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metso superior gyratory crushers - metso automation - pdf catalogs | technical documentation | brochure

metso superior gyratory crushers - metso automation - pdf catalogs | technical documentation | brochure

Metso SUPERIOR primary gyratory the first step in high-capacity crushing Years of experience and thousands of primary gyratory installations combine to create the best gyratory the industry has to offer. Metso SUPERIOR gyratory crushers are built to help you meet the challenges of highcapacity primary crushing. With thousands of units operating in mines and quarries around the world, Metso has the experience and capabilities to provide the top performance, throughput and efficiency. Low cost per ton In todays competitive market, environmental concerns and energy costs are on the rise....

The perfect blend of experience and innovation The SUPERIOR gyratory crushers combine Metsos trusted technology with the latest advancements in metallurgy to achieve peak efficiency and high output by offering: Easy maintenance and service Designed for low service requirements and ease of operation, the SUPERIOR primary gyratory will readily fit into any existing or proposed crushing plant. steep crushing chamber and long crushing surfaces for A exceptionally high capacity and maximum liner life Automatic spider lubrication extra heavy-duty frame, large diameter integral mainshaft An...

Metso Services Make the most of your investment Achieve your goals with a partner who will be there wherever and whenever you need them. Metso offers a host of value-added services that can enhance your bottom line and help you make the most of your SUPERIOR primary gyratory. Whether youre installing an entire customized system, a complete circuit, or simply replacing or updating a single piece of equipment, you can count on us to help you make sure your crusher is running at peak efficiency. Life cycle thinking Using our long-term experience in crushing equipment and processes, Metso has...

Plant diagnostics and upgrade Engineering analysis of your crushing circuit can substantially increase production. Metso experts can determine the correct set up of your primary and downstream crushers for optimum equipment application and plant productivity. Training Metso training can ensure that your operators are familiar with all the features of the crusher they are using. Properly trained operators gain knowledge of proper procedures, all feature functions, productivity tips, and important safety measures. We offer a broad range of training courses coached by experienced professionals...

Advanced features Metso has optimized the SUPERIOR design with one thing in mind to be the most productive, reliable and efficient primary gyratory crushers on the market. The SUPERIOR range provides innovative, exclusive features with the power and performance to operate in the most demanding conditions. Mainshaft position control The mainshaft position system successfully used for decades is a hydraulic method of vertical adjustment to compensate for wear. It consists of a pump, controlled by a push-button, and a heavy-duty hydraulic cylinder that supports and adjusts the mainshaft...

SUPERIOR gyratory crusher features 1 Crushing chambers are matched to each individual application, optimizing crushing performance 7 Patented headnut with burning ring allows for simple removal of the mantle 2 Manganese wearing parts are standard chrome alloy option is available for concaves and bottomshell liners 8 High-strength shell design, proven in the toughest applications, provides trouble-free operation and long life 3 Effective dust seal is equipped with an overpressure air blower to keep dust out of the eccentric and drive, increasing crusher bearing life 9 Mainshaft and head...

Proper installation is key Feed and discharge arrangements can greatly affect crusher reliability and performance. Basic recommendations are: Proper feeding will result in the following: Position spider arm in line with truck discharge. The arm will split material flow into the crushing chamber for more even feed distribution Increased crushing chamber wear life Construct a stone box around the spider so material discharge from truck dumping falls on dead stone bed before entering the crushing chamber Avoid direct impact of dumped material on the spider cap or mainshaft assembly ...

Total crusher and process control Metsos TC1000-C automation system contributes to a higher return on your investment by improving overall crusher control, maximizing availability, and minimizing maintenance and energy costs. Total crusher control Every aspect of the crusher is controlled by the TC System. The entire lubrication system is controlled, including the air blower, immersion heaters, lube pump, and oil coolers. The TC1000-C automation system (available as an option) simplifies operation and provides real-time information about the condition of the crusher: Asset protection...

Capacities Open side settings of discharge opening The above capacities are based on an assumed feed where 100% of the feed passes 80% of the feed opening. 80% of the feed passes 60% of the feed topsize, and 50% of the feed passes a sieve size that is 10% of the topsize. The capacities are for feed materials with a bulk density of 1.6 metric tons per cubic meter (100 pounds per cubic foot). All capacities are calculated at a maximum throw for each respective machine. All capacities are relative to individual application. Material characteristics, feed size, distribution, work index, percent...

