Analysis of the causes of water pump unit vibration and vibration reduction measures
DATE:2024-08-20 10:17:11
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This paper analyzes the causes of vibration for the vibration of the various components of the pump unit. From the pump hydraulic, mechanical structure design, to the pump installation, operation, maintenance and other aspects of several proposed measures to reduce pump vibration.
Vibration is an important indicator for evaluating the reliability of pump unit operation. The hazards of vibration exceeding the standard are mainly:
Vibration caused by the pump unit can not run normally;
Lead generator and pipeline vibration, resulting in machine destruction and injuries
Causing damage to bearings and other parts;
Causing loosening of connecting parts, foundation cracks or motor damage;
Causing the pipe fittings or valves connected with the pump to be loose and damaged;
Formation of vibration noise.
The causes of pump vibration are manifold. Pump shaft is generally directly connected with the drive motor shaft, making the dynamic performance of the pump and the dynamic performance of the motor to interfere with each other; high-speed rotating parts, dynamic and static balance Mu can meet the requirements; and the role of the fluid components by the water flow conditions have a greater impact; the complexity of the fluid movement itself, but also to limit the stability of the dynamic performance of the pump is also a factor in the stability of the pump.
I. Motor
Loose motor structural parts, loose bearing positioning device, iron core silicon steel sheet is too loose, bearing due to wear and tear caused by the decline in support stiffness, will cause vibration.
Mass eccentricity, rotor bending or uneven rotor mass distribution caused by mass distribution problems, resulting in static and dynamic balance amount exceeds the standard.
In addition, the squirrel cage motor rotor cage bars have broken, resulting in the rotor by the magnetic field force and rotor rotational inertia force imbalance caused by vibration, motor phase, each phase of the power supply imbalance and other reasons can also cause vibration.
Motor stator winding, due to the installation process of the operation of quality problems, resulting in the resistance between the winding of the various phases of the imbalance, which leads to the generation of the magnetic field is not uniform, resulting in an imbalance of the electromagnetic force, this electromagnetic force becomes the excitation force triggered by vibration.
Second, the foundation and pump bracket
The contact fixing form used between the drive frame and the foundation is not good, and the foundation and motor system have poor ability to absorb, transfer and isolate vibration, resulting in vibration of both the foundation and the motor exceeding the standard.
Pump foundation loose, or pump unit in the installation process to form an elastic foundation, or due to oil flooding and blistering caused by the foundation stiffness weakened, the pump will produce and vibration phase difference 1800 another critical speed, so that the pump vibration frequency increases, if the increased frequency and an external factor frequency is close to or equal to the amplitude of the pump will increase.
In addition, the foundation foot bolt is loose, resulting in a reduction in the constraint stiffness, which will make the motor vibration increase.
Third, the coupling
Coupling connection bolt circumferential spacing is bad, the symmetry is destroyed; coupling lengthening section eccentric, will produce eccentric force; coupling taper degree is too poor; coupling static or dynamic balance is not good; elastic pin and coupling with too tight, so that the elastic pin to lose the elastic adjustment function caused by the coupling can not be very well centered; coupling with the shaft with the clearance is too large; coupling rubber ring caused by mechanical wear of couplings The coupling and the shaft fit gap is too large; the coupling rubber ring mechanical wear caused by the coupling rubber ring with the performance decline; coupling used on the transmission bolt quality is not each other. These reasons can cause vibration.
Fourth, the impeller
Impeller quality eccentricity. Impeller manufacturing process quality control is not good, for example, casting quality, machining accuracy is not qualified; or transported liquid with corrosive, impeller channel by the scouring corrosion, resulting in eccentricity of the impeller.
The number of blades of the impeller, the exit angle, the package angle, the throat spacer tongue and the impeller outlet edge of the radial distance is appropriate.
The use of impeller mouth ring and pump body between the mouth ring, between the stage bushing and spacer bushing, from the initial contact, gradually become mechanical friction wear, these will aggravate the vibration of the pump.
Fifth, the drive shaft and its auxiliary parts
Shaft is very long pump, prone to shaft stiffness, deflection is too large, poor straightness of the shaft system, resulting in moving parts (drive shaft) and static parts (sliding bearings or mouth ring) between the touch, the formation of vibration.
In addition, the pump shaft is too long, affected by the impact of flowing water in the pool is greater, so that the pump underwater part of the vibration increases. The balance disk clearance at the end of the shaft is too large, or the amount of axial work tampering is not properly adjusted, which will cause the shaft low frequency tampering, resulting in vibration of the shaft tile. Eccentricity of the rotating shaft will lead to shaft bending vibration.
Sixth, the pump selection and variable operating conditions
Each pump has its own rated operating point, the actual operating conditions and design conditions in line with whether or not the dynamic stability of the pump has an important impact.
Pumps in the design condition is relatively stable, but in the variable operating conditions, due to the role of radial force generated in the impeller, the vibration has increased; improper selection of a single pump, or two types of pumps do not match the parallel connection. These will cause the pump vibration.
Seven, bearing and lubrication
Bearing stiffness is too low, will cause the first critical speed reduction, causing vibration.
In addition, the performance of the guide bearing closed bad lead to poor wear resistance, fixed bad, excessive clearance between the shaft tile, also easy to cause vibration.
The wear and tear of the thrust bearing and other rolling bearings will make the longitudinal runout vibration as well as bending vibration of the shaft intensify at the same time.
Improper selection of lubricating oil, deterioration, impurity content exceeds the standard and lubrication pipeline is not smooth and lead to lubrication failure, will cause the deterioration of the bearing working conditions, triggering vibration.
