ASME 8 Div. 2 Fatigue analysis 1

[Danybony]

Hello! I have a vessel with the following characteristics: design pressure=12 bar, operating pressure=8 bar, pressure cycle duration (0-8-0 bar)=18 min, life=20 years. If I'm not wrong, I should perform a fatigue analysis in accordance with ASME 8 Div. 2. I'd like to know, according to your opinion/experience, which is the best way to carry out that analysis.

Thank you.

Daniele

 

[TGS4]

Yes, you need to perform a fatigue analysis. Unless you've done this before, please find an experienced engineer to do this for you. Hire a consultant, etc, but don't attempt yourself unless you have a VERY good mentor who will help you every step of the way.

 

[Danybony]

Thanks for your answer TGS4. I'd like to know, according to your experience or anybody else's, which are the possible analysis techniques that can be used to carry out the fatigue analysis (software): FEA for example? Thanks again!!

Daniele

 

[ColonelSanders83]

When perfoming fatuige analysis in accordance with ASME Section VIII Div 2 we always use FEA. Depending on your vessel and geometry this can become quite the daunting task, especicially if you run into problems.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/

 

[Metaljon]

Yes FE analysis is a good start. After FEA, develop a linear elastic model of the structure which includes the critical design features and weldments. Then determine the relevant loading conditions and determine the resultant pseudo elastic force. Calculate the stress caused by the applied displacement. The stresses calculated are usually pseudo elastic stresses. Without any plasticity correction, enter the fatigue design curve with the calculated pseudo elastic stress and determine the permitted cycles. As indicated in the other posts above it is not a trivial exercise and best left to an experienced consultant.