ASME VIII Div 2 Factored Load Combinations 2

[PeterSleet]

Can anyone tell me why the Global criteria required factored load combination in table 5.5 is higher than the local criteria one and could be higher than the hydrostatic test one.

 

[TGS4]

They are based on two different failure modes. The global criteria are based on paragraph 5.2.4. The local criteria are based on 5.3.3.

You should also note that there is an error in those tables, and these errors will be corrected in the 2009 Addenda. The combinations should be:
2.4(P+Ps+D)
2.1(P+Ps+D+T)+2.7L+0.86Ss
2.1(P+Ps+D)+2.7Ss+(1.7L or 1.4W)
2.1(P+Ps+D)+2.7W+1.7L+0.86Ss
2.1(P+Ps+D)+1.7E+1.7L+0.34Ss

Your question about the factor for hydrostatic test conditions requires a thorough understanding of Part 8. Have you read through Part 8?

 

[PeterSleet]

Thanks TGS4 I now understand the difference between the local and global failure modes.
Despite rereading Part 8 several times I still don't understand why the Factored Load at test could be less than the operational Factored Load.
I should say that I'm more used to working with API 6A and I'm only looking at this because the analyst doing the FEA for this project is insisting that the entire ASME VIII division 2 is applicable because 6A references Appendix 4 of the 1998 edition in one place. Whilst I'm on the subject did Appendix 4 become part 4 in the new edition?

 

[TGS4]

No. Most of the rules that were contained in the old Appendix 4 are now contained in Part 5. The rules from Appendix 5 are also in Part 5. However, the rules have changed significantly - as you have pointed out.

 

[PeterSleet]

Thanks for your help. I guess I now need to find an old copy of ASME VIII division 2.