ISO 4145:1986

Overview

ISO 4145:1986 - "Non‑alloy steel fittings threaded to ISO 7‑1" defines dimensional, material and performance requirements for non‑alloy steel pipe fittings used primarily for industrial threaded connections. The standard standardizes types and symbols (Table 1), tabulates fitting dimensions for common nominal sizes (DN 6 to DN 100; thread designations 1/8 to 4) and includes sockets up to DN 150. It ensures interchangeability, leak‑tight performance and consistent designation across manufacturers.

Key topics and technical requirements

• Scope and fittings covered: elbows (equal and reducing), tees, crosses, sockets, half‑sockets, reducing bushes, hexagon nipples, caps, plugs and unions - each illustrated with symbols in Table 1.
• Dimensional data: detailed dimension tables (Tables 2, 3, 4, 5, 6, 7, 8, 9–12) for nominal sizes DN 6 to DN 100; sockets in Table 6 up to DN 150; reducing fittings tabulated across specific tables.
• Threading: fittings are to be threaded in accordance with ISO 7‑1. External threads are generally tapered at 1:16; internal threads are normally parallel (tapered internal threads allowed in some cases). Non‑pressure‑tight threads of union nuts and mating parts follow ISO 228‑1.
• Materials: made from rolled or forged unalloyed steel with properties at least equivalent to steels referenced in ISO 2546 and ISO 2547; free‑cutting grades permitted for machined parts.
• Mechanical/inspection requirements: outlets should be chamfered; widths across flats to comply with ISO 272 (with specific exceptions for caps/unions); manufacturers may perform hydraulic or equivalent leak‑tightness tests.
• Hydraulic test pressure: fittings shall withstand a hydraulic test pressure of 50 bar (or an equivalent test ensuring leak‑tightness).
• Designation: standard prescribes a clear naming sequence (type, reference to ISO 4145, symbol, thread designation) to ensure unambiguous identification.

Applications and who uses it

• Where used: industrial piping systems, machine construction, process plants, instrumentation and maintenance where threaded steel fittings are required.
• Who uses it: pipe and fitting manufacturers, procurement/specification engineers, plant designers, maintenance teams, quality inspectors, and third‑party testing organizations.
• Practical value: ensures compatibility and interchangeability of threaded non‑alloy steel fittings, supports reliable pressure‑tight joints, simplifies procurement by standard designations and dimension tables, and helps meet inspection/test requirements.

Related standards

• ISO 7‑1 - Pipe threads where pressure‑tight joints are made on the threads
• ISO 228‑1 - Non‑pressure‑tight pipe threads (for union nuts)
• ISO 272 - Fasteners - widths across flats (hexagon products)
• ISO 2546 / ISO 2547 - Reference steels for plain‑end tubes and fittings

Keywords: ISO 4145, non‑alloy steel fittings, threaded to ISO 7‑1, fittings dimensions, DN sizes, elbows, tees, sockets, unions, hydraulic test 50 bar, pipe fittings standard.