wet ball mill/wet type ball mill/wet ball milling machine--zhengzhou bobang heavy industry machinery co.,ltd

wet ball mill/wet type ball mill/wet ball milling machine--zhengzhou bobang heavy industry machinery co.,ltd

Wet type ball mill are mostly used in the industry production. It is to increase the high grinding efficiency under the ball mill grinding and striking, from which the granularity is even and no flying dust with little noise, being the most universal powder machine in the benefication as powder grinding the ferrous metal like gold, silver, plumbum, zinc,copper,molybdenum,manganese,tungsten etc, as the nonmetal powder grinding like graphite,feldspar, potash feldspar, phosphorus ore, fluorite, clay, and swell soil etc. The wet type ball mill need to add the liquid into the grinding ball media auxiliary (water or ethanol). The material output gate is trumpet shape, with screw device inside, easy to discharging the material.

Copyright Zhengzhou Bobang Heavy Industry Machinery Co.,Ltd. E-mail : [email protected] Tel0086- 86656957 Address No.11 West Construction Road, Zhongyuan District,Zhengzhou City,Henan Province, China

how to install and align the girth gear and pinion | prmdrive

how to install and align the girth gear and pinion | prmdrive

There are two kinds of transmission forms of ball mill, i.e. center transmission and edge transmission. The two kinds of transmission have their own advantages and disadvantages. The central transmission adopts a high-speed planetary reducer, which is safe and reliable, with a service life of up to 10 years, low maintenance cost, but large one-time investment.

The girth gear(big ring gear) and pinion are the key of the edge transmission device. Their reliable operation is directly related to the stable production of the mill. In order to ensure their reliable operation, in addition to strengthening the daily maintenance and regular maintenance, the installation and alignment of the girth gear and pinion are also important.

Cleaning of gear ring and mill flange positioning of gear ring coarse alignment of large gear ring positioning and coarse alignment of pinion installation of motor reducer primary grouting fine alignment of large gear ring fine alignment of pinion fine alignment of motor reducer.

In order to reduce the workload of installing gears on site, hobs with similar wear conditions should be selected during finishing of large and small gears, so as to make the meshing profile of large and small gears as close as possible and increase the contact area. Before the gear is installed, the tooth thickness vernier caliper can be used to check the tooth thickness of the gear ring indexing circle chord, or the tooth shape template can be made of sheet steel to retest the tooth shape. If necessary, it needs to be repaired on site.

After the ring gear is closed to the cylinder according to the installation mark, tighten the connecting bolts on the mating surface, and check whether there is a step on the side of the gear (the step is required to be as small as possible, otherwise it will affect the end runout of the ring gear). Use a feeler gauge of 0.04mm to check the matching condition. It is required that the insertion depth is not more than 50mm, and the cumulative length of the gap is not more than 1 / 4 of the tooth width.

When measuring the radial jump, a winch shall be used for disc grinding. Before disc grinding, the sliding shoes or hollow shaft oil station of the mill must be opened, and the floating capacity of the mill shall be checked with a dial indicator. Only when the floating capacity reaches 0.15mm can the disc grinding be carried out.

Most on-site dial gauges are installed in Figure 1 or figure 2, both of which have advantages and disadvantages. The position in Figure 1 can directly measure the radial jump at the top of the gear, but a worker is required to press and hold the dial indicator under the gear ring, and release the dial indicator when the tooth to be measured turns around, which is complex to operate and easy to cause injury to workers; the position in Figure 2 is simple to operate, but it is not the real radial jump of the gear. Therefore, we suggest to make a measuring tool (Figure 3) and install it on the head of the dial indicator, so that it is easier to measure the radial jump (Figure 4).

When measuring the end jump, a winch is still needed for disc grinding. Before disc grinding, the sliding shoes or hollow shaft oil station of the mill must be opened, and the floating capacity of the mill shall be checked with a dial indicator. Only when the floating capacity reaches 0.15mm, can the disc grinding be carried out. If the site personnel are sufficient, the end jump and the radial jump can be measured at the same time.

The end run out must be detected by double meter method to eliminate the error caused by the axial movement of the mill. When two dial indicators are installed on the same side of the ring gear, as shown in the left side of Figure 6, calculate the end jump according to line 4 of Table 1; when two dial indicators are installed on both sides of the ring gear, as shown in the right side of Figure 6, calculate the end jump according to line 5 of Table 1. The installation position of the two dial indicators must be 180 and 8 points need to be measured around the ring gear, as shown in Figure 5.

After the alignment of the big gear ring is completed, the pinion device shall be put in place according to the requirements of the drawings, the center height of the pinion shall be retested with a level gauge, and the sizing block shall be replaced if necessary to adjust the elevation. Use feeler gauge to roughly find tooth top clearance and tooth side clearance, and install diaphragm coupling, main reducer, auxiliary transmission device and main reducer lubricating oil station.

Grouting the anchor bolts of the pinion device once. After the primary grouting strength reaches 70% of the design strength, use the auxiliary drive plate to grind, and retest the runout of the big gear ring again, and then start the fine alignment of the pinion.

