Ball mill is used to crush materials after they are crushedKey equipment。A certain number of steel balls are loaded into the barrel of this type of mill as the grinding medium.
It is widely used in cement,Silicate products，New building materials、Refractory、chemical fertilizer, black and non-ferrous metal beneficiation andGlassware and CeramicsDry or wet grinding of various ores and other grindable materials in the production industry.Ball mill is suitable for grinding all kinds of ores and other materials. It is widely used in mineral processing, building materials, chemical industry and other industries. It can be divided into dry grinding and wet grinding.According to the different ways of ore discharge, it can be divided into lattice type and overflow type.
On August 15, 2023, the overflow type ball mill independently developed by CITIC Heavy Industries with a diameter of 8.2 meters and a length of 12.7 meters successfully completed factory commissioning and was delivered to customers.[11]
Ball mill is suitable for grinding all kinds of ores and other materials. It is widely used in mineral processing, building materials, chemical industry and other industries. It can be divided into dry grinding and wet grinding.According to the different ways of ore discharge, it can be divided into lattice type and overflow type.According to the shape of the cylinder, it can be divided into four types: short cylinder ball mill, long cylinder ball mill, tube mill and cone mill.[1]
working principle
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Working principle of ball mill
The ball mill is composed of horizontalCylinder, incoming and outgoing materialsHollow shaftAnd grinding head. The cylinder is a long cylinder with grinding body inside. The cylinder is made of steel plate, with steel lining plate fixed to the cylinder. The grinding body is generally a steel ball, which is loaded into the cylinder according to different diameters and certain proportions. The grinding body can also be steel sections.It is selected according to the particle size of the grinding materials. The materials are loaded into the cylinder by the hollow shaft at the feed end of the ball mill. When the cylinder of the ball mill rotates, the grinding body is attached to the cylinder liner plate and taken away by the cylinder due to inertia, centrifugal force and friction. When it is taken to a certain height, it is thrown down due to its own gravity,The falling grinding body breaks the materials in the cylinder like a projectile.
The materials enter the first bin of the mill evenly and spirally from the feeding device through the feeding hollow shaft. There are stepped lining plates or corrugated lining plates in the bin, which are filled with steel balls of various specifications. The rotating cylinder generates centrifugal force to bring the steel ball to a certain height and then fall down, causing heavy impact and grinding on the materials.After coarse grinding in the first bin, materials enter the second bin through a single-layer partition board. The bin is inlaid with a flat lining board and steel balls inside to further grind the materials.The powder is discharged through the discharge grate to complete the grinding operation.
In the process of rotating the cylinder, the grinding body also slides. In order to effectively use the grinding effect, the grinding body cylinder is divided into two sections by a partition plate when the general 20 mesh grinding with large particle size is used, that is, double bins. When the materials enter the first bin, they are crushed by steel balls. When the materials enter the second bin,The steel section grinds the materials, and the qualified materials are discharged from the hollow spindle at the discharge end. When grinding the materials with small feed particles, such as No. 2 slag, coarse fly ash, the mill barrel can be a single bin barrel mill without a partition, and the grinding body can also be made of steel sections.
Raw materials are fed into the hollow cylinder through the hollow journal for grinding, and the cylinder is equipped with grinding media of various diameters (steel balls, steel rods or gravel, etc.).When the cylinder rotates around the horizontal axis at a certain speed, the medium and raw materials loaded in the cylinder, under the action of centrifugal force and friction, will fall or roll off the inner wall of the cylinder when their gravity is greater than the centrifugal force as the cylinder reaches a certain height, and the ore will be crushed due to the impact force.At the same time, in the process of mill rotation, the sliding motion between grinding media will also have grinding effect on raw materials.The ground material is discharged through the hollow journal.[2]
Ball loading of ball mill
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In ball millsteel ballIts main function is to impact and crush materials, and also play a certain role in grinding.Therefore, the purpose of grading steel balls is to meet these two requirements.The grinding effect directly affects the grinding efficiency, and ultimately affects the output of the ball mill. Whether the grinding requirements can be met depends on whether the grading of steel balls is reasonable, mainly including the size of steel balls, the number of ball diameters, and the proportion of balls of various specifications.
To determine these parameters, not only the size of the ball mill, its internal structure, product fineness requirements and other factors should be considered, but also the characteristics of the materials to be grinded (grindability, particle size, etc.).
In order to effectively crush materials, the following principles must be followed when determining the gradation:
firstThe steel ball shall have enough impact force to makeBall mill steel ballIt has enough energy to break granular materials, which is directly related to the maximum diameter of the steel ball.
secondlyThe steel ball should have enough impact times on the material, which is related to the filling rate of the steel ball and the average ball diameter.When the filling amount is fixed, on the premise of ensuring sufficient impact force, try to reduce the diameter of grinding body and increase the number of steel balls to increase the number of impacts on materials, so as to improve the crushing efficiency.
lastThe material has enough residence time in the mill to ensure that the material is fully crushed, which requires the steel ball to have a certain ability to control the material flow rate.
