Covered hopper
Encyclopedia
Bulk cargo
Bulk cargo is commodity cargo that is transported unpackaged in large quantities. This cargo is usually dropped or poured, with a spout or shovel bucket, as a liquid or as a mass of relatively small solids , into a bulk carrier ship's hold, railroad car, or tanker truck/trailer/semi-trailer body...
loads, varying from grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...
to products such as sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
and clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
. The cover protects the loads from the weather - dried cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
would be very hard to unload if mixed with water in transit, while grain would be liable to rot if exposed to rain. However, they are unsuitable for perishables such as fruit or meat - these are transported in refrigerator car
Refrigerator car
A refrigerator car is a refrigerated boxcar , a piece of railroad rolling stock designed to carry perishable freight at specific temperatures. Refrigerator cars differ from simple insulated boxcars and ventilated boxcars , neither of which are fitted with cooling apparatus...
s, where they can be kept at low temperatures as well. Similar to an open hopper car
Hopper car
A hopper car is a type of railroad freight car used to transport loose bulk commodities such as coal, ore, grain, track ballast, and the like. The name originated from the coke manufacturing industry which is part of the steel industry ....
, covered hoppers tend to contain 2, 3 or 4 separated bays. Each of these can be loaded and emptied individually, with access at the top to load the materials and visible chutes at the bottom for unloading.
Covered hoppers in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n service have been built by most of the freight car manufacturers of the 20th century. Originally, boxcar
Boxcar
A boxcar is a railroad car that is enclosed and generally used to carry general freight. The boxcar, while not the simplest freight car design, is probably the most versatile, since it can carry most loads...
s were used for the transport of bulk materials, but these had many disadvantages. Not having been specifically designed for this, it was very hard to use any form of machine
Bulk material handling
Bulk material handling is an engineering field that is centered around the design of equipment used for the handling of dry materials such as ores, coal, cereals, wood chips, sand, gravel and stone in loose bulk form...
to load or unload them. Also, a large amount of product was liable to be lost, either during loading or unloading, or in transit - since the cars had to be boarded up, rather than using the doors, to enclose the products.
Hoppers with 2, 3 or 4 bays are used for different purposes - 2 bay hoppers are used for the most dense loads (such as sand), while 4 bay hoppers are more suited to lighter loads. This is due to axle load
Axle load
The axle load of a wheeled vehicle is the total weight felt by the roadway for all wheels connected to a given axle. Viewed another way, it is the fraction of total vehicle weight resting on a given axle...
limits - for example, dry cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
is very heavy in bulk quantities, and a 4-bay hopper of sand would be very likely to exceed these limits, while also having problems with increased strain upon the central span. Therefore, by trading off cubic capacity, 2 bay hoppers are able to transport these heavy loads. As technology has advanced, some of the heavier loads formerly assigned to 2-bay hoppers have been assigned to larger, more efficient 3-bay hoppers.
Large unit train
Unit train
A unit train, also called a block train, is a railway train in which all the cars making it up are shipped from the same origin to the same destination, without being split up or stored en route...
s of various grain crops are a common sight in North America, reaching up to 125 cars long. These predominantly haul grain from the large farming areas of the great plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...
to various markets - however, there are also a number of unit trains which originate from other major farming areas, such as Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
and Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
. These trains may originate from a single grain elevator
Grain elevator
A grain elevator is a tower containing a bucket elevator, which scoops up, elevates, and then uses gravity to deposit grain in a silo or other storage facility...
, or may be marshalled in a yard
Classification yard
A classification yard or marshalling yard is a railroad yard found at some freight train stations, used to separate railroad cars on to one of several tracks. First the cars are taken to a track, sometimes called a lead or a drill...
from various locals (short trains which serve nearby industries). The destinations tend to be large flour mills, port
Port
A port is a location on a coast or shore containing one or more harbors where ships can dock and transfer people or cargo to or from land....
s (for export) or split up and delivered to multiple locations. The empty cars may return as a whole train, or may be sent back in smaller quantities on manifest trains (trains which carry just about any type of freight). These trains are used primarily for hauling products such as corn
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
and barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
.