Av average of ten “solid bulk cargo” carriers are lost at sea each year
September 2, 2018 7:42 PM   Subscribe

Under certain circumstances, granular solids can undergo liquefaction, and start acting like a fluid. If this happens to the cargo you are carrying on your ship, the results can be very bad.
posted by Chrysostom (37 comments total) 46 users marked this as a favorite
 
Holy crap is that terrifying.
posted by Literaryhero at 9:46 PM on September 2, 2018 [1 favorite]


This is a fascinating thing I'd never heard of. Neat!
A solid bulk cargo that is apparently stable on the quayside can liquefy because pressures in the water between the particles build up as it is loaded onto the ship. This is especially likely if, as is common practice, the cargo is loaded with a conveyor belt from the quayside into the hold, which can involve a fall of significant height.
I'd be very curious to find out what the person the reporter interviewed actually said. It's hard to believe it was recognizably similar to this. (I can believe falling material increases local pressure on the timescale of seconds. But, we're not talking about ships sinking while being loaded.)
posted by eotvos at 9:47 PM on September 2, 2018 [4 favorites]


I'd be very curious to find out what the person the reporter interviewed actually said. It's hard to believe it was recognizably similar to this. (I can believe falling material increases local pressure on the timescale of seconds. But, we're not talking about ships sinking while being loaded.)

Right, you're not talking about ships sinking while being loaded. You're talking about potential energy being stored up amongst solids dispersed in a liquid due to how they're being dropped into a containment unit...a containment unit that subsequently vibrates for weeks while sloshing about in a chaotic manner.
posted by trackofalljades at 9:57 PM on September 2, 2018 [3 favorites]


The International Maritime Organisation have codes governing how much moisture is allowed in solid bulk cargo in order to prevent liquefaction. So why does it still happen?

I won’t pretend to understand the physics here, but isn’t this a case where economic and safety/liquefaction prevention motives are aligned? after all, moisture has weight, so the more of it you can get rid of, the more salable material you can haul, right?
posted by juv3nal at 9:59 PM on September 2, 2018


It’s more profitable to sell wet ore by weight than to dry it out before shipping. A few sailors dying is a minor impact on the bottom line.
posted by monotreme at 10:18 PM on September 2, 2018 [6 favorites]




I'm certainly no expert, and there are likely reasons it wouldn't work, but it seems that if cargo shifting when it liquefies is the problem, the simplest solution would be to prevent it from shifting.  Something like an inner lid inside the container that could be cranked down against the material to prevent it from moving.  If I'm understanding the issue and that video properly, they can't be full to the rim or the material couldn't slosh around.
posted by los pantalones del muerte at 10:26 PM on September 2, 2018 [1 favorite]


This is probably a stupid question, but don’t we routinely transport actual liquids on ships, like oil? Can’t we use whatever anti-sloshing measures are used on those ships to stop sloshing on the ones transporting granular solids?
posted by good in a vacuum at 10:39 PM on September 2, 2018 [5 favorites]


Something like an inner lid inside the container that could be cranked down against the material to prevent it from moving.

That assumes that liquification results in a uniform density. For example if 30% of the cargo remained solid, that would be a mass that could be tossed back and forth inside the liquid even though the liquid itself was perfectly constrained. Or even if the whole thing liquified there might be some portions that were much more dense than others.
posted by Tell Me No Lies at 10:41 PM on September 2, 2018 [5 favorites]


That assumes that liquification results in a uniform density

Ah, that's a very good point.  I'm not surprised I was missing something obvious.
posted by los pantalones del muerte at 10:49 PM on September 2, 2018


anti-sloshing measures

Internal baffles. But they make loading and unloading more difficult when the cargo is not actually a liquid. (I'm sure that problem could be overcome with a little more expense in the conveyor system.)
posted by ryanrs at 10:58 PM on September 2, 2018 [2 favorites]


Drainage holes or a pump would be the simplest solution. No need for internal baffles or crankable ceilings or anything else. Get the water overboard.

And pressure to deliver the same tonnage of cargo as was loaded may discourage the crew of the vessel draining cargoes during the voyage.

Oh. Never mind then.
posted by Leon at 11:25 PM on September 2, 2018


Isn't this what happened to the food payload of the rescue rocket in The Martian?
posted by ericales at 11:32 PM on September 2, 2018 [3 favorites]


Isn't this what happened to the food payload of the rescue rocket in The Martian?

I don’t have a copy handy but I’m pretty sure it is.
posted by Tell Me No Lies at 11:34 PM on September 2, 2018 [2 favorites]


A few sailors dying is a minor impact on the bottom line.

Even if you don't count loss of life, losing an entire ship is awfully expensive.
posted by rokusan at 11:45 PM on September 2, 2018 [4 favorites]


I'd be very curious to find out what the person the reporter interviewed actually said. It's hard to believe it was recognizably similar to this.

