A few decades ago, there were rotary unloaders. They were used with special cars, that had a coupler on one end that would rotate. A train would be separated into cuts of a few cars, which were then run onto the unloader by a switcher. The big unloader would "grab" the car and turn it upside-down to dump it.
But they were expensive, relatively slow, and rather Rube Goldberg-type affairs.
Now, most are unloaded without uncoupling from the whole train, while it runs at 1 to 3 mph on a trestle-like structure, with automated arms that open the dump doors on the hopper bottoms, letting the coal drop through the trestle onto the ground. The coal is then scooped up by large front-end loaders, and either piled up until needed or dumped directly into the intakes. A whole 175-car train can be unloaded in an hour or two.
Rotary car dumpers are still used. Today most coal cars are not technically hopper cars, but are gondolas. Gondolas do not have discharge doors. Coalporters, which you'll see go by standing trackside in unit trains are gondolas. Same with what's known as bathtub gons. These must be emptied using rotary dumpers.
Most newer coal cars are made of aluminum to decrease the cars emtpy weight and increase its load limit. As part of this weight reduction, doors and their mechanisms were removed. The car's bottom was lowered between the trucks.
jktrains
Actually, most are still unloaded from the bottom:
http://smtc.uwyo.edu/coal/trains/unit.asp
It takes an iron man to play with a toy iron horse.
I know that Indianapolis Power & Light still uses their rotary dumper all the time.
http://local.live.com/default.aspx?v=2&cp=qmtgkx7tkc6q&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=2380752&encType=1
Reality...an interesting concept with no successful applications, that should always be accompanied by a "Do not try this at home" warning.
Hundreds of years from now, it will not matter what my bank account was, the sort of house I lived in, or the kind of car I drove...But the world may be different because I did something so bafflingly crazy that my ruins become a tourist attraction.
"Oooh...ahhhh...that's how this all starts...but then there's running...and screaming..."
There was a previous thread which noted that one part of the US tends to carry coal in Gons while another part tends to use hoppers. I think hoppers tended to be to the east but can't recall for sure or where the divide ran.
As always the cars would be era specific.
Hoppers come in different sizes which are generally identified by the number of bays - which can be seen fast by the number of unloading gates showing along the bottom of the side.
There have been various styles of unloading gates over the years. From a modelling point of view the easy solution to this is to rely on the model makers' application of doors to cars.
Similarly there have been numerous variations on the shape of the car body.
While it might be epected that hoppers would drop their loads through their bottom doors they can also be dumped using rotary and other dumpers. Rotary dumpers were the most common. The axis of the dumper is usuallyb in line with the drawgear of the cars. Some required cars to be loaded into them individually, others, mainly later ones, can dump the cars while they are in the train as it is passed through the machine. The essential thing for dumping without uncoupling is that the cars have rotary couplers at at least one end. The rotary end is frequently denoted by a very wide coloured band or the whole end coloured.
In addition to hoppers there have been hopper-bottomed-gondolas, standard gons, medium gons,high sided gons, Bathtub gons and specialised coal gons such as Bethgons, Coalporters, Alluminators and more.
The larger gons tend to be provided with rotary couplers.
Gons can be unloaded with clamshell buckets or backhoes. This is less likely at anything but a small power plant because of the amount of coal to be shifted on a regular basis. However stockpiles at remote corners of power plants' might be unloaded from both hoppers and gons in this way.
There are generational/era and size differences between power plants. Clearly an earlier/smaller plant will be more likely to use hoppers or shovel/grab coal from Gons. Larger, more modern plant tends to the big stuff.
The same distinctions also apply to the types of coal used. The big difference that is easily seen is between modern powdered coal that can be blown into furnaces and the older lump coal of variou sizes. One of the medium sizes was (IIRC) pea coal.
Powdered coal can be flood loaded easily and does not have a significant breakage problem - it is already small.
Lump coals had to have attention paid to keeping the lumps within limits so as not to jam doors or other equipment but also to avoid losses by shattering and turning to dust that could not be used in the furnaces.
Dave-the-Train wrote: Lump coals had to have attention paid to keeping the lumps within limits so as not to jam doors or other equipment but also to avoid losses by shattering and turning to dust that could not be used in the furnaces.
