Spare Parts

Load transfer and support: The vertical mill will generate various complex forces during operation, including the pressure of the material on the grinding roller, the gravity of the grinding roller itself, etc. These forces are ultimately transmitted to the grinding roller shaft and the mill body through the tapered roller bearing. The inner ring of the tapered roller bearing cooperates with the grinding roller shaft, and the outer ring cooperates with the mill body or related components. When the grinding roller is subjected to external force, the force is transmitted to the tapered roller through the inner ring, and then transmitted to the outer ring by the tapered roller, thereby achieving support for the grinding roller and other components of the vertical mill, ensuring that the grinding roller can rotate stably around the axis.

Rolling friction achieves efficient operation: The design of the tapered roller bearing makes the raceways of the inner and outer rings and the apex of the imaginary cone formed by the rollers converge at one point on the bearing axis. When the vertical mill is working, the grinding roller shaft drives the inner ring to rotate, and the large rib on the inner ring guides the trapezoidal tapered roller to roll in the raceway. Since the tapered roller is in line contact with the inner and outer ring raceways, and the rolling generatrix and the raceway generatrix of the gasket converge at a certain point on the axis of the bearing, the rolling surface can form pure rolling, thus converting the sliding friction into rolling friction, greatly reducing the friction coefficient, reducing energy loss, and improving the transmission efficiency of the vertical mill, so that the roller can operate efficiently and smoothly.

Bearing of axial and radial loads: In the process of grinding materials, the vertical mill not only has radial loads such as the weight of the roller itself and the vertical pressure of the material on the roller, but also axial forces generated by the extrusion and grinding of the material by the roller. Tapered roller bearings can bear radial and axial loads at the same time. For radial loads, it is mainly borne by the contact between the tapered roller and the inner and outer ring raceways; for axial loads, it is borne by the cooperation between the tapered surface of the tapered roller and the inner and outer ring raceways, converting the axial force into the normal force between the tapered roller and the raceway, thereby achieving effective bearing of the axial load and ensuring the stable operation of the vertical mill.

1. Preparation work
Check whether the number and model of bearings are consistent with the requirements of the equipment, ensure the quality is qualified, and there are no dimensional deviation, burrs, wear and other problems.

Prepare installation tools such as special wrenches, installation sleeves, hydraulic press-in devices, flat-nose pliers, screwdrivers, tensioners, etc.

Ensure that the assembly site is clean, dry, dust-free, the ground is flat, and there is no debris.
Check the size, shape and position tolerances of the shaft, bearing seat and other parts that match the bearing to ensure that they meet the assembly requirements and keep records.

Clean the installation surface of the shaft and bearing seat to remove oil, impurities, burrs, etc., which can be wiped with detergent and soft cloth, and a metal brush if necessary.

Prepare an appropriate amount of grease to apply to the bearing surface to reduce friction.

2. Assembly process
Install the inner ring and roller assembly: If it is an interference fit, the inner ring of the bearing can be heated by oil bath heating or induction heating. The heating temperature is controlled at 80℃-100℃, and the maximum does not exceed 120℃. Then install the inner ring and roller assembly on the shaft so that it is close to the shaft shoulder. After cooling, the inner ring will be tightly fixed on the shaft. For the inner ring of the cylindrical roller bearing, it is usually heated to about 80℃ before installing it on the shaft shoulder.

Install the inner spacer: Install the inner spacer on the shaft, located on one side of the inner ring of the tapered roller bearing.

Install the hub: Heat the hub to about 80℃, then install the outer ring of the cylindrical roller bearing and the roller assembly into the inner hole of the hub, and then install the outer spacer in the inner hole of the hub.

Install the outer ring of the tapered roller bearing: Install the outer ring of the tapered roller bearing into the inner hole of the bearing seat.

Assemble the shaft and hub: Lift the hub, place it on the installation workbench, insert the shaft into the inner hole of the hub, and rotate the shaft during insertion to avoid collision between the inner ring of the cylindrical roller bearing and the cylindrical roller, and to arrange the tapered rollers neatly.

Install the outer spacer of the bearing: Install the outer spacer on one side of the outer ring of the tapered roller bearing.

Install the gland and hub cover: Use the gland to press the inner ring of the tapered roller bearing and tighten the bolts; use the hub cover to press the outer ring of the tapered roller bearing and tighten the bolts.

