8 ms·

Cryogenic CO2 could end rail delays caused by leaves on the line

73 points by azalemeth 5y ago

colechristensen 5y ago
Wouldn't a powerful fan or a small spinning brush be mostly as good and much cheaper and simpler to deploy?
- brink 5y ago
  I'd think the brush would muck up
  - alar44 5y ago
    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?
    - chipsa 5y ago
      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.
    - robertlagrant 5y ago
      https://www.forbes.com/sites/lauriewinkless/2021/10/27/why-leaves-on-the-line-cause-problems-for-trains/ https://www.forbes.com/sites/lauriewinkless/2021/10/27/why-l...
    - jandrese 5y ago
      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.
    - kodah 5y ago
      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.
    - robbedpeter 5y ago
      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.
- throwaway0a5e 5y ago
  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.
- danbruc 5y ago
  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/ https://www.railengineer.co.uk/cleaning-the-rail-head/ [2] Non-native speaker, not sure if that is the proper term.
  - OJFord 5y ago
    Great link, more informative (even if not so newsy) than the submission IMO. And that's a fine term for it.
  - StillBored 5y ago
    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 5y ago
      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-leaf-season/ https://www.amodernli.com/lirr-launches-new-tech-to-fight-le... (From 3 years ago.)
- jeroenhd 5y ago
  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 5y ago
    > 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.
  - heywoodlh 5y ago
    Thanks for this explanation. The article didn't do a good job at explaining why leaves were such a problem -- it just repeated that it was a big problem. Maybe it should have been obvious but it definitely wasn't to me!
  - arantius 5y ago
    But why is a brush/blade on _every train_ not good enough? Remove the leaves before they turn into a sticky pulp?
giantg2 5y ago
"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 5y ago
  > 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/der-herbst-der-herbst-der-herbst-ist-da.html https://s-bahn.hamburg/magazin/s-bahn/betrieb-und-technik/de... [2]: https://www.youtube.com/watch?v=V-Cb9x70gYQ https://www.youtube.com/watch?v=V-Cb9x70gYQ
  - Symbiote 5y ago
    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.
davidhyde 5y ago
> “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.
- mcronce 5y ago
  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 5y ago
    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 5y ago
      Obviously they forgot to add Sharks. Sharks with lasers is the ultimate solution.
      - mrlonglong 5y ago
        Just in time for Sharknado 6 then!
  - hetspookjee 5y ago
    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.
- 5y ago
sschueller 5y ago
Something similar already exists and is in use for example in Zürich 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 5y ago
  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 5y ago
    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.
toss1 5y ago
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 5y ago
  Is it not going to wear down the tracks at an accelerated rate though? (Which also implies delays for maintenance)
  - lostapathy 5y ago
    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.
  - extrapickles 5y ago
    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.
zbrozek 5y ago
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.
- robbedpeter 5y ago
  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 5y ago
    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 5y ago
      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.
      - flaviut 5y ago
        CO2 density: 1562 kg/m^3 Sand density: 1520-1680 kg/m^3 LN2: 806 kg/m^3 CO2 is just disappearing sand as far as these systems are concerned. They probably use the same equipment that they use for sand. Plus LN2 is way colder and harder to handle and also it's a liquid.
bitwize 5y ago
Neat. Maybe this will help reduce cold weather delays on the T?
aatharuv 5y ago
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 5y ago
  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.
Terry_Roll 5y ago
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 5y ago
  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 https://en.wikipedia.org/wiki/Dry-ice_blasting
- sandworm101 5y ago
  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.
_joel 5y ago
Interesting juxtaposition of technology, cryogenic CO2 spray heads on the rattler.
danw1979 5y ago
Glad the article doesn't sugar coat it and shows an actual photo of one of the ancient diesel clunkers in use by Northern.
deegles 5y ago
How loud is it?
ggm 5y ago
my second or first trip back to the UK from OZ in the 90s, we got stuck at Kings X because of "leaves on the line" and I remember how we cracked up laughing at the image of the entire network stalled because of leaf litter, but in truth its a real problem. Rail corridors are some of the last vestiges of semi-wild connected space in the UK, since they stopped spraying herbicide. This in turn was responsible for the extent of what londoners call "fire weed" into northern britain -Rose Bay Willowherb: it was a southern plant, carried by wind borne dispersal of seed due to trains passing along the lines.
drjasonharrison 5y ago
Long Island Rail Road has been testing and using high powered lasers to clear the pectin from the rails. Explanation of the problem and the solutions: https://www.youtube.com/watch?v=zL21bWhNsv0 https://www.youtube.com/watch?v=zL21bWhNsv0 https://new.mta.info/LIRR-Industry-Leading-Leaf-Fighting-Technology-Fewer-Delays-and-Cost-Savings https://new.mta.info/LIRR-Industry-Leading-Leaf-Fighting-Tec... https://getpocket.com/explore/item/choo-choo-pew-pew-how-a-new-york-railroad-uses-scorching-lasers-to-stay-on-schedule?utm_source=pocket-newtab https://getpocket.com/explore/item/choo-choo-pew-pew-how-a-n...
tejtm 5y ago
I can't imagine it is for the same reasons but frozen CO2 is used to clean telescope mirrors without damaging them https://en.wikipedia.org/wiki/Carbon_dioxide_cleaning https://en.wikipedia.org/wiki/Carbon_dioxide_cleaning

