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Integrity Test

2015-02-02

Introduction:
Integrity test is a fundamental requirement of critical process filtration applications, including bubble point test, diffusion test and water intrusion test (also called HydroCorr). The most widely used integrity test is the bubble point test. Bubble point is based on the fact that liquid is held in the pores of the filter by surface tension and capillary forces. The minimum pressure required to force liquid out of the pores is a measure of the pore diameter.
In bubble point test, it is necessary to wet the filter with appropriate fluid, typically purified water for hydrophilic membranes or a 60/40% IPA/water mixture for hydrophobic membranes. The accuracy of automated integrity tester and leak-tightness of filter should be checked and assured prior to use. Besides, inlet pressure should also be assured at 5~7 bar, and testing temperature at 20~25℃.


Materials:
Stainless steel housing, cartridge, pressure gauge, clean compressed air, water tank (for solvent), stainless steel fitting, pump, automated integrity tester, adjacent piping, etc.. (Please see the picture below)



Procedure:
Wetting Procedure
(Take cartridge with 0.22 um hydrophilic membrane for example)
1. Finish the system above.
2. Close valve 1 and valve 3; Open valve 2, valve 4, vent valve and water pump; control valve 4 and close vent valve until water seen in the vent valve. Then begin to flush the cartridge.
3. Open valve 4 completely to flush for 5 to 10 seconds, and then control valve 4 to make pressure ranging from 4 to 4.5 bar displayed in pressure gauge 1. And flush at more than 5 L/min per 10-inch cartridge, for more than 10 minutes. Cartridges can be wetted more completely and results can be more accurate with higher flow rate and longer time when flushing.


Advantages:

● The membrane disc could be wetted more thoroughly and easily to ensure accuracy.
● Cleanliness of cartridges could be ensured.


Integrity test
Partially close water pump, valve 2 and valve 4; open valve 3 and connect filter and integrity tester. Then open valve 1 to start the test. It’s recommended to start diffusion test first and then bubble point test.


Attention:
1. Cartridges should be wetted thoroughly. Otherwise, restart this test after thorough wetting.
2. A bubble point value lower than the specification is an indication of one of the following:
● incompletely wetted membrane: re-wetting the membrane
● non-integral membrane or seal: check O-ring
● structure damage after cartridge use.

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