Patent ID: 8616292

Claim:
An apparatus for connection in a tubing string at a subterranean location in a well and for preventing the torque transmitted by the apparatus from exceeding a specified magnitude, comprising: a tubular body having a passageway therethrough and having first and second ends mounted to rotate relative to each other; means on the ends of the body for connection in a tubing string; a piston assembly having a passageway therethrough mounted in a chamber in the body for movement into and out of an engaged position, coupling the first and second ends to rotate together and transmitting torque between the ends of the body, the piston assembly comprising a resilient member and pressure relief valve; and a hydraulic fluid in the chamber in the body locking the piston assembly in the engaged position and the pressure relief valve in fluid communication with the hydraulic fluid releasing the piston assembly to move from the engaged position when the specified torque magnitude is exceeded.