If it was the fuel supply then wouldnt they have had the same issue when the emergency generator came online?
Baltimore bridge collapse
- Thread starter Ekkie Thump
- Start date
Thanks for your responses on this topic - great to get some expert opinion - as a landlubber myself, can you explain what are the issues with them going from full ahead to full reverse? - I've also seen some talk of "dirty fuel" being a potential cause - any thoughts on this?
I think most will panic in a situation where they experience a blackout that close to a structure. Was it 2 mins from first blackout to impact? I can only imagine that it must have been complete chaos when they realized they were in a proper shit situation.
I have read this a couple of times and as an ex engineer with a small amount of experience of Marine systems, it makes perfect sense to me.
Marine diesel engines are inherently extremely reliable; especially considering that there would be a number of such diesel engines providing the primary power. Both for propulsion and electrical power.
Only if the demand exceeded the available power supply.
which makes sense if they went full power astern on emergency generator
If lack of fuel supply caused first blackout then how would they suddenly have fuel supply when the emergency generator kicked in less than a minute later?
Perhaps it has its own separate fuel line and feed system exactly for this purpose ?
Yes exactly.
I had assumed in that case that the emergency supply could have been battery.
You’re possibly right:
5) There should be a separate fuel oil tank provided for the emergency generator and the flash point of the fuel oil should not be less than 43 deg C.
Looks like separate tank is a requirement, so makes it very plausible.
Its not like container ships have to do a lot of ballasting/de-ballasting, so they wouldnt have a lot of heavy consumer pumps starting up at the same time, which have caused problems for tankers/lng
Basically, going full ahead to full astern in one swift move is counterproductive and can also damage your gearbox, prop shaft or propellors.
The reason it's counterproductive is because doing it in one fast movement doesn't allow the propellers time to stop before turning the opposite way. What normally happens is they not only take a few seconds to turn the opposite way, while doing that they have created a wash/flow in the water so essentially cannot grip the water properly to propel themselves backwards. This will result in huge air pockets which make them shudder which is known as cavitating and that can be felt and heard throughout the vessel and can also cause issues through vigorous shaking. Obviously the exact same thing happens if going from full astern to ahead.
You should always go from astern or ahead to neutral for a second or two first.
As for the other discussion above, back up generators absolutely have a completely separate fuel tank than the main engines. Quite often on fishing boats ours were petrol generators because if for some reason you had dirty fuel in the diesel engines, you would be able to run the generators without worrying about getting the same problem.
Possibly.
It depends on the configuration of the fuel supply to the diesel engines.
I doubt they would be in series. More like parallel.
But there must have been a Common Source Failure. Something that affected them all at the same time. Possibly diesel fuel. On the basis that they had just left port where they would have taken on fuel, but had enough in the fuel lines to get to where they were.
But that seems unlikely because in that case other ships would have been equally affected.
So a loss in fuel pressure could be more likely.
Diesel engines need fuel at high pressure. So there could be a LP system to suck fuel from the tanks and a HP system to supply the engines.
But all this is speculation and the Investigation will determine the cause.
Very interesting.
Regarding the counterproductive case you mentioned, would they not have had to test for that as part of the failure case certification?
Sorry, I don't understand what you mean.
They might not have bunkered in Baltimore, unless it’s already been stated that they have.
The full accident report will be miles away, but i would assume they already know what caused the blackouts.
I was referring to the immediate selection to fully astern. You mentioned that it would have been counterproductive in the Baltimore case which I can understand.
But what I was wondering was whether the immediate selection to full astern would not have been evaluated during the ship certification testing.
It will be interesting to find out what caused the failure.
I wonder how much liability insurance a massive cargo ship owner like that has. $10M? More? What will the cost be to replace that bridge?
This article has some good details, bridge value estimated at $1.2 billion:
https://www.reinsurancene.ws/reinsu...st-of-baltimore-bridge-collapse-says-am-best/
I don't think insurance providers give $1.2 billion dollars worth of insurance coverage. Yeesh
It's not typical but when they do they spread the risk by using reinsurance and reinsurers spread that risk by using other reinsurers or pooling to limit individual exposure to a massive loss event.
