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Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT), in collaboration with ClassNK, released an updated report today on the investigation into what caused the high seas break-up and sinking of the containership MOL Comfort this past summer.
The primary findings of the investigation so far indicate that the predicted structural loads on the MOL Comfort at the time of the casualty, were 9.4 million kN-m, or 33 percent less than the overall hull strength of the vessel.
The total calculated force acting on the vessel was a combination of three things, the bending moment of the vessel in still water, wave-induced bending moment, and the whipping effect (superposition of the load due to ship motion and hull girder vibration.) In this case, the forces were 2.0 million kN-m (wave), 1.4 million kN-m (whipping), and 6.0 million kN-m (still).
The investigation committee notes that buckling deformations of approximate 20mm had been found on the sister vessels of the MOL Comfort, however the committee was unable to reproduce the deformations under their structural simulations, “even when applying loads near the ultimate hull girder strength,” according to the report.
In addition, the committee was unable to simulate the conditions of the ship’s fracture when taking into account the cargo loading effect on the vessel, or given the possible presence of “residual deformations” in the bottom shell plates in the vessel, similar to those deformations found in sister vessels.
The committee notes that according to the ship’s log, “the ship had encountered sea states in which it withstood a load of approximately 10.0 million kN-m around three and a half years prior to the accident, and no such fracturing accident had occurred in that instance.”
So what happened?
Considering the extreme conditions encountered three and a half years ago, the committee notes three possible scenarios:
The committee admits that considering their simulations were unable to replicate the disaster that unfolded this summer, further investigations will be needed to gain more insight into what specifically went wrong. Further investigations will include numerical simulations of the wave loads and the hull structure strength as well as full-scale stress measurements of sister ships, as well as similar measurements on other large containerships.
Temporary Safety Measures
The Committee recommends that the following actions be taken as temporary safety measures for existing container ships with loading capacities similar to or greater than 8,000 TEU class:
Read the full report HERE
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