
Cargo ships that sink when their cargo suddenly liquefies - YeGoblynQueenne
https://theconversation.com/mystery-of-the-cargo-ships-that-sink-when-their-cargo-suddenly-liquefies-101158
======
hectorr1
If you want a quick primer on buoyancy physics and ship design, Marine Insight
has a good writeup:

[https://www.marineinsight.com/naval-architecture/intact-
stab...](https://www.marineinsight.com/naval-architecture/intact-stability-of-
surface-ships/)

As the article mentioned, wave action will cause the center of gravity (CG) of
the liquid to shift, and with it the overall ship's CG. This puts the ship in
a new stable equilibrium heeled over to that side. If the compartment isn't
dewatered, this process can repeat until the 'stable' equilibrium includes
upper decks taking on sea water. CG shifts up, righting arm becomes flipping
arm, hull experiences stress beyond tolerances, breaches kill remaining
buoyancy, and down she goes.

By the way, the easiest way to tell if a ship is in danger of hitting critical
(aka neutral aka very very bad) stablility, watch how long it takes to rock
from side to side. A ship that has an excessively long roll period and appears
to be hanging to one or both sides can in serious danger.

~~~
eecc
Segmenting the cargo hold? Not necessarily all the way to the bottom, just
enough of disrupt superficial sloshing?

~~~
cwkoss
I wonder if sheets of a cloth-like material could be used in loading similar
to Mechanically Stabilized Earth

Practical Engineering has a great video on this simple but pervasive
technology.
[https://www.youtube.com/watch?v=0olpSN6_TCc](https://www.youtube.com/watch?v=0olpSN6_TCc)

------
pasta
This is a very old problem and solutions and knowledge has been available for
over 20 years.

But I think the main problem is cost: not waiting for the rain to clear, not
making time to install temporary bulk heads, and so on.

Edit. for example this article from 1998:
[http://www.gard.no/web/updates/content/52980/shifting-
solid-...](http://www.gard.no/web/updates/content/52980/shifting-solid-bulk-
cargoes)

~~~
soneil
That was my first thought too. Shipping liquids is a solved problem. You
baffle containers to limit shifting and slapping. Doing the same for dry bulk
seems like a no-brainer? There must be a consideration I'm entirely missing.

~~~
VLM
Normalcy bias. Its the oldest killer in the world.

Dry goods are supposed to be dry... soak wheat in fresh or salt water for a
couple weeks you may as well dump it in the ocean, its rotted (its brewing,
technically). The problem is SOME dry goods (bauxite, etc) are not the driest
to begin with and of course the usual leaks and accidents.

The crew knows exactly what to do if there's a storm or the engine stops or a
fire breaks out, but dry goods are supposed to be dry, so when they aren't,
the blind spot kills the crew. You could give up training for storms or fires
to run liquefaction drills, but that'll kill more people on long term average,
because storms are more common than weird cargo issues. Even if labor money is
no object, brains can only hold so much at one time.

~~~
craftyguy
> You could give up training for storms or fires to run liquefaction drills,

Why do you have to do one or the other? ¿Por que no los dos?

~~~
dredmorbius
Time. Training time is limited, nonfungible, and rivalrous. Adding material at
one end sacrifices it at another, ssomething has to give: other parts of the
curriculum, or prodctive time.

There's a similar problem, at scale, for civilisation as a whole. Given a
lifespan of 85 years, and working span of 65, we spend 18 years on basic
education. The managing/professional class need another 4-6 for undergraduate
education, plus 2 for professional degrees, 6-12 for engineering and some
medical specialties. We're drawing people into the workforce in their late
20s, early 30s, and hope to get 30-40 years contribution.

At the same time, technology, or practices, or standards, obsolete much that
information in 10-15 years.

How many times do you, and can you, effectively retrain someone before their
prior knowledge is an inescapable impediment, and there's no useful retraining
benefit regardless. Confound further with the distiction between explicit
(book-learned) and taxit (experiential) knowwledge. The first can be
effectvely taught through technical reproduction: lectures, books, A/V,
computer-distributed or aaided materials. The latter requires small-ratio
master-student raatios for transmission. Skills lacking sufficient masters (or
those effective at training) die out.

------
userbinator
I find it sad that the article speaks of "new technology" and proposes lots of
complex (thus error-prone and not cheap) solutions, when the very simple
solution has been known for a very very long time:

[https://en.wikipedia.org/wiki/Free_surface_effect#Mitigation](https://en.wikipedia.org/wiki/Free_surface_effect#Mitigation)

Keep the cargo in containers which are always full or nearly so. If it doesn't
have room to slosh around or shift, it won't.