3. Clearance adjustment and inspection
Axial clearance measurement: Stand the grinding roller upright with the hub at the bottom and the shaft facing up. Remove grease and burrs on the sealing cover flange, clean the roller shaft, and install two magnetic micrometers 180 degrees apart, and the micrometers should be installed at a right angle to the surface of the object being measured. Stand the hub cover firmly and vertically on a flat horizontal surface, rotate the shaft clockwise and counterclockwise for a few weeks to ensure that the bearing rolling elements are in the correct position, then mark the intersection of the two micrometers and the sealing cover flange with a marker pen, and adjust the meter to "zero". Lift the grinding roller to fix the shaft, rotate the hub clockwise and counterclockwise for a few weeks, put the tapered roller in the correct position again, align the mark on the flange sealing cover with the micrometer measurement position, read the measurement value of the micrometer and record the data. Put down the grinding roller, rotate the shaft in both directions for a few weeks, and align the mark of each micrometer. The reading of the meter should be zero. If the reading of the meter is not "zero", this test is invalid. Repeat the above steps until a constant reading is obtained, and when returning to step C, the reading of the meter is zero. Repeat steps B and C at least three times until the reading of the meter is a constant measurement value.3.

Determination and adjustment of the spacer size: Determine the size of the spacer according to the measured axial clearance and preload. If the axial clearance is less than the specified value, it means that the size of the bearing spacer is too small. It is necessary to remove the spacer, weld the spacer end face to increase the spacer width, or grind the spacer to meet the size requirements. The parallel difference between the two end faces of the spacer should be controlled within 0.050 mm. Then reinstall the bearing spacer, outer ring and hub cover, and tighten the bolts.

4. Final inspection and trial run
Check the installation status of the bearing to ensure that the bearing is firmly installed, without looseness or offset, and the components are tightly connected and the bolts are tightened in place.
Check whether the lubrication system is normal to ensure that the bearing can obtain proper lubrication.

Manually rotate the shaft or bearing box to check whether the bearing rotates freely and whether there is any abnormal sound.

Turn on the power supply, perform a no-load, low-speed operation test, observe the operation of the bearing, and detect noise, vibration and temperature rise. If there is no abnormality, gradually increase the rotation speed and load, continue to observe, and only put it into formal use after confirming that there is no problem.

Wear: During the long-term use of tapered roller bearings, common fault types are diverse. Wear is a common problem. Long-term repeated friction between the rolling element and the raceway, coupled with insufficient lubrication or impurity intrusion, will cause the bearing clearance to increase and the precision to decline. Taking the tapered roller bearings in mining machinery as an example, due to the harsh working environment, dust can easily enter the bearing, aggravating the degree of wear. When the equipment is running, wear failures are manifested as abnormal noise, increased vibration, temperature rise and reduced precision.

Fatigue: Under the continuous action of alternating loads, contact fatigue stress is easily generated on the surfaces of the rolling elements and raceways. Once the fatigue limit of the material is exceeded, tiny cracks will appear, and then develop into fatigue spalling. For example, in motor equipment that is frequently started and stopped, the alternating load on the bearing is large, and fatigue spalling is relatively common. When fatigue spalling occurs, the bearing operation will produce periodic shock and vibration, and the noise will increase significantly, seriously affecting the normal operation of the equipment.

Lubrication: Poor lubrication is also a major source of failure. Small amounts of grease or lubricating oil, poor quality, inconsistent models, and failures in the lubrication system can all cause such problems. For example, some old equipment, due to untimely maintenance, the grease has not been replaced for a long time, gradually deteriorating and drying, and cannot play a good lubrication role. The manifestation of poor lubrication is a sharp increase in bearing temperature, abnormal heating, and even bearing burns and locking in severe cases.

Over-heat: In addition, in addition to poor lubrication, bearing overheating can also be caused by factors such as over-tight installation, excessive load, excessive speed, and poor heat dissipation. For example, in a high-speed machine tool spindle, if the tapered roller bearing is installed too tightly, the friction resistance will increase during operation, which will cause the bearing surface temperature to far exceed the normal range, reduce material properties, and accelerate wear and fatigue.

Corrosion: Bearings are prone to corrosion in humid environments or when in contact with corrosive media, or when the grease contains moisture or acidic substances. For example, in chemical companies, some equipment needs to operate in a corrosive gas environment, and the bearing surface will show traces such as rust spots and pitting, increase roughness, reduce contact accuracy, and affect performance and life.

Installation: Improper installation, such as inaccurate installation position, large coaxiality error between the shaft and the bearing seat, and inappropriate installation tightness, will also have adverse effects on the bearing. Taking fan equipment as an example, if the coaxiality error of the bearing is too large during installation, abnormal vibration and noise will occur during operation, and problems such as wear and fatigue will occur prematurely. In severe cases, the equipment may not be able to operate normally.

Appearance inspection: Carefully check the surface of the bearing. If the rolling element and raceway are obviously damaged by wear, fatigue peeling, cracks, corrosion, deformation, etc., or the cage is deformed or broken, it usually means that the bearing needs to be replaced. For example, when peeling pits are found on the raceway surface, it will cause the bearing to run unsteadily and need to be replaced in time.

