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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.


The HT-100 offers many desirable qualities in a single easy-to-use system.

Short Test

An HT-100 test can be completed in 1 hour. The minimum leak rate detectable in this 1-hour test is 0.0021% of the line volume per hour.

Fully Automated

The HT-100 is a fully automated system that is easily installed and operated. Once a test is initiated, a programmable logic controller governs the system operations. On-the-Spot Results. A report is automatically generated upon completion of the test.

Owner/Operator Control

The HT-100 test can be run, and its results easily interpreted, by the owner or operator of the pipeline. Tests can be conducted with any desired frequency.

Mobile Option

The HT-100 can be permanently installed and used for on-line monitoring and testing, or it can be mounted in a van and used for tightness testing. The HT- 100 system attaches to the line at a single point.

Certified Performance

The performance of the HT-100, in terms of the smallest leak that can be detected with a probability of detection (PD) of 95% and a probability of false alarm (PFA) of 5%, is 0.0021% of line capacity. If the line contains 9500 gallons, the minimum detectable leak at these probabilities is 0.2 gallons per hour. This performance is certified by an independent third party, Ken Wilcox Associates, Inc., which based its evaluation on six months of test results obtained on an operational airport hydrant pipeline containing 300,000 gallons of jet fuel and operating at a pressure of 175 psi. (The evaluation performed by KWA followed all test and reporting procedures required by ASTM and EPA.) The HT-100 has been approved for use in Florida by the Florida Department of Environmental Protection as an alternative to API standard RP 1110 (hydrostatic testing). The HT- 100 evaluation is also listed with the National Work Group on Leak Detection Evaluations as being in compliance with EPA protocols.


The HT-100 sensor unit is attached to the line at a single location, by means of a valve. Any convenient location along the line will do. The most common point of attachment for the HT-100 is at the fuel farm. The fuel remains in the line during a test, but all transfer operations must be suspended. The line must be completely isolated, by means of valves, from any storage tanks connected to it and from other sections of line not being tested. If the valves used to isolate the line do not seal properly, either a double block and bleed valve or valve blinds must be installed.

Mobile HT-100

The mobile version of the HT-100, Vista's best-selling leak detection system for underground bulk pipelines and airport hydrant fueling systems, delivers the same performance as the standard HT-100 while offering greater flexibility. It is a popular choice at facilities that want to make maximum use of their equipment across a widespread network of lines.

Like the standard, permanent installation, the mobile HT-100 combines high performance with ease of use. The mobile HT-100 is mounted in the back of a small truck or trailer. Tucked next to the HT-100, at either the front or back of the truck/trailer, is a compact but fully functional office that houses a computer, a printer, and other electronics. The operator starts the test from here, using the HT-100 software. Results are automatically archived on the computer's hard drive.

The mobile HT-100 can be transported to distant lines for periodic testing. In some cases it is used by different facilities, which apportion costs commensurate with usage. Vista's testing services are conducted with a mobile HT-100 housed in a trailer.