## 4 Results and Discussion
### Possibilities of Streamlining TR-7A Conveyer Maintenance  
The data obtained for the scraper conveyer TR-7A, regarding the number of failures, their frequency, and their remedial times (Table 2), were collected from one of Jiu Valley's mining exploitation sites, over a period of two years. The main defect found was in the conveyor chain (21.28%), for which the reliability and maintainability analysis presented below were carried out. The operating times between two faults and the repair times for the conveyor chain are specified in Table 3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Part** & **Number of** **Failures** & **Failure Frequency** **f\({}_{\text{c}}\) (\%)** & **Repair Time** **(min)** & **Repair Time** **(min)** \\ \hline Chain & 10 & 21.28 & 530 & 16.56 & 53 \\ Failure of coupling & 9 & 19.15 & 580 & 18.13 & 6.44 \\ Electric failure & 7 & 14.89 & 290 & 9.06 & 41.43 \\ Born out motor & 6 & 12.77 & 390 & 12.19 & 65 \\ Switch PVI & 6 & 12.77 & 380 & 11.88 & 63.33 \\ Chain lifter & 4 & 8.51 & 420 & 13.12 & 105 \\ Gear assembly & 2 & 4.25 & 240 & 7.50 & 120 \\ Return drum & 2 & 4.25 & 230 & 7.19 & 115 \\ Drive drum & 1 & 2.13 & 140 & 4.37 & 140 \\ TOTAL & 47 & 100 & 3200 & 100 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Centralizer of the failures and repair times for the TR-7A conveyer. Figure 6: Ishikawa diagram (cause–effect) for burnt-out motor failure. The data thus obtained have been analyzed using Weibull++ soft (ReliaSoft 2022, produced by ReliaSoft Company, Tucson, AZ, USA) with a view to obtaining the indicators and parameters of reliability and maintainability [37]. The stages followed in the analysis of reliability and maintainability are:  
1. Establishing the acceptance ranking of the distribution law suitable for the respective fault--in this example, it is the conveyer chain (Table 4)--and the remedy times, respectively (Table 5), the individual study of each repartition law no longer being necessary. Depending on the practical experience of the user, the first or one of the first laws of this classification can be used. In the present case, we chose the first laws (Tables 6 and 7). 2. Determination of the reliability (Table 6) and maintainability (Table 7) indicators of the adopted law; \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Current Results Matrix** & & & & \\
**Matrix Order:** & **Ranking** & **LKV** & **BIC** & **AIC** \\
**Distribution 1** ** & & & & \\ \hline Normal & 1 & \(-\)66.45 & 137.5 & 136.9 \\
2P-Weibull & 2 & \(-\)66.48 & 137.6 & 137 \\ Gamma & 3 & \(-\)66.61 & 137.8 & 137.2 \\
1P-Exponential & 3 & \(-\)67.75 & 137.8 & 137.5 \\
2P-Exponential & 4 & \(-\)66.81 & 138.2 & 137.6 \\
3P-Weibull & 5 & \(-\)66.34 & 139.6 & 138.7 \\ Loglogistic & 5 & \(-\)67.47 & 139.5 & 138.9 \\ Lognormal & 6 & \(-\)67.81 & 140.2 & 139.6 \\ Gumbel & 7 & \(-\)70.19 & 145 & 144.4 \\ G-Gamma & 8 & \(-\)1 \(\times\) 10\({}^{99}\) & 2 \(\times\) 10\({}^{99}\) & 2 \(\times\) 10\({}^{99}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Classification of the distribution law acceptance for the chain failure. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Time** & & & & & & **Value 1** & & & \\ \hline Operating times between two failures (hours) & 385 & 126 & 343 & 175 & 28 & 322 & 378 & 357 & 756 & 336 \\ \hline Repair times (minutes) & 50 & 60 & 55 & 60 & 55 & 65 & 65 & 45 & 35 & 40 \\ \hline \hline \end{tabular}  
* values collected from Jiu Valley coal basin.  
\end{table} 
Table 3: Values of operating time between failures and time to repair.