Clearance measurement: Use professional measuring tools, such as feeler gauges and clearance gauges, to measure the radial clearance and axial clearance of the bearing. If the clearance exceeds the specified range, it means that the internal wear of the bearing is serious, which will affect the accuracy and stability of the equipment. At this time, it is necessary to consider replacing the bearing.

Vibration and noise detection: With the help of vibration testers, stethoscopes and other tools, monitor the vibration and noise level of the bearing during operation. If the bearing vibration value increases significantly, or abnormal noise occurs, such as piercing screams, periodic impact sounds, etc., there may be a fault inside the bearing, such as rolling element wear, poor lubrication, etc., which requires further inspection and consideration of replacement.

Temperature monitoring: Use a thermometer or temperature sensor to measure the temperature of the bearing during operation. When the bearing temperature is too high and exceeds the normal operating temperature range (generally speaking, the normal operating temperature of the bearing is 60-80℃, which may vary in different application scenarios and equipment), and other factors (such as lubrication, heat dissipation, etc.) are excluded, it is likely that the internal friction of the bearing is too large, there is a fault, and it needs to be replaced.

Operation performance evaluation: Observe the overall operation performance of the equipment. If there is unstable speed, reduced accuracy, reduced transmission efficiency, etc., and after excluding the influence of other components, it may be a problem with the tapered roller bearing. The bearing needs to be inspected and evaluated to determine whether it needs to be replaced.

1. Preparation before installation
Check the model and quality: Carefully check the model of the SKF tapered thrust roller bearing to ensure that it fully matches the equipment requirements. At the same time, conduct a comprehensive quality inspection of the bearing to check whether there are any appearance defects, such as raceway scratches, roller deformation, cage damage, etc., to avoid the subsequent use affected by the bearing quality problems.

Cleaning work: Use a special cleaner and a clean soft cloth to thoroughly clean the journal and bearing seat hole that match the bearing, remove oil, rust, impurities, etc., and ensure that the installation surface is smooth and flat. After cleaning, apply a thin layer of lubricating oil on the surface of the journal and bearing seat hole to facilitate subsequent installation.

Choose installation method and tools: Select the appropriate installation method according to the specific application scenario. If the bearing size is small and the interference fit is not large, the mechanical installation method can be used to knock the bearing in smoothly with the help of tools such as copper rods, sleeves and hammers. For bearings with larger sizes and high interference fit requirements, the hot installation method is more suitable. Use oil bath heating or induction heating equipment to heat the bearing to 80℃-100℃ (note that the heating temperature should not exceed 120℃ to avoid affecting the performance of the bearing material), expand the inner ring of the bearing, and then quickly install it on the journal. If the installation space is limited or the installation accuracy is extremely high, the hydraulic installation method can be used. Use hydraulic nuts, hydraulic pumps and other equipment to install the bearing by precisely controlling the pressure. The SKF rolling bearing installation and removal web application can provide detailed installation methods and tool recommendations for different types of bearings, which can be used by installers for reference.

2. Installation process
Mechanical installation: Align the sleeve with the inner ring of the bearing, and gently tap the sleeve with a hammer to slowly and evenly push the bearing toward the journal. During the tapping process, always maintain the concentricity of the bearing and the journal to avoid tilting the bearing. If the bearing installation resistance is too large, do not force it. Check whether there are foreign objects or unevenness on the installation surface, and continue installation after eliminating the problem.

Hot installation: quickly remove the heated bearing from the heating equipment, use a special fixture to quickly put it on the shaft neck, and ensure that the bearing is in place. During the cooling process of the bearing, the shaft cannot be rotated or external force applied to prevent the inner ring of the bearing from relative displacement with the shaft neck, which affects the installation accuracy.

Hydraulic installation: first install the hydraulic nut on the shaft, and then put the bearing into the shaft neck. Connect the hydraulic pump and hydraulic nut, slowly increase the pressure according to the specified pressure value, so that the bearing is accurately installed to the predetermined position under the action of hydraulic pressure. After the installation is completed, slowly release the pressure and remove the hydraulic equipment.

3. Preparation before disassembly
Develop a disassembly plan: According to the equipment structure and the bearing installation method, develop a detailed disassembly plan, clarify the disassembly sequence and the tools used. For complex equipment, draw a disassembly diagram when necessary to ensure that the disassembly process is orderly.

Prepare disassembly tools: According to the disassembly plan, prepare appropriate tools, such as pullers, ejectors, presses, etc. For large bearings or bearings with tight interference fits, heating equipment may be required to assist in disassembly. At the same time, ensure that the tools are intact and the accuracy meets the requirements.

