[Core tip] With the increase in the size of cement grinding equipment, large-diameter mills with a diameter of 3.8 m or more have adopted sliding bearing technology for tube mills. The sliding bearings are large-scale bus alloy bearings because of the contact between the bearings The surface is on the outer diameter of the mill barrel, the bearing diameter is increased, the linear velocity of the bearing is more than doubled, and the frictional resistance torque generated by the mill is more than double that of the hollow shaft mill.
With the increase in the size of cement grinding equipment, large-diameter mills with a diameter of 3.8 m or more have adopted sliding bearing technology for tube mills, which are large-scale bus alloy bearings because the contact surfaces of the bearings are being ground. On the outer diameter of the barrel, the bearing diameter increases, and the linear velocity of the bearing more than doubles. The frictional resistance torque generated by the mill when it rotates is more than double that of the hollow shaft mill, and the friction power consumption increases. The power consumed by the bearings of the sliding shoe mill needs about 15%. The calculation of the power required to overcome the frictional resistance torque is the weight of the mill × the radius of rotation of the bearing × the number of revolutions of the mill × the friction coefficient. It is not difficult to see that the radius of rotation of the bearing The increase will directly lead to an increase in frictional resistance torque, resulting in an increase in power consumption. In addition, there are many parts of the sliding shoe bearing that the friction temperature rises too high, which results in the need to stop grinding and reduce the temperature, which reduces the operating rate of the mill. For this reason, we propose that the transformation should be carried out as soon as possible.
The sliding bearing bearing mill is in surface contact with the sliding bearing during operation. Under the action of positive pressure, the phenomenon of grease deterioration is very serious. As the temperature of the ball mill shoe rises, the viscosity of the lubricating oil decreases, the bearing capacity decreases, and even dry friction is caused, and the tile will be burned seriously. The temperature rise of the sliding shoe mainly comes from the large heat generated by the collision and sliding between the grinding bodies inside the mill, part of which is taken away by the material and gas, and part of it is emitted by the cylinder, and the heat of the cylinder is transmitted to the slide. On the ring, the temperature of the shoe rises accordingly. In order to solve these problems, our company has carefully studied and consulted a large amount of data. With many years of production experience, we have formulated the following technical transformation plans:
1 Remove the sliding bearing support of the sliding mill and change to the rolling bearing support to reduce the frictional resistance moment of the mill bearing.
Because the cylinder and the rolling bearing are in line contact during work, the amount of oil used is small, and the deterioration of grease is very small. By looking up the data, we know that the friction coefficient of the sliding bearing is 0.04-0.035, and the friction coefficient of the rolling bearing is 0.0025, which is almost 16 times the difference. Therefore, after the transformation, the friction resistance torque of the main bearing can be reduced to achieve the purpose of reducing the power used by the motor and saving electrical energy. The calculation method of the friction resistance torque conversion motor power is:
Mill weight × load factor × friction factor × bearing turning radius × mill revolution / 97360 (power conversion factor)
Motor power consumed by Φ4.2 × 13m mill 3 bearing types:
Rolling bearing: 630.000kg × 0.7 × 0.0025 × 1.00cm × 15.6 ÷ 973.60 = 17.66kw.h
Bus alloy (hollow shaft): 630.000kg × 0.70 × 0.035 × 1.00cm × 15.6 ÷ 973.60 = 247.31kw.h
Sliding bearing: 630.000kg × 0.70 × .035 × 2.00cm × 15.6 ÷ 973.60 = 494.6kw.h
For example: rolling bearing Ф32 × 13m mill; motor power 1600kw, grinding body 135t. The power of Ф4213 mill is 3550kw, and the grinding body should be loaded with 280t. Now the calibration load is 230t. It can be seen that due to the use of sliding shoe bearings and the increase of the rotating diameter of the mill, the loading of the grinding body has been correspondingly reduced by nearly 50t. This has a significant impact on the output of the mill. See, Babbitt bearing consumes 198kw more motor power than rolling bearings, and shoe bearings consume 477kw more motor power than rolling bearings. For this reason, transforming sliding bearings into rolling bearings will have great potential for energy conservation and consumption reduction.
Motor power of 3 types of bearings of Φ3.8 × 13m mill:
Rolling bearing: 480.000kg × 0.7 × 0.0025 × 1.00cm × 16.3 ÷ 973.60 = 14.06kw.h
Bus alloy (hollow shaft): 480.000kg × 0.7 × 0.035 × 1.00cm × 16.3 ÷ 973.60 = 196.88kw.h
Sliding bearing: 480.000kg × 0.7 × 0.035 × 2.00cm × 16.3 ÷ 973.60 = 393.77kw.h
For example: Ф3.2 × 13m mill; motor power 1600kw, grinding body 130t. The power of Ф3.8 × 13m mill is 2500kw, and the grinding body should be loaded with 225t. Now the calibration load is 174t. It can be seen that due to the use of sliding bearing and the increase of the rotation diameter of the mill, the load of the grinding body has been correspondingly reduced by 51t. This has a significant impact on the output of the mill. From the perspective of the motor power consumed by the three different types of bearings, Babbitt alloy bearings consume 182kw more motor power than rolling bearings, and sliding shoe bearings consume 379kw more motor power than rolling bearings. For this reason, transforming sliding shoe bearings into rolling bearings has great potential for energy conservation and consumption reduction.
