TM 9-4120-357-14
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 disconnecting the nitrogen cylinder and the discharge hose.
g. Charging the System. Prepare the refrigeration system for charging by attaching a pressure 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 escaping refrigerant gas. Irre-
versible tissue damage can result from sudden freezing. Be espe-
cially 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 of 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/CM2). Close the suction service valve and
the cylinder shutoff valve.
(3) Transfer the charging line to a cylinder of dry nitrogen, open cylinder shutoff valve and suction service valve,
and let nitrogen flow into the refrigeration system until the discharge pressure gauge reads 350 PSI (21.4 KG/CM2).
Close the suction and discharge service valves and cylinder shutoff valve.
Disconnect charging line from suction
service valve.
(4) Test the refrigeration system for leaks, using an electronic leak detector, Halide torch or soap bubble method.
Discharge the system by attaching a hose to the discharge valve gauge port, and discharging the gas slowly to avoid
blowing oil out of the system. If leaks are detected repair and retest as directed above. If system is leak-tight proceed as
follows:
(5) Connect a vacuum pump to the suction service valve gauge port, and a vacuum gauge to the discharge serv-
ice valve gauge 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 (6). 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:
(a) Presence of water vapor in the system. Continued pumping will correct this problem.
(b) Leaks in the refrigeration system. Break vacuum with dry nitrogen, and retest for leaks.
(c) Internal leakage of 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.
(6) With the suction line service valve closed, disconnect the vacuum pump and attach cylinder of dry nitrogen.
Leave the connection to 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 the suction service valve and the
cylinder shutoff valve, and disconnect the nitrogen cylinder.
(7) Reconnect the vacuum pump to the suction line service valve gage port, and start the pump. Open the 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 discharge line valve, and remove the vacuum gage.
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