ISO 10976:2023

Overview - What ISO 10976:2023 covers

ISO 10976:2023, “Refrigerated light hydrocarbon fluids - Measurement of cargoes on board LNG carriers,” is the international standard that defines accepted methods and procedures for measuring, reporting and accounting the quantities of liquefied natural gas (LNG) on board LNG carriers. The third edition (2023) updates measurement practices used in custody transfer and operational reporting, addressing static and dynamic measurement systems, safety, calibration, sampling and cargo calculations. The standard is written primarily in SI units (with US customary equivalents where relevant).

Key technical topics and requirements

• Scope of measurement: measurement of liquid volume, vapour volume, temperature and pressure, and overall cargo quantity accounting.
• Measurement systems: descriptions and requirements for static (tank gauging, tank capacity tables, trim & list corrections, tank gassing-up / cool-down tables) and dynamic systems (flow metering during transfer).
• Instrumentation and performance: requirements for liquid level, temperature and pressure measurement equipment, automatic tank gauges and automatic tank thermometers, plus performance, calibration and certification.
• Verification & inspection: procedures for calibration, verification between dry-dockings and inspections during transfer operations.
• Operational safety & procedures: general operating safety precautions, electrical classification, electromagnetic disturbance, maintenance and personnel protection.
• Cargo calculations: LNG volume and density determination, handling levels below the lower measurable limit, and examples/calculation methods.
• Sampling & documentation: guidance on LNG sampling methods and custody transfer documentation; includes informative annexes with examples, checklists and calculation examples.

Practical applications - who uses ISO 10976:2023

• Ship operators and crew - to standardize on-board measurement and reporting procedures during loading, voyage and discharge.
• Terminal and shore personnel - for consistent custody transfer practices and documentation.
• Cargo surveyors and independent inspectors - to witness, verify and certify quantity measurements.
• Metering and instrumentation engineers - for calibration, installation and verification of gauges and flowmeters.
• LNG traders, charterers and regulators - to ensure transparent, auditable quantity accounting in sales and purchase agreements (SPAs).

Related standards

Relevant normative references cited by ISO 10976:2023 include:

• ISO 6578:2017 (static measurement calculation procedures)
• ISO 8310 (automatic tank thermometers)
• ISO 8943:2007 (LNG sampling)
• ISO 18132-1 (automatic tank gauges for LNG)
• ISO 19970 (metering of gas as fuel during cargo transfer)
• ISO 21903 (flowmeter calibration & installation for LNG)
• Relevant IEC publications

ISO 10976:2023 is essential for consistent, accurate LNG cargo measurement and custody transfer, helping reduce disputes and improve operational safety across the LNG shipping value chain.