In all ore dressing and milling Operations, including flotation, cyanidation, gravity concentration, and amalgamation, the Working Principle is to crush and grind, often with rob mill & ball mills, the ore in order to liberate the minerals. In the chemical and process industries, grinding is an important step in preparing raw materials for subsequent treatment.In present day practice, ore is reduced to a size many times finer than can be obtained with crushers. Over a period of many years various fine grinding machines have been developed and used, but the ball mill has become standard due to its simplicity and low operating cost.
A ball millefficiently operated performs a wide variety of services. In small milling plants, where simplicity is most essential, it is not economical to use more than single stage crushing, because the Steel-Head Ball or Rod Mill will take up to 2 feed and grind it to the desired fineness. In larger plants where several stages of coarse and fine crushing are used, it is customary to crush from 1/2 to as fine as 8 mesh.
Many grinding circuits necessitate regrinding of concentrates or middling products to extremely fine sizes to liberate the closely associated minerals from each other. In these cases, the feed to the ball mill may be from 10 to 100 mesh or even finer.
Where the finished product does not have to be uniform, a ball mill may be operated in open circuit, but where the finished product must be uniform it is essential that the grinding mill be used in closed circuit with a screen, if a coarse product is desired, and with a classifier if a fine product is required. In most cases it is desirable to operate the grinding mill in closed circuit with a screen or classifier as higher efficiency and capacity are obtained. Often a mill using steel rods as the grinding medium is recommended, where the product must have the minimum amount of fines (rods give a more nearly uniform product).
Often a problem requires some study to determine the economic fineness to which a product can or should be ground. In this case the 911Equipment Company offers its complete testing service so that accurate grinding mill size may be determined.
Until recently many operators have believed that one particular type of grinding mill had greater efficiency and resulting capacity than some other type. However, it is now commonly agreed and accepted that the work done by any ballmill depends directly upon the power input; the maximum power input into any ball or rod mill depends upon weight of grinding charge, mill speed, and liner design.
The apparent difference in capacities between grinding mills (listed as being the same size) is due to the fact that there is no uniform method of designating the size of a mill, for example: a 5 x 5 Ball Mill has a working diameter of 5 inside the liners and has 20 per cent more capacity than all other ball mills designated as 5 x 5 where the shell is 5 inside diameter and the working diameter is only 48 with the liners in place.
Ball-Rod Mills, based on 4 liners and capacity varying as 2.6 power of mill diameter, on the 5 size give 20 per cent increased capacity; on the 4 size, 25 per cent; and on the 3 size, 28 per cent. This fact should be carefully kept in mind when determining the capacity of a Steel- Head Ball-Rod Mill, as this unit can carry a greater ball or rod charge and has potentially higher capacity in a given size when the full ball or rod charge is carried.
A mill shorter in length may be used if the grinding problem indicates a definite power input. This allows the alternative of greater capacity at a later date or a considerable saving in first cost with a shorter mill, if reserve capacity is not desired. The capacities of Ball-Rod Mills are considerably higher than many other types because the diameters are measured inside the liners.
The correct grinding mill depends so much upon the particular ore being treated and the product desired, that a mill must have maximum flexibility in length, type of grinding medium, type of discharge, and speed.With the Ball-Rod Mill it is possible to build this unit in exact accordance with your requirements, as illustrated.
To best serve your needs, the Trunnion can be furnished with small (standard), medium, or large diameter opening for each type of discharge. The sketch shows diagrammatic arrangements of the four different types of discharge for each size of trunnion opening, and peripheral discharge is described later.
Ball-Rod Mills of the grate discharge type are made by adding the improved type of grates to a standard Ball-Rod Mill. These grates are bolted to the discharge head in much the same manner as the standard headliners.
The grates are of alloy steel and are cast integral with the lifter bars which are essential to the efficient operation of this type of ball or rod mill. These lifter bars have a similar action to a pump:i. e., in lifting the product so as to discharge quickly through the mill trunnion.
These Discharge Grates also incorporate as an integral part, a liner between the lifters and steel head of the ball mill to prevent wear of the mill head. By combining these parts into a single casting, repairs and maintenance are greatly simplified. The center of the grate discharge end of this mill is open to permit adding of balls or for adding water to the mill through the discharge end.
