Patent ID: 7954550

Claim:
A downhole tool operable with hydraulic pressure, comprising: a housing having a passage therethrough between connections for mounting to a tubing string and at least one control system connection for delivery of hydraulic pressure; a movable element in said passage exposed to pressure therein; an actuation system responsive to the pressure delivered to said control system connection for selectively moving said movable element; said movable element comprises a flow tube mounted for reciprocal motion for rotation of a flapper mounted in said passage by selective pressure application to said control system connection; flow tube seals disposed between said flow tube and said housing to put said flow tube in pressure balance from pressures in said passage; said control system further comprises an operating piston connected to said flow tube between said flow tube seals, said flow tube seals isolating said piston from pressure in said passage; said flow tube seals are mounted to either or both said housing and said flow tube; said piston comprises identical spaced piston seals exposed to passage pressure if at least one of said flow tube seals contacting said flow tube fail; a portion of said piston between said piston seals is in pressure balance to passage pressure if at least one of said flow tube seals contacting said flow tube fail.