|
Issue Date: August 23, 1999
Revision Date: December 21, 2005
Varec,
Inc.
(originally listed as
Coggins Systems, Inc. and later as Endress + Hauser Systems
and Gauging)
Fuels
Manager with Barton Series 3500 ATG (48 hour test) (72 hour
test)
BULK
UNDERGROUND STORAGE TANK LEAK DETECTION METHOD (50,000 gallons
or greater)
|
Certification
|
Leak
rate is proportional to product surface area (PSA).
For tanks with PSA of 6,082 ft², leak rate is 2.0 gph
with PD = 97.8% and PFA = 2.2% for 48 hour test and PD
= 98.5% and PFA = 1.5% for 72 hour test.
For other tank sizes, leak rate equals [(PSA in ft² ÷
6,082 ft²) x 2.0 gph].
Example:
For a tank with PSA = 10,000 ft²; leak rate = [(10,000
ft² ÷ 6,082 ft²) x 2.0 gph] = 3.29 gph.
Calculated minimum detectable leak rate is 1.59 gph with
PD = 95% and PFA = 5% for 48 hour test and 1.44 gph with
PD = 95% and PFA = 5% for 72 hour test. Leak rate may
not be scaled below 0.2 gph.
|
|
Leak
Threshold
|
Leak
threshold is proportional to product surface area (PSA).
For tanks with PSA of 6,082 ft², leak threshold is 1.0
gph. For other tank sizes, leak threshold equals [(PSA
in ft² ÷ 6,082 ft²) x 1.0 gph].
Example:
For a tank with PSA = 10,000 ft²; leak threshold = [(10,000
ft² ÷ 6,082 ft²) x 1.0 gph] = 1.64 gph.
A tank system should not be declared tight if the test
result indicates a loss or gain that equals or exceeds
the calculated leak threshold.
|
|
Applicability
|
Gasoline,
diesel, aviation fuel.
Other liquids may be tested after consultation with the
manufacturer.
|
|
Tank
Capacity
|
Use
limited to single field-constructed vertical tanks 50,000
gallons or greater.
Maximum product surface area (PSA) is 15,205 ft². Performance
not sensitive to product level.
|
|
Waiting
Time
|
Minimum
of 12 hours, 20 minutes after delivery or dispensing.
Valve leaks and pump drain-back may mask a leak.
Allow sufficient waiting time to minimize these effects.
Waiting times during evaluation ranged from 7.3 to 17.2
hours.
|
|
Test
Period
|
Minimum
of 48 hours (48 hour test). Minimum of 72 hours (72 hour
test).
There must be no dispensing or delivery during test.
|
|
Temperature
|
Measurement
not required by this system.
|
|
Water
Sensor
|
None.
Water leaks are measured as increase in mass inside tank.
|
|
Calibration
|
The
differential pressure sensor must be checked regularly
and, if necessary, calibrated in accordance with manufacturer's
instructions.
|
|
Comments
|
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.
Evaluated in a nominal 600,000 gallon, vertical underground
tank with product surface area (PSA) of 6,082 ft².
|
|
Varec, Inc.
|
Evaluator: Ken Wilcox Associates
|
|
5834
Peachtree Corners East
|
Tel: (816) 443-2494
|
|
Norcross,
GA 30092
|
Date
of Evaluation: 05/20/98
|
|
Tel: (770) 447-9202
|
|
|
