Mystery of the Cargo Ships That Sink When Their Cargo Suddenly Liquefies (theconversation.com)

An anonymous reader writes (condensed for space): On average, ten "solid bulk cargo" carriers have been lost at sea each year for the last decade. Solid bulk cargoes -- defined as granular materials loaded directly into a ship's hold -- can suddenly turn from a solid state into a liquid state, a process known as liquefaction. And this can be disastrous for any ship carrying them -- and their crew. A lot is known about the physics of the liquefaction of granular materials from geotechnical and earthquake engineering. The vigorous shaking of the earth causes pressure in the ground water to increase to such a level that the soil "liquefies." Yet despite our understanding of this phenomenon, and the guidelines in place to prevent it occurring, it is still causing ships to sink and taking their crew with them.

Solid bulk cargoes are typically "two-phase" materials as they contain water between the solid particles. When the particles can touch, the friction between them makes the material act like a solid (even though there is liquid present). But when the water pressure rises, these inter-particle forces reduce and the strength of the material decreases. When the friction is reduced to zero, the material acts like a liquid (even though the solid particles are still present). 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. The vibration and motion of the ship from the engine and the sea during the voyage can also increase the water pressure and lead to liquefaction of the cargo. You can read more on this here.

Comments

This makes it sink?

[sanosuke001]

Why does the ship sink, though? Is the material stable in its granular form but without the water binding it is it corrosive or something? TFS wasn't very helpful in explaining why this effect is dangerous or what is being done about it at all. It, however, explained the effect itself fairly well.

Re: This makes it sink?

[Anonymous Coward]

From the linked article:
When a solid bulk cargo liquefies, it can shift or slosh inside a shipâ(TM)s hold, making the vessel less stable. A liquefied cargo can shift completely to one side of the hold. If it regains its strength and reverts to a solid state, the cargo will remain in the shifted position, causing the ship to permanently tilt or list in the water. The cargo can then liquefy again and shift further, increasing the angle of list.

Re:This makes it sink?

[randm.ca]

Paragraphs 3 and 4 under the "Solid bulk cargoes" subheading explain why.

Re:This makes it sink?

[SCVonSteroids]

The liquefied solid probably sloshes around, and when you displace this amount of weight in a cargo ship, it can lead to some pretty nasty things structurally.

Re:This makes it sink?

[gshegosh]

"When a solid bulk cargo liquefies, it can shift or slosh inside a ship’s hold, making the vessel less stable. A liquefied cargo can shift completely to one side of the hold. If it regains its strength and reverts to a solid state, the cargo will remain in the shifted position, causing the ship to permanently tilt or “list” in the water. The cargo can then liquefy again and shift further, increasing the angle of list. At some point, the angle of list becomes so great that water enters the hull through the hatch covers, or the vessel is no longer stable enough to recover from the rolling motion caused by the waves. Water can also move from within the cargo to its surface as a result of liquefaction and subsequent sloshing of this free water can further impact the vessel’s stability. Unless the sloshing can be stopped, the ship is in danger of sinking."

Re:This makes it sink?

[toonces33]

There are examples of liquefaction that take place during earthquakes, where what had been solid ground seems to just dissolve.

I believe the theory is that vibrations of the correct frequency and amplitude can cause the cargo in a cargo ship to liquefy in a similar fashion, but the specifics are going to depend a lot on what the cargo is and what the water content is. The article was pretty light on specifics, however.

Re: This makes it sink?

[v1]

the obvious solution to this is to have partitions inside the ship, to limit the amount of shift possible.

Also, picking "the right ship for the job" such that your cargo comes as close as possible to completely filling the hold to the top, to limit the amount of possible shifting.

I'm just surprised that the pressures added by "drop-filling" the cargo at port have any effect on the possibility of liquifying long after the ship has sailed. I would have expected that only the vibrations during the voyage would have affected it.

I wonder how much of a role uneven loading at port plays? Like if the hold is filled from only a relatively small number of hold covers, leading to cargo that's in roughy pyramid-shaped piles in the hold. If they have just barely enough cohesion to maintain that pyramid shape, I could definitely see how that could shift suddenly and significantly on a rolling sea. Once the shift starts, it's like the article describes, with the entire mass moving as a liquid, a lot like an avalanche, until the pressure drops below critical. And then the cargo "freezes" in place in its new position, quite likely creating a dangerous imbalance in the load.

I've always found watching avalanche videos to be fascinating, how snow, seemingly solid, can flow like a river, and then suddenly stop as if hit by a freeze ray, cementing everything in place. Trees, cars, people, buildings, everything is moved like it's being carried away by a tsunami, and then suddenly it all just stops. Landslides are the same eerie way. It's like god is playing "red-light-green-light" with giant hunks of material.

Re: This makes it sink?

[orlanz]

They rolled over it to simply the explanation. But that specific type of friction effectively goes to zero. Similar to a standing vs rolling ball. The former has effectively zero rolling friction and the latter has effectively zero static friction. And of course neither has sliding friction.

Re:This makes it sink?

[gotan]

I took this as "friction between the solid particles". Maybe the particles shrink more from compression due to pressure than the surrounding liquid, at some point they are no longer in direct contact, and before that the force with which the particles are pressed against each other at contact points goes to zero, which also makes the friction between particles go to zero.

Or maybe it's just engineers talk meaning "the friction is reduced by some orders of magnitude".

Re:This makes it sink?

[Anonymous Coward]

Why does the ship sink, though? Is the material stable in its granular form but without the water binding it is it corrosive or something? TFS wasn't very helpful in explaining why this effect is dangerous or what is being done about it at all. It, however, explained the effect itself fairly well.

Likely it's the "free surface effect". Basically, if tanks or holds aren't full, when the ship rolls to one side, the cargo flows to that side too, moving the ship's center of gravity towards the low side. Get enough of a flow and the vessel can capsize, or the momentum of the flow can damage the ship:

The free surface effect is a mechanism which can cause a watercraft to become unstable and capsize.

It refers to the tendency of liquids — and of unbound aggregates of small solid objects, like seeds, gravel, or crushed ore, whose behavior approximates that of liquids — to move in response to changes in the attitude of a craft's cargo holds, decks, or liquid tanks in reaction to operator-induced motions (or sea states caused by waves and wind acting upon the craft). When referring to the free surface effect, the condition of a tank that is not full is described as a "slack tank", while a full tank is "pressed up".

Stability and equilibrium

In a normally loaded vessel any rolling from perpendicular is countered by a righting moment generated from the increased volume of water displaced by the hull on the lowered side. This assumes the center of gravity of the vessel is relatively constant. If a moving mass inside the vessel moves in the direction of the roll, this counters the righting effect by moving the center of gravity towards the lowered side. The free surface effect can become a problem in a craft with large partially full bulk cargo compartments, fuel tanks, or water tanks (especially if they span the full breadth of the ship), or from accidental flooding, such as has occurred in several accidents involving roll-on/roll-off ferries.

If a compartment or tank is either empty or full, there is no change in the craft's center of mass as it rolls from side to side (in strong winds, heavy seas, or on sharp motions or turns). However, if the compartment is only partially full, the liquid in the compartment will respond to the vessel's heave, pitch, roll, surge, sway or yaw. For example, as a vessel rolls to port, liquid will displace to the port side of a compartment, and this will move the vessel's center of mass to port. This has the effect of slowing the vessel's return to vertical.

The momentum of large volumes of moving liquids cause significant dynamic forces, which act against the righting effect. When the vessel returns to vertical the roll continues and the effect is repeated on the opposite side. In heavy sea states, this can become a positive feedback loop, causing each roll to become more and more extreme, eventually overcoming the righting effect leading to a capsize. While repeated oscillations of increasing magnitude are commonly associated with the free surface effect, they are not a necessary condition. For example, in the cases of both the SS Normandie and MS al-Salam Boccaccio 98, gradual buildup of water from fire-fighting caused capsizing in a single continuous roll.

Google "free surface effect" images

Re:This makes it sink?

[Anonymous Coward]

liquid sloshing around goes bad really quickly, see: MS Herald of Free Enterprise

Re:This makes it sink?

[dwywit]

I guess fitting baffles or compartments to bulk carriers costs more than the insurance when a ship goes down.

Re:This makes it sink?

