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/*728*90 created on 2018/5/16*/ var cpro_id = "u3440131"; Home>Bearing knowledge>The cause of pump oscillation and its elimination Pump oscillation reason and its elimination
Align the oscillations of the various components of the pump unit; analyze the cause of the oscillations. From the hydraulic and mechanical layout of the pump; to the pump equipment, operation, protection, etc., several ways to reduce the pump oscillation are proposed. The results are marked; The pump component layout scale and accuracy are compatible with the hydraulic characteristics of the pump without overload function; ensure that the pump's practical operating conditions meet the pump's drawing conditions; ensure the consistency of machining accuracy and drawing accuracy; Consistency of quality with its operational requirements; ensuring consistency of inspection quality and component wear rules; reducing pump oscillations. /*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';
Oscillation is an important goal to evaluate the reliability of the pump unit. The damage of the oscillation overrun is mainly: the oscillation constitutes the pump unit can not operate normally; the oscillation of the motor and the pipeline is caused; the machine is destroyed; the components such as bearings are damaged; The connecting parts are loose; the bottom crack or the motor is damaged; the pipe or valve that is connected with the water pump is loose or damaged; and the oscillation noise is formed.
The cause of the pump oscillation is multi-faceted. The shaft of the pump is usually directly connected to the drive motor shaft; the dynamic function of the pump and the dynamic function of the motor are dry with each other; the high-speed rotating parts are more; the dynamic and static balance can meet the demand; The fluid-effect components are greatly affected by the water flow; the complexity of the fluid motion itself; it is also an element of the stability of the dynamic function of the pump.
Analysis of the cause of the pumping oscillation caused by 1 pair
1.1 Motor motor layout parts loose; bearing positioning equipment loose; iron core silicon steel sheet is too loose; bearing due to wear and tear caused by support stiffness; will cause oscillation. Quality is painful; rotor twist or mass dispersion problem caused by rotor mass distribution The squirrel-cage cage of the squirrel cage motor has cracks; the magnetic field force of the rotor and the rotational inertia of the rotor are unbalanced and cause oscillation; the motor is out of phase; The imbalance of the power supply of each phase can also cause oscillation. The stator winding of the motor; the operation quality problem due to the equipment process; the imbalance of the resistance between the windings of each phase; therefore, the magnetic field caused by the attack is not uniform; the electromagnetic force of the imbalance is attacked. This electromagnetic force becomes an exciting force that causes oscillation.
1.2 The bottom and the pump bracket drive equipment frame and the base are selected by the touch fixing method is not good; the base and motor system absorption, transmission, and blocking oscillation can be poor; the root and motor oscillations are overrun. The pump root is loose; perhaps the pump The unit constitutes an elastic base in the process of the equipment. 蛘哂æŽè°Ÿå¾’è°æ–è‹« "Another critical speed of the è·ž è·ž 凰 凰 凰 é• å²µèƒç©¸è¾”徊 1800; then the pump oscillation frequency is added; if the frequency is added with a certain The frequency of an external element is close or flat; it will increase the amplitude of the pump. Others; the anchor bolts at the base are loose; the restraining stiffness is reduced; the oscillation of the motor is aggravated.
1.3 Coupling coupling bolts have poor circumferential spacing; symmetry is damaged; couplings have long joint pain; will have partial pain; coupling cone is out of tolerance; coupling static Balance or dynamic balance is not good; the cooperation between the elastic pin and the coupling is too tight; the elastic pin loses the elastic conditioning function and the coupling is not well centered; the cooperation gap between the coupling and the shaft is too large; The mechanical wear of the rubber ring causes the coupling function of the coupling apron to be reduced; the quality of the transmission bolts used on the coupling varies from each other. These causes will constitute oscillation.
1. 4 impeller 1 impeller mass is miserable. The quality control in the process of impeller production is not good; for example; casting quality, processing accuracy is unqualified; perhaps the liquid transported is corrosive; the impeller is corroded and corroded; pain.
2 The number of blades of the impeller, the exit angle, the wrap angle, the radial spacing between the throat tongue and the impeller exit can be appropriate.
3 between the use of the impeller ring and the pump body ring between the interstage bushing and the baffle bushing; from the beginning of the rub; gradually become mechanical conflict wear; these will increase the pump's oscillation.
