ASME B16.34 Standard applies to new construction and covers pressure–temperature ratings, dimensions, tolerances, materials, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated flanged, threaded, and welding end and wafer or flangeless valves of steel, nickel-base alloys, and other alloys shown in Table 1. Wafer or flangeless valves, bolted or through-bolt types, that are installed between flanges or against a flange are treated as flanged-end valves.
1.5.1 Pressure Rating Designation. Class followed by a dimensionless number is the designation for pressure–temperature ratings. Standardized designations are as follows:
Class 150 300 600 900 1500 2500 4500
Class 400, an infrequently used flanged-end valve designation, is regarded as an intermediate class designation.
1.5.2 Size. NPS followed by a dimensionless number is the designation for nominal valve size. NPS is related to the reference nominal diameter, DN, used in international standards. The relationship is, typically, as follows:
For NPS ≥ 4, the related DN = 25 × NPS number.
1.6 Cryogenic Service
Valves in cryogenic service shall meet the additional requirements specified in MSS SP-134.