[Jarik C-Bol]

Because, "When the friction goes to zero" refers to the friction between the pieces of granular cargo. So if the particles of granular cargo are suddenly not touching each other, due to water in between them, the friction between those particles of granular cargo is, of course, zero.
Because really, when considering how water moves in a container such as a ship, calculating the friction *within* the actual water itself *technically* would make the simulation more accurate, but on such a unbelievably small scale that it literally makes zero difference to the outcome of the simulation.
Essentially, its like saying the angle of repose for water is close enough to zero, that calling it zero is sufficient for the tolerances and scope of this piece of engineering. Sure, there is such a thing as surface tension, and a droplet of water can essentially have an angle of repose of 90 degrees (i know angle of repose is applied wrongly here, but i't makes my point). it matters in a test tube, but not in a swimming pool.

Re:This makes it sink?

[The Fat Bastard]

Is glass a solid or a liquid? Only time will tell.

Window glass at room temperature has a nearly incalculable relaxation time, approaching the age of the universe itself. For all practical observations, this glass is a solid. But its solidity is in the eye of the beholder.

Re: This makes it sink?

[Anonymous Coward]

This. Baffles for liquid transport (even fuel tanks in vehicles designed for non-cargo purposes) along with sectioning tanks is not even remotely new. So

a) treat bulk solid powders like bulk liquid
b) dehumidify the hold
c) have a spray down for offload if getting every last grain is desired (adding baffles and bulkheads increases surface area, which will increase losses due to product sticking to surfaces)

Re: This makes it sink?

[Anonymous Coward]

Have you not seen The Martian? They straight up talk about this process and it causing the resupply launch to fail.

Re: This makes it sink?

[Anonymous Coward]

Amazing how mudslides work, too. So much solid material "flowing" with a bit of mud. Even large boulders

Re: This makes it sink?

[mjwx]

the obvious solution to this is to have partitions inside the ship, to limit the amount of shift possible.

Also, picking "the right ship for the job" such that your cargo comes as close as possible to completely filling the hold to the top, to limit the amount of possible shifting.

Baffles will increase mass, weight and make loading and unloading of cargo much slower.

As for the second point, what will all the specialised ships do whilst not being employed for a single task? Freighters cost millions to make, every day they sit empty or idle is a day they're costing money.

The best and simplest solution is to find out why cargoes are liquefying, its not something that happens that often. 10 ships a year. There are an estimated 11,000 bulk carriers in service.

Re:This makes it sink?

[Entrope]

If you're right, that merely elevates the article from "crackpot claptrap" to "shoddily written clickbait". The mystery is less what happens than why it happens only to some ships, and why ship owners don't take the safety measures that are described in other comments here.

Re: This makes it sink?

[Anonymous Coward]

the obvious solution to this is to have partitions inside the ship, to limit the amount of shift possible.

...

Except that might make loading and unloading cargoes such as bulk ores difficult or impossible, depending on the vessel and the port facilities.

The large machine in TFS sure looks a lot like a Hulett unloader, and those only work with wide-open, flat-bottomed holds.

Re:This makes it sink?

[Zorpheus]

Well, the viscosity of water is low, but not zero. So the friction does not really go to zero. Compared to friction in air it is still quite high.

Re: This makes it sink?

[Anonymous Coward]

Not arriving at port also makes unloading much slower...

Re:This makes it sink?

[Anonymous Coward]

Ok, you know how you can walk on sand, press on it with all your weight, and it supports you, right, like normal dirt, it's a solid.

BUT - you can take sound and pass it through sand, and what happens, suddenly things SINK, the sand no longer acts like a solid, it's acting like a liquid. And this can happen in the desert also and has nothing to do with water. The sand, as sound, or kenectic energy passes through the sand, a SOLID, it stops acting like a solid, and moves, like a liquid.

Now, take 2 buckets - both the same volume,. NOT weight. like a 5 gal bucket filled with water and one with sand. The sand is heavier, same volume, but notice, it doesn't move like one filled with water. So, if you lay say 10 of those buckets out you would expect the sand buckets to react each like a solid, and not slosh around, like the water ones do. But as kinetic energy passes through the solids, at times they start to slosh, like a liquid.

So your ship that you planned to handle full of stuff that doesn't move, like buckets of sand, can suddenly start to all act like liquids and slosh around. When they shift and slosh, it does not stay like that. So enough energy passes through the mass to cause it to shift, the solid material will not move back into it's old place, if not enough kinetic energy comes back through, that is not a problem for a liquid. If you shake a bucket of liquid it will slosh around and come back to center, if you stop shaking it, it will shift back. Sand does not do that.

It's like of like how buildings and sink when standing on solid ground, the kinetic energy into the ground makes it stop acting like a solid an let's the building sink, like a liquid would.

Re:This makes it sink?

[Nidi62]

I guess fitting baffles or compartments to bulk carriers costs more than the insurance when a ship goes down.

Retrofitting would be expensive, but I could see building new ships with a different hold layout. Instead of multiple holds aligned one in front of the other forward to aft, have them run forward to aft and be aligned side to side port to starboard. This way if the load shifts you still have weight to counterbalance.

Re: This makes it sink?

[sanosuke001]

Just put them in sealed containers? If it's a known problem that affects a dozen ships a year (very expensive ships with lots of cargo) then wouldn't containers for the cargo be pretty straightforward? I know it adds weight but wouldn't that be preferable to losing ships every year? (And my confusion was more with the summary as it should have had the basic info... thanks slashdot)

Re:This makes it sink?

[Anonymous Coward]

Is Chris a moron or an unmedicated autistic?

Re:This makes it sink?

[dohzer]

Yup... seriously. That would have been the most obvious thing to put in the summary, and they didn't!
I guess it's effectively like a load-shift in an aircraft.

Re: This makes it sink?

[Anonymous Coward]

> Baffles will increase mass, weight and make loading and unloading of cargo much slower.

otoh, the cargo and crew won't be at the bottom of the ocean.

Re:This makes it sink?

[Highdude702]

True, due to the shape I could imagine it being more resilient to weight shifting front to back rather than side to side.

Re: This makes it sink?

[Anonymous Coward]

So according to the article you linked Huletts have been largely obsolete for 30 years due to self-unloading cargo ships and there's all of six left in the world. That doesn't sound like a technical challenge.

Re: This makes it sink?

[Krakadoom]

Probably not preferable, no. Adding weight and complexity and therefore costs to all haul of 11.000 ships vs. losing 10 ships a year - I'd expect it's cheaper to just lose the ships.

Re:This makes it sink?

[BigDogCH]

Ships don't just travel one route. They are generic, to handle many things. With that said, this makes me think something like shipping containers would maybe work better than bulkheads for grain then. Maybe that's still impractical at the scale we are talking though.

Re: This makes it sink?

[Anonymous Coward]

Baffles will increase mass, weight and make loading and unloading of cargo much slower.

Pick one: Dead sailors, or what you complained about.

Re: This makes it sink?

[SCVonSteroids]

I'm sure someone in the industry has run the numbers before you and determined the risk/reward was worth the loss.
Yes, believe it or not, people's lives money. Stupid isn't it?

Re: This makes it sink?

[bickerdyke]

As for the second point, what will all the specialised ships do whilst not being employed for a single task? Freighters cost millions to make, every day they sit empty or idle is a day they're costing money.

That point is moot as bulk cargo ships ARE the specialised ships compared to the generic container frighters.

But if the problem is actually the water between solid particles.... wouldn't a drain and a bilge pump in the hold not get rid of the excess water?

Re: This makes it sink?

[Applehu Akbar]

the obvious solution to this is to have partitions inside the ship, to limit the amount of shift possible.

Take a look at the commentary on Ars. Partitions in the hold are the first thing every nerd proposed, but apparently maritime cargo operates by the same bean-counting rules as the automobile industry: any innovation that costs more than pennies per unit is rejected as too costly. Losing a rusty freighter with a developing-nation crew every so often is just a cost of doing business.

Re:This makes it sink?

[jrumney]

Think about what happens to the ship's center of mass when the cargo is sloshing around down below.

Re:This makes it sink?

[Anonymous Coward]

I love the shrill of creimertards in the morning. ~ CaptainDork

Re: This makes it sink?

[Anonymous Coward]

I'm just surprised that the pressures added by "drop-filling" the cargo at port have any effect on the possibility of liquifying long after the ship has sailed. I would have expected that only the vibrations during the voyage would have affected it.

If I had to guess dropping from height would create more dust from the grains impacting one another which would act as a lubricant and facilitate liquefaction.

Re:This makes it sink?

