| 摘要 |
The following invention relates to an actuator for controlling a valve (100) in a subsea installation, the valve having a spring (108) to return the valve to a failsafe condition upon loss of pressure. The actuator comprises an actuator module (10) that is exchangeably connected to the valve and comprising a cylinder with a movable piston (14), the piston being mechanically connected to said valve element, a fluid pump (47) operatively connected to said hydraulic cylinder, said pump adapted to supply fluid through a first hydraulic line (36) operatively connected between said hydraulic cylinder and said pump, said hydraulic line supplying a sufficient pressure to move the piston to said second position to cause the valve element to move to its second position, and a second hydraulic line (48) providing a fluid passage between the first hydraulic line and a reservoir (44) whereby a bypass control unit (39) is located in said second hydraulic line and comprising a movable element operating to open or close said fluid passage through the second hydraulic line providing a failsafe function to the valve. According to the invention a third hydraulic line (49) is connected to the second hydraulic line and acting on the movable element, forcing the control unit towards opening said passage. |
