A centrifugal pulp screen device including a perforate wall cylindrical screen, an outer enclosing housing, a centrally located stock supply conduit and a distributor for the stock including an annular distribution slice opening having a fixed lower lip and movable upper lip with the slice discharging against fixed angular vanes which direct the stock in a spiralling centrifugal flow along the inner surface of the screen with the volume of flow controlled by adjustment of the slice opening and the velocity controlled by a variable delivery supply pump and the velocity affecting the spiralling centrifugal action by impact of the stock against the vanes. A corresponding method for screening the stock is also disclosed.