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 TM 55-1905-220-14-8
4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
Never use oxygen to build up pressure. An explosion may result.
CAUTION
Do not use the compressor to build up pressure. If used to
compress air, overheating and damage may result.
(3) To pressurize the system and test for leaks proceed as follows:
(a) With all refrigerant piping connections completed, open all liquid and suction line stop valves.
(b) Disconnect refrigerant lines to condenser water regulating valve, high and low pressure
control switches, and suction pressure gauge. Close any stop valves in actuating lines to this equipment or
close the lines with flared fitting plugs or flared caps. This is done to prevent injury to bellows by the high test
pressure.
(c) Break the union in condenser overboard discharge line and plug line to prevent loss of
pressure through overboard discharge relief valve. The relief valve is left in the line for later testing.
NOTE
The safety head type bursting disc diaphragm or the
throwaway type rupture disc assembly, located between the
union and the overboard discharge relief valve, is not to be
installed until after pressure tests and dehydration of the
system have been completed.
(d) Connect a refrigerant-12 (R-12) drum to charging valve in liquid line.
(e) Open valves between R-12 drum and liquid line and introduce enough refrigerant to raise
system pressure to 20 psig (137.9 kPa). Close valves and disconnect drum. Test for leaks with an electronic
or an halide leak detector. Repair any leaks.
(f) Connect a drum of dry nitrogen to charging valve and add gas until system pressure is 150
psig (1034 kPa).
4-894
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