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 TM 55-1905-219-14-9
4-35.6. REFRIGERANT TUBING - AIR CONDITIONING - MAINTENANCE INSTRUCTIONS.
a.
Repair refrigerant piping as follows:
b.
Use a solder having a melting point of approximately 1160 F (626.7 ) and a flow point of
C
1175 (635.0 ).
F
C
c.
The refrigerant system must be clean before the compressor is connected to it. Refrigerant-12
and related refrigerants are excellent cleaners and will carry dirt through the system to the compressor.
d.
Refrigeration piping is usually shipped clean, deoxidized, dehydrated, and sealed by the mill
that produced it. Keep it as near this condition as possible, and seal the ends of the tubing that is left.
e.
When tubing or pipe in questionable condition must be used, clean it. Blow out each length of
pipe or tubing with a blast of dry air, then draw a cloth swab back and forth in the tube until it is clean and shiny.
The swab should be tight enough to clean the tube without binding. Do not use waste or other linty material.
f.
If a dark discoloration is found in copper tubing, pull a swab of 00 steel wool through the tube
with a wire until the inside is bright and clean. After that remove any dirt, grease, or steel wool particles by
pulling a lintless cloth swab saturated with compressor oil through the tube.
g.
Steel and iron pipe may have dirt or scale to be cleaned out. Remember, sand particles from
cores used to make pipe bends may still be present in the bends.
h.
If copper tubing is brazed or soldered in the presence of air, a scaly black oxide forms on the
tube. If the oxide is left inside the tube, the refrigerant flakes it off and carries it into the compressor. Oxidation
can be prevented by filling the tube with a stable gas such as nitrogen. A small amount of gas flowing through
the tubing will assure a neutral atmosphere while the work is being done.
i.
When soldering or brazing parts that have been in an operating system, blow them out and
clean off the oil film. This prevents a carbon deposit from forming in the tubing when it is heated.
j.
Avoid getting dirt in the system. When preparing piping and fittings for installation, keep filings
or cuttings from entering the pipe. Small particles of copper must be kept out or removed since finely divided
copper may pass through the suction strainer and collect in the compressor crankcase lubricating oil. There,
together with small quantities of air and moisture, copper particles may promote oil gummings and sludging and
often, through chemical reaction, cause derangement of the system. Cut tubing square and remove
4-978
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