so-calledTwo graded ball methodThat is to use steel balls of two different sizes and diameters to grade.The theoretical basis is that the space between the big balls is filled by small balls to fully improve the packing density of steel balls.In this way, on the one hand, the impact capacity and impact times of the mill can be improved, which is in line with the functional characteristics of the grinding body; on the other hand, the higher stacking density can enable the materials to get a certain grinding effect.In the two graded balls, the role of the big ball is mainly to impact and crush the materials. The role of the small ball is to fill the gap between the big balls, improve the stacking density of the grinding body, so as to control the material flow rate and increase the grinding capacity;The second is to transfer the impact energy of the big ball to the materials;The third is to squeeze out the coarse particles in the gap and place them in the impact zone of the big ball.[3]
Mechanical structure
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The ball mill is composed of feeding part, discharging part, rotary part, transmission part (reducer, small transmission gear, motor, electric control) and other main parts.The hollow shaft is made of cast steel, and the lining can be replaced. The rotary gear is processed by casting hobbing. The cylinder body is inlaid with wear-resistant lining plate, which has good wear resistance.The machine operates stably and reliably.
The main machine of the ball mill includes a cylinder, which is lined with wear-resistant materials, has bearings to carry the cylinder and maintain its rotation, and also has drive parts, such as motors, and transmission gears, pulleys, V-belts, etc.
As for the parts called blades, they are generally not the main parts. There are internal screws in the feed inlet of the parts at the feed end, which can be calledHelical bladeThere is an internal spiral in the part discharge port at the discharge end, which can also be called the internal spiral vane.
In addition, if it is used in the auxiliary equipment at the discharge endScrew conveyorThere will be parts called spiral blades in this equipment, but strictly speaking, they are not included in the ball mill.
Selectable according to material and ore discharging modedry ball mill And wetLattice ball mill。Energy saving ball mill adopts automatic self-aligning double row centripetal spherical roller bearing, with small running resistance and remarkable energy saving effect.For the cylinder part, a section of conical cylinder is added at the discharge end of the original cylinder, which not only increases the effective volume of the mill, but also makes the medium distribution in the cylinder more reasonable.This product is widely used as material grinding in nonferrous metal, ferrous metal, non-metallic ore dressing field, chemical industry and building materials industry.
Ball mill accessories
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Big gear of ball mill
Ball mill accessories include ball mill big gear, ball mill pinionHollow shaft of ball mill, gear ring of ball mill, big gear ring of ball mill, ball of ball mill, partition plate of ball mill, transmission device of ball mill, bearing of ball mill, end lining of ball mill, etc.
Including big gear of ball milltexture of materialchoice:
According to different working conditions of large gears, large gears are usually made of the following materials:
(1) Medium carbon structural steel
(2) Medium carbon alloy structural steel
(3) Carburized steel
(4) Nitrided steel
The structure of the big gear of the ball mill has different shapes due to different use requirements, but from the perspective of technology, the gear can be seen as consisting of two parts: the ring gear and the wheel body.According to the distribution form of gear teeth on the gear ring, it can be divided into straight teeth, helical teeth, herringbone teeth, etc.[4]
increase of efficiency
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(1) Increase effective volume
Increasing the effective volume of the mill can increase the productivity of the mill on a year-on-year basis. The lining plate is thick and heavy, increasing power consumption, reducing the effective volume of the cylinder, and reducing the production efficiency of the ball mill.If the magnetic lining plate is selected, the effective volume of the cylinder can be increased, while the weight is relatively reduced, and the power consumption is reduced.However, the selection of thin magnetic lining plate has certain disadvantages. Due to its small thickness, its impact resistance is not as good as the existing Cr Mn Mo alloy cast steel lining plate, which is prone to fracture.For example, for the lining plate problem, some manufacturers use grooved annular lining plates, which increase the contact surface of the ball ore, strengthen the grinding effect, and have the ability to lift the ore, reduce energy consumption, and are widely used.
(2) Increase filling rate and rotating speed
The processing capacity of the ball mill increases with the increase of the filling rate of the steel ball, and the increase of the filling rate increases the probability of the steel ball crushing and grinding ore and the ore self grinding effect.When the ball filling rate is 45%, the load of the ball mill is the largest, and when the ball filling rate is more than 45%, the load decreases significantly with the increase of the ball filling rate.This is mainly because with the increase of the filling rate, the starting point of the steel ball is raised, and the action point of the combined impact force of the steel ball falling is accelerated closer to and more than the rotation center. The resultant torque is greatly shortened and becomes O to negative. The load required for the combined impact torque of the steel ball (containing ore) falling is changed from large to 0 until it becomes the power to drive the rotation of the cylinder (that is, the resultant action point is more than the center, and the resultant torque is negative).
(3) Change the shape of grinding medium
The ellipsoid medium can be selected to replace the current spherical medium. Compared with the spherical medium, the ellipsoid has the following advantages:
one
Compared with the round ball with the same diameter, the weight of the elliptical ball increases by 62%, the impact force is strong, and the crushing capacity is improved;
two
Line contact is used between ellipsoids instead of point contact between spheres, and the contact area is 4 times larger than that of spheres. It has selective crushing and good screening effect on materials, and the product size is uniform, reducing the over crushing phenomenon;
three
Compared with the round ball with the same diameter, the surface area of the elliptical ball increases by 8%, which enlarges the contact surface between the steel ball medium and the material, and improves the grinding ability;
four
The elliptical ball and the mill liner replace the point contact of the ball with the line contact, reducing the wear of the steel ball medium on the liner, reducing the impact of the steel ball medium and the mill liner, thus reducing the wear of the steel ball medium and the mill liner, and extending the service life;
five
The ellipsoid also has antistatic and anti moisture effects, which can reduce the adsorption of fine powder and reduce the phenomenon of full grinding.
