Debris in steering gear caused bulk carrier to strike navigational aid in Michigan's St Mary's River, NTSB report finds
A steering system failure led to a bulk carrier’s contact with a navigational aid in the St Marys River near Sault Ste Marie, Michigan, the US National Transportation Safety Board (NTSB) said on Tuesday, May 13.
The bulk carrier American Mariner struck the Munuscong Channel Junction Light as it was transiting upbound in the St. Marys River on March 28, 2024.
The Munuscong Channel Junction Light is comprised of a navigational light and signal mounted on a concrete, fixed structure.
After the contact, the vessel began taking on water but was stabilised using pumps. None of the 18 crewmembers on board were injured and no pollution was reported.
Damage to the vessel was approximately US$800,750 and damage to the Munuscong Channel Junction Light was estimated at US$1.25 million.
American Mariner was on its first voyage of the season following its winter lay-up period, during which annual preventative maintenance was performed and a new steering control system was installed.
During the voyage leading up to the contact, alarms for the vessel’s steering system sounded intermittently, but the crew could not determine the cause, and the rudder appeared to properly respond to input commands.
Following the contact, electronic technicians recalibrated the steering control system and the steering alarms stopped, indicating likely issues with the newly installed control system’s calibration parameters.
Crewmembers inspected the steering system after the contact and determined that the number one control motor, which controlled the stroke of the main hydraulic pump, had failed.
The motor was disassembled, and a piece of black, pliable debris was found to be lodged in between the rotating gears of the control motor, preventing it from rotating properly.
Once a replacement control motor was installed, the steering system responded properly to steering commands from the bridge.
The NTSB determined the probable cause of the contact was O-ring-type material debris in the steering gear system’s hydraulic oil becoming lodged within a control motor, which caused it to seize, resulting in the rudder locking at its last ordered position.
The investigation report into the incident is available online.
American Mariner had also been involved in an earlier incident.
On January 2, 2023, the ship ran aground as it was departing the Ontario side of Sault Ste Marie en route to Superior, Wisconsin. The master, acting alone on the bridge during complicated manoeuvres, overshot a turn and grounded on shoals, damaging three ballast water tanks.
"While manoeuvring in confined waters, it is difficult for a single bridge crewmember to effectively drive, lookout, and monitor and use available bridge equipment," the NTSB said in a report following the 2023 incident.
