Reassessment of the M.V. Derbyshire Sinking With the Focus on Hull-Girder Collapse

Abstract

During the last two decades, extensive investigations into the possible causes of the loss of the Capesize bulk carrier M.V. Derbyshire have been made. A total of 13 risk components were considered within the framework of a formal safety assessment. The prime concern was with abnormal wave effects on hatch cover failure and subsequent flooding into forward cargo holds. No serious speculation on hull-girder collapse was raised in the previous investigations. The present paper studies this possible cause, which involves the vessel's sinking due to structural progressive collapse from extreme wave bending actions. The safety measure of the vessel is defined as a ratio of the ultimate hull-girder strength to the applied extreme vertical bending moment. The computed safety measure is found to be quite marginal while the vessel was trapped in typhoon Orchid, indicating that the M.V. Derbyshire could have sunk by hull-girder collapse with or even without hatch cover failure and subsequent water ingress into the forward cargo holds. The results and insights developed from the present study are summarized. Important recommendations for improved ship safety are made.