| ABSTRACT: | HYDROGEN AS TRACER GAS FOR LEAK DETECTION
M. Block
Sensistor Technologies, Muehlheim, Germany
When it comes to leak detection, Helium has been the most common tracer gas of all. There are, however, a
number of limitations preventing the use of Helium tracer gas in many industrial applications. Hydrogen
molecules weights only half of a Helium atom and has a much higher molecular velocity, hence Hydrogen
spreads quickly inside test objects, and dissipates very much quicker than Helium. Besides the low cost,
these properties make Hydrogen a very attractive alternative to Helium for leak detection.
There are essentially only two reasons why Hydrogen hasn’t become a more common tracer gas than
Helium long ago; a) the perception that Hydrogen would be too dangerous and b) the availability of suitable
Hydrogen detectors.
The flammability problem is easily overcome by using a readily available standard mix of 5% Hydrogen in
nitrogen, which is classified as non-flammable.
The other obstacle was solved by the advent of a new type of Hydrogen detectors, based on microelectronic
Hydrogen sensors. These detectors have a high sensitivity and high selectivity to Hydrogen. At the same
time they are robust and cost-effective for industrial use, allowing leaks down to 5x10-7 atm cc/s to be
detected using the 5% Hydrogen mix. The use of Hydrogen as a tracer gas is now increasing rapidly in a
number of industries, such as in automotive, chemical, power generation, aerospace and even telecom.
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