[Anonymous Coward]

Get my family freindly Goat C shirt! ~ CaptainDork

Re: This makes it sink?

[crunchygranola]

10 ships a year. There are an estimated 11,000 bulk carriers in service.

And assuming 10 voyages a year this is one loss per 10,000 loads delivered. Using the Wikipedia bulk carrier article (which is quite good) and taking a large carrier of 80,000 tons that costs $40 million new, it would deliver 800 million tons per ship lost, or about 5 cents per ton as the "lost ship toll". Actual shipping fees listed are on the order of $15-70 per ton, so this is hardly even round-off error to the huge corporations that own these ships.

The crew of 20 to 30 people, almost entirely recruited from the third-world, are of course inexpensive write-offs to the corporations (their loss is much cheaper than the ship itself), so only international regulation protects them from being treated as expendables.

Re: This makes it sink?

[Anonymous Coward]

So according to the article you linked Huletts have been largely obsolete for 30 years due to self-unloading cargo ships and there's all of six left in the UNITED STATES. That doesn't sound like a technical challenge.

FTFY.

Huletts are a specific type of ore unloader that were used in the US.

Other parts of the world likely still use something similar.

You got another explanation for the large machine that looks a lot like a Hulett in TFS, Einstein?

Re: This makes it sink?

[Anonymous Coward]

the obvious solution to this is to allow all the ships prone to liquefaction problems sink, claim the insurance and continue on.

Fixed that for you. You just need to think like a corporate CEO.

Re: This makes it sink?

[Anonymous Coward]

Baffles will increase mass, weight and make loading and unloading of cargo much slower.

This is why we have regulations. It levels the playing field so EVERYONE has this expense. And it also solves the "Someone elses problem" of ships sinking. The ship is insured, so the shipping company doesn't have any vested interest in safety. The people who run the company are safe on dry land, so they're just apt to say "shit happens". There's likely smaller companies where the captain/crew might also be the owners, but normally there's just no way for them to compete with MegaCorp, AND put in the baffles because of the downsides you mention.

Re: This makes it sink?

[teaman2000]

Also, the ship is insured. So other than increased premiums (and the sailors, who the companies treat as expendable), the monetary risk to the shipper isn't that great.

Re: This makes it sink?

[Anonymous Coward]

The loss in cargo capacity should be outweighed by the cost of replacing a ship and it's entire cargo, even at small probabilities, due to the massive cost in total loss of the ship, personnel, liability, and cargo.

The article indicated liquefaction occurs due to particle pressure, and implies it's because as the ship hums and vibrates along the particles eventually collapse into more dense (more ordered) positions that reduces overall volume and increases the pressure felt by individual particles on one another (and any remaining liquid coating particle surface).

It's like sifting sand through sand. Eventually you end up with more compact sand as all the grains find ways of fitting into denser layers. Overall volume of the sand pile goes down and the grains, along with the water in them, are going to be under more pressure the deeper you go in the pile. Taken to an extreme, you would get sandstone--the problem is you get sand slushie before that.

For particle physics, think Macro-scale Bose-Einstein condensate.

Re:This makes it sink?

[ljw1004]

If you're right, that merely elevates the article from "crackpot claptrap" to "shoddily written clickbait". The mystery is less what happens than why it happens only to some ships, and why ship owners don't take the safety measures that are described in other comments here.

The article and accompanying discussion addresses these questions and was technically interesting and high quality. "A lot is known about the physics of the liquefaction [...] Yet despite our understanding of this phenomenon (and the guidelines in place to prevent it occurring), it is still causing ships to sink and take their crew with them."

The technical answer is that the existing guidance on stowing and shipping solid bulk cargoes is too simplistic. Liquefaction potential depends not just on how much moisture is in a bulk cargo but also other material characteristics, such as the particle size distribution, the ratio of the volume of solid particles to water and the relative density of the cargo, as well as the method of loading and the motions of the vessel during the voyage.

The economics make it clear that it's not worth spending huge amounts of money (that also make ships more awkward to load) for an event that's comparatively rare. It's doubly not worth spending money on refits when we don't even have a good physics model of it, one that's backed by data+observations. And if we kitted out some experimental ships but they proved to be in the 99.9% of ships that aren't affected by the phenomenon, then we won't have gathered any data.

The main idea in this thread was lengthwise bulkheads. I've never seen a ship designed that way. Not sure why. Maybe because it's a bulkhead that would need to be seriously strong (to stop the millions of tonnes) and would contribute nothing to the structure of the ship; only weight. Another idea was pumps to remove the water. Those would have to be exceptionally robust to handle being hammered by lumps of bauxite, and not get clogged by the finer bauxite. Maybe you could put a pump behind a mesh, if you could invent a mesh that would stand up to the millions of tons. The article suggests that another cause might actually just be the *speed* of loading. If that's true, how would we measure+test that? Could we invent a different loading technique that's mostly as fast? It'd be massively cheaper than lengthwise bulkheads.

There's a good video too: https://www.youtube.com/watch?...

In the video, the Australian Maritime Safety Organizations suggests a different preventative measure which is - captains should be aware that this is a phenomenon, aware of what are the warning signs, should pay attention to those first signs, and should consider seeking a Port of Refuge.

In short - excellent article, interesting phenomenon that even though we know about liquefaction and know about ocean shipping most of us still wouldn't have thought of, is deeper than "just add bulkheads".

Re: This makes it sink?

[Anonymous Coward]

The best and simplest solution is to find out why cargoes are liquefying, its not something that happens that often. 10 ships a year. There are an estimated 11,000 bulk carriers in service.

Is that 10 ships a year, or 10,000 ships a year but it only developed into a situation that caused an accident 10 times?

Re:This makes it sink?

[jeff4747]

why it happens only to some ships

Citation?

It probably happens to 100% of bulk haulers, but the shifted load is not enough to sink the ship.

why ship owners don't take the safety measures that are described in other comments here

The ship is insured and the crew are expendable.

Roughly 1% of bulk haulers sink from this, so your fix is going to have to be cheaper than the insurance premium for a 1% chance of sinking for the owners to care.

Re: This makes it sink?

[Anonymous Coward]

Reminds me of my friend back in '73, who thought it would be cool to put a waterbed mattress in the back of his van.

First corner he took flipped the van.

Re:This makes it sink?

[Nidi62]

These types of ships aren't generic, though. Look at the "bulk cargo ship" Wikipedia entry. There's no provision for stacking containerized cargo on deck. Containers could probably go in the holds but they obviously aren't designed for that and neither are the onboard cranes. Plus you would lose efficiency as you would inevitably have unused space between containers, plus the container walls themselves taking up space. Ships are very specialized these days with bulk vessels, container ships, tankers, RO/ROs, etc.

Re:This makes it sink?

[Anonymous Coward]

You mean Chris who created 60 videos in the last nine months? Genius!

Re: This makes it sink?

[Anonymous Coward]

Just pack it tighter so it CAN'T shift

Re: This makes it sink?

[lgw]

Almost all freight is containerized. If bulk cargo were reasonable to containerize, it would have happened long ago, to avoid specialized ships entirely.

Re:This makes it sink?

[lgw]

Solid materials have "friction"; liquids have "viscosity". So, technically there's no friction once it liquefies. It could have been put better, clearly.

Re:This makes it sink?

[lgw]

There's an urban legend that glass is a liquid that just flows slowly, purporting to explain why old glass panes are wavy, and thicker at the bottom than the top. But that's all BS - old glass was wavy when installed, and of course you put the thicker side down so it doesn't fall over while you put the frame around it. Smooth glass of even thickness, "float glass", is a surprisingly recent invention, only commercially viable in the late 1950s.

Re: This makes it sink?

[pz]

the obvious solution to this is to have partitions inside the ship, to limit the amount of shift possible.

As others have pointed out, this idea becomes impractical for various reasons.

A perhaps better solution is to control liquification to a greater degree. One idea that comes to mind is to lower the ratio of solid to water during loading, so as to ease the loading process and better even-out the cargo, and then raise the ratio by pumping out some of the water, locking the load into place. During unloading, the reverse happens.

The extra time required can be mitigated by performing some of the pumping out in the relatively calm waters near the port upon departure, and by pumping in solar-distilled water upon approach to the arrival port.

Re: This makes it sink?

[Bloke down the pub]

As for the second point, what will all the specialised ships do whilst not being employed for a single task?

Make the baffles removable. They could either drop into rails attached to the side of the hold, or there are these new-fangled fasteners that sort of have a sloping ridge going around them. You twist them the other way and they come off!

