Getting the Most From Your Pressure Decay Leak Test

Posted by LACO Technologies on Jan 14th 2020

When should I use pressure decay?

Pressure decay is a widely used leak air test method for many reasons: it’s relatively simple, low-cost, and can yield quantitative data of your leak test process. Typically used to test for leaks in the range of 0.1 sccm and larger, the pressure decay method can be applied in several ways:

Pressure decay: Measure out-leakage of pressurized parts;
Chamber pressure decay: Measure in-leakage on sealed parts within a test chamber;
Volume dump chamber pressure decay: Incorporates the use of a known reference volume to ensure gross leaks are detected when testing in-leakage of sealed parts.

What are the benefits?

Yet, many users of air leak test method experience some degree of frustration. A lack of trust in leak results or a failure to troubleshoot issues can affect our confidence in effective leak testing. Using an air leak test controller such as LACO’s AURA Air Leak tester will minimize these concerns and result in operator-independent leak testing that is automated, fast, repeatable, and can be calibrated.

What can go wrong?

While developing a process using the pressure decay leak test method, operators must be aware of factors that affect leak rate measurement, such as:

Test conditions
Part characteristics
Fixture design
Test instrument
Test environment

Developing a leak test process that considers these variables will lead to a more reliable pressure decay leak test. In applications where customization is needed, the AURA Multi-Test Chamber Pressure Decay Leak Tester provides complete flexibility with the ability to interface and control more complex tooling including pneumatic clamping, part handling, safety relays, part presence sensors and auto start circuits. Automation support, customizable software, test recipes, and data logging add key functionality that supports fast, accurate, and meaningful leak testing.

In addition to being a standalone pressure decay leak test system, the AURA Compact Pressure Decay Leak Tester can be integrated into your existing process flow or assembly process.

When should pressure decay not be considered?

While pressure decay leak testing is very common, applications using large test volumes and/or tight leak rates (less than 0.01 atmcc/sec) may not be ideal for the pressure decay test method due to excessive test time. Even with the best pressure transducers and high resolution A/D converters, several factors can make it a difficult test, including environmental and part characteristics. Examples include:

The part or test tooling is not mechanically stable (e.g. a balloon or other flexible plastic part)
The part temperature is not stable (e.g. resulting from a welding operation, environmental changes or adiabatic heating from the filling process)
The parts have inconsistent part-to-part volume

There are many factors that contribute to the successful development and implementation of a pressure decay leak test system. For a more detailed analysis of successful pressure decay leak testing, see LACO CEO Paul Chamberlain’s presentation Succeeding with Production Air Leak Testing Methods.