Compared with the round ball, the elliptical ball can greatly improve the crushing and grinding capacity of the ball mill, and correspondingly reduce the equipment loss.[5]
Mechanical classification
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cement ball mill
cement ball mill
The cement ball mill is a horizontal cylindrical rotating device with external gear transmission.The cylinder rotation produces centrifugal force to bring the steel ball to a certain height and then fall down.
The cement ball mill is used for grinding cement raw materials, which is divided into dry method and wet method.
Tubular ball mill
The key equipment for crushing materials after crushing.
Ultra-fine laminating mill
The ultra-fine laminated ball mill is the most famous high-efficient and energy-saving mill at present, and it is also the first mill in China.
1 set of ultra-fine laminated ball mill=crushing and screening system+1/2 grinding and classification system
Ultra fine laminated autogenous millThe "more crushing and less grinding" is really realized. After the ultra-fine laminated autogenous mill is adopted, the comprehensive benefits are remarkable: the fine crushing screening plant and equipment are omitted, and the dust removal unit is omitted. Taking a concentrator with a capacity of more than 1500 tons/day as an example, the investment can be saved by more than 2 million to 10 million yuan, and the energy can be saved by 20-30%. It is a truly dust-free crushing grinding energy-saving and environment-friendly beneficiation process.
Conical ball mill
Cone ball mill
Cone ball millIt is a common ball mill in mineral processing production. This machine has changed the original mill structure to integrate the body and underframe. It can be installed once and placed on the foundation plane. The main bearing adoptsDouble row self-aligning roller bearingIt can reduce energy by 30%, increase fine particle size, and increase processing energy by 15-20%.Cone ball mill is the key equipment for crushing materials after crushing.Ball mills are widely used in cement,Silicate products，New building materials, refractory materials, fertilizer, ferrous and non-ferrous metal beneficiation andGlassware and CeramicsDry or wet grinding of various ores and other grindable materials in the production industry.
This machine is a horizontal cylindrical rotating device, with external gear transmission, two bins, lattice ball mill.[6]
ball grinding mill
ball grinding mill
Ceramic ball mill is the key equipment for crushing materials after crushing.Ball mill is widely used in cement and silicate products to dry or wet mill various ores and other grindable materials.The ball mill is a horizontal cylindrical rotating device, driven by external gear, with two bins and a grid type ball mill.
Intermittent ball mill
Ball mill
Intermittent ball millIt is the key equipment for crushing materials after crushing.Ball mills are widely used in cement,silicateProducts, new building materials, refractory materials, fertilizer, black and
Non ferrous metal beneficiation, glass ceramics and other production industries, dry or wet grinding of various ores and other grindable materials.External gear drive, two bins, grid ball mill.[7]
Overflow ball mill
Overflow ball millWith the rotation of the cylinder and the movement of the grinding medium, ore and other materials gradually spread to the right after crushing, and finally overflow from the hollow journal on the right, hence the name.
Lattice ball mill
The grid type ball mill is equipped with a grid plate at the discharge end, which is composed of several fan shaped orifice plates. The width of the grid hole on the grid plate is 7mm-20mm. The ore enters the space between the grid plate and the end cover through the grid hole, and then the material is lifted up by the lift plate. The material slides along the lift plate, and then passes through the conical block to the right to the hollow journal to be discharged out of the machine.
Pneumatic discharge ball mill
The material of the pneumatic discharge ball mill enters the ball mill from the feeding port. After the grinding medium impacts and grinds the material, the material moves gradually from the inlet of the mill to the outlet. The outlet end is connected with the air duct. The inlet of the separator, powder concentrator, dust remover and fan is connected in series in the system. When the pneumatic discharge starts to operate, the relative negative pressure in the ball mill body is low,The crushed and ground materials enter the pipeline system from the discharge port with the wind force. The coarse particles are separated by the separator and then sent back to the ball mill inlet. The ground materials are separated and recovered by the separator.
Double chamber ball mill
After passing through the hollow journal, the materials of the double bin ball mill do not directly enter the grinding ball medium inside the cylinder. Instead, when the cylinder rotates around the horizontal axis at a certain speed, it starts further sorting, making large pieces of materials fall into the crushing bin and small pieces of materials enter the grinding bin through the conveying device.In this way, when their own gravity is greater than the centrifugal force, they will splash or roll off from the inner wall of the cylinder, so that the impact force generated on the lining plate will carry out targeted crushing work according to the different needs of different compartments.
ball grinding mill
1. Use of energy-saving ball mill:
Energy saving ball mill is the key equipment for crushing materials after crushing.Energy saving ball mill is widely used in cement, silicate products, and dry or wet grinding of various ores and other grindable materials.
