TM 9-4120-378-14
REFRIGATION SYSTEM SERVICING - (EVACUATION) - Continued
5.8
Remarks
Action
Location/Item
e. Open charging manifold valves.
f . Run the vacuum pump until approximately a 300
micron vacuum is reached.
NOTE
Inability to reach 300 microns may indi-
cate either a leak or a problem with the
pump.
Close manifold valves and check compound gage.
g.
Record reading. Let unit sit for 1 hour. Observe
compound gage reading.
if the system holds the vacuum without change of
h.
pressure, proceed to Step j.
i.
If the vacuum cannot be held for 1 hour, one of the
following reasons may account for the problem:
(1)
Presence of water vapor in the system. Con-
tinued pumping will correct this condition.
Leak in the refrigeration system. Break the See paragraph 5.7.
(2)
vacuum with dry nitrogen and retest for leaks.
(3)
Internal leakage of vacuum pump. Test the
pump by connecting a vacuum gage directly
to the vacuum pump intake and continue to
pump. If pump still fails to reach approximately
300 microns, the pump is faulty.
j . Close both unit service valves.
k.
Close charging manifold valves.
l.
Stop vacuum pump.
m.
Disconnect pump from center hose connection.
See paragraph 5.9.
n.
Charge system with refrigerant-22.
5-23