Expect results It is our promise to our customers and the essence of our strategy. Metso Minerals Industries, Inc., 20965 Crossroads Circle, Waukesha, WI 53186, USA, tel +1 262 717 2500, fax +1 262 717 2501, www.metso.com SUPERIOR Gyratory Crushers Brochure 2012.indd 2 It is the attitude we share globally; our business is to deliver results to our customers, to help them reach their goals.

gyratory crusher - an overview | sciencedirect topics

gyratory crusher - an overview | sciencedirect topics

Gyratory crushers were invented by Charles Brown in 1877 and developed by Gates around 1881 and were referred to as a Gates crusher [1]. The smaller form is described as a cone crusher. The larger crushers are normally known as primary crushers as they are designed to receive run-on-mine (ROM) rocks directly from the mines. The gyratory crushers crush to reduce the size by a maximum of about one-tenth its size. Usually, metallurgical operations require greater size reduction; hence, the products from the primary crushers are conveyed to secondary or cone crushers where further reduction in size takes place. Here, the maximum reduction ratio is about 8:1. In some cases, installation of a tertiary crusher is required where the maximum reduction is about 10:1. The secondary crushers are also designed on the principle of gyratory crushing, but the construction details vary.

Similar to jaw crushers, the mechanism of size reduction in gyratory crushers is primarily by the compressive action of two pieces of steel against the rock. As the distance between the two plates decreases continuous size reduction takes place. Gyratory crushers tolerate a variety of shapes of feed particles, including slabby rock, which are not readily accepted in jaw crushers because of the shape of the feed opening.

The gyratory crusher shown in Figure 2.6 employs a crushing head, in the form of a truncated cone, mounted on a shaft, the upper end of which is held in a flexible bearing, whilst the lower end is driven eccentrically so as to describe a circle. The crushing action takes place round the whole of the cone and, since the maximum movement is at the bottom, the characteristics of the machine are similar to those of the Stag crusher. As the crusher is continuous in action, the fluctuations in the stresses are smaller than in jaw crushers and the power consumption is lower. This unit has a large capacity per unit area of grinding surface, particularly if it is used to produce a small size reduction. It does not, however, take such a large size of feed as a jaw crusher, although it gives a rather finer and more uniform product. Because the capital cost is high, the crusher is suitable only where large quantities of material are to be handled.

However, the gyratory crusher is sensitive to jamming if it is fed with a sticky or moist product loaded with fines. This inconvenience is less sensitive with a single-effect jaw crusher because mutual sliding of grinding surfaces promotes the release of a product that adheres to surfaces.

The profile of active surfaces could be curved and studied as a function of the product in a way to allow for work performed at a constant volume and, as a result, a higher reduction ratio that could reach 20. Inversely, at a given reduction ratio, effective streamlining could increase the capacity by 30%.

Maintenance of the wear components in both gyratory and cone crushers is one of the major operating costs. Wear monitoring is possible using a Faro Arm (Figure 6.10), which is a portable coordinate measurement machine. Ultrasonic profiling is also used. A more advanced system using a laser scanner tool to profile the mantle and concave produces a 3D image of the crushing chamber (Erikson, 2014). Some of the benefits of the liner profiling systems include: improved prediction of mantle and concave liner replacement; identifying asymmetric and high wear areas; measurement of open and closed side settings; and quantifying wear life with competing liner alloys.

Crushers are widely used as a primary stage to produce the particulate product finer than about 50100mm. They are classified as jaw, gyratory, and cone crushers based on compression, cutter mill based on shear, and hammer crusher based on impact.

A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake. A Fritsch jaw crusher with maximal feed size 95mm, final fineness (depends on gap setting) 0.315mm, and maximal continuous throughput 250Kg/h is shown in Fig. 2.8.

A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.

Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing hard metal scrap for different hard metal recycling processes. Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor. Crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough to pass through the openings of the grating or screen. The size of the product can be regulated by changing the spacing of the grate bars or the opening of the screen.

