Support with rotary symmetric openings for filter aid, method and apparatus

Claim 1

In a process of filtering fluids utilizing as the active filtering component a layer of filter aid particles settled directly on and supported by a sheet-metal support provided with openings for passage of the filtered fluid moving through said filter aid layer, said filter aid particles being from the group comprising kieselguhr and other particles with similar irregular surfaces which promote bridging and are smaller in particle size diameter than the smallest diameter of said openings, wherein the liquid to be filtered is introduced on the side of said filter aid layer opposite said support and removed downstream of said support, the improvement of using as said support a support penetrated by a multitude of rotary symmetric openings of circular cross-section throughout their length and having a diameter of their narrowest point in the range of 50 to 250 microns, the walls of said opening making an angle of less than about 20° with the opening axis, whereby the particles form bridges over the openings in the configuration of dome-shaped arches, and said support provides around the margin of each such opening a generally flat stable bearing surface for supporting the end of said dome-shaped arch and having a width at least corresponding to the opening diameter, whereby said filter aid layer exhibits an increased stability to breakdowns of said bridges due to sudden pressure changes in the unfiltered fluid or high pressure drops over said layer.