If the part is made IAW standard material specification ASTM/ASME A-192A - A-192M, consult the document. The requirements for repairs by welding are listed in section 13.
The PWHT requirements are based on the material type. If it is SA-105 material, grind, weld, and blend as necessary and call it a day. If the repair is documented, there shouldn't be any cause for concern.
SA-105 is a material specification for forgings in piping applications.
The material specification I listed in my earlier post was incorrect. The correct material specification is A-182A -A-182M (SPECIFICATION FOR FORGED OR ROLLED ALLOY AND STAINLESS STEEL PIPE FLANGES, FORGED FITTINGS, AND VALVES AND PARTS FOR HIGH TEMPERATURE SERVICE)
Whether or not PWHT is required will be determined by the material and nature of the defect.