Re:This makes it sink?

[Anonymous Coward]

You sound bitter, sweet tits.

Re: This makes it sink?

[PrimaryConsult]

Too many regulations that reduce profit and the ships (and owners) will flag from a different country.

Re: This makes it sink?

[tlhIngan]

Also, picking "the right ship for the job" such that your cargo comes as close as possible to completely filling the hold to the top, to limit the amount of possible shifting.

Can't. You might not know this, but ships sail in water, and water around the wrold is quite different. How full you can load a ship depends on the waters it's going to sail in - different salt content, etc. really affect the loading of the ship.

While loading is calculated by computer nowadays, Plimsoll Lines help anyone looking at the ship determine the loading at a glance. And the modern lines even make variances for the seasons (summer and winter waters differ in density). Depending on the seasons and where you're going, there can be a huge amount of head space you cannot fill just to avoid overloading the ship.

Re:This makes it sink?

[Anonymous Coward]

And who promised a January 1 2018 publication date for his opus "Unemployable"?

You could always read the poems for free.

And who promised a new video every Friday, then slipped... and stopped? (Mercifully).

60 videos over nine months (36 weeks) is 1.67 videos per week. It's now every Sunday.

Re: This makes it sink?

[Darinbob]

The problem comes from the desire to more rapidly load and unload a ship to increase profits. Having partitions or baffles will slow this process down. Like anything to do with profits, the risks are evaluated and considered acceptable by those in charge.

Re:This makes it sink?

[fahrbot-bot]

Why does the ship sink, though? Is the material stable in its granular form ...

Other people did a good job explaining this, but you can also see this effect in the movie, and chapter 15 of the book, The Martian, during the launch failure of the Iris re-supply probe. (The scene also explained here).

From The Martian, Chapter 15:

At the microscopic level, the protein cubes were solid food particles suspended in thick vegetable oil. The food particles compressed to less than half their original size, but the oil was barely affected at all. This changed the volume ratio of solid to liquid dramatically which in turn made the aggregate act as a liquid. Known as "liquefaction," this process transformed the protein cubes from a steady solid into a flowing liquid.

Stored in a compartment that originally had no leftover space, the now-compresses sludge had room to slosh.

The shimmy also caused an imbalanced load, forcing the sludge toward the edge of the compartment. This shift in weight only aggravated the larger problem and the shimmy grew stronger.

This was part of a cascade failure. The vibrations from the rocket caused the protein cubes to liquefy, which sloshed around, creating an unbalanced load, causing a procession, causing a launch failure.

Re: This makes it sink?

[Mr D from 63]

Another perspective; If you look at the list of possible safety improvements, why would this one be chosen to invest in?

Re: This makes it sink?

[SCVonSteroids]

What's even more stupid is my "less than" symbol was completely removed from my post. Great job Slashdot.

Re: This makes it sink?

[Solandri]

But a ship sinking is a relatively rare occurrence. Whereas baffles are going to complicate every loading and unloading operation.

Actually, there's no reason for the baffles to extend all the way to the bottom of the hold. The bottom could still be open to allow material at the bottom to shift around. If your unloading mechanism is built into the bottom of the ship (as they are on newer bulk carriers), then the baffles will barely affect unloading operations. Fuel tanks are built this way

Re: This makes it sink?

[Anonymous Coward]

Rare occurance? The summary says 10 per year, almost every month is not rare. Especially when it means losing a ship and the crew dies. I guess you mean relatively rare but that is just splitting hairs.

Re:This makes it sink?

[Anonymous Coward]

Why does the ship sink, though?

Shoddy maintenance and unsafe practices. But it's easier to fool insurance companies with pseudo-science bullshit.

Re: This makes it sink?

[Anonymous Coward]

Pretty much like a slack tank in a crab boat, never a good thing

Re: This makes it sink?

[JackieBrown]

10 out of how many? We are talking about ships sailing everyday all over the world.

There are more car accidents per second than that.

Re: This makes it sink?

[JackieBrown]

LOL - And who sets and enforces these regulations?

Or did you think we were just talking about one country's ships?

Re: This makes it sink?

[JackieBrown]

We need a regulation outlawing dying!

Then we can live forever or face fines :)

Re:This makes it sink?

[JackieBrown]

Or... the crew is much more likely to die on their way to work than from this situation sinking their ship and destroying their means to escape that sinking ship.

Re: This makes it sink?

[Anonymous Coward]

Not arriving at port also makes unloading much slower...

10 ships per year to the global shipping fleet when there's around 12,000 dry bulk carriers in the global fleet:

https://www.statista.com/statistics/264024/number-of-merchant-ships-worldwide-by-type/

The lowest cost measure is insurance. Even with the risk to the crew, frankly being a sailor is a risky job; this is just one of many ways the ocean tries to kill you.

Re: This makes it sink?

[Anonymous Coward]

That irrelevant. Like I said, "relatively rare" is BS. Now you are bringing up cars? Keep hanging onto that diploma from the school of non-sequitors.

Re:This makes it sink?

[Jarik C-Bol]

And I reiterate, for the purposes of this model, zero is sufficient. There is no point wasting cycles dealing with the viscosity of water in a hold that can cary 10,000 tons of cargo, as the viscosity of water is irrelevant in relation to the other forces involved when things start going wrong at those scales.

Re: This makes it sink?

[Anonymous Coward]

Bullshit; it's not black and white. As much as people like to say you can't put a cost on human life, we can and do every day. We could stop all deaths in traffic accidents by outlawing cars and making everyone stay in their homes where it's safe, but the cost to society for that would outweigh the benefits and everyone would agree.

Being a sailor is a risk, simple as that. More sailors die from work related accidents such as equipment failures or falls than die from the ship sinking.

Re: This makes it sink?

[Cederic]

I risk dead farmers, dead lorry drivers, dead bakers every time I buy a loaf of bread.

You really think I'm going to give a shit about risking dead sailors?

Head to a poverty stricken port. "Guys, starve to death or work on this ship which is likely to sink at some point in the next 600 years, leaving you drifting in a modern well equipped lifeboat"

I'm not going to pretend it's ideal, but it compares well to, "Guys, I have no jobs today. I couldn't operate a raw materials transport business at sufficient profit so I sold the ships for scrap."

Re: This makes it sink?

[Cederic]

No.

Even at a macro level, you water pot plants by putting water in the base of the pot and letting it rise up through the soil to reach the roots. You aren't going to completely dry the soil again by draining the base.

At a more detailed level, very few materials are truly dry. Solid rock contains water and (m)any granular material can be subject to fluid dynamics. I suspect liquefaction uses the trace lubrication inherent to the materials being transported, rather than a simple excess of water.

Re: This makes it sink?

[bickerdyke]

I understand and agree with that, but my flowerpot doesn't suffer from sudden liquidification.... I understood that happens when the water that is usually safely contained within the material escapes and acts as lubrication, like the air in this video:

https://www.youtube.com/watch?...

but as the water is then no longer contained, it could be drained and removed (as the added air bubbles off on top of the sand in the video)

Re: This makes it sink?

[Cederic]

Have you tried gently rocking your flower pot from side to side for four weeks without a break? :)

Someone lower down posted a more informed response detailing how it works, so I'll let you read their reply rather than repeating it badly here.

Re: This makes it sink?

[jtgd]

I would think if they could completely fill the cargo hold then there could be no shifting. If they can't do that, maybe fill the air void with something inert, like styrofoam peanuts.

Re: This makes it sink?

[bickerdyke]

As with vibrations or sugar I would expect the soil in my flower pot to settle and become even more solid

But I'll check out the better explanation.

Re:This makes it sink?

[BigDogCH]

You are spot on. I should have clarified that the ships are not specific to one specific cargo. They are designed for different types of bulk cargo though, you are correct.

I was thinking they could change them to use something more similar to cargo container ships.

Since return shipping is almost-free to whichever country has the trade surplus, the ship benefits if it work for that cargo demand as well. That probably opens up another can of worms with food vs whatever as cargo in the same ship. I guess if this was easy it would have already been solved.

Re:This makes it sink?

