Weld Neck Flange

A flange is a connection between pipes, valves, pumps, and other equipment. It also allows for simple washing, inspection, and alteration.

Materials– Carbon Steel, High Yield Carbon Steel, Alloy Steel, Stainless Steel, Duplex and Super Duplex, and various Nickel Alloy Grades such as Monel, Inconel, Hastelloy, and Incoloy.

Components– gasket, flanges, and bolting

Welded neck flange as the name suggests has a long tapered hub(neck). It is butt welded with the pipe through the hub inserted in the pipe. This long tapered hub is useful in severe conditions, sub-zero, and elevated temperatures. This hub (neck) is only responsible for transmitting pressure or stresses to the pipeline.

The bore of the welded neck flange is matched with the pipeline’s bore to allow the material’s free flow. This is also done to reduce erosion and disturbance in the pipeline. Welded neck flange ensures that there is no high pressure at the bottom of the flange as it relocates the stress to the pipe. This flange is useful for water, hydrocarbons, vapors, gases, food fluids, and corrosives.

Dimensions: 1/2”, 2”, 3”, 4”, 6”, 8”, 10”, up to 24”.
Class range: Class 150 to 2500(# or LB). PN 2.5 to PN 250.
Flange face type: RF (Raised Face), RTJ (Ring Type Joint)

Types:

• Long weld neck flange-

A long weld neck flange is a normal weld neck flange with an elongated hub or neck. It is like a nozzle attached to the pipe. They are specially designed for heavy pressure and temperature applications. Lengths are based on the parts needed for each application, so no universal standard length exists for these industrial long neck flanges. These connections improve the pipe flow. This keeps the piping system safe.

• Reducing weld neck flange-

These flanges are used to connect 2 different diameter pipes. Reducing weld neck flange as the name suggests has a reducing neck that is being welded with the pipe. These are considered ideal for connecting 2 different-sized flanges. It has 1 large flange and one small flange connected by a neck or hub in the middle. The small flange will be again connected with a pipe. Thus, the material will flow from a smaller flange to a larger flange. If this is reversed, then it can cause severe turbulence in the system.  Reducing weld neck flange is used to reduce the speed or pressure of the material flowing through the pipe. They are available in classes of 150-2500.

• NW Long weld neck flange- As the name suggests, NW long weld neck flange has a very long hub or neck. These are known as high hub flanges. These are designed to reduce the high stress from the bottom of the flange and transfer it to the pipe. The main purpose of the NW Long weld neck flange is to decrease the stress concentration from the bottom of the flange. NW long welding neck flange is the most suitable butt welding flange for design.

Materials:

304/304L (1.4301/1.4307) • 321/321H (1.4541)
316/316L (1.4401/1.4404) • 316Ti (1.4571)
904L (1.4539) • (Super)Duplex • Nickel Alloys

Material Standards

• ASTM A105/N For carbon steel weld neck flange
• ASTM A182 F11, F22 for alloy steel
• ASTM A182 F304 / F304L, F316 / F316L for stainless 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

Uses of weld neck flanges:

• These flanges are ideal for extreme fluctuations in temperature.
• They are ideal in environments where there may be a lot of bending and handling of the flanges.
• Preferred in an environment with extreme temperature conditions.
• This type of flange is preferred for every severe service condition—resulting from high pressure or sub-zero elevated temperature.
• They are used in situations where loading conditions are substantially constant or fluctuate between wide limits.
• This is probably the best welding flange available because of its high, heavy neck.