Ten reasons for vibration of centrifugal pump

Shaft is a long pump, easy to cause the lack of axial stiffness, deflection is too large, the situation of poor straightness of the shaft, resulting in moving parts (transmission shaft) and static parts (sliding bearing or mouth ring) between the rub, the formation of vibration. In addition, the pump shaft is too long, the impact of the flow of water in the pool is greater, so that the vibration of the lower part of the pump to increase. The shaft end of the balance disc gap is too large, or the axial runout to adjust properly, will cause the low frequency shifting shaft, lead to bearing vibration. The eccentricity of the rotating shaft will cause the bending vibration of the shaft. 

The contact fixed form between the driving device and the base is not good, the foundation and the motor system absorb, transmit, isolate the vibration ability difference, causes the foundation and the motor vibration to exceed the standard. Pump or pump unit based loose, during the installation process to form elastic foundation, or due to oil blisters weakened the foundation stiffness, the pump will produce vibration and phase difference of another 1800 critical speed, so that the pump vibration frequency increase, if the increased frequency and a frequency close to or equal to external factors, it will cause the pump the amplitude of the increase. In addition, the foundation anchor bolts loosening, resulting in constraint stiffness decreased, will make the motor vibration. 

The coupling bolts circumferential spacing, symmetry is broken; the coupling extension will produce eccentric, eccentric force; coupling cone ultra poor or dynamic balance is not good; static balance coupling; with the tight and elastic pin coupling, the elastic pin coupling caused by the loss of elasticity function is not well of; with the gap is too large and the shaft coupling; coupling ring coupling caused by mechanical wear aprons with decreased performance; transmission quality bolt used on the coupling ranging from each other. These causes can cause vibration. 

 

The non symmetric pressure field generated by the rotation of the impeller suction tank and the water inlet pipe; eddy current; and disappeared inside the impeller and volute, guide vane vortex; semi open vortex caused by vibration of the valve caused due to the limited number of impeller blades; the outlet pressure caused the uneven distribution of flow in the round; leaf removal; surge; the fluctuating pressure of flow; cavitation; water flow in the pump body, a pump friction and impact on the experience, such as front, the tongue and the guide vane flow impact caused by vibration; boiler feed pump for conveying high temperature water cavitation vibration; pump pressure pulsation, the main pump impeller sealing ring, pump clearance body sealing ring is too large, causing the pump body leakage loss, severe reflux, imbalance and pressure fluctuation caused by the axial force of the rotor, the vibration will increase. In addition, the hot water pump for conveying hot water, if not the preheating start before the pump, or pump sliding pin system does not work properly, causing the pump thermal expansion, vibration will induce the start-up phase of the pump body; from thermal expansion and other aspects of the internal stress cannot release, will cause the change of the stiffness of the the shaft support system, when the change of stiffness of the system frequency is integer multiple relationship when resonance occur. 

The motor structure is loose, the bearing positioning device is loose, the iron core silicon steel piece is too loose, the bearing wear and lead to the decline of the support stiffness, can cause vibration. Mass eccentricity, rotor bending or mass distribution problems lead to uneven distribution of the rotor, resulting in excessive static and dynamic balance. In addition, the squirrel cage motor rotor squirrel cage fracture, rotation inertia force caused by the rotor by magnetic force and rotor imbalance caused by vibration, motor phase, each phase power imbalance can also cause vibration. The stator winding of the motor, due to quality problems caused by the installation process, the resistance between each phase winding is not balanced, thus resulting in the inhomogeneous magnetic field, the unbalanced electromagnetic force, the electromagnetic force becomes the exciting force caused by vibration.