An electrical generator set (genset) failure and subsequent loss of steering led to the grounding of a towing vessel near Greenville, Miss., the National Transportation Safety Board says.
The incident occurred when the towing vessel Marquette Warrior was pushing 35 loaded dry cargo barges down the Lower Mississippi River on November 21, 2021, when several barges grounded on the riverbank. Four barges were damaged, including a hopper barge with bean cargo that partially sank. None of the nine people on board the Marquette Warrior were injured.
Like so many other grounding incidents, this one proved expensive. It resulted in $1.24 million in damages to the vessel, barges and cargo.
“Following the grounding, the Marquette Warrior, aided by several nearby Good Samaritan vessels, corralled the scattered barges and rebuilt the tow. Four of the barges sustained damage, mostly to their rake bottoms and side shell plating, with the steel plating being dented or inset,” says the NTSB report. “One barge partially sank and was later salvaged; its bean cargo was contaminated with water and was declared a loss. The total damage to the barges was estimated to be $215,000, and the lost cargo was estimated to be worth $1,020,000. The Marquette Warrior also sustained an estimated $7,500 in damage as a result of the casualty.”
As the vessel was transiting, the engineer saw flickering lights and a ground fault indication on the main switchboard. The engineer contacted the pilot in the wheelhouse to request that the pilot stop the vessel so he could troubleshoot what he suspected was a problem with the electrical system. The pilot was not able to stop the vessel due to the size of the tow and its location.
The engineer identified an issue with the online port electrical genset. At the same time, the pilot noticed that he had lost steering control. Hearing that the vessel had lost steering, the engineer decided to switch online gensets, which necessitated a temporary loss of the towboat’s electrical power. Although the engineer resolved the electrical issue by switching gensets and restored steering relatively quickly, the loss of steering in the swift current and limited maneuverability of the large tow prevented the pilot from avoiding grounding.
Electricians’ analysis of the genset’s alternator following the grounding indicated that the most likely cause of the failure was rubbing or chaffing of the sensing wiring harness, which led to arcing between terminal block posts, heat buildup, insulation failure and eventual winding ring terminal connection failure.
NTSB investigators determined it is likely the chaffing of the wiring harness took place over the 72 hours the genset ran between a November 7 maintenance inspection and the grounding on November 21.
The NTSB determined the probable cause of the grounding was a loss of steering, likely due to a wiring harness within an electrical generator that was improperly positioned during a maintenance inspection, resulting in the harness contacting the terminal posts, eventually causing the loss of 3-phase electrical power to the steering pump motors.
“Proper operation and maintenance of electrical equipment is required to avoid damage to vessel critical systems and prevent potentially serious crew injuries, particularly for electrical systems with high and medium voltage and equipment with uninsulated and exposed components,” the report said. “Electrical equipment should be installed, serviced, and maintained by qualified personnel familiar with the construction and operation of the equipment and the hazards involved.”
- As always, there’s much more in the complete NTSB report