Baltimore Bridge Collision and Collapse

[Capt. Eric]

I love it when guys like that, who clearly have never been on a vessel bigger than his buddy's fishing boat, let alone this particular ship, try to explain things like they are experts. He clearly never saw a main bus breaker on a ship of that size. It's just a little different than the one your house. The only grain of truth in that part is that it is possible for a dirty breaker to have problems staying closed. That's why the main ones throughout the board are inspected and cleaned every shipyard at 2.5-5 year intervals. I wouldn't rule out issues with a breaker, but that shouldn't take the ship down. Rather than try to explain it like he knows what happened, let's wait for the NTSB. They'll know more.

 

[OverTheTop]

Even the linebreaker (main circuit breaker) in a tram is bigger than that whole box he was gesticulating at. DC too, which means a ceramic arc chute and magnet to direct the arc into the chute. I'll let you guess what happens if someone installs the magnet backwards...

I suspect ship breakers would be serious. Any idea what the normal current ratings you would expect to see?

The NTSB report will be a good read.

 

[Capt. Eric]

Even the linebreaker (main circuit breaker) in a tram is bigger than that whole box he was gesticulating at. DC too, which means a ceramic arc chute and magnet to direct the arc into the chute. I'll let you guess what happens if someone installs the magnet backwards...

I suspect ship breakers would be serious. Any idea what the normal current ratings you would expect to see?

The NTSB report will be a good read.

I'm not an engineer, so I can't answer your question accurately, but I will say the main bus breakers on a ship like that are about the size of case of legal paper. Weighs about that much too! You don't just flip it with a finger!

 

[wsume99]

Curious about the FBI opening an investigation. NTSB is focused on determining probable cause. With the FBI now on scene I'm assuming the NTSB saw enough to at least think there may be criminal charges in play?

Edit - Found the statement below on the NTSB website. So the FBI investigation does signal there is at least the suspicion of a criminal element to this accident. I'm talking about criminal negligence, not a cyber attack or other conspiracy theory.

In cases of suspected criminal activity, other agencies may participate in the investigation. We do not investigate criminal activity. Our focus is solely on transportation safety and determining probable cause. If a transportation tragedy is determined to be a criminal act, local law enforcement or the FBI becomes the lead investigative body.

 

[Capt. Eric]

Curious about the FBI opening an investigation. NTSB is focused on determining probable cause. With the FBI now on scene I'm assuming the NTSB saw enough to at least think there may be criminal charges in play?

Standard procedure in big accidents like this. They'll be looking for negligence on a criminal level. But also, according to law, ANY discharge of oil is a criminal offense. Since a small amount of oil was leaked and hit the water, the Captain and others may be subject to criminal prosecution. So the FBI being there is not a surprise. Doesn't necessarily mean anything dramatic.

 

[boatgeek]

Even the linebreaker (main circuit breaker) in a tram is bigger than that whole box he was gesticulating at. DC too, which means a ceramic arc chute and magnet to direct the arc into the chute. I'll let you guess what happens if someone installs the magnet backwards...

I suspect ship breakers would be serious. Any idea what the normal current ratings you would expect to see?

The NTSB report will be a good read.

You're an electrical engineer and I'm not, so you might know better than me. Per the classification society, the ship has 5 generators with a total rating of 20 MVA. A stab in the dark would say that 75%-80% of that might be running at once in very high load configurations (running the bow thruster, chilling a lot of refrigerated containers down, etc.). Wikipedia also says that the largest generator is 4400 kW.

We have a diesel-electric boat under construction with similar size generators. Its main bus runs at 4160 VAC, and the largest breakers are 600-700 amps in a 1200-amp frame. The largest wires are a bundle of 6 (2 for each phase) wires, each 373 kcmil (185 mm^2 if I'm reading the table right). The propulsion motors are 730 VDC, with 1800 amp breakers in 2000A frames. 15 of those 373 kcmil cables for those loads. Once you get down to smaller loads (a hundred kW or less), transformers will take it down to 690 and 480 VAC three phase, then to 208/120 three/single phase for lighting and fractional horsepower motors.

