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Cargo ships that ‘liquefy’ (2018)
- Scoundreller 7y ago> about the possible liquefaction of the relatively new solid bulk cargo bauxite (an aluminium ore). Is bauxite really new cargo? Or do they mean ship-operators need to be careful when switching to bauxite cargo? And any particular reason for loading these cargoes with water? Why not dry?
- jacobush 7y agoI think this is the lead: "The International Maritime Organisation has codes governing how much moisture is allowed in solid bulk cargo in order to prevent liquefaction. So why does it still happen? The technical answer is that the existing guidance on stowing and shipping solid bulk cargoes is too simplistic."
- Brian_K_White 7y agoAt a guess, it's probably easier to pump slurry than to shovel dry material. Maybe also dust.
- raws 7y agoSounds like they may want to remove water out of the cargo for transport and pump it back in for unloading
- nicthesailor 7y agoYes for the first part, but we definitely don't want to pump it back in for discharge. Dry bulk cargo is almost always discharged with grabs and cranes, not pumps.
- scoot 7y ago”[...] if, as is common practice, the cargo is loaded with a conveyor belt from the quayside into the hold.” So, no.
- jmts 7y agoIs bauxite really new cargo? Or do they mean ship-operators need to be careful when switching to bauxite cargo? My read on it was that bauxite was new as a solid bulk cargo, not that bauxite itself was a new cargo in general. I know nothing of the industry however, so I'm not sure whether this is a legitimate interpretation or not.
- jschwartzi 7y agoAt a guess, they have to do the loading, hauling, and dumping outside in all weather and also probably barge it out to the hauler in some cases. All of these things can add a significant amount of water to an otherwise "dry" solid.
- nicthesailor 7y agoSeafarer here. This is basically correct, but the problem is mainly storage before loading. Ideally, is mined, then either stored somewhere dry, out of the weather, or delivered directly to the ship in a covered train/conveyor belt. In reality, it's usually mined, then stored in a big pile outside in the weather for weeks/months until it's loaded. It won't pass the pre-loading transportable moisture limit (TML) tests, so they falsify the results. A cargo with a slightly high TML can appear dry on loading, but the vibration causes the moisture to migrate down to the bottom of the hold and cause the cargo at the bottom to liquify. When the ship rolls, this layer shifts, and the rest with it. Obviously, if the TML is way too high, the whole thing turns to slurry.
- russfink 7y agoCan they just pump the water out?
- nicthesailor 7y agoTo pump out, we need it to settle out of the cargo so that we can get it to the pumps. That works for certain types of cargo (iron ore and most types of coal are easy), but if it forms slurry instead, we can't get it out unless we can somehow pump the slurry out. Normal bilge pumps can't cope with slurry.
- deleted 7y ago[deleted]
- dwater 7y agoReposted by the BBC from The Conversation: https://theconversation.com/mystery-of-the-cargo-ships-that-sink-when-their-cargo-suddenly-liquefies-101158 https://theconversation.com/mystery-of-the-cargo-ships-that-... Discussion of the original article: https://news.ycombinator.com/item?id=17884382 https://news.ycombinator.com/item?id=17884382
- ClintEhrlich 7y agoFunny, I posted this today specifically because HN prompted me to. Not sure what led to my submission of the BBC article from 10 months ago being targeted for a re-post. But thanks for the link to the earlier discussion!
- mlurp 7y agoInteresting article, but the sporadic bolding of a few words is killing me: >The International Maritime Organisation has codes governing...
- ryandvm 7y agoI don't get it. The IMO is the organization that regulates international shipping.
- Bjartr 7y agoThose are actually links, but they've decided to sure them in a way that hides that for some reason
- DoreenMichele 7y agoBased on a spot check of some of the bolded words, bolding seems to be used here to highlight links. The old way of indicating "this is a link" was underlining. That seems to have largely fallen out of favor and most websites seem to use color coding these days.
- mlurp 7y agoAhhhh, that makes sense. I'm on mobile. The choice of "bolded" words seemed to make no sense...
- ohazi 7y agoWhat about anti-slosh baffles?
- err4nt 7y agoThis might be a stupid question - but could ships tug or tow their cargo, and let it roll around?
- hirundo 7y agoI'd think that towing anything in violent weather would be dangerous. If self propelled rather than towed your idea becomes a merchant submarine. That would have to greatly complicate things and be slower and/or use much more fuel.
- gpm 7y agoIt doesn't have to be underwater to be either towable or self propelled. See the other comment about barges on the Mississippi for towing and SpaceX's "of course I still love you" (and friends) for self propelled. Autonomous and underwater would be hard, radio doesn't travel well through water.
- TeMPOraL 7y ago> Autonomous and underwater would be hard, radio doesn't travel well through water. You mean "remote-controlled and underwater"? As "autonomous" kind of implies not being in need of constant communication.
- gpm 7y agoNo, I mean autonomous too. Autonomous vehicles still want access to GPS, you still want to know where your stuff is, you still want to be able to give new orders if something changes, etc.
