New Technique Could Fill Need for Leak Test Technology in Many Different Applications

National Center for Manufacturing Sciences
Ann Arbor, Michigan

Working with the National Center for Manufacturing Sciences (Ann Arbor, Michigan) Argonne National Laboratory has developed a new leak detection technology – known as the speed of sound or "SOS" detector – that employs an ultrasonic pulse train to measure the concentration of trace gas, such as helium, hydrogen, or SF6. The system measures the speed of sound and attenuation in. the leaking gas-air mixture, from which the concentration and type of the trace gas are determined. Here, co-inventor Hual-Te Chien prepares to test the prototype device in the Acoustic and Ultrasonic Laboratory in Argonne's Sensors, Instrumentation and Nondestructive Evaluation Section, which is part of Argonne's Energy Technology Division. Argonne National Laboratory photo.

The prototype device has been tested on Navy jet planes with good results. The Navy plans additional testing of the SOS technology and anticipates that it will eventually be adopted as a standard means of checking the planes for fuel leaks. Further development of the sensor for additional applications is underway.

Leak Detection in Navy Jets

The F-14 Tomcat thunders off the aircraft carrier's deck into the morning sky, its wings automatically sweeping back to a 60-degree angle as the two afterburning turbofan engines each kick out 27,000 pounds of thrust, propelling the fighter at more than twice the speed of sound. Inside the wings and fuselage, five internal fuel tanks must securely hold up to 9,000 liters of highly volatile jet fuel under extremes of temperature, vibration, high G forces and other adverse conditions. If a sufficiently large leak in the fuel system should occur near a heat source, there could be disastrous consequences.

Helping prevent such accidents is why the F-14's fuel system is one of the very first things technicians check when the Tomcat pulls in for scheduled maintenance. Any leak in the fuel system can be critical, even one that isn't visible to the human eye. Finding the smaller leaks can be extremely difficult. Current maintenance practice involves a low-tech approach to finding larger leaks – having technicians run their bare hands along the accessible areas of the fuel line. However, this hands-on approach can miss small leaks completely, or when small leaks are felt by technicians, the precise location may not be readily apparent if the leak is covered by a flange or coupling.

The Navy could soo. have a faster and more accurate way to detect and locate even very small leaks in the F-14 fuel system without interfering with other maintenance procedures.

According to Don Waller, F-14 maintenance supervisor at the Naval Aviation Depot in Jacksonville, Florida, "using the Argonne SOS detector we were able to locate a small fuel leak in an F-14 engine bay area that we would not have found without an extended pressure decay test or after disassembling the plane. The result was a significant savings in time and manpower." Waller adds that the Navy plans additional testing of the SOS technology and anticipates that it will eventually be adopted as a standard means of checking the planes for fuel leaks.

the ability of the sos detector to identify even very small leaks and locate their precise position can be a valuable tool in helping speed up f-14 maintenance. "we have been very satisfied with the performance of the SOS leak detector," says Waller, "the system is rugged and demonstrates excellent repeatability in our tests..

Researchers at Argonne are investigating other applications for the SOS ultrasonic sensor technology, including testing helicopter blades for stress cracks (the blades are hollow and can be filled with gas). The detector can also be used to detect heavier gases, such as freon during inspections of cooling and air conditioning systems. .

The Argonne sensor development team development consists of the co-inventors, Shuh-Haw Sheen, who served as project leader, Hual-Te Chien, and Paul Raptis (Manager of the Sensors, Instrumentation and Nondestructive Evaluation Section) and William Lawrence. The prototype instrument was created in the Electronic Engineering Section of Argonne's Electronics and Computing Technologies Division by Istvan Naday (Section Manager), Alan McArthur, James Minich, and Richard Voogd.

Funding for the research was provided by the National Center for Manufacturing Sciences (NCMS) in Ann Arbor, Michigan and its member companies, Ford Motor Company and DaimlerChrysler Corporation, under an award from the Department of Defense and the Defense Logistics Agency. .

Argonne's Sensor Research

Argonne's Acoustic and Ultrasonic Laboratory is in the forefront of acoustic and ultrasonic technology, developing innovative sensors and instrumentation and solving difficult applications problems. The laboratory also develops NDE techniques for material characterization and monitoring. The Laboratory's scientists and engineers are continuously searching for practical solutions to on-line, real-time process monitoring and control problems. An Ultrasonic Viscometer developed by the ultrasonics group won an R&D100 Award in 1994. More about Argonne's Sensors, Instrumentation, and Nondestructive Evaluation R&D

Based on material prepared by Paul Boisvert of Argonne's Technical Services Division.

For More Information

• For more information on Argonne's sensor research and development, visit the sensor technology web site or contact Argonne's Office of Technology Transfer at 800-627-2596 (partners@anl.gov).