Self-excitation of the motor sliding bearing oil film will also produce vibration.
Back
Vibration is an important indicator for evaluating the reliability of pump unit operation. The hazards of vibration exceeding the standard are mainly:
Vibration caused by the pump unit can not run normally;
Lead generator and pipeline vibration, resulting in machine destruction and injuries
Causing damage to bearings and other parts;
Causing loosening of connecting parts, foundation cracks or motor damage;
Causing the pipe fittings or valves connected with the pump to be loose and damaged;
Formation of vibration noise.
The causes of pump vibration are manifold. Pump shaft is generally directly connected with the drive motor shaft, making the dynamic performance of the pump and the dynamic performance of the motor to interfere with each other; high-speed rotating parts, dynamic and static balance Mu can meet the requirements; and the role of the fluid components by the water flow conditions have a greater impact; the complexity of the fluid movement itself, but also to limit the stability of the dynamic performance of the pump is also a factor in the stability of the pump.
I. Motor
Loose motor structural parts, loose bearing positioning device, iron core silicon steel sheet is too loose, bearing due to wear and tear caused by the decline in support stiffness, will cause vibration.
Mass eccentricity, rotor bending or uneven rotor mass distribution caused by mass distribution problems, resulting in static and dynamic balance amount exceeds the standard.
In addition, the squirrel cage motor rotor cage bars have broken, resulting in the rotor by the magnetic field force and rotor rotational inertia force imbalance caused by vibration, motor phase, each phase of the power supply imbalance and other reasons can also cause vibration.
Motor stator winding, due to the installation process of the operation of quality problems, resulting in the resistance between the winding of the various phases of the imbalance, which leads to the generation of the magnetic field is not uniform, resulting in an imbalance of the electromagnetic force, this electromagnetic force becomes the excitation force triggered by vibration.
Second, the foundation and pump bracket
The contact fixing form used between the drive frame and the foundation is not good, and the foundation and motor system have poor ability to absorb, transfer and isolate vibration, resulting in vibration of both the foundation and the motor exceeding the standard.
Pump foundation loose, or pump unit in the installation process to form an elastic foundation, or due to oil flooding and blistering caused by the foundation stiffness weakened, the pump will produce and vibration phase difference 1800 another critical speed, so that the pump vibration frequency increases, if the increased frequency and an external factor frequency is close to or equal to the amplitude of the pump will increase.
In addition, the foundation foot bolt is loose, resulting in a reduction in the constraint stiffness, which will make the motor vibration increase.
Third, the coupling
Coupling connection bolt circumferential spacing is bad, the symmetry is destroyed; coupling lengthening section eccentric, will produce eccentric force; coupling taper degree is too poor; coupling static or dynamic balance is not good; elastic pin and coupling with too tight, so that the elastic pin to lose the elastic adjustment function caused by the coupling can not be very well centered; coupling with the shaft with the clearance is too large; coupling rubber ring caused by mechanical wear of couplings The coupling and the shaft fit gap is too large; the coupling rubber ring mechanical wear caused by the coupling rubber ring with the performance decline; coupling used on the transmission bolt quality is not each other. These reasons can cause vibration.
Fourth, the impeller
Impeller quality eccentricity. Impeller manufacturing process quality control is not good, for example, casting quality, machining accuracy is not qualified; or transported liquid with corrosive, impeller channel by the scouring corrosion, resulting in eccentricity of the impeller.
The number of blades of the impeller, the exit angle, the package angle, the throat spacer tongue and the impeller outlet edge of the radial distance is appropriate.
The use of impeller mouth ring and pump body between the mouth ring, between the stage bushing and spacer bushing, from the initial contact, gradually become mechanical friction wear, these will aggravate the vibration of the pump.
Fifth, the drive shaft and its auxiliary parts
Shaft is very long pump, prone to shaft stiffness, deflection is too large, poor straightness of the shaft system, resulting in moving parts (drive shaft) and static parts (sliding bearings or mouth ring) between the touch, the formation of vibration.
In addition, the pump shaft is too long, affected by the impact of flowing water in the pool is greater, so that the pump underwater part of the vibration increases. The balance disk clearance at the end of the shaft is too large, or the amount of axial work tampering is not properly adjusted, which will cause the shaft low frequency tampering, resulting in vibration of the shaft tile. Eccentricity of the rotating shaft will lead to shaft bending vibration.
Sixth, the pump selection and variable operating conditions
Each pump has its own rated operating point, the actual operating conditions and design conditions in line with whether or not the dynamic stability of the pump has an important impact.
Pumps in the design condition is relatively stable, but in the variable operating conditions, due to the role of radial force generated in the impeller, the vibration has increased; improper selection of a single pump, or two types of pumps do not match the parallel connection. These will cause the pump vibration.
Seven, bearing and lubrication
Bearing stiffness is too low, will cause the first critical speed reduction, causing vibration.
In addition, the performance of the guide bearing closed bad lead to poor wear resistance, fixed bad, excessive clearance between the shaft tile, also easy to cause vibration.
The wear and tear of the thrust bearing and other rolling bearings will make the longitudinal runout vibration as well as bending vibration of the shaft intensify at the same time.
Improper selection of lubricating oil, deterioration, impurity content exceeds the standard and lubrication pipeline is not smooth and lead to lubrication failure, will cause the deterioration of the bearing working conditions, triggering vibration.
Self-excitation of the motor sliding bearing oil film will also produce vibration.