ISO 9329-3:1997

Overview

ISO 9329-3:1997 - "Seamless steel tubes for pressure purposes - Technical delivery conditions - Part 3: Unalloyed and alloyed steels with specified low temperature properties" - defines the technical delivery conditions for seamless circular steel tubes intended for low‑temperature piping systems. It replaces ISO 2604‑2:1975 and complements general delivery requirements in ISO 404 and pressure‑equipment guidance such as ISO 5730. The standard covers chemical and mechanical requirements, production and delivery conditions, testing and inspection, marking and documentation for tubes with specified low‑temperature toughness.

Key topics and technical requirements

• Scope and tube type: Applies to seamless tubes of circular cross‑section made from unalloyed and alloyed steels with specified low temperature properties for pressure piping systems.
• Information by purchaser: Orders must specify tube denomination, hot‑ or cold‑finished condition, dimensions (outside diameter × wall thickness), lengths, steel grade and test/inspection category.
• Manufacturing & delivery condition:
  • Tubes shall be manufactured by a seamless process (hot‑ or cold‑finished).
  • Full‑length heat treatment is required: typical treatments include normalizing, normalizing + tempering, or quenching + tempering, depending on grade.
  • Steels for these tubes shall be fully killed (deoxidation requirement).
• Metallurgical and chemical controls:
  • Heat analysis and optional product (check) analysis with permissible deviations are specified.
  • Typical steel grades used (examples in the standard) include PL 21, PL 23, PL 25, PL 26, 26CrMo4, and various Ni‑bearing low‑temperature steels.
• Mechanical properties and testing:
  • Room‑temperature tensile, yield and elongation requirements are defined.
  • Low‑temperature toughness is specified by Charpy V‑notch impact tests at defined temperatures (examples include −196 °C, −120 °C, −110 °C, −60 °C), with minimum absorbed‑energy values.
  • Additional tests include flattening, ring expanding/drift expanding, hydraulic tests, and non‑destructive ultrasonic or electromagnetic leak‑tightness testing where applicable.
• Dimensions and tolerances: Outside diameter, wall thickness and mass tolerances reference established ISO dimensional tables; machining allowances for dressed areas are addressed.
• Inspection, marking and documentation: Test categories and required certificates (e.g., inspection certificate 3.1.B per ISO 10474) are specified.

Applications and users

• Applications: Low‑temperature piping systems for cryogenic plants, LNG/LPG transport and storage lines, refrigerated process piping, and other pressure systems where cold‑toughness is critical.
• Primary users: Tube manufacturers, mill quality engineers, procurement/specification writers, pressure‑equipment designers, fabricators and inspection authorities involved in specifying, producing or verifying seamless steel tubing for low‑temperature service.

Related standards

• ISO 404 - General technical delivery requirements for steel products
• ISO 5730 - Stationary shell boilers (pressure equipment reference)
• ISO 148 - Charpy impact test (V‑notch)
• ISO 377, ISO 3205, ISO 4200, ISO 9302–9305 series - sampling, dimensions and NDT methods cited by ISO 9329‑3

Keywords: ISO 9329‑3, seamless steel tubes, low temperature properties, technical delivery conditions, Charpy impact, pressure piping, heat treatment, seamless tubes standard.