Piper Navajo PA-31 Service Manual page 65

PIPER NAVAJO SERVICE MANUAL
3. Using care not to contaminate the tape, encircle the threads and conform the tape to the
shape of the threads and join together with .250 of an inch overlap. Press the broken ends into the threads.
4. Make the joint required and remove the excess material after the joint is made.
2-64. FILLING OXYGEN CYLINDER. The filler valve for the oxygen system is accessible through a door
located on the lower left side of the nose section below the baggage door (station 49.3).
a. To fill the oxygen cylinder, open the access door; remove the cap from the filler valve and attach
the filler hose from the oxygen recharge unit to the filler valve. Ascertain that all fittings are free from oil,
grease, dirt, etc.
NOTE
If the airplane's oxygen cylinder pressure is below 50 psi, the
system should be purged as described in Section XIV.
b. 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 figures given in Table
II-III.
c. When using a recharge unit consisting of one supply cylinder, slowly open the valve of the supply
unit and allow the oxygen to transfer.
d. 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 still 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 airplane, do not attempt using it for filling.
Use the storage cylinder that has a pressure higher than the airplane'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 airplane'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 airplane'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.
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 a pressure something less than the
1800 pounds, 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 600 psi; then return for filling.
Reissued: 10/12/79
HANDLING AND SERVICING
1C17