Mance: Quarry Industry of Southern Indiana 65 



in the selection of engines of low steam consumption, when in 

 reality the most important part of a steam power plant is the 

 boiler equipment and its proper operation. Boiler operation 

 represents the largest share of the operating expenses of any 

 power plant. The best efficiences can be secured only in plants 

 where skill, good judgment, and continued vigilance are practiced. 

 The development of the steam boiler has reached a point where 

 the same evaporation rate can be reached by all if the proportions 

 of grate and heating surface are correct and the operating con- 

 ditions are the same. The present method of boiler rating is 

 very misleading, since any rate based upon the square feet of 

 heating surface regardless of its position cannot be accurate. 

 The ability of a surface to transmit heat to the contained water 

 depends upon its position with regard to the grate and the point 

 of maximum combustion. The proper ratio of grate area to 

 heating surface for boilers using the local grades of bituminous 

 coals should be about 1 to 45. 



Some of the principal factors governing the selection of a 

 steam boiler are: space occupied, weight, capacity, first cost, 

 adaptability to the particular condition under which it is to operate 

 and the location of the plant in which it is to be placed. It is 

 necessary to determine which are the best proportions for the 

 boiler for the use to which it is to be put. 



Even in small plants expert advice should be obtained and 

 followed. Mr. H. C. Meyer in his work on Steam Power Plants 

 (pp. 1, 2), says: 



No better service can be done the non-expert about to construct a steam 

 plant than to advise him to engage at the outset of the project some capable 

 engineer to design the plant and superintend its installation. . . . It is 

 the practice of many engineers in steam plant construction to invite bids on 

 apparatus described very generally in the specifications and intended to 

 perform a service under the conditions named, the idea of the engineer 

 being to allow each bidder to proportion the parts of the apparatus he is to 

 furnish and to quote a price on it. When bids are received under these 

 conditions, it generally follows that there are many variations in the sizes 

 of the machinery offered by the different makers to do the same work, and 

 the lowest in price ma.y not be the best adapted for the conditions. 

 The expert engineer, of course, is able to detect and reject bids on deficient 

 apparatus. 



While an engine may give the required power, its cylinders 

 may be so small that it requires an excessively large amount of 

 steam to run it, or a boiler may be so small that an abnormal 

 amount of coal must be burned in order to generate the steam 



