ASME B 31.4 D/T RATIO VERIFICATION 1

[GabrieleB]

The verification imposed by ASME B 31.4 on the D/t ratio (Section 403.2.5) shall be carried out on the selected wall thickness (the commercial one) or in the selected wall tickness removing the Corrosion Allowance?
I suppose that being defined for installation purposes, the wall thickness to be considered should be the selected wall thickness (new and not corroded).

Thanks for the response.

 

[LittleInch]

The selected wall thickness for transportation and construction issues.

Susceptibility for operational loads such as buckling, shear, bending etc should use the design thickness.

D/t >100 is really pretty thin and a figure of 80-90 is better, especially for pipes <24".

There is no "verification" in 403.2.5, more a cautionary note. Sometimes with really thin large diameter pipe you find the acceptable limits of ovality mean that pipe could pass that requirement, but not be able to be welded together as the wall could mismatch by more than the thickness... So it not like D/t of 99 is OK and 101 isn't - A D/t of 85 might not be satisfactory.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GabrieleB]

Thanks, you confirm also my position on this matter.