ASME B16.5 Class 2500 Weld Neck (WN) flange stands as the ultimate benchmark for structural integrity. As the highest pressure rating under the B16.5 standard (covering NPS 1/2 to NPS 24), these flanges are designed to withstand extreme mechanical stress and thermal fluctuations. HT PIPE supply all different types and scales of flanges. Please feel free to contact us for further product information and pricing.
Why the "Weld Neck" Design?
In Class 2500 applications, "Slip-on" flanges are almost never used due to their lower fatigue resistance. The Weld Neck design is preferred for several reasons:
- Butt-Weld Connection: The flange is joined to the pipe with a full-penetration V-prep weld. This allows for easy radiography (X-ray) to ensure weld quality.
- Vibration Resistance: The long hub acts as a buffer, absorbing vibrations and preventing "flexing" at the flange face.
- Bore Matching: By specifying the pipe schedule (e.g., Sch 160 or XXS), the flange bore is custom-machined to ensure a smooth transition, minimizing erosion.
Forging Quality and Grain Flow
Class 2500 flanges are almost exclusively forged (ASTM A105, A182, or A350) rather than cast.
- Grain Flow: Forging aligns the internal grain structure of the steel with the shape of the flange. This provides superior impact strength and fatigue resistance at the hub-to-flange junction-the most common point of failure.
- Heat Treatment: For materials like A105, Class 2500 flanges are typically required to be "Normalized" to refine the grain structure, ensuring the metal doesn't become brittle under high-stress conditions.
