ISO 20257-2:2021

Overview

ISO 20257-2:2021 - "Installation and equipment for liquefied natural gas - Design of floating LNG installations - Part 2: Specific FSRU issues" provides specific design and operational requirements and guidance for Floating Storage and Regasification Units (FSRUs). It complements ISO 20257-1 and applies to offshore, near‑shore or docked FSRUs, including both new‑build and converted units. The standard also covers requirements for the jetty when an FSRU is moored alongside.

Key topics and technical requirements

ISO 20257-2 addresses a wide range of FSRU‑specific engineering, safety and environmental issues, including:

• Basis of design: functional description, main process criteria, reliability/availability/maintainability and studies specific to FSRUs (environmental impact of seawater intake/discharge, recirculation, scour protection).
• Health, safety and environment (HSE): water heating/cooling environmental considerations, safety layout constraints, risk‑prevention measures and facility arrangement.
• Mooring and stationkeeping: guidance for safe mooring arrangements for offshore, near‑shore and jetty moored FSRUs.
• Hull and storage design: hull considerations, LNG cargo tank pressure management, rollover risk and overpressure protection.
• Transfer systems and send‑out: LNG transfer, natural gas send‑out functional requirements, emergency disconnection and operating envelope.
• Boil‑off gas (BOG) handling and recovery: recondenser and compressor requirements, tank pressure flexibility and BOG recovery strategies.
• Regasification equipment: LNG pumps, vaporizer types and materials selection, trim heaters, venting and marine growth considerations.
• Gas send‑out control and metering: high‑integrity pressure protection systems (HIPPS), send‑out metering, gas analysis and odorization.
• Utilities, control and operations: cooling/heating media, nitrogen and fuel gas systems, process/control interfaces, communications, commissioning, inspection, maintenance, preservation and corrosion protection.
• Conversion guidance: considerations when converting existing vessels into FSRUs.

Practical applications and who uses this standard

ISO 20257-2 is used by professionals involved in the lifecycle of floating LNG installations:

• Naval architects, marine and process engineers designing FSRUs
• Owners/operators and terminal designers implementing regasification and send‑out systems
• Shipyards, conversion contractors and equipment suppliers (pumps, vaporizers, compressors)
• Port and jetty designers integrating FSRU mooring and transfer systems
• Safety and environmental compliance teams, regulators and classification societies assessing HSE and operational suitability

This standard helps ensure safe, reliable and environmentally responsible design and operation of floating LNG installations, supporting project specification, procurement, commissioning and regulatory compliance.

Related standards

• ISO 20257-1 (Design of floating LNG installations - general requirements)
• Applicable national and international maritime, environmental and LNG industry regulations and classification society rules (as referenced during project implementation).