ECONOMICAL USE OF FUEL IN CREAMERIES. 31 
a greater economy may be obtained by using a gas engine or an 
electric motor that can be put into or out of service as required. 
The relative cost of coal, gasoline, or electricity delivered at the 
factory must also be taken into account in selecting the kind of 
power best suited for any particular plant. In some cases the factory 
is a considerable distance from the railroad, and the inconvenience 
and expense of getting coal to the plant may be such as to prohibit 
the use of a steam engine. In other cases the cost of electricity may 
be so small as to make its use profitable. By utilizing the heat in the 
jacket water and exhaust gases of internal-combustion engines it is 
possible in some plants to produce the necessary quantity of hot 
water for heating, or the heat may be used to supplement that of a 
steam boiler, thus reducing the size of the boiler. A typical arrange- 
ment of such an equipment is illustrated in figure 9. In short, there 
is such a wide variation in the operating conditions of creameries 
throughout the country that it is impracticable to state in general 
just which form of power is the most economical, as each case re- 
quires a special study. 
UTILIZING THE EXHAUST STEAM. 
It should be the aim of any one in charge of a steam plant to 
utilize as much of the heat energy contained in the fuel as practic- 
able, and there are few classes of steam plants that offer more varied 
opportunities for the utilization of exhaust steam from the engine, 
pumps, and other steam-driven machinery than those used in the 
dairy industry. In plants in which steam is generated for power 
purposes only, even with the best possible apparatus- and arrange- 
ment, only a small portion of the heat in the coal is utilized. In the 
dairy industry, however, where much low-temperature heating is re- 
quired which can be accomplished through the use of exhaust steam, 
even the smallest plants with little or no extra expense can be made 
much more efficient than the most modern steam plant when used only 
for the generation of power. There are dairy plants, however, that are 
taking advantage of their opportunities to use the heat available in 
the exhaust steam. 
In the, dairy industry large quantities of hot water are required 
for washing apparatus and utensils, pasteurizing, boiler feed water, 
and other purposes around the plant. The heating is done at present 
for the most part by live steam from the boiler, whereas the large 
amount of exhaust steam going to waste might be used for the pur- 
pose. 
Exhaust steam at atmospheric pressure contains between 85 and 
90 per cent of the heat of the live steam at 70 pounds' gauge pressure. 
