Weld Repair in HAZ

[timmckee]

I have a set of 10" WNRF 600# flanges on an superheated steam line (765 deg F service temp) that need to be replaced The existing pipe is A335 Gr. P1 Sch 40 (P No. 3, 1/2Mo, no Chrome). The flanges are A182 F11 (P No. 4, 1-1/4Cr, 1/2Mo). There was no PWHT on the original welds nor do we plan to perform any on the repair. 250 deg F preheat will be maintained during the replacement as it was on the original welds. A GTAW/SMAW procedure with ER80S-B2/E8018-B2 filler will be used.

Is it advisable to avoid the HAZ of the original welds? Any studies you can site one way or the other would be helpful.

 

[BigInch]

What do you think?

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[Duwe6]

As the HAZ of non-PWHT'd welds tends to have the worst of both items: large grain-size due to the heat input, and no chemistry enrichment like the weld [weld filler is 'richer' than base metal], it would be best to cut out the existing HAZ's during your repair.

Second-best choice it to make sure your HAZ does not intersect with the old HAZ.

 

[BigInch]

That is pretty much it as Duwe says. It doesn't take a study, just simply knowing what a heat affected zone means to the steel's makeup and resulting properties is enough to answer your question, with no prior PWHT, its the same but so much more so.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus