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16th WCNDT 2004 - World Conference on NDT
CD-ROM Proceedings, Internet Version of ~600 Papers
Aug 30 - Sep 3, 2004 - Montreal, Canada
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SESSION: NEW TECHNIQUES
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 hasnít 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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MAIN AUTHOR:Matthias Block, Sensistor Technologies GmbH, Germany
Paper CODE: 523

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