PWHT is needed only once per weld over 38mm (CS, or 32mm if not preheated during welding).
If it has undergone PWHT already I would think only the new weld would be needing PWHT.
Same thing when making a vessel in two parts, pwht-ing them.
Then welding a closure seam and local pwht on the...
An outer ring is a way of confining a gasket. So if I were to use a spiral wound gasket and add an outer ring to it, it would be confined and ok with TEMA R.
The reason of the confinement is 'blow out' of the seal. I don't see how a camm profile would 'blow out'. Tema however specifically tells...