Two OSV Capsized and sank during double towing | Repeated Collisions Led incident investigation

Repeated Collisions Led to Maersk PSV Sinkings

The two Danish offshore supply ships capsized and sank December 22, 2016 in the Bay of Biscay approximately 65 nautical miles off the French coast while being towed by another offshore supply ship, Maersk Battler, while en route to a scrapyard in Turkey.

The supply ships were unmanned at the time and configured in a side-by-side towing setup during the voyage. But during passage through the English Channel, the fenders between the ships on tow failed, and the ships started to collide. The constant battering caused extensive damage to the vessels and eventually compromised the watertight integrity of the Maersk Searcher, causing it to take on water and sink. Subsequently, the Maersk Shipper was also pulled under, so the crew on the Maersk Battler cut both ships loose.

The report stated that the side-by-side towing configuration, which was criticised by some in the aftermath of the incident, was one of three towing methods considered for the job. The two others included a double tow using two winches and a serial tow (one after the other).
In an after-accident analysis, DMAIB concluded that:

- the fendering was not sufficient to withstand the force of the repeated impact of the two vessels.

- the crew failed to recognize the developing emergency, in part because they assumed that the damage was acceptable for the decommissioned vessels.

- the impact damage penetrated the vessels’ watertight envelopes, leading to progressive flooding and capsize.

- the towing arrangement and towing plan made no provisions for disconnecting the two vessels in an emergency, raising the risks from a casualty involving one ship.
More broadly, DMAIB noted that Maersk Supply had used industry-standard tools to evaluate the risks associated with the voyage and had moved ahead anyways – pointing to the limitations of the risk management system itself:

“The risk management system offers to handle risk as an objective value and to provide a structure for handling risk. However, there is no aid or control of what is put into the system . . .The numeric risk value is based solely on how imaginative the involved persons are,” DMAIB wrote. “The assessment of the risk reduction is highly sensitive to one or more individuals’ subjective risk perception, which will be strongly influenced by the desire to make the operation possible. Thereby, the risk management system will rarely limit activities prone to risk. In fact, the risk
management system instead tends to facilitate the carrying out of risk prone operations.”

link PDF investigation results

https://drive.google.com/file/d/1WbsekE9LccX5pFgFasFtLa_sq0QJL1VX/view?usp=drivesdk

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