Hello,

I'm trying to model a rather odd nozzle connection. I have a 20" inch pipe crossing over, and with half its diameter in the top of, a 42" pipe. (see attached picture @ nodes 65 and 1015 {lower crossover})

I tried to use CNodes and offsets to make the connection, but the offsets didn't seem to do anything (see picture at upper connections {between nodes 20 and 30}). I either don't know how to use the offsets (and I thought I did)or something is wrong with my CAESAR II install [running 2011 5.30.02 (Build 110830)]. (node 6040 has a CNode 25 and an offset of 1'-9" {see Offsets pic.png})

I was able to use 0 weight rigid elements to position the connections at nodes 65 and 1015 correctly, but I think that is going to give me a stiffer result, and will thus be less accurate.

Can anyone tell me what is wrong with my offsets or give me a better way to model these connections?

Thanks!

Dear Levim,
this is the typical situation where I would not model that part of system in a beam-analysis piping stress calculation software, because:
1) this connection can't be reduced to a beam connection (some people uses rigids)
2) if I understood you are modeling an equipmetn, so you are modeling something that is outside piping code's scope. I only do that when I have a simple geometry.
3) it could be difficult to calculate the flexibility of that 3D asymmetrical system without a FEA.
I would stop my model to the first flange and ask to the vendor the displacements and allowables forces and moments.

Regards


Corrado Vannella
www.vannella.com