232 BOILER TESTS. 



Horse-power developed, . 189.3 H. P. 



Boiler pressure, 72.9 Ibs. 



Temperature of feed-water, 66 deg. 



Temperature of escaping gases, 523 deg. 



Draught suction, . . . . . . . . . 0.21 in- 



Percentage of moisture in steam, ...... 0.4 per cent. 



Water per pound of coal, 8.68 Ibs. 



Water per pound of coal from and at 212 degrees, . .10.28 Ibs. 



Water per pound of combustible from and at 212 degrees, 10.98 Ibs. 



The test on Boiler No. 71 shows the performance of a water 

 tube boiler using Cumberland bituminous coal. The condi- 

 tions under which the tests were made are all favorable to 

 good economy with the exception of one, that is, the tempera- 

 ture of the escaping gases. This is so far above the economic 

 point that it fully accounts for the somewhat low evaporative 

 result secured, this being 10.98 pounds of water from and at 

 212 per pound of combustible. It is difficult to assign a 

 satisfactory cause for the high temperature of the waste gases 

 in this case. It is evidently due to inefficiency of heating 

 surface, but the difficulty lies in determining the cause of the 

 inefficiency. It is known that the interior surfaces of the 

 boiler were clean ; the exterior surfaces were as clean as the 

 thorough use of a steam jet could make them. Either this 

 method of removing the deposits of soot from the exterior of 

 the pipes did not accomplish its purpose, or there is some 

 fault in the arrangement of the heating surface, whereby it 

 fails to properly absorb the heat. 



Preparatory to the test on this boiler the cracks in the brick 

 work, and all the crevices around the doors, with which the 

 boiler is provided for purposes of cleaning, were filled with 

 fire clay. The effect of reducing by this means the quantity 

 of air which was drawn in was revealed by means of the 

 draught gauge. With no fire in the furnace, and the fire and 

 ash doors closed, a draught of 0.31 of an inch in the main 

 flue, with wide open damper, produced a draught of 0.25 of 

 an inch between the damper and the boiler, before the open- 

 ings were closed, and the full draught of 0.31 of an inch after 

 they were closed. When the damper was in a partly closed 



