added to water under the atmospheric pressure, the temperature is increased until it reaches 212 Fahr. After this the addition of heat does not further increase the temperature, but causes the water to evaporate and become steam that is, it changes the condition from that of a liquid to that of a gas. Again, if heat be abstracted from water, the temperature is reduced till it reaches 32 Fahr., after which the diminution of heat does not further decrease the temperature, but changes the condition of the water from the liquid to the solid state, forming ice. The quantities of heat passing from one body to another can thus be estimated by the effects produced, so that it is clear that heat is something that can be both transferred and measured. The true nature of heat has been determined by experiments on friction. It is a matter of common observation that the work ex- pended in friction is apparently lost that is, it appears no longer in the form of mechanical work*; but at every place where friction occurs, heat is developed, and the greater the friction the greater is the amount of heat produced. Experiments have shown that the amount of heat generated by friction is exactly equivalent to the HEAT AND ITS EFFECT ON WATER 28 amount of work lost, and we therefore infer that heat is of the same nature as mechanical work that is, it is one of the forms of energy. British thermal unit. The unit by which heat is measured is called a thermal unit, and in British measurements represents the quantity of heat necessary to raise one pound of water at its maximum density, which corresponds to a temperature of about 39 Fahr., through one degree Fahr. Joule's equivalent. The honour of determining the relation between heat and mechanical work belongs to Mr. Joule, who proved, by an elaborate series of careful experiments on the friction of oil, water, mercury, and other substances, that one thermal unit is equal to a definite number of foot-pounds of mechanical work. This number, originally fixed by Joule at 772, is now known by later investigation to be 778 that is, the quantity of heat necessary to raise the tempera- ture of one pound of water at its maximum density, one degree Fahr., can be made to perform work equal to the raising of 778 Ibs. one foot high. In honour of the discoverer of the law, this important con- stant, 778, expressing the relation between heat and mechanical work, is called Joule's equivalent, and is frequently denoted by the letter J. The convertibility of heat and work, in a definite ratio, is ex- pressed in the following statement, generally known as the mechanical theory of heat, viz. : Heat and mechanical energy are mutually con- vertible, and heat requires for its production, and produces by its disappearance, mechanical energy in the proportion of 778 foot-pounds for each unit of heat. This statement forms also the first law of the science of thermo- dynamics. Communication of heat. Heat may be communicated from one body to another in three different ways, viz., by radiation, conduction, and convection. Eadiation. Radiant heat is given off from hot bodies in straight lines, and the rays of heat are subject to the same laws as the rays of light. As far as the genera tion of steam is concerned the useful radiation is confined to the furnace, the crowns and sides of which, intercepting the rays of heat from the burning fuel, become themselves heated, and the heat passes through them to the water in the boiler. A consider- able amount of heat is given off by radiation from burning coal, and it is very important, therefore, to intercept this, and to insure that as far as possible the whole of the heat diffused in this way should be trans- mitted, either directly or indirectly, to the water in the boiler, and not wasted on the external air or other bodies. Radiation is an important item to be considered with reference to the economical employment of steam, for it always causes a certain loss of heat, and unless proper precautions are taken this loss may become very considerable. The surfaces of the boilers, steam-pipes, cylinders, &c., when the engines are at work, are very much hotter than the surrounding bodies, and consequently, in order that loss of heat by radiation may be avoided as far as possible, all those surfaces should be clothed with some non-conducting material. Hair-felt has been largely employed for this purpose, and this is usually kept in its place by an outer 24 THE MARINE STEAM-ENQINE covering of canvas, wood, or sheet-iron. Preparations of cork and other non-conducting materials have also been used. These substances, however, when applied to very hot surfaces, are in danger of being burnt away, and various incombustible non-conductors, such as asbestos, silicate cotton, fossil meal, &c., are now used. The efficient clothing of the hot surfaces is of great importance, and if it be neglected the economical working of the machinery may be seriously impaired. Conduction. The second way in which heat may be transferred from one body to another is by conduction. There are two kinds of conduction, called respectively internal and external conduction. The conduction that takes place between the contiguous particles of one continuous body is called internal conduction. The term external conduction is used when heat passes through the points of contact of two distinct bodies. In boiler plates and flues the resistance offered to heat entering and leaving the surfaces of the plates is in general so much greater than the resistance offered to its passage through the body of the plate, that the nature and thickness of the plate have little effect on the rate of conduction through it, so that the rate depends on the difference of temperature of the fluids on the two sides of the plate. The following approximate rule was given by Rankine for the rate of conduction through boiler plates and flues, but its accuracy is some- what doubtful : ,_(?.- TI)* where q = rate of conduction through the plate, in thermal units per square foot of surface per hour ; Tj and T 2 = the temperatures on the opposite sides of the plate ; and a = a constant, which is in ordinary cases between 160 and 200. Convection. The third method of transfer of heat is by convection. This is the way in which gases and liquids are heated. Conduction, in the true sense of the word, is very slow in liquids, and almost, if not wholly, inappreciable in gases. When heat is applied to the bottom of a vessel containing a fluid, the particles in contact with the bottom are first heated, and become less dense and therefore rise through the superincumbent mass of fluid, allowing cooler particles to take their place, which become themselves heated, and rise and circulate through the mass in a similar manner. It is essential that circulation and mixture of all the particles of a fluid should take place to cause the temperature to be uniform throughout the mass. In order that heat may be efficiently trans- mitted through boiler plates and flues, each of the fluids in contact with them viz. the water on the one side, and the heated gases on the other should have free circulation, so that the particles in contact with the plates should not be considerably different in temperature from those at some distance from the plates. Boilers are sometimes fitted with circulating plates to set up currents in the water, and with bafflers and bridges in the flues to break up the currents of hot gas and form eddies, in order to promote circulation and mixture in the respective fluids. HEAT AND ITS EFFECT ON WATER 25 It can easily be proved that for the most efficient transfer of heat from a fluid on one side of a plate, to another fluid on the other side, the least difference of temperature between the two sides of the plate should differ as little as possible from the greatest difference of temperature, so that the hottest parts of the two fluids should be adjacent to each other, and therefore the coolest parts will also be adjacent. Consequently the surface of a condenser will be most efficient when the cold condensing or circulating water enters the condenser at the end where the condensed steam leaves it, so that the entering steam gives up its heat to the heated circulating water leaving the condenser. Similarly in a boiler the best arrangement from this point of view would be that in which the general motion of the entering feed water is in the opposite direction to the motion of the hot gases. Application of heat to water. We will now consider the effects produced by the application of heat to water. At first the tempera- ture of the water is raised. The particles of water in contact with the heating surface, which in a marine boiler consists of the plates of furnace, combustion chamber, and tubes, become heated, and rise and circulate through the mass of water, their places being taken by cooler particles, till at length the whole of the water is raised to the boiling point by the convection of heat. Sensible heat. The heat added to the water up to the temperature at which boiling occurs is generally called sensible heat, its effect being simply to change the temperature, and not the state, of the water, and its amount may be calculated by means of the thermometer. Latent heat. After