Friction cited as cause in bulker breaking free of moorings in strong current

While loading a cargo of coal on March 27, 2023, the bulk carrier Sirocco broke free from its moorings at the Convent Marine Terminal dock in Convent, Louisiana, drifted a half mile down the Mississippi River and collided with a barge moored at the Mosaic Uncle Sam dock, the National Transportation Safety Board (NTSB) said on Thursday, September 19.

An examination of the winch brake liners on Sirocco’s bow found they exhibited extreme heat and friction, indicating that the tension on the forward mooring lines exceeded the forward mooring winches’ brake capacity. This then caused the lines to slip in a strong river current, resulting in the vessel breaking away from the dock.

​“To reduce the risk of a vessel breakaway, it is important for vessel crews to understand the forces that act on a vessel when it is moored into a strong current at a dock,” investigators said. “Crews should ensure that slack is taken out of lines as the vessel loads, especially as the forward draught increases and the bow begins to sit lower in the water, exposing more of the hull to the current. Continuously monitoring and taking up any slack from bow lines as forward holds are loaded can help to ensure that the bow does not come away from the dock.”

The NTSB also said that developing a response plan for a breakaway can ensure that crews are prepared to respond when one occurs.

“Vessel masters should also consider incorporating additional safety measures such as keeping propulsion, thrusters, and steering systems on short standby and having anchors ready for immediate use (even if not required by the loading facility),” investigators said. “Vessel masters should be familiar with how to request tug support on short notice.”

No injuries or pollution were reported. Damage to Sirocco, the barge, and the Mosaic Uncle Sam dock was estimated at US$5 million.

Marine Investigation Report 24-25 is available online.