Instead of the complications of a rotary dump system,,,, why don't they just vacuum the coal out of hopper cars at their destination?
Modeling the "Fargo Area Rapid Transit" in O scale 3 rail.
Time it takes to unload. 1-2 minutes for a rotary car dumper to unload a car compared t0 1 hour to vacucum out a car. We use pressure to force off our liquid tanks they can unload 5K gallons in less than 45 mins time. If the customer wants gravity unload we are talking 2 hours. On our plastic hoppers we can unload them with 15 psi we can unload 24 tons in less than 40 mins but then we areate the load before we open the valves.
Boyd Instead of the complications of a rotary dump system,,,, why don't they just vacuum the coal out of hopper cars at their destination?
Potentially, balancing the costs of a rotary dump facility against a vacuum sustem effect the decision of which system to be implemented. The rotary dump offers a higher volume of product movement in a shorter time. The vacuum system would require much more time, and a more complicated process (ie; it becomes a pretty expensive system to implement).
A pnematic OTR tanker is unloaded by an on-board blower ('trucker' pays for fuel,and unloading time, and also any equipment maintenance issues, if they should arise). It depends on the 'flow rate' of the product transported, as to the amount of time utilized in the unload. Generally, those 'loads' are gravity loaded while the truck is 'scaled' to gain its capacity.
Unloading from a railcar or other bulk source can be very 'trying' for the driver, as the load needs to be ' road legal'; not to mention time consuming, [ all sorts of 'variables', come into play,] in this scenario,in order to go to delivery. And at deliver, the driver may unload by 'b;owing off' the product into a silo type storage facility, or in a lot of cases with deliver of types of plastic pellets, he may have to "Box' the load off [ ie; into whatever system a plant may use to get its raw materials to the end use point... gaylord-type cardboad boxes, or metal type hopper boxes] This kind of unload become an industrial ballet; driver, employees of the receiver, containers, forklift(s), and physical location...stressful.
While on the subject of speed in delivery, do tank cars that carry molasses have heaters in them (especially useful in January delivery)?
Johnny
DeggestyWhile on the subject of speed in delivery, do tank cars that carry molasses have heaters in them (especially useful in January delivery)?
Don't know about molasses specifically, however 'molton sulphur' gets connected to steam sources at destination to ensure that the sulphur remains in liquid form for unloading. Suspect similar procedures may be employed for molasses in January (and most of the rest of the year).
Never too old to have a happy childhood!
Yes, Johnny, cars for stuff like molasses, corn syrup, asphalt, and such usually are insulated, and have steam coils in them. I'm not sure about the physics here, but I remember one time when we had a corn-syrup tank car with a defective system in it...what basically happened is that the steam in the coils cooked the load, solidifying it. Somebody had to buy that load and the car containing it. (Think about the "Fireless Cooker" technology--a little steam with a bit of pressure can work for a long time!)
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
Why do they have heating coils in them simple you try pumping out liquid that thinks it is a solid at 50 degrees when the temp is 0 outside it becomes peanut butter in the hoses. You add a little heat to the product and it flows right out of the tank car. Sulphar is actually solid unless it is heated above 220 degrees IIRC sorry been a while since I read the MSDS on pure elemental Sulphar for the melting point. It is pumped in liquid turns into a block of rock basically reheated into liquid and is pumped out of the cars.
BoydInstead of the complications of a rotary dump system, why don't they just vacuum the coal out of hopper cars at their destination?
Two reasons not so far mentioned:
1) Trituration. Coal grinds up against itself (this is where the 'coal dust fines' come from) and it is likely (to me) that any vacuum system going to a storage pile and not directly to bunkers/grinders/burners is going to cause considerable breakage and fines above what a simple gravity dump and conveying/loading would.
2) There's no such thing as a 'vacuum' system -- it's an induced-wind system. The amount of air that has to be moved to levitate a gon-full of coal against its own weight in the 'short time' comparable to a train advance plus rotary dump, without passing the coal through the inducing fan with the air that levitates it, is going to be considerable ... as is the power needed to accelerate the airflow at the start of extraction, or to keep the fan speed up between cars.
In addition, something has to move the vacuum nozzle around (like those old leaf collection 'elephant trunks'), prevent the levitation equivalent of bridging, deal with the situation when a slug of air gets pulled between two slugs of coal load, and so forth. I see no big savings here, and unless you have the aspirin concession for the unloading facility you're unlikely to want to use that approach.
