Meaning
Quantification of gas escaping through microscopic pores or defects provides a measure of the hermetic seal quality in a closed system. Helium micro leak rates are used to validate the integrity of battery enclosures and cooling circuits where even tiny openings could lead to moisture ingress. This standard defines the maximum allowable discharge for a component to be considered airtight.
Tracer Gas
Helium is used as the detection medium due to its small atomic size and low atmospheric presence. Measuring helium micro leak rates involves placing the component in a vacuum chamber and using a mass spectrometer to count the atoms. The sensitivity of this method far exceeds that of traditional air-pressure decay tests.
Failure Threshold
Specifications for long-life energy storage often set the limit at ten to the minus eight mbar liters per second. If helium micro leak rates exceed this value, the risk of electrolyte evaporation or external contamination increases. Poorly executed welds or compromised gaskets are the most common sources of leakage.
Testing Procedure
Hard vacuum testing provides the most accurate results for high-reliability components. In this setup, the internal volume is pressurized with the tracer gas while the exterior is evacuated. This pressure differential forces the gas through any existing pathways in the material.
To maintain accuracy, the equipment must be calibrated using a reference leak standard that provides a known flow rate under identical conditions. Any contamination in the vacuum lines can lead to a rise in the background signal, which makes the detection of small leaks difficult.
