Method for maintaining a clamping force between bolted parts in high temperature

A method for maintaining a clamping force between bolted parts while operating at a temperature of 800° F. to 1200° F., said method including the steps of:

• selecting an elongated fastener having a stress generator and a connector at opposite ends of a shank portion, the shank portion having a coefficient of thermal expansion similar to a coefficient of thermal expansion of such bolted parts to minimizing differential dimensional changes due to temperature variations, the shank portion, having an elastic limit sufficiently great for maintaining a clamping force between such bolted pats throughout a temperature range from ambient temperature to an operating temperature of between 800 degrees F to 1200 degrees F, the shank portion having a creep strength several times greater than the creep strength of such bolted parts at said operating temperature, said stress generator having a circular ring with a threaded central opening engageable with threads on an end portion of said shank portion and jack bolts threadedly engaged with said circular ring, said fastener having a slightly tapered thread with the maximum diameter thereof at a terminal end portion of the fastener for creating a differential thread pitch between said elongated fastener and said one of such bolted parts whereby stress concentrations shift along said connector from a site proximate the shank portion of the fastener to the site of said maximum diameter of the tapered thread of the fastener, said fastener further providing a hollow cavity having a form of a truncated conical wall with the maximum diameter thereof at the terminal end portion of the fastener for providing elasticity to more evenly contribute contact stressed between a male and female threads;
• installing the selected fastener to mechanically join such bolted parts;
• and
• operating the stress generator substantially at an ambient temperature to stress the shank part sufficiently within elastic limits thereof to maintain said clamping force at the operating temperature of between 800 degrees F to 1200 degrees F.

A method for maintaining a clamping force between bolted parts while operating at a temperature of 800° F. to 1200° F., said method including the steps of:

• selecting an elongated fastener having a stress generator and a connector at opposite ends of a shank portion, the shank portion having a coefficient of thermal expansion similar to a coefficient of thermal expansion of such bolted parts to minimizing differential dimensional changes due to temperature variations, the selected shank having an elastic limit sufficiently great for maintaining a clamping force between such bolted parts throughout a temperature range from ambient temperature to an operating temperature of between 800 degrees F to 1200 degrees F, the selected fastener shank having a creep strength several times greater than the creep strength of such bolted parts at said operating temperature;
• installing the selected fastener to mechanically join such bolted parts;
• operating the stress generator substantially at an ambient temperature to stress the shank part sufficiently within elastic limits thereof to maintain said clamping force at the operating temperature of between 800 degrees F to 1200 degrees F;
• and
• heating an internal cavity extending trough said stress generator and along at least a part of said shank portion to relieve said clamping force for removal of the stress generating flange from such bolted parts.