Failure Risk Assessment And Reliability Study Of Icebreaker Electric Propulsion System

The reliability of the electric propulsion system is an important guarantee of the icebreaker’s ability to break ice and navigate in harsh environments,and a failure of the electric propulsion system could cause serious damage.Although there are many risks in the operation of the electric propulsion system of an icebreaker,the research results of failure risk assessment and reliability analysis for the system are very rare.Therefore,this paper fully considers the failure risk characteristics of the icebreaker electric propulsion system,combines the FMEA method,FTA method and Multi-index Comprehensive Decision-making method based on grey correlation degree,carries out the failure risk assessment and reliability analysis of the icebreaker electric propulsion system,quantitatively evaluates the identified risks,and finally selects the optimal risk control option to provide the basis for decision-making.The main research contents are as follows:（1）The icebreaker electric propulsion system is a typical complex system with multiple and interrelated failure modes of components,coupled with the fact that actual operational failure data is not yet complete,this paper analyses the icebreaker electric propulsion system of the“Xuelong 2”using the FMEA method combining fuzziness and correlation.Firstly,the expert knowledge is quantified by triangular fuzzy number and integrated,then the Technique for Order Preference by Similarity to Ideal Solution is used to process the integration results,and the risk ranking of failure causes based on relative proximity is obtained.The fuzzy DEMATEL method is used to calculate the cause degree between the failure modes,which is used as the basis for the correlation ranking.The secondary comparison of the failure causes that cannot be effectively distinguished by the relative proximity is carried out,and the final risk ranking of all failure causes considering the correlation is obtained.It is calculated that the risk of“propeller blade damage-sea ice collision”is the highest.The result shows the risk degree of different failure causes of“Xuelong 2”icebreaker electric propulsion system,and the ranking has significant discrimination.（2）In this paper,the fault tree is established based on the failure of the electric propulsion system of“Xuelong 2”icebreaker,and the bottom event and intermediate event are set according to the FMEA results,the real ship system and the relevant literature records.The failure rate of the bottom event is used as the input to quantitatively analyze the fault tree,and the failure rate,MTTF and the key importance of each bottom event of the icebreaker electric propulsion system and its subsystems are solved.The failure rate of the electric propulsion system was obtained as 3.95×10^-4h^-1,with an MTTF of 2531.6 hours The failure rate results of electric propulsion system are compared with the statistical data,which proves the applicability of the fault tree model to the risk assessment of the icebreaker electric propulsion system.Finally,this paper further deepen the analysis of the underlying failure causes,build a more complete extended dynamic fault tree based on the above-mentioned fault tree that has completed quantitative calculations,and carry out qualitative analysis work to obtain all minimum cut sets.（3）Taking the three most dangerous system failure causes in the risk assessment results as the accident scenarios that need to be improved,the corresponding risk control option（RCO）is proposed,and the priority ranking of each option is given.Firstly,this paper selects the appropriate evaluation index of the fault risk control option of the icebreaker electric propulsion system.The grey relational analysis method is used to calculate the grey correlation degree of each risk control option in the above index system,and the option comparison is carried out accordingly.The results show that under the evaluation index system of risk control option,the application of grey correlation analysis method can effectively optimize the risk control option of icebreaker electric propulsion system,and provide decision-making basis.