## 3 Results and Discussion
### Quantitative Analysis
#### 3.2.1 Preliminary Analysis  
Over the analyzed period, a total of 147 service works were performed, consisting of 204 repairs. The preparatory and service works required 979 workers, and this number does not include rescue workers, who participate in the preparatory works. The most common repairs included replacements of the vertical sealings B, replacements of the through lining A, and replacements of hopper linings C. Less frequent repairs were required in the case of the feeder trough G, the running rails F and the lining on the back wall of the hopper H. The number of repairs made to individual elements is presented in Figure 8.  
Based on Figure 9 which presents what type of repair and how many of them were done on the specific shift, it is concluded that in the majority of cases, the replacement of the feeder trough linings A was accompanied by the replacement of the vertical sealings B, as dictated by the design of the receiving bin and the operation of the device. Moreover, this procedure is frequently preceded by the ripping of rock overhangs inside the bunker. Also, on multiple occasions the repairs of A and B were accompanied by the replacement of the hopper lining C. For this reason, similar wear rates of the three elements (A, B, and C) would represent an optimal scenario. To identify relations between A, B, and C repairs association rule mining was implemented. Results of metrics for different association rules are presented in Table 1.  
Figure 8: Total number of the A-H elements repairs.  
For rule if A then B, support value indicates that around 25% of analyzed repairs involved A and B element repair the same day in specific bunker. The confidence value means that out of all A repairs, around 65% of the repairs also contained B element repair. The last metric shows that repair of B element is 1.58 times more likely when A repair is done. If A then B and C are considered, the support value shows that 31% of analyzed repairs contained A, B, and C repairs the same day for specific bunkers. The confidence value means that out of all A repairs, nearly 53% of the repairs also contain B and C repair. Finally, the lift indicates that B and C repair is 1.49 times more likely to be done while A repair is carried out.  
In view of above results, A, B, and C elements are crucial for bins maintenance from mining units management perspective. The repair or replacement of mentioned elements generates a considerable part of the cost, since more mining workers are needed than for regular repair. Therefore, the total number of repairs of A, B, and C elements were calculated and are presented in Table 2. Because results show that the highest number of works was done in II and III units, histograms of time between A, B, and C elements repair was prepared and showed in Figures 10 and 11.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Rule** & **Metrics** & **Support** & **Confidence** & **Lift** \\ \hline If A then B & 24.49\% & 65.45\% & 1.58 \\ If A then B and C & 31.03\% & 52.94\% & 1.49 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Results of association rule.  
Figure 9: Repairs of A, B and C elements performed over the shifts (I, II, III).  
The mean time between A, B, and C elements repair in II mining unit equals 31, 29, 35 days, respectively. In comparison, for III mining unit values increase to 65, 88, and 135 days, respectively. The difference in achieved results comes from the location of the mining unit in the transportation system and amount of transported material.