Patent ID: 6041804
Filing Date: 2000-03-28
Classification: E21B,F16K,Y10T

Abstract:
A method of assembling a subsea gate valve actuator for operating a gate valve with a bonnet and a valve stem, said valve stem being operable for moving a gate of said gate valve between a first rate 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 in said actuator housing for controlling actuator housing internal hydraulic pressure;sealing said actuator housing for containing internal hydraulic pressure within said actuator housing;removably securing a hydraulic cylinder having a cylindrical portion to an end portion of said actuator housing, said end portion being distal with respect to said bonnet;providing a spring external to said hydraulic cylinder such that said spring is in surrounding relationship to said hydraulic cylinder, a first end of said spring being secured with respect to 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, said hydraulic piston being provided with an outer diameter less than an inner diameter of said spring;providing a first hydraulic passageway to a first side of said hydraulic cylinder for applying a first pressure to said first side of said hydraulic piston that when sufficient moves said hydraulic piston to said first piston position so as to move said gate to said first gate position; andproviding a second hydraulic passageway to a second side of said hydraulic cylinder for applying a second pressure to said second side of said hydraulic piston that when sufficient moves said hydraulic piston to said second piston position so as to move said gate to said second gate position, said second side of said hydraulic cylinder being in communication with said actuator housing internal hydraulic pressure; andproviding a spring lifter in telescoping relationship to said hydraulic cylinder such that at least a portion of said second passageway is provided through said spring lifter for communicating said actuator housing internal hydraulic pressure to said second side of said hydraulic cylinder to produce said second pressure at said second side of said hydraulic piston such that said second pressure is produced by said actuator housing internal pressure, said spring lifter being engaged with said spring at a second end of said spring.