2 Transformation methods
Method (1): Design the supporting ring at the position where the sliding shoe bearing was originally installed, design two sets of supporting rollers at the lower part of the supporting ring, each supporting roller design two supporting rollers, install the rolling bearing at both ends of the supporting roller, supporting A connecting plate is designed on each side of the roller, which is fixed on the connecting plate with a shaft, and the other supporting roller is also designed. The connecting plate is designed to be almost triangular, and a pin is connected to the fixed base at the bottom. When the mill rotates, it automatically finds the center of the circle under the effect of positive pressure. Because the bearing capacity is taken into consideration in the design, each set of rollers is designed into two to ensure that there are 4 rollers on one end of the mill barrel, which is safe and reliable, reduces wear and improves service life.
Method (2): The inner ring, rolling element and cage of the rolling bearing are installed by using the belt of the shoe bearing, and the outer ring is installed on the main bearing seat. This modification method is relatively simple, the investment is slightly higher, the bearing size is relatively large, and the operation smooth. Reconstruction and manufacturing time: 50 days-60 days, on-site installation 1 week-10 days.
3 The characteristics of the LMGU rolling bearing changed to mill:
3.1 Reduce working current
Select a reasonable rolling bearing to be used on the mill, and the friction coefficient generated when it rotates is only 0.0025, which is 1/16 of the sliding bearing. Slipper bearings consume nearly 14% of the motor power. Through calculation and application examples, the motor power consumed by the rolling bearing when the mill rotates only accounts for about 0.5-7% of the power of the supporting motor. This will reduce the normal working power consumption, achieve savings in electricity costs, reduce production costs, and improve economic efficiency of the enterprise. aims.
3.2 Reduce starting current
Due to the large frictional resistance of the sliding bearing, until the phase friction between the shaft and the bearing reaches a fixed number of revolutions based on the acceleration principle at the time of starting, the motor must overcome a large frictional resistance torque. Generally, the starting current is 5 to 6 times the working current. many. After the rolling bearing is used, the starting current is only about two times the working current. The reason for the large surplus power of the motor when the old mill is normally working is because of the sliding bearing. After the main bearing is changed to a rolling bearing, the power of the supporting motor can be reduced or the amount of the grinding body of the mill can be increased, which not only improves the efficiency of the motor, reduces useless power, but also increases the output of the table.
3.3 Save a lot of lubricant
Because the lubrication of sliding shoe bearings uses high and low pressure oil supply, generally a high pressure system is used before the mill starts and when the mill is stopped, and the low pressure system is used to supply oil during normal operation. The low-pressure system pipeline is designed in three ways, two of which are connected to the oil pan in front of the two sliding shoes, the cooling slip ring and the oil-supply dynamic bearing are lubricated; the other is connected to the oil shower pipe above the shoe cover, and the slip ring The upper part cools down and consumes a lot of lubricating oil. After the rolling bearing energy-saving transformation, the thin oil lubrication station and oil pool lubrication can be canceled. After the rolling elements of the bearing pass in the lower oil pool, it will bring lubricating oil, which can meet the lubrication requirements. Change the lubricating oil once every six months, only 200kg can be replaced once. If the roller bearing method is adopted, the low-pressure system is used to supply oil between the carrier ring and the roller. When the barrel temperature is transmitted to the roller, the frictional power consumption is reduced under the action of the lubricant, the friction and heat are reduced, and the lubricant is lubricated at the same time. When the oil passes through the friction place, it can take away the heat from it. Under the effect of the cooling water in the thin oil station, the temperature is reduced to ensure a good equipment operation rate. Only a small amount of circulating oil is required. Can save 80% of lubricant.
3.4 Increase the load of grinding body and increase the output of the mill
Because the working current of the mill is reduced by about 15%, the loading of the grinding body can be increased by more than 10%. The increase of the grinding body will inevitably increase the output of the mill. When Taiwan's output increases by about 15%, production costs will fall, and profit margins per ton of cement will increase.
3.5 years of maintenance and cleaning of bearings are very convenient
Because the rolling elements of the bearing and the upper half of the cage are all exposed, waste oil and debris are easy to clean. For national standard bearings, the overall outer ring has a small amount of movement, and the rolling elements and cages cannot be exposed. Therefore, it is impossible to clean all the waste oil and debris, which will affect future functions.
3.6 Rolling bearings can be replaced
LMGU rolling bearings are composed of four major components: inner ring, outer ring, cage and rolling elements. Each component can be replaced at any time, which avoids the disadvantage of replacing the entire set of bearings when each component of the old-style bearing is broken. In order to make this kind of bearing develop towards serialization and standardization, our company has undertaken the drafting work of the building material industry standard "Cement Industry Bearings (Bearings)" of the People's Republic of China, and has passed the review of experts in the industry. And the Reform Commission approved the promulgation and implementation on December 1, 2006.
3.7 Reduce maintenance and improve operation rate
The service life of sliding bearings is generally 1 to 3 years, and the main shaft of the mill will also wear. If the maintenance is not good, some manufacturers will have to replace a pair of bearings in a few months. During normal operation of the sliding bearing, lack of lubricating oil, cooling water or excessive temperature rise of the bearing must not occur. Once it occurs, it will be shut down for maintenance, so the phenomenon of low operating rate is common. After the rolling bearing is used, as long as a small amount of dry oil is added in time, it can operate normally without special care of the grinder, and the actual service life of the rolling bearing is 8 to 12 years. Users can rest assured. This will reduce part of the maintenance and downtime, and improve the equipment operation rate.
3.8 Save cooling water and improve environmental sanitation
After the rolling bearing is adopted, the wet grinding and cement raw material grinding can eliminate the bearing circulating cooling water device, which does not affect the bearing life. After the rolling bearing seat is lubricated with dry oil, no oil pollution occurs, which improves the environmental sanitation.
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