ISO 3419:1981

Overview

ISO 3419:1981 specifies requirements for non-alloy, low-alloy and alloy steel butt-welding fittings used in piping work. This second edition (1981) cancels ISO 3419:1975 and covers geometry, dimensional tolerances, commonly used steel grades, heat treatment, marking and certification for fittings such as bends (type 2D and 3D), concentric and eccentric reducers, tees, caps and stub ends.

Example designation: Butt-welding bend 3D-90-60,3 x 2,9-TS4 ISO 3419

Key topics and technical requirements

• Scope of fittings: Bends - 2D (90° and 180°) and 3D (45°, 90° and 180°); concentric/eccentric reducers; equal and reducing tees; caps; stub ends (under consideration).
• Steel grades: Lists commonly used grades from ISO 2604 series and related standards (e.g., TS4, TS9, TW4, P5, E24-1, E29, E32, E36, E39, E41, E45). Other grades from ISO 2604 parts may be supplied by agreement.
• Dimensions and tolerances: Detailed tables for outside/inside diameters, wall thicknesses, centreline and face dimensions, conventional masses and tolerance bands. Alignment and bevel tolerances are specified (e.g., ends cut square; thicknesses > 3.6 mm shall be bevelled).
• Manufacture options: Fittings may be made from seamless tubes, welded tubes or welded plate material (welds to use filler metal and be subjected to agreed non‑destructive testing), or from plate.
• Heat treatment: Non-alloy steel fittings formed between 640 °C and 940 °C may be exempt from heat treatment if cooled in still air; alloy steel fittings require heat treatment after final forming per referenced ISO tables.
• Testing and certification: Acceptance tests are by agreement between purchaser and manufacturer. Manufacturer marking and, when requested, certificates of conformity shall be supplied in accordance with ISO 464 requirements.

Applications and users

ISO 3419 is used by:

• Pipe fabricators and manufacturers of butt-welding fittings
• Engineering, procurement and construction (EPC) firms in oil & gas, petrochemical and utility industries
• Piping designers and specifiers drafting procurement documents or inspection plans
• Quality and inspection teams requiring dimensional, material, heat treatment and marking specifications

Practical applications include pipeline construction, high‑pressure piping systems and general industrial piping where standardized butt-welding steel fittings are required.

Related standards

• ISO 2604 (steel products for pressure purposes - Parts 2–4)
• ISO 6708 (nominal size definitions)
• ISO 3183 / ISO 3845 (line pipe standards)
• ISO 4200, ISO 3545 (tube dimensions and symbols)
• ISO 464 (certification requirements)

Keywords: ISO 3419:1981, butt-welding fittings, steel pipe fittings, bends, reducers, tees, caps, dimensions, tolerances, heat treatment, piping standard.