Most of the site is to use feeler gauge and red lead powder to detect the contact condition of the gear. There is no basis for the adjustment of this detection method, so the adjustment amount of the bearing seat can only be determined by experience, which is time-consuming and laborious. Compared with this method, the lead wire method can accurately calculate the amount of each adjustment, which is more accurate and saves installation time.

Before alignment, the lead wire shall be used to make a measuring tool as shown in Figure 7. In the figure, the left tool is used to measure the side gap and the right tool is used to measure the top gap. Set 12 sets of jackscrews at the 1-12 positions of the pinion bearing pedestal, and set 8 dial indicators at the 1-8 positions, as shown in Figure 8.

If there is no error in the processing of large and small gears, the graduation circle shall be tangent during installation, and its top clearance shall be 1 / 4 gear module. Considering the processing error caused by the hob wear and the floating amount of the mill when it is running relative to the static state and other factors, in order to avoid the gnawing back of the gear when it is running, it is recommended to increase the top clearance by 1.5-2.5mm during the installation, which can be adjusted according to the actual situation on site.

On the basis of meeting the above requirements, the larger the top clearance and side clearance is, the better, and the side clearance deviation on both sides of the gear is not more than 0.1mm, and the top clearance deviation on both sides of the gear is not more than 0.3mm. 8 points are measured in a week, and 5 points meet the requirements.

(3) Measuring points: 4, 7. If another point meets the requirements, the alignment is completed (i.e. at least 5 of the 8 points meet the requirements), otherwise, it is necessary to re measure after adjustment.

When adjusting the top clearance, refer to the reading of 5-8 position dial indicator and adjust 1-4 jacking screws; when adjusting the side clearance, refer to the reading of 1-8 position dial indicator and add or remove the adjusting gasket under the bearing pedestal.

After the lead wire method is used for alignment, the contact condition of the engagement surface of the large and small gears shall be retested with blue or red lead powder. The contact area shall not be less than 40% of the tooth height and 50% of the tooth width, and the contact on both sides of the gear shall be uniform, and only one side contact is not allowed, otherwise further adjustment is required.

rod mill | henan deya machinery co., ltd

rod mill | henan deya machinery co., ltd

The final stages of comminution are performed in tumbling mills using steel balls as the grinding medium and so designated ball mills. Since balls have a greater surface area per unit weight than rods, they are better suited for fine finishing. The term ball mill is restricted to those having a length to diameter ratio of 1.5 to 1 and less. Ball mills in which the length to diameter ratio is between 3 and 5 are designated tube mills. These are sometimes divided into several longitudinal compartments, each having a different charge composition; the charges can be steel balls or rods, or pebbles, and they are often used dry to grind cement clinker, gypsum, and phosphate. Tube mills having only one compartment and a charge of hard, screened ore particles as the grinding medium are known as pebble mills. They are widely used in the South African gold mines. Since the weight of pebbles per unit volume is 35-55% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly higher operating cost. However, it is claimed that the increment in capital cost can be justified economically by a reduction in operating cost attributed to the lower cost of the grinding medium. This may, however, be partially offset by higher energy cost per tonne of finished product. Read more

Ball mills are a similar shape to that of the rod mills except that they are shorter with length to diameter ratios of1 to 1.5.As the name implies, the grinding media in these mills are steel balls.The particles size of the feed usually does not exceed 2.5 cm.The grinding is carried out by balls being carried up the side of the mill such that they release and fall to the point where they impact the ore particles in trailing bottom region of the slurry.If the mill is rotated too fast, the balls can be thrown too far and just strike the far end of the mill and conversely, if the mill is rotated to slow, the efficiency of the grinding process significantly reduced. Ball mills are suited for finer grinding as larger particles do not impede the impact on to smaller particle as in rod mills.

Rod mills are long cylinders filled with steel rods that grind by compressive forces and abrasion. The length of the cylinder is typically 1.5 to 2.5 times longer than the diameter. As the mill turns, the rods cascade over each other in relatively parallel fashion. One of the primary advantages of a rod mill is that it prevents over-grinding of softer particles because coarser particles act as bridges and preferentially take the compressive forces. Rod mills can take particles as coarse as 5 cm. Many of the newer operations tend to install ball mills in combination with SAG mills and avoid rod mills due the cost of the media, the cost of replacing rods and general maintenance costs. Many older operations have rod mills in combination with ball mills.

