MILK-PLANT EQUIPMENT. 37 
A supply of natural ice is uncertain, depending on weather condi- 
tions; some years there is a shortage, and in the South, of course, 
natural ice can not be obtained. Aside from the possibility of acci- 
dent a refrigerating machine can be depended upon to supply the 
requisite amount of refrigeration at all times. Furthermore, it re- 
sults in cool, dry air in the storeroom, produces lower temperatures 
than ice, and permits more accurate control of temperature. Where 
artificial refrigeration is used less ice is required on the delivery 
wagons, since the original temperature of the milk is lower. Many 
plants find it profitable to manufacture ice for sale as well as for 
their own use. This requires very little extra labor and overhead, 
and yields an additional cash income. 
USE OF EXHAUST STEAM. 
If exhaust steam from the engine is allowed to escape unused a 
valuable by-product is wasted and the coal bill is correspondingly 
high. Exhaust steam can be used successfully for pasteurizing milk 
or cream, heating boiler-feed water and water for washing purposes, 
and for heating the building. By using an exhaust-steam water 
heater an abundant supply of water at a temperature of about 200° 
F. is made available. 
If a plant has an engine and in pasteurizing uses the exhaust 
steam instead of live steam direct from the boiler, the cost of the 
steam for heating the milk and pasteurizing is practically eliminated. 
Generally the exhaust from the engine will furnish all the necessary 
heat. Therefore, in figuring the size of the boiler required, at a 
plant using an engine to run the pasteurizers, bottle washers, and 
other apparatus required in the ordinary retail milk plant, the 
amount of steam to run the engine only need be considered, if the 
exhaust steam is utilized for pasteurizing. 
To heat 300 gallons of milk from 60° to 145° F. requires about 30 
pounds of coal, and with that quantity of milk handled daily an ex- 
haust-steam heater would effect an annual saving of more than 5 
tons of coal. In case the water from the heater is too hot for the type 
of pasteurizer used, the temperature should be regulated automati- 
cally. 
The equipment for utilizing the heat in the exhaust steam in a 
medium-sized plant is simple and inexpensive. 2 Information in re- 
gard to these heaters can be obtained by writing to the Dairy Divi- 
sion, United States Department of Agriculture, Washington, D. C. 
The water used in cooling the milk should be saved and not run 
down the sewer, as is done in many plants. By piping it back to the 
heater or to a tank, not only would the water itself be saved but also 
a considerable quantity of coal. Much water in a milk plant can be 
2 See United States Department of Agriculture Bulletin 747. 
