The causes of losing containers overboard are numerous and often complex, though very often basic operational errors are a factor. The consequences of container loss should justify time, cost and effort by ship owners and operators in reviewing and improving preventative measures.
Causes
Heavy weather
Quite apart from casualties, resulting in containers being lost overboard due to e.g. grounding, foundering or collision, heavy weather is often the most common factor resulting in stack collapse during otherwise routine voyages. In the SVENDBORG MAERSK waves of 10 metres reportedly caused rolling in excess of 40 degrees. The master had reportedly prepared for bad weather but did not foresee how much worse the actual weather and wave situation turned out to be. Recent claims experience is that ship handling in heavy weather is also a relevant factor in losing containers. In one case a master proceeded at full speed in an unsuccessful attempt to outrun a typhoon; and in another, a master failed to heed warnings issued by the IMO relating to synchronous and/or parametric rolling by slowing down in following seas.
Failure to comply with the ship’s Container Securing Manual (CSM)
A more common cause of stack collapse is the failure to comply with limits for stack or tier weights or stack heights stipulated in the ship’s CSM. In some cases we have seen, the CSM itself has not catered for different stability conditions or the use of non-standard containers, such as high cubes. When a container ship is on charter, we have also seen communication breakdowns between the charterer’s container planners and the crew, even when using the same computer stowage planning programme. Charterers will naturally look to optimise stowage, but the crew may be reluctant to intervene and upset tight schedules.
Lashing issues particularly relevant to large container ships
The sheer scale of the lashing arrangements on larger ships makes it difficult for a crew to check them against the CSM and a feeling may prevail that there is little danger to the ship if some containers are lost and that it is charterer’s problem. The larger the ship, the more lashing equipment there is to maintain, which stevedores may have little interest in handling carefully. Maintenance is not an easy task to keep on top of and incidents do occur because of defective equipment.
The increasing number of containers on board has an obvious effect on the time taken to lash and unlash them, much to the concern of charterers. The use of fully automatic locks, such as those designed to disengage when there is a slight slew of the container around its vertical axis, has raised questions as to whether this sort of movement may be reproduced at sea in heavy weather. Concerns surrounding these locks were first raised in 2006 (See LP Circular No 08.06). Fully automatic locks were reportedly in use throughout the deck on the SVENDBORG MAERSK. The Danish Maritime Accident Investigation Report comments that these locks reach their minimum breaking load at lower forces than semi-automatic locks and allow stacks to swing considerably due to higher vertical tolerance. The report does not conclude on the causative effect of these locks. This is obviously a complex issue and it appears further investigations are being made. In at least two of the significant container loss cases seen, fully automatic locks were in use and it was surprising that in both cases it was the owners providing fully automatic locks, albeit with the charterer’s approval. The concern surrounding the use of the locks, or at least the suitability of certain designs, continues.
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