Overview - EN ISO 21593:2019 (Ship and marine technology)
EN ISO 21593:2019 specifies technical requirements for dry-disconnect/connect couplings used in LNG bunkering systems. It covers design, minimum safety and functional requirements, marking, interface types and dimensions, materials and comprehensive testing procedures for couplings intended for use on LNG bunkering ships, tank trucks, shore-based facilities and other bunkering infrastructures. The standard applies to coupling sizes from DN 25 to DN 200 and excludes hydraulically operated quick connect/disconnect couplers (QCDC) covered by ISO 16904.
Keywords: EN ISO 21593:2019, dry-disconnect/connect couplings, LNG bunkering, bunkering liquefied natural gas, ship and marine technology.
Key Topics and Technical Requirements
- Scope & Definitions: Clear terms for bunkering, dry-disconnect, nozzle, receptacle and coupling assembly to ensure consistent interpretation across marine and shore installations.
- Design Principles: Basic design intent to minimise LNG or natural gas release during connection/disconnection (dry-disconnect) and to support safe, rapid coupling operations without bolts.
- Materials & Manufacturing: Requirements for coupling bodies, bolting, springs, seals and welding quality aligned with recognized welding quality standards.
- Interface Types & Dimensions: Specified mating interfaces and dimensional requirements for compatibility across ships, trucks and shore systems for sizes DN 25–DN 200.
- Marking & Traceability: Mandatory marking elements to identify manufacturer, size, pressure class and relevant information for maintenance and inspection.
- Testing & Performance: Detailed test procedures including ambient and cryogenic test conditions, shell tightness and strength, internal valve tightness and strength, operation tests at minimum working temperatures, electrical conductivity, manual force in cold/frost conditions, bending, drop, endurance and high-pressure tests.
- Referenced Normative Documents: Includes ISO 3834 (welding quality), ISO 5208, EN 12266-1, EN 1092-1 and relevant ASME piping/flange standards.
Applications and Who Uses This Standard
EN ISO 21593:2019 is intended for:
- Shipyards and naval architects specifying bunkering connections on LNG-fuelled vessels.
- Manufacturers of dry-disconnect/connect couplings and LNG hose assemblies.
- LNG bunker vessel operators, terminal and port facility designers, and tank truck suppliers.
- Classification societies, regulators and inspection bodies assessing safety, testing and conformity.
Practical applications include design specification, procurement, testing acceptance, installation guidance and maintenance planning for LNG bunkering equipment.
Related Standards
- ISO 16904 - hydraulically operated QCDC for hard loading arms (not covered by EN ISO 21593)
- ISO 3834, ISO 5208, EN 12266-1, EN 1092-1, ASME B16.5, ASME B31.3 - referenced for welding, testing and flange/piping compatibility.
This standard helps ensure interoperable, safe and tested dry-disconnect couplings across the LNG bunkering value chain, improving operational safety and reducing fugitive releases during bunkering operations.
