(5)
Improper Installation of Fittings
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Nov 15/78 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-11-0 Page 801
(a) Fittings and connections attached to or passing through tank boundaries are sealed with O-rings. When installing O-rings, they can be pinched, scored, twisted, or otherwise improperly installed, causing a fuel leak.
3. Leak Evaluation and Repair Requirements
A. For information on how to evaluate a leak as it relates to leakage rate and appropriate action to be taken, refer to 28-11-0 D&O.
B. Typical Repair Requirements
(1)
Failed fillet or fastener seal - Faulty sealant material must be removed, surfaces thoroughly cleaned, and new sealant applied to produce a seal of the same size and shape as the original seal.
(2)
Failed faying surfaces or prepack seal - These seal types require disassembly of structure or removal of fasteners. Accomplish such removals as directed in the Structural Repair Manual. Another repair method for this type of leak is to raise the seal plane. The new seal plane must completely isolate the failed seal from fuel, but the seal plane should not be raised an extensive amount. In many cases, structure removal and replacement is the best method.
(3)
Failed injection seal - All faulty sealant material must be removed and channel must be thoroughly clean. Channels must be completely filled with sealant. Trapped air causes a void and is cause for rejeection of sealing job. As an option the failed injection seal may be repaired by raising the seal plane.
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4. Repair of Sealant Leaks in Tank Structure
A. Sealant repair requires the use of toxic and flammable material for cleaning or surface sealant or finish application. The importance of providing adequate ventilation and observing fire safety precautions can not be over emphasized.
WARNING: PROVIDE ADEQUATE VENTILATION AND OBSERVE ALL FIRE SAFETY PRECAUTIONS WHEN USING TOXIC AND FLAMMABLE MATERIALS.
B. Equipment and Materials
NOTE: All equipment used for application of sealing compound must be clean. All equipment used must be cleaned thoroughly after each sealing job. Two part compounds, those mixed with an activator, will harden and make cleaning of equipment extremely difficult.
(1)
Sealant removal and fairing tools (Fig. 801)
(2)
Paint brushes
(3)
Neoprene or rubber gloves
(4)
Unsterilized gauze pads - all material shall contain less than 0.75 percent oil by carbon tetrachloride extraction
(5)
Pipe cleaners
(6)
Funnel brush
(7)
Polyethylene wash for bottles, nozzles, cartridges, and plungers
(8)
Sealing gun
(9)
Sealing tool (Fig. 802)
(10)
Explosion proof air blower, with sufficient flexible hose to reach all areas inside fuel tanks. Capacity to be 90 to 100 cubic feet per minute
(11)
Explosion proof centrifugal exhaust fan, capacity to be 125 to 150 cubic feet per minute, and approximately 75 feet of 3-inch diameter flexible suction hose, plus sufficient delivery hose to carry exhausted air outside hangar or working area
WARNING: MAKE SURE THE CAPACITY OF THE EXHAUST FAN IS MORE THAN THE CAPACITY OF THE AIR BLOWER. THIS WILL MAKE SURE THERE IS A GOOD FLOW OF AIR. THERE ARE POISONOUS AND FLAMMABLE COMPOUND WHICH CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
(12)
Full Face Supplied Air Type Respirator, U.S. Bureau of Mines Approved
(13)
Abrasive pad (Ref 20-30-51)
(a)
Aluminum oxide abrasive - Scotch Brite Sheet, TYPE A.
(b)
Aluminum oxide nylon pad, TYPE F.
(c)
Aluminum oxide - Bear-Tex
(d)
Aluminum oxide - Microlon
(14)
Abrasive Paper - 320 grit or finer
(15)
B01013 Solvent - Final Cleaning Prior to Fuel Tank Sealing (Series 93) (Ref AMM/SOPM 20-30-93).
(16)
Sealant BMS 5-26 Type II: Class A - For brush application; Class B - For sealing gun application; Class C - For extrusion gun, roller. Spatula application (Ref 20-30-11).
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A02328 A02544 A02609
Sealant Removal and Fairing Tools 502
28-11-0 Figure 801 (Sheet 1) Feb 20/92
Page 804
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
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