UPDATE: Friday, Mar 29, 2024 · 12:32:34 PM +00:00
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RustyRobot
I have never posted an update for any article before so here is my very first attempt. The article is edited with some new videos added at the top for readers who want to dive much deeper into the situation. All info is accurate as far as I know. Ignore any conspiracy theories as there is no evidence to back anything other than an engineering incident.
Updates
Previous collision incident in 1980 resulting in minimal damage.
- Previous collision in 1980
The NTSB has released five videos about the MV Dali incident.
- NTSB Media Briefing - Francis Scott Key Bridge struck by Cargo Ship Dali
- NTSB Media Briefing 2 - Francis Scott Key Bridge struck by Cargo Ship Dali
- NTSB B-Roll - Aerial Imagery of Francis Scott Key Bridge and Cargo Ship Dali
- NTSB B-Roll - Investigators Aboard the Cargo Ship Dali
- NTSB B-Roll - Hazardous Material Investigators and Engineers Aboard the Cargo Ship Dali
A Statement from the American Pilots Association
- Containership DALI suffered a total blackout before the collision with bridge
Route of the MV Dali
- Container ship DALI struck and collapsed Francis Scott Key Bridge
Charts of the area
- Chart of the Upper Chesapeake Bay Navigation
- Chart of the Baltimore Harbor Navigation
Introduction and Warning
I am not a ship’s officer or crew and never have been. I do watch nerdy Youtube channels like those by actual merchant marine Chief Engineers because I just like these big ships. Much of me never really grew up so understand that I am writing this just to give a better picture of the details of what happens in the engine room as I understand it, but I could be wrong about anything. Caveat Emptor and all that.
The engines and equipment of these ships are simply big, really big. They are also not like your car or truck as they operate in different ways (this is what makes them interesting to me). I will mostly do text for this article but if there is interest I can expand it with additional descriptions and graphics.
The Ship
Facts and figures for the MV Dali
- Named after Salvador Dali
- Built in South Korea from October 2014 to March 2015
- Displacement of 149,000 tons
- 984 feet length by 158 feet wide
- 49 foot draft (hull depth in the water fully loaded)
- Propulsion is a single shaft with a fixed pitch propeller
- Power is from a MAN-B&W 9S90ME-C9.2 two stroke diesel engine of 55,000 hp
- Design speed is 22 knots or 25 mph at 82 RPM
- Fuel usage is around 200 tons per day
- Engine cylinder bore is 900 mm and stroke is 3260 mm (I think 9 cylinders)
I was not able to find a trustworthy number for fuel consumption but 200 tons of heavy fuel oil per day is close. At that rate of fuel burn it is obvious why optimizing the engine and propeller is an important design task.
The Engine Room
The cargo type ships (bulk, oil, container, LNG, etc) usually have just one propeller and one engine. In this ship the engine turns at just 82 RPM, matching the optimal rotational speed of the propeller, so no reduction gear is needed. There is also no reversing gear so, to generate reverse thrust, the engine is stopped and restarted turning the opposite direction.
In a big ship it is most accurate to think of all the equipment in the engine room as the engine. The ship’s main engine can not operate without all of the other equipment around it. The main engine does only one thing — it turns the propeller. This is very different from a car engine where the engine provides all the power to operate the vehicle. In addition to the main engine is three or more auxiliary engines and all they do is generate electricity. That electricity is used to power everything on the ship (except turning the prop). Everything includes systems needed to operate the main engine itself.
This is a cutaway of a cargo ship (not exactly like the MV Dali but close enough). You can see the main engine attached to the propeller shaft and behind it are three purple things which are the auxiliary engines. Ships can certainly have more than three aux engines depending on how much power is needed and the MV Dali has four.
Here is a picture from a similar engine room (not the MV Dali). The big beast in the center is the top of the main engine and I do mean the “top” of the engine. The three machines at the back of the picture are the auxiliary power engines or generators and are about 5,000 hp.
Here are two pictures of the rest. What you see above is just the very top platform and shown only on the right side of the engine due to the cutaway.
The next pic shows two engines under construction (these have more cylinders that the MV Dali engine but are otherwise the same). This gives an idea of how huge these things are. The cylinder bore diameter is almost 36 inches.
The Operation and Power Loss
Everything is run from the aux engines including the fuel feed pumps, lubricating oil pumps, cooling water pumps, and the exhaust valves (hydraulic actuators controlled by computer). Without the aux engine electric power that huge beast of a main engine is dead weight. The other systems run by the aux power are the rudder hydraulic pumps (two units), lights, navigation, communication, and almost everything else on the ship.
During port maneuvering at least three aux engines are operating and synched to the power bus so even if two engines go down the third engine can still run the ship. It looks to me like all the power was lost over the entire ship which means that all the aux engines shut down or the entire aux power bus tripped of line. After that the main engine would have shut down and the rudder locked in place. At that point the Francis Scott Key bridge was doomed. There was not enough time to restart the aux systems and restart the main engine before hitting the bridge pier - although the crew really tried.
The rudder locked at whatever position it was when power was lost since both hydraulic pumps (for redundancy) need electric power from the aux engines. The ship was coasting but something started the bow turning right. Maybe it was a cross current or maybe the helm had turned the wheel slightly to the right for a small course correction. It takes a few seconds for the 100,000 ton ship to actually start turning but eventually it did and headed directly into the bridge pier.
The Worst Possible Timing
It’s hard to say how bad the timing was for losing all power. If the incident had happened a minute earlier the engine room crew could have recovered power (at least to the rudder) and avoided the impact. If the power loss had happened maybe 15 seconds later the ship would have coasted under and through the bridge without striking anything (maybe a very close call though). But that is not what happened and now we clean up the horrible mess.
Maybe we will start putting more protection on the bridge piers — there was no protection at all for the Key bridge. The last time this happened was the Sunshine Bridge disaster in Florida around 1980. The replacement span has great protection against ship strikes now. We have left these issues to fix themselves for far too long. I think that the Biden-Harris administration really does want to tackle these issues, so maybe we should get out the vote for November. Does anyone think the other guy would do a better job?
If anyone wants more info just ask and I will do what I can. Youtube is a great resource to learn more.
Some Youtube Videos
The Engine
Engine Room Tour
Different Ship Engine Room
Engine Starting Procedure