Spare Parts

Ceramic grinding roller is a composite casting structure formed by embedding ceramic blocks in the roller sleeve during casting. The composite structure of ceramic block embedded roller sleeve has three layers of material (as shown in Figure 1 below): yellow is ductile iron (Nodular Cast Iron), gray is high chromium cast iron (Hi-Chrome), and orange is wear-resistant ceramic block (Refractory Oxides). These composite parts have undergone complex composite casting and heat treatment processes to achieve a high enough hardness to resist wear while maintaining sufficient toughness. It has the following advantages:

1) Good crack resistance. Generally, high chromium cast steel roller sleeves and roller sleeves repaired and regenerated by surfacing welding have increased hardness at the expense of impact toughness, which has an adverse effect on crack resistance, causing the entire roller sleeve to peel off or crack during operation, causing the equipment to stop production. The ceramic block embedded roller sleeve uses ductile iron as the matrix, has good mechanical properties, a hardness of 30HRC, and an elongation of 7%. It can effectively absorb the impact damage energy during operation, greatly improving the crack resistance of the roller sleeve.

2) More wear-resistant. The hardness of the wear-resistant ceramic block is very high, reaching 66HRC, which is much higher than the hardness that can be achieved by surfacing welding, and is more wear-resistant than surfacing welding.

3) Uniform wear and stable mill operating parameters. The special design of the ceramic block inlaid grinding roller sleeve reduces the common sharp corners and furrows in high-chromium cast steel roller sleeves and surfacing repair roller sleeves. The working surface wears evenly, so the mill output is more balanced and the screen residue is more stable throughout the service life of the roller sleeve.

4) Higher grinding efficiency. The working surface of the wear-resistant ceramic block is like a honeycomb (Figure 2). It is this peculiar structure that increases the bite force of the powdered material and improves the grinding efficiency.

The service life of the ceramic roller of Tongli vertical mill is generally more than 20,000 hours. Of course, the wear time for different materials is also different.

Cement industry: If the grinding material is easy to grind and the production conditions are stable, the service life of the ceramic roller of the vertical mill may reach 3 years or even longer; if the material is hard and abrasive, such as limestone containing a large amount of hard minerals such as quartz, or there are frequent start-up and shutdown, load fluctuations, etc. during the production process, the service life may be shortened to 15,000 hours.

Mining industry: When processing ores with higher hardness, such as iron ore and quartz stone, the ceramic roller of the vertical mill wears relatively quickly, and the service life is generally 20,000 hours; for ores with lower hardness, such as kaolin, the service life may be extended to 10,000~15,000 hours.

Power industry: In the preparation of coal powder, due to the relatively moderate hardness and abrasiveness of coal and the relatively stable production process, the service life of the vertical mill ceramic roller is usually 2.5-3 years. However, if the coal quality is poor and contains more impurities such as gangue, the wear of the ceramic roller will be accelerated, shortening the service life to 2-2.5 years.

Chemical industry: For relatively easy-to-grind chemical raw materials such as calcium carbonate and talcum powder, the service life of the vertical mill ceramic roller is generally 2.5-3 years; if corrosive chemical raw materials are processed, even if the ceramic roller has good corrosion resistance, the service life may be reduced to 2-2.5 years due to the combined effect of corrosion and wear.
From the perspective of different product quality and process, the vertical mill ceramic roller produced with advanced technology and high-quality materials: such as using high-precision molding technology and high-purity, high-performance ceramic materials, its internal structure is more uniform and dense, the wear resistance is better, and the service life will be relatively long, up to 3-5 years.

Vertical mill ceramic rollers produced with common processes and materials may have problems such as uneven distribution of ceramic particles and insufficient bonding strength. The ceramic layer is prone to peeling and increased wear during use, and the service life may be only 1-2 years.

Temperature monitoring: Watch out the temperature changes of the ceramic roller of the vertical mill during operation, and obtain temperature data in real time through the temperature sensor installed on the roller body or bearing. Generally speaking, the normal operating temperature should be kept within a certain range. If it exceeds the specified temperature, it is due to insufficient lubrication, bearing damage or excessive material friction, and it is necessary to stop the machine for inspection in time.

Vibration detection: Use vibration monitoring instruments to regularly check vibration detection on the ceramic roller of the vertical mill. Under normal circumstances, the vibration amplitude of the roller body is small and stable. If the vibration value suddenly increases, it may be caused by loose installation of the roller body, uneven gap between the grinding disc and the roller body, or changes in the particle size of the material. It should be checked and resolved in time.

