Welding P91 to SA-106 Gr. C
Welding P91 to SA-106 Gr. C
(OP)
Aside from the issues with carbon migration and PWHT, what are some of the other negative considerations when joining P91 and carbon steel (SA-106c) materials?
While we are forced into a current situation in which we are required to make a series of these welds, I am looking for further justification as to why we would prohibit joining these two materials without a transition piece on future projects.
While we are forced into a current situation in which we are required to make a series of these welds, I am looking for further justification as to why we would prohibit joining these two materials without a transition piece on future projects.





RE: Welding P91 to SA-106 Gr. C
RE: Welding P91 to SA-106 Gr. C
Second reason, there is such a strength mismatch between these two grades of materials at ambient and elevated temperature this would be a poorly design weld joint.
RE: Welding P91 to SA-106 Gr. C
The manufacturer's justification behind it was that the CS was more economical (thinner wall thickness than P22 because of the allowables), is acceptable per code, has been done in the past, and is "just fine."
RE: Welding P91 to SA-106 Gr. C
You may also remediate but at additional cost.
RE: Welding P91 to SA-106 Gr. C
In discussing matters with the client, they agreed with my stance on the matter and will be sending the valves back for weld buildups/remachining and having the supplier provide suitably sized P22 replacement spools.