Reasons for pump vibration

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There are many reasons that cause vibration in the turbine hall and pump house structures; some of these factors are interconnected and interact with one another. Generally speaking, there are mainly four such reasons. 1. In terms of electricity, the motor is the main component of the unit; imbalances in the magnetic field within the motor and defects in other electrical systems often cause vibration and noise. For example, in an asynchronous motor during operation, the radial alternating magnetic pulling force between the stator and rotor generated by the interaction of the harmonic fluxes from the stator and rotor teeth, or in a large synchronous motor during operation, situations such as misalignment of the magnetic centers of the stator and rotor or air-gap differences in various directions exceeding the allowable limits, can all cause periodic vibration of the motor and the generation of noise. 2. On the mechanical side, issues such as uneven mass in the rotating components of motors and pumps, poor manufacturing quality, inadequate installation, asymmetry in the axis of the unit, oscillations exceeding allowable limits, low mechanical strength and stiffness of the components, wear and damage to bearings and sealing elements, as well as resonance caused by the critical speed of the pump coinciding with the natural frequency of the unit, can all lead to severe vibration and noise. 3. In terms of hydraulics, uneven flow velocity and pressure distribution at the pump inlet, pressure fluctuations of the fluid flowing in and out of the pump, fluid bypassing, deviation from the normal flow path, and fluid separation from the pump surface, as well as operating conditions that are not within the specified parameters and pump cavitation caused by various factors, are all common causes of vibration in pump units. Dynamic transition processes such as the start-up and shutdown of water pumps, the opening and closing of valves, changes in operating conditions, and emergency shutdowns in case of accidents, which cause sudden pressure changes in the water delivery pipelines and water hammer effects, often also lead to vibrations in the pump house and the pumping units. 4. Hydraulic aspects and other factors: An unreasonable design of the water intake channel for the unit, or a design that is not compatible with the unit; an inappropriate submersion depth of the pump; as well as an unreasonable sequence for starting and stopping the unit – all these can deteriorate the water intake conditions, cause vortices, lead to cavitation, or increase the vibration of the unit and the pump house. In units that use destructive siphon vacuum interruption for shutdown, during startup, if it is difficult for air to be entrained in the hump section, the siphon formation time becomes excessively long ； The gate design of the units with gate-driven flow shutdown is unreasonable; it opens and closes repeatedly, constantly striking the gate seat ； Reasons such as uneven settlement of the foundation supporting the water pump and motor, or poor rigidity of the foundation, can also cause vibration in the unit.