Information on ball mill coal mills

Installation and Operation Manual for Wet Overflow Ball Mills Table of Contents 1. Purpose of the mill 2. Technical parameters of the mill 3. Working principle and structure of the mill 4. Installation of the mill 5. Commissioning and acceptance of the mill 6. Operation of the mill 7. Maintenance and lubrication of the mill 8. Lifting equipment Installation and Operation Manual for FGDM Series Wet Overflow Ball Mills FGDM Series SM, 18 pages in total Page 2 1. Purpose of the machine The FGDM series wet overflow ball mills are used for grinding limestone in limestone-gypsum wet process systems. 2. The technical parameters of the machine are shown in Table 1. Table 1: Specifications – Effective volume (m³), Actual rotational speed (rpm), Power (kW), Output capacity (t/h): 2150, 15.1, 23.2, 200; 5; 2254, 18, 21.8, 280; 7; 2458, 23.27, 21.2, 380; 10; 2558, 25.37, 20.8, 400; 12; 2760, 30.4, 20.8, 500; 14; 2765, 32.94, 20.8, 560; 16; 2965, 38.33, 19.34, 630; 18; 2970, 41.28, 19.34, 710; 20; 3264, 46.45, 18.7, 800; 23; 3270, 50.81, 18.7, 1000; 25. Note: The output capacity listed in the table is based on a feed particle size of ≤20 mm, an overflow weight percentage of 30%, 90% passing through a 325-mesh sieve, and a grindability coefficient of 11 kW•h/t. 3. Working Principle and Structure of the Mill 3.1 Working Principle The mill is composed of a dedicated asynchronous motor, a reducer, and pinions that directly drive the large gear located on the cylinder, thereby causing the cylinder to rotate. Appropriate grinding media – steel balls – are placed inside the cylinder; under the action of centrifugal force and friction, these media are lifted to a certain height before falling back down. The material to be ground, along with water, enters the cylinder continuously through the feed pipe. The FGDM series wet overflow ball mill user manual: 18 pages in total, page 3. The material is then crushed and ground by the moving grinding media, and the resulting product is discharged through overflow and continuous feeding. It is also subjected to preliminary screening using a stainless steel cylindrical sieve before proceeding to the next processing stage. 3.2 Main structural features of the mill: The mill is primarily composed of a main motor, reducer, transmission unit, main bearing assembly, cylinder section, feed and discharge sections, foundation, as well as high and low pressure lubrication stations. There are also auxiliary machines such as slow-speed transmission devices, lifting devices, and spray lubrication devices. The structure of the mill is shown in Figure 1. 3.2.1 Drive mechanism: The main motor is a high-power asynchronous motor designed specifically for mills. The drive shaft bearings are double-row radial spherical roller bearings, and the peripheral gears are made of cast steel gears with a large module, which ensures smooth operation, low noise, and a long service life. The large gear is equipped with a radially sealed gear cover to ensure effective sealing. The large gear is lubricated using a spraying device, which periodically sprays a measured amount of lubricant onto the working surface of the gear to achieve lubrication. 3.2.2 Main bearing section: The main bearings feature a completely enclosed, self-aligning 120° “rocker” type design. The bearing shells are made of lead-based or tin-based babbitt, with serpentine cooling tubes embedded beneath them to supply cooling water and thereby reduce the temperature of the bearing shells. The bearing features a hydrostatic structure and is lubricated by high and low pressure light oil stations. During startup and shutdown, the high-pressure system is used to lift the rotating part; it is also interlocked with the main motor to lift it for 30 seconds before starting up, thereby reducing the starting torque and wear on the bearings. During normal operation, low-pressure feed of continuous oil flow is used to achieve good dynamic pressure lubrication. The sealing between the main bearing and the outside environment is achieved using a fully enclosed piston ring system, with rubber strips and lubricant being used to ensure good sealing in order to prevent dust from entering and to keep the bearing surfaces clean, thus reducing the risk of bearing damage ； The main bearing also features steps and oil return holes to prevent the leakage of lubricating oil, which is known as a \"triple seal\". The bearing is equipped with a platinum thermistor, which is interlocked with the main motor. The shutdown temperature can be set manually or adjusted according to the actual conditions on site. 3.2.3 Instruction Manual for the Cylinder Section of FGDM Series Wet Overflow Ball Mills. The FGDM series SM version has a total of 18 pages; this is page 5. The inner wall of the cylinder is lined with butyl rubber sheets thicknessing 2–6 mm, which prevents corrosion of the cylinder by the slurry. Rubber linings and rubber lifting strips are also installed there, which not only prevent corrosion of the linings but also reduce noise. The connection to the inlet and outlet end caps is achieved using external flanges. The cylinder is equipped with an externally accessible grinding door, which facilitates maintenance and the replacement of various wear-prone components inside the cylinder, as well as the loading and unloading of grinding media. 