Abstract: The present invention relates to a screen cylinder for screening fiber suspensions of the wood processing industry. The screen cylinder comprises a rotationally symmetric screen surface located on the side of the pulp to be screened, and support rings supporting the screen surface on the opposite side; the screen surface mainly comprising grooves and screen apertures in connection with the grooves, the grooves being comprised of a side surface on the upstream side, a bottom surface, and a side surface on the downstream side, characterized in that the bottom surface of the groove rises towards the side surface of the upstream side.

Abstract: A fiber suspension, such as an in a pulp mill, is treated in an manner which minimizes both the investment and the operating costs associated with a screening plant. A single pump has an outlet connected to a knotter and primary and secondary screening states so that the pump provides substantially the sole motive force to the pulp moving it through the knotter and screening stages. The knotter and screening stages are provided in a common housing with the knotter vertically above the screening stages, and the screening stages one above the other. A single motor may be provided to rotate rotatable elements associated with the knotter and screening stages. The knotter may be connected to a knot washer external of the housing by a valved conduit less than two meters in length, and the secondary screening stage can be connected to a tertiary screening stage exterior of the housing by a valved conduit less than two meters long.