| 摘要 |
Actuators for subsea downhole chokes have tended to include hydraulic pistons which are prone to failure and crude in accuracy. The invention provides an actuator (1) having first and second rotary motors (2, 16) and an output region (3) arranged to engage a load, such as a choke sleeve. In a first mode of operation, the first rotary motor (2) imparts linear motion to the output in a first screw connection (4, 5). In a second mode of operation, the second rotary motor (16) imparts linear motion to the output via a second screw connection (12, 14). The provision of screw connections permits gradual linear motion of the output to be achieved. The provision of two motors permits continuing performance in the event of failure of one of the motors. |
