Overview - ISO 4845:2023 (Combined rigging for deep-sea mooring)
ISO 4845:2023 specifies types, dimensions, tests and technical requirements for combined rigging assemblies used to moor and position offshore structures in water depths of 1 000 m to 5 000 m. The standard covers combined rigging made of HMPE (high modulus polyethylene) fibre ropes, mooring chains, and shackles, and sets minimum performance, design and testing expectations to ensure long-term reliability for deep‑sea mooring operations.
Key topics and technical requirements
- Scope and components: Defines combined rigging as assemblies of HMPE fibre rope, mooring chain and shackles, with thimbles and protective layers at rope ends.
- Design rules:
- Strength design must ensure the fibre rope and chain meet minimum breaking strength (MBS) at end of service life.
- Strength ratio between mooring chain and fibre rope: 1.05–1.10. End‑link size = 1.2 × common link; shackle size = end‑link size.
- Length design must account for fibre rope creep, keep the rope below the surface during service, and avoid seabed friction.
- Fibre rope specifics:
- Rope structure: core rope + particle‑resistant isolating layer + protective layer + thimbles.
- Raw HMPE tenacity ≥ 2 500 MPa; core rope minimum tenacity ≥ 1 300 MPa; protective layer (if polyester) ≥ 730 MPa.
- Protective layer thickness ≥ 7.0 mm; MBS values range by size (examples in the standard).
- Mooring chains and shackles: Material grade and mechanical performance must comply with ISO 20438:2017 (material, breaking load, chain/studless design, and D‑type shackle references).
- Performance & service life: Assemblies designed for a minimum service time of 10 years and component interchangeability.
- Testing and inspection:
- Fibre rope tests, MBS, tenacity, anti‑particle penetration and creep per ISO 18692‑3.
- Chain and shackle mechanical tests per ISO 20438 and classification society rules.
- Marking & documentation: Permanent marking (manufacturer, specs, MBS, date), plus test reports, dimensional and material reports, and a certificate with serial number.
Applications and who uses this standard
- Offshore engineers and mooring system designers specifying combined rigging for deepwater floating platforms, FPSOs, production units and research moorings.
- Manufacturers and suppliers of HMPE ropes, mooring chains and shackles ensuring compliance with design, test and marking requirements.
- Classification societies, shipyards, asset owners and maintenance teams validating performance, interchangeability and service life for deep‑sea mooring assemblies.
Related standards
Keywords: ISO 4845:2023, combined rigging, deep‑sea mooring, HMPE fibre rope, mooring chain, shackles, ISO 18692‑3, ISO 20438.
