Belt conveyors are the most commonly used bulk handling conveyors in history, due to their reliability, versatility and range of capacities. They are comprised of an endless belt that transverses between two or more pulleys, and is supported by idler rollers at intermediate points. Materials from fine powders to large lumpy stones can be handled on a belt conveyor. It operates at belt speeds ranging from 20 to 300m/min and material can be transported at rates of over 500t/h.