Abstract：Fracture often occurs suddenly at the start-up to the impeller of high-temperature tower bottom slurry oil pump when it has been used for a period of time.To find the cause of this phenomenon,some possible factors are considered.A series of experiments were done from the macroscopic inspection which was aimed at the breakpoints to the microscopic tests,such as material composition test and hardness measurement to the impeller.Metallurgical structure test to the breakpoints were done to the model in which this phenomenon most occurred.Thermal shock theory was also applied to the failure analysis to the impeller.The analysis and test proved that there are serious casting defect in the impeller and deviation during the heat treatment and strength reduction in high temperature environment.Among them,stress derived thermal shock were the main cause for the failure of impeller.Through the improvements in the aspects of impeller structure,casting and heat treatment process,and the operating regulation during star-up,the problem of impeller fracture has been basically solved.
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