Leak Detection and
Testing with Hydrogen Tracer Gas
Up to 1000x more sensitive than pressure decay testing is only one of the many advantages of switching from pressure decay leak testing to using the Gas –FET (Gas – Field Effect Transistor) diluted hydrogen method. Pressure decay systems are limited in sensitivity to, typically, a pressure drop of 0.01 mbar/sec (0.0001 psi/sec) for ideal conditions. For a test volume of 100cc this equates to a leak flow rate of 1x 10-3 cc/sec and for a test volume of 1,000cc it equates to a leak flow rate of 1x10-2 cc/sec. As previously stated to be able to test to these limits the test object conditions have to be ideal – no flexing due to elastic materials ( flexing increases volume and therefore changes the pressure) – no temperature changes, temperature changes may be due to the part being hot from a manufacturing process( welding) or due to pressurizing the object ( a temperature change will result in a change in pressure) . The effects of both of these conditions can be calculated using the Ideal Gas Law - P1.V1/T1 = P2.V2/T2. Volume or temperature changes may result in false positive or negative test results.
The Gas-FET method as well as being at least 3 orders more sensitive ( 5x10-7 cc/sec) than pressure decay testing for the conditions stated above will also address the other pressure decay testing drawbacks.
1/The test is not component volume dependant - the high sensitivity is the same regardless of the test volume.
2/The test is not effected by flexing or creep of the test object – the test is measuring the actual leakage flow rate from the test object and not the resultant pressure change
3/The test is not effected by the temperature of the part - the test is measuring the leakage flow rate from the object and not the resultant pressure change
4/The test will pinpoint the leak position.