When reviewing the code compliance check i notice that the allowable stress varies from node to node. I do not understand why this is happening, since all nodes refer to the same spec of pipe with the same material properties assigned and under the same temperature conditions.

I would expect to see that the allowable stress would remain constant in agreement with BS EN 13480-3:2002 equation 12.1.3-1.

Any ideas?

"liberal stress", equation 12.3.4-2.

Regards,

The maximum allowable expansion case stress can be calculated using the conservative method, where the maximum allowable is calculated and used. A second option (the one CAESAR II uses by default) is the progressive formula, where the stress check is done using the following method:
max allowable progressive exp stress = max all. exp stress + max all. sus stress - occuring sus stress.
This formula is also given in the EN-13480-3 (formula for Sigma4) (and other piping codes by the way).

First time when I was reading EN I thought that "liberal stress" is not allowed, but it is all about wording.

I understand that the stress check is taking account of the expansion, sustained and alternating loads.

What i do not understand is the right hand side of the equation 12.3.4-2 of BS EN 13480,
< f.h + f.a
(i.e. the allowable stress which the summation of the actual pipe stresses calculated by CAESAR must be less than)

Surely f.h + f.a should remain constant (assuming pipe material properties/pipe temperature is constant throughout the model)? I interpret f.h + f.a to be the allowable stress quoted in the code compliance check - this is the parameter that i am finding is varying between each node in the model.

CAESAR II has re-arrangend the formula 12.3.4-2 to: f.a = (f.a+f.h) - sustained stress.

Yes. I agree with Corne. Maybe in the future it will be changed like for B31.3 Appendix P.

Regards,

Thanks corne/Dan, my results certainly seem to suggest that equation is valid.