There are thousands of Symons 7 crushers and units with similar technology working all over the world. As there are more effective technologies available, Metso has solutions to either upgrade or replace the Symons 7 effectively in second crushing stage.
The Symons 7 is a legend in the world of cone crushers. Yet operating one is becoming more and more challenging in a business environment that puts increasing emphasis on safety and sustainability. Productivity requirements, such as the need to maximize production uptime, are also increasing, and call for flexible on-line process adjustments.
In mining, the goal is to maximize the reduction of the ore throughout the whole crushing process. In aggregates, global megatrends in developed countries are showing increased demand of finer aggregates, while developing markets still call for more coarse aggregates. Altogether, this sets a flexibility challenge for new technology.
Mines and quarries are often faced with a decision whether to upgrade existing crusher or replace it with new and more effective technologies. Metso offers a range of important Crusher upgrades for Symons machines aimed at improving safety, operating and maintenance features of your existing crusher. However, sometimes this is simply not enough and a new machine such as the Nordberg GP7 secondary gyratory crusher should be considered.
The Nordberg GP7secondary gyratory crusher has been developed to crush feed materials efficiently, reliably and economically. With 560 kW (750 hp) power and 61 tonnes (135 000 lbs) ofweight, Nordberg GP7 has the highest performance in its weight class.
Nordberg GP7 can easily be configured to work efficiently with the rest of the crushing plant thanks to the number of strokes available. The robust design of the crusher guarantees that Nordberg GP7 adapts to varying operation and on/off feed conditions. In addition, the excellent capacity of Nordberg GP7 is the result of a constant feed opening, efficient stroke and steep cavity.
Due to the fact that Nordberg GP7 allowed power is clearly bigger than of Symons 7, the increased energy is used for making your end-product curve finer. Finer and well prepared end product curve already after secondary crusher means better feed for the downstream process, ie. the next crushing and screening stage. In mining, crushing finer reduces the costs of grinding for instance.
Replacing the Symons 7' with Nordberg GP7 secondary gyratory crusher will increase your crushing plant's productivity. Nordberg GP7 can process more ore to the same reduction or the same quantity of ore to a finer reduction than Symons 7'. Nordberg GP7 is designed to fit onto a Symons 7' cone crusher foundation and it has exactly the same footprint.That translates into higher productivity with substantial savings in plant modifications or building and foundation costs.
Cone crusher, being used to crush hard materials, was designed by the American Simmons Brothers in 1920. With nearly 100 years of development, it has become an indispensable role in the line of various medium-hard materials crushing and metal raw ore beneficiation.
It is estimated that about 5-6 billion tons of raw ore need to be crushed and ground each year. In order to meet the rapid development requirements of the construction industry and mining industry, the technology of cone crushing is also progressing.
There are 5 most popular types of cone crushers on the market: spring cone crusher, Symons cone crusher, hydraulic cone crusher, multi-cylinder hydraulic cone crusher, and single cylinder hydraulic cone crusher, according to their advancement. And the advancement mainly manifested in 4 aspects: technology, structure, degree of automation and overall machine control.
Spring cone crusher, as the earliest cone crusher formed by absorbing advanced technology in the 1980s in various countries, is equipped with reinforcing ribs at the heavy load part, and there are 10-16 groups of springs around for the removal of hard materials and iron protection.
After many years of practical experience, in order to avoid the overload of the crusher caused by the large stiffness of the spring, the design was added with a hydraulic cylinder, which is now called Symons cone crusher. The hydraulic cylinder can remove excess material in the crushing cavity in time and reduce downtime, which improves the production efficiency greatly.
With the development of hydraulic technology, the Allis-Chalmers company from America first produced hydraulic cone crusher in 1948. This cone crusher completely abandoned the spring-type safety device and adopted the technology of hydraulic adjustment for changing discharge and overload protection.
And after about ten years of research and improvement of the hydraulic technology, in order to meet the needs of larger capacity, the Nordberg Company in the United States launched a multi-cylinder hydraulic cone crusher. The 10-16 sets of spring cone-broken springs are replaced by 10-16 safety cylinders.
Based on one hydraulic clear cylinder of hydraulic cone crusher, the latter added two other hydraulic cylinders: pushing cylinder and locking cylinder for outlet discharge adjustment and overload protection.
The single-cylinder cone crusher is the most advanced cone crusher with the largest capacity on the market. With the American technology of the lamination crushing principle and the static pressure theory, it is another important breakthrough based on the multi-cylinder hydraulic cone crusher.
On the basis of retaining the functions of the pushing cylinder, locking cylinder and hydraulic cylinder, the three are creatively combined into one to realize one cylinder for three kinds of uses.
Not only the appearance and operation are more concise, but also the improvement of the cavity shape has greatly improved the crushing capacity. Besides, optimizing the details makes the maintenance of the cone crusher easier and more convenient.
From the perspective of the overall structure, the development of the cone crusher tends to be more concise and easier to operate. It is mainly manifested in two aspects: the abandonment of spring safety devices and the development of hydraulic safety devices.
Spring safety devices are used for spring cone crusher and Symons cone crusher. And at the stage of hydraulic cone crusher, they are completely replaced by hydraulic safety devices. More than 50 related parts have also been gradually streamlined, which makes the entire structure simpler and easier to operate and maintain.
The hydraulic safety device has undergone the model of multi cylinders for different uses and one single cylinder with all functions, which reduces production costs and increases capacity effectively. Besides, the structure of the whole crusher is simpler and the operation is more stable.
Types of cone crusher crushing cavity can be divided into 3 types: standard type, medium type, and short head type. The choice of cavity type is determined by the use of ore, the standard type is suitable for medium crushing, the medium type is suitable for fine crushing, and the short head type is suitable for ultra-fine crushing.
As the crusher that rely on extrusion crushing, the grain shape of cone crusher is not as good as the impact crusher. To improve this shortcoming, the multi-cylinder hydraulic cone crusher has added the design of lamination crushing and constant cavity. Based on these, not only the grain shape can be guaranteed, but also the energy consumption and cost can be reduced greatly.
The hydraulic safety device of the single-cylinder cone crusher is designed to be a single cylinder with three functions, which effectively increases the volume of the crushing cavity. The upper part of the crushing cavity is deeper, so its capacity is the largest. With the same diameter of the moving cone, the capacity is 35% -60% higher than the old-fashioned spring cone crusher.
