Any of you that are at all familiar with the Gyratory crushersand Cone Crushers that the former are used as Primary crushers will probably note many similarities between the types.Each use a cone shaped crushing surface, and the same principal in the eccentric is employed to develop the crushing action required.
The difference between the two is first the speed that the mantle travels while crushing the ore. A primary revolves at 100-200 R.P.M. While the Secondary and the Tertiary crushers travels between 500-600 R.P.M. This difference in the speed results in a HAMMERING type crushing action over the SQUEEZING type employed by the primary.
The other most noticeable change is the crushing action of the mantle. In the Gyratory all the movement is in the bottom of the crusher mantle. This is due to the angle that the main shaft is on. The greater angle of the cone crusher puts the pivot point below the distributor plate. While the pivot point for the gyratory crusher is at the spider cap. This difference in the pattern of gyration has a purpose.
The primary crusher produces a product that is gauged by the size of the open side of the mantle. This is because the slow speed of the gyration allows a high percentage of material to fall through the larger opening without being crushed by the smaller opening. With the cone crusher however the gyration has a greater arc and an equally greater speed. If we look at a profile of the crushing surface we will see an area of the two surfaces that are parallel to one another.
This area is called the PARALLEL ZONE. Because of the speed, the primary crusher produces a product that is gauged by the size of the open side of the mantle. This is because the slow speed of the gyration allows a high percentage of material to fall through the larger opening without being crushed by the smaller opening. With the cone crusher however the gyration has a greater arc and an equally greater speed. If we look at a profile of the crushing surface we will see an area of the two surfaces that are parallel to one another that the mantle is travelling at, it is very hard for the ore to pass through this zone without being hit at least once by the crusher.
In the quarry, crushing is handled in four potential stages: primary, secondary, tertiary and quaternary. The reduction of aggregate is spread over these stages to better control the product size and quality, while minimizing waste.
The primary stage was once viewed merely as a means to further reduce stone following the blast or excavation prior to secondary crushing. Today, primary crushing is viewed as more important within the balance of production and proper sizing needs. The size and type of the primary crusher should be coordinated with the type of stone, drilling and blasting patterns, and the size of the loading machine. Most operations will use a gyratory, jaw or impact crusher for primary crushing.
In the secondary and subsequent stages, the stone is further reduced and refined for proper size and shape, mostly based on specifications to produce concrete and asphalt. Between stages, screens with two or three decks separate the material that already is the proper size. Most secondary crushers are cone crushers or horizontal-shaft impact crushers. Tertiary and quaternary crushers are usually cone crushers, although some applications can call for vertical-shaft impact crushers in these stages.
A gyratory crusher uses a mantle that gyrates, or rotates, within a concave bowl. As the mantle makes contact with the bowl during gyration, it creates compressive force, which fractures the rock. The gyratory crusher is mainly used in rock that is abrasive and/or has high compressive strength. Gyratory crushers often are built into a cavity in the ground to aid in the loading process, as large haul trucks can access the hopper directly.
Jaw crushers are also compression crushers that allow stone into an opening at the top of the crusher, between two jaws. One jaw is stationary while the other is moveable. The gap between the jaws becomes narrower farther down into the crusher. As the moveable jaw pushes against the stone in the chamber, the stone is fractured and reduced, moving down the chamber to the opening at the bottom.
The reduction ratio for a jaw crusher is typically 6-to-1, although it can be as high as 8-to-1. Jaw crushers can process shot rock and gravel. They can work with a range of stone from softer rock, such as limestone, to harder granite or basalt.
As the name implies, the horizontal-shaft impact (HSI) crusher has a shaft that runs horizontally through the crushing chamber, with a rotor that turns hammers or blow bars. It uses the high-speed impacting force of the turning blow bars hitting and throwing the stone to break the rock. It also uses the secondary force of the stone hitting the aprons (liners) in the chamber, as well as stone hitting stone.
With impact crushing, the stone breaks along its natural cleavage lines, resulting in a more cubical product, which is desirable for many of todays specifications. HSI crushers can be primary or secondary crushers. In the primary stage, HSIs are better suited for softer rock, such as limestone, and less abrasive stone. In the secondary stage, the HSI can process more abrasive and harder stone.