[st0nes]

A phenomenon called free surface effect. When carrying an actual liquid cargo as in a tanker the tanks are 'pressed up,' i.e. the cargo is filled to the very top of the tank, which prevents it from moving from side to side with the motion of the ship. Solid cargoes are not loaded in this way, so if they liquefy they move from side to side with the rolling of the ship. This can result in catastrophic instability, and the ship can capsize. Remember the Spirit of Free Enterprise that capsized in Zeebrugge harbour when the OOD forgot to close the stern doors and the car deck flooded? Wikipedia has a short article on the free surface effect (https://en.wikipedia.org/wiki/Free_surface_effect) that explains it better.

Re: This makes it sink?

[lsatenstein]

From the linked article:
When a solid bulk cargo liquefies, it can shift or slosh inside a shipâ(TM)s hold, making the vessel less stable. A liquefied cargo can shift completely to one side of the hold. If it regains its strength and reverts to a solid state, the cargo will remain in the shifted position, causing the ship to permanently tilt or list in the water. The cargo can then liquefy again and shift further, increasing the angle of list.

Take a raw egg and give it a spin. Boil the egg to "hard boiled state" and give the egg a spin.
Its a way to detect which egg of a pair has been cooked

Preventable

[BrendaEM]

I guess the economics of letting the occasional ship sink with lives lost, is cheaper than securing the load.

Re:Preventable

[Gilgaron]

Yeah if it happens that regularly and anyone cared they'd spend the extra to put this cargo in suitable containers, from the sound of it.

Re: Preventable

[Anonymous Coward]

Another mystery solved! Great work, team.

Re:Preventable

[rtb61]

Which also points to the most likely cause, poor maintenance of the drive line and hull harmonics. That would be the whole drive line, engine, engine mounts, transmission, transmission mounts, drive shaft, bearings, and the propeller. Environmental conditions would be to slow to promote liquefaction, not of the entire cargo but more likely only the bottom half, with the top half floating on top and shifting. Drive shaft load and balancing versus changes in hull shape under load, would be a likely source of extreme vibrations, dependent upon how much the hull is bending.

Focus on the bottom half of the load, easy fix, longitudinal upside V running the length of storage, reaching at least half way up storage loads. Better engine mounts, eliminate drive shaft and go with electric drives.

Re: Preventable

[Anonymous Coward]

Doubling the number of compartments by adding a centerline wall is a huge structural challenge because it requires a completely different structure in the keel and ads structure to the deck which is otherwise mostly a walkway and rain cover. it also increase hugely the time required in port to load and unload. Liquid takers deal with this through hooks in the balls but that doesn't work for our shops, as the outs is much more mud than liquid.

Re:Preventable

[Anonymous Coward]

It makes you smarter if you type it in monospace font!

Re: Preventable

[Evtim]

I remember reading about the marking on a ship's hull that indicate the maximum load you should carry in different seas. The reserve floatability should be larger the rougher the seas. Thus NA meaning North Atlantic is the roughest, FT meaning Fresh Tropical is easiest (you can load the ship to maximum).
Now what was really interesting was how long it took for the British parliament to pass the law. Decades. And the merchants tried everything to stop it up to attempts to discredit the politician that proposed it (name sounds like Plinsmall, read the story in my native tongue so no guarantee. The markings were called "the disc of Plin...."
At that time more than 2000 vessels were lost per year!!! And still the merchants did not care....neither did the captains who would try to squeeze just a bit more cargo to increase their own profit. Utter hell!
On a related note, how long it took to get rid of Pb in fuell and pesticides in the soil? Decades. And in both cases there was an attept to ruin the scientists, activists and politicians involved.
Far be it from me to declare the dead of capitalism but some aspects of it can really get put of hand....not that the communists were any better in protecting the lives of employees or soldiers....my father was killed by his job just like half the men in the apartments block we lived (belonged to the construction company so every man was employed there).
Well, life sucks!

Re:Preventable

[Anonymous Coward]

What are the economies of typing in a shitty font and forcing my browser to render MY page the way you want me to see it? Fuck you, bitch.

Fake news

[Anonymous Coward]

Liquid cargo doesnâ(TM)t sink ships. Bad engineering, terrible sailors, storms all sink ships.

Re:Fake news

[Anonymous Coward]

Loose lips are happy to finally be footloose and fancy free following years of stigma.

Re: Fake news

[Anonymous Coward]

I think what you meant to blame was a lack of meaningful regulation, which articles like this will be quoted to help change. ...then promptly all regulations will be ignored because of race-to-the-bottom competition, no international enforcing body, lax flagging rules, deference to insurance to cover risk, increased costs, and complete lack of oversight when ships are out of sight.

Re:Female to Male Body Massage in Delhi

[Anonymous Coward]

-1 spam

Could injecting gas from the bottom help?

[gotan]

As far as i understand they have a mixture of solid particles surrounded by liquid, the particles are more compressible, so under pressure the whole structure loses coherence as effectively the solid fraction is reduced, since the liquid is less compressible.

I wonder if this could be helped by injecting some gas from the bottom after loading, so there are pockets where the granular solid is surrounded by compressible gas instead of liquid. If the density of the liquid is less than that of the solid surplus liquid would be driven to the top where it could be extracted.

It might help if the gas pockets are well enough dispersed.

Re:Could injecting gas from the bottom help?

[Anonymous Coward]

Bottom gas is sledom helpful.

Re:Could injecting gas from the bottom help?

[Anubis IV]

I’m thinking that might be a bad idea. Or at least something that would need to be done carefully.

Re:Could injecting gas from the bottom help?

[drinkypoo]

As far as i understand they have a mixture of solid particles surrounded by liquid, the particles are more compressible, so under pressure the whole structure loses coherence as effectively the solid fraction is reduced, since the liquid is less compressible.
I wonder if this could be helped by injecting some gas from the bottom after loading,

The short answer is no. If you inject gas into a mixture of solid particles, you reduce the friction between them as the gas passes through them. You'd actually be making the problem worse. Some people have experimented with sand tubs using precisely this effect. You inject a bunch of air into the bottom and it makes the sand act a lot like a liquid. You can sink into it, and move your limbs through it.

Re:Could injecting gas from the bottom help?

[PPalmgren]

The reason bulk carriers work is because they're simple. The weight that goes into these ships is almost unbelievable, and adding moving components to the very bottom of that weight is a recipe for disaster. Bulk carriers are used for homogeneous goods sold in mass quantities for prices low enough that putting them in containers is cost prohibitive. I'm surprised that this is an issue, but I could see why the hold would have limited possible fixes for a situation like this. I think the eventual fix would more likely employ sensors of some sort to understand what types of resonance are causing the issue, or spotting them as they occur.

Re:Could injecting gas from the bottom help?

[Anonymous Coward]

Interesting video. I particularly like the clip of the pigeons going down the hopper in the grain elevator. Something every vegan needs to see.

Re:Could injecting gas from the bottom help?

[gotan]

Sure, it's always a question of cost effectiveness. If that were not the case subdividing the hold into small enough compartments to avoid fatal shifts of cargo would do the trick, so any solution should be cheaper than that. A system that injects gas (not necessarily with moving components) raises the cost of the carrier and will require at least some maintenance. If and how it can be implemented at low enough cost is really an engineering question.

Probably the risk analysis of insurance companies can express in dollars what a system that mitigates the risks of loss of carrier, cargo and crew would be worth.

So i agree: cost effectiveness is paramount, the question is, can my idea be implemented cost effectively (after finding out if it works at all).

And sure, a monitoring system might be the cheapest to install, but i wonder how it helps unless there are also means to stop or reverse the shift of cargo.

Re:Could injecting gas from the bottom help?

[Anonymous Coward]

High interstitial pore pressure is what causes liquefaction.

Gas is a fluid, too. You would just be displacing a liquid fluid with a gaseous one under high pressure.

You'd be creating the perfect circumstances for liquefaction.

Mystery?!?!?

[Anonymous Coward]

Mystery of the Cargo Ships That Sink When Their Cargo Suddenly Liquefies

Inconceivable!

Cargo?

[wisnoskij]

What sort of cargo are they carrying that is a granular solid filled with water?

Re:Cargo?

[Anonymous Coward]

Sand, clay or perhaps some solid waste matter from sewage works?

Re:Cargo?

[tazan]

Mineral Ores. Basically they have a hold full of dirt. If it's loaded during rainy season it's a hold full of mud and can act just like a landslide does in an earthquake.

Re:Cargo?

[gtall]

Grain too contains water. Drying is necessary to prevent spoilage but it cannot drive out all water and then there is humidity to consider.

Re:Cargo?

[bugs2squash]

maybe quick clay

Re:Cargo?

[AndroSyn]

In this case, bauxite.

