I am experiencing difficulties understanding and passing the load cases around PSV's. First is I modeled everything properly with the guide and stopper location the hold-down with gaps etc. However, stress fails expansion case, in the reducer portion.

The way I understand it, due to the geometric figure of the reducer it is CAESAR II considers its thickness and dimater to the smaller portion that is why it fails, now as another method I tried modeling the reducer as pipe.


Diameter = Average of the two connecting pipes
Thickness = Average of the two connecting pipes

And now it passed the stresses. I am not sure if this is applicable and they also mention something like model it with a pipe but with an SIF, though this is the same thing with a reducer or is there any difference? Any comments will be appreciated. Thank you.