Abstract: An improved apparatus and process for fractionating pulp suspensions consists of multiple interchangeable modular treating compartments stacked atop one another. Pulp suspension is fractionated in the first compartment, and one of the two resulting fractions flows gravitationally to a second compartment where it is fractionated further. Any of the resulting fractions may be fractionated still further in subsequent compartments as many times as desired. The treating compartments are interchangeable, so removal, addition, or replacement of compartments is relatively easy and quick. Fractionation in each compartment is carried out through centrifugal force.

Abstract: An assembly for straining of pulp suspensions and the like comprises a strainer drum (1) mounted in a strainer house (2). One or a plurality of devices (5-9) are provided, in order to free impurity particles from fibers, preferably designed like an impact plate, in the strainer house (2) in the flow path, so that the particles in the stream partly are subject to an impact action, and so that the stream is subjected to a variation in velocity.