Starting from the multi-cylinder hydraulic cone crusher, the mortar wall and the body, the copper cone sleeve, and the main shaft have been designed with zero gaps. The integrated design makes the disassembly and maintenance of the cone crusher more convenient.
To keep the crusher always in good condition for operating, a complete lubrication system has been provided from the initial spring cone crusher. It is worth mentioning that at the stage of hydraulic cone crusher, the lubrication system is replaced by a more advanced model, thin oil lubrication station. The new lubricating system is smaller in size and simpler to maintain.
In addition, the hydraulic cone crusher uses a non-contact labyrinth seal with no wear, based on the dry oil sealing, which improves the reliability of blocking dust and fundamentally eliminates common faults such as oil-water mixing of spring cone crushers.
The adjustment of spring and Symons cone crusher are in a manual way. Adjustment cap can be tightened to reduce the distance between the mortar wall and the crushing wall. And then the discharge port changes.
From the hydraulic cone crusher, the adjustment of the discharge port became automatic. Gears of hydraulic cone crusher and multi-cylinder hydraulic cone crusher can be turned deasil or widdershins so that to push the pushing cylinder to adjust the discharge port. The only thing being different is its degree of automation. the latter is more advanced.
To save maintenance time, Symons cone crusher, hydraulic cone crusher, and multi-cylinder hydraulic cone crusher are added with the clearing cylinder. When the material of is overloaded, the clearing cylinder will lift the part to discharge the material. Automatic cavity cleaning can effectively reduce downtime and ensure production efficiency.
When the hard material enters into the crushing cavity, it will give an upward force to the bottom of the rolling mortar wall, and force the fixed cone to move upward, then the spring fixed on the support sleeve and the frame will be stretched. As the fixed cone moves up, the gap between the crushing wall and the mortar wall will expand, and the hard material will fall to the discharge port.
Due to the excessive rigidity of the spring, the hydraulic cone crusher and multi-cylinder hydraulic cone crusher use the hydraulic cavity clearing cylinder and locking cylinder hydraulic insurance system for iron protection.
The clearing cylinder will be released by releasing the hydraulic cylinder in the case of iron passing and when the cone crusher be jammed instantly. The support sleeve and the fixed cone part can be lifted to automatically eliminate the faults in the crushing cavity so that the fault can be handled without disassembly.
Controlling the machine manually is time-consuming and laborious. With the continuous development of technology, the design of the hydraulic cone crusher adopts a fully automatic control system, which realizes remote and machine-side control, making the control of machine more convenient.
The multi-cylinder hydraulic and single-cylinder cone crushers use a more advanced full-automatic control system based on PLC + touch screen, which is not only easy to operate, but also more sensitive and reliable in touch.
Cone crusher can crush harder materials compared with other crushers, which determines its irreplaceable position in ore beneficiation and rock crushing line. Over the years, cone crushers have become the mainstay for metal ore beneficiation and high hardness rocks crushing.
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During the using process, if the worker operates and maintains the crusher according to correct standards, it will have great significance in normal production, output, quality, service life, working efficiency and the prevention of accidents, etc.
At present, the common cone crushers are mainly the single toggle cone crusher and compound cone crusher (Symons cone crusher). Although both types of cone crushers are totally different, they have the same operation procedure.
The operation procedure of cone crusher can be divided into four stages: before the start, at start-up, at run time and turning-off time. All conditions should be paid attention in each stage, and the potential problems can be found and solved timely and the service time can be prolonged.
Turn on the lubricating oil pump to run for three to five minutes. After everything runs well, turn on the crusher as required. After the crusher idles for one to two minutes, confirm that all things are well, and feed the rocks or stones.
During the crushing process, there is a great impact on the concave which makes the filled zinc layer be out of shape. Therefore, the U-type bolt should be tightened frequently to make the concave fix and avoid concave from deformation.
The mantle is fixed by the upper bolt of the main shaft. The looseness of the bolt can make the mantle unstable, even the filled layer may fall off to cause downtime. Hence, the bolts should be often checked and fixed to avoid looseness.
The spherical bearing should be installed in the borehole of crusher closely. After a long period of working, the tightness of crusher' parts can be broken. The tightness of spherical bearing must be checked frequently, and the oil gallery of the spherical bearing should be kept clean.
Water seal is the equipment for preventing crusher from dust, which is very important to the normal operation of cone crusher. Therefore, daily maintenance and checking its integrality are very necessary.
Through the study of this article, you must have a deeper understanding of the operation and maintenance of the cone crusher. In the case of the above-mentioned failure of the crusher, the problem is analyzed and solved by referring to the method given in this article.
Roll crushers are generally not used as primary crushers for hard ores. Even for softer ores, like chalcocite and chalcopyrite they have been used as secondary crushers. Choke feeding is not advisable as it tends to produce particles of irregular size. Both open and closed circuit crushing are employed. For close circuit the product is screened with a mesh size much less than the set.
Fig. 6.4 is a typical set up where ore crushed in primary and secondary crushers are further reduced in size by a rough roll crusher in open circuit followed by finer size reduction in a closed circuit by roll crusher. Such circuits are chosen as the feed size to standard roll crushers normally do not exceed 50mm.
Cone crushers were originally designed and developed by Symons around 1920 and therefore are often described as Symons cone crushers. As the mechanism of crushing in these crushers are similar to gyratory crushers their designs are similar, but in this case the spindle is supported at the bottom of the gyrating cone instead of being suspended as in larger gyratory crushers. Fig. 5.3 is a schematic diagram of a cone crusher. The breaking head gyrates inside an inverted truncated cone. These crushers are designed so that the head to depth ratio is larger than the standard gyratory crusher and the cone angles are much flatter and the slope of the mantle and the concaves are parallel to each other. The flatter cone angles helps to retain the particles longer between the crushing surfaces and therefore produce much finer particles. To prevent damage to the crushing surfaces, the concave or shell of the crushers are held in place by strong springs or hydraulics which yield to permit uncrushable tramp material to pass through.
The secondary crushers are designated as Standard cone crushers having stepped liners and tertiary Short Head cone crushers, which have smoother crushing faces and steeper cone angles of the breaking head. The approximate distance of the annular space at the discharge end designates the size of the cone crushers. A brief summary of the design characteristics is given in Table 5.4 for crusher operation in open circuit and closed circuit situations.
The Standard cone crushers are for normal use. The Short Head cone crushers are designed for tertiary or quaternary crushing where finer product is required. These crushers are invariably operated in closed circuit. The final product sizes are fine, medium or coarse depending on the closed set spacing, the configuration of the crushing chamber and classifier performance, which is always installed in parallel.
