(b)  
Disconnect the coupling assembly from the crew oxygen cylinder.

 (c)  
Loosen the screws on the support clamp on the pressure transducer.

 (d)  
Disconnect the supply line from the bulkhead fitting at the supply line B-nut.

 (e)  
Hold the coupling assembly with the pressure transducer and the pressure reducer, then remove the retaining nut on the bulkhead fitting.

 (f)  
Remove the coupling assembly.

 S 034-009
 (7)  Install the protective caps or the plugs to the open lines, fittings or ports to prevent contamination of the system.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400 MAINTENANCE MANUAL
 S 024-010
 (8)  Remove the pressure reducer:
 (a)  
Remove the bulkhead fitting from the upper end of the pressure reducer.

 (b)  
Remove the metal seal between the bulkhead fitting and the pressure reducer.

 NOTE: Keep the serviceable seal and fitting for the
____
 installation.

 CAUTION: HOLD A WRENCH ON THE COUPLING ASSEMBLY WHEN YOU TURN
_______ THE PRESSURE REDUCER. IF NOT, DAMAGE TO THE COUPLING ASSEMBLY CAN OCCUR.
 (c)  
Remove the pressure reducer from the coupling assembly.

 (d)  
Remove the metal seal between the pressure reducer and the coupling assembly.

 NOTE: Keep the serviceable seal for the installation.
____
 TASK 35-11-04-404-011
 3. Pressure Reducer Installation (Fig. 401)
_____________________________
 A. Consumable Material
 (1)  
G00091 Compound - Oxygen System Leak Detection (MIL-L-25567)

 (2)  
G00713 Cloth - Clean, Dry, Lint-Free, White, Cotton

 B. References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 35-00-00/201, Oxygen

 (3)  
AMM 35-11-00/501, Crew Oxygen System

 (4)  
IPC 35-11-04

 (5)  
SSM 35-11-01

 (6)  
WDM 35-11-13

 C. Access
 (1)  Location Zone 124 Forward Cargo Container Compartment, Aft Half Right
 D. Procedure
 S 914-032
 (1)  
Read and obey the safety precautions and general instructions before you do the maintenance (AMM 35-00-00/201).

 S 434-012

 (2)  
Remove the protective caps or the plugs from the lines, fittings and the ports.

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747-400
MAINTENANCE MANUAL

 S 214-036
 (3)  
Examine the threads on the bulkhead fitting to make sure they are clean.

 S 424-013

 (4)  
Install the pressure reducer:

 (a)  
Put the metal seal with the flat face in the direction of the coupling hex nut.

 (b)  
Make sure the ball face of the metal seal is in the direction of the pressure reducer.

 CAUTION: MAKE SURE YOU TIGHTEN THE PRESSURE REDUCER WITH
_______ THE GIVEN INSTRUCTIONS OR THE OXYGEN CYLINDER COULD LEAK. HOLD A WRENCH ON THE COUPLING ASSEMBLY WHEN YOU TURN THE PRESSURE REDUCER. IF NOT, DAMAGE TO THE COUPLING ASSEMBLY CAN OCCUR.
 (c)  
Install the pressure reducer on the coupling assembly. Tighten to a torque of approximately 300 pound-inches.

 (d)  
Continue to tighten the pressure reducer until a sudden increase in torque occurs. This will make sure the parts are in full contact with the seal.

 NOTE: The inlet ports on the pressure reducer are
____ different in size. This makes sure the pressure reducer is installed with the oxygen flow in only the correct direction.
　
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