Research On Fault Diagnosis Approach Based On Fuzzy-SDG Of Boiler System

Boiler is as the auxiliary equipment of the chemical system. Its safe and reliable operation is directly related to the safe and economic operation of the chemical system. Therefore, effective fault detection and fault diagnosis for the boiler becomes particularly important. The core of the boiler diagnosis is fault diagnosis method.The fault diagnosis method based on SDG model is one of the qualitative fault diagnosis method. It is from the development of graph theory. It can be created even if there is less information of the system. The SDG model can be able to show the relationship between system’s variables and make the fault propqgation path be at a glance. Therefor, it becomes a commonly used model in the fault diagnosis method based on model. The SDG model’s completeness and robustness are very great. But when the use of the SDG model is to reason fault sources, the’combinatorial explosion’is easier to happen for the bigger system. And resulting in ambiguity is to make the fault diagnosis resolution be low and the diagnosic process is added more artificial constraints.The fuzzy theory is a purely quantitative mathematics. It can use to mathematical method to express vague concept, and this method is conducive to solve fuzzy problem.In order to solve the problems of SDG fault diagnosis for definitive diagnosis and resolution being low, this article will introduce the idea of Fuzzy concept to the SDG model and fault resoning, proposed the fault diagnosis method based on fuzzy-SDG.Specific researchs and work in this text are as follows:(1) Due to conventional SDG model being qualitative, so this paper use fuzzy theory to come ture the quantitative SDG model. This model is called fuzzy SDG model. Its node’s status is fuzzy vector by way of the membership function of fuzzy. Its slip is fuzzy matrix which express the relationship between nodes. The fault propagation is by the way of fuzzy compatibility slip.(2) Due to conventional SDG fault diagnosis being qualitative, so this paper proposed a fuzzy reasoning algorithm based on fuzzy theory. This algorithm which use the computation between fuzzy vetor and fuzzy matrix is easy to effectuation by computer.(3) Because resolution in the algorithm of SDG fault diagnosis is low, this paper has combined work1and work2to propose the fault reasoning method based on fuzzy-SDG. This method takes the fuzzy largest-smallest operator between the fuzzy vector of node and the fuzzy matric of slip, and then use the maximum membership principle to fault reasoning for improving the resolution of fault diagnosis.(4) Under normal circumstances, the result of diagnosis is not unique. So for solving this problem this paper use the weighting method to prioritize candidate fault source. This can reduce workload of maintenance staff, and save time.(5) This paper establish SDG model of65t/h boiler by way of the SDG model based on flow chart and the SDG model based on empirical knowledge. And doing fault diagnosis for65t/h boiler system are used by the fault diagnosis method based on SDG and fuzzy-SDG. Then comparing the diagnosis results to verify that the fault diagnosis method based on fuzzy-SDGmodel can quantitatively derive the fault and high resolution of its diagnosis result.