ISO 18821:2025 PDF

Overview

ISO 18821:2025 - Ships and marine technology - Marine combined connecting mooring line defines classification, structure and codes, design requirements and testing methods for a marine combined connecting mooring line (a “combined line” made up of a mooring line, connection device and tail). The standard specifically applies to the design, manufacture and inspection of combined lines for tankers and is intended to harmonize safety, performance and test procedures for these assemblies.

Key topics and technical requirements

• Scope and classification
  • Defines three combined-line types: T (link without roller), M (link with roller) and C (cow hitch), with recommended configurations and coding.
• Design requirements
  • Line design break force (LDBF) shall be 100–105% of the ship design minimum breaking load (MBL).
  • Working load limit (WLL): steel wire ropes 55% of ship design MBL; fibre ropes 50%.
  • Connection devices: ultimate load ≥ 3 × safe working load; test tension ≥ 2 × SWL.
  • Tail design break force (TDBF): 125–130% of ship design MBL.
  • Environmental and operational factors: break forces specified at multiple temperatures (−20 °C to 80 °C); D/d ratios for bend-induced degradation; cyclic loading considerations.
• Materials and specifications
  • Steel wire ropes per ISO 2408 (IWRC classes, min tensile strength 1 770 N/mm²).
  • Synthetic fibre ropes per ISO 9554, ISO 2307 for test/dimension methods.
  • Acceptable rope types: HMPE (ISO 10325), LCP, aramid ropes, and various tail materials (polyamide, polyester, polyolefin blends).
• Test methods
  • Standardized tests for surface quality, dimensions, linear density, breaking force, proof and ultimate loads, cyclic loading, immediate strain and angled endurance. Annexes provide specimen specifications and example test reports.

Applications and users

ISO 18821:2025 is relevant to:

• Ship designers and naval architects (mooring system design and D/d specification)
• Shipyards and manufacturers of mooring assemblies for tankers
• Classification societies, inspection bodies and testing laboratories
• Ship operators, riggers and mooring planners responsible for procurement, maintenance and safety management
• Suppliers of steel wire and synthetic fibre mooring ropes, connection devices and tails

Related standards

Normative references incorporated include:

• ISO 2408 (steel wire ropes)
• ISO 2307 (fibre ropes - test methods)
• ISO 9554, ISO 1140, ISO 1141, ISO 10325, ISO 10556 (fibre rope types)
• ISO 16143-1 (stainless steel flat products)

ISO 18821:2025 provides a single reference to ensure combined mooring lines used on tankers meet consistent safety, testing and performance expectations.