Safety protection: Before disassembly, maintenance personnel are equipped with complete safety protection equipment, such as safety helmets, protective gloves, goggles, etc., to prevent accidents during disassembly.

4. Disassembly process
General disassembly: For bearings that are not too tight, a puller can be used for disassembly. Hook the claw hook of the puller firmly to the inner ring of the bearing, adjust the puller screw to keep it consistent with the center of the shaft, and then slowly rotate the screw to evenly apply tension to pull the bearing out of the shaft. If the bearing is installed in the bearing seat, the ejector can be used to eject the bearing from the bearing seat hole. During operation, pay attention to the accurate ejection position to avoid damage to the bearing and the bearing seat.

Hot disassembly: If the bearing and the shaft neck are too tight and difficult to disassemble directly, the hot disassembly method can be used. Use a heating device to evenly heat the inner ring of the bearing to expand it, and use a puller or other tools to assist in quickly removing the bearing from the shaft during the heating process. Strictly control the temperature and heating time during heating to prevent the shaft neck from being damaged due to overheating.

Hydraulic disassembly: In some specific equipment, the hydraulic system can be used to disassemble the bearing. By injecting high-pressure oil into the oil cavity between the bearing and the journal or bearing seat, the oil pressure is used to separate the bearing from the mating surface, making it easy to disassemble. When using this method, the oil pressure must be strictly controlled in accordance with the equipment operating procedures to ensure safety.

The installation and removal of SKF tapered thrust roller bearings must strictly follow the correct methods and procedures and use tools reasonably. During the installation and removal process, always pay attention to the safety of equipment and personnel to ensure the normal use and maintenance of bearings and related equipment. If you still have questions about the installation and removal operations, you can always refer to the detailed instructions of the SKF rolling bearing installation and removal web application.

1. Pitting
Metal surface fatigue: During the operation of the vertical mill, the inner ring raceway of the bearing is subjected to periodic alternating loads. When the load exceeds the fatigue limit of the material, tiny cracks will gradually form on the metal surface. Over time, these cracks expand and connect, eventually leading to pitting on the surface. For example, for a certain model of vertical mill bearing, when the contact stress reaches 800-1000MPa, fatigue pitting may occur after a certain number of cycles (such as 10^6-10^7 times).

Inclusions or large carbides in the subsurface: Inclusions or large carbides in the bearing material will destroy the continuity of the metal matrix. When subjected to load, these parts are prone to stress concentration, thereby accelerating the formation of pitting. Studies have shown that when the size of the inclusion exceeds 50μm, or the hardness of the carbide particles is 2-3 times higher than the hardness of the matrix, the probability of pitting will increase significantly.

Improper assembly or poor lubrication: If the bearing is installed too tightly or too loosely during assembly, the stress state inside the bearing will be uneven, and the local area will be subjected to excessive pressure, which is easy to cause pitting. At the same time, poor lubrication will increase the friction coefficient between the roller and the inner ring raceway, generate excessive heat, reduce the load-bearing capacity of the oil film, and make the metal surface directly contact, thus forming pitting. For example, when the viscosity of the lubricating oil is 10% - 15% lower than the design requirement, insufficient lubrication may occur, increasing the risk of pitting.

2. Bearing skinning
Early fatigue of metal surface: Similar to pitting, early fatigue is also caused by long-term cyclic load. The difference is that skinning usually occurs when a very thin layer of the metal surface peels off after the fatigue crack expands to a certain extent. Generally speaking, skinning caused by early fatigue may occur when the bearing operation time reaches 30% - 50% of its design life.

Poor heat treatment of materials: If the bearing material is heated at uneven temperatures, the holding time is insufficient, or the cooling speed is inappropriate during the heat treatment process, the material structure will be uneven, the hardness and strength distribution will be inconsistent, thereby reducing the fatigue strength of the bearing and easily causing skinning. For example, for quenched bearings, if the hardness deviation after quenching exceeds HRC 2-3, it may affect its fatigue resistance and cause skinning failure.

Poor lubrication: Good lubrication is the key to ensuring the normal operation of bearings. Poor lubrication will increase the friction on the bearing surface, generate heat, and accelerate the wear and fatigue of the metal surface. When the impurity content in the lubricating oil exceeds 0.05%-0.1%, these impurities will form abrasive wear on the bearing surface, destroy the oil film, and then cause skinning.

Overload stress effect: During the operation of the vertical mill, if material blockage, motor overload, etc. occur, the load on the bearing will exceed its rated load capacity. Long-term operation under overload conditions will cause excessive stress on the bearing surface, which will easily lead to plastic deformation and fatigue peeling of the metal surface, forming skinning. For example, when the actual load on the bearing reaches 1.5-2 times its rated load, the service life of the bearing will be significantly shortened and the probability of skinning failure will be increased.

