Particle flow mechanism into cable shovel dippers

• Movement of a cable shovel dipper through crushed limestone is physically modelled.
• Video results are analyzed to discern a mechanism for particle flow into a dipper.
• Recorded force and hoist speed is used to examine machine efficiency.
• Results revealed that flow patterns are independent of digging conditions.
• Machine efficiency improved with lower pitch angle and faster hoist speed.

Electric cable (or rope) shovels are critical equipment in the surface mining industry. An improved understanding of the factors which affect the flow of broken material into the dipper during loading can help to evaluate the performance of the excavator, define the criteria for equipment selection and develop ways to mitigate equipment damage caused by broken particles. In this paper, the mechanism of granular material flow was investigated through a series of laboratory tests by moving 1:32 and 1:20 (cube root scale) models of a 44 m3 dipper through a test bin filled with angular crushed limestone. It was found that neither dipper angle nor hoist speed has significant influence on the general flow pattern. It was also found that the general flow mechanism is independent on the size of the dipper. Quantitatively, it was determined that hoist speed and pitch angle affect the productivity of the machine with lower pitch angle resulting in higher payload, and faster hoist speed results in shorter dig time. While both lower pitch angle and faster hoist speeds also produce a higher rate of energy consumption, overall both contribute to improved machine productivity.