TM 9-4120-395-14&P
5-7. BRAZING, DEBRAZING PROCEDURES-Continued.
NOTE
Grade IV or VI brazing alloy and Type B flux, as specified in MIL-B-7883, must be used for all copper to brass joints
Grade III brazing alloy may be substituted for Grade IV or VI for copper joints; flux is not required for copper to copper
joints. All tubing in the refrigeration system is seamless copper with bright internal finish that permits thorough cleaning
and prevents entrapment of moisture and 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 required.
a.
Debrazing.
(1) Determine which joints are to be debrazed. Due to the limited work space Inside the air conditioner, it may be
more convenient to remove a part of the interconnecting tubing with the component rather than debrazing the joint on the
component itself.
(2) Before debrazing a joint on a valve, disassemble the valve as much as possible, then wrap all but the joint with a
wet rag to act as a heat sink.
(3) Protect insulation, wiring harnesses, cabinet, and other surrounding components with appropriate shields.
(4) Be sure the work area is well ventilated and that dry nitrogen is flowing through the refrigeration system at a rate
of 1 to 2 cfm (0.028 to 0.057 rn3 or cubic meters/minute). See para 5-6.
(5) Apply sufficient heat uniformly around the joint to quickly melt the filler alloy. If heat is applied slowly, or only on
one side, the entire component or length of tubing will be heated and filler alloy in adjacent joints may also be melted.
Remove heat as soon as the joint separates.
b. Cleaning Debrazed Joints. All filler alloy must be cleaned from debrazed joints before reassembly. Heat each piece
of the joint until the filler alloy is melted and then wipe it away with a damp cloth. Be sure no filler alloy or other debris is
left inside any tubing, filling, or component.
c. Reassembly If tubing sections or fittings were removed with a component, debraze them from the component, clean
the joints, and braze them to the new component before installation.
d. Brazing.
(1) Position the component to be installed.
(2) To prepare a joint on a valve for brazing, disassemble the valve as much as possible, then wrap all but the joint
with a wet rag to act as a heat sink.
(3) Protect insulation, wiring harnesses, and surrounding components with appropriate shields.
(4) Be sure the work area is well ventilated and that dry nitrogen is flowing through the refrigeration system at a rate
of 1 to 2 cfm (0.028 to 0.057 m3 or cubic meters/minute). See para 5-6.
(5) Apply sufficient heat uniformly around the joint to quickly raise It to a temperature that will melt the filler alloy.
Remove the heat as soon as brazing is completed.
(6) Leak test the new joints. See para 5-8.
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