[HN Gopher] Cryogenic CO2 could end rail delays caused by leaves...
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Cryogenic CO2 could end rail delays caused by leaves on the line
Author : azalemeth
Score : 64 points
Date : 2022-04-25 14:59 UTC (8 hours ago)
(HTM) web link (www.sheffield.ac.uk)
(TXT) w3m dump (www.sheffield.ac.uk)
| giantg2 wrote:
| "This is the first time that passenger trains have been used to
| clean the line anywhere in the world"
|
| This sounds unbelievable to me. Has there really never been a
| single occurrence of a passenger train clearing the tracks in
| history?
| chmod775 wrote:
| > Has there really never been a single occurrence of a
| passenger train clearing the tracks in history?
|
| I'm not sure if it was ever used while the train was also
| moving passengers, but I'm aware of at least a special cleaning
| wagon nicknamed "Schrubbi" operated by the S-Bahn Hamburg[1].
| It's a repurposed passenger wagon that contains a large water
| tank and uses pressurized water to clean tracks. In theory you
| could add that to a regular passenger train, subject to some
| speed limits (like the tech in the article), but in practice I
| don't know whether that ever happened.
|
| Because of the speed limit required to get decent results, I
| have doubts any such tech will be used outside of special
| cleaning trains...
|
| Also I suppose there's snow plows on passenger trains, though
| nowadays that's probably also (mainly) done by specialized
| trains. Does this[2] count as cleaning?
|
| [1]: https://s-bahn.hamburg/magazin/s-bahn/betrieb-und-
| technik/de...
|
| [2]: https://www.youtube.com/watch?v=V-Cb9x70gYQ
| Symbiote wrote:
| It wouldn't just be the special vehicle, but also the route.
|
| There's no point running it through long tunnels, but it does
| need to clean junctions and so on in an order that is
| unlikely to follow a passenger train's path.
| toss1 wrote:
| This looks like an excellent application for 'Dry Ice Blasting',
| which is essentially 'sandblasting' done with a different medium.
| For cleaning fouled surfaces and/or for preparing new surfaces
| for bonding or coating, there is a surprisingly large range of
| related technologies and materials, everything from near-diamond
| to soft like walnut shells. Dry Ice offers great advantages of
| leaving no solid residue itself, and being relatively mild on the
| underlying surfaces, while also having the extra boost of wedging
| slightly under the grime as a solid and then vigorously
| expanding, providing extra lifting action.
|
| Applying this to rail seems like a great idea, since the weight
| and mass of the apparatus is not really a problem in that
| situation.
|
| Cool stuff!
| xchaotic wrote:
| Is it not going to wear down the tracks at an accelerated rate
| though? (Which also implies delays for maintenance)
| extrapickles wrote:
| You use CO2 blasting to clean optics as it can be quite
| gentle when the system is tuned right. For some optical
| coatings, CO2 is pretty much the only way to mechanically
| clean them without damage.
| lostapathy wrote:
| No. Dry ice cleaning is nuts - you can calibrate the pressure
| and granular size to not damage the substrate. High end car
| blasters can clean 40 year old plastic and rubber parts with
| dry ice and make them look like new.
| danw1979 wrote:
| Glad the article doesn't sugar coat it and shows an actual photo
| of one of the ancient diesel clunkers in use by Northern.
| sschueller wrote:
| Something similar already exists and is in use for example in
| Zurich Switzerland. Some light rails (specifically the Forchbahn
| built by Stadler rail) have compressed air jets which clean/dry
| the track on wet days to help when the track is slippery. You can
| hear them going off when the train leaves on wet days especially
| on a hill and the wheels are spinning on the track.
|
| The jets may also mix in some chemical solution to help with
| adhesion but I don't know.
| iggldiggl wrote:
| Are you certain that those really are compressed air jets? The
| thing I'm familar with are _sanders_ - those are commonly
| operated via compressed air, too, but their goal isn 't
| blasting contaminants off the track, but rather just getting
| sand onto the rails in order to improve adhesion.
| sschueller wrote:
| I am not 100% certain. It could definitely be sand being
| sprayed. The old trains don't have it, only the newer ones. I
| just hear compressed air being sprayed under the train when
| it's wet and the train is skipping on the track. Something is
| being sprayed onto the track.
| zbrozek wrote:
| What makes solid CO2 better for the purpose than liquid nitrogen
| or just the high-pressure air or maybe air mixed with super-
| chilled water? I'm sure the folks involved have thought about
| alternatives, but I'm most curious what properties solid CO2 has
| that make it especially good.
