Piping Fabrication to B31.3

With reference to the ASME B31.3 para 302.3.5 , "w" factor shall be taken as 1 at temperature of 510 deg c and 0.5 at 815 deg c for all materials.

If nozzle is intersecting with longitudinal weld seam of pipe , then the product of SEW (S-stress value, E-weld joint quality facor & E- joint strength reduction factor) shall be use for calculating run pipe strength as well as in branch thickness calculation .

yes if you are using welded pipe (100 % radiography) instead of seamless pipe ,and if base metal design temperture is less than 510 Deg c , welded pipe also comply with this "w" factor as a1.

weld heat treatment in branch connection not only govern by thickness of work but also by throat thickness .

but i did not get where it is written we can use 0.375" wall thickness , can give me page and para as a reference

with regards