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what are the differences between ball mill and rod mill? | fote machinery

what are the differences between ball mill and rod mill? | fote machinery

Ball mill and rod mill are the common grinding equipment applied in the grinding process. They are similar in appearance and both of them are horizontal cylindrical structures. Their cylinders are equipped with grinding medium, feeder, gears, and transmission device.

The working principle of ball mill and rod mill machine is similar, too. That is, the cylinder drives the movement of the grinding medium (lifting the grinding medium to a certain height then dropping). Under the action of centrifugal force and friction, the material is impacted and ground to required size, so as to realize the operation of mineral grinding.

Grate discharge ball mill can discharge material through sieve plate, with the advantage of the low height of the discharge port which can make the material pass quickly so tha t to avoid over-grinding of material. Under the same condition, it has a higher capacity and can save more energy than other types of mills;

It is better to choose a grate discharge ball mill when the required discharge size is in the range of 0.2 to 0.3 mm. Grate discharge ball mill is usually applied in the first grinding system because it can discharge the qualified product immediately.

Overflow discharge ball mill can grind ores into the size under 0.2 mm, so it is very suitable for the second grinding system. The capacity of it is about 15% lower than grate discharge ball mill in the same specification, and the loaded grinding medium is also less than that one.

It can be divided into three types of rod mills according to the discharge methods, center and side discharge rod mill, end and side discharge rod mill and shaft neck overflow discharge rod mill.

It is fed through the shaft necks in the two ends of rod mill, and discharges ore pulp through the port in the center of the cylinder. Center and side discharge rod mill can grind ores coarsely because of its structure.

This kind of rod mill can be used for wet grinding and dry grinding. "A rod mill is recommended if we want to properly grind large grains, because the ball mill will not attack them as well as rod mills will."

It is fed through one end of the shaft neck, and with the help of several circular holes, the ore pulp is discharged to the next ring groove. The rod mill is mainly used for dry and wet grinding processes that require the production of medium-sized products.

The diameter of the shaft neck is larger than the diameter of the feeding port about 10 to 20 centimeters, so that the height difference can form a gradient for ore pulp flow. There is equipped with a spiral screen in the discharge shaft neck to remove the impurities.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It is made of several elements such as chromium and molybdenum, which has high hardness and good toughness. Under the same work condition, the service of this kind of ball is one time longer than the high manganese steel ball.

After the professional technology straightening and quenching processing process, a high carbon steel rod has high hardness, excellent performance, good wear resistance and outstanding quality.

The steel ball of ball mill and the mineral material are in point contact, so the finished product has a high degree of fineness, but it is also prone to over-grinding. Therefore, it is suitable for the production with high material fineness and is not suitable for the gravity beneficiation of metal ores.

The steel rod and the material are in line or surface contact, and most of the coarse particles are first crushed and then ground. Therefore, the finished product is uniform in quality, excellent in particle size, and high in qualification rate.

The cylinder shape of the rod mill and the ball mill is different: the cylinder of the rod mill is a long type, and the floor area is large. The ratio of the length to the diameter of the cylinder is generally 1.5 to 2.0;

The cylinder of the ball mill is a barrel or a cone. And the ratio of the length to the diameter of the cylinder is small, and in most cases the ratio is only slightly larger than 1, and the floor area is small, too.

The above is the main content of this article. The ball mill and the rod mill are the same type of machine on the appearance, but there are still great differences in the interior. It is very necessary to select a suitable machine for the production to optimize the product effect and maximize its efficiency.

As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.

Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.

continuous rod and ball mill | sepor, inc

continuous rod and ball mill | sepor, inc

Sepors 16 x 32 continuous ball or rod mill is ideal for pilot plant studies of ore grinding and processing or just regular small scale grinding requirements you may have. The mill can be used in a closed circuit, with a spiral classifier, screen or cyclones or as a single pass grinding mill. The spiral classifier is popular in pilot plant grinding due to the ease in which the oversize is returned to the mill when a specific grind size is your target.

