Differential Pressure Decay Leak Detection - dP and dP/dT



Differential Pressure TestPressure decay leak tests involve measuring the drop in pressure on the interior of a part. To conduct the test, the air is injected into the test part until reaches the target pressure. The air source is then cut to isolate the pressure and the loss of pressure (decay) is measured over a specified time period. A loss in pressure indicates the presence of a leak.

Differential pressure decay leak testing uses traditional pressure decay parameters, but tests for leaks by measuring a pressure change between a reference volume of air and the test part volume. In differential pressure decay leak detection, the test measures the rate of pressure loss between the reference volume and the part volume as a leak. It is quick, reliable, and sensitive enough to detect small leaks.

Versatile Differential Pressure and Pressure Decay Test Systems

Cincinnati Test Systems’ differential pressure decay leak detection instruments provides both dP and dP/dT testing options. The dP test reports the “pressure drop” over the full test time, while the dP/dT test measures the pressure drop and reports the “average leak” to specify the pressure loss per second.
Our MH, LPC 528, and I28 instruments provide the following measurement ranges for differential pressure decay leak detection:
  • Test pressure range: vacuum to 13.8 bar (gauge)
  • Test pressure control accuracy: 1.5% FS
  • Measuring range: 0 to 0.345 bar (differential)
  • Measuring accuracy: ±0.006 % FS
  • Resolution: 0.007 Pa
The system is also designed to conduct standard vacuum and pressure decay tests, and differential vacuum decay tests, creating a versatile solution that can be used across a range of testing applications. It also features data collection and storage of up to 5,000 test results so you can easily review historical differential pressure decay leak testing data.

dP and dP/dT Differential Pressure Leak Test Cycles

The pressure decay leak detection test cycle fills a test part and an equally sized reference tank to specified test pressure. The air source is then cut off, the test pressure stabilizes, and the reference air isolation valves are closed. The differential pressure transducer measures for a change in pressure between the test part volume and the non-leaking reference volume during the programmed test time.
At the conclusion of the test, the instrument reports the change in the differential pressure. If the differential pressure decay is within the “target pressure window,” the part passes the leak test. If outside the target limits, the part fails the leak test and is rejected.  Both tests use a differential pressure transducer to measure pressure loss correlated to a flow rate in scc/m. See diagram below.

Differential Pressure Test Circuit


Customizable Pressure Decay Leak Test Systems for Any Industry Testing Needs

Our customizable differential pressure decay leak testing systems are used across a range of applications including automotive, powertrain, consumer goods, energy, HVAC/R, medical, military, and other transportation.
Depending on the testing application, differential pressure decay leak detection can provide a higher level of sensitivity than standard pressure decay tests. It is important to note that object size and testing interval can both impact the sensitivity of the test, and it is not an ideal method for testing parts made from elastic materials.
Read our market application case study below to see how CTS created a 2-station semi-automatic differential pressure test system for testing master cylinder assemblies.

Contact Us for Reliable Differential Pressure Decay Test Systems

Cincinnati Test Systems designs and manufactures the most accurate and most reliable leak test systems on the market. We also offer recalibration service for our leak testing instruments and provide 24/7 technical assistance.  Contact us today for the differential pressure decay testing solution you need.