3.2.4 Feed and Discharge Section: Rubber linings are installed on the feed and discharge end caps of the mill, and their cross-sectional shape is designed based on the degree of wear. The feeding method employs a self-feeding approach into the mill, which features a simple structure and low resistance. The material will first pass through the counter-spiral tube in the discharge end cover, and then enter the cylindrical sieve for screening and discharge. To prevent slurry leakage, a combined seal is also used at the inlet and outlet ends. The cylindrical screen is of a split-type design, facilitating maintenance and replacement. 3.2.5 Foundation Section: The foundation section specifies the relative positions of the anchor bolts in various components as well as the elevation of the base surface, along with the anchor bolts and related embedded components. 3.2.6 Slow-speed drive mechanism: This mechanism, via a motor and reducer, enables the main unit to achieve a rotation speed of 0.15~0.2 rpm, which is used for turning the shaft, maintenance, and when loosening loads. When the machine is shut down for more than four hours, the material inside the cylinder may clump together. Before starting the main motor, it is advisable to use a slow-speed driving device to rotate the cylinder, which helps to loosen the material. The dog clutch in the slow drive device is one-way in order to protect the safety of maintenance personnel. This device also offers various installation options for users, allowing it to be installed at the main motor end, the reducer end, or the pinion drive shaft end. 3.2.7 Lifting device This device consists of a jack, a square box, and brackets. During shutdown for maintenance, the lifting device can be placed under the cylinder to lift it up for inspection and repair. This device is available in both electric and manual versions, allowing users to choose according to their needs. 3.2.8 Others: All grinders are available in two rotation directions – \"left-handed\" and \"right-handed\" – as well as two installation types – \"internal\" and \"external\" – for users to choose from. It must be specified clearly at the time of ordering. User Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM – 18 pages in total. Page 6: 4. Installation of the mill. 4.1 Precautions during installation. 4.1.1 It is necessary to pay attention to personal safety and the safety of the equipment during installation; in particular, care must be taken to prevent the cylinder from rotating due to uneven weight when installing the lining plates. 4.1.2 Be careful to prevent ring grinding and ring burning. Before assembly, the main bearing and shaft journals should be carefully inspected for any damage or dirt, and such issues should be removed; furthermore, the lubricating oil must be kept clean. 4.1.3 Pay attention to the gear oscillation and meshing requirements during gear installation to ensure transmission quality. 4.1.4 All mating surfaces, friction surfaces, etc. must be thoroughly cleaned before installation. Thin oil should be injected into the mating surfaces, while lubricant should be applied to the friction surfaces. 4.1.5 After installation, pay attention to the control and operating procedures when powering on; the grinder must not be started casually. 4.1.6 The no-load and full-load tests must be carried out continuously, and the duration should be extended as much as possible. 4.1.7 In addition to this manual, the technical requirements for installation shall also refer to the «Code for Installation of Mechanical Equipment» and the technical specifications of various relevant sections. 4.2 Installation sequence 4.2.1 Foundation bolts and base plate 4.2.2 Main bearing section 4.2.3 Rotating section (including the cylinder, feed and discharge sections; the manhole cover on the cylinder is installed later) 4.2.4 Transmission section, gears, couplings, and slow-speed transmission device 4.2.5 Electric motor and coupling 4.2.6 Feeding section 4.2.7 Gear cover and spraying device 4.2.8 High and low pressure lubrication stations, oil and water pipelines, safety guards, handrails, fences, etc. 4.3 Foundation installation 4.3.1 The mill must be installed on a reinforced concrete foundation designed to support the weight of the equipment as well as the loads that occur during operation. The foundation diagram in the random drawings provides only the relative elevation of the foundation as well as the dimensions of the anchor bolt positions; details such as the size and strength of the foundation must be determined by the user based on the natural geographical conditions of the specific site. The foundation diagram is intended solely for reference during the design and construction of the foundation. Instruction Manual for FGDM Series Wet Overflow Ball Mills – FGDM Series SM, 18 pages in total, Page 7: The design details shall be decided by the user according to the local natural conditions, and the foundation diagram is used only as a reference for foundation design and construction. 