ClassNK Releases its Findings on the MOL Comfort Sinking

The Japanese ship was en route from Singapore to Saudi Arabia when the ship's middle buckled and split in half. 

The split and sinking of Mitsui O.S.K. Lines, Ltd. (MOL) containership MOL Comfort last year was due to a fractured hull girder, a final investigation released this week concluded. 

The Japanese ship was en route from Singapore to Saudi Arabia in the Indian Ocean during June 2013 when it split in half 400 nautical miles off the coast of Oman. 

Three days later, the aft section sank into the ocean along with its cargo, with the fore section following in a fiery blaze almost three weeks after. 

Japanese classification society ClassNK confirmed in the report that the bottom shell plates in a butt joint in the middle of the ship buckled and collapsed, causing the fracture.

A definitive cause was not identified, though the report speculated on the effect of lateral loads. 

"The investigation concluded that it was actually possible that the load of the vertical bending moment exceeded the hull girder ultimate strength at the time of the accident when the effects of the deviations of the uncertainty factors were taken into account, although the overlap between the strength and the load was very narrow," ClassNK wrote.

The society had previously said that the ship had been in full compliance with its rules and International Association of Classification Societies (IACS) regulations.

Previous finite element modeling done by ClassNK also found that MOL Comfort's hull should have been able to withstand the journey, though the report said that uncertainties over yield stress, weather conditions and declared cargo weight versus true weight may have contributed to the fracture. 

In the future, "It is necessary to assess hull girder ultimate strength in proper consideration of the effects of lateral loads and to assess the buckling collapse strength of stiffened bottom panels in the middle parts of the holds," the report said. 

MOL is currently locked in a lawsuit with shipbuilder Mitsubishi Heavy Industries over the sinking, with the MOL Comfort considered by some in the industry as the worst containership loss in history.

The ship was estimated to have sunk with roughly 3,100 metric tonnes of fuel oil aboard.