TastyBake ISL

[FCIN]

Ed, can you give me, and others?, a short lesson how to identify on a model of a covered hopper if it is designed for gravity discharge or pressure air.

Sort of a tall order, but I'll try to make it as simple as possible.

As you mentioned, gravity discharge covered hoppers designed for transporting grain, fertilizer and similar commodities generally have trough hatches down the center of the roof to facilitate rapid loading and sliding discharge gates on the bottom of the hoppers. They come in all sizes from 2 bay (frequently used to transport cement) to the new large 4 bay cars that are designed for transporting distillers dried grain. The 3 bay cars, are primarily used for transporting grain and similar commodities.

The next variation would be covered hoppers intended to transport plastic pellets and/or some types of products in pellet form. These will usually have the small circular roof hatches and a pipe connection on either side of the hopper bottom. To unload them, the industry will attach a hose to the pipe connection and vacuum out the contents. There are some variations of these that have both the discharge pipe and a sliding gate which would permit unloading by either gravity or vacuum. You will see these in abundance around facilities that produce plastic products and most will have at least 4 bays and be about 62ft in length.

The pressure aid type covered hoppers are the ones you see with a pipe running along one side (perhaps both) that connects to the hopper bottoms and generally have a single discharge connection on one or both sides. Where there is only one discharge connection, you'll see the cars lettered to "Unload This Side" and "Unload Other Side". Air pressure is introduced when unloading to assist in removing the commodity. Most of these tend to have the small circular loading hatches and these cars have airtight seals on them.

The Airslide covered hopper is basically a gravity discharge type covered hopper, but with small circular type roof hatches that seal airtight. The cars have a fabric type lining and air is forced in to them to help the commodity "flow" when unloading. They have very small discharge gates on the bottom of the hoppers, to which the customer will attach small conveyors which are supposed to prevent contamination of the commodity. Although I still see many Airslide covered hoppers, the pressure aid type car is rapidly replacing them these days.

If I had the time right now, I'd point you to photographs of the various types of covered hoppers in use today or perhaps available models of them; but you should be able to find plenty of examples doing an Internet search. I would also suggest looking at leasing company or rail car manufacturing web sites such as Trinity Industries, ACF, etc. for some good examples. There are so many variations of what I'd call the basic car type, it would take quite a while to look up examples of them all.