4.3.2 Before installation, the positions and dimensions of the foot bolts as well as those of the related equipment should be checked; installation may proceed only after it is confirmed that the actual components match the drawings exactly. 4.3.3 Each base plate shall be at the required elevation; self-made shims and adjustment washers may be used for adjustment, but the shims must maintain full contact with the bottom surface of the base plate to ensure firm fixation after grouting. 4.3.4 The top surface of the secondary layer shall be lower than the top surface of the base plate, but shall not be more than half the thickness of the base plate. 4.3.5 To ensure a tight bond with the original foundation during the second grouting, the surface of the foundation to be grouted must be roughened. The method of removing the rough surface involves using a steel flat shovel to create individual pits on the surface of the foundation; these pits have a diameter of about 30–50 mm. The distance between these pits varies depending on the size of the foundation, but is generally around 150 mm. Notches should be created at the corners of the foundation in order to make the structure stronger after the second pouring. 4.3.6 Before installing the foot bolts, remove any rust or oil from them; however, apply grease to the threaded parts to prevent rusting. Also, check whether the fit between the bolts and nuts is good. 4.3.7 The axial distance deviation between the two bearing bases shall not exceed 0.5 mm. 4.3.8 The relative elevation of the two bearing bases shall not differ by more than 0.5 mm, and it must be ensured that the discharge end is not higher than the feed end. 4.3.9 Before the secondary pouring of the foundation, the anchor bolts may be tightened only when the concrete strength reaches 75% or more. Clean the bearing housing, shims, and the foundation of any oil, paint, rust, dust, etc. Pay special attention to filling the area beneath the bearing housing with cement mortar; it must be compacted properly during pouring so that there are no gaps. 4.3.10 The final levelness of the installed fixed base plate shall not exceed 0.1 mm per meter in any direction. 4.3.11 After the secondary grouting layer has dried and the anchor bolts have been tightened, the aforementioned distances, elevations, and levelness must remain unchanged. Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM, 18 pages in total. Page 8: 4.4 Installation of the main bearings. 4.4.1 The installation of the main bearings must be carried out only after the strength of the foundation reaches 75% or more, and once it has passed the relevant inspection. 4.4.2 Before installing the bearing base plate, it should be cleaned thoroughly. Vertical and horizontal center lines should be marked on the upper surface of the base plate to serve as reference lines for alignment during installation. Then, the foot bolts along with the base plate are installed on the foundation, and the base plate is adjusted to the correct position. 4.4.3 The gaskets can be made from 25X100 steel plates, with the length of each gasket being no greater than the width of the base plate; there should be no less than 8 base plates for the main bearings, while the number of base plates for the remaining components can be reduced accordingly. 4.4.4 The adjustment plates can be made of thin steel plates of different thicknesses, with no more than 2 plates per shim. 4.4.5 The center distance between the bottom plates of the two bearings should generally comply with the provisions in the design drawings or equipment documents. At the same time, the actual dimensions of the cylinder body after assembly with the end cover should be measured, and appropriate adjustments should be made. 4.4.6 The relative elevation of the two main bearing pedestals is generally measured using a liquid level gauge or a theodolite, with an allowable tolerance of 0.5 mm. It must be ensured that the feed end is at a higher elevation than the discharge end. Both the elevation and levelness of the bearing pedestals should be measured simultaneously, with level adjustment being made as measurement proceeds. 