Integrity test failures can be caused by a range of root causes, some of which are listed below:
- System leaks (filter housing, fittings, tubes, etc.)
- Insufficient test time
- Incorrect temperature of wetting fluid
- Insufficient stabilization time
- Temperature influence
- Incomplete wetting of the filter
- Incorrect test limits
- Incorrect pressure source
- Filter defects or damage
- Compromised O-ring seal
- Incorrect filter selection
When an integrity test failure occurs, the first step is to verify the system setup and test parameters. After all of these conditions have been verified, the filter should be re-wet and tested again (using the Forward Flow test, even if the initial failure was recorded using a bubble point test, except for small area filters (<200cm2).
If the result is a pass, then the filter is integral. If it fails, the Forward Flow test should be repeated after a more vigorous wetting step. This can include a larger flush volume, application of back pressure (downstream flow restriction), or increased differential pressure. If the filter fails again, a flush and Forward Flow integrity test with a low surface tension wetting fluid, such as 60:40 IPA/water, should be performed. If the filter fails the integrity test again, the filter (still installed in the housing if possible) should be returned to Pall Corporation for further analysis.