Rod mills are charged initially with a selection of rods of assorted diameters, the proportion of each size being calculated to provide maximum grinding surface and to approximate to a seasoned or equilibrium charge. A seasoned charge will contain rods of varying diameters ranging from fresh replacements to those which have worn down to such a size as to warrant removal. Actual diameters in use range from 25 to 150mm. The smaller the rod the larger is the total surface area and hence the greater is the grinding efficiency. The largest diameter should be no greater than that required to break the largest particle in the feed. A coarse feed or product normally requires larger rods. Generally, rods should be removed when they are worn down to about 25 mm in diameter or less, depending on the application, as small ones tend to bend or break. High carbon steel rods are used as they are hard, and break rather than warp when worn, so do not entangle with other rods. Optimum grinding rates are obtained with new rods when the volume is 35% of that of the shell. Thus reduces to 20-30% with wear and is maintained at this figure by substitution of new rods for worn ones. This proportion means that with normal voidage, about 45% of the mill volume is occupied. Overcharging results in inefficient grinding and increased liner and rod consumption. Rod consumption varies widely with the characteristics of the mill feed, mill speed, rod length, and product size; it is normally in the range 0.1-1.0 kg of steel per tonne of ore for wet grinding, being less for dry grinding. Rod mills are normally run at between 50 and 65% of the critical speed, so that the rods cascade rather than cataract; many operating mills have been sped up to close t0 80% of critical speed without any reports of excessive wear. The feed pulp density is usually between 65 and 85u/o solids by weight, finer feeds requiring lower pulp densities. The grinding action results from line contact of the rods on the ore particles; the rods tumble in essentially a parallel alignment, and also spin, thus acting rather like a series of crushing rolls. The coarse feed tends to spread the rods at the feed end, so producing a wedge- or cone-shaped array. This increases the tendency for grinding to take place preferentially on the larger particles, thereby producing a minimum amount of extremely fine material. This selective grinding gives a product of relatively narrow size range, with little oversize or slimes. Rod mills are therefore suitable for preparation of feed to gravity concentrators, certain flotation processes with slime problems, magnetic cobbing, and ball mills. They are nearly always run in open circuit because of this controlled size reduction.

henan mining machinery and equipment manufacturer - aligning a train drive on a ball mill

henan mining machinery and equipment manufacturer - aligning a train drive on a ball mill

Whether you operate a ball mill, ... Pinion maintenance can be one area of the mills drive train that is often neglected by the ... Fixed Plant Maintenance ...CachedUsed Ball Mills Capacity Cost for Cement Plant in USA. ... In cement grinding plant, ball mill firstly is applied to grind cement materials for example crushed ...

Ore beneficiation equipment, sand making equipment, crushing equipment and powder grinding equipment, which are widely used in various industries such as metallurgy, mine, chemistry, building material, coal, refractory and ceramics.

ball mill services world leader in hot kiln alignment

ball mill services world leader in hot kiln alignment

We are well experienced in various design of OEM makes ball mills in order to evaluate the condition of ball mill. An inspection to be executed by our Geoservex Mill specialists with in-depth knowledge of complete mill components for ensuring optimal, trouble-free operation.

When inspections of mill components have been carried out, our specialists provide a final comprehensive technical evaluation and analysis report, as well as recommendations for repairs, spare parts, adjustments and optimizations.

The report is an essential document to help production and maintenance departments plan future maintenance activities, such as ensuring that the right spare parts are available, and most importantly avoid unscheduled, costly shutdowns.

ball mills - an overview | sciencedirect topics

ball mills - an overview | sciencedirect topics

A ball mill is a type of grinder used to grind and blend bulk material into QDs/nanosize using different sized balls. The working principle is simple; impact and attrition size reduction take place as the ball drops from near the top of a rotating hollow cylindrical shell. The nanostructure size can be varied by varying the number and size of balls, the material used for the balls, the material used for the surface of the cylinder, the rotation speed, and the choice of material to be milled. Ball mills are commonly used for crushing and grinding the materials into an extremely fine form. The ball mill contains a hollow cylindrical shell that rotates about its axis. This cylinder is filled with balls that are made of stainless steel or rubber to the material contained in it. Ball mills are classified as attritor, horizontal, planetary, high energy, or shaker.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles, as well as collision energy. These forces are derived from the rotational motion of the balls and movement of particles within the mill and contact zones of colliding balls.

By rotation of the mill body, due to friction between mill wall and balls, the latter rise in the direction of rotation till a helix angle does not exceed the angle of repose, whereupon, the balls roll down. Increasing of rotation rate leads to growth of the centrifugal force and the helix angle increases, correspondingly, till the component of weight strength of balls become larger than the centrifugal force. From this moment the balls are beginning to fall down, describing during falling certain parabolic curves (Figure 2.7). With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls are attached to the wall due to centrifugation:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 6580% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

The degree of filling the mill with balls also influences productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 3035% of its volume.

The mill productivity also depends on many other factors: physical-chemical properties of feed material, filling of the mill by balls and their sizes, armor surface shape, speed of rotation, milling fineness and timely moving off of ground product.

where b.ap is the apparent density of the balls; l is the degree of filling of the mill by balls; n is revolutions per minute; 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption; a mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, i.e. during grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction, and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles as well as collision energy. These forces are derived from the rotational motion of the balls and the movement of particles within the mill and contact zones of colliding balls.

By the rotation of the mill body, due to friction between the mill wall and balls, the latter rise in the direction of rotation until a helix angle does not exceed the angle of repose, whereupon the balls roll down. Increasing the rotation rate leads to the growth of the centrifugal force and the helix angle increases, correspondingly, until the component of the weight strength of balls becomes larger than the centrifugal force. From this moment, the balls are beginning to fall down, describing certain parabolic curves during the fall (Fig. 2.10).

With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls remain attached to the wall with the aid of centrifugal force is:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 65%80% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

where db.max is the maximum size of the feed (mm), is the compression strength (MPa), E is the modulus of elasticity (MPa), b is the density of material of balls (kg/m3), and D is the inner diameter of the mill body (m).

