TM 9-4120-411-14
5.5
PURGING THE REFRIGERANT SYSTEM.
THIS TASK COVERS
a. Purge
Initial Setup:
Tools
Materials/Parts
Nitrogen Regulator
Nitrogen
Item 4, Section III, Appendix B
Item 14, Section II, Appendix E
a. Purge . The refrigeration system must be purged with dry nitrogen before brazing is performed on any
component. A flow of dry nitrogen should be continued during all brazing operations to minimize internal
oxidation and scaling.
WARNING
Never pressurize refrigerant lines with oxygen, mixture with oil could cause an
explosion.
The pressure in a nitrogen cylinder can exceed 2000 psi. A nitrogen pressure
regulator should be used at all times to avoid personal injury.
Nitrogen is an inert gas that can cause suffocation and must be discharged in a
well ventilated area.
(1) Remove and recover system refrigerant per paragraph 5.4.
(2) Disconnect charge hose from recovery unit and connect to nitrogen regulator and nitrogen tank.
(3) Disconnect the compound gage hose from the service manifold and place end in a suitable container to
catch any oil that may come out.
(4) Be sure the service manifold compound gage and vacuum valves are closed.
(5) Open the service manifold pressure gage and charge valves.
(6) Open the nitrogen tank valve and adjust the regulator so that approximately 1-2 cfm (0.028-0.057 m
/minute) of nitrogen flows through the system.
(7) Check discharge from the hose attached to the suction service valve to be sure that no oil is being forced
out of the system.
(8) Perform any brazing/ debrazing operations necessary per paragraph 5.6.
(9) When purging is completed, close nitrogen tank valve.
(10) Disconnect the charge hose from nitrogen regulator.
(11) Connect the compound gage hose to service manifold.
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