Substantial use of combustible materials caused 2022 towing vessel fire, NTSB report finds

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, Texas, the US National Transportation Safety Board (NTSB) said on Thursday, June 29.

On June 25, 2022, the four-person crew aboard the towing vessel Mary Dupre departed Port Comfort, Texas, 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 estimated at US$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.

The NTSB said 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 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 – and 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, vessel owners and operators should consider using handheld equipment—such as inspection mirrors, video equipment, or thermal imaging equipment—to detect deficiencies.”

Marine Investigation Report 23-12​ is available online.