# New Method to Study the Effectiveness of Mining Equipment: A Case Study of Surface Drilling Rigs
## 4 Discussion
The production rate in Mine 1 ranges between 38.94 m/Ho and 36.05 m/Ho, achieving always optimal values over time, while it is between 33.99 m/Ho and 28.30 m/Ho in Mine 2, reaching low performance levels compared to the overall average value, 37.12 m/Ho, which is also reducing over time. The productivity index enables analysis of the operating conditions, the management strategy, and the operator's skill in both open-pit mines. Mine 1 reaches values between 0.97 and 1.05, fluctuating around 1 over the years, whichimplies that the equipment performance is adequate and the management strategy and the operating conditions are appropriate. On the other hand, the productivity index ranges from 0.76 and 0.91 in Mine 2, together with a low production rate, which shows that the management strategy and the operating conditions in Mine 2 are not accurate. Operator skill could be considered appropriate as some operators have been working in both mines using different drilling rig equipment without suffering relevant deviations in the production rate and the productivity index. Concerning the production rate, it remained stable over the years in both case studies, indicating the maintenance strategy is appropriate. Thus, this study shows how the OMEE index is a crucial parameter in determining the effectiveness of the drilling rig equipment. It allows us to estimate the performance accuracy of the equipment through the analysis of the availability rate, utilization rate, and productivity index. Furthermore, it enables comparative analysis between current and historical performances of the mining equipment or similar mining equipment fleets, located in different mines, working under similar conditions. Results obtained show that the OMEE index is 0.75 in Mine 1, which means that the drilling rig equipment performance is accurate and the management strategy, the management maintenance, and the operation conditions are appropriate. Figure 8 shows that the OMEE index trends slightly downward over time in Mine 1 due to its continued degradation. There is an important relationship between maintenance, productivity, and replacement in mining equipment [1,3] and, for this reason, the OMEE index could be a potential tool to analyze this relationship. On the other hand, the OMEE index obtained from Mine 2 runs from 0.57 to 0.38, showing a downward trend over time, indicating inaccurate equipment performance due to inappropriate utilization rate and low productivity index. The case studies analyzed are an example of the potential that this method can offer to the mining industry in achieving sustainable goals, with a user-friendly approach. The method presented can be used to analyze individual and collective performance of mining equipment, identify the key influencing factors in the mining process [52], pinpoint the weak areas of the process, and estimate the potential improvements [53]. Mining equipment is subjected to continuous degradation throughout its operation life, and most of the replacement models study the life cycle cost (LCC) [24,30]. This research shows that the OMEE method could be an important tool for replacement decisions, analyzing the trend over time of the mechanical and technical availability rates and the production index. The flexibility of the approach extends its applicability to other types of mining and similar sectors such as civil works. It is also found that an appropriate preventive and predictive culture anticipates failures while improving availability and reliability, in accordance with previous research [39,44]. Further research could be conducted in the KPIs' selection, analyzing potential additional factors to include for other types of equipment. Following the recommendations of [PERSON] et al. [8], KPIs could be modified in future studies to standardize data and facilitate interpretations for similar mining operational activities.