Research On Ultrasonic Leak Detection Methods Of Fuel Tank

Fuel tank quality was closely related to major social issues such as personal security, public environment and resource conservation. At present ultrasonic leak detection based on water immersion pulse echo method was commonly used to detect leakages of fuel tanks. The method worked as followed, fuel tank being tested was placed in a tailor-made sink, then it was inflated with continuous air supply and maintaining a constant pressure. Simultaneously ultrasonic waves were emitted by probes above the testing fuel tank in water, then leakage could be judged by observing the ultrasonic echo reflected by leaking air bubbles. The reflected echoes could also confirm the location and extent of the leakage.This paper introduced the research significances and the present developments of ultrasonic leak detection for fuel tank in China and abroad. According to the studies on traditional ultrasonic leak detection method and the characteristics of ultrasonic reflection field of probes, we proposed multi-channel parallel scanning detection method for rapid and accurate test of fuel tank on line. At first the paper studied the characteristics of ultrasonic sound field of probes, made theoretical analysis of small ball reflection sound field for a single probe, obtained the characteristics of near-field and far-field, and calculated divergence angle of the effective sound field. Then research on interfered sound fields of adjacent probes was done, the sound pressure changing curve at the same path was calculated, and the practical sound fields were measured. Then we analyzed the factors influencing the bubble detection rate in ultrasonic leak detection for fuel tank, and proposed a new 8-channel parallel scanning detection mode, maximizing the repetition frequency of each probe and improving the detection rates. Then multi-channel parallel ultrasonic detection equipment was built based on ultrasonic probe array, detection sink and ultrasonic DAQ card. And the ultrasonic detection software was programmed for acquiring and processing the ultrasonic wave signals. Finally comparative experiment tests were conducted between our 8-channel parallel ultrasonic leak detector and the traditional one for defects of different size. The results showed that, compared to single-channel scanning mode, the multi-channel parallel testing method had much higher detection rates when the single air bubble or long time interval bubbles need to be detected. So this method was more effective to detect smaller tank leakage (μm diameter).Above all, multi-channel ultrasonic leak detection method could greatly improve working efficiency and more effectively to detect out smaller leakage. And it would also play an increasingly important key role in ultrasonic leak detection for fuel tank. At the same time it had certain reference values on characteristics research of probes’ multi-channel parallel detecting sound fields.