3. Bearing peeling
Poor bearing material: The quality of bearing materials directly affects its performance and life. If the purity of the material is not high and contains more impurities, pores or segregation defects, these defective parts are easy to become crack sources under the action of high contact stress, and then expand to cause metal flaking. For example, if the sulfur content in bearing steel exceeds 0.02%-0.03%, it will reduce the toughness and fatigue strength of the material and increase the possibility of peeling.

Improper heat treatment: Heat treatment is an important process to improve the performance of bearing materials. If the heat treatment process parameters are unreasonable, such as the quenching temperature is too high or too low, the tempering is not sufficient, etc., the organization and performance of the bearing will not meet the requirements, the hardness and toughness will not match, and peeling is easy to occur during use. For example, if the content of retained austenite after quenching is too high (more than 10%-15%), it will reduce the hardness and wear resistance of the bearing, causing the surface to peel off easily under high stress.

Impurities mixed in grease: Impurities in lubricating oil, such as dust and metal chips, will enter the bearing with the grease, form abrasive particles between the roller and the raceway, destroy the oil film, and aggravate wear and contact stress concentration. When the size of the impurity particles reaches 5-10μm, it may damage the bearing surface and cause peeling.

Brutal operation during assembly: During the assembly of bearings, if improper installation methods such as hammering and forced pressing are used, local plastic deformation, cracks and other defects will occur inside the bearing. These defects will become stress concentration points when the bearing is running, accelerate the expansion of fatigue cracks, and eventually lead to bearing peeling. For example, when installing the bearing, if the impact force applied exceeds the yield strength of the bearing material, tiny cracks will form on the bearing surface. As the running time increases, these cracks will gradually expand and cause peeling.

4. Bearing burn-in
Bearing clearance is too large or too small: Bearing clearance refers to the radial or axial clearance between the inner and outer rings when the bearing is not installed. If the clearance is too large, the bearing will generate greater vibration and impact during operation, resulting in increased contact stress between the roller and the raceway, which is prone to heat and burning. On the contrary, if the clearance is too small, the friction resistance inside the bearing will increase, generating too much heat that cannot be dissipated in time, which will also cause the bearing temperature to rise and burn. Generally speaking, for vertical mill bearings, the appropriate radial clearance range is between 0.05-0.15mm, and the axial clearance is between 0.1-0.3mm. Exceeding this range may cause burning failure.

Poor lubrication or impurities in the grease: Poor lubrication will increase the friction coefficient of the bearing and generate a lot of heat. If the grease contains impurities, these impurities will form abrasive wear on the bearing surface, destroy the integrity of the oil film, and make the metal surfaces directly contact, further aggravating friction and heat, and eventually leading to burning. For example, when the dropping point of the grease is 10-15℃ lower than the operating temperature of the bearing, the grease will be lost prematurely, unable to provide good lubrication, and increase the risk of burning.

Severe scratches: If there are scratches between the roller and the raceway during the operation of the bearing, the surface roughness will increase, the contact area will decrease, and the contact stress will increase. The scratched area will also generate heat, causing local temperature rise, which will cause the migrated molten metal to adhere to the metal surface of the bearing, that is, burning. For example, when the scratch depth on the bearing surface reaches 0.05-0.1mm, it needs to be handled in time, otherwise it may cause burning failure and seriously affect the service life of the bearing.

1. Viscosity
Appropriate viscosity is the key to ensure that the lubricant forms a good oil film in the bearing. If the viscosity is too low, the oil film thickness is insufficient and cannot effectively carry the load, which will lead to direct contact between the metal surfaces, increase wear and friction, and even cause failures such as burning; if the viscosity is too high, the fluidity of the lubricant will deteriorate, increase stirring resistance, and lead to energy loss and oil temperature rise. Generally speaking, the viscosity of the tapered thrust bearing lubricant is usually 46-100mm²/s at 40℃, and the specific value needs to be determined according to the working conditions of the vertical mill, bearing speed, load and other factors. For example, under high speed and low load conditions, a lubricant with a lower viscosity, such as about 46mm²/s, can be selected; while at low speed and high load, a lubricant with a higher viscosity, such as about 100mm²/s, should be selected.

2. Lubricity
The lubricant should have good lubrication properties, be able to form a firm adsorption film and reaction film on the metal surface, reduce the friction coefficient, and reduce wear. This is especially important for tapered thrust bearings, because they not only bear axial thrust, but also bear certain radial loads. Good lubricity can effectively protect the bearing surface and extend the bearing service life. The lubricity of lubricants is usually improved by adding additives such as oiliness agents and extreme pressure anti-wear agents.

