Aboveground liquid storage tank leakage detection
AssigneeASTTest Services, Inc.
InventorDonald E. Boren
Life of this patent
Estimating the term…
Abstract
An aboveground storage tank is provided with a mass balance system for quantitative detection of leakage of liquid from a tank. Arrays of temperature sensors measure the exterior wall temperature of the tank and temperature sensors in an open-ended standpipe within the tank measure the temperature of stored liquid. The temperature measurements and measurements of liquid level change in a chamber mounted at the upper end of the standpipe are polled at intervals to detect changes of the mass of liquid within the tank.
Claims14
A method for quantitative detection of leakage from an aboveground storage tank, defined by a surrounding tank shell, a tank top and a tank bottom and containing liquid whose level is below said tank top, comprising vertically positioning in the tank a standpipe with an open bottom end thereof on said tank bottom permitting said liquid to enter the standpipe, said standpipe extending upward to an open top end thereof above said liquid level, said standpipe further having a liquid level measuring chamber portion within the length of the standpipe and having a length portion above and a length portion below the level of said liquid within the tank;
- positioning a first array of vertically spaced temperature sensors within and along said standpipe including said chamber portion for measuring temperatures of liquid within the standpipe and the liquid level measuring chamber portion;
- and positioning a second array of vertically spaced temperature sensors against the outside of said shell of the tank for measuring temperatures along the tank shell;
- and including the steps of:
- polling the sensors of said first and second arrays to obtain average temperatures of the liquid within the standpipe including said chamber portion and of the tank shell at a time n;
- measuring any change in the level of liquid within the liquid level chamber portion during a time interval between the time n and a time n+1;
- polling the sensors of said first and second arrays to obtain average temperatures of the liquid within the standpipe including said chamber portion and of the tank shell at the time n+1;
- comparing the average temperatures at the times n and n+1 to obtain temperature difference measurements for the liquid within the standpipe including said chamber portion representing the change in the average temperature of the liquid in the tank and a change in the average temperature of the tank shell related to a change in the cross sectional area of the tank;
- and using the temperature difference measurements and the liquid level change measurements to determine an amount of leakage from the tank during said time interval.
The method of claim I and including measuring the temperature within the liquid level measuring chamber above the liquid level.
A system for detecting liquid leakage from an aboveground storage tank defined by a tank bottom, a tank top and a cylindrical tank shell wall for containing said liquid to a level below said tank top, comprising a vertical standpipe having a lower portion mounted on and open at its bottom end to receive said liquid at the tank bottom and extending upward from the tank bottom to a liquid level chamber portion of the standpipe which extends vertically across an anticipated surface level of said liquid within the tank, an upper portion of said standpipe extending vertically upward from communication with said liquid level chamber portion through said top of the tank, and a liquid level change detector in the liquid level chamber portion for detecting any change in the surface level of liquid therein, an array of vertically spaced temperature sensors mounted within and along the standpipe from substantially the bottom of said lower portion at least to and including said liquid level chamber portion for measuring temperatures of liquid within the standpipe, a second array of vertically spaced temperature sensors mounted on the outside of the tank shell for measuring temperatures thereon, means for polling the sensors of said first and second arrays to obtain average temperature measurements, and means for periodically combining the average temperature measurements with information obtained by the liquid level change detector to determine any change of mass of liquid in the tank within any time period between said combining of measurements.
Dependencies are inferred from the claim text.