Abstract: The subject matter of this specification can be embodied in, among other things, a valve assembly that includes a valve body having a fluid inlet, fluid outlet, and a movable closure member adapted to block fluid flow from the inlet to the outlet through a housing. The housing has an opening adapted to receive an actuator assembly that includes a central stationary shaft having at least one stator vane. A rotating collar is disposed around the stator vane and a portion of the central stationary shaft. The rotating collar has a housing and at least one stop member disposed inwardly in a cavity of the rotating collar. The rotating collar has at least two actuation chambers defined by the inner wall of the cavity in the rotating collar, the stationary vane, and the stop member. The rotating collar is coupled to the movable valve closure member.