Code Stress for B31.4

I have read in CaesarII Reference Guide Page 11, mentioned for the code stress.

Regardinging to B31.4, what does FAC stands for ? And how can I check the allowable stress value in operating cases ? I am now designing for an A403 WP 316 which does not show in the material database.

Best Regards,

CHK

In which section / para did you find FAC ?

FAC is a C2 term here. FAC=1 indicates a "fully restrained" line and FAC=0 indicates an "unrestrained line" as defined in B31.4 paragraph 419.6.4. These definitions control the limits on allowable longitudinal expansion stress.
There's a vast "gray area" between these two extremes. C2 will bridge this gap with the soil modeled as restraints and FAC set to 0.001.

Dear Dave,

Thank you very much for your reply. I have input FAC=1 and the allowable stress shows up 0.9(Syield) but when I input FAC=0 the allowable stress shows 0.00.

Can you please tell me what is happening ? How can I get the allowable stress shown ?

Thank you very much,

Regards

Chanatip,

Read, and interpret, the Code.

The operating stress state has an allowable limit of 90% yield for "Fully Restrained" pipe. There is no operating stress limit defined for other pipe conditions - i.e. "Unrestrained" pipe.

Seldom does C2 list an allowed limit for operating stress. Here's one.

The operating condition seems like the most likely candidate for stress evaluation but most piping codes consider this a mix of two separate causes of failure - collapse and fatigue. Collapse is evaluated using stress due to sustained. Collapse is also measured using the stress due to sustained loads plus the stress due to occasional loads. Fatigue is evaluated using the expansion stress range.

Thank you very much Dave

Dear Mr. Dave,

we are facing a problem, showing that there is no operating allowable stress for the restrained case.

Our operating parameters are,

Pipe-API 5L Gr.B
8" Dia. Sch. 40
Temp-135 Deg. C
Pressure - 10 barg

Please clarify...

Dear Richard,

I am confused in inputting the allowable stress value for ASME B31.4 code in Caesar-II (i.e.) as per ASME B31.4, the allowable stress is calculated as Sy = E*F*SMYS, but in Caesar, do we have to put the calculated values of Sy or SMYS in the input.

The help function seems to show a two meaning.

Please clarify.....

For B31.8, it shows that SMYS must be input directly.....