When investigating an integrity test failure, one of the first steps is to determine if any leaks are present in the system under test. Integrity test instruments perform the measurements on the upstream side of the filter, thus preserving the downstream sterility of the system.  The test instrument is not able to differentiate gas flow through the filter from gas flow through a leak in the hardware.

Prior to performing the leak test, a visual inspection of the system is recommended to identify any potential leak sources.  Damage to the housing or to the o-ring seals are common sources of leaks.  Such signs of damage include cuts on the O-rings, or misshapen or dented housings.

Pall recommends performing a leak test using the Palltronic® Flowstar® IV,  as follows:

  1. The leak test can be performed on a filtration system with or without a filter installed.  If a filter is installed, as is the case with capsule filters, the filter must be dry.  Diffusive or bulk gas flow through a wet filter cannot be differentiated from leaks in the assembly.
  2. The outlet of the housing should be sealed with either a blank endcap, valve, or other suitable termination method.
  3. All drain and vent valves must be in the closed position, except in cases where the connection to the instrument is made through a vent.
  4. A length of pneumatic tubing with the Palltronic Flowstar IV external vent valve installed should be used to connect the OUT port of the Palltronic® Flowstar IV integrity test instrument to the housing vent port.
  5. From the Palltronic Flowstar IV main menu, select the “Leak Test” function.
  6. The Forward Flow test pressure that is used to test the filters should be used as the pressure for the leak test. 
  7. The maximum system size for the leak test is 50 liters.

If the Palltronic Flowstar IV integrity test instrument is not able to detect a pressure loss in the volume or the leak rate is too small to be detected, it will report “no leak detectable” or “flow within limits’ as the result.  These results confirm that the filter system under test is free of significant upstream leaks.

If the test reports “flow outside limits” (> 1 mL/min)

  • Ensure that the test is being carried out under stable temperature conditions.
  • Re-check the connections and housing enclosure are tightened fully.
  • If sanitary fittings are an integral part of the filter housing, then the elastomeric seals should be examined and changed if necessary.
  • For smaller housings, submerging the pressurized system in a water bath and looking for bubbles will indicate the location of the leak.
  • A soap-based leak detecting product can be used around the fittings and connections to locate a leak.

For more information, please contact Pall’s NEW Equipment Support Hotline.