Bureau Veritas about recent incidents of container losses at sea
French-based classification society Bureau Veritas says that a spate of recent incidents of container losses at sea all involved the use of fully automatic twistlocks.
BV says three separate incidents involving the loss of more than two hundred containers from large containerships have recently been reported to the classification society.
Apart from the use of fully automatic twistlocks the incidents also had a number of other features in common: the losses occurred abaft the vessel’s superstructure, took place in heavy seas and with the vessel experiencing large combined roll and pitch. BV also notes that the twistlocks were often observed to be subject to wear, on the lower level of container stacks.
BV says that it has conducted computer-generated tests of wave-induced accelerations on container stacks, and of the forces generated in container frames and twistlocks. It has reviewed full-scale tests of manufacturers’ container lashing methods, and plans to conduct measurements of acceleration on containers at sea.
The society’s Jean-François Segretain says, “Our investigations show that fully automatic twistlocks, when correctly fitted, are able to withstand the forces which are allowed for in classification rules. But our preliminary studies show that defective positioning of twistlocks, and wear on the locks and container corners, are contributory factors in the losses. Other significant factors are an exceptionally large roll amplitude, combined with severe pitching, and slamming on the afterbody of the vessel. As a preliminary conclusion, it seems that some types of automatic twistlocks, while effective in normal conditions, are more sensitive to defective lashing than are their semi-automatic counterparts.
