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ABSOLUTE PRESSURE DECAY METHOD

The absolute pressure decay method is, without doubt, the most used and known one, and the most competitive in terms of costs. 

The test cycle is divided into three phases: 
- FILLING (time T1): 
the test equipment fills the product being tested to the programmed rated test pressure, then the air flow is stopped with an electronic controlled pneumatic circuit.
- SETTLING (time T2):
the equipment waits for the pressure to settle in the product being tested, checking that the pressure is inside the specificed tolerance range.
- LEAK MEASUREMENT (time T3): 
the pressure drop in the product being tested is measured, if the drop is lower than the specified limit the test is passed, otherwise is failed.

The system accuracy is about 1 cm3/min.

  • The piece to be tested is filled up with air at a given test pressure. This filling phase is followed by a settling phase to stabilize the piece inner pressure. During the leak measure the decay measure (pressure drop) is measured with reference to the end of the settling phase.

  • A leak decrease the inner pressure of a piece as an inverse proportion respect to the volume; by consequence, the higher is the volume, the more time will be needed to measure a microleak. In other words, the smaller is the leak to be detected, the more time will be needed in order to measure with certainty a relevant pressure decay.

Disadvantages

  • The test effectiveness is directly proportional to the measurement time and inversely proportional to the volume of the tested piece;

  • The test duration is in function of the piece volume;

  • The test accuracy depends on the least pressure variation detectable by the leak tester equipment;

 

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