Abstract: A method for manufacturing a screen plate with screen slots from a thin plate (1), which screen slots (5, 13) are achieved by cutting. The plate is formed by bending to a screen plate of a desired shape. The screen slots (5, 13) are produced by a laser beam for cutting, which hits the plate from one of its sides, the inlet side. Focus for the beam is situated on a predetermined depth between both sides of the plate. The slot is obtained by at least two cutting operations following each other, in which the direction (3, 4) of the laser beam forms two different angles with the main plane of the plate. There is obtained a screen slot (5, 13), the cross section of which increases against the other side of the plate, the outlet side.

Abstract: In a pressure screening device for separating undesired particles from a fibre suspension a cylindrical screen (2) is provided. The screen has an outer side and an inner side and is provided with a plurality of projections (19) on the outer side of the screen (2) which extend in the circumferential direction of the screen (2), grooves (17) formed on the inner side of the screen (2) and extending in a direction having an axial component, and screening passages in the form of slots (18) disposed in the area of each groove (17) and diverging from the inner side of the screen (2) towards its outer side. According to the invention, the projections (19), grooves (17) and slots (18) of the screen (2) are produced by working of a substantially planar screen plate bent into cylindrical shape subsequent to the working. Thereby it is possible to form a screen (2) having uniform slots (18), the width of which at the inner side of the screen (2) is only about 0.1 mm.

Abstract: A hydrocyclone plant comprises a multiplicity of hydrocyclones arranged in groups of at least two hydrocyclones, each group being made in a single piece. The hydrocyclones extend substantially radially in an annular space for a liquid mixture to be separated. The inlet space extends concentrically around a cylindrical heavy fraction space for receiving a heavy fraction of the liquid mixture from the hydrocyclones. According to the invention, the hydrocyclone groups are distributed around the cylindrical heavy fraction space in the circumferential direction and are spaced from one another in the inlet space to allow the liquid mixture to flow between adjacent hydrocyclone groups.

Abstract: A hydrocyclone separator for separating a materials mixture into fractions with an upper covered cylindrical part and a lower concial part, the upper part having a tangential inlet, and an axial outlet on its cover; the lower part having an outlet at its bottom.A cylindrical shell or mantle surrounds the container to receive leakage. The shell and container form three compartments with individual openings in which are pressure-sensitive or other sensitive indicators to show the presence of leakage.

Abstract: A fibre-containing liquid is sprayed on the inlet side of a first strainer, there being a flow path for medium passing therethrough and leading from the outlet side of the strainer. A second strainer spaced from the first strainer covers said flow path and has mesh openings larger than those of the first strainer but small enough so that fibres passing through the first strainer, due to rupture thereof, will rapidly obstruct the second strainer.