4.4.7 Place the bearing housing on the bearing base plate such that their centerlines align; the bearing housing and the bearing base plate should be in even contact, with no local gaps exceeding 0.1 mm. The continuous length of such gaps must not exceed 1/4 of the side length, and the depth must not exceed 100 mm; otherwise, grinding shall be performed. Clean the surface of the saddle seat and the bearing bush, apply lubricant, then insert the bearing bush into the saddle seat. The working surface of the bearing bush must be lapped; the contact angle should be between 70º and 90º, with no fewer than 4 contact points over an area of 25x25 square millimeters. 4.4.8 After the bearing shells are installed, a pressure test should be conducted on them; the pressure applied should not be lower than the rated operating pressure of the high-pressure oil pump. The test must last for at least 30 minutes, and any leakage detected must be completely eliminated. 4.4.9 Before installing the upper cover, the cooling water pipes of the main bearings should be connected and subjected to a hydrostatic test. The test pressure should be 0.4~0.6 Mpa, and the test duration should be 30 minutes; no leaks should occur. 4.4.10 After the bearing housing is installed, check whether the cooling water hoses inside the housing come into contact with the shaft surface. Refer to the instruction manual for FGDM series wet overflow ball mills, page 9 out of 18 pages in total. Finally, remove any foreign objects from inside the bearing housing, plug up the unnecessary holes in the housing’s exterior using bolts, and immediately fill the grooves in the sealing rings at the contact points between the main bearing housing and the shaft with lubricant. Also, test to ensure that the oil flow is unobstructed. 4.5 Installation of the cylinder body 4.5.1 Before installing the cylinder body section, it is necessary to inspect the end caps and repair any surface damage on them, such as rust or scratches. At the same time, remove burrs, flash, and rust preventive paint from the mating surfaces; if assembly cannot be carried out immediately after cleaning, apply a layer of rust preventive grease to the machined surfaces as well and pack them up. 4.5.2 Before installing the cylinder section on the bearings, pre-install the gear lower cover in the drive section in place. The interior of the main bearing as well as the shaft journals must be thoroughly cleaned. It is strictly prohibited to tie steel wires to the shaft journals when installing the cylinder, to avoid scratching their surface. During installation, try to prevent dust and debris from falling on the surface of the bearing shells. It should be kept in mind to prevent damage to the bearings caused by shocks during handling; for this purpose, a lifting device can be used. Place the rotating part on the top frame of the lifting device at a height of 20–30 mm above its final position, and then slowly lower it into the bearing. Alternatively, first tie the bearing bush with a strap and place it at the predetermined position on the hollow shaft, then lower it together onto the bearing seat in order to change the first point of contact and prevent damage to the bearing. 4.5.3 The axial clearance between the feed end bearing and the shaft journal should be at least 5 mm on the outside of the cylinder. 4.5.4 The vibration of the end face of the main bearing liner caused by the different shaft tolerances of the two hollow shafts after assembly must not exceed 0.8 mm, and it must be ensured that the feed end is higher than the discharge end. The levelness of the busbar shall not exceed 0.8 mm. 4.5.5 It is strictly prohibited to lift the entire rotating section using the lugs on the end cover; the lugs can only be used to lift the end cover itself. 4.6 Installation of the large gear 4.6.1 Before installing the large gear on the cylinder, it is necessary to confirm whether the gear cover is in place, and inspect the gear cover; if any leakage is detected, it must be eliminated immediately. 4.6.2 The connection between the two half-gears must be secure; all bolts should be tightened. 4.6.3 The alignment of the large gear with the cylinder flange should be carried out repeatedly using the adjustment bolts on the large gear, so as to ensure that its radial and axial runout meet the requirements specified in the drawings. Only then can the tightening and fixing of the alignment bolts be performed. FGDM Series Wet Overflow Ball Mill Operation Manual, FGDM Series SM – 18 pages in total, Page 10. If necessary, the user can prepare pin holes for fixation on site. 4.8 Installation of the liner 4.8.1 When lifting the liner in and out of the mill, it is essential to pay attention to safety to prevent the mill from rotating due to an uneven weight distribution. In order, first install the manhole liner, then the other liners. 4.8.2 All bolts of the joint gasket plate must be tightened securely; they must not be loose. 