Hello everyone,

Would you confirm these load cases in (ASMEB31.8 VIII) and (ASME B31.8 for Unrestrained piping)? I've read previous discussions but haven't come up with a final answer.

ASMEB31.8 VIII:

L1 W+T1+P1 OPE STRESS/LOAD/DISP
L2 W+P1 SUS STRESS/LOAD/DISP
L3 W+D1+T1+P1 OPE STRESS/LOAD/DISP
L4 W+D2+T1+P1 OPE STRESS/LOAD/DISP
L5 W+T1+WIN1 OPE STRESS/LOAD/DISP
L6 W+T1+WIN2 OPE STRESS/LOAD/DISP
L7 W+T1+WIN3 OPE STRESS/LOAD/DISP
L8 W+T1+WIN4 OPE STRESS/LOAD/DISP
L9 W+T1+U1 OPE STRESS/LOAD/DISP
L10 W+T1-U1 OPE STRESS/LOAD/DISP
L11 W+T1+U2 OPE STRESS/LOAD/DISP
L12 W+T1-U2 OPE STRESS/LOAD/DISP
L13 W+T1+U3 OPE STRESS/LOAD/DISP
L14 W+T1-U3 OPE STRESS/LOAD/DISP




ASME B31.8 for Unrestrained piping:

L1 W+T1+P1 OPE LOAD/DISP
L2 W+P1 SUS STRESS/LOAD/DISP
L3 W+D1+T1+P1 OPE LOAD/DISP
L4 W+T1+U1 OPE LOAD/DISP
L5 L3-L2 EXP STRESS/LOAD/DISP
L6 L4-L1 OCC STRESS/LOAD/DISP
L7 L6+L2 OCC STRESS/LOAD/DISP

Where OCC allowable is the same as SUS allowable.




Another question is, in ASME B31.8 VIII, sustained code allowable is defined as FacxSh, in which Fac is defined as Hoop stress factor(F1) according to CAESAR explanation:

"(B31.8 Chapter VIII - F1, Hoop stress design factor, according to Table A842.22 of B31.8. Appropriate values are 0.72 for pipelines or 0.50 for platform piping and risers.)"

Why is it not defined as F2xSh, where F2 is longitudinal stress allowable as per code?

Thanks

Would anyone help me with this Please?

With just a quick look at your load cases - you have both + & - U1 but your do not have + & - WIN1. Do you have WIN1 as +X and WIN2 as -X? In your second set, why is P1 missing from L4?

B31.8 VIII has three stress checks: 1)hoop, 2)longitudinal, & 3)combined. Their limits are: 1)F1ST, 2) F2S, 3) F3S. F2 & F3 are the same value for
both pipelines and platforms/risers (F2=0.8 & F3=0.9). F1 is different depending on the application. You enter the appropriate value (either 0.72 for pipelines or 0.5 for platforms/risers) as "FAC" in CAESAR II.

Your final question does not make sense to me. Are you asking why F2*Sh is not the "sustained code allowable"? Do not confuse Sh with hoop stress or a basic allowable stress at temperature. VIII does not use Sh in the allowable limits, it uses S (specified minimum yield stress).

Thanks Dave. yes WIN 1-4 are the four wind directions and yes, sorry P1 is missing. I'll fix it.

About the other question, but I'm asking why is F1xS considered as "Sustained code allowable" in CAESAR? Why is it not F2xS?

I see my sustained allowable changing with the Fac number I enter in CAESAR, which is related to F1.

Thank you

Both of these checks apply to the "sustained" load case. F1S is the limit for hoop (pressure) stress and F2S is the limit for longitudinal (axial & bending) stress. As you know, CAESAR II has only one "Code Stress" column. CAESAR II will print the stress (hoop or long.) that produces the largest stress/allowable ratio, i.e., MAX(hoop/F1S, Long/F2S). You can tell which value is displayed by watching the allowable stress column (F1S or F2S).

Ok,thanks David