Tracer-gas leak testing method

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As part of the recommended leak testing methods for nondestructive testing several tracer-gas leak testing ones exist among which the methods of choice are:

• Helium mass spectrometer or helium leak detection, providing the highest sensitivity
• Hydrogen leak testing or hydrogen leak detection, providing the best mobility
• Refrigerant gas leak detection, for refrigeration applications.

The nature of the process and the process gases will help determine the most suitable method.

Typical applications of tracer gas leak testing include:

• Chemical plant ^[1]
• Petrochemical plant: hydrocracker ^[2], vapocracker, catalytic reforming, steam reforming are all Hydrogen based processes were Hydrogen leak testing will be very appropriate,
• Semiconductor industry; all processes taking place in a process chamber at atmospheric pressure or under vacuum; Diffusion, Oxidation, LPCVD ^[3], PECVD, PVD, Etch, Ion Implant, typically the later that implies vacuum will require Helium leak testing, while the other will make good use of Hydrogen leak testing,
• Automotive: with airbag ^[4] being the most demanding leak testing application (small gas tank, very high pressure, long shelf life) and air conditionning system (for best efficiency), fuel system (for low emission), exhaust system (for lowest pollution), engine and transmission (for no oil dripage), rims to keep tyre safe,
• Medical: to ensure safe and long life implant (pacemaker) ^[5] or a safe catheter
• Airplane: to quickly and safely locate fuel leaks ^[6], to check oxygen distribution devices and cabin pressurization systems
• Refrigeration and air conditionning systems-residential, commercial or industrial- in order to deliver best efficiency at the lowest loss rate of refrigerant gases (ozone depletion)^[7]
• Power distribution for high voltage circuit breaker using SF6 as a dielectric ^[8]
• Drinking water distribution grid ^[9]as today average leakage rate or efficiency is above 25%, wasting precious resources, water and power.
• Sewage water collecting network as leaks can contaminate drinking water collection process;

Another element of consideration is the dimension of the part to be tested as well as to take into consideration the law of physics, specially the rules that govern the flow of gas at different pressure.

Several standards apply to leak testing and more specifically to tracer-gas leak testing methods, for example

• BS EN 1779:1999; leak tightness by indication or measurement of gas leakage,
• BS EN 13185:2001 Non-destructive testing. Leak testing. Tracer gas method,
• BS EN 13192:2002 Non-destructive testing. Leak testing. Calibration of reference leaks for gases.

[edit] References

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