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’ LPC 528 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 LPC 528'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 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 LPC 528 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. See diagram below.