The NTSB issued an investigation report on the engine room fire and explosion onboard the towing vessel ‘J.W. Herron’ on Big Bayou Canot near Mobile, Alabama in December 2017. The report identified leaking lube oil from a propulsion diesel engine hose or tubing fitting that was ignited off an exposed hot engine surface, as the key cause of the accident.
The incident
About 1340 local time on 13 December 2017, the towing vessel J.W. Herron was shifting barges on Big Bayou Canot near Twelvemile Island, approximately 8 miles north of Mobile, Alabama, when a fire began in the lower engine room and quickly spread.
After the crew of three partially secured the engines and fuel supply, heavy smoke and fire prevented them from attempting to extinguish the fire, forcing an immediate evacuation of the vessel to the barges. No pollution or injuries were reported. The estimated damage to the vessel was $1.5 million.
Probable cause
- The National Transportation Safety Board determines that the probable cause of the engine room fire aboard the towing vessel J.W. Herron was leaking lube oil from a propulsion diesel engine hose or tubing fitting that was ignited off an exposed hot engine surface or slipping clutch.
- Contributing to the severity of the fire was the location of the emergency engine shutdowns and fuel supply shutoffs near the exterior engine room doors, which proved to be inaccessible.
- Contributing to the spread of the fire was the inability to secure ventilation to the engine room.
Analysis
Although there was no evidence of the engineer, who tested positive for methamphetamine, being impaired in behavior or decision-making ability on the morning of the accident, any drug use by a crew member poses a safety hazard while onboard a vessel.
Although the captain was in the wheelhouse when smoke was first noticed, the crew was on the barges. During the few minutes taken to re-board the vessel and begin firefighting, the crew could not start the fire pump, shut the starboard engine fuel supply valves, stop the starboard engine, or secure the ventilation, as these areas were overcome by smoke.
The speed of which the fire grew to encompass the engine room and the location of primary fire equipment within that same space together eliminated the opportunity for the crew to effectively fight the fire; thus, immediate evacuation from the vessel was reasonable. Had the crew been able to reach the port engine shutdowns, the additional diesel fuel in the day tank would not have been available to fuel the fire.
In addition, the engine room supply and exhaust fans remained in operation during the fire because they were controlled from the engine room and thereby could not be shut down. Nevertheless, if they had been secured, the engine room inlet and exhaust vents would still not have been able to be shut because they were fitted with fixed louvers. At the time of the fire, both the port- and starboard-side doors to the engine room were open, as were the engine room windows, although this practice risks expanding engine room fires.
However, even if the crew could shut the engine room windows, given that they were not marine grade the windows would have likely cracked or blown out in the fire. The inability to secure all ventilation allowed for a continued oxygen supply to the fire, hastening its growth and spread.
Furthermore, the small confines of the engine room space and the location of fire equipment within that same space demonstrated a risk to crews fighting engine room fires. Even if the crew could have reached the start button for the fire pump (located in the engine room), their sole means to try to control and extinguish the fire would have been to place a hose through an engine room window or door.
On smaller vessels such as tows, the risk to crews fighting engine room fires has led to the development of designs that incorporate both a means for securing ventilation to the engine room and a fire suppression system, such as a fixed CO2 system, to extinguish the fire without requiring crews to enter the space.
Safety issue – Accessing remote engine room shutdowns
The location of remote emergency shutdowns to the engine room—quick-closing valves for fuel and lube oil systems, remote stops for ventilation fans, and engine stops—as well as fire pump start controls may not be accessible during a fire. Therefore, the accessibility of these shutdowns and controls should be evaluated during fire-response planning.
Alternative remote emergency shutdown locations, such as the wheelhouse, should be considered for redundancy.
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