Screw conveyor of Decanter Centrifuge

The screw conveyor (or scroll) is in the form of an Archimedian screw. fitting inside the beach and bowl between the two end hubs, with a small clearance of less than 2 mm radially. It has a number of functions. Not only does it convey the solids, after they form a cake. along the cylindrical bowl section and up the beach, it also accepts the feed and accelerates it up to bowl speed.

In its simplest form, the conveyor has a cylindrical central hub with a set of flights welded onto it, to form one continuous helix. The conveyor bearings and associated seals are housed in both ends of its central hub. Somewhere in between the bearings will be a chamber called the feed zone, sealed and isolated from both bearings.

The conveyor flights are normally protected against wear by means of an abrasion resistant material such as stellite, wear resistant alloys or sintered tungsten carbide tiles. The feed slurry is introduced into the decanter through feed openings in the conveyor body.

The conveyor rotates slowly relative to the bowl thus conveying the sediment towards the solids discharge openings in the small end of the bowl. The axial advancement of the flight in one turn is the pitch. The conveyor usually is single flighted, but some have double (two start) flights. e.g. for olive oil process. The flights are either perpendicular to the centre line or have a forward inclination (canted flights).