Cracked exhaust muffler cited in towboat fire

The Mary Dupre after the fire.
The Mary Dupre after the fire.
The Mary Dupre after the fire.

Cracks in a muffler and the substantial use of combustible materials in accommodation spaces led to a fire aboard a towing vessel last year on the Gulf Intracoastal Waterway near Freeport, Tx., according to the final report on the incident released by the National Transportation Safety Board (NTSB). 

‘X’ marks the point on the Gulf Coastal Waterway where the fire broke out.
‘X’ marks the point on the Gulf Coastal Waterway where the fire broke out.

On June 25, 2022 the four-person crew aboard the towing vessel Mary Dupre departed Port Comfort, Tx. for Houston, pushing a single barge loaded with bio-diesel fuel. The following day a fire broke out, leading to a total loss of the vessel, which was estimated at $1 million. 

Nearby Good Samaritan towing vessels retrieved the barge, extinguished the fire and evacuated the crewmembers. No injuries were reported.

The fire started behind the wood-paneled bulkheads in the pilot’s stateroom, which was located between the vessel’s two stacks. The stacks contained engine exhaust mufflers and piping. Investigators found cracks in the welds of the muffler located inside the starboard stack. The cracks allowed hot exhaust gases from the starboard main engine to escape from the muffler into the stack area.

Investigators also found the muffler’s exhaust blanket was disconnected. The disconnected blanket left a section of the muffler uninsulated, allowing heat to radiate into the stack area. It is likely the leaking exhaust gases from the crack in the muffler and the radiated heat from the uninsulated portion of the muffler raised the temperature in the stack area.

The crew was not aware of the cracks or disconnected blanket as the size of the stack prevented personnel from entering the space.

The NTSB determined the fire aboard Mary Dupre – built in 1974 and operated by Houma, La.-based Dupre Marine Transportation – was caused by undetected cracks in the starboard muffler that allowed exhaust gases from an operating engine to escape and ignite wooden structures affixed to the common bulkhead of an accommodation space. Contributing to the fire damage was the substantial use of combustible materials in the joinery, outfitting and furnishings in the accommodation spaces.

“Engine and other machinery exhaust systems generate heat — which can radiate from exhaust components – are potential ignition sources,” the report said. “These systems often run through tight spaces that are difficult to access and inspect and are often located near materials or equipment that obstruct entry and direct observation. It is good practice to include these areas in periodic fire safety inspections.”

When conducting inspections of these systems, the report concluded, “Vessel owners and operators should consider using handheld equipment – such as inspection mirrors, video equipment or thermal imaging equipment – to detect deficiencies.”

After the fire, Dupre Marine Transportation completed an internal investigation report, developed lessons learned, and instituted corrective actions. 

According to the NTSB, the company emailed the lessons learned to all vessels in their fleet and discussed them during management visits to the vessels. The items for discussion included a description of the event aboard the Mary Dupre, fire prevention methods, a review of Dupre Marine Transportation’s fire response procedures, and procedures for testing smoke detectors. Managers from the company stated that they did not have any other vessels that had staterooms adjacent to stacks similar to the Mary Dupre, but their drydocking procedures for any vessel they acquired with a similar arrangement would be revised to include muffler inspections within the stack spaces.

The NTSB has investigated previous casualties involving fires aboard vessels constructed with substantial use of combustible materials in interior spaces and/or without structural fire protection. 

On August 13, 2016 a fire erupted in the engine room on board the uninspected towing vessel Jaxon Aaron while pushing a tow upbound on the Lower Mississippi River. The agency determined that the substantial use of combustible materials in the interior spaces contributed to the extent of the fire damage. 

On December 28, 2013, the fish processing vessel Juno caught fire while moored at a pier in Westport, Wa. The NTSB determined that the vessel’s lack of structural fire protection and use of combustible materials in interior finishes contributed to the fire.