PWHT for welded patch 1

[starships]

Good day to you,

We're performing repair work for pressure vessel

That fell down to the ground during lifting, and then after window-cutting damaged area, now on welding.
But, our client has insisted to carry out PWHT after repair welding for replacing patch. Originally, PWHT was not required during fabration at shop based on EN 13445, but client has strongly insisted PWHT due to locked stress generated by repair welding.

Any guy theoretically explains to me why it is necessary?

 

[APItips]

Hello Starships
ASME VIII Div. 1 mandates the vessel to be PWHT if the substance is lethal (UW-2) or due to thickness requirement(UCS-56). therefore , if the vessel was built as per ASME VIII and neither of the above is true, PWHT is not required.

 

[stanweld]

Very small patches can lock in considerable stress, which could prove detrimental in a particular service environment. There is no such problem with a relatively large patch properly tied in at the corners.

 

[GenB]

It depends who damaged it and who is paying. Repair matter before stamping is Asme if after stamping is N.B. if pwht not obligated by codes. Then it is a dispute between the mfr and customer. Get a contractor with an electric blanket and pwht the patch only. Good luck.