Replacing Tubing, Valves And Fittings
It is extremely important when installing any oxygen line
in an aircraft that no petroleum product is used as a thread lubricant, and
that the lines are thoroughly cleaned of any trace of oil that was used in the
flaring or presetting operation. Trichloroethylene or some similar solvent may
be used to clean the tubing and fittings, and after they are thoroughly clean,
they should be dried either with heat or by blowing them dry with water pumped
dry air or dry nitrogen.
Tapered pipe
threads must never be lubricated with a thread lubricant that contains any form
of petroleum. Oxygen-compatible thread lubricant that meets specification
MIL-T-5542 maybe used, or the male threads may be wrapped with Teflon tape and
the fittings screwed together.
Before any
tubing or fitting is replaced in an oxygen system, the part must be thoroughly
cleaned and inspected. Check the part for evidence of corrosion or damage, and
degrease it with a vapour degreaser or ultrasonic cleaner. Flush the new line
with stabilized trichloroethylene, acetone, or some similar solvent, and dry it
thoroughly with water-pumped dry air or nitrogen. If neither water pumped air
nor nitrogen are available, the part may be dried by holding it at a
temperature of about 250 °F until it is completely dry. When the parts are dry,
close them with properly fitting protective caps or plugs, but never use tape
in any form to seal the lines or fittings, as small particles of the tape are
likely to remain when it is removed.
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