 

[cls]

The propulsion motors are 730 VDC,

I'd like to see the diodes that rectify that much power!

 

[Art Upton]

I'd like to see the diodes that rectify that much power!

I though the whole Idea of AC motors invented by Tesla was there was no need for that so why are they using DC motors ? [What do I know}

 

[Art Upton]

.

 

[jsdemar]

I though the whole Idea of AC motors invented by Tesla was there was no need for that so why are they using DC motors ? [What do I know}

Linear actuators use DC.

 

[boatgeek]

I'd like to see the diodes that rectify that much power!

The black boxes that hold the rectifiers and AC-DC equipment are about 2' x 10' footprint, likely around 6' tall.

I though the whole Idea of AC motors invented by Tesla was there was no need for that so why are they using DC motors ? [What do I know}

I'm not an electrical engineer, so I don't really know. I do know that there are sometimes advantages to using DC instead of AC with large propulsion motors. That's as much of the dark arts as they let me know. More would likely kill the weak and drive the strong insane.

 

[Greg Furtman]

I though the whole Idea of AC motors invented by Tesla was there was no need for that so why are they using DC motors ? [What do I know}

Diesel locomotives use DC motors. The diesel is there just to drive a DC generator. DC is easier to control speed wise usually through pulse width modulation.

 

[Dotini]

The FBI has opened a criminal investigation.

 

[modeltrains]

Diesel locomotives use DC motors. The diesel is there just to drive a DC generator.

AC has alos been an option for some years now.
One contemporary example,
https://www.wabteccorp.com/locomotive/heavy-haul-locomotives/es58aci-locomotive

The ES58ACi locomotive is the most powerful Wabtec heavy-haul diesel-electric unit in operation. It incorporates the latest model GEVO V16 cylinders diesel engine on an AC traction-system backbone.
The GEVO16 engine operates on a 4-stroke cycle, is fully turbocharged via two turbochargers and an intercooler producing 6000 GHP. The AC-propulsion technology with individual traction motor control maximize the traction effort and achieves higher levels of rail horsepower.

See also:

https://www.republiclocomotive.com/ac-traction-vs-dc-traction/

AC Traction vs DC Traction
AC TRACTION
The AC (alternating current) Drive, also known as Variable Frequency Drive, has been the standard in industry for many years. While it has been used in locomotives for over two decades (especially in Europe), it has only been recently that the price of the drives has allowed them to be used in most of the new diesel-electric locomotives in the United States. The AC drive works by converting the traction alternator output to DC (direct current) and reconverting it to a variable frequency AC which powers AC traction motors. Because AC motors operate at approximately the frequency of the current, the drives must adjust the frequency so that the motors can have a speed range of zero to maximum rpm.

AC traction for locomotives is a major improvement over the old DC systems. The primary advantages of AC traction are adhesion levels up to 100% greater than DC and much higher reliability and reduced maintenance requirements of AC traction motors.

The tractive effort of a locomotive (whether AC or DC) is defined by the equations:

Tractive effort = Weight on drivers x Adhesion
Adhesion = Coefficient of friction x Locomotive adhesion variable

also see:

https://www.progressrail.com/en/Segments/RollingStock/Locomotives/FreightLocomotives/GT42AC.html

EMD® GT42AC OVERVIEW
...
The EMD® GT-Series locomotive platform includes GT38AC, GT42AC and GT46AC models. These locomotives integrate EMD® 710-Series engines together with AC traction technology to provide superior efficiency and performance for a broad range of operations. We pioneered development of AC traction for heavy haul diesel-electric locomotives, and today thousands of EMD® AC locomotives operate worldwide providing enhanced adhesion performance and lower life cycle costs.