Cone crushers are similar to gyratory crushers in that they have a mantle that rotates within a bowl, but the chamber is not as steep. They are compression crushers that generally provide reduction ratios of 6-to-1 to 4-to-1. Cone crushers are used in secondary, tertiary and quaternary stages.
With proper choke-feed, cone-speed and reduction-ratio settings, cone crushers will efficiently produce material that is high quality and cubical in nature. In secondary stages, a standard-head cone is usually specified. A short-head cone is typically used in tertiary and quaternary stages. Cone crushers can crush stone of medium to very hard compressive strength as well as abrasive stone.
The vertical shaft impact crusher (or VSI) has a rotating shaft that runs vertically through the crushing chamber. In a standard configuration, the VSIs shaft is outfitted with wear-resistant shoes that catch and throw the feed stone against anvils that line the outside of the crushing chamber. The force of the impact, from the stone striking the shoes and anvils, fractures it along its natural fault lines.
VSIs also can be configured to use the rotor as a means of throwing the rock against other rock lining the outside of the chamber through centrifugal force. Known as autogenous crushing, the action of stone striking stone fractures the material. In shoe-and-anvil configurations, VSIs are suitable for medium to very hard stone that is not very abrasive. Autogenous VSIs are suitable for stone of any hardness and abrasion factor.
Roll crushers are a compression-type reduction crusher with a long history of success in a broad range of applications. The crushing chamber is formed by massive drums, revolving toward one another. The gap between the drums is adjustable, and the outer surface of the drum is composed of heavy manganese steel castings known as roll shells that are available with either a smooth or corrugated crushing surface.
Double roll crushers offer up to a 3-to-1 reduction ratio in some applications depending on the characteristics of the material. Triple roll crushers offer up to a 6-to-1 reduction. As a compressive crusher, the roll crusher is well suited for extremely hard and abrasive materials. Automatic welders are available to maintain the roll shell surface and minimize labor expense and wear costs.
These are rugged, dependable crushers, but not as productive as cone crushers with respect to volume. However, roll crushers provide very close product distribution and are excellent for chip stone, particularly when avoiding fines.
Hammermills are similar to impact crushers in the upper chamber where the hammer impacts the in-feed of material. The difference is that the rotor of a hammermill carries a number of swing type or pivoting hammers. Hammermills also incorporate a grate circle in the lower chamber of the crusher. Grates are available in a variety of configurations. The product must pass through the grate circle as it exits the machine, insuring controlled product sizing.
Hammermills crush or pulverize materials that have low abrasion. The rotor speed, hammer type and grate configuration can be converted for different applications. They can be used in a variety of applications, including primary and secondary reduction of aggregates, as well as numerous industrial applications.
Virgin or natural stone processing uses a multi-stage crushing and screening process for producing defined aggregate sizes from large lumps of rock. Such classified final fractions are used as aggregates for concrete, asphalt base, binder and surface course layers in road construction, as well as in building construction. The rock is quarried by means of drilling and blasting. There are then two options for processing the bulk material after it has been reduced to feeding size of the crushing plant: mobile or stationary plants.
When stone is processed in mobile primary crushing plants, excavators or wheel loaders feed the rock into the crusher that is set up at the quarry face, gravel pit or in a recycling yard or demolition site. The crushed material is then either sent to the secondary/tertiary processing stage via stacking conveyors or transported by trucks. Some mobile crushers have an independent secondary screen mounted on the unit, effectively replacing a standalone screen.
The higher the compressive strength of rock, the higher also is its quality, which plays an important role particularly in road construction. A materials compressive strength is delineated into hard, medium-hard or soft rock, which also determines the crushing techniques used for processing to obtain the desired particle sizes.
The materials quality is influenced significantly by particle shape. The more cubic-shaped the individual aggregate particles are, the better the resulting particle interlock. Final grains of pronounced cubic shape are achieved by using several crushing stages. A cubicity showing an edge ratio of better than 1-to-3 is typical of high-quality final aggregate.
