Issue
Date: November 22, 1995
Revision Date: November 14, 1997
Triangle
Environmental, Inc.
TEI
System 4000, Version 1.0
VOLUMETRIC
TANK TIGHTNESS TEST METHOD (UNDERFILL)
|
Certification
|
Leak
rate of 0.1 gph with PD = 99% and PFA = 4.8%.
|
|
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.
|
|
Applicability
|
Gasoline,
diesel, 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 between 50 and 100% full.
|
|
Waiting
Time
|
Minimum
of 6 hours between delivery and testing.
There must be no dispensing or delivery during waiting
time.
|
|
Test
Period
|
Minimum
is determined by system's computer.
Average was 4 hours during the evaluation.
Leak rate is calculated from last 2 hours of test period
data.
Test data are acquired and recorded by system's computer.
There must be no dispensing or delivery during test.
|
|
Temperature
|
Average
for product is determined by a minimum of 3 thermistors.
|
|
Groundwater
|
Depth
to groundwater in tank excavation backfill must be determined.
If groundwater is above bottom of tank, product level
must be adjusted to provide a minimum net pressure of
1 psi at bottom of tank during test.
|
|
Calibration
|
Thermistors
must be calibrated before each test in accordance with
manufacturer's instructions.
|
|
Comments
|
Not
evaluated using manifolded tank systems.
Tests only portion of tank containing product. As product
level is lowered, leak rate in a leaking tank decreases
(due to lower head pressure).
Consistent testing at low levels could allow a leak to
remain undetected.
EPA leak detection regulations require testing of the
portion of the tank system which routinely contains product.
May also be used as an overfill test method.
|