RME Boyd Two reasons not so far mentioned: 1) Trituration. Coal grinds up against itself (this is where the 'coal dust fines' come from) and it is likely (to me) that any vacuum system going to a storage pile and not directly to bunkers/grinders/burners is going to cause considerable breakage and fines above what a simple gravity dump and conveying/loading would. 2) There's no such thing as a 'vacuum' system -- it's an induced-wind system. The amount of air that has to be moved to levitate a gon-full of coal against its own weight in the 'short time' comparable to a train advance plus rotary dump, without passing the coal through the inducing fan with the air that levitates it, is going to be considerable ... as is the power needed to accelerate the airflow at the start of extraction, or to keep the fan speed up between cars. In addition, something has to move the vacuum nozzle around (like those old leaf collection 'elephant trunks'), prevent the levitation equivalent of bridging, deal with the situation when a slug of air gets pulled between two slugs of coal load, and so forth. I see no big savings here, and unless you have the aspirin concession for the unloading facility you're unlikely to want to use that approach.
Boyd
The only thing I can see from a 'vacuum unloading' system is complexity beyond belief, repetitive failures, extended unloading times and consuming money faster than what ever the system is trying to unload. Gravity is wonderfully simple and free.
"Vacuum" systems capable of moving a fair amount of coal exist - DPW's use them all the time to pick up leaves and clean out catch basins. It's just a matter of how big the blower has to be. The coal wouldn't actually pass through the blower, any more than the dirt passes through the blower in your home vacuum cleaner.
The biggest problem would be dealing with various sized lumps of coal. Such a system might work for graded coal, such as used to be regularly sold for use in homes and businesses for heating (and cooking). The individual lumps in any given grade are almost all the same size, so would more easily pass through the system.
That said, virtually every town had the necessary facilities to bottom dump coal - there was no need to use any other manner of unloading. And labor was cheap - even if the coal arrived in a gondola and had to be shovelled out, it wasn't as expensive as the machinery for vacuuming would be.
Short of perhaps cleaning cars of lighter materials (grain), I don't see a vacuum as a viable tool for unloading cars.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68The coal wouldn't actually pass through the blower, any more than the dirt passes through the blower in your home vacuum cleaner.
You must never have owned a Hoover.
Or an Oreck.
Of course, it's a very poor idea to run dirt through the fan. For a variety of reasons. But the argument was 'it didn't lose suction' as the bag filled up.
The reason for not feeding the coal through the fan is almost self-explanatory. (In addition, lump and pulverized coal is surprisingly abrasive.)
Remember that the whole premise of the low-tare-weight coal gon was that it didn't have the complex and failure-prone mechanism for bottom gravity dump. And -- at least in theory -- you had far less trouble with radiant heating or air or whatever you needed to get icebound or frosted-together coal, a surprisingly tenacious composite material at low temperature, out of a bathtub gon when inverted.
On the other hand, the ability of bottom dump to discharge continuously at a reasonable track speed has kept unit trains of bottom-dump equipment in service. (The ones I see have horizontal shoes that activate the doors; they are gagged 2" in while the train is in motion, and presumably the air to the dump mechanism is disabled so a shoe coming 'ungagged' in transit would do nothing more than hang itself up on a clearance restriction.)
I still remember the old mining operation that had rubber-tired truck wheels on the sides of its hoppers. with a raised ramp to wind the mechanical doors open and another on the other side to wind them shut afterward. American ingenuity in action.
Originally I was going to post this 4-1-17 but couldn't wait that long.
RMEOf course, it's a very poor idea to run dirt through the fan. For a variety of reasons.
Ever seen the result of a penny getting vacuumed up by a Hoover? It ain't pretty. OUCH!!
Norm
Larry, rapid-discharge coal-train hoppers are not passe. They are used primarily in the Southeast, where freezing is less likely, and new ones were built at least as recently as any rotary-dump coal gons. Their capacity in cubic feet is not much less than the gons (maybe 200 off an average of 4400 cubic feet), and they are usually equipped with rotary couplers to enable them to be dumped in dumpers as well. Rapid-discharge hoppers are the fastest way designed (short of a catastrophic derailment) to unload a car. Their design basically gives the effect of the bottom falling out of the car. The downsides to this type of car are the initial price, maintenance, and the fact that the dumping line has to be charged up before it arrives at the plant, which usually means stopping and using the air normally used for brakes. I don't know how long it takes to charge up a trainload of these cars.