The advanced technologies of EMD® GT-Series Locomotives provide key product solutions for safety, reliability, efficiency and sustainability, with GT38AC, GT42AC and GT46AC locomotives delivering optimal rail solutions in service across South America, the Middle East, Africa and Southeast Asia.

Additionally,

https://www.railpictures.net/photo/671097/

The latest in Norfolk Southern’s DC to AC conversion program is SD70ACC 1800, seen here fresh out of the Juniata Paint Shop in Altoona, PA. Original built in 9/1994 as EMD SD70 #2537, 1800 was rebuilt by Progress Rail’s facility in Muncie, Indiana, to include a new safety cab and electrical upgrades to provide AC traction. The yellow color represents Progress Rail’s parent company, Caterpillar. The unit will work in revenue service across the NS system. Photo by Casey Thomason.
» Juniata Locomotive Shop
» Altoona, Pennsylvania, USA (more..)
» September 18, 2018

 

[Tractionengines]

I'd like to see the diodes that rectify that much power!

You would probably be surprised how small the actual diode is.... NOW the heatsink the diode is mounted to on the other hand; is probably huge if air cooled, or uses water cooling, especially if they are using SCRs for PWM power level control and rectification at the same time thru a phase control sysem.

 

[Banzai88]

I'm not an engineer, so I can't answer your question accurately, but I will say the main bus breakers on a ship like that are about the size of case of legal paper. Weighs about that much too! You don't just flip it with a finger!

There will be a variety of breakers, from as small as the ones in your house in the hotel services panel, all the way up to the main breakers that can be, and often are, as large as a 3 drawer file cabinet and weigh in the neighborhood of 1000+ pounds, necessitating a manufacturer approved (and often provided) hoist to remove and install them, and every size in between. Most common would be individual equipment breakers, which are usually about the size of a shoe box, and are often paired with a motor controller box which has the individual monitor lights and such on it.

The medium and large breakers have either spring loaded or hydraulic ratchet systems that build up a preload pawl, and pressing the button releases the pressure and slams the breaker closed. This is done in a fraction of a second with a tremendous amount of force. It minimizes contact bounce and arcing and ensures near instantaneous contact.

Just about all of them are, as you noted, serviced at either main yard periods or during equipment modernization/overhaul. In my years in industry between Navy and .gov, we pulled, cleaned, rebuilt, tested and recertified, and installed thousands of breakers, as well as main feeder lines and copper buss bars (which are how most of the main feeds through the circuit breaker panels are built. Mains will be as thick as a half inch and as wide as 6 inches, going all the way down to other feeders about 1/4 inch thick and 1 inch wide. ALL of that could be layered as much as 6-8 layers to provide the necessary current carrying capacity). The breaker housings are bolted to the buss bars, and the nearly all breakers are modular and are plug-and-play replaceable. The circuit output feeders will then be soft line cables to the equipment.

 

[OverTheTop]

You're an electrical engineer and I'm not, so you might know better than me. Per the classification society, the ship has 5 generators with a total rating of 20 MVA. A stab in the dark would say that 75%-80% of that might be running at once in very high load configurations (running the bow thruster, chilling a lot of refrigerated containers down, etc.). Wikipedia also says that the largest generator is 4400 kW.

We have a diesel-electric boat under construction with similar size generators. Its main bus runs at 4160 VAC, and the largest breakers are 600-700 amps in a 1200-amp frame. The largest wires are a bundle of 6 (2 for each phase) wires, each 373 kcmil (185 mm^2 if I'm reading the table right). The propulsion motors are 730 VDC, with 1800 amp breakers in 2000A frames. 15 of those 373 kcmil cables for those loads. Once you get down to smaller loads (a hundred kW or less), transformers will take it down to 690 and 480 VAC three phase, then to 208/120 three/single phase for lighting and fractional horsepower motors.

Great information. Thanks. That really puts some context on it for me. So around 1000A at 4kV on the main bus . I used to work for the tramways and the large articulated trams weighed 40 tonnes and drew maximum 800A from the 600VDC. You are talking an order of magnitude larger, so around about what our substations were putting out (could handle four or five trams at once on a "section" of overhead).

