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Container Ship Breaks In Two, Sinks
Cliff Stoll writes "Along with 7000 containers, ship MOL Comfort broke in half in high seas in the Indian Ocean. The aft section floated for a week, then sank on June 27th. The forward section was towed most of the way to port, but burned and sank on July 10th. This post-panamax ship was 316 meters long and only 5 years old. With a typical value of $40,000 per container (PDF), this amounts to a quarter billion dollar loss. The cause is unknown, but may be structural or perhaps due to overfilled containers that are declared as underweight. Of course, the software used to calculate ship stability relies upon these incorrect physical parameters."
It was my understanding that the cranes weigh each container as they are loaded on the ship. This is done because they can't afford mistakes in calculating the center of gravity of the ship. There is no honor system.
oddly enough there are special rules around this: http://en.wikipedia.org/wiki/Maritime_salvage
Perhaps they could paint a line on the side of a large vessel floating in water and see if the containers displace enough water to submerge the line. Oh wait, that's what they do with all container ships. It's impossible for the whole ship to be over weight. It is possible to have a poorly distributed load, but that's not likely to cause the type of accident that happened here (it would more likely lead to capsizing).
Overweight containers are more of a financial issue than a safety issue. Leaving 500 containers on the dock or leaving under-loaded are both bad for business.
Moments, how do they work?
If you load the shit out of the topmost containers, it gets tippy as fuck. As an example of "huh", there's a thing that's going on the mast of a ship that I've worked on. The thing doesn't weigh that much -- although it's being loaded by crane, I could lift it by myself.
To compensate, way more ballast than I can lift is going in the hull.
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ECHELON is a government program to find words like bomb, jihad, plutonium, assassinate, and anarchy.
Many cranes DO have a scale built in. 250,000 Kg capacity accurate to 50Kg. That should do the job.
The usual tariff is based on a concept called "weight-measure", which works like this:
- For cargo less dense than water, a given tariff is per cubic meter.
- For cargo denser than water, the tariff is per metric ton (one cubic meter of water weighs one metric ton).
If you think about it, this makes perfect sense, because anything heavier than denser than water has to be accompanied by enough air (i.e. empty space inside or outside the container) to make the average density of the shipment equal one, and anything lighter than water takes up just as much space in the ship as heavier cargo would. The result is that if you have e.g. a 2000 TEU ship, and each TEU is 35 cubic meters, a full ship will always generate 70,000 tariff units, whether it be laden with cotton candy or iron pellets.
Of course, shipping companies play both ends against the middle and can, with optimization, get better than 100% billing (e.g. by using fluffy stuff like household goods to provide the airspace needed to compensate for containers full of car engines).
In a previous incarnation I was a Systems Designer at a major container shipping company.
No. Well...maybe. Actually, yes. It really just depends.