Weld Neck Flange
Weld neck flange (WN flange) has a neck that redistributes stress along the pipe, reducing pressure concentration at the flange base. It is suitable for pipelines operating under high or low temperatures and high pressure, especially when PN exceeds 2.5 MPa.Our Supply Range
- Material: Carbon, Alloy and Stainless Steel
- Standards: ASTM A105, ASTM A182
- Sizes: 1/2” to 24”, Customized up to 48”
- Thickness: Schedule 10(S) to SCH 160
- Pressure Ratings: Class 150 to 2500
- Face Type: RF, RTJ
Two Shapes of Welding Neck Flange
Welding neck flanges are available in two main forms. One type features a reducing neck, known as a reducing weld neck flange. The other type has a uniform diameter with a longer neck, commonly referred to as a long weld neck flange.Reducing Weld Neck Flange
Reducing Weld Neck Flange
As its name suggests, it is a combination of a pipe reducer and a flange, allowing it to be directly welded to a smaller pipe.
Long Weld Neck Flange (LWN)
Commonly referred to as an LWN flange, the neck resembles an elongated pipe connected to a flange. It is typically used as a nozzle for columns or barrels in industrial applications.
Long Weld Neck Flange Options
You can choose between a standard thickness long weld neck flange or a heavy LWN flange with increased thickness and a different design, depending on your application requirements.
Face Type
Like other flanges, it is available in Raised Face (RF) and Ring Type Joint (RTJ) configurations.
RTJ Weld Neck Flange
Raised Face Weld Neck Flange
The bottom side of a raised face weld neck flange features a small portion surrounding the bore that protrudes from the face. The gasket seat is placed in this raised area. Depending on pressure ratings, the height of the raised face varies.
For example, for Class 150 and 300 flanges, the raised face height is typically 1/6”, while for ratings above 300, the height exceeds 1/4”.
RTJ Weld Neck Flange
The ring-type joint (RTJ) weld neck flange features a specially machined groove designed to accommodate a metal gasket. This design ensures a secure and reliable seal, making it ideal for high-pressure and high-temperature applications.
Standards Referred for WN Flange
Material Standards
- ASTM A105/N for carbon steel weld neck flange
Manufacturing Standards
- ASME B16.5
- ASME B16.47
- BS 3293
- DIN 2630 PN 1 and PN 2.5, 2631 PN 6, 2632 PN 10, 2634 PN 16, 2634 PN 25, 2635 PN 40
Applications & Features
Weld neck flanges are mainly used for connecting medium and high-pressure pipelines. Due to the welding process, they provide strong and reliable performance in demanding applications.
However, installation requires higher labor, time, and additional materials, as the process involves multiple steps compared to other flange types.