The PDF linked from the article has a FAR better explaination:

http://www.imo.org/en/MediaCen...

Re:Cargo?

[Applehu Akbar]

One of the major bulk cargos cited was bauxite, aluminum ore. Though most ores are smelted near the mine, the economics of aluminum are weird because this element requires vast amounts of electricity to refine. It actually pays to mine bauxite in Australia but smelt it in places like New Zealand, where there is cheap hydro, or Iceland, where there is cheap geothermal electricity.

Re:Cargo?

[Anonymous Coward]

If you were to dry grain excessively, would it be an explosion hazard?
Or just a fire hazard. A thousand tonne of carbohydrates is somewhat scary.

Re:Cargo?

[kqc7011]

Many of the sinking were ships carrying nickel ore and here is a pretty good article about this.https://safety4sea.com/carrying-nickel-ore-worlds-dangerous-cargo/

Re:Cargo?

[Anonymous Coward]

It actually pays to mine bauxite in Australia but smelt it in places like New Zealand

Just to note... bauxite must first be refined (normally a caustic-washing type process) to Alumina, then smelted to Aluminium. Bauxite is not transported to New Zealand, Alumina is. Alumina can be readily "liquefied" using air and vibrations and is often conveyed using this property, I'm not sure of the likelihood of it happening spontaneously during shipping.

Liquefaction

[MagicM]

For a fun example of liquefaction, check out Mark Rober's video on YouTube.

Re:Liquefaction

[Anonymous Coward]

Excellent link

Clickbait headline

[Potor]

There is absolutely no "mystery" here.

Re:Clickbait headline

[Anonymous Coward]

Still, this was interesting to me. No, it's not exactly computer science, but it is definitely news for nerds, and maybe even stuff that matters.

Re:Clickbait headline

[Diddlbiker]

You are absolutely correct! Visit a maritime website like gcaptain.com and you'll see that the process is well understood. Wet bulk cargo, people who make the decision to load it anyway and don't have to deal with the consequences... There's no mystery. Just greed and the wrong people paying for it with their lives.

Re:Clickbait headline

[Anonymous Coward]

Yeah, I noticed the contradiction in the writing.

There's "A lot is known about the physics of the liquefaction of granular materials..." and "...despite our understanding of this phenomenon, and the guidelines in place to prevent it occurring...".

And then there's "Mystery of the Cargo Ships That Sink ...".

So which is it? Is it a well-understood phenomena, or a big mystery? Or is it actually a problem with a known solution, that no one wants to implement because it will be inconvenient and cost money?

Compartmentalization

[Nidi62]

Out of curiosity, do these bulk cargo vessels store their loads in one big hold, or are the holds compartmentalized? If the ships have multiple holds (say 3), each side by side and running lengthwise, then even if the loads in each hold liquefy and shift to port, the loads in the center and starboard holds may still have enough weight to counteract the shift.

A quick google search turns up this image, showing a stern to bow layout. So if the load in one hold shifts it is likely that all the others will shift too. So running the holds bow to stern and stacking them port to starboard would solve that issue. Given the size of these vessels I would assume that loads shifting forward or aft would be less of an issue or concern, but you could always make 6 holds by running 3 along the length of the ship and separating them midship.

Re:Compartmentalization

[Anonymous Coward]

Except that they have to load and unload the cargo through hatches. Think, for a moment, how you would arrange the hatches so that all of the cargo could be reached through them if the holds are running lengthwise, and for that matter, how the loaders and unloaders would need to change from the current setup.

Re:Compartmentalization

[thegarbz]

So running the holds bow to stern and stacking them port to starboard would solve that issue.

Changing loading / unloading practices internationally due to a handful of ships being lost a year is not something that will gain much traction, especially not when the changes affect the one party who is otherwise completely by the loss of a ship and cargo.

Re:Compartmentalization

[crunchygranola]

There is a good Wikipedia article on bulk cargo ships. It contains such useful information as this (edited excerpts from two paragraphs):

Bulk carriers are designed to be easy to build and to store cargo efficiently... Double hulls have become popular in the past ten years... One of the advantages of the double hull is to make room to place all the structural elements in the sides, removing them from the holds. This increases the volume of the holds, and simplifies their structure which helps in loading, unloading, and cleaning.

So these vessels are all about doing stuff as cheaply as possible to minimize the cost of operation, and a key strategy is to keep all obstructions out of the hold. With compartments they would then have to be loading and unloading and cleaning each compartment separately, taking more time and effort. Putting in compartments defeats the design goal of the bulk carrier. Also it might make it harder to load it evenly in the first place.

Re:Compartmentalization

[Anonymous Coward]

Then what's the point of the article? We know liquefaction happens, we know what liquefaction is, we know how to avoid the problem (not liquefaction, the consequence), but the shipping lines are too cheap to implement the workaround. There is no mystery at all.

Re:Compartmentalization

[Nidi62]

Except that they have to load and unload the cargo through hatches. Think, for a moment, how you would arrange the hatches so that all of the cargo could be reached through them if the holds are running lengthwise, and for that matter, how the loaders and unloaders would need to change from the current setup.

They already load/unload these ships from the deck and down into the hold. What would change? At worst you just need more/bigger hatches.

Re:Compartmentalization

[Nidi62]

So running the holds bow to stern and stacking them port to starboard would solve that issue.

Changing loading / unloading practices internationally due to a handful of ships being lost a year is not something that will gain much traction, especially not when the changes affect the one party who is otherwise completely by the loss of a ship and cargo.

What's to change? They load from the top through hatches using cranes on the vessel. So, instead of 3 long holds make them 2, one port and one starboard with a bulkhead amidship making 4 total holds(port/forward, port/aft, starboard/forward, starboard/aft). Run the cranes amidship as well so they can service both holds. Problem solved.

Re:Compartmentalization

[thegarbz]

What's to change? They load from the top through hatches using cranes on the vessel.

Practices. I didn't say the change is big or complicated, just that it won't be done. For the past 30 years the industry has been talking about an emergency stop signal for unloading pumps on hazardous material vessels. The cost would be a relay, a connector and a cable on each boat. 2018 and they are still *talking* about it.

To say the entire industry is resistant to change would be the understatement of a lifetime. The only reason what you say can't be done is because it isn't done. Nothing more than that.

The shipping industry is full of very easy problems to solve.

Re:Compartmentalization

[lgw]

Some use cranes on the ships. Some use cranes on the port. Some use conveyor belts, which can be the cheapest and fastest. Ships that "unload themselves" use conveyor belts.

Think about parallelizing movement of bulk freight between ship and port. A bunch of cranes or belts spaced out along the length of the ship, with roughly square hold compartments, is straightforward. A bunch of long, thin compartments running lengthwise not so much. Conveyor loading into long, thin compartments doesn't really work (the pile will hold a certain angle, which may be steep). Also, you can't load a heavy cargo onto a port compartment and a light cargo into a starboard compartment, while you do have some options with the current system.

I'm not saying it was Aliens

[Ol Olsoc]

But it was Aliens.

Re: This makes it sink? - A Solution?

[Anonymous Coward]

use water tight seal-able containers then after the metals liquefy the liquid doesn't escape the container and cause a weight imbalance in the ship's hold causing it to tip and sink.

Summary

[bluegutang]

This is a remarkably good summary for Slashdot.

Re: Summary

[Anonymous Coward]

Not sure if there's a whoosh here, the summary is literally an extract from TFA. Granted, they've left out anecdotal examples but not much primary summarisation going on here...

Re:Summary

[Anonymous Coward]

This is a remarkably good summary for Slashdot.

The editor who did it must be new here.... ;)

no water in earthquake liquefaction

[Anonymous Coward]

A lot is known about the physics of the liquefaction of granular materials from geotechnical and earthquake engineering. The vigorous shaking of the earth causes pressure in the ground water to increase to such a level that the soil "liquefies."

Nope!

Ground water in the soil has nothing to do with earthquake liquefaction. Liquefaction can occur without any water present at all.

See, e.g., https://www.britannica.com/science/soil-liquefaction

TL:dnr: [vibration] causes otherwise solid soil to behave temporarily as a viscous liquid.

As for cargo ships filled with bulk wheat, rice, etc.; it's kinda stating the obvious that, while they are solids, in the sense that they are not liquids, they also aren't solid like a blocks of wood, rolls of steel, or pigs of aluminum. They behave much more like liquids.

