PWHT Concerns for a vessel welded into piping system

[jjjimenezjr]

I have a pressure vessel that is to be welded directly to the piping. The vessel has been fabricated and stamped per ASME Section VIII and was heat treated by the manufacturer due to the thickness. We have 3 large diameter piping connections to the drum which per ASME B31.3 are required to be heat treated. I have seen documentation such as WRC-452 which would indicate that for localized PWHT of a piping connection, it may be recommended to perform heat treatment of a section of the vessel to avoid inducing stresses into the shell-nozzle joint. I have only seen single thickness piping connections in WRC, but my vessel has heavy wall self reinforced nozzles. If you use only the weld thickness, then I do not believe that the weld itself will cause any problems at the shell joint, but I am concerned with the PWHT temperature and duration and the location of the electrical bands being very close to the transition to the heavy wall of the nozzle. I cannot find any references in B31.3 or Section VIII on this issue. Is there any specific governing codes or advice for this situation?

Vessel-ID=5500mm Shell Thickness=105mm
Nozzle1-Dia=60" Tnozzle=365mm Tweld=35mm Len=735mm
Nozzle2-Dia=24" Tnozzle=175mm Tweld=22mm Len=384mm

 

[metengr]

jjjimenezjr;
Look at 331.2.6 in ASME B31.3 (2004 Edition) for local heat treatment. What I would do is to review ASME Section VIII, Div 1 for local PWHT guidance, and combine with the information from B31.3 and develop a generic PWHT procedure.

 

[kennyc71]

JJJ,
Just curious, is your concern that the localized HT would actually induce stress?

Thanks for a great question!

 

[TGS4]

What you have seen in WRC-452 is right on the mark. The localized HT will induce stresses if it is not done correctly. I've ssen this happen several times now, and I have personally performed calcs comparing a "bullet" HT to a full circumference HT, and the WRC-452 method is much much better.