A screw conveyor intended and formed for use in a decanter centrifuge for separation of solid particles from a fluid compound, comprising a central body, at least one conveyor thread and at least one baffle bridging a flow path formed between different parts of the conveyor thread. The screw conveyor has at least two originally separate parts, each of which comprises a portion of said conveyor thread and which are kept together axially. The baffle constitutes a separate member arranged to be kept in place between said parts of the screw conveyor, when these parts are kept together axially, and has a portion which forms a part of the conveyor thread in an area where the conveyor thread intersects with and extends past the baffle.