245.jpeg)
Helium Leak Testing
- Evacuate both the part and chamber
- Back fill the test volume with certified clean dry nitrogen
- Re-evacuate
- Fill the part with the test gas
Helium leak testing is used to find small leaks or larger leaks in bigger volumes. The helium is used as a tracer gas and its concentration is measured. This guide to helium leak testing should outline the basics of using this leak testing method.
Helium is one of the smallest gas molecules and is inert. Being inert, helium is relatively safe to use (rather than hydrogen) and will not react with any of the materials within the part to be tested. In most helium leak testing applications, a mass spectrometer is used to detect helium. Although, it is also possible to use a residual gas analyser. Helium leak testing can generally be between one thousand and one million times more sensitive than using pressure decay techniques.
Helium can and will get everywhere if it can. It gets quite difficult sometimes to determine where the helium is coming from. There is approximately 5 ppm Helium in the atmosphere. If the part under test is filled with helium it is important that the test charge is removed properly and not just released into the immediate area. For just a few tests, the helium can be diluted in the immediate area. For more frequent testing, this may mean piping the extracted test gas away to the outside of the building on the downwind side and well clear from doors or windows that could allow it back in.