TM 9-4120-388-14
PROCEDURES.
INITIAL SETUP:
Materials/Parts Required
a. General. All tubing in the refrigeration system is seam less 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 cop-
per. 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.
b. Filler Alloy. Grade IV or Vl brazing alloy and Type B flux (item 5, Appendix E), as specified in MIL-B-7883, must
be used for all copper to brass joints, Grade Ill brazing alloy (item 4, Appendix E) 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:
c.
All refrigerant-22 must be discharged from the system and the entire system must
be purged with dry nitrogen (item 9, Appendix E) before beginning any debrazing
operation.
(1)
Determine which joints are to be debrazed. Due to the limited workspace inside the air conditioner, it may
be more convenient to remove apart 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.
The polyurethane foam used as insulation in the air conditioner will breakdown
to form toxic gases if exposed to the flame of a torch at brazing temperature.
Protect insulation, wiring harnesses, cabinet, and other surrounding components with appropriate shields.
(3)
Be sure the work area is well ventilated and that dry nitrogen is flowing through the refrigeration system
(4)
at a rate of less than 1-2 cfm (0.028-0.057 m3/minute).
Apply sufficient heat uniformly around the joint to quickly melt the filler alloy. If heat is applied slowly, or only
(5)
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 for 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.
Reassembly. If tubing sections or fittings were removed with a component, debraze them from the component,
e.
clean the joints, and braze them to the new component before reinstallation.