Movement at berth due to ineffective moorings

The Master should determine an optimum mooring plan

After completing loading operations our gas tanker’s crew secured the ship’s accommodation ladder. As a routine pre-sailing procedure, the terminal had rigged a temporary gangway from the shore for two representatives, who boarded to disconnect the loading arm.

A large tanker passed our vessel, causing it to surge and sway away from the jetty by about two metres. The shore end of the gangway came away from the jetty and fell on top of taut mooring ropes (after backsprings). Immediately, our crew safely re-moored the vessel and the shore gangway was
repositioned and secured. The gangway and loading arm were visually examined after the incident.

Damage caused:

1. The wire operating the counterweight of the loading arm was stretched during the incident and will need renewal;
2. The triple swivel of the loading arm was found to be stuck after the incident and will need to be surveyed and repaired.

Potential losses

1. There was a risk of death/or serious injury to the terminal personnel if they happened to be on the gangway at the time of the incident;
2. The loading arm will be out of service for some time, resulting in financial consequences for the terminal;
3. The shore gangway could have been lost overboard;
4. The vessel’s mooring ropes were suddenly overstretched, and this could have resulted in damage to ropes and equipment;
5. Other commercial losses for the terminal, charterer, cargo owner and vessel owners/managers due to this incident.

Root cause/contributory factors

1. Slack in mooring ropes – the large tidal range caused slack in the vessel’s moorings allowing the vessel to move dangerously at the berth;
2. Passage of large tanker in channel Ð AIS data and visual observation confirmed that the tanker’s speed was not excessive and it was not abnormally close. It is speculated that its size, draught, and the channel blockage factor may have generated the large disturbing forces;
3. Mooring configuration – the vessel was moored port side alongside with two headlines, two forward backsprings, two after backsprings and two sternlines. The position of our vessel and configuration of the shore bollards did not allow the deployment of breastlines. The four backsprings were all belayed on one bollard. This configuration was not effective in countering athwartship forces;
4. The crew underestimated the possible consequences of this ineffective mooring configuration;
5. The responsible officer of the watch and the deck watch did not properly check and adjust the tension of the moorings during the loading operation
6. The vessel was kept alongside by the wind and tide and the crew became complacent and did not observe that the vessel was not moored safely.

Lessons learnt

1. In consultation with the berthing pilot and the terminal, the Master should determine an optimum mooring plan;
2. If unavoidable, a mooring configuration with lines predominantly extending parallel to the berth must be closely and continuously monitored and tended; lines must always be maintained under optimum tension and never left slack;
3. Environmental conditions (wind, tides, currents etc) and their effects should be correctly predicted/anticipated and closely monitored.

Source: Mars/Nautical Institute