MILK-PLANT EQUIPMENT. 
35 
In some plants the refrigeration medium is expanded directly into 
the cooling coils, while in others brine is used. (The brine is kept 
cold by passing the ammonia pipes through it.) The brine is 
pumped into the cooling coils, or it may remain in the tank, thus 
keeping the room cool a long time after the refrigerating machine 
has been stopped. Both the direct-expansion ammonia system and 
the brine system have their advantages. In large plants where re- 
frigeration is needed continuously for cooling the milk and the cold- 
storage room the direct-expansion system is more economical than 
the brine storage. In small plants where the cooling is done in a 
comparatively short time it is more economical to use the brine- 
storage system of refrigeration, owing to the fact that a smaller 
compressor may be used and refrigeration for use in cooling the 
milk and storage room may be stored in a large quantity of brine 
and held for quick action when needed. However, when the larger 
part of the day is consumed in pasteurizing, so that uniform re- 
frigeration is required, the direct-expansion system is often used. 
In order that the refrigerating machine need not be run contin- 
uously most plants use brine tanks in the cold room, so that the 
room can be kept cold for a considerable time after the machine is 
shut down. 
Table 7. — Systems of cooling milk at 84 milk plants. 
Quantity of milk handled daily. 
Number of 
plants using 
direct- 
expansion 
ammonia. 
Number of 
plants using 
the brine- 
circulating 
system. 
Number of 
plants using 
ice water. 
Total. 
250 or less gallons 
1 
2 
10 
12 
15 
6 
1 
5 
10 
6 
2 
1 
6 
251 to 500 gallons 
12 
501 to 1,000 gallons 
16 
1,001 to 2,000 gaUons 
2,001 to 5,000 gallons 
3 
7 
2 
1 
17 
23 
5,001 to 10,000 gallons 
8 
Over 10,000 gallons 
2 
Total 
13 
47 
24 
• 84 
There are many advantages in the use of brine over direct expan- 
sion alone in a milk plant, some of which are : 
1. The system is more elastic ; the brine can be stored up for cooling 
after the refrigerating machine has been shut clown or in case of a 
breakdown. 
2. There is less danger of freezing the milk on the cooling pipes with the 
brine system of cooling. 
3. Pipes need not be so strong as those required for the direct-expansion 
system of cooling milk. 
4. There is less danger of leaks in the pipes than if direct expansion is 
used, and therefore less danger of tainting the milk. 
5. For small or medium-sized plants the machine would have to run 
longer if direct expansion only were used, because with the brine system 
the machine may store up refrigeration in the brine to last for 10 or 12 
hours, while only 2 or 3 hours are required for cooling the milk. 
