Abstract: A housing defining a generally cylindrical chamber is provided and the chamber is closed at one end. Inlet structure is provided for admitting fluid flow suspended materials into the chamber intermediate the opposite ends thereof and in a direction extending generally tangentially of the chamber. A tubular vortex finder opens centrally into the housing through the closed end thereof and a generally frusto-conical closure wall is provided at the other end of the chamber and opens toward the closed end thereof. The apex of the closure wall defines a restricted outlet and the tubular vortex finder includes an open inlet end opening toward the outlet and spaced intermediate the closure wall and the inlet structure. The inlet structure is fixed in position longitudinally of the housing, but the frusto-conical closure wall and vortex finder are supported relative to the housing for independent adjustment relative thereto in a direction extending longitudinally of the chamber.