3. Antioxidation
During the operation of the vertical mill, the bearing lubricant will be in a high temperature state for a long time and easily undergo oxidation reactions with oxygen in the air. The oxidized lubricant will generate acidic substances, colloids and precipitation, etc. These substances will reduce the performance of the lubricant, corrode the metal surface of the bearing, block the lubrication system, and affect heat dissipation. Therefore, the lubricant for tapered thrust bearings needs to have good antioxidant properties and be able to maintain stable chemical properties under long-term high temperature environments. Generally, the oxidation stability index of the lubricant is required to be high. For example, the oxidation life measured by the rotating oxygen bomb test should not be less than a certain time, usually 1000-2000 hours.

4. Anti-foaming
During the high-speed operation of the bearing, the lubricant is easily stirred and produces foam. Foam will expand the volume of the lubricant, causing the oil tank level to rise, affecting the normal operation of the lubrication system. At the same time, foam will also reduce the heat dissipation and load-bearing capacity of the lubricating oil, and accelerate the oxidation and deterioration of the lubricating oil. Therefore, the lubricating oil of the tapered thrust bearing should have good anti-foaming properties, be able to quickly defoam, and prevent the formation and stable existence of foam. It is generally required that the foam tendency of the lubricating oil under the specified test conditions does not exceed a certain value, such as not exceeding 100ml, and the foam stability does not exceed 10ml.

5. Cleanliness
Clean lubricating oil is essential for the normal operation of tapered thrust bearings. Impurities in the lubricating oil, such as dust, metal chips, sand particles, etc., will form abrasive wear on the bearing surface, destroy the oil film, aggravate the wear and fatigue of the bearing, and even cause the bearing to get stuck or burn. Therefore, the lubricating oil of the tapered thrust bearing needs to have a high degree of cleanliness. It is usually required to use high-precision filtering equipment to filter the lubricating oil so that the particle size of the impurities in the oil is controlled within a certain range, such as not exceeding 5-10μm. At the same time, the water content in the oil should also be strictly controlled, generally not exceeding 0.05%-0.1%.

6. Rust resistance
During operation, vertical mill bearings may be affected by external factors such as moisture and air, causing rust on the metal surface of the bearing. Rust spots will damage the finish and precision of the bearing surface, affecting the performance and life of the bearing. Therefore, the lubricating oil of the tapered thrust bearing should have good rust resistance and be able to form a protective film on the metal surface to prevent moisture and oxygen from contacting the metal and play a rust-proof role. Generally, rust inhibitors are added to improve the rust resistance of the lubricating oil, so that the bearing can be effectively protected in a humid or corrosive environment.

1. Load capacity
Radial load: A vertical mill will generate a large radial force during operation. The radial load to be borne should be calculated based on the specifications of the vertical mill, the characteristics of the grinding material, the weight of the grinding roller and other factors, and a bearing that can withstand the load should be selected. For example, for a large vertical mill, the grinding roller has a larger diameter and heavier weight, so a tapered roller bearing with a higher radial load capacity needs to be selected.
Axial load: When the vertical mill is working, a certain axial force will also be generated due to the extrusion of the grinding roller on the material and factors such as the transmission device. To accurately evaluate the size of the axial load, the axial load capacity of the tapered roller bearing is usually related to its contact angle. The larger the contact angle, the stronger the axial load capacity. The bearing with a suitable contact angle can be selected according to the actual axial load.

2. Speed ​​requirement
The speed of the vertical mill is relatively low, but the speed of vertical mills of different models and specifications also varies. The speed capacity of the bearing is usually expressed in terms of the limit speed. It is necessary to ensure that the limit speed of the selected tapered roller bearing can meet the actual operating speed requirements of the vertical mill, leaving a certain safety margin to ensure that the bearing will not overheat or wear due to excessively high speed during operation.

3. Accuracy level
Vertical mills have high requirements for bearing accuracy. Generally, tapered roller bearings with an accuracy level of P5 or higher are required to ensure the rotation accuracy and stability of the grinding roller, reduce vibration and noise, and improve grinding efficiency and product quality. High-precision bearings can better control the gap between the grinding roller and the grinding disc, making the grinding process more uniform.

4. Clearance selection
The appropriate clearance is crucial to the performance and life of the tapered roller bearing of the vertical mill. It is usually necessary to select the appropriate clearance based on the operating temperature, installation method, load characteristics and other factors of the vertical mill. For vertical mills working in high temperature environments, due to the influence of thermal expansion, bearings with larger clearance need to be selected to prevent the bearings from getting stuck due to too small clearance during operation; for vertical mills with large loads and high rigidity requirements, bearings with smaller clearance may need to be selected.

