Ball Mill

Ball Mill Main Bearing Burning Tile Preventive Measures

The main bearing of the ball mill burns tiles and explains five reasons and preventive measures. The main bearing is an important part of the ball mill. It consists of a bearing base, a bearing shell, a bearing cap and a lubrication system. The bearing shell is its core component. The burning of the main bearings of the ball mill is a catastrophic accident of the cement plant because once the tiles are burned, the down time of the treatment is long and the maintenance workload is large, which not only affects the equipment operation rate, but also reduces the service life of the bearing bush. Therefore, the correct use and maintenance of the ball mill main bearings, to avoid burning tile accidents and shorten the maintenance time, etc., have important implications for cement companies.

Bearing temperature high and its temperature control

The temperature of the bearing bush is affected by the environment and the hollow shaft. The ambient temperature is high and the temperature of the bearing bush increases. The temperature of the hollow shaft is affected by the temperature of the material in the grinding, the temperature of the grinding gas, and the lubrication status of the hollow shaft and the bearing bush. The methods to reduce the temperature of the bearing bush include increasing the amount of oil to be sprayed, increasing the amount of cooling water in the bearing bush and the thin oil station, and spraying the water in the barrel. Because the location of the bearing temperature measuring point is special, it can only reflect the local temperature. When the bearing shell heats up locally, especially when the new tile is tested, it cannot reflect the temperature of the entire bearing bush in a timely manner. At the same time, sometimes the temperature measuring device fails.

Inaccurate conditions. Through the experience accumulated in the field, the temperature of the hollow shaft surface or the temperature of the main bearing return oil is measured with a temperature measuring gun. According to experience, the surface temperature of the hollow shaft is generally 10буC~15буC higher than the temperature of the tile surface, and the return temperature of the main bearing is approximately 5буC lower than the bearing temperature, that is, the return oil temperature can be controlled at 60буC or the hollow shaft. The surface temperature is 75буC. In addition, by measuring the temperature of the surface of the hollow shaft with a temperature measuring gun, the temperature difference of the surface of the hollow shaft can be found, thereby judging whether the contact between the hollow shaft and the bearing bush is normal and whether the lubrication state is normal, so as to make a treatment. At present, many lubricating oils increase the extreme pressure and wear resistance of greases, and there are special lubricating oils for ball mill bushings to increase the bearing capacity of lubricating oils, allowing the bearing bushes to be allowed to operate at an elevated temperature of 75буC or higher. It is more conducive to preventing the temperature of the mill's bearing shell from rising.

Ball Mill Main Bearing Ball Mill

The main reason for burning the main bearing

There are many reasons for burning tile, mainly from the following aspects: design, manufacturing, installation, use and maintenance. Design: The thickness of the steel plate in the cylinder body makes it easy to cause the cylinder to have excessive deflection, permanent bending and thermal deformation. The design of tile gaps is unreasonable, poor oil entry or failure to form bearing oil film, and other design defects may also constitute a burning tile accident. Manufacturing: The hollow shaft has a large radial runout, and the two hollow shafts are factory-installed with different concentricity; the bearing bushing has poor casting quality, and there are large voids or shells in the bearing area. Installation: improper bearing scratching, small gap between bearing bushes or poor contact between bush and hollow shaft or bearing bushing and bearing base cannot be flexibly oscillated, or allow bearing bushes to swing within a certain range within the bearing seat (but not bearing bush from the bearing base The detached positioning bolts resist the bearing, so that the bearing does not swing flexibly. Use and maintenance: improper use of lubricating oil, low oil viscosity or extreme pressure resistance, poor wear resistance, etc., bearing bushes and thin oil stations with small amount of cooling water or high inlet water temperature, less oil, lack of oil or dirty oil, etc. Failure of the temperature device resulted in inaccurate temperature measurement and failure to detect abnormal temperature in time.

Main Bearing Burning Tiles Prevention Measures

Among the above reasons, the main bearings of most companies are burned due to lubrication failure. Therefore, it should be prevented from the following aspects:

