UST Programs - LG 113

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	Evaluator: Ken Wilcox Associates
8900 Shoal Creek Blvd. , Building 200	Tel: (816) 443-2494
Austin , TX 78757	Date of Evaluation: 02/15/93
Tel: (800) 800-4633

Appearance on this list is not to be construed as an endorsement by any regulatory agency nor is it any guarantee of the performance of the method or equipment.
Equipment should be installed and operated in accordance with all applicable laws and regulations.
For full details, please refer to our expanded "DISCLAIMER" page.