For finer product sizes, i.e. less than 6mm, special cone crushers known as Gyradisc crushers are available. The operation is similar to the standard cone crushers except that the size reduction is caused more by attrition than by impact, . The reduction ratio is around 8:1 and as the product size is relatively small the feed size is limited to less than 50mm with a nip angle between 25 and 30. The Gyradisc crushers have head diameters from around 900-2100mm. These crushers are always operated in choke feed conditions. The feed size is less than 50mm and therefore the product size is usually less than 6-9mm.
Crushing is accomplished by compression of the ore against a rigid surface or by impact against a surface in a rigidly constrained motion path. Crushing is usually a dry process and carried out on ROM ore in succession of two or three stages, namely, by (1) primary, (2) secondary, and (3) tertiary crushers.
Primary crushers are heavy-duty rugged machines used to crush ROM ore of () 1.5m size. These large-sized ores are reduced at the primary crushing stage for an output product dimension of 1020cm. The common primary crushers are of jaw and gyratory types.
The jaw crusher reduces the size of large rocks by dropping them into a V-shaped mouth at the top of the crusher chamber. This is created between one fixed rigid jaw and a pivoting swing jaw set at acute angles to each other. Compression is created by forcing the rock against the stationary plate in the crushing chamber as shown in Fig.13.9. The opening at the bottom of the jaw plates is adjustable to the desired aperture for product size. The rocks remain in between the jaws until they are small enough to be set free through this opening for further size reduction by feeding to the secondary crusher.
The type of jaw crusher depends on input feed and output product size, rock/ore strength, volume of operation, cost, and other related parameters. Heavy-duty primary jaw crushers are installed underground for uniform size reduction before transferring the ore to the main centralized hoisting system. Medium-duty jaw crushers are useful in underground mines with low production (Fig.13.10) and in process plants. Small-sized jaw crushers (refer to Fig.7.32) are installed in laboratories for the preparation of representative samples for chemical analysis.
The gyratory crusher consists of a long, conical, hard steel crushing element suspended from the top. It rotates and sweeps out in a conical path within the round, hard, fixed crushing chamber (Fig.13.11). The maximum crushing action is created by closing the gap between the hard crushing surface attached to the spindle and the concave fixed liners mounted on the main frame of the crusher. The gap opens and closes by an eccentric drive on the bottom of the spindle that causes the central vertical spindle to gyrate.
The secondary crusher is mainly used to reclaim the primary crusher product. The crushed material, which is around 15cm in diameter obtained from the ore storage, is disposed as the final crusher product. The size is usually between 0.5 and 2cm in diameter so that it is suitable for grinding. Secondary crushers are comparatively lighter in weight and smaller in size. They generally operate with dry clean feed devoid of harmful elements like metal splinters, wood, clay, etc. separated during primary crushing. The common secondary crushers are cone, roll, and impact types.
The cone crusher (Fig.13.12) is very similar to the gyratory type, except that it has a much shorter spindle with a larger-diameter crushing surface relative to its vertical dimension. The spindle is not suspended as in the gyratory crusher. The eccentric motion of the inner crushing cone is similar to that of the gyratory crusher.
The roll crusher consists of a pair of horizontal cylindrical manganese steel spring rolls (Fig.13.14), which rotate in opposite directions. The falling feed material is squeezed and crushed between the rollers. The final product passes through the discharge point. This type of crusher is used in secondary or tertiary crushing applications. Advanced roll crushers are designed with one rotating cylinder that rotates toward a fix plate or rollers with differing diameters and speeds. It improves the liberation of minerals in the crushed product. Roll crushers are very often used in limestone, coal, phosphate, chalk, and other friable soft ores.
The impact crusher (Fig.13.15) employs high-speed impact or sharp blows to the free-falling feed rather than compression or abrasion. It utilizes hinged or fixed heavy metal hammers (hammer mill) or bars attached to the edges of horizontal rotating discs. The hammers, bars, and discs are made of manganese steel or cast iron containing chromium carbide. The hammers repeatedly strike the material to be crushed against a rugged solid surface of the crushing chamber breaking the particles to uniform size. The final fine products drop down through the discharge grate, while the oversized particles are swept around for another crushing cycle until they are fine enough to fall through the discharge gate. Impact crushers are widely used in stone quarrying industry for making chips as road and building material. These crushers are normally employed for secondary or tertiary crushing.
If size reduction is not completed after secondary crushing because of extra-hard ore or in special cases where it is important to minimize the production of fines, tertiary recrushing is recommended using secondary crushers in a close circuit. The screen overflow of the secondary crusher is collected in a bin (Fig.13.16) and transferred to the tertiary crusher through a conveyer belt in close circuit.
Primary jaw crushers typically operate in open circuit under dry conditions. Depending on the size reduction required, the primary jaw crushers are followed by secondary and tertiary crushing. The last crusher in the line of operation operates in closed circuit. That is, the crushed product is screened and the oversize returned to the crusher for further size reduction while the undersize is accepted as the product. Flow sheets showing two such set-ups are shown in Figs. 3.1 and 3.2.
Jaw crushers are installed underground in mines as well as on the surface. When used underground, jaw crushers are commonly used in open circuit. This is followed by further size reduction in crushers located on the surface.
When the run of mine product is conveyed directly from the mine to the crusher, the feed to the primary crusher passes under a magnet to remove tramp steel collected during the mining operation. A grizzly screen is placed between the magnet and the receiving hopper of the crusher to scalp (remove) boulders larger than the size of the gape. Some mines deliver product direct to storage bins or stockpiles, which then feed the crushers mechanically by apron feeders, Ross feeders or similar devices to regulate the feed rate to the crusher. Alternately haulage trucks, front-end loaders, bottom discharge railroad cars or tipping wagons are used. In such cases, the feed rate to the crusher is intermittent which is a situation generally avoided. In such cases of intermittent feed, storage areas are installed and the feed rate regulated by bulldozers, front loaders or bin or stockpile hoppers and feeders. It is necessary that the feed to jaw crushers be carefully designed to balance with the throughput rate of the crusher. When the feed rate is regulated to keep the receiving hopper of the crusher full at all times so that the volume rate of rock entering any point in the crusher is greater than the rate of rock leaving, it is referred to as choke feeding. During choke feeding the crushing action takes place between the jaw plates and particles as well as by inter-particle compression. Choke feeding necessarily produces more fines and requires careful feed control. For mineral liberation, choked feeding is desirable.
