Baltimore Bridge collapse after ship collision 125

[Tomfh]

https://amp.9news.com.au/article/b73620ea-64ab-4253-8cb0-37102418fcab

 

[TugboatEng]

The rudder was ineffective due to loss of electrical power...

 

[Nukeman948]

If you are going to post a picture, it would be nice if you could include a bit of commentary so that we might have some idea of the point you are trying to make, especially when the picture is of an entirely different ship. (hint: the Dali only has one bow thruster)
Also, speculating about a faulty bow thruster when there is no evidence or even reporting that there was any attempt to use the bow thruster during this mishap seems like a pointless exercise to me. There was certainly no reason to be using the bow thruster between the time it left the dock and got turned around, and when it began showing signs of an electrical problem.

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[waross]

Picture from Wiki.
General idea of the arrangement of bow thruster(s).
I think it is strange that there has been no mention of the bow thruster, used, unused or failing.
A failing bow thruster could explain the so far unexplained electrical problems and the brown out and the black smoke.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

This link has some useful information on bow thrusters.
The Essential Guide to Bow Thruster Construction and Functionality - ByMohit January 30, 2024

Some specifics

https://en.wikipedia.org/wiki/MV_Dali[/URL]]For maneuvering in ports, Dali has a single 3,000 kW (4,000 hp) bow thruster. Electricity is generated onboard by two 3,840 kW (5,150 hp) and two 4,400 kW (5,900 hp) auxiliary diesel generator

This thruster most likely needs two of the service generators on line to reliably start. It could not be operated from the emergency bus or from one generator due to not enough generating capacity. The bow thruster is interesting, but not in play for this event (my opinion). I was not able to find anything referencing the Dali's emergency generator size.

 

[TugboatEng]

At 8 knots the ship would not have been using its now thruster.

For those that are unaware of what an auxiliary blower is, this video has a short description at the beginning.

https://youtu.be/9uajoqlvIx0?si=bGEEQ5iaVFEA6ra7

 

[KevinK2]

-> I haven't seen any speculation concerning the bow thruster.

Based on my limited research, a thruster is sized to maneuver the ship at low-idle speeds, as during docking proceedures, not to change the direction of the ship underway. When the drive was lost, limited linearized tracking data showed a 2 step direction change, with the ship increasingly veering off course. Still not clear as to why.

-> There is speculation concerning the relative ineffectiveness of the rudder without propulsion.

In an illusrated presentation, they showed the rudder operated directly behind the propeller and redirected the thrust it created off center to make a turn. Without the prop shaft working, the rudder would have little effect on the ship's path.

-> A progressively failing phase in the thruster motor could easily make one or possibly two of those auxiliaries "Roll Coal". Just an FYI, "Rolling coal (also spelled rollin' coal) is the practice of modifying a diesel engine to emit large amounts of black or grey sooty exhaust fumes—diesel fuel ..."

Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists

 

[TugboatEng]

This ship is 2016 vintage. It has electronically controlled engines and should not roll coal under any load conditions except in the event of a mechanical fault such as a turbocharger failure.

 

[Alistair_Heaton]

I suspect the thrusters propellers will stall trying to suck water in from a flow going at 8 knts going horizontal across a hole face.

 

[Murph 9000]

The hydrodynamics of the bow thrusters are probably a factor, but I think it's also a v-squared thing. You've got considerably more momentum at 8 knots compared to dead slow maneuvering in and out of a dock. The thruster is sized to provide enough energy for slow speed use. I'm not an expert on it, just thinking from first principles, and I think it's a bit like the steering tyres on a car, where the ability to redirect the momentum greatly diminishes with speed.

 

[Alistair_Heaton]

Its fluids there must a cubed in there somewhere as well

But yes there will be that as well.

There is a theory that they teach in Europe apparently which is to turn the tug sideways so the broad side of the boat and kegg acts as a colossal brake but you need vectored thrust on the tug plus its structurally unsound afterwards.

 

[stevenal]

The focus here seems to be about the bow thrusters' ability to re-direct momentum. What if the thruster could simply push the bow out without affecting overall momentum? The ship might have struck more sideways with a deeper part and possibly a better outcome.

 

[KevinK2]

.. thrusters' ability to re-direct momentum ..

Momentum is a vector quantity M = m * V , caps imply vector, and m = huge

So the bow thruster would work against a resistive, momentum based torque. That's why their use is only effective when V is near zero, as in docking.

Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists

 

[RoopinderTara]

Here's a call for action on bridge protection, mainly bigger dolphins and more of them, an article by our author and resident civil engineer/bridge inspector, Joshua Sadlock. I helped with some of the writing. Let me know what you all think.

Roopinder Tara
Director of Content
ENGINEERING.com

 

[KevinK2]

Here's a call for action on bridge protection, mainly bigger dolphins ...

By coincidence new 80ft dolphins are currently being installed nearby for Delaware Memorial Bridge over the Delaware River. The bridge is massive, and MV Ships travel under it to major ports in Philadelphia. Dolphin design details:

https://delawarelive.com/memorial-bridge-dolphins-designed-to-stop-ships-like-dali/

Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists

 

[3DDave]

I'm concerned that the dolphins can stop the ship but then tear into the hull in a way the overhanging portion still reaches the bridge pillars.

 

[TugboatEng]

That's ok. These ships are operating with very little under keel clearance. If you tear a hole into the hull and sink the ship it will likely end up only a few feet lower than it was when it was floating.

 

[IRstuff]

I'm concerned that the dolphins can stop the ship but then tear into the hull in a way the overhanging portion still reaches the bridge pillars.

I think that the article touches on that; the dolphins have to have some give, like crumple zones; ripping the the bottom out of a ship and sinking it isn't exactly a win-win.

TTFN (ta ta for now)
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[3DDave]

MV Dali had the hull torn open and did not sink because of it; sinking is not a problem that needs addressing. Refloating a ship that is a few feet lower in the water than normal isn't a huge problem and, as in this case, if it sinks because the ship was not seaworthy? Shug.

 

[KevinK2]

MV Dali had the hull torn open and did not sink because of it; sinking is not a problem that needs addressing. Refloating a ship that is a few feet lower in the water than normal isn't a huge problem ...

This video opens with a view of the reinforced concrete support that the Dali hit. Soon the focus is on the part of the upper hull that was removed by the collision with the support. This shark-bite from the hull went below the deck, but not below the waterline. Don't know if the hull was opened below it, via other contact..

https://www.youtube.com/watch?v=sB1UwdFART8&t=579s

Based on this image, the ship seems to be listing away from the impacted support. Most likely due to the massive part of the bridge hanging off that side, but less likely due to that side resting on the severed upper parts of the bridge support, now below the hull.

Link



Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists

 

[TugboatEng]

It likely doesn't contribute much to the conversation but the bow of ship is likely hard on the bottom due to the weight of the bridge components laying across it, flooding not required.

This does put it in a severe hogging condition and, depending on tides, could fatigue and break the hull over time.