CSA Z245 and low temperature material 1

[JediInTraining]

While reviewing some CSA low temp piping spec I noticed that all piping 4" and larger was A333 Gr 6, but 3" and smaller was A106 Gr B. The corresponding ASME low temp piping spec was A333 Gr 6 regardless of size.

I looked through CSA Z245.1 but could find no explanation for this.

Would anyone be able to explain this?

Thank you

 

[pastyl]

For low temperature all the piping should be A333Gr6

 

[SNORGY]

I think it's probably because of the clause(s) in CSA Z662 Section 4.--- that basically exempts pipe sizes below 4" NPS and wall thicknesses below 6 mm from having to have proven notch toughness properties. It is rationalized that considerations other than fracture toughness become more important with respect to failures in smaller and thinner pipe, and that it becomes impractical anyway to get meaningful notch toughness test accuracy in thinner wall pipe due to the fact that such testing requires half size or smaller Charpy impact test specimens. Moreover, inspection of Z662 Table 5.2 shows that the values for PTSV1 are well in excess of the SMYS for A106 and A333 pipe (241 MPa) in smaller pipe, so even on that basis alone, fracture toughness would not be expected to be a requirement by Z662, since pressure design requirements would never allow for a wall thickness thin enough to have DOS > PTSV1. (Here one assumes that we are not dealing with carbon dioxide service and that the footnotes in Z662 Table 5.1 might be employed for "limited pipe runs".) I do agree that the preference would be to at least meet A333-6 (CSA Z662 Category III) notch toughness because it would be more in line with matching up to surface piping that might be alternatively be designed to ASME B31.3, where ASME Code rules such as Section VIII Div. 1 UCS 66--- and B31.3 323.2.2--- would be invoked. We run into situations like this often in midstream / upstream oil and gas facilities, where even today a lot of confusion exists as to where the jurisdictional split is made between ASME and CSA. That is why the ERCB, Shell and ABSA jointly authored the "Reference Tool For Interpreting Jurisdictional Relationships For Pipeline, Pressure Equipment, And Pressure Piping" in June 2006.

 

[SNORGY]

I apologize for not proofing my grammar thoroughly.