The separator consists of a feeding section provided with compensator tank and overflow hopper. The stainless steel casing includes a conveyor screw (inside a cylindrical screen basket) for material transport towards the outlet. The screen provides the separation of the solid from the liquid phase flowing through by pushing the solids towards the outlet where two counter-pressure diaphragms generate a material plug. This allows automatic operation of the separator and avoids flushing through of the liquid phase.