Volumetric Fill is a leak test method used to test sealed parts. It is a two-step leak test performing a gross and fine leak test on the test part. Sealed parts cannot be tested using conventional pressure or vacuum decay testing because they are ‘sealed’ and do not have ports to apply pressure or vacuum to test for leaks. To test a sealed part the part is placed inside a sealed chamber and the leak test is conducted on the air or space inside the chamber surrounding the outside of the part and test for air being forced inside the part or for air to escape the part. The volumetric fill test, the gross leak test, will make sure there are no gross leaks in the part prior to conducting the fine decay leak test. Without a volumetric test, you could fill up the volume of a gross leaking part during the fill stage of the test and never be able to check for a small leak because there wouldn’t be an air pressure differential on the part chamber.
Volumetric Fill leak test
The Volumetric Fill introduces a known reference volume into the test circuit and uses equalization of a known pressure to accurately measure the leak. If the part has a gross leak the test would not meet ‘target pressure window’ specification and fail the gross leak test. If the passes the gross leak test the program automatically performs the fine pressure decay leak test.
See diagram for example below.
Imagine the volume of your reference air tank being the same of the volume of the free space of the chamber surrounding the outside of the part and neglect all the tubing and inefficiencies. If the reference volume, example 5 psig, is allowed to flow into the test chamber with a good part then the equalized pressure would be around 2.5 psig. If there was a gross leak in the part and the part was the same volume as the reference tank then the new pressure would be 01.25 psig and the test would fail. If the part passes the gross leak test a ‘fine’ pressure decay leak test is performed on the part.
Performing a Volumetric Fill leak test on ‘seal parts’ ensures your parts are leak tight and conform to IP67 ingress contamination standards.