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Aiming at the problems of poor operating conditions, low operating efficiency, and improper maintenance of mine down-hole equipment, a new maintenance strategy model for cycle prevention is proposed. The model comprehensively considers the effect of down-hole environment on the equipment failure rate and the effect of preventive maintenance and minor repairs to the cost. Based on the historical fault data, the equipment failure rate function parameters are estimated by the least square method and correlation coefficient method. Considering the down-hole environment, the fuzzy rate theory is used to correct the failure rate function, and the cycle prevention maintenance strategy model aiming at optimizing the equipment maintenance cost is established. Finally, an example is given. The research shows that the maintenance period is shortened to 23.64 h after optimization, and the total cost of maintenance is reduced from 574,621 yuan to 378,942.44 yuan, saving maintenance costs of 195,678.56 yuan. The maintenance strategy is in line with the actual situation of down-hole equipment in mining enterprises, and it can provide effective maintenance solutions for down-hole equipment in mine enterprises. [ABSTRACT FROM AUTHOR]

In order to identify key processes in coal mining and preparation processes for optimized process control and quality improvement, a modified causal matrix method is proposed to reduce quality defects and avoid unnecessary investments. The limitations of existing key processes identification methods are reviewed with the identified key process identification requirements in the context of the coal mining industry. The Key Process Identification Method of Coal Preparation (CP-KPIM) is proposed based on a redesigned causal matrix method, which considers four aspects, i.e., the systematic production data set, multi-dimension quality measures, the correlation between processes and quality characteristics, and a unified total process criticality assessment method. The implementation steps of CP-KPIM are demonstrated in details through a case study in a heavy medium coal preparation plant. Based on the total process criticality assessments, eleven key processes were identified from a total of fifty-three processes. In addition, the CP-KPIM has demonstrated significant productivity improvement through the process capability analysis. [ABSTRACT FROM AUTHOR]