The mechanical engineering of steam power plants

Front matter

Class TJ'^OO RnnV //' 7 ^

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COFWRIGHT DEPOSnV

Preface

The Power Plant lies at the basis of the comfort and the life of a modern community, and has an interest for nearly every one. There are, however, six groups whom it concerns specially.

The first is the general public, who are supplied with light and power from it, for street transportation, in business and domestic economy, and in the railway, steamer, and motor vehicle; in the waterworks and the factory. To such, the one requisite is reliability; the stoppage or shutdown of the plant must not invade their comfort or convenience in activities or pleasures, in their wage-earning or their safety.

The second group is the business man of the investor or stock-holding class, who has put capital into the power plant, or into the factory which rests upon it. His object is the sale of his product, either in the form of energy or horse power to users of power, or to the other departments of the works which it serves. He also is mainly concerned with the reliability of the plant, both because a stoppage means a loss of income directly, or a future loss in good- will ' towards his investment; but in addition he must demand that the design and combinations in the plant are in accordance with advanced applications of science in order that efficiency and economy shall be attained, and these to the degree that he can still produce at a profit when the market price of his power commodity shall be low. He will not be a designer himself, but will get his designing from others whom he pays.

The third class will be the power-house operators, or engineers-incharge. Their interests are the same as those of the investors as respects reliability and economy, with the added one of convenience, since these must stand by and maintain the efficiency of the plant as the object of their daily toil. They will not be designers or creators as a rule, but are often charged with the responsibility of critical selection from competing apparatus, and to do the duty of the consulting engineer for the second class. Of all the classes, these perhaps have the keenest personal interest and touch with the problem.

The fourth class may be called the contractors. These are not' primarily users of the plant, but are business men who make a specialty of the design, erection, and sale of complete installations. They do not iv PREFACE

usually create the details which they combine into a harmonious whole, although they may manufacture certain elements. They will have engineers of the highest grade working with and under them, as coordinators of design, and may be engineers themselves. In this class are district managers of large producing concerns, certain sales-managers and agents. Their interests are in reliability, economy, and acceptability as in the previous group, since the continuity of their business is involved in satisfying their customers and the consequent reputation. The consulting engineers in this fourth class will be representatives of the seller of the plant.

In a fifth class will be the consulting engineers representing the buyers. These will rarely be creative designers of detail, but as office practitioners will write specifications and draw general plans, for the contractor class or productive manufacturers to meet. Their interests and requirements are the same as with the contractors, and for the same reasons.

Finally, in the sixth class are the creative designers of the details in the plant, who are usually also producers or manufacturers, or who are employed by such as engineers or draftsmen. They are required to meet all the foregoing demands, and in addition to be consulting experts scientifically and professionally, and both as scientific men and shop executives. The demand for such men is continually narrowing the scope of the fifth group; and the commercial effectiveness of business done by the fourth group is as steadily broadening their field, and bringing the producer, who is also the creator through the engineers in his employ, into the first rank and securing increasing consideration for him.

The student of engineering may become a member of any group of the foregoing. The broadest field for him on graduation and where he is best paid is in the growing fourth group. His study of the power plant may therefore wisely be directed to fit him for usefulness in that class, leaving his later specialization in design or creation to be the result of circumstances in his life.

The view-points for power-house problems are two. The one is the functional requirement : what is to be accomplished, and what apparatus is needed to do this work. The other is quantitative : how large must the apparatus be to do a certain quantity of such required work. Plainly the first three groups are concerned only with the first; and only the engineers of the fourth group with the second. The engineers and designers of the sixth class are mainly concerned with proportions or

PREFACE V

quantities; but they also must begin the study of their specialty at the functional end, which will be the basis for quantitative design in any case. Hence the object of this book is largely the study of function and purpose of power-plant apparatus. It is not to be regarded as a- treatment of design of the elements of the power plant, but only of the power plant as an aggregate of elements. To have included machine design would have rendered its real contents hard to get at in the multiplicity of topics, and would have made the conditions prohibitory as respects size and price. Furthermore, power-plant design should be taken up with a more mature knowledge than is supposed to belong to the beginner, and should cover many matters difficult to treat fairly in a text-book. The last chapter is intended as an open door to some of these questions, and for more advanced students.

The basis of theoretical mechanics under some elements of power-plant practice has been given in smaller type than the main trend, so that those to whom it is of secondary interest may skip it without sacrifice of continuity.

