66 



Indiana University Studies 



required of it. Non-expert purchasers are liable to accept 

 machinery which is not the best adapted to the service for which 

 it was intended. 



Professor G. F. Gebhardt in his book Steam Power Plant 

 Engineering (first edition, p. 681), gives the following description 

 of the horizontal tubular boiler: 



These [boilers] are the most common in use and are constructed in sizes 

 up to 200 horse-power. They are simple and inexpensive and, when properly 

 operated, durable and economical. . . . The grate is independent of 

 the boiler and the products of combustion pass beneath the shell to the 

 back end, retm-ning thi'ough the tubes to the front, and into the smoke 

 connection. 



The tubes are from 3 to 4 inches in diamater and from 14 to 18 feet long 

 and are expanded into the tube sheets. The portion of the tube sheet not 

 supported by the tubes is secm-ed against bulging by suitable stays. Access 

 to the interior is obtained through manholes. 



The following suggestions were made by Mr. G. W. Bissell 

 in his paper on "Selection of Power Plants and Equipment for 

 the Quarries of Iowa," and are published in the Iowa Geological 

 Survey, Vol. xvii, pp. 151-183: 



For the local coals as fuel the boiler should be relatively long and should 

 be set high above the grate and should have liberal grate area and stack 

 capacity. All boiler tubes for the use of local coals should be at least 4 

 inches in diameter, on account of the excessive accumulation of soot. Twelve 

 square feet of heating surface should be allowed for each boiler horse-power 

 desired. One square foot of grate sm-face should be allowed for every 40 

 square feet of heating sm-face. That would requu-e 33 square feet of grate 

 area for a 100 horse-power boiler. A 72-inch boiler should be at least 36 

 inches above the fu^e. 



In this respect most of the boilers of this district are at fault 

 since few" of them are more than 30 inches above the grate. The 

 coals of Indiana coal fields are slightly lower in volatile matter, 

 and the amount of soot is not quite so high, nevertheless the above 

 suggestions may well be foUow^ed here, since the differences 

 are not great enough to materially affect the result. 



The following table (from Bissell's paper on ''Selection of 

 Power Plants" in Vol. xvii of the Iowa Geological Survey, p. 

 158), contains approved dimensions for fire-tube boilers for use 

 in ordinary" quarry service: 



1 



