API St 526-2023 PDF

Full title and description

API Std 526 — Flanged Steel Pressure‑relief Valves. Specification and purchase requirements for flanged steel direct spring‑loaded and pilot‑operated pressure‑relief (safety) valves, including orifice designation, valve sizes and ratings, materials, pressure–temperature limits, and center‑to‑face dimensions (SI and USC units).

Abstract

API Std 526 (8th edition, 2023) provides standardized dimensional, material, and marking requirements used when specifying flanged steel pressure‑relief valves for petroleum, petrochemical and natural gas industry service. The standard is intended as a purchaser’s specification to ensure interchangeability of fit, form and function among manufacturers and to define nameplate/stamping and annexed unit conventions.

General information

• Status: Active / Most current edition.
• Publication date: 1 August 2023 (Eighth edition).
• Publisher: American Petroleum Institute (API).
• ICS / categories: Valves / Pressure‑relief devices (relevant ICS groups for valves and safety devices; commonly referenced with valve and pressure‑safety classifications).
• Edition / version: 8th edition (2023).
• Number of pages: 160 pages (approx.).

Scope

This standard is a purchase specification for flanged steel pressure‑relief valves. It sets basic requirements for both direct spring‑loaded and pilot‑operated designs, covering standard effective orifice areas (letter designations), inlet/outlet sizes and pressure ratings, acceptable materials and alloys, pressure‑temperature limitations, center‑to‑face dimensions (SI and USC tables), and nameplate/stamping information (annexes for metric and U.S. customary units). It does not prescribe installation design or sizing calculations (see API Std 520 and API RP 521 for sizing/installation and system guidance).

Key topics and requirements

• Standard effective orifice areas and letter designations (D, E, F … T) for capacity specification.
• Valve nominal sizes, flange pressure‑class ratings and center‑to‑face dimensional tables (SI and USC tables provided).
• Materials and construction requirements for bodies, bonnets, seats and optional bellows; acceptable alloys and service limits.
• Pressure–temperature limits and service ratings for both spring‑loaded and pilot‑operated valves.
• Nameplate nomenclature, stamping and marking requirements (annexes covering metric and U.S. customary unit options).
• Optional/special construction features and purchaser‑vendor agreement items (custom features outside the standard scope must be specified on drawings).

Typical use and users

Used by plant engineers, procurement/specification teams, rotating/static equipment engineers, valve manufacturers, and inspection/quality personnel in the oil & gas, petrochemical, and refining industries who require standardized purchase specifications for flanged steel pressure‑relief valves to ensure interchangeability, traceability and compliance with facility design. Vendors reference API 526 when offering flanged PRVs and when producing GA drawings and nameplate data.

Related standards

Commonly used alongside and referenced by: API Std 520 (Parts 1 & 2) — sizing, selection and installation of pressure‑relieving devices; API RP 521 — guide for pressure‑relieving and depressuring systems; API Std 527 — seat tightness testing of PRVs; ASME B16.5 / B16.34 — flange and valve pressure‑rating and dimensional references; JIP/IOGP supplementary specifications for flanged steel PRVs (industry data/quality supplements).

Keywords

API Std 526; flanged pressure‑relief valve; safety valve; PRV; pilot‑operated; spring‑loaded; orifice designation; center‑to‑face; nameplate; pressure‑temperature limits; valve specification.

FAQ

Q: What is this standard?

A: API Std 526 is the American Petroleum Institute’s purchase specification for flanged steel pressure‑relief valves (direct spring‑loaded and pilot‑operated). It standardizes dimensions, orifice designations, materials, ratings and nameplate requirements.

Q: What does it cover?

A: It covers orifice areas and letter designations, valve nominal sizes and flange pressure ratings, center‑to‑face dimensions (SI and USC tables), materials and construction limits, pressure–temperature ratings, and nameplate/stamping information; it does not replace sizing/installation guidance (see API 520 and API RP 521).

Q: Who typically uses it?

A: Plant and design engineers, procurement/specification writers, valve manufacturers, quality/inspection personnel and OEMs in oil & gas, refining and petrochemical sectors use API Std 526 when specifying or supplying flanged PRVs.

Q: Is it current or superseded?

A: Current — the 8th edition (published 1 August 2023) is the most recent edition in force. Always check with API or your standards library for any errata or subsequent revisions.

Q: Is it part of a series?

A: It is part of API’s suite of pressure‑relief and valve standards (for example API Std 520, API RP 521, API Std 527) and is commonly used in combination with ASME flange and valve standards for complete procurement and installation specifications.

Q: What are the key keywords?

A: Flanged pressure‑relief valve; API Std 526; safety valve; orifice designation; center‑to‑face; PRV specification; pilot‑operated; spring‑loaded; nameplate.