BRAZING/DEBRAZING PROCEDURES - TM-5-4110-234-140146

TM5-4110-234-14

TO 40R7-5-7-1

5-12. BRAZING/DEBRAZING PROCEDURES

All Refrigerant R12 must be discharged from the system (para 58) and the section of the system being

repaired must be purged with dry nitrogen before beginning any debrazing operation. When R12 comes

in contact with flames, phosgene gas is formed. This is a deadly poison (it has the odor of new mown

hay). Be sure of sufficient fresh air and ventilation when brazing, soldering or using the halide torch.

Debrazing.

(1) Before debrazing a joint on a valve, disassemble the valve to the extent possible, then wrap all but the

joint with a wet cloth to act as a heat sink.

No attempt should be made to repair a leak while the system is under pressure. Neither should bad joints

be repaired by remelting and adding more brazing material. The joints should be taken apart, thoroughly

cleaned and remade as a new joint.

(2) Protect insulation, wiring harnesses, and other surrounding components with appropriate shields.

(3) Be sure the work area is well ventilated and that dry nitrogen is flowing through the repair area at a rate

of 1-2 cfm (0.0283 - 0.0566 m3/minute).

(4) 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.

Wear welder's gloves or other thermal protective gloves when performing the following operation.

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 fiber-glass cloth. Be sure no filler alloy or

other debris is left inside any tubing, fitting, 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 reinstallation.

d. Brazing.

(1)

Position the component to be installed.

(2) To prepare for brazing a joint on a valve, disassemble the valve to the extent possible, then wrap all but

the joint with a wet cloth to act as a heat sink.

(3)

Protect insulation, wiring harnesses, and surrounding components with appropriate heat shields.

(4) Be sure the work area is well ventilated and that dry nitrogen is flowing through the refrigeration system

at a rate of 1-2 cfm (0.0283-0.0566 m3/minute).

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