2. Working principle of energy-saving ball mill:
This machine is a horizontal cylindrical rotating device, with external gear transmission, two bins, lattice ball mill.[8]
Installation and commissioning
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Ball mill installation:
a) The installation plan is designed according to the user's basic engineering, and shall be installed according to the direction, location and space shown in the drawing;
b) The lower plane of the machine body shall be firmly grounded, and the levelness of the bottom plane of the cylinder after horizontal adjustment shall not be greater than 1.5/1000;
1. Installation
a) Remove the foreign matter in the reserved hole of the installation equipment foundation, especially the inner wall of the hole shall be free of dust, oil stain, water and other liquids;
b) After unpacking the packing case, move the host machine to the installation position with appropriate lifting facilities (crane/forklift);
c) Put the equipment in position,Foundation boltIn the installation hole, put the "movable feet" attached with the machine on the foundation studs and weld them on the chassis of the rack, and then carry out secondary grouting;
d) After installing the cement for 24 hours, tighten the nuts and load the machine;
e) Connect to the power supply;
f) Installation inspection and correction of improper parts;
g) The electrical cabinet is placed in the auxiliary machine room, without the installation of anchor.
2. Test run:
After the ball mill is installed and inspected as qualified, the no-load test run can be carried out. The test run of the ball mill should be carried out by skilled ball mill operators and strictly comply with the requirements of the ball millSafe Operation Procedures。
(1) The continuous operation time of idle running shall not be less than 12-24 hours, and problems found during operation shall be solved in time.
(2) The load test run can be carried out when the idle running test machine is normal. The load test run should be carried out in stages. During the load run, feeding should be carried out according to the discharge condition to avoid unnecessary wear loss and damage of the steel ball and cylinder liner.
a) Add appropriate materials and 1/3 of steel balls (see the general drawing of ball mill for the maximum ball loading) and run in for 12-24 hours.
b) Add 2/3 of the steel balls and run for 24-48 hours.
c) According to the discharge condition of the ball mill, the output of qualified products, and the actual ball load of the ball mill of the same concentrator, determine the reasonable ball load of this ball mill, and conduct a test run of not less than 72 hours.
(3) The increase of the above load and the length of the test run time shall be determined based on the running in conditions (temperature rise, noise, tooth surface contact, etc.) of the big and small gears and the reducer gears.It is not allowed to operate at full load until the contact accuracy of tooth surface fails to meet the design requirements.
(4) During the test run, the cooling and lubrication systems should work normallyDrive bearingThe reducer temperature shall be normal.
(5) After 24-48 hours of commissioning with 2/3 steel balls installed, check and tighten all bolts again.
(6) The commissioning work shall be carefully recorded.
Ball mill is mainly used for mixing and grinding of ceramic raw materials, and is an essential equipment for the production of various ceramic products. The machine is started by self coupling decompression to reduce the starting current. Its structure is divided into integral type and independent type.V-belt drive, single or double reduction, equipped with independent small power motor for loading and unloading.[5]
Installation precautions
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The ball mill shall be installed on a firm concrete foundation.For the foundation design and construction of the ball mill, please refer to the general assembly drawing and foundation drawing of the ball mill.In order to ensure that the position accuracy of all parts of the ball mill will not change greatly during use, the foundation of the ball mill shall be of a monolithic structure.
The ball mill can be installed on the concrete foundation after the compressive strength of the concrete foundation reaches more than 75%.Before installation, the quality of the foundation shall be inspected. It is required that the concrete has no defects that affect the strength, the number and location of the reserved holes meet the requirements, and the reserved holes are free of sundries, water and oil.When the "ground wire method" is used for installation, the "central target plate" shall be embedded on the upper surface of the foundation.Before installation, draw all center lines on the foundation and make striking punch marks on the "center target plate" as the center line datum during installation.
Before hoisting, the ball mill shall be fully accepted by its parts, and any problems found shall be handled in time.
1. Refer to the assembly drawing of main bearing components for specific requirements of main bearing.
2. See the assembly drawing of rotary part for the cylinder part.
3. See the assembly drawing of transmission part for transmission part.
4. See the general assembly drawing for the overall relative position.[5]
Structural characteristics
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Schematic diagram of ball mill
(1) The main bearing adopts a large diameter double row self-aligning roller bearing instead of the original sliding bearing, which reduces friction and energy consumption, and the mill is easy to start.
(2) The end cover structure of the ordinary mill is retained, and the large diameter inlet and outlet has a large processing capacity.
(3) Feeders are divided into combined feeder and drum feeder, with simple structure and separate installation.