When installed above ground, the object of the crushing circuit is to crush the ore to achieve the required size for down stream use. In some industries, for example, iron ore or coal, where a specific product size is required (iron ore 30+6mm), careful choice of jaw settings and screen sizes are required to produce the minimum amount of fines (i.e. 6mm) and maximum the amount of lump ore within the specified size range. For hard mineral bearing rocks like gold or nickel ores where liberation of minerals from the host rock is the main objective, further stages of size reduction are required.
A gold ore was crushed in a secondary crusher and screened dry on an 1180micron square aperture screen. The screen was constructed with 0.12mm diameter uniform stainless steel wire. The size analysis of the feed, oversize and undersize streams are given in the following table. The gold content in the feed, undersize and oversize streams were; 5ppm, 1.5ppm and 7ppm respectively. Calculate:
The self tuning control algorithm has been developed and applied on crusher circuits and flotation circuits [22-24] where PID controllers seem to be less effective due to immeasurable change in parameters like the hardness of the ore and wear in crusher linings. STC is applicable to non-linear time varying systems. It however permits the inclusion of feed forward compensation when a disturbance can be measured at different times. The STC control system is therefore attractive. The basis of the system is:
The disadvantage of the set up is that it is not very stable and therefore in the control model a balance has to be selected between stability and performance. A control law is adopted. It includes a cost function CF, and penalty on control action. The control law has been defined as:
A block diagram showing the self tuning set-up is illustrated in Fig. 18.27. The disadvantage of STC controllers is that they are less stable and therefore in its application a balance has to be derived between stability and performance.
Bone recycling is a simple process where useful products can be extracted. Minerals such as calcium powder for animal; feed are extracted from the bone itself. The base material for cosmetics and some detergent manufacturing needs are extracted from the bone marrow.
The bone recycling process passes through seven stages starting from crushing and ending with packing. Figure 13.14 gives a schematic diagram showing the bone recycling process which goes through the following steps:
Following the standard procedures in the Beijing SHRIMP Center, zircons were separated using a jaw crusher, disc mill, panning, and a magnetic separator, followed by handpicking using a binocular microscope. The grains were mounted together with the standard zircon TEM (417Ma, Black etal., 2003) and then polished to expose the internal structure of the zircons. Cathodoluminescence (CL) imaging was conducted using a Hitachi SEM S-3000N equipped with a Gatan Chroma CL detector in the Beijing SHRIMP Center. The zircon analysis was performed using the SHRIMP II also in the Beijing SHRIMP Centre. The analytical procedures and conditions were similar to those described by Williams (1998). Analytical spots with 25m diameter were bombarded by a 3nA, 10kV O2 primary ion beam to sputter secondary ions. Five scans were performed on every analysis, and the mass resolution was 5000 (at 1%). M257 standard zircon (561.3Ma, U=840ppm) was used as the reference value for the U concentration, and TEM standard zircons were used for Pb/U ratio correction (Black etal., 2003). Common Pb was corrected using the measured 204Pb. Data processing was performed using the SQUID/Isoplot programs (Ludwig, 2001a,b). Errors for individual analyses are at 1, but the errors for weighted average ages are at 2.
A stockpile can be used to blend ore from different sources. This is useful for flotation circuits where fluctuations ingrade can change the mass balance and circulating loads around the plant. Blending can also be done on the ROMpad.
The lowest cost alternative is to have no surge at all, but rather to have a crushing plant on line. This is workable for small-scale plant with single-stage jaw crushers as the availability of these simple plant is very high provided control over ROM size is maintained.
The second alternative is to use a small live surge bin after the primary crusher with a secondary reclaim feeder. Crushed ore feeds this bin continuously and the bin overflows to a small conveyor feeding a dead stockpile. In the event of a primary crusher failure, the crusher loader is used to reclaim the stockpile via the surge bin, which doubles as an emergency hopper.
For coarse ore, the next alternative is a coarse ore stockpile. Stockpiles of this type are generally 1525% live and require a tunnel (concrete or Armco) and a number of reclaim feeders to feed the milling circuit.
Multi-stage crushing circuits usually require surge capacity as the availability of each unit process is cumulative. A fine-ore bin is usually required. Smaller bins are usually fabricated from steel as this is cheaper. Live capacity of bins is higher than stockpiles but they also require a reclaim tunnel and feeders.
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The cone crusherwas designed primarily with a view to achieving top performance in the field of fine-reduction crushing. It has also been adapted to what is designated simply as fine crushing, which extends into a range below that ordinarily defined by the term fine-reduction. Although the eccentric speeds of the various sizes of this type are not quite so high as the speeds used for the Newhouse crusher, the Hydro-cone crusher definitely rates as a high-speed machine, its product comparing quite closely to that of the former type, for equal close-side settings.Probably the outstanding feature of the. Hydrocone crusher is the hydraulic support, from which its name is derived and which is clearly shown in the sectional view. This device makes it possible to adjust the crusher to any desired setting within its range in a matter of seconds;adjustments may be made while the crusher is running, although the feed must be shut off before operating the adjusting pump. An accumulator in the hydraulic system provides protection against tramp iron or packing.
Cone crushers are used in AG and SAG grinding circuits to increase tonnage by effectively dealing with any pebble (critical size) build-up problem. Normally, heavy-duty short-head crushers are employed to crush pebbles. Power and crusher cavity level are the key variables for monitoring and controlling the crusher operation. Crusher product size is adjusted by changing the closed side setting.
On the left is a diagram of the Hydro-cone crushing chamber. A comparison of this chamber with those previously discussed is interesting. It will be noted that the choke-point has been raised far above the discharge level, in fact, to a point not far below the nip-point for the recommended maximum one-way feed dimension. By virtue of the decided flare of the head, and the corresponding flare of the top shell bore, the line-of-mean-diameters slopes sharply away from the crusher centerline. For some, distance above the discharge point the angle between head and concave is very acute; in fact, at the open-side position of the head, this zone is almost parallel. For recommended operating conditions, i.e., for safe combinations of throw and setting, and with screened feed, this type of crushing chamber does not approach anything like a choke or near-choke condition. For the combination shown in the diagram the ratio of volume reduction is almost 1:1 from zone 0-1 to zone 2-3 at the choke-point; consequently, if the crusher is given a screened feed (as all fine-reduction crushers should be) the reduction in voids by the time the choke-point is reached cannot very well reach serious proportions. The diagram shows the standard chamber. With screened feed, these crushers will operate at closed-side discharge settings equal to the throw of the head at the discharge point (usually spoken of as eccentric-throw.)