The degree of filling the mill with balls also influences the productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 30%35% of its volume.

The productivity of ball mills depends on the drum diameter and the relation of drum diameter and length. The optimum ratio between length L and diameter D, L:D, is usually accepted in the range 1.561.64. The mill productivity also depends on many other factors, including the physical-chemical properties of the feed material, the filling of the mill by balls and their sizes, the armor surface shape, the speed of rotation, the milling fineness, and the timely moving off of the ground product.

where D is the drum diameter, L is the drum length, b.ap is the apparent density of the balls, is the degree of filling of the mill by balls, n is the revolutions per minute, and 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption. A mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, that is, during the grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

Milling time in tumbler mills is longer to accomplish the same level of blending achieved in the attrition or vibratory mill, but the overall productivity is substantially greater. Tumbler mills usually are used to pulverize or flake metals, using a grinding aid or lubricant to prevent cold welding agglomeration and to minimize oxidation [23].

Cylindrical Ball Mills differ usually in steel drum design (Fig. 2.11), which is lined inside by armor slabs that have dissimilar sizes and form a rough inside surface. Due to such juts, the impact force of falling balls is strengthened. The initial material is fed into the mill by a screw feeder located in a hollow trunnion; the ground product is discharged through the opposite hollow trunnion.

Cylindrical screen ball mills have a drum with spiral curved plates with longitudinal slits between them. The ground product passes into these slits and then through a cylindrical sieve and is discharged via the unloading funnel of the mill body.

Conical Ball Mills differ in mill body construction, which is composed of two cones and a short cylindrical part located between them (Fig. 2.12). Such a ball mill body is expedient because efficiency is appreciably increased. Peripheral velocity along the conical drum scales down in the direction from the cylindrical part to the discharge outlet; the helix angle of balls is decreased and, consequently, so is their kinetic energy. The size of the disintegrated particles also decreases as the discharge outlet is approached and the energy used decreases. In a conical mill, most big balls take up a position in the deeper, cylindrical part of the body; thus, the size of the balls scales down in the direction of the discharge outlet.

For emptying, the conical mill is installed with a slope from bearing to one. In wet grinding, emptying is realized by the decantation principle, that is, by means of unloading through one of two trunnions.

With dry grinding, these mills often work in a closed cycle. A scheme of the conical ball mill supplied with an air separator is shown in Fig. 2.13. Air is fed to the mill by means of a fan. Carried off by air currents, the product arrives at the air separator, from which the coarse particles are returned by gravity via a tube into the mill. The finished product is trapped in a cyclone while the air is returned in the fan.

The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 11.5 times the shell diameter (Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, AG mills, or SAG mills.

Ball mills are filled up to 40% with steel balls (with 3080mm diameter), which effectively grind the ore. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture.

When hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. As mentioned earlier, pebble mills are widely used in the North American taconite iron ore operations. Since the weight of pebbles per unit volume is 3555% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus, in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly a higher capital cost. However, the increase in capital cost is justified economically by a reduction in operating cost attributed to the elimination of steel grinding media.

In general, ball mills can be operated either wet or dry and are capable of producing products in the order of 100m. This represents reduction ratios of as great as 100. Very large tonnages can be ground with these ball mills because they are very effective material handling devices. Ball mills are rated by power rather than capacity. Today, the largest ball mill in operation is 8.53m diameter and 13.41m long with a corresponding motor power of 22MW (Toromocho, private communications).

Modern ball mills consist of two chambers separated by a diaphragm. In the first chamber the steel-alloy balls (also described as charge balls or media) are about 90mm diameter. The mill liners are designed to lift the media as the mill rotates, so the comminution process in the first chamber is dominated by crushing. In the second chamber the ball diameters are of smaller diameter, between 60 and 15mm. In this chamber the lining is typically a classifying lining which sorts the media so that ball size reduces towards the discharge end of the mill. Here, comminution takes place in the rolling point-contact zone between each charge ball. An example of a two chamber ball mill is illustrated in Fig. 2.22.15

Much of the energy consumed by a ball mill generates heat. Water is injected into the second chamber of the mill to provide evaporative cooling. Air flow through the mill is one medium for cement transport but also removes water vapour and makes some contribution to cooling.

Grinding is an energy intensive process and grinding more finely than necessary wastes energy. Cement consists of clinker, gypsum and other components mostly more easily ground than clinker. To minimise over-grinding modern ball mills are fitted with dynamic separators (otherwise described as classifiers or more simply as separators). The working principle is that cement is removed from the mill before over-grinding has taken place. The cement is then separated into a fine fraction, which meets finished product requirements, and a coarse fraction which is returned to mill inlet. Recirculation factor, that is, the ratio of mill throughput to fresh feed is up to three. Beyond this, efficiency gains are minimal.

For more than 50years vertical mills have been the mill of choice for grinding raw materials into raw meal. More recently they have become widely used for cement production. They have lower specific energy consumption than ball mills and the separator, as in raw mills, is integral with the mill body.

In the Loesche mill, Fig. 2.23,16 two pairs of rollers are used. In each pair the first, smaller diameter, roller stabilises the bed prior to grinding which takes place under the larger roller. Manufacturers use different technologies for bed stabilisation.

