TM 9-4120-357-14
WARNING
Avoid contact with liquid refrigerant or escaping refrigerant gas. Ir-
reversible tissue damage can result from sudden freezing. Be es-
pecially careful to protect the eyes. Avoid inhaling high concentra-
tions of refrigerant gas, and prevent gas coming into direct contact
with flame or hot metal surfaces; lethal phosgene gas can be
formed.
(1) Connect a cylinder or refrigerant, R22, to the pressure hose. Open the cylinder shutoff valve slightly to purge
the hose of air, then tighten the hose connection to the suction service valve gage port.
(2) Open both service valves and the cylinder shutoff valve, and charge the system with refrigerant gas until the
gauge on the discharge (high-pressure) service valve registers 70 PSI (5 KG/SM2). 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 the 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 a electronic leak detector, Halide torch or soap bubble method.
The electronic leak detector method is preferred. Use GE type H10 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 were 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 port and a vacuum 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 condi-
tion for at least three hours. If the system holds the vacuum without change, continue with step (b). If 500-Micron vac-
uum cannot be held for three hours, break the vacuum with dry nitrogen and retest for leaks. If 500-Micron vacuum can-
not 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 the Vacuum Pump. Test the pump by connecting gage directly to the vacuum
pump intake and continuing to pump. If the pump still fails to reach 500-Microns the pump is faulty.
(b) With the suction line service valve closed, disconnect the vacuum pump and attach a cylinder of dry nitro-
gen. 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 suction line service valve open slightly to break vacuum. Leave
in this configuration until system reaches atmospheric pressure (760MM), then close the suction service valve and cylin-
der shutoff valve, and disconnect the nitrogen cylinder.
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