WARNING: KEEP CLEANERS AND SOLVENTS AWAY FROM HEAT, SPARKS, AND OPEN FLAME. USE WITH ADEQUATE VENTILATION. KEEP CONTAINERS CLOSED WHEN NOT IN USE. AVOID BREATHING OF VAPORS OR CONTACT WITH SKIN.
503
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4) Examine O-ring groove and adjoining flat surface for cuts, scratches, dents,
distortions, and foreign material. Defective fittings must be repaired or replaced. 5) Check new O-ring for defects; if defective, discard it. 6) Stamp rubber cure date of O-ring on assembly in which it is installed. 7) Check O-ring fit in groove. See Fig. 826 for proper fit. 8) Install O-ring and assemble part. 9) In the assembly of parts where difficulty is experienced holding an O-ring in
position, it may be cemented into the groove as follows:
a) Clean and examine parts as directed in steps 3) thru 7).
b) Apply a light coating of B.F. Goodrich No. 4 rubber cement.
502 Fuel Tank Ventilation
Nov 15/77 Figure 825 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-11-0 Page 835
c) Apply a light coating of the same cement to the surface of the O-ring.
NOTE: B.F. Goodrich No. 4 rubber cement can be thinned by adding white gasoline, W-G-109 or naptha, TT-N-95.
d) When cement on O-ring and in the groove becomes "tacky," turn O-ring, cement side down, and press into groove.
e) Remove excess cement from flat surface of fitting by rubbing the thumb or finger over the surface. Cement will roll or peel off.
f) Assemble parts.
NOTE: As an option a thing film of petrolatum VV-P-236 may be applied to O-ring.
6. Examination and Closure of Repaired Fuel Tanks
A. Any time an integral fuel tank has been entered it must be given a very thorough examination before closure. If repair sealant has been applied, the tanks must be carefully cleaned and examined before closure. The following steps shall be used for closure of repaired integral fuel tanks.
WARNING: COMPLY WITH ALL TANK ENTRY PRECAUTIONS AS GIVEN IN 28-10-0, MAINTENANCE PRACTICES.
(1)
Remove all coverplates, plugs, and equipment used in leak isolation tests.
(2)
Remove all tools, solvent containers, rags, and brushes used for sealant repairs.
NOTE: A check list should be maintained recording all tools, equipment, material, and personnel as they enter and leave the tank. The check list should be verified before tank closure.
(3)
Vacuum clean the repaired tank thoroughly to remove lint and pieces of old sealant. If tank is wet with fuel, wipe the contaminated areas clean with cotton rags or sponges.
WARNING: ALL EQUIPMENT AND HOSES USED IN OR NEAR THE OPENED FUEL TANK MUST BE PROPERLY GROUNDED.
(4)
Examine all repair sealant and topcoating for proper application.
(5)
Replace any rib braces or structure removed for accessibility.
(6)
Install access doors.
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7. Fueling Repaired Integral Fuel Tanks
A. Integral fuel tanks repaired and topcoated shall not be refueled until topcoating has cured. Under normal conditions, 12 hours at a minimum of 65°F is required for the topcoat to cure before fueling.
B. Integral fuel tanks repaired without topcoating may be refueled when the sealant becomes tack-free providing pressure of the refueling stream is not directed against the new sealant.
C. Fill repaired integral tank with fuel (Ref 12-11-0, Fuel Servicing). Check the external leak area periodically for 1 hour. There shall be no leakage.
502 O-Ring Groove Preparation and Fit
May 01/98 Figure 826 28-11-0
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8. Secondary Fuel Barrier Sealant Approved Repairs
A. On airplanes with integral center wing section fuel tank, the outside surface of the front spar and the entire upper panel of the center wing section is coated with a secondary fuel barrier sealant (Fig. 827). This sealant is used to prevent the escape of fuel liquid or vapor into the pressurized cabin area in the event of failure of the primary seal at the rivet and inner fillet and faying surface seals. All areas of secondary fuel barrier sealant where sealant is removed or damaged must be replaced or repaired.
WARNING: MAINTAIN A COMPLETE AND UNDAMAGED SECONDARY FUEL BARRIER SEALANT COATING OR LEAKING FUEL OR FUMES COULD CAUSE AN EXPLOSION OR BREATHING HEALTH HAZARD.
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