Comminution in ball mills and vertical mills differs fundamentally. In a ball mill, size reduction takes place by impact and attrition. In a vertical mill the bed of material is subject to such a high pressure that individual particles within the bed are fractured, even though the particles are very much smaller than the bed thickness.

Early issues with vertical mills, such as narrower PSD and modified cement hydration characteristics compared with ball mills, have been resolved. One modification has been to install a hot gas generator so the gas temperature is high enough to partially dehydrate the gypsum.

For many decades the two-compartment ball mill in closed circuit with a high-efficiency separator has been the mill of choice. In the last decade vertical mills have taken an increasing share of the cement milling market, not least because the specific power consumption of vertical mills is about 30% less than that of ball mills and for finely ground cement less still. The vertical mill has a proven track record in grinding blastfurnace slag, where it has the additional advantage of being a much more effective drier of wet feedstock than a ball mill.

The vertical mill is more complex but its installation is more compact. The relative installed capital costs tend to be site specific. Historically the installed cost has tended to be slightly higher for the vertical mill.

Special graph paper is used with lglg(1/R(x)) on the abscissa and lg(x) on the ordinate axes. The higher the value of n, the narrower the particle size distribution. The position parameter is the particle size with the highest mass density distribution, the peak of the mass density distribution curve.

Vertical mills tend to produce cement with a higher value of n. Values of n normally lie between 0.8 and 1.2, dependent particularly on cement fineness. The position parameter is, of course, lower for more finely ground cements.

Separator efficiency is defined as specific power consumption reduction of the mill open-to-closed-circuit with the actual separator, compared with specific power consumption reduction of the mill open-to-closed-circuit with an ideal separator.

As shown in Fig. 2.24, circulating factor is defined as mill mass flow, that is, fresh feed plus separator returns. The maximum power reduction arising from use of an ideal separator increases non-linearly with circulation factor and is dependent on Rf, normally based on residues in the interval 3245m. The value of the comminution index, W, is also a function of Rf. The finer the cement, the lower Rf and the greater the maximum power reduction. At C = 2 most of maximum power reduction is achieved, but beyond C = 3 there is very little further reduction.

Separator particle separation performance is assessed using the Tromp curve, a graph of percentage separator feed to rejects against particle size range. An example is shown in Fig. 2.25. Data required is the PSD of separator feed material and of rejects and finished product streams. The bypass and slope provide a measure of separator performance.

The particle size is plotted on a logarithmic scale on the ordinate axis. The percentage is plotted on the abscissa either on a linear (as shown here) or on a Gaussian scale. The advantage of using the Gaussian scale is that the two parts of the graph can be approximated by two straight lines.

The measurement of PSD of a sample of cement is carried out using laser-based methodologies. It requires a skilled operator to achieve consistent results. Agglomeration will vary dependent on whether grinding aid is used. Different laser analysis methods may not give the same results, so for comparative purposes the same method must be used.

The ball mill is a cylindrical drum (or cylindrical conical) turning around its horizontal axis. It is partially filled with grinding bodies: cast iron or steel balls, or even flint (silica) or porcelain bearings. Spaces between balls or bearings are occupied by the load to be milled.

Following drum rotation, balls or bearings rise by rolling along the cylindrical wall and descending again in a cascade or cataract from a certain height. The output is then milled between two grinding bodies.

Ball mills could operate dry or even process a water suspension (almost always for ores). Dry, it is fed through a chute or a screw through the units opening. In a wet path, a system of scoops that turn with the mill is used and it plunges into a stationary tank.

Mechanochemical synthesis involves high-energy milling techniques and is generally carried out under controlled atmospheres. Nanocomposite powders of oxide, nonoxide, and mixed oxide/nonoxide materials can be prepared using this method. The major drawbacks of this synthesis method are: (1) discrete nanoparticles in the finest size range cannot be prepared; and (2) contamination of the product by the milling media.

More or less any ceramic composite powder can be synthesized by mechanical mixing of the constituent phases. The main factors that determine the properties of the resultant nanocomposite products are the type of raw materials, purity, the particle size, size distribution, and degree of agglomeration. Maintaining purity of the powders is essential for avoiding the formation of a secondary phase during sintering. Wet ball or attrition milling techniques can be used for the synthesis of homogeneous powder mixture. Al2O3/SiC composites are widely prepared by this conventional powder mixing route by using ball milling [70]. However, the disadvantage in the milling step is that it may induce certain pollution derived from the milling media.

In this mechanical method of production of nanomaterials, which works on the principle of impact, the size reduction is achieved through the impact caused when the balls drop from the top of the chamber containing the source material.

A ball mill consists of a hollow cylindrical chamber (Fig. 6.2) which rotates about a horizontal axis, and the chamber is partially filled with small balls made of steel, tungsten carbide, zirconia, agate, alumina, or silicon nitride having diameter generally 10mm. The inner surface area of the chamber is lined with an abrasion-resistant material like manganese, steel, or rubber. The magnet, placed outside the chamber, provides the pulling force to the grinding material, and by changing the magnetic force, the milling energy can be varied as desired. The ball milling process is carried out for approximately 100150h to obtain uniform-sized fine powder. In high-energy ball milling, vacuum or a specific gaseous atmosphere is maintained inside the chamber. High-energy mills are classified into attrition ball mills, planetary ball mills, vibrating ball mills, and low-energy tumbling mills. In high-energy ball milling, formation of ceramic nano-reinforcement by in situ reaction is possible.

