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Four causes of main bearing Burning of Ball Mill and five Preventive measures

Date:2019-07-01 10:17 Source:未知Views:

The main bearing is an important part of the ball mill. It is composed of bearing base, bearing bush, bearing cap and lubricating system. The bearing bush is the core part.

The main bearing tile burning of ball mill is a catastrophic accident in cement plant, because once the tile is burned, the shutdown time is long and the maintenance workload is large, which not only affects the running rate of the equipment, but also reduces the service life of the bearing.

Therefore, it is of great significance for cement enterprises to use and maintain the main bearing correctly, to avoid the occurrence of tile burning accident and to shorten the maintenance time.

High temperature of bearing and its temperature Control


The temperature of the bearing bush is affected by the environment and the hollow shaft, the ambient temperature is high, the temperature of the bearing bush is increased, and the temperature of the hollow shaft is affected by the temperature of the material in the mill, the temperature of the gas in the mill, the lubrication state of the hollow shaft and the bearing bush, and the like.

The method for reducing the temperature of the bearing bush includes the following steps of: increasing the amount of the ice cream, increasing the cooling water amount of the bearing bush and the thin oil station, and pouring water and the like.

Because the position of the temperature measuring point of the bearing is special, it can only reflect the local temperature. When the bearing is heating up locally, especially when the new pad is tested, it can not reflect the temperature of the whole bearing width direction in time. At the same time, sometimes the temperature measuring device will fail and the temperature measurement will not be accurate. Through the experience accumulated in the field, the surface temperature of hollow shaft or the oil return temperature of main bearing are measured by temperature measuring gun.

According to experience, the surface temperature of hollow shaft is 10 ℃ ~ 15 ℃ higher than that of tile surface, while the oil return temperature of main bearing is about 5 ℃ lower than that of bearing, that is to say, the return temperature can be controlled at 60 ℃ or 75 ℃.

In addition, by measuring the temperature on the surface of the hollow shaft with a temperature measuring gun, the temperature difference on the surface of the hollow shaft can be found, so as to determine whether the contact between the hollow shaft and the bearing is normal and whether the lubrication state is normal.

At present, many lubricating oils increase the extreme pressure and wear resistance of the grease, and have the lubricating oil specially used for the bearing pad of the ball mill, thus improving the bearing capacity of the lubricating oil and raising the allowable working temperature of the bearing pad to 75 ℃ or more, which is more beneficial to prevent the temperature of the bearing pad of the mill from rising.

The main reason of main bearing Burning

There are many reasons for burning tile, mainly from the following aspects: design, manufacturing, installation, use and maintenance:

1. Design aspect


Because of the thin thickness of the steel plate, the deflection of the cylinder is too large, and the permanent bending and thermal deformation are easy to occur. The design defects such as unreasonable gap design, poor oil intake or poor bearing oil film may also constitute tile burning accident.

2、 Manufacturing aspect


The radial deflection of the hollow shaft is large, and the two hollow shafts are factory-mounted with different centers; and the bearing bush is poor in casting quality, and the bearing area is provided with a large cavity or a shell-out phenomenon and the like.

3. Installation


The bearing is not properly scratched, the gap between the bearing bush and the gap of the bearing bush or the poor contact between the bearing bush and the hollow shaft or the spherical surface of the bearing bush and the bearing base cannot be flexibly swung, or the bearing bush is allowed to swing in a certain range in the bearing base (but the bearing bush is not allowed to be separated from the bearing base), and the bearing bush is supported by the positioning bolt, So that the bearing bush can not swing flexibly and the like.

4. Use and maintenance.


Improper selection of lubricating oil, low viscosity or extreme pressure resistance of oil, poor anti-wear ability, small cooling water quantity or high influent temperature, less oil, lack of oil or oil, etc., the failure of temperature measuring device leads to inaccurate temperature measurement and failure to detect temperature anomaly in time, etc.

Preventive measures for burning tile of main bearing

Among the above reasons, the main shaft bearing burning pad of most enterprises is caused by lubrication failure. Therefore, it should be prevented in the following ways:


1. Strengthen lubrication management, select appropriate lubricating oil, and change oil according to the season; at the same time, it is necessary to maintain the reliability and flexibility of the control system of dilute oil station, so as to make the oil supply temperature protection and oil supply pressure protection of dilute oil station play a role, and avoid burning tiles caused by high or less oil supply temperature and lack of oil.

2、 Pay attention to the sealing of the main bearing to prevent dust entry and lubricating oil leakage. After the dust enters the main bearing, it will not only accelerate the wear of the bearing, but also make the lubricating oil deteriorate and reduce the service life of the lubricating oil.