Sepor, Inc. began business in 1953 with the introduction of the Sepor Microsplitter , a Jones-type Riffle splitter, developed by geologist Oreste Ernie Alessio for his own use in the lab. Sepor grew over the next several decades to offer a complete line of mineral analysis tools, as well as pilot plant equipment for scaled operations.

ball mills vs rod mills

ball mills vs rod mills

When the mill is rotated without feed or with very fine feed, the rods are in parallel alignment and in contact with one another for their full length. New feed entering at one end of the mill causes the rod charge to spread at that end. This produces a series of wedge shaped slots tapering toward the discharge end.

The tumbling and rolling rods expend most of their crushing force on the coarse fractions of the feed material and only to a lesser degree on the finer material filling the interstices in the rod charge. The horizontal progression of material through the mill is not rapid compared to the movement of the rods and material resulting from rotation of the mill. The average particle is subjected to an action similar to many sets of rolls in series, before it is discharged. Because of this, the rod mill can effectively reduce 1 feed size to 10 mesh or finer in open circuit.

The voids (or interstitial space) within a rod load are approximately half those in a ball mill grinding load. Rods in place weigh approximately 400 pounds per cu. ft. and balls in place approximately 300 pounds per cu. ft.. Thus, quantitatively, less material can progress through the voids in the rod mill grinding media than in the ball mill, and the path of the material is more confined. This grinding action restricts the volume of feed which passes through the mill, without causing an overload condition.

The conical or convex head of our Rod Mill forms a receiving pocket at the feed end which facilitatesentrance of the feed to the grinding charge uniformly. This permits maximum grinding efficiency at the maximum rate possible before an overload occurs. In addition, this type of head construction permits the use of rods the full mill shell length, and reduces wear on the end liners.

The discharge end pocket receives and readily discharges broken rod pieces which otherwise may remain in the rod charge and reduce grinding effectiveness.Vertical feed or discharge end liners may be substituted for the conical liners, when and if desired.

The old and common terms impact and attrition are not satisfactory for designating types of grind. The reason will be obvious when it is seen that high speed and low speed gave about the same type of grind. Furthermore, the term attrition is not as specific as it was formerly regarded when it was used to signify the undesirable work of excessively small media. The reason why it is not specific is shown in this report; in batch tests, when the amounts of subsieve material were the same, the excessively big media left too many coarse particles of ore and in that respect failed as would excessively small balls. Surely attrition does not apply to the failure of the large balls; hence, attrition does not suit. Nonselective is a better term because it covers both extremes of poor work, and selective is descriptive of good work on the coarse material.

The term overgrinding is much used in conversation with mill men, but search of the literature indicates that a good definition does not exist. This is due probably to the absence of a satisfactory antonym. Selective and non-selective grinding are used here to compare products that have the same amount of the subsieve size. Then the product with the least amount of coarse sizes shows good selective grinding and the others are ground nonselectively. Stage grinding which is by repeated passes followed by removal of the finished material, is the best means of obtaining selective grinding. These terms must not be confused with differential grinding, which has to do with the relative grinding rates of two or more minerals in an ore.

Is it better to use a grinding mill with large balls or will small rods? How do you decide between using a ball mill or a rod mill? Many investigators have attributed the selective grinding of rods to line contact. Other things should be considered. In the two pairs of tests shown in table 12 the relative deportment of large balls and small rods in batch wet grinding is shown. The two loads had the same volume. The rods required about 12 percent more power and their better selective grinding is obvious.

In considering the selective grinding of the rods, it must be remembered that the rods were heavier than the heaviest balls; they weighed 7 pounds each, whereas the largest balls weighed only 5 pounds each. On the basis of weight, the rods were larger than the balls although their diameters were much smaller. The rods, being only 35 inches long, may be regarded as much more rigid than rods regularly used.

