Reliability Analysis Method of a Control System for Subsea All-Electric Christmas Tree

The subsea all-electric Christmas tree (XT) is a key equipment in subsea production systems. Once it fails, the marine environment will be seriously polluted. Therefore, strict reliability analysis and measures to improve reliability must be performed before a subsea all-electric XT is launched; such measures are crucial to subsea safe production. A fault-tolerant control system was developed in this paper to improve the reliability of XT. A dual-factor degradation model for electrical control system components was proposed to improve the evaluation accuracy, and the reliability of the control system was analyzed based on the Markov model. The influences of the common cause failure and the failure rate in key components on the reliability and availability of the control system were studied. The impacts of mean time to repair and incomplete repair strategy on the availability of the control system were also investigated. Research results show the key factors that affect system reliability, and a specific method to improve the reliability and availability of the control system was given. This reliability analysis method for the control system could be applied to general all-electric subsea control systems to guide their safe production.