Minutes before the cargo ship Dali glided under the Francis Scott Key Bridge in Baltimore, the ship's alarm began to sound. The lights went out. The engine stopped. Even the rudder, which the crew uses to steer the ship, was frozen.
Desperate efforts to repair the ship were underway, and the pilot soon realized that the aimless ship was drifting towards disaster and called for help.
A cascading failure of the ship's most critical operating system caused the Dali to drift adrift, eventually colliding with the key bridge, causing it to fall into the river and killing six people. But while the crew this week was still figuring out how to disentangle the ship and recover the bodies of those who died, investigators were also looking at the most central question: The question was: What could have caused such a catastrophic failure at the worst possible moment?
At a time when the industry's largest ships can carry four times as much cargo as they did just a few decades ago, navigating crowded city ports under bridges that could carry tens of thousands of cargo, Engineers, captains and shipping officials are waiting for answers. How many people a day?
Several key questions have already emerged, according to engineers and maritime experts monitoring the investigation, most of which are related to lighting, navigation and steering, as well as nearly everything on board the 984-foot ship. It is said to be related to the generators that power the system. A pump that supplies fuel, oil, and water to a huge diesel engine.
The “total power outage” reported by the pilot is difficult to explain in today's shipping world. In today's shipping world, large commercial ships are operated with extensive automation, computerized monitoring, and built-in redundancy and backup systems designed to avoid just such disasters.
“Over the last 30 to 40 years, that level of redundancy has increased quite significantly,” said John Carleton, professor of ocean engineering at City, University of London. “The ship of today is very different from the ship of her 30 years ago.”
But there are a wide range of factors that could have caused the accident, which investigators will have to sift through as they interview the crew, examine the fuel supply and examine the ship's systems that malfunctioned that night. Dew.
Inadequate maintenance may result in a delay in starting the emergency backup generator, or an electrical failure that may prevent the generator from continuing to operate. If the fuel is contaminated or a valve is accidentally closed, the main generator can become dirty and lose power. Human error can cause problems or prevent you from overcoming them. Automation on the ship itself may have caused the equipment failure. Or perhaps a fire broke out and important equipment was damaged.
The answer will affect not only international shipping, but also liability for damages, which S&P Global Ratings estimates at more than $2 billion.
Singapore-based Grace Ocean Private, which owns Dali, said it was “cooperating fully with federal and state government agencies.” Grace Ocean is owned by Yoshimasa Abe, a Japanese national who owns at least two shipping companies and more than 50 vessels, including the world's largest container ship. The Dali was insured, but depending on the findings of accident investigators, Abe's company could face hefty claims.
Given the scope of the failure, there may have been multiple issues. Timothy McCoy, a professor of ocean engineering at the University of Michigan, said that, like a plane crash, a major failure of a ship's systems usually involves a series of events.
A closer look at the underlying factors includes many of the most important factors in modern cargo ship operations. This also includes the fuel supplied to her 55,000 horsepower diesel engines, which power the ship's propellers.
The fuel also powers the giant generators that power the container ship. And a ship like the Dali runs its main engine, and the fuel injection system, for example, is powered by electricity and requires electrical power to steer. Without electricity, a ship could become adrift.
The generation of contaminated fuel caused problems for 32 ships heading from Texas to Singapore in August last year, with several of them reportedly losing power and propulsion at sea, according to reports from maritime industry sources. ing.
Last year in Washington state, a large passenger ferry lost power and ran aground after bacterial and fungal growth in its fuel tanks contaminated the ship's filtration system.
According to shipping data service S&P Maritime Portal, the Dali had four generators on board when it was built in 2015. Container ships leaving a port usually have additional generators running to provide backup power if needed, although they usually do not all run at the same time. “At least two ships should be online at the same time,” said Mark Blalack, a maritime scholar and former container ship engineer.
If all generators were running on a common bad fuel source, all generators could have failed.
Henry Lipian, a forensic collision investigator who previously worked for the Coast Guard, said the sudden loss of the ship's generator led him to consider a fuel problem as a potential cause.
He said investigators would need to look at the fuel on board, how it was transported, whether it had been tested beforehand and what filtration systems were installed on the ship. But he said a fuel valve issue could be another explanation.
“I want to start tracing all these fuel lines,” he said.
National Transportation Safety Board Chairwoman Jennifer Homendy said investigators in Baltimore are taking fuel samples from the Dali to check for quality, viscosity and signs of contaminants.
But other experts said there was also reason to doubt the dirty fuel scenario. New fuels are usually tested, and a dual filtration system helps remove problematic components that were not picked up by testing. There have been no reports of other ships having problems with the same batch of fuel.
Marine engineers say an electrical chain reaction may have caused all generators to shut down. If one generator fails, a situation can occur where there is too little power supply and too much demand. Richard Burke, a professor of naval architecture and ocean engineering at the State University of New York Maritime College, said the system would also shut down other generators because they were at risk of being damaged.
“It’s like you and I were both carrying a heavy weight and I let it go,” he said. “I drop the weight because I can’t hold it alone.”
Capt. Morgan McManus, a lecturer at the State Maritime College of New York, said hay generators could also disrupt a ship's power distribution system.
If all main generators fail, the vessel relies on a backup generator, typically located above the waterline in another area of the vessel and with its own fuel source.
Marine engineers say the backup generators provide power to run some lighting, navigation systems and, importantly, the ship's control systems. At least you can't move the rudder without backup power.
After Dali suffered his first power outage, a backup generator appeared to kick in as some lights came back on, but only after a delay of about a minute. Still, the lights seemed to go out and come back on, making it more likely that the problem was with the backup generator.
The NTSB's Ms. Homendy said this week that investigators had collected data “consistent with a power outage” but were still trying to determine its extent.
Clay Diamond, president of the American Pilots Association, an industry group that works closely with pilots at Maryland ports, said steering was restored after emergency generators were activated. But even with a sharp left turn and dropping anchor, there was not enough time to turn the ship around or stop it.
Blalack, the marine engineer, said the backup generator is to be tested regularly by turning it on for two hours once a month. “What I want to know is when was the last time that emergency diesel generator was tested,” he says.
The Coast Guard inspected the Dali after it entered New York Harbor in September and found no defects on the ship. The Coast Guard has not disclosed details of the inspection.
Modernization of ships may have introduced other ways in which ships can fail. We are increasingly relying on computers to monitor troubles and respond when problems are identified. In a sense, this is a built-in layer of automatic protection. If one component becomes overloaded, it can automatically shut down to prevent further damage. But these shutdowns can themselves cause problems.
“We couldn't rule out the possibility that a computer failure shut off all the valves or stopped the pumps supplying the fuel,” Lipian said.
michael forsythe and jenny gross Contributed to the report.