Should Bolt Preload be classified as a Primary and Secondary Stress?
Should Bolt Preload be classified as a Primary and Secondary Stress?
(OP)
I seek advice whether bolt preload should be included as a primary stress when performing an assessment using the stress limits of ASME VIII Div 2 Appendix 4. Should bolt preload be included against the general primary membrane, and membrane plus bending stress limits of ASME 4-133 and 4-134, or is preload a seconadry stress?
I note that ASME VIII Appendix 4 Subsection 4-141 gives the allowable stresses limits to assess the bolt itself, which includes preload. However, should the preload be included as a primary stress when assessing the remainder of the vessel?
Thanks for your help, any advice or references would be appreciated.
I note that ASME VIII Appendix 4 Subsection 4-141 gives the allowable stresses limits to assess the bolt itself, which includes preload. However, should the preload be included as a primary stress when assessing the remainder of the vessel?
Thanks for your help, any advice or references would be appreciated.





RE: Should Bolt Preload be classified as a Primary and Secondary Stress?
RE: Should Bolt Preload be classified as a Primary and Secondary Stress?
I have performed a stress analysis of the component using FE software. Would I be correct to include the calculated stresses due to preload, in the assessment of the shell and head, according to the primary stress limits?
I wasn't sure whether preload should be classed as producing secondary stresses?
RE: Should Bolt Preload be classified as a Primary and Secondary Stress?
When you go to the design condition with pressure applied, of course bolt preload is not any more considered as, at least for a flange per App.2 (gasket inside the bolt circle), the preload is cancelled by flange deflection (once again you can check this in App.2).
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RE: Should Bolt Preload be classified as a Primary and Secondary Stress?
I have looked up Appendix 2 and indeed I see that ASME states that preload (gasket seating load) should be considered separately to operating conditions. The worst case should then be considered. I also note that it there are even more cases to consider when a tube sheet is included, to identify the worst case loading.
Thanks very much for your help to resolve my query.