Method and apparatus for detecting leaks in the ullage of a liquid storage tank

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. Flow rate, temperature and pressure can be reached manually or fed to a suitable computer or chart recorders for permanent records and/or automated testing.

Dependencies are inferred from the claim text.