PWHT

I know these comments are from ASME B31.3 but what he has asked is pwht requires in seal weld

In the case of fillet welds used at slip-on and socket welding flanges and connections in piping 2 in. (50 mm) and smaller, for seal welding of threaded joints in piping 2 in. (50 mm) and smaller, and for attachment of external non-pressure-containing parts such as lugs or other pipe supporting elements in all pipe sizes, heat treatment is required when the thickness through the weld is more than twice the thickness requiring heat treatment (even though the thickness of the component at the joint is less than the thickness requiring heat treatment.) However, PWHT is not required for P-1 materials when weld throat thickness is ^5/₈ in. (16 mm) or less, regardless of base metal thickness.

I think as you asked the question is about seating (renewable seats) of valves which normaly vendors provide with seal welding. if body thickness is greater than 19 mm than is there any requirement of PWHT because of seal welding?