ASME B16.34 - Valves: Flanged, Threaded and Welding End

ASME B16.34 is the base American standard for industrial valves in flanged, threaded and welding end connections. It defines pressure-temperature ratings for Materials Groups, wall thickness minimums, face-to-face and end-to-end dimensions, and marking requirements.

Pressure classes

The standard covers ASME Classes 150 through 4500. Each class pairs with a material group to produce the pressure-temperature rating table engineers use for valve selection. A Class 150 carbon steel valve, for example, is rated for about 19.6 bar at 38 C, derating continuously with temperature.

Relation to other standards

API 600 (gate valves), API 602 (compact forged valves) and API 603 (corrosion-resistant cast valves) all reference B16.34 dimensions and ratings. When a datasheet cites B16.34, the buyer can expect mating flange dimensions per B16.5 / B16.47 and butt-weld ends per B16.25.

Buyer checklist

Confirm the valve nameplate lists material group and class, verify body marking matches the certificate, and check that the pressure-temperature table used matches the actual body material rather than a generic group value.