Overview
ISO 5145:2017 - Gas cylinders - Cylinder valve outlets for gases and gas mixtures - Selection and dimensioning - provides practical criteria for selecting and dimensioning valve outlet connections for gas cylinders. It defines a logical system that groups gases and gas mixtures and allocates non‑interchangeable valve outlet connections to those groups to reduce the risk of incorrect gas interconnection. The standard excludes connections used for cryogenic withdrawal and gases for breathing equipment, which are covered by other International Standards.
Key topics and technical requirements
- FTSC coding and gas grouping: Uses the four‑digit FTSC code (see ISO 14456) to classify gases by flammability, toxicity, oxidizing ability, physical state and corrosiveness, enabling assignment to one of 15 compatible gas groups (group 15 reserved for specific mixtures).
- Normative references: Selection relies on related standards for property determination - ISO 10156 (flammability/oxidizing), ISO 10298 (toxicity), ISO 13338 (corrosiveness), and ISO 14456 (FTSC codes).
- Connection design principle: Defines a double‑recess “step index” system - valve outlet (faucet), connector (spigot) and union nut - engineered so connectors only fit the assigned group, ensuring non‑interchangeability.
- Dimensional specifications: Specifies three nominal connection diameters (24 mm, 27 mm, 30 mm) and a Whitworth thread with a pitch of 2 mm, producing 42 non‑interchangeable combinations (see Annex A).
- Leak tightness and sealing: Sealing is achieved by the connector end bearing on the valve outlet’s conical surface and retained by the union nut (Annex B gives guidance on union nuts requiring tools). Materials must be compatible with the gas but specific materials are not mandated.
- Marking: Outlets and corresponding connections must be marked with the allocated outlet number (refer to Table 3).
Practical applications - who uses ISO 5145
- Cylinder manufacturers and valve designers - to design and size valve outlets and connectors in accordance with internationally harmonized allocation rules.
- Gas producers and filling stations - for correct valve selection when preparing cylinders for specific gases or mixtures.
- Equipment installers and maintenance teams - to ensure safe, non‑interchangeable connections during use and servicing.
- Regulators and safety engineers - to reference a practical allocation system where national standards are absent or when introducing new industrial gases.
- Healthcare and industrial users - as guidance for grouping and connection selection (note: specific breathing‑equipment connections are outside this standard).
Related standards
- ISO 10156, ISO 10298, ISO 13338, ISO 14456 - all used for property assessment and FTSC assignment. Annexes A, B (normative) and C (informative examples, including medical gases) provide dimensional tables and implementation guidance.
Keywords: ISO 5145, gas cylinders, cylinder valve outlets, valve outlet connections, FTSC code, step index connections, Whitworth thread, non‑interchangeable connections, leak tightness.
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