|
Certification |
Leak rate
of 0.1 gph with PD = 100% and PFA = 0%. |
|
Leak Threshold |
A tank
system should not be declared tight if the ratio of the ultrasonic signal
(when the tank is under vacuum) to the background signal (prior to
evacuation) equals or exceeds 1.5 for either 12 kHz or 25 kHz frequencey
band. |
|
Applicability |
Gasoline,
diesel, aviation fuel, fuel oil #4, waste oil. |
|
Tank Capacity |
Maximum of
30,000 gallons. |
|
Waiting Time |
None
between delivery and testing. |
|
Test Period |
2 minutes reference plus 2
minutes test.
Test data are acquired and
recorded by system's computer.
There must be no dispensing or
delivery during test. |
|
Test Pressure |
Minimum of
-0.5 psi to a maximum of -2 psi. |
|
Temperature |
Acoustic/ultrasonic and background signals are independent of product
temperature. |
|
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, this method cannot be used. |
|
Comments |
Method can also be used on
double wall tanks to test the primary tank where a dry interstice is
present.
Microphone was 25 ft away from
leak source during evaluation.
Although not tested on completely 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.
More than 4 psi pressure differential across the tank wall at any location
in the tank could damage tank. |
