Research On Fault Diagnosis Of FCC Unit Based On SDG-FTA Method

As an important part of the refining process,the catalytic cracking unit has a complex production process,a wide variety of operating variables and equipment,which has a high probability of failure.Therefore,the research on fault diagnosis of the device has important practical significance.In this paper,based on the advantages of symbolic directed graph(SDG)to reveal the potential fault propagation law and completeness,and the advantages of fault tree analysis(FTA)in quantitative analysis,the fault diagnosis research based on SDG and FTA has been completed.First,the easily failed FCC unit is taken as the research object.On fully considering the working condition,a SDG model based on flow chart method and empirical knowledge method is proposed,and a fault tree model based on SDG model is proposed.Then,the SDG model and fault tree model of reaction regeneration system,flue gas energy recovery system,fractionating system and absorption stability system are established respectively.And using the "downlink method" to complete the fault tree qualitative analysis,the model minimum cut set is obtained.Secondly,according to the basic events fuzzy problem of the each fault tree model,the basic event fuzzy number of the probability is obtained by using the triangular fuzzy theory,then the probability fuzzy number of the minimum cut set is obtained,and the probability of the top event and the basic event probability importance are determined,and comparing the probabilistic importance of each basic event in each system,determine the location of the most prone to failure in each system.Finally,based on the C# software development platform,we completed the development of FCCU fault diagnosis system.The research in this paper provides an effective method for the diagnosis of catalytic cracker faults,providing a basis for further improving the accuracy of fault diagnosis and safe operation of the catalytic cracking unit.