As the earths natural resources are becoming ever more scarce, recycling is becoming ever more important. In the building industry, recycling and reuse of demolition concrete or reclaimed asphalt pavement help to reduce the requirements for primary raw materials. Mobile impact and jaw plants are uniquely positioned to produce high-quality reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA) for reuse in pavements, road bases, fill and foundations.
Use of RAP and RCA is growing dramatically as road agencies accept them more and more in their specs. But because RAP and RCA come from a variety of sources, to be specified for use by most departments of transportation they must be processed or fractionated and characterized into an engineered, value-added product. RCA or RAP are very commonly crushed and screened to usable sizes often by impact crushers and stored in blended stockpiles that can be characterized by lab testing for use in engineered applications.
Impact crushers are increasingly used for crushing recycling material. Impact crushers are capable of producing mineral aggregate mixes in one single crushing stage in a closed-cycle operation, making them particularly cost-effective. Different crusher units can alternatively be combined to process recycling material. A highly efficient method of processing recycling material combines crushing, screening and separation of metals. To produce an end product of even higher quality, the additional steps of washing to remove light materials such as plastics or paper by air classification and via electromagnetic metal separator are incorporated into the recycling process.
Mobile impact crushers with integrated secondary screens or without integrated screen used in conjunction with an independent mobile screen are ideal for producing large volumes of processed, fractionated RAP or RCA on a relatively small footprint in the plant. Mobile impactors are especially suited for RAP because they break up chunks of asphalt pavement or agglomerations of RAP, rather than downsize the aggregate gradation. Compression-type crushers such as jaws and cones can clog due to packing (caking) of RAP when the RAP is warm or wet.
Contaminants such as soil are part of processing demolition concrete. Mobile impact and jaw crushers when possessing integrated, independent prescreens removing dirt and fines before they ever enter the crushing circuit reduce equipment wear, save fuel, and with some customers, create a salable fill byproduct. A lined, heavy-duty vibrating feeder below the crusher can eliminate belt wear from rebar or dowel or tie bar damage. If present beneath the crusher, this deflector plate can keep tramp metal from degrading the conveyor belt. That way, the feeder below the crusher not the belt absorbs impact of rebar dropping through the crusher.
These mobile jaw and impact crushers may feature a diesel and electric-drive option. In this configuration, the crusher is directly diesel-driven, with the conveyor troughs, belts and prescreen electric-driven via power from the diesel generator. This concept not only reduces diesel fuel consumption, but also results in significantly reduced exhaust emissions and noise levels. This permits extremely efficient operation with low fuel consumption, allowing optimal loading of the crusher.
Jaw crushers operate according to the principle of pressure crushing. The raw feed is crushed in the wedge-shaped pit created between the fixed crusher jaw, and the crusher jaw articulated on an eccentric shaft. The feed material is crushed by the elliptic course of movement and transported downwards. This occurs until the material is smaller than the set crushing size.
Jaw crushers can be used in a wide range of applications. In the weight class up to 77 tons (70 metric tons), they can be used for both virgin stone and recycled concrete and asphalt aggregates processing as a classic primary crusher for natural stone with an active double-deck grizzly, or as a recycling crusher with vibrating discharge chute and the crusher outlet and magnetic separator.
Output for mobile jaw crushers ranges from 100 to 1,500 tph depending on the model size and consistency of the feed material. While larger mobile crushers produce more aggregate faster, transport weights and dimensions may limit how easily the crusher can be shipped long distances. Mobile jaw crushers can have either a vibratory feeder with integrated grizzly, or a vibrating feeder with an independent, double-deck, heavy-duty prescreen. Either way, wear in the system is reduced because medium and smaller gradations bypass the crusher, with an increase in end-product quality because a side-discharge conveyor removes fines. A bypass flap may provide easy diversion of the material flow, eliminating the need for a blind deck.
Jaw crusher units with extra-long, articulated crusher jaws prevent coarse material from blocking while moving all mounting elements of the crusher jaw from the wear area. A more even material flow may be affected if the transfer from the prescreen or the feeder trough is designed so material simply tilts into the crushing jaw.