These observations should be compared with table 4, which shows that the heavier stuffed pipes did more selective grinding than the light pipes. There the diameters were the same, and unquestionably selective grinding was due to the greater weight. Hence, weight as well as diameter of the medium has to be considered in appraising selective grinding and ball milling generally.

ball mills

ball mills

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.

rod/ball mill| eriez lab equipment

rod/ball mill| eriez lab equipment

MACSALAB Drive Rolls for Rod / Ball Mills are Rubber coated and manufactured in Double and Triple Roll models. The Rolls are 120 mm diameter x 1200 mm long and powered by a 0.37 KW 220 Volt Motor with a variable speed controller.

The Ball/Rod mills are meant for producing fine particle size reduction through attrition and compressive forces at the grain size level. They are the most effective laboratory mills for batch-wise, rapid grinding of medium-hard to very hard samples down to finest particle sizes.

A horizontal rotating cylinder (vessel) is partially filled with balls/rods (grinding media), usually stone or metal, which grinds material to the necessary fineness by friction and impact with the tumbling balls/rods. A rotating drum throws material and balls/rods in a counteracting motion which causes impact breakage of larger particles and compressive grinding of finer particles. Attrition in the charge causes grinding of finer particles.

Try to limit the size of the batch to 25% of the total vessel volume which is sufficient to fill the voids and slightly cover the grinding Media. Any larger batches cause the balls to spread out throughout the mass of solids so they cannot make effective contact with each other, because of the layers of material between them. This greatly reduces the grinding efficiency of the mill and in some cases makes it impossible to attain the desired results.

The Feed size should preferable be 8 mesh or smaller, although many operations start with much larger pieces. Having the feed material as fine as possible enables the use of smaller sizes of grinding media, which are always best for fine uniform grinding and dispersions. For hard material it is especially advantageous to start with a fairly fine product.

what is a rod mill? (with picture)

what is a rod mill? (with picture)

A rod mill is an ore grinding mechanism that uses a number of loose steel rods within a rotating drum to provide its attrition or grinding action. An ore charge is added to the drum, and as it rotates, friction between the tumbling rods breaks the ore down into finer particles. Although similar in operation, a rod mill is often more effective than a ball mill as it requires lower rotational speeds and less steel to achieve the same results. It is, however, limited to maximum rod and drum lengths of approximately 20 feet (6 meters) and is generally only used for wet grinding processes. The rod mill also tends to suffer from accelerated drum liner and lifter wear due to the increased weight of the rods.

Mills of various types have been used for centuries to break solids or coarse particulate materials down into finer finished products. From the humble mortar and pestle through animal, wind, and water driven mills to the giant electrically driven versions common in modern industrial applications, all share one common characteristic: mechanical attrition or grinding. All mill types utilize a grinding process of one or another description to gradually reduce the size of the initial charge of material. In older mills, for example, this action was achieved by placing the coarse material between two mill stones and turning one against the other to produce a finer end product.

Modern rotary mills make apply the same principle by tumbling loose grinding elements around in a closed drum to which the charge material is added. Common examples are rod and ball mills, both of which are of the rotary drum type which rely on internal grinding agents to achieve their milling action. Unlike the ball mill which utilizes a large number of hardened steel balls to impart the grinding action, the rod mill uses steel rods lying within the drum and parallel to its axis. When the drum rotates, these rods roll around inside it, thereby crushing the feed material between them.

The rod mill is generally more efficient than the ball mill due to its more effective cascading action and the greater bearing surface offered by the rods. This means it can operate at lower speeds and with less grinding agents and producing less undesirable slimes byproduct. Rod mills do, however, require more attention during operation to prevent rod tangles and are generally ineffective at dry milling operations. They are also limited to a maximum rod length of approximately 20 feet (6 meters) which means they are generally smaller than ball mills. Rod mills also exhibit more liner and lifter wear than other mill types due to the comparatively high weights of the rods.

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.

ball mill | henan deya machinery co., ltd

ball 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 mill is key equipment for grinding in mineral processing plant, it is widely used in cement, silicate, new-type building material, refractory material, fertilizer, ore dressing of ferrous metal and non-ferrous metal, glass ceramics etc.There are dry grinding and wet grinding, ball mill can be divided into tabular type and flowing type according to different forms of discharging materials.