Sound monitoring: When the equipment is running, the working status of the ceramic roller of the vertical mill is judged by monitoring the running sound of the ceramic roller of the vertical mill. The sound is stable and uniform during normal operation. If there is abnormal friction, impact or vibration sound, it may mean that the surface of the roller body is unevenly worn, the ceramic layer is peeling off, or there is interference between components. The machine should be stopped for inspection immediately.

Cleaning and maintenance: Clean the ceramic roller of the vertical mill regularly. After stopping, use compressed air or high-pressure water gun to remove material residues, dust, oil and other impurities on the surface of the roller. For some stubborn adhesions, special cleaning agents can be used for wiping, but be careful to avoid using chemical agents that are corrosive to ceramic materials.

Lubrication and maintenance: Lubricate the bearings and transmission parts of the ceramic roller of the vertical mill regularly according to the recommendations of the equipment manufacturer. Select suitable lubricants, such as high-temperature lithium-based grease, etc., and determine the lubrication cycle according to the operating time and working environment. Generally, the grease is replenished or replaced every 1000-2000 hours of operation.

Wear inspection: At regular operating times, such as 2000-3000 hours, conduct a comprehensive inspection of the wear of the ceramic roller of the vertical mill. Evaluate the degree of wear by measuring the diameter of the roller body and observing the surface condition of the ceramic layer. If local wear is found to be severe, repair measures can be taken, such as welding the ceramic coating; if the wear exceeds the specified limit, the grinding roller should be replaced in time.
Other precautions

Material control: strictly control the particle size, moisture and hardness of the material entering the mill to meet the design requirements of the vertical mill ceramic roller. Avoid excessively large and hard materials entering the mill to prevent excessive impact and wear on the roller body; at the same time, control the moisture content of the material within a reasonable range, generally not exceeding 10%, so as not to affect the grinding effect and cause the material to adhere to the roller surface.
Operation specification: Operators should strictly abide by the operating procedures to avoid unnecessary adjustments and operations during the operation of the equipment. During the start-up and shutdown process, the prescribed sequence and steps should be followed to prevent the roller body from being subjected to additional stress and impact due to improper operation.

There are many ways please check the below:
Degree of wear: Directly observe the surface of the ceramic layer. If the ceramic layer is severely worn, a large area of ​​thinning and flattening occurs, especially when the thickness of the ceramic layer in the local area is less than one-third of the original thickness, it will seriously affect the grinding effect and roller performance, and replacement is usually required.

Peeling and cracks: Check carefully whether the ceramic layer has peeling or peeling, or a large number of deep and long cracks. If the peeling area is large, such as a single peeling block area exceeding 10 square centimeters, or the cracks are interwoven into a mesh, the integrity and strength of the ceramic layer will be damaged, and the ceramic layer may need to be replaced.
Discoloration and corrosion: If the surface of the ceramic layer has obvious discoloration, such as from the original white or gray to black, brown, etc., and accompanied by corrosion pits, pitting, etc., it indicates that the ceramic layer may have been chemically eroded. When the corrosion area accounts for more than 20% of the surface area of ​​the ceramic layer, the performance of the ceramic layer will be reduced, and it may need to be replaced.

Performance testing
Grinding efficiency: Compare the grinding efficiency data of the vertical mill ceramic roller during normal operation. If the grinding efficiency is significantly reduced, for example, the output is reduced by more than 15~20%, and after excluding factors such as material properties and failure of other equipment components, it is likely to be caused by ceramic layer wear and other reasons. It is necessary to further check whether the ceramic layer needs to be replaced.

Product quality: Check the quality indicators of the product after grinding, such as particle size distribution, specific surface area, etc. If the product particle size becomes coarser and does not meet the production requirements, for example, the target product requires more than 90% of the particles to be below 80 microns, but only 70% are actually achieved, and it cannot be improved by adjusting other process parameters, it may be that the ceramic layer is unevenly worn or damaged, affecting the grinding effect. At this time, it is necessary to consider replacing the ceramic layer.

