ASME "U/U2" certification requirements for vessel under fatigue loading.

[Vitalis 1977]

Hello everybody, greetings from Greece.
I would really appreciate your replies on the following matter which troubles me a lot.
During bidding phase of a project, client requested for an ASME VIII Div.1 vessel c/w with internally welded perforated plate to be ASME "U" certified and also "the whole vessel" to be "calculated" under given cyclic loading (fatigue).
Section VIII division 1 allows the designer to choose the best method that the Authorized Inspector will agree to, for conditions not covered specifically in the Code. For instance, for regular fatigue, ASME Section VIII div 1 does not provide a method to perform the calculations, but U-2 and UG-22 require the designer to account for their effects. ASME VIII div.2 part 5, (design by analysis) provides fatigue evaluation for components subjected to cyclic operation on the basis of the number of applied cycles of a stress or strain range.
My queries are the following:
1)Should we inform potential client that vessel will be ASME "U2" certified (not "U") and its design code will be ASME VIII Div.2 ?
2) Neither PVELite, nor Autopipe vessel software takes into consideration internally welded perforated plate as part of the whole assembly when vessel is analyzed as per ASME VIII Div.2 under fatigue loading. I assume that special FEA software has to be utilized for this component and separate report will have to be issued. This way the " whole vessel" calculation requirement is not covered.How can i overcome this issue?
3) If FEA software is applied for the calculation of the whole vessel (including perforated vessel)under cyclic loading and since FEA software does not take under consideration ASME VIII Div.2 requirements, what will ASME inspector expect from me in terms of design calculation reports in order to issue ASME "U2" certification?
Please provide assistance on these complicated (at least for me)issues since I'm in a big confusion.
Thank you in advance.

 

[Geoff13]

Your vessel can be Division 1 certified.

U-2(g) requires you to use equally safe rules when Division 1 has none. Use of the Division 2 rules in this case is what I've always done. The fact that I elect to use the Division 2 rules to meet U-2(g) and UG-22(e) does not change the fact that it's a Division 1 certified vessel.

 

[TGS4]

If you have access to the 2019 Edition of the Code, this process is much more clear. See the revised U-2(g) and the new Appendix 46 (some additional information on this)

As already mentioned, you are building a Division 1 vessel, but using additional rules to supplement where there are none in Division 1.

Specific to your inquiries:
1) No - design and build the vessel to Division 1 "U" stamp.
2) You will design your vessel using whatever software you typically use, and then use specialty software (typically FEA, but not necessarily) to check whether or not the vessel, as designed, will achieve the fatigue requirements.
3) You will need to get an engineer who specializes in this type of work involved, who can assist you to guide you through the specifics. Most fabricators will sub-contract this work to a specialty firm who performs such work.

 

[Vitalis 1977]

Geoff13, TG24, I appreciate your replies.
TG24, I will proceed with the purchase of latest issue of ASME VIII Div.1.
To my understanding, for query 1, revised U-2(g) and the new Appendix 46 of Div.1 code handles this issue and dictates the utilization of ASME VIII Div.1 for these types of vessels. Am'I correct?
Pressure vessel software does not calculate internal perforated plate under fatigue loading whereas FEA software calculates the whole vessel including this plate under the same loading. Given that, your reply on query 2 is not comprehensible in terms of special software utilization. It will be a supplementary calculation to the pressure vessel calculation only for the internal part or for the whole vessel?
Also what happens if code calculations are different than FEA calculations for all the vessel (excluding internal plate)?
Finally, concerning your reply on issue 3, of course a specialist is required. My question was concentrated on what ASME inspector expects in terms of design calculation report in order to issue ASME "U" certification. To my understanding, since typical pressure vessel softwares do not cover the whole vessel,only FEA results can be provided (without of course ASME code reference). Am'I correct?
Thank you advance and I hope I didn't trouble you much.!!

 

[TGS4]

Use the Code calculations as your first pass to determine thickness. Then check to see if that thickness satisfies the fatigue requirements. Only if it does not, then you will need a higher thickness.