ISO 9809-4:2021

Overview

ISO 9809-4:2021 - "Gas cylinders - Design, construction and testing of refillable seamless steel gas cylinders and tubes - Part 4" - specifies minimum requirements for refillable seamless stainless steel gas cylinders. It applies to cylinders with water capacities up to and including 150 L (with optional extension up to 450 L) and to cylinders made from stainless steels whose maximum actual tensile strength (Rma) is less than 1 100 MPa. The standard covers materials, design, construction, workmanship, manufacturing processes, examinations and testing at the time of manufacture for cylinders intended for compressed, liquefied and dissolved gases.

Key technical topics and requirements

ISO 9809-4 details the full product lifecycle from material selection to final marking and certification. Major technical topics include:

• Materials and metallurgy
  • Requirements for stainless steel chemical composition, heat treatment, cold working/cryoforming and controls on mechanical properties.
• Design
  • Calculation and requirements for shell thickness, convex and concave ends, neck and foot/neck rings, and complete design drawings.
• Construction and workmanship
  • Manufacture tolerances: wall thickness, out-of-roundness, mean diameter, straightness, verticality and surface imperfections.
• Non-destructive and destructive testing
  • Ultrasonic examination, hydraulic burst tests, proof pressure and volumetric expansion tests, tensile, bend/flattening and impact tests, intergranular corrosion testing and leak tests.
• Type approval, batch testing and certification
  • Prototype testing (including pressure cycling and base checks), type approval certificates, specific production/batch tests and acceptance procedures.
• Marking and documentation
  • Manufacturer marking, capacity checks and certification records; annexes provide examples and evaluation criteria for manufacturing imperfections.

Practical applications and users

ISO 9809-4 is used by:

• Cylinder manufacturers and fabricators who design and produce refillable seamless stainless steel cylinders.
• Quality and testing laboratories performing type approval, batch testing and NDT (ultrasonic, hydraulic, tensile).
• Gas producers, distributors and end users requiring safe supply containers for compressed, liquefied and dissolved gases.
• Regulators, inspection bodies and transport authorities referencing accepted international requirements for cylinder safety and conformity.
• Procurement/specification teams writing technical specifications for gas cylinder purchases.

Related standards

• Other parts of the ISO 9809 series (referenced for alternative materials or cylinder classes).
• The standard is suitable to be referenced in the UN Model Regulations for transport of dangerous goods.
• Prepared by ISO/TC 58, Subcommittee SC 3 (Cylinder design).

Keywords: ISO 9809-4, stainless steel gas cylinders, refillable seamless cylinders, cylinder design, cylinder testing, hydraulic burst test, ultrasonic examination, gas cylinder certification.