ASME STP-PT-036:2016 pdf free download

ASME STP-PT-036:2016 pdf free download.BOLTED FLANGED CONNECTIONS IN ELEVATED TEMPERATURE SERVICE.
The tests indicated that “Nut Distortion” accounted in general for less than 10% of the overall bolt creep occurring. Nut Distortion was the term used to describe the embedment and localized creep occurring in the nut to flange and nut to bolt thread regions. This value was determined as the residual delbrmaüon when the remaining elastic and creep strain at the end of the test was subtracted from the initial assembly strain of the bolt. The paper also recommends a preliminary soak at temperature and re-tightening of the bolts after the soak as a way of increasing the life of the joint due to the fact that the majority of the relaxation occurs in the first portion of the joint life.
Bailey continued his work on high temperature flange behavior by establishing elastic stress and deflection relationships for the joint components based on ring theory in Part I of Bailey 161. In Part II of the same paper he examined the high temperature behavior and listed a “Life Factor” for the joint (until leakage) that was equal to the ratio of the component sum of the initial elastic strains divided by the sum of the component creep strains, multiplied by the stress relaxation relationship outlined in Figure 2. The method outlined was based on the assumption that the joint life was determined by the relative component deformation (both elastic and creep). That is, once the creep deformation had reduced the elastic deformation by an appreciable amount, leakage would occur. He also found that. depending on the relative flexibility and creep rates of the pipe wall and flange huh, it may either reinforce the flange against creep or actually increase the creep deformation of the flange due to excessive diametrical growth of the vessel wall due to creep. Bailey also assumed that the effect of creep associated with shear stress was negligible and examined the effect of bolt holes in increasing the creep of the flange by testing perforated strips of mild steel at various ratios of drilled hole spacing. Bailey suggested the use of a factor ) to adjust for the effect of bolt holes on the strength of the flanges. The factor is a basic multiplier on flange deformation and was found, for standard BS piping flanges, to be approximately 1.17. He points to the need for creep results on flanges with the effect of bolt stress relaxation occurring. Initial results presented on C-O.5Mo material indicated that the 100,000 hr life of a joint corresponded to a similar stress level for a tensile creep test with 0.1% strain rate in 100,000 hrs.