REFRIGERATION SYSTEM SERVICING - (EVACUATION) - continued

TM 5-4120-386-14

5-14. REFRIGERATION SYSTEM SERVICING -(EVACUATION) -Continued.

REMARKS

ACTION

LOCATION/ITEM

Open charging manifold valves.

Run the vacuum pump until

approximately a 300 micron

vacuum is reached.

NOTE

Inability to reach 300 microns may

indicate either a leak or a problem

with the pump.

Close manifold valves and check

compound gage. Record reading.

Let unit sit for one hour. Ob-

serve compound gage reading.

h. If the system holds the vacuum

without change of pressure,

proceed to step j.

If the vacuum cannot be held

for one hour, one of the follow-

ing reasons may account for the

problem:

( 1 ) Presence of water vapor

in the system.

Continued pumping will

correct this condition.

( 2 ) Leak in the

refrigeration system.

Break the 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.

5-49