A separator includes a first piston and a second piston both mounted on a drum assembly. The first piston is moveable between a first piston open position and a first piston closed position. In the first piston open position drum ejection passages are open for ejection of material from a maximum diameter of a separator volume, while in the first piston closed position the first piston blocks the drum ejection passages to prevent the ejection of material from the maximum diameter of the separator volume. A number of intermediate ejection paths are formed in the separator, each extending from an intermediate ejection path inlet at an intermediate region of the separator volume to an intermediate ejection path outlet. The second piston is moveable to alternately open or close the intermediate ejection paths for fluid communication to the separator volume.