# Hardware Reliability Analysis of a Coal Mine Gas Monitoring System Based on Fuzzy-FTA
## 3 Reliability Analysis Process of Gas Monitoring System Based on Fuzzy-FTA
### Analysis of Fault Tree Results  
By analyzing the results of the fault tree, the following conclusions can be drawn.  
1. The main reasons for the hardware failure of a coal mine gas monitoring system are associated with the control system hardware failure as follows: (i) The factors that cause the failure of the industrial computer include the industrial computer motherboard failure, display failure, and accessory failure; (ii) the factors that cause sensor failures include the gas sensor failure, temperature sensor failure, wind speed sensor failure, power sensor failure, switch sensor failure, power-off device failure, and PLC controller failure; (iii) the factors that cause communication line failures include the mechanical pull and open circuit, self-aging short circuit, and poor contact; (iv) the factors that cause power outages include the abnormal power outages, power line open circuits, and power line short circuits; (v) the factors that cause poor maintenance are insufficient sense of responsibility, lack of spare parts, and insufficient maintenance technology. By analyzing the fault tree structure, we can see that the number of logic OR gates is far greater than the logic AND gates, making the probability of accidents very high.
2. Through the qualitative analysis, it can be seen from the minimum path set that there are only four ways to prevent the occurrence of T events. Coal mine gas monitoring system accidents are prone to occur, and there are a few ways to prevent accidents.
3. There are 19 basic events that lead to accidents. However, since the current hardware equipment has a long mean time between failures (MTBF), the probability of accidents is very low. The accident probability of other basic events related to human operations  
\begin{table}
\begin{tabular}{c} **Top Event Occurs** \\ **Probability Interval** \\ \end{tabular} \\ \hline
0 & [0.000095, 0.000135] & 0.6 & [0.000107, 0.000123] \\
0.1 & [0.000097, 0.000133] & 0.7 & [0.000109, 0.000121] \\
0.2 & [0.000099, 0.000131] & 0.8 & [0.000111, 0.000119] \\
0.3 & [0.000101, 0.000129] & 0.9 & [0.000113, 0.000117] \\
0.4 & [0.000103, 0.000127] & 1 & [0.000115] \\
0.5 & [0.000105, 0.000125] & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Top event probability intervals according to the value of \(\lambda\).  
is generally higher. Therefore, in the failure of coal mine gas monitoring systems, human factors are the main cause of failure [27].
4. From the analysis of structural importance, it can be seen that the three basic events of insufficient sense of responsibility, lack of spare parts, and insufficient maintenance technology occupy the most important weight, and therefore are the top priority for accident prevention.
5. The quantitative analysis shows that the probability of failure of the coal mine gas monitoring system under normal conditions is approximately 0.011%, which is highly dangerous.  
In summary, the management of coal mine gas monitoring systems should be based on human factors, such as the awareness of the job responsibilities of the monitoring personnel, the training and supervision of the monitoring personnel, and the technical ability to maintain the system should be strengthened. This reduces the failure of the coal mine gas monitoring system as much as possible, thereby reducing mine gas outburst accidents.