Overview
ISO 20475:2018 - "Gas cylinders - Cylinder bundles - Periodic inspection and testing" specifies requirements and general principles for the periodic inspection, testing and maintenance of cylinder bundles containing compressed, liquefied and dissolved gases. It covers procedures from receipt and identification through depressurization, disassembly, cylinder and component inspection, reassembly, testing, stamp marking and documentation. Annex A gives additional requirements for acetylene cylinder bundles. The standard is intended for use alongside national/regional transport regulations and is written to be compatible with the UN Model Regulations.
Key topics and requirements
- Scope & exclusions
- Applies to transportable cylinder bundles (not to solvent‑free acetylene cylinders and excludes bundles that are part of a battery vehicle).
- Additional application‑specific requirements (e.g., offshore) may apply.
- Inspection workflow
- Identification of bundle, cylinders, valves, manifold and ownership before work.
- Safe depressurization of manifold and individual cylinders with appropriate safety measures.
- Disassembly and devalving following safe procedures (ISO 25760 referenced).
- Cylinder periodic inspection and testing performed in accordance with the relevant cylinder standards (e.g., ISO 10460, ISO 10462, ISO 11623, ISO 18119).
- Inspection of frame, manifold, valves and fittings for structural integrity, corrosion, damage or leaks.
- Bundle reassembly, pressure testing and verification, followed by stamp marking and documentation of results.
- Competence, equipment & calibration
- Inspections/tests must be performed by a competent person or approved inspection body.
- Instruments must be calibrated and maintained per an established programme.
- Safety
- Emphasis on hazard control when removing valves or handling bundles previously in flammable gas service.
Applications and users
- Practical for organizations that design, manufacture, service or transport cylinder bundles:
- Gas cylinder manufacturers, assemblers and bundle designers
- Inspection bodies and certified maintenance workshops
- Gas distributors, transport operators and fleet managers
- Safety and compliance officers ensuring conformity with transport regulations
- Industrial sectors using bundled cylinders: welding, medical gases, specialty gases, offshore and petrochemical operations
- Helps ensure safe re‑introduction of bundles to service and legal compliance during retest cycles.
Related standards
By following ISO 20475:2018, organizations can standardize periodic inspection and testing procedures for cylinder bundles, reduce safety risks and meet regulatory and transport compliance requirements.
