Integrity Testing of Hydrophilic Membrane Filters


All integrity test procedures outlined below should be followed when performing integrity testing of membrane filters only.  Use of these procedures on other types of filters such as polypropylene or glass fiber cartridges will not give consistent or accurate results.

Cartridge Wetting

  1. Prior to any integrity test procedure, the cartridge membrane must be thoroughly wetted.  If the membrane is not fully wetted, hydrophobic or un-wetted spots will give a false failure for any of the tests outlined below.  Refer to Figure 1 for the Wetting and Integrity Test Set-up.
  2. Cut off the polyethylene bag at the O-ring end of the cartridge.  Be careful not to damage the Orings.
  3. Remove the polyethylene sleeve from the cartridge.  The cartridge must be handled consistent with its intended use.  For example, some applications may require special procedures such as, wearing of gloves, pre-sterilization of the cartridge, etc.
  4. Place the cartridge into the housing, closing the housing securely. With the downstream valves (V8 and V9) and vent valve (V7) open, slowly open the upstream valve (V1) to allow filtered water or the selected test fluid into the housing.  Once fluid is observed coming out the vent valve (V7) with no bubbles present in the fluid, close the vent valve and allow the fluid to pass through the housing at 2 liters per minute. 
  5. Allow fluid flow for a total of 10 minutes 
  6. Start closing the downstream valve (V9 and V8) to reduce water flow and increase inlet pressure. Bring the inlet pressure up to 15-20 psi by reducing the flow through the downstream valve. 

Figure 1 - Wetting and Integrity Test Set-up

 

NOTE: If the cartridge integrity test will be conducted when the filter is installed in the process system, but the filter requires wetting with a fluid different from the normal process fluid to be filtered, the user may wet the filter in a separate housing using the same procedure as described above, then remove the wetted filter and install it in the process system.  If the filter application is bacteria removal, then the filter and system should be disinfected or sterilized after the integrity test is complete and before use.

Diffusive Flow Test

Refer to Figure 1, which represents a typical layout for an integrity test system. 

  1. Install and rinse cartridges as per Cartridge Wetting instructions.
  2. Starting with all valves in the closed position, open valves V8 and V9.  Downstream must be open to ambient pressure.
  3. Connect a pressure regulated air (gas) supply and open valve V4. (If possible, pressure should be regulated to the desired test pressure.)
  4. Open the drain valve (V6) and vent valve (V7) and purge upstream test fluid at 2 psig. Close valves V6 and V7 when flow becomes mostly air.
  5. Slowly increase the air pressure, as measured on the upstream pressure gauge (G1) or mass flow meter to the amount on the test specification supplied by Critical Process Filtration (usually 80% of the specified bubble point). 
  6. Allow the system to equilibrate. If the regulated air supply is not set at the test pressure, maintain the specified pressure as measured at G4 by adjusting the flow of air using valve V4.
  7. Record the air flow.
  8. A diffusional flow (diffusion rate) reading higher than the specification indicates that the system is not integral.

Note: If the cartridge appears to fail the test, repeat the Cartridge Wetting procedure and increase the rinse time to twice the initial amount to insure that the membrane is properly wetted.  Then retest.  If necessary, check the cartridge seal in the housing.