1.5 drive shaft and its auxiliary shaft long pump; easy to occur shaft stiffness is lacking; deflection is too large; shaft straightness is poor; constitute moving parts (drive shaft) and static parts (sliding bearings or ring) Between the two; the oscillation is too long; the pump shaft is too long; the impact of the impact of the active water in the pool is large; the oscillation of the pump is increased. The balance disc at the shaft end is too large; perhaps the axial operation The adjustment of the turbulence is not proper; it will constitute the low frequency turbulence of the shaft; the oscillation of the bearing bush will be caused. The yaw of the rotating shaft will cause the tortuous oscillation of the shaft.
1. Pump selection and variable working conditions Each pump has its own additional operating point; the actual operating conditions can match the working conditions; it has an important impact on the dynamic stability of the pump. The operation is relatively stable under the condition of drawing; but it is operated under variable working conditions; due to the effect of radial force in the impeller; the oscillation is increased; the single pump is not properly selected; or the two types of mismatched pumps Parallel. These will constitute the oscillation of the pump.
1.7 bearing and smooth bearing stiffness is too low; will constitute the top critical speed reduction; inducing oscillation. Other; poor bearing function closure causes poor wear resistance, poor fixing; bearing bush gap is too large; The wear of the thrust bearing and other rolling bearings will increase the longitudinal turbulence oscillation of the shaft and the tortuous oscillation together. The smooth oil selection is not appropriate, the enthalpy change, the impurity content is excessive, and the smooth pipe is not smooth, which will constitute the bearing. The working condition deteriorates; the oscillation is caused. The self-excitation of the oil film of the motor sliding bearing also oscillates.
1.8 pipe and its equipment fixed pump outlet pipe bracket stiffness is not strong; deformation is too large; the pipe is pressed down on the pump body; the pump body and the motor are neutral damage; the pipe is too strong in the process of equipment; When the outlet pipe is connected with the pump, the internal stress is large; the inlet and outlet pipes are loose; the restraint stiffness is reduced or even failed; the outlet flow path is partially cracked; the debris is stuck in the impeller; the pipe is not smooth; if the outlet has airbags; Or not open; the intake has intake; the flow field is uneven; the pressure is shaken. These causes will directly or indirectly cause oscillations in the pump and pipeline.
1. 9 cooperation between the parts of the motor shaft and pump shaft concentricity; the coupling between the motor and the drive shaft uses a coupling; the concentricity of the coupling is out of tolerance; between the moving and static parts (such as impeller The wear of the gap between the port and the mouth ring becomes larger; the gap between the center bearing bracket and the pump cylinder is excessive; the gap of the seal ring is unsuitable; the imbalance is formed; the gap around the seal ring is not uniform; The partition is not a trough; this will happen. These unfavorable elements can constitute oscillation.
1.10 The asymmetric pressure field of the pump's own impeller rotation; the vortex of the suction pool and the inlet pipe; the inside of the impeller and the vortex, the vortex of the guide vane and the invisible; the valve half-opening constitutes a vortex and the oscillation of the attack; The number of impeller blades is limited and the outlet pressure is unevenly distributed; the outflow in the impeller; surge; the pulsating pressure in the flow channel; cavitation; water in the pump body; there will be conflicts and impacts on the pump collar; The leading edge of the tongue and the guide vane; constitutes an oscillation; the boiler feed water pump that transports the high temperature water is prone to cavitation oscillation; the pressure fluctuation in the pump body; mainly the pump impeller seal ring, the gap of the pump body seal ring is too large; Leakage loss is large; the backflow is severe; and thus the rotor axial force imbalance and pressure pulsation; will enhance the oscillation. Others; about the pump to transport hot water; if the preheating of the pump before the start is uneven; perhaps the pump sliding pin system The operation is not normal; it constitutes the thermal expansion of the pump set; it will induce severe oscillation during the start; the internal stress of the pump body from thermal expansion cannot be released; it will cause the change of the stiffness of the shaft support system. When the stiffness of the system to the angle after changing the frequency of an integral multiple contact; flared resonance.
