(22)
After the leak repair, perform another test with the Helitest equipment before removing the helium chamber from the outside of the tank.
NOTE: This procedure makes sure the leak was repaired correctly.
(23)
Do the following steps to put the repaired 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).
(24)
Do this same procedure with the Helitest equipment for other leaks.
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INTEGRAL FUEL TANKS - CLEANING/PAINTING
1. General
A. This section contains information on the following subjects:
(1)
Integral fuel tank cleaning, fungus and corrosion removal.
(2)
Application of corrosion resistant finish.
NOTE: The application of corrosion resistant material over repaired integral fuel tank sealant material is covered in 28-11-0 AR.
2. Integral Fuel Tank Cleaning, Fungus and Corrosion Removal
A. General
(1)
Integral fuel tanks may become corroded by fungus growth, present in hydrocarbon fuels, which becomes attached to lower surfaces of tanks. Fungus may be removed from tank surfaces by entering tank and hand scrubbing tank surfaces with a fiber brush and water, or steam cleaning as outlined in par. C. The use of wet steam helps remove fuel fumes and locate loose or deteriorated topcoating by causing poorly bonded topcoating to peel or blister.
(2)
While tanks are still wet, presence of fungus is evident as a black sludge or slimy material. When tanks are dry, presence of fungus is evident as solid deposits on tank surfaces. These deposits may turn light brown when dry. If fungus is present, it is usually limited to lower panel of the wing and areas immediately adjacent to lower panel where water accumulates. In addition, fungus growth may contribute to corrosion of structure. If corrosion is found, refer to Structural Repair Manual, Chapter 51, General Repair Procedures.
(3)
Precautions and instructions for use of wet steam.
(a)
Operator should be protected with asbestos gloves, full face mask and asbestos or rubber hood.
(b)
Use steam line equipped with "dead man" valve. Station one person outside tank to observe any sign of distress.
(c)
Ventilate tanks using air movers (Ref 28-10-0 MP). Continue ventilation during tank cleaning to assist dissipation of steam vapors.
(d)
Do not direct steam at one spot for any length of time. The speed of the pass over an area should be approximately 6 inches per second. Several rapid passes are preferable to one slow pass.
(e)
Do not direct steam at feathered edge of sealing compound as this tends to loosen joint. Using a spray of approximately 100 psi, do not exceed 150°F at tank surface as a prolonged concentration of heat on sealant is very destructive.
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Nov 15/80 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-11-0 Page 701
B Equipment and Materials
(1)
Source of saturated steam
(2)
Source of cold water (at approximately 50 psi)
(3)
Steam Nozzle - Trigger T-Jet, Spraying Systems Co., Bellwood, Illinois
NOTE: It is recommended that teflon bushing supplied with this nozzle be replaced with a locally fabricated brass bushing. Nozzle is designed to have a source of saturated steam and a source of cold water attached; each supply to be adjusted by a set of valves to maintain a working spray of approximately 100 psi, with a temperature not to exceed 150°F, 6 inches from nozzle end.
(4)
Full face supplied air type respirator, U.S. Bureau of Mines Approved
(5)
Rubber pants, boots and jacket with hood
(6)
Asbestos gloves - Jackson Products - Warren, Michigan
C. Clean Integral Fuel Tank
(1)
Defuel and purge applicable fuel tank (Ref 28-23-0, 28-10-0 MP).
(2)
Remove fuel sump drain valve (Ref 28-11-21 R/I).
(3)
Remove wing access panels (Ref 28-11-11, 28-11-31 R/I, as applicable).
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