Lessons Learnt: Wash damage due to excessive speed
This partly laden tanker was proceeding inbound along a narrow river channel with a pilot on board. The transit was taking place in the early morning hours on a flood tide. Shortly before entering a stretch of the channel with occupied river berths, the pilot ordered the vessel's speed to be reduced from full ahead to half ahead. After passing the berths, the speed was again increased to full ahead. Later that day, the tanker's Master received notice that his vessel was alleged to have caused wash damage to a bulk carrier alongside one of the river berths due to proceeding at excessive speed. The damage included the destruction of the accommodation ladder and the parting of a number of mooring ropes due to the bulk carrier ranging forward and aft when the tanker was passing.Analysis
It was determined that the tanker's speed at the time of passing the berths was about 9.5 knots whereas port regulations imposed a speed limit of 7 knots in this stretch of the river. Although the tanker was proceeding along the middle of the channel, its relative narrowness meant that vessels alongside the river berths could potentially be affected by the wash of other vessels passing at excessive speed. The engine revolutions could have been reduced earlier to comply with the regulatory speed limit thus lessening the wave disturbance generated by the vessel's movement. Although the pilot stated concern that a lower speed could adversely affect manoeuvrability as the vessel was trimming by the head due to squat, the effect of such interaction with the ground would decline with a reduction in speed.Lessons Learnt
- Passage planning in confined waters should take into account both safe speed and compliance with regulatory speed limits. The speed of the vessel should be closely monitored and adjusted as required.
- Areas where speed limits are critical should be identified and discussed during the Master/Pilot information exchange.
- Good bridge resource management would require any potential non-compliance with speed limits to be brought to the attention of the master and/or pilot.
- Necessary reductions in speed should be made gradually and in good time as circumstances allow.
- Master, officers and pilots should be fully aware of the effects of interaction on draft, manoeuvrability and wave generation in restricted waters.
- Vessels berthed alongside river/channel berths should ensure that moorings are frequently tended and not allowed to become slack.