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Pneumatic Testing for Leakage

Leak Testing by Pressure Decay

Leak testing is a branch of the non-destructive inspection methods aimed to guarantee the tightness of the components under test.

The most common leak test methods are able to determine the value of the leak (typically measured in cc/min or mbar/sec) by using:

  • Pressure decay (with or without reference volume)
  • Flow inspection (for big volumes)
  • Tracer gas inspection (high performances)

Few technologies are able to identify the position and the value of the leak by using:

  • Air bubble (under water inspection)  
  • Tracer gas (using sniffing probes)

The pressure decay is the most common leak inspection technology used to test the automotive components like cylinder blocks and heads, gear boxes and housings as well as assembled engines.

The part under test is tightened and pressurised or subjected to a vacum and if it has a leak, the pressure inside the component will change. The pressure variation per time unit between the reference volume and the volume under test is measured by a differential pressure transducer.

The figure shows the typical  pressure decay measuring cycle: