500 Leakage Tracing Device
Jun 20/93 Figure 103 28-11-0
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L. Internal Pressure and Bubble Method
(1) Where difficulty is experienced localizing leaks on outside surface of wing, fuel tank may be pressurized and a bubble solution applied to the wing. Appearance of bubbles, should reveal the external leak points.
WARNING: DO NOT USE PRESSURIZATION METHOD UNTIL ALL OTHER METHODS HAVE FAILED. DO NOT EXCEED MAXIMUM SAFE PRESSURE OF 5.20 PSIG. OBSERVE ALL SAFETY PRECAUTIONS FOR TANK ENTRY PER 28-10-0, FUEL STORAGE SYSTEM . MAINTENANCE PRACTICES.
NOTE: Size of leak may be such that bubbles form very slowly. Constant observation may be required to detect leak.
(2) Prepare Main Tank No. 1 or 2, or Integral Center Tank for Leak Check . Pressure Method
WARNING: DO NOT COMPROMISE THE SAFETY PRECAUTIONS GIVEN FOR PURGING AND FUEL TANK ENTRY.
(a) Prepare Main Tank No. 1 or 2 (Fig. 104).
NOTE: Check of either main tank includes its respective surge tank.
1) Prepare tank for entry by defueling and purging tank (Ref 28-23-0 and 28-10-0 MP).
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540 Integral Tank Pressure Check Configuration
Apr 01/97 Figure 104 28-11-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
2) Manually close center tank boost pump removal valve. a) For tank No. 1, close LH pump valve through access panel No. 7201. b) For tank No. 2, close RH pump valve through access panel No. 7401.
3) On airplanes with boost pump bypass valves with valve lock actuating arms, manually close boost pump bypass valve, for the tank being checked, by removing access plug from lower wing surface, inserting valve lock ME65-16713, and pulling plunger down.
4) Check that the following valves are closed: a) APU fuel valve b) Crossfeed manifold valve c) Engine shutoff valve
5) Remove wing fuel tank access panels No. 13 and 14 (Ref 28-11-11 R/I).
6) Enter surge tank through No. 13 panel and block off center tank vent duct and surge tank drain. a) Install vent plug, F80080-100 or 7TE65-46517, in center tank vent duct. b) Install structural vent cover assembly, F80080-56, in rectangular slot in
center tank vent duct. c) Install surge tank drain tube plug assembly, F80080-55, on opening to
surge tank drain line. 7) Remove blower and air mover used for tank purging and ventilation. 8) Install Surge Tank Pressure Door Assembly F80080-82 or F80080-5 in access
opening No. 13 (Ref 28-11-11 R/I). 9) Install Vent Scoop Closure Plug F80080-88 or 9TE65-45412 in access opening No. 14. 10) Install filler cap on overwing fueling port.
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(3) Perform Leak Check
(a)
Connect safety relief manometer (Fig. 105) to the tank test door.
WARNING: MAKE SURE THAT SAFETY RELIEF MANOMETER OPERATES SAFELY BY BLOWING INTO MANOMETER HOSE AND NOTING THAT WATER LEVEL FLUCTUATES. CHECK THAT OPEN END OF MANOMETER IS COMPLETELY FREE OF ANY OBSTRUCTION.
(b)
Connect pressure hose to air valve on tank test door.
(c)
Fill manometer with water to fill mark on manometer corresponding to desired pressure (Fig. 105).
CAUTION: DRAIN MANOMETER COMPLETELY IMMEDIATELY AFTER PRESSURE CHECKING IN COLD WEATHER. MAKE CORRECTION TO WATER COLUMN HEIGHT WHEN USING ANTIFREEZE SOLUTION.
NOTE: Use of colored water or a small floating ball facilitates observation of water level in manometer. Antifreeze solution may be used when pressure checking in very cold weather.
(d)
Open air valve and apply 4.0 psig air pressure to the tank. Observe water level and partially close air valve to slow down movement of lower level as it approaches lower bend of manometer tube.
CAUTION: MONITOR THE EQUIPMENT AT ALL TIMES TO MAKE SURE 4 PSI PRESSURE IS NOT EXCEEDED. DAMAGE TO THE AIRPLANE COULD OCCUR IF MORE THAN 4 PSI PRESSURE IS USED.
(e)
Close air valve as soon as the lower level passes the bend. The upper level should not reach open end or upper bend of manometer.
(f)
Apply bubble solution on the outside surface of the wing, in the area you think there is a leak.
(g)
Mark location of bubbles, remove bubble solution from surface with a damp rag, and depressurize tank.
(h)
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