APPLICATION OP REFRIGERATION TO HANDLING OP MILK. 33 



The suction and discharge valves should be wide open while the 

 machine is being charged. When one tank is emptied the charging 

 valve should be closed and another tank placed in position, this being 

 repeated until the system is sufficiently charged for work, when the 

 charging valve should be closed and the main expansion valve 

 adjusted. The ammonia drums should be weighed before and after 

 being emptied or partially emptied, and a record kept of the amount 

 necessary for charging. The glass gage on the liquid receiver will 

 show the amount of liquid contained, and the pressure gages, as well 

 as the gradual cooling of the brine in the refrigerator and the frost 

 collecting on the expansion pipe, will indicate when a sufficient 

 amount of the refrigerant has been inserted to start working. 



OPERATING. 



After the machine has been started and the expansion valve ad- 

 justed, the temperature of the delivery pipe should be carefully 

 noted, and should a tendency to heat be observed, the expansion 

 valve should be opened wider, while, on the other hand, if it should 

 become cold, the valve should be slightly closed, the adjustment 

 being continued until the temperature of the pipe is the same as that 

 of the cooling water leaving the condenser. If there is an insufficient 

 'charge of the refrigerant, the delivery pipe will become heated, even 

 though the expansion valve is wide open. 



Some of the signs which indicate the proper working of the plant, 

 other than the fact that it is satisfactorily performing its refrigerating 

 functions, are: The vibrations of the pointers on the high and low 

 pressure gages ; the frost on the exterior surface of the refrigerating 

 pipes; the liquid refrigerant can be plainly heard passing through the 

 expansion valve; and the difference in temperature between the 

 liquid leaving the condenser and the final temperature of the cooling 

 water, and between the refrigerator and the brine. 



Should it become necessary to disconnect any part of the ammonia 

 system for any reason, the ammonia must be pumped out of that part 

 and stored in another part of the system. After making repairs, 

 all the air must be exhausted from that part of the system before the 

 ammonia is again allowed to enter. 



To pump ammonia out of the condenser. — Close valves in the liquid 

 pipe, the main suction, and discharge valves, and open the by-pass 

 valves after draining the water from the condenser to prevent freezing 

 and bursting of the pipes. Start the machine and pump out the ammo- 

 nia until a partial vacuum is indicated by the high-pressure gage; 

 then stop the machine and allow it to stand for two or three hours 

 in order that any liquid ammonia lying in the pipes may have time to 

 evaporate. Start up the machine again and pump down to a 25-inch 

 40083°— Bull. 98—14 3 