A former edition of this book, issued in 1897, embodied the study and experience of the author gathered during the previous twenty years and brought together for teaching purposes. The years since then have been a period of great and rapid progress in the power plant and in all engineering departments contributory thereto; and while the old edition was modernized here and there and year by year, the time had come with the opening decade of the twentieth century that it be rewritten entirely. The present edition is the result of such rewriting.

It is a new book so much enlarged that the old plates could not be used, but the size of page has been increased, new illustrations chosen, and many new topics and treatments have been introduced. While the former approved analytical view-point is retained and amplified, there has also been introduced a discussion in many chapters of the principles and data of applied mechanics attaching to the subject in hand. This has been done to enable teachers who desire to enliven the drill in the mathematical classes to find practical problems and applications of interest and future meaning, and to encourage teachers of the applications of theory to find easily the links and bases for such sound applications. The distinction between the applied thermal principles and those derivable from other departments of theory should tend also to clearness and benefit.

The new treatments which are specially noteworthy are those of

Vi PREFACE

the analysis of the power plant and its diagram, and the separation between the simple and the complex phases of this problem; the treatment of the steam pipe as an element of co-ordinate importance in the plant with the boiler and the engine; the chapters on the auxiliaries as distinguished from the essentials; the steam turbine chapter, the engine mechanism chapter, and the establishment of the philosophy of the expansion of the elastic medium as the basis for the valve gear, the governor, the condensing and the compound engine. This is new, and it is believed that it will be helpful and illuminating. Some data and tables have been introduced, but only sparingly. The author prefers that students should acquire the habit of going to the ^'Engineers' Pocket Books" for statistical or quantitative information, using this book to give a perspective or setting to make clear the meaning and interpretation of such data and constants as these excellent books are prepared to furnish.

The book has been written with other objects as well as for its use as a text-book in schools of engineering. But the recognition of the basal and fundamental importance of the power plant in all kinds of engineering enterprises has necessarily given this possible use a great share of consideration. It may not be amiss therefore to suggest some methods for such use which have been tried out in the author's experience, and have been before his mind in preparing the text.

1. The primary purpose of the educational process should be to make the learner think. While it is true that knowledge is power, such knowledge and power are only really possessed for any time by him whose faculties have exercised themselves in the process of deducing principle from fact. Hence the recitation process is far to be preferred to the lecture method of instruction in such a subject as this.

2. The recitation method at the blackboard by sketch or upon the drawing-pad is far the best. The sketch cannot be vague or indefinite, and hence the knowledge which it reveals must be equally precise and definite. This in itself has an educational value.

3. The reproduction of the illustration in outline should be so done that the principle is laid bare, and the accidental or accessory detail is relegated to second place or omitted. The illustrations have been chosen to favor this procedure; and old cuts have been retained even when newer practice differs from the old, where the principle was clearer in the old than it would have been in the new. This explains

PREFACE Vii

further the copiousness of illustration; it justifies the use of figures from commercial sources as giving living and present interest to what might else be dry and unattractive.

4. The instructor should reaUze that in any class the number is small who will be called on to design and construct any detail of the power plant; but that all are sure to be called on to buy some or all of these elements, or to design power plants as a whole, in which such elements are to function. Hence the training in the process of selection, of critically weighing arguments for and against an apparatus, and evaluating advantages and disadvantages, becomes a most valuable discipline. The treatments designed to this end should be diligently so used.

5. It would be impossible to make the treatment and particularly the illustrations cover every embodiment of principle which is now in use. The book would exceed the intelligent limits of size and price with even current practice; and the progress of science, invention, and design is continually bringing new material. The instructor is urged to bring such new illustrations into class in the form of photographs, lantern-slides, trade-catalog literature, and the articles from the technical press and society proceedings; and to use them in the same way as in Nos. 2, 3, and 4 above in supplement to what the text covers. The country is so large that standard practice in one section may not be well known in another, but a broad view requires consideration of all practical solutions.

6. For the more advanced student whose instruction should be more personal, and in seminars or conferences, there are no better text-books to suggest topics for discussion than the technical newspapers and magazines. These offer up-to-date and live issues, new problems and their solutions, accidents and failures, queries and opinion. But to utilize such material by partly trained students or those having limited experience only, recourse should be had to fundamental principles, accepted standards, and the teachings of the past and of experience. For such elements the treatments of this book may be conveniently used, and such advanced students will find more material upon a re-study than they found in the first contact with the text.