The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure, forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions. A design for a hammer crusher (Fig. 2.9) essentially allows a decrease of the elevated pressure of air in the crusher discharging unit [5]. The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, the circulation of suspended matter in the gas between A and B zones is established and the high pressure of air in the discharging unit of crusher is reduced.

Crushers are widely used as a primary stage to produce the particulate product finer than about 50100 mm in size. They are classified as jaw, gyratory and cone crushers based on compression, cutter mill based on shear and hammer crusher based on impact.

A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake.

A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.

Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing of hard metal scrap for different hard metal recycling processes.

Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor and crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough pass through the openings of the grating or screen. The size of product can be regulated by changing the spacing of the grate bars or the opening of the screen.

The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around of the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions.

A design for a hammer crusher (Figure 2.6) allows essentially a decrease of the elevated pressure of air in the crusher discharging unit [5]. The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, circulation of suspended matter in the gas between A- and B-zones is established and high pressure of air in the discharging unit of crusher is reduced.

Jaw crushers are mainly used as primary crushers to produce material that can be transported by belt conveyors to the next crushing stages. The crushing process takes place between a fixed jaw and a moving jaw. The moving jaw dies are mounted on a pitman that has a reciprocating motion. The jaw dies must be replaced regularly due to wear. Figure 8.1 shows two basic types of jaw crushers: single toggle and double toggle. In the single toggle jaw crusher, an eccentric shaft is installed on the top of the crusher. Shaft rotation causes, along with the toggle plate, a compressive action of the moving jaw. A double toggle crusher has, basically, two shafts and two toggle plates. The first shaft is a pivoting shaft on the top of the crusher, while the other is an eccentric shaft that drives both toggle plates. The moving jaw has a pure reciprocating motion toward the fixed jaw. The crushing force is doubled compared to single toggle crushers and it can crush very hard ores. The jaw crusher is reliable and robust and therefore quite popular in primary crushing plants. The capacity of jaw crushers is limited, so they are typically used for small or medium projects up to approximately 1600t/h. Vibrating screens are often placed ahead of the jaw crushers to remove undersize material, or scalp the feed, and thereby increase the capacity of the primary crushing operation.

Both cone and gyratory crushers, as shown in Figure 8.2, have an oscillating shaft. The material is crushed in a crushing cavity, between an external fixed element (bowl liner) and an internal moving element (mantle) mounted on the oscillating shaft assembly. An eccentric shaft rotated by a gear and pinion produces the oscillating movement of the main shaft. The eccentricity causes the cone head to oscillate between the open side setting (o.s.s.) and closed side setting (c.s.s.). In addition to c.s.s., eccentricity is one of the major factors that determine the capacity of gyratory and cone crushers. The fragmentation of the material results from the continuous compression that takes place between the mantle and bowl liners. An additional crushing effect occurs between the compressed particles, resulting in less wear of the liners. This is also called interparticle crushing. The gyratory crushers are equipped with a hydraulic setting adjustment system, which adjusts c.s.s. and thus affects product size distribution. Depending on cone type, the c.s.s. setting can be adjusted in two ways. The first way is by rotating the bowl against the threads so that the vertical position of the outer wear part (concave) is changed. One advantage of this adjustment type is that the liners wear more evenly. Another principle of setting adjustment is by lifting/lowering the main shaft. An advantage of this is that adjustment can be done continuously under load. To optimize operating costs and improve the product shape, as a rule of thumb, it is recommended that cones always be choke-fed, meaning that the cavity should be as full of rock material as possible. This can be easily achieved by using a stockpile or a silo to regulate the inevitable fluctuation of feed material flow. Level monitoring devices that detect the maximum and minimum levels of the material are used to start and stop the feed of material to the crusher as needed.

Primary gyratory crushers are used in the primary crushing stage. Compared to the cone type crusher, a gyratory crusher has a crushing chamber designed to accept feed material of a relatively large size in relation to the mantle diameter. The primary gyratory crusher offers high capacity thanks to its generously dimensioned circular discharge opening (which provides a much larger area than that of the jaw crusher) and the continuous operation principle (while the reciprocating motion of the jaw crusher produces a batch crushing action). The gyratory crusher has capacities starting from 1200 to above 5000t/h. To have a feed opening corresponding to that of a jaw crusher, the primary gyratory crusher must be much taller and heavier. Therefore, primary gyratories require quite a massive foundation.

