What Are The Causes And Solutions Of Centrifugal Pump Vibration

Sep 02, 2025

Vibration is an important indicator for evaluating the operational reliability of water pump units. The hazards of excessive vibration mainly include: vibration causing the pump unit to malfunction; Causing vibration of the motor and pipelines, resulting in damage to the machine and injury to people; Causing damage to bearings and other components; Causing loose connecting components, foundation cracks, or motor damage; Causing loose or damaged fittings or valves connected to the water pump; Generate vibration noise.

The causes of pump vibration are multifaceted. The shaft of the pump is generally directly connected to the drive motor shaft, causing the dynamic performance of the pump and the dynamic performance of the motor to interfere with each other; There are many high-speed rotating components, and the dynamic and static balance can meet the requirements; Components that interact with fluids are greatly affected by water flow conditions; The complexity of fluid motion itself is also a factor that limits the stability of pump dynamic performance.

motor

The motor structural components are loose, the bearing positioning device is loose, the iron core silicon steel sheet is too loose, and the bearing's support stiffness decreases due to wear, which can cause vibration. Uneven distribution of rotor mass caused by quality eccentricity, rotor bending or quality distribution issues, resulting in excessive static and dynamic balance. In addition, the squirrel cage bars of the rotor of the squirrel cage motor are broken, causing an imbalance between the magnetic field force acting on the rotor and the rotational inertia force of the rotor, resulting in vibration. Other reasons such as motor phase loss and unbalanced power supply of each phase can also cause vibration. The stator winding of the motor, due to quality issues in the installation process, causes an imbalance in resistance between the windings of each phase, resulting in an uneven magnetic field and an unbalanced electromagnetic force, which becomes the excitation force and causes vibration.

Foundation and pump bracket

The contact fixing form between the drive device frame and the foundation is not good, and the foundation and motor system have poor ability to absorb, transmit, and isolate vibrations, resulting in excessive vibrations of both the foundation and motor. If the foundation of the water pump is loose, or if the water pump unit forms an elastic foundation during installation, or if the foundation stiffness is weakened due to oil immersion bubbles, the water pump will produce another critical speed with a phase difference of 1800 from the vibration, thereby increasing the vibration frequency of the water pump. If the increased frequency is close to or equal to the frequency of an external factor, it will increase the amplitude of the water pump. In addition, the loosening of the foundation anchor bolts leads to a decrease in constraint stiffness, which will intensify the vibration of the motor.

coupling

The circumferential spacing of the coupling connecting bolts is poor, and the symmetry is damaged; The eccentricity of the coupling extension joint will generate eccentric force; The taper degree of the coupling exceeds the tolerance; Poor static or dynamic balance of the coupling; The tight fit between the elastic pin and the coupling causes the elastic column pin to lose its elastic adjustment function, resulting in poor alignment of the coupling; The clearance between the coupling and the shaft is too large; The mechanical wear of the coupling rubber ring leads to a decrease in the fitting performance of the coupling rubber ring; The quality of the transmission bolts used on the coupling is not equal to each other. These reasons can all cause vibration.

impeller

① The quality of the impeller is eccentric. Poor quality control during the impeller manufacturing process, such as inadequate casting quality and machining accuracy; Or the conveyed 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, package angle, and radial distance between the throat baffle and the outlet edge of the impeller are appropriate.

③ The initial friction between the impeller mouth ring and the pump body mouth ring, as well as between the inter stage liner and the baffle liner, gradually turns into mechanical friction wear, which will intensify the vibration of the pump.

Pipeline and its installation and fixation

The stiffness of the outlet pipeline bracket of the pump is insufficient and the deformation is too large, causing the pipeline to be pressed down on the pump body, resulting in the neutral damage of the pump body and motor; The pipeline is subjected to too much pressure during installation, resulting in high internal stress when connecting the inlet and outlet pipelines to the pump; Loose inlet and outlet pipelines, decreased or even failed constraint stiffness; The outlet flow channel is completely broken, and fragments are stuck in the impeller; The pipeline is not smooth, such as air pockets at the outlet; The outlet valve has fallen off or is not open; There is air intake at the water inlet, uneven flow field, and pressure fluctuations. These reasons can directly or indirectly cause vibration in pumps and pipelines.

Bearings and lubrication

The stiffness of the bearing is too low, which can cause a decrease in the first critical speed and vibration. In addition, poor performance of the guide bearing leads to poor wear resistance, poor fixation, and excessive clearance between the bearing shells, which can also easily cause vibration; The wear of thrust bearings and other rolling bearings will intensify the longitudinal and bending vibrations of the shaft. Lubrication failures caused by improper selection, deterioration, excessive impurity content, and poor lubrication pipelines of lubricating oil can lead to deterioration of bearing conditions and vibration. The self-excited oil film of the sliding bearing of the electric motor can also generate vibration.

