Editing Hopper car (section)

{{short description|Railroad freight car used for transporting loose bulk commodities}}
{{use dmy dates|date=October 2019}}
[[File:Covered hopper car.jpg|thumb|Covered hopper cars carrying [[Fracking proppants|frac sand]] on the [[BNSF Railway]] through [[La Crosse, Wisconsin]]]]
[[File:Squared tank car.jpg|thumb|Hopper cars may carry [[hazardous materials]], such as this one in the Midwestern United States.  Its payload of [[ammonium nitrate]] is indicated by the [[UN number]] on the diamond-shaped [[Placard#United States Department of Transportation|U.S. DOT placard]].<ref name=":0">{{Cite web |last=Beaucham |first=Catherine C. |date=August 2023 |title=Evaluation of Potential Exposures to Railway Hazardous Material Inspectors |url=https://www.cdc.gov/niosh/hhe/reports/pdfs/2022-0049-3387.pdf |access-date=2024-05-04 |website=U.S. National Institute for Occupational Safety and Health |type=[[Health Hazard Evaluation Program|Health Hazard Evaluation Report]]}}</ref>]]
A '''hopper car''' ({{abbr|NAm|North America}}) or '''[[Open wagon#Hopper wagons|hopper wagon]]''' ({{abbr|UIC|International Union of Railways}}) is a type of [[railroad]] [[Railroad car#Freight cars|freight car]] that has opening doors or gates on the underside or on the sides to discharge its cargo.  They are used to transport loose solid [[Bulk cargo|bulk commodities]] such as [[coal]], [[ore]], [[cereal|grain]], and [[track ballast]].<ref>{{cite web|url=http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Covered+Hopper/ |archive-url=https://web.archive.org/web/20100916213706/http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Covered+Hopper/ |url-status=dead |archive-date=16 September 2010 |title=Covered Hopper Railcars |publisher=GATX Corporation |access-date=11 September 2012 }}</ref><ref>{{cite web|url=http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Small+Cube+Open-Top+Hoppers/ |archive-url=https://web.archive.org/web/20100916213808/http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Small+Cube+Open-Top+Hoppers/ |url-status=dead |archive-date=16 September 2010 |title=Small Cube Open-Top Hoppers and Gondolas |publisher=GATX Corporation |access-date=11 September 2012 }}</ref><ref>{{cite web|url=http://www.crdx.com/coveredHop.html |title=Covered Hopper Cars |publisher=Chicago Freight Car Leasing Company |access-date=11 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120416165540/http://www.crdx.com/coveredHop.html |archive-date=16 April 2012 }}</ref>  Plastic pellets and some finely ground material, similar to flour, are transported in hopper cars that have pneumatic unloading. The bottom gates on the pneumatic hoppers connect to a hose attached to industrial facilities' storage tanks. Air is injected to fluidize the railcar contents for unloading.<ref>{{Cite web |title=5660 Pressureaide® Covered Hopper |url=https://www.gbrx.com/railcars/5660-pressureaide-covered-hopper/ |access-date=2025-01-12 |website=The Greenbrier Companies |language=en-US}}</ref> The hopper car was developed in parallel with the development of automated handling of such commodities, including automated loading and unloading facilities.

Hopper cars are distinguished from [[gondola (rail)|gondola cars]], which do not have opening doors on their underside or sides.  Gondola cars are simpler and more compact because sloping ends are not required, but a [[rotary car dumper]] is required to unload them.  Some "dual-purpose" hoppers have a rotary coupler on one or both ends, so they can be used in both rotary and bottom-dump operations.