Mobile jaw and impact crushers alike can be controlled by one operator using a handheld remote. The remote also can be used to move or relocate the crusher within a plant. In other words, the crusher can be run by one worker in the cab of an excavator or loader as he feeds material into the crusher. If he sees something deleterious going into the hopper, he can stop the crusher.
Impact crushing is totally different from pressure crushing. In impact crushing, feed material is picked up by a fast moving rotor, greatly accelerated and smashed against an impact plate (impact toggle). From there, it falls back within range of the rotor. The crushed material is broken again and again until it can pass through the gap between the rotor and impact toggle.
A correctly configured mobile jaw or impact crusher will enhance material flow through the plant and optimize productivity. New-design mobile jaw and impact crushers incorporate a highly efficient flow concept, which eliminates all restriction to the flow of the material throughout the entire plant. With this continuous-feed system, each step the material goes through in the plant is wider than the width of the one before it, eliminating choke or wear points.
For example, a grizzly feeder can be wider than the hopper, and the crusher inlet wider than the feeder. The discharge chute under the crusher is 4 inches wider than the inner width of the crusher, and the subsequent discharge belt is another 4 inches wider than the discharge chute. This configuration permits rapid flow of crushed material through the crusher. Also, performance can be significantly increased if the conveying frequencies of the feeder trough and the prescreen are adapted independently to the level of the crusher, permitting a more equal loading of the crushing area. This flow concept keeps a choke feed to the crusher, eliminating stops/starts of the feed system, which improves production, material shape and wear.
Users are focused on cost, the environment, availability, versatility and, above all, the quality of the end product. Simple crushing is a relatively easy process. But crushing material so that the particle size, distribution and cleanliness meet the high standards for concrete and asphalt requires effective primary screening, intelligent control for optimal loading, an adjustable crusher with high drive output, and a screening unit with oversize return feed.
This starts with continuous flow of material to the crusher through a variable-speed control feeder. Having hopper walls that hydraulically fold integrated into the chassis makes for quick erection of hopper sides on mobile units. If available, a fully independent prescreen for either jaw or impact models offers the ability to effectively prescreen material prior to crushing this allows for product to be sized prior to crushing, as opposed to using a conventional vibrating grizzly. This has the added value of increasing production, reducing wear costs and decreasing fuel consumption.
This independent double-deck vibrating screen affects primary screening of fines and contaminated material via a top-deck interchangeable punched sheet or grizzly, bottom-deck wire mesh or rubber blank. Discharged material might be conveyed either to the left or to the right for ease of positioning. The independent double-deck vibrating prescreen improves flow of material to the crusher, reducing blockages and feed surges.
Modern electrical systems will include effective guards against dust and moisture through double-protective housings, vibration isolation and an overpressure system in which higher air pressure in the electrical box keeps dust out. Simple and logical control of all functions via touch panel, simple error diagnostics by text indicator and remote maintenance system all are things to look for. For crushing demolition concrete, look for a high-performance electro- or permanent magnet with maximum discharge capacity, and hydraulic lifting and lowering function by means of radio remote control.
For impact crushers, a fully hydraulic crusher gap setting with automatic zero-point calculation can speed daily set-up. Featured only on certain mobile impact crushers, a fully hydraulic adjustment capability of the crushing gap permits greater plant uptime, while improving quality of end product.
Not only can the crushing gap be completely adjusted via the touch panel electronic control unit, but the zero point can be calculated while the rotor is running. This ability to accurately set the crusher aprons from the control panel with automatic detection of zero-point and target-value setting saves time, and improves the overall efficiency and handling of the crusher. On these mobile impact crushers, the zero point is the distance between the ledges of the rotor and the impact plates of the lower impact toggle, plus a defined safety distance. The desired crushing gap is approached from this zero point.
While the upper impact toggle is adjusted via simple hydraulic cylinders, the lower impact toggle has a hydraulic crushing gap adjustment device, which is secured electronically and mechanically against collision with the rotor. The crushing gap is set via the touch screen and approached hydraulically. Prior to setting of the crushing gap, the zero point is determined automatically.
