Abstract: A control system for a subsurface safety valve addresses normal open and closed operation and a failsafe operation if key system components fail. It features a single control line from the surface that splits at the subsurface safety valve and goes to one end of two discrete piston chambers that are aligned and isolated from tubing pressure. The piston in one chamber is larger than in the other and the pistons are connected for tandem movement. Each side of the unbalanced system's piston has a seal mounted to it and another for the rod attached to it that exits the chamber. A jumper line connects the chambers at a point between the seals in each chamber and features a large reservoir. The jumper line is filled with a compressible fluid. Fail safe closure of the valve occurs if any of the four seals fail.

Abstract: A control system for a downhole tool, such as a subsurface safety valve, features an operating piston that is insensitive to tubing pressure in the valve. The hydrostatic forces from the single control line from the surface are significantly reduced with a branch line to a piston bottom that is slightly smaller than the piston top. A variable volume between piston seals is connected to a low pressure compressible fluid reservoir to permit piston movement. The piston can be modular to facilitate assembly or bore offsets in the valve body. Failsafe closure upon seal failures is contemplated.

Abstract: A control system for a downhole tool, such as a subsurface safety valve, features an operating piston that is insensitive to tubing pressure in the valve. The hydrostatic forces from the single control line from the surface are significantly reduced with a branch line to a piston bottom that is slightly smaller than the piston top. A variable volume between piston seals is connected to a low pressure compressible fluid reservoir to permit piston movement. The piston can be modular to facilitate assembly or bore offsets in the valve body. Failsafe closure upon seal failures is contemplated.

Abstract: A control system for a subsurface safety valve addresses normal open and closed operation and a failsafe operation if key system components fail. It features a single control line from the surface that splits at the subsurface safety valve and goes to one end of two discrete piston chambers that are aligned and isolated from tubing pressure. The piston in one chamber is larger than in the other and the pistons are connected for tandem movement. Each side of the unbalanced system's piston has a seal mounted to it and another for the rod attached to it that exits the chamber. A jumper line connects the chambers at a point between the seals in each chamber and features a large reservoir. The jumper line is filled with a compressible fluid. Fail safe closure of the valve occurs if any of the four seals fail.

Abstract: A single-turn miniature potentiometer includes a first substrate having an annular conductive track formed thereon and a second substrate facing the first and having an annular resistive track formed thereon. An insulating layer is placed between the two substrates and has an opening provided therein for receiving a disk-like rotor which bears an electrically conductive wiper for simultaneously contacting both the conductive and resistive tracks. Electrical connections are made between the resistive and conductive tracks by means of external U-shaped clips.