BRAZING/DEBRAZING PROCEDURES (Continued)

TM 5-4120-359-14

b. Filler Alloy. 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 may be substituted for Grade IV or VI for copper to copper joints; flux is not required for

copper to copper joints.

Debrazing. Debraze joints for removal of refrigeration system components as follows:

WARNING

All Refrigerant-22 must be discharged from the system and the entire system must

be purged with dry nitrogen before beginning any debrazing operation.

(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 joints on the

component itself.

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

with a wet rag to act as a heat sink.

WARNING

The polyurethane foam used as insulation in the air conditioner will break down to

form toxic gases if exposed to the flame of a torch or brazing temperature.

(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 less than 1 - 2 cfm (0.028-0.057 m3/minute).

(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.

d. 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 are left inside any tubing, fitting or component.

e. 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.

Brazing. Braze joints within the air conditioner as follows:

(1) Position the component to be installed.

(2) To prepare a joint on a valve for brazing, disassemble the valve to the extent 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 less than 1 - 2 cfm (0.028-0.057 m3/minute).

(5) Apply sufficient heat uniformly around the joint to quickly raise it to a temperature that will melt the filler alloy.

Remove heat as soon as brazing is completed.

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