Flexibility of Nozzle Loads

[nikolastrojman]

Hi

Basically, I want someone to explain to me in more detail, the difference between the rigid and the flexible nozzle (what actually happens with the nozzle when we model the nozzle according to WRC297 for example, why do we get lower nozzle load values).

 

[C2it]

I am assuming thatyou are interested in nozzle / pipe connections.

There really is no such thing as a rigid nozzle.

The effect of a flexible nozzle on a pipe end is to relieve longitudinal moments and axial forces by local rotation and translation of the pipe end.

The question to answer is whether inclusion of the flexibility of a vessel shell in a pipe stress calculation will have any real effect. It may be worthwhile adding it or it may have a negligable effect on loads and stresses. It's easy to do with Caesar II but painful to calculate spring data by hand.

In nearly all cases, assuming a nozzle to be rigid (with thermal movements) is conservative. However I am sure we can all come up with geometry where ignoring nozzle flex is a bad thing, so that's down to professional judgement.

 

[DSB123]

Cit,
Assuming the Nozzle to be a rigid is not always conservative as you say. In particular if you are after accurate support load distribution then nozzle flexibility can have significant effects on the support loads.

 

[XL83NL]

You might want to review the methods for and discussions of including nozzle flexibility in chapter 8.3, respectively 8.3.2, of Peng & Pengs's (excellent book on) 'Pipe Stress Engineering'.