The main components of a helium leak detector are:
1. The analyzer – which enables the separation of tracer gas from other gases inside the leak detector. The most common type is a magnetic deflection type analyzer or a quadrupole type in the event of testing multi-gasses (as used in the refrigeration industry). This device allows partial pressure measurement of helium.
- high vacuum pump, which is able to reduce the pressure in the analyzer down into the 10-6 mbar pressure range. Most leak detectors today are equipped with either a turbo molecular pump, a molecular drag pump or a pump that includes the combination of both. These pumps are ideally suited for contra-flow operation, where the lighter gas molecules, such as helium, can contra flow through the turbo back into the analyzer. This contra flow principle provides the opportunity to start testing at high system pressures, which is ideal for finding larger leaks as common in industrial leak detection.
3. A backing pump to support the turbo pump. This pump can be an oil sealed rotary vane pump. For hydrocarbon free applications, one can select a screw pump or a scroll pump.
Now we will move on to discuss and define partial pressure on the next page.