Cause Analysis of Vibration of ATOX 50 Vertical Mill

Date: 2019-07-03 Views:

Large vertical roller mill is mostly used in raw meal preparation system. In the process of process production, the vibration of vertical mill has a great influence on the whole process production operation, equipment maintenance and use, equipment spare parts cycle, and sometimes even determines the factors. In this paper, the causes of vibration in the operation process of vertical mill and the countermeasures are summarized as follows, in order to provide a reference for future production management and equipment management.

The causes of vibration of standing mill are more complex, some reasons may not be recognized, but as far as the vibration encountered at present is concerned, the reasons can be basically summarized as follows: (1) the change of material properties; (2) equipment failure; (3) system problems and process operation.

(1) the influence of the change of material properties on vibration

1. Particle size of material

The material layer formed in the process of vertical grinding has a certain particle gradation, so it has a certain range of requirements for the particle size of raw materials. Too large or too small particle size will lead to the destruction of gradation balance, resulting in the weakening of toughness and rigidity of the material layer, which is very harmful. First of all, the large particle size reduces the success rate of primary grinding, increases the number of material cycles, and obviously weakens the "medium particle size" material which does not meet the fineness requirements above the wind ring. This situation also affects the smooth passage of particles that meet the requirements of fineness, thus causing a vicious circle.
At the same time, with the increase of the amount of the powder, the ratio of the powdery material on the material layer is increased, the original grading balance is broken, the stability of the material layer is deteriorated, and the vibration is increased. This situation is common to the change of the vertical mill system due to the excessive mass of the large particles of the heap after the limestone is changed. The material can be appropriately reduced in operation to stabilize the pressure difference and the material layer.

Secondly, when the material is too small, or even the powder material is too much, because of the poor adhesion of fine particles, good mobility, it is not easy to form an effective material layer, the roller is not easy to "nibble" the material to carry on the normal rolling, easy to cause the relative sliding of the grinding roll and the grinding disk, resulting in the violent vibration of the vertical grinding.

In addition, the existence of a large quantity of powdery material can increase the dust concentration, the pressure difference is increased, the ventilation resistance is increased, the normal running track of the air flow is destroyed, the lifting capacity of the gas is reduced, and if the material is not greatly reduced in time, the necessary adjustment is carried out, and the vertical grinding and vibration stopping can be quickly caused. It is difficult to control if a large amount of the powdery material is suddenly put into the ground and the vertical grinding is suddenly stopped and the time of the adjustment is not.

When it is found that the material is too fine, especially the pressure difference has increased obviously, the material should be greatly reduced in time, the grinding pressure should be reduced, the outlet humidity should be reduced, the water injection should be increased, the rotating speed of the powder separator should be properly reduced, the stability of the material layer and the pressure difference should be taken as the center, and the grinding pressure should be gradually increased when there is a certain material layer. In addition, when the uniform particles are mixed with large pieces of material, it will also cause the fluctuation of the roller.

1.2 ease of material

In fact, the material grindability has been taken into account in the selection and design of the vertical mill. In general, the ATOX50 vertical mill mainframe is 3500kw, because the material grindability of our factory is poor, and when it becomes worse, the ability of the vertical mill will be reduced and can only be forced to reduce the material operation, otherwise it will cause the vibration of the vertical mill and cause the operation instability.

Therefore, the grindability of materials is a very important index for vertical grinding operation and assessment. When the material grindability becomes worse, the grinding times of the vertical mill to the material will obviously increase, especially the pressure difference will become very large, the ventilation will not be smooth, the material will basically be suspended in the grinding body, the material layer is extremely unstable, the load of the powder separator will become larger, the raw material fineness will become thicker, and the mill load will also become larger. If the material is not reduced in time, the vibration of the vertical grinding will be very intense.

