Valve Testing with Helium and Mass Spectrometry

When Helium Testing Is Used

Standard hydrostatic and pneumatic leak tests detect large leakage rates but cannot verify extremely low leakage. Helium mass spectrometer testing is used when fugitive emission standards, valve class, or process safety requirements demand detection at the ppb level.

How Helium Leak Detection Works

• Valve is pressurized with pure helium or helium/nitrogen mixture

• Mass spectrometer (leak detector) sniffs potential leak paths

• Detects helium concentrations as low as 10^-10 mbar·L/s

• Much more sensitive than soap bubble or pressure decay methods

Test Methods

• Accumulation method: enclose valve in sealed bag, measure helium concentration buildup

• Sniffing method: probe moved around potential leak sites

• Vacuum chamber method: place valve inside evacuated chamber, measure helium ingress

Standards and Acceptance Criteria

ISO 20485 covers leak testing using mass spectrometers. For fugitive emission compliance, API 624 and API 641 define acceptance criteria for rising-stem and quarter-turn valves respectively, specifying maximum methane equivalent emission rates.

Applications Requiring Helium Testing

• Nuclear industry valves (radioactive process isolation)

• Semiconductor process gas valves

• Space and aerospace fluid systems

• Critical hydrocarbon valves in high-consequence pipeline areas