The Analysis On Vibration Characteristics Of Thermal Power Plant Circulating Pump And Foundation Structure

Circulating pump is main auxiliary equipment of modern thermal power plant, it is very important in the running entire unit. The stable operation or not of circulating pump is directly influence the operation of the whole power plant. The operation stability is imperative to note the operation performance of the pump unit, the size of vibration value is one of the main technical index to character the running stable of the pump unit and installation quality. The hydrodynamic coupling is used to change the rotating speed of feed pump to accommodate the starting condition of the unit pump. The four equipments booster pump, motor, hydrodynamic coupling, main pump, make up of the pump unit. Once the vibration value exceeds the scope in the running operation by one of equipments, the other equipments running would be surely effected. The circulating pump is vertical pump, the motor and pump lay on different floor, whose foundation are independent, which is different from the normal pump. In the same time, the brace types of the pump and motor are different too. Because of the special foundation structure of the circulating pump, the study is carried to make sure the safety of circulating pump and its foundation and to avoid the resonance do not effect the production.In this paper, the finite element structural analysis software ANSYS and SAP2000 are used to simulate the pump-motor system itself. The model analysis and steady analysis methods are used, and the rotor's critical speed is calculated that the rotor's critical speed higher than the circulating pump's work speed; the natural vibration frequencies, mode shapes and linear vibration displacements are acquired. The resonance is not happened and the vibration displacement under the standard requirement.The different models with different boundary conditions were built up by the finite element software SAP2000, and foundation structure vibration characteristics (nature vibration frequencies, shapes) , and linear vibration displacements by forced vibration are calculated. From analyzed the different models, the circulating pump foundation separated from the pump house foundation can be reflected the vibration characteristics, but the pump house foundation is better. Interaction between structure and foundation is simulated by the model is analyzed, and the conclusion that the bottom supported by the pile base can be simulated by "rigid connected". The motor frame floor unconnected or integral cast in-situ have a great effect on structure dynamic characteristic by analyzed the motor frame floor vibration properties. Mutual influence between pumps is little by analyzed the structure foundation vibration amplitudes with different working conditions, the forced vibration mainly happened between the pump and its foundation. Though comparing with the structure disturbing force points amplitudes can be found that the motor's floor integral cast in-situ model has good integrity and little amplitude. The motor's floor unconnected has bad integrity and the models vibration amplitude value is greater than the floor integral cast in-situ model, but does not exceed pump station design code limit value. The resonance can be effectively avoid between circulating pump and its foundation by proper choosing the structure foundation.