David J Peck

US Patent:

52953912, Mar 22, 1994

Filed:

Feb 11, 1992

Appl. No.:

7/833681

Inventors:

John R. Mastandrea - Redondo Beach CA
Stewart H. Wells - North Hills CA
David B. Peck - Torrance CA
Steven T. Jersey - Redondo Beach CA

Assignee:

NDE Environmental Corporation - Torrance CA

International Classification:

G01M 332

US Classification:

73 492

Abstract:

Apparatus and method for detecting leaks within underground or aboveground tanks and their associated piping whether the tank and/or piping is partially filled or empty. The apparatus is partially insulated to minimize temperature effects when injecting a test gas into the tank to be tested. The tank is pressurized to a fill pressure by injecting (bubbling) the test gas through any liquid in the tank. Once stabilized the pressure is reduced to a test pressure while the gas injection continues. The flow rate of gas into the tank is monitored by a flow meter able to measure small flows while the pressure is held constant by a pressure regulator having a high accuracy and the temperature of the ullage is monitored. A tight or leaking tank is determined by evaluating the flow rate of constant pressure against reference criteria which when met identify a tight tank and when not met identify a leaking tank under EPA guidelines. Temperature, deflection, and other effects on leak rate detection are compensated for by prescribing waiting periods, filling times, and multiple and repeat threshold exceedance criteria.