Issue
Date: November 22, 1995
Revision Date: January 12, 2015
Triangle
Environmental, Inc.
TEI
Ullage Test, Version 1.0 (Vacuum Test)
NON-VOLUMETRIC
TANK TIGHTNESS TEST METHOD (ULLAGE)
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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
|
A
tank system should not be declared tight when an increase
in the acoustic noise level (above background) of the
tank under vacuum is detected due to air or water ingress.
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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 15,000 gallons.
Microphone should be located within 24 feet of all points
within the ullage.
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Waiting
Time
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None
if test is conducted after the underfilled tank test.
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Test
Period
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Minimum
of 1 minute.
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.
If vacuum cannot be maintained, see manufacturer's instructions.
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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 the groundwater in tank excavation backfill must be
determined.
If groundwater is above product level, vacuum must be
adequate to detect an ingress of groundwater.
|
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Calibration
|
Sensors
must be calibrated before each test in accordance with
manufacturer's instructions.
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Comments
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Manifolded
tank systems must be isolated prior to test. Evaluated
using unleaded gasoline.
Tests only ullage portion of tank.
Product-filled portion of tank must be tested using an
underfill test method.
Microphone was 24 feet away from the leak source during
evaluation.
Headphones are used during test to listen for the signal
of air ingress.
Noise signals are tape recorded (not digitally recorded).
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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