34 BULLETIN 98, U. S. DEPAETMENT OF AGEICULTUEE. 



vacuum. After all ammonia has been exhausted from the system, 

 close the valve in the ammonia discharge pipe and the condenser may 

 then be disassembled. 



To pump the air out of condenser. — The main suction and discharge 

 valves should remain closed. The by-pass valve on the discharge 

 side must be open and the one on the suction side closed. Manufac- 

 turers provide some means of opening the by-pass piping, either by a 

 pipe tee or some form of cock; this should be opened and the machine 

 run until all air is exhausted from the condenser. After all air has 

 been exhausted the opening in the discharge by-pass must be closed 

 and all A^alves set as they were originally. Ammonia may now be 

 allowed to reenter the condenser, and after turning on the cooling 

 water the plant is again ready for operation. 



To pump ammonia out of cold-storage room or cooler coils. — All 

 expansion valves must be closed, also the suction stop valves, except 

 the suction stop valve on the coil which it is desired to pump out. 

 This valve must be left open and the machine run until a 10 or 15 

 inch vacuum is obtained, when the machine should be stopped for 

 two hours in order to allow any remaining liquid in the coils to evapo- 

 rate. After the evaporation of the remaining liquid, start the machine 

 again and pump down to a 25-inch vacuum. If all liquid has evapo- 

 rated and the ammonia valves are tight, the coils should maintain - 

 the 25-inch vacuum until broken. The suction and discharge valves 

 on the machine may now be closed and the part of the system which 

 has been pumped out may be opened with safety. 



To pump air out of storage rooms or cooling coils. — See that the main 

 discharge stop valve is closed and remove the plug from tee or open 

 cock, as the case may be, in the by-pass just below the discharge 

 stop valve. The machine should be started slowly and run until all 

 the air is exhausted from the coils, then stop machine and replace 

 plug in tee or close cock in the by-pass. 



To pump out compressor. — -The same method as above is followed, 

 except that the suction stop valve only is closed, as no part of the 

 system except the compressor is to be pumped out. 



CARE OF REFRIGERATING MACHINERY. 



In caring for machinery of any kind, one of the most important 

 things is cleanliness, and especially is this true of refrigerating appa- 

 ratus. If the cooling and condensing surfaces are allowed to become 

 coated even slightly their heat-transferring efficiency will be lowered 

 materially. 



Where atmospheric condensers are used it is an easy matter when 

 the surfaces become coated to clean them with a brush, provided 

 the coating is not of the nature of a scale. If the substance is hard, 

 it will be necessary to employ files or steel scrapers in removing the 