4.9 Installation of the ring seal 4.9.1 Clean the ring seal in accordance with the drawings, and use an emery stone and fine file to dull all sharp edges, burrs, and protrusions. Clean the bearing seat and the sealing surfaces of the hollow shaft using the same method, and then apply lubricant to each of them separately. 4.9.2 First, place a sealing rubber strip in the lower half of the groove, ensuring that the rubber strip protrudes at least 2 mm from the groove; secure the end where it enters using tape. Then, gently guide the half-ring along with the rubber strip into the groove from the side without any fixing pins. 4.9.3 Install the upper half-ring and apply adhesive at the joint of the rings; similarly, adjust the joints of the sealing rubber strips and secure them with adhesive. 4.9.4 Install other parts as shown in the diagram: block off the unused holes, connect the oil pipes, and then fill in the lubricant. 4.10 Installation of the transmission section 4.10.1 Before assembly, the rolling bearings, bearing housings, as well as the drive shafts and pinions must be thoroughly cleaned before installation can proceed. 4.10.2 The drive bearing base plates, bearing housings, and the position of the drive shaft must all be carefully inspected to ensure good gear meshing performance. 4.10.3 When installing the coupling, the dimensions of all the mating parts should be checked in advance (such as diameter, length, keyways, chamfers, and interference amount). During hot installation, an oil bath can be used to raise the temperature to the specified level; direct heating with open flames is strictly prohibited. The coaxiality error between the various drive shafts that need to be connected must not exceed 0.2 mm, and the gap between the two halves of the coupling should be adjusted according to the specifications. 4.10.4 The tooth side clearance between the large and small gears after assembly shall meet the requirements specified in the drawings (1.4~2.18 mm). Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM, 18 pages in total. Page 11: 4.10.5 The contact area where the large and small gears mesh should be no less than 45% of the tooth height, and it should be no less than 60% along the length of the tooth. 4.10.6 Install the gear seals and gear covers, and conduct a thorough inspection and adjustment to ensure a tight seal with no mechanical interference. 4.11 Installation of the low-speed drive mechanism: After the motor and planetary gear reducer are in place, the drive clutch should be able to engage and disengage smoothly, without any sticking or failure to engage properly. The sliding surfaces of the guide sleeves as well as the sliders (grooves) should be coated with lubricant. 4.12 Installation of the lubricating oil station 4.12.1 The installation of the oil station shall be carried out in accordance with the installation and operation instructions for the lubricating oil station. 4.12.2 During installation, it is necessary to ensure that the oil drain hole of the fuel tank extends beyond the base of the tank and is at least 300 mm above the ground; otherwise, draining the oil will be difficult. 4.12.3 The lubrication pipelines and accessories shall be provided by the user; after connection, there shall be no leaks, and they must be thoroughly cleaned so that no residues remain in the lubrication equipment pipelines or bearing housings. 4.12.4 After the lubrication system is assembled, tests shall be conducted, and the test pressure of the cooling water channels in all areas shall meet the requirements of the system. 4.13 The lifting device is mobile and can be removed when not in use. During installation, the base must be leveled and secured properly; it must not be tilted, and the load on both sides should be roughly equal. 4.14 Others: As required by the drawings, assemble the remaining components to meet the design specifications, and install walkways, handrails, railings, guards, etc. 5. Commissioning and acceptance of the mill: After the equipment has been installed and passed inspection, it can be commissioned for trial operation. 5.1 Operation of the grinder 5.1.1 Thoroughly check and confirm that there are no residues left inside the equipment, that all sealing points are properly sealed, and that the connection points are firm and reliable. 5.1.2 Check whether the oil level at each lubrication station has reached the specified level; in winter, heat the lubricating oil to 20–25ºC, as stated in the instruction manual for the FGDM series wet-type overflow ball mills, FGDM series SM, page 12 out of 18, and check the flow rates and pressures of oil, air, and water. 5.1.3 Before no-load testing, a thorough inspection should be carried out on the high and low pressure lubricating oil stations, the spray lubrication systems, and the bearing water cooling system to ensure they are in good working condition. 