CHART 3503. FILLING PRESSURE FOR CERTAIN AMBIENT TEMPERATURES
2. If a cylinder has less than 5 psi, pressure or has insufficient pressure to produce an audible hissing sound
when the valve is cracked, it should be removed and shall not be refilled.
3. Make sure both the charge valve and recharge "cart" fittings are clean and free of contamination.
— WARNING —
BE CERTAIN THERE IS NO OIL ON THE FITTINGS OR NEAR THE
IMMEDIATE VICINITY.
4. Attach service cart hose to recharge port. Fill the system at a rate not exceeding 200 psig per minute
proceeding as follows:
A. To obtain the correct filling pressure for the oxygen system at various ambient temperatures, a table is
included for your convenience. The pressures given are not exact, but sufficiently accurate for
practical purposes of working pressures between 1800 and 2400 psig cylinders. The cylinder should be
allowed to cool to a stabilized temperature after filling before checking against the values in Chart
3503.
B. When using a recharge unit consisting of one supply cylinder, slowly open the valve of the supply unit
and allow the oxygen to transfer.
C. When using a recharge unit consisting of two or more supply cylinders (cascade storage system), it is
recommended that the following procedure be used:
(1). Before opening any valves~ check the pressure remaining in the airplane's oxygen cylinder. If it is
partly charged, note the pressure indicated on the cylinder gauge. Then open and close each valve on
the cascade storage system and determine which cylinder has the lowest pressure. When found if this
cylinder has a pressure lower than the oxygen cylinder in the aircraft, do not attempt using it for
filling; use the storage cylinder that has a pressure higher than the aircraft's cylinder but lower than the
others.
(2). Open the valve on only the one storage cylinder with the lowest pressure. When the pressure indicated
on the aircraft's oxygen gauge and charging gauge has become equal, close the valve of the storage
cylinder; then go to the storage cylinder with the next higher pressure and repeat the procedure.
(3). If after using the last storage cylinder the aircraft's oxygen system is still not fully charged, a full
storage cylinder should be put in place of a cylinder with the lowest pressure and used in the same
manner.
Ambient Temperature Filling Pressure Ambient Temperature Filling Pressure
0 1650(PSI) 70 1975 (PSI)
10 1700 80 2000
20 1725 90 2050
30 1775 100 2100
40 1825 110 2150
50 1875 120 2200
60 1925 130 2250
NOTE: Filling pressures are for 1850 PSI at 70° F. Table assumes 25° F rise due to heat of compression with
max fill rate.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3 5 - 11 - 1 5
Page 35-16
Revised: May 15, 1989
2J24
PIPER AIRCRAFT
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