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 TM 55-1905-220-14-8
4-30. COMPRESSOR - HVAC - MAINTENANCE INSTRUCTIONS (Continued).
Stop compressor, close liquid line stop valve downstream of receiver, and open water valves
to obtain maximum flow through condenser. When compressor discharge gauge holds a
steady pressure (no further decrease is noted in discharge pressure), read corresponding
refrigerant temperature on outer scale of gauge. If this temperature is more than 5 (-15 )
F
C
higher than the condenser water outlet temperature, noncondensable gases are present.
Purge condenser. Refer to paragraph 4-31b.
3
Condenser tubes or water strainer may be clogged or dirty. Clean the strainer and tubes
regularly. Refer to paragraph 4-31c.
4
Refer to troubleshooting in Volume 3 for other possible causes of high head pressure.
b. Purging.
(1) Check for the presence of air or other noncondensable gases in the refrigerant side of the condenser
as outlined in paragraph 4-31a(2)(b)2.
(2) To purge noncondensable gases from the condenser shell, stop the compressor for ten or fifteen
minutes leaving all valves in their normal operating positions. Close condenser-receiver equalizing line valve.
Open purge valve connected to top of condenser and allow gas to blow for a few seconds. Purge slowly to
keep refrigerant loss to a minimum.
(3) Refrigerant-12 resembles carbon tetrachloride in odor, but it is odorless in concentrations of less
than 20% by volume of air. If odor cannot be detected at the purge valve, the necessity for further purging may
be determined on the basis of pressures. Purging noncondensable gases such as air causes a pressure drop
after the purge valve is closed. Observe the discharge gauge after each opening of purge valve. Repeat
purging until there is no further pressure drop or until the temperature comparison test (paragraph 4-31a(2)(b)2
no longer indicates the presence of noncondensable gases.
(4) Avoid unnecessary waste of refrigerant. If the temperature comparison test does not indicate that
purging is necessary, but head pressure is still high, drain condenser, remove water heads, and clean tubes as
required.
c. Cleaning and Inspection.
(1) The frequency of condenser cleaning and inspection will vary depending on the condition of
circulating sea water. The internal surface of condenser tubes should be cleaned at least once ever three
months or more often if necessary.
4-944
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