Mechanical failure caused fire on board Brochu in Port-Cartier, Quebec
A pilot and 2 tugs—the Vachon and the Brochu were then tasked with assisting the bulk carrier out of the harbour, Transportation Safety Board of Canada's (TSB) reports says.
At 0330, the engineer on watch started each tug's engines to warm them up. At 0400, the pilot boarded the AM Tubarao.
The Vachon was positioned forward of the bulk carrier and its towing cable was attached to the bulk carrier's bow. The Brochu was positioned aft, and its towing cable was attached to the bulk carrier's stern.
The plan was for the tugs to manoeuvre the bulk carrier out of the harbour by pulling the bulk carrier away from the dock, then pulling it astern while its engine was astern to enable the bow to pass the dock corner.
After the bow was clear of the corner, the Vachon would position the bow of the bulk carrier toward the centre of the harbour channel, and both tugs would guide the bulk carrier into the channel.
Once the bulk carrier was clear of the channel, the tugs would retrieve their towing lines, pick up the pilot, and return to their berth.
At 0419, the AM Tubarao's mooring lines were cast off and the pilot ordered the tugs to pull at different power levels (between 0% and 80% power, as needed) in order to help the bulk carrier move away and maintain a safe distance from the dock.
A short time later, the pilot on the AM Tubarao noticed that the stern of the bulk carrier had stopped moving.
At approximately 0427, at the pilot's request and as per standard procedure, the master of the Brochu removed the lock on the tug's propulsion control lever, and the tug pulled on the bulk carrier at maximum power (power level 10).
Shortly after 0433, the Brochu's starboard fluid coupling's visual and aural high-temperature alarm (which was located in the wheelhouse) activated, indicating that the coupling oil had reached 125 °C.
The bridge teams were not aware of the significance of this alarm. The Brochu continued to pull at maximum power, causing the internal temperature of the starboard fluid coupling to increase further.
At approximatively 0434, the Brochu's starboard fluid coupling oil reached 140 °C and the 3 fusible plugs melted. Once the plugs melted, the hot oil released into the tug's machinery space.
With no oil in the coupling, the starboard cycloidal propeller disengaged and the overspeed protection system shut the engine down.
The hot oil vaporized and ignited, either when it made contact with a hot surface such as the engine exhaust manifold, or owing to a spark that may have come from the nearby generator.
At 0436, the master of the Vachon called the master of the Brochu on the VHF radiotelephone to inform him that fire could be seen coming out of the Brochu's funnel.
The master of the Vachon also called the owner's marine agency so that the agency could notify the municipal and company fire departments and call in a replacement tug.
The pilot on the AM Tubarao then called the master of the Brochu to discuss the situation.
While speaking with the pilot, the master detected smoke in the Brochu's wheelhouse.
The master then reduced power to the port main engine and ordered the engineer to assess the situation in the engine room.
Seeing the fire through the engine room door's porthole, and seeing smoke enter the tug accommodation area from around the door, the engineer did not enter the engine room.
Smoke began to fill the wheelhouse, and the master opened the wheelhouse external doors in order to ventilate the space.
The master ordered the engineer to wait to release carbon dioxide in the engine room, as the port main engine was needed to detach the tug's towing cable from the bulk carrier. Around 0443, the Brochu disconnected its towing cable from the bulk carrier and returned to its berth.
By 0445, the Brochu had returned to its berth, and the crew had activated the fuel shutoff valves, which shut down the remaining port main engine and generator, and closed the engine room ventilation dampers. The crew searched the engine room's external bulkhead for hot spots but did not find any.
At approximately 0540, the company's fire department entered the tug engine room and, with the help of a thermographic camera, determined that the fire had not spread beyond the engine room and was extinguished.
A post-occurrence examination of the Brochu determined that the starboard fluid coupling's thermal control element had activated, triggering the alarm in the wheelhouse. The examination also showed that the 3 fusible plugs had melted.
The thermal control element and thermal plugs were found to have worked within their design parameters. Hydraulic fluid samples were extracted from the port and starboard fluid couplings for testing.
The oil sample from the starboard coupling contained significantly more metallic particles than did the sample from the port coupling; some of the particles were relatively large. This may indicate abnormal wear or internal damage to the coupling, Transportation Safety Board of Canada said. ■