The level in the crusher feed pocket is an important variable since it can indicate whether the feed is building up. A build-up could lead to a plugin the feed chute, a spill through the skirting on the crusher feed, or a crusher plug. None of these are desirable.
In a normal feed situation, the level in the crusher cavity is kept fairly low, just enough to ensure that there is sufficient feed to keep the crusher working, but if the feed has to be suspended suddenly because of impending plugging, the crush-out wont take too long (10 seconds or less). Normal feed is usually used in standard crushers where the feed particle size is quite large, say greater than 65 mm.
Choke feed is when the crusher cavity is kept full, without spilling out through the skirting. Choke feeding is usually used in short-head crushers where the feed particle is smaller than that for a standard crusher.
This crusher is a modification of the standard machine, developed for fine-crushing duty. Mechanically, the machine is the same in every respect as the standard crusher of the same type, but for each developed size of machine a special top shell and the concave ring has been designed, with reduced receiving opening, reduced angularity between head and concave, and, consequently, superior characteristics at the finer settings. Medium crushing chambers may be operated at close-side settings of one-half the eccentric-throw, on screened feed; hence capacities at the finer settings are better than those of the standard type. Fine crushing chambers operate at one-fourth the eccentric throw. Inasmuch as the maximum feed size is smaller in the case of the fine chamber, the ratios of reduction are approximately the same for both machines.
There are two main types of cone crushers: standard and shorthead. They differ by the shape of the cavity. The standard crusher cavity is wider to accommodate larger feed-size material. The short head crusher is designed to crush finer material and to produce a finer product.
The closest approach between the mantle and the bowl liner is called the closed side setting. This is usually specified by the metallurgist to give the desired crusher product discharge size. It can be checked by running the crusher empty, hanging a lead plug into the crusher bowl, and then removing it to measure the gap. The gap is adjusted by rotating the bowl. Some crushers are equipped with a hydraulic jack mechanism on the crushing head assembly instead of having a bowl adjustment ring. The head can be raised or lowered to meet the operators needs. It can be very helpful in operation and process control.
The Symons Cone Crusher has come into almost universal use during the last few years for the final stage of crushing. It is a development of the secondary gyratory crusher, which is merely a small gyratory crusher designed to break the product of the primary machine down to about 1-in. size; but the main shaft of a cone crusher instead of being suspended from a spider is supported on a large socket bearing situated immediately under the crushing head and protected from grit and dust by a sealing assembly, this bearing taking the whole of the crushing load.
Fig. 8 gives a sectional view of the machine. The main shaft is carried in a long gear-driven eccentric, the rotation of which causes the gyration of the head in the usual way, but the center of gyration is at the apex of the crushing head instead of in the spider. At the top of the bowl, therefore, the lumps of ore entering the crushing zone are cracked by short powerful strokes; but at the bottom the head has a much longer but less powerful stroke, enabling the ore in the finishing stages to be rapidly crushed and quickly discharged without any tendency to choke, a condition which reduces over crushing to a minimum. This, together with the curved shape of the bowl, accounts for the large reduction ratio possible with this type of machine and makes it superior to other secondary crushers and coarse rolls.
It will be seen that the head and the bowl are parallel at the lower part of the crushing zone. The parallel space is deep enough, in conjunction with the speed of gyration, to ensure that no piece of ore can pass through it without being struck two or three times by the head before it falls clear. It follows that, unlike the jaw and gyratory crushers, the size of the product is determined by the distance apart of the bottom edges of the head and bowl in the position when they are closest together.
Coarse buttress threads on the outer circumference of the bowl fit into corresponding threads on the inner side of the adjusting ring, which is held down to the mainframe by a circle of long heavy springs, flexible enough to allow the whole assembly to rise should tramp iron or other uncrushable material enters the crushing zone. By means of a windlass and chain, the bowl can be rotated in the threads that support it in the adjusting ring while the machine is running, thus enabling the bowl liner to be adjusted for wear or the size of the product to be changed without stopping. The cone crusher is usually set to give a 3/8-in. or -in. product when discharging to ball mills.
Table 9 gives particulars of the different sizes of crushers. The capacity figures are based on material weighing 100 lb. per cubic foot and must be increased in direct proportions for heavier ores. It will be noted that each size of machine has two ranges of capacity; this is due to the fact that it can be fitted with a coarse or a fine crushing bowl according to the duty that is required of it. With either one, the range of reduction is greater than is economically possible with any other type of dry crushing machine.
A possible disadvantage of the cone crusher is that as a rule it cannot be choke-fed, but must be given an even feed of ore if it is to do efficient work. Should circumstances call for the installation of a machine that can be run if necessary with the ore piled up over the top of the head, a secondary gyratory crusher of the suspended shaft type will be required. The Traylor Reduction Crusher Type TZ, which is constructed on the principles of an ordinary gyratory crusher, but is fitted with a curved bowl liner similar to that of the Symons Cone Crusher, is designed to meet the case. Although the suspension of the shaft restricts the movement of the head to a smaller circle of gyration than that of the cone crusher, the ratio of reduction is still large enough to enable it to crush the product of the primary breaker to -in. size (-in. for the large machines), and it fulfills the condition that it can be choke-fed. Owing to the smaller movement of the head, however, the capacity for a given range is much less than that of the equivalent size of cone crusher, and the latter is therefore preferred when choke-feeding can be avoided.
The Symons Shorthead Cone Crusher, which is constructed on the same general principles as the larger machine, is designed to follow the latter, taking its product at 1-in. and reducing it to about -in. size. The strains imposed on the crushing members, however, would be very heavy if the machine were run with the discharge opening set to -in. or less. It is usual, therefore, to crush in closed circuit with a screen, the discharge opening of the bowl being set to 5/8 or in. Thus a circulating load is built up and a certain amount of choke-crushing takes place, but the method actually gives greater efficiency with a finer product than can be obtained in an open circuit, whatever the discharge setting of the bowl in the latter case.
In ordinary crushing practice, the grinding section is supplied with -in. or 3/8-in. material direct from Symons Cone Crushers. But the demand is for a finer feed and it seems likely that the Shorthead Cone Crusher will satisfy this demand to the exclusion of fine crushing rolls.
Symons Cone Crushers have been used extensively for secondary crushing in metallic, non-metallic, rock products, and industrial operations. The Symons Cone was developed to give large capacity, fine crushing. The combination of high speed and wide travel of the cone results in a series of rapid, hammer-like blows on the material as it passes through the crushing cavity and permits the free flow of material through the cavity.
