Figure 4-77.--Injection of sealing compound.
the tank must be heated above 70°F before sealing is
attempted. This may be accomplished in a heated
hangar or by using portable heating units or electric
Do not use toluene for cleaning any surface with
a corrosion-resistant or fuel-resistant coating.
NOTE: If the sealing compound does not appear
Toluene will remove the coating and cause the loss of
after approximately 4 to 5 minutes, you may assume
the coating's protective properties.
that the compound is too cold, the groove is plugged, or
the surface gap is excessive. In this case, the injection
should be discontinued until the discrepancy is
If the sealant is exceptionally slow to inject, the
tank may be heated to 110°F. Heating can be
accomplished by using electric blankets.
When an integral fuel cell has been repaired, it
must be pressure checked before it is filled with fuel.
Since the pressure testing procedure will vary with
Do not heat the tank in excess of 110°F to seal the
different types of aircraft, you should always consult
injection groove as higher temperatures are con-
the structural repair manual for the aircraft concerned
sidered as a fire hazard.
for the proper procedure. The following equipment is
used for pressure testing a system:
The proper temperatures for sealing are 79° to
· A source of nitrogen and a means of regulating
84°F. If the tank is exposed to temperatures below 50°F,