The gas
Leak Detection with the Hydrogen Method

The Sensistor Leak Detectors belongs to a family of instruments based on the hydrogen method. This method and INFICON hydrogen detectors is the natural choice when soapwater, pressure decay, or water dunking does not give you the quality testing you need. Thanks to the high sensitivity of the instrument, and the user friendly behaviour in high tracer gas background situations, it may also be an alternative to helium in some applications.

The hydrogen method involves injecting a safe, environmentally-friendly tracer gas containing 5% hydrogen in nitrogen into the test object. A unique 100% selective hydrogen sensor tells the operator where the leak is and how big it is. Using the inexpensive forming gas as tracer gas makes the Hydrogen Leak Detectors an excellent option for a wide range of production and maintenance applications, especially for finding leaks of a size that would leak liquids such as water, fuel and oils. Compared to using soap spray and water dunking you get better sensitivity and the method is also a cost-effective alternative to helium.

It is a widespread misconception that the flammability of Hydrogen would make it impossible to benefit from its advantageous properties in leak testing. In fact, Hydrogen is only flammable in the concentration range 4% – 75% in air, and can only detonate in the range 18% – 60% in air.

By using pre-diluted Hydrogen one can avoid the flammable concentration range altogether. Standard Hydrogen/Nitrogen mixtures are for example commonly used as shielding gases for welding purposes.
Hydrogen can therefore safely be employed for leak testing if used at the right concentration. A suitable concentration to use is the standard 5% Hydrogen / 95% Nitrogen mixture which is available in industrial grade from most gas suppliers. The price is only a fraction for example of the price for helium.

The 5% mixture is classified as non-flammable according to international standard ISO 10156. This standard not only describes how flammability limits of gas mixtures are to be determined, but also states that Hydrogen/Nitrogen mixtures containing less than 5.5% Hydrogen are non-flammable, irrespective of how this mixture, in turn, is mixed with air.

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Leak Detectors for Industry
Leak Detectors for Utility