TM 9-4120-357-14
e. Purging the System.
CAUTION
Whenever the refrigeration system has been opened to the atmosphere. you must install a
new drier-strainer (dehydrator) before purging and recharging the system.
With the refrigeration system discharged and a hose attached to the gage port of the suction service valve, connect a
cylinder of oil-pumped dry nitrogen to the gage port of the high-pressure service valve. Open the high-pressure service
valve, and crack open the cylinder shutoff valve to establish a flow of 1-2 CFM (0.5 - 1 M3) through the system. Purge
for at least 30 minutes to expel all other gases, impurities and water vapor. Turn off both service valves before discon-
necting the nitrogen cylinder and the discharge hose.
f. Charging the System. Prepare gage to the high-pressure service valve gage port, and 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 of refrigerant, R22, to the pressure hose, open the cylinder shutoff valve slightly to purge the
hose of air, the 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
gage on the discharge (high-pressure) service valve registers 10 PSI (0.7 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) . Close 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 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 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 the light 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 retested. With the solution from all joints, and mark any point at
which a leak is found.
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