Reduction in size of any particle, with each impact of the head, is regulated by the opening between the head and bowl at that point. A threaded arrangement of the bowl affords a quick and easy method for changing the size of the product or to compensate for wear. This adjustment can be made while the crusher is operating. A parallel zone between the lower portion of the crushing members assures uniform sizing.
Frame, adjustment ring, and cone are made of cast steel; gears are made of specially treated steel and have cut teeth; all bearings are bronze; mantle and bowl liners are manganese steel. The head and shaft can be removed as a unit, and other parts such as the eccentric and thrust bearings can easily be lifted out after the head is removed. The countershaft assembly can also be removed as a complete unit.
The circle of heavy coil springs, which holds the bowl and adjustment ring down firmly onto the frame, provides automatic protection against damage due to tramp iron. These springs compress, allowing the bowl to rise the full movement of the head until non-crushable material passes through. The springs then automatically return to their normal position.
Symons Cone Crushers are made in Standard and Short Head types. They are of the same general construction but differ in the shape of the crushing cavity. The Standard cone is used for intermediate crushing. The Short Head cone is used for finer crushing. It has a steeper angle of the head, a shorter crushing cavity, and greater movement of the head at the top of the crushing cavity.
If you observe the illustrations you will notice that the center line of the main shaft is at an angle to the center line of the crusher. The center of the main shaft bisects the center line of the crusher at the opening of the crushing chamber. As the MANTLE revolves that point is the pivot point of the mantle. This means that both the top and the bottom of the crusher mantle have a circular gyrating motion.
Tramp iron had long been a source of worry to those engaged in fine crushing.Here is what one operator had to say.Shutdowns were frequent, costs were uncertain because of enforced delays due to excessive breakage. Plugged machines had to be freed continually with a torch tocut out frozen and wedged-in tramp iron.The cone crusher overcame these troubles,helped reduce and stabilize costs. The bestevidence of this statement is the universalacceptance of the cone as the outstandingcrusher in its field.
While tramp iron is not recommended as a regular diet for a Cone Crusher, its construction is such that damage will not result should any ordinary noncrushable material get into the crushing cavity. The band of heavy coil springs encircling the frame allows the bowl to lift from its seat with each movement of the head until Such non-crushable object passes off into the discharge. The tramp iron shown in the accompanying illustration passed the protective devices installed for its removal and would have resulted in expensive repairs and long shutdown periods for any crusher except the Symons Cone.
Cone crushers can have two types of heads, standard and short head types. The principle difference between the two is in the shape (size and volume) of the crushing cavities and feed plate arrangements. Standard head cone crushers have cavities that are designed to take a primary crushed feed ranging up to 300mm generating product sizes around 20mm to 40mm. For finer products, short head cone crushers are normally used. They have a steeper angle of the head and a more parallel crushing cavity than the standard machines. Due to the more compact chamber volume and shorter working crushing length, the much needed higher crushing forces/power can be imparted to the smaller-sized material being fed to the crusher. Cavities for the short head machine are designed to produce a crushed product ranging from 5mm to 20mm in a closed circuit.
At the discharge end of the cone crusher is a parallel crushing section, where all material passing through must receive at least one impact. This ensures that all particles, which pass through the cone crusher, will have a maximum size, in at least one dimension, no larger than the set of the crusher. For this reason, the set of a cone crusher can be specified as the minimum discharge opening, being commonly known as the closed side setting (CSS).
Here are facts about the conecrusher known as Hydrocone. This line of hydraulically adjusted gyratory crushers was developed in smaller sizes some fifteen years ago by Allis-Chalmers to meet a demand for improved secondary or tertiary crushing units. The line is now expanded to include sizes up to 84-in. diameter cones.
This modern crusher is the result of many years of experience in building all types of crushing equipment, when the first gyratory or cone crusher, the Gates, was put into operation. Overall these years AC has followed a continuing policy of improvement in crusher engineering, changes in design being based on operating experience of crushers in actual operation.
The Hydrocone cone crusher is the logical outgrowth, a crusher having a means of rapidly changing product size or compensating for wear on the crushing surfaces a crusher which produces a better, more cubical product than any comparable crusher and a crusher so designed that it can be operated and maintained with a minimum of expense.
The most important fact about the Hydrocone crusher is its hydraulic principle of operation. Hydraulic control makes possible quick, accurate product size adjustments fast unloading of the crushing chamber in case of power failure or other emergency protection against tramp iron or other uncrushable materials in the crushing chamber. Another important fact about this crusher is its simplicity of design and operation. The accompanying sketch shows the simplicity of the Hydrocone crushers principle of operation. The main shaft assembly, including the crushing cone, is supported on a hydraulic jack. When oil is pumped into or out of the jack the mainshaft assembly is raised or lowered, changing the crusher setting.
Since the crushing cone is supported on a hydraulic jack, its position with respect to the concave ring, and therefore the crusher setting, can be controlled by the amount of oil in the hydraulic jack.
Speed-Set control raises or lowers the crushing shaft assembly hydraulically, and permits quick adjustment to produce precise product specifications without stopping the crusher. Speed-Set control also provides a convenient way to compensate for wear on crushing surfaces.
On Hydrocone crushers in sizes up to 48-in., the Speed-Set device is a hand-driven gear pump; on the larger sizes a motor-driven gear pump operated by push-button. On all sizes the setting can be changed in a matter of minutes by one man without additional equipment, reducing downtime materially.
Protection against tramp iron or other uncrushable materials is afforded by an accumulator in the hydraulic system. This consists of a neoprene rubber oil-resistant bladder inside a steel shell. This bladder is inflated with nitrogen to a predetermined pressure higher than the average pressures encountered during normal crushing.
Ordinarily, the Automatic Reset remains inoperative, but if steel or some other foreign material should enter the crushing chamber, the oil pressure in the hydraulic jack will exceed the gas pressure in the accumulator. The bladder will then compress, allowing the oil to enter the steel shell. This permits the crushing cone to lower and discharge the uncrushable material without damage to the crusher.
After the crushing chamber is freed of the foreign material, the gas pressure in the accumulator will again exceed the oil pressure in the hydraulic system. Oil is then expelled from the accumulator shell and the crushing cone is returned to its original operating setting automatically.
