When you specify a flanged valve, you are actually specifying two separate components that must work together: the valve itself and the mating flange. Each is governed by its own ASME standard, and compliance with one does not guarantee compatibility with the other. This guide explains the roles of ASME B16.34 and ASME B16.5, and provides a practical procurement checklist to ensure your valve-flange pairs are correctly matched.
The Two Standards: What Each Covers
ASME B16.34 – Valves—Flanged, Threaded, and Welding End
ASME B16.34 applies to new construction of valves with flanged, threaded, or welding ends. It covers pressure-temperature ratings, dimensions, tolerances, materials, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated valves made of steel, nickel-base alloys, and other alloys. Importantly, wafer or flangeless valves that are installed between flanges or against a flange are treated as flanged-end valves under this standard. The standard also provides alternative rules for valves NPS 2½ and smaller.
