Help me!!
In most of the systems i have done with PSV, the most stressed node is reducer's smaller end node.
1.How does CII takes reducer in analysis ? How it is different from a normal pipe element?
2.Why reducer smaller end node is always most stressed?
Help me!!!

If bending moment is calculated along pipe having reducer. The section modulus is least at nozzle neck( small end) portion hence always it's more stressed as there are sif's also high.

Hello Sridhar,
but if i model a pipe element between reducer end and flange, the stresses are reduced drastically and
Does reducer has SIF? If yes please tell me the equation for SIF.

SIF are based on geometry, Hence SIF remains same.

when the reducer modeled directly welded to the flange. Its point of highest bending moment and SIF as well.

when the pipe spool is modeled the maximum bending moment remain at same point but sif of plain pipe which is 1.00.

at reducer point sif is high but BM is less. hence bending stress gets lowered and you may see the pipe passed in code stress.

Reducers can have SIFs - it depends on the piping code you're using. If an SIF is implemented, you will see this value in the stress report.