28-11-00
 ALL  ú ú 01 Page 624 ú Mar 12/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 S 796-259
 WARNING:_______KEEP THE DETECTOR AND THE PUMP AWAY FROM THE TANK. INJURY TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.
 (16)
 The HeliTest detector and the auxiliary pump must be kept away from the open fuel tank at all times.

 S 796-260

 (17)
 Go into the tank with the HeliTest Visual Probe (intrinsically safe for Class I, Div I areas).

 S 796-261

 (18)
 Slowly interrogate the inside of the tank around the area where you expect to find the leak.

 NOTE:____Patience is important. With a systematic approach, slowly move away from the area where you expect to find the leak until you find the exact location of the leak.
 S 796-262
 CAUTION:_______DO NOT PUT THE PROBE INTO FUEL PUDDLES. IT CAN CAUSE DAMAGE TO THE INSTRUMENT.
 (19) If there is a puddle of fuel in the area where you expect to find the leak, use compressed air to dry the area.
 (a)  
Build rag dams to soak up additional running fuel.

 (b)  
Completely dry hidden areas.

 (c)  
If fuel is drawn into the HeliTest probe, immediately remove it to a safe area and permit it to operate until all the fuel is vaporized. 1) Disconnect the Visual Probe gas line and permit it to run

 dry also. 2) Replace the wet filter on the visual probe tip with a dry filter. 3) Do not shut the HeliTest off while it is contaminated with fuel because permanent damage can occur.
 S 796-263
 (20) If you do not find the leak, increase the helium pressure to
 0.6 psig, and then 1.2 psig.
 (a)  Continue to increase the helium pressure in similar increments until the leak is found.
 NOTE: The compression chamber can hold 2 to 5 psig maximum.
____ The maximum pressure depends on the size of the chamber. A smaller chamber can hold a larger pressure.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 S 396-264
 (21)
 When you find the leak, repair it with the applicable repair procedure (AMM 28-11-00/801).

 S 796-265

 (22)
 After the leak repair, do another test of the leak with the HeliTest equipment before you remove the helium chamber from the outside of the tank.

 NOTE: This procedure makes sure the leak was repaired correctly.
____
 S 796-266
 (23) Do these steps to put the area back to its usual condition:
 (a)  
Remove the pressure chamber or pressure cup and the tape.

 (b)  
Clean the area around the leak with solvent, Series 82 (AMM 20-30-82/201 or SOPM 20-30-82).

 S 796-267
 (24) Do this same procedure with the HeliTest equipment for other leaks.
 TASK 28-11-00-216-098
 5. Leak Path Analysis
__________________
 A. General
 (1)  After you find the external leak point and the internal leak source, find the point where the leak path goes through the seal plane. The area where you saw the bubble or the dye on the inner surface of the tank is usually the point where the leak path goes through the seal plane. But if there is a bad hidden seal (an injection seal, prepack seal, or faying surface seal), fuel can go into the structure and go a long distance before it shows at the external leak point. If there is a bad hidden seal and you repair only the seal where the bubbles or dye were shown, it is possible that the repair is only temporary. These leaks can occur again many times until you find the correct point where the leak path goes through the seal plane and repair it. Thus it is important to think about all of the possible leak paths between the internal leak source and the external leak point.
 NOTE: You can lift the seal plane as an alternative to the
____ procedure to repair the hidden seal (AMM 28-11-00/801).
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