A centrifugal separator (10) includes a rotor shroud (24) which reduces the fine scale mixing of liquid components. The rotor shroud (24) minimizes liquid-liquid shear, but does not adversely affect the pumping action of the rotor (14). The separator (10) comprises a housing (12) having a cylindrical inner surface defining an interior chamber. A hollow rotor (14) is rotatably disposed within the chamber, the rotor (14) having upper and lower (28) openings and a cylindrical rotor wall with an inner and outer surface. The outer surface of the rotor wall is spaced apart from the inner surface of the housing (12) and thereby defines the annular mixing zone (18). The rotor shroud (24) comprises a cylinder only slightly larger than the rotor (14). The shroud (24) is fixed relative to the housing (12), thereby preventing liquid within the annular mixing zone (18) from contacting the rotating outer surface of the rotor (14). The reduction in mixing action increases the separation efficiency for shear-sensitive liquid mixtures.
