ASME B16.34-2020 PDF

Full title and description

ASME B16.34-2020 — Valves — Flanged, Threaded, and Welding End. Standard that specifies pressure–temperature ratings, dimensions and tolerances, materials, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated flanged, threaded, welding-end and wafer/flangeless valves of steel, nickel‑base alloys and other alloys.

Abstract

This 2020-designated ASME standard defines engineering, manufacturing, inspection and marking requirements to ensure safe, interchangeable valve construction and reliable pressure‑temperature performance for industrial piping systems. It provides classed pressure–temperature tables, construction and material rules (including special and limited class provisions), mandatory test procedures (shell and closure tests), and appendix guidance (e.g., cryogenic and small‑valve rules). Note: ASME B16.34-2020 has been superseded by a later ASME revision (ASME B16.34-2025).

General information

• Status: Superseded by ASME B16.34-2025 (the 2025 revision is the current ASME edition).
• Publication date: Designation year 2020 (ASME designation 2020; distributors and standards resellers report implementation/publication activity in early 2021).
• Publisher: American Society of Mechanical Engineers (ASME).
• ICS / categories: 23.060 (Valves) — piping components and valve standards.
• Edition / version: 2020 edition (ASME B16.34-2020).
• Number of pages: ~229 pages (commonly listed page count for the 2020 edition in standards catalogs).

Scope

Applies to new construction of valves with flanged, threaded, welding ends and wafer or flangeless types installed between flanges. Covers pressure–temperature ratings by class, materials permitted, dimensional and tolerance requirements, nondestructive examination (NDE) rules, mandatory pressure testing (shell and closure), marking and identification, and alternative rules for valves NPS 2½ and smaller (Mandatory Appendix V). Also includes provisions for Special and Limited Class valves and guidance for cryogenic and high‑temperature service.

Key topics and requirements

• Pressure–temperature ratings and class designations (Classes 150–2500 and Class 4500 limitations for welding ends).
• Material selection and grouping; minimum mechanical/chemical requirements for cast, forged and fabricated parts.
• Dimensions and tolerances for flanged, threaded and welding ends (interchangeability requirements).
• Nondestructive examination (radiographic, ultrasonic, magnetic particle, liquid penetrant) and weld quality rules tied to ASME BPVC/Section VIII as applicable.
• Mandatory pressure testing: shell tests and closure/leakage tests with specified pressures and durations.
• Special and Limited Class rules (additional examinations and restrictions for elevated ratings or small sizes).
• Marking and identification plate requirements (manufacturer, rating, material, Case numbers when applicable).

Typical use and users

Used by valve manufacturers, purchasers/specifiers, piping and mechanical designers, inspection and quality personnel, plant engineers and maintenance teams in industries such as oil & gas, petrochemical, power generation, shipbuilding, and process industries where high‑pressure/high‑temperature valves are employed. Also used by regulatory bodies and certification/inspection organizations as a technical reference for procurement and acceptance.

Related standards

Commonly used together with other ASME B16 series documents and ASME codes, for example ASME B16.5 and B16.47 (pipe flanges), ASME B31 piping Codes, ASME Boiler & Pressure Vessel Code (BPVC) requirements for welds and heat treatment (Section VIII references), and MSS or industry documents for cryogenic or special testing (e.g., MSS SP‑134). International and industry standards may also reference B16.34 as a normative document.

Keywords

valve standard, ASME B16.34, flanged valve, threaded valve, welding‑end valve, pressure–temperature ratings, NDE, pressure testing, valve dimensions, valve materials, Special Class, Limited Class, valve marking

FAQ

Q: What is this standard?

A: ASME B16.34-2020 is an ASME technical standard that sets engineering and inspection requirements for flanged, threaded and welding‑end valves used in pressure‑containing piping systems.

Q: What does it cover?

A: It covers pressure–temperature rating tables and class designations, permitted materials and material properties, dimensional and tolerance requirements, nondestructive examination requirements, mandatory pressure testing (shell and closure), marking/identification, and special provisions for small valves and cryogenic/high‑temperature service.

Q: Who typically uses it?

A: Manufacturers, specification authors, purchasers, piping and mechanical engineers, QA/QC and inspection teams, plant maintenance staff, and regulatory or certifying organizations in process, power, oil & gas and marine industries.

Q: Is it current or superseded?

A: The 2020‑designated edition has been superseded by a later ASME revision (ASME B16.34-2025); users should reference the 2025 edition for the most current mandatory requirements and any revised tables or rules. If you must maintain historical procurement or inspection records, use the specific edition referenced in contract documents.

Q: Is it part of a series?

A: Yes — it is part of the ASME B16 series of piping component standards and is intended to be used with related ASME standards (for example B16.5, B16.47, ASME B31 piping codes and the ASME BPVC where weld and fabrication rules are referenced).

Q: What are the key keywords?

A: Valve, pressure–temperature rating, flanged, threaded, welding end, dimensions, materials, nondestructive examination, pressure testing, ASME B16 series.