## 4 Discussion and Results
### Impact of Uncertain Problems on Reliability  
The wellhead connector works in the harsh environment of the deep sea for a long time; thus, many uncertain accidents may occur. When an accident occurs, the subsea monitoring system will detect which failures occur, and these failures will directly affect the reliability of the system. The algorithm proposed in this paper can make a timely analysis of the impact of uncertain problems on the system.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Results** & **Fault Tree** & **Fuzzy** & **Bayesian** & & & \\
**Analysis** & **Analysis** & **Comprehensive** & **Networks** & **Petri** & **Markov** & **Fuzzy** \\
**Capability** & **(FTA)**[38,43] & **Evaluation**[10] & **[44,45]** & **Nets** [46] & **[41,42] & **Markov** \\ \hline Risk & \(\times\) & \(\surd\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\ Failure rate & \(\times\) & \(\surd\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\ Reliability & \(\surd\) & \(\times\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Availability & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) & \(\surd\) \\ Maintainability & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) & \(\surd\) \\ MTTF & \(\times\) & \(\times\) & \(\surd\) & \(\times\) & \(\surd\) & \(\surd\) \\ Uncertain & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\ problems & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Method comparison.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Transfer Rate** & **Value** & **Transfer Rate** & **Value** \\ \hline \(\lambda_{1}\) & \(3.44859\times 10^{-12}\) & \(\lambda_{13}\) & \(6.32781\times 10^{-14}\) \\ \(\lambda_{2}\) & \(4.2376\times 10^{-12}\) & \(\lambda_{14}\) & \(3.58388\times 10^{-11}\) \\ \(\lambda_{3}\) & \(4.32267\times 10^{-11}\) & \(\lambda_{15}\) & \(5.83985\times 10^{-13}\) \\ \(\lambda_{4}\) & \(6.21879\times 10^{-12}\) & \(\lambda_{16}\) & \(6.04799\times 10^{-11}\) \\ \(\lambda_{5}\) & \(3.58388\times 10^{-11}\) & \(\lambda_{  
For example, when an accident such as a trawl or a falling object occurs, the monitoring system detects the deformation of pressure ring. At this time, the \"Failure Cause Probability\" of the pressure ring deformation is directly changed from the original level to \"5\", keeping the \"Failure Effect Severity\" as constants. According to Equations (2)-(17), the new _FFR_ of the pressure ring deformation is \(1.417\times 10^{-9}\). According to Equation (21), when uncertain accidents occur, the new system reliability can be obtained, as shown in Figure 10.  
It can be seen from Figure 10 that if the pressure ring deformation occurs at t = \(10^{9}\) h, the reliability of the system decreases from 0.61 to 0.15. Absolutely, it is also possible to evaluate the impact of simultaneous occurrence of different failure modes on system reliability. The \"Failure Cause Probability\" of the corresponding failure modes only needs to be changed to \"5\" if it happened seriously; the new system reliability can be obtained according to the model in this paper.