Preparing for Integrity Testing
Before integrity testing, it is necessary to ensure that the test filter material has been fully wetted. The method of manual infiltration is generally: put the filter material into the infiltration solution and fully infiltrate it for about 20 minutes, and lift the filter material every 3 minutes to remove air bubbles so that the atmospheric pressure will press the infiltration hydraulic pressure into the membrane pores. Product infiltration liquid does not refer to water, nor a product or process fluid, but a solvent. After infiltration of the product, the integrity test results of the same filter material may be different. The reason for their difference is the infiltration of the product. The surface tension coefficient of the liquid is different. The solubility and diffusivity of the test gas in the diffusion stream can also cause inconsistent test results. For this system, the recommended infiltration fluid is fluorocarbon, absolute ethanol, or a 60% isopropanol and water mixture. Due to the molecular attraction of the interfacial tension, the infiltrating liquid is firmly locked in the microporous gaps of the filter material.
Bubble point testing of integrity testing
When the gas pressure on the high-pressure side of the sample is greater than the capillary pressure and surface tension in the sample membrane pores, it is released from the other side of the sample, and the infiltrating liquid in the capillary pores will be pressed out by the gas pressure to the low-pressure side of the sample. The pressure on the side is regarded as the bubble point pressure, and the phenomenon at this time should be the first series of continuous bubbles in the sample.