Split backing rings to ASME RCB-5.141

[RonJeremy]

Is TEMA RCB-5.141 method valid for the split backing ring of a U-stamped exchanger? The method appears to permit the use of 100% moment instead of the 200% used in ASME div 1 App 2.9. The justification for that approach seems to be that certain geometries inherently resist bending as the backing ring rotates. While I understand the logic, I am unsure how the inspector would view that, being as App 2.9 specifies 200% moments, without exception.

Any thoughts would be appreciated.

RJ

 

[DG72]

The TEMA method is appropriate for a floating head BUR. Appendix 2 of ASME code is for designing flanges subject to pressure--the BUR does not see any pressure loads.

 

[gr2vessels]

Ron,
This topic has been discussed on this forum, last time sometimes last month.
The TEMA website ofers a Technical Inquiries page, related to the Eight Edition clarifications (note that the 9th edition will be mandatory in about a week time). TEMA has replied to your question by saying that the formula for bending is correct as is, doesn't have to be multplied by 2, due to limited rotation of the split ring. That should be sufficient to any recalcitrant AI and he should allow the U stamping. This is a very old issue and it has been accepted as per TEMA clarification long time ago. Have faith, the AI is not that bad, ask him.
Cheers,
gr12vessels

 

[RonJeremy]

Thanks both for your posts. I thought I'd seen a thread but couldn't find it (something wrong with Eng-Tips search tool?) Anyway, the thread in question is thread794-215180.

I already knew about the TEMA clarification, but wasn't sure the AI wouldn't say "No, use the ASME 2.9 method". Seems that the concensus is that he won't.

Many thanks.