I have seen some U-Tubes about rotary dumpers. What is the big advantage for using rotary dumpers ?
The U tube videos are in real time & it seems to me that bottom dumpers move along faster. So please
educate me. Thank You John
Many rotary dumpers can achieve 1.5-2 minutes per car and the bottom dump gates do not have to be locked closed again after dumping. Also dumping in cold weather usually is better, but most of the rotary dumpers here in the Upper Midwest have ‘thaw’ sheds several car length long with heaters to thaw out the load before it is dumped. Unloading a bottom dump hopper on a frozen weather day can be next to impossible at times. Another advantage is that there is weight savings because there are no bottom dump gates and the coal load can sit lower(Bethgon and Coalporters).
Jim
Simply you push or pull a train of rotary dump cars through the dumper, the train stops, a car is rotated upside down to empty, rotated back to plumb, and train moves up a car length and the process repeated. Theoretically the train does not have to be uncoupled and then recoupled car by car; but it was done in groups depending on the tail track when there was no continuous loop. Dumping was complete with no grates or doors or any other appliances and attachments getting stuck. Less manpower used, too.
Seems like I’ve seen pictures of two-car dumpers, too, but I could be mistaken.
Having worked near a bottom dump operation, 1.5 to 2 cars a minute would be lightning fast compared to bottom dumping. I never actually timed how long it took them to dump a car there, but 5-6 minutes, maybe longer, would be a reasonable guess. I know they had a car shaker (which shook nearby buildings pretty well, too) in the dump shed.
Another consideration regarding rotary dumping is where the coal is going. The operation I speak of used conveyors to move the coal to the pile - rotary dumping would have emptied the car faster, but you wouldn’t be able to dump the next one until the receiving hopper was ready for more. Bottom dump fed the coal at a “doable” rate. Most rotary dump operations I’m aware of can handle the entire load en mass (ie, the hold of a ship).
The two I am familiar with and saw in operation were 1) DL&W Hoboken/Jersey City barge loader and 2) LV -New York State Electirc and Gas Co. Milliken Sta. power plant on Cayuga Lake which stock piled.
Most of the power plant rotary dump operations I have seen handle one car at a time. IIRC, the BNSF ore dumper in Superior handles two ore cars at a time. I have watched the car dumper at Alma, WI and they can have a 117 car coal train through the dumper, back around the loop and out on the main line in 2 to 2.5 hours. Most of the dumpers have ‘positioner’ that is a large ‘finger’ that moves the train through the dumper. I was in the Midwest Energy site a number of years ago(OreTran then), and they state they can dump 4300 tons/hour - Under 3 hours for unloading a train. And it was noisy in that dumper bldg when they were unloading! The massive conveyor systems have no problem keepi
Another reason for the increased use of Rotary Dumped Gondola cars vs. traditional Hopper Cars is that Gondolas (which have to be unloaded by a Rotary dumper) are cheaper to maintain than Bottom Dump cars. Miantenance and repair of the doors on the latter can be a major expense.
In fact there are many coal cars in rotary service that were built as conventional bottom dump hoppers but have had the doors pinned for top unloading.
The pneumatically-operated rapid-dumping hoppers are more expensive to build and maintain, but–at the proper unloading sites–they are much faster to unload. They are not your grandpa’s old open-one-door-at-a-time-onto-a-conveyor-belt cars. When their trip shoes are actuated, it’s like the bottom falls out of the car…less than 30 seconds is all it takes. But the dumping had better be on a proper trestle with enough room below to accommodate a lot of coal, and probably with a water supply to keep the dust down. The train shouldn’t even have to stop if it has the proper loop for continuous operation. But all of this runs into money, too.
Another disadvantage of the hoppers is that they have to be charged with air to operate, and that’s usually done by the locomotives of the incoming train–which has to stop, transfer the hose from the trainline to the dumping line, charge up the system, than back to refill the brake reservoirs after the air had been dumped. That’s a time factor that may negate some of the savings of the faster dumping rate.
Anyone know the time cycle of the bottom dump cars at NS’s Norfolk ship loading site? I’ve been led to believe it’s quite rapid.
You dont use trainline air to open and close rapid discharge cars, main reservoir air is connected
to the cars dumping air hose, if you have D.P. you can feed it from both ends. 120 cars in about
an hour, train speed while unloading about 3 MPH if the two guys doing the unloading are
experienced hands
On my carrier where air operated rapid discharge cars are the train to be dumped; the train is stopped (by TTSI) at a point about 1 hour from the dumping location and Main Res. air is introduced to the dumping trainline. Train then proceeds to the dumping location and is dumped. The travel time gives the Dump Trainline time to get fully charged by arrival at the dumping location.
Thanks, you two…this takes care of my misunderstanding. I knew about the stop for charging, and that it was some distance from the plant, but connecting it to the main reservoir at that point and charging on the way in (almost sounds militaristic!) is much more logical than what I was imagining.
Is there special piping from the main reservoirs to the hose connection to the first car? Specific locomotives equipped for this? Or is it all temporary hoses around the cab and across the walkway?
Its the M.U. Hose nearest to the coupler, this would be on all modern locomotives, the air pressure in this line is 130 to 140 PSI
It just gets better and better, and you just caught me at another “Duh!” moment!
Like mentioned above, In the northern states in the winter the coal can freeze in the hopper car. Or some of the coal can come out and then it stops. Then they try to get it freed up with crow bars. I think that would be dangerous to do when it finally gets loose since coal is very heavy.
I haven’t noticed the capacity issue mentioned, a bathtub gon has no slope sheets like a bottom dump, only inside bracing rods, so the amount of product in each car is greater than what fits a normal bottom dump car.
deleted.
Why deleted?
Come on, it was a perfect set up, with a good lead in line and everything……![;)]
The point I was going to make was already made by someone else. Missed it reading the thread the first time.
Bottom dump car is funny, though.
There are dumpers that handle two cars at a time. CN at Escanaba MI has oine that handles 3 short ore cars at a time. By the way, BNSF does not rotary dump pellet cars.
For frozen loads, the frozen part can extend several feet into the car. When the train starts in Montana and ends in Minnesota it can go through lots of cold. For a bottom dump the car has to be pretty much all thawed. For a rotary dump only an inch or two against the car skin needs thawing. The rest breaks up when it is dumped.
As for how fast either system works, LTV (Erie Mining) used to bottom dump a 10,000 ton pellet train with specially equipped cars on a trestle in about 15 minutes. CN can do about half this rate on their ore docks in Duluth. BNSF in Superior can do about 3000 tons an hour of pellets bottom dumped in Superior. Usually bottom dumps are a lot slower.
Rotary dumps are primarily limited by the conveyors that take the ore or coal away. Midwest Energy in Superior WI can dump about 6000 tons of coal an hour. Most individual power plants are closer to 1000 to 3000 tons an hour. It’s a compromise between the cost of larger conveyors and a longer dwell time for the train.