Another recipe for disaster is fill a cargo hold full to the top with rice, seal the hatches, and then add some water (e.g. from a leak), and watch the ship literally burst apart in slow motion.

Re:no water in earthquake liquefaction

[Comboman]

Another recipe for disaster is fill a cargo hold full to the top with rice, seal the hatches, and then add some water (e.g. from a leak), and watch the ship literally burst apart in slow motion.

Or aim a laser at a ship full of popcorn kernels.

Re:no water in earthquake liquefaction

[DRJlaw]

Ground water in the soil has nothing to do with earthquake liquefaction. Liquefaction can occur without any water present at all.

https://www.britannica.com/sci...>Your own link says otherwise. "The phenomenon occurs in water-saturated unconsolidated soils affected by seismic S waves (secondary waves), which cause ground vibrations during earthquakes."

And then reading further:
"When earthquake shock occurs in waterlogged soils, the water-filled pore spaces collapse, which decreases the overall volume of the soil. This process increases the water pressure between individual soil grains, and the grains can then move freely in the watery matrix. This substantially lowers the soilâ(TM)s resistance to shear stress and causes the mass of soil to take on the characteristics of a liquid. In its liquefied state, soil deforms easily, and heavy objects such as structures can be damaged from the sudden loss of support from below."

So water has everything to do with it. As the GP helpfully noted.

Re:no water in earthquake liquefaction

[reg]

Liquefaction absolutely requires a fluid between the particles - that can be air, water or a mixture of both. All that is required is that the effective stress be reduced to zero. Most granular materials, regardless of particle size distribution (grading), will exhibit zero shear resistance when the effective stress is zero, and so any loading will cause them to move. Liquefaction in particular is caused by vibration, where the shaking builds up pore water pressure which cannot dissipate fast enough because the permeability of the material is too low. Materials which are susceptible to liquefaction are all normally consolidated (i.e. not over-consolidated), so the shaking has the effect of consolidating the particles (or the consolation may return to normal compression curve if the shaking is high enough). If the material is very fine (like a clay), and wet, it will tend to have some shear resistance at zero effective stress because of inter-particle bonding, so it will not liquefy, even though it has very low permeability.

Air/gas can have the same impact (e.g. this happens when frozen gasses unfreeze), but you typically need a lot more air to get the required pressures, since it is compressible.

Liquefaction is not the same as the material looking like it is behaving like a liquid (looking like it is flowing, like sand in an hour glass). That is just what granular materials look like when they do flow...

The way that you make soil samples for liquefaction testing is by slowly dropping the sand into the test mold, preferably with the mold already filled with water. This causes them not to consolidate during production. This is exactly how they are loading these cargoes. The article implies this increase the pore water pressure, but that is not the case.

The cheap solution for ships would be to monitor the pore water pressure in the cargo hold, and trigger an alarm if there is any sudden increase. Also, if the material was prone to liquefaction, then it can be consolidated during loading by vibrating the cargo (like with a concrete vibrator). Rather than baffles, another approach would be to put vertical drains into the material (pipes from the bottom of the hold up). You could just pull these out (vertically) before unloading. If you couldn't discharge the drained water, you could just pump it back on top.

well, sure

[cascadingstylesheet]

Solid bulk cargoes are typically "two-phase" materials as they contain water between the solid particles. When the particles can touch, the friction between them makes the material act like a solid (even though there is liquid present). But when the water pressure rises, these inter-particle forces reduce and the strength of the material decreases. When the friction is reduced to zero, the material acts like a liquid (even though the solid particles are still present). 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. The vibration and motion of the ship from the engine and the sea during the voyage can also increase the water pressure and lead to liquefaction of the cargo.

Um, yeah, I was gonna say that. Sure. Everyone knows that, right?

;)

Yes it will cost more

[sjbe]

Baffles will increase mass, weight and make loading and unloading of cargo much slower.

And that is somehow worse than the loss of the ship and possibly the crew?

As for the second point, what will all the specialised ships do whilst not being employed for a single task?

Sit idle. Yes this will make the cargo cost more to carry. That's just how the cookie crumbles sometimes. Ships for liquefied natural gas don't get converted to haul coal when not carrying cargo. If safety demands a specialized ship then so be it.

The best and simplest solution is to find out why cargoes are liquefying, its not something that happens that often.

And then what? They evidently already know why they are liquefying. The question is what to actually do about it which will almost certainly involved some amount of change to ship design and cargo procedures.

Re: Yes it will cost more

[Anonymous Coward]

The ship is insured and the crew expendable.

Re:Yes it will cost more

[thegarbz]

And that is somehow worse than the loss of the ship and possibly the crew?

In-humanness of the response aside, the risk is quite low, ships are replaceable, and crews are typically from poor countries where life is cheap. These aren't your western well paid sailors who are mourned and whose companies get sued into oblivion for providing unsafe work locations.

Unfortunately the answer to your question is yes.

Sit idle. Yes this will make the cargo cost more to carry.

Only if the costs are spread across the industry. If the costs are only carried by the one company prioritizing safety over cost then cargo won't cost more to carry, it will simply put one competitor with a conscience out of business.

If safety demands a specialized ship then so be it.

Are you talking about the customer who doesn't want to pay or the hauler who doesn't want to bear an additional cost when their competitors don't?

The question is what to actually do about it which will almost certainly involved some amount of change to ship design and cargo procedures.

Indeed. But the answer is not to jump to expensive and impractical solutions that won't see implementation without a concerted effort across the entire industry. Shit man for hazardous cargo the industry in the past 30 years hasn't even agreed to a standardised way to emergency shutdown their unloading pump. Good luck getting them to implement something that actually cost them money.

Re:Yes it will cost more

[CrimsonAvenger]

Baffles will increase mass, weight and make loading and unloading of cargo much slower.

And that is somehow worse than the loss of the ship and possibly the crew?

hmmmm....

So, if we reduce the cargo capacity (and at the same time, increase time required to unload the ship) by, say, 5%, we have a ship that makes ~90% as much as "normal". And costs, say, 5% more.

So we have to charge ~15% more per ton moved to pay for the ship. Which makes us the last choice of anyone trying to move cargo, since they're having to pay that extra 15% for the privilege of using our ship.

Given the number of bulk haulers in service and the number lost every year, there's a 1% chance of losing the ship and cargo every year, which'll translate into a (maximum) 1% increase in insurance cost for shipping something.

So, you need to find a business that's willing to pay a 15% premium in order to avoid a 1% premium on insurance to make the "improved" ship pay for itself.

Good luck with that....

Re: Yes it will cost more

[Anonymous Coward]

The ship is insured

If the shipping company redesigns their ships, they can reduce the likelihood of a ship being lost.
If they reduce the likelihood of a ship being lost, they reduce how much insurance pays out to them.
If they reduce how much insurance pays out to them, they can successfully argue for lower rates.

So I can only conclude that either, 1) it would cost more to redesign the ships than would be saved, or 2) the insurance companies don't know that the shipping companies are choosing to not do more to mitigate ships being lost at sea and so are not charging appropriately for that.

Re:Yes it will cost more

[Anonymous Coward]

How did you get from 5% higher one-time built cost to charging 15% more on every journey for its entire working life?

Time at sea outweighs the time loading/unloading. Many ships already have their hold in sections. The sections between baffles would still be quite large so the baffles aren't going to make it take that much longer. 90% is an overexageration, it'd be more like 99%

The 5% extra build cost would amortize to almost nothing over its working life (decade) so you're just left with that 1%. Ever carrier would be making the same safety improvements so no-one would be undercutting you. At least not without the risk a loss of your entire cargo.

Horizontal baffles might stop the liquefaction happening at all (limit the depth of the pile thereby limiting the pressure) but I'll concede that'll make loading/unloading far too complex.

Re:Yes it will cost more

[Anonymous Coward]

One is a cost every single day, the other is a low probability occurrence. Shipping companies don't care about the low probability one, just the insurance companies do.

Re:Yes it will cost more

[Anonymous Coward]

Baffles need not be from top to bottom and I think the ship would require a min amount of baffles having no bearing on loading and unloading.
The issue would be expense maybe only apply this to new ships only or perhaps they should spend some money studying this.

Re:Yes it will cost more

[Bloke down the pub]

Replaceable isn't the same as disposable; I'd suspect the owners still need to insure them. And if a particular type of ship or a particular operator starts having a bad record then premiums for them will go up.

