Baltimore's Francis Scott Key Bridge Collapses after Ship Strike

[OmCheeto]

So your suspicion is, ahem, Reefer Madness?

It was mentioned here about a month before the report was issued.

Shortly after the bridge crash, I stumbled across a report that the electrical problems whle still in port were caused by power being supplied to too many refrigerated containers. The electrical load was re-distributed several time to stop tripping the circuit breakers.

I was not aware that refrigerated containers were electrically driven.

I also have not been able to find the report again, so please take the above with a bit of scepticism.

I found this news reference that mentions that theory

https://www.wcnc.com/article/news/n...apse/507-02e9a160-2ab6-463c-99ce-08f9862d9e45

I would like to see an official report, as jedishrfu's reference states;

The Dali experienced apparent electrical issues before leaving port, according to someone with knowledge of the situation. The person, who spoke on the condition of anonymity because they weren’t authorized to comment, said alarms went off on the ship’s refrigerated containers while it was still docked in Baltimore, likely indicating an inconsistent power supply.

Not quite enough information to form an educated guess, IMHO.

According to Gmax's reference in post #247, this class ship has a capacity for 1400 reefer containers. That's fine and dandy, but it doesn't tell me anything about the total load, or split partial loads, or surge currents if a bank of such reefers were being cycled on and off. Was the 30 man crew playing some kind of whack-a-mole game, plugging in and out 1400 extension cords to keep alarms from going off?

 

[Swamp Thing]

Speed running container ship...

 

[Astronuc]

Speed running container ship...

Ship at full throttle in harbor causes major South Carolina bridge to close until it passes safely
https://apnews.com/article/bridge-c...hrottle-ship-1bf6e945d5170314dfbfb1c761698217

A large cargo ship lost control of its engines and went nearly full throttle through a South Carolina harbor Wednesday, prompting the closure of one of the busiest bridges in the state.

Harbor pilots were able to help the nearly 1,000-foot (300-meter) ship, which was going nearly 20 mph (32 kmh), get under the Ravenel Bridge safely and eventually anchor several miles offshore while the Coast Guard investigates, said Randy Preston, commander of the U.S. Coast Guard’s Charleston Section.

 

[sophiecentaur]

Speed running container ship...

Why didn’t they just pull the valve lifter knob on the bulkhead? It worked for my Volvo twin 22hp without fail.
The equivalent could be built in surely as a manual override. I do realise the ship’s cylinders are bigger than my whole boat.

 

[gmax137]

Why didn’t they just pull the valve lifter knob on the bulkhead?

Maybe it's a two stroke?

 

[Flyboy]

Maybe it's a two stroke?

In all seriousness, it might actually be. But I think they still have a valve system that’s more complicated than the port-based ones you find on most small 2-stroke engines.

 

[gmax137]

In all seriousness, it might actually be. But I think they still have a valve system that’s more complicated than the port-based ones you find on most small 2-stroke engines.

Yeah even the two stroke engines have a fuel injection system. I'm not sure how marine engines are stopped, but I would guess there is a way to shut off the fuel.

 

[Vanadium 50]

Speed running container ship...

A little faster and it would give new meaning to the term "harbor pilot".

 

[Swamp Thing]

And a new meaning to "airship".

 

[sophiecentaur]

Yeah even the two stroke engines have a fuel injection system. I'm not sure how marine engines are stopped, but I would guess there is a way to shut off the fuel.

It makes you wonder about the qualifications of ships' engineers these days. The knowledge level of some may be restricted to 'operator' level and not 'fixit' level. Of course, there will be Engineers who really know their stuff but the accountants may not rate that s necessary.

 

[russ_watters]

Yeah even the two stroke engines have a fuel injection system. I'm not sure how marine engines are stopped, but I would guess there is a way to shut off the fuel.

Maybe they decided a fast but otherwise under control and powered ship was a lower risk than shutting off the engine and.....

 

[berkeman]

Maybe they decided a fast but otherwise under control and powered ship was a lower risk than shutting off the engine and.....

Yeah, the first thing I thought of was how closing that exhaust damper on the Dali killed the engine. Then I remembered that it resulted in a loss of steering...

 

[Vanadium 50]

Do we cut them a break for having made decisions that avoided an accident?

 

[russ_watters]

Do we cut them a break for having made decisions that avoided an accident?

Yes.

 

[berkeman]

Yeah, the first thing I thought of was how closing that exhaust damper on the Dali killed the engine. Then I remembered that it resulted in a loss of steering...

Do we cut them a break for having made decisions that avoided an accident?