For automatic zero-point determination with the rotor running, the impact toggle moves slowly onto the rotor ledges until it makes contact, which is detected by a sensor. The impact toggle then retracts to the defined safe distance. During this procedure, a stop ring slides on the piston rod. When the zero point is reached, the locking chamber is locked hydraulically and the stop ring is thus fixed in position. The stop ring now serves as a mechanical detent for the piston rod. During the stop ring check, which is carried out for every crusher restart, the saved zero point is compared to the actual value via the electronic limit switch. If the value deviates, a zero-point determination is carried out once again.
These impact crushers may feature a new inlet geometry that allows even better penetration of the material into the range of the rotor. Also, the wear behavior of the new C-form impact ledges has been improved to such an extent that the edges remain sharper longer, leading to improved material shape.
The machines come equipped with an efficient direct drive that improves performance. A latest-generation diesel engine transmits its power almost loss-free directly to the crushers flywheel, via a fluid coupling and V-belts. This drive concept enables versatility, as the rotor speed can be adjusted in four stages to suit different processing applications.
Secondary impact crushers and cone crushers are used to further process primary-crushed aggregate, and can be operated with or without attached screening units. These crushers can be used as either secondary or tertiary crushers depending on the application. When interlinked to other mobile units such as a primary or screen, complicated technical processing can be achieved.
Mobile cone crushers have been on the market for many years. These machines can be specially designed for secondary and tertiary crushing in hard-stone applications. They are extraordinarily efficient, diverse in application and very economical to use. To meet the diverse requirements in processing technology, mobile cone crushing plants are available in different sizes and configurations. Whether its a solo cone crusher, one used in addition to a triple-deck screen for closed-loop operation, or various-size cone crushers with a double-deck screen and oversize return conveyor, a suitable plant will be available for almost every task.
Mobile cone crushers may be available with or without integrated screen units. With the latter, an extremely efficient triple-deck screen unit may be used, which allows for closed-loop operation and produces three final products. Here the screen areas must be large so material quantities can be screened efficiently and ensure that the cone crusher always has the correct fill level, which is particularly important for the quality of the end product.
Mobile, tracked crushers and screen plants are advancing into output ranges that were recently only possible using stationary plants. Previously, only stationary plants were used for complicated aggregate processing applications. But thanks to the advancements made in machine technology, it is becoming increasingly possible to employ mobile technology for traditional stationary applications.
Mobile crushers are used in quarries, in mining, on jobsites, and in the recycling industry. These plants are mounted on crawler tracks and can process rock and recycling material, producing mineral aggregate and recycled building materials respectively for the construction industry. A major advantage of mobile crushers is their flexibility to move from one location to the next. They are suitable for transport, but can also cover short distances within the boundaries of their operating site, whether in a quarry or on the jobsite. When operating in quarries, they usually follow the quarry face, processing the stone directly on site.
For transport over long distances to a new location or different quarry, mobile crushers are loaded on low trailers. No more than 20 minutes to an hour is needed for setting the plant up for operation. Their flexibility enables the mobile crushers to process even small quantities of material with economic efficiency.
Mobile plants allow the combination of prescreening that prepares the rock for the crushing process and grading, which precisely separates defined aggregate particle sizes into different end products to be integrated with the crushing unit into one single machine. In the first stage, the material is screened using an active prescreen. After prescreening, it is transferred to the crusher, from where it is either stockpiled via a discharge conveyor or forwarded to a final screen or a secondary crushing stage. Depending on the specified end product, particles are then either graded by screening units or transported to additional crushing stages by secondary or tertiary impact crushers or cone crushers. Further downstream screening units are used for grading the final aggregate fractions.
The process of prescreening, crushing and grading is a common operation in mobile materials processing and can be varied in a number of ways. Mobile crushers with up to three crushing stages are increasingly used in modern quarries. Different mobile crushing and screening plants can be combined for managing more complex crushing and screening jobs that would previously have required a stationary crushing and screening plant.
Interlinked mobile plants incorporate crushers and screens that work in conjunction with each other, and are coordinated in terms of performance and function. Mining permits are under time constraints and mobile plants provide faster setup times. They provide better resale value and reusability, as mobile plants can also be used individually. They also reduce operating costs in terms of fewer haul trucks and less personnel.