I'd like to see the diodes that rectify that much power!

They are really not that impressive. In the early days it was done with massive rotary converters. It was scary to walk around them while they were running. Notice the limited use of guard-rails.

These were last run back in the 80's. There were only three locations in the world still running them at the time. Bombay, Calcutta, and Melbourne, Australia. What was really scary was switching the knife switches on the DC distribution wall. That was done using essentially a broom handle with a hook on the end.

Eventually they moved to mercury arc rectifiers, then solid state.


The basic diodes we used in the substations are "hockey puck" diodes, around 4" diameter and 1.5" thick. They were connected in parallel to achieve the necessary current capability. Connection is made by clamping them between large heatsinks. Heatsinks generally end up being live.

The black boxes that hold the rectifiers and AC-DC equipment are about 2' x 10' footprint, likely around 6' tall.

Sounds similar to what our substations were like. Judging by the size I think they have built in plenty of thermal margin in the design .

You would probably be surprised how small the actual diode is.... NOW the heatsink the diode is mounted to on the other hand; is probably huge if air cooled, or uses water cooling, especially if they are using SCRs for PWM power level control and rectification at the same time thru a phase control sysem.

Yes, significant heatsinks. Our trams use 2000A hockey puck SCRs. I have one at home somewhere. Good paperweight.

Apologies for the digression, but I hope people find it interesting .

 

[Capt. Eric]

The FBI has opened a criminal investigation.

Sensationalist yellow journalism at its finest! It's pretty hard to characterize the FBI as having "raided" the ship. Those two fembots are just adding as many adjectives as they can.

 

[boatgeek]

Great information. Thanks. That really puts some context on it for me. So around 1000A at 4kV on the main bus . I used to work for the tramways and the large articulated trams weighed 40 tonnes and drew maximum 800A from the 600VDC. You are talking an order of magnitude larger, so around about what our substations were putting out (could handle four or five trams at once on a "section" of overhead).


They are really not that impressive. In the early days it was done with massive rotary converters. It was scary to walk around them while they were running. Notice the limited use of guard-rails.
View attachment 640963View attachment 640964
These were last run back in the 80's. There were only three locations in the world still running them at the time. Bombay, Calcutta, and Melbourne, Australia. What was really scary was switching the knife switches on the DC distribution wall. That was done using essentially a broom handle with a hook on the end.

Eventually they moved to mercury arc rectifiers, then solid state.
View attachment 640966

The basic diodes we used in the substations are "hockey puck" diodes, around 4" diameter and 1.5" thick. They were connected in parallel to achieve the necessary current capability. Connection is made by clamping them between large heatsinks. Heatsinks generally end up being live.
View attachment 640967


Sounds similar to what our substations were like. Judging by the size I think they have built in plenty of thermal margin in the design .


Yes, significant heatsinks. Our trams use 2000A hockey puck SCRs. I have one at home somewhere. Good paperweight.

Apologies for the digression, but I hope people find it interesting .

One advantage that ships have over land installations is that there's an essentially infinite heat sink just on the other side of the shell plate. You usually want to run it through a heat exchanger so you're not running seawater through electrical components. For those of us up in the North Pacific, it's really nice because the seawater is at ~45 degrees F all year, which is lovely for dumping waste heat. Down in more tropical places (including the Gulf of Mexico and likely the Chesapeake), the water gets pretty warm in the summer so you have to move more of it to get the same amount of cooling.

 

[rharshberger]

There will be a variety of breakers, from as small as the ones in your house in the hotel services panel, all the way up to the main breakers that can be, and often are, as large as a 3 drawer file cabinet and weigh in the neighborhood of 1000+ pounds, necessitating a manufacturer approved (and often provided) hoist to remove and install them, and every size in between. Most common would be individual equipment breakers, which are usually about the size of a shoe box, and are often paired with a motor controller box which has the individual monitor lights and such on it.

