Issue Date: August 23, 1999
Revision Date: May 28, 2008
Mass Technology Corp.
Precision Mass Measurement Systems SIM-1000 and CBU-1000 (24 hour test)
Bulk Underground Storage Tank Leak Detection (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%. 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. Calculated minimum detectable leak rate is 0.078 gph with PD = 95% and PFA = 5%. Leak rate may not be scaled below 0.1 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, diesel, aviation fuel, fuel oil #4. Other liquids may be tested after consultation with the manufacturer. |
| Tank Capacity | Use limited to single field-constructed vertical tanks. Maximum product surface area (PSA) is 3,143 ft² (approximately 63 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 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. |
- Mass Technology Corp.
P. O. Box 1578
Kilgore, TX 75663
Tel: (903) 986-3564
Email: info@mtctesting.com
URL: www.mtctesting.com - Evaluator: Ken Wilcox Associates
Tel: (816) 443-2494
Date of Evaluation: 03/25/98
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