Issue Date: November 22, 1995
Revision Date: November 21, 2002
Tanknology - NDE
Computerized VPLT Testing System
Volumetric Tank Tightness Test Method (Underfill)
| Certification | Leak rate of 0.1 gph with PD = 99.9% and PFA = 0.1%. |
|---|---|
| Leak Threshold | 0.05 gph. A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds this threshold. |
| Applicability | Gasoline, diesel, aviation fuel, fuel oil #4, waste oil. Other liquids with known coefficients of expansion and density may be tested after consultation with the manufacturer. |
| Tank Capacity | Maximum of 18,000 gallons. Tank must contain minimum 24 inches of product. |
| Waiting Time | Must be long enough between delivery and testing to ensure a temperature change of less than 0.09 degrees F per hour, typically a minimum of 2 hours. None between dispensing and testing. There must be no delivery during waiting time. |
| Test Period | Minimum of 2 hours. Test data are acquired and recorded by system's computer. Leak rate is calculated from average over data window. There must be no dispensing or delivery during test. |
| Temperature | Average for product is typically determined by 5 thermistors. A minimum of 1 thermistor is required. |
| Groundwater | Depth to groundwater in tank excavation backfill must be determined. If groundwater is above bottom of tank, product level must be adjusted to provide a minimum net pressure of 1 psi at bottom of tank during test. |
| Calibration | Thermistors must be checked annually and, if necessary, calibrated in accordance with manufacturer's instructions. |
| Comments | Not evaluated using manifolded tank systems. 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. EPA leak detection regulations require testing of the portion of the tank system which routinely contains product. |
- Tanknology - NDE
8900 Shoal Creek Blvd., Building 200
Austin, TX 78757
Tel: (800) 800-4633 - Evaluator: Ken Wilcox Associates
Tel: (816) 443-2494
Date of Evaluation: 02/15/93
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