Pressure Decay / Differential Pressure Decay

In pressure decay leak testing, the measurement of change in pressure is compensated for test time and part volume to prove a reading of leakage in sccm. Pressure decay leak testing is usually used to leak test small parts. Higher resolutions are achieved by differential pressure decay transducers. A differential pressure decay leak detector is typically used for test pressures in excess of 150 psig (10 bars).

With valves 1 and 2 open, the test item and reference volume are pressurized and then isolated by closing valve 1. The reference volume is then isolated from the test item by closing valve 2. The transducer reads the pressure differential between the reference volume and the test item twice over time. A downside to this method is that the larger the volume, the smaller the change in pressure for a given leak rate, resulting in longer test times as test volume increases.

The Nature Of Pressure Decay Leak Testing

The indirect nature of the differential pressure decay testing process and the time needed to track pressure changes and take two measurements create inherently longer testing times. This means a greater probability of measurement error exists than for methods that require only one measurement. The probability of measurement error is directly related to the interval length between the two measurements. These factors are what lead many engineers to consider and use mass-flow leak testing as a preferable and more reliable option.

Providing the Highest Quality Standards

InterTech’s Applications Engineers are on-call to provide no-cost consultations on your specific medical device leak testing, functional testing, pressure decay test instrumentation, or assembly and test challenge. ISO 17025 accreditation of InterTech’s Calibration and Applications Laboratory’s quality management system compliments its ISO9001 accreditation ensuring customers and end-users are assured of quality and proven standards at all stages within their supply chains.

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