The present invention provides a pump system comprising a bearing housing coupled to a pump liner, the pump liner defining a fluid conduit, the pump liner comprising a fluid inlet and a fluid outlet; and at least one rotor having a first rotor portion and a second rotor portion, the first rotor portion being disposed within the fluid conduit and the second rotor portion being disposed within the bearing housing; the first rotor portion comprising a first conveying stage adjacent to the bearing housing, and a second conveying stage adjacent to the first conveying stage, the first and second conveying stages being configured to convey a fluid, the first conveying stage being configured to convey the fluid from the bearing housing into the fluid conduit. The new pump systems rely on a dynamic restriction to reduce the need for mechanical seals between bearing housings and raw process fluid.