Operation status monitoring
Vibration and noise: Using vibration monitoring equipment and noise detection instruments, if the vibration value of the vertical mill ceramic roller increases significantly during operation, exceeding 30% of the normal operating value, or abnormal noise occurs, such as sharp friction and impact sounds, it may be that the ceramic layer is partially detached or unevenly worn, resulting in unstable operation of the roller body. It is necessary to check and determine whether the ceramic layer needs to be replaced.

Temperature abnormality: The temperature of the ceramic roller is monitored by a temperature sensor. If under normal working conditions, the temperature of the ceramic roller continues to rise, exceeding the normal operating temperature by more than 20°C, and other components such as the cooling system are fault-free, it may be that the ceramic layer is worn, resulting in increased friction and excessive heat, which may also be a signal that the ceramic layer needs to be replaced.

Iron ore: such as magnetite, hematite, etc., which have high hardness and cause great wear on the vertical mill parts during the grinding process. The high wear resistance of the vertical mill ceramic roller can maintain a stable grinding effect, reduce the frequency of roller replacement and production costs.

Copper ore: Chalcopyrite and chalcocite usually have a certain hardness and toughness. The high strength and good wear resistance of the vertical mill ceramic roller effectively crush and grind the ore, and process it into the required particle size to meet the needs of subsequent mineral processing and smelting.

Limestone: It is an important raw material for cement production, with large output and high grinding demand. The vertical mill ceramic roller can grind limestone efficiently. Its smooth surface can make the material flow smoothly, reduce adhesion and accumulation, and improve grinding efficiency. At the same time, its chemical stability can avoid chemical reactions with limestone during the grinding process.

Kaolin: As an important clay mineral, it has high requirements for particle size and purity after grinding. The surface smoothness of the vertical mill ceramic roller is high, which can make the particle size of kaolin after grinding more uniform, and its good wear resistance and chemical stability can ensure the grinding effect while avoiding the introduction of impurities.

Quartz sand: high hardness and strong abrasiveness. The high wear resistance of the vertical mill ceramic roller can effectively reduce the wear rate of the grinding roller, extend the service life, reduce production costs, and ensure the grinding quality and particle size requirements of quartz sand.

Calcium carbonate: widely used in plastics, rubber, coatings, inks and other industries. The vertical mill ceramic roller can grind calcium carbonate into products of different fineness according to different application requirements. Its thermal shock resistance and chemical stability can ensure the stability of product quality during the grinding process.

Barium sulfate: It has high hardness and chemical stability. With its own chemical stability and wear resistance, the vertical mill ceramic roller can not only ensure the grinding efficiency when grinding barium sulfate, but also avoid chemical reactions with barium sulfate, ensuring the purity and quality of the product.

Coal: In the power, chemical and other industries, coal grinding is an important production link. The ceramic roller of the vertical mill can effectively grind coal. Its high thermal shock resistance can adapt to the local high temperature that may be generated during the grinding process of coal. At the same time, its good wear resistance can reduce the wear of the grinding roller.

Biomass materials: such as straw, sawdust, etc., although the hardness is relatively low, have certain fibrousness and toughness. The surface characteristics of the ceramic roller of the vertical mill help the smooth transportation and grinding of materials, and can process biomass materials into suitable particle sizes for use in biomass fuels, biochemical engineering and other fields.

The maximum particle size of the vertical mill is related to the roller diameter. It is not allowed to exceed 5% of the roller diameter. The actual control is 2%-3% of the roller diameter. The material that exceeds the size entering the vertical mill is easy to cause the roller to peel off.

The high-chromium cast steel roller sleeve can be repaired by surfacing welding after peeling, but the ceramic roller sleeve cannot be repaired. Therefore, it is necessary to strictly control the particles entering the mill and foreign iron blocks to avoid damage to the ceramic roller sleeve. In addition, from the principle of powder, the "heavy crushing and less grinding" of raw materials has a significant effect on improving the output, vibration, power consumption, and maintenance cost of the vertical mill.

Electromagnetic iron removers and metal detectors must be installed on the belt conveyor entering the vertical mill to prevent iron parts in the raw materials from entering the vertical mill and causing damage to the roller and lining.

Ceramic roller sleeves and ceramic linings are made of super microcrystalline wear-resistant ceramic blocks embedded in high-chromium cast iron. They are wear-resistant and non-renewable. When they encounter large iron pieces or foreign objects that cause peeling, they cannot be repaired. Severe peeling will cause the entire roller sleeve to be scrapped.

