Recently, I ran an analysis of a pump station piping system. The code I used was ASME B31.4 and the material was A-106 Gr. B. The temperature was 100F and the pressure was 1440 psig.

What I'm curious about is that the program showed the allowable Sustained stress was 18,900 psi (which is 54% of the yield stress).

I'm still learning ASME B31.4, but from what I read, the standard design factor is 0.72. The code lists the allowable stress for A-106 Gr. B as 25,200 psi. I've also read that the design factor should not exceed 0.72, so the 0.54 is acceptable.

My question: why is the default design factor in CAESAR II 0.54 for this material? I'm assuming that the design factor is the reason the allowable stress is so low.

Please help me. Maybe there's something I'm missing in the code.

No input on this?