Dear all
I have encountered a problem. please go through this

As we know: Allowable stress range for expansion case:
Sa = f(1.25*Sc + 0.25*Sh) [For Power Piping ASME B31.1]
Now, particularly for SA335 P91 material there is a mismatch in the value of 'Allowable stress range' calculated by the above mentioned formula and CAESAR II 5.2.

For eg. At T=510 deg.c Sc=16753.877 N/cm2;Sh= 12273.749 N/cm2, f=1

As per formula Sa= 24010.78 N/Cm2
As per CAESAR II 5.2 Sa= 20304.9 N/Cm2

This mismatch happens with SA335 P91 material [ASME B31.1], irrespective of the temperature. Please suggest.

Go back and check the Code (I don't have it with me now). There is a limit of 20ksi (13789.5 N/cm2) on the allowables for the Expansion case. So you really have:

(1.25*13789.5) + (.25*12273.7) = 20305

Richard
I went back and checked the code. The foot note on page no. 13 of ASME B31.1 2007 EDITION says it clearly.

But again with sustained stresses which we compare with 'Sh'(allowable) value there is no such limit.i mean, why not 20ksi in this case?

thanks alot

High strength steels may have high yield limits but they are not necessarily tougher. That's why the 20ksi limit applies to the allowed expansion stress range and not to the sustained and occasional limits.

Perhaps I do not understand your question.

Dears

I would like to know the safety factor, which is applied to CAESAR. As you know, there is discrepancy between yield strength on ASTM and CAESAR. So how much safety factor is adopted at CAESAR? As I understand, results from CAESAR are somewhat cevere than I expect. THX!