It is an inexpensive and easy process which enables industrial scale productivity. As grinding is done in a closed chamber, dust, or contamination from the surroundings is avoided. This technique can be used to prepare dry as well as wet nanopowders. Composition of the grinding material can be varied as desired. Even though this method has several advantages, there are some disadvantages. The major disadvantage is that the shape of the produced nanoparticles is not regular. Moreover, energy consumption is relatively high, which reduces the production efficiency. This technique is suitable for the fabrication of several nanocomposites, which include Co- and Cu-based nanomaterials, Ni-NiO nanocomposites, and nanocomposites of Ti,C [71].

Planetary ball mill was used to synthesize iron nanoparticles. The synthesized nanoparticles were subjected to the characterization studies by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques using a SIEMENS-D5000 diffractometer and Hitachi S-4800. For the synthesis of iron nanoparticles, commercial iron powder having particles size of 10m was used. The iron powder was subjected to planetary ball milling for various period of time. The optimum time period for the synthesis of nanoparticles was observed to be 10h because after that time period, chances of contamination inclined and the particles size became almost constant so the powder was ball milled for 10h to synthesize nanoparticles [11]. Fig. 12 shows the SEM image of the iron nanoparticles.

The vibratory ball mill is another kind of high-energy ball mill that is used mainly for preparing amorphous alloys. The vials capacities in the vibratory mills are smaller (about 10 ml in volume) compared to the previous types of mills. In this mill, the charge of the powder and milling tools are agitated in three perpendicular directions (Fig. 1.6) at very high speed, as high as 1200 rpm.

Another type of the vibratory ball mill, which is used at the van der Waals-Zeeman Laboratory, consists of a stainless steel vial with a hardened steel bottom, and a single hardened steel ball of 6 cm in diameter (Fig. 1.7).

The mill is evacuated during milling to a pressure of 106 Torr, in order to avoid reactions with a gas atmosphere.[44] Subsequently, this mill is suitable for mechanical alloying of some special systems that are highly reactive with the surrounding atmosphere, such as rare earth elements.

In spite of the traditional approaches used for gas-solid reaction at relatively high temperature, Calka etal.[58] and El-Eskandarany etal.[59] proposed a solid-state approach, the so-called reactive ball milling (RBM), used for preparations different families of meal nitrides and hydrides at ambient temperature. This mechanically induced gas-solid reaction can be successfully achieved, using either high- or low-energy ball-milling methods, as shown in Fig.9.5. However, high-energy ball mill is an efficient process for synthesizing nanocrystalline MgH2 powders using RBM technique, it may be difficult to scale up for matching the mass production required by industrial sector. Therefore, from a practical point of view, high-capacity low-energy milling, which can be easily scaled-up to produce large amount of MgH2 fine powders, may be more suitable for industrial mass production.

In both approaches but with different scale of time and milling efficiency, the starting Mg metal powders milled under hydrogen gas atmosphere are practicing to dramatic lattice imperfections such as twinning and dislocations. These defects are caused by plastics deformation coupled with shear and impact forces generated by the ball-milling media.[60] The powders are, therefore, disintegrated into smaller particles with large surface area, where very clean or fresh oxygen-free active surfaces of the powders are created. Moreover, these defects, which are intensively located at the grain boundaries, lead to separate micro-scaled Mg grains into finer grains capable to getter hydrogen by the first atomically clean surfaces to form MgH2 nanopowders.

Fig.9.5 illustrates common lab scale procedure for preparing MgH2 powders, starting from pure Mg powders, using RBM via (1) high-energy and (2) low-energy ball milling. The starting material can be Mg-rods, in which they are processed via sever plastic deformation,[61] using for example cold-rolling approach,[62] as illustrated in Fig.9.5. The heavily deformed Mg-rods obtained after certain cold rolling passes can be snipped into small chips and then ball-milled under hydrogen gas to produce MgH2 powders.[8]

Planetary ball mills are the most popular mills used in scientific research for synthesizing MgH2 nanopowders. In this type of mill, the ball-milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial and the effective centrifugal force reaches up to 20 times gravitational acceleration. The centrifugal forces caused by the rotation of the supporting disc and autonomous turning of the vial act on the milling charge (balls and powders). Since the turning directions of the supporting disc and the vial are opposite, the centrifugal forces alternately are synchronized and opposite. Therefore, the milling media and the charged powders alternatively roll on the inner wall of the vial, and are lifted and thrown off across the bowl at high speed.

In the typical experimental procedure, a certain amount of the Mg (usually in the range between 3 and 10g based on the vials volume) is balanced inside an inert gas atmosphere (argon or helium) in a glove box and sealed together with certain number of balls (e.g., 2050 hardened steel balls) into a hardened steel vial (Fig.9.5A and B), using, for example, a gas-temperature-monitoring system (GST). With the GST system, it becomes possible to monitor the progress of the gas-solid reaction taking place during the RBM process, as shown in Fig.9.5C and D. The temperature and pressure changes in the system during milling can be also used to realize the completion of the reaction and the expected end product during the different stages of milling (Fig.9.5D). The ball-to-powder weight ratio is usually selected to be in the range between 10:1 and 50:1. The vial is then evacuated to the level of 103bar before introducing H2 gas to fill the vial with a pressure of 550bar (Fig.9.5B). The milling process is started by mounting the vial on a high-energy ball mill operated at ambient temperature (Fig.9.5C).

