Costa Concordia Disaster - What happened?

Professional Mariner Forum
704

[QUOTE=ryanwood86;66487]Come on, doesn’t anyone watch Myth Busters!?! Everyone knows you have to use ping pong balls![/QUOTE]

An excellent retort Sir…although I am concerned about your maths.

Now the volume of a sphere is…V =4/322/7rrr…allegedly.

The Gross Tonnage of the CC is in the order of 114,000 tonnes…ie cu.mtrs.

Therefore, it can be reasonably assumed that the volume of a ping pong ball is…0.000033523 cu. mtrs.

This leads me to the conclusion that we will require 3,400,650,299 ping pong balls to fill the patient.

Do you have any other suggestions?

705

[QUOTE=ryanwood86;66487]Come on, doesn’t anyone watch Myth Busters!?! Everyone knows you have to use ping pong balls![/QUOTE]

It is much simpler with e.g. eight 15 000 dwt pontoons, total 120 000 dwt, that you put four on each side of CC (weight 50 000 tonnes) and then connect together with wires below CC. Then you ballast the pontoons with say 100 000 tons of water so they float deeper, then you tighten the wires and pump out (de-ballast) 100 000 tons of water from the pontoons and, voila … the CC floats … between the pontoons resting on the wires. Be sure to attach the wires on both sides P+S of the pontoons so the pontoons will not heel due to wire forces. Each pontoon thus carries average 6250 tonnes … via the wires (and uses 42% of its dwt to carry CC).
Pls note that with this method no water is pumped out from CC or no air is pumped into CC - only outside (buoyancy) forces are used of the pontoons transmitted to the wreck via the wires.

You cannot beat Archimedes!

706

[QUOTE=AustralianPilot;66493]

Do you have any other suggestions?[/QUOTE]

Read the International Convention on Tonnage Measurement of Ships.

707

Heiwa

I’ve just re-read the Daily Mail article again (upon which you seem to have based everything you have said about the complete guesses about the proposed salvage arrangements.)

According to the DM, Mr Gabrielli (who is in overall charge of the whole thing) says that the wreck of the Costa Concordia is going to be removed in one, complete piece but Mr Gabrielli has refused to release any more details until the salvors have been named, which he says will happen in mid-April 2012.

The DM also go on about their theories about how this salvage will be organised. Please note that in the absence of definite information, the DM can only be speculating.

However, even the DM (not known for their marine expertise) say:
[B][I]“in essence the holes will all be sealed up and water pumped out and air pumped in to the compartments to get her buoyant again.”[/I][/B]

Please forgive my own ignorance about the principles of engineering - I guess it must be “engineering principles.”

However, with the arrangements to remove Costa Concordia’s fuel, I vaguely understood that they were going to pump the fuel out of the bottom of the tanks whilst pumping air in at the top of the tanks. It seemed that the air coming in at the top would press down on the remaining fuel and would prevent air-blocks in the pipes pumping out the fuel (or something roughly along those lines.) Presumably one can use compressed air in this situation to make sure that the fuel will be firmly pressed down and that there will be no air-bubbles to block the pumps/lines being used for the removal of the fuel?

If I am roughly right about what happened with the fuel, is there any reason why the same principle couldn’t be used in order to ensure that water would also be removed without any problems? I do vaguely understand that fuel, water and air all weigh different amounts but can this be overcome by using compressed air? Presumably compressed air is heavier than ordinary air?

I would agree with you that a lot of the wreck has suffered water ingress in areas where there would normally be no reason to seal up the relevant areas like a drum but presumably this could be done?

After all, the wreck is not a viable cruise ship at the moment and if she is ever to become one again, I would think that quite a bit of initial “damage” to her is likely before she could be taken away and either fully repaired or cut up for scrap in some other place?

I am guessing - completely guessing. I studied Law so if I need an Engineer, I just summon one. However, I do wonder whether you and some of the others are squabbling about non-issues here?

I would also comment that there is no point in anyone getting hot under the collar about any of this. That does not help to try to unravel the various mysteries about what really happened to Costa Concordia that night, or what can be done now to try to sort it all out, surely?

708

I didn’t say a ping pong ball. I can’t remember how many it took to float a little 23’ boat they tested it on, but I know it was a lot. I would image ping pong balls wouldn’t be the fastest or most cost effective neither.

