Helium maser method for leak detection by helium mass spectrometry
Helium mask method in helium mass spectrometry leak detection, also known as helium mask integration method, is the second helium mass spectrometer leak detection method to be introduced by vacuum pump manufacturers.
The helium cover method is to cover the part or whole part of the inspected part by using the leak detection cover. The material of helium leak detection cover can be made of plastic film. For a large number of small parts to be tested, a special leak detection cover with good rigidity can also be made, which can make the helium pressure higher than the atmospheric pressure, so as to improve the leak detection sensitivity. In leak detection, the air in the cover is removed first, and then helium or the mixture of helium and other gases is filled. Then, the leakage rate and the existence of the leakage hole are characterized by the output signal of the leak detector.
As shown in the figure above, both the local and the whole helium leak detection cover can be seen as a nozzle with a large diameter, which surrounds some or the whole inspected parts. Therefore, what the leak detector indicates is the sum of the leakage rate of all the leaks surrounded by the helium leak detection cover. Because the result presented is a total leakage rate, it is impossible to determine the exact location of the leakage hole by helium mask method. Therefore, if we want to determine the exact location of the leak, we need to cooperate with the injection method for further leak detection.
In addition, if the volume of helium leak detection cover is large, it is necessary to recover helium in the cover, or solve the ventilation problem of leak detection site, so as to reduce the partial pressure of helium in the air.