(4) There is no inertial impact, the equipment runs smoothly, and reduces the downtime of the mill for maintenance, thus improving the efficiency.[9]
technical parameter
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Model of middling ball mill
Cylinder speed
(per minute)
Ball load
(ton)
Feed size
(mm)
Discharge particle size
（mm）
yield
(t/h)
Motor power (kw)
Weight (t)
MQ750×1060
one point six
four
≤20
1.075-0.89
1.14~0.34
one point five
one point six
Ф900×3000
thirty-six
one point seven
≤20
1.075-0.89
1.1-3.5
twenty-two
one point six
Main technical parameters of cone ball mill:
Specification and model
Feed size
(mm)
Discharge particle size
(mm)
yield
(t/h)
Motor power
(kw)
weight
(kg)
GZM900×2100
≤15
1.075-0.83
1.7-3.5
fifteen
three thousand and nine hundred
GZM1200×2800
≤25
1.075-0.6
2-6
thirty-seven
thirteen thousand
GZM1500×3500
≤25
1.075-0.4
1.5-12
seventy-five
seventeen thousand and five hundred
GZM1830×3600
≤25
1.075-0.4
5-22
one hundred and thirty
thirty-three thousand and five hundred
GZM2100×3600
≤25
1.075-0.4
15-36
two hundred and ten
forty-six thousand and eight hundred
GZM2400×3000
≤25
1.075-0.4
22-44
two hundred and forty-five
fifty-nine thousand
Main technical parameters of cement mill:
Product specification
(m)
throughput
(t/h)
Mill
form
transmission
form
power
(kw)
Reducer
weight
(t)
remarks
model
speed ratio
Φ2.2×7m
8-9
Open current
edge
three hundred and eighty
ZD70
five
fifty-four
Φ2.2×7.5m
10-11
Open current
edge
three hundred and eighty
ZD70
five
sixty-three
Φ2.2×8m
10-12
Open current
edge
three hundred and eighty
ZD70
five
sixty-five
Φ2.2×9.5m
14-16
Open current
edge
four hundred and seventy-five
ZD70
five
seventy
Φ2.4 ×10m
19-19
Open current
edge
six hundred and thirty
JR75
one point six four
one point five
Excluding motor
Φ2.4×11m
19-21
Open current
edge
six hundred and thirty
RZD80
one point three
one point two
Excluding motor
Φ2.4×13m
21-23
Open current
edge
eight hundred
MBY710
one point one
one point two
Excluding motor
Φ2.6×13m
28-32
Open current
edge
one thousand
MBY800
one point one
one hundred and forty-eight
Φ2.6×13m
28-32
Open current
core
one thousand
MFY100
one point five
one point seven three
Φ3×12m
32-35
Open current
edge
one thousand two hundred and fifty
MBY900
one point one
one point six
Φ3×13m
34-37
Open current
edge
one thousand and four hundred
MBY900
one point one
one point two six
Φ3.2×13m
45-50
Open current
edge
one thousand and six hundred
MBY1000
one point one
one point two six
Φ3.8×13m
60-62
Open current
core
two thousand and five hundred
MFY250
one point five
two hundred and four
Φ4.2×13m
85-87
Open current
core
three thousand five hundred and thirty
JQS3550
one point six
two hundred and fifty-four
Technical parameters of ceramic ball mill:
model
Loading capacity
(ton/time)
Barrel speed (r/min)
Power (kw)
600 × 700
one point zero five
fifty
one point zero two
800 × 600
one point zero seven five
forty-two
three
900 × 1200
one point two
one point five
one point five
1300 × 1500
one point five
thirty-three
one point five
1500 × 1800
one point two
one point five
eleven
1800 × 2000
one point five
twenty-four
fifteen
2600 × 2800
five
one point five
thirty-seven
3000 × 3800
ten
one point five
one point two
3200 × 4600
fifteen
one point five
seventy-five
3400 × 6600
eighteen
thirteen
one hundred and thirty-five
Operating Procedures
1. Before starting, check all parts of machinery and electrical appliances, and check whether all connecting bolts are loose;Whether the lubrication of each lubricating point is normal, whether the transmission device is normal and reliable, whether the protective device is intact, and whether the electrical instruments are sensitive,Motor carbon brushGood contact.
2. Turn the gear for one week, check whether there are obstacles in or around the rotating part of the equipment, and remove them.No one is allowed to stand around during startup.
3. After checking, press the start button to start the motor and pay attention to the current change.The ball grinder shall not be started for more than two consecutive times, with an interval of more than 5 minutes between the first time and the second time. If it is started for the third time, it must be checked with the electrician and fitter before starting.It shall not be started together with other equipment, and shall be started alternately to avoid tripping.
4. After the ball grinder operates normally, it shall strictly follow the provisions of water supply, ore feeding and steel ball adding. Overload operation is prohibited. The idle time shall not exceed 15 minutes to avoid damaging the lining plate.
5. During operation, pay attention to check whether the cylinder leaks slurry, carefully observe whether the current, voltage, feeding and water supply are normal, check that the temperature of the motor and spindle is not more than 60 °С every half an hour, and timely deal with problems found.
6. During operation, pay attention to whether the hollow shaft and oil ring are rotating with oil, and whether the temperature of the hollow shaft is normal. If the hollow shaft is found to be hot and close to burning the tile, take forced cooling measures immediately, and do not stop immediately, so as to avoid "holding the shaft".At the same time, pay attention to check the oil quantity and temperature of each lubricating part, and add oil regularly.
7. Stop feeding ore before stopping the ball mill, and stop feeding water after the concentrate treatment in standby.Press the stop button and pull down the switch.
Maintenance procedures
（1） Maintenance cycle:
1. One month after repair;
2. Minor repair 1 - 3 months;
3. Medium maintenance 12-24 months;
4. Overhaul for 60-120 months.
（2） Maintenance content:
1. Repair: mainly check the oil quantity, adjust the clearance of each part, firm the bolts of each part, replace individual lining plates or check the wear of lining plates, and repair the feeder.
2. Minor repair: check, clean and measure the wear of tooth surface, check the wear of lining plate, and replace it if necessary.
3. Medium repair: replace the feeding parts, replace the transmission pinion runner and bearing, and disassemble the gearbox for inspection.The big gear can be adjusted and used according to the situation after 3-5 years of operation, and the hollow shaft shall be measured after 3-5 years of operation.