The cone crusher is a modified gyratory crusher. The essential difference is that the shorter spindle of the cone crusher is not suspended, as in the gyratory, but is supported in a curved, universal bearing below the gyratory head or cone (Figure 8.2). Power is transmitted from the source to the countershaft to a V-belt or direct drive. The countershaft has a bevel pinion pressed and keyed to it and drives the gear on the eccentric assembly. The eccentric assembly has a tapered, offset bore and provides the means whereby the head and main shaft follow an eccentric path during each cycle of rotation. Cone crushers are used for intermediate and fine crushing after primary crushing. The key factor for the performance of a cone type secondary crusher is the profile of the crushing chamber or cavity. Therefore, there is normally a range of standard cavities available for each crusher, to allow selection of the appropriate cavity for the feed material in question.

Depending on the size of the debris, it may either be ready to enter the recycling process or need to be broken down to obtain a product with workable particle sizes, in which case hydraulic breakers mounted on tracked or wheeled excavators are used. In either case, manual sorting of large pieces of steel, wood, plastics and paper may be required, to minimise the degree of contamination of the final product.

The three types of crushers most commonly used for crushing CDW materials are the jaw crusher, the impact crusher and the gyratory crusher (Figure 4.4). A jaw crusher consists of two plates, with one oscillating back and forth against the other at a fixed angle (Figure 4.4(a)) and it is the most widely used in primary crushing stages (Behera etal., 2014). The jaw crusher can withstand large and hard-to-break pieces of reinforced concrete, which would probably cause the other crushing machines to break down. Therefore, the material is initially reduced in jaw crushers before going through any other crushing operation. The particle size reduction depends on the maximum and minimum size of the gap at the plates (Hansen, 2004).

An impact crusher breaks the CDW materials by striking them with a high-speed rotating impact, which imparts a shearing force on the debris (Figure 4.4(b)). Upon reaching the rotor, the debris is caught by steel teeth or hard blades attached to the rotor. These hurl the materials against the breaker plate, smashing them into smaller particle sizes. Impact crushers provide better grain-size distribution of RA for road construction purposes, and they are less sensitive to material that cannot be crushed, such as steel reinforcement.

Generally, jaw and impact crushers exhibit a large reduction factor, defined as the ratio of the particle size of the input to that of the output material. A jaw crusher crushes only a small proportion of the original aggregate particles but an impact crusher crushes mortar and aggregate particles alike and thus generates a higher amount of fine material (OMahony, 1990).

Gyratory crushers work on the same principle as cone crushers (Figure 4.4(c)). These have a gyratory motion driven by an eccentric wheel. These machines will not accept materials with a large particle size and therefore only jaw or impact crushers should be considered as primary crushers. Gyratory and cone crushers are likely to become jammed by fragments that are too large or too heavy. It is recommended that wood and steel be removed as much as possible before dumping CDW into these crushers. Gyratory and cone crushers have advantages such as relatively low energy consumption, a reasonable amount of control over the particle size of the material and production of low amounts of fine particles (Hansen, 2004).

For better control of the aggregate particle size distribution, it is recommended that the CDW should be processed in at least two crushing stages. First, the demolition methodologies used on-site should be able to reduce individual pieces of debris to a size that the primary crusher in the recycling plant can take. This size depends on the opening feed of the primary crusher, which is normally bigger for large stationary plants than for mobile plants. Therefore, the recycling of CDW materials requires careful planning and communication between all parties involved.

A large proportion of the product from the primary crusher can result in small granules with a particle size distribution that may not satisfy the requirements laid down by the customer after having gone through the other crushing stages. Therefore, it should be possible to adjust the opening feed size of the primary crusher, implying that the secondary crusher should have a relatively large capacity. This will allow maximisation of coarse RA production (e.g., the feed size of the primary crusher should be set to reduce material to the largest size that will fit the secondary crusher).

The choice of using multiple crushing stages mainly depends on the desired quality of the final product and the ratio of the amounts of coarse and fine fractions (Yanagi etal., 1998; Nagataki and Iida, 2001; Nagataki etal., 2004; Dosho etal., 1998; Gokce etal., 2011). When recycling concrete, a greater number of crushing processes produces a more spherical material with lower adhered mortar content (Pedro etal., 2015), thus providing a superior quality of material to work with (Lotfi etal., 2017). However, the use of several crushing stages has some negative consequences as well; in addition to costing more, the final product may contain a greater proportion of finer fractions, which may not always be a suitable material.

