TM 9-4120-357-14
(d) Test the refrigeration system for leaks, using an electronic leak detector, Halide torch or soap bubble
method. The electronic leak detector is preferred.
CAUTION
The electronic leak detector and the Halide torch are sensitive to the presence of refrig-
erant 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.
1. Electronic Leak Detector. Turn the electronic unit on, and slowly pass the probe around all points of
the refrigeration 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.
2. 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 indicated by the flame turning from blue to green. A large leak will be indicated by the flame turning from blue to
indigo with red tip, or the torch may be extinguished.
3. 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.
(e) Discharge the system in accordance with paragraph 5-6. If leaks are detected, repair and retest as di-
rected above. If system is leak-tight, proceed as follows:
(f) Connect a vacuum pump to the suction service valve gage port, and a vacuum gage to the discharge
service valve gage port. Start the pump, and open both service valves. Operate vacuum pump until pressure in the
system is reduced to not more than 500-Microns. Close suction line service valve, and turn 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 (g). 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.
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.
(g) With suction line service valve closed, disconnect the vacuum pump and attach a cylinder of dry nitro-
gen. Leave connection to suction service valve loose. Turn on cylinder shutoff valve for a few seconds to purge the line
of air. Tighten connection, and crack the suction line service valve open slightly until system reaches atmospheric pres-
sure (760 MM). Close the suction service valve and cylinder shutoff valve, and disconnect the nitrogen cylinder.
(h) Reconnect vacuum pump the suction line service valve gage port, and start pump. Open 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 dis-
charge line service valve, and remove the vacuum gage.
(i) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve. Open the cylinder
shutoff valve for a few seconds to purge line of air. Tighten service valve connection. Charge refrigeration system as
directed in the following steps:
1. Place the refrigerant cylinder on a scale of sufficient capacity, with the shutoff valve down, or suspend
the cylinder from spring scale or beam scale, with the valve end down.
NOTE
If cylinder is equipped with both liquid and gas (vapor) valves, connect the line to
the liquid value.
6-7
