I am analyzing some high yield piping to ASME B31.1 and am having trouble understanding the (non-liberal) allowable displacement stress calculated by CII.

The Material is (1)Low Carbon Steel, with Sc=332.267 MPa, Sh=322.0 MPa, f=1.0, and Sy=483.0 MPa.

I am expecting the Displ. Stress Range Allowable to be Sa=f(1.25 Sc + 0.25 Sh) = 495.83 MPa, but the allowable from CII is only 206.84 MPa (or 30 ksi). I would expect this value using B31.3, as in B31.3 Sc and Sh are limited to 138 MPa (20 ksi), but B31.1 has no such restriction on Sc and Sh.

Has anyone else run across this? Am I missing something, or does CII apply the B31.3 Sc and Sh limitations to B31.1 as well?

hi~
refer to b31.1(2016) 102.3.2 note. 2

"For materials with a minimum tensile strength of over 70 ksi
(480 MPa), eqs. (1A) and (1B) shall be calculated using Sc or Sh
values no greater than 20 ksi (140 MPa), unless otherwise justified."

Thanks, I had missed that footnote in B31.1.

I was actually trying to get Caesar II to use the B31.3 Chapter IX High Pressure Piping allowable displacement stress (without the Sh Sc 20 ksi limitation), but I guess I'm stuck with manually changing the allowable in the reports.

For what it's worth - the next version of CAESAR II (due out this month) will directly address B31.3 Chapter IX criteria.

Good to know Dave, thanks.

Canadian Pipeline Code CSA Z662, Annex I for Steam Distribution Pipelines, also references B31.3 Chapter IX for stress allowables, so this will be helpful when using that code.