Electrically Operable Rotary Actuator Assembly

An electrically operable rotary actuator assembly is disclosed for opening and closing a rotary gate valve. The assembly comprises an operating shaft for operating the valve, an electrically operable actuator for imparting a rotational drive to the shaft to cause the shaft to rotate from a first rotational orientation to a second rotational orientation and biasing means for imparting a rotational bias to the shaft to cause the shaft to rotate from the second rotational orientation to the first rotational orientation. The assembly further comprises a clamp arrangement for clamping the shaft in the second rotational orientation.