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Issue Date: August 23, 1999
Revision Date: December 29, 2011
Mass
Technology Corp.
Precision Mass
Measurement Systems SIM-1000 and CBU-1000 (24 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 1,257
ft² or less, leak rate is 0.1 gph with PD = 97.9% and PFA = 2.1%.
Calculated minimum detectable leak rate is 0.078
gph with PD = 95% and PFA = 5%.
For tanks with larger PSA, leak rate equals [(PSA in
ft² ÷ 1,257 ft²) x 0.1 gph].
Example:
For a tank with
PSA = 2,000 ft²; leak rate = [(2,000 ft² ÷ 1,257 ft²) x 0.1 gph] = 0.16 gph. |
| Leak
Threshold |
Leak threshold is
proportional to product surface area (PSA).
For tanks with PSA of 1,257
ft² or less, leak threshold is 0.05 gph.
For tanks with larger PSA, leak
threshold equals [(PSA in ft² ÷ 1,257 ft²) x 0.05 gph].
Example:
For a tank with PSA = 2,000 ft²; leak threshold = [(2,000 ft² ÷ 1,257
ft²) x 0.05 gph] = 0.08 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, ethanol
blends up through E100, diesel,
aviation fuel, fuel oil #4.
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| Tank
Capacity |
Use limited to
single field-constructed vertical tanks.
Performance not sensitive to product level. |
| Waiting
Time |
Minimum of 1
hour, 6 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 62 minutes to 31 hours. |
| Test
Period |
Minimum of 24
hours.
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 |
Differential
pressure sensor must be checked regularly 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 120,000 gallon, vertical underground tank with
product surface area (PSA) of 1,257 ft².
Averaging of
multiple tests may be used to improve the performance of the system. |
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Mass Technology Corp.
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Evaluator:
Ken Wilcox Associates
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P. O. Box 1578
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Tel: (816) 443-2494
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Kilgore, TX
75663
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Dates of Evaluation:
03/25/98, 02/04/11
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Tel: (903) 986-3564
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E-mail:
info@mtctesting.com |
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URL: www.mtctesting.com |
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