Instead of being constructed of bars cast into a frame, Grates are cast entire and have cored holes which widen toward the outside of the mill similar to the taper in grizzly bars. The grate type discharge is illustrated.
The peripheral discharge type of Ball-Rod Mill is a modification of the grate type, and is recommended where a free gravity discharge is desired. It is particularly applicable when production of too many fine particles is detrimental and a quick pass through the mill is desired, and for dry grinding.
The drawings show the arrangement of the peripheral discharge. The discharge consists of openings in the shell into which bushings with holes of the desired size are inserted. On the outside of the mill, flanges are used to attach a stationary discharge hopper to prevent pulp splash or too much dust.
The mill may be operated either as a peripheral discharge or a combination or peripheral and trunnion discharge unit, depending on the desired operating conditions. If at any time the peripheral discharge is undesirable, plugs inserted into the bushings will convert the mill to a trunnion discharge type mill.
Unless otherwise specified, a hard iron liner is furnished. This liner is made of the best grade white iron and is most serviceable for the smaller size mills where large balls are not used. Hard iron liners have a much lower first cost.
Electric steel, although more expensive than hard iron, has advantage of minimum breakage and allows final wear to thinner section. Steel liners are recommended when the mills are for export or where the source of liner replacement is at a considerable distance.
Molychrome steel has longer wearing qualities and greater strength than hard iron. Breakage is not so apt to occur during shipment, and any size ball can be charged into a mill equipped with molychrome liners.
Manganese liners for Ball-Rod Mills are the world famous AMSCO Brand, and are the best obtainable. The first cost is the highest, but in most cases the cost per ton of ore ground is the lowest. These liners contain 12 to 14% manganese.
The feed and discharge trunnions are provided with cast iron or white iron throat liners. As these parts are not subjected to impact and must only withstand abrasion, alloys are not commonly used but can be supplied.
Gears for Ball-Rod Mills drives are furnished as standard on the discharge end of the mill where they are out of the way of the classifier return, scoop feeder, or original feed. Due to convertible type construction the mills can be furnished with gears on the feed end. Gear drives are available in two alternative combinations, which are:
All pinions are properly bored, key-seated, and pressed onto the steel countershaft, which is oversize and properly keyseated for the pinion and drive pulleys or sheaves. The countershaft operates on high grade, heavy duty, nickel babbitt bearings.
Any type of drive can be furnished for Ball-Rod Mills in accordance with your requirements. Belt drives are available with pulleys either plain or equipped with friction clutch. Various V- Rope combinations can also be supplied.
The most economical drive to use up to 50 H. P., is a high starting torque motor connected to the pinion shaft by means of a flat or V-Rope drive. For larger size motors the wound rotor (slip ring) is recommended due to its low current requirement in starting up the ball mill.
Should you be operating your own power plant or have D. C. current, please specify so that there will be no confusion as to motor characteristics. If switches are to be supplied, exact voltage to be used should be given.
Even though many ores require fine grinding for maximum recovery, most ores liberate a large percentage of the minerals during the first pass through the grinding unit. Thus, if the free minerals can be immediately removed from the ball mill classifier circuit, there is little chance for overgrinding.
This is actually what has happened wherever Mineral Jigs or Unit Flotation Cells have been installed in the ball mill classifier circuit. With the installation of one or both of these machines between the ball mill and classifier, as high as 70 per cent of the free gold and sulphide minerals can be immediately removed, thus reducing grinding costs and improving over-all recovery. The advantage of this method lies in the fact that heavy and usually valuable minerals, which otherwise would be ground finer because of their faster settling in the classifier and consequent return to the grinding mill, are removed from the circuit as soon as freed. This applies particularly to gold and lead ores.
Ball-Rod Mills have heavy rolled steel plate shells which are arc welded inside and outside to the steel heads or to rolled steel flanges, depending upon the type of mill. The double welding not only gives increased structural strength, but eliminates any possibility of leakage.
Where a single or double flanged shell is used, the faces are accurately machined and drilled to template to insure perfect fit and alignment with the holes in the head. These flanges are machined with male and female joints which take the shearing stresses off the bolts.
