B31 Branch Calculation or Section VIII Div2

[Mumawalde]

I have an application where a number of branch connections and a section of run pipe are cast into a special fitting. The cast boss for the branches however is not cylindrical, it actually contains many of the branches in the single boss. The bores for each branch however are cylindrical. I would normally use a Section VIII Div 2 style analysis or maybe a Div 1 UG-101 test, however it occurred to me that it could be construed as integral branch connections with extra material around them, and therefore B31.3 area replacement calculations and reinforcement requirements could potentially be used.

Any thoughts?

 

[Mumawalde]

No replies?

 

[TGS4]

Just a suggestion - but you would probably draw some responses if you added bits of information such as:
- Jurisdiction where this would be installed
- Code of Construction where this would be used

Also, asking "any thoughts?" is little too open-ended. Ask a specific question.

 

[KernOily]

I think you should do FEA on this fitting and be done with it. In my opinion, I think you are stretching the 31.3 area replacement calcs for this application. The 31.3 calcs assume cylindrical cross-sections blah blah blah (technical term) and without seeing a picture I don't see how your special part is even close to the diagrams in 31.3 for branch connections/reinforcement calcs.

Another way to look at this: If there is a failure of your part and you get dragged into court, you need to be able to stand up with a straight face and be able to show that your approach to this was reasonable and prudent and that the same approach would have been taken by any another engineer, i.e. the "standard of reasonable care" monkey business. If I was called as an expert witness on the failure, I would want to see FEA having been done on this. I think applying 31.3 to this situation is a s-t-r-e-t-c-h.

You did ask for opinions Godd luck! Sounds like an interesting problem.

 

[Mumawalde]

Hello,

Thanks for the replies.

@TGS4: The item is a special pipe fitting which will be installed in an existing ASME B31.3 pipeline.
I understand "any thoughts" is open ended, and it was my intent to start a discussion rather than ask a direct question.

@KernOily: I agree with your comments, my plan was to use a 304.7.2(d) " detailed stress analysis (e.g., finite element method) with results evaluated as described in Section VIII, Division 2, Part 5. "

This certainly is an interesting problem, as there are enough of these fittings to procure a mold and cast them. This is why I wanted to open this to discussion prior to performing any analysis. I am generally a Section VIII Div 1 and 2 designer, and I wanted to get a feel from some people more familiar with B31.3 before I defaulted back to my comfort zone.

Thanks, and as before: Any thoughts?