Helium Leak Testing
The preferred choice: Helium leak testing
Helium is the best tracer gas for many reasons. Helium is an inert gas it is not flammable it is non-toxic and there are only (5ppm) in the atmosphere. The helium atom is very small and will pass through the smallest leaks and read by the Mass Spectrometer.
Helium Leak Detection
Helium Leak detection is a process used to measure the size of cracks, holes, leaks in the product or system being tested. Helium is introduced into the part being tested, there are multiple ways to test parts, the use of a vacuum chamber is essential to some leak testing operations. A leak detector is also known as a mass spectrometer (MSLD). The Mass Spectrometer pumps out the atmosphere in the test piece or the vacuum chamber this creates negative pressure. After introducing the helium to the test piece the tracer gas will travel through the imperfection and the leak detector will read the size of the leak.
Mass Spectrometers have following components:
A mass spectrometer to detect helium
A vacuum system to maintain the pressure in the mass spectrometer
A mechanical pump to evacuate the part to be tested
Valves which enable the various stages of detection: evacuation, test & venting
An amplifier and readout instrumentation to monitor the output signal
A turbo to reach a deeper vacuum test cycle
Methods of Leak Testing Parts
Leak detection of test parts can be done in many ways but there are two methods that are used the most:
Adding positive pressure to the part and sniffing the outside to detect helium leaking through holes and imperfections.
Creating a vacuum on the inside of your part and spraying helium on the outside of the part to find leaks and imperfections.
In Vacuum testing, the part is evacuated of the atmosphere with a pumping system. To locate a leak, helium is introduced to the suspected leak using a spray probe with adjustable flow.
In Pressure Testing, the part is pressurized with helium. To Locate a Leak, the potential leak sites of the part are scanned using a Sniffer Probe connected to the inlet of the leak detector.
Helium Leak Detection Applications
Production parts and assemblies using helium leak detectors can help assure the integrity of your production process.
Examples include hermetically sealed packages, valves, manifolds, seals, vacuum vessels and systems, medical devices, high purity piping, brake lines, fuel lines, hydraulic lines, refrigeration assemblies, radiators, heat exchangers, condensers, storage tanks.
Industrial process tools that use vacuum systems or pressure systems must be tested to check for occasional leaks. This can be part of preventative maintenance or in the event of an unexpected failure.
Examples of vacuum systems include Vacuum furnaces, vacuum coaters, electron microscopes, glove boxes, linear accelerators, electron beam and ion beam process equipment, semiconductor process equipment, laser process equipment.
Examples of pressurized systems include Power plants, gas handling systems, bioreactors, liquid gas facilities, underground tanks, underground cables, and pipes.
Types of leaks
Leaks in detachable connections: Flanges, machined mated surfaces, doors
Leaks in permanent connections: Welding seams, glued joints
Leaks due to porosity: Weld joints, Bent joints, Rubber seal imperfections or glued seam
Thermal leaks: Material warpage from sealing surface, material decay from thermal induction
Virtual leaks: Gas under vacuum that is liberated from hollows and cavities inside parts, blind holes, and joints, liquids in vacuum
Indirect leaks: leaking supply lines in vacuum systems or furnaces
Serial leaks: This is the leak at the end of several “spaces connected in series”, e.g. a leak in the oil-filled section of the oil pan in a rotary vane pump
One-way leaks: these will allow gas to pass in one direction but are tight in the other direction (very seldom) An area which is not gas-tight but which is not leaky in the sense that a defect is present would be the
Permeation: gas that passes through and is absorbed into materials such as rubber o-ring seals in a vacuum system