Pump Vibration Causes and Elimination Measures

Aiming at the vibration existing in every part of pump unit, the reason of vibration was analyzed. From the pump hydraulic and mechanical design, to the pump installation, operation, maintenance and other aspects of the proposed pump vibration reduction measures. The results show that it is ensured that the structure and size of the pump components and the accuracy are compatible with the hydraulic characteristics of the pump such as no overload; to ensure that the actual operating point of the pump is consistent with the design conditions of the pump; to ensure the consistency of processing accuracy and design accuracy; To ensure the quality of parts and components installed with the consistency of its operational requirements; to ensure the quality of repair and wear parts of the same consistency, can reduce pump vibration. Vibration is an important indicator to evaluate the reliability of pump units. Vibration caused by excessive harm are: vibration caused by the pump unit can not operate normally; lead to vibration of the motor and pipeline, causing machine damage; cause damage to bearings and other parts; resulting in loose connection parts, the basis of cracks or motor damage; resulting in Pump connected to the pipe or valve loose, damaged; the formation of vibration noise. The causes of pump vibration are manifold. The shaft of the pump is generally connected directly with the shaft of the driving motor, so that the dynamic performance of the pump and the dynamic performance of the motor interfere with each other; the rotating parts with high speed, the movable and the static balance are able to meet the requirements; the components with the fluid are greatly influenced by the water flow; The complexity of the fluid movement itself is also a factor that limits the stability of the dynamic performance of the pump. 1 pairs of causes of pump vibration analysis 1.1 Motor motor structure loose, bearing positioning device loosening, iron core silicon steel is too loose, the bearing wear due to decreased stiffness caused by the support, will cause vibration. Eccentric mass, rotor bending or mass distribution problems caused by uneven rotor mass distribution, resulting in static and dynamic balance exceeded Sichuan. In addition, squirrel-cage motor rotor cage cages have broken, causing the rotor suffered magnetic field force and rotor inertia imbalance caused by the imbalance caused by vibration, lack of phase motor, the power supply imbalance and other causes can cause vibration. Motor stator windings, due to the quality of the operation of the installation process, resulting in unbalanced resistance between the phase windings, resulting in uneven magnetic field, resulting in an imbalance of electromagnetic force, the electromagnetic force as the excitation force to cause vibration. 1.2 Basic and pump bracket drive device used between the base and the form of contact fixed is not good, the basis and the motor system absorption, transmission, isolation vibration poor, resulting in vibration of the foundation and motor are exceeded. The pump foundation is loosened or the pump unit forms an elastic foundation during installation or the water pump creates another critical speed difference 1800 from the vibration due to weakening of the foundation stiffness due to the oil blisters which increases the vibration frequency of the pump. Frequency and an external factor frequency close to or equal to, it will increase the pump amplitude. In addition, the foundation anchor bolts loose, resulting in lower restraint stiffness, will make the motor vibration increased. 1.3 Coupling Coupling The connecting bolt's circumferential spacing is bad, the symmetry is destroyed; Coupling plus section eccentricity, will have eccentric force; Coupling cone degree tolerance; Coupling static balance or dynamic balance Not good; elastic pin and the coupling with the tight, so that elastic loss of elasticity of the pin to adjust the function of the coupling can not be well on the center; Coupling and shaft with the gap too large; Mechanical wear and tear caused by coupling with the rubber ring with a decline in the performance of the coupling bolts used on the quality of each other. These causes vibrations. 1.4 impeller â‘  impeller eccentric mass. Poor quality control during manufacture of the impeller, such as casting quality and machining accuracy, or corrosiveness of the fluid being conveyed, resulting in erosion of the impeller runner resulting in eccentricity of the impeller. â‘¡ the impeller blade number, exit angle, wrap angle, laryngeal tongue and impeller exit side of the radial distance is appropriate. â‘¢ use between the middle wheel mouth ring and the pump mouth ring, interstage bushing and baffle bushing, from the initial Rub, gradually become mechanical friction and wear, which will aggravate the pump vibration. 