A radiator drips on a valuable carpet, an injection pump sprays fuel on a hot engine, contents escape from gas cylinders or pipes. When a leak remains undetected until the equipment is installed and in service, the results can be expensive. The quality of parts operating under pressure must therefore be carefully tested before they leave the factory. Two Fraunhofer Institutes have developed a new ultrasonic gasbubble detector which will make it possible to perform automatic leak testing during production. Instead of spot checks, manufacturers can now carry out 100percent tests at an acceptable cost.
The same technique which cyclists use to find a leak in an inner tube is also widespread in industrial quality control: the part is pressurized and immersed in a tank of water. Bubbles of gas issue from any leak. But such a visual check takes time, and time is money. The reliability of the method depends entirely on a person who spends up to eight hours a day staring into a water bath looking for bubbles. What is needed is a rapid and reliable test that can be carried out automatically, particularly for massproduced items such as gas fittings or radiators for domestic heating systems.
In the new method, it is not a human eye but an ultrasonic sensor that watches for bubbles. The problem is that ultrasonic waves are scattered by any particles suspended in the water. The new sensor system can distinguish between solid particles and gas bubbles down to 10 microns in diameter. It can also determine the precise position of the leak by calculating the time that elapses before an echo from the ultrasonic wave is received.
This ultrasonic technology was developed by the Fraunhofer-Institut für Biomedizinische Technik IBMT (Fraunhofer Institute for Biomedical Engineering). The Fraunhofer-Technologie-Entwicklungsgruppe TEG (Technology Development Group) in Stuttgart implemented it as automatic test equipment for testing massproduced radiator components. "The system provides reliable detection of gas bubbles in under a second. Up to 720 parts can be tested per hour", is how Klaus Dietrich of the TEG describes the advantages of the robust, maintenancefree system, which is incorporated in the production line. Now the Fraunhofer developers hope that other fields of industry will recognize the advantages of this test method, because minor leaks with major consequences are all too common.
See also the Technical leaflet
For further information, please contact:
Klaus Dietrich
Tel. +49 7 11/9 70 36 20
Fax +49 7 11/9 70 39 98
Fraunhofer-Technolgie-Entwicklungsgruppe TEG
Nobelstraße 12
D-70569 Stuttgart
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