Measurements of loads on belt conveyor idlers operated in real conditions

Abstract

In typical high-capacity belt conveyors operated in open cast lignite mines, the top run is supported with flexible, “garland” idler sets comprising three rollers. Idlers in such sets are subjected to random loads which act in both radial and axial directions and which result from variable stream of transported material and from constant interaction with the belt. Loads acting on bolts in such flexible systems may be used as a measure of loads acting on belt conveyors. Shearing forces exerted on the bolts may be determined with the use of strain gauges, but their installation requires specially prepared surfaces and may decrease bolt strength. The very arrangement of three idlers in a garland system causes the resultant shearing forces on bolts to be significantly greater than the forces carried by the idlers, and therefore has a major effect on the accuracy of measurements. Experiences with direct measurements of the resulting forces acting on bolts led to the implementation of a special measuring frame, which retains the mobility and geometry typical of a garland system, but takes some of the forces from the idlers, leaving only those components which have a direct effect on idler loading. As a result, more accurate measurement results were obtained, especially in relation to axial forces. Owing to the special measuring frame, loads acting on idlers could be determined in the whole range of belt conveyor capacities.