ISO 21593:2019

Overview

ISO 21593:2019 - Ships and marine technology - Technical requirements for dry-disconnect/connect couplings for bunkering liquefied natural gas (LNG) defines minimum design, safety, functional, marking, interface and testing requirements for two-part dry-disconnect/connect couplings used in LNG bunkering systems. The standard applies to couplings sized DN 25 to DN 200 for use on LNG bunkering ships, tank trucks, shore-based facilities and other bunkering infrastructures. It is intended to ensure safe, leak-minimizing connections between hoses (nozzles) and ship manifolds (receptacles) during LNG transfer.

Key Topics

• Scope and definitions: Clear terminology for dry-disconnect, nozzle, receptacle, manifold and bunkering operations.
• Design requirements:
  • Minimum design pressure: 1.6 MPa.
  • Design temperature range: −196 °C to +85 °C.
  • Coupling consists of a nozzle and a receptacle; receptacle must include a seal.
  • Wall thickness and pressure containment must follow recognized pressure-equipment design codes.
• Functional requirements:
  • Interlock function to guarantee valves are closed/open in correct sequence (connection: sealed first; disconnection: valves closed first).
  • Minimize trapped volume between internal valves; manufacturer must report this volume.
  • Couplings must remain liquid- and gas-tight under operating, thermal and mechanical loads, including ice accretion.
  • Disconnect capability under manifold loads with specified ice thickness (10 mm for DN25–DN80; 25 mm for DN100–DN200).
• Materials and components: Requirements for body, bolting, springs, seals and welding consistent with cryogenic service.
• Interface types and dimensions: Standardized interfaces and flange connections for compatibility.
• Testing and verification:
  • Production and verification tests including shell and internal-valve tightness/strength, cryogenic operation, endurance, bending, drop, high-pressure and electrical conductivity tests.

Applications

ISO 21593:2019 is used by:

• Manufacturers of dry-disconnect/connect couplings and LNG hose assemblies.
• Shipyards and naval architects integrating LNG bunkering manifolds.
• Bunkering operators, port authorities and terminal designers specifying safe LNG transfer equipment.
• Inspection bodies, certifiers and regulators for compliance testing and acceptance.
• Design engineers selecting couplings for tank trucks, shore facilities and bunker vessels.

Related Standards

• ISO 16904 (hydraulically operated QCDC for hard loading arms)
• ISO 3834 (welding quality)
• ISO 5208, EN 12266, EN 1092-1, ASME B16.5, ASME B31.3 (pressure/flange/valve testing and design codes)

Keywords: ISO 21593:2019, dry-disconnect/connect couplings, LNG bunkering, liquefied natural gas, nozzle, receptacle, cryogenic couplings, bunkering safety, coupling testing.