5. Bearing material
The working environment of the vertical mill is relatively harsh, and the bearing needs to have good wear resistance, corrosion resistance and fatigue resistance. High carbon chromium bearing steel (such as GCr15) is generally selected as the material of the bearing. This material has high hardness, strength and good wear resistance, which can meet the working requirements of the vertical mill. For some special working conditions, such as vertical mills working in humid or corrosive environments, stainless steel bearings can be considered to improve the corrosion resistance of the bearings.

6. Sealing method
During the operation of the vertical mill, impurities such as dust will enter the bearing part, affecting the normal operation and life of the bearing, so it is necessary to select a suitable sealing method. Common sealing methods include contact sealing and non-contact sealing. Contact sealing, such as lip seals, has a better sealing effect, but will produce a certain amount of friction; non-contact sealing, such as labyrinth seals, has less friction, but the sealing effect is relatively poor. You can choose a suitable sealing method according to the specific working environment and requirements of the vertical mill, or you can use a combined seal to improve the sealing performance.

7. Brand and quality
Choose tapered roller bearings from well-known brands, such as SKF, FAG, NSK, etc. These brands of bearings have good guarantees in terms of quality, performance and reliability. Well-known brands usually have advanced production processes, strict quality control systems and a complete after-sales service network, which can provide users with high-quality products and technical support. At the same time, pay attention to checking the quality certificates and packaging of the bearings to ensure that you buy genuine bearings.

8. Cost factors
On the premise of meeting the working requirements of the vertical mill, the cost of the bearings should be considered comprehensively. The prices of bearings of different brands, specifications and precision grades vary greatly. The appropriate bearings should be selected according to the economic strength and budget of the enterprise. However, price cannot be the only selection criterion. Factors such as bearing performance, life and maintenance cost should be weighed to select products with high cost performance.

SKF: A Swedish brand founded in 1907, with a century-old history and professional strength in the field of bearings. Its tapered roller bearings are of reliable quality, with high precision, long life, low friction and other characteristics. They can provide stable support and operating performance for vertical mills and are widely used in mechanical equipment in various industrial fields, including vertical mills.

FAG (under the Schaeffler Group): A German brand, a global leader in rolling and sliding bearing technology. FAG tapered roller bearings use advanced design and manufacturing processes, can withstand large radial and axial loads, and are suitable for heavy-duty equipment such as vertical mills. They have good wear resistance and fatigue resistance, and can maintain stable performance in harsh working environments.

NSK: A leader in the Japanese bearing industry, founded in 1916. NSK tapered roller bearings have high precision, low noise and strong reliability. In vertical mill applications, they can effectively reduce vibration and wear, improve the operating efficiency and stability of equipment, and their products are widely used in the global industrial field.

TIMKEN: An American brand, an expert in special steel and tapered roller bearings. TIMKEN tapered roller bearings have advantages such as high temperature use characteristics, which can meet the needs of vertical mills under different working conditions, especially in terms of bearing heavy loads and impact loads. The products are widely used in heavy-duty equipment in many fields.

HRB (Harbin Bearing): A well-known Chinese bearing brand, founded in 1950. HRB tapered roller bearings have mature production technology and stable product quality. They can meet the use requirements of general vertical mills and have high cost performance. They are widely used in domestic industrial fields, including vertical mills in mining, cement and other industries.

ZWZ (Wafangdian Bearing): A well-known Chinese bearing brand with a high technical level and market share in the field of bearing manufacturing. ZWZ tapered roller bearings have complete specifications, high precision, can withstand large loads, and are suitable for large mechanical equipment such as vertical mills. Its products are not only recognized in the domestic market, but also exported to many countries and regions.

LYC (Luoyang Bearing): It is a large domestic bearing manufacturer with strong R&D and production capabilities. LYC tapered roller bearings adopt advanced technology and craftsmanship, with reliable product quality, can provide good support and operating performance for vertical mills, and are widely used in vertical mill equipment in domestic cement, mining and other industries.

Temperature factors: When the vertical mill is working, it will generate heat, which will increase the bearing temperature. The thermal expansion coefficients of the materials of the inner and outer rings of the bearing are different, and temperature changes will cause changes in the clearance. In a high temperature environment, the material expands. In order to avoid the increase of internal friction, overheating or even damage of the bearing due to thermal expansion, a larger clearance needs to be selected. For example, when the operating temperature of the vertical mill often exceeds 80°C, a larger clearance group should be selected than when working at normal temperature.

Load characteristics: If the vertical mill is subjected to a large load, especially an axial load, a smaller clearance can be selected to ensure that the bearing has sufficient rigidity to withstand the load and reduce deformation. However, the clearance cannot be too small, otherwise the deformation caused by the load will cause excessive stress inside the bearing, affecting its life. For vertical mills with smaller loads and relatively stable, the clearance can be relatively larger to reduce friction and wear.