4. Overhaul: disassemble, check, clean and measure, repair or replace big gears, hollow shafts, spherical pads, transmission shafts, pinions and cylinders according to wear conditions, repair and replace electrical components, and conduct trial operation acceptance after overhaul of electrical equipment.
（3） Maintenance standard:
1. The upper processing surface of the two bearing pedestals is on the same horizontal plane, the tolerance of the center distance is 1mm, the deviation of the non parallelism of the longitudinal centerline is 0.5mm, and the deviation of the transverse centerline is 0.5mm per meter.
2. The spherical contact surface of the pad seat shall be evenly angled;At least 1-2 points in every 50 Ⅹ 50mm2;The contact surface between the hollow shaft and the pad shall be 90 ° - 100 °, and there shall be no less than 2 points per square inch. The clearance between the journal and both sides of the bearing is approximately the same.
3. The matching surface between the cylinder flange and the front end cover shall be in good contact, and no gasket shall be added. The tolerance of different axes of the two hollow shafts shall be less than 0.8mm.When connecting, assembling and calibrating the big gear ring and the cylinder end cover, the thrust shall be firm, the positioning pin shall be installed, and the radial swing of the gear ring shall not be greater than 0.5mm, and the axial swing shall not be greater than 0.84mm.
4. When installing the lining plate, the end cover should be installed first. The cylinder lining plate should start from the entrance and proceed according to the assembly requirements. All screws should be tightened evenly without water leakage.rubber liner There shall be no gap in the cooperation, and the gap shall be blocked with sponge.
5. The centerline of the pinion shall be parallel to the centerline of the big gear, and the deviation shall not be greater than 0.2mm per meter.The tooth tip clearance is 1/4 module, the tooth side clearance is 1.06 --- 1.8mm, the tooth surface contact area is not less than 50% of the tooth length, and 40% of the tooth height.
6. The transmission couplings of the reducer, motor and transmission shaft shall maintain high coaxiality. The different axes of the center line shall not be more than 0.3mm, and the inclination of the center line shall be less than 1/1000.[10]
Maintenance
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The maintenance and overhaul of the ball mill is a regular work. The quality of the maintenance work directly affects the operation rate and service life of the ball mill. How to properly maintain and overhaul the ball mill during use is described below:
1. All lubricating oil shall be drained, thoroughly cleaned and replaced with new oil when the mill is put into continuous operation for one month.In the future, the oil shall be changed every 6 months in combination with intermediate repair.
2. The lubrication condition and oil level of each lubricating point shall be checked at least every 4 hours.
3. When the mill is running, the mainBearing lubricating oilThe temperature rise of shall not exceed 55 ℃.
4. During the normal operation of the mill, the temperature rise of the drive bearing and reducer shall not exceed 55 ℃, and the maximum temperature shall not exceed 60 ℃.
5. The driving of big and small gears is stable without abnormal noise.Timely adjust the clearance if necessary.
6. The ball mill operates stably without strong vibration.
7. The motor current shall have no abnormal fluctuation.
8. All connecting fasteners shall be free of looseness, and the joint surface shall be free of oil leakage, five tax leakage and ore leakage.
9. The steel ball shall be added in time according to the wear condition.
10. If abnormal conditions are found, the mill shall be stopped immediately for maintenance.
11. The mill liner plate shall be replaced when it is worn by 70% or has a 70mm long crack.
12. Replace the lining plate when the lining plate is loose due to damaged bolts.
13. Replace the main bearing when it is severely worn.
14. The grate plate of the lattice ball mill shall be replaced when it is worn out and cannot be repaired by welding.
15. The big gear surface can be turned over for further use after being worn to a certain extent.
16. The pinion is severely worn and should be replaced.
17. When the feeding and discharging screw is worn, it shall be repaired by welding in time. When the screw is worn to the point where it cannot be repaired by welding, it shall be replaced.
18. The loose or damaged foundation bolts shall be repaired in time.
The maintenance of the ball mill is a regular work, and the quality of the maintenance work directly affects the operation rate and service life of the ball mill.In order to find defects and eliminate hidden dangers in time to ensure the normal operation of the mill, in addition to routine maintenance, the mill also needs to be stopped regularly (recommended once a month), and important parts such as hollow shaft, main bearing, cylinder, reducer, big and small gears, etc. should be carefully inspected and recorded in detail.Properly handle and arrange the intermediate repair and overhaul plan according to the priority of defects.[5]
Problem handling
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The bearing position and bearing chamber of the ball mill reducer are subject to metal fatigue and permanent deformation under the action of heavy load, low speed, heavy load, high speed and high torque starting, equipment vibration and radial impact;There is clearance fit between the bearing inner race and the shaft or between the bearing outer race and the bearing chamber, resulting in wear due to relative movement.Once this problem occurs, it will seriously affect the normal production of the equipment.Ball millReducer bearingIf there is wear in the chamber, it is difficult to repair such problems on site by traditional methods, and it is difficult to repair by outsourcing repair due to the limitation of component materials and wear dimensions, which is usually solved by replacing new components;And the reducer is constantly improving, the parts are updated quickly, and the spare parts take up a huge amount of money.Most developed countries in the 21st century adoptPolymer compositesConduct on-site repair.For different equipment, different operating conditions and different wear conditions, the corresponding repair process can be used to repair quickly, simply and effectively. Especially because of the yield of polymer materials, 100% of the contact area is always maintained, avoiding the generation of fit clearance, making the service life of repaired equipment even exceed that of new equipment, fundamentally solving the wear problem of ball mill shafts.