7. It is an admirable drill in the thought-compelling process and for its impress on the student, to compel him to formulate the questions upon the sketch or illustration. This can be done most effectively by the lantern-slide, exhibited by an electric projection lantern to a whole class in a room not wholly darkened. If one student- can ask the questions for another to answer, not only is the answerer forced to think, but the questioner even more. The instructor can reach the

VIU PREFACE

perspective and view-point of the class for a guiding and stimulation of the discussion and for an effective summing up.

8. Finally, there is no engineering literature of greater teaching value than the specifications which have been used in successful practice. To use and digest these, however, a certain previous knowledge is requisite. If the student can have these specifications given to him, and be compelled to defend the requirements therein set forth on the basis of discussions in such a text-book as this, he receives an unequaled training for his future work. Advanced students can be drilled with specifications in evaluating alternate requirements, on the basis of what they can find in the fundamental treatments in the text.

The critical student of power-house problems may propound two questions: Is not the development of the steam turbine to render valueless a treatise of this sort in a year or two, in so far as it relates to the reciprocating engine? and will not the spread and development of the internal combustion motor or gas engine render valueless the space devoted to both boiler and steam engine?

There are several categories to the answer to the first question:

1. The turbine will not displace the reciprocating engine in cases where the starting resistance is high at necessarily low speed* of turning.

2. The turbine is not so much better in economy or convenience than a good economical reciprocating engine that owners and users are going to displace the latter. The turbine may be installed for new developments, but the reciprocating engines will run for years yet.

3. The turbine is at its best for electrical transmission of the power: where some other medium is better the reciprocating engine will remain.

4. The turbine is at its best for large units; for small and medium conditions the reciprocating engine still has a field of its own.

5. Everything in this treatise concerning the boiler, the piping, and the auxiliaries remains untouched by such a change if it occurs. Perhaps the auxiliaries receive enhanced importance in a turbine plant, and what attaches to the details of the main motor herein will be equally true for the greater part of the enlarged auxiliaries.

6. The turbine will not displace the reciprocating engine where the resistance must be slow-moving, calling for a gearing down of the speed of the motor element.

7. The most complete disappearance of the reciprocating steam engine will occur, if at all, when all industry is carried on by transmitting electrical energy distributed from central generating stations. The driving engines in these central stations will be turbines or gas engines,

PREFACE ix

and there will be no isolated or independent steam engines at all, in the plants of individual parties.

The second question, concerning the vogue of the gas engine, is also one which' is not to be answered by a single sentence.

1. . There is no doubt that enormous increase is to be foreseen in the use of the small internal combustion engine using carbureted air from liquid fuel. This will be in motor boats, in motor vehicles, in railway branch service, and in stationary practice, and it will displace the small steam engine and be used in places where the reciprocating engine will not go.

2. But for large installations, the cost of liquid fuel compared with coal becomes prohibitory under economic conditions, and the gas producer must be provided. As soon as this happens, many advantages of the gas engine begin to balance up with those of the steam plant, although the avoidance of the auxiliaries of the steam plant leaves a heavy balance in favor of the other system.

3. But when the largest size of generating unit is called for, the big gas engine meets its limiting condition, just when the steam engine is reaching its best. The problem of cooling the big engine with a large diameter cylinder, and disposing of the great quantity of heat released in the combustion of masses of gas, introduces difficulties with the gas engine which are not yet solved, and perhaps are not going to be. The big gas engine becomes costly, bulky, and occupies great space. Repairs and maintenance mount up; auxiliaries for starting appear, and the advantages of the big steam plant begin to emerge anew.

4. Finally, in any industry where the exhaust from the steam engine is required in the industrial process for heating solutions, or for drying as in the paper and textile industries, or for the heating of buildings in winter as in the office-buildings of the congested cities, the steam engine as source of needed power will have the balance in its favor.

The gas turbine, if it becomes reahzable by discovery of new laws or methods to avoid the prohibitive action of known old ones, will of course revolutionize many departments. But until these steps are taken there will be some time during which the steam engine will justify the study this book encourages and provides for.