5.1.4 The rotation direction of the motor must meet the requirements specified in the drawings (this should be checked by rotating the motor manually). 5.1.5 Clean the site and remove any obstacles that could affect the operation of the mill; it is strictly prohibited to have people standing on either side when the mill is started up. 5.1.6 Start the high-pressure system to lift the rotating part, ensuring that an oil film of sufficient strength is formed and that there is enough lubricating oil in the bearing housing. 5.1.7 Start the cooling circulating water. 5.1.8 Use a grease gun to fill the annular sealing chamber with sufficient grease. 5.1.9 Apply an appropriate amount of grease manually at the gear meshing points, and grease should also be applied between the sealing felts of the gear rims. 5.1.10 Start the low-speed drive mechanism to rotate the rotating part, and at the same time start the injection device to spray fuel continuously for 10 minutes. (Make the host rotate slowly one full turn). 5.1.11 Check all parts of the mill for any movement interference, collisions, or loose bolts. If so, immediate stopping is required to resolve it. 5.2 No-load test: Conduct a formal no-load test by restarting the high and low pressure oil pumps; let the oil pumps that are interlocked with the main motor operate for 3 minutes. Once a feedback signal is received, indicating that an oil film has been formed, the main motor will start automatically. After the mill has been running for 30 minutes, the following requirements should be met: (1) The lubrication at all lubrication points is proper, with no signs of leakage ； (2) The temperature of the main bearing of the grinder shall not exceed 60ºC ； (3) The grinder should operate smoothly, with no abnormal noises from the gear transmission and good contact between the gear surfaces ； (4) The gaskets and all rotating parts are not loose. 5.3 Load Testing 5.3.1 After successful no-load operation, steel balls can be added to the mill, along with appropriate material, in order to prevent damage to the lining plates and steel balls. Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM, 18 pages in total. Page 13: 5.3.2 The filling ratio and load capacity specified in the mill specifications represent the maximum values; the mill must not be operated under overloaded conditions. The additional media and materials should be balanced with those consumed and the products. 5.3.3 During the load test, 20–30% of steel balls, equivalent to 50% of the total weight of the material, should be added to the mill first. It should be started following the prescribed procedures; once operation is normal, 10% of the total amount of medium should be added every 30 minutes, with an appropriate amount of material being fed continuously until the mill reaches full load, after which it should operate continuously for 24 hours. The following requirements must be met: (1) The operation shall be smooth, without sudden periodic vibrations ； (2) The current value of the main motor is within the allowable range ； (3) All components are operating normally ； (4) There is no powder leakage at the bolt locations of the backing plate; if any leakage occurs, tighten the bolts promptly ； (5) Check whether the bolts in various parts are loose, broken, or missing ； The main bearing temperature is below 60ºC, and the return oil temperature is below 50ºC. 6. Operation of the mill 6.1 Startup sequence: Low-pressure oil pump — High-pressure oil pump — Main motor — Feeding section motor. Under normal circumstances, it is not advisable to start the mill twice in a row within one hour. 6.2 Shutdown sequence: Stop the feeder — stop the main motor — the high-pressure oil pump starts automatically — 5 minutes after the mill stops rotating, stop the low-pressure oil pump. The jet lubrication system operates automatically when the main motor is running, and stops automatically when the main motor comes to a halt. When the main motor is operating, the low-speed drive cannot start; when the low-speed drive is operating, the main motor cannot start. 6.3 Emergency Shutdown: During operation, the mill may encounter certain special situations; to ensure the safety of the equipment, emergency shutdown measures must be taken in the following circumstances. Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM, 18 pages in total. Page 14: (1) Abnormal meshing of the large and small gears, resulting in sudden severe vibrations or unusual noises ； (2) When the lubrication system fails and cannot supply oil properly ； (3) The gusset plate bolts are loose or broken and have fallen off ； (4) When the cylinder is running idly with no material inside ； (5) The temperature rise of the main bearings and main motor exceeds the specified value, or the current of the main motor exceeds the specified value ； (6) When the conveying equipment fails and loses its conveying capacity ； (7) When the anchor bolts of the main bearings, transmission device, and main motor are loose ； (8) In the event of other emergency shutdown situations. In the event of an unexpected stop due to an accident, feeding must be stopped immediately, and the power to the motor and other equipment must be cut off before any troubleshooting can be carried out. 6.4 Long-term shutdown of the mill 6.4.1 During a long-term shutdown, the cylinder gradually cools and contracts, causing the shaft journals to slide on the bearing shells. To reduce friction and the axial force resulting from the contraction of the cylinder, the high-pressure oil pump should automatically supply oil for 3 minutes every 30 minutes, once every 24 hours of shutdown, in order to maintain a certain thickness of oil film between the shaft journals and the bearing shells. 6.4.2 During the shutdown of the mill in winter, all cooling water in the water-cooling sections should be drained completely (using compressed air) to prevent the relevant pipes from cracking due to freezing. 6.4.3 Under normal circumstances, feeding should be stopped before shutting down the mill, which will cause it to stop operating shortly thereafter. 6.4.4 In the event of a long-term shutdown, the steel balls should be removed to prevent deformation of the cylinder. 6.5 During normal operation, operators must comply with and pay attention to the following points: (1) The mill must not run for long periods of time when no material is being fed, in order to avoid damaging the lining plates and wasting the medium ； (2) Uniform feeding is one of the important conditions for mills to achieve optimal performance; therefore, operators should ensure the uniformity of the material fed in ； (3) Regularly check the wear of the linings and the medium inside the mill cylinder; worn-out or damaged linings should be replaced promptly, and loose or broken bolts should be tightened or replaced in a timely manner to prevent the cylinder from being worn through. FGDM Series Wet Overflow Ball Mill User Manual, FGDM Series SM – 18 pages in total, Page 15 ； (4) Regularly check and ensure that there is sufficient and clean lubricating oil (grease) at all lubrication points, including those at the main bearing seals. The return oil filter in the light oil station should be cleaned at least once a month, and the quality of the lubricating oil should be checked every six months; replace it with new oil if necessary ； (5) Check the meshing condition of the large and small gears in the grinder, as well as whether the fixing bolts are loose; the reducer must not exhibit any abnormal vibrations or noises during operation ； (6) Adjust the amount and grading of steel balls added according to the particle size requirements of the feed material and the product, and replenish steel balls into the mill in a timely manner to keep the steel balls in the mill in optimal condition. The steel balls used for replenishment should be of the largest diameter specified for the initial addition (however, if no balls have been added for an extended period, balls of smaller diameter should also be added). (7) The protective covers for the mill couplings and clutches, as well as other safety devices, must be in good condition and reliable, and warning signs should be installed in hazardous areas ； (8) No disassembly or maintenance work on the machine shall be carried out while it is in operation. When it is necessary to work inside the cylinder, it is essential to contact the relevant personnel in advance and implement proper monitoring measures. If observing the interior of the main bearing while the mill is in operation, special care must be taken to avoid being scratched by the bolts on the end cover. (9) When inspecting, maintaining, and repairing the auxiliary equipment of the grinder, low-voltage lighting equipment should be used. When welding parts on the grinder, attention must be paid to grounding protection to prevent electric current from scorching the tooth surfaces and bearing surfaces ； (10) The temperature and flow rate of the cooling water for the main bearings and various oil stations should be adjusted as appropriate, ensuring that the temperature of the bearings does not exceed the allowable level ； (11) A regular inspection system should be established during use to maintain the machine ； (12) The equipment must be carefully maintained; the surrounding area should be kept clean, with no leaks of water or slurry, no oil stains, no loose bolts, and no debris around the equipment. 7. Maintenance and Lubrication of Mills 7.1 Maintenance of Mills In addition to routine inspections, mills should undergo regular maintenance checks. A maintenance plan should be developed based on the specific conditions of the equipment, and regular inspections should be carried out. FGDM Series Wet Overflow Ball Mill User Manual, FGDM Series SM – 18 pages in total, Page 16 Based on the degree of equipment damage, it is classified into minor repairs, medium repairs, and major repairs. 