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Certification: |
Leak rate of 0.1 gph with PD = 100% and PFA = 1.6%.
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Leak Threshold: |
A tank system should not be declared tight
when the acoustic signal detected is different from the baseline
signal before a vacuum is placed on the tank, or when water
ingress is detected by the water sensor.
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Applicability: |
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: |
Maximum of 30,000 gallons.
Ullage volume must exceed the greater of 1% of tank volume or
50 gallons. Maximum of 30,000 gallons per tank for manifolded
tank systems with microphone, water sensor and pressure monitoring
gauges in each tank.
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Waiting Time: |
None between delivery and testing.
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Test Period: |
When groundwater level in tank excavation backfill is
below bottom of tank:
A few minutes to determine background noise and about 2 minutes
to run the test after desired vacuum is reached.
When groundwater level in tank excavation backfill is above
bottom of tank or when the groundwater level in the tank excavation
backfill has not been determined:
The time it takes for water ingress to increase the water level
in the tank to allow the water sensor to detect the "minimum
detectable change in water level" (see "Water Sensor"
section below).
Test period based on water ingress is dependent on tank size.
For example, the test period is 36 minutes for a 10,000 gallon
(96" dia x324" lg) tank.
Before starting test, water sensor must be calibrated to "minimum
detectable water level" (see "Water Sensor" section
below) according to manufacturer's instructions.
There must be no dispensing or delivery during test.
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Test Pressure: |
Pressure differential across tank wall at bottom of tank
must be at least 0.5 psig.
Pressure differential across tank wall is equal to the absolute
value of vacuum applied to tank, plus pressure of tank excavation
backfill on tank, plus groundwater pressure on tank, minus pressure
of liquid in tank.
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Temperature: |
Acoustic signal is independent of product temperature.
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Water Sensor: |
Conductivity water sensor must be used
to detect water ingress and must be calibrated for every test
when groundwater level in tank excavation backfill is above
bottom of tank or when the groundwater level in the tank excavation
backfill has not been determined.
Minimum detectable water level is 0.014 inch.
Minimum detectable change in water level is 0.0095 inch.
Minimum water level in tank must be adjusted to at least 0.014
inch (sensor's minimum detectable water level) before calibrating
sensor and starting test.
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Groundwater: |
Groundwater level in tank excavation backfill must be
determined by observation well or soil probe in tank excavation
backfill.
If groundwater level in tank excavation backfill is above bottom
of tank or the groundwater level in the tank excavation backfill
has not been determined, water sensor must be used and test
time extended to ensure water ingress detection during test.
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Comments: |
Microphone was 25 ft away from leak source during evaluation.
Although not tested on empty tanks, a third party acoustics
specialist has certified the device is equally effective when
tanks are empty as when tanks contain product.
Test may be inconclusive if there is high background noise.
Vacuum test method may not be effective in some tank excavation
backfill (such as clay) because it may plug holes in tank.
If free product is present in tank excavation backfill, a leak
in the free product zone may not be detected by a vacuum test
method.
An observation well or soil probe in tank excavation backfill
may help determine backfill material, water level in tank excavation
backfill, and free product. Manufacturer must certify operator
at least every 2 years.
More than 4 psi pressure differential across the tank wall at
any location in the tank could damage tank.
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