TM 9-4120-357-14
5-7.
Purging the System.
CAUTION
Whenever the refrigeration system has been opened to the atmos-
phere, 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 suction 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 gages, impurities and water vapor.
Turn off both service valves before disconnecting the nitrogen cylinder and the discharge hose.
5-8.
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. Pro-
ceed as follows:
WARNING
Avoid contact with liquid refrigerant or escaping refrigerant gas. Ir-
reversible 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 surface; lethal phosgene gas can be formed.
NOTE
Whenever available, use recycled refrigerant for charging the refrig-
eration system.
a. 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.
b. 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 (5KG/CM2). Close the suction service valve and the
cylinder shutoff valve.
c. Transfer the charging line to a cylinder of dry nitrogen. Open cylinder shutoff valve and suction service valve.
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 charging line from suction service valve.
d. 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 gage 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:
e. 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 suction line service valve, and turn vacuum pump off. Let unit stand in
this condition for at least three hours. If the system holds the vacuum without change, continue with Step F. 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 refrigeration system. Break vacuum with dry nitrogen, and retest for leaks.
(3) Internal leakage in vacuum pump. Test pump by installing gage directly on vacuum pump intake and con-
tinuing to pump. If pump still fails to reach 500 Microns, pump is faulty.
5-8
