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The National Transportation Safety Board (NTSB) has determined that a failed O-ring seal and misaligned fuel system components caused a major engine room fire aboard the bulk carrier Lem Verbena while the vessel was docked in Mobile, Alabama.
The January 4, 2025 incident occurred at the Alabama State Docks on the Mobile River with 19 crewmembers on board, resulting in $5.5 million in damage but no injuries or pollution, according to the agency’s marine investigation report.
The fire ignited at approximately 2323 local time in the vessel’s upper engine room near the composite boiler, shortly after cargo operations had concluded and the boiler burner unit had completed a normal operating cycle.
Within seconds of the alarm, crew members observed burning fuel dropping from the upper deck, spreading flames to lower engine room platforms. The vessel’s water mist system automatically activated, but the fire continued to grow.
The crew shut down fuel systems, secured ventilation, and ultimately released the vessel’s CO? fixed firefighting system, which successfully extinguished the fire with support from shoreside responders.
Investigators traced the origin of the fire to the boiler’s burner unit oil fittings block, where an O-ring seal had been improperly seated between two misaligned fuel ports.
The NTSB found that the misalignment caused the O-ring to become pinched and unable to form a proper seal, allowing pressurized diesel fuel—at roughly 43 psi—to leak, atomize, and ignite on a nearby hot surface.
Compounding the issue, a software configuration error prevented the fuel pump from shutting off between burner cycles as designed, keeping the system continuously pressurized and accelerating degradation of the compromised seal.
Over time, the weakened O-ring failed, releasing atomized fuel into the engine room.
While investigators could not definitively identify the ignition source, they concluded the atomized fuel likely ignited on a hot surface near the boiler or exhaust system, which remained heated from recent operation.
Post-fire damage was concentrated around the burner unit, fuel flow meter, and adjacent components, with additional fire spread to lower platforms below.
The NTSB credited the crew’s response—including rapid shutdown of fuel systems, sealing of the engine room, and proper deployment of CO?—with preventing injuries and limiting further damage.
Coordination with Mobile Fire-Rescue allowed for effective monitoring and ensured the space remained sealed long enough for the CO? system to suppress the fire completely.
The investigation highlights how small mechanical misalignments combined with software errors can create high-risk conditions in fuel systems, particularly in high-temperature environments like engine rooms.
It also underscores the importance of proper assembly, verification of sealing components, and correct control system configurations in preventing fuel leaks and subsequent fires.
The NTSB’s full report can be found here.
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