Measures to reduce vibration

Eliminating vibration from the design and manufacturing process

1) Axis design. Increase the number of support bearings for the transmission shaft, reduce the support spacing, reduce the shaft length within an appropriate range, increase the shaft diameter appropriately, and increase the shaft stiffness; When the pump shaft speed gradually increases and approaches or is an integer multiple of the natural vibration frequency of the pump rotor, the pump will vibrate violently. Therefore, in design, the natural frequency of the drive shaft should avoid the angular frequency of the motor rotor; Improve the manufacturing quality of the shaft, prevent quality eccentricity and excessive form and position tolerances.

2) Selection of sliding bearings. Adopting sliding bearings that do not require lubrication; In chemical pumps such as liquid hydrocarbons, sliding bearing materials should be made of materials with good self-lubricating properties, such as polytetrafluoroethylene; In deep well hot water pumps, the guide liner is filled with materials such as polytetrafluoroethylene, graphite, and copper powder, and its structure is designed reasonably to ensure reliable fixation of the sliding bearings; Friction pairs with low friction coefficients, such as M20lK graphite material and steel, are used at the impeller sealing ring and pump body sealing ring; Limit the maximum speed; Improve the bearing capacity of the bearing shell and the stiffness of the bearing seat.

3) Use a stress relief system. For pumps that transport hot water, the design should release the structural stress between the connecting parts caused by the deformation of the pump body, such as adding bolt sleeves on the pump body anchor bolts to avoid direct contact between the pump body and the highly rigid foundation.

Precautions for hydraulic design of water pumps

1) Reasonably design the impeller and flow channel of the water pump to minimize cavitation and flow separation inside the impeller; Reasonably select parameters such as blade number, blade outlet angle, blade width, and blade outlet displacement coefficient to eliminate the hump of the head curve; The distance between the outlet of the pump impeller and the tongue of the snail shell is believed to be one tenth of the outer diameter of the impeller, and the pulsating pressure is minimized; Tilt the outlet edge of the blade at an angle of about 20 degrees to reduce impact; Ensure the clearance between the impeller and the volute; Improve the working efficiency of the pump. At the same time, optimize the design of the pump's outlet channel and other related channels to reduce vibration caused by hydraulic losses. Reasonably designing the suction chamber at the inlet section of various pumps, as well as the mechanical structure of the compression stage, can reduce pressure pulses, ensure stable flow field, improve pump efficiency, reduce energy loss, and also enhance the stability of pump vibration dynamic performance.

2) Cavitation vibration is an important part of pump vibration. When the population pressure of the pump is lower than the sum pressure at the corresponding water temperature, cavitation accompanied by severe vibration will occur. The measures to reduce cavitation include: when determining the installation height of the water pump, making the effective cavitation allowance of the device greater than the minimum device cavitation allowance of the pump; Appropriately increase the diameter of the inlet pipe, shorten the length of the inlet pipe, reduce pipeline accessories, strive to minimize the change rate of the flow section, and improve the roughness of the pipe wall; Reduce the number of bends and increase the turning angle of the pipeline; Reduce the working speed of the water pump; Using materials that resist cavitation, such as stainless steel, or applying epoxy resin to areas prone to cavitation; The design of the inlet channel should be reasonable, striving for smoothness, ensuring even distribution of water flow velocity and pressure entering the impeller, and avoiding local low-pressure areas; Improve manufacturing and processing quality to avoid excessive local flow velocity and pressure drop caused by inaccurate blade profile; Improve the anti cavitation performance of the pump device, including installing a hydraulic booster at the inlet of the pump, the structure of the booster, increasing the suction head of the pump, thereby increasing the cavitation allowance of the pump device; Increase the geometric backflow height; Minimize the head loss of the inlet pipeline as much as possible; Adopting a double suction pump.

The causes of pump vibration include mechanical, hydraulic, and electrical reasons. Vibration control comprehensively reflects the mechanical processing technology, the operational level of mechanical installation personnel, the quality of water pump operators, the functionality of hydraulic design software, the performance status of various materials, and the performance of monitoring instruments. In practical work, eliminating vibration requires a combination of experience and theoretical analysis, combining vibration mechanism analysis with data obtained from actual detection instruments. Many vibrations can be eliminated by improving design and installation quality, enhancing operational proficiency, and strengthening daily maintenance. With the development of new material technology and the emergence of new processes, as well as the advancement of electronic computer technology and numerical methods, and the basic theory of fluid mechanics, coupled with the rise and development of vibration and noise diagnosis technology, the design, use, and maintenance level of water pumps will surely thrive, and their performance will also become increasingly optimized, and their dynamic performance will become increasingly stable.