Tank Tightness Testing
How does the UST2000 underfill method work...
The UST2000 system underfill test identifies changes in tank fluid levels by measuring the speed that sound travels through petroleum products. Fiberglass probes are lowered into each tank. The UST2000 System stimulates a transducer at the bottom of each probe that creates ultrasonic sound waves inside the tank and subsequently measures the time required for a sound wave to travel to specific calibration points on the probe and the fluid level itself. The data is recorded and stored on a computer and mathematical formulas provided in the computer program compensate for thermal expansion or contraction of the fluid.
The Ullage (empty or dry portion of a tank) is tested using the UST2000 System. A sonic microphone is lowered into a tank, the tank is sealed, and a reading is taken of the noise level in the tank. Non-toxic, non-flammable nitrogen gas is then pumped into the tank and another reading is taken. A leak in the ullage portion of the tank can be detected by the testing equipment as it "listens" for the sound signature of air escaping through a hole. As an alternative, the UST2000 System can conduct a test without nitrogen by utilizing a one-pound vacuum combined with a computerized sonic signature identification system.
How does the Alert 8200 underfill method work...
The Alert 8200 underfill test uses a load cell to directly measure the net buoyancy force on the patented glass probe which is inserted in the tank under test and is long enough to run vertically through all of the product in the tank. Net buoyancy force is the difference between the weight of the glass probe out of the tank and the weight of the fluid that is displaced by the probe when in the tank.
Data from the load cell is recorded on the powerlogger, eliminating the need to keep a truck with a computer at the site during a test. When the test is concluded, the powerlogger, loadcell and probe are removed from the tank under test. The powerlogger is connected by an adapter cable to the serial port of a personal computer. Using Alert Technologies software, Viewall, the data is removed from the powerlogger. It is analyzed using Viewall to filter out tank activity and calculate mass change in the tank and leak rate.
The Alert 8200 System mass probe is based on Archimede's Principle which states that any object floating in a fluid will displace an amount of fluid equivalent to its own weight. Our probe has a fixed weight when ballasted and out of the tank. When it is installed, it displaced most of its weight in product. As long as there is no leak in or out of the tank the net buoyancy force, the difference between the probe's weight and the displaced product's weight, does not change.
The Ullage (empty or dry portion of a tank) is tested using the Alert 8200 System by comparing an ultrasonic reference signal to an ultrasonic signal generated when the tank system is under pressure or vacuum.