By Rodion Andreev, Tim Joseph, John Sammut, and Mark Curley
An analysis of dig performance for a hydraulic excavator versus an electric rope shovel of similar size class was performed in terms of the energy required to excavate a unit quantity of the same material from a mining face. The outcome of the analysis was that the energy per unit excavation quantity of rope shovels and hydraulic excavators are in fact identical. This is, for the most part, a material property; such that for any given material the amount of energy to excavate a unit quantity, regardless of the excavating tool, is constant.
But this does not mean that one device is better than another; nor does it represent the total picture driving the selection of one excavating tool over another. The total ‘cost’ of ownership including capital (plus sustaining capital), operating and maintenance costs, time, availability and utilization (productivity and efficiency of use) must also include the qualitative decisions regarding mining method and the mode of application; much of which is driven by the geological, operating and environmental conditions that are highly site specific.
Thus in parallel, a comparative study of rope shovel and hydraulic excavator performance focusing on availability, productivity and life cycle cost (with a sub-focus on maintenance costs) was undertaken for 60,000 operating hours per machine, where data was available. Each machine’s performance was assessed by operating hours, maintenance activity impacting availability and productivity per m3 bucket capacity as a comparison normalizing factor, regardless of excavator size. Cost of ownership including: capital outlay, operating and maintenance costs including but not limited to spare parts, fuels, lubricants, electricity and consumables, were considered.
The results indicated higher production rates by excavator of similar capacity and age. In general, electric rope shovels, with higher initial purchase cost, exhibited lower service cost per m3 capacity, becoming overall more cost effective within 5 years (~30,000 hours) of operation over the hydraulic excavator counterpart of similar capacity.