Pilot Captain, I can stop the engine!

No.

 

[Nik_2213]

A similar argument to car throttle jamming open ?
Yes, you may turn off ignition, but you then lose the power steering etc...
Better to negotiate a few 'mild' bends, albeit scary-fast, and kill engine on 'straight'...

 

[berkeman]

Better to negotiate a few 'mild' bends, albeit scary-fast, and kill engine on 'straight'...

Better yet to click the transmission into Neutral and stop ASAP (safely).

 

[Nik_2213]

True !! FWIW, the example I half-remembered had the gearbox / shift jam, too...

 

[Vanadium 50]

Better yet to click the transmission into Neutral and stop ASAP (safely).

When you do that, the engine revs up instantly. It's pretty terrifying.

 

[berkeman]

When you do that, the engine revs up instantly. It's pretty terrifying.

Sure, but that's why engines have rev limiters.

 

[Vanadium 50]

And why seats have Scotchguard.

 

[Astronuc]

Baltimore shipping channel fully reopens after bridge collapse
https://apnews.com/article/baltimor...nnel-reopens-cf12f3b3e2914efa05a91dd399b0dd64

BALTIMORE (AP) — The main shipping channel into Baltimore’s port has fully reopened to its original depth and width following the March 26 collapse of the Francis Scott Key Bridge, which blocked most maritime traffic into the harbor.

Officials announced the full reopening in a news release Monday evening. It comes after a massive cleanup effort as crews removed an estimated 50,000 tons of steel and concrete from the Patapsco River.

After the Dali was moved, crews opened a channel that was 50 feet (15 meters) deep and 400 feet (122 meters) wide. The full federal shipping channel is 700 feet (213 meters) wide, which means two-way traffic can resume, officials said. They said other additional safety requirements have also been lifted because of the increased width.

Officials said a total of 56 federal, state and local agencies participated in the salvage operations, including about 500 specialists from around the world who operated a fleet of 18 barges, 22 tugboats, 13 floating cranes, 10 excavators and four survey boats.

 

[DrClaude]

 

[sophiecentaur]

"faulty wiring" fgs

 

[OmCheeto]

While Chief MAKOi has supplied us with more information, it appears to me that he's guessing.
Also, while I have zero knowledge of this type of vessel, it strikes me as very peculiar that the chief's schematic shows the 'reefer containers' and 'bow thrusters' running on 6600 volts. A quick google shows that these type of 'reefers' run on 440 volts, which would be more in line what I would suspect.

https://www.elecdirect.com/pin-sleeve-devices/reefer-plugs-sockets

As a general rule, I don't like being pedantic, but this makes me question whether he really knows what he's talking about or is just mansplaining.

 

[BillTre]

or is just marinesplaining

 

[Vanadium 50]

he's guessing.

Until we get an official report, isn't everyone just guessing?

 

[gmax137]

it strikes me as very peculiar that the chief's schematic shows the 'reefer containers' and 'bow thrusters' running on 6600 volts. A quick google shows that these type of 'reefers' run on 440 volts, which would be more in line what I would suspect.

Maybe the reefer banks have transformers not shown on that schematic?

I don't have any background in marine design but ... In stationary plants I've seen 440 volts for small stuff, 4160 volts for motors up to 400 to 500 hp, and 6600 volts for big motors. How big do you suppose the thruster motors are?

 

[gleem]

Generally vessels are fitted with very weak bow thrusters (Ex: A small chemical tanker of 150 mtr may have BT of 700HP, A large container vessel of length 300 mtr may have BT of abt 2000 HP).
https://www.shiphandlingpro.com/thr...lly vessels are fitted with,BT of abt 2000 HP).

 

[Swamp Thing]

Maybe the reefer banks have transformers not shown on that schematic?

I don't have any background in marine design but ... In stationary plants I've seen 440 volts for small stuff, 4160 volts for motors up to 400 to 500 hp, and 6600 volts for big motors. How big do you suppose the thruster motors are?

https://chiefengineerlog.com/2022/1...ine industry, voltages below,6.6 kV and 11 kV.

The 6600 volts seems to be used for distribution over long distances, with step down transformers located near the loads. Maybe some simplified diagrams don't show the transformers separately, but merge them with the 440V loads, as gmax suggests.

 

[OmCheeto]

How big do you suppose the thruster motors are?

According to wiki "For maneuvering, Dali has a single 3,000 kW (4,000 hp) bow thruster."

That's about 3/4 of the capacity of one of its four 4 megawatt diesels. Going back to the original NTSB report, it does show the bow thruster being powered off of the 6600v bus. My bad!