A hell of a lot more than $10M. I own a small business with 4 employees and have $2M.
The other factor is that big ships are good at going forward. Slamming it in reverse whilst still in forward motion would introduce yaw which unfortunately appeared to have turned it towards the bridge support.
Yeah, that's where I don't understandz I'm not sure what you mean by failure case certification?
Basically it's just a rookie error and no trained skipper/captain or pilot would ever do it anyway. You would just bring the thrust back to neutral, hold for a second then to full astern.
It really wouldn't have made any difference in this case though as the power went out so close to impact anyway and as I pointed out previously a ship that size and weight travelling a few knots would take at least a mile or so to stop anyway so putting it hard astern would haven't really made any difference.
Evaluated for what?
The consequence of going from ahead to astern without going through neutral is common knowledge in the maritime world.
Thank you for this.
The failure case I was referring to.
During the design of the ship, they would have had to carry out a series of tests in order to be able to certify it.
And I was referring to an emergency situation where they might have to go from full ahead immediately to full astern in order to test the integrity of the ship systems. Mechanical, electrical, control etc.
Thank you.
Evaluation of the ship systems, mechanical, electrical, control in order to be able to demonstrate that the design works in accordance with the Maritime certification requirements.
I'm not sure what relevance that has though. A ship that big, it doesnt matter how you put it in reverse its not stopping.
As I said above I think a big lesson will be that engaging reverse whilst in forward motion will change the direction of the ship.
I don’t think anyone thought it would actually stop. They were trying to slow it down.
That a single screw vessel will swing when reversing is also something that is common knowledge.
This was the post I was initially referring to.
It mentioned that going from full ahead to full astern could damage the gearbox, prop shaft and propeller.
All I was suggesting was that this manoeuvre ought to have been tested for during the certification of the ship systems to meet the marine specification requirements.
They do…
Yeah, none of that would be required or would happen. It's also of little relevance in this accident.
Depending on which country the ships were built and then registered to of course they would undergo lots of safety tests and risk assessments etc before they were launched and then while afloat before being allowed to sails and then some while fully laden and prior to sailing.
However the thing that appears to have sidetracked this conversation somewhat isn't relevant at all. It's not something that could or would be tested for on the ship itself. However the captain's/skippers would have been told about it and had to perform emergency stops or man overboard drills whilst obtaining their very first licences which would have been (again depending on country) anything from basic local licences, under 10 meter fishing licences, varying passenger or powerboat licences then yacht masters etc.. All require varying lengths of time served at sea and increasingly.kore difficult medical training, navigational training including meteorology, astral navigation, radio operators licences, air rescue at sea, fire at sea etc etc etc.
To pilot a vessel of this size I'm 99% sure you would require a Master Mariners degree and they take years of piloting and seamanship experience and dozens upon dozens of exams and certificates.
Again, the slamming in reverse talk has sidetracked and possibly confused this a little and isn't relevant as it wouldn't have made a difference either way.
Thank you and I do understand this.
As you say, it is irrelevant.
It was more of an academic question simply in response to that post.
Appreciate your clarification.
Perhaps it doesn't need to be.
I know aircraft are held to higher standards but there's no testing for selecting reverse thrust whilst airborne; no pilot would ever do it and if they tried the aircraft says no.
I'd assume anybody licensed to steer a 300m ship knows not to do it but the panic sets in and who knows. They were supposedly heading for the bridge span so likely panicked and inadvertently steered towards the one bit of the bridge that would be worse to hit.
Tweet
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Thread outlining how the pilot saved lives with the immediate action of calling to close the bridge.
I think we can't know until the report comes out. Personally I think they aimed for the pillar thinking it would stop the vessel and cause less damage. There were cars and people on the bridge and if they hit that they knew they would have taken that part of the bridge apart and not stopped likely killing everyone on there at the time and definitely destroying the bridge before continuing on out of control and without power.
I don't think they thought for one minute if they hit where they did that the entire bridge would have collapsed. If I was at the helm I would have done exactly the same (if it was intentional) and of course, that's just my opinion of what happened.