I have to two questions, is this coal hopper only rotary dump?http://www.coloradorailfan.com/gallery/photo.asp?id=102172
And when the locomotives detach from coal hoppers at a power plant do they go though the rotary dump or go off to the side?
Those are called Rapid Discharge Hoppers, they dump through the gates visible on the bottom of the cars.
If locomotives are detached at the unloading locations then they will not be going through the dumper. Not many rotary dumpers can accommodate locomotives passing through because of the need for the dumper to clamp down on the car or cars to be unloaded. Most often a mechanical cable power “Train Indexer” moves the cars for unloading. Conversely the Rapid Discharge Hoppers in the picture you cited are normally unloaded without disconnecting the train locomotives.
These particular cars are equipped with both bottom discharge hoppers and a rotary coupler on one end. Using them at a bottom-dump facility would be most efficient, of course, but these cars can be unloaded virtually anywhere.
Yes, engines can pass through a dumper during the unloading process, but the coupler of the car coupled to it had better be a rotary coupler. There was a picture floating around a couple of years ago that showed what could happen otherwise.
The red paint on the high end of the car should indicate the end with the rotary coupler. Since the red ends point in both directions, this train could not be used in a rotary dumper, and must unload thru the bottom.
Phil
I hope no one minds if I offer some clarifications?
- The cars in those photographs are “rotary/rapid-discharge.” They can be dumped either in a rotary dumper or on a rapid-discharge pit. These are not an uncommon type. The advantage to this flexibility is it enables a coal consumer to swap destinations without having to swap trainsets on a real-time basis, and it enables a lessor to rent the cars on short-term leases for either type of service without having costly repositioning or storage charges. The disadvantage is that the rapid-discharge car costs more to build, costs more to maintain, and hauls significantly less coal (because it is carrying more metal around) than the comparable gross weight rotary-dump car. The addition of the rotary coupler to a rapid-discharge car doesn’t add much weight, capital cost, or maintenance cost, so it’s a “why not?” particularly for lessor-owned fleets or for coal consumers that operate both rotary-dump and rapid-discharge power plants, or who expect to have coal demand fluctuations that make it economically attractive to place their cars into short-term leases during periods when their coal needs are low.
- It doesn’t matter which way each car is pointing (rotary end leading or trailing) as long as there is at least one rotary coupler in each pair of couplers at each end. Whichever car happens to own the rotary coupler – either the car being dumped or the car remaining stationary – matters not. If there is a situation where there are two standard couplers facing each other at the dumper, that’s not the end of the world; the train can be broken in two, the car dumped, and the train reassembled. You’d rather NOT do that because it adds time, and time on a unit train is a lot of money, but it does happen. Often what happens with the rapid-discharge/rotary trainsets is they get out-of-order in pure rapid-discharge service, as
RWM, are there not rotary dumpers capable of unloading two coal cars at once? If there are, it wouldn’t matter which way the individual cars were oriented–the worst that could happen is that you might have to advance the train only one carlength instead of two to keep the non-rotary/non-rotary joint in the middle of the dumper. If there aren’t such creatures, maybe you could tell me how to patent the idea!
Dual dumpers (two cars at once) are really rare. I’ve never actually seen one. We’ve thought about them at various times but the dollars never penciled out. The throughput goes up about 50% but the cost goes up about 100%. I think the only instance where the dollars make sense is at a highly constrained location where there wasn’t enough room to simply build another loop track (nested or otherwise) and a another single dumper, but it was critical to have the higher throughput. In other words, a very large power plant on a very small site, or a port with a high throughput goal and lack of land. I prefer having two single dumps than one dual because there’s still throughput capacity when one is down for maintenance or an accident.
RWM
Perhaps some day you could come up this way and have a look?
Roberts Bank has a dual dumper on one track, and a single on the other track. I believe Canadian cars go through the dual while American cars go through the single dumper.
Ridley Island (Prince Rupert) is listed as having a tandem dumper, which I presume is two cars at once. http://www.rti.ca/en_dumper.html
Lamberts Point, as shown on pages 63-65 of the April Trains, looks like it is a lot less efficient in comparison. Then again, it doesn’t have room for ground storage.
One minor nit to pick: Rail To Water Transfer (KCBX to the younger crowd) does not use kickback tracks (there’s no space) or rotary dumpers. Car shakers are used which are lowered to the top of the car and shake the car on its springs to empty it.
Yes rapid discharge. Once those gates are opened up it almost like the whole floor of the car disappears! The coal really flows out if I’m not mistaken.
