Bubble Point Method Test Principle: When the filter membrane and filter element are completely wetted with a certain solution, pressure is applied to one side via a gas source (Our instrument has an intake control system to stabilize and regulate the intake pressure). As the pressure increases, gas is released from one side of the filter membrane, resulting in bubbles of varying sizes and numbers appearing on that side. The corresponding pressure value is determined by the instrument; this is the bubble point.
Diffusion Flow Method Test Principle: The diffusion flow test refers to the process where, when the gas pressure is at 80% of the filter element's bubble point value, a large amount of gas has not yet perforated the pores. Only a small amount of gas dissolves in the liquid phase of the membrane and then diffuses from that liquid phase to the gas phase on the other side. This portion of gas is called the diffusion flow.
Why the Diffusion Flow Method is Better: The bubble point value is only a qualitative value. The process from the initial bubbling to the final mass bubbling is relatively long and cannot be accurately quantified. Measuring the diffusion flow value, however, is a quantitative value. It can not only accurately determine the integrity of the filter but also reflect issues such as membrane porosity, flow rate, and effective filtration area. This is why foreign manufacturers use the diffusion flow method to test integrity.
Water intrusion test principle: The water intrusion method is specifically used for testing hydrophobic filter cartridges. Hydrophobic membranes resist water, and the smaller the pore size, the greater the pressure required to force water into the hydrophobic membrane. Therefore, under a certain pressure, the flow rate of water forced into the filter membrane is measured to determine the pore size of the filter cartridge.