7.1.1 Minor repairs: Minor repairs are generally carried out once every 1 to 2 months; they can be performed at any time in case of special circumstances. The main tasks involved include the following: (1) Inspecting the oil pumps, oil filters, and lubrication systems, and cleaning them as well as replacing the lubricating oil when necessary ； (2) Inspect all connection bolts and replace any defective fasteners ； (3) Clean and inspect the pinion for defects such as cracks, check the meshing condition and record its wear depth, and check whether the bolts securing the gear gear are loose ； (4) Inspect the coupling and clutch and replace worn parts ； (5) Inspect and repair the wear-prone parts of the feeding and discharging devices ； (6) Replace some liner plates of the mill cylinder ； (7) Check the thickness of the main bearing bushing ； (8) Inspect the cooling water system to check for blockages or leaks, and replace the aged oil-resistant rubber hoses (in the main bearing housing). 7.1.2 Medium maintenance: The cycle for medium maintenance is generally 12 months, and the maintenance tasks mainly include the following: (1) Including the minor maintenance tasks ； (2) Replace the liner plate ； (3) Inspect, repair, or replace the pinion gear ； Check and adjust the horizontal position of the cylinder, and check the coaxiality of the drive shaft and the motor ； (4) Clean the oil residue inside the large gear cover ； (5) Inspect and calibrate various instruments and meters ； (6) Other items that require repair. Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM – 18 pages in total. Page 17: 7.1.3 Major Overhaul. The routine period for major overhauls is generally 5 to 10 years, depending on the degree of damage to the equipment. The main tasks involved in such overhauls include the following: (1) Tasks related to minor and medium-scale repairs ； (2) Replace the spindle bearing and spur gears ； (3) Repair or replace the inlet and outlet end caps of the mill ； Inspect the foundation, realign it, and carry out a second pouring. 7.2 Lubrication of the mill: This series of mills is equipped with high and low pressure thin oil lubrication systems. These systems are used to lubricate the main bearings of the mill, providing high-pressure, low-flow lubrication for starting and stopping, as well as low-pressure, high-flow lubrication for normal operation. For the specific structure, commissioning, operation, maintenance, and electrical control of the oil station, please refer to the \"Instructions for High and Low Pressure Thin Oil Stations\". 7.3 Jet Lubrication Unit: This unit is designed to lubricate the large and small gears; it operates in conjunction with the main motor to deliver oil automatically on a periodic basis. For its structure, commissioning, operation, maintenance, and electrical control, please refer to the \"Instructions for the Jet Lubrication Unit\". 8. Lifting device 8.1 The lifting device is a specialized lifting accessory for mills, available in both manual and electric versions; users can choose either one according to their needs. The hydraulic jack among them can also be used separately. When lowering the cylinder after completing the maintenance work, care should be taken not to release pressure rapidly; instead, it should be shut down gradually so that the shaft journal can descend slowly. 8.2 The technical specifications and usage requirements for the hydraulic jack are specified in its corresponding user manual. 8.3 The jack can be equipped with a pressure gauge to help monitor the actual load. 8.4 The lifting device should be inspected before it is inserted under the cylinder. First, check the hydraulic system to ensure that there is no dirt or blockages in any components. Both jacks need to have their operating conditions checked, and they must also be inspected simultaneously. 8.5 The center line of the lifting device should be aligned with the axis of the cylinder, so that the resultant load force passes through the center line of the jack piston. Instruction Manual for FGDM Series Wet Overflow Ball Mills. FGDM Series SM, 18 pages in total. Page 18: 8.6 The lifting device must be properly supported and secured before operation can begin. 8.7 Vibration and impact should be avoided during the use of the lifting device to prevent damage. 8.8 The working oil should be kept clean at all times; it should be filtered once per quarter or before each use. 8.9 Oil pumps and pipeline connections must be kept clean; no dirt is allowed. 8.10 The jacks and oil pumps should be regularly inspected and maintained according to their usage; if any wear of the parts is detected, they should be replaced promptly. 8.11 Oil pumps, pipelines, and jacks should be stored in a well-ventilated area equipped with protection against moisture and sunlight.