Re:Yes it will cost more

[Solandri]

In-humanness of the response aside, the risk is quite low, ships are replaceable, and crews are typically from poor countries where life is cheap. These aren't your western well paid sailors who are mourned and whose companies get sued into oblivion for providing unsafe work locations.

This is a common trope, but it's simply not true. The number of cargo ships lost at sea about equals the number of lives lost aboard those ships. That is, on average about 1 person dies for each ship that sinks.

The vast majority of people aboard a cargo ship which sinks are rescued. Life rafts are required by all shipping regulators. And satellite locator beacons have become so cheap that I suggest you get one if you do things like boating or hiking.. Their cost (a few hundred dollars, though a commercial model will run a few thousand) is much less than the liability and bad publicity of someone dying because your ship sank. When someone dies, it's usually because they were unable to reach the life raft in time (injured or blocked in due to the accident which sank the ship).

In fact, the fatality rate works out to (100 deaths) * (100,000) / (1.25 million) = 8 per 100,000. That makes it safer than a variety of jobs as mundane as taxi driver or landscaper. The fatality rate is right around the average for all jobs if you account for those people being aboard the ship 24/7, while people are at the other occupationss on average for less than 6 hours a day.

Re: Yes it will cost more

[Anonymous Coward]

You legit just pulled all those numbers out of the air lol.

Re: Yes it will cost more

[Anonymous Coward]

10 ships a year isn't a low probability.

Re: Yes it will cost more

[JackieBrown]

It really is. Do you have any idea how many ships are out in sea this very second?

Re: Yes it will cost more

[Anonymous Coward]

I worked in this industry for many years. Your conclusions use absolutes and don't properly assess the risks associated.

There are 11,100 dry cargo ships in the world as of January 2017. Around 250 to 500 are produced every year (depending on demand). 10 are lost due to this liquefaction issue.

Ship owners do not design ships. They set specs and buy an existing design from a ship designer, modified to meet their specs, and a yard to produce it.

Bulk carriers have wide open spaces to fill; they primarily transport granular goods like cement powder, grains, metal ore, etc. Adding specialized compartments to redesign the ship results in 2 things:

1) a major overhaul of the class of bulk carrier being built, as bulkheads designed to separate the holds to deal with liquefaction will alter the nautical characteristics of the ship (it's stability in the water, it's weight and thus fuel efficiency, it's overall cost in material, and will reduce total cargo capacity) = net result a loss in revenue per voyage and an increase in operating cost per voyage + an increase in design and manufacturing costs

2) most port facilities are designed around the single open hold; bulk carriers are specifically designed to reduce time-at-port for both the ship and the port's efficiency. Multiple holds will require a different operation to fill the ship, meaning that the ship will be limited in what port facilities it can go into if they're not designed to accommodate this new method.

All to save 10 ships out of 12,000, for maybe a reduced insurance premium. The lives of the crew are certainly an issue, but being a sailor is just a risky business; this is just one of many ways the sea can kill you. The highest cause of death for sailors is fatal accidents, such as a fall from a high railing or equipment operation.

Re: Yes it will cost more

[dgatwood]

All to save 10 ships out of 12,000, for maybe a reduced insurance premium.

Except it isn't really 10 ships out of 12,000. It is ten per year out of 12,000. This means the half-life of a ship is only 600 years. That seems way too short to me.

But the more alarming statistic is that only about two dozen large ships go down in a typical year. Thus, this one cause alone is responsible for about 42% of the major ship losses, which is to say nearly as much as all other causes combined. That's staggering, as it means that the cost of insuring that cargo would drop nearly in half if they could figure out why this happens and find a cheap, effective way to prevent it.

Re:Yes it will cost more

[thegarbz]

This is a common trope, but it's simply not true.

So you conclude that it's not true and back your data by showing that the industry none the less kills many people each year? I'm not sure what you're trying to prove here. The fatality rate of shipping seems to be quite in line with fatality rates in other industries and just like other industries the fatality rate is higher in cargo hauling than it is in localised western sea faring industries like fishing.

Just because the numbers are low or trending down doesn't make it any less true.

And yes I own an EPIRB.

Re: Yes it will cost more

[Cederic]

I think most people would consider a 600 year old ship a national treasure :)

I like your insight though, it's more useful context than the raw '1 in 12000' number.

Re: Yes it will cost more

[novakyu]

What kind of houses do you live in? Half-life of a house (a fixed installation, not something that floats on a tumultuous sea) is much shorter than 600 years, even in U.S., where they don't demolish houses every few decades or so like they do in Japan.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Comment removed

[account_deleted]

Comment removed based on user account deletion

Small problem with the article....

[Anonymous Coward]

Beyond all the navel gazing that everyone has done.. there is a small problem with the article.

Liquefaction does not require water (or other fluid) to occur. Put flour, sugar, salt, etc. in a qt mason jar and start to turn it over, roll it on the counter, etc. Observe the material and enlightenment will soon follow.

Heck it doesn't even require air - and can even occur in a vacuum.

Water, other liquids, air, etc. change the properties of the bulk material.

Here we have a tale of two solutions:
Lasers, range finders, and all other sorts of high-tech wizardry that can easily fail, get whacked, broken, stolen, etc.
Add some baffles to reduce the travel path of the material when it liquefies. Something so simple any shipyard can install. Something so durable you would need a cutting torch to get it to fail.

One thing I do agree with other posters on - more research needs to be conducted on liquefaction so as to install a more minimal set of baffles.

Solution

[Anonymous Coward]

Install baffles in the hold

Comment removed

[account_deleted]

Comment removed based on user account deletion

Liquid Evil

[mentil]

So THIS is why the TSA only allows a few ounces of liquids on carry-on. Down with those fucking liquids! I'm doing my part by boycotting all liquids, for approximately the next three days.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Mystery...

[Anonymous Coward]

I know that RTFA is a bit of a faux pas, but I did and I'm confused. Wet granular solids liquefy, causing ships to list dangerously and sometimes sink. Which part is the mystery?

So Compartmentalize the hold. There fixed it for u

[Anonymous Coward]

Seriously, if you have a problem with shit moving around, then make sure it's less mobile by compartmentalising the hold *more* until this shit can't happen even if it's liquefied repeatedly. Sort out the loading and unloading problem (it's /really/ not that hard)

Removable noughts and crosses style vertical baffles should do this a piece of piss.

The well known solution...

[Anonymous Coward]

...is rejecting wet cargoes. It's commercial pressure that needs to be solved.

Baffles aren't a good solution. They would hugely complicate loading and unloading, vastly increase vessel complexity, cost, maintenance and crew requirements. Possible but impractical. Gone are the days you could just send the deck apes below to ship shifting boards.

Liquefaction

[Brett Buck]

Note that it doesn't really turn into a liquid - it turns into individual particles that as a group and flow and appear to act much like a liquid. TFS (and TFA) slightly confuse the issue by suggesting or implying that the water turns it into something like mud. The same thing is possible in materials that are effectively free of water, it's just vanishingly unlikely.

      The same effect can happen during earthquakes on "landfill" like most of the land around the edges of the SF Bay area.

     

Old tankers

[Anonymous Coward]

This explains, at least to me the comment on another site that the conversion of tankers to bulk carriers is a bad idea. Lack of baffles.
www.fleetmon.com/maritime-news/2018/21601/stellar-daisy-lifeboat-spotted-deep-atlantic-almos/
www.fleetmon.com/vessels/stellar-daisy_9038725_27132/

It's not a mystery

[nospam007]

...if they know why and how it happens.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Comment removed

[account_deleted]

Comment removed based on user account deletion

Danger to the crew?

[mu51c10rd]

it is still causing ships to sink and taking their crew with them.

Are crews actually being lost? Seems like it wouldn't sink so fast that they wouldn't be able to abandon ship to lifeboats first. That seems a bit dramatic unless the ships capsize so suickly there is no hope for reaching the boats.

Re:Danger to the crew?

[Anonymous Coward]

Seems like it wouldn't sink so fast that they wouldn't be able to abandon ship to lifeboats first.

The ocean is a pretty inhospitable place.

Getting into a lifeboat and successfully launching it from an unstable ship is far from easy.
And even if you do manage to launch the lifeboat, that's far from a guarantee of recue in hostile locations like mid-ocean, or in stormy seas, or in rough coastal waters.

Re: This makes it sink? - A Solution?

[Darinbob]

They're not in containers. They solids are directly into the hold, so it acts like a giant dump truck filled with sand.

"quayside"

[Anonymous Coward]

Today I learned the word "quayside."