MECHANICAL REFRIGERATION 211 



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 