| scratcheee wrote:
| liquid nitrogen would require better insulation at the least,
| since its much colder.
|
| I suspect they're also taking advantage of the fact that dry
| ice is solid, so they're effectively sand-blasting the track
| (rather than merely pressure-washing it), but they're using
| sand that helpfully sublimates into the atmosphere without
| leaving residue (or poisoning anyone).
|
| I imagine blasting sand or chemicals has the downside of
| leaving residue that can build up, meaning regular cleanup is
| required, and care required to use enough but not too much,
| with this you can spray as much as you can afford to buy/carry
| on the train and you don't have to worry about over-doing it.
|
| Dry ice blasting is already a thing, so I guess they just
| realised it was a particularly promising technology for this
| application.
| robbedpeter wrote:
| It's cheaper and safer using co2 pellets propelled with
| ordinary air than liquid nitrogen. It gets sufficiently cold,
| and sufficiently abrasive to freeze, shatter, and disperse the
| sap and plant fats and other sticky stuff. Co2 cleaners are
| used in high end auto cleaning and detailing, so there's
| established use, safety, and equipment out there.
|
| The use is novel, the tech is decades old.
| arcticbull wrote:
| The temperature alone - dry ice is only like -109F and sold
| at most Safeways for a few bucks a pound (and safe enough to
| ship via all standard postal carriers with nothing more than
| an optional sticker) while LN2 is -320F. That requires a
| completely different storage and handling protocol.
| robbedpeter wrote:
| Interesting rabbit hole, I can't find any detailed reasons
| why co2 is better or not to use LN2.
|
| LN2 might also then be too cold and affect the temper of
| the steel, or it might evaporate too quickly, requiring a
| lot more mass than co2. Or maybe it could be a perfectly
| fine alternative but the co2 pellet systems have market
| advantage.
| adhesive_wombat wrote:
| Temperature and injuries aside, a dewar of LN spilled in a
| room temperature enclosed space will boil and evaporate
| into an asphyxiating cloud very, very quickly. A box of dry
| ice dumped on the floor will take quite a bit longer to
| sublimate enough, partly because the phase change
| temperature is much higher, and also because thermal
| contact between a very low viscosity liquid and surfaces is
| very much higher than a solid pellet sitting on the
| surface.
|
| Nitrogen will also kill you silently, while you will
| definitely know when CO2 levels are getting high (because
| it really really hurts).
| bitwize wrote:
| Neat. Maybe this will help reduce cold weather delays on the T?
| deegles wrote:
| How loud is it?
| _joel wrote:
| Interesting juxtaposition of technology, cryogenic CO2 spray
| heads on the rattler.
| aatharuv wrote:
| I wonder what the net carbon impact of this is. Use of
| _reclaimed_ Carbon Dioxide, that could allow for trains to not do
| a start/stop which uses large amounts of fuel (or even just
| electricity that might have been generated using fuel).
|
| Or would the trains have just stopped at their normal stop
| instead waiting for leaves to be cleared?
| namibj wrote:
| The trains would run slower or be cancelled entirely depending
| on whether they needed their adhesion to stop in time while
| going fast, in case traffic backed up and they'd be about to
| participate in a pile-up if they didn't stop fast enough, or
| whether they needed their adhesion to drive up/down slopes
| without slipping.
| colechristensen wrote:
| Wouldn't a powerful fan or a small spinning brush be mostly as
| good and much cheaper and simpler to deploy?
| danbruc wrote:
| This is what I was also initially thinking, but after a bit of
| reading [1] I quickly learned that the actual problem is not
| some leafs neatly sitting on top of the rails but leafs being
| turned into a wet grime [2] that gets worked into the surface
| and makes the rails really slippery. Other candidate solutions
| for the problem are plasma and laser treatments, so I think
| they considered using fans and brushes before. The problem is
| probably closer to removing oil stains from concrete than
| blowing leafs off the lawn.
|
| [1] https://www.railengineer.co.uk/cleaning-the-rail-head/
|
| [2] Non-native speaker, not sure if that is the proper term.
| StillBored wrote:
| Yah, its pretty clear from those pictures its not the leaf
| but the resulting compressed pulp, which looks pretty similar
| to the stuff I spray off my driveway every year with a
| 3200psi pressure washer. That i largly a mix of leaf/etc with
| black mold, which actually grows into the concrete pores.