The added bonus is that it costs less per volume to ship, if the vessel is
always full.

~~~
jonny_eh
And/or load less of the stuff onto a ship. I'm surprised that wasn't suggested
either.

~~~
glenneroo
I believe it was mentioned, albeit somewhat indirectly:

> Commercial agendas also play a role. For example, pressure to load vessels
> quickly leads to more hard loading even though it risks raising the water
> pressure in the cargoes. And pressure to deliver the same tonnage of cargo
> as was loaded may discourage the crew of the vessel draining cargoes during
> the voyage.

If crews don't want to dump some cargo to restore balance, they surely don't
plan to to ship less cargo.

------
itissid
So ship shakes. The aluminum ore, bauxite, turns to liquid due to pressure
increasing (or friction decreasing). Ore moves to one side of the ship.
Pressure drops as shaking subsides. Ship becomes side heavy and lists and
sinks. This is as weird as things can get with reality.

~~~
rory096
They refer to "the relatively new solid bulk cargo bauxite". Surely bauxite
shipping is as old as the advent of electrolysis (Hall–Héroult + Bayer
processes)?

~~~
hinkley
I think you guys are parsing that sentence as “relatively new cargo, bauxite”.
At the top of the article they define “solid bulk cargo” as a shipping jargon
term, for a fine granulated material. This seems like a dangerous misnomer to
me...

I’m assuming that means that historically, the refiner owner the pulverizing
equipment and shipped in bauxite rock or gravel as raw material. When you hear
of liquefaction in terms of earthquake damage, they are always talking about
saturation of fine materials. Saturated gravel doesn’t behave as badly as
saturated sand or clay.

------
johnnyletrois
This is called free surface effect with liquids and as has been mentioned by
other posts is a common and known problem with liquids. Free surface effect is
a core component of vessel stability and is part of maritime stability
education.

------
ChuckMcM
So here is a random observation for some enterprising grad student or postdoc;
is electric charge responsible for liquefaction on packaged solids?

Triboelectric charging is not well understood yet, it happens in dust storms
and volcanic eruptions where charge is transferred to particulates from the
air. As charge increases this results in "dry lightning" or other discharges.

If you wanted a research topic, I think you could look into the hypothesis of
whether or not a powdered material could be charged to exhibit liquid
properties.

Note that the way these bulk solids are loaded on to ships it typically by
conveyor belt where they then drop through the air (charging opportunity) and
then dropped into a conductive container (the hull of a steel ship).

If someone has looked into this already I'd love to read the paper on it.

~~~
contact_fusion
Liquefaction has nothing to do with triboelectricity.

The article has a pretty good description of how liquefaction proceeds: higher
pressure -> water present in material reduces contact between solid particles
-> material friction reduced -> material behaves like a fluid. If you want
more, find a book on basic rheology. I'm certain there are civil engineering
textbooks that contain the material.

Further, it does not stand to reason that charged materials would suddenly
acquire fluid properties. Solid materials are quite capable of sustaining
charge without changing their bulk properties. Prior to significant change,
local voltages would exceed the breakdown voltage and the charge would be
neutralized.

~~~
ChuckMcM
You are offering to do the experiment? The physics is pretty straight forward,
particles which share the same charge will repel each other, this will hold
them apart and allow them to 'slide past' each other just as diamagnetic
material float along a magnetic field.

------
winceschwab
So, this is kind of similar to the whole corn-starch-and-water non-newtonian
solid kind of problem, right? A little different, because this isn’t entirely
about mixtures, aqueous solutions or colloidal suspensions, but more about the
fundamental behavior of large quantities of particulate solid mass.

The title could differentiate between being a total loss at sea, versus
sinking while docked in a harbor, at least in terms of statistics and death.
Also, how is there not one picture of a listing ship in this article?

------
dk1138
Totally fascinating read. What's amazing to me is what the insurance costs and
payouts happening must be. I imagine the losses are staggering.

~~~
holmet
The losses are most prevalent on ULBCs, resulting in the biggest ships of all
capsizing.

Insurers work with ship regulators and ship owners to prevent this, as not
only does it mean they've lost the ship and cargo, but picking up a new ULBC
is not a quick process.