The medium and large breakers have either spring loaded or hydraulic ratchet systems that build up a preload pawl, and pressing the button releases the pressure and slams the breaker closed. This is done in a fraction of a second with a tremendous amount of force. It minimizes contact bounce and arcing and ensures near instantaneous contact.

Just about all of them are, as you noted, serviced at either main yard periods or during equipment modernization/overhaul. In my years in industry between Navy and .gov, we pulled, cleaned, rebuilt, tested and recertified, and installed thousands of breakers, as well as main feeder lines and copper buss bars (which are how most of the main feeds through the circuit breaker panels are built. Mains will be as thick as a half inch and as wide as 6 inches, going all the way down to other feeders about 1/4 inch thick and 1 inch wide. ALL of that could be layered as much as 6-8 layers to provide the necessary current carrying capacity). The breaker housings are bolted to the buss bars, and the nearly all breakers are modular and are plug-and-play replaceable. The circuit output feeders will then be soft line cables to the equipment.

I was thinking of all the commercial power breakers I moved up 6 flights of stairs in an old DOE building with no working elevator using a stair climber hand truck, each breaker weighed approximately 600lbs and was less than 2'x2'x2'....lots of copper among other things. Moved 8 of them iirc.

 

[wsume99]

As expected ....

Dali’s owner declares ‘general average’ in Key Bridge disaster

 

[Bravo52]

As expected ....

Dali’s owner declares ‘general average’ in Key Bridge disaster

Absolutely. Any opposition to the owner doing that or invoking the "Titanic Law" is pointless. What this becomes is an emotional issue, but not a legal or business issue. These are the laws in place at the time of this incident. It's no different when someone complains about corporations following the tax law and paying what they legally owe.

I suspect there will be changes in the laws over time, however, it will be a long time. Much longer than the legal issues of this crash will take and I think that will be a long, long time.

 

[wsume99]

Absolutely. Any opposition to the owner doing that or invoking the "Titanic Law" is pointless. What this becomes is an emotional issue, but not a legal or business issue. These are the laws in place at the time of this incident. It's no different when someone complains about corporations following the tax law and paying what they legally owe.

I suspect there will be changes in the laws over time, however, it will be a long time. Much longer than the legal issues of this crash will take and I think that will be a long, long time.

I have found this entire incident to be very interesting because I'm learning a lot along the way. I'm not complaining about the company using the laws, they are doing exactly what they should be doing. I thought their filing was interesting for two reasons-
1) This is playing out exactly as was predicted.
2) It took them this long to declare.

I also found it interesting that the other parties who would share the cost of recovery due to the general average declaration can sue to be excused from that liability if the NTSB investigation determines the ship was not seaworthy when it left the dock. My gut tells me the NTSB is not likely to make that clean of a declaration. There will likely be issues identified but they'll stop short of saying the ship was not seaworthy. The courts will have to make that determination. The only apparent winner in this huge mess are the teams of lawyers handling all of the legal filings.

 

[boatgeek]

I have found this entire incident to be very interesting because I'm learning a lot along the way. I'm not complaining about the company using the laws, they are doing exactly what they should be doing. I thought their filing was interesting for two reasons-
1) This is playing out exactly as was predicted.
2) It took them this long to declare.

On the last, it's a marathon, not a sprint. They don't really need to lay down those claims for some time. Issuing it now may help fend off some lawsuits since there are going to be some plaintiffs (families of workers killed and State of Maryland) who will get the lion's share. If liability is limited, there may not be much pie left.

I also found it interesting that the other parties who would share the cost of recovery due to the general average declaration can sue to be excused from that liability if the NTSB investigation determines the ship was not seaworthy when it left the dock. My gut tells me the NTSB is not likely to make that clean of a declaration. There will likely be issues identified but they'll stop short of saying the ship was not seaworthy. The courts will have to make that determination.

