302 MARKET DAIRYING 
ting plant will require some of the butter maker’s time 
and attention, but this is probably no more than would be 
consumed in the handling of ice in the creamery. 
Charging and Operating an Ammonia Plant. This 
subject is so ably discussed in The Engineer by H. H. 
Kelley that the author feels he can do no better than 
present the following extracts from that article. 
“When about to start an ice or refrigerating plant, the 
first thing necessary is to see that the system is charged 
with the proper amount of ammonia. Before the ammonia 
is put in, however, all air and moisture must be removed ; 
otherwise the efficiency of the system will be seriously 
interfered with. Special valves are usually provided for 
discharging the air, which is removed from the system 
by starting the compressor and pumping the air out, the 
operation of the gas cylinder being just the reverse of that 
when it is working ammonia gas. It is practically impos- 
sible to get all the air out of the entire system by this 
means, so that some other course must be taken to remove 
any remaining air after the compressor has been started at 
regular work. This can be accomplished by admitting the 
ammonia a little at a time, permitting the air to escape 
through a purge valve, the air being thus expelled by dis- 
placement. The cylinder containing the anhydrous am- 
monia is connected to the charging valve by a suitable 
pipe, and the valve opened. The compressor is then kept 
running slowly with the suction and discharge valves wide 
open and the expansion valve closed. When one cylinder 
is emptied put another in its place, being careful to close 
the charging valve before attempting to remove the empty 
cylinder, opening it when the fresh cylinder is connected 
up. 
“From sixty to seventy-five per cent of the full charge is 
