ISO 9330-3:1997

Overview - ISO 9330-3:1997 (Welded steel tubes for pressure purposes)

ISO 9330-3:1997 specifies the technical delivery conditions for electric resistance welded (ERW) and induction welded steel tubes of circular cross‑section intended for low temperature piping systems. It covers unalloyed and alloyed steels with specified low‑temperature toughness, for tubes with wall thicknesses up to and including 16 mm. The standard addresses manufacture, heat treatment, chemical and mechanical requirements, inspection and testing, marking and delivery documentation.

Key topics and technical requirements

• Scope and product form
  • ERW and induction welded tubes (no filler metal) of circular cross‑section, hot‑ or cold‑finished.
  • Wall thickness ≤ 16 mm; tubes intended specifically for low‑temperature service.
• Chemical and metallurgical requirements
  • Heat analysis and permissible deviations are defined (see table of steel grades and composition in the standard).
  • Steels are normally fully killed; deoxidation and grain‑size considerations are specified.
• Heat treatment
  • Tubes shall be supplied suitably heat treated over full length - options include normalizing, normalizing and tempering, or quenching and tempering depending on grade.
• Mechanical and toughness testing
  • Tensile tests at room temperature and Charpy V‑notch impact tests at specified low temperatures to verify cold toughness.
  • Other mechanical tests: flattening, drift expanding, bending where applicable.
• Inspection and non‑destructive testing
  • Hydraulic leak‑tightness, ultrasonic and electromagnetic weld seam testing referenced (ISO 9302, ISO 9303, ISO 9764 and related).
  • Inspection/test categories and certificate types (example: inspection certificate 3.1.B) are defined.
• Dimensions, tolerances and marking
  • Reference dimensional standards (ISO 4200, ISO 1129) and tolerance systems (ISO 5252).
  • Marking, protection and delivery documents requirements are included.

Practical applications and users

Who uses ISO 9330-3:

• Manufacturers of ERW / induction welded steel tubes who must supply tubes with verified low‑temperature properties.
• Engineers, specifiers and purchasers of low temperature piping systems requiring traceable mechanical and impact performance.
• Inspection and testing bodies that perform mechanical and non‑destructive tests and issue certificates.

Typical applications:

• Piping where verified low‑temperature toughness is critical (cryogenic or refrigerated services and other cold‑temperature process lines).
• Pressure piping where welded tubes are preferred and full delivery documentation, inspection and testing are required.

Related standards

• ISO 4200 - Plain end steel tubes: dimensions and masses
• ISO 10474 - Inspection documents for steel products
• ISO 148 - Charpy impact test (V‑notch)
• ISO 6892 - Tensile testing
• ISO 9302 / ISO 9303 / ISO 9764 - Ultrasonic / electromagnetic testing for weld verification
• ISO 5730 - Stationary shell boilers (for boiler/pressure vessel applications)

Keywords: ISO 9330‑3, welded steel tubes, ERW, induction welded, low temperature properties, technical delivery conditions, pressure purposes, tube inspection, Charpy V‑notch.