I believe that is accurate. However, the NTSB report will be heavily used as evidence one way or the other. You will probably be able to make a good guess about whether the ship will be considered unseaworthy based on the NTSB report.

The only apparent winner in this huge mess are the teams of lawyers handling all of the legal filings.

'Twas ever thus.

 

[bjphoenix]

Can it be rebuilt quickly? Here is an industry opinion:

https://www.aisc.org/modernsteel/ne...he-francis-scott-key-bridge-in-baltimore-yes/

 

[Capt. Eric]

One advantage that ships have over land installations is that there's an essentially infinite heat sink just on the other side of the shell plate. You usually want to run it through a heat exchanger so you're not running seawater through electrical components. For those of us up in the North Pacific, it's really nice because the seawater is at ~45 degrees F all year, which is lovely for dumping waste heat. Down in more tropical places (including the Gulf of Mexico and likely the Chesapeake), the water gets pretty warm in the summer so you have to move more of it to get the same amount of cooling.

I've never seen an electrical panel or breaker on a ship that was water cooled. Not saying they don't exist, just never saw or heard of it. Usually they are in well air conditioned control rooms. Yes, it's nice when the sea water is 45f. But in the Persian Gulf it can be in the high 80's. Sometimes main engines run a little hot there and I've had to slow down slightly because of high cylinder temps. On the other hand, no need to heat the fuel.

 

[Capt. Eric]

As expected ....

Dali’s owner declares ‘general average’ in Key Bridge disaster

I'm not a lawyer, but I don't see how general average would apply. (Didn't read the article, so maybe it explains it.) But they can throw a lot on the wall and see what sticks.

 

[Capt. Eric]

I have found this entire incident to be very interesting because I'm learning a lot along the way. I'm not complaining about the company using the laws, they are doing exactly what they should be doing. I thought their filing was interesting for two reasons-
1) This is playing out exactly as was predicted.
2) It took them this long to declare.

I also found it interesting that the other parties who would share the cost of recovery due to the general average declaration can sue to be excused from that liability if the NTSB investigation determines the ship was not seaworthy when it left the dock. My gut tells me the NTSB is not likely to make that clean of a declaration. There will likely be issues identified but they'll stop short of saying the ship was not seaworthy. The courts will have to make that determination. The only apparent winner in this huge mess are the teams of lawyers handling all of the legal filings.

Declaration of unseaworthyness is another of those rabbit holes we could fall down. It's not always as dramatic as "there's a hole in the bow." It can be declared over some seemingly silly things. For example, a little hydraulic oil spilled on the floor that someone slips and falls on can be an "unseaworthy condition." So if there was a remotely preventable or foreseeable issue (as seen by Monday morning quarterbacks) that caused the electrical shutdown, someone is going to call it unseaworthy and negligent. Plaintiffs, Insurance, courts, NTSB, USCG. Somebody. Everybody. Fairly routine and expected. It's an important legal distinction that tv newscasters will repeat without really understanding what it means. (I know. It's shocking, right?)

 

[teepot]

The FBI has opened a criminal investigation.

 

[boatgeek]

I've never seen an electrical panel or breaker on a ship that was water cooled. Not saying they don't exist, just never saw or heard of it. Usually they are in well air conditioned control rooms. Yes, it's nice when the sea water is 45f. But in the Persian Gulf it can be in the high 80's. Sometimes main engines run a little hot there and I've had to slow down slightly because of high cylinder temps. On the other hand, no need to heat the fuel.

Panels and breakers, no. Large (say >500 hp) electric motors and VFDs sometimes get water cooling, though it depends on the boat. Must be nice to have all the space that a big ship offers. In most of the littler boats we work on, the switchboard and half the panels are all jammed into the engine room and run at 100-120F ambient. We're packing 8 pounds of [stuff] into a 1-pound bag on those. The diesel-electric one I discussed above has separate control rooms for the VFD though.