Failure Mechanism Research And Lifetime Evaluation Of Boiler Tubes In Power Station

The tubes of waterwall. superheater, reheater and economizer are the main component of the heat exchangers in boiler. Whether they run safely and stably or not is directly count for much the safe of the whole plant operation. And the frequent tube leakage of heat surface impact upon the economy benefits and the society benefits of the power plant.The dissertation goes deep into the tube failure mechanism and the reliability theory in order to improve the diagnosis and monitor veracity and tone up the operation reliability. The parameters of the tube life lapse is expressed by the Weibull distribution function and the effect of the parameters on the life lapse is derived. And it is confirmed the operation temperature and the pressure and the service time are the main factors of the life lapse.Then the practical run conditions are characterized and predigested in view of the material mechanics, and the tube life lapse model is built and applied to estimate the tube remain life. The cell differential matrix equation is founded on the basis of mechanics analysis of the waterwall and superheater tubes. It is computed by the ANSYS FEA software the effect on the heat and stress coupling field of some operation parameters, which is the theory guidance for accelerated lifetime tests and the accurate life evaluation.It is researched that the influence on the tube lifetime of the metallographic structure and the alloy element and the rigidity by the test the superheater and reheater tube which is made of 12Cr2MoWVTiB steel. The metallographic change after the tube has run in the high temperature and high pressure condition for long time is more believable and frank than the intensity lifetime analysis to evaluate the tubes remain lift time.In the end of the dissertation, a tube lifetime evaluation software system is developed with the utility of the Finite Element Analysis stress computation and the metallographic tests. The lifetime of the platen superheater tube is evaluated by the software system.