Effects of Machine Parameter and Natural Factors on the Productivity of Loading and Haulage Equipment

Abstract

The purpose of this research is to investigate the factors which affect the performance of the loading and hauling equipment at Skorpion zinc mine, Namibia and also to find possible solutions to eliminate them, so that the weekly Zinc Oxide and ex-pit waste tonnages required could be produced. This is due to the high demand of Zinc on the market. The investigation on road conditions was focused on the effects of rolling resistance, grade resistance and road widths from the road between bench 540 in pit 103 to the Zinc oxide medium grade stockpile. Cycle time data were obtained by time and motion study of the load/haul/dump cycle from bench 540 loading site to the stockpile. The data used for equipment matching by queuing theory (excel modelling) was obtained when the loaders where loading Arkose at different loading sites. The effects of different weather conditions i.e. mist, rain and wind on production where determined by collecting actual shift production tonnages and comparing with target shift production targets during this conditions. The results produced from time and motion studies show that the haul trucks have an average availability of 80.4% and utilization at 49.7% which are very low when compared to the benchmark value of 89% and 69% for availability and utilization respectively. Decline in performance time is caused by factors such as daily safety meetings, lunch breaks, blasting, tools break down and the daily machine service. Rolling resistance is also one of the factors affecting production time at the mine. The rolling resistance of different segments was determined by roughness defect scores (RDS). From calculations, it is clearly seen that if the RR could be reduced to 2% on every road segment, then each cycle period per truck can be reduced by 1.24 minutes. This will increase the production of the haulers and decrease the operating cost. It was recommended that the wearing course of the road surface be treated with a bitumen based dust suppression product in order to keep the surface’s rolling resistance to an absolute minimum (i.e. RR = 2%) [1]. The current average hauling road width is 15.987 m while the correct road width at Skorpion Zinc Mine must be 21.35 m to prevent bunching of trucks. It is therefore recommended that the haul roads be widened to 21.35 m width per segment.