For quality control and quality assurance of filter media, the bubble point test has been the standard for many years. It is used to determine the diameter of the largest pore in a filter medium. This is done by translating the pressure value measured in a laboratory test into a pore diameter value using a predefined capillary pressure constant. These capillary pressure constants – determined according to the bubble point pressure standard BS 3321:1986-02-28 – relate specifically to circular pores. But in reality, due to the way they are constructed, this is not the case for woven filter meshes. As a result, for woven meshes, the linear correlation between measured pressure and pore size using the standard constants has so far only allowed relative statements to be made about the actual pore size – even when using the capillary correction factor C, which was specifically introduced to cater for random pore geometries. Consequently, to get an absolute value for the diameter of the largest pore, time-consuming screenings were always necessary. Now, through the simulation of the bubble point test and the application of capillary pressure constants determined from the simulation, GKD – GEBR. KUFFERATH AG (GKD) has found a method with which the maximum pore size for all standard woven meshes can be precisely established in no time at all. But the international technology leader for woven filter media uses these “Computational Fluid Dynamics” (CFD) tools for more than just quality control. The method is also uniquely suitable for purposeful development of new precision filter meshes or for application-specific adjustment of existing woven mesh types to meet customer-specified bubble point values.
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