| Spring full-open safety valve is a widely used over-pressure protection device and it’s reliability makes the directly affect to the safety and economic benefits. This paper uses the the FMECA method to analysis the cause and the effects of the failure modes, such as vibration, leakage, frequency hopping and so on. Because of the weakness of the traditional FMECA method, such as the poor in distinguish the failure modes if they have the same risk priority number, the improved FMECA method is proposed and applied to analysis the safety valve. The improved FMECA method analysis the safety valve by combining the method of the fault tree and the stochastic petri nets, that provides a whole new way of thinking for the quantitative assessment to the safety valve, and it has a prominent practical significance. The main work and results are as follows:1. The advantages and disadvantages of usual reliability calculation methods such as the fault tree, the FMECA method and the Markov method are compared. The paper also proposes an improved FMECA methods which is described in detail about it’s method and construction step. The improved FMECA method combinates the fuzzy algorithms as well as fault tree method to fully consider the impact of different factors on the failure type, therefore, it can separate the failure modes with the same risk priority number, that can increase the logical and intuition of the result.2. The causes which result the failure modes of the spring full-open safety valve is analysised, and the paper gives the corresponding improvements to each failure mode. The important degree of various components and the fault tree of various failure modes are given by the improved FMECA method.3. Considering the result of improved FMECA and the conversion relationship between the fault tree and stochastic petri nets, the paper takes a reliability analysis to the spring full-open safety valve and gets some reliability date in the last. |
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