1.5 shaft and its auxiliary shaft shaft pump is very long, prone to lack of shaft stiffness, deflection is too large, shaft straightness difference between the situation, resulting in moving parts (drive shaft) and static parts (sliding bearing or mouth ring) between Rub friction, the formation of vibration. In addition, the pump shaft is too long, affected by the impact of the flow of water in the pool larger pump to increase the vibration of the underwater part. Shaft end of the balance plate gap is too large, or axial adjustment of the amount of work properly adjusted, will cause the shaft low-frequency movement, resulting in bearing vibration. Eccentricity of the rotary shaft can cause flexural vibration of the shaft. 1.6 pump selection and variable operating conditions Each pump has its own rated operating point, the actual operating conditions and design conditions are consistent, the dynamic stability of the pump has a significant impact. Pump running in the design conditions relatively stable, but under variable operating conditions, due to the radial force generated in the impeller, the vibration has increased; single pump improper selection, or two models do not match the pump in parallel. These will cause the pump to vibrate. 1.7 bearing and bearing stiffness is too low, will result in lower first critical speed, causing vibration. In addition, the guide bearing poor performance led to bad wear resistance, poor fixing, bush clearance is too large, but also easily lead to vibration; and thrust bearings and other rolling bearing wear, it will make the shaft longitudinal vibration and bending vibration simultaneously aggravate . Improper selection of lubricants, deterioration, excessive levels of impurities and lubrication problems caused by poor lubrication pipes, will cause deterioration of bearing conditions, triggering vibration. Motor self-excitation of the sliding bearing oil film will also produce vibration. 1.8 pipeline and its installation Fixed pump outlet pipe stent stiffness is not enough, the deformation is too large, causing the pipe under the pressure on the pump body, making the pump and the motor neutral damage; pipe during the installation is too big, import and export pipe Road and the pump connection when the internal stress; import and export pipe loose, restraint stiffness decline or failure; all part of the export runner rupture, fragment card impeller; poor pipeline, such as the outlet has a balloon; Did not open; inlet intake, uneven flow field, pressure fluctuations. These causes can directly or indirectly lead to the vibration of pumps and pipes. 1.9 Matching between components The concentricity of the motor shaft and the pump shaft is out of tolerance; the coupling between the motor and the transmission shaft is used, and the concentricity of the coupling shaft is out of tolerance; the dynamic and static parts (such as the impeller Yi Hekou Rings between the design gap wear larger; intermediate bearing bracket and pump cylinder clearance exceeded; ring gap inappropriate, resulting in an imbalance; seal ring around the gap uneven, such as the mouth ring groove or not partition No one groove, it will happen. These negative factors can cause vibration. 1.10 factors pump itself when the impeller rotation asymmetry pressure field generated; suction pool and inlet vortex; impeller inside and the volute, guide vortex vortex occurs and disappears; valve half-open vortex caused by the vibration; as the impeller blades Inadequate distribution of outlet pressure due to limited number; Outflow in impeller; Surge; Pulsation pressure in runner; Cavitation; Water flows in the pump body and may have friction and impact on the pump body, The leading edge of the guide vane, causing vibration; high temperature water boiler feed pump prone to cavitation vibration; pump pressure pulsation, the main pump impeller seal ring, pump seal ring gap is too large, causing the pump body leakage loss , Serious backflow, which in turn causes imbalance and pressure pulsation of the rotor axial force, which will increase the vibration. In addition, for hot water pump delivery, if the pump before the start of uneven heating, or pump sliding pin system is not working properly, resulting in thermal expansion of the pump group will trigger the start-up phase of the violent vibration; pump from thermal expansion and so on Of the internal stress can not be released, it will cause the spindle support system stiffness changes, when the stiffness changes and the system angular frequency integral multiple relationship, the resonance occurs. 2 measures to reduce vibration