Abstract: Since the reform and opening up, the national economy has developed rapidly, and the coal industry, as an important part of my country’s national economy, is also growing vigorously. The roller bearing of the machine is an important element to ensure its normal operation. Based on the author’s years of experience, the article deeply analyzes the reasons for the abnormal temperature of the roller bearing of the coal mill and the corresponding treatment strategies, aiming to prolong the service life of the bearing and avoid premature bearing damage, hoping to help everyone.
introduction
Today, under the advocacy of the state, coal enterprises must also continue to develop in the direction of environmental protection and energy saving. Directly adding pulverized coal ground from raw coal to the blast furnace can greatly reduce the degree of coalification and reduce the use of coke. Because the price of raw coal and raw coal that has not been washed and processed is much lower than that of coke in the market, this can reduce the production cost of blast furnaces to a certain extent, which can not only utilize resources efficiently, but also save energy and protect the environment. The blast furnace model used by most iron smelters now is 3210S42, and the coal injection system is equipped with a ZXL225M33 medium-speed roller mill. Due to the late start of our country in this regard, the equipment function and operation rules of the coal mill are not well understood, which leads to the failure of the coal mill. In particular, the abnormal temperature of the grinding roller bearing leads to frequent power failure of the electric switch of the coal mill, which seriously affects the production progress of pulverized coal. Below, I will share with you the common causes and basic treatment methods of abnormal roller bearing temperature.
1 The working principle of the coal mill and the main structure of the grinding roller
ZXL225M33 coal mill is a medium-speed roller disc coal mill, which consists of a rotatable grinding ring and three fixed grinding rollers rolling along the grinding ring. The raw coal first descends from the central coal grinding tube to the grinding ring, and then moves the raw coal to the grinding rollers with the help of centrifugal force through the rotation of the grinding ring for grinding. The three fixed grinding rollers are installed on the four corners of the rolling disc track, and the liquid pressure is the main source of the grinding force, and then the three rolling grinding rollers apply the rolling force in the liquid pressure cylinder, and then pass the Conduction reaches the bottom grinding disc[1]
- Analysis and treatment method of abnormal temperature of grinding roller bearing
2.1 Insufficient lubrication
2.1.1 Cause analysis. The reason for the lack of lubricating oil is generally due to the problem of the selection of the type of lubricating oil. Generally speaking, the working temperature of the roller bearing is relatively high, and the temperature inside the bearing is close to 200. If the type of lubricating oil is wrong, the oil used for lubricating will be deteriorated or evaporated due to high temperature and high pressure, thus losing the function of protecting and lubricating the roller bearing, which will increase the heat generated by the friction of the roller bearing. , resulting in an abnormal increase in bearing temperature. In addition, if the lubricating oil is too small or the replacement is not timely, the lubricating oil may lose its original function, resulting in insufficient lubrication of the roller bearing, and the bearing temperature will also rise, resulting in premature bearing damage. [2].
2.1.2 Processing method.
In order to ensure the lubrication of the roller bearings, manufacturers should try their best to choose synthetic greases with viscosity and stability at high temperature when selecting lubricating oils. Based on years of experience, it is recommended to use No. 500 polymerized hydrocarbon high-temperature resistant industrial gear oil imported from Japan. The lubricating oil must be replaced in time every time the bearing has been running for four months, and the lubricating oil must not be less every time it is added. in forty liters. 2.2 The inner bearing of the grinding roller enters a large amount of pulverized coal
2.2.1 Cause analysis.
If a large amount of pulverized coal enters the internal bearing, the pulverized coal will bond with the lubricating oil and become a viscous and extremely poor fluidity pulverized oil mixture, which will not only not have any lubricating effect on the bearing, but also It will aggravate the wear of the bearing and cause the temperature of the roller bearing to rise abnormally. The main reason for this phenomenon is that the oil seal of the grinding roller is partially damaged, because the surrounding of the grinding roller is often scattered with a large number of pulverized coal generated when the coal is crushed. , The working environment is very bad, so once there is a problem with the oil seal, a large amount of pulverized coal will enter the roller bearing, causing damage [3].