I dunno - you guys are pretty good ! [bow] I can’t read any reporting marks or car numbers in that photo, and didn’t see any in the caption either, though I can see the 5 bottom hoppers on each car. Also, that roughly half of the cars - but not strictly alternating - have both the red vertical panel at the car end and the red triangle on the same upper end of the car side, which I can understand would indicate a rotary coupler - although here in the east, those colors are often yellow instead. [*-)] But is there some characteristic of the Rapid-Discharge Cars that enables identification of them apart from other bottom-hopper cars, without a close-up view or the reporting marks, etc. ? In other words - How could you tell that ?
[quote user=“Railway Man”]
From the 1st ‘bullet point’: [snip] The disa
That’s right! Tandem dumper is also used as a term, and both of those locations have tandems due to site footprint agony. Not my railway. Haven’t put my feet on the ground at either location.
RWM
Paul, on page 59 of the April Trains it mentions that bottom dump coal trains can be unloaded at the Stanton Energy Center in under 3 hours, but the train unloaded during the visit took 4’25". It also mentions it took an hour to couple the air hoses required. That seems much slower than the unloading rate of 6,000 tonnes per hour at Prince Rupert. http://www.rti.ca/en_dumper.html
Couple of things here, Paul: first of all, the hoppers on the end have a slightly different shape than those in the middle of the car. They have gates on only one slope, whereas the ones in the middle have gates as both sloped sides (as Justin said, it’s like the bottom falls out).
Second, you might notice on the nearer cars (where the ribs don’
Thanks for that reference, Dale - both times - I’ll have to take a look at it again.
Perhaps the unloading speed of the rapid-discharge cars is a myth, or advertising ‘puffery’ ?
On the other hand, I read someplace that they can unload in the range of 10 to 20 seconds. Using the latter/ slower figure for 100-ton cars would be 18,000 TPH, and a 100-car train would be unloaded in about 34 minutes.
For 60-ft. long cars, traveling their length during that 20 seconds - so that the next car is in a positino to unload just as this one finishes - is 3.0 ft. per second = about 2 MPH. The distance across the pit/ bridge would need to be about 2 car-lengths, since I understand that all the doors open simultaneously - or about 120 ft. in this scenario, which is not too bad - say, 6 spans of 20 ft., 4 of 30 ft., 3 of 40 ft., or 2 of 60 ft., etc. would all be reasonable.
Since the typical density of coal - either bituminous or lignite - can range from around 40 to 57 lbs. per cubic foot - per http://www.engineeringtoolbox.com/classification-coal-d_164.html - I’ll use 50 lbs. per cu. ft. as a convenient middle or average number. Thus, a 2,000 lb. to
Do any of the locations using rotary dumpers require car shakers as well?
No one else asked, so I guess I will:
What is a gravity-kickback rotary dumper?
This is a set-up that was used on coal docks on Lake Erie and probably other locations. The rotary dumper is similar to those used at power plants and is set up at the crest of a hump type trestle. Two or three hoppers at a time are moved by a car pusher, either sidearm or between the rails, up the grade into the dumper. After they are emptied, they are pushed onto a downgrade through a spring switch onto a steep upgrade, which stops the empties by gravity. Gravity then pulls the cars downgrade through the spring switch into the departure yard.
What if the using plant has the train volume and wants the cost advantages, but doesn’t have or can’t acquire the real estate to build the loop with 6,500+ ft. - that’s almost 1-1/4 miles - of ‘headroom’ on each side of the dumper ? And/ or, the terrain is unfavorable to doing that on grades the railroad can live with, and/ or construction costs that the user can live with ? Some power plants are blessed with being out in the flatlands with lots of farms on each side - but it seems unlikely to me that most of the industry-desirable sites have those facilitating characteristics - instead, the otherwise better available sites are often space-constricted in some fashion.
I’ve never seen that combination. All of the rotary dumpers that I’ve seen here in the NorthEast US had ‘thaw sheds’ or the equivalent, yes - but no car shakers.
Car shakers are usually needed to encourage the load to unclog and move through the bottom hopper doors - again, often with thawing in the winter.
But rotary car dumpers don’t use the bottom hopper doors - those are really not even needed to unload a car that way - and so there’s no need for the car shaker. And once a car is thawed, flipping it over is usually more than enough to get most of the load out. The shaker wouldn’t get that much more out to make it worthwhile, I believe.
- Paul North.