Overview
ISO 23116:2020 - Ships and marine technology - Ship’s mooring and towing fittings - Seats for Panama chocks - specifies the types, nominal sizes, dimensions, materials, construction, manufacturing, inspection and marking requirements for seats used to lead mooring and towing ropes through Panama chocks. It is intended for ships transiting the Panama Canal (locomotive-assisted or tug-assisted operations) and aligns seat design with normal mooring and Panama Canal requirements. The standard also notes alternatives for Panamax Plus / Neopanamax installations (see ISO 23113).
Key topics and technical requirements
- Types and sizes: Defines three installation types - Type A (deck-mounted), Type B (deck and side shell-mounted) and Type C (bulwark/brackets). Nominal opening widths are 310 mm and 360 mm with dimensional tables and figures.
- Materials: Requires weldable steel plates with yield strength ≥ 235 N/mm².
- Construction & foundation: Foundations must be designed for actual load directions so loads transmit to hull structure without plastic deformation or cracking.
- Manufacturing & inspection:
- All surfaces (including welds) must be free from visible flaws.
- Rope-contact surfaces must be smooth to avoid abrasion.
- External anti‑corrosion coating is required.
- Marking & documentation:
- Safe Working Load (SWL) must be marked on the fitting (in tonnes) and recorded on the ship’s towing and mooring plan as per IMO MSC/Circ.1175.
- The actual on‑board SWL must account for under‑deck reinforcement and shall not exceed values indicated in the standard.
- Strength assessment:
- Strength evaluation by finite element analysis (FEM) is described in Annex A.
- Loading cases include horizontal and vertical loads (treated individually).
- Combined stress under SWL limited to 85% of material yield.
- Reference values: The standard includes example SWL and dimensional tables (for guidance only); final SWL is to be agreed between manufacturer and shipowner based on installation.
Applications and users
ISO 23116:2020 is used by:
- Shipbuilders and naval architects designing mooring arrangements for Panama transits
- Manufacturers of Panama chocks and seats
- Classification societies, flag administrations and port authorities reviewing compliance
- Ship operators and shipmasters referencing SWL on towing/mooring plans
- Marine surveyors and maintenance teams inspecting fittings
Practical uses include selecting correct seat type and size, specifying material and welding, verifying FEM strength checks, ensuring rope protection and corrosion protection, and documenting SWL for safe mooring/towing operations.
Related standards
- ISO 13728 - Panama chocks
- ISO 23113 - Closed chocks (alternative for larger vessels)
- IMO MSC/Circ.1175 - Guidance on shipboard towing and mooring equipment
- IACS UR A2 and OCIMF MEG4 - industry mooring guidelines
Keywords: ISO 23116:2020, Panama chocks, seats for Panama chocks, ship’s mooring and towing fittings, SWL, Panama Canal, mooring equipment, finite element analysis.