Inventory reconciliation for above ground storage tanks

Apparatus for reconciling the volume of liquid dispensed from a liquid storage reservoir with the amount of liquid contained in the storage reservoir comprising:

• an inert gas source;
• a conduit connected to said gas source and having an opening near the bottom of the liquid storage reservoir;
• a pressure transducer positioned in said conduit to measure pressure to generate data proportional to the measured pressure;
• a volumetric flow meter positioned at an outlet from the reservoir to generate data proportional to the volume of liquid dispensed therethrough;
• means for regulating the flow of the inert gas in said conduit at a level sufficient to overcome the pressure resulting from the volume of liquid in the reservoir at the opening of said conduit;
• a computer having a program stored therein for:
• storing a table correlating the volume of liquid in the reservoir to the pressure at the bottom of the reservoir resulting from the storage of liquid therein,
• calculating the volume of liquid dispensed from the reservoir using the data from said flow meter,
• calculating the change in volume resulting from the liquid dispensed from the reservoir using the data from the pressure transducer and the volume correlation table, and
• comparing the calculated liquid volume with the calculated change in volume to measure any error in the calculated liquid volume.

Apparatus for detecting a leak in a liquid storage tank comprising:

• a source of inert gas;
• a flow regulator connected to said gas source;
• a first conduit for routing the gas from said gas source to the bottom of the liquid stored in the liquid storage tank, said first conduit terminating in an opening cut into the side wall of said first conduit at angles of approximately 30 and 60 degrees relative to the side wall of said first conduit at the highest and lowest points of the cut, respectively, wherein the gas exits from said first conduit into the liquid at the highest point of the cut;
• a second conduit opening into the liquid storage tank above the liquid;
• a pressure transducer connected between said first and second conduits;
• and
• means for storing data output by said pressure transducer for continually monitoring the pressure in the liquid storage tank, thereby signalling any change in the pressure which could be the result of a leak of the liquid from the liquid storage tank.