Patent ID: 8302509

Claim:
A hydraulic bolt tensioning device for tightening and releasing highly loaded threaded bolts, the hydraulic bolt tensioning device comprising: a cylinder that is supported on a machine part that is to be clamped by a threaded bolt and a nut; an exchangeable bushing having a first end adapted to be screwed onto a free threaded end of the threaded bolt which free threaded end projects past the nut; a pressure-loadable tensioning piston that is seal-tightly guided in the cylinder and is supported on an extension of a second end of the exchangeable bushing; a pressure medium supply supplying pressure medium into an annular space between the cylinder and the piston; a control device for setting a nominal pressure of the pressure medium corresponding to a nominal pretension of the threaded bolt; a pressure relief device; a pressure sensor; a yield limit detection device for detecting that a yield limit of the threaded bolt is reached during tensioning of the threaded bolt; a controller acting on the pressure relief device for pressure relief of the bolt tensioning device at the time of reaching, or shortly after reaching, the yield limit of the threaded bolt being tensioned.