Tracer-gas leak testing
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:- Detection of leaks using helium mass spectrometer, which provides high sensitivity
- Hydrogen leak testing, which provides the best mobility
- Refrigerant gas leak detection, for refrigeration applications
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 |
| 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.| Method | Sensitivity |
| 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 industrial quality control with
- 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, 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.
- Sewage and drinking water networks, to reduce loss of water and make sure drinking water is not contaminated by sewage.
Standards
- 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.