I have to fabricate pressure vess 1

[66851230797]

I have to fabricate pressure vessel made by SA516 Gr.70 (ASME section I,shell thickness is 140mm)with using 2 plates per 1 shell course. Our fabricator propose to weld 2 plate together and then rolling to the expected diameter. WPS/PQR require preheat and PWHT as per code requirement.
Our fabricator propose to preheat and weld the plates together without PWHT at this step and then roll the plate to make shell course,PWHT will be done after complete all pressure vessel welding as a final PWHT.
Could I ask whether this procedure can be done and acceptable by ASME and there are any ASME code state about this? or we need to complete PWHT as per WPS of the weld joint before rolling.

 

[DriveMeNuts]

Edit: I've just noticed that your post relates to ASME Section I. My comments below are for ASME VIII rules. I expect that the rules of Section 1 will be identical or very similar.

My instinct is that the rolled shell will be of better dimensional quality if the residual stresses caused by welding are removed prior to rolling. UW-39 does suggest that peening the weld can achieve this.
When welding plates together to form a head, the weld does not need to be PWHT prior to head cold forming. I presume the same applies to your application.
USC-79 provides the rules for forming parts. It has rules for post forming heat treatment. There is no mention of pre-forming heat treatment.

That is a very thick shell. Perhaps you will need to roll the two shell halves prior to welding both long seams in accordance with UG-79(b). With such a thick shell, I don't see how you can possibly weld the flat plates together and then roll the resulting tier so that the roundness requirements of UG-80 can be complied with. "adjoining edges of longitudinal joints of cylindrical vessels shall first be shaped to the proper curvature by preliminary rolling or forming in order to avoid having objectionable flat spots along the completed joints".

I guess the method is up to you and if you use a poor fabrication method, it will be revealed by the mandatory post forming 100% radiography (Table UCS-57). Or the AI will reject the vessel for having large flat spots.

I have asked myself your question many times. I am no expert, however above is my experience and interpretation of the code. It would be great to know how you get on.

 

[DekDee]

Does your company not employ a Welding Engineer ?
Serious thicknesses and you are looking for answers on an internet forum ?

 

[DriveMeNuts]

If you read the post, the welding engineer at the "fabricator" is providing information to the poster at another company.
The poster is doing a good job in querying the welding engineers decision. This forum is a good resource to get a few pointers and advise.
Large corporates with 20 vessels engineers often don't have the work capacity to have a welding engineer. They will rely on the fabricators welding engineer or have a consultant who is on call.