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Causes and characteristics of vertical mill vibration

  At present the vertical mill is the main equipment of cement raw material grinding.

  Vibration of vertical mill not only damages equipment, but also causes instability of roller lift and roller drop, which affects output.

  According to the author's experience, the reason and characteristic of vertical mill vibration are discussed.

  Analysis of vibration of vertical mill

  Vertical mill vibration, the reasons are various, transmission, material layer, foreign bodies, roller surface, grinding disc, particle size, pressure can cause vertical mill vibration, the following analysis for reference.

  1. Vibration characteristics caused by transmission

  The transmission part of vertical mill includes motor, coupling and reducer. Any fault in any link can cause vibration.

  Specifically, if the coupling installation accuracy is insufficient, that is, the alignment error is large, it will cause the vibration mainly axial vibration;

  If the rotor of the motor does not coincide with the stator center, the alternating magnetic field will change along with the direction of the magnetic field, and the rotor will be pulled to move back and forth, thus causing axial vibration.

  Gear reducer bearing damage, gear broken teeth and so on will cause the vibration of the mill.

  When bearing damage, roller, cage, set each other inside and outside the interference caused by vibration, the axial positioning failure, installed on the shaft of the gear mesh can produce abnormal, such as moment bite root, meshing, causing severe vibration, at this point is often accompanied by a crush, friction shriek, when its relative stability, the vibration frequency is associated with the speed of the shaft.

  When the tooth is broken, there will be periodic vibration and related to the shaft speed. When the broken fragments are squeezed in the root of the tooth, the top tooth will inevitably make a dull sound, and the frequency is synchronous with the speed.

  2. Vibration and characteristics caused by unstable material layer

  When the material layer is unstable, the distance between the grinding roller and the grinding disc changes constantly.

  The reason for the instability of the material layer may come from the unstable feeding, or the material may flow too fast on the grinding disc, in short, it is not stable material layer;

  The height of the baffle ring is not suitable, such as too low, it is difficult to block the material, it can not form stable material layer, and the material is too dry, too fine and so on.

  3. Excessive particle size of the material block causes vibration

  If the particle size of raw material is too large, for example, the thickness of the material layer is too high, when the grinding roller passes, it will suddenly lift up the grinding roller and then suddenly fall down, which will inevitably cause vibration of the grinding machine.

  Such vibration has no obvious characteristics and is determined by the quantity of the bulk and the fragility of the material.

  4. Vibration and characteristics caused by foreign matter entering the mill

  When iron and other foreign bodies enter the mill, the mill roll cannot crush them, which will inevitably cause the roller to fluctuate and cause the mill vibration. If the foreign bodies circulate in the system, it will cause the vibration within the cycle time.

  If the foreign body is stuck near the grinding disc, such as the baffle ring, its vibration frequency is the product of the mill speed and the number of rollers.

  5. Vibration and characteristics caused by roundness of grinding roller

  Grinding roll wear layer once appear slag, drop, grinding roll will be out of round, every rotation will suddenly rise and fall once, forming a regular vibration, if a pit, vibration frequency is basically two times the speed of the mill (or nearly two times the speed of the mill), the more pits vibration frequency is higher.

  6. Grinding disc is broken or seriously peeled off

  When the lining plate of the grinding disc is broken or seriously peeled off, the grinding disc will be pitted, and the grinding roller will suddenly sink at this point, causing vibration. The vibration frequency is the product of the grinding speed and the number of rollers.

  7.Improper operation causes vibration

  Improper operation of vertical mill can also cause vibration. When the wind speed of the wind ring is too high, the external discharge of the mill decreases, and the materials that need to be recycled are turned onto the grinding disc. Too many powdery materials form a solid material layer, and the pressure difference inside the mill rises and the mill vibrates.

  Poor grindability of materials the speed of the separator is too high, and the fine powder returned to the grinding disc is too much, resulting in unstable material layer, rising pressure difference in the grinding and vibration of the mill.

  The vibration period is related to operation frequency.

  After lifting roller and stopping material by vibration, the fine powder is gradually discharged and the falling roller is normal. When the pressure difference in grinding reaches a certain value, the vibration starts again.

  8. Roll too low

  When the roller is too low, it is difficult to crush lumpy materials. The rolling roller, knocking the grinding disc back and forth, inevitably causes vibration. If the air pressure of the accumulator is also low, the shock of the hydraulic oil in the cylinder will also cause the rise of oil temperature.

  Conclusion: this paper is only a brief analysis of the causes and characteristics of the vibration of the vertical mill. Due to the limited experience of the author, the analysis is not comprehensive or improper. We sincerely request criticism and correction.

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