ACTUATOR FOR A VALVE

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.

主权项

1: An actuator for a valve in a subsea installation, the valve having a valve element which is movable between a first position and a second position and a spring which biases the valve element toward the first position, the actuator comprising:
a hydraulic cylinder which includes a movable piston, the piston being mechanically connectable to said valve element; a fluid pump which is connected to said hydraulic cylinder through a first hydraulic line, said fluid pump being adapted to supply fluid to the hydraulic cylinder through the first hydraulic line at a sufficient pressure to move the piston and thereby move the valve element to the second position; a reservoir for storing a quantity of hydraulic supply fluid at a pressure that is less than said sufficient pressure; a second hydraulic line which provides a fluid passage between the first hydraulic line and said reservoir; a bypass control unit which is located in said second hydraulic line and which comprises a movable element that operates to open or close said fluid passage; first and second force generating means, both of which bias the movable element to a position to close the fluid passage; and a third force generating means which biases the movable element to a position to open the fluid passage.