The first step of physical beneficiation is crushing and grinding the iron ore to its liberation size, the maximum size where individual particles of gangue are separated from the iron minerals. A flow sheet of a typical iron ore crushing and grinding circuit is shown in Figure 1.2.2 (based on Ref. [4]). This type of flow sheet is usually followed when the crude ore contains below 30% iron. The number of steps involved in crushing and grinding depends on various factors such as the hardness of the ore and the level of impurities present [5].

Jaw and gyratory crushers are used for initial size reduction to convert big rocks into small stones. This is generally followed by a cone crusher. A combination of rod mill and ball mills are then used if the ore must be ground below 325 mesh (45m). Instead of grinding the ore dry, slurry is used as feed for rod or ball mills, to avoid dusting. Oversize and undersize materials are separated using a screen; oversize material goes back for further grinding.

Typically, silica is the main gangue mineral that needs to be separated. Iron ore with high-silica content (more than about 2%) is not considered an acceptable feed for most DR processes. This is due to limitations not in the DR process itself, but the usual customer, an EAF steelmaking shop. EAFs are not designed to handle the large amounts of slag that result from using low-grade iron ores, which makes the BF a better choice in this situation. Besides silica, phosphorus, sulfur, and manganese are other impurities that are not desirable in the product and are removed from the crude ore, if economically and technically feasible.

Beneficiation of copper ores is done almost exclusively by selective froth flotation. Flotation entails first attaching fine copper mineral particles to bubbles rising through an orewater pulp and, second, collecting the copper minerals at the top of the pulp as a briefly stable mineralwaterair froth. Noncopper minerals do not attach to the rising bubbles; they are discarded as tailings. The selectivity of the process is controlled by chemical reagents added to the pulp. The process is continuous and it is done on a large scale103 to 105 tonnes of ore feed per day.

Beneficiation is begun with crushing and wet-grinding the ore to typically 10100m. This ensures that the copper mineral grains are for the most part liberated from the worthless minerals. This comminution is carried out with gyratory crushers and rotary grinding mills. The grinding is usually done with hard ore pieces or hard steel balls, sometimes both. The product of crushing and grinding is a waterparticle pulp, comprising 35% solids.

Flotation is done immediately after grindingin fact, some flotation reagents are added to the grinding mills to ensure good mixing and a lengthy conditioning period. The flotation is done in large (10100m3) cells whose principal functions are to provide: clouds of air bubbles to which the copper minerals of the pulp attach; a means of overflowing the resulting bubblecopper mineral froth; and a means of underflowing the unfloated material into the next cell or to the waste tailings area.

Selective attachment of the copper minerals to the rising air bubbles is obtained by coating the particles with a monolayer of collector molecules. These molecules usually have a sulfur atom at one end and a hydrophobic hydrocarbon tail at the other (e.g., potassium amyl xanthate). Other important reagents are: (i) frothers (usually long-chain alcohols) which give a strong but temporary froth; and (ii) depressants (e.g., CaO, NaCN), which prevent noncopper minerals from floating.

tips to maximize crushing efficiency - pit & quarry : pit & quarry

tips to maximize crushing efficiency - pit & quarry : pit & quarry

To apply what this means to your crusher, operations produce the exact sizes in the reduction process that their market demands. In the past, quarries produced a range of single-size aggregate products up to 40 mm in size.

In practice, many jaw crushers are not fed to their designed capacity. This is because the subsequent processing plant does not have sufficient capacity to handle the volume of material that would be produced if the jaw crusher was working to capacity.

If you seek fewer fines, trickle feeding material into the jaw crusher could achieve this. But this would have an adverse effect on particle shape, and it also reduces throughput capacity, hindering the crushers efficiency.

Ideally, the feed rate should not be switched from choke to non-choke, as this can cause problems downstream at the secondary processing plant. In practice, many jaw crushers are fed in this intermittent fashion due to gaps in the delivery of feed material from the quarry.

