I have just been made aware of a mid-project change order requiring that all NPS 2 Sch.40 butt weld carbon steel pipe and fittings be changed to Sch. 80 due to welding problems encountered by the pipe spooling fabricators. Does anyone with a welding background have a comment on this? The difference in wall thickness between NPS 2 Sch. 40 and NPS 2 Sch. 80 is 0.064″ (1.63mm), or approximately 1/16th of an inch. I’ve worked on many projects for several decades where NPS 2 Sch. 40 butt weld has been the norm and this is in our piping specs. I find it hard to understand why it would be such a problem now so as to warrant a change in the middle of a project.

My understanding on this is that it is a done deal approved by project management, but for my own edification I’m curious about what your expert thoughts may be on the subject.