The ball mill is a horizontal rotating device transmitted by the outer gear. The materials are transferred to the grinding chamber through the quill shaft. There are ladder liners and ripple liners and different specifications of steel balls in the chamber. The centrifugal force caused by rotation of barrel brings the steel balls to a certain height and impact and grind the materials. The ground materials are discharged through the discharging board thus the grinding process is finished.

Pebble mills are similar to ball mills except that the grinding media is closely sized rocks or pebbles.Pebble milling is a form of autogenous milling as no steel media is used in the process however, the type of rocks used are selected more carefully than in convention AG milling.

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.

ball mill vs rod mill | how to choose ball mill or rod mill | m&c

ball mill vs rod mill | how to choose ball mill or rod mill | m&c

As grinding equipments, ball mills and rod mills are both high efficiency grinding equipments. Their common points are: 1. They have the same function, they are all used to grind materials, so that the materials can reach the state of powder; 2. The shape of ball mills and rod mills are similar, they are all horizontal and rotatable cylinder; 3. The overall design of ball mills and rod mills are compact, with simple operation and easy maintenance. But the both are different in performance and applications. In this article, the similarities and differences between ball mills and rod mills are analyzed from 9 aspects, and suggest how to choose ball mill or rod mill.Table of Contents Ball Mills vs Rod Mills1. Shape and Structure2. Ore Discharge Types3. Grinding Medium4. Medium Filling Rate5. Fineness of Product6. Running Cost7. Performance Aspects8. Stability Aspects9. Application AspectsHow To Choose Ball Mill or Rod Mill1. According to Ore Properties2. According to Granularity Properties3. According To Mill Properties

The ratio of cylinder length to diameter of rod mill is generally 1.5-2.0, and the inner surface of liner plate on end cover is vertical plane. In most cases, the ratio of the length to the diameter of the ball mill is only slightly greater than 1.In addition, with same specificationthe, the cylinder rotating speed of the rod mill is lower than that of the ball mill.

The rod mill usually uses 50-100mm diameter steel rod as grinding medium, while the ball mill uses steel ball as grinding medium. The length of steel rod is 25-50mm shorter than the cylinder, and it is usually made of high carbon steel with carbon content of 0.8% 1%; the loading capacity of rod is about 35% 45% of the effective volume of rod mill.

In the ball mill, there are lattice ball mill and overflow ball mill in common use (named by different ore discharge structure), while there are only overflow type and open type rod mill. Generally, with the same specification, the diameter of the hollow shaft at the ore discharge end is larger than that of the ball mill.

Medium filling rate refers to the grinding medium percentage in the mill volume. For different grinding methods, mill structures, medium shapes and operating conditions, the medium filling rate has a available range.Generally, the filling rate of ball mill is 40% 50%, and that of rod mill is 35% 45%.

The power consumption of the ball mill is slightly higher than that of the rod mill, and the wear rate is also higher than that of the rod mill. The daily maintenance requires constant addition of a certain amount of steel balls, while the rod mill only needs to be inspected and replaced in a period of time.

To a great extent, the hardness and granularity of ore will affect the selection of grinding equipment. Some ores with dense structure, small crystal and high hardness are difficult to grind. Therefore, a longer grinding time, a harder grinding medium and a larger grinding capacity are required in the grinding process.

Rod mill adopts high carbon steel rod with carbon content of 0.8% 1% and diameter of 50-100 mm as grinding medium. In the grinding operation, most of the coarse particles are ground first, and a small part of the fine particles are ground. Therefore, the products of rod mill are rough, uniform in texture, excellent in particle shape and high qualified rate of products.

Ball mill uses steel ball as grinding medium. Because the steel ball is in point contact with the ore, the grinding products are of high fineness, and the particle size of the products is relatively fine, which is prone to over grinding, so ball mill is not suitable for the re-selection production line in ore dressing.

It is necessary to design the layout plan of the grinding workshop for concentrator in advance, so it should be considered whether it can meet the installation conditions of the mill. The cylinder of the rod mill is long cylinder type, and the cylinder of the ball mill is cylinder type or cone type.

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