Overview
EN ISO 23208:2019 (identical to ISO 23208:2017) specifies minimum cleanliness requirements for cryogenic vessels and associated accessories that contact cryogenic fluids at any expected operating condition. The standard defines acceptable levels of surface and particle contamination to reduce equipment malfunction risk and to ensure safety against ignition when components contact oxygen or oxidizing fluids.
Key topics and requirements
- Scope: Applies to all surfaces in contact with cryogenic fluids (refrigerated gases, evaporated liquids, supercritical fluids).
- Contamination limits: Particles visible to the naked eye under daylight/white light are unacceptable. For oxygen/oxidizing service, the maximum recommended hydrocarbon contamination is 500 mg/m² (guidance from CGA G‑4.1); lower limits may be required for specific applications.
- Prohibited residues: Chips, oxide scale, weld spatter, free water and detectable hydrocarbons, paints, adhesives or incompatible coatings are not acceptable for oxygen service unless demonstrated oxygen-compatible (see ISO 21010).
- Welding practice: Root passes of pipe welds must be protected (e.g., with forming gas) to avoid gross porosity.
- Cleaning procedures: Any method is acceptable provided the cleanliness requirements are met. Solvents/agents must be compatible with all materials (including plastics) and removed completely when cleaning for oxygen service.
- Inspection and evaluation: Select inspection/sampling methods that complement the cleaning technique. Annex A lists practical inspection methods such as direct visual (white light), UV fluorescence, wipe/solvent flush and solvent immersion/drain techniques. Inspection methods must not introduce contamination.
- Post‑cleaning protection & packaging: Cleaned items must be protected (sealed, purged, or packaged) to prevent recontamination. Protective gases must be dry, oil‑free and dust‑free; packaging must be removable without leaving residues.
- Identification & documentation: Conformity must be evidenced by a certificate or label: “ISO 23208 – cleaned oxygen” for oxygen/oxidizing fluids or “ISO 23208” for other cryogenic fluids. Protective gas type and pressure should be indicated if used.
Applications and users
- Who uses it: Cryogenic vessel manufacturers, industrial gas suppliers, LNG and hydrogen system integrators, OEMs, commissioning and maintenance teams, QA/QC inspectors, and cleaning service providers.
- Typical applications: Storage and transport tanks, transfer piping, valve bodies and accessories used with oxygen, nitrogen, LNG, hydrogen and other cryogenic fluids where contamination control is critical to performance and safety.
Related standards
- ISO 21010 - Cryogenic vessels: gas/materials compatibility
- ISO 10156 - Oxygen/oxidizer properties and combustibility guidance
- Referenced guidance: CGA G‑4.1 and EIGA documents (for hydrocarbon guidance and contamination migration)
Keywords: EN ISO 23208:2019, ISO 23208:2017, cryogenic vessels, cleanliness, oxygen service, oxidizing fluids, inspection methods, hydrocarbon contamination, post‑cleaning protection.