The Ball-Rod Mill Heads are oversize in section, heavily ribbed and are cast from electric furnace steel which has a strength of approximately four times that of cast iron. The head and trunnion bearings are designed to support a mill with length double its diameter. This extra strength, besides eliminating the possibility of head breakage or other structural failure (either while in transit or while in service), imparts to Ball-Rod Mills a flexibility heretofore lacking in grinding mills. Also, for instance, if you have a 5 x 5 mill, you can add another 5 shell length and thus get double the original capacity; or any length required up to a maximum of 12 total length.
On Type A mills the steel heads are double welded to the rolled steel shell. On type B and other flanged type mills the heads are machined with male and female joints to match the shell flanges, thus taking the shearing stresses from the heavy machine bolts which connect the shell flanges to the heads.
The manhole cover is protected from wear by heavy liners. An extended lip is provided for loosening the door with a crow-bar, and lifting handles are also provided. The manhole door is furnished with suitable gaskets to prevent leakage.
The mill trunnions are carried on heavy babbitt bearings which provide ample surface to insure low bearing pressure. If at any time the normal length is doubled to obtain increased capacity, these large trunnion bearings will easily support the additional load. Trunnion bearings are of the rigid type, as the perfect alignment of the trunnion surface on Ball-Rod Mills eliminates any need for the more expensive self-aligning type of bearing.
The cap on the upper half of the trunnion bearing is provided with a shroud which extends over the drip flange of the trunnion and effectively prevents the entrance of dirt or grit. The bearing has a large space for wool waste and lubricant and this is easily accessible through a large opening which is covered to prevent dirt from getting into the bearing.Ball and socket bearings can be furnished.
Scoop Feeders for Ball-Rod Mills are made in various radius sizes. Standard scoops are made of cast iron and for the 3 size a 13 or 19 feeder is supplied, for the 4 size a 30 or 36, for the 5 a 36 or 42, and for the 6 a 42 or 48 feeder. Welded steel scoop feeders can, however, be supplied in any radius.
The correct size of feeder depends upon the size of the classifier, and the smallest feeder should be used which will permit gravity flow for closed circuit grinding between classifier and the ball or rod mill. All feeders are built with a removable wearing lip which can be easily replaced and are designed to give minimum scoop wear.
A combination drum and scoop feeder can be supplied if necessary. This feeder is made of heavy steel plate and strongly welded. These drum-scoop feeders are available in the same sizes as the cast iron feeders but can be built in any radius. Scoop liners can be furnished.
The trunnions on Ball-Rod Mills are flanged and carefully machined so that scoops are held in place by large machine bolts and not cap screws or stud bolts. The feed trunnion flange is machined with a shoulder for insuring a proper fit for the feed scoop, and the weight of the scoop is carried on this shoulder so that all strain is removed from the bolts which hold the scoop.
High carbon steel rods are recommended, hot rolled, hot sawed or sheared, to a length of 2 less than actual length of mill taken inside the liners. The initial rod charge is generally a mixture ranging from 1.5 to 3 in diameter. During operation, rod make-up is generally the maximum size. The weights per lineal foot of rods of various diameters are approximately: 1.5 to 6 lbs.; 2-10.7 lbs.; 2.5-16.7 lbs.; and 3-24 lbs.
Forged from the best high carbon manganese steel, they are of the finest quality which can be produced and give long, satisfactory service. Data on ball charges for Ball-Rod Mills are listed in Table 5. Further information regarding grinding balls is included in Table 6.
Rod Mills has a very define and narrow discharge product size range. Feeding a Rod Mill finer rocks will greatly impact its tonnage while not significantly affect its discharge product sizes. The 3.5 diameter rod of a mill, can only grind so fine.
Crushers are well understood by most. Rod and Ball Mills not so much however as their size reduction actions are hidden in the tube (mill). As for Rod Mills, the image above best expresses what is going on inside. As rocks is feed into the mill, they are crushed (pinched) by the weight of its 3.5 x 16 rods at one end while the smaller particles migrate towards the discharge end and get slightly abraded (as in a Ball Mill) on the way there.
We haveSmall Ball Mills for sale coming in at very good prices. These ball mills are relatively small, bearing mounted on a steel frame. All ball mills are sold with motor, gears, steel liners and optional grinding media charge/load.
Ball Mills or Rod Mills in a complete range of sizes up to 10 diameter x20 long, offer features of operation and convertibility to meet your exactneeds. They may be used for pulverizing and either wet or dry grindingsystems. Mills are available in both light-duty and heavy-duty constructionto meet your specific requirements.
