Flat Welded Flange with Neck

A Flat Welded Flange with Neck (also known as a ”Slip-On Flange with Hub” or ”Hubbed Slip-On Flange”) is a type of flange designed for easy welding and alignment in piping systems. It combines features of both Slip-On Flanges and Weld Neck Flanges, offering a balance between cost-effectiveness and structural strength.

Key Features

1. Hub (Neck) Design
   • Unlike a standard Slip-On Flange (flat-faced), this flange has a short integrated hub (neck) that provides better reinforcement and stress distribution.
   • The hub allows for a smoother transition between the pipe and flange, reducing turbulence and wear.
2. Welding Method
   • The flange is slipped over the pipe and then welded both inside and outside (fillet weld on the hub side and butt weld on the pipe side).
   • This double welding ensures a strong, leak-proof connection.
3. Material & Standards
   • Common materials: Carbon Steel (ASTM A105), Stainless Steel (A182 F304/F316), Alloy Steel
   • Standard dimensions: ASME B16.5, EN 1092-1, DIN, JIS, etc.

Advantages

✔ Easier Alignment – The hub helps guide the pipe into place, simplifying installation.
✔ Cost-Effective – Cheaper than Weld Neck Flanges but stronger than standard Slip-On Flanges.
✔ Good for Low-Pressure Systems – Suitable for moderate pressure and temperature applications.
✔ Smooth Bore – Reduces turbulence and erosion in fluid flow.

Disadvantages

❌ Not for High-Pressure/Temperature – Less robust than Weld Neck Flanges in extreme conditions.
❌ Double Welding Required – More welding work compared to Lap Joint or Threaded Flanges.

Common Applications

• Water & wastewater systems
• Oil & gas (low-pressure pipelines)
• Chemical processing
• HVAC & industrial piping

Comparison with Other Flange Types

Conclusion

The Flat Welded Flange with Neck is a versatile and economical choice for piping systems requiring better strength than a Slip-On Flange but without the high cost of a Weld Neck Flange. It is widely used in industries where moderate pressure and alignment ease are key factors.

Mila