Risk Analysis Of Joint Welding Of Pressure-bearing Parts Of High-pressure Boilers

With the continued implementation of Made in China 2025 plan,driven by a series of related policies such as structure adjustment,capacity cutting,steady growth and economy transformation,China's demand for energy efficiency-is increasing.At the same time,high pressure boiler also gradually develops at the aspects of high parameter,large capacity and complexity.However,high pressure boiler pressure parts,as the heart of high pressure boiler,are prone to risk even accident because they serves for a long time under the working conditions of the coupling of high temperature,high pressure,corrosion,vibration and so on.Therefore,the risk analysis of the potential factors for high pressure boiler pressure parts joint welding has practical significance in order to prevent systemic accidents of the high pressure boiler pressure parts.Based on the actual production of Kunming Boiler Company Limited,the analysis of welding strength and its risk focuses on the four aspects:1)The research object is conducted through risk identification by using AHP(Analytic Hierarchy Process)combined with Bayesian network,causal analysis method.And then the risk degree of pressure parts joint welding is half-quantitatively estimated by using Bow-tie model technology;2)The pressure parts joint strength and its fatigue life is analyzed and predicted by adopting GM(1,1)model so as to reasonably evaluate the fatigue life of pressure parts joint welding under the effect of multiple coupling;3)Through the improved ant colony algorithm,the welded joint is built three-dimensional path modeling and optimization in order to reduce the residual stress of welded joint after welding and decrease the risk accumulation of the welded joint in the processing and manufacturing.4)The basic risk events are analyzed and sorted by introducing the risk matrix analysis method so as to improve the ability of overall risk control.Through NDT(Non-destructive Testing),mechanical property test,electron microscope scanning,microstructure histology analysis and macroscopic fracture analysis of the boiler welded specimen,and also the data comparison analysis of mechanical property test and numerical simulation,the causes and consequences of the joint welding defects of the high pressure boiler pressure parts are systematically analyzed.And the stress distribution is also studied under the influence of the multi-factor coupling.Then,based on the related national standards and design specifications,through application of Finite Element Method,Ant Colony Optimization and Bayesian Network,the joint welding joint failure cause mechanism and micro and macro fracture mode are analyzed and studied.Finally,the stress concentration weak welding area based on the finite element calculation of stress concentration weak welding area,combined with the safety factor analysis,risk matrix method,the risk of high pressure boiler pressure parts joint welding is put forward some targeted control measures and suggestions.