Tumbling mill is cylindrical shell (Fig.9.6AC) that rotates about a horizontal axis (Fig.9.6D). Hydrogen gas is pressurized into the vial (Fig.9.6C) together with Mg powders and ball-milling media, using ball-to-powder weight ratio in the range between 30:1 and 100:1. Mg powder particles meet the abrasive and impacting force (Fig.9.6E), which reduce the particle size and create fresh-powder surfaces (Fig.9.6F) ready to react with hydrogen milling atmosphere.

Figure 9.6. Photographs taken from KISR-EBRC/NAM Lab, Kuwait, show (A) the vial and milling media (balls) and (B) the setup performed to charge the vial with 50bar of hydrogen gas. The photograph in (C) presents the complete setup of GST (supplied by Evico-magnetic, Germany) system prior to start the RBM experiment for preparing of MgH2 powders, using Planetary Ball Mill P400 (provided by Retsch, Germany). GST system allows us to monitor the progress of RBM process, as indexed by temperature and pressure versus milling time (D).

The useful kinetic energy in tumbling mill can be applied to the Mg powder particles (Fig.9.7E) by the following means: (1) collision between the balls and the powders; (2) pressure loading of powders pinned between milling media or between the milling media and the liner; (3) impact of the falling milling media; (4) shear and abrasion caused by dragging of particles between moving milling media; and (5) shock-wave transmitted through crop load by falling milling media. One advantage of this type of mill is that large amount of the powders (100500g or more based on the mill capacity) can be fabricated for each milling run. Thus, it is suitable for pilot and/or industrial scale of MgH2 production. In addition, low-energy ball mill produces homogeneous and uniform powders when compared with the high-energy ball mill. Furthermore, such tumbling mills are cheaper than high-energy mills and operated simply with low-maintenance requirements. However, this kind of low-energy mill requires long-term milling time (more than 300h) to complete the gas-solid reaction and to obtain nanocrystalline MgH2 powders.

Figure 9.7. Photos taken from KISR-EBRC/NAM Lab, Kuwait, display setup of a lab-scale roller mill (1000m in volume) showing (A) the milling tools including the balls (milling media and vial), (B) charging Mg powders in the vial inside inert gas atmosphere glove box, (C) evacuation setup and pressurizing hydrogen gas in the vial, and (D) ball milling processed, using a roller mill. Schematic presentations show the ball positions and movement inside the vial of a tumbler mall mill at a dynamic mode is shown in (E), where a typical ball-powder-ball collusion for a low energy tumbling ball mill is presented in (F).

operations and maintenance training for ball mills

operations and maintenance training for ball mills

Learn how to optimise your ball mill systems in this 5-day training seminar focused on best practices for operations and maintenance (preventive and reactive) to achieve energy savings, reduced maintenance costs and overall improved productivity of the ball mill systems. Ball mills are used for many applications in cement production: raw meal grinding, coal and petcoke grinding as well as finish cement grinding. Each of these systems have their similarities and differences. This ball mill seminar is designed to train your personnel on the overall technology, operation and maintenance of your ball mill cement grinding system. The seminar focuses on the latest best practices for the operation and maintenance of ball mill systems to allow for optimal cement production, energy savings, reduced maintenance costs as well as the continuous improvement of the overall equipment operation. The course offers classroom instruction from our FLSmidth ball mill specialists and case studies based on real situations at different ball mill installations. Working sessions are scheduled to allow for a thorough study of the design and function of the main equipment, including but not limited to the latest methods for optimisation and possibilities for upgrades and modernisation of the current systems and operations. Maintenance training is focused on routine preventive maintenance to minimize downtime in ball mill systems, as well as developing preventive maintenance programmes and troubleshooting techniques to quickly identify and fix problems. Beyond what you will learn about your ball mill systems, this seminar provides excellent networking opportunities with our specialists as well as your counterparts from the cement industry.

Learn how to optimise your ball mill systems in this 5-day training seminar focused on best practices for operations and maintenance (preventive and reactive) to achieve energy savings, reduced maintenance costs and overall improved productivity of the ball mill systems.

Ball mills are used for many applications in cement production: raw meal grinding, coal and petcoke grinding as well as finish cement grinding. Each of these systems have their similarities and differences. This ball mill seminar is designed to train your personnel on the overall technology, operation and maintenance of your ball mill cement grinding system.

The seminar focuses on the latest best practices for the operation and maintenance of ball mill systems to allow for optimal cement production, energy savings, reduced maintenance costs as well as the continuous improvement of the overall equipment operation.

The course offers classroom instruction from our FLSmidth ball mill specialists and case studies based on real situations at different ball mill installations. Working sessions are scheduled to allow for a thorough study of the design and function of the main equipment, including but not limited to the latest methods for optimisation and possibilities for upgrades and modernisation of the current systems and operations.