The reduction ratio is then calculated by comparing the input feed size passing 80 percent versus the discharge size that passes 80 percent. The finer the closed-side setting, the greater the proportion of fines produced.

The closed-side setting of a jaw crusher helps determine the nip angle within a chamber, typically 19 to 23 degrees. Too large of an angle causes boiling in the crushing chamber. This is where the jaw plates cannot grip onto the rock, and it keeps slipping up and down, avoiding being crushed. The nip angle gets flatter as the machine is set tighter.

The settings on a jaw crusher are designed to produce material ideal for secondary crushing. The best particle shape is typically found in material that is about the same size as the closed-side setting.

Smaller sizes will contain a higher proportion of elongated particles because they have passed through the crusher without being touched. Larger sizes may also contain a higher proportion of elongated particles because they are further from the closed-side setting. This can cause bridging issues in downstream machines.

It is critical that a cone-type crusher be choke fed to produce the best product shape and quality. It is not as important in a jaw, as material is not generally stockpiled after the jaw. Because the cone is part of the secondary and tertiary stations, particle shape assisted by a choke-fed chamber is important because finished products are created in these stages.

Choke feeding is important for cone crushers because it maintains a good particle shape by facilitating an inter-particle crushing action. Trickle feeding is not the best option because it increases the proportion of flaky material in the crusher product, hindering its efficiency.

It is a good rule to maintain about 10 to 15 percent of material finer than the closed-side setting in the feed to assist crushing action. More than 10 to 15 percent will likely cause ring bounce due to the pressures in the chamber.

Its important to find the right liner for the feed gradation and desired product. If the liner is too large, feed material will drop too far in the chamber before being crushed. Too fine of a liner will prevent material from entering the chamber at all.

Monitoring the crushing force as registered through the load on the crusher motors, as well as the pressure on the hydraulic mantle adjustment mechanism, will give forewarning of crusher packing problems before they affect your efficiency.

Try to match the closed-side setting of the crusher to the top size of the product to be produced. If closing the circuit at 1 in. to produce a 1-in.-minus product, set the crusher at or near 1 in. or slightly below.

The initial impact is responsible for more than 60 percent of the crushing action, with the remainder made up of impact against an adjustable breaker bar and a small amount of inter-particle collision.

This is why it is vitally important that the feed arrangement to an impact crusher ensures an even distribution of feed material across the full width of the rotor. This will allow for even distribution of energy into the feed material and uniform wear patterns, ensuring consistent product gradation and power consumption.

Slower rotor speeds can be used as a means of reducing fines but may result in a product with more oversize or return than is desired. Slower rotor speeds are preferable as a means of minimizing the wear on crusher components, as well as for achieving less fines production and optimal product size.

The product grading from an impact crusher will change throughout the life of the wear parts, particularly the impact hammers or blow bars. As the profile of the hammer changes with increased wear, the product grading becomes coarser. Many modern impact crusher installations have a variable speed drive arrangement that allows an increase in the rotor speed to compensate for wear on the impact hammers.

In many impact crushers, a third curtain or crushing chamber can be added to increase reduction in every pass through the machine. This can be important in finer product applications where the third chamber can provide the desired output gradation. A third chamber that increases the reduction will also increase the power needs and, normally, the wear cost.

One tip to consider: Decreasing the gap between the hammers and impact curtain increases particle retention in the chamber. This increases the size reduction ratio, but it also reduces efficiency throughput capacity and increases fines production.

Follow the steps outlined in this article to achieve the best crushing efficiency for jaw, cone, gyratory and impact crushers and to ultimately increase profits and reduce fines production. By taking these steps, youre reducing the amount fines produced and adding dollars to your pocket.

gyratory and cone crusher - sciencedirect

gyratory and cone crusher - sciencedirect

Detail descriptions of designs are given of large gyratory crushers that are used as primary crushers to reduce the size of large run-of-mine ore pieces to acceptable sizes. Descriptions of secondary and tertiary cone crushers that usually follow gyratory crushers are also given in detail. The practical method of operation of each type of gyratory crusher is indicated and the various methods of computing operating variables such as speed of gyration, capacities and power consumption given are prescribed by different authors. The methods of calculations are illustrated to obtain optimum operating conditions of different variables of each type using practical examples.

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