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Issue Date: April 18, 1997
Revision Date: August 23, 1999
Universal
Sensors and Devices, Inc.
LTC-2000
(Differential Pressure Probe)
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 14,244 ft², leak rate is 3.0 gph with PD = 98.8%
and PFA = 1.2%.
For other tank sizes, leak rate equals [(PSA in ft² ÷ 14,244 ft²) x 3.0
gph].
Example:
For a tank with PSA = 20,000 ft²; leak rate = [(20,000 ft² ÷ 14,244
ft²) x 3.0 gph] = 4.2 gph.
Calculated minimum detectable leak rate is 2.15 gph with PD = 95% and PFA
= 5%.
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 14,244 ft², leak threshold is 0.7 gph.
For other tank sizes, leak threshold equals [(PSA in ft² ÷ 14,244 ft²)
x 1.5 gph].
Example:
For a tank with PSA = 20,000 ft², leak threshold = [(20,000 ft² ÷
14,244 ft²) x 1.5 gph] = 2.1 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, fuel oil #4. |
| Tank
Capacity |
Use limited to
single field-constructed vertical tanks larger than 50,000 gallons.
Maximum product surface area (PSA) is 35,610 ft² (approximately 213 ft
diameter).
Performance not sensitive to product level. |
| Waiting
Time |
Minimum of 3
hours, 30 minutes after delivery.
Valve leaks and pump drain-back may mask a leak.
Allow sufficient waiting time to minimize these effects.
None between dispensing and testing. |
| Test
Period |
Minimum of 48
hours, 18 minutes.
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 |
Probe must be
checked 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 2,000,000 gallon, vertical underground tank with
product surface area (PSA) of 14,244 ft². |
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Universal
Sensors and Devices, Inc.
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Evaluator:
Ken Wilcox Associates
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9205 Alabama Ave.
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Tel:
(816) 443-2494
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Chatsworth,
CA
91311
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Date
of Evaluation:
05/17/96
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Tel:
(800) 899-7121, (818) 988-7121
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