3. Keep the cooling water of the bearing pad smooth, prevent blockage, leakage cause lubrication failure and cause the bearing pad to overheat or even burn the pad.

4. In operation, on the one hand, we should pay attention to the change of bearing temperature and control the temperature within the allowable range, at the same time, we should compare the hollow shaft temperature, the oil supply temperature and oil return temperature of dilute oil station, so as to prevent the failure of thermal resistance of bearing pad temperature measurement and the burning tile caused by wrong temperature measurement. Central control room operators should often check the current and bearing temperature curve, timely discovery and timely processing.

5. When grinding is stopped, the auxiliary slow rotating mill should be used for about 30 minutes to reduce the bearing temperature and wait for the bearing temperature to be normal before stopping; when the grinding time is long, it is also necessary to open the high and low pressure oil pump slow rotating mill in the middle of the dilute oil station or the high pressure dilute oil station, in order to avoid the bearing of the mill cylinder being blocked by heat expansion and cold shrinkage without lubricating oil.

In order to prevent the cylinder from producing excessive deflection during hot shutdown, some factory jacks hold the cylinder in the middle of the mill cylinder, which also plays a certain role.

Plan for emergency treatment of tile burning fault

1. Case of mild burning

Failure phenomenon:


The time of mild tile burning is short, the injury degree of tile surface is small, but the local wear or high point appears, what is worn and brought out is only flake Babbitt alloy, and the gap between the tile mouth of the oil inlet is not blocked, and so on. According to the traditional treatment method, it is both time-consuming and laborious to grind and scrape the tiles.

Approach:


In this paper, the rapid treatment method of no top grinding tile is summarized.

The auxiliary slow rotating mill increases the ventilation volume of the mill and the leaching oil at the tile burning place, on the one hand, it makes the bearing and the hollow shaft cool down quickly; On the other hand, in the process of slow rotation, the Babbitt alloy adhered to or sintered on the surface of the hollow shaft is scraped off, and the hollow shaft is polished with oil stone. After the temperature of the hollow shaft is normal, the bearing cover is stopped, the Babbitt alloy chips at the inlet and outlet of the tile mouth are cleaned (mainly cleaning the gap between the tile mouth), the filter net and the inlet oil filter net at the return oil of the dilute oil station are cleaned, and the lubricating oil should be replaced when the oil is dirty.

Then according to the normal production to reduce the feed amount to start the mill, increase the amount of oil in the tile to make the mill in operation to grind the high point of the tile surface. In operation, attention should be paid to controlling the temperature of the hollow shaft surface not exceeding 75 ℃. When the temperature is high, the mill stops, slowly rotates and cools, and the temperature of the hollow shaft surface drops to 30 ℃ before restarting the mill. After several running-in, the high point can be ground away, and the hollow shaft temperature can reach the normal range.

2、 Case of severe tile burning

Failure phenomenon:


The duration of severe tile burning is long, the degree of tile burning is serious, the amount of Babbitt alloy belt is more, the tile mouth at the oil inlet is seriously blocked, the hollow shaft is cut out of the groove and the whole tile lining can no longer be used. Each time the heavy tile is burned, the 0.4~0.7mm Babbitt alloy will be lost lightly, and the service life of the spindle bearing pad will be shortened by 3 years. The heavy Pap alloy will soften at high temperature and be extruded out under the pressure of the hollow shaft, which will eventually lead to the scrapping of the Babbitt alloy layer.

Approach:


In case of severe burning, it is necessary to pour out the inner ball section, the top mill and the back grinding pad, and repair the time length. The novel scraping method saves time and saves time,

The concrete steps are as follows: the two sides of the width direction of the bearing bush are inclined with a slope of about 30 mm, the contact angle is 30 degrees, the surface of the sand paper is polished to be smooth, the clearance of the gas outlet at the oil inlet is appropriately increased, the spherical surface of the bearing bush is ground with a sand paper, and the periphery of the bearing bush is ground and scraped, and the middle part is not scratched and the like.

After four times of development with the hollow shaft, put into the bearing base with all the ball section test run. During the test run, the highest temperature of the hollow shaft is 43 ℃, and most of the temperature is 38 ℃. When the operation is normal, the temperature of the hollow shaft is 28 ℃ and the local temperature is 43 ℃.

There are a lot of methods to prevent the main bearing burning, in which the control temperature is the main. The present mill control system adopts PLC programmable control to set the rated temperature. When the temperature of the main bearing bush rises to 60 ℃, the end face thermal resistance sends a signal to realize the automatic stop and timely eliminate the fault.

The large ball mill with high and low pressure dilute oil station can also be controlled by oil pressure and temperature to provide reliability for the safe operation of ball mill. Timely maintenance, good maintenance, reduce hidden trouble, effectively improve equipment operation efficiency.

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