~~~
seem_2211
What's a ULBC?

~~~
jsjohnst
[https://en.m.wikipedia.org/wiki/Bulk_carrier](https://en.m.wikipedia.org/wiki/Bulk_carrier)

(Which uses this as it’s source:
[https://web.archive.org/web/20070408154846/http://www.nautin...](https://web.archive.org/web/20070408154846/http://www.nautinst.org/info/acrnm_abbrev.htm))

------
LeonM
Fascinating read!

Can this situation can be avoided if the loading bay has a cover/lid on top of
the material?

As long as the loading bay is 'full' (or the top is movable to fit the cargo)
the material won't be able to slosh around, thus preventing the situation
described in the article.

~~~
chillydawg
The usual solution, as with petrol tanks in cars and elsewhere, is to use
baffles. It effectively turns one large tank into several smaller ones and
stops the liquid from freely sloshing from one side to another. The sloshing
causes problems non-linearly with size of tank, so reducing one tank into 4 or
8 has a huge impact on the risks of sloshing. The partitions/baffles are
always vertical (although I expect aerospace baffles are a bit more fancy).

~~~
amelius
Yeah, but the original state of the material was solid. You can't
compartmentalize a solid unless you break it.

~~~
winceschwab
It’s not a true liquid, but rather solid dust mixed with trace amounts of
water. Drier than mud, but powder and rock that can shift in a fluid-like way.

It’s like an avalanche or rock slide.

~~~
hfdgiutdryg
The article mentions moisture several times, as well as draining moisture
during the trip. It also explains liquefaction in terms of water acting on the
solid, whereas I always thought it was just about granularity.

From the article, it doesn't sound like it's about trace amounts of water at
all. It sounds like water is somehow involved in the loading process...?

~~~
Retric
The liquid is simply acting as a lubricant. So, it takes a very small amount
to make a large difference. Really it's less soggy than simply damp.

~~~
hfdgiutdryg
So why do they mention draining?

------
_carl_jung
Why don't they treat this cargo under the assumption that it is a liquid and
transport it accordingly (e.g. in large barrels)? I mean this question
genuinely as someone with little knowledge of logistics.

~~~
holmet
Try putting 200,000 tons of coal into barrels, transport it, and then unbarrel
it at the other end. The extra cost and time would be massive.

~~~
lqet
What about just compartmentalizing the ship's cargo space?

~~~
holmet
They are also compartmentalised. Bulkers tend to have four or five large tanks
to hold stuff in.

------
vermontdevil
10 ships a year + 10 years = 100. Wow.

I’m guessing insurance going to be even more expensive now unless 10 ships a
year out of however many ships out there is minimal.

~~~
holmet
This has been a problem for decades and is already priced into the insurance.
It's also not a big part of the world fleet.

------
spurcell93
If I recall, this problem was used in "The Martian" by Andy Weir, when one of
the rockets carrying supplies failed. At high pressures, some of the cargo
liquified and the rocket exploded due to shifting weight distribution. It may
have been another book...

~~~
JshWright
Yep (spoilers), that was what happened to the rocket that was supposed to
bring supplies to Watney so that he could survive until the next scheduled
mission (prompting the crew currently returning to earth to "turn around")

------
pohl
This reminds me of the meme that goes "when I was a kid, I thought quicksand
was going to be a much bigger problem than it is."

------
lordnacho
Pardon my ignorance, but what would happen if you just divided the hold into
smaller compartments? That way sloshing would only move things slightly to one
side.

~~~
rriepe
It's already divided into smaller compartments, through the containers
themselves.

Think of a ship transporting prisoners in their own little cells. Then think
of all the prisoners working together to throw their weight against the walls
of the cells at just the right moment in an effort to sink the ship.

The prisoners would only have enough of an effect to make the guards a little
nervous. The ore sloshing around in the containers weighs tons and tons,
though, enough to actually sink the ship.

~~~
blt
but the article suggests that permanent accumulation in one side, rather than
transient force, is the cause.

------
peteretep
There's a very similar phenomenon as a plot point in Neal Stephenson's The
Baroque Cycle, involving waves in medieval Japan

~~~
gliese1337
I have read The Baroque Cycle, but it is _huge_ and my memory is imperfect.
Mind reminding me of the details of this plot point, so I don't searching
through the whole un-indexed stack of bricks on my bookcase? :)

~~~
dwater
When they are leaving Japan after trading the damascus steel ingots for
quicksilver, the Japanese fill all the quicksilver bottles to a level that
will cause it to slosh along with the same frequency, causing harmonic
resonance to sink the ship. Before leaving they open all of the bottles and
transfer the quicksilver so that they are filled to the top and can't slosh.
This is from memory and may not be completely accurate.

~~~
saltcured
Not only tuned to a common frequency but tuned to match a predominant wave
pattern in the mouth of the harbor they were departing.

I had a hard time reading this part, as the puzzle placement seemed so forced
and nonsensical to the plot. What did the Japanese gain from this stunt if it
worked? A sunken ship in their harbor leaking mercury from hundreds of smashed
jars...?

