(WASHINGTON) — On Jan. 4, 2025, about 2323 local time, the bulk carrier Lem Verbena was docked at the Alabama State Docks on the Mobile River in Mobile, Ala., with 19 crewmembers on board when a fire started in the engine room. The crew activated the vessel’s carbon-dioxide fixed fire extinguishing system. Shoreside firefighters later determined the fire had been extinguished.
There were no injuries and no pollution was reported. Damage to the vessel was estimated at $5.5 million.
The National Transportation Safety Board (NTSB) determined that the probable cause of the fire was the failure of an O-ring seal on the oil fittings block on the composite boiler burner unit. It was due to the radial misalignment of the two fuel ports on the block modules, causing pressurized diesel fuel to atomize and ignite on a nearby hot surface.
lower and upper module fuel ports as indicated by the arrow. Right: Upper module of oil fittings
block and fuel flow meter showing the pinched O-ring as indicated by the arrow. NTSB/Lemissoler Shipmanagement photos
“After the fire, the Lem Verbena operating company and Coast Guard investigators found that an O-ring on the oil fittings block upper module of the boiler’s burner unit had become pinched on the fuel port for the lower module. This O-ring was intended to provide a seal between the corresponding fuel ports on the lower and upper modules (when bolted together) to contain pressurized fuel as it moved through the system to the burner unit igniter,” the NTSB report said. “O-rings are designed to protect against leaks by lying flat and becoming compressed between two machinery surfaces that are secured together, typically containing a material under pressure. If any portion of the O-ring does not lay flat between the two surfaces, full compression of the O-ring cannot be achieved. This weakens the seal created by the O-ring and increases the likelihood of failure.”
“In this case, a portion of the O-ring on the upper module overlapped into the fuel port on the lower module, preventing the O-ring from lying flat and providing an adequate seal. This was because the two modules’ ports were not aligned radially and created an uneven clearance gap when the ports were bolted together. This gap could not be seen or detected when the ports were bolted together. (Investigators could not determine whether the block modules had been disassembled since they were manufactured or initially installed on the vessel.)”
Click here to read the complete report.
– National Transportation Safety Board