All Mills feature electric cast steel heads and heavy rolled steelplate shells. Self-aligning main trunnion bearings on large mills are sealedand internally flood-lubricated. Replaceable mill trunnions. Pinion shaftbearings are self-aligning, roller bearing type, enclosed in dust-tightcarrier. Adjustable, single-unit soleplate under trunnion and drive pinionsfor perfect, permanent gear alignment.
Ball Mills can be supplied with either ceramic or rubber linings for wet or dry grinding, for continuous or batch type operation, in sizes from 15 x 21 to 8 x 12. High density ceramic linings of uniform hardness male possible thinner linings and greater and more effective grinding volume. Mills are shipped with liners installed.
Complete laboratory testing service, mill and air classifier engineering and proven equipment make possible a single source for your complete dry-grinding mill installation. Units available with air swept design and centrifugal classifiers or with elevators and mechanical type air classifiers. All sizes and capacities of units. Laboratory-size air classifier also available.
A special purpose batch mill designed especially for grinding and mixing involving acids and corrosive materials. No corners mean easy cleaning and choice of rubber or ceramic linings make it corrosion resistant. Shape of mill and ball segregation gives preferential grinding action for grinding and mixing of pigments and catalysts. Made in 2, 3 and 4 diameter grinding drums.
Nowadays grinding mills are almost extensively used for comminution of materials ranging from 5 mm to 40 mm (3/161 5/8) down to varying product sizes. They have vast applications within different branches of industry such as for example the ore dressing, cement, lime, porcelain and chemical industries and can be designed for continuous as well as batch grinding.
Ball mills can be used for coarse grinding as described for the rod mill. They will, however, in that application produce more fines and tramp oversize and will in any case necessitate installation of effective classification.If finer grinding is wanted two or three stage grinding is advisable as for instant primary rod mill with 75100 mm (34) rods, secondary ball mill with 2540 mm(11) balls and possibly tertiary ball mill with 20 mm () balls or cylpebs.To obtain a close size distribution in the fine range the specific surface of the grinding media should be as high as possible. Thus as small balls as possible should be used in each stage.
The principal field of rod mill usage is the preparation of products in the 5 mm0.4 mm (4 mesh to 35 mesh) range. It may sometimes be recommended also for finer grinding. Within these limits a rod mill is usually superior to and more efficient than a ball mill. The basic principle for rod grinding is reduction by line contact between rods extending the full length of the mill, resulting in selective grinding carried out on the largest particle sizes. This results in a minimum production of extreme fines or slimes and more effective grinding work as compared with a ball mill. One stage rod mill grinding is therefore suitable for preparation of feed to gravimetric ore dressing methods, certain flotation processes with slime problems and magnetic cobbing. Rod mills are frequently used as primary mills to produce suitable feed to the second grinding stage. Rod mills have usually a length/diameter ratio of at least 1.4.
Tube mills are in principle to be considered as ball mills, the basic difference being that the length/diameter ratio is greater (35). They are commonly used for surface cleaning or scrubbing action and fine grinding in open circuit.
In some cases it is suitable to use screened fractions of the material as grinding media. Such mills are usually called pebble mills, but the working principle is the same as for ball mills. As the power input is approximately directly proportional to the volume weight of the grinding media, the power input for pebble mills is correspondingly smaller than for a ball mill.
A dry process requires usually dry grinding. If the feed is wet and sticky, it is often necessary to lower the moisture content below 1 %. Grinding in front of wet processes can be done wet or dry. In dry grinding the energy consumption is higher, but the wear of linings and charge is less than for wet grinding, especially when treating highly abrasive and corrosive material. When comparing the economy of wet and dry grinding, the different costs for the entire process must be considered.
An increase in the mill speed will give a directly proportional increase in mill power but there seems to be a square proportional increase in the wear. Rod mills generally operate within the range of 6075 % of critical speed in order to avoid excessive wear and tangled rods. Ball and pebble mills are usually operated at 7085 % of critical speed. For dry grinding the speed is usually somewhat lower.
The mill lining can be made of rubber or different types of steel (manganese or Ni-hard) with liner types according to the customers requirements. For special applications we can also supply porcelain, basalt and other linings.
