Bow Mariner, 2004: chemical tanker loss off Virginia
The 28 February 2004 explosion and sinking that killed 21 of 27 crew, and the gas-freeing failure that put unwashed MTBE tanks into the flammable range.
The Bow Mariner was a Singapore-flagged chemical tanker lost about 45 nautical miles off the Virginia coast on 28 February 2004. Two explosions less than two minutes apart were followed by sinking in roughly an hour and a half. Twenty-one of her twenty-seven crew died; six survived in a liferaft.
The mechanism is the reason the casualty is still taught. The ship had discharged MTBE from 22 cargo tanks at New York on 25 February, and the master ordered those tank lids opened for cleaning although the tanks had been neither washed nor mechanically ventilated. Their atmospheres were above the upper explosive limit, so admitting air brought them into the flammable range rather than out of it, and heavier-than-air vapour spread on deck. The ignition source could not be determined.
The United States Coast Guard, investigating on behalf of Singapore as flag State, found that inerting was not required by the regulations then applicable to that ship but was required by the operator’s own safety management system and was not used, and recorded the failure of the operator and senior officers to implement that system as a contributing cause. Drills were not effectively conducted and the general alarm was never sounded. The full article will cover the ship, the voyage, the investigation and the standing lesson that a tank atmosphere above the upper explosive limit is not a safe atmosphere.