TM 9-4120-357-14
(4) Test the refrigeration system for leaks, using an electronic leak detector, Halide torch or soap bubble method.
The electronic leak detector method is preferred. Use a GE type H-10 electronic leak detector or equivalent.
CAUTION
The electronic and the Halide torch leak detectors are sensitive to the
presence of refrigerant 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
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.
(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
indicated 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 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 the suction line service valve, and turn the vacuum pump off.
Let the unit stand in this condition for at least three hours. If the system holds the vacuum without change, continue with
step (8). 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 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 open slightly to break the vacuum. Leave
in this configuration until system reaches atmospheric pressure (760 MM), then close suction service valve and cylinder
shutoff valve, and disconnect the nitrogen cylinder.
(c) Reconnect vacuum pump to the suction line service valve gage port, and start pump. Open suction line serv-
ice valve, and again pump until a 500-Micron vacuum is achieved. This double evacuation will remove all traces of wa-
ter vapor from the system, close the suction line service valve, and disconnect the vacuum pump. Close the discharge
line service valve, and remove vacuum gage.
(d) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve. Open cylinder shutoff valve
for a few seconds to purge line or 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 a spring scale or beam scale, with the valve end down.
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