## 4 Results and Discussion
### The Analysis of the Fundamental Reliability and Maintainability Indicators  
Figures 7-11 show the functions: of failure probability (Figure 7), unreliability (Figure 8), density of probability (Figure 9), failure rate (Figure 10), and repair rate, respectively (Figure 11).  
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Results Reports 1****} \\ \hline
**Report Type** & **Weibull++ Results** \\ \hline Name & **User Info** \\ Company & & [PERSON] \\ Date & & University of Petrosani \\  & **Parameters** \\ Distribution & & Normal 2P \\ Analysis & & RRX \\ CB Method & & FM \\ Ranking & & MED \\ Mean (hr) & & 320.600028 \\ Std (hr) & & 196.819109 \\ LK Value & & \(-\)66.449307 \\ Rho & & 0.924127 \\ Fail\(\backslash\)Susp & \(10\backslash\)0 \\  & **LOCAL VAR/COV MATRIX** & \\ Var-Mu = 3873.776177 & CoVar = 0.000671 \\ CoVar = 0.000671 & Var-Sigma = 2330.451737 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Adopted exponential repartition law parameters for the chain failure.  
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Results Reports 1****} \\ \hline
**Report Type** & **Weibull++ Results** \\ \hline Name & **User Info** \\ Company & & [PERSON] \\ Date & & University of Petrosani \\  & **Parameters** & \\ Distribution & & Weibull 2P \\ Analysis & & RRX \\ CB Method & & FM \\ Ranking & & MED \\ Beta & & 5.411076 \\ Eta (hr) & & 57.303281 \\ LK Value & & \(-\)36.954764 \\ Rho & & 0.986964 \\ Fail\(\backslash\)Susp & & \(10\backslash\)0 \\  & **LOCAL VAR/COV MATRIX** & \\ Var-Beta = 2.130158 & CV Eta Beta = 0.418039 & CV Eta Beta = 0.418039 \\ CV Eta Beta = 0.418039 & Var-Eta = 12.663176 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Adopted exponential repartition law parameters for the chain repair.  
Figure 8: Unreliability function for the chain.  
Figure 7: Probability function for the chain.  
Figure 10: Failure rate for the chain.  
Figure 9: Probability density function for the chain.  
The great number of the results obtained allowed graphs to be developed regarding the chain reliability evolution in time (Figures 12 and 13).  
Figure 11: Repair rate for the chain.  
Figure 12: Chain reliability values, for a 39.9% confidence level.  
From these graphs, we see low values of the conveyer chain reliability result, so that the probability for it not to fail after 371 h of operation in effect is as low as 40% (Figure 12). This shows that for a 40% confidence level (a 60% risk margin being very high), we should expect the replacement of the chain after approximately 15 days of operation (the conveyer operates 5 h a day for 5 days a week).  
If an 80% reliability is imposed (Figure 13), which is a value imposed by the beneficiaries of the underground mining equipment, only 156 h of operation will result in no failure, which means that after approximately 7 days of operation in effect, it will be necessary to replace the chain.  
From the analysis of the maintainability of the conveyer chain, it is noticed that in order to replace the chain in approximately 47 min, the maintainability is only 30% (Figure 14), with an increase of approximately one hour for a maintainability of 80% (Figure 15).  
Figure 14: Chain maintainability values, for a 29.9% confidence level.  
Figure 13: Chain reliability values, for a 79.9% confidence level.