(f)
Make sure the ball face of the metal seal is in the direction of the pressure reducer.
(g)
Install the hex head fitting in the outlet end of the pressure reducer.
CAUTION: HOLD A WRENCH ON THE HEX FITTING WHEN YOU TURN THE
_______ PRESSURE REDUCER. IF NOT, DAMAGE TO THE PRESSURE REDUCER CAN OCCUR.
(h) Tighten the hex fitting to a torque of approximately 300 pound-inches.
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747-400 MAINTENANCE MANUAL
(i) Continue to tighten the hex fitting until a sharp increase in torque occures.
NOTE: This will make sure the parts are in full contact
____
with the seal.
S 434-014
(5) Install the coupling assembly:
(a) Put the coupling assembly with the pressure transducer and pressure reducer through the hole in the support bracket.
NOTE: The pressure reducer here is attached in its
____ position on the pressure transducer.
(b)
Make sure the pressure transducer is installed into the support clamp and the coupling assembly fitting is aligned with the cylinder port.
(c)
Install the retaining nut on the bulkhead fitting above the support bracket to connect the pressure reducer.
(d)
Connect the supply line to the bulkhead fitting.
(e)
Tighten the screws on the support clamps on the pressure transducer.
(f)
Tighten the coupling assembly on the cylinder nut to a torque of 650 to 700 pound-inches.
(g)
Tighten the connections downstream of the pressure reducer.
S 434-015
(6) Connect the electrical connector to the pressure transducer.
S 864-033
WARNING:_______OPEN THE SHUTOFF VALVE ON THE CREW OXYGEN CYLINDER SLOWLY. IF NOT, HIGH TEMPERATURES CAN OCCUR WHICH CAN START AN IGNITION WITH THE OXYGEN. THIS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO THE AIRPLANE AND EQUIPMENT.
CAUTION: DO NOT TIGHTEN THE SHUTOFF VALVE ON THE CREW OXYGEN CYLINDER
_______ MORE THAN 25 POUND-INCHES. THIS CAN CAUSE DAMAGE TO THE SHUTOFF VALVE.
(7) Open the shutoff valve on each crew oxygen cylinder:
NOTE: Some airplanes have an optional second oxygen cylinder.
____
(a) Slowly turn the shutoff valve until it is fully open.
NOTE: The shutoff valve can be closed by hand which is
____
equivalent to 25 pound-inches.
(b) Close the shutoff valve one-fourth of a turn.
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747-400 MAINTENANCE MANUAL
(c) Install a lockwire on the shutoff valve.
NOTE: Use the 0.020 inch diameter copper lockwire
____
(AMM 20-11-28/401).
S 794-019
(8)
Do a check of all connections for leaks with the leak detection compound for the oxygen system.
S 144-035
(9)
Rub off the leak detection compound with a clean cotton cloth.
S 864-020
(10)
Supply the electrical power (AMM 24-22-00/201).
S 864-021
(11)
Remove the DO-NOT-CLOSE tag and close this circuit breaker:
(a) P7 Overhead Circuit Breaker Panel.
1) 7D4 OXYGEN VALVE & IND
S 714-037
(12) Do this Task: Operation Test - Crew Oxygen (AMM 35-11-00/501).
NOTE: It is only necessary to do up to the paragragh "Crew
____ Oxygen Pressure Indication Test" on the task "Operation Test
-Crew Oxygen".
S 414-023
(13)
Close the cylinder access door.
(14)
Remove electrical power if it is not necessary (AMM 24-22-00/201).
S 864-024
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