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MEASUREMENT PRINCIPLE OF HYDROGEN LEAK TEST

The hydrogen leak test is a testing device that detects leak by charging gas that includes hydrogen in the tested work and detecting leaked gas using a hydrogen sensor.
Tracer Gas
Hydrogen is used as the tracer gas for the hydrogen leak test. Industrial mixed gas of hydrogen 5% + nitrogen 95% is recommended to be used as the tracer gas. It can be used safely since the industrial mixture of hydrogen 5% + nitrogen 95% is defined as non-flammable gas. (ISO101562) * Although highly-concentrated hydrogen gas can be used, it is not defined as non-flammable gas.
Principle of Detection
The hydrogen detection sensor used for the hydrogen leak detector applies a semiconductor type gas sensor with a sintered structure in which tin oxide is vitrified. The semiconductor type gas sensor does not allow electricity to flow in normal room temperature. Electricity starts to flow when the sensor is in high temperature of approximately 400°C by a heater in an ambient with no oxygen.  Oxygen in the atmosphere is adsorbed to the sensor surface of the hydrogen leak detector when measured in the atmosphere. The adsorbed oxygen inhibits the flow of electron causing high electric resistance and a condition where electricity is difficult to flow. When hydrogen gas is sucked during the measurement, hydrogen molecules attach to oxygen (oxidation reaction) and oxygen attached to tin oxide decreases. Since the amount of oxygen on the sensor surface decreases, the electric resistance value decreases and electricity starts to flow easily. Leak of hydrogen gas and gas concentration are detected through this change of electric current.
[Figure] Principle of Hydrogen Leak Test
Applicable product

Measurement Method of Hydrogen Leak Test

Sniffer methodTo localize the leak point.   Suction cup methodTo measure the leak from known location.
 
The probe with the suction function rises to the surface of the test work to guide the leak gas and detection.   When the test location is limited, prepare the local suction cup and suppress the diffusion of the leaked Hydrogen in order to measure with high sensitivity.
Atmospheric pressure chamber methodTo measure the integrated chamber method   Vacuum flow method (Patent pending)To measure the integrated chamber method
 
Cover the total work with the chamber and detect the leaked and accumulated tracer gas.   Increases vacuum within the chamber and allows highly sensitive measurements due to a compressed pipe in front of the sensor. Please contact us if you'd like further information

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