Manufacturers & Suppliers of ASTM A182 Duplex S31803 WNRF Weldneck Flange, 3-1/2\" WNRF Flanges Sch 120, ASME B16.5 Class 900# Weldneck Flange, ASME SA182 S31803 Duplex WNRF Welding Neck Flanges, ANSI B16.5 WNRF, DIN 1.4462 Welding Flange, UNS S31803 WNRF Flange.