Fifteen years’ ago the Bow Mariner sank following an explosion, with considerable loss of life. Procedural errors concerning inertion of the vessel’s tanks were blamed for the tragedy
When the 174-m Singapore-flagged chemical and oil tanker Bow Mariner caught fire, exploded and sank on 28 February 2004, some 72 km off the Virginia coast in the eastern US, 21 of the 27 crewmembers on board perished.
The fire began when residual chemical fumes from a previous cargo escaped into the cargo holds when the crew were ordered to open the cargo accesses to clean the vessel's tanks.
At the time, the vessel was transporting more than 11M litres of ethyl alcohol on a voyage from New York to Texas, after discharging methyl tert-butyl ether (MTBE) from 22 of its cargo tanks while in New York.
The fumes that escaped while the crew cleaned residual MTBE out of the vessel's empty tanks created a highly-flammable mix of gases that ultimately caused the conflagration on board.
While the US Coast Guard (USCG) did not determine an exact ignition source in its formal investigation report for the vessel's flag state of Singapore, it did highlight several contributing factors.
The report said Bow Mariner failed to "properly fully implement the company and vessel safety, quality and environmental protection management system, (SQEMS)". Inert gas was not used during the discharge of MTBE, a precaution the vessel's SQEMS required to prevent fires on board.
“The fumes that escaped while the crew cleaned residual MTBE out of the vessel's empty tanks created a highly-flammable mix of gases that ultimately caused the conflagration on board”
The International Safety Management (ISM) code requires that an SQEMS be implemented by the vessel and its managing company; however, because the vessel was built before 1986, US law did not require it to inert its tanks when discharging its MTBE cargo. The lack of inerting and the opening of the empty MTBE cargo tanks for cleaning significantly increased the likelihood of fire on board, USCG investigations found.
Ultimately, the captain's decision to open the cargo tanks was a major safety violation that defied any explanation, according to the USCG report.
In the international and US regulatory regimes in place at the time of the incident, Bow Mariner’s tanks were not required to be inerted due to its date of construction and cargo. However, the vessel owner’s SQEMS required inertion of the vessel’s tanks. According to IMO’s report on the investigation into the incident, one crew member said that in his experience aboard the vessel he had never known the IGS to be used, a statement corroborated by other former crew members.
An engineer reported that Bow Mariner’s inert gas system (IGS) had an inoperable blower for several months before the explosion, but on reviewing Bow Mariner’s records no report of the failure was found, and there was no requisition for a new motor. “These facts are further indication that Ceres (the vessel owner) and the senior officers did not consider the IGS a critical piece of safety equipment,” the IMO report notes.
Commenting on the incident and the lessons learned from it, North P&I Club loss prevention executive David Patterson said: “The relevant procedure in the companies Safety Management System (SMS) stated that vessels fitted with an IGS operate cargo and slop tanks in inert condition at all times.
“It is likely that if the procedures were followed then the incident would not have occurred.”
He added: “Eliminating complacency and lack of awareness is an extremely difficult task for a shipping company to undertake and can be considered as the human element.”
A company may have a well-maintained vessel with excellent procedures in place due to its SMS; however, if the procedures are not followed then accidents are likely to occur.
“The company needs to achieve a strong safety culture on board the vessel, which is what the tanker industry has worked hard to achieve,” said Mr Patterson. “A strong safety culture will include good safety behaviour and safety awareness, which includes following procedures, effective risk management and reporting incidents and near misses,” he added.