Thermal Fatigue Analysis And Prototype Monitoring Technology For High Temperature And Pressure Pipeline

For high temperature and pressure pipeline, when it occurs temperature transient, thermal stratification, or turbulence penetration phenomenon, which cause high thermal alternating stress in pipeline, maybe result in cumulative fatigue damage on welded joint and regions of stress concentration.In order to ensure long-term safety, it requires a real time assessment of cumulative fatigue damage in high temperature and pressure pipeline.Thermal fatigue phenomenon occurs when the high temperature and pressure pipeline is operating, as a result of lack of information in fatigue failure mechanism. It is necessary to acquire more information for researching the thermal fatigue problem of high temperature and pressure pipeline by prototype monitoring technology. In this paper we will research the fatigue monitoring technology for high temperature and pressure pipeline. The main contents are as follows:Firstly, an analysis work is carried out for the special fluid behaviors, which maybe cause thermal fatigue in high temperature and pressure pipeline, to determine the monitoring objective. From the monitoring objective, a technology roadmap of thermal fatigue monitoring method on high temperature and pressure pipeline is built.Secondly, thermal shock, thermal stratification and turbulence penetration, the phenomenon that occurs on pipeline, are simulated by finite element software. Based on the simulation, there is an analysis for pipeline temperature and regions of thermal fatigue. According to the result of temperature field on pipeline, RBF network method is used to predict the temperature in pipe inner wall. And then, neural network is proved to be feasible.Thirdly, thermal stress in pipeline is calculated in combination with Green’s Function and finite element software. The through-wall thermal stress distribution can be represented by Lagrange Polynomial fit. Then, we can calculate cumulative fatigue damage.Finally, based on the method of thermal fatigue monitoring in high temperature and pressure pipeline, a monitoring system is designed in primary circuit pipeline system of PWR nuclear power plants.