Fuel
Systems
Tests
FEDERAL LAW
183.580 - Static pressure test for
fuel tanks
(b) Examine each tank fitting and seam
for leaks using a leak detection method other than the
pressure drop method.
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The static pressure test must be supplemented
with another method to check for leaks. Soapy water or a detergent
solution, both of which should be non-corrosive and non-toxic,
can be used as well as total immersion of the tank in water.
Most small leaks do not produce an immediately detectable
drop on the face of the pressure gauge, but soap solutions
or immersion will reveal very small leaks by bubbling.
CAUTION
It is suggested that
soapy test solutions be non-corrosive and non-toxic.
Ammonia, which is present in some soaps and detergents,
creates a condition which attacks brass fittings like
those used in fuel systems. Undetectable at first, in
a matter of months these fittings may develop cracks
creating a very hazardous situation. |
If immersion of the tank is used, remember that
immersion increases the pressure on the outside of the tank
above normal atmospheric pressure. The testing pressure in
this case must be the differential in actual pressures. For
example, if the head of water over a tank will produce 1 pound
of pressure and the tank is to be tested to a label pressure
of 3 pounds of pressure, then, when underwater, the pressure
inside the tank must be 4psl. For every foot of head, the
pressure correction is 0.433 psig.
There are also several devices available that
are designed to detect small leaks of the nature of those
that might appear in fuel systems. Most work by a principle
of amplification of sound or detection of sounds of certain
frequencies.
Inspect all seams and attachments - fill, vent,
fuel lines, fuel level indicator, etc. for leakage.
To determine the height of the head pressure,
measure from the top of the fuel fill plate, or the vent system;
if it is lower than the deck fill, measure to the lowest point
in the system.
FIGURE
38 - Test Pressure Determination
FIGURE 39 - Fuel System Test Pressure
For a given measured height, this chart gives
you the required test pressure.
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