192 BOILER TEXTS. 



The tests on Boiler No. 53 were made to determine the 

 economy of the boiler when burning anthracite coal, both with 

 natural and forced draught, and that obtained when using athra- 

 cite screenings with forced draught. Comparing test No. 107 

 with No. 106, the use of the blower increased the power 

 developed by the boiler from 64.3 horse power to 91.2 horse 

 power, or 42 per cent., and this was accompanied by a reduc- 

 tion in the evaporation per pound of combustible of 7.5 per 

 cent. After allowing for the small difference in the amount of 

 superheating, the reduction becomes 6.7 per cent. The effect 

 of the higher rate of combustion was to increase the tempera- 

 ture of the escaping gases from 478 to 573 degrees, and to 

 this large increase in the amount of waste heat may be 

 attributed the reduction in economy noted. Comparing these 

 results with those obtained from boilers having a less propor- 

 tion of water heating surface, it is seen that this boiler has the 

 advantage. In Boiler No. 51 for example, the ratio of water 

 heating surface to grate surface is 20.6 to 1, and the evapora- 

 tion per pound of combustible from and at 212 degrees, 

 corrected for superheating, is 9.94 pounds. In Boiler No. 53, 

 under consideration, the ratio of water heating surface to 

 grate surface is 32.3 to 1, and the result obtained, corrected 

 for superheating, is 10.34 pounds of water per pound of com- 

 bustible. The result obtained by the use of screenings with 

 forced draught compares favorably with that obtained under 

 the same circumstances with the standard coal, being inferior 

 to the coal result only 8.1 per cent. No allowance is made in 

 the tests with forced draught for the cost of power required to 

 operate the blower. 



Boiler No 54. 



Kind of boiler, Vertical tubular (rolling pin ) . 



Number used, One. 



Horse-power ( basis 10 square feet ), . One hundred and forty. 



v - f , / Two parts Anthracite Screen- 

 Kind of coal, | . ngs onc part Cumber iancl. 



A.ge, Ten years. 