2.2.2 Processing method.
ZXL225M33 medium-speed roller mill generally has two oil seal layers, one is used for sealing the external environment, and the other is used for the interior. When it is found that the coal powder enters the bearing and causes the bearing temperature to rise abnormally, the oil seal should be replaced immediately, and the quality of the lubricating oil should be reviewed to ensure that it has not deteriorated. If there is too much pulverized coal accumulated inside the bearing, and the pulverized oil mixture cannot be discharged with the oil outlet, then the inner end cover of the bearing can be opened, and the pulverized oil mixture can be discharged by compressing air or adding hydrogen, and then refilling new lubricant. Figure 1 shows the change curve of pulverized coal value and roller bearing temperature.
2.3 Damage to the sealed air system
2.3.1 Cause analysis.
The sealing air system is the key link to ensure that the oil seal of the grinding roller is not damaged. The sealed air system consists of a sealed fan and an air duct. The blown air starts from the sealed fan and finally reaches the sealed air duct. The three grinding rollers installed on the grinding disc of the coal mill seal the air to form the gold space. In this way, an annular seal cleaning system can be formed, which can not only ensure that the pulverized coal does not enter the bearing of the grinding roller, but also prevent the pulverized coal from damaging the oil seal. All links are closely connected and are indispensable. If there is a problem in any link, air leakage in the air duct or debris, it will cause the pressure of the air seal ring to decrease and the air volume to be insufficient, so that the annular air seal system cannot be Formed, and then caused a series of conditions such as oil seal damage, coal dust entry, and bearing temperature rise.
2.3.2 Processing method.
The blower must be matched with each coal mill, and it must be ensured that the pressure is greater than 14kPa, and the air volume is greater than 3m/h. When the sealing air and wind pressure is less than or equal to 1.47kPa, or when the temperature of the roller rises abnormally, stop production immediately and Investigate, from the sealed fan to the direction of the wind, carry out a step-by-step inspection, so as to plug the loopholes, seal up and unseal in time. Combined with my years of work experience, due to the difficult working environment of the coal mill, and the long-term and large amount of coal powder, the filter screen of the blower is easy to be blocked, so the technicians should clean it frequently, and try to do it every half a month. And because the working environment temperature is high, the air duct is easy to soften and deform or air leakage occurs. It should also be checked every half month to kill the fault in the cradle [4].
2.4 Partial damage of roller bearing
2.4.1 Cause analysis. Roller bearings pay special attention to the quality of the bearings, but local damage will also occur during long-term operation, such as ball wear, loose joints, and so on. At this point, the roller bearing temperature will definitely be abnormal.
2.4.2 Processing method. When the surface of the grinding roller bearing is uneven, the local rotation is blocked, the left and right swing is increased, and there is noise inside; or the bearing temperature is overloaded or fluctuated at the moment when the coal mill is turned on, it is necessary to stop production immediately, carry out maintenance inspection or If the damage is serious, the roller bearing should be replaced in time to ensure production safety [5].
2.5 Excessive internal grease and impurities
2.5.1 Cause analysis.
At the beginning of production, the running resistance of the roller bearing is relatively large, and the grease accumulates too much.
2.5.2 Processing method. Immediately open the side end cover of the bearing to take an oil sample for testing. If the metal content in the grease exceeds the standard, it means that the bearing has been worn, and the production should be stopped and the bearing replaced.
3 Conclusion
The role of the roller bearing in the coal mill is very huge. As a technician, we should try our best to learn the relevant knowledge, understand the performance of the roller bearing as soon as possible, master the cause and treatment method of its abnormal temperature rise, and carry out the bearing in time. Replacement and maintenance to ensure the normal production work of the factory.
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