73 points by azalemeth 5y ago

colechristensen 5y ago

Wouldn't a powerful fan or a small spinning brush be mostly as good and much cheaper and simpler to deploy?

brink 5y ago
I'd think the brush would muck up
- alar44 5y ago
  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?
  - chipsa 5y ago
    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.
  - robertlagrant 5y ago
    https://www.forbes.com/sites/lauriewinkless/2021/10/27/why-leaves-on-the-line-cause-problems-for-trains/ https://www.forbes.com/sites/lauriewinkless/2021/10/27/why-l...
  - jandrese 5y ago
    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.
  - kodah 5y ago
    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.
  - robbedpeter 5y ago
    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.
throwaway0a5e 5y ago
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.
danbruc 5y ago
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/ https://www.railengineer.co.uk/cleaning-the-rail-head/ [2] Non-native speaker, not sure if that is the proper term.
- OJFord 5y ago
  Great link, more informative (even if not so newsy) than the submission IMO. And that's a fine term for it.
- StillBored 5y ago
  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 5y ago
    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-leaf-season/ https://www.amodernli.com/lirr-launches-new-tech-to-fight-le... (From 3 years ago.)
jeroenhd 5y ago
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 5y ago
  > 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.
- heywoodlh 5y ago
  Thanks for this explanation. The article didn't do a good job at explaining why leaves were such a problem -- it just repeated that it was a big problem. Maybe it should have been obvious but it definitely wasn't to me!
- arantius 5y ago
  But why is a brush/blade on _every train_ not good enough? Remove the leaves before they turn into a sticky pulp?

giantg2 5y ago

"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 5y ago
> 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/der-herbst-der-herbst-der-herbst-ist-da.html https://s-bahn.hamburg/magazin/s-bahn/betrieb-und-technik/de... [2]: https://www.youtube.com/watch?v=V-Cb9x70gYQ https://www.youtube.com/watch?v=V-Cb9x70gYQ
- Symbiote 5y ago
  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.

davidhyde 5y ago

> “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.

mcronce 5y ago
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 5y ago
  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 5y ago
    Obviously they forgot to add Sharks. Sharks with lasers is the ultimate solution.
    - mrlonglong 5y ago
      Just in time for Sharknado 6 then!
- hetspookjee 5y ago
  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.
5y ago

sschueller 5y ago

Something similar already exists and is in use for example in Zürich 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 5y ago
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 5y ago
  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.

toss1 5y ago

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 5y ago
Is it not going to wear down the tracks at an accelerated rate though? (Which also implies delays for maintenance)
- lostapathy 5y ago
  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.
- extrapickles 5y ago
  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.

zbrozek 5y ago

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.

robbedpeter 5y ago
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 5y ago
  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 5y ago
    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.
    - flaviut 5y ago
      CO2 density: 1562 kg/m^3 Sand density: 1520-1680 kg/m^3 LN2: 806 kg/m^3 CO2 is just disappearing sand as far as these systems are concerned. They probably use the same equipment that they use for sand. Plus LN2 is way colder and harder to handle and also it's a liquid.

bitwize 5y ago

Neat. Maybe this will help reduce cold weather delays on the T?

aatharuv 5y ago

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 5y ago
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.

Terry_Roll 5y ago

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 5y ago
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 https://en.wikipedia.org/wiki/Dry-ice_blasting
sandworm101 5y ago
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.

_joel 5y ago

Interesting juxtaposition of technology, cryogenic CO2 spray heads on the rattler.

danw1979 5y ago

Glad the article doesn't sugar coat it and shows an actual photo of one of the ancient diesel clunkers in use by Northern.

deegles 5y ago

How loud is it?

ggm 5y ago

my second or first trip back to the UK from OZ in the 90s, we got stuck at Kings X because of "leaves on the line" and I remember how we cracked up laughing at the image of the entire network stalled because of leaf litter, but in truth its a real problem. Rail corridors are some of the last vestiges of semi-wild connected space in the UK, since they stopped spraying herbicide. This in turn was responsible for the extent of what londoners call "fire weed" into northern britain -Rose Bay Willowherb: it was a southern plant, carried by wind borne dispersal of seed due to trains passing along the lines.

drjasonharrison 5y ago

Long Island Rail Road has been testing and using high powered lasers to clear the pectin from the rails. Explanation of the problem and the solutions: https://www.youtube.com/watch?v=zL21bWhNsv0 https://www.youtube.com/watch?v=zL21bWhNsv0 https://new.mta.info/LIRR-Industry-Leading-Leaf-Fighting-Technology-Fewer-Delays-and-Cost-Savings https://new.mta.info/LIRR-Industry-Leading-Leaf-Fighting-Tec... https://getpocket.com/explore/item/choo-choo-pew-pew-how-a-new-york-railroad-uses-scorching-lasers-to-stay-on-schedule?utm_source=pocket-newtab https://getpocket.com/explore/item/choo-choo-pew-pew-how-a-n...

tejtm 5y ago

I can't imagine it is for the same reasons but frozen CO2 is used to clean telescope mirrors without damaging them https://en.wikipedia.org/wiki/Carbon_dioxide_cleaning https://en.wikipedia.org/wiki/Carbon_dioxide_cleaning