Abstract: Stud bolts are threaded into the body of a nuclear reactor vessel and tenned by exerting forces on tensioning nuts located on the upper end of the studs. While the studs are under tension, a cover is attached to the vessel by tightening nuts on the studs against the cover. The tensioning nuts are applied to the studs by immobilizing the studs axially and rotationally, and rotating the tensioning nuts with a pair of driven, diametrically opposed striking rollers. External threads on the striking rollers, external threads on the nut and internal threads on the nut all have the same pitch so that the threads on the striking roller remain engaged with the external threads on the nut as the nut moves axially while being threaded onto the immobilized stud.

Abstract: Apparatus for screwing, unscrewing, and handling large bolts such as stud bolts for the cover of the core tank of a nuclear reactor. A circular guide rail is positioned above the periphery of the core tank. A main chassis is suspended from and movable along the guide rail. The main chassis includes two vertical beams and a plurality of horizontal guide beams which extend over the core tank periphery toward the interior thereof. A secondary chassis includes a number of bars which cooperate with the guide beams to permit horizontal movement of the secondary chassis in a direction substantially perpendicular to the direction of movement of the main chassis. A screwing mechanism is vertically movable on the secondary chassis and includes a gripping device for gripping the screw and a jack for compensating for the weight of the screw. A second gripping device can be included for gripping a washer.

Abstract: Device having movable jaws for gripping the shank of a pin or bolt is provided with ridges or grooves on the jaws which mate with corresponding ridges or grooves on the shank. The jaws are mounted to slide toward and away from each other and this sliding movement is induced by linkage pivotally connected to the jaws. An abutment is provided for limiting the movement of one of the jaws so that actuation of the linkage causes movement of said one jaw until it strikes the abutment followed by movement of the other jaw.

Abstract: Hydraulic device for exerting a pre-stressing traction on bolts or pins comprises three stages, with each stage comprising a piston within a chamber. The thickness of the skirts of the piston increases from stage to stage in proportion to the pressure to which the piston of that stage is subjected during a stretching operation.