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Pressure Decay Leak Test

What is a Pressure Decay Leak Testing?

The Pressure Decay Leak test, also known as gauge decay, absolute pressure, leak drop or delta pressure leak test.  This test method measures the drop in pressure on a gauge (transducer) during the leak test.  Pressure decay testing is used to test products for leaks by trapping pressure inside a product and then measuring pressure loss.

In this test method the component is pressurized with air and the pressure transducer monitors the pressure for negative changes. Any pressure drop indicates a leak. The pressure change from the first measurement to the last measurement made during the test phase of a test is what is important.

The test is very fast, a matter of seconds, and is therefore popular for leak testing in high-volume industries such as automotive components, castings, medical devices and consumer goods.

How is a Pressure Decay Test performed?

To bein the Pressure Decay leak test, the test part [TP] is attached to the test port. The tester then pressurizes the part with pressure [+P] to the desired test pressure set by the pressure regulator [R1] during the Fill step by opening valves [V1] and [V2].

Upon completion of the Fill step, pressure is trapped inside the part as [V2] closes.  After a slight delay, [V1] closes allowing the line between [V1] and [V2] to vent to atmosphere through [V1] allowing any leakage through [V2] to cause the tester to see this leakage and fail all tests. The extra valve allows for a fail-safe configuration.

Trapped pressure inside the test circuit is held through the Stabilize step and then measured by the testers pressure sensor [PS] during the Test step.
If the part exceeds the programmed leak tolerance (pressure drop over time or quantified leak rate), the tester’s display indicates the reason for the test failure and displays the pressure loss or leak rate in user defined units of measure.

Upon completion of the Test step, pressure trapped in the part is vented to atmosphere through [V1] by opening [V2] during the Vent step, and the tester is ready for the next test.

Pressure Decay Test Pneumatic Diagram
Pressure Decay Test Pneumatic Diagram

Which Uson Testers can perform a Pressure Decay leak test?

Optima vT – A versatile and customizable leak tester with up to two channels and eight sensor inputs that supports pressure decay, differential pressure, mass flow and other common tests

Uson Innovative Systems (UIS) – Custom made manual, semi automatic and fully automatic leak test systems and fixtures

Qualitek – Fast, sensitive and accurate pressure decay, differential pressure and mass flow leak testers

Sprint – Small foot print single or multi channel pressure decay and flow testers

Vector – Uson’s most powerful and configurable leak and flow tester, fully customizable pneumatics, up to ten independent test channels supporting a wide variety of input sensors

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