The mill power is approximately directly proportional to the charge volume within the normal range. When calculating a mill 40 % charge volume is generally used. In pebble and ball mills quite often charge volumes close to 50 % are used. In a pebble mill the pebble consumption ranges from 315 % and the charge has to be controlled automatically to maintain uniform power consumption.
In all cases the net energy consumption per ton (kWh/ton) must be known either from previous experience or laboratory tests before mill size can be determined. The required mill net power P kW ( = ton/hX kWh/ton) is obtained from
Trunnions of S.G. iron or steel castings with machined flange and bearing seat incl. device for dismantling the bearings. For smaller mills the heads and trunnions are sometimes made in grey cast iron.
The mills can be used either for dry or wet, rod or ball grinding. By using a separate attachment the discharge end can be changed so that the mills can be used for peripheral instead of overflow discharge.
Single Angle Chamfering Cutters have a conical, tapering cutting head for milling at a 45 or 60 angle in dovetail work and angle cutting. Dovetail cutters are similar, but have an inverted cone which widens at the end for producing dovetail cuts. Double Angle End Mills (also known as V-slot milling cutters) have a diamond-shaped cutting head profile with peripheral teeth, and are designed for machining a V-shaped slot in one pass, as well as milling notches, chamfers, serrations, and angles.
There are many different designs and styles of ball mill liners. As with grinding balls local economics and ultimately operating costs determine the best design and material to use. The initial set of liners is rarely the final design selected. Based upon individual experience, mill superintendents develop preferences for liner designs. The following is given as a guideline for the initial set of liners.
For 60 mm (2.5) and smaller top size balls for cast metal liners use double wave liners with the number of lifters to the circle approximately 13.1 D in meters (for D in feet, divide 13.1 D by 3.3). Wave height above the liners from1.5 to 2 times the liner thickness. Rubber liners of the integral molded design follow the cast metal design. If using the replaceable lifter bar design in either metal or rubber the number of lifters should be about 3.3 D in meters (for D in feet* divide 3.3 D by 3.3) with the lifter height above the liners about twice the liner thickness. The use of double wave liners, particularly when using 50 mm (2) or larger balls, may show a loss of 5% or so in the mill power draw until the waves wear in and the balls cannest between the lifters.
When liners, and double wave liners in particular, wear with circumferential grooves, slipping of the charge is indicated, and this warns of accelerated wear. When the top size ball is smaller than 50mm (2.5) and mill speed is less than 72% of critical wear resistant cast irons can be used. For other conditions alloyed cast steel is recommended.Rubber liners are well suited to this same area and not onlyreduce operating costs but can reduce noise levels.
Single wave liners are recommended for larger size balls (50mm/2.5 and larger). The number of the lifters to the circle equals approximately 6.6 D in meters (for D in feet, divide 6.6 D by 3.3). The liners are from 50 to 65 mm thick (2 to 2.5) with the waves from 60 to 75 mm (2.5 to 3) above the liners. The replaceable lifter bar design madeof either metal or rubber in about the same design proportions can be used. There could be a loss in power with rubber particularly if the mill speed is faster than about 72% of critical speed, and the ball size is larger than 75 mm. Because of the impacting from the large balls, single wave liners for ball mills are usually made from alloyed steels or special wear-resistant alloyed cast irons. Because of the difficulty of balancing growth and wear with work hardening manganese steel is used infrequently and then with extreme care to allow for growth.
When a grate discharge is used the grates and wear platesare normally perpendicular to the mill axis while the discharge pans conform to the slope of the mill head. The grates and wear plates are normally made from alloy wear resistant cast steel or rubber. They are ribbed to prevent racing and excessive wear. The dischargers and pans are generally made from either wear resistant cast ironor rubber, or wear resistant fabricated steel.Slot plugging can be a problem in grate discharge mills. Whether the grates are made of metal or rubber the slots should have ample relief tapered toward the discharge side. Total angles 7 to 10 degrees (3.5 to 5 degrees per side) are commonly used. Metal grates often havea small lead-in pocket or recess which can fill in with peened metal rather than have the slot peen shut. With the proper combination of metal internals and rubber surfaces, rubber grates have flexibility that tend to make them self cleaning and yet not fail due to flexing.
