Flange Types
Weld Neck Flanges
The highest-strength flange type, preferred for critical high-pressure service.
Weld neck flanges are the most robust and widely specified flange type for critical piping applications. Their distinguishing feature is a long, tapered hub that transitions gradually from the thick flange ring to the pipe wall thickness. This taper distributes mechanical stress across a broader area, reduces stress concentration, and provides excellent resistance to dishing and fatigue from cyclic bending loads.
The flange is attached to the pipe by a single circumferential butt weld at the end of the hub, which produces a full-penetration joint that can be 100% radiographically examined. This is essential for piping systems governed by ASME B31.3 (Process Piping) or B31.1 (Power Piping) where weld quality assurance is mandatory. The bore of the weld neck flange matches the pipe ID, providing a smooth, unobstructed flow path.
Flanges.IO stocks weld neck flanges in sizes from 1/2" through 60" (per B16.5 and B16.47) in pressure classes 150 through 2500. Materials include carbon steel (A105), stainless steel (A182 F304/F316), chrome-moly alloys (F5, F9, F11, F22, F91), and specialty metals. Long weld neck (LWN) variants for vessel nozzles are also available. Contact us for a competitive quote.
