ASME B16.5 Standard Reference

ASME B16.5 is the preeminent international standard for pipe flanges and flanged fittings, published by the American Society of Mechanical Engineers. First issued in 1927 and continuously updated, it covers flanges from NPS 1/2 (DN15) through NPS 24 (DN600) in seven pressure classes: Class 150, 300, 400, 600, 900, 1500, and 2500. The standard is referenced globally by engineers, EPC contractors, and procurement specifications for industrial piping systems in oil and gas, power generation, chemical processing, and water treatment industries.

ASME B16.5 specifies complete dimensional requirements including flange outside diameter, bolt circle diameter, number and size of bolts, flange thickness, hub dimensions, facing dimensions, and gasket contact surface finish. It also provides pressure-temperature ratings for all listed material groups, defining the maximum allowable working pressure at temperatures ranging from -29°C to 540°C (-20°F to 1000°F) depending on the material. These ratings are the basis for safe flange selection in pressure piping design.

The standard recognizes multiple flange facing types including raised face (RF), flat face (FF), ring-type joint (RTJ), and large and small male-and-female and tongue-and-groove facings. It also establishes marking requirements, bolting recommendations, and the criteria for acceptable flange materials, which are organized into material groups based on their mechanical and metallurgical characteristics. Our manufacturing processes and quality control systems are fully aligned with ASME B16.5 requirements.