1、 Motor

1. Loose motor structural components, loose bearing positioning devices, loose iron core silicon steel sheets, and reduced support stiffness due to bearing wear can cause vibration.

2. Uneven distribution of rotor mass caused by quality eccentricity, rotor bending, or quality distribution issues, resulting in excessive static and dynamic balance.

3. The squirrel cage bar of the squirrel cage motor rotor is broken, causing an imbalance between the magnetic field force on the rotor and the rotational inertia force of the rotor, leading to vibration. Factors such as motor phase loss and unbalanced power supply in each phase can also cause vibration.

4. Due to quality issues in the installation process of the motor stator winding, the resistance between each phase winding is unbalanced, resulting in uneven magnetic field and unbalanced electromagnetic force, which becomes the excitation force causing vibration.

2、 Foundation and pump bracket

1. The contact fixing form used between the drive device frame and the foundation is not good, and the foundation and motor system have poor absorption, transmission, and isolation vibration capabilities, resulting in excessive vibration of the foundation and motor.

2. If the foundation of the centrifugal pump becomes loose, or the centrifugal pump unit forms an elastic foundation during installation, or the stiffness of the foundation is weakened due to oil immersion and foaming, the centrifugal pump will generate another critical speed that is 180 ° different from the vibration phase, thereby increasing the vibration frequency of the centrifugal pump. If the increased frequency is close to or equal to a certain external factor frequency, it will increase the amplitude of the centrifugal pump.

3. Loose foundation bolts can lead to a decrease in constraint stiffness and exacerbate motor vibration.

3、 Coupling

1. Poor circumferential spacing and symmetry of the coupling connecting bolts;

2. The eccentric extension of the coupling will generate eccentric force;

3. The taper of the coupling exceeds the tolerance;

4. Poor static or dynamic balance of the coupling;

5. The tight fit between the elastic pin and the coupling causes the elastic pin to lose its elastic adjustment function, resulting in the coupling not being properly aligned;

6. The clearance between the coupling and the shaft is too large;

7. The mechanical wear of the coupling rubber ring leads to a decrease in the fitting performance of the coupling rubber ring;

8.The quality of the transmission bolts used on the coupling is not equal to each other.

4、 Impeller

1. Eccentricity of impeller quality: Poor quality control during impeller manufacturing process, such as unqualified casting quality and machining accuracy; Or the transported liquid may be corrosive, causing erosion and corrosion of the impeller flow channel, resulting in eccentricity of the impeller.

2. Whether the number of blades, outlet angle, wrap angle, throat tongue, and radial distance from the outlet edge of the impeller are appropriate.

3. During use, the friction between the impeller mouth ring and the pump body mouth ring, as well as between the stage liner and the partition liner, gradually changes from initial collision wear to mechanical friction wear, which will intensify the vibration of the pump.

5、 Transmission shaft and its auxiliary components

1. A pump with a long shaft is prone to insufficient shaft stiffness, large deflection, and poor straightness of the shaft system, resulting in friction and vibration between moving parts (transmission shaft) and stationary parts (sliding bearings or mouth rings).

2. The pump shaft is too long and is greatly affected by the impact of flowing liquid in the centrifugal pump, resulting in increased vibration in the lower part of the pump.

3. Excessive clearance between the balance plates at the end of the shaft, or improper adjustment of the axial working displacement, can cause low-frequency shaft displacement, leading to bearing vibration.

4. Eccentricity of the rotating shaft can cause bending vibration of the shaft.



6、 Pump selection and variable operating conditions

1. Each pump has its own rated operating point, and whether the actual operating conditions match the design conditions has a significant impact on the dynamic stability of the pump.

2. Centrifugal pumps operate relatively stably under design conditions, but during variable operating conditions, the vibration increases due to the radial force generated in the impeller;

3. Improper pump selection or parallel connection of two mismatched pump models.

7、 Bearings and lubrication

1. If the stiffness of the bearing is too low, it will cause a decrease in the first critical speed and cause vibration.

2. Poor bearing performance leads to poor wear resistance, poor fixation, and excessive clearance between bearing shells, which can also easily cause vibration;

3. The wear of thrust bearings and other rolling bearings will exacerbate both longitudinal and bending vibrations of the shaft.

4. Improper selection of lubricating oil, deterioration, excessive impurity content, and lubrication failures caused by poor lubrication pipelines can all lead to deterioration of bearing conditions and cause vibration.

5. The self-excited oil film of the sliding bearing of the electric motor can also generate vibration.



8、 Pipeline and its installation and fixation

1. The stiffness of the outlet pipeline support of the pump is insufficient, and the deformation is too large, causing the pipeline to press down on the pump body, resulting in neutral damage to the pump body and motor;

2. The pipeline is installed with too much force, resulting in high internal stress when connecting the inlet and outlet pipelines to the pump;

3. Loose inlet and outlet pipelines, reduced constraint stiffness, or even failure;

4. The outlet channel is completely broken, and fragments are stuck in the impeller;

5. The pipeline is not smooth, such as an airbag at the outlet of the centrifugal pump;

6. The outlet valve of the centrifugal pump falls off or does not open;

7. The inlet of the centrifugal pump has intake, uneven flow field, and pressure fluctuations.

All of these reasons can directly or indirectly cause vibration in the pump and pipelines.

9、 Coordination between components

1. The concentricity of the motor shaft and pump shaft exceeds the tolerance;

2. A coupling is used at the connection between the motor and the transmission shaft, and the concentricity of the coupling exceeds the tolerance;

3. The wear of the design clearance between dynamic and static components (such as between the hub and the ring) increases;

4. The gap between the intermediate bearing bracket and the pump barrel exceeds the standard;

5. Inappropriate gap between sealing rings, resulting in imbalance;

6. Uneven gaps around the sealing ring, such as the mouth ring not entering the groove or the partition not entering the groove, can cause this situation.

All of these unfavorable factors can cause vibration.



10、 Factors of centrifugal pump itself

1. The asymmetric pressure field generated during impeller rotation;

2. The suction pipe generates eddy currents;

3. The occurrence and disappearance of vortices inside the impeller, as well as in the vortex shell and guide vanes;

4. Vibration caused by vortex caused by valve half opening;

5. Uneven distribution of outlet pressure due to limited number of impeller blades;

6. Flow separation inside the impeller;

7. wheezing;

8. Pulsating pressure inside the flow channel;

9. Cavitation;

10. Centrifugal flow in the pump body causes friction and impact on the pump body, such as centrifugal flow hitting the leading edge of the baffle and guide vanes, causing vibration;

11. Boiler feedwater pumps that transport high temperatures are prone to cavitation vibration;

12. The pressure pulsation inside the pump body is mainly caused by the large gap between the pump impeller sealing ring and the pump body sealing ring, which leads to large leakage loss and severe backflow inside the pump body, resulting in imbalance of axial force and pressure pulsation of the rotor, and will enhance vibration.

13. For centrifugal pumps that transport hot media, if the preheating of the pump is uneven before startup or the sliding pin system of the centrifugal pump is not working properly, causing thermal expansion of the pump group, it will induce severe vibration during the startup stage;

14. If the internal stress of the pump body from thermal expansion and other aspects cannot be released, it will cause a change in the stiffness of the shaft support system. When the stiffness after the change is an integral multiple of the system angular frequency, resonance occurs.