Dragline cycle time analysis

Abstract

Draglines operate in a cyclic nature. Excluding the infrequent walking, a dragline spends its major operational time by digging the dirt and paying it out on a spoil pile. Considering the fact that a dragline performs tens of thousands of cycles per year, it is evident that even a small reduction in a single cycle time would result in a significant increase in productivity. Thus, it is to the benefit of a mine that dragline cycles need to be critically analyzed and corrective measures be taken. Although there exist different opinions on what segments constitute a dragline cycle, in this study it is accepted that a dragline cycle is composed of the following phases: (i) Filling the bucket by dragging it towards the dragline; (ii) Swinging the loaded bucket along a predetermined arc; (iii) Paying out the dirt onto a spoil pile; (iv) Swinging the empty bucket back to excavation face; and (v) Positioning the bucket to re-load. The study is based on field investigation conducted on six draglines with different capacities and operating modes. Stopwatch study is performed. Influence of cut dimensions, nature of material excavated, mode of digging, type of bucket employed, swing angle, operators’ judgements and condition of dragline on cycle time are analyzed. The results are presented by tabular data and illustrations.