Portable - Oxygen System; Testing For Leaks - Piper PA-44-180 SEMINOLE Maintenance Manual

(4). A good deal of oxygen will remain in the large cylinders used in the cascade system after filling only
one of the cylinders but such remaining oxygen will be at pressure something less than the 1850 psi
which is not sufficient pressure to completely refill another aircraft cylinder, although it will refill
several smaller cylinders.
(5). It is not economical even on a three or four cylinder cascade system to begin recharging with oxygen
at less than 300 psi pressure in the 300 cubic foot bank of cylinders. So use 300 cubic foot cylinders
down to approximately 300 psi; then return for refilling. In two cylinder systems use to approximately
100 psi; then return for filling.
D. When the pressure gauge on the recharge unit or in the aircraft reaches 1800 to 1850 psi, close the
pressure regulator valve on the recharge unit. Disconnect the filler hose from the filler valve; replace
the protective cap on the filler valve and close the access cover. Check the cylinder pressure according
to Chart 3503 after the cylinder temperature stabilizes.
5. After detaching the service cart, cap hose and fittings to prevent contamination.
6. Perform a leak check of the high pressure lines and clean off solution afterwards. If solution is not properly
cleaned off, unusual corrosion may result.
PORTABLE - OXYGEN SYSTEM. (Refer to Figure 35-2.)
Due to the nature of the process used to test compressed gas tanks, it is recommended that overhaul, service, or
hydrostatic tests be conducted by an FAA, DOT, or manufacturer (Scott Aviation) approved shop. The following
material gives recommended inspection and maintenance information for the various parts of the oxygen system.
Oxygen cylinders are identified by the ICC or DOT identification stamped on the
cylinder. The standard weight cylinder (3AA 1800) must be hydrostatically tested at
the end of every five years.Light weight cylinders (3HT 1850) must be tested every 3
years and be replaced after 4380 refills or 24 years whichever comes first. The month
and year of the last test is stamped on the cylinder beneath the identification.
1. Inspect outlets, and test for leaks in the "use" and "non-use" condition. Refer to next subject paragraph.
2. Check pressure gauge for accuracy by removing the back section of the unit and connecting a gauge of
known accuracy to the fill port.
3. Inspect tank for dents, bulges, major strap chafing marks or corrosion. Should any of these conditions exist.
the tank should be hydrostatically tested.

TESTING FOR LEAKS.

Apply detector fluid Leak-Tec Formula #16-OX (see Chart 9101 ) or an equivalent. The solution should be
shaken to obtain suds or foam. The solution should be applied sparingly to the joints of the system while looking
for traces of bubbles. Visible leaks are not allowed and any defective parts replaced or repaired. The system
should be further observed for leaks when fully pressurized. All traces of detector fluid should be wiped off at the
conclusion of the examination.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
2K1
3 5 - 1 2 - 0 1
Page 35-17
Revised: May 15, 1989