  1. Strengthen lubrication management, select suitable lubricants, and change oils according to the season; at the same time, maintain the reliability and flexibility of the control system of thin oil stations, and make the oil supply temperature protection and oil pressure protection of thin oil stations play a role. The effect is to avoid the burning of tiles due to high oil supply or low oil or lack of oil.
  2. Pay attention to the seal of the main bearing to prevent dust from entering and the oil from leaking out. After the dust enters the main bearing, it not only accelerates the wear of the bearing bush, but also deteriorates the lubricating oil and reduces the service life of the lubricating oil.
  3. Keep the cooling water of the bearing tile unblocked, prevent clogging, leaking and causing lubrication failure, causing the bearing to overheat or even burn tiles.
  4. During operation, on the one hand, pay attention to changes in the temperature of the bearing pad, control the temperature within the allowable range, and compare the temperature of the hollow shaft, the oil supply temperature of the dilute oil station, and the return oil temperature, so as to prevent the bearing from measuring the temperature. Resistor failure, inaccurate temperature measurement caused by burning tile. Central control room operators should always check the current and bearing temperature curve, and timely find timely treatment.
  5. When stopping the grinding, it is necessary to pass the slow-rotating mill for about 30 minutes to reduce the temperature of the bearing bush and stop the engine after the normal temperature of the bearing bush is normal. When the grinding time is long, the thin oil station or high-pressure oil station must be opened halfway. The high and low pressure oil pumps are slow-rotary mills to prevent the mill barrel from being stuck due to thermal expansion and contraction under the condition of no lubricating oil and to pull the bearing bushes.
In order to prevent the cylinder from generating excessive deflection when it is shut down in the hot state, some plants use the jacks to hold the cylinder in the middle of the mill barrel, which also has a certain effect.

Emergency plan for burning tiles

Mild burning tile case

Symptoms: Mild burned tile refers to short burned tile, less extent of tile surface damage, only local wear or high point, worn and brought out only flaky babbitt alloy, and the gap at the inlet of the tile is not Blocked, etc. If traditional methods are used, it is necessary to top-grind and remove the tiles, which is both time-consuming and labor-intensive.

Treatment method: This article summarizes the quick processing method for non-top-grinding tile: auxiliary auxiliary slow-rotary mill, which increases the ventilation volume of the mill and the oil-spraying volume at the burning tile. On the one hand, it rapidly cools the bearing shell and hollow shaft. On the other hand, during the slow-rotation process, the babbitt alloy adhered or sintered on the surface of the hollow shaft is scraped off, and the hollow shaft is polished with whetstone. After the temperature of the hollow shaft is normal, the bearing cap is stopped and lifted to clean the inlet and outlet. At the oil's pasteurization (mainly clearance of the gap), clean the thin oil station back to the oil filter and the oil filter. When the oil is dirty, replace the oil.

Then start the mill according to the normal production to reduce the amount of feed, and increase the amount of oil in the burning tile so that the grinding machine wears the high point of the tile surface during operation. During the operation, it is necessary to control the temperature of the surface of the hollow shaft not to exceed 75буC. When the temperature is high, the mill is stopped, and the mill is cooled slowly. The temperature of the hollow shaft surface is reduced to 30буC and the mill is restarted. After several times of running-in, the high point can be ground away and the hollow shaft temperature is within the normal range.

Severely burned tile case

Symptoms: Severely burned tiles refer to long duration of burned tiles, severe burned tiles, high amount of babbitt metal withdrawn, serious blockage at inlet port, hollow shaft being marked out of grooves and the entire tile lining can no longer be used, etc. . Each time severe burning of tiles, the loss of 0.4-0.7mm babbitt alloy is required, shortening the service life of the main bearing bush for 3 to 5 years, and making the babbitt alloy soften at high temperature and being squeezed under the pressure of the hollow shaft. Pressing out, eventually leading to scrapping of the babbitt alloy layer.

Treatment method: When dealing with heavy burned tiles, it is necessary to pour out the inner ball section, top-grind the roof, and re-study and scrape the bearing bushes. The new type of scraping method saves time and time.

The specific steps are as follows: about 30mm on both sides of the width direction of the bearing bush, the contact angle is not scratched within 30бу, it can be polished smooth with the back of the sandpaper, and the gap of the mouth of the oil at the oil inlet is appropriately increased. After the bearing surface of the bearing bush is polished with sandpaper, Scraping around, the middle is not scratching and so on. After four times with the hollow shaft, it is placed in the bearing base and all the ball sections are tested. During the test run, the hollow shaft temperature was 43буC, and most of the temperature was 38буC. When the operation was normal, most of the hollow shaft temperature was 28буC and the local temperature was 43буC.

There are many ways to prevent the main bearing from burning tiles, of which the main one is controlling the temperature. The current mill control system adopts PLC programmable control and sets the rated temperature. When the temperature of the main bearing tile rises to 60буC, the end surface thermal resistance signals to achieve automatic trip and timely troubleshooting. Larger ball mills are equipped with high and low pressure dilute oil stations. They can also be double controlled by oil pressure and temperature to provide reliability for the safe operation of ball mills. Timely maintenance, maintenance, reduce hidden troubles and effectively improve the efficiency of equipment operation.

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