|
| Which makes me wonder why no one bothered to try something
| like that, are pressure washers common in the UK? Mine is
| hardly the highest PSI, and it frequently needs to be turned
| down because at that pressure it can actually etch soft
| concrete. And at 2.5GPM its not using a lot of water either.
| jrockway wrote:
| Pressure washers are the current solution to this problem.
| Here's a news article about the LIRR switching from a 4000
| PSI pressure washer to a 20000 PSI pressure washer:
| https://www.amodernli.com/lirr-launches-new-tech-to-fight-
| le... (From 3 years ago.)
| OJFord wrote:
| Great link, more informative (even if not so newsy) than the
| submission IMO.
|
| And that's a fine term for it.
| jeroenhd wrote:
| The problem isn't just a bunch of leaves, it's the pulp that
| gets generated by a layer of leaves that gets run over by heavy
| trains several times an hour. That pulp is particularly
| difficult to remove.
|
| There are existing solutions for this, of course. For example,
| the Dutch railways deploy a mush of sand, potato fibers and
| iron particles on top of the mush to give trains the necessary
| grip when they brake while they take the caked on goop with
| them at the same time. This solution can be applied by separate
| trains running at relatively high speeds.
|
| This approach, like the novel CO2 approach, has advantages and
| disadvantages, but it should be clear that "just attach a fan
| and a brush to the front" isn't going to cut it. You'd need a
| hell of a fan to blow sticky mush off the tracks at 60-65mph
| (average UK train speeds).
| iggldiggl wrote:
| > For example, the Dutch railways deploy a mush of sand,
| potato fibers and iron particles on top of the mush to give
| trains the necessary grip when they brake
|
| That sounds like Sandite, which is definitively in use on the
| UK rail network. But I think the cleaning effect of that is
| still relatively limited, and the adhesion improvement only
| lasts a certain number of trains, after which the material
| needs to be re-applied again to the track.
| brink wrote:
| I'd think the brush would muck up
| alar44 wrote:
| Ok so use a piece of metal?
|
| I really really don't understand how leaves are an issue with
| trains.
|
| Anyone know why they can't just use a cowcatcher like device?
| jandrese wrote:
| I'm guessing not all of the tracks are welded rails and so
| they have expansion joints, which means a cow catcher like
| device trying to scrape a rail clean might hang up on a
| joint and get destroyed. Plus it would wear down quickly
| with the metal on metal contact.
| robbedpeter wrote:
| It's the sticky crap - sap, cellulose, sugars, plant fats.
| This can fix larger debris in place, accelerating pitting
| and weathering of the rail. The co2 pellets freeze the
| sticky crap, which then gets shattered and dispersed,
| leaving clean bare metal behind. A scraper or brush would
| leave nasty residue.
| robertlagrant wrote:
| https://www.forbes.com/sites/lauriewinkless/2021/10/27/why-
| l...
| kodah wrote:
| The problem isn't necessarily the leaves but the cellulose
| that's driven out of the leaf and onto the steel rail when
| it's run over. Additionally, the steel wheels of a train
| get _really_ hot and probably turn the cellulose (and
| whatever else is in a tree leaf) into a pretty hard to deal
| with substance that coats the rail and (likely) the wheel.
| That makes braking difficult and can probably contribute to
| safety problems.
| chipsa wrote:
| It's not leaves on the line that are in a pile, it's leaves
| on the line that get smashed onto the rail, and make the
| already low friction rails even lower friction. If you
| can't stop and you can't go, then the railroad isn't going
| to take you anywhere.
| throwaway0a5e wrote:
| Trains run over a stupendous amount of debris. A more involved
| mechanical solution would just break more.
|
| If a simple mechanical solution worked they'd have implemented
| it a century ago.
| davidhyde wrote:
| > "The system is also much better for the environment as it uses
| reclaimed carbon dioxide."
|
| That is most likely not the reason it is cleaner as releasing
| captured carbon dioxide back into the atmosphere is kind of
| polluting isn't it! I think it's supposedly cleaner because the
| alternatives like blasting the tracks with additives and sand is
| worse but they don't really say why.
| chrisco255 wrote:
| No CO2 is not a pollutant. It is an essential gas for life
| itself.
| cogman10 wrote:
| Water is essential for life. That doesn't mean you can't
| drown in a swimming pool.
| bitwize wrote:
| When there's excess of it heating up the planet, it's a
| pollutant.
