ISO 5251-1981 PDF
Name in English:
St ISO 5251-1981
Name in Russian:
Ст ISO 5251-1981
Original standard ISO 5251-1981 in PDF full version. Additional info + preview on request
Full title and description
ISO 5251:1981 — Stainless steel butt-welding fittings. Specifies dimensions, tolerances and commonly used stainless‑steel grades for butt‑welding fittings used in piping work, including elbows (3D and 5D types), concentric and eccentric reducers, tees, caps and stub ends, with associated quality requirements.
Abstract
Defines geometric dimensions, tolerances and material grade recommendations for stainless‑steel butt‑welding fittings intended for piping systems (bends 3D and 5D, 90° and 180° where applicable, reducers, tees, caps, stub ends), together with quality requirements applicable to manufacturing and acceptance of these fittings.
General information
- Status: Published (confirmed current following ISO systematic review).
- Publication date: April 1981.
- Publisher: International Organization for Standardization (ISO).
- ICS / categories: 23.040.40 (fasteners and metal fittings / related mechanical products).
- Edition / version: Edition 1 (1981).
- Number of pages: 25.
Scope
Applies to stainless‑steel butt‑welding fittings used in piping applications and specifies the dimensions, tolerances and generally used stainless‑steel grades for standard fitting types (3D and 5D elbows, concentric/eccentric reducers, tees, caps, stub ends), together with basic quality requirements for manufacture and inspection.
Key topics and requirements
- Standardized external and internal dimensions for common butt‑welding fittings (elbows, reducers, tees, caps, stub ends).
- Tolerances for dimensions and ends (including fittings with and without straight ends).
- Recommended stainless‑steel grades for the fittings covered.
- Quality and acceptance requirements applicable to production and inspection of fittings.
- Definitions of fitting types (3D and 5D elbows, concentric/eccentric reducers, etc.).
Typical use and users
Used by piping designers and engineers, manufacturers and fabricators of stainless‑steel fittings, quality and inspection personnel, procurement specialists specifying compliant fittings, and standards/technical committees referencing dimensional and material requirements for piping components.
Related standards
National equivalents and related documents exist (for example several French national standards that correspond to or are similar to ISO 5251). The standard is maintained under ISO/TC 5/SC 5, which produces coordinating documents for metallic pipe fittings and related components.
Keywords
stainless steel; butt‑welding fittings; elbows; reducers; tees; caps; stub ends; dimensions; tolerances; piping; ISO 5251; ISO/TC 5.
FAQ
Q: What is this standard?
A: ISO 5251:1981 is an International Standard that specifies dimensions, tolerances and commonly used stainless‑steel grades and quality requirements for butt‑welding pipe fittings such as elbows, reducers, tees, caps and stub ends.
Q: What does it cover?
A: It covers geometric dimensions and tolerances for specified fitting types (notably 3D and 5D elbows, concentric and eccentric reducers, tees, caps and stub ends), recommended stainless‑steel grades and basic quality/acceptance requirements for use in piping work.
Q: Who typically uses it?
A: Piping and mechanical designers, fitting manufacturers and fabricators, inspection and quality personnel, and procurement/specification writers who need standardized dimensional and material requirements for stainless‑steel butt‑welding fittings.
Q: Is it current or superseded?
A: As published in April 1981 (Edition 1), ISO 5251:1981 was reviewed and confirmed in ISO’s systematic review process (most recently confirmed in 2020) and therefore remains the current edition unless a newer ISO edition or replacement has been published after that review.
Q: Is it part of a series?
A: It is a standalone ISO document under the work of ISO/TC 5/SC 5 (metallic pipe fittings). While not a numbered multi‑part series, it sits alongside other ISO standards covering pipe fittings, flanges and related piping components produced by the same technical committee.
Q: What are the key keywords?
A: Stainless steel, butt‑welding fittings, elbows (3D/5D), reducers (concentric/eccentric), tees, caps, stub ends, dimensions, tolerances, piping.