Cracks in a muffler led to fire on towing vessel reveals NTSB report

Cracks in a muffler coupled with the use of combustible materials in accommodation spaces caused a fire on a towing vessel last year on the Gulf Intracoastal Waterway near Freeport, Texas, is the key finding in the National Transportation Safety Board’s (NTSB) report.

On June 25, 2022, the towing vessel, Mary Dupre, left Port Comfort, Texas, bound for Houston. She was pushing a single barge loaded with bio-diesel fuel. The fire broke out the following day. No injuries were reported, and nearby Good Samaritan towing vessels retrieved the barge, extinguished the fire, and evacuated the crewmembers. However, the Mary Dupre was a total loss, with damages estimated at $1 million.

The fire started behind wood-paneled bulkheads in the pilot’s stateroom, which was located between the stacks containing engine exhaust mufflers and piping. Cracks in the welds of the muffler inside the starboard stack allowed hot exhaust gases to escape into the stack area.

Whilst investigating, NTSB discovered that a disconnected exhaust blanket on a muffler left a section of it uninsulated, which allowed heat to radiate into the stack area. This, combined with leaking exhaust gases from a crack in the muffler, is believed to have raised the temperature in the stack area. The crew was unaware of cracks or disconnected blanket due to the size of the stack preventing personnel from entering the space.

NTSB determined that the fire on the Mary Dupre was caused by undetected cracks in the starboard muffler, which allowed exhaust gases to ignite wooden structures in the accommodation space. Contributing to the damage was the use of combustible materials in the joinery, outfitting, and furnishings.

“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.”

Download the NTSB report:MIR-23-12 Mary Dupre

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