Boiler tube welding TP347H with P22

[Raai2015]

Dear All, This is for the Boiler final Superheater. FSH tube material is TP347H (please dont ask why as customer forced me use this as this is EFW Boiler). Header material is P22. I suggested Intermediate material of T91 otherwise i say they have welding issues due to different expansion and filler material (im not a welding engineer but process engineer). But customer wants to weld Austenite (TP304H) with Ferritic(P22). Can somebody through some insight and supporting codes if any??
Baskar

 

Please do not double post.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[ijzer]

Indeed not a bit uncommon for a boiler. I would suggest to weld P22 studs to the P22 header and than weld the 347H tubes to the P22 studs using ERNiCr-3 filler.

 

[davefitz]

ijzer is generally correct, but is has also been found that the life of the dissimilar metal weld will last longer if it is welded with an orbital welder ( not manual welded) with a a thicker weld then normally used, to ensure adequate weld penetration and to minimize the shear stress at the P22- inconel interface. It is also essential that the weld zone have minimum bending moment , for this reason the length of the P22 stud to be extended as neccesary so that the weld zone be located at a location of minimum bending moment over the complete cycle of startup - shutdown.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick