(a) The area inside the tank from which the leak appears to be coming is examined. Examination may reveal the cause of leakage in the form of missing or faulty sealing. In many instances, this method will not reveal the cause of leakage and the following method will prove to be the most rapid.
(2)
Air Hose and Internal Bubble Method
(a) A stream of air is directed at the point of leakage on the outside of the tank while at the same time the suspected area inside the tank is brushed with soap solution.
CAUTION: DO NOT USE A SOLUTION WHICH WILL CORRODE ALUMINUM OR DETERIORATE THE SEALANT. SOLUTION MUST BE WIPED CLEAN AFTER CHECK.
(3)
Air Hose and External Bubble Method
(a) This method is the same as the internal bubble method, except that the air is applied at the inside point and the soap solution applied at the outside.
(4)
Dye Injection Method
(a) This method is particularly useful when very small leaks cannot be detected by the air methods. Dye is forced through the leak path into the tank from the exterior leak point. One man enters the tank to observe the flow of dye from the internal leak source. The flow of dye can more readily be detected if fluorescent dye and an ultra-violet light, which causes the dye to glow, is used.
(5)
Internal Pressure and Bubble Method
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(a) If the dye injection test fails to show the leak source, the exterior outflow point should be verified by the pressure test. For test procedure, refer to Integral Fuel Tank . Trouble Shooting.
WARNING: DO NOT EXCEED THE MAXIMUM SAFE PRESSURE OF 5.20 PSIG.
The pressure test will verify both the tank and the outflow point. The tank must be closed and sealed to do this procedure. When the tank is correctly pressurized, if bubble solution applied to the exterior leak point indicates the exterior outflow point to be different from the one used in the dye injection test, then the dye injection test should be repeated using the new outflow point.
(6) Hollow Bolt Method
(a) The hollow bolt method of leak detection can be used to locate leaks in areas of structural buildup. The hollow bolt may be used with air and bubble method or dye injection.
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INTEGRAL FUEL TANK -TROUBLE SHOOTING
1. General
A. Integral fuel tank fuel leaks are usually the result of improper fitting installation, failed or damaged sealant, improperly installed or damaged O-rings, loose fasteners, and electrical or equipment installations that pass through tank boundaries not being properly installed.
B. Fuel leakage from a tank is divided into four groups to provide a means of evaluating the safety of flying the airplane with fuel leaks present. The four groups are stain, seep, heavy seep, and running leak. Refer to 28-11-0 AP for size patterns and evaluation of leaks.
C. The various methods used to locate a leak are described in detail in subsequent paragraphs. Equipment and Materials
A. Flashlight -explosionproof
B. Extension Light -P/N MIL-L-83762
C. Ultraviolet Light -explosionproof, EXP1525/50-Ultraviolet Light, Rice Safety Equipment, Seattle, Washington
D. Fuel tanks leak detection dyes
(1)
Fluorescent Dye -Intense Green (OS-31) or Bluish White (OS-80) (Ref 20-30-51)
(2)
Nonfluorescent Dye -Automate Red BSF (Ref 20-30-51)
E. Testing Device -P/N F71329
F. Pressure box (fabricated) (Fig. 102)
G. White talcum powder
H. Absorbent cotton cloths
I. Leak detection solutions
(1)
Tereco 210 (thin), Tereco 211 (thick), and Tereco 602 -Technical Research Co., Seattle, Washington
(2)
Turco Car Shampoo -Turco Products Incorporated, Seattle, Washington
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J. Air supply -90 to 100 psig
K. Air supply -0 to 10 psig
L. Camel-hair brush
M. Closure plugs and cover items
CAUTION: ATTACH RED, COTTON WEBBING, STREAMERS TO ALL PLUGS AND CLOSURE ITEMS USED IN THE TANKS.
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