S 414-028-003

 (19)
 Close the access panels to the oxygen cylinders.

 NOTE: The access panel to the oxygen cylinders is attached by
____
 snaps and velcro tape.

 S 864-029-003
 (20) Remove electrical power if it is not necessary (AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 TASK 35-21-04-704-030-003
 4.  Flow Control Unit Leak Test (Fig. 401)___________________________
 A. Consumable Materials
 (1)  
G02311 Tape - Masking Non Residue, 3M-266

 (2)  
0.125 OD Elastomer Tubing

 B. References
 (1)  
AMM 20-22-01/601, Electrical Grounding

 (2)  
AMM 35-00-00/201, Oxygen

 (3)  
AMM 35-21-00/501 Passenger Oxygen - Operational/Leak Test

 (4)  
AMM 35-21-04/401 Flow Control Unit

 (5)  
IPC 35-21-04

 C. Access
 (1)  Location Zone 124 Forward Cargo Container Compartment, Aft Half Right
 D. Preconditions
 S 844-031-003
 (1)  The systems that follow must be installed and in serviceable condition to complete this test.
 (a)  
Electrical Power (AMM 24-22-00/201).

 (b)  
Passenger Oxygen system (AMM 35-21-00/501).

 (c)  
Airplane in Ground Mode (AMM 32-09-02/201).

 E. Procedure
 S 914-032-003
 (1)  
Read and obey the safety precautions and general instructions before you do the maintenance (AMM 35-00-00/201).

 S 864-033-003

 (2)  
Make sure the Flow Control Unit (FCU) is in the OFF mode and the Passenger Oxygen system is pressurized.

 S 884-034-003

 (3)  
Make sure the FCU is cooled to a temperature of approximately 32 degrees Fahrenheit or zero degrees Celsius.

 NOTE: Pressure loss during flight or cold weather operation
____ below freezing may cause the FCU to leak at the first stage diaphragm. To effectively test an installed FCU, It must be exposed to an ambient temperature of less than 32 degrees Fahrenheit or zero degrees Celsius.
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 (4)  S 484-035-003Install 0.125 outside diameter elastomer tubing in one of the two smaller holes of the first stage cap assembly (Fig. 401).
 (5)  S 954-036-003Cover the two remaining holes of the first stage cap with tape.
 (6)  S 484-037-003Place the other end of the elastomer tubing in a container of water.
 (7)  S 774-038-003Look in the water container for bubbles, leakage shall not be more than 0.01 liter per minute.
 (8)  S 794-039-003If the first stage cap leaks by more than 0.01 liter per minute, replace the flow control unit (AMM 35-21-04/401).
 (9)  S 844-040-003Remove tubing and tape from the FCU.

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747-400 MAINTENANCE MANUAL
 UNITIZED VALVE ASSEMBLY - REMOVAL/INSTALLATION
______________________________________________
 1.  General
_______
 A.  These tasks are included in this procedure:
 (1)  
Supernumerary Unitized Valve Assembly Removal

 (2)  
Supernumerary Unitized Valve Assembly Installation.

 B.  The unitized valve assembly is installed on each oxygen box which is installed in each supernumerary service unit (PSU). You must open the oxygen box to get access to the unitized valve assembly.
　
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