Except when using rubber liners, the mill surfaces are covered with a protective rubber or plastic material toprotect the surfaces from pulp racing and corrosion. This is done in wet grinding mills. Since dry grinding mills get hot due to heat from grinding generally rubber liners and rubber materials cannot be used.
Shell liners may be furnished of various materials and of several designs. In each case the material used is the best obtainable, resulting in the lowest cost per ton of ore ground. The liner contours are selected for the specific grinding application and take into consideration liner wear, scrap loss, and mill capacity.
Liners cast of Manganese Steel, Ni-Hard, Chrome-moly, or other similar materials may be of the step type, block type, wave type, or the two-piece plate and lifter construction. These are illustrated on the right. During the past years of building ball Mills various other shapes of liners have been tried, such as the pocket type, spiral liners, etc.; in most cases it is found that these special shapes and designs are not justifiable from the standpoint of economics. They involve additional costs which are not generally recovered from an increased efficiency in milling operation.
Lorain Shell Liners consist of high carbon rolled steel plates accurately formed to the mill shell radius. These are held in place by rolled alloy steel heat treated lift bars. This type liner is carefully engineered for the specific grinding application. Variations in lift bar design and liner plate thickness provide this flexibility of design for application.
All shell liners designed for ball mill operations are of such size and shape that they will easily pass through the manhole opening to facilitate relining operations. In rod mill work the design is such that they will easily pass through the large ball open end discharge trunnion.
Where cast liners are used, and especially in rod mill applications, we furnish rubber shell liner backing to help cushion the impact effect of the media within the mill and prevent pulp racing. With the Lorain type of liner such shell liner backing is not required. For special applications where severe corrosive conditions exist a shell liner of special alloys can be furnished and also the interior surface of the shell can be treated to protect such parts from the corrosive conditions.
Head liners are of the segmental type constructed of Manganese Steel, Chrome molybdenum, or Ni-Hard and are designed to pass easily through the manhole opening or discharge opening in the case of rod mills. For ball mill work ribs are cast with the feed head liners to deflect the ball mass and minimize wear on the headliner itself.
Where cast liners are used shell liner bolts and head liner bolts are made of forged steel with an oval head to prevent turning and loosening within the liners. These are held in place with two hex nuts and a cut washer. For wet grinding applications special waterproof washers can be furnished.
Theeffect of liner design upon mill performance appears to have received little attention. Clearly, the main function of the liner is to form a removable surface to the null body, which may be replaced when seriously worn.
It is also clear however, that the metal plates which serve this purpose may have a surface which ranges from smooth in one which carries an intricate pattern of raised bars or sunken depressions. The merits of the various types do not appear, however, to have been studied.
where smooth liners are those which have projections insufficient to give appreciable keying between the liner and the ball charge, whilst lifter liners are those which are so heavily ribbed as to give rise to appreciable interlocking between the balls and the liners.
Various common types of liners are illustrated in Fig. 6.12. Although these liners have various patterns of projections, or depressions, to give an amount of interaction between the liner and the grinding medium, it would be expected that wear would round the edges. It is doubtful whether, after some time in service, the performance of a mill with these liners differs appreciably from that of a mill with a smooth surface. Liners furnished with heavy lifter bars are also sometimes used and in such a case the locking of the ball charge to the shell must be very effective. Nevertheless, although a few vague general statements to the effect that a lifter mill gives a product with different size characteristics to that of a smooth mill have appeared, the point does not appear to have been widely investigated. It is probable, however, that, on the grounds of differences in the size characteristics of the products, there exists no sound reason for the use of lifters in preference to the normal smooth liners.
It is possible that, when a material with a low coefficient of friction is milled, the charge might slip on a smooth mill shell, with consequent loss of grinding capacity, and in such a case the use of lifter bars might well be the solution. It has also been suggested by one of the authors, Rose, that the use of lifter bars might eliminate the surging of the charge sometimes encountered in mill operation.
