For a Milestone centrifugal pump with a long shaft, it is easy to have insufficient shaft stiffness, too large deflection and poor straightness of the shaft system, which causes friction between moving parts (transmission shaft) and static parts (sliding bearing or mouth ring) and vibration. In addition, the Milestone centrifugal pump shaft is too long, which is greatly affected by the impact of flowing water in the pool, so that the vibration of the underwater part of the Milestone centrifugal pump increases. If the balance plate gap at the end of the shaft is too large, or the axial working displacement is not adjusted properly, the low-frequency displacement of the shaft will be caused, resulting in the vibration of the bearing bush. The eccentricity of the rotating shaft will lead to the bending vibration of the shaft.
The Milestone centrifugal pump base and the cement base is not good, and the absorption, transmission and isolation ability of the foundation and the motor system are poor, resulting in the vibration of the foundation and the motor exceeding the standard. If the Milestone centrifugal pump foundation is loose, or the Milestone centrifugal pump unit forms an elastic foundation during installation, or the foundation stiffness is weakened due to the oil immersed water bubble, the Milestone centrifugal pump will generate another critical speed with the vibration phase difference of 1800, so as to increase the vibration frequency of the Milestone centrifugal pump. If the increased frequency is close to or equal to the frequency of an external factor, the amplitude of the Milestone centrifugal pump will increase. In addition, the foundation anchor bolts loose, resulting in reduced constraint stiffness, will make the vibration of the motor intensified.
The circumferential spacing of the coupling connecting bolts is poor, and the symmetry is damaged; the eccentric force will be generated if the coupling extension is eccentric; the taper of the coupling is out of tolerance; the static balance or dynamic balance of the coupling is not good; the coordination between the elastic pin and the coupling is too tight, which makes the elastic pin lose the elastic adjustment function, so that the coupling cannot be well aligned; the coordination gap between the coupling and the shaft is too large; The mechanical wear of coupling rubber ring leads to the decrease of coupling rubber ring matching performance, and the quality of transmission bolts used on the coupling is not equal to each other. All of these causes cause vibration.
Too low stiffness of the bearing will reduce the first critical speed and cause vibration. In addition, the poor performance of the guide bearing leads to poor wear resistance, poor fixation, too large bearing bush clearance, and also easy to cause vibration; while the wear of the thrust bearing and other rolling bearings will make the longitudinal vibration and bending vibration of the shaft increase at the same time. Improper selection of lubricating oil, deterioration, excessive impurity content and unsmooth lubricating pipeline will lead to the deterioration of bearing condition and vibration. The self-excited oil film of motor sliding bearing will also produce vibration.