In general, the easy-to-use inspection of the object should be carried out on a regular basis, which provides a certain basis for the operation of the vertical mill and the procurement and exploitation of the feeding department. The change of the material property is more than the influence of the grinding, the change of the material property can lead to the excessive wear of the lining plate, and the wear progress of the lining plate can be accelerated, and a larger impact and damage can be generated to the lining plate in order to ensure that the output is forced to increase the grinding pressure; The over-wear of the liner, in turn, will cause the mill to vibrate, so the material supply department's change in the material properties should take into account the impact of the opposing mill. The cost control should be considered in a comprehensive way.

2. Equipment failure on the shadow of vibration

2.1 New replacement liner

Due to the new roller, the grinding disk liner ratio is smooth, not stable and "suction" material, will lead to certain vibration, in the operation can properly increase the thickness of the material layer, increase water spray, in addition, can increase the material ring. After a period of operation, the surface of the liner will gradually adapt to the properties of the material and run smoothly.

2.2 excessive wear of liner

Due to the centrifugal force of the grinding disk, the large part of the material of the grinding disk is concentrated in the outer edge of the grinding disk, which leads to the wear of the outer side of the roller and the disc liner is larger than that of the inner side during operation. When the material layer fluctuates greatly or the material layer is thin, the unbalanced wear may cause the hard impact on the inside of the roller liner and the inner side of the disc liner, resulting in vibration. When the roller liner turns around, it may also cause this vibration because the wear parts can not be completely matched.

2.3 damage to button moment rods and "beef tendons"

The function of button moment and "beef bar" is to prevent the roller from moving radially on the disk. When they are damaged, the radial swing of the roller is too large, the normal "suction" angle is destroyed, and the relative sliding and vibration of the roller and the grinding disk can be caused in serious cases. At the same time, due to their damage, it may lead to the eccentricity of the central tripod and aggravate the vibration.

2.4 failure of hydraulic system

Hydraulic system is one of the most important equipment systems in vertical grinding, and the huge grinding force applied by roller to material is provided by it. However, due to the inconsistent action of the drawing rod caused by the failure of the hydraulic system, the vibration of the mill may be caused by the dissynchronization of the three rollers when the falling roll and the rising roll are out of sync.

2.5 Failure of the return powder hammer valve

due to the excessive grinding or mechanical failure of the back powder hammer valve, a part of the air can leak from the vertical hammer valve, so that the air volume of the upward strip is reduced, and the normal lifting of the material is influenced; on the other hand, the air leaking into the vertical hammer valve can cause the air flow in the powder selection machine to be disordered, A large amount of powdery material is accumulated in a conical hopper, and once the accumulated material suddenly falls, it must be a large amount of powdery material, which will inevitably cause large vibration on the grinding disc, and the vibration is relatively regular.

2.6 The accumulator pressure is insufficient or the nitrogen air bag is broken

The pre-charge gas pressure of the nitrogen in the accumulator shall be 60% -70% of the normal grinding pressure, and when the accumulator pressure is insufficient or the nitrogen air bag is damaged, the buffer action will be lost, and the hard falling of the grinding roller can be caused, and the large amplitude vibration can be easily caused.

2.7 Water spraying system

Water spraying system plays a very important role in stabilizing the material layer, especially in the case of more powder. In general, no matter how much the feed, the sprinkler will be activated to increase the toughness and rigidity of the material. When one of the three spray pipes is blocked or leaking, it will lead to the imbalance of the material layer, the fluctuation of the roller, and the vibration. In addition, once the spray system stops during operation, the inner material layer will lose toughness and rigidity, resulting in vertical grinding vibration.

2.8 retaining ring

When the material properties and the working parameters of the mill are stable, the degree of the retaining ring basically determines the maximum thickness of the material layer. When the retaining ring is too low, the material layer as buffer pad will become thinner, the buffering effect will be weakened, and the vibration will intensify.

