ISO 16903:2015

Overview - ISO 16903:2015 (LNG characteristics and material selection)

ISO 16903:2015 provides guidance on the characteristics of liquefied natural gas (LNG) and the cryogenic materials used across the LNG industry. Intended as a reference for designers and operators, the standard describes LNG physical and thermodynamic properties, health and safety considerations, and factors that influence design and material selection for LNG facilities. It supports the implementation of other LNG standards and codes.

Key Topics covered

• General LNG properties: composition (predominantly methane with ethane, propane, butane, nitrogen, etc.), typical density ranges (about 420–470 kg/m3, occasionally up to 520 kg/m3), boiling temperatures (around −166 °C to −157 °C), and viscosity behavior at cryogenic temperatures.
• Measurement and sampling: guidance on representative sampling and analysis methods (gas chromatography; references include ISO 6578, ISO 6568, ISO 6974, ISO 8310).
• Boil-off gas (BOG): generation from heat ingress, composition, and implications for pressure control and handling systems.
• Physical hazards and phenomena: spillage, expansion and dispersion of gas clouds, ignition and flammability limits, pool fires, rollover, rapid phase transition (RPT), BLEVE and pressure-wave effects-important for quantitative risk assessment (QRA) and emergency planning.
• Health & safety: exposure to cold (frostbite, hypothermia), exposure to gas (asphyxia, toxicity), recommended protective clothing, signage and fire protection measures.
• Materials of construction: selection of materials for components in direct contact with LNG and those exposed to cold but not in direct contact; consideration of thermal stresses and cryogenic performance.

Practical applications and users

ISO 16903:2015 is a practical reference for:

• LNG plant and terminal designers (storage tanks, piping, vaporisers)
• Materials and mechanical engineers selecting cryogenic-compatible alloys and components
• Safety, process and risk engineers performing QRA, layout, and mitigation studies
• Operations and maintenance teams developing safe handling procedures and PPE requirements
• Regulators and consultants referencing consistent LNG properties and hazard descriptions

Use cases include material selection for cryogenic service, tank and containment design, spill and dispersion modelling inputs, emergency response planning, and harmonizing design assumptions across standards.

Related standards (reference examples)

• EN 1473 - Design of onshore LNG installations
• NFPA 59A - Production, storage and handling of LNG
• ISO 6568 / ISO 6974 / ISO 6578 / ISO 8310 - analytical and instrumentation methods referenced in ISO 16903

Keywords: ISO 16903:2015, LNG characteristics, cryogenic materials, LNG design, material selection, boil-off gas, LNG safety.