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Helium Accumulation (HA): An automated method of capturing and accumulating helium in an enclosure surrounding a part pressurized with helium. Helium Sniffing (HS): A manual method of sniffing a pressurized part to detect helium escaping a leak. This might require thick wall or cladding on the vacuum chamber, or installing the vacuum chamber in a protective room. Considerations should also be made for the possibility of shrapnel from a failed part.

When performing chamber leak testing, precautions should be employed that relieve gas pressure from the vacuum chamber in a safe manner in case of a part failure. The vacuum chamber is evacuated and connected to the helium leak detector at the appropriate time to perform the leak test. In this case the test part is placed inside a vacuum chamber and a charging process similar to what is described above is employed. If the test part requires a global leak test or a tighter leak rate, a helium hard vacuum chamber method can be employed. A safety interlock can be employed which may insure a safety door or shield is in place prior to filling the part to the proof pressure.

Back-fill with low pressure nitrogen (optional) Safety Precautions for high pressure testingĭue to the high pressures often used in proof testing safety precautions should be taken to protect personnel from failure of the part during the proof test step.

Helium evacuation with optional recovery.

When sniffing is employed it is often desirable to have a dedicated helium charge station that is designed to perform the following steps: The helium sniffing (detector probe) method is often employed on large parts where the leak rate limit is near 1 x 10 -5 atmcc/sec and larger. Products requiring a pressure proof test may have a wide range of leak testing requirements. Extreme caution and appropriate safety guidelines should be employed when pressurizing any vessel or component with gas for proof testing. Dry compressed air or nitrogen is often used as the test gas. If desired, a proof test of pressurized parts can be conducted on the same equipment that leak testing is performed. Similarly, under ASME Boiler and Pressure Vessel Code an optional gas pressure proof testing can be used in place of a hydrostatic test method.

For example, pressure proof testing is required for UL 207 Standard for Refrigeration-Containing Components. Some products, including refrigeration compressors and coils, require a high pressure gas proof test in addition to a leak test.