Helium Leak Testing
Helium Leak Testing
Helium is an inert, stable, and non-condensable gas that is often used as a tracer gas to identify leaks in parts and systems. The very small atomic size allows the helium to easily pass through leaks, and because it is inert, it will not react with virtually any of the materials within the part or system that is being tested. Since helium is only naturally present in the atmosphere in small amounts (~5 ppm), qualitative helium leak testing can be performed in ambient air to test areas that need rewelding, fittings that need tightening, failed gaskets, and other pressure system leak points. It is also used to determine what the total leak of a system is before it is put into service.
For the aerospace industry, the ability to test for leaks with high-level sensitivity is imperative to ensuring mission success, and at times, safety. Failure to identify and repair even small leaks can have detrimental consequences. During regular operations, all aircraft, satellites and rocket systems are subjected to different temperatures, atmospheric pressures and other stressors that can result in more severe leaks. An airplane leaking fuel may have a fire and not reach its destination safely. Spacecraft missions, with their limited resource supplies, will be compromised if the gas within a tank or primed system leaks out before the mission is complete.
Helium leak detection has been used for many years in the aerospace industry for the following:
- Critical gas lines
- Fuel systems and COPV tanks
- Sealed electronic enclosures
- Missile guidance systems
- Solid rocket booster cone assemblies
- Heat exchangers
- Hydraulic systems
- Cockpit instruments
Helium leak detection methods are also used across a variety of other industries including medical, automotive, and oil and gas processing. Helium leak detectors are used in the quality control of production parts such as medical devices, hydraulic lines, condensers, radiators, manifolds, fuel lines, fittings, and COPV tanks. Pressurized systems such as those found in oil and gas processing and vacuum systems, including vacuum furnaces, isolation glove boxes and laser process equipment, also utilize helium leak detectors to ensure the integrity of those systems prior to start-up and as part of their preventative maintenance procedures.
What are the Benefits of Helium Leak Testing?
There are many benefits associated with helium leak testing, which include:
- Leaks can be detected and quantified with a high level of sensitivity
- No adverse impact on the materials being tested due to the inert properties of helium
- The test process is essentially dry and temperature independent
- Microscopic leaks can be fixed before they do significant damage
- Lost production, time and costs can be avoided by repairing leaks before putting the part into service
- Reduced operational and maintenance costs for equipment through preventative maintenance
How Does Helium Leak Testing Work?
Helium leak testing utilizes a Helium Leak Detector, also referred to as a Mass Spectrometer Leak Detector (MSLD), to find a leak inside or outside of a system and then measure the leak rate. The helium leaks in/out of the tested product and is measured by the detector. The detector determines the leak rate based on the helium concentration and flow rate.
A complete Helium Leak Detector system contains the following elements:
- Helium mass spectrometer to detect the mass of the helium
- Vacuum system to maintain sufficiently low pressure for the spectrometer
- Valves which control individual steps of the measuring cycle: evacuation, testing, and venting
- Electronic measuring and control systems
- Power sources for individual components – valves, circuits, etc.
- Fixtures, which connect the tested product to the detector