Ravi ASME Code gives general guidelines only. For specific application, like Amine, Catacarb, DMEA etc used in process chemical / refinieries/petro chemical plants, user experience counts a lot. PWHT of carbon steel used from strength and cost + S.S 304 L from C.R points (whether integral clad shell plates or overlay welding or strip cladding approaches) is a "must" in such process streams to prevent SCC - due to chlorides or sulphides or from caustic SCC. Engineering standards of reputed international consulting firms like M.W.Kellog and other companies would help you to understand. M.W. Kellog and other large corporate consulting companies (Bechtel etc) use their own internal engineering standards for design of equipment and guideline for fabrication of vessels manufactured for such process conditions. Each engineering standard stipulates and advocates use of PWHT of Carbon steel used in amine, catacarb, DME, etc processes with corrosion protection liners - Ni, Monel, S.S etc. You will not find reference of these in ASME code sections. These are derived over the last 40-50 years users' experience in using with PWHT and without PWHT and the problems faced in each process and corrosion variables with or without PWHT of main strength bearing C.S back up for such usage. With S.S over lay, PWHT done to suit C.S may not adversely affect performance of S.S 304 L liner or liner weld in amine service provided the operating temperature, corrodent variables and the process chemistry conditions are within normal operating or design parameters. This is international experience of users. From reducing possibilities of SCC problem in amine service, at a later date after some years, you would be better off with PWHT of C.S and S.S 304 L liner. Hope this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India May 16, 2008 E-mail: nishi@vsnl.com >Dear forum, > >We have a CS exchanger in Amine service, which is proposed >to be replaced wtih CS+3mm SS304L cladding/overlay material. >Is PWHT required in this case too? I have seen UCL of Sec. >VIII Div. 1, which says if base metal requires PWHT, then >Austenitic Clad steels also require PWHT. However the >temperature range of PWHT falls in the sensitization range >of 18-8 steel, which is detrimental to the same. > >would like to have your valuable inputs on this issue, and >if PWHT is not required, i would like to know where is it >mentioned, i.e. which Standard or Code. > >regards >ravi.