TM 9-4120-357-14
g. Charging the System. Prepare the refrigeration system for charging by attaching a pressure gage to the high-
pressure service valve gage port. Connect a pressure hose and drier-strainer, loosely, to the suction service valve
gage port. Leave both valves closed. Proceed as follows:
WARNING
Avoid contact with liquid refrigerant or escaping refrigerant gas. Irreversible tissue dam-
age can result from sudden freezing. Be especially careful to protect the eyes. Avoid in-
haling high concentrations 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. 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 cyl-
inder shutoff valve.
(3) Transfer the charging line to a cylinder of dry nitrogen. Open the cylinder shutoff valve and 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 cylinder shutoff valve. Disconnect the charging line from 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, 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 gage 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 the
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 the 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.
5-62
