Tossing out the question for more experienced minds, is there a difference between the two types of cars? The PP covereds I've seen still discharged into a pan to be conveyored to truck, but I didn't get any good pics then. Some shots look like they're 4 bay vs 3 bay, others look likeit could be either, but then it could also be google giving me pictures of "covered hoppers" more than it is specifying.
-Morgan
The two major differences are on the top and bottom. On the top, the hatches on a PP hopper are small round hatches and there are about ten of them lined up single file down the center.
The grain hopper is on the left and the PP hopper is on the right.
[View:http://cs.trains.com/TRCCS/themes/trc/utility/:550:0]
On the bottom of the PP hopper are discharge chutes that are connected with hoses that keep from outside contaminants from entering the load.
You can see these here:
The PP are discharged from the car via a vacuum system which then places the PP in storage silos or in a specially made semi trailer.
The grain hoppers on the other hand have the large, long hatches that run down the middle of the car. The bottom discharge hatches are bigger and the grain flows freely into a floor grate or an auger. It doesn't matter if the grain has contaminants or not as long as the grain is dry.
Here is a pic of the grain hopper's discharge chutes:
Will
What about the interior? Isn't there some kind of lining on a car that transports edibles?
Dave
Just be glad you don't have to press "2" for English.
http://www.youtube.com/watch?v=zQ_ALEdDUB8
http://www.youtube.com/watch?v=6hqFS1GZL4s
http://s73.photobucket.com/user/steemtrayn/media/MovingcoalontheDCM.mp4.html?sort=3&o=27
I don't know exact details... but a lot of H0 covered hoppers come printed with instructions on the car side about various linings. The instruction is usually about cleaning the inside of the car - usually about not using steam.
One thing to think about as a "basic" difference between grain and plastic pellet is the density of the load. Grain (broadly speaking) is pretty heavy.
Then again plastic pellet varies in weight depending on which of may plastics it is, You can get light fluffy stuff (which is likely to be blown by air pressure (makes a real mess if a coupling in the pipe comes apart), medium stuff that can be vacuumed and (usually tiny grain) dense stuff that is augered ir moved by conveyor belt or even bucket chain. PP comes in lots of different colours. A plant may use only one colour or many.
Looking at cars Athearn does the 4 Bat Centre Flows... with a chemical or oil company name and the small round hatches these are likely to carry a heavier grade of PP. Walthers (And Atlas I think) do cars specificsally described as PP cars... these are usually the larger high-volume / low density PP product cars.
As much as they don't want PP contaminated these days they don't want the PP getting out and contaminating the environment. Grain will rot or grow but PP will either leach toxic nasties or stay around forever (possibly both).
I don't know how they get contamination out of grain when milling it. A contaminated batch of PP would probably have to be dumped (carefully) as most PP use in plants involves heat and any contamination could easily mess up the machines.
(That said I've seen PP in paper sacks... but kept "sterile").
That was a great question, and Wholeman's reply was just as great. Now I have something else to look for when I'm out railfanning. This is why I love these forums. You can learn something new everyday.
Tom
Pittsburgh, PA
Pellet cars normally have a round hatch in the roof as shown in the pictures. Grain cars typicaly have a trough hatch for loading.
Pellet cars have a pnuematic unloading gate, the product is "vacc'ed" out of the car. Grain cars have a sliding gate and gravity unload.
Pellet cars are owned by car lessors or chemical companies.
Grain cars are owned by railroads, grain companies or lessors.
Pellet cars are typically 4 bay, grain cars are normally 3 bay but can be more.
Here is a pellet car being unloaded.
Here is a plastic pellet "warehouse" a Storage In Transit (SIT) yard.
Closeup of the cars
A grain covered hopper:
Dave H. Painted side goes up. My website : wnbranch.com
Alrighty then, thanks guys! Learned something new. Though I coulda sworn I saw green pellets moved by trough
dehusman Here is a plastic pellet "warehouse" a Storage In Transit (SIT) yard.
Learned something else new. Cool! I am noticing a few side ribbed cars in that mix as well. Not many, but a few.
My thoughts were that usually plastic pellet cars were considerably bigger. The four bays instead of three reflect a greater length. The name of the game is to design a freight car so the volume available matches the weight limit of the car. (Ore is usually very heavy, so the cars are very small.) Plastic pellets do not have the same density, even less than grain, and so those hoppers have something like 1000 cu.ft. greater capacity.