The writer of to-day is under profound obligations to those who have preceded him, and this edition in particular owes much to writers whose work has appeared since the earlier publication was made. Besides repeating the acknowledgments of the earlier edition, special recognition should be made for valuable co-operation from Mr. Charles L. Hubbard,

X PREFACE

author of " Power Heating and Ventilation;" from Mr. Lester G. French and Prof. C. C. Thomas in the discussion of the steam turbine; from Mr. Henry C. Meyer, author of '' Power Plants," and to their publishers for permission to make use of cuts in convenient form. The help of manufacturers and designers is also gratefully acknowledged in the matter of illustrations and special designs of such producers. Prof. John Goodman of Leeds, and Prof. John Perry of London, England, have been strong influences upon the author in his more mathematical discussions of topics, and he is glad to recognize these obhgations. He would heartily thank those instructors and other users of the text-book for their appreciative comment and helpful criticism.

Attention should finally be called to the re-arrangement of topics, whereby the boiler and its accessories has been made to precede the engine and its problems. This will be found to offer a teaching advantage in that the phenomena of the boiler and combustion belong to the simpler problems of chemistry, physics, and mechanics, and their study can begin early in a progressive course. The moving engine using transformed heat in the form of pressure and changing pressure into work compels an outlook upon the principles and data of thermodynamics, and is conveniently placed later where greater maturity and a wider range of study will permit the theory and the practice to be more effectively co-ordinated than with the older arrangement upon a different logical basis. Hence also much of the book can be made to precede the study and practice of the practical or experimental engineering laboratories of the schools, as well as courses in engineering design on the drawing board; and with manifest advantage.

It is the wish and hope of the author that the material here brought together and the methods of treatment may be found serviceable in the work of engineering education to which he has given so many happy years.

F. R. HUTTON.

New York City,

September, 1908.

PART I. Introductory

PAGE

1. The Function of the Power Plant. , , 1

2. Sources of Motor Energy for the Power Plant. Internal and

External CombustioiT 2

3. Measurements of the Work Unit of Output. Indicated Horsepower,

Brake Horsepower 3

4. Elements and Analysis of the Steam Power Plant 4

CHAPTER I. The Quantitative Basis of the Steam Power Plant

6. The Horsepower of a Piston Motor. The Cylinder Volume 10

7. The Work Unit and Heat Unit are Convertible. The Volume of

Steam per Horsepower 12

8. The Water Rate of Steam Engine 13

9. The Heating Surface of a Steam Boiler. Transfer of Heat 14

10. The Horsepower of a Boiler. A.S.M.E. Standard. 15

11. The Pounds of Coal to Evaporate a Weight of Water 16

12. Grate Surface to Burn a Weight of Fuel in a Given Time. Rate of

Combustion 16

13. The Cost of a Horsepower 18

14. Summary and Conclusions 18

Chapter II

The Boiler. Forms, Material and Manufacture.

21. The Function of the Boiler or Steam Generator ...._. , , . 19

22. The Storage of Energy in a Steam Boiler 20

23. The Problems of Physics respecting Transfer of Heat . 23

xi xii TABLE OF CONTENTS

PAGE

24. Combustion 26

25. The Problems of Mechanics respecting Form and Internal Stress. 26

26. Values of the Stresses in Boiler Shells. Thickness of Boiler Plate ... 28

27. Materials for the Boiler Shell. Specifications and Tests 30

28. Shaping the Shell Elements. Curving Plates 32

29. Arrangement of Rings of Plate in Shells 34

30. Shaping the Shell Elements. Flanging Heads . 35

31. Joints in Boiler Shells. Welding 37

32. Riveted Joints for Boiler Shells 39

33. Construction of a Riveted Joint. Punching and Drilling 40

34. Punching and Drilling Compared 41

35. Hand and Machine Riveting ? . 43

36. Mechanics of the Stress in a Thin Cylinder 47

37. Copper, Cast Malleable and Wrought Iron for toiler Shells 47

CHAPTER III. Boiler Riveting, Staying, and Structural Details

40. Mechanics of the Riveted Joint. Efficiency 49

41. Arrangement of Rivets in a Joint. Special Joints 51

42. Failure of the Riveted Joint 56

43. The Drift Pin '. 56

44. Stays and Staying , .... 57

45. Manholes . 66

46. Handholes 70

47. Edge-Planing and Calking 70

48. Disengagement-Area, Water Space and Steam Space 72

49. Domes and Steam Drums 73

50. Mud-drums 79

51. Concluding Comment. Classification of Types 80

CHAPTER IV. Fire-Tube Boilers Externally Fired

55. Types of Boiler in the Fire-tube Class 84

56. The Tubular or Multitubular Type 84

57. The Tubes for Fire-tubular Boilers 87

58. Ribbed Tubes. Retarders 90

59. Arrangement of Fire-tubes 90

60. The Fhie Boiler 92

61. Reinforced Flues for Long Boilers 95

62. Conditions Suggesting Choice of Tubular or Flue Types . , 96

63. U. S. Formulae for Flues 97

TABLE OF CONTENTS xiii

Chapter V

Fire-Tube Boilers. Internally Fired.

