S 286-108

 (9)  
The best procedure to find the internal leak point is the backblowing procedure.

 S 286-109

 (10)
 If you have a suspected internal leak point but cannot get it to bubble, reverse the backblowing procedure:

 (a)  Apply air pressure to the suspected internal point and apply the soap solution to the suspected external point.
 S 286-110
 (11) The leak path between the internal leak point and the external leak point can be a long distance.
 (a)  If the internal leak point is not directly inside the tank from the external leak point, continue to look for the internal leak point along the same joint which is directly inside the external leak point.
 S 286-111
 (12) Use a maximum air pressure of 100 psi for small leaks.
 (a)  Use less air pressure for larger leaks.
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 S 286-112
 (13) More than one internal leak point can lead to the same external leak point.
 (a)  When this occurs, there are multiple leak paths.
 S 286-113
 (14) More than one external leak point can lead to the same internal leak point.
 (a)  When this occurs, there are multiple leak paths.
 S 286-114
 (15)
 Think about alternative procedures of leak detection when
 Backblowing is not possible.

 S 286-115

 (16)
 Find the leak path before you do the leak repair.

 E. Leak Repair Tips
 S 366-116
 (1)  
Make sure you have trained persons to do the leak repair.

 S 366-117

 (2)  
Make sure you have materials and equipment to safely do leak repairs.

 S 366-118

 (3)  
Remove the bad sealant around the internal leak point before you apply the repair sealant.

 S 366-119

 (4)  
Sealant with bad adhesion to the structure can be pulled up easily by hand.

 (a)  Replace this sealant.

 (5)
Use the correct solvents for cleaning and surface preparation.

 S 366-120
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 (6)  S 366-121Clean the structure after you remove bad sealant.
 (7)  S 366-122If you apply primer, heat cure the new primer.
 (8)  S 366-123Use BMS 5-26 type II sealants before the expiration date.
 (9)  S 366-124Apply sealants to surfaces between 10 degrees Celsius and 49 degrees Celsius.
 S 366-125

 (10)
 Apply a precoat of sealant before a new fillet seal. S 366-126

 (11)
 Apply a corrosion resistant finish (topcoat) if it is necessary. S 366-127

 (12)
 Make sure the sealant is tack-free before you close the tank.

Figure 617

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WING CENTER

Tank Access Panels
Figure 618

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