Weld Neck Flanges (ASME B16.5 / B16.47)
What Is a Weld Neck Flange?
Weld neck flanges feature a long tapered hub that gradually transfers stress from the flange to the pipe. This design significantly reduces stress concentration at the base of the flange and provides superior strength compared to other flange types.
Because the pipe is butt-welded directly to the flange neck, weld neck flanges are widely used in demanding applications where pressure, temperature, and mechanical loads must be carefully controlled.
These flanges are commonly manufactured in accordance with ASME B16.5 for pipe sizes up to 24 inches and ASME B16.47 for larger diameters.
Common Uses
- Oil & gas pipeline systems
- Chemical processing plants
- Power generation facilities
- Municipal water infrastructure
- Industrial manufacturing systems
- Energy and refinery projects
Key Characteristics
- Long tapered hub for gradual stress distribution
- Butt-weld connection to pipe
- Suitable for high-pressure and high-temperature systems
- Excellent fatigue resistance in cyclic service conditions
- Compatible with ASME B16.5 and ASME B16.47 standards
- Available in multiple pressure classes and material grades
Available Materials
- Carbon steel
- Stainless steel
- Alloy steel
- Duplex stainless steel
- Nickel alloys for specialty applications
Pressure Classes
- Class 150
- Class 300
- Class 600
- Class 900
- Class 1500
- Class 2500
Dimension Standards
Weld neck flange dimensions are defined by recognized industry standards.
For most piping systems:
ASME B16.5 covers pipe sizes from ½ inch to 24 inches.
ASME B16.47 covers larger diameter flanges used in large-scale industrial and infrastructure systems.
These standards define:
- Flange diameter
- Bolt hole pattern
- Hub dimensions
- Thickness requirements