Abstract: A centrifuge comprising an elongated rotary drum and a rotor journalled coaxially within the drum for rotation at a slightly different speed. Means are provided for supplying a raw material containing a solid and a liquid phase to the separating space defined by the drum and the rotor. The rotor carries at least two continuous screw helices for transporting solid matter axially towards one end of the separating space. An aperture is provided in each helix whereby the axial movement of at least some of the transported solid matter is temporarily stopped when that matter passes through the aperture. A washing liquid is supplied through openings in the rotor shortly upstream of each aperture for acting upon the solid matter during the period in which its axial movement is interrupted. The apertures in the helices are off-set relative to one another along the circumference of the rotor.

Abstract: A centrifuge for separating one or more liquid phases from a raw material, in which the liquid level in the centrifuge -- and in case more liquid phases are withdrawn separately also an interface between different liquid phases -- is determined by means of one or more inserts which are mounted in an outer wall of the centrifuge. The insert or inserts form part of a conduit or conduits through which the liquid phase or phases are withdrawn via a chamber in which a stationary skimmer disc is mounted. The inserts are accessible and replaceable from the outside of the centrifuge so that the liquid level or levels referred to may be varied by replacement or radial adjustment of the inserts after the centrifuge has been stopped, without dismantling any other parts of the centrifuge.