2 ways to reduce the oscillation
2.1 Eliminate oscillations from the depiction of the production process
2.1.1 The problem of mechanical layout depiction
1) Shaft drawing. Add the number of support shaft support bearings; reduce the support interval, reduce the shaft length within the appropriate range; properly increase the shaft diameter; add the shaft stiffness; when the pump shaft speed is gradually added and close or integer When the natural oscillation frequency of the pump rotor is exceeded; the pump will oscillate strongly; therefore, when drawing, the natural frequency of the drive shaft should be avoided from the motor rotor angular frequency; the manufacturing quality of the forward shaft; avoiding mass misalignment and excessive Shaped public service.
2) Selection of sliding bearings. Select sliding bearings without smoothing; in chemical pumps such as liquid hydrocarbons; materials for sliding bearings should use materials with outstanding self-smoothing properties; for example, PTFE; in deep well heat pumps; The raw materials filled with PTFE, graphite and copper powder are selected; and the layout is reasonably drawn; the fixing of the sliding bearing is firmly fixed; the conflicting pair with the small collision factor is selected at the impeller sealing ring and the pump sealing ring; for example, the M20lK graphite material is Steel; the maximum speed of restraint; the bearing capacity of the bearing bush and the rigidity of the bearing housing.
3) Applying a stress release system. Regarding the pump for transporting hot water; when drawing; the layout stress between the joints caused by the deformation of the pump body should be released; for example, adding a bolt sleeve on the pump body anchor bolt; avoiding the pump Direct and rigid base touch.
2.12 hydraulic pumping attention to matters
1) Reasonably depict the pump impeller and runner; make less cavitation and de-flow in the impeller; reasonably select the number of blades, blade exit angle, blade width, blade exit overhead coefficient, etc.; eliminate the head curve hump; pump impeller exit and The spacing of the volute tongue; there is information that the value is one tenth of the outer diameter of the impeller; the pulsating pressure is the smallest; the angle of the outlet of the blade is made to be inclined (for example, about 20.) to reduce the impact; The gap between the impeller and the volute; the working efficiency of the forward pump. Together; optimize the depiction of the associated flow passages such as the pump outlet passage; reduce the oscillation caused by the hydraulic loss. Reasonably depict the suction at the inlet section of each pump. Room; and the mechanical layout of the tightening level; reduce the pressure pulse; ensure the stability of the flow field; work efficiency of the forward pump; reduce energy loss; also can advance the stability of the pump's oscillation dynamic function.
2) Cavitation oscillation is a very important part of pump oscillation. When the pump's green tooth pressure is lower than the corresponding water temperature and pressure; it will attack the cavitation with strong oscillation. The method of reducing cavitation includes: determining the pump The height of the equipment is such that the available NPSH of the equipment is greater than the minimum equipment NPSH of the pump; the diameter of the inlet pipe is appropriately increased; the length of the inlet pipe is shortened; the pipe fittings are reduced;å–鼙诘 å–鼙诘 诙 诙; cut the number of elbows and increase the view point of the pipeline; reduce the operating speed of the pump; use anti-cavitation cavitation data; for example, stainless steel; or apply epoxy resin in the simple cavitation area; The water flow channel should be drawn reasonably; the water flow should be smooth; the water flow velocity and pressure of the impeller should be evenly distributed; some low pressure zones should be avoided; the processing quality should be advanced; the flow velocity should be too large due to the inaccuracy of the blade profile; the pressure drop is too much; The anti-cavitation function of the pump equipment; including the hydraulic energy booster at the inlet of the pump; the layout of the energizer; the suction head of the forward pump; and then the NPSH of the pump equipment; adding a few sprinkling heights; Head loss reduction in water intake pipe; double-suction pump selection.
In order to ensure that there is no air accumulation in the suction pipe or the pressure pipe; any of the suction pipe can not be higher than the inlet of the water pump. In order to reduce the pressure pulsation at the human nozzle; the diameter of the suction pipe should be one order of magnitude larger than the diameter of the pump tooth; So that the water flow has a certain shortening at the pump tooth; the flow velocity is evenly distributed; together, there should be a straight pipe before the pump is born; the length of the straight pipe is not less than 10 times the diameter of the pipe.
Pay attention to the invention of outstanding water inlet conditions; the water flow in the inlet pool should be smooth and even; to eliminate the oscillation of the Karman vortex.
