ULTRASONIC AIR LEAKAGE TESTING
The Method, Applications & Avantages
Ultrasounds are high frequencies beyond 20 kHz. They are inaudible to the human ear, extremely directional. They are subjected to a diminution of exponential amplitude in the estrangement of the spring.
The escaping fluid (gaseous or liquid) pass from the circuit internal pressure (generally 7 bars for the compressed air) to the atmospheric pressure. This sudden variation of pressure creates turbulence, source of important ultrasound energy. The detector gets and converts this energy in audible signal by heterodyning.
- air leakage reduction,
- detection of nitrogen leakage on inertia networks,
- leak detection on welding and cutting gas networks,
- vacuum leakage tracking on primary networks,
- leak detection on heat exchangers,
- leak dectection on hydrogen circuit of powerplant overhead stands and alternators.
Advantage of ultrasonic detection is to be made on working machines in a workshop. The operator works with a helmet on the head which frees him from the ambient noise. The ultrasounds detector allows to localize exactly the leak (in spite of a high background noise) and to examine the piping or distant equipments for which detection by hearing is impossible. The ultrasonic method allows detecting practically all the leaks on a system, even those whom we do not hear during a production outage. This very sensitive detector allows to track down leaks so weak as 0,1 cfm which are generally not worth being sealed.
She allows doing a finest detection than with hearing method.
Leaks in Pressure
The method begins by tracking the most important leaks and goes on smaller and smaller.
The operator begins by scanning the area to be checked. In this way, he locates the most important leaks and the possible sources of parasites.
Leaks in Depression
The method in depression remains identical to the method in pressure. However, two parameters differ:
- The turbulence of a leak is generated inside the piping.
- Generally, the difference of pressure is lower.
Consequently, the signal got by the detector will be less powerful.
On the other hand, the control of an insulated installation is more delicate.
When a leak is suspected, a punctual dismantling of the insulation could be necessary to confirm the first diagnosis.