ASME B16.34

Covers — cast, forged, and fabricated valves with flanged, threaded, or welding ends, in Classes 150 through 4500. Scope includes:

• Pressure-temperature ratings (standard, special, and limited classes) by material group.
• Minimum body/bonnet wall thickness tied to size and class.
• Acceptable materials and marking, plus the shell testing basis (seat testing by reference).

Does NOT cover (exclusions) — the following are governed elsewhere:

• Face-to-face / end-to-end laying lengths → ASME B16.10.
• Detailed valve inspection and seat-leakage acceptance → API 598 (or MSS SP-61).
• Product-specific valve designs (e.g., gate/ball/butterfly detail) → the applicable API/MSS valve standard, which invokes B16.34 ratings.

When a datasheet says "rated to B16.34," it is the rating tables here that fix the allowable pressure at temperature.

B16.34 sets minimum requirements for valve pressure integrity:

• Materials — approved material groups with allowable stresses that set each rating; special-class ratings require additional NDE.
• Design — minimum wall thickness for body and bonnet as a function of size and class; rating determined by the standard/special/limited class basis.
• Examination & Testing — shell (hydrostatic) test to prove the pressure boundary; special-class valves require supplementary examination (RT/UT/MT/PT).
• Marking — pressure class, material, and manufacturer identification (per MSS SP-25).

ASME B16.34 establishes pressure-temperature ratings, minimum wall thickness, materials, and testing for valves with flanged, threaded, and welding ends. It provides the standard, special, and limited class rating tables that most valve standards reference.

The standard ties valve body wall thickness and rating to the material group and class (150–4500), and defines shell and (by reference) seat testing expectations. Valve face-to-face dimensions come from ASME B16.10, and testing details are commonly taken from API 598.

Engineering Note: When a datasheet lists a valve "Class 300 to B16.34," it is invoking this standard's rating tables to define the allowable pressure at temperature.