Reliability and Safety Modelling of the Electrical Control System of the Subsea Control Module Based on Markov and Multiple Beta Factor Model

Replacement of the subsea control module (SCM) and halting production caused by the failure of the SCM are costly, and the electrical control system plays a large role in the failure modes of the SCM. Hence, the analysis of its reliability and safety is important. Markov processes and the multiple beta factor model are used to model the reliability and safety for the electrical control system of the SCM that consider the effects of multiple factors, including the failure detection rate, common-cause failure, and the failure rate of each module, for evaluating system reliability and safety. The Morris screening method that is based on a large amount of random data with equal probability is applied to reliability and safety models that vary with time for quantifying the effect levels of each factor on the system reliability and safety in the time interval. The effect of each factor on the system and its interaction degree with other factors are evaluated in the time interval. Finally, the system model is simulated in MATLAB. The simulation demonstrates that the system reliability and safety gradually decrease and the effect of each factor on them increases over time; the reliability is most sensitive to the failure rates of the input, central processing unit, and output modules, whereas the safety is most sensitive to the failure detection rate. The common-cause failure and the comparator module have some effects on the reliability and safety of the system.