Abstract: A high temperature bolting system for clamping steam turbine housings and similar high temperature parts together while operating at a temperature of 800° F. to 1200° F. An elongated fastener shank and housing material have similar coefficient of thermal expansion. The shank has a tensile strength several times greater than the housing to maintain a clamping force during thermal excursions. The diameter of the shank is reduced due to the large creep strength difference between the elongated fastener shank and the clamped parts. The reduced shank diameter allows an increased in the clamping load by providing an increased surface area in the clamped part. A stress generating flange is provided with jackbolts to establish the clamping load at room temperature. A threaded sleeve is interposed between the threads at the end of the shank and the threads of the housing so that the housing threads have a sufficiently large area for withstanding the clamping load.

Abstract: A high temperature bolting system for clamping steam turbine housings and similar high temperature parts together while operating at a temperature of 800° F. to 1200° F. An elongated fastener shank and housing material have similar coefficient of thermal expansion. The shank has a tensile strength several times greater than the housing to maintain a clamping force during thermal excursions. The diameter of the shank is reduced due to the large creep strength difference between the elongated fastener shank and the clamped parts. The reduced shank diameter allows an increased in the clamping load by providing an increased surface area in the clamped part. A stress generating flange is provided with jackbolts to establish the clamping load at room temperature. A threaded sleeve is interposed between the threads at the end of the shank and the threads of the housing so that the housing threads have a sufficiently large area for withstanding the clamping load.

Abstract: Jackbolts for multi jackbolt tensioner embody a thread construction which taper from a maximum diameter adjacent to torque receiving end of the jackbolt when threadedly engaged with a threaded opening in the outer peripheral part of a jackbolt body. The threads of the jackbolt have a different thread pitch than the threads in the jackbolt body and the tooth flank of the jackbolt threads for an angle with the tooth flanks of the thread in the jackbolt body. By this thread construction, there is formed a helical volume of ever increasing size along the jackbolts commencing at a metal to metal relation at the torque receiving end. Stressing of the jackbolt closes the helical volume bringing the threads to a metal to metal load transfer relation. The end of the jackbolts has a protruding central end portion that elastically flattens under stress to reduce torque requirements.