709

[QUOTE=AustralianPilot;66476]Burong,

This link will give you an idea on modern cruise vessel watertight/fireproof bulkhead layout in addition to other relevant information. If you scroll right you will find a key to identify the different areas.

http://dvo.free.fr/techdatas.htm

Double hulled vessels also have their own problems with regard to reduced stability (raising of the centre of gravity), maintenance issues with corrosion between the two skins and in the event of this significant allision on CC, it is highly likely that the inner shell would have been bilged. Of course…any changes to construction regulations will take a great deal of time and not protect existing tonnage.

AP.[/QUOTE]

Thank you, AP

I now understand the whole thing much better than I did before, thanks to your most helpful link.

I also watched the TV programme again last night. The programme makers did not discuss whether extending the double-hull further upwards might cause other problems for other reasons. They just implied that it ought to be done with cruise ships, which led me to shout at the screen, “Wouldn’t it just be easier to ensure that a cruise ship cannot/does not get into a ‘Costa Concordia situation’ in the first place?”

In the UK at the moment, there is a huge amount of “Titanic Hype” because it is now so close to the centenary of her sinking. (The night of 14/15 April 1912, apparently.) So the programme irritated me because Concordia did not hit an iceberg in 1912! Also, the programme contains the usual ghastly allegations that Capt Schettino might have “freaked out” and done nothing useful, plus the usual allegations that Capt Smith (the Master of the Titanic) was equally useless when push came to shove.

However, an American man who is a marine expert commented that if a ship the size of Costa Concordia hits a rock even at slow speed, it is going to cause serious damage just because of the ship’s weight etc. He seemed to be hinting at exactly what you have said, which is that extending the height of the double-thickness hull would not necessarily have made any material difference to what happened in Concordia’s initial allision with the rock.

They then showed a [I][B]long[/B][/I] ribbon of very thick-looking steel that had been ripped right off Concordia’s side and ended up on the bottom - very similar to what one sees when one opens a tin of corned beef, only giant. It is sort-of curled up on itself but if it were stretched out it would obviously be very long.

I must say, I thought, “If this rock could have caused so much damage to such thick steel, would an inner hull really have been able to prevent a problem?”

710

[QUOTE=Burong;66498]Heiwa

Presumably compressed air is heavier than ordinary air?

[/QUOTE]

Well, 1 kg of ordinary air weighs same as 1 kg of compressed air but when air is compressed it occupies less volume.

711

The comments about using compressed air are definitely a tried and proven technique for raising sunken, foundered vessels. This even works on vessels that have breached hulls on the bottom, or multiple holes. However it only works upon vessel hulls which are (or can be made) air tight. I really believe the way the CC (and all cruise ships) hull is only compartmentalized for longitudinal stability, and not vertically, the compressed air option won’t work.

The use of compressed air is NOT to inflate the ship but to displace the water from tanks that are holed below the waterline. And it typically only needs 1 or 2 PSI to accomplish this.

712

I’m pretty sure steamers comment about compressed air wasn’t as much that it would work in this case as it was about that compressed air is a valid technique for floating a vessel. Spurred on by heiwa being a smart ass and insisting that pumping air in does nothing, you have to pump water out to make a vessel float.

713

[QUOTE=cappy208;66510]The use of compressed air is NOT to inflate the ship but to displace the water from tanks that are holed below the waterline. And it typically only needs 1 or 2 PSI to accomplish this.[/QUOTE]

The pressure required is greater than the hydrostatic pressure at the lowest point. If the lowest hole in the hull was at, for the sake of discussion 50 feet, it would require the air pressure in the compartment to be around 22 psig to keep water from entering at the bottom and a higher pressure to force water out. Air would escape through all the leaks above the 50 foot level. That is why salvage air compressors are low pressure, high volume devices.

714

I think if you inflated any hull to that figure you would blow the hull up prior to full water ejection. I don’t believe you would necessarily have to eliminate ALL the water from all the compartments.

Not all the compartments are holed.

715

[QUOTE=cappy208;66510]The comments about using compressed air are definitely a tried and proven technique for raising sunken, foundered vessels. This even works on vessels that have breached hulls on the bottom, or multiple holes. However it only works upon vessel hulls which are (or can be made) air tight. I really believe the way the CC (and all cruise ships) hull is only compartmentalized for longitudinal stability, and not vertically, the compressed air option won’t work.

The use of compressed air is NOT to inflate the ship but to displace the water from tanks that are holed below the waterline. And it typically only needs 1 or 2 PSI to accomplish this.[/QUOTE]

A vessel’s hull is evidently never airtight as the hull’s top - the bulkhead deck is full of holes so you can get into the hull in the first place. Only if the hull is upside down you can fill it with compressed air … and the hull floats up. Upside down. That’s why a ship that capsizes and floats upside down … doesn’t sink. It is full of compressed air. Basic.