Entries on the Conversation are written directly by the academics listed as author, not by reporters. (Unless there's shenanigans afoot but I don't think that's what you were suggesting?)
posted by Trivia Newton John at 12:30 AM on September 3, 2018 [1 favorite]


I bet the effect of the conveyor belt also has to do with size segregation or stratification of the material. Not all grains in a bulk material are the same size, depending on how you move it around and load it you'll end up with a more or less homogeneous configuration: it tends to end up with the finer particles (having greater bulk density) on the bottom and the coarser particles on top.
posted by each day we work at 12:36 AM on September 3, 2018 [1 favorite]


It may involve more than liquifaction - hacking loading management software to cause sinkings seems to be a concern (shipping security site). There's some happy ideas on that site Not!. This isn't about liquefaction per se but explores the potential of hacking to destabilize bulk and container cargoes. That site seems to be mainly concerned with fraud, all part of late capitalism's (literal) race to the bottom.

There used to be a display at Te Papa that used soap powder and model houses to show how dry liquefaction would happen - you wound a handle which shook the table and all the houses started tilting and sliding into holes.
posted by unearthed at 2:08 AM on September 3, 2018 [7 favorites]


Isn't this what happened to the food payload of the rescue rocket in The Martian?

Yeah, they skip the payload testing due to time constraints, and don't realise that the supplies they're sending (some sort of compressed survival ration) will liquefy due to the vibrations during launch.
posted by EndsOfInvention at 2:18 AM on September 3, 2018


Drainage holes or a pump would be the simplest solution. No need for internal baffles or crankable ceilings or anything else. Get the water overboard.

The areas around the port are probably not cool with the inevitable water contamination that would occur particularly as drainage from ocean going vessels is a big part of the disruption of local sealife by invasive species..

Dealing properly with raw materials is bad enough that the local storage of things like ore or coal are actually deliberately wetted down to try keep too much of the dust from blowing all over the surrounding area.

Chicago actually had to sue a Kock brothers subsidiary to deal with petcoke dust from mountains of petcoke stored along the calumet river that was engulfing parts of the south side recently because they are too damn cheap to even keep it wet enough that it is properly contained.

As always with regards to safety and the lack thereof it seems it comes down to billionaire's profit margins.
posted by srboisvert at 2:53 AM on September 3, 2018 [6 favorites]


:: Isn't this what happened to the food payload of the rescue rocket in The Martian?

Yeah, they skip the payload testing due to time constraints, and don't realise that the supplies they're sending (some sort of compressed survival ration) will liquefy due to the vibrations during launch.


And in the book version there’s also a slightly imperfect bolt that fails, causing a shear when weight slams against the rest.
posted by tilde at 3:00 AM on September 3, 2018


Get the water overboard.

once you've done this, you haven't necessarily fixed the issue nor even improved your lot, as the dynamic situation (oscillating) may fix at an especially bad point (significantly off axis now and forever).
posted by zippy at 3:02 AM on September 3, 2018 [3 favorites]


One way to solve this would be to turn the bulk commodity to its final form before shipping it--for example, have the bauxite turned into aluminium billets at a local smelter. But that might raise the cost of the raw materials for your next iphone by six cents per unit, reducing the profit margin to 785%. So, no way.
posted by maxwelton at 3:07 AM on September 3, 2018 [4 favorites]


Regarding processing locally, I have run some numbers on this because I was surprised that it was viable to process bauxite from New Zealand here in Iceland, shipping it literally half way around the world. In short, shipping is around 3% of the total cost, and electricity is 40%. If you can save 10% on electricity, it is cheaper to ship it literally anywhere on earth with a sea port. The electricity cost here is more than 30% cheaper than New Zealand.

Liquefaction also happens on land during earthquakes, which is where I was familiar with the phenomenon from. Makes sense that it would happen in ships with bulk cargo too, I'd just never thought about it.
posted by Nothing at 4:01 AM on September 3, 2018 [17 favorites]


This is probably a stupid question, but don’t we routinely transport actual liquids on ships, like oil?

Yes, but oil stays liquid. So it can't resolidify off balance, it will settle back down with gravity.
posted by jeather at 4:46 AM on September 3, 2018 [4 favorites]


the relatively new solid bulk cargo bauxite

It's been an important cargo since the 1940's at latest, when they suddenly needed to make large numbers of aluminium airplanes. I suppose that's relatively new, compared to grain and spices.
posted by sfenders at 5:01 AM on September 3, 2018 [3 favorites]


Isn't this what they think happened to the Edmund Fitzgerald? Water got into the hold during the storm, and as the ship hit waves the cargo began slipping forward, the bow sank deeper and deeper until the entire ship was swamped.
posted by AzraelBrown at 5:36 AM on September 3, 2018 [2 favorites]


I was just coming to ask the same question, AzraelBrown.
posted by TedW at 6:21 AM on September 3, 2018


Isn't this what they think happened to the Edmund Fitzgerald

I think the theory is that she went down *just* from the flooding, not the cargo liquefying and shifting. The Edmund Fitzgerald was carrying taconite pellets; the larger, marble-sized pellets might reduce the dangers of liquefaction.
posted by nathan_teske at 6:49 AM on September 3, 2018 [2 favorites]


Internal baffles. But they make loading and unloading more difficult when the cargo is not actually a liquid. (I'm sure that problem could be overcome with a little more expense in the conveyor system.)

