PWHT of Entire Heat Exchanger

[MrBTU]

We have a type NEU complete carbon steel heat exchanger that needs to be post weld heat treated in it's entirety. I had planned to PWHT the shell and the bonnet, then welding the closing seams and do a local PWHT on them. The tube to tubesheet joints are strength welded.
I have one person in my organization that says I am being too conservative - he says I should put the whole, assembled unit in the furnace and heat it all to 1100 degrees - that the tubes will be OK. I think that any residual stresses in the tubes will deform them and cause problems.
Do any of you have experience PWHT an entire heat exchanger with a set of U-tubes in it?
Thanks!

 

[metengr]

Yes. Do NOT PWHT the entire Hx. The problem is called distortion both external and internal to the Hx. Go with your original plan, only the weld regions (weld and surrounding base metal) require PWHT, not the base material away from the weld regions.