I could have explained a littel better...PWHT is mandatory for vessel and most exemptions will refer to other parts of UW-2, but some things may not be done prior to PWHT.
Standard Designation: BPV Section VIII Div 1
Edition/Addenda:
Para./Fig./Table No:
Subject Description: Section VIII, Division 1 (1998 Edition, 1999 Addenda); UCL-51 and Table UCS-56
Date Issued: 03/22/2000
Record Number: BC00-080
Interpretation Number : VIII-1-98-108
Question(s) and Reply(ies):
Question (1): A pressure vessel is constructed of P-No. 1 and P-No. 8 materials, and is intended for lethal service. The vessel is PWHT. After PWHT, but before performing the hydrotest, the interior of the vessel has a stainless steel lining applied using plug welds. Does Note (2)(c)(5) of Table UCS-56 in Section VIII, Division 1 permit the liner to be applied after the vessel has been PWHT without the need to perform any additional heat treatment?
Reply (1): Yes, provided that the preheat requirements are met.
Question (2): Does UCL-51 permit the liner to be repaired by welding to the P-No. 1 base material after the vessel has been PWHT without the need to perform any additional heat treatment?
Reply (2): Yes, with the acceptance of the Authorized Inspector.