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Baltimore Bridge Collapse

Circuit breakers tripped on Dali prior to Baltimore bridge strike: NTSB

Photo: USCG Petty Officer 1st Class Brandon Giles USCG officials survey Baltimore bridge wreckage on container ship Dali
The National Transportation Safety Board (NTSB), the agency investigating the late March collapse of the Francis Scott Key bridge in Baltimore, has released its Preliminary Report into the incident.

In the report, the NTSB points to a pair of electrical power failures aboard Dali - beginning at 01:25 hrs on March 26th, with the second occurring two minutes later.  The report goes into second-by-second details of what was happening aboard the vessel as electrical circuit breakers were tripped into the off position. These breakers shut power to the main engine cooling water pumps, which controlled engine cooling water pressure and steering gear pumps.

It was noted that the engine itself is independent of four diesel powered generators which shut down when the circuit breakers tripped, however, as stated in the report, “the loss of electrical power to the pumps required for its operation resulted in the main engine being automatically shut down, and the vessel lost main propulsion, meaning its propeller stopped.”

Ultimately, following the second blackout, with a total loss of electrical power, and, hence, propulsion, electricity was restored as the crew manually flipped the circuit-breakers on, at 01:27 hrs, but unfortunately, the vessel was within 0.2 miles of the bridge and could not avoid the allision- which occurred less than two minutes later. Though there had been emergency calls for the two McAllister tugs which had assisted in un-docking the vessel a half hour before the allision, they were three miles away and could not reach the ship in time.

Rumblings about previous electrical problems aboard the vessel, while it was docked in Baltimore, were discussed in detail within the NTSB Preliminary Report. The report highlights that: “On March 25, about 10 hours before leaving Baltimore, the Dali experienced a blackout (loss of electrical power to the HV and LV buses) during in-port maintenance.  While working on the diesel engine exhaust scrubber system for the diesel engine driving the only online generator (generator no. 2), a crewmember mistakenly closed an inline engine exhaust damper. Closure of this damper effectively blocked the engine’s cylinder exhaust gases from traveling up its stack and out of the vessel, causing the engine to stall.”

The NTSB explains that when the crew restored power, the crew had switched the configuration of the circuit breakers from its previous arrangement.

One concern early on had been bad fuel aboard Dali; the NTSB squashes this concern, saying: “The test results did not identify any concerns related to the quality of the fuel.”

The agency is continuing its investigation, with a full report to be published sometime in 2025, noting: “The NTSB will continue evaluating the design and operation of the Dali’s power distribution system (including its breakers). Examination of damage to the vessel will continue when the ship is clear of debris and moved to a shoreside facility.”   

In the report, they mention that: “The NTSB is still investigating the electrical configuration following the first in-port blackout and potential impacts on the events during the accident voyage.”  The investigation will also delve into other bridge strikes by vessels, as the NTSB’s remit also includes motorway, and railway transport.

Resources:

https://www.ntsb.gov/investigations/Pages/DCA24MM031.aspx

https://www.ntsb.gov/investigations/Documents/DCA24MM031_PreliminaryReport%203.pdf