PWHT is mandatory for all special services, i.e lethal, cryogenic and Unfired steam boilers, whatever the thickness is, see UW-2 (a)
As per ASME section VIII division 1, Table UCS-56.1, General notes (b)
LPG is not a special service.
1- PWHT is mandatory for welded joints over nominal thickness...
As per ASME section VIII division 1, UG-25, " the user or designated agent shall specify corrosion allowance other than required by rules of this division.where corrosion allowance is not specified, this fact shall be indicated in data report."
For corrosion allowance of vessel, this is the...
