1. Shaft.
Pumps with longer shafts are prone to insufficient shaft stiffness, too much deflection, and poor shaft straightness, which causes friction between the moving parts (drive shaft) and the static parts (sliding bearings or mouth rings), resulting in vibration. In addition, the shaft of the fluoroplastic centrifugal pump is too long, and the impact of the flowing water in the pool is relatively large, which increases the vibration of the underwater part of the pump. The balance plate gap at the end of the shaft is too large, or the axial working movement is improperly adjusted, which will cause low-frequency movement of the shaft and lead to bearing vibration. The eccentricity of the rotating shaft will cause bending vibration of the shaft.
2. Foundation and pump bracket.
The contact and fixing form between the drive frame and the foundation is poor, and the foundation and motor system have poor absorption, transmission and isolation vibration capabilities. The foundation of the fluoroplastic centrifugal pump is loose, or the fluoroplastic centrifugal pump unit produces an elastic foundation during the installation process, or the stiffness of the bubble foundation caused by oil immersion is weakened, which causes the pump to produce another critical speed of vibration phase difference, which increases the vibration frequency of the pump. If the frequency of external factors is close to or equal to the frequency, the pump amplitude will increase. In addition, loosening of the foundation bolts will reduce the constraint stiffness, thereby aggravating the vibration of the motor.
3. Coupling.
The circumferential distance of the coupling bolt is poor, and the symmetry is destroyed; the coupling is long and eccentric, which will generate eccentric force; the coupling taper is poor; the static balance or dynamic balance of the coupling is not good; the elastic pin and the coupling are too tight, so that the elastic adjustment function of the elastic pin cannot make the coupling coordination gap between the shafts too large; the coupling performance is reduced, causing mechanical wear of the coupling rubber ring; the quality of the transmission bolts on the coupler. These reasons will cause vibration.
4. Factors of the water pump itself.
Asymmetric pressure field generated by impeller rotation; vortex in the suction box and intake pipe; generation and disappearance of vortex in the impeller, volute and guide vane; vibration caused by vortex caused by half-opening of the impeller; uneven outlet pressure distribution caused by the limited number of impeller blades; impeller imbalance; flow channel; cavitation; flow channel, loss of friction at the leading edge of the impeller; In addition, if the hot water pump, if the preheating of the pump is uneven, or the sliding pin system of the pump does not work properly, resulting in thermal expansion of the pump group, it will cause strong vibration in the startup phase; thermal expansion and other internal stresses cannot be released, which will cause the stiffness of the rotor support system to change, and the stiffness and system angular frequency will change.
5. Motor
Loose motor parts, loose bearing positioning device, too loose core silicon steel sheet, and reduced support stiffness due to wear of bearings will cause vibration. Uneven rotor mass distribution caused by mass eccentricity, rotor bending or mass distribution problems will cause static and dynamic balance to exceed the standard. In addition, the cage bars of the squirrel cage motor rotor are broken, causing the magnetic field force on the rotor and the rotational inertia force of the rotor to be unbalanced, causing vibration. The motor is missing phase, and the power supply of each phase is unbalanced. Other reasons can also cause vibration. The stator winding of the motor, due to the quality of the operation of the installation process, causes the resistance between the windings of each phase to be unbalanced, resulting in an uneven magnetic field and an unbalanced electromagnetic force. This electromagnetic force becomes an exciting force to cause vibration.
6. Pump selection and variable operating conditions.
Each pump has its own rated operating point. Whether the actual operating conditions are consistent with the design conditions has an important interference with the dynamic stability of the fluoroplastic centrifugal pump. Fluoroplastic centrifugal pumps operate relatively stably under designed working conditions, but when operating under variable working conditions, the vibration increases due to the radial force generated in the impeller; improper selection of single pumps, or parallel connection of two unmatched pumps, all of which will cause pump vibration.
7. Bearings and lubrication.
If the stiffness of the bearing is too low, the first critical speed will be reduced, causing vibration. In addition, poor bearing performance leads to poor wear resistance, poor fixation, and excessive bearing clearance, which can easily cause vibration; and the wear of thrust bearings and other rolling bearings will increase the longitudinal vibration and bending vibration of the shaft at the same time. Lubrication failures caused by improper selection of lubricating oil, deterioration, excessive impurity content, and poor lubrication pipelines will cause the bearing working condition to deteriorate and cause vibration. The self-excitation of the oil film of the motor sliding bearing will also cause vibration.
8. Pipeline and its installation and fixation.
The outlet pipe support of the fluoroplastic centrifugal pump is not rigid enough and deforms too much, causing the pipe to press down on the pump body, which damages the alignment of the pump body and the motor; the pipe is too stiff during installation, and the internal stress is large when the inlet and outlet pipes are connected to the pump; the inlet and outlet pipes are loose, and the constraint rigidity decreases or even fails; part of the outlet flow channel is completely broken, and the fragments are stuck in the impeller; the pipeline is not smooth, such as air bags at the outlet; the outlet valve falls off or is not opened; there is air intake at the inlet, uneven flow field, and pressure fluctuations. These reasons will directly or indirectly cause vibration of the pump and pipeline.