TM 9-4120-357-14
(2) Open both service valves and the cylinder shutoff valve, and charge the system with refrigerant gas until the
gage on the discharge (high-pressure) service valve registers 70 PSI (5 KG/CM2) . Close the suction service valve and
the cylinder shutoff valve.
(3) Transfer the charging line to a cylinder of dry nitrogen. Open the cylinder shutoff valve and the suction service
valve, and let nitrogen flow into the refrigeration system until the discharge pressure gage reads 350 PSI (21.44
KG/CM2) . Turn off suction and discharge service valves and the cylinder shutoff valve. Disconnect the charging line
from the suction service valve.
(4) Test the refrigeration system for leaks, using an electronic leak detector, Halide torch or soap bubble method.
The electronic leak detector is preferred. Use GE type H-10 electronic leak detector or equivalent.
CAUTION
The electronic leak detector and the Halide torch are sensitive to the presence of refriger-
ant gas in the atmosphere. When refrigerant gas is present in the atmosphere of the work
area, false indications can result. Use in a well ventilated but draft-free area.
(a) Electronic Leak Detector. Turn the electronic unit on, and slowly pass the probe around all points of the refrig-
eration system at which a leak could exist. Depending upon the type of detector used, a leak will be indicated by an
audible signal, a light, or by meter deflections.
(b) Halide Torch. Turn on the gas from the cylinder and light the torch. Adjust to obtain a stable light-blue flame.
Pass the open end of the sensing tube slowly around all locations at which a leak could exist. A small leak will be indi-
cated by the flame turning from blue to green. A large leak will be indicated by the flame turning from blue to indigo with
a red tip, or the torch may be extinguished.
(c) Soap Solution. Brush soap solution on all possible points of leakage, and watch for bubbles. Follow a definite
sequence to avoid missing any points that should be tested. Wipe the solution from all joints, and mark any point at
which a leak is found.
(5) Discharge the system in accordance with paragraph 5-6. If leaks are detected, repair and retest as directed above.
If system is leak-tight, proceed as follows:
(a) Connect a vacuum pump to the suction service valve gage port, and a vacuum gage to the discharge service
valve port. Start the pump, and open both service valves. Operate the vacuum pump until pressure in the system is
reduced to not more than 500-Microns. Close the suction line service valve, and turn the vacuum pump off. Let unit
stand in this condition for at least three hours. If the system holds the vacuum without change, continue with step (b) . If
500-Micron vacuum cannot be held for three hours, break the vacuum with dry nitrogen and retest for leaks. If 500-
Micron vacuum cannot be achieved, one or more of the following reasons may account for the problem.
1. Presence of water vapor in the system. Continued pumping will correct this problem.
2. Leaks in the refrigeration system. Break vacuum with dry nitrogen, and retest for leaks.
3. Internal leakage of vacuum pump. Test pump by connecting the gage directly to the vacuum pump intake and
continuing to pump. If pump still fails to reach 500-Microns, pump is faulty.
(b) With the suction line service valve closed, disconnect the vacuum pump and attach a cylinder of dry nitrogen.
Leave the connection to the suction service valve loose, and open the cylinder shutoff valve for a few seconds to purge
the line of air. Tighten the connection, and crack the suction line service valve slightly to break vacuum. Leave in this
configuration until system reaches atmospheric pressure (760 MM) , then close the suction service valve and cylinder
shutoff valve, and disconnect the nitrogen cylinder.
(c) Reconnect the vacuum pump to the suction line service valve gage port, and start the pump. Open the suction
line service valve, and again pump until a 500-Micron vacuum is achieved. This double evacuation will remove all
traces of water vapor from the system. Close the suction line service valve, and disconnect the vacuum pump. Close
the discharge line service valve, and remove the vacuum gage.
(d) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve, and open the cylinder shut-
off valve for a few seconds to purge tile line of air. Tighten the service valve connection. Charge the refrigeration sys-
tem as directed in the following steps:
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