....and the wetting agent/ water makes for interesting clumps of coal (and breaking it up to get it out of the hopper car)
Mudchicken you want interesting see what happens when a plastic resin that sticks together when wet has a top seal failure and the load gets wet. We had a Hopper car delivered to us that someone had popped open one of the manholes on the roof and then it rained into the car. Oh the screams of our crew that had to jackhammer that stuff out of the car. 40 Tons of resin that fused into 1 block of ruined plastic that we had to get out of the hopper before we could give it back to the BNSF.
Shadow the Cats ownerMudchicken you want interesting see what happens when a plastic resin that sticks together when wet has a top seal failure and the load gets wet. We had a Hopper car delivered to us that someone had popped open one of the manholes on the roof and then it rained into the car. Oh the screams of our crew that had to jackhammer that stuff out of the car. 40 Tons of resin that fused into 1 block of ruined plastic that we had to get out of the hopper before we could give it back to the BNSF.
Time to call Mythbusters vehicle cleaners
In my train watching at Lyle, WA on the Columbia River, the coal trains I saw pass on the BNSF line were about equally divided between trains using rotary dump gon or ones using rapid discharge cars.
In one train of rotary dump gons, however, I did see one rapid discharge car.
Note that the rapid discharge cars can also be dumped as rotaries. At least, mostly.
Ed
CShaveRRLarry, rapid-discharge coal-train hoppers are not passe.
No question. Even regular bottom dump cars are still pretty common - we used to see them at the co-gen when it was still getting coal and petcoke (the plant changed over to bio-mass - wood chips). During the winter, though, buildings nearby the dump building got a regular shaking when they were unloading.
Norm48327Ever seen the result of a penny getting vacuumed up by a Hoover? It ain't pretty. OUCH!!
Ever seen the result of a paper clip getting vacuumed up by a Hoover? I've never yet seen it fail that the belt pulls the clip wire out and wraps it around the central stem that drives the belt -- and then the wire chews up the belt in short order. (And will chew up the replacement in short order if you're not checking carefully for the neat little spirally-wound 'addition' to the shaft...)
I went to Electrolux tank vacuums really early; in fact, I still have the first 'family' PL-1. It's been through the factory reconditioning steps four times and still runs perfectly well.
It occurs to me that a good starting point would be the self-serve vacuums at my local car wash. Those things really suck; keep small pets and children clear.
ChuckCobleigh It occurs to me that a good starting point would be the self-serve vacuums at my local car wash. Those things really suck; keep small pets and children clear.
The WC had an operation where the loaded coal cars were unloaded at the power plant then placed into ore service.
The taconite went over Minturn and was unloaded at Geneva steel. The cars then went to the powder river basin and were reloaded with coal.
They hired a contractor with a vac truck to clean the coal cars before they were sent back for ore loading.
It was a good business and improved car cycle times and utilization.
ChuckCobleighIt occurs to me that a good starting point would be the self-serve vacuums at my local car wash. Those things really suck; keep small pets and children clear.
The problem is not really whether you can build a vacuum that moves enough air to do the trick (there are limits, but once you have shakers and the right kind of heaters the issue can be managed). It's how you get the load out of the car as quickly, cheaply, and 'undamagedly' as rotary or bottom dumping would do.
Cleaning out when changing loads -- that's another matter, and as noted a significant one.
Randy Stahl The WC had an operation where the loaded coal cars were unloaded at the power plant then placed into ore service. The taconite went over Minturn and was unloaded at Geneva steel. The cars then went to the powder river basin and were reloaded with coal. They hired a contractor with a vac truck to clean the coal cars before they were sent back for ore loading. It was a good business and improved car cycle times and utilization.
Thanks to Chris / CopCarSS for my avatar.
All I can say is I wouldn't want the job in the coal car vaccuming plant. That job would suck.
Murphy Siding All I can say is I wouldn't want the job in the coal car vaccuming plant. That job would suck.
She who has no signature! cinscocom-tmw
But you'd still have to leave the little pine tree air freshener in the gon when you were done, wouldn't you?
In the manufacture of semiconductor devices, many steps are done under extremely low pressure, some on the order of microns of mercury. One evening, I asked one of the techs who maintained such equipment, "How's High Vac?" His response: "It sucks."
Our community is FREE to join. To participate you must either login or register for an account.