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A

747-400
MAINTENANCE MANUAL

PRESSURE RELIEF

AIR FILTER  ADJUSTABLE PRESSURE REGULATOR (80 PSIG MAXIMUM)
Pressure Relief Valve Test
Figure 202

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747-400 MAINTENANCE MANUAL
 S 722-016
 (2)  Do a check of the relief pressure.
 (a)  
Connect these components to a source of compressed air that does not have oil, as shown in Fig. 202. 1) Relief valve 2) Control valve 3) Pressure gage 4) Pressure regulator 5) Air filter

 (b)  
Close the control valve.

 (c)  
With the initial pressure at zero psig, slowly open the pressure regulator.

 (d)  
Look at the pressure gage while you increase pressure.

 (e)  
Keep a record of the pressure at which you find airflow or a sudden increase in airflow through the pressure relief valve.

 NOTE: This pressure must be between 57 and 63 psig.
____
 S 682-017
 (3)  
If the relief pressure is not in the 57 to 63 psig range, replace the relief valve.

 (4)  
Do the steps in paragraph 3 that install the relief valve.

 S 412-018
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747-400 MAINTENANCE MANUAL
 PRESSURE SWITCH - MAINTENANCE PRACTICES
_______________________________________
 1.  General_______
 A.  This procedure gives the instructions for three tasks. The first task is for the removal of the pressure switch. The second task is the installation of the pressure switch. The third task is an operational test to make sure the pressure switch operates correctly.
 TASK 38-15-67-382-001
 2.  Pressure Switch Removal (Fig. 201)_______________________
 A.  References
 (1)  
AMM 25-52-01/401, Containerized Cargo Compartment Ceiling and Sidewall Linings

 (2)  
AMM 38-15-60/201, Water System Pressurization

 B.  Access
 (1)  Location Zone 124 Forward Cargo Container Compartment Aft Half, Right
 C.  Procedure
 S 862-002
 WARNING: MAKE SURE YOU REMOVE THE AIR PRESSURE FROM THE WATER
_______ PRESSURIZATION SYSTEM BEFORE YOU START TO REMOVE THE PRESSURE SWITCH. AIR WITH HIGH PRESSURE AND TEMPERATURE CAN CAUSE INJURY TO PERSONS.
 (1)
Do this task: "Water System Depressurization (AMM 38-15-60/201).

 S 012-003

 (2)  
Do the "Containerized Cargo Compartment Ceiling and Sidewall Linings Removal" task (AMM 25-52-01/401) to remove the RH upper 12 inches of the vertical sidewall panels between stations 840 and 860.

 S 012-004

 (3)  
Do the "Containerized Cargo Compartment Ceiling and Sidewall Linings Removal" task (AMM 25-52-01/401) to remove the ceiling panels adjacent to the sidewall panels that you removed.

 (4)
Disconnect the electrical connectors from the pressure switch.

 S 032-005
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A

747-400
MAINTENANCE MANUAL

PRESSURE SWITCH SEE

UNLOADER CHECK VALVE (REF)
Pressure Switch - Installation
Figure 201

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