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Analysis of 4 causes of vertical mill vibration and detailed

  The internal structure of the vertical mill is compact, and the external equipment is less, which can save a lot of space and reduce the early investment.

  Vertical grinding also has the advantages of small dust, low noise, low degree of environmental pollution, in the grinding powder production has a wide range of applications.

  Under normal conditions, the vertical mill runs smoothly, and the noise is basically no more than 90 db, but if the operation is not good, it will cause vibration, resulting in a lot of noise.

  For the vertical mill, reasonable vibration is allowed, but if the vibration is too large, will inevitably lead to the damage of some parts of the vertical mill, so, in the production process must strictly control the vibration of the vertical mill.

  Analysis of vibration of vertical mill

  In the actual production operation, many vibration are caused by improper operation, such as vibration caused by unstable material control.

  Because the material layer is too thin, there will be few materials that can be ground, so the output of grinding will be reduced.

  At the same time, too thin material layer will also lead to rigid contact between the grinding disc and grinding roller, which will cause a lot of vibration, leading to serious wear and tear of vertical grinding equipment, increasing energy consumption.

  If the material layer is too thick, the grinding capacity of the vertical mill will be reduced, and the load of its internal circulation will be increased, causing the up and down jump of the grinding roller, causing serious damage to the equipment and affecting the safe use of the equipment.

  Therefore, the control of the material layer is very important, there are many kinds of reasons affecting the change of the material layer, among which the material characteristics include the moisture content of the material, friction factor and the particle size of the material into the grinding, in addition to the temperature and pressure differential and other factors.

  The material properties

  Material friction factor: directly reflects the size of internal friction generated when grinding various materials.

  It is directly related to whether the material layer can form a stable thickness of the abrasive layer, and whether the stable thickness of the material layer can directly affect the grinding degree of the vertical grinding.

  Materials with small friction factors will be extruded out of the groove due to extrusion, which will inevitably lead to excessively thin material layer, which will easily lead to direct contact between the grinding disc and the grinding roller, resulting in vibration damage to the internal equipment.

  If the friction factor is very large, the material will be very small rolling and form a cake, it is difficult to loose, resulting in grinding difficulties.

  Particle size of materials: the particle size of materials entering the grinding disc should match the grinding roller and the grinding disc.

  As the diameter of the grinding roller increases, the peripheral linear velocity of the grinding roller also increases, so the friction force also increases. Therefore, the grinding roller is more likely to bite with materials, and the grinding materials are more likely to be rolled into the material layer. Therefore, the particle size of materials can be appropriately increased.

  However, when the material size is too large, it will lead to a great impact on the grinding roller, resulting in the vibration caused by the imbalance of the three rollers.

  Because the particle size of the material is too small, the material will enter the powder separator with the hot air blower, and the material layer cannot be formed on the grinding disc, which causes the direct contact between the grinding disc and the grinding roller to produce vibration.

  In general, the size of the particles entering the vertical mill should be about 5% of the roller diameter for the best.

  Moisture content of materials: the amount of moisture contained in materials has a great impact on the grinding process. If the moisture content is too high, the materials are not easy to dry. If the moisture content is too high, the materials will be coated and adhered to other materials, or even coated with grinding rollers.

  If the water content of the material is too small, the viscosity of the material will be too low, and the friction factor between the materials will be reduced, making it difficult to stay on the grinding disc for a long enough time, unable to form a certain thickness of the material layer, which will lead to rigid contact between the grinding disc and the grinding roller, aggravating the vibration.

  The difference between the grinding pressure in and the grinding pressure out

  The difference between the in-mill pressure and the out-mill pressure is the pressure difference, which is one of the main reasons affecting the vibration of vertical mill.

  The change of pressure difference directly reflects the change of circulating load rate in vertical mill, which is related to many factors, such as material size, material characteristic, grinding pressure, grinding ventilation, material moisture and feed quantity.

  For example, the material into the grinding particle size is too small, grinding pressure, low moisture, feed quantity and ventilation, etc., will cause differential pressure rise, material layer thickening;

  On the contrary, it will lead to the reduction of differential pressure and the thinning of the material layer, resulting in the vibration of the vertical mill. If not adjusted in time, it will cause the vertical mill to stop.

  The temperature of a hot wind

  The temperature of hot air will have a great impact on the vibration of the opposite mill, because in the fixed vertical mill its ventilation to ensure the drying efficiency of the material, therefore, must control the temperature of the hot air into the mill, which is mainly based on the water content of the material in and out of the mill.

  However, poor air temperature control will also affect the grinding efficiency of vertical mill to a certain extent. If the air temperature is too high, good drying effect and grinding effect can be achieved, but the material layer is too thin.

  If the wind temperature is too low, it will cause drying material difficulties, powder tribulation to carry on, the material is easy to be pressed into a cake, causing vertical mill vibration.

  In general, blast temperature is 200 ℃ ~ 250 ℃ advisable at the entrance, on the basis of the material at the exit of water content and ground water, the temperature should be controlled at 80 ℃ ~ 120 ℃ advisable.

  Under this parameter, the vertical mill runs smoothly and efficiently, without producing much vibration.

  The grinding pressure

  Grinding pressure is mainly from the center frame, hydraulic system and grinding roller self-weight of the total pressure, grinding pressure is directly related to the compression ratio of materials and material layer thickness, grinding pressure increases, thickness becomes thinner;

  Conversely, the pressure decreases and the thickness increases.

  Countermeasures to control vibration of vertical mill

  01

  Feeding operation

  When the water content of the material is very high, the outlet temperature should be appropriately increased to improve the grinding pressure difference to the ideal value.

  In case of insufficient feeding and less feed back, the feeding should be increased to ensure the normal pressure difference in the grinding to avoid vibration.

  If the material layer is too thick, should promptly reduce the amount of feeding, and ensure that the outlet is unobstructed;

  Instead, increase the amount of feed.

  02

  Grinding pressure control

  If the value of grinding pressure feedback of the vertical mill is less than the set value, it proves that the accumulator pressure is too low, and nitrogen must be added in time.

  03

  The temperature control

  If the temperature is too high can be adjusted by the mill power or directly open the cold air valve.

  04

  Differential pressure control

  When the feeding amount is large and the grinding capacity is insufficient, the pressure difference in the grinding will rise. At this time, the feeding amount should be appropriately reduced according to the mill power.

  The product is too fine will make the internal circulation load increase, so that the pressure difference will lead to vibration, so it is appropriate to reduce the speed of the separator.

  In the actual production process, we should combine the specific situation of the opposite mill for proper operation, in addition to the summary of the above reasons, in the production must also strengthen the maintenance of equipment and safety inspection, to ensure that the vertical mill has a stable and safe operating environment.

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