| chrisco255 wrote:
| We're talking spraying rail lines with CO2. It's not going
| to heat the planet. That's like dropping a table shaker of
| salt in the ocean and worrying about the impact on
| salinity.
|
| https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-
| fer...
| horsawlarway wrote:
| If you watch the video in the article, they briefly mention it
| - Basically, they're using captured CO2 that would have been
| released anyways, from industries like brewing.
|
| And they mention it's better than the sand approach since
| they're not leaving a contaminate around afterwards, since the
| CO2 will just sublimate back into gas, both which improves the
| cleaning and makes it more consistent when done repeatedly.
|
| The movie is still borderline sales-pitch, so I'd take it with
| a grain of salt, but it adds some detail.
| danuker wrote:
| > that would have been released anyways
|
| By any chance, does money change hands? "Carbon credits"?
|
| Guess what! I'll start a brewery and brew billions of tons of
| CO2 unless you pay me!
|
| The carbon credit industry is a scam, and it does not
| actually affect the CO2 concentration in the atmosphere.
| aeternum wrote:
| It might be a scam as currently implemented but doesn't
| need to be.
|
| Cap and trade worked very well for CFCs. In your example,
| why doesn't the brewery need to pay a tax for the CO2
| released both in manufacture and as part of product-use?
| MobiusHorizons wrote:
| To be fair, in order to produce co2 as a brewer, you must
| first have a sugar source for the yeast to eat. This is
| typically grain, which captures the co2 from the air using
| solar energy. Farming clearly also has an impact on the
| environment requiring energy and water to produce and
| transport, but the co2 locked up in that grain would be
| released to the environment most of the other ways that
| grain could get metabolized. Seems like not that bad of an
| outcome really.
| gorkish wrote:
| Well the entire supply chain for commercial CO2 is
| "reclaimed" so anything they have to say on the matter is
| entirely for the purpose of spin.
|
| They needed something solid that can sublimate and be
| relatively safe. Media blasting with CO2 is really a super
| common thing everywhere in industry. I could drive over to
| Grainger and buy a CO2 blasting machine today.
| cogman10 wrote:
| It's an unfortunate effect of some climate change worries.
| We have a problem with letting "Perfect" be the enemy of
| "Good".
|
| Far too many people worry about the 100lbs of CO2 emitted
| because of rail cleaning while ignoring the fact that a
| diesel train is spewing (literally) tons of CO2 in the
| atmosphere. And the trains are one of the best options for
| low carbon shipping!
| mlindner wrote:
| You missed what the original poser was saying. Their point
| was that if you're capturing the CO2, it's better to keep it
| captured, rather than just releasing it again.
| cure wrote:
| s/poser/poster/, presumably!
| mcronce wrote:
| I guess it's better than, like, burning something specifically
| for the purpose of capturing CO2 to put in a tank on the
| railways...but has anybody ever actually proposed that?
| jandrese wrote:
| There was one proposal to use a high power blowtorch device
| to burn off the crud ahead of the train, but it had a number
| of problems and never went anywhere. The lasers were an
| evolution of this, but they have their own issues.
| xchaotic wrote:
| Obviously they forgot to add Sharks. Sharks with lasers is
| the ultimate solution.
| mrlonglong wrote:
| Just in time for Sharknado 6 then!
| hetspookjee wrote:
| I belief the Netherlands uses a high powered laser much like
| a rust removal laser in some parts. But it's not widely
| rolled out. On the co2 argument. The release of the co2
| itself is one thing. But keeping it cryogenic and applying it
| isn't free either. Not sure if it's more energy intensive
| than a high powered laser though.
| Terry_Roll wrote:
| So freezing the surface of the rail so the detritus freezes and
| disintegrates should do alright, but I wonder how the line or
| section of line could get taken out of action when the line is
| already below freezing. Wouldn't it become a layer of ice then,
| or is that when we get the laser out to heat the rails?
| dihydro wrote:
| It's more like sand blasting, but with dry ice instead of sand.
| This has been used for paint prep in industry and automotive
| for some time now. https://en.wikipedia.org/wiki/Dry-
| ice_blasting
| sandworm101 wrote:
| This isn't just freezing. Dry ice is far colder than wet ice.
| Whether the ambient temperature is above/below 0c won't make
| that much difference.
|
| The lasers were never meant to heat the rails. Heating a shiny
| metal is very difficult. The leaf-cleaning laser system works
| specifically because it doesn't heat the metal. It bounces off
| the metal surface, heating only the non-shiny gunk on the rail.
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