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The "Bow Mariner" Photo: Lennart Rydberg

Human error led to the sinking
of the ”Bow Mariner”
The final report by the US Coast Guard on the explosion and sinking of the 1982-built, chemical/product tanker ”Bow Mariner” on February 28 last year in the Atlantic, is grim reading and bears witness of human error and inadequate operational management.

At 18:05 local time on the 28th of February 2004, the 39,821 DWT Bow Mariner caught fire and exploded while the crew was cleaning out residual methyl tert-butyl ether (MTBE). At 19:37 hours, the vessel sank. Of the 27 crew members onboard, six abandoned ship and were rescued by the US Coast Guard from a raft. An unknown number of crew members abandoned ship into the water. Of these, three were recovered, one dead. 18 crew members remain missing and are presumed dead.

The cause of this casualty, as established by the US Coast Guard, was the ignition of a fuel/air mixture, either on deck or in the cargo tanks, which were within its flammable limits. What ignited the mixture has not been accurately established. J.R. Crooks Jr., the US Coast Guard Investigating Officer, concludes that a contributing factor in the casualty was the failure of the ship’s operator, Ceres Hellenic Enterprises Ltd, and the senior officers of the Bow Mariner to properly implement the company’s and vessel’s safety, quality and environmental protection management system (SQEMS).

Damning conclusions
These are pretty damning conclusions. The tank cleaning procedure for MTBE is quite detailed. On the 28th of February 2004, the Bow Mariner was engaged in a standard procedure for tank cleaning, or gas freeing. The master ordered the crew to open all the cargo tank hatches for empty tanks once the vessel was at sea. He did not explain these instructions, and the crew did not question the order. Since neither he nor the chief officer survived, his intentions could not be determined; however, it appears that he intended to ventilate all cargo tanks at once while cleaning the sumps of residual cargo, and then mechanically ventilate the cargo tanks.

After the explosion, Ceres officials asserted that the charterer’s Commodity Book60 contained instructions for freeing gas from the tanks by cleaning the sumps and ventilating the tanks, and that the master may have been following those instructions, according to the report.

The Greek master of the Bow Mariner, Efstratios S. Kavouras, perished after he had abandoned ship, not as the last person. Prior to the explosion, he gave the order to open the 22 cargo tanks that previously held MTBE. These contained flammable vapours, which accumulated on the deck. According to the US Coast Guard, he may have followed instructions, but the order was a “stunning breach of normal safe practices for a tanker and defies explanation or excuse. Opening tanks exposed the crew to toxic fumes, permitting flammable vapours that were heavier than air to accumulate on the deck”. When the explosion took place, there was no proper response from the master. To sum up, the master and the Chief Engineer abandoned ship less than ten minutes after the first explosion. A Filipino third officer took charge and saved any lives.

Capacities
The Bow Mariner was a single side, double bottomed chemical and oil tanker capable of carrying 28 different cargoes with double valve segregation. Two longitudinal bulkheads and ten transverse bulkheads formed nine centre tanks and nine pairs of wing tanks, subdividing the cargo space. The number nine centre tank was subdivided by a longitudinal bulkhead to form two tanks, which were designated as slop tanks. The centre tanks had external stiffening members and the wing tanks had internal stiffening members. The tank bottoms were sloped to facilitate drainage to the sumps. All tanks were constructed of mild steel and were coated with zinc or epoxy. The total capacity of all cargo tanks was 47,004.8 cubic meters at 98 percent full.

The Bow Mariner was equipped with segregated ballast tanks, the total capacity of which was 12,266.6 cubic meters at 100 percent full. The tanks designated for ballast included five port and starboard double bottom tanks of varying lengths; the fore peak tank; the aft peak tank; and the number six port and starboard wing tanks, which were primarily used for cargo.

//Petter Arentz