Specific application case of ball mill: equipment name: ball mill reducer, model: LDH80-6.74, speed ratio: 6.74, input shaft speed: 992 rpm, bearing chamber diameter: 400mm, bearing width: 106mm, wear depth: about 0.5mm.The bearing hole of the output shaft of the reduction gearbox of the pulverizer is worn out, and the upper and lower parts of the bearing chamber are worn to varying degrees. There are 4 bearing chambers in total.Equipment value: several hundred thousand yuan for reducer housing.Equipment problem: 4 bearing chambers of low-speed shaft of 2 reducers are worn.Solution: Metal repair 2211F polymer composite material has excellent adhesion, compression resistance and various comprehensive propertiesBearing chamberFor the purpose of the wear surface benchmark and the corresponding relationship between the bearing and the bearing chamber, rapid construction can realize online repair of the worn bearing chamber, avoid scrapping and replacement, and extend the service life of the equipment.Polymer composite materials and application technologies can enable enterprises to quickly and effectively repair on site at the first time, effectively avoiding the benefit loss caused by long-term equipment downtime and shutdown;Effectively avoid comprehensive factors such as transportation costs, lifting costs and construction safety, ensure personal safety and enterprise losses, and save valuable production time for enterprises.[5]
Troubleshooting
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1. When the ball mill is running, there is regular knocking sound, and the sound is very loud.Some lining plate bolts are not tightened. When the ball mill rotates, the lining plate knocks the grinding cylinder of the ball mill.Judging by soundball mill lining Position, find out the loosenessBolt, otherwise fasten.
2. The temperature of ball mill and motor bearing rises, exceeding the regulations.Manually test whether the temperature of the bearing is too high locally or completely. Check and handle the ball mill from the following points.
（1）lubricationCheck whether the brand of lubricating oil used is consistent with the factory manual of the equipment.
(2) Deterioration.
(3) It is blocked, or the lubricating oil does not enter the lubricating point directly, and the insufficient oil quantity causes heating.
The above problems shall be handled according to their causes. Only the side clearance of the bearing bush is too small, or the bottom contact angle is too large, the grinding cylinder must be jacked up with an oil jack, the bearing bush shall be pulled out from one side of the shaft, and the pad mouth shall be scraped.
3. Bearing heating of ball mill reducer:
In addition to the inspection according to the temperature rise of the ball mill bearing, check whether the exhaust hole of the reducer is blocked, and dredge the exhaust hole.
4. After the ball mill motor with reducer is started, the vibration occurs. The main reason is that the outer ring of the bearing is active.
Treatment method: adjust according to the specified coupling clearance to make the two shafts concentric.Tighten the coupling bolts symmetrically with the same torque.
Rotor imbalanceWhen the ball millrotorDraw out and find static balance separately.
5. Huge vibration occurs when the ball mill reducer drives the mill:
When installing the lining plate of the mill, the secondary grouting was not carried out, or the anchor bolts after the secondary grouting were not fastened properly, so the winch was used to rotate the mill barrel, causing one end of the mill barrel to move, while the two axes were not in a straight line, causing the reducer to drive the mill and generate vibration.
Treatment method: readjust to make the axis of ball mill and reducer on the same plane axis line.Large ball millLarge volume and heavy weight make the foundation sink;Displacement occurs.Set monitoring settlement points beside the foundation;Carry out observation and make adjustment in case of subsidence.
6. Abnormal running sound of ball mill reducer:
The sound of normal operation of ball mill reducer shall be uniform and stable.If the gear has a slight knocking sound, hoarse friction sound, and there is no obvious change during operation, continue to observe, find out the cause, and stop the ball mill for treatment. If the sound is getting louder, stop the ball mill immediately for inspection.
It is worth noting that the balance wheel and intermediate wheel of the ball mill reducer are not installed according to the specified meshing tooth elevation, which will cause the pinion of the high speed shaft of the ball mill to drive the big gear of the intermediate shaft on one side, while the pinion of the intermediate shaft of the ball mill drives the balance wheel, and the balance wheel of the ball mill turns to drive the intermediate shaft on the other side, so that the ball millReducerThere is no even load rotation on both sides, which is very dangerous.[5]
Development issues
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one
The configuration of ball mill is quite expensive: because the rotating speed of ball mill barrel is very low (15~25 revolutions per minute), if ordinary motor is used for driving, expensive speed reducer should be configured.
two
High production cost: the grinding body itself will be abraded and peeled while impacting and grinding materials, and the lining plate and other parts in the cylinder will also be abraded and peeled. Therefore, in the whole cement production process, the amount of iron plates consumed by crushing operations (raw meal preparation, cement grinding) is large. According to analysis, about 1 kg of steel is consumed for each ton of cement produced.
three
Low work efficiency: for example, in the process of producing cement, the electricity used for crushing operations accounts for about 2/3 of the whole plant. According to statistics, the electricity consumption per ton of cement produced is not less than 70 kilowatt hours, but the effective utilization rate of this part of electricity is very low. According to analysis, the power input by the cement ball mill for crushing materials (doing useful work) accounts for only a small part of the power consumption, about 5%~7%,The vast majority of electric energy is consumed in other aspects, which is mainly transformed into heat energy and sound energy and disappears, which is a great waste.
