ISO 18172-2:2007

Overview

ISO 18172-2:2007 - "Gas cylinders - Refillable welded stainless steel cylinders - Part 2: Test pressure greater than 6 MPa" specifies minimum requirements for the design, materials, manufacture and testing of refillable, transportable welded stainless steel gas cylinders. It applies to cylinders with water capacities from 0.5 L to 150 L, manufactured from stainless steels with maximum tensile strength below 1 100 MPa, and having a test pressure greater than 6 MPa (60 bar). The standard supports safe use for compressed and liquefied gases and is written for regulatory conformity and transport safety.

Key topics and technical requirements

• Materials and heat treatment: requirements for stainless steel categories, solution annealing, cryoforming and heat-treatment controls.
• Design: calculation of cylindrical shell wall thickness, design of convex or other end shapes, bungs, openings and minimum permitted thicknesses; use of a design stress factor (F) and related symbols.
• Construction and workmanship: welding qualifications, cryoforming and cold-forming procedures, welded joints, valve protection, neck threads and visual examination.
• Testing regime:
  • New design tests and certification requirements for prototype designs.
  • Batch tests: tensile, bend, impact, hardness, macroscopic examination of weld cross-sections, plus acceptance criteria.
  • Tests on every cylinder: hydraulic/pressure testing, leakage and hardness checks.
• Non-destructive testing: radiographic and visual testing of welds (annexes and references specify techniques and acceptance).
• Marking and certification: mandated markings and documentation for conformity with transport regulations.

Practical applications

• Ensures safety and reliability of refillable welded stainless steel cylinders used in industry, medical gas supply, specialty gases, and laboratory settings.
• Guides manufacturers through material selection, welding procedures, production controls and quality assurance for cylinders intended for high-pressure service (>60 bar).
• Provides the technical basis for type approval, batch certification and conformity assessment, and for demonstrating compliance with transport of dangerous goods rules.

Who uses this standard

• Cylinder manufacturers and designers
• Welding and quality-control engineers
• Testing and inspection laboratories
• Regulatory authorities, certification bodies and transport safety organizations
• Purchasers and specifiers of high-pressure gas cylinders

Related standards

Commonly used with other ISO documents referenced in the standard, e.g.:

• ISO 11114-1 (compatibility of materials with gas contents)
• ISO 13769 (stamp marking)
• ISO 17636 / ISO 17637 (radiographic and visual testing of welds)
• ISO 6892 (tensile testing)

Keywords: ISO 18172-2, gas cylinders, refillable welded stainless steel cylinders, test pressure greater than 6 MPa, high-pressure cylinders, cylinder design, welding, batch tests, pressure testing.