44 
BTTLLETIX 
U. S. DEPARTMENT OF AGRICULTURE. 
largest and one that can be reduced only slightly by careful firing 
and by stopping all air leaks in the setting, firing doors, doorframes, 
and other places. Even in the case of a well constructed and main- 
tained boiler setting, 10 pounds of coal per horsepower capacity of 
boiler will be required for raising steam. With poorly constructed 
and maintained settings this quantity of coal will be exceeded. 
The loss of small particles of unburned coal which fall through the 
openings in the grate bars and are removed with the ashes may be 
reduced by more careful firing. The coal is broken up and falls 
through into the ash pit on account of stirring the fuel bed with the 
firing tools. If proper attention is given to the fire it is not neces- 
sary to stir up the fuel bed, and the percentage of unburned coal in 
the ashes will thus be reduced. While it is impracticable to eliminate 
this loss entirely, careful firing will greatly reduce it. 
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Fig. 14. — Graphic illustration of the possible distribution of heat energy in a creamery 
making 500.000 pounds of butter annually from pasteurized cream. 
The quantity of heat radiated from the setting, uptakes, breeching, 
and from the exposed positions of the boiler itself depends, of course, 
on the arrangement of the particular plant, and while it is given in 
the table at 4 per cent, it is often considerably more. While some 
loss by radiation is unavoidable, the greater portion can be prevented 
through insulating the exposed surfaces. Efficient insulation not 
only conserves the heat but reduces the temperature in the boiler 
room, increases the draft, and when applied to iron surfaces prolongs 
their life. The insulation of the uptake and breeching may be effected 
by applying asbestos or magnesia blocks held in position and covered 
with a half -inch coat of asbestos or magnesia plaster. The walls of 
the boiler setting should be made amply thick to begin with, and 
should have a 2-inch space constructed in the wall. The United 
States Bureau of Mines, through exhaustive experiments, has proved 
that a wall with an air space will lose more heat than one of the same 
thickness constructed of solid masonry. The air space, however, is 
valuable in reducing the liability to crack. It should be filled with 
