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Certification
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Leak
rate of 0.1 gph with PD = 95.24% and PFA = 0%.
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Leak
Threshold
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A
tank system should not be declared tight when the make-up
gas flow rate into ullage equals or exceeds 0.275 cubic
feet/hour.
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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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Maximum
ullage volume is 7,500 gallons.
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Waiting
time
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Minimum
of 2 hours between delivery and testing.
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Test
Period
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Minimum
of 20 minutes, consisting of 2 consecutive 10-minute test
periods.
Test data are acquired and recorded manually.
There must be no dispensing or delivery during test.
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Test
Pressure
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Pressure
must be increased in ullage such that total pressure at
bottom of tank does not exceed 5.0 psi.
Pressure must be maintained for a minimum of 5 minutes
per 1,000 gallons of ullage.
At conclusion of this stabilization period, ullage pressure
must be reduced by 0.5 psi for remainder of test.
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Temperature
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Ullage
must be monitored for rate of temperature change, which
must not exceed manufacturer's tabulated values.
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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, net pressure must
exceed 1 psi in the 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 tank. Product-filled
portion of tank must be tested using a volumetric underfill
test method.
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