2.9 the wear of the scraping plate,

the uneven wear of the guide blade and the uneven damage of the windshield can lead to the uneven distribution of the air flow in the grinding ring and the inner air volume, resulting in the different thickness of the material on the grinding plate and the corresponding vibration.

3. The influence of system problems and process parameters on vibration

3.1 Foreign matter in the mill

Metal is hard because of its hard texture, so when the grinding roller grinds it, the impact and damage of the liner is more serious. At the same time, the grinding roller will also produce a large beat, causing sudden vibration. Although the grinding material has gone through several iron removal devices, the large pieces of the liner will still cause large vibration.

3.2 The belt scale is out of control and fluctuates greatly.

Due to the change of the season and the material, the belt scale will show the phenomenon of the material and the material, especially the sudden thinning of the material layer when the limestone and the rock are broken, and the buffering effect is reduced, and the grinding pressure is still relatively large, thereby causing the vibration.

When the belt weigher is out of control and the flycar, the feeding materials increase abnormally, causing the material layer to be too thick and the grinding effect is reduced. Due to the large amount of materials, the pressure difference becomes larger, and the ventilation is not smooth, when certain limit is reached, the mill will vibrate suddenly. When the feeding fluctuation is large, the wave form of the material layer will be caused.

3.3 Sudden change of system air volume and wind pressure

When SP furnace, kiln feeding, stopping and collapse are put into and out, the air volume of the system will be changed, and the normal movement track of the air flow in the mill will be changed by the large fluctuation of wind pressure, which destroys the balance of the established system and causes vibration.

3.4 the material layer is too thin or too thick

The material layer is actually a buffer pad sandwiched between the grinding roller and the grinding plate. Under normal circumstances, the extrusion of the grinding disk to the material is the extrusion of the material layer. When the material layer is too thin, its buffering effect will weaken and the vibration will increase. When the material layer is too thick, the buffering effect is too large, which leads to the decrease of grinding capacity and the decrease of production capacity, and the pressure difference will gradually rise. When a certain limit is reached, the vibration will suddenly increase. Therefore, in normal operation, the thickness of the material layer should be closely monitored and the parameters should be adjusted in time to make the material layer stable in a certain range.

3.5 excessive temperature in the mill

The high grinding temperature can lead to the damage of the toughness and rigidity of the material layer, especially when the temperature is too high, the material is very loose, not only is the material thin, but also is not easy to be rolled by the grinding roller "to hold on" to cause severe vibration. In general, the corresponding control can be made by adjusting the grinding baffle and the water spray quantity.

3.6 The system air volume, the amount of material and the grinding pressure do not match.

The air volume, feed quantity and grinding pressure in the vertical grinding system should be a flat whole. A parameter should be changed in the normal operation process, and its parameters should also be adjusted accordingly. If the parameters do not match, the vibration will also occur.

For example, when the air volume of the system is too low, the slag is too much, the gas can not blow the medium particle material back to the grinding disk, the material layer is too thin; at the same time, the too small air volume can not lift the material smoothly, but suspended in the grinding tire, which increases the resistance of ventilation. A vicious circle can cause a great deal of vibration soon.

For example, the grinding pressure is too large, which will cause the material layer to become thinner and cause the vibration to increase; when the material layer fluctuates greatly, it will also cause the hard connection of the grinding roller disc, which will cause severe vibration.

3.7 Timing of lifting roller

When the lowering roller is too early when the mill is on, there is no material or too little on the grinding disc, and there is no material layer. When the roller is falling, it is bound to be caused to move by the impact disc lining plate.

When the grinding and lifting roller is too late, it is possible to cause the material layer to be too thin or not to be ground on the grinding disc when the material layer is too thin or there is no material layer, and the vibration is bound to be caused. Therefore, it is necessary to accumulate experience in daily production to grasp the timing of the roll-up roll.

Because the general production line takes the form of a kiln, it is necessary to give enough attention to the vibration that affects the running of the vertical mill, otherwise, the equipment has problems, and the loss is great.

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