Dear All,

Good morning.

I am working on a reactor (shell & tube type). Outside the shell there are two ring-type header connections for coolant passage (bottom & top). I have modelled the entire equipment for getting real stiffness-es from shell and header. Inserted "custom nozzle flexibility(s)" produced from nozzle-pro at the Shell#Nozzle and Header#Branch junctions. Also, this configuration has piping loads on both the headers (Bottom header node - 1255, top header nodes - 3000, 3010, 3020, 3030).

Analysing to decide whether a support is required for bottom header or not.

Without flexibility(s) at bottom header failed (in EXP case alone) at it's branch junction. Later I have increased the branch spool length (other way to increase flexi), then it was passed and well under the allowable(s).

But there is a requirement from client and internal mfg teams - not to increase the spool length, so I added stiffness-es from nozzle-pro and everything is OKAY.

Following are my doubts:
1. Do the Stiffness-es calculated for header#branch junction from nozzle-pro are really correct? Because the header is in ring shape and but in nozzle-pro the shell is assumed as straight.
2. Is the modelling correct according to the connections and rigid elements?
3. If I have to model top head and inline nozzle for this reactor where I have further piping, how can I model that configuration? I feel that there is no provision to model heads in CAESAR. Can I go with vertical rigid element with head attributes? Or do we have any equivalent method to model head as pipe element?
4. If Piping loads of bottom header alone want to translate from the input nozzle (node-1255) to shell#nozzle junctions (12 nos., example node-80), what is the procedure you suggest? I feel finding out local element forces would give us the required forces and moments at the shell junction. Is it correct? Also since shell-node and nozzle-node are at the same location in space, which element or node forces and moments are to be considered?

NOTE: CAESAR file (version: C-II 2018 Ver.10.00.00.7700) attached for reference.

Thanks in advance.