Gasket Compression Calculations for Pressure Transducer Port Glands
Optimizing transducer port sealing demands balancing 15 to 25 percent gasket squeeze against volumetric fill below 85 percent to prevent mechanical die offset.
Helium Leak Testing ISO 20485
Nondestructive Procedure
Industrial non-destructive standards establish the principles for determining the leak rate of sealed components using tracer gases. Under helium leak testing ISO 20485, a test specimen is evacuated or pressurized with helium to measure the rate of gas escape. This procedure detects micro cracks and structural flaws that bypass ordinary hydraulic pressure tests.
Sealing integrity is quantified by measuring the tracer flow rate.
Mass Spectrometry
Mass spectrometers are used to detect helium ions in a high vacuum environment during helium leak testing ISO 20485. The instrument ionizes the entering gas and filters the ions by mass to charge ratio. This process isolates the helium molecules from other ambient atmospheric gases.
Measurement results are output as a volumetric flow rate expressed in pascal cubic meters per second.
Metrological Precision
Calibration of the leak detector is performed using a certified reference leak that has a known flow rate within the range of the expected measurement. This reference leak must be connected directly to the test manifold to account for the vacuum conductance of the system. Discrepancies between the reference leak temperature and the test environment can cause measurement errors.
The test certificate must detail the correction factors applied for temperature variations. Surface degassing of water vapor or nitrogen from the chamber walls can mimic a leak, so a thorough pump down is necessary before opening the sensor.
Operational Variable
Ambient temperature and atmospheric pressure affect the gas diffusion rate and sensor response time. Elevated temperatures increase the kinetic energy of the gas, leading to higher observed flow rates. System response times grow longer when large volumes are tested, because gas takes time to reach the spectrometer.