3) The description of the base. The weight of the base should be more than three times the sum of the mechanical components such as the pump and the motor; the base of the sink should have the proper strength; the motor bracket and the base should be the best or face touch; A vibration isolation pad or a vibration isolator is arranged between the pump and the bracket. Others; the vibration damping data is connected between the pipelines; the pipeline arrangement is reduced; the oscillation caused by the elastic touch and the hydraulic loss can be eliminated.
2. 2 Eliminate oscillations from devices and protection processes
1) Axis and shaft system. Check whether the water pump shaft, motor shaft and drive shaft have any tortuous deformation and mass misalignment before the equipment; if there is; it is necessary to correct or further processing; view the drive shaft touched with the guide bearing; Whether the bearing bush or bushing conflicts due to twists and turns, so that the individual is excited. If the monitoring is marked; the shaft has been bent in practice; correct the pump shaft. Together; check the end gap value of the shaft; if the value is too large, indicate The bearing is worn; the bearing needs to be replaced.
2) Impeller. Whether the dynamic and static balance can be qualified.
3) Coupling. Whether the bolt spacing is outstanding; the elastic pin and the elastic ferrule should not be too tight; the cooperation between the inner hole of the coupling and the shaft can be too loose; if it is too loose, it can be reduced by the method of spraying The inner diameter of the small coupling until it reaches the scale required for the transition cooperation; then the coupling is fixed on the shaft.
4) Sliding bearing. Whether the gap value can meet the specification; whether the smoothness of the ground can be outstanding; the level of the bushing maintenance process of the forward pump; strictly follow the cycle procedure of first scraping, post-grinding and re-scraping; ensure the touch area of ​​the bearing bush and the journal The specification of the arrival rule:
1 pump journal and bearing clearance value; after replacement, bearing, grinding, scraping, adjustment and other methods to reach the qualified.
2The pump bearing body and the bearing box spherical top clearance value are qualified. 3 pump shaft bearing lower tile and pump shaft journal touch point and touch viewpoint: under the normative rule, the tile back and bearing seat touch area should be above 60%; the journal slide The touch point density on the touch surface is maintained at 2 to 4 points per square centimeter; the touch viewpoint is maintained at 60"-90".
5) Bracket and bottom plate. The fatigue condition of the oscillating support member is found in time; avoiding the decrease of the natural frequency due to the decrease of strength and rigidity.
6) Clearance and wearing parts. Ensure that the motor bearing clearance is suitable; properly adjust the gap between the impeller and the volute; regularly view and replace the impeller ring, pump body ring, interstage bushing, diaphragm bushing, etc. Components.
2. 3 Eliminate the oscillation due to the selection and operation of the pump. The two pumps should be connected in parallel to ensure the pump function is the same. The pump function curve should be the descending type as well; there should be no hump. When using it, pay attention to: eliminate the pump overload. Element; analog flow channel blockage; properly extend the pump start time; reduce the disturbance to the drive shaft; reduce the collision and conflict between the transition member and the stop part; and the thermal deformation caused thereby; In the process of launching, pre-smooth water should be added; avoid dry start; until the pump is out of water, stop the water injection; timed to over-fill the bearing with demand for oil injection; about the long-axis liquid centrifugal pump; due to the change of the shafting oscillation; There is a thrust tile; the main damage is the thrust tile; at this time, the viscosity of the smooth oil can be properly advanced; the damage of the liquid dynamic smooth film can be avoided. Finally, in order to avoid the excessive amplitude of the pump, the measurement can be used to analyze the oscillation. To determine the best operating parameters of the pump.
3. The cause of the pump oscillation is the cause of mechanical, hydraulic and electric power.
The oscillation control induction reflects the machining process, the operation level of the mechanical equipment personnel, the nature of the pump operator, the function of the hydraulic drawing software, the function of each data, and the function of the monitoring instrument. In the practice operation; the sweeping oscillation should be related to the experience and theory. Anatomy; linking the analysis of the oscillatory mechanism with the data obtained from the practice of the instrumentation. Many oscillations can be traced and the quality of the equipment; the level of forward operation; the elimination of normal protection is eliminated. The development of new data skills and the presentation of new processes; The advancement of computer skills and numerical methods and the theory of fluid mechanics; together with the spurt and development of the vibration noise diagnosis skills; the portrayal, application and protection level of the pump will be prosperous; the function will also be increasingly optimized; the dynamic function will also become more and more Safe.
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Source: Bearing network time: 2018-07-22