HT-100
Leak detection in large pipeline systems & airport hydrant fuel systems
The award-winning Vista HT-100 leak detection system for underground bulk pipelines and airport hydrant fueling systems combines high performance with ease of use. The HT-100 is the only U.S.-made system that can compensate for thermally induced changes in fuel volume—the most common cause of error in testing for leaks.
The Vista HT-100 is a dual pressure volumetric leak detection system for testing underground bulk and hydrant fuel piping (it is certified for use on lines with a capacity of 3400 gallons or more). Its high performance is due to a novel method of compensating for the thermally induced changes in fuel volume that occur during a test. In 1999, Aviation Week & Space Technology selected the HT-100 for one of its Annual Technology Innovation Awards.
The HT-100 is a computer- controlled, fully automatic system. All data are acquired and processed electronically. As shown in the schematic diagram at right, the HT-100 sensor unit consists of (1) a measurement cylinder (Tank 1); (2) a storage cylinder (Tank 2); (3) a differential pressure sensor to measure level changes in the measurement cylinder electronically; (4) a pump for transferring fuel from the measurement cylinder or storage cylinder to the line in order to increase line pressure to a specified level; and (5) two pressure relief valves and a bypass valve for removing fuel from the line and adding it to the measurement cylinder or storage cylinder in order to decrease the pressure in the line to a specified level. When combined, the pump and the pressure relief valves can be used to maintain a constant pressure in the line at a specified level. The size of the cylinders is determined by the capacity of the largest pipeline segment that will be tested at a given site.
The storage cylinder is normally used to set or change the overall pressure in the line. (Pressure can also be set or changed with the pressure management system used to operate the line or by adding or removing fuel from a nearby tank, tanker truck, or pipeline.) The measurement cylinder is normally used to maintain constant pressure during a test and to make the volume measurements required during the test. A test can be conducted with the measurement cylinder alone if there is no need for the extra storage capacity that Tank 2 provides. The pump and pressure-relief-valve system are used to adjust and maintain a constant pressure in the line. As shown by the valves on the "ladder," the system can be operated at three pressures: a high pressure, a low pressure, and atmospheric pressure (by means of the bypass valve). The high- and low-pressure relief valves can be set to operate at any desired pressure. Finally, a pressure relief valve and an overfill alarm in each cylinder ensure safe operation of the system.
