Backpressure grid plate for pressure filtration system

In a pressure filtration system of the type comprising a housing with an inlet and outlet for conducting a pressurized fluid to be treated, a filter disposed in said housing between said inlet and outlet, and a backpressure grid means arranged between said filter and said inlet, the improvement wherein said backpressure grid means comprises a plate containing minute openings which conduct fluid onto said filter, said openings being equal in size and distributed unevenly over the surface area of the plate in such manner that the surface distribution density of a plurality of the openings within an inner impact area of the plate which receives inflowing fluid to be filtered is substantially lower than the surface distribution density of a plurality of the openings within a proximity area of the plate located immediately adjacent to and surrounding the impact area;

• the surface distribution density of a plurality of the openings within an outer area surrounding said proximity area is lower than that of said proximity area and higher than that of said impact area.