Flange Types
Long Weld Neck Flanges
Extended hub flanges for pressure vessel nozzles and equipment connections.
Long weld neck (LWN) flanges have an extended tapered hub that replaces the standard flange hub plus a section of pipe, creating a single forged piece from the flange face to the vessel shell or equipment nozzle. This eliminates a circumferential weld joint and provides a stronger, more inspectable connection than a separate flange and pipe nipple assembly.
The hub length is specified by the project engineer based on vessel wall thickness, reinforcement calculations, and access requirements for radiographic examination of the nozzle-to-shell weld. Standard connection dimensions follow MSS SP-97. LWN flanges are typically manufactured from forgings with full volumetric ultrasonic examination per ASME SA-388 to ensure internal soundness.
LWN flanges are commonly used on pressure vessels, columns, reactors, and heat exchangers where the nozzle connection is critical to structural integrity. Flanges.IO supplies long weld neck flanges in carbon steel, stainless steel, chrome-moly, and specialty alloys. Custom hub lengths are available to match your fabrication drawings. Contact us for a quotation on your LWN requirements.
