Tracer-gas leak testing

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A tracer-gas leak testing method is a nondestructive testing method that detects gas leaks. A variety of methods with different sensitivities exist. Tracer-gas leak testing is used in the petrochemical industry, the automotive industry, and in the manufacture of semiconductors, among other uses.

Types[]

Several tracer-gas leak testing methods exist, including:

Method selection[]

Typical leakage rates[]

The nature of the product or the process and the process gases will set the leak rate requirement:

System Allowed leak rate (mbar l/s)
Chemical process equipment 10−1–1
Beverage can 10−5 –10−6
Vacuum pumped system 10−5–10−7
IC-package 10−7–10−8
Airbag cartridge 10−8
Pacemaker 10−9
Closed vacuum system 10−9

Sensitivity of methods[]

Based on the target leak rate, the table below will help to choose the most suitable method.[1]

Method Sensitivity (leak rate in mbar l/s)
Ultrasonics 10−1
Bubble test in water 10−2
Pressure decay 10−2
Vacuum decay 10−2
Acoustic emission detectors 10−3
Bubble test in soapy water 10−4
Gas-specific thermal conductivity detector 10−5
Halogen detector 10−5
Photoacoustic spectroscopy 10−6
Hydrogen sniffer 10−6
Residual gas analyser 10−7
Dye penetrant 10−8
Radioactive tracer 10−10
Helium mass spectrometry vacuum testing 10−11

Applications[]

Typical applications of tracer-gas leak testing include:

  • In petrochemical plants, hydrocracking, vapocracking, catalytic reforming, and steam reforming are all hydrogen-based processes, in which were hydrogen leak testing is required.
  • When manufacturing semiconductors, all processes taking place in a process chamber at atmospheric pressure or under vacuum – diffusion, oxidation, LPCVD, PECVD, PVD and ion implantation – require helium or hydrogen leak testing.
  • In vehicles, airbags have to be tested for leaks so they remain functional for a long time. As well as airbags, the air conditioning system, fuel system, and exhaust system require testing for leaks.
  • Pacemakers and catheters have to be tested for efficacy and longevity.
  • On planes, tracer-gas leak testing is used to quickly and safely locate fuel leaks,[2] as well as to check oxygen distribution devices and cabin pressurization systems.
  • Refrigeration and air conditioning must have the lowest possible rate of loss of refrigerant gases (contributing to ozone depletion).
  • Sewage and drinking water networks, to reduce loss of water and make sure drinking water is not contaminated by sewage.

Standards[]

See also: Leak detection § Rules and regulations

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.

References[]

  1. ^ "Leak Detection Sensitivity Guide - VIC Leak Detection". VIC Leak Detection. Retrieved 2017-06-15.
  2. ^ Townsend, Mark; correspondent, defence (2007-11-11). "MoD accused over spy plane deaths". The Guardian. ISSN 0261-3077. Retrieved 2017-06-15.
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