Weld Neck Flange Dimensions

Weld neck flanges are among the most reliable and widely used flange types in piping systems, offering superior strength and leak-tight performance for critical applications. These flanges feature a distinctive tapered hub that provides a smooth transition from the pipe to the flange face, minimizing stress concentrations and ensuring optimal structural integrity.

ASME B16.5 is the primary standard governing weld neck flange dimensions, covering pressure classes from 150 to 2500 for pipe sizes ranging from NPS ½" to 24". The standard specifies precise dimensional requirements including outside diameter, bolt circle diameter, thickness, and hub geometry to ensure proper fit and performance across different manufacturers.

Each pressure class is designed for specific operating conditions, with Class 150 flanges suitable for low-pressure applications and Class 2500 flanges engineered for high-pressure, high-temperature service. The raised face (RF) configuration is most common, providing excellent sealing capabilities when paired with appropriate gaskets.

Understanding proper dimensions is crucial for engineers, procurement specialists, and installation teams to ensure compatibility with existing piping systems. Accurate dimensional data helps prevent costly field modifications and ensures compliance with industry standards and safety requirements.

The following sections provide comprehensive dimensional charts, technical specifications, and detailed information for each pressure class to support your project requirements and engineering calculations.