Issue
Date: November 22, 1995
Revision Date: April 4, 2007
USTest,
Inc.
(previously
listed as Sound Products Manufacturing, Inc.)
UST
2000/U
(Pressure and Vacuum Test)
NON-VOLUMETRIC
TANK TIGHTNESS TEST METHOD (ULLAGE)
|
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 there is
a substantial increase in the acoustic noise signal (when
the tank is under pressure or vacuum) above the background
signal (prior to pressurization or evacuation) in the
frequency interval of 10 kHz to 20 kHz.
The acoustic signal to noise ratio is preprogrammed into
the system's computer and is not revealed to or adjustable
by the operator.
|
|
Applicability
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Gasoline,
diesel, aviation fuel, fuel oil #4, waste oil.
Other liquids may be tested after consultation with the
manufacturer.
Equipment is not in contact with the product.
|
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Tank
Capacity
|
Maximum
ullage volume is 7,550 gallons for pressure test and 5,250
gallons for vacuum test.
|
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Waiting
Time
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None
if test is conducted after an underfilled tank tightness
test.
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Test
Period
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Minimum
of 15 minutes (includes collection of background information).
There must be no dispensing or delivery during test.
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Test
Pressure
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Net
pressure of 2.0 psi or vacuum of 1.0 psi must be maintained
in ullage.
|
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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 must
not be used.
Pressure test must be conducted using net pressure exceeding
2.0 psi in the ullage.
|
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Calibration
|
Test
equipment must be checked and, if necessary, calibrated
by tester before each test.
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Comments
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Not
evaluated using manifolded tank systems.
Evaluated using unleaded gasoline as test product.
Tests only ullage portion of tank.
Product-filled portion of the tank must be tested using
an underfill test method.
Microphone was less than 8 feet, 6 inches from the leak
source during evaluation.
If the background noise is too high, test is inconclusive.
Maximum background noise is preprogrammed into system's
computer and not revealed to or adjustable by the technician.
Vibration due to nearby equipment or dripping condensation
may interfere with test.
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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