Weld Neck Flange

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wnf flange 1The weld neck flange, abbreviated as WNF, is a flange type that is usually used with pipes, as opposed to pressure vessels. The design of the flange allows for a full penetration weld at its base where it connects to the pipe.  This weld can be X-ray inspected for quality control.  

weld Neck Flange Index

The weld neck flange comes in two types, regular and long. The hub of the weld neck is designed to reduce the stress at the base of the flange. Regular weld neck flanges are used with buttweld fittings and connecting two pieces of pipe together.  Long weld neck flanges are usually used with equipment and vessel nozzles. A long weld neck flange is rarely used with pipe.

Both types of flanges are bored to match the inside diameter of the pipe or fitting to which it will be welded to. However, if the bore does not match, the inner diameter can be ground out to match the larger bore pipe.  Weld neck flanges are suitable where high pressure, extreme temperatures, shear impact and vibratory stresses apply.



weld Neck Flange Advantages and Disadvantages

  • Weld neck flanges provide high structural integrity due to the butt welded connection, which results in a continuous and strong joint between the pipe and the flange.
  • The tapered hub of weld neck flanges helps in reducing stress concentrations at the base of the flange, which enhances their resistance to high pressures and temperatures.
  • Weld neck flanges are well-suited for high pressure applications due to their robust design and the strength of the welded joint.
  • The smooth transition from the pipe to the flange and the rounded shape of the hub contribute to excellent flow characteristics, minimizing turbulence and pressure drop in the system.
  • Weld neck flanges generally exhibit good fatigue resistance, making them suitable for applications where cyclic loading is a concern.
  • Installation of weld neck flanges can be more complex compared to some other types of flanges.  Precise alignment and welding skills are crucial to ensure a proper joint.
  • Weld neck flanges may take more time to install compared to flanges with simpler designs, as the welding process requires careful attention to detail.
  • Weld neck flanges can be more expensive than some other types of flanges due to their design and the welding process involved.
  • Once welded in place, weld neck flanges have limited rotation capability.  Proper alignment during installation is crucial to avoid misalignment issues.
  • Weld neck flanges are not suitable for applications where frequent disassembly and reassembly are required, as cutting and rewelding are involved.
  • The long tapered hub design of weld neck flanges may require more space compared to some other flange types, which can be a consideration in tight spaces.
  • The welded joint can be susceptible to corrosion, especially if proper corrosion protection measures are not implemented.


Weld Neck Flange Datasheets

The datasheets we have on this site are shown below. For simplicity sake, only datasheets that adhere to B16.5 are shown. ASME B16.5 covers flange dimensions from ½” to 24”. For sizes larger than this, please visit our flange datasheets page.

ClassFlat FaceRaised FaceRing Type Joint
ANSI 150 WN Flange ANSI 150 FF (in) WN Flange ANSI 150 RF (in) WN Flange ANSI 150 RTJ (in)
ANSI 300 WN Flange ANSI 300 FF (in) WN Flange ANSI 300 RF (in) WN Flange ANSI 300 RTJ (in)
ANSI 400 WN Flange ANSI 400 FF (in) WN Flange ANSI 400 RF (in) WN Flange ANSI 400 RTJ (in)
ANSI 600 WN Flange ANSI 600 FF (in) WN Flange ANSI 600 RF (in) WN Flange ANSI 600 RTJ (in)
ANSI 900 WN Flange ANSI 900 FF (in) WN Flange ANSI 900 RF (in) WN Flange ANSI 900 RTJ (in)
ANSI 1500 WN Flange ANSI 1500 FF (in) WN Flange ANSI 1500 RF (in) WN Flange ANSI 1500 RTJ (in)
ANSI 2500 WN Flange ANSI 2500 FF (in) WN Flange ANSI 2500 RF (in) WN Flange ANSI 2500 RTJ (in)


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Tags: Pipe Flange