Turning coal into dust should not be a problem. Coal is usually pulverised into a powder just prior to being burned in stationary power plants. As a powder, it can be sprayed into the furnace in a manner similar to oil -fired furnaces. Lump coal is not burned by power plants like home furnaces or steam locomotives used.
Leon Silverman wrote: Dave-the-Train wrote: Lump coals had to have attention paid to keeping the lumps within limits so as not to jam doors or other equipment but also to avoid losses by shattering and turning to dust that could not be used in the furnaces.Turning coal into dust should not be a problem. Coal is usually pulverised into a powder just prior to being burned in stationary power plants. As a powder, it can be sprayed into the furnace in a manner similar to oil -fired furnaces. Lump coal is not burned by power plants like home furnaces or steam locomotives used.
And the next generation of coal-fired generating stations will change that. For air emissions reasons, etc. many new stations now in the proposal phase will be Intergrated Gassification Combined Cycle ("IGCC") wherein the coal will be converted to a gas, and then burned in turbines (similar to aircraft jet engines) attached to the electric generator, and the hot exhaust gas from the turbines routed through a steam generator and that steam used in a steam turbine turning an electric generator. IGCC plants will be much more efficient and have close to zero harmful emissions except for CO2. And as to the latter, the plants will be designed to capture (sequester) the carbon once that technology is developed. One proposal has carbon dioxide compressed and shipped by rail tank cars to be pumped into depleted oil and natural gas fields to "sequester" the carbon.
For modelers, a generator could be located at the mine mouth and an electric transmission line built to customer load centers (power by wire) or the railroad could deliver coal to the generator near the load center or as for my electric company employer, coal is delivered by rail to tidewater Virginia, loaded into ocean going barges, and tugs pull the barges to the station in New Jersey. So there are three diffenent scenarios that could be modeled, plus the fourth futuristic scheme of a generating station shipping tankcars of CO2.
---Ken
Modern coal is pulverised but older facilities used (if they don't still use) the big stuff.
I don't know but I suspect that the small stuff munched off the face of opencast mines in the Powder River Basin is carried in big gons and rotary dumped because the gons don't leak from hopper doors. this wuld tend to the demise of hoppers... but hoppers remain - only observation/ pics would indicate the sizes of coal usually shipped in hoppers. it is probably much smaller these days than the sort of thing carried by PRR and NW in steam days. Then again... US loco coal had to be of a size suitable for mechanical stoking...
The end result for modellers is that hopper or gon car loads should probably look like fine gravel or ballast loads as far as grain size is concerned. The cars also load dfferently depending on whether it is poured in from above as the train moves slowly under a spout or on it being tipped in from chutes (often two per car) from the side.
Well if you are going back in time you'll find that a lot of the coal was presorted at the mines into different size coal (lump, egg, pea, etc). So all the coal in the hopper was pretty much exactly the same size. Some of the coal was "mine run" (as is virtually all the coal shipped today) will different sizes.
The reason that they use gons for rotary unloading is because the cars are lighter, so you can haul more coal, the same reason modern coal hoppers are made of aluminim. The object to to move the most coal you can. If the cap is 263000 lb and 40000 lbs is car then only 223000 lbs of coal can be hauled in the car. If the cap is 263000 lb and 30000lbs is car then you can haul 233000 lbs of coal, 10 tons more. That's 1000 tons more per 100 car train. You just made the train 8 cars "longer" with spending a dime on more engines, maintenance or increased siding length.
Ca-Ching goes the cash register.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
at our power plant in fremont neb (25,000 pop) we unload out of bottom of cars an payloads feed the plant and stockpile. guess they used to load dump trucks ant then truck to the plant downtown labout 4 miles away. the plant we use now was built in the 60s
ray
How old and how large is this power plant?
At the steam heat plant at Loring AFB in Maine they had a large cement pad with two tracks running through them. They would put the cars on the cement pad and just open the hopper bottem doors and use a Cat with a blade to push the coal up into really big piles. They would do this all summer, maybe 15 cars a week, then they would truck the coal during the winter from the piles all the way across the street and down the block about 500 yards, where they would dump it into the day hopper for the power (steam heat actually)plant. They would stockpile in the summer as the Bangor and Aroostook would get snowed in during the winter (November til April or so) and couldn't deliver then. This was egg coal, usually in L&N four bay hoppers.
