Quote Originally Posted by hazel-e View Post
hi

according API 5L PSL2 X70

Yield Strength (min-max)between 483 - 621 MPa
and
UltimateTensile Strength (min-max) between 565 - 758 MPa


i wonder if i can use 600 MPa as UltimateTensile Strength
for wall thikness calculation ??
Dear Friend,

We never use ultimate Tensile Strength for wall thickness calculation. But we use the minimum Yield Strength of 483 MPa (70,000 psi).

But I think you are looking at the wrong place for the design of your Pipeline.

You should use :
- ASME B31.3 for process piping
- ASME B31.4 for liquid pipelines
- ASME B31.8 for gas pipelines (Appendix D gives the right values to use for Yield Strength for various grades)

I hope this helps