Investigators of Key Bridge collapse focus on small electrical component of massive ship

Federal safety investigators looking for an explanation as to why the massive container ship that collapsed the Francis Scott Key Bridge in March lost power while approaching the span have narrowed in on an electrical component about the diameter of a soda can.

The 984-foot Dali, which weighed some 112,000 tons loaded with cargo, lost power twice while at a berth at the Port of Baltimore’s Seagirt Marine Terminal the day before its doomed voyage, then twice again as it approached the Key Bridge early on March 26.

Without power or propulsion, the ship drifted into one of the bridge’s support columns, collapsing the mile-long span and sending six construction workers who were filling potholes on Interstate 695 plummeting to their deaths.

Investigators with the National Transportation Safety Board attributed the in-port blackouts to mistakes during routine maintenance, saying the Dali’s crew fixed the issue by switching breakers for its electrical power system.

Those replacement breakers tripped when the Dali was about three ship lengths from the Key Bridge, causing the second pair of power losses, according to the NTSB. Investigators have been trying to get to the bottom of the circuit breaker failures.

Having interviewed all crew members, examined the ship’s engineering mechanisms and tested its electrical systems, investigators took a small component of a circuit that connects two wires, known as a “terminal block,” to a lab for further testing, the NTSB said in a statement Monday, the same day the Dali departed Baltimore for Norfolk, Virginia, leaving for the first time since the devastating crash.

The terminal block — 1 inch tall by 2.5 inches wide — was part of an abnormality investigators noticed that may have caused a mechanism called an “undervoltage release” to open one of the breakers that tripped during the tragic voyage, the NTSB statement said. Investigators also removed two portions of wiring associated with a terminal block, which costs about $8.

“We will continue to evaluate the design and operation of the vessel’s electrical power distribution system, and investigate all aspects of the accident to determine the probable cause and identify potential safety recommendations,” the NTSB’s statement said.

That the investigation would appear to focus on a simple, inexpensive component surprised Thomas Roth-Roffy, a former NTSB marine casualty investigator and licensed chief maritime engineer.

“Compared to the other components that are part of that electrical breaker system, this is one of the simplest and cheapest,” Roth-Roffy told The Baltimore Sun.

Roth-Roffy suspected that there was a fault with the insulation designed to prevent adjacent wires from leaking voltage, or that the terminal block could have been defective. He said the NTSB likely has, or will, looked X-ray the terminal block to look for microscopic imperfections, such as a crack caused by vessel vibrations.

“This minor component could bring a whole ship’s electrical system down,” Roth-Roffy said.

A spokesperson for Grace Ocean Private Ltd. and Synergy Marine Group, the Singaporean companies that own and manage the Dali, did not immediately respond to a request for comment.

The NTSB statement did not indicate when the investigation would be finished. It typically takes a year from an incident.