Occasionally, claims arise regarding damages to Members’ ships caused by interactions or surges alongside the berth with nearby port infrastructures. These damages typically involve the ship’s gangway placed on the pier, incidents with mooring lines parting, or even contact damages between moored ships and berth facilities, reports Britannia P&I.
Causes of Damage
Hydrodynamic Interactions
Hydrodynamic interaction occurs when a ship moves through the water, creating a pressure field around the hull that interacts with other ships or fixed objects such as quayside structures or the seabed. These interactions are common in shallow waters, narrow channels, or when ships pass too closely to other vessels or fixed structures.
Ship-to-Ship (STS) Interactions
STS interactions generate significant hydrodynamic forces impacting the manoeuvrability of ships. Ships experience repulsive or attractive forces, especially when overtaking or passing each other on reciprocal courses at close range.
Factors Affecting Interaction
- Speed Through Water:
- Hydrodynamic force is influenced heavily by the speed through water, not just speed over ground.
- As a rule of thumb, the change in hydrodynamic force is proportional to the square of the speed. Doubling the speed can quadruple the interaction force.
- Passing Distance:
- The interactive force decreases significantly as the passing distance increases.
- Navigators should allow for larger passing distances in busy waterways and reduce speed when close passing is unavoidable.
- Blockage Effect:
- Larger ships create a more significant blockage, displacing more water and having a larger impact on surrounding ships.
Damage Without Contact
Ships can cause damage to other ships without physical contact by generating hydrodynamic pressure fields that cause moored ships to surge. This is commonly referred to as ‘wash damage,’ ‘wake damage,’ or ‘surge damage.’
Mooring Arrangements
Effective mooring involves positioning headlines, stern lines, and spring lines according to best practices. The lines should be positioned close to the horizontal line of the ship’s fore and aft, with sufficient lead to absorb and dissipate hydrodynamic energy.
Training and Safety Measures
- Proper training for the ship’s crew on berthing procedures, effective communication, and coordination with the terminal.
- The Safety Management System (SMS) should support suitable risk assessments and provide guidance on mooring equipment condition, effectiveness of mooring arrangements, and proximity to hazards.
- Additional safeguards may include extra mooring lines, having the main engine on short notice, or making provisional arrangements for tugs.
Passing Ships and Precautions
- Navigators should understand the waterway characteristics, weather conditions, and terminal locations sensitive to surge damage.
- Compliance with local speed limits and passage planning are crucial.
- Reducing speed can mitigate the impact of waves and hydrodynamic surges, but maintaining control over the ship’s steerage and heading is also important.
- Trained crew and proper ship handling techniques are essential to minimise surge damage risks in confined waters.
Evidence Preservation
- Take pictures of the berth and fenders before and after berthing, especially in terminals known for damage claims.
- Use electronic data playback (AIS, VDR, ECDIS) to establish the circumstances of passing ships during alleged incidents.
- Record details of passing ships, including speed and passing distance.
- Collect third-party information from traffic control, VTS, and shore CCTV footage.
- Retain physical evidence such as mooring brakes, parted mooring lines, and maintenance records.
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Source: Britannia P&I