~~~
logfromblammo
I think the idea was to sink the ship by capsizing it, then bring up the
intact bottles with free divers. Any mercury leaks would immediately sink, and
would probably stay inside the hold of the ship long enough to recover it. If
it escaped, it would run into the nearest local minimum on the harbor bottom.
If rock bottom, just scoop it up into fresh bottles. If sandy bottom, scoop up
the sand with it and separate it on the surface.

So they keep the wootz payment, they recover the cargo, and they don't lose
reputation by just murdering the crew of a merchant vessel outright. If the
merchants capsize instead, that's a shame, and a result of poor seamanship,
and they'll just go ahead and pretend to be sad during the salvage operation.

------
Atreus
The loading and pseudo-solidification can cause residual internal stresses
that change the dynamic response so that a small signal input gets a big
change as a result.

I'd imagine that the exact values are not monitored, so that what is written
as "in the hold" and what is actually there are subject to natural variation,
which can be asymmetric, and thus theory and practice are not the same thing.

If seawater gets into the mix, it will have more water.

There are thermal phase changes in the liquefication. It can behave very
differently at 10 deg C warmer than one expects from 0 deg C warmer.

Over a relatively long trip, with agitation, the mean particle size is going
to change. Big particles are going to break into smaller particles. This is
going to change the liquefication physics.

------
failrate
Awesome. My boy and I were talking about liquefaction and phase solids last
night when he was showing me how the sea salt behaves as a solid in the shaker
(humid here) until he bangs on thr glass.

~~~
mcguire
Check out the physics of ketchup.

------
srtjstjsj
[https://www.youtube.com/watch?v=My4RA5I0FKs](https://www.youtube.com/watch?v=My4RA5I0FKs)

YouTube science educator Mark Rober's "Liquid Sand Hot Tub - Fluidized air
bed"

------
tomc1985
They mention that solids are stored in a sort of liquid suspension. Why is
that? I feel like a solid, airtight box (like a shipping ocntainer) 100% full
of sand wouldn't doo too much.

~~~
hermitdev
Ever moved a large pile of sand that's been stored outside? Once you get a
foot or so into it, there's going to be some moisture. It's not going to be
much by weight, but it's there. Of course, it's going to vary depending upon
environmental factors (humidity, temperature how recently it rained, etc).
That contributes partially to the liquefaction.

------
breitling
Interesting read. I thought all along that materials change state due to
temperature changes. Time to track down my teachers and show them this
article.

You learn something new everyday

------
nappy-doo
Although unlikely that liquefaction caused this wreck, my mind went first to
the SS Edmund Fitzgerald.

~~~
24gttghh
There appear to be many factors that went into that sinking: huge storm, 30-35
ft waves, possible rogue waves even larger; improperly secured hatch covers,
no water-tight bulkheads(!!); regulations that allowed overloading and
decreased freeboard, etc, etc.[0]

[0][https://en.wikipedia.org/wiki/SS_Edmund_Fitzgerald#Theories_...](https://en.wikipedia.org/wiki/SS_Edmund_Fitzgerald#Theories_on_the_cause_of_sinking)

------
vvpan
I don't understand the point of "two-phase" materials. Why would you add water
to ore?

~~~
tialaramex
First up, we're not talking about a soup here, this isn't like it's a litre of
water for every kilo of ore, it's just that it's enough to allow the solids to
move without the friction they'd incur if entirely dry.

Ore starts out as rock buried in the ground. So, you're going to need to get
that out of there. While you could do that with a bloke and a pickaxe I'm sure
lots of the processes actually involved add water, even if not terribly much.

Also, this stuff isn't expensive, it's basically just slightly valuable dirt,
so if it's stored somewhere they're not going to be keeping it in water-tight
containers, it'll be in an open truck, or an open freight car somewhere,
getting rained on.

Now, shipping dirty water across the ocean is pointless and costs money, so
it's not as though they're going to add more water just for fun, but if the
contracts involved don't specify that it has to be less than so-and-so much
water in the cargo, then it's nobody's job to ensure it isn't damp.

~~~
vvpan
Ah! Thanks. I imagined an intentional mix for some reason.

------
pvaldes
I was expecting a Sperm whale's reference somewhere ;-)