Speed: Although the speed of the vertical mill is relatively low, it varies from model to model. When the speed is high, the friction and heat between the rolling elements and the rings inside the bearing will increase, and the clearance needs to be appropriately increased to facilitate heat dissipation and reduce wear. For vertical mills with lower speeds, the clearance selection can be relatively flexible, but it is also necessary to ensure that the bearing can operate normally at low speeds to avoid sliding friction between the rolling element and the ring.

Installation method: Tapered thrust roller bearings usually need to be installed in conjunction with other components, and the installation method will affect the clearance. For example, when using interference fit installation, the inner ring of the bearing will swell and the outer ring will shrink, resulting in a decrease in clearance. At this time, when selecting the initial clearance, the effect of the interference on the clearance should be considered, and a larger initial clearance should be appropriately selected to ensure that the working clearance after installation is within the appropriate range.

Equipment accuracy requirements: The vertical mill has high requirements for the rotation accuracy and stability of the grinding roller to ensure grinding efficiency and product quality. If higher accuracy is required, the clearance should be selected in a smaller and more precise range to reduce the shaking and displacement of the bearing during operation. However, this needs to be done on the premise that the bearing can dissipate heat normally and bear the load, otherwise the bearing life may be affected due to too small a clearance.

1. Structural features
Spherical roller bearings: double-row rollers, one common spherical raceway on the outer ring, and two raceways on the inner ring that are tilted at an angle relative to the bearing axis. This structure enables it to have self-aligning performance and can adapt to the angle error between the shaft and the bearing housing or the bending of the shaft.
Tapered roller bearings: It is a separable bearing. The inner and outer rings of the bearing have tapered raceways, and the tapered rollers are arranged between the two. The projection lines of all tapered surfaces converge at the same point on the bearing axis.

2. Carrying capacity
Spherical roller bearings: large carrying capacity, the rated dynamic load ratio is generally 2.3 - 5.2. It mainly bears radial loads, and can also bear certain bidirectional axial loads, but cannot bear pure axial loads.
Tapered roller bearings: single-row tapered roller bearings can bear unidirectional axial loads, and will generate additional axial forces under the action of radial loads. They are usually used in pairs; double-row and four-row tapered roller bearings can bear bidirectional axial loads. Its rated dynamic load ratio is 1.5 - 2.5 for single row, 2.6 - 4.3 for double row, and 4.5 - 7.4 for four row.

3. Self-aligning performance
Spherical roller bearing: good self-aligning performance, can compensate for coaxiality error, allow a certain inclination of the shaft, and can work normally when there is an angle error or shaft deflection between the shaft and the bearing box.
Tapered roller bearing: In general, tapered roller bearings do not have self-aligning performance, and require high installation accuracy between the shaft and the bearing seat, otherwise it will affect the normal operation and life of the bearing. However, double-row and four-row tapered roller bearings have better tolerance for installation errors to a certain extent, but their self-aligning ability is still not as good as that of spherical roller bearings.

4. Limiting speed
Spherical roller bearings: Due to their structural characteristics and relatively large friction, the limiting speed is low.
Tapered roller bearings: Single-row tapered roller bearings have low limiting speed; double-row tapered roller bearings have medium limiting speed; four-row tapered roller bearings have low limiting speed. In general, the limiting speed of tapered roller bearings is generally lower than that of high-speed bearings such as angular contact ball bearings, but they can work well in some low-speed to medium-speed heavy-load applications.

5. Installation and disassembly
Spherical roller bearings: When the tapered bore spherical roller bearing is matched with a tapered shaft neck, the inner ring moves axially to slightly adjust the radial clearance of the bearing; the spherical roller bearing with a tightening sleeve can be installed on a smooth shaft without a shoulder, which is suitable for occasions where bearings are frequently installed and disassembled.
Tapered roller bearings: They are separable bearings with separable inner and outer rings, which are relatively easy to install and disassemble. For example, the inner ring assembly (with rollers and cages) of a single-row tapered roller bearing can be installed separately from the outer ring, which facilitates installation, disassembly and maintenance inspection procedures.

6. Application scenarios
Spherical roller bearings: Applicable to papermaking machinery, reduction gears, railway vehicle axles, rolling mill gearbox bearing seats, rolling mill rollers, crushers, vibrating screens, printing machinery, woodworking machinery and other equipment that need to withstand large radial loads and have requirements for aligning performance.
Tapered roller bearings: widely used in automobile, rolling mill, mining, metallurgy, plastic machinery and other industries, especially in situations where large radial and axial loads need to be simultaneously borne, such as cone crushers, automobile wheel hub bearings, etc.