200610 Heavy weather damage

10 Jan 2006 MARS

 

Three container vessels have recently suffered heavy-weather damage to deck equipment, bow structure, anchor and containers. After studying the vessel's reports submitted to the company, we are of the opinion that such damages could have been avoided or at least minimised if the ships' officers had taken necessary measures/actions.

We would like to bring to the attention of ships' officers the following for their guidance and to assist them in operating their vessel safely whilst in heavy weather. This information is based on studies made by the classification society.

Container ships are often built with considerable bow flare to accommodate as many containers on deck as possible. Some of the small and medium-sized container vessels have a bow form comparable to that of a cruise liner. These container vessels are usually equipped with significant reserve power to compensate for extra resistance encountered in heavy seas and therefore remain within the generally tight schedule.

Despite the above, there have been many cases where the bow or the stern structure of a container ship has been overloaded and could not withstand the heavy impact load from the waves. In some cases the structure suffered considerable damage. For most ships' officers, especially newly promoted masters with little experience in shiphandling, it is often difficult to recognise that the ship's structure is being overloaded because the view to the bow is blocked by containers on deck. This sometimes makes it impossible to see if green water is being shipped on deck. Also, it is difficult to judge when the damage is not dangerous to the overall safety of the vessel but needs attention to avoid or at least to minimise the damage to the ship and the containers.

Masters should be made aware of the damages of the heavy bow flare impact in operation when heavy weather is encountered. Depending on the loading condition of the vessel, sea and wave conditions in relation to the ship's dimensions, necessary measures should be taken by the master.
  1. In heavy weather, ship's speed should be reduced if excessive rolling, propeller emergence, shipping water on deck or heavy slamming occurs.
  2. Special attention should be paid when the vessel experiences rolling in a following or stern quartering seas. This phenomenon, parametric rolling, may in rare cases lead to the vessel capsizing. Up to now the usual measure has been to turn the vessel into the seas and reduce speed. Theoretical as well as experimental investigation indicates that, as the container ships get larger and their stability increases, parametric rolling may in fact develop when the ship is heading into the seas. The ship is very stiff with a short rolling period, the resonance frequency of encounter with large waves is found in head seas rather than following seas. Research and studies are ongoing.
  3. Reliance on automatic steering in heavy weather may be dangerous as this prevents ready change to the heading of the vessel, which may be needed in certain occasions.
  4. The master should also appraise and establish specific lower and upper limits of stability by his own experience to improve the behaviour of the vessel at sea and especially in severe weather.
  5. Container stowage on deck has come into focus world-wide with respect to damage to the containers in heavy weather. An increasing number of containers are lost. Therefore before a voyage commences, care should be taken to ensure that the containers have been properly secured/lashed to avoid loss of the container while at sea, under the effect of acceleration caused by pitching and rolling.
  6. According to some statistics it was observed that most of these damages occur during night-time, since the officers are in the dark and not able to estimate the wave height properly.
  7. To avoid possible speed claims that might be issued by the charterer against the owner and to protect owner's interest, the master should keep the charterer regularly informed about weather conditions, currents, reduction of the speed and deviation.

In this regard we would like to bring the ships' officers' attention to Solas regulation 10-1 master's discretion for safe navigation:

'The master shall not be constrained by shipowner, charterer or any other person from taking any decision which, in the professional judgement of the master, is necessary for safe navigation, in particular in severe weather and in heavy seas.'
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