Issue
Date: November 22, 1995
Revision Date: November 6, 1997
Leak
Detection Systems, Inc.
Tank
Auditor, Version RTD V.2.16
VOLUMETRIC
TANK TIGHTNESS TEST METHOD (OVERFILL)
Certification
|
Leak
rate of 0.1 gph with PD = 99.98% and PFA = 0.02%.
|
Leak
Threshold
|
0.05
gph.
A tank system should not be declared tight if the test
result indicates a loss or gain that equals or exceeds
this threshold, except as noted below.
If using two level testing, the level is changed by 3
feet between the two tests and a tank system should not
be declared tight if the net change between the two tests
is greater than 0.02 gph.
|
Applicability
|
Gasoline,
diesel, aviation fuel, fuel oil #4.
Other liquids with known coefficients of expansion and
density may be tested after consultation with the manufacturer.
|
Tank
Capacity
|
Maximum
of 15,000 gallons.
Tank must be minimum 100% full.
|
Waiting
Time
|
Minimum
is variable depending on site conditions, but not be less
than 6 hours between delivery and testing.
Minimum of 1 hour between "topping off" and
testing.
There must be no dispensing or delivery during waiting
time.
|
Test
Period
|
Minimum
of 1 hour.
Test data are acquired and recorded by system's computer.
Leak rate is calculated from data determined to be valid
by statistical analysis.
There must be no dispensing or delivery during test.
|
Temperature
|
Average
for product is determined by a temperature averaging probe.
|
Groundwater
|
If
depth to groundwater cannot be determined, two tests must
be performed with a level change of at least 3 feet between
tests.
If depth to groundwater in tank excavation backfill can
be determined and it is above bottom of the tank, product
level must be adjusted to provide height differential
of 3 feet between product and groundwater in tank excavation
backfill during test.
|
Calibration
|
Temperature
averaging probe and level sensors must be calibrated in
accordance with manufacturer's instructions before each
test.
|
Comments
|
Not
evaluated using manifolded tank systems.
Evaluation of system did not include a field evaluation
of groundwater compensation by two level testing.
|