Valve, change schedule by weld overlay

[MoReSo]

Hello,

I have a 20" #1500 PSV Gate valve. The schedule of but weld ends should be changed from 120 to 160. and then this valve will be welded to pipes.
I want to know if there is any PWHT requirements for this.
Also is this allowed to overlay around 12mm (change sch from 120 to 160 for 20") then PWHT and then prepare the but weld end to weld to the pipe? any requirement in ASME B31.3 for PWHT and preparation?

appreciate your advise.

MRSohrabi;
Materials and Welding Eng.

 

[racookpe1978]

No.

 

[Ripz]

I'm assuming it's Carbon Steel.

Carbon Steel over 3/4" thick requires PWHT as per ASME B31.3.

20" Sch 120 is 1.5" thick.