Cable Shovel Stress & Fatigue Failure Modeling - Causes and Solution Strategies Review

Material excavation is the primary activity in surface mining operations; and shovel excavators are the primary production equipment in mining industry. The active population of cable shovels is about 2400 units around the world out of which 1700 are 20mt or larger capacity (http://parkerbaymining.com/mining-equipment/ electric-shovels.htm). Joy Global (P&H), Caterpillar (formerly under Bucyrus) and OMZ(IZ-KARTEX) are the largest electric shovels OEM around the world. The cable shovel is the preferred equipment for excavating larger capacities economically over its economic life. The capital investment in cable shovels can be as high as $25 million. The efficiency of the overall surface mining operations, where shovel-truck system is the primary mining system, is largely dependent on shovel efficiency. There is a trend in the mining industry towards excavating and loading more tons per scoop to achieve the economies of scale and reduce per ton excavation and haulage costs. There has been an increasing trend in cable shovel capacities as the capacity improved from 5yd3 in 1960 to 44+ yd3 today. Modern day cable shovels have the payload capacities of 100+ tons per scoop. The excavation of 100+ tons per scoop, combined with the weight of the dipper, and diggability variation of the formation result in varying mechanical energy inputs and stress loading of the boom and dipper-and-tooth assembly across the working bench. Furthermore, the repeated loading and unloading cycles of the shovel induce fatigue stresses in the shovel components. The induced stresses over time may exceed the yield strength of steel/ material of the shovel leading to fatigue failure, teeth losses, and boom and handle cracks. These frequent breakdowns result in increased shovel downtime, reduced efficiency, higher repair costs, and increased production costs.