716

In the case of the “Pasha Bulker”, she had bilged her aft double bottom WBT’s and was fully upright. In order to expel the seawater from the damaged tanks, low pressure air was fed down the two for’d airpipes and the balance of airpipes to that particular tank were blanked off. She effectively floated on her tank tops all the way to the repair yard with compressors running constantly.

The hot tapping of CC’s fuel tanks involved the replacement of fuel with seawater. I can only summise that this is a means of maintaining some clarity on the vessel’s initial stability prior to salvage.

The interesting thing about CC’s construction is one can only assume that both the horizontal and vertical watertight/fireproof subdivision around the machinery spaces should provide a reasonable opportunity for injecting low pressure air apart from exhaust trunking which may or may not be sealable via undamaged dampers. There will be losses although one would thiink that the injection of air will be employed in conjunction with the use of high capacity airbags.

So if the salvors drive legs into the seabed to provide stability and purchase for lifting equipment, expel seawater from the lower machinery spaces by injecting air, employ airbags, get the vessel upright, drain water from the upper spaces to provide some semblance of stability…it is a long bow.

717

[QUOTE=Steamer;66497]Read the International Convention on Tonnage Measurement of Ships.[/QUOTE]

Quite correct…my apologies…I forgot the multiplier. Let us assume an internal volume of 500,000 cu. mtrs.

Make that a lot more ping pong balls.

http://kwc.org/mythbusters/2004/11/mythbusters_ping_pong_balls_an.html

718

In this case (the CC) this is only partly true. But it seem apparent that her hull should have enough stability once the gash is covered with a hard patch that once she is rolled upright to clear the upper decks of water to re establish WT integrity she could then be pumped out. The compressed air only works on sealed tanks. In the CC case those would be the fuel DBs and the flume and ballast tanks.

719

[QUOTE=cappy208;66520]I think if you inflated any hull to that figure you would blow the hull up prior to full water ejection. I don’t believe you would necessarily have to eliminate ALL the water from all the compartments.[/QUOTE]

Quite true. Considering the CC’s lightship draft, less than 10 psig would do nicely. And, as you wrote, you don’t have to expel all the water. Just enough to let hydrostatics do the work you need.

Exxon Valdez was lifted off the reef by pushing around 3 feet of water out if I recall correctly.

By the way, does anyone know what a “bulkhead deck” or a “hull top” is?

720

I think this is in reference to the molded depth. The upper most deck that is a part of the water tight integrity. On the CC I believe this is approximately the embarkation deck. If they are going to right her and try to refloat her this deck is the deck they must either get above the water line, or they must make the deck penetrations water tight so they can pump out the majority of water. Cruise ships are a particularly funny design. Their water tight bulkheads do NOT extend from the keel up to the upper most deck, but only to the height which is called the molded depth. I know the small ferry I used to run only had water tight from the main deck down to the keel. One of the issues I see with these types of ships is they have double the height or more above the watertight upper limit or are higher than wide by a lot. Doesn’t make sense.

Rather than trying to describe it, here is a dramatic animation of the over flooding that occurred aboard the Titanic. It also shows the relationship between the height of the water tight bulkheads and how high they were/are. http://www.youtube.com/watch?v=iPns595buP4

721

Vanity Fair have a short piece about “Concordia” on their website which acts as a teaser for the article proper that appears in the current print edition:

Anecdotal recollections of the night.

Hopefully they will publish the complete article on their website at some later date.

722

One huge (and thus far unmentioned) advantage of pumping in air vs. pumping out water is that you don’t have the issues of clogged strainers and sucking items into the pumps and causing failures/damage. Judging from some of the interior divers photos and the location of crew quarters there will be everything from fines (soggy toilet paper) up to furniture in the interior spaces needing to be dewatered. There is also a factor of efficiency per unit volume. Much less energy is required to move high volumes of low pressure air than (debris filled sea) water.

723

When there is unwanted water in the bilges of a ship hull, you pump out this water using a bilge pump. You do not pump in air because the hull is already full of air. Attention: it there is oil on top of the water in the bilge, you pump this oily water to a special holding (slop) tank.
If you want to remove water from, e.g. a ballast tank = deballast the ship, you evidently pump out the water of the tank. You do not pump air into the tank … as it will escape out of the air vents of the tank.
Air vents? When you pump out the water of the tank, the water is replaced by air via the air vent. If air cannot enter the tank while emptying it, the top of the tank may collapse (due to the vacuum pulling it down).

Evidently same energy is required to pump 1 ton of water 10 meter up than to compress 1 cubic meter of air 1 bar.