Overview
ISO 23115:2020 - Ships and marine technology - Ship's mooring and towing fittings - Seats for mooring chocks - specifies requirements for the seats for mooring chocks used to guide mooring and towing ropes from inboard to outboard. The standard covers classification (type), nominal sizes, dimensional details, materials, construction, manufacturing and inspection, strength assessment methodology, and marking requirements including safe working load (SWL) notation. It is intended for shipbuilders, naval architects, manufacturers of mooring fittings, ship operators and classification societies.
Key topics and technical requirements
- Scope and classification
- Defines three installation types: Type A (deck-mounted), Type B (deck and side shell-mounted) and Type C (bulwark brackets).
- Nominal sizes and dimensions
- Nominal sizes reference the same sizes used for mooring chocks (ISO 13713); typical sizes include 250 × 200, 300 × 250, 350 × 250, 400 × 250, 450 × 250, 500 × 250A/B. Detailed dimensions and welding details are provided in tabulated figures.
- Materials
- Seats shall be made from weldable steel plates with a yield strength of at least 235 N/mm².
- Construction and manufacture
- Foundations and weld connections must transmit maximum mooring loads to hull structure without plastic deformation or cracking.
- All rope-contact surfaces must be free of roughness or irregularities; welded surfaces must show no visible flaws.
- External surfaces require an anti‑corrosion protective finish.
- Strength assessment
- Loads considered include specified horizontal and vertical load cases (rope deflection scenarios).
- Strength is verified by finite element model (FEM) analysis with a mesh size of approximately 2× plate thickness and shell elements.
- Stress criterion: combined stress under SWL limited to 85% of material yield stress.
- Marking and documentation
- SWL must be recorded in the ship's towing and mooring plan (per IMO Circular MSC/Circ.1175) and clearly marked on the seat or deck in tonnes (e.g., “SWL XXX t”).
- Actual on‑board SWL considers under‑deck reinforcement and must not exceed the SWL given in the standard.
Applications and users
- Shipbuilders and shipyards specifying or installing mooring fittings
- Manufacturers of mooring chocks and seats for mooring chocks
- Naval architects and structural engineers performing hull‑fitting integration and FEM strength checks
- Classification societies, ship operators, port engineers and OEMs ensuring compliance with safety and marking rules
- Useful for mooring system design, procurement specs, and regulatory conformity checks
Related standards
- ISO 13713 - Ship’s mooring and towing fittings - Mooring chocks
- IMO Circular MSC/Circ.1175 - Guidance on shipboard towing and mooring equipment
- Relevant industry guidance: IACS UR A2, OCIMF Mooring Equipment Guidelines (MEG4)
Keywords: ISO 23115:2020, seats for mooring chocks, ship mooring fittings, SWL, mooring chocks, ship's mooring and towing fittings, FEM strength assessment.