At the end of the steaming period, check for residual fuel vapors using an explosive vapor detector MIL-D-
16191. If explosive vapors are detected, repeat the steam cleaning operation, and recheck for explosive
During repair operations, check the fuel tank every 30 minutes for explosive vapors. If explosive vapors
are detected during a check suspend work immediately, and repeat the cleaning and checking procedures.
Inspection. See Figure 2-16.
Check all threaded holes for damaged or stripped threads, and mark them for repair.
Mark obvious cracks and punctures in the tank (43) or filler pipe assembly (15), for repair. If damage to
the tank is such that a patch would be required, replace the fuel tank
Check for rust and corrosion on the tank or filler pipe assembly (15) that could become a source of future
leaks. Test these areas by tapping them with a sharp punch. If they are easily penetrated, replace the fuel
tank or the filler pipe assembly (15).
Temporarily install the filler pipe assembly (15), plug all openings, then apply and maintain an air pressure
of 3 psi (21 kPa) to the tank. Apply soap solution to the welds and suspected leak areas. Mark all leaks for
repair, blood off the air pressure, and remove the filler pipe.
Repair. All welding shall be performed by qualified technicians in accordance with MIL-STD-1261, following the
safety practices set forth by the American Welding Society publication Z49.1-67.
Repair minor thread damage to fittings by chasing. Repair stripped or severely damaged threads in
accordance with paragraph 2-12.
Welding operations produce heat, highly toxic fumes, injurious radiation, metal sing, and
airborne particles. Welding goggles, the proper tinted lenses, apron or jacket and welders
boots are required to avoid injury to personnel.
Repair leaks or cracks in the filler pipe assembly (15, Figure 2-16) by welding. Replace the filler pipe
assembly if the flange is badly warped, or the tube is badly dented or out of round.
To avoid explosions and injury to personnel during future repairs, do not weld patches on
damaged areas of the fuel tank. Such patches will form fuel pockets. Fuel will gather in these
pockets and be difficult or Impossible to remove or detect. The heat from welding operations
will vaporize this fuel and form explosive gases.
Weld cracks shorter than 2 inches (51 mm) in one pass. To prevent warping on longer cracks, tack weld
the crack every 4 inches (102 mm), and use the back stop method of welding. Do not patch any crack or
rusted through area; if a patch would be required, replace the fuel tank.
Grinding operations create airborne, abrasive dust and particles. Respiratory and eye
protection is required to prevent injury to personnel.
Repair cracked or porous welds by grinding out the defect and rewelding.
Check all new welds in accordance with step c (4), above.
Install. Install the fuel tank in accordance with paragraph 2-18.