Local Post Weld Heat Treatment

[ALA445]

Dear Experts, How can we post weld heat treat longitudinal weld seams in ASME VIII Div.1 pressure vessels in accordance with UW-40 and UCS-56 if car bottom furnace or oven is not available to heat treat the vessel in one go and we don't have any vendor providing PWHT services around. Thanks for your kind inputs. Is it ok to heat treat the nozzle welds with vessel shell (Cat. D joints) in donut form rather than heat the whole circumferential band around the vessel if we don't get any distortion? I have seen almost all similar posts eng-tips form but couldn't get my mind made up.

 

Is your intention to PWHT some welds and not others? Not sure how that works Code-wise.
Practically, I don't see how you can PWHT one entire long seam without also affecting the intersecting circ seams.

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

 

[0707]

ALA445 make a drawing of what do you want please.

luis

 

[TGS4]

If you are asking about just heat treating a longitudinal seam, then I'm not sure how you would physically do that. Can you explain?

If it's what I think it is, then you will do significant damage to the rest of the vessel and not leave the longitudinal seam in a stress-relieved situation when you are done. Any local PWHT needs to be full-encirclement.

 

[marty007]

How can we post weld heat treat longitudinal weld seams in ASME VIII Div.1 pressure vessels in accordance with UW-40 and UCS-56 if car bottom furnace or oven is not available to heat treat the vessel in one go and we don't have any vendor providing PWHT services around

Are you able to ship the vessel to a PWHT shop somewhere else?

For very large vessels, I have heard of shops insulating the vessel, then directly firing a natural gas burner inside the vessel. As long as the heat/cool ramp requirements are met with enough thermocouples, this is a valid approach.

-Marty

 

[LJthien]

@ALA445
How can your welding engineer qualify the WPS if he doesn't know how to physically conduct PWHT since the method as advised by Marty007, which normally applies for heavy thickness sphere tanks (LPG sphere tanks), is much different from local or furnace PWHT in term of the actual Heating rate and Cooling rate.

 

[r6155]

@ ALA445
See your post

https://www.eng-tips.com/viewthread.cfm?qid=471587

My comment was:
"Ultrasonic stress relief can be used for very big and heavy metal parts and metal constructions. We can avoid heat treatment and make it fast, without spending a lot of energy on thermal cycling. Very big metal parts usually cannot be treated thermally since it's impractical to find sufficiently big ovens, or to use the huge amount of energy to heat them"

Regards