- superice 7y agoThey're not only common on the Mississippi, but also the Rhine area in the Netherlands and Germany as hinterland operations for the port of Rotterdam, as well as the Danube area in eastern Europe. Both self-propelled barges and push barges have been used for ages already in inland shipping in Europe, but have not been used a lot in the rest of the world. They also seem to only be suitable for river transport. With small scale transport over sea you have so-called feeder ships, which have an entirely different build, and never push extra barges/ships.
- JackFr 7y agoAdd rice to the hold. Problem solved. https://en.wikipedia.org/wiki/Mr._Midshipman_Hornblower https://en.wikipedia.org/wiki/Mr._Midshipman_Hornblower "Hornblower and the Cargo of Rice"
- DoreenMichele 7y agoIs this just a joke? If not, do you have a better source to back up the suggestion? I'm asking because it's a fictional story and the sink ships because of the wet rice expanding. It doesn't actually save the ship, though it does likely delay its demise.
- m463 7y agoIt must be a joke because the rice took down the ship.
- DoreenMichele 7y agoThat's what I'm guessing, but I know basically nothing about cargo ships. I'm googling around to see if there are any potential prevention methods along the lines of "just add a bit of rice to your ore..." 0_o
- m463 7y agoI would assume if you dropped your cargo in water, putting it in rice should dry it out. Like your phone...
- JackFr 7y agoJoke
- jotm 7y agoThe TV series was great, btw.
- transitionnel 7y agoSeems like an effective solution to this would be to intentionally "thump" the hull at calculated nodes within the structure, resettling the cargo at calculated points in time when the ship is undergoing a motion within certain predicted bounds.
- crummy 7y agoIs this the same process that doomed the supply rocket to Mark Watney in The Martian?
- jschwartzi 7y agoPretty much.
- mnw21cam 7y agoI was going to point that out until I saw your comment, so yes.
- rolltiide 7y agowell that's terrifying the cargo containers should just vibrate the whole time to keep things in liquefied state throughout the whole trip.
- uponcoffee 7y agoThe amount of energy to vibrate 25-25000 tonnes for any extended duration of time would be staggering. Then you have to manage forces this subjects the ship to... maintence would be a fright
- ulrikrasmussen 7y agoCan't cargo hulls be compartmentalized to alleviate this? Or are the forces too great for this to be practical?
- simonh 7y agoCompartmentalisation is fine for liquid cargoes, but make it a lot harder to load and unload particulate solids like these because the walls and baffles get in the way.
- killjoywashere 7y agoThis problem is well understood in naval architecture. Some good engineering articles: https://en.wikipedia.org/wiki/Free_surface_effect https://en.wikipedia.org/wiki/Free_surface_effect https://en.wikipedia.org/wiki/Metacentric_height https://en.wikipedia.org/wiki/Metacentric_height tl;dr version as I recall: keep holds either mostly full or mostly empty, make assymetric holds and tanks, and use baffles if you have no other options.
- loneranger_11x 7y agoTrue but most of the research is around how to safely handle liquid cargoes. What the article talks about is 2-phase cargoes, cargoes which are expected to behave as solids but could turn to liquid under certain unpredictable conditions. Accounting for these scenarios might involve upsetting the economics of said cargo. Edge cases basically :D
- gingabriska 7y agoBut it seems it can be easily solved having dividers in cargo compartment. Think of box with a grid inside it Once the cargo is filled The grid lines are raised (hydraulics) which compartmentize the whole cargo into blocks. Invidual compartment will not have enough mass of material inside it to break the dividers if designed properly.
- dsfyu404ed 7y agoSounds expensive and complicated. It's probably cheaper to just have baffles and vacuum the cargo out. The status quo is cheaper still
- xyzzy_plugh 7y agowhy on earth does bbc.com redirect to http from https??
- hexadec 7y agoBecause they like to verify the integrity of the data they send you and HTTPS should be the default for all web traffic possible. https://https.cio.gov/everything/ https://https.cio.gov/everything/
- bzbarsky 7y agoYes, but the point is that if you load it over HTTPS they will redirect to HTTP. So if you type https://www.bbc.com/future/story/20180905-the-cargo-ships-that-liquefy https://www.bbc.com/future/story/20180905-the-cargo-ships-th... in your web browser url bar, you will end up at http://www.bbc.com/future/story/20180905-the-cargo-ships-that-liquefy http://www.bbc.com/future/story/20180905-the-cargo-ships-tha... instead. That's the somewhat-surprising part.
- zcat 7y agovideo demonstrates this https://www.youtube.com/watch?v=zdyrQSypPBQ https://www.youtube.com/watch?v=zdyrQSypPBQ
- nbevans 7y agoWhy not pump the 'water' out of the bulk into a separate containment vessel. This way the ship's crew could neutralise the risk without reducing the weight of their cargo. When unloading they can give back the 'water' component of the cargo separately. So the weight of the cargo is basically unchanged.
- RWSen 7y agoBecause the water would need to be separated from the sand grains. The "water" in the sand is very little: it's more akin to damp sand we're talking about, or in the "wettest" case mud. Drying that would require a lot of area, effort, and sun, or some type of oven. Any method of making sand drier costs orders of magnitutde more than the sand itself.
- deleted 7y ago[deleted]