Maintenance training is focused on routine preventive maintenance to minimize downtime in ball mill systems, as well as developing preventive maintenance programmes and troubleshooting techniques to quickly identify and fix problems.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

ball mill - retsch - powerful grinding and homogenization

ball mill - retsch - powerful grinding and homogenization

Ball mills are among the most variable and effective tools when it comes to size reduction of hard, brittle or fibrous materials. The variety of grinding modes, usable volumes and available grinding tool materials make ball mills the perfect match for a vast range of applications.

RETSCH is the world leading manufacturer of laboratory ball mills and offers the perfect product for each application. The High Energy Ball Mill Emax and MM 500 were developed for grinding with the highest energy input. The innovative design of both, the mills and the grinding jars, allows for continuous grinding down to the nano range in the shortest amount of time - with only minor warming effects. These ball mills are also suitable for mechano chemistry. Mixer Mills grind and homogenize small sample volumes quickly and efficiently by impact and friction. These ball mills are suitable for dry, wet and cryogenic grinding as well as for cell disruption for DNA/RNA recovery. Planetary Ball Mills meet and exceed all requirements for fast and reproducible grinding to analytical fineness. They are used for the most demanding tasks in the laboratory, from routine sample processing to colloidal grinding and advanced materials development. The drum mill is a type of ball mill suitable for the fine grinding of large feed sizes and large sample volumes.

mining industry benefits from 3d metrology services

mining industry benefits from 3d metrology services

Mining operations are challenging environments for most in the precision measurement field. The older, more traditional mechanical methods are limited in the volume that they can cover and depend heavily upon the skill level of the operator. Innovative and portable 3D metrology solutions such as laser trackers, make the inspection and alignment of mining equipment much faster and more reliable and traceable than traditional methods.

There are many mining applications that benefit from the use of a laser tracker including the inspection, alignment and rebuild of conveyor idlers, pulleys and bearings. Additionally the laser tracker is ideal for inspecting and aligning large rotating equipment such as railcar dumpers and ball mills and the power transmission to this equipment.

OASIS has completed a variety of 3D metrology inspections and alignments in the mining industry. Here we provide several examples of jobs completed for this industry by our team of metrology engineers.

When a large iron ore mining operation knew they needed to replace the gear segments on one of their railcar dumpers, they contacted OASIS to assist with the inspection of the axis of rotation of the dumper and the alignment and installation of the new segments. Even though the customer did not have the original drawings, with a laser tracker the OASIS metrology engineer was able to quickly and precisely map the axis of rotation of the dumper. Using this data, the OASIS engineer accurately positioned the gear segments for the planar, circumferential and radial attributes. Following the sector gear rebuild, all of the data previously acquired was used to properly position and align the drive pinion.

A large iron ore and steel supplier in Canada hired OASIS to assist with the inspection and alignment of the components of one of their ball mills. This location was replacing the pinion and gear wheel of the ball mill after 25 years of continuous production.

Once the original parts were removed, OASIS began the first step of the inspection portion of the project. An OASIS metrology engineer used a laser tracker to survey the mounting surfaces of the gear segments. The data collected allowed for the exact amount of shim to be placed in order to planize the mounting surfaces. This is important because the gears must be mounted to a surface that is flat and perpendicular to the axis rotation of the drum.

After the gears were installed, the next step was to measure the gear segments to ensure they had the same radius to the axis of the drum and that the backlash was the same between gear teeth. Accuracy is of high importance in order to avoid gear wear, jamming and breakage all of which leads to costly downtime.

There are many benefits of using a laser tracker for ball mill inspection. In this case, one of the most valuable benefits was the speed with which the OASIS metrology engineer was able to gather the data from each step of the inspection process and link all data to the axis of rotation of the drum. When downtime is extremely costly, speed is of the utmost importance.

Because the customer was so impressed with the results, OASIS has been hired for additional metrology inspections at this mine and at their other mines across Quebec. Projects include conveyor inspection, excavator reducer inspection and emergency conveyor drive repair.

Mining conveyor systems are key to a prosperous mine operation. Conveyors are typically thousands of feet long and with one belt alone costing upwards of $50,000 to replace; a precision aligned conveying system is certainly in the mines best interest.

In this example, a gold ore mine was having constant bearing failure issues in the pulley sections of one its conveyor systems and called in OASIS to inspect for misalignment. Using a laser tracker, an OASIS metrology engineer surveyed the entire conveyor and established a coordinate system using its centerline and level to earth. Once the coordinate system was determined, all pulleys were aligned to that coordinate system. The next step involved aligning the pillow blocks (bearing housings) perpendicular to the pulleys. In order to do this, all mounting plates for the pillow blocks were inspected and shimmed as required in order to make them perpendicular to the pulleys.

If you are interested in learning more about the ways mining operations can benefit from 3D metrology services, please contact us for more information. Be sure tovisit our blog regularly for more on precision measurement solutions for the mining industry and other industrial environments.

If you have any questions about the content in this post or would like to speak with any of our precision alignment and measurement professionals, feel free to fill out the contact form below. Of course, you can also give us a call at 603-332-9641.

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