Differential Pressure Decay - dP and dP/dT
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. Differential pressure decay leak detection measures the rate of pressure loss between the reference volume and the part volume as a leak.
Cincinnati Test Systems’ Sentinel C28DP differential pressure decay leak detection instrument 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.
dP and dP/dT Leak Test Cycles
The Sentinel C28DP’s pressure decay leak detection test cycle fills a test part and an equally sized reference tank to a specified test pressure. The air source is then cut off, the test pressure stabilizes, and the reference air isolation valve is closed. Pressure on both sides of the differential pressure transducer is measured on the test part volume side for the programmed test time, monitoring a change in pressure.
At the conclusion of the test, the C28DP reports the change in the differential pressure. If 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. See diagram below.