 

[Nugatory]

Sure, but that's why engines have rev limiters.

I was going to mention that my 70’s vintage cars do not have rev limiters, but I was wrong. An out of control over rev situation is automatically corrected when a con rod comes out through the block.

 

[PeterDonis]

An out of control over rev situation is automatically corrected when a con rod comes out through the block.

So it's a "rev limiter" in much the same way as the ground is a "fall limiter"?

 

[Tom.G]

I was going to mention that my 70’s vintage cars do not have rev limiters, but I was wrong. An out of control over rev situation is automatically corrected when a con rod comes out through the block.

Or when you run out of oil on the Interstate Highway.

 

[renormalize]

Also, while I have zero knowledge of this type of vessel, it strikes me as very peculiar that the chief's schematic shows the 'reefer containers' and 'bow thrusters' running on 6600 volts. A quick google shows that these type of 'reefers' run on 440 volts, which would be more in line what I would suspect.

I think you badly underestimate the power requirements for thrusters on large ships. Below are some specifications for a fairly large vessel built to transport and deploy loads of rock that underlays submerged pipelines: (https://www.ingeteam.com/Download/2574/attachment/case-study-joseph-plateau.pdf.aspx)

All of the electric motors for thrust and propulsion provide multiple-megawatts of mechanical power and all run at over 3000V, so each draws currents of multiple-hundreds of amps. If they all ran at 440V instead, their draw would increase to multiple-thousands of amps each. Can you imagine the size of the conductors needed to carry that much current and the additional weight-penalty that the vessel would have to bear?

 

[OmCheeto]

Can you imagine the size of the conductors needed to carry that much current and the additional weight-penalty that the vessel would have to bear?

You are of course correct. I guess I should have done the maths after I found the actual wattage rating (Post # 281).

3,000,000 watts/6600 volts = 450 amps * 1 cable
3,000,000 watts/440 volts = 6800 amps ≈ 15 cables * 450 amps

I would love to see the control circuitry for that monster. I wonder how long it takes to get up to full speed. Might be a factor in the incident.

 

[berkeman]

 

[gmax137]

Your backordered part here

From the start, I was wondering about people who had their personal belongings in the containers - household property, antique cars or bikes, artwork, etc. etc. I guess if you're going to ship your stuff across the ocean you'd better have it insured for replacement cost.

 

[Vanadium 50]

It's complicated. There is something called "general average" in maritime law. If I am shipping $1M worth of stuff and you are shipping $1M of stiff, and yours is lost - say tossed overboard to save the ship - then I owe you $500K if general average applies.

If you have cargo insurance, then the insurance pays you $500K and I or my agent pays you $500K.

Of course in real life there are many shippers, many cargoes, many insurance policies. and this rule may apply in some cases and not others. Oh, and the lost cargo may be salvaged. This keeps the lawyers busy.

 

[gmax137]

. This keeps the lawyers busy

So has it always been...

 

[Astronuc]

AP News - Loose electrical cable found on ship that caused Baltimore bridge collapse
https://apnews.com/article/baltimor...-loose-cable-57c8260759fd313de006cf02bcf3ccfb

BALTIMORE (AP) — Investigators working to pinpoint the cause of Baltimore’s Francis Scott Key Bridge collapse discovered a loose cable that could have caused electrical issues on the Dali, the massive cargo ship that lost power and disastrously veered off course before striking the bridge.

When disconnected, the problematic cable triggered an electrical blackout on the ship similar to what happened as it approached the bridge on March 26, according to new documents released Wednesday by the National Transportation Safety Board.

The documents don’t include any analysis or conclusions, which will be released later in the board’s final report. A spokesperson for the board declined to comment as the investigation is ongoing.

Waiting for NTSB final report - https://www.ntsb.gov/investigations/Pages/DCA24MM031.aspx

 

[Vanadium 50]

I assume this is some kind of control cable and not the power itself? Those cables are...beefy. Really beefy. Not like a Taco Bell burrito. I couldn't find more details, though.

 

[OmCheeto]

I assume this is some kind of control cable and not the power itself? ...

Control cable connector. 110 vdc portion of an undervoltage trip circuit.

from page 39

I can't figure out how to link to the document directly, and it appears you can only read it if you download it.

41 pages. 1.1 Mb. Dated September 11, 2024: '...ort (download link) we ...'

Source of the link: https://maritime-executive.com/arti...ntsb-dali-investigation-could-cause-blackouts

 

[nsaspook]

That guy loose wire really gets around.

Brothers?