Tracer-gas leak testing method is a nondestructive testing

Nondestructive testing

Nondestructive testing or Non-destructive testing is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage....

 method.

Types

Several tracer-gas leak testing methods exist among which the methods of choice are:

• Helium mass spectrometer
  Helium mass spectrometer
  A helium mass spectrometer is an instrument commonly used to detect and locate small leaks. It was initially developed in the Manhattan Project during World War II to find extremely small leaks in the gas diffusion process of uranium enrichment plants. It typically uses a vacuum chamber in which a...
  
   or helium leak detection, providing the highest sensitivity
• Hydrogen leak testing
  Hydrogen leak testing
  Hydrogen leak testing is the normal way in which a hydrogen pressure vessel or installation is checked for leaks or flaws. There are various tests....
  
   or hydrogen leak detection, providing the best mobility
• Refrigerant gas leak detection, for refrigeration applications.

Method selection

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

Chemical process equipment	10-1 to 1 mbar l/s	high process flows
Beverage can	low 10-5 to 10-6 mbar l/s	retention of CO2
Vacuum pumped system	10-5 to 10-7 mbar l/s	permanent pumping
IC-package	10-7 to 10-8 mbar l/s	lifetime control
Airbag cartridge	10-8 mbar l/s	lifetime control
Pacemaker	10-9 mbar l/s	Bio compatibilty
Closed vacuum system	10-9 mbar l/s	X-Ray tube

Based on the target leak rate the table below wil help to choose the most suitable method.
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Bubble test in water

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Bubble test soapy water

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Pressure decay

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Acoustic (US)

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Vacuum decay

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Corona tester

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Thermal conductivity

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Halogen sniffer*

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Hydrogen sniffer

Helium sniffer

Halogen detector*

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Dye penetrant

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Radio-isotope

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Mass spectrometer

• Restriction of use (F-Gas Directive)

Typical applications of tracer gas leak testing include:

• Chemical plant
• Petrochemical plant: hydrocracker , vapocracker, catalytic reforming
  Catalytic reforming
  Catalytic reforming is a chemical process used to convert petroleum refinery naphthas, typically having low octane ratings, into high-octane liquid products called reformates which are components of high-octane gasoline...
  
  , steam reforming
  Steam reforming
  Fossil fuel reforming is a method of producing hydrogen or other useful products from fossil fuels such as natural gas. This is achieved in a processing device called a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in industry to...
  
   are all Hydrogen
  Hydrogen
  Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
  
   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 , PECVD, PVD
  Physical vapor deposition
  Physical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
  
  , Etch, Ion Implant
  Ion implantation
  Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into another solid. This process is used to change the physical, chemical, or electrical properties of the solid...
  
  , 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
  Airbag
  An Airbag is a vehicle safety device. It is an occupant restraint consisting of a flexible envelope designed to inflate rapidly during an automobile collision, to prevent occupants from striking interior objects such as the steering wheel or a window...
  
    being the most demanding leak testing application (small gas tank, very high pressure, long shelf life) and air conditioning 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
  Pacemaker
  An artificial pacemaker is a medical device that uses electrical impulses to regulate the beating of the heart.Pacemaker may also refer to:-Medicine:...
  
  ) or a safe catheter
  Catheter
  In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
  
  
• Airplane: to quickly and safely locate fuel leaks , to check oxygen distribution devices and cabin pressurization
  Cabin pressurization
  Cabin pressurization is the pumping of compressed air into an aircraft cabin to maintain a safe and comfortable environment for crew and passengers when flying at altitude.-Need for cabin pressurization:...
  
   systems
• Refrigeration and air conditioning systems-residential, commercial or industrial- in order to deliver best efficiency at the lowest loss rate of refrigerant
  Refrigerant
  A refrigerant is a substance used in a heat cycle usually including, for enhanced efficiency, a reversible phase change from a liquid to a gas. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion...
  
   gases (ozone depletion
  Ozone depletion
  Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon...
  
  )
• Power distribution for high voltage circuit breaker using SF₆ as a dielectric
• Drinking water distribution grid 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.

Standards

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.