PAGE

65. Definition of Internal Firing. Advantages and Disadvantages of the

. Principle 100

66. The Cornish and Lancashire Boiler 102

67. The Galloway Tube in Lancashire Boiler 103

68. The Scotch or Cylindrical Marine Boiler 103

69. The Rectangular Marine Boiler 107

70. The Locomotive Boiler 109

71. The Locomotive Boiler with Corrugated Furnace 116

72. Derivatives of the Locomotive Boiler , : 119

73. The Upright Boiler 120

74. Modifications of the Upright Boiler 126

75. The Fire-engine Boiler 127

76. Combinations of Type 129

CHAPTER VL

Water Tube Boilers.

81. The Plain Cylinder Boiler 132

82. The Elephant Union and French Boiler 132

83. The Sectional Principle 134

84. Advantages of the Sectional Principle 134

85. Disadvantages of the Sectional Principle . 135

86. Classes of Sectional Boiler 137

87. Spheroidal Unit Type 138

88. Vertical Straight Open Tube Type 140

89. Horizontal Straight Open Tube Type 141

90. Vertical Curved Open Tube Type 149

91. Horizontal Curved Open Tube Type 152

92. Closed Straight Vertical Tube Types. Field Tubes 152

93. Closed Straight Horizontal Tube Types 154

94. Bent or Curved-Tube Types 154

Chapter VII

Coil and Pipe Boilers. Flash and Semi-Flash Boilers.

96. Tube -and -Fittings Boiler 155

97. The Coil Boiler 156

98. Sundry Types. Conclusions 157

99. Spray Boilers 160

100. Flash and Semi-Flash Boilers 160

XIV TABLE OF CONTENTS

CHAPTER VIII. Boiler Furnaces, Chimneys and Setting

PAGE

105. The Fire as the Source of Energy 165

106. Principles Underlying the Boiler Grate 167

107. Principles Underlying the Chimney 167

108. Discussion of Peclet's Theory of Chimney Draft 170

109. Some Accepted Chimney Formulae and Data 171

110. Dilution of the Products of Combustion 174

111. The Grate Bars. Stationary Grates 174

112. Shaking and Dumping Grate Bars 176

113. Step Grates : 179

114. Mechanical or Traveling Grates. 179

115. Mechanical Stokers 181

116. Inclined and Horizontal Grates 181

117. The Firing on the Grates 184

118. The Dead-plate and Furnace Mouth-piece 184

119. The Ash-pit 186

120. The Bridge-wall 187

121. The Combustion Chamber 190

122. The Back Connection 194

123. The Front Connection 195

124. The Flue to the Chimney-stack 195

125. The Damper and Damper Regulator '. . . . 196

126. The Chimney 198

127. Artificial or Mechanical or Forced Draft 202

128. Advantages of Artificial Draft 205

129. Disadvantages of Artificial Draft 206

130. Smoke prevention 208

131. Boiler Setting. Side walls 215

132. Buck Stays and Tie-Rods 217

133. Hanging of Boilers 218

134. Boiler Fronts 220

135. Concluding Comment. Gallows Frame Supports 225

CHAPTER IX. Firing Boilers with Gas or Liquid Hydrocarbon or with Pulverized

Fuel.