At Toledo Ohio in the 60s and later they use dumpers like the ones previously mentioned in a post from Sandusky. The literally picked up one car at a time about 40 feet, turned it upside down and dumped the coal out into Lake Boats. They also had rotary dumpers therein that time frame that would roll two cars at a time 360 degrees and the coal was taken by conveyor up to the level of the Boats. They would dump any kind of hopper cars in these dumpers, but I have never seen them dump coal gons, bethgons or anything of the more modern age. I would kind of think anything over the normal four bay would be to heavy for these machines.
Small power plants frequently would have a chute under the tracks where a car or two would be spotted and the cars bottem doors opened.The coal would gravity feed out of the car, into the hopper and into the basement of the power plant. The cars could be re-spotted using a cable type car puller rather than needing a locomotive that would be only used a couple of times a day to move the cars. This was also done frequently at manufacturing companies that produced their own power (steam or electric) and this kind of operation tapered off in the 50s and later. Many locomotive facilities had such an operation on or near the roundhouse and machine shops. There was frequently a seperate building that would produce steam and electricity and both were sent over to the roundhouse, machine shop, Carshops and whatever other building that was needed a the terminal. Of course at a railroad terminal they probably didn't have a cable car puller as there was usually a locomotive available for that task.
Earlier than the 30s they used the same ideas only smaller, but not usually rotary dumpers. The T&OC RR and the Hocking Valley RR docks in east Toledo on the Maumee River near downtown used dumpers that picked up the cars and inverted them to dump them. These were built as near as I can tell in the early 1900sand later they were later moved out to the Lakefront Docks and Presqui Isle on Maumee Bay at the west end of the Lake Erie. I am not sure who manufactured these behemoths, but they were larger than most power plants needed, thats for sure.
I am rambeling like usual, but I get on a roll, and start thinking of my childhood, SORRY!
Paul
Dayton and Mad River RR
In the late 60s and early 70s I worked at a couple of places that had coal fired industrial boilers.
At one place, they had a silo where the coal was stored. The car would be placed over an unloading grate, and the bottom doors would be opened. The coal would spill out on the grate and surrounding concrete. An auger or bucket loader under the grate would drew the coal into the silo. It was slow, but the volume of coal used was not that great.
I do not remember the details of the under the track parts at the other place, but they had a vibrating shaker that was lowered on top of the hopper sides with an electric hoist. The shaker had a motor that drove an eccentric weight and vibrated the car, shaking loose the coal that would hang up inside. It did a good job of shaking and breaking up the sides of the car also.
George In Midcoast Maine, 'bout halfway up the Rockland branch
modelbuilder wrote:This may be a dumb question but how would coal be unloaded from coal hoppers at a power plant?
From the far, far reaches of the wild, wild west I am: rtpoteet
I hope this helps:
http://maps.live.com/default.aspx?v=2&cp=40.703084~-74.129657&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=7969906#JnE9eXAuNDQxMTQlN2Vzc3QuMCU3ZXBnLjEmYmI9NDAuNzExMDcyNDI2ODExJTdlLTc0LjE0MjQ0NjY0Nzg3MDElN2U0MC43MDk3MzA1MTg5MjkyJTdlLTc0LjE0NDkyNDY1Njk2Mw==
This is an aerial view of the power plant near me, now this is a huge facility that dwarfs all the local power plants. If you pan around the picture with your mouse you'll see the coal hoppers lined up near the dumping station. There is a switcher pushing the loaded hoppers into a building where a rotary dumper sends the coal to different conveyers. Surplus coal is stored in the large pile to the West. The baby silo is for the cinders left over from the burning process. Those are hauled away by truck. If you pan north you will see the water intake and the hot water discharges. The hot water passes under the bridge to the big J hook and the cold water comes in the small half moon break wall.
If cutting and pasting the above link does not work go to: http://maps.live.com/ and type in 44114 in the search field box, then follow the highway to the east until you see the power plant. This plant is located along the former NYC (Conrail) Youngstown Line)
Lee
BM1 Lee Soule USCG (ret) L.S.&W Railroad Serving the Lower Great Lakes