(c)  
Loosely connect the coupling nut on the high pressure cylinder to the oxygen cylinder port.

 (d)  
Loosely connect the overboard discharge line at the B-nut.

 (e)  
Do these steps to install the band strap clamp: 1) Make sure that the toggle lever is in the extended position, and connect the clamp halves.

 2)  Move the T-bolt head into position through the two holder assembly fingers.
 CAUTION: DO NOT ADJUST THE SPRING TENSION DURING THE
_______ INSTALLATION. THE SPRING TENSION IS SET AT THE FACTORY. ADJUSTMENT CAN CAUSE DAMAGE TO THE SPRING.
 3) Move the toggle lever to the closed position (this applies tension to the spring). 4) Install the safety pin.
 (f)  
Tighten the connection to the overboard discharge line.

 (g)  
Tighten the coupling nut on the high pressure cylinder to a torque of 650 to 700 pound-inches.

 (h)  
Install the tubing clamps that were removed.

 S 793-222
 (3)  Do these steps to make sure that there are no leaks from of the oxygen cylinder:
 WARNING:_______OPEN THE SHUTOFF VALVE ON OXYGEN CYLINDERS SLOWLY. IF YOU OPEN THE VALVE QUICKLY, HIGH TEMPERATURES CAN OCCUR IN THE LINES. THIS CAN CAUSE INJURIES TO PERSONNEL AND DAMAGE TO THE AIRPLANE AND EQUIPMENT.
 CAUTION: DO NOT TIGHTEN THE SHUTOFF VALVE ON EACH OXYGEN CYLINDER
_______ TO MORE THAN 25 POUND-INCHES (2.8 NEWTON-METERS). TOO MUCH TORQUE CAN CAUSE DAMAGE TO THE SHUTOFF VALVE.
 (a)  Slightly open the oxygen cylinder shutoff valve to let the system pressurize slowly.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400 MAINTENANCE MANUAL
 (b)  
Close the shutoff valve.

 (c)  
Use leak detection compound to make sure that the connections do not have leaks.

 (d)  
If there are leaks, make applicable repairs to the connections, and do the leak test again.

 (e)  
When the leak test is complete, remove the leak detection compound with a clean cotton cloth.

 S 843-223
 (4)  Prepare the oxygen system for service:
 (a)  Open the shutoff valve:
 1)  Slowly turn the shutoff valve with your hand until it is fully open.
 NOTE: A maximum of 25 inch-pounds (2.8 newton-meters) is
____ necessary to seat the valve in the open position.
 2) Close the shutoff valve one-quarter turn. 3) Use 0.020-inch diameter copper lockwire to safety the shutoff valve (AMM 20-11-28/401).
 (b)  
Close all the access panels to the oxygen cylinders which are attached by snaps and velcro tape.

 (c)  
Remove the DO-NOT-CLOSE tag and close this circuit breaker:

 1)  P7 Overhead Circuit Breaker Panel a) 7D4 OXYGEN VALVE & IND

 (d)  
To make sure that the pressure shows on the EICAS status page, do this task: Oxygen System Operational Test (AMM 35-21-00/501).

 TASK 12-15-08-603-041
 3.  Crew Oxygen System Servicing (Cylinder Replacement) (Fig. 302)___________________________________________________
 A.  General
 (1)  
Read and obey the safety precautions and general instructions before you start maintenance (AMM 35-00-00/201).

 (2)  
Use this procedure to replace one oxygen cylinder. Do this procedure again for each oxygen cylinder that you replace.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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 ALL  ú ú 08 Page 308 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

747-400
MAINTENANCE MANUAL

CREW OXYGEN 
CYLINDERS 
SEE  A 
T-BOLT  AFT MOUNT 
NUT 
CREW OXYGEN 
CYLINDERS 
CREW SUPPLY 
LINE 
FORWARD MOUNT 
HIGH PRESSURE 
　
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