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Certification
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Leak
rate of 0.1 gph with PD = 100% and PFA = 0%.
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Leak
Threshold
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A
tank system should not be declared tight when the acoustic
signal detected is different from the baseline.
Baseline is the acoustic signal before tank is pressurized
or evacuated.
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Applicability
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Gasoline,
diesel, aviation fuel, fuel oil #4, waste oil.
Other liquids may be tested after consultation with the
manufacturer.
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Tank
Capacity
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Maximum
ullage volume is 16,500 gallons.
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Waiting
Time
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None
between delivery and testing
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Test
Period
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A
few minutes to determine background noise and a leak.
Depends on background noise at the site and on the size
of the leak.
After the desired pressure has been reached, the tank
should be allowed to settle for 10 minutes.
There must be no dispensing or delivery during test.
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Test
Pressure
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Vacuum
of 1 psi must be maintained in ullage by a vacuum blower,
or total pressure at bottom of tank of 4 psi must be maintained
using nitrogen.
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Temperature
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Acoustic
signal is independent of product temperature.
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Groundwater
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Depth
to groundwater in tank excavation backfill must be determined.
If groundwater is above product level, vacuum test should
not be used.
Pressure test may only be used if net pressure can be
maintained at a minimum 1 psi throughout ullage during
test.
If this requires more than 5 psi total pressure at tank
bottom, the ullage test must not be used.
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Comments
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Not
evaluated using manifolded tank systems.
Evaluated using diesel.
Tests only ullage portion of the tank.
Product-filled portion of tank must be tested with an
underfill test method. Microphone was 25 feet away from
the leak source during evaluation.
If background noise is too high, test is inconclusive.
Noise signals are tape recorded (not digitally recorded).
Vacuum test method may not be effective in some tank excavation
backfill (such as clay) because it may plug holes in tank.
If soil is saturated with product, air or water ingress
may not be declared by vacuum test.
A well point in tank excavation backfill may help identify
presence of this condition.
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