Certification
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Leak
rate is proportional to product surface area (PSA).
For tanks with PSA of 564 ft², leak rate is 0.2 gph with
PD > 99.9% and PFA < 0.1%.
For other tank sizes, leak rate equals [(PSA in ft² ÷
564 ft²) x 0.2 gph].
Example: For a tank with PSA = 846 ft²; leak rate = [(846
ft² ÷ 564 ft²) x 0.2 gph] = 0.3 gph.
Leak rate may not be scaled below 0.2 gph.
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Leak
Threshold
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Leak
threshold is proportional to product surface area (PSA).
For tanks with PSA of 564 ft², leak threshold is 0.1 gph.
For other tank sizes, leak threshold equals [(PSA in ft²
÷ 564 ft²) x 0.96 gph].
Example: For a tank with PSA = 846 ft²; leak threshold
= [(846 ft² ÷ 564 ft²) x 0.1 gph] = 0.15 gph.
Leak threshold may not be scaled below 0.1 gph.
A tank system should not be declared tight if the
test result indicates a loss or gain that equals or exceeds
the calculated leak threshold.
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Applicability
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Gasoline,
diesel, aviation fuel, fuel oil #4.
Other liquids may be tested after consultation with the
manufacturer.
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Tank
Capacity
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Use
limited to single, field-constructed, vertical-walled
tanks having a capacity of 50,000 to 75,000 gallons
Maximum product surface area (PSA) is 846 ft².
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Waiting
Time
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Minimum
of 4 hours, 48 minutes after delivery or transfer.
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Test
Period
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Minimum
of 6 hours. There must be no delivery, transfer, or dispensing
during test.
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Temperature
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Average
for product is determined by five resistance temperature
detectors (RTDs)
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Water
Sensor
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Must
be used to detect water ingress.
Minimum detectable water level in the tank is 0.874 inch.
Minimum detectable change in water level is 0.011 inch.
For tanks with a product surface area (PSA) of 564 ft²
and containing 0.874 inches of water, system takes more
than 64 days to detect a 0.20 gph water ingress rate.
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Calibration
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System
must be checked and, if necessary, calibrated in accordance
with manufacturer's instructions.
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Comments
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Tests
only portion of tank containing product.
As product level is lowered, leak rate in a leaking tank
decreases (due to lower head pressure).
Consistent testing at low levels could allow a leak to
remain undetected.
Evaluated in nominal 50,000 gallon tank with PSA of 564
ft².
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