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Standing Vacuum Test
When performing the standing vacuum test, or machine dehydration, use a manometer or a
wet bulb indicator. Dial gages cannot indicate the small amount of acceptable leakage during a
short period of time.
1.
Attach an absolute pressure manometer or wet bulb indicator to the machine.
2.
Evacuate the vessel (see Pumpout and Refrigerant Transfer Procedures section) to at least
18 in. Hg vac, ref 30-in. bar (41 kPa), using a vacuum pump or the pump-out unit.
3.
Valve off the pump to hold the vacuum and record the manometer or indicator reading.
4.
a.
If the leakage rate is less than 0.05 in. Hg (.17 kPa)
in 24 hours, the machine is suffi-
ciently tight.
b.
If the leakage rate exceeds 0.05 in. Hg (.17 kPa)
in 24 hours, repressurize the vessel and
test for leaks. If refrigerant is available in the other vessel, pressurize by following Steps
2-10 of Return Refrigerant to Normal Operating Conditions section. If not, use nitrogen
and a refrigerant tracer. Raise the vessel pressure in increments until the leak is
detected. If refrigerant is used, the maximum gas pressure is approximately 70 psig
(483 kPa) at normal ambient temperature.
5.
Repair leak, retest, and proceed with dehydration.