four
Heavy body: the total weight of a large ball mill can be more than several hundred tons, so the one-time investment must be large.
five
At present, most ball mills in China are still under manual control, resulting in large changes in materials in the mill, low grinding efficiency, large unit power consumption, and large loss of steel balls and liners.Moreover, due to the large change of grinding state, it is difficult to ensure the uniformity of material fineness.Planetary ball mill is designed for crushing, grinding and dispersing powders, and is widely used in laboratory research.Its working principle is to use the high-speed running force in the grinding tank of the mill to grind the materials. During the overturning process, the materials will go through a series of shearing, impact, rolling, dispersion, and finally complete the grinding operation.There are four grinding tanks on a rotary table of the planetary ball mill, and they rotate with the grinding shaft during operation, that is, the planetary motion.In the process of movement, the four can bodies grind materials through mutual friction and collision.The mill can select the corresponding friction method according to the size of abrasive particles of materials, and the final abrasive particle diameter can reach 0.1 μ m.It can well meet the requirements of various process parameters, and is the preferred equipment for research on crushing process, new materials and coatings.[5]
Operation steps
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In order to increase the output of the ball mill, we should not only start from the process factors and mechanical factors, but also ensure the effective management and control of the ball mill!The main purpose of management is to prevent the occurrence and elimination of defective operation status, realize the fine operation of equipment, and achieve high-quality and high platform production with low power consumption and ball consumption.
Steps to achieve fine operation: reasonable production index refers to the operation target, and the upper and lower limits of the index must be determined;Correct operating parameters are the process path that must be controlled;Troubleshooting measures refer to the prompt and quick troubleshooting of faults when operating methods are implemented.Today, we will elaborate the steps of fine operation:
1. Reasonable indicators
Reasonable production indicators can not only improve the enthusiasm of employees, but also be a measure of cost control for enterprises. Indicators with upper and lower limits can be determined through the performance of equipment and various factors within the enterprise.
2. Correct operating parameters
The operation and control of ball mill is mainly aimed at the two parameters of circulating load and powder selection efficiency, and the three parameters of air, material and fineness are reasonably matched to control the grinding condition and fineness of finished products.
3. Troubleshooting
Troubleshooting, how to find the cause in time, and how to remove the fault safely and reliably are necessary for fine operation.
Correct operation steps
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1. Before starting the equipment, we first need to check the lubrication between the mechanical parts. After confirming that all the preparations have been completed, first start the discharge device of the ball mill, the main power supply of the ball mill, and finally start the feeding device.
2. Before materials enter the box, first check whether the steel plate balls installed in the box are properly set and the quantity is appropriate.3. After starting the ball mill, it is necessary to carry out an empty box test run, and the operation can be started only after ensuring that the contact surface between the box and the mechanical parts is sealed and well lubricated.4. Moreover, the start-up of the ball mill is carried out in cooperation with the personnel of other posts. The personnel operating the machine must see the corresponding command signal before proceeding.5. The discharge port can be closed only after it is confirmed that both the material and the feed port are stopped.6. At ordinary times, the maintenance of equipment should be timely, reasonable and comprehensive.After the ball mill is completely stopped, the grinding medium in the box needs to be carefully cleaned to extend the service life of mechanical equipment and reduce industrial costs.
Shopping Skills
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1. Ensure the production capacity of the mill
The selected grinding equipment can achieve the specified output under the condition of ensuring the required grinding fineness.
2. The production capacity should be higher than the design
The design shall consider the change of ore hardness and fineness. Generally, when the ore in the deep part of the deposit becomes hard or thin, the selected grinding machine shall also be able to adapt to it and ensure the smooth production at the initial stage.
3. Grinding test must be conducted
If there is no actual data as the basis in the design, the grinding test must be required. Especially for large concentrators, the selection calculation and scale up of grinding machines should be carried out from the obtained basic data.
4. Due consideration shall be given to equipment enlargement
Large scale equipment is the trend of design since the 21st century.Due to the large-scale equipment, the total equipment is light in weight, occupies less land, has fewer production systems, fewer operators and auxiliary systems, and the corresponding investment and production costs are low.However, the operation and management level of large equipment is high. If the operation rate is slightly reduced, the output of the concentrator will be greatly reduced.
5. Select equipment with high operation rate
In the same type of equipment, there are good and bad, new and old.Sometimes the operation rate of rod mill and autogenous mill is lower, but they are still applicable under specific conditions.In principle, equipment with high operation rate shall be selected to reduce maintenance and shutdown time.
6. Understand the hardness, grade and other properties of minerals, and try to choose energy-saving ball mill;
7. Know the fineness required by mineral grinding, and select the aperture and bin location of the closed plate according to the fineness required by your own mineral;
8. The diameter and length of ball mill shall be properly selected according to the production requirements
9. Select a new generation of modified ball mill, and it is better to purchase it from a professional ball mill manufacturer corresponding to your mine
10. Select the manufacturers of the big teeth and small teeth of the ball mill, as well as the motor and reducer. According to the price of the ball mill, the materials of the lining plate and the thickness of the mill body steel plate are required.[5]
