Eliminating vibration from design and manufacturing process
1. Mechanical structural design aspects of attention problems
1) Axis design. Increase the drive shaft support bearing the number, reducing the spacing of the support, in a proper range reduced axial length, an appropriate increase in the diameter of the shaft, increase the stiffness of the shaft; when the pump shaft speed increased gradually and to integer times the natural frequency of the rotor pump, pump will be violent vibration, so in the design should be so that the transmission shaft natural frequency to avoid motor rotor angular frequency; improve the manufacturing quality of the shaft to prevent mass eccentricity and form and position tolerance.
2) The selection of sliding bearing. Need not use lubricating sliding bearing; in liquid hydrocarbons and other chemical pump, sliding bearing materials should be with good self lubrication performance of the materials, such as PTFE; in the deep well water pump, guide bushing choice filled PTFE, graphite and copper powder materials, and design its structure, the sliding bearing of reliable fixation; impeller sealing ring and the pump body seal ring with small friction coefficient friction pair, such as M20lK graphite materials a steel; limit maximum speed; improving the bearing load bearing capacity and bearing stiffness.
3) Using the stress release system. For conveying hot water pump, design, should make the pump body deformation caused by the connection between the structure stress can be released, such as above the pump body bolts increase bolt sleeve, avoid the pump body directly and stiffness greatly based contact.
2. Attention to the hydraulic design of the pump
1) reasonable design of pump impeller and the flow passage and the impeller less cavitation flow separation and; reasonable choice of blade number and outlet blade angle, blade width, blade outlet crowding coefficient to eliminate lift curve hump; pump outlet of impeller and volute separation tongue distance, data, it is concluded that the value is one tenth of the diameter of impeller, pressure pulsation minimum; the blade outlet edge to make angle (such as made 20. To reduce the impact; ensure the gap between the impeller and the spiral case; improve the efficiency of the pump. At the same time, to optimize the design of the relevant flow channel of the pump, reduce the vibration caused by the loss of the hydraulic power. Reasonable design of various pump water inlet of the suction chamber, and the compression level of mechanical structure, reduce the pressure pulse, can guarantee the stability of the flow, improve the work efficiency of the pump, reduce the energy loss, but also can improve the stability of the pump vibration and dynamic performance.
2) cavitation vibration is a very important part of pump vibration. When the pump population pressure is lower than the corresponding temperature and pressure, will be accompanied by violent vibration cavitation. The measures include reducing cavitation: the installation height of the pump when the device npsha is greater than the pump minimum NPSH; increasing the inlet pipe diameter, shorten the length of a water inlet pipe, reducing pipe attachment, flow section change rate to the minimum, improve the wall roughness; reduce the number and increase the pipeline elbow turning angle; reduce the pump speed; the anti cavitation materials, such as stainless steel, or prone to cavitation in parts with epoxy resin; inlet design must be reasonable, in order to smooth, flow velocity and pressure distribution in the impeller evenly and avoid the local low pressure area; improve manufacturing quality, avoid because of blade profile of inaccurate local velocity is too large, excessive pressure drop; improve the anti cavitation performance of the pump device, including the pump inlet hydraulic booster set, The increase of structure, improve the pump suction pressure head, so as to improve the pump NPSH; increase the geometric intrusion height; minimize the water head loss of pipeline; use of double suction pump.
In order to ensure the water pipe or pressure pipe without air stockpile, the import of any part of the suction pipe is not higher than the pump. In order to reduce the pressure pulsation of the villain outlet and suction pipe diameter should be than the population of pump diameter a size bigger orders of magnitude to flow at the pump population have a certain amount of shrinkage, the velocity distribution is more uniform, but also should have a section of straight pipe in front of the pump population, straight pipe length not less than 10 times the diameter of the pipe.
Attention should be made to create good water inlet conditions, and the water flow in the influent should be stable and uniform, so as to eliminate the vibration of the Carmen vortex.
3) basic design. Basis weight is more than three times the pumps and motors and other machinery weight summation; Sheng pool should have considerable strength; motor bracket and foundation made the best one or make contact surface; between the pump and bracket set alternate isolation pad or vibration isolator. In addition, the pipeline is connected with the vibration reducing material, and the arrangement of the pipeline can be reduced, and the vibration caused by the elastic contact and the hydraulic loss can be eliminated.
From the installation and maintenance of the process as a way to eliminate the vibration of pumps
1. Shaft and shaft. Installed before the inspection of the pump shaft and motor shaft, a transmission shaft has no bending deformation, the mass eccentricity, if there is, you must correction or further processing; check and guide bearing contact transmission shaft, whether due to bending and friction bearing or sleeve and make yourself by exciting force. If the monitor indicates that the shaft has actually been bent, the pump shaft is corrected. At the same time, check the shaft end clearance value, if the value is too large, it indicates that the bearing has been worn, need to replace the bearing.
2. Impeller. Whether the dynamic and static balance is qualified.
3. Coupling. Bolt spacing is good; elastic column pin and an elastic ferrule binding can not be too tight; the inner hole of the coupling and shaft fit is too loose, if too loose, can be used such as spraying method to reduce the coupling diameter until reach the transition with the required size and coupling is fixed on the shaft.
4. Sliding bearing. Clearance values are in accordance with the standard; everywhere lubrication is good; improve the pump bearing maintenance technology level, strictly follow the first shave tile, after grinding, shave watt cycle program to ensure the contact area of the bearing and the shaft neck to reach the required standard:
1)Pump shaft journal and bearing clearance value, through the replacement of bearings, grinding, scraping, adjustment and other means to achieve qualified.
2)The gap between the pump bearing body and the spherical cap of the bearing box is qualified.
3)The pump shaft bearing tile and pump shaft neck contact points and contact angle: standard under the shoe back and bearing seat contact area should be in more than 60%, the shaft neck sliding contact surface contact point density remains in per square cm 2 a four point, the contact angle is maintained at 60 "90".
5. Support and bottom plate. In time to find the vibration of the support of the fatigue of the case, to prevent the decrease of the inherent frequency because of the strength and stiffness.
6. Clearance and vulnerable parts. To ensure that the motor bearing clearance is appropriate; appropriate adjustment of the gap between the impeller and the vortex shell; regular inspection, replacement of the impeller mouth ring, pump body, the level of the bushing, spacer sleeve, such as easy to wear parts.
Due to the centrifugal pump selection and improper operation caused by vibration
Two pumps in parallel shall ensure that the pump performance is the same. Pump performance curve should be slow down for good, can not have a hump. Use with caution: to eliminate the factors causing pump overload, such as clogging; appropriate to extend the opening time of the pump, reduce the disturbance on the transmission shaft, reduce the collision and friction between moving parts and stationary parts, and the resulting thermal deformation; for water lubricated sliding bearing, the startup process should add enough pre run water skiing, avoid dry start, stop the water until the pump outlet; regularly to the bearing oiling amount needs oiling; for axis liquid centrifugal pump, because there is a shafting torsional vibration, if the use of the thrust pad, is affected by the damage is the main thrust, then can improve oil viscosity, prevent liquid lubricant film failure. Finally, in order to prevent the pump amplitude is too large, you can also use the measurement and analysis of vibration conditions to determine the best operating parameters of the pump.