Other commodities also prefer round hatches, such as cement and potash. Again, cement is quite dense, which is why shorter two-bay covered hoppers are bought for that service. If a longer car is used, it can only be partially filled because of the weight limit. I don't know exactly why round hatches seem to be preferred. Maybe they give a more robust seal to keep the contents absolutely clean and dry, or perhaps the loading process is kept cleaner.
John
cx500 My thoughts were that usually plastic pellet cars were considerably bigger. The four bays instead of three reflect a greater length. John
My thoughts were that usually plastic pellet cars were considerably bigger. The four bays instead of three reflect a greater length. John
Your theory is right, your practice in this case I am almost sure is wrong. The three and four bay covereds all appear to be of the same length-55' and some change. The bays are just spaced differently and may themselves be different sized. I do notice in the provdied pictures that the pellet cars have bowed sides, instead of the grain having flat sides, and the pellet cars appear to be a lick taller.
A 263000 lb max pellet car will be larger than a 263000 lb max grain car because pellets are lighter than grain and so you need more cu ft to make 263000 lb of pellets.
A 286000 lb max grain car will be about the same size as a 263000 lb max pellet car.
By making a car with 4 bays, you gain more cu ft of capacity because you loose less to slope sheets and the extra bay holds more. So for a car where cu ft is to be maximized (light commodity) , 4 bays make sense. On a grain car there is no advantage to extra bays because the cubic capy of 3 bays will max out the weight capy.
I see I was not quite as accurate as I wish, once again the hazard of not doing enough research first. Checking photographs, including my own, I see that many 4-bay covered hoppers are in the 4750 cu.ft range, typical for grain. But if you look at this picture, you can see how stretched out a plastic hopper can become. This particular car is stencilled for plastic on the right hand end and has a capacity of 6245 cu.ft. That is at the high end of the range; I have seen others in the high 5000 cu.ft. range. I have no idea of the actual length of the car but if someone has access to the UMLER database they can perhaps look it up.
The special stencil concerning Agriculture and a census is rather misleading since the car is assigned to plastics service for the petrochemical industry. Perhaps there is some farm product that is light enough for this type of car but it certainly isn't grain!
It
Ah. Makes more sense.
Found this: http://www.ethanolproducer.com/article.jsp?article_id=1592 It claims a 70ft grain car for dried grains for distillers, has a date of November not April, and seems to be an exception not a rule.
Potash hoppers usually have trough hatches. http://www.rrpicturearchives.net/showPicture.aspx?id=617750
The last I heard DCLX was assigned to Dow Chemical of Canada, so a DCLX hopper would not be carrying an agricultural product.
"No soup for you!" - Yev Kassem (from Seinfeld)
I'm not sure about the angles of slope of the bays of different cars. Where there are different angles it may be due to specific requirements of different materials loaded. Some materials flow moer easily than others. I would guess that this would apply more to gravity discharge than assisted.
Then again the unloading of some materials is assisted by car shakers... and have pads on the bays for these to engage with. I think that grain cars routinely have shaker pads but I don't recall seeing these on the larger (low density PP) cars.... I will have to take a look...
Something else to consider is whether a load will become compacted in transit making it more difficult to unload... which heads me off in the direction of PD and Airslide cars... (I'm pretty sure none of those have shaker pads).
When I was a kid my buddy and I liked to start the morning's railfanning with a visit to a siding that had two tanneries, an oil facility, was a team track for a lumber yard, and had a factory that makes plastic bags, such as those that dry cleaners use. They also made the bags that used to be used to pick up yard wastes before the bio-degradable preference took over.
All those industries were rail served to one degree or another. Anyway they usually had center flo cars, and I do recall some of them being El Rexene cars. The factory was actually across the street from the unloading facility so there is your prototype for an industry where you might not model the actual building. You can see the relationship in one of the photos on their website (see below).
My point to the post is that there was some spillage of the platsic pellets at the unloading hose. A small pile of translucent pellets about the size of a One-A-Day multiple vitamen, or small aspirin. That is a detail you might want to include if you model an unloading facility.
That factory even though very very small has a small website with the kind of background information not always available for modeled industries: http://luetzowind.com/index.html
And they have some historic photos. http://luetzowind.com/history.html
Note the small photo of their first rail load from Dow -- it appears to be an airslide car lettered for Dow, and a reference to Texas and Freeport. The larger cars I remember also had lettering to be returned to Texas when empty.
Dave Nelson