Subsea actuator with override function, as well as a method of operating an actuator

It is described a subsea electric actuator (100) operating a linear valve (200), the actuator (100) comprising a roller-screw (2) for translating a rotational movement of a motor (3) to a linear movement of a gate rod (4) operating the valve (200), the actuator (100) comprising: -an actuator housing (101); -an outer roller screw part (2′) rotationally connected to the motor (3) and comprising internal threads forming a first part of a first connection (10), -an inner roller screw part (2″) comprising external threads forming a second part of the first connection (10) and being arranged inside the outer roller screw part (2′), a surface of the inner roller screw part (2″) having a first interface forming a first part of a second connection (20′; 20″) connecting the inner roller screw part (2″) to a non-rotational part of the actuator (100), the second connection (20′, 20″) is configured to rotationally lock the inner roller screw part (2′) giving linear movement of the inner roller screw part (2″) when the outer roller screw (2′) is rotated, -a gate rod (4) arranged axially movable inside the inner roller screw part (2″), the external surface of the gate rod (4) comprising an interface forming a first part of a third connection (30′; 30″), -an override housing (6) arranged outside the gate rod (4) and adjacent the inner roller screw part (2″) forming an axial stop for the inner roller screw part (2″), the override housing (6) comprising an interface forming a second part of the third connection (30′; 30″), and wherein, when the third connection (30′; 30″) is connected, the inner roller screw part (2″) is locked to the gate rod (4) such that the gate rod (4) follows any axial movement of the inner roller screw part (2″), and when the third connection (30′; 30″) is disconnected, the gate rod (4) is allowed to move in the axial direction relative the inner roller screw part (2″) such that the linear valve (200) can be operated independently of the motor (3), outer roller screw part (2′) and inner roller screw part (2″). It is further described a method of performing override of a subsea electric actuator (100).