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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 796-074
 (13)
 Make sure there are no leaks around the cap assemblies.

 S 796-062

 (14)
 Close the air supply valve.

 S 976-068

 (15)
 Make a record of how much time is necessary for the pressure to decrease from 32.0 - 34.0 psig to 13.0 - 15.0 psig (221 - 234 kPa gage to 89.7 - 103 kPa gage).

 S 796-077

 (16)
 Make sure the time is greater than 2.5 seconds.

 S 796-070

 (17)
 Decrease the pressure to the ambient pressure.

 S 796-075

 (18)
 Open the air supply valve.

 I. Put the Airplane to Its Usual Condition
 S 086-085
 WARNING: MAKE SURE THE AIR SUPPLY VALVE IS OPEN BEFORE YOU REMOVE THE
_______ CAP ASSEMBLIES FROM THE HEAT EXCHANGER. THE HEAT EXCHANGER IS PRESSURIZED UNTIL THE AIR SUPPLY VALVE IS OPENED. YOU CAN BE INJURED IF YOU REMOVE THE CAP ASSEMBLIES WHEN THE HEAT EXCHANGER IS PRESSURIZED.
 (1)  
Remove the cap assemblies and the seals from the primary heat exchanger.

 S 966-076

 (2)
If the heat exchanger leak was more than specified (time less than

 2.5 seconds), replace the heat exchanger (Ref 21-51-03/401).

 (3)  
Disconnect the test equipment from the cap assemblies.

 S 416-046

 (4)  
Install the ducts to the heat exchanger inlet and outlets (4 locations) (Ref 36-11-01/401).

 S 036-065

 (5)  
Remove the plug from the water aspirator boss, on the heat
 exchanger.

 (6)  
Install the water aspirator (Ref 21-51-11/401).

 S 086-045
 S 436-047
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 S 416-048
 (7)  Close the applicable access panel 191E-L, 192E-R, or 191M-L (Ref 06-09-03/201).
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747-400 MAINTENANCE MANUAL
 HEAT EXCHANGER - CLEANING/PAINTING
__________________________________
 1.  General_______
 A.  This procedure has instructions to clean the primary and secondary heat exchangers. A primary and secondary heat exchanger is installed in the aft end of each air cooling pack.
 TASK 21-51-03-107-001
 2.  Clean the Heat Exchanger________________________
 A.  Standard Tools and Equipment
 (1)  
Shop air at 80 to 100 psi (550 to 700 kPa)

 (2)  
Shop vacuum (cleaning)

 B.  References
 (1)  
AMM 06-09-03/201, Body Section 44 Access Doors and Panels

 (2)  
IPC 21-51-03 Fig. 2

 C.  Access
 (1)  
Location Zone
 133 Air Conditioning Equipment Bay, LH
 134 Air Conditioning Equipment Bay, RH

 (2)  
Access Panel
 191E-L Air Conditioning Access Panel
 192E-R Air Conditioning Access Panel
 191M-L Air Conditioning Access Panel

 D.  Prepare to Clean the Heat Exchanger
 S 867-002
 (1)  
Set the applicable PACKS (1, 2 and 3) switch to OFF, at the P5 overhead panel.

 S 017-003

 (2)  
Open the applicable access panel (AMM 06-09-03/201):

 -191E-L for pack 1
 -192E-R for pack 2
 -191M-L for pack 3.

 (3)  
Disconnect the ram-air exit door from its actuator.

 S 037-004
 NOTE: This will permit better access to the heat exchanger core.
____
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