An entirely different conception of the duty of the mill liner underlies the design of the studded liner developed by Usines Emile Henricot of Count St. Etienne. These liners, illustrated in Fig. 6.12 and Fig. 6.13, consist of comparatively thin plate liners with uniformly spaced studs on the working surface; these studs being integral with the plate. Provided the spaces between the studs are not allowed to become choked with tramp-iron, etc., the studs furnish a good key between the shell and the charge which, it is claimed, leads to a greater power consumption and to improved grinding. Furthermore it would appear that the studs impose a definite geometrical arrangement in the outer layer of balls which, in turn, brings about a closer packing, throughout the ball mass, than obtains with conventional types of liner. This effect would also lead to improved performance. Evidence of this effect of the studs upon the packing of the charge appears in Fig. 6.13b, for the balls are clearly seen to lie in rows in the mill instead of in completely random array.
An incidental merit claimed for these liners is that the high bearing pressure between the balls and the studs of the liners leads to work hardening of the studs; with a consequential reduction of the rate of metal wear.
The Henricot liners, which have been discussed in a paper by Belwinkel, appear to be the only attempt so far made to influence the grinding characteristics of a mill by means of correctly designed liners. It would therefore appear that there is some room for development in this direction.
A Grinding Ball mill consists of a hollow cylindrical shell rotating about its axis. The axis of the shell may be either horizontal or at a small angle to the horizontal. It is partially filled with balls. The grinding media is the balls, which may be made of steel (chrome steel), stainless steel or rubber. The inner surface of the cylindrical shell is usually lined with an abrasion-resistant material such as manganese steel or rubber. Less wear takes place in rubber lined mills, such as theSepro tyre drive Grinding Ball Mill. The length of the mill is approximately equal to its diameter... more info
8 Ft x 21 Ft Traylor Ball Mill, one extra head in good condition, Bull: 266 tooth excelent condition, Pinion: 20 tooth one spare good condition, 500hp Synchronous Motor, speed 300 RPM, 4000v, shell can be resize to any size.
12 Ft x 14 Ft Marcy Ball Mill, complete with 1,750 HP Synchronous Motor, 200 RPM, 2,300 Volts. New Trunnion Bearing base plates, New Pinion, 3 Shells to choose from, three discharge heads and 3 intake heads to choose from, two bull gears
12.5 Ft x 15 Ft Allis Chalmers Ball Mill, complete with 1,500 HP Synchronous Motor, 277 RPM, 4160, Mill rpm 16.8, Trunion 26'' x 54'', Pinion 17 Teeth, Bull Gear 280 Teeth, Face 26.75'', Bearing SKF 23238C-C3W33
12.5 Ft x 25.5 ft Nordberg Ball Mill, with a 1,500hp Westinghouse Synchronous Motor, 720rpm, 4,000volts, Flak Drive Reducer 720rpm in, 239 rpm out, Bull Gear 236 Teeth, 1/25 DP, 26''face, Pinion 19 Teeth
24 Ft dia x 8ft SAG Mill, Hardinge, with a 2,250hp Synchronous Motor, 720rpm and 4,000volts, Bull Gear 318 Teeth, 1 1/4PD, 26'' face, two sections, Herringbone design, Pinion 29 Teeth, 26'' face, 11'' dia Shaft
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In Grinding, selecting (calculate)the correct or optimum ball sizethat allows for the best and optimum/ideal or target grind size to be achieved by your ball mill is an important thing for a Mineral Processing Engineer AKA Metallurgist to do. Often, the ball used in ball mills is oversize just in case. Well, this safety factor can cost you much in recovery and/or mill liner wear and tear.
Ball End Mills have a hemispherical tip used to machine rounded details, such as the metal bearing grooves found in machines. Also called Ball Nose End Mills, they are used extensively in manufacturing tools & dies, and machining complex three dimensional contours with a smooth finish. Ball End Mills are very durable, and come with an array of surface coatings tailored for milling a wide range of materials, from plastics to titanium and steel alloys.
Particle size reduction of materials in a ball mill with the presence of metallic balls or other media dates back to the late 1800s. The basic construction of a ball mill is a cylindrical container with journals at its axis. The cylinder is filled with grinding media (ceramic or metallic balls or rods), the product to be ground is added and the cylinder is put into rotation via an external drive causing the media to roll, slide and cascade. Lifting baffles are supplied to prevent the outer layer of media to simply roll around the cylinder.
Mill cylinders are typically supplied with a cooling jacket on their cylindrical portion for temperature control, especially when processing temperature-sensitive materials. For extreme temperatures, the ends of the cylinder can also be furnished with cooling apparatus.