A Hydrocone crusher will produce a cubical product with excellent size distribution and a minimum of flats and slivers. This is especially important in the crushed stone industry where a cubical stone is required to meet rigid product specifications. It is also of considerable significance in the mining industry where the elimination of large amounts of tramp oversize reduces circulating loads or makes open circuit crushing possible.
The reason why the Hydrocone crusher will produce such a uniform, cubical product is that it has a small eccentric throw with respect to the crusher setting. This means a smaller effective ratio of reduction during each crushing stroke, and therefore, the production of fewer fines and slivers. Likewise, a small eccentric throw means a small open side setting, which results in a smaller top size of the product. A large percentage of the product from a Hydrocone crusher will be of a size equal to or finer than the close side setting.
For fine crushing, or in installations where the feed to the crusher is irregular, the use of a wobble plate feeder is recommended. This feeder is installed in place of the spider cap and affords a means of controlling the feed to the crusher, as well as a means of distributing the feed evenly around the crushing chamber.
Essentially, the feeder consists of a plate that is oscillated by a shaft extending down into the crushers main shaft. The motion of the main shaft oscillates or wobbles the feeder plate. The plate is supported on a rubber mounting which permits its motion and, at the same time, positively seals the top of the spider bearing against the entry of dust. Maintenance is reduced by the use of self-lubricating bushings between the feeder plate shaft and the crusher main shaft.
Hydrocone crushers are mounted on rubber machinery mountings in order to reduce installation costs and make it possible to locate these machines on the upper floors of crushing plants. These mountings operate without maintenance, absorb the gyrating motion of the crusher, thereby eliminating the need for massive foundations. Rubber mountings also prolong the life of the eccentric bearing, since this bearing is not subjected to the severe pounding encountered when rigid mountings are used.
The exclusion of dust and dirt from the internal mechanism of the crusher is of extreme importance from a maintenance standpoint. To accomplish this, Hydrocone crushers are equipped with one of the most effective dust seals yet devised.
This seal consists of a self-lubricating, graphite impregnated plastic ring which is supported from the head center in such a way that it is free to rotate, or gyrate, independently of the head center.
The plastic ring surrounds the dust collar with only a very slight clearance between the two parts. With the plastic ring being free to move as it is, it accommodates the rotation, gyration, and vertical movement of the main shaft assembly, maintaining the seal around the dust collar at all times. Because of its lightweight and self-lubricating characteristics, wear on the plastic ring is negligible.
The ease with which any wearing part can be replaced is of the utmost importance to any crusher operator. With this in mind, the Hydrocone crusher has been designed so that any part can be replaced by disturbing only a minimum number of other parts.
For example, the Mantalloy crushing surfaces are exposed by simply removing the top shell from the crusher. This can be done easily by removing the nuts from the studs at the top and bottom shell joint. The eccentric and hydraulic support mechanisms are serviced from underneath the crusher without disturbing any of the feeding arrangements, or the upper part of the crusher.
Efficient lubrication of all wearing parts is one of the reasons why crushing costs are low with the Hydrocone crusher. On most sizes, lubrication is divided into three distinct systems, each functioning independently.
This bearing, whether of the ball and socket type as on the smaller sizes, or of the hourglass design (as shown) found on the larger Hydrocone crushers, is pool lubricated. On the 51, 60 and 84-inch sizes, provision is made for introducing the lubricant from outside the top shell through the spider arm. On the smaller crushers, oil is introduced through an oil inlet in the spider cap. On all sizes, oil is retained in the bearing by a garter-type oil seal located in the base of the spider bearing.
All Hydrocone crushers are provided with a compact external lubrication system consisting of an oil storage tank, an independently motor-driven oil pump, a pressure-type oil filter, and a condenser-type cooler.
Cool, clean oil is pumped into the crusher from the conditioning tank, lubricating first the three-piece step bearing assembly. The oil then travels up the inner surface of the eccentric, lubricating the eccentric bearing and main shaft.
At the top of the eccentric, the oil is split into two paths. Part of the oil flow passes through ports in the eccentric and down its outer surface, lubricating the bronze bottom shell bushing, driving gears and wearing ring. On the 48-in. and smaller crushers, the balance of the oil overflows the eccentric and returns over the gears to the bottom of the crusher where it flows by gravity back into the conditioning tank. On the 51-in. and larger Hydrocone crushers, any oil which overflows the top of the eccentric is returned directly to the conditioning system without coming into contact with the gears.
On all but the 36 and 48-in. Hydrocone crushers, the countershaft bearings are of the anti-friction type with separate pool lubrication. Both ends of the countershaft bearing housing are sealed by garter spring-type oil seals to prevent dirt or other contaminants from entering the system.
Rather than use one eccentric throw under all operating conditions, Hydrocone crushers are designed to operate most efficiently with a predetermined ratio of eccentric throw to the crusher setting. By operating with an eccentric throw specifically selected for a given application, the most desirable crushing conditions are attained the most economical use of Mantalloy crushing surfaces reduced crusher maintenance a more cubical product.
The eccentric throw is controlled by a replaceable bronze sleeve in the cast steel eccentric. This sleeve, being a wearing part, can be renewed readily in the field. Also, should operating conditions change, the throw or motion of the crushing head can be changed accordingly.
Because of the large choice of eccentric throws available and the variety of crushing chambers that may be obtained a Hydrocone crusher may be selected that will fulfill the requirements of almost any secondary or tertiary crushing operation.
They may be used in the crushed stone industries to produce a premium cubical product in the mining industries to produce a grinding mill feed having a minimum of oversize, thereby reducing circulating loads and making open circuit crushing possible. The Hydrocone crusher is used in the cement industry to reduce cement clinker prior to finish grinding.
One of three general types of crushing chambers can be furnished for any size Hydrocone crusher to suit your specific needs. The selection of the proper chamber for a given application is dependent upon the feed size, the tonnage to be handled and the product desired. A crusher already in use can be readily converted to meet changing requirements, making this machine highly flexible in operation.
The Coarse crushing chamber affords the maximum feed opening for a given size crusher. Crushers fitted with a Coarse chamber can be choke fed, provided that product size material in the feed is removed.
The Coarse chamber has a relatively short parallel zone and is designed to be operated at a close side setting equal to or greater than the eccentric throw. For example, a crusher with a 3/8-in. the eccentric throw should be operated at a 3/8-in. (or more) close side setting, and therefore a -in. open side setting. Optimum capacity and product will result when operated under these conditions, as well as most economical wear on the mantalloy crushing surfaces.
