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Issue Date: August 23, 1999
Revision Date: May 28, 2008
Mass
Technology Corp.
Precision Mass
Measurement Systems SIM-1000 and CBU-1000 (48 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 0.294 gph with PD = 95% and PFA = 5%.
For other tank sizes, leak rate equals [(PSA in ft² ÷ 6,082 ft²) x
0.294 gph].
Example:
For a tank with PSA = 4,000 ft²; leak rate = [(4,000 ft² ÷ 6,082 ft²)
x 0.294 gph] = 0.19 gph.
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 0.147 gph.
For other
tank sizes, leak threshold equals [(PSA in ft² ÷ 6,082 ft²) x 0.147
gph].
Example:
For a tank with PSA = 4,000 ft²; leak threshold = [(4,000 ft² ÷ 6,082
ft²) x 0.147 gph] = 0.1gph.
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.
Maximum product surface area (PSA) is 6,082 ft² (approximately 88 ft
diameter).
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 48
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 600,000 gallon, vertical underground tank with
product surface area (PSA) of 6,082 ft². |
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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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Date of Evaluation:
03/25/98
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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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