Yeah, my immediate thought when I read the article was that they should just containerize it while on land and load the containers instead of filling holds with loose bulk. This of course seems so obvious that I'm sure there's an obvious fault of which I'm unaware, since I don't work in the shipping industry. Presumably the cost of loose bulk is significantly lower than the cost of containerized shipping, even factoring for loss.
posted by fedward at 8:05 AM on September 3, 2018 [2 favorites]


That is so horrifying I had to stop reading.

Is there an SCP number for this yet.
posted by nikaspark at 8:36 AM on September 3, 2018


Presumably the cost of loose bulk is significantly lower than the cost of containerized shipping, even factoring for loss.

Considering the scales involved in bulk shipping, this is almost certainly the answer.
posted by tobascodagama at 8:46 AM on September 3, 2018 [1 favorite]


Yeah, containers are more expensive in handling costs than bulk - you need specialised equipment on the ships to slide the containers into (think Connect 4) and instead of just pouring the cargo in or vacuuming it back up to a pile on the shore, you need to pick up each container separately with a gantry crane, put it on a truck-thing, drive it to its place in the depot and use another crane to stack it up. And at some point you need to unload each of them separately.

Mind you, in Europe we're lately seeing quite a bit of containerisation of bulk cargo on the land side, because with one container on a truck or two on a train platform the loading's faster, there's less chance of contamination and it lets shippers use cheap rail to get cargo fast to places that don't have rail line access, so it's becoming popular for things like grain and animal feed. Thus far that's only land side, origin to port, and pouring things out in a pile at the quayside for loading into a bulk carrier. But technically there's nothing stopping people from loading those standardised containers on a small container ship (because they're not up to much stacking)...
posted by I claim sanctuary at 8:48 AM on September 3, 2018 [1 favorite]


This is probably a stupid question, but don’t we routinely transport actual liquids on ships, like oil? Can’t we use whatever anti-sloshing measures are used on those ships to stop sloshing on the ones transporting granular solids?

What is different in this situation is that you have a relatively thin layer of liquid sloshing around on top of a solid layer. Since it is a thin layer, it sloshes more than the case of a uniform bulk liquid.

Think of a tilting a half cup of water on a dinner plate compared to tilting a glass of water filled nearly to the brim. When you tilt the dinner plate, the water builds up speed and slops right over the edge of the plate when you try to tilt it back. The water in the glass does not build up speed, it just tilts. And, the liquid layer is well above the center of gravity in the ship so when it sloshes, it contributes a lot of tipping force on the ship.
posted by JackFlash at 9:34 AM on September 3, 2018 [2 favorites]


Even if you don't count loss of life, losing an entire ship is awfully expensive.

Yes, but that expense is borne by the insurers. International trade couldn't exist without insurance, but it means that ship owners' incentives are directly opposed to those of the crew. They'll do anything they can to skimp on maintenance, push captains to take unsafe routes, have masters overload cargo, and get stevedores to cut corners at the docks. In fact, ship owners have notoriously plotted the accidental-on-purpose sinking of their own vessels as a way of recouping value from elderly or uneconomic ships.

Modern maritime safety (e.g., the Plimsoll Line) has been almost entirely driven by insurers' desire to avoid being milked by greedy ship owners. According to the International Maritime Organisation's page on the International Convention on Load Lines,
Various amendments were adopted in 1971, 1975, 1979, and 1983 but they required positive acceptance by two-thirds of Parties and never came into force.
Who do you think lobbies to block those amendments? Ship owners, and the disreputable ship registries that allow the registration of unsafe vessels.
posted by Joe in Australia at 3:23 PM on September 3, 2018 [7 favorites]


Since the issue is moisture inherent in the ore, why not pump the moisture that separates out into chambers on the ship? When the ship comes back into port, they could then spray the stored water back onto the load. This would maintain the tonnage as loaded. Or, why not pay for ore by the “dry-ton”? Meaning you pay for weight of the ore but not constituent moisture. This would allow shippers to pump off excess moisture without penalty.
posted by Big Al 8000 at 11:24 PM on September 3, 2018 [1 favorite]


I think there are probably a lot of technical mitigations that would work; the problem is more economic, driven by the extremely thin margins of long-haul shipping. If it's cheaper to mitigate the risk via paying a slightly higher insurance premium than install a safety system, the safety system isn't going to get installed (unless it's required, but as Joe in Australia points out, international shipping sits at an intersection of various national laws and international treaties, so it's difficult to get anything to change). At best, individual nations can prohibit certain types of ship from docking at their ports, but this tends to just shift the problem around.

E.g. it took until 2005 for dangerous single-hull oil tankers to be phased out internationally, and my read of the rules suggests that there are a lot of exceptions that will keep old ones around in poorer parts of the world for some time. And that was after dozens of incidents including the huge spills like Valdez, Prestige, and Sea Empress, which would have been prevented with newer designs. The US prohibited these tankers from offloading at US ports earlier, but it took coordinated action to finally get rid of them.
posted by Kadin2048 at 10:40 AM on September 4, 2018 [6 favorites]


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