To achieve good separation performance, the interface between the light and heavy phases, which has a significant effect on separation, must remain at the appropriate position. The position of the interface is mainly adjusted through the variable diameters of the heavy phase weir, the design of which is very important. The relation between the diameter of the heavy-phase weir and the interface position can be calculated. In Fig. 2, the dashed and dotted line refers to the medial axis; Rh is the heavy-phase weir radius, mm; Rl is the light-phase weir radius, mm; b is the heavy- phase channel width, mm; Rn is the interface radius, mm; and R is the inner radius of the rotor, mm.