A helium leak detector is the best way to detect small leaks. The leak diameter for 1×10 -12 is 1A. This is the diameter of a Helium molecule. It is the smallest leak rate that can be detected.
Although there are many ways to leak-test components and vacuum vessels using helium in different ways, all of them use the same principle. The unit being tested is either helium pressurised from the inside or helium pressured from outside.
Any gas that could leak is collected and 'pumped into' a mass-spectrometer to analyse. Anything above the background level indicates a leak. Learn more about leak detectors by browsing this website.
- There are many reasons that helium is used in leak detection, other than its diameter.
- It is only 5 ppm in the air so background levels are low
- Its low mass makes it very mobile (i.e. It mixes well with other gases very quickly
- It is inert/non reactive, non-flammable, and completely harmless
- It is readily available and relatively inexpensive
The spectrometer works as follows: Any helium molecules that flow into it will be ionized. These helium ions then "fly" to the ion detector where they are analysed and recorded. The ions must pass through a magnetic field that deflects any ions other than the helium ones before they reach the detector. The leak rate can be calculated based on the ionization current.
These helium tests, also known as vacuum and sniffer, are able to detect leaks with precision and certainty. The term "certainty", which is a combination of the words vacuum and sniffer, refers to the fact that no other method can be used to locate small leaks and measure them quantitatively.