SWITCHING APPARATUS BETWEEN INDEPENDENT CONTROL SYSTEMS FOR A SUBSURFACE SAFETY VALVE

摘要

A system is provided for switching between redundant control systems for a subsurface safety valve (SSV) while being able to isolate the closure spring from hydrostatic pressure in the control line of the system that is not being used. There are two control lines that connect to discrete operating pistons that are both coupled to the flow tube. Each operating piston is connected to a control rod with the control rods terminating near opposed ends of a pivoting member. Pushing down on one rod pushes up on the other rod so that the other rod is held supported and the hydrostatic pressure in its associated control line doesn't affect the force needed by the closure spring to close the SSV. Releasing control line pressure puts the system in neutral to allow either of the systems to be reselected.