Nitrogen is an inert gas. However, it also presents danger as a suffocant and,
therefore, must also be discharged in a ventilated location.
Assuming that the system has been discharged using a manifold as described in paragraph 4-5, proceed as follows.
a. See specific component removal/repair instructions.
b. Be sure that refrigerant has been discharged. See paragraph 4-5.
Connect the center hose from the charging manifold to a nitrogen regulator and dry nitrogen tank.
d. The hose from the high pressure service valve to the charging manifold should be connected.
e. The hose from the low pressure service valve should be disconnected from the charging manifold.
Open both service valves on the unit.
g. Close the unused valve on the charging manifold, and open the one with the nitrogen tank hook up.
h. Open the nitrogen cylinder valve and adjust the regulator so that less than 1 - 2 cfm (0.028-0.057 m /minute) of
nitrogen flows through the system.
i. Check discharge from hose attached to the low pressure charging valve to be sure that no oil is being forced out
of the system.
j. Allow nitrogen to sweep through the system at the rate of less than 1 -2 cfm (0.028-0.057 m /minute) for a
minimum of 5 minutes, before starting any brazing operation. Then allow it to continue to flow at the same rate until all
brazing operations are completed. (See paragraph 4-7 for brazing/debrazing procedures.)
After installation brazing operations are completed, allow nitrogen to flow for a minimum of 5 minutes.
I. Close nitrogen cylinder valve, nitrogen regulator, charging manifold valve, and both high and low pressure service
valves on the unit.
m. Disconnect the hose from the nitrogen tank.
n. Assuming that all repairs are completed, go to paragraph 4-7.
4-7. BRAZING/DEBRAZING PROCEDURES
Supplies: Brazing alloy (silver and copper) (items 3 and 4, Appendix E)
Nitrogen cylinder (item 2. Appendix E)
Brazing flux (item 5, Appendix E)
Abrasive cloth (item 6, Appendix E)
Rags (item 7, Appendix E)
a. General. All tubing in the refrigeration system is seamless copper with a bright internal finish that permits
thorough cleaning and prevents entrapment of moisture or other impurities. Rigid grade copper is used for straight
sections and soft grade for sections that must be bent All interconnecting fittings, such as elbows, tees, etc., are also
copper. The bodies of all valves and all connections on other components are brass. All joints, except those provided
with flare fittings, are made by brazing in accordance with MIL-B-7883, except that radiographic examination is not
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