TM 9-4120-370-14
TO 35E9-229-1
PURGING THE REFRIGERANT SYSTEM - Continued.
5-8.
m. Disconnect the hose from the nitrogen tank.
n.
BRAZING/DEBRAZING PROCEDURES.
Supplies:
General. All tubing in the refrigeration system is seamless copper with a bright internal finish that permits thor-
a.
ough 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 MILB-7883, except that radiograph-
ic examination is not required.
b.
Filler Alloy. Grade IVor Vl brazing alloy and Type B flux, as specified in MILB7883, must be used for all copper
to brass joints. Grade Ill brazing alloy 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 refrigerant22 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 debraz-
ing the joints on the component Itself.
Before debrazing a joint on a valve, disassemble the valve to the extent possible, then wrap all but the joint
(2)
with a wet rag to act as a heat sink.
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 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 12 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 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.
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.
f.
Brazing. Braze joints within the air conditioner as follows: