Subsea valve actuator and method

A method of assembling a subsea valve actuator for controlling a valve stem for use with a gate valve having a bonnet, said valve stem being operable for moving a gate of said gate valve between a first gate position and a second gate position for controlling flow through said gate valve, said method comprising:

• adapting an actuator housing to be removably securable to said bonnet;
• providing at least one hydraulic port into said actuator housing for controlling actuator housing internal hydraulic pressure;
• sealing said actuator housing so as to control internal hydraulic pressure within said actuator housing;
• providing a hydraulic cylinder having a cylindrical portion within said actuator housing;
• providing a spring within said actuator housing;
• positioning a spring lifter to be slidably moveable with respect to said hydraulic cylinder, said spring being positioned between said spring lifter and an interior of said actuator housing;
• sealing a hydraulic piston for use in said cylindrical portion of said hydraulic cylinder, said hydraulic piston having a first side and a second side, said hydraulic piston being moveable between a first piston position and a second piston position, said hydraulic piston being operatively connected to said valve stem for moving said gate between said first gate position and said second gate position;
• providing a first hydraulic passageway to said hydraulic cylinder for producing a first pressure on said first side of said hydraulic piston that when sufficient moves said hydraulic piston to said first position so as to move said gate to said first gate position;
• providing a second hydraulic passageway to an opposite end of said hydraulic cylinder for producing a second pressure on said second side of said hydraulic piston that when sufficient moves said hydraulic piston to said second position so as to move said gate to said second gate position, said second pressure being produced by said actuator housing internal hydraulic pressure;
• and
• providing a drift adjustment that is selectively adjustable in position with respect to said actuator housing, said spring lifter being mountable for movement with respect to said actuator housing in response to movement of said hydraulic piston, said drift adjustment limiting movement of said spring lifter and said hydraulic piston to provide selective adjustment of a gate valve drift of said gate for at least one of said first or second gate positions.

A subsea valve actuator for a valve with a bonnet and a valve stem, said valve stem being operable for moving a control element of said valve between a first valve position and a second valve position for controlling flow through said valve, said actuator comprising:

• a hydraulic actuator housing, said hydraulic actuator housing defining at least one hydraulic housing port to permit assist line hydraulic fluid into said housing;
• housing seals for said hydraulic actuator housing to permit production of internal actuator housing hydraulic pressure within an interior of said hydraulic actuator housing;
• a hydraulic cylinder within said hydraulic actuator housing, said hydraulic cylinder defining a line port for receiving hydraulic control line fluid;
• a cap for said hydraulic actuator housing monolithically formed with a cylindrical portion of said hydraulic cylinder and at least one of said housing seals being fitted around a portion of said cap for sealing an upper portion of said actuator housing, said cap defining said line port;
• a hydraulic piston slidably mountable within said hydraulic cylinder for movement between a first piston position and a second piston position, said hydraulic piston having a first side and a second side, said hydraulic piston being operably connectable to said valve stem for moving said control element of said valve between said first valve position and said second valve position, said hydraulic piston being moveable to said first piston position within said cylindrical portion in response to a sufficient first pressure produced on said first side of said hydraulic piston by said hydraulic control line fluid and in response to a sufficient second pressure produced on said second side of said hydraulic piston by said assist line hydraulic fluid;
• a spring lifter mountable surroundingly to said hydraulic cylinder;
• a spring mountable for engagement with said spring lifter at a first end of said spring and being supported within said hydraulic actuator housing at a second end of said spring;
• and
• said spring lifter containing at least one hydraulic flow path for flow of said assist line hydraulic fluid into said hydraulic cylinder from said interior of said hydraulic actuator housing.