One way dimension (slot size) of the feed to a crusher fitted with a Coarse chamber should not exceed two-thirds to 70 percent of the feed opening. The maximum feed size to an 848 Hydrocone crusher would therefore be about 5-in. one way dimension.
The use of a wobble plate feeder, furnished as optional equipment, is recommended if the feed size is relatively large, if the crusher is to be operated in closed circuit, or if the feed to the crusher is irregular.
If the Hydrocone crusher is operated with a Coarse crushing chamber, the product will average about 60% passing a square mesh testing sieve equal to the close side setting of the crusher. On certain materials which break very slabby, this percentage will be somewhat lower, and on cubically breaking material the percentage will be somewhat higher. As an average, approximately 90% of the product will pass a square mesh testing sieve corresponding to the open side setting, although this percentage frequently runs higher.
The Intermediate crushing chamber has a feed opening somewhat less than a coarse crushing chamber, but because of its longer parallel zone, is designed to be operated at a close side setting equal to or greater than half the eccentric throw. For example, with a -in. eccentric throw, the minimum close side setting would be 3/8-in.
Crushers fitted with this type of chamber can be choke fed, provided that product size material in the feed be removed ahead of the crusher. The one-way dimension or slot size of the feed to a crusher should not exceed approximately half the receiving opening. A 436 Hydrocone crusher with a 5/8-in. the eccentric throw could be operated at 5/16-in. close side setting and feed size should not exceed 2-in. one-way dimension.
The wobble plate feeder, although not required under most circumstances, is recommended if the feed is irregular, or if the crusher is operated as a re-crusher, at a relatively close setting, or in a closed circuit.
Because of the longer parallel zone in this crushing chamber, a somewhat greater percentage of the product will pass a square mesh testing sieve equal to the close side setting. This will usually average about 65 to 70%, with this percentage varying, depending on the material being crushed. Very frequently, 100% of the product will pass a square mesh testing sieve equal to the open side setting of the crusher.
The Fine crushing chamber has the longest parallel zone and therefore the smallest feed opening for any given size crusher. It can be operated at ratios of eccentric throw to close side setting of up to 4 to 1. With a -in. throw, for example, a 236 Hydro-cone crusher could be operated at 3/16-in. on the close side.
Because of their design, crushers with Fine crushing chambers cannot be choke fed but must be equipped with the wobble plate feeder. The maximum one-way dimension of the feed approaches the crusher feed opening. A 348 Hydrocone crusher can be fed with material up to 3-in. one-way dimension.
The Fine crushing chamber will give the highest percentage passing the close side setting of any of the chambers discussed here. The product will average approximately 75% passing a square mesh testing sieve equal to the close side setting. Because of the long parallel zone, the top size of the product will be only slightly larger than the close side setting of the crusher.
In addition to the three general types of crushing chambers described here, special chambers can be designed to meet varying operating requirements, giving the crusher even greater flexibility than can be obtained with these three main types.
For example, a special concave ring can be used in a 636 Hydro-cone crusher which will reduce the feed opening to 5 inches and permits a two to one ratio of eccentric throw to close side setting. Thus, the crusher can be furnished to fit the exact requirements of any application.
The following capacity table gives a complete range of all Hydrocone cone crusher capacities with varying crushing chambers and eccentric throws. This table shows the minimum recommended setting for any given eccentric throw, the recommended maximum one-way (slot size) dimension of the feed, and the maximum recommended horsepower for any eccentric throw.
Capacities given are based on crushing dry feed from which the product size material has been removed. The material must readily enter the feed opening and be evenly distributed around the crushing chamber. The table is based on material weighing 100 lb per cubic foot crushed. Any variation from this must be accounted for.
The curves on the following page can be used to approximate the screen analysis of the product from any given Hydrocone crusher. These curves are only approximations since the actual screen analysis of the product of a Hydrocone crusher will depend upon the nature of the material being crushed, the feed size and a number of other considerations which could not be taken into account in these curves. Within these limits, the curves should give fairly accurate estimates.
Note that the Coarse crushing chamber is represented as giving a product of which 60 percent will pass the close side setting, the Intermediate chamber 67 percent and the Fine chamber 75 percent passing the close side setting. These percentages are the averages of a large number of tests and some variations from these must be expected. If material breaks slabby the percentage with a coarse crushing chamber may be as low as 50 percent; if it breaks very cubically it might be as high as 70 percent, or even higher.
These curves have been prepared so that they can be used for any crushing chamber. To estimate the product of any Hydrocone crusher, it is necessary to know the type of crushing chamber used (Coarse, Intermediate or Fine), the close side setting and the eccentric throw.
If the crusher is a 636 Hydrocone crusher with a 3/8-in. throw and a 3/8-in. close side setting, the approximate screen analysis would be the curve that would pass through the 3/8-in. horizontal line and the vertical line representing the close side setting for the Coarse crushing chamber, which is the 60 percent passing line. If no curve passes through the precise point of intersection between the horizontal and vertical lines, an approximate curve can be sketched in which parallels the other curves. The same procedure can be used for approximating the products from any other crushing chamber.
Barite..170 Basalt.100 Cement Clinker.95 Coal..40-60 Coke.23-32 Glass..95 Granite100 Gravel.100 Gypsum..85 Iron Ore.125-150 Limestone..95-100 Magnesite.100 Perlite..95 Porphyry.100 Quartz..95 Sandstone..85 Slag..80 Taconite125 Talc..95 Trap Rock100
We canprovide testing to solve the most difficult crushing problems. Laboratory equipment makes it possible to measure the crushing strengths and characteristics of rock or ore samples accurately, and this data is used in the selection of a crusher of proper size and type.
Impact and batch tests are frequently sufficient to indicate the type and size crusher that will be the most economical for a particular application. However, batch testing is often followed by pilot plant tests to provide additional information about large-scale operations, or to observe rock or ore reduction under actual plant operating conditions.
Pilot plant tests duplicate a continuous crushing operation provide a practical demonstration of the commercial potential of the process on a pilot scale. Such tests are useful because they may disclose factors that affect the full-scale operation, favorably or otherwise, but which remain hidden in tests on limited samples.
All Laboratory tests are guided by modern scientific knowledge of crushing fundamentals and by ourinvaluable backlog of experience in engineering and building all types of crushing equipment for any crushing application.
In addition to the facilities for crushing tests, the Laboratory maintains complete batch and pilot mill facilities for use in investigating an entire process. Tests in grinding, sizing, concentrating, thickening, filtering, drying, and pyro- processing can be made.