Overview
ISO 21154:2026 specifies the boil-off-rate (BOR) measurement method for cargo containment systems (CCS) in liquefied natural gas (LNG) ships. This international standard provides principles, measurement conditions, required equipment, processes, data collection and processing, and reporting procedures for accurately assessing the BOR of CCS. The BOR is a critical metric for evaluating the performance and thermal efficiency of containment systems in LNG carriers, LNG floating storage and regasification units (FSRUs), and LNG bunkering vessels. Additionally, this standard serves as a reference for evaluating fuel containment systems (FCS) in LNG-fueled ships.
By applying ISO 21154:2026, ship owners, operators, designers, and marine surveyors gain a consistent methodology for measuring natural evaporation rates in LNG containment, directly impacting safety, cost-effectiveness, and environmental compliance.
Key Topics
ISO 21154:2026 covers the following essential aspects of BOR measurement for marine LNG cargo systems:
- Measurement Principle: Establishes a heat balance approach to determine the mass loss of LNG due to natural evaporation over a 24-hour period under rated vapor pressure.
- Measurement Parameters: Requires the monitoring and recording of key data, including:
- LNG composition and density
- Liquid and vapor temperatures within the CCS
- LNG levels and vapor pressure
- Insulation system temperature at specified points
- Ambient conditions (air and water temperature, pressure)
- Voyage and operational conditions affecting the tank
- Measurement Facility Requirements: Specifies the use of precise liquid level, temperature, and pressure measuring devices with set accuracy standards and automatic data recording.
- BOR Measurement Procedure: Details the phased measurement approach-before, during, and after voyage-ensuring repeatability and reliability.
- Data Acquisition and Processing: Outlines the systematic recording of measurement data, calculation methodology for BOR and active BOR, and requirements for correction factors reflecting voyage, environment, and equipment conditions.
- Reporting: Specifies the structure of BOR test reports including data tables to document results for each tank and measurement period.
Applications
ISO 21154:2026 is vital for a range of marine technology and LNG shipping contexts:
- LNG Carriers: Ensures rigorous evaluation of cargo containment systems, enabling optimal design and verification of thermal insulation performance.
- LNG FSRUs and LNG Bunkering Vessels: Provides standardized reference for monitoring and assessing LNG loss during storage, bunkering, or regasification operations.
- LNG-Fueled Ships: Assists in benchmarking and verifying the fuel containment system’s effectiveness, supporting compliance with emissions and safety regulations.
- Marine Engineering and Surveying: Offers a thorough method for shipbuilders, designers, and inspectors to verify containment system integrity and operational performance across varied operating conditions.
- Operational Optimization: Enables shipowners and operators to reduce overall LNG losses, manage voyage costs, and enhance environmental performance by minimizing unwanted boil-off.
Implementing this standard supports the ongoing demand for high-efficiency, low-emission LNG shipping solutions in alignment with international maritime environmental goals.
Related Standards
To ensure comprehensive compliance and optimal performance, ISO 21154:2026 references and complements the following standards and codes:
- ISO 16903 - Characteristics of LNG, influencing design and material selection
- IMO IGC Code - International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk
- IMO IGF Code - International Code of Safety for Ships Using Gases or Other Low-Flash Point Fuels
- Classification Society Guidelines - Such as Lloyd’s Register rules for thermal analysis of ships carrying liquefied gases
- Industry Guidelines - For climate operations and vessel winterization (e.g., DNV GL guidelines)
ISO 21154:2026 provides a critical foundation for safe, efficient, and environmentally responsible transport and storage of LNG by ship. For organizations involved in LNG maritime operations, employing this standardized methodology enhances operational transparency, safety, and regulatory compliance.