137. Gas Firing of Boilers 227

138. Liquid Fuel Burners 228

139. Liquid Fuel Furnaces 230

140. Precautions in Oil Firing 231

TABLE OF CONTENTS XV

PAGE

141. Advantages of Oil Fuel , 232

142. Disadvantages of Oil Fuel 233

143. Pulverized Fuel Systems 234

144. Sundry Special Fuels 234

145. Conclusion. Heat Balance , 236

CHAPTER X. Boiler Accessory Apparatus

147. The Feed-Pump , 240

148. The Attached Pump or the Independent Feed-Pump 241-3

149. -The Fly-Wheel Pump 244

150. Direct Acting Pump 245

151. The Feed Pipe and its Valves 249

152. Introduction of the Feed Water 250

153. Blow-off Pipe 252

154. Loss in Blowing-ofi 253

155. The Injector 253

156. Mechanical Principles underlying the Injector. Induced Current

Principle o 255

157. Heat Transfer; Work and Efficiency in the Injector 256

158. Mechanical Principles of Impact in the Injector 257

159. Double Tube Injector. The Inspirator 258

160. Re-starting or Automatic Injectors 259

161. Exhaust Steam Injectors 260

162. Advantages of the Injector , 260

163. Disadvantages of the Injector 260

164. Water Gages 260

165. The Glass Water Gage and Water Column .' . . 261

166. The Gage-Cocks 266

167. Float Water Gages .' 266

168. Low Water Alarms 268

169. Fusible or Safety Plugs 268

170. Automatic Feeding Apparatus 269

171. The Steam Gage 271

172. Standardizing or Calibration of Steam Gages 274

173. Recording Gages 274

174. The Relief or Safety Valve , . 275

175. Forms of Safety Valve 275

176. Safety Valve Formulae , 277

177. Computations for the Lever Safety Valve 278

XVI TABLE OF CONTENTS

CHAPTER XL Care and Management of Boilers.

PAGE

180. The Firing 279

18L Cleaning Fires 279

182. Banking Fires 280

183. Regulation of the Fire and Pressure of Steam , 280

184. Cleaning the Heating Surface Outside 281

185. Boiler Scale or Incrustation 282

186. Inconveniences Due to Boiler Scale 285

187. Removal of Boiler Scale 286

188. Prevention of Scale Formation , 287

189. Previous Purification of Feed Water • • 290

190. Filtration of Feed Water 291

191. Determination or Wear and Tear of Boilers 292

192. Overheating of Boilers 292

193. Unequal Expansion and Contraction of Boilers 292

194. Corrosion External 293

195. Corrosion Internal 294

196. Pitting, Wasting and Grooving 295

197. Repairs General. 296

198. Patches 297

Chapter XII

Boiler Inspection and Testing. Boiler Explosions.

200. Boiler Inspection. 298

201. The Steam Pressure Test 298

202. The Hot Water Pressure Test 299

203. The Cold Water or Hydrostatic Test , . 299

204. The Hammer Test ' 299

205. Boiler Explosions. General 300

206. Boiler Ruptures because too Weak 300

207. Boiler Ruptures from Excess of Pressure 301

208. Theory of Boiler Explosions 302

209. Energy Resident in Hot Water under Pressure 302

210. Reaction in Boiler Explosions 303

211. Procedure when a Boiler is in Danger of Rupture 303

212. Heating Effect of Steel Plate and Cooling Effect of Water 304

213. Time Required by Boiler to absorb Heat and Pressure Energy 304

214. Steam Boilers as Magazines of Explosive Energy 305

TABLE OF CONTENTS xvii

CHAPTER XIII. Boiler Plant Auxiliaries

PAGE

221. Coal Handling Machinery 307

222. Ash Handling Machinery 308

223. Mechanical Stokers 309

224. The Forced or Induced Draft by Fan and Motor or Engine 315

225. Preheating of Feed Water 315

226. Flue Heaters or Economizers 316

227. . Exhaust-steam Feed Water Heaters 317

228. Superheating of Steam 321

229. Methods of Superheating 325

230. Advantages of Superheating 327

231. Disadvantages of Superheating 329

232. Combustion Indicators 330

233. Water Meters 332

Chapter XIV

The Piping of Pressure to the Engine and its Accessories.

236. The Stresses in a Steam Pipe and its Requirements 336

237. The Material for a Steam Pipe 339

238. Steam Pipe Joints and Fittings 340

239. Expansion of the Steam Pipe by Heat 345

240. Hangers and Carriers for Steam Pipe 347

241. Valves for Steam Pipe 348

242. Grading of Steam Pipe 354

243. Drainage of Steam Pipe. Separators 354

244. Non-conducting Coverings for Steam Pipe 360

245. Exhaust Pipe 362

247. Exhaust Heads 366

248. Back-pressure valves 367

249. Reducing valves 368

250. Drip-Connections 369 xviii TABLE OF CONTENTS

CHAPTER XV. The Engine

PAGE

255. The Ordinary Steam Engine 372

256. The Kinematics of the Crank-connecting-rod Mechanlsmo Some

Engine Mechanisms 376

257. Deductions from the Kinematic Chain of the Steam Engine 385

258. Effectiveness of the Crank-connecting-rod Mechanism 387