| 摘要 |
A screen cylinder or plate with a screening surface (11) for separating accepts from rejects, the surface including a number of parallel macro grooves (22) and a number of parallel micro grooves (24) formed within each macro groove generally transverse to the flow direction. The macro grooves induce shear stress in the reject material preventing it from forming a mat on the screening surface. The micro grooves induce micro turbulence into the pulp at the screening openings (27) improving accepts flow through the openings. Each micro groove within a macro groove is located further away from the accepts surface (12) moving in the flow direction. The contour of each micro groove preferably includes an upstream wall (39), a sloped downstream wall (40), and a depression (41) therebetween. The screening openings are provided in the depression. It is possible to screen with a rejects rate of about 3-10 % at debris removal efficiency of above about 85 %.
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