The company's raw material management reaches a certain level, the iron removal equipment is complete and operates well, the inspection workers and workshop management personnel are of high quality, and they are highly sensitive to abnormal phenomena of the vertical mill, then the company basically has the conditions to use ceramic roller sleeves and ceramic linings.

In the production workshop, different mills use ceramic grinding bodies differently. The No. 4 raw mill uses the Loeshce LM56.4 model mill, which began to use ceramic grinding bodies in July 2013, and the service life is guaranteed to be greater than 20,000 hours; the No. 5 raw mill uses the Hefei Institute HRM4800 model mill, which began to be used in September 2013, and the service life is also guaranteed to be greater than 20,000 hours; the No. 6 raw mill is also the Hefei Institute HRM4800 model mill, which began to be used in February 2014, and the service life is guaranteed to be greater than 20,000 hours. The No. 1 coal mill uses the Loesche LM23.2D model mill, which was put into use in March 2014, and its service life is guaranteed to be greater than 25,000 hours; the No. 3 coal mill is the same model as the No. 1 coal mill, which was also put into use in March 2014, and its service life is guaranteed to be greater than 25,000 hours; the No. 4 coal mill uses the Loesche LM28.2D model mill, which was put into use in July 2013, and its service life is guaranteed to be greater than 25,000 hours; the No. 5 and No. 6 coal mills both use the Tianjin Institute TRM31.3 model mills, which were put into use in September 2013 and February 2014 respectively, and their service life is guaranteed to be greater than 25,000 hours.

Regarding the relationship between the wear of the raw meal mill ceramic roller and the output, taking the HRM4800 mill as an example, when it runs for 548 hours and the maximum grinding depth of the grinding roller is 3mm, the mill output is 520t/h, and the output change is 0; when it runs for 2071 hours, the maximum grinding depth of the grinding roller is 9mm, the mill output is 515t/h, and the output change is -0.10%; when it runs for 3403 hours, the maximum grinding depth of the grinding roller is 15mm, the mill output is 522t/h, and the output change is 0; when it runs for 6150 hours, the maximum grinding depth of the grinding roller is 26mm, the mill output is 515t/h, and the output change is -0.10%; when it runs for 8263 hours, the maximum grinding depth of the grinding roller is 31mm, the mill output is 510t/h, and the output change is -1%; when it runs for 11308 hours, the maximum grinding depth of the grinding roller is 65mm, the mill output is 510t/h, and the output change is -1%. The grinding roller of this mill is a tire type, with a ceramic layer thickness of about 65mm. It can be turned over for use, and the service life of both sides is about 20,000 hours. The ceramic layer thickness of other mill conical grinding rollers is about 100mm, and the service life can also reach more than 20,000 hours.
2) As can be seen from Figure 7, the surface of the surfacing cast steel roller sleeve is smooth after 7500 hours of use, and the bite force on the material is poor, and there is slippage. As can be seen from Figure 8, the ceramic roller sleeve can still maintain its original shape after 10146 hours of use. The surface is honeycomb-shaped, has extremely strong bite force, and will not slip, which greatly improves the grinding efficiency.

