Chosing Pipe grade

[WAT]

According to API 5L standards for pipe line there are the following grades :
A25 A B X46 X 52..........
I need to know what is the rules to chose the suitable grade???

thank all

[mohamedellejmi]

It's a matter of finding an optimum between allowable corrosion rate (pipeline lifetime) and wall thickness... as these grades have different compositions and different stress values.

[hazel-e]

hi

i want to ask about the differencee betwin API 5L X70 PSL1 and API 5L X70 PSL2 ?? No chemical diffence but mechanical ( stress value).

regards

[mohamedellejmi]

hi

i want to ask about the differencee betwin API 5L X70 PSL1 and API 5L X70 PSL2 ?? No chemical diffence but mechanical ( stress value).

regards

Hazel-e,

API 5L is a specification (a "spec" as we say) for line pipe.
In that spec, two "Product Specification Levels" (PSL) are presented PSL1 and PSL2.

PSL2 is a more stringent and much more demanding than PSL1 (less tolerance, no repairs allowed, much more certificates,...etc ) and you can see the difference in Appendix J of the Spec.

And even in terms of Chemical Composition , PSL1 and PSL2 might be different even for the same grade (e.g. X70) since the maximum and minimum limits for compositions are not the same.

I hope this helps...

[hazel-e]

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 ??

[mohamedellejmi]

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