The reliability of watercraft depends to a large extent on the reliability of main propulsion plant. It should be distinguished on the base of mission variation charged by watercraft during study of main propulsion plant’s reliability. The mission reliability under rated and economical speed is studied via one main propulsion plant as subject in this paper, while the influence performance degradation of main propulsion plant on its mission reliability mostly studied. Relative curve between mission reliability and working time has been found. The results show that, reliability model in view of performance degradation has good expansibility, approach more to actual malfunction of main propulsion plant, as well as evaluates performance of main propulsion plant well and truly. The results could be guidance for user to establish maintenance schedule in order to improve the mission reliability of main propulsion plant.

The component and mission of CODOG propulsion system were analyzed in this paper. According to the mission variation, different operation conditions were introduced and mission reliability models of each condition were established by the use of reliability theory. After reliability data of main component of CODOG propulsion system been obtained, mission reliability of each condition was calculated and its phased mission was simulated through MATLAB software. Relative curve between system reliability and working time was found. The results show that, mission reliability of cruise condition is the biggest while phased mission reliability is the smallest. System availability is bigger than reliability after taking maintainability into account. System reliability can increase to a great extent and its useful life is longer by improving maintainability of its component.

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