In the cost-benefit analysis of production equipment, the performance of different types of rollers and liners in raw mills and coal mills is significantly different.
Let's look at the raw mill first. The purchase price of a single ceramic roller is $56,700. There is no need for surfacing in a 2.8-year service life. The total cost is $56,700, and the annual use cost is $20,400; while the purchase price of a single high-chromium surfacing roller is $99,800, the annual surfacing cost is $30,000, and the total surfacing cost in 2.8 years is $84,000. The total cost in one cycle is $184,500, and the annual use cost is $62,700. It can be seen that a single ceramic roller of a raw mill can save $45,800 per year in one service life. If there are 4 ceramic rollers, it can save $181,100 per year.
Looking at the coal mill, the ceramic roller sleeve has a purchase price of $25,600 for a single ceramic roller, and there is no surfacing cost in the 4.5-year cycle, with a total cost of $25,600 and an annual use cost of $5,600; the purchase price of a single high-chromium surfacing roller is $36,500, with an annual surfacing cost of $7,500, a total surfacing cost of $33,700 in 4.5 years, a total cost of $70,400 in one cycle, and an annual use cost of $14,500. The ceramic roller has a service life of about 25,000 hours, and the high-chromium surfacing roller sleeve has a service life of about 7,500 hours. A single ceramic roller saves $8,600 per year.
In terms of ceramic lining, the purchase price of a single set of ceramic lining is $23,100, there is no surfacing cost in the 4.5-year cycle, the total cost is $23,100, and the annual use cost is $6,900; the purchase price of a single set of high-chromium surfacing lining is $44,000, the annual surfacing cost is $7,500, the total surfacing cost in 4.5 years is $33,700, the total cost in one cycle is $77,600, and the annual use cost is $16,300. The service life of coal mill ceramic lining is about 25,000 hours, and the service life of high-chromium surfacing lining is about 7,500 hours. A single set of ceramic lining saves $16,300 per year, and the high-chromium surfacing lining will be scrapped after about 4 times of regeneration and repair, and each surfacing will affect the operation of the entire production line.
In general, the No. 4 raw material mill, No. 5 raw material mill, and No. 6 raw material mill save $181,100 each year due to the use of ceramic rollers, the No. 1 coal mill, No. 3 coal mill, and No. 4 coal mill save $34,700 each year due to the use of ceramic rollers and ceramic linings, and the No. 5 coal mill and No. 6 coal mill save $43,400 each year due to the use of ceramic rollers and ceramic linings, with a total cost saving of $737,000 each year. Moreover, ceramic rollers and ceramic linings do not require surfacing during their service life. Raw material mill rollers and linings can be overhauled within a 2.8-year cycle, and coal mill rollers and linings can be overhauled within a 4.5-year cycle. This greatly reduces the downtime of the production line, especially during the peak production and sales season, and can create greater economic benefits for the company.

Prepare tools: Prepare corresponding disassembly tools according to the specific situation, such as electric wrench, manual hoist, crane, wire rope, shackle, T-type tool, hydraulic oil top, cutting gun, spiral top, etc.

Disassemble the roller inspection door: Use an electric wrench to remove the roller inspection door bolts, and use a manual hoist to pull the inspection door and the vertical mill shell to prevent the inspection door from falling suddenly. Use a crane and wire rope to lift the inspection door out.
Disassemble the hydraulic cylinder joint bearing pin: Install the lower part of the hydraulic cylinder with the assistance of a 25T crane, open the hydraulic station, extend the hydraulic rod slowly to align it with the upper seat of the hydraulic pull rod, and install the joint bearing pin.

Disassemble the connecting bolts between the roller and the rocker arm: Make a T-type tool and two 50T hydraulic oil tops, pull out the roller and rocker arm taper pins and unload the bushings on both sides. If one taper pin is removed, the remaining taper pins and withdrawal sleeves can be disassembled with the assistance of φ60×2500 steel pipes and sledgehammers, or with the assistance of heating.

Roller flipping: Use the mobile hydraulic station to flip the two diagonal grinding rollers out of the mill. Pay attention to controlling the roll flipping speed to prevent the hydraulic cylinder from being damaged by excessive speed.

Remove the pressing block, roller sleeve and roller core connection bolts: Use a 100 cutting gun to cut off the roller sleeve and roller core connection bolts, make a T-shaped tool and two 50T spiral tops, and use a sledgehammer to knock. Use a crane to assist in disassembling the roller sleeve pressing block. Before disassembling the roller sleeve pressing block, the order should be marked to prevent the installation order from being disordered and the bolt holes from not matching.

Install the roller disassembly tool: set up the scaffolding, make a roller sleeve disassembly channel with 30mm steel plate and weld it directly to the sealing grooves on both sides of the roller. The distance between the disassembly channel and the roller sleeve should be the same as the height of the 100T oil top. Use a φ120 steel pipe on the ground to directly support the bottom of the channel.

Eject the roller sleeve: install two 100T oil tops between the disassembly channel and the roller sleeve, start the oil top oil station, and pressurize it to about 120MPa, then the roller sleeve can be disassembled. If not, the roller sleeve can be heated by heating. After disassembly, make 4 roller sleeve hooks (Note: the inner curvature of the hook should be the same as the curvature of the roller sleeve surface), and use a 25T crane to lift the worn roller sleeve (about 4T).

After completing the above steps, the disassembly of the vertical mill roller is completed. During the disassembly process, attention should be paid to safety matters and equipment protection measures to prevent damage to equipment and personnel. If you encounter problems or difficulties during operation, it is recommended to contact professionals for assistance or guidance in time.