With a so-equipped mobile crusher, the feed operator can shut the machine down or change the size of the material, all using the remote control, or use it to walk the crusher from one part of the site to the other, or onto a flat bed trailer for relocation to a different quarry or recycling yard. This reduces personnel and hauling costs compared to a stationary plant. With the mobile jaw or impact primary crusher, the only additional personnel needed would be a skid-steer operator to remove scrap steel, and someone to move the stockpiles.
Thanks to better technology, mobile plants can achieve final aggregate fractions, which previously only were possible with stationary plants. Production availability is on par with stationary plants. Theyre applicable in all quarries, but can be used for small deposits if the owner has several quarries or various operation sites. For example, an operator of several stone quarries can use the plants in changing market situations at different excavation sites. In addition, they also can be used as individual machines. A further factor is that mobile plants, in general, require simpler and shorter licensing procedures.
The high cost of labor keeps going up. A stationary crusher might be able to produce multiple times the amount of product, but also would require about seven or eight workers. Aggregate producers can benefit when producing material with the minimized crew used for mobile jaw and impact crushers.
Using correct maintenance practices, mobile crushers will remain dependable throughout their working life. Crushing and processing material can result in excessive wear on certain components, excessive vibration throughout the plant, and excessive dust in the working environment. Some applications are more aggressive than others. A hard rock application is going to require more maintenance on top of standard maintenance, as there will be more vibration, more dust and more wear than from a softer aggregate.
Due to the nature of its purpose, from the moment a mobile crusher starts, the machine is wearing itself out and breaking itself down. Without routine, regular maintenance and repair, a mobile crusher will not be reliable nor provide the material customers demand.
The first area of wear on any machine is the feed system. Whether its a feeder with an integrated grizzly, or a feeder with an independent prescreen, how the machine is fed contributes to wear. When setting up and maintaining a machine, the machine must be level. A machine that is unlevel left to right will experience increased wear on all components, including the feeder, the screens, the crushing chambers and the conveyor belts. In addition, it reduces production and screening efficiency, as the whole area of the machine is not being effectively used. Also, having the machine sit high at the discharge end will have the effect of feeding the material uphill in the feeder and reducing its efficiency, thus reducing production.
Another area for consideration is the equipment used to feed the machine. The operator using a loader to feed the crusher will have no control over the feed size, as he cannot see whats in the bucket. Whereas with an excavator, the operator can see whats inside and has more control over the feed into the hopper. That is, the operator is not feeding so much material all at once and is controlling the size of the feed. This reduces wear in the feed hoppers impact zones and eliminates material blockages due to feed size being too large to enter the chamber.
Dust is a problem in its own right, especially for the power plant of the mobile crusher. In a very dusty application, it is easy to plug the radiator and have engine-overheating problems. High dust levels cause increased maintenance intervals on air filters, and if not controlled properly, can enter the diesel tank and cause problems with the fuel system. Also, dust that gets inside the crusher increases wear. But if systems are put in place to remove the dust, it should keep it from going into the machine in the first place.
Dust also is a hazard on walkways and a problem for conveyors. If maintained, side-skirting and sealing the conveyors keeps dust from spilling out, building up underneath the conveyor, or building up in rollers, pulleys, bearings, and causing wear on shafts. Its important to maintain the sealing rubbers on the conveyor belts to avoid those issues. Routine maintenance calls for removing accumulated dust from inside and under the machine.
Dust also is a problem for circuit boards and programmable controllers. Dust causes electrical switches to malfunction because it stops the contacts from correctly seating. Electrical systems under positive air pressure dont permit dust to penetrate the control system. In control panels with a correctly maintained positive pressure system, filters remove dust from air that is being pumped into the cabinets. If the filters are plugged, the system will not pull as much air through, allowing dust, moisture and heat to build in the cabinet.
There are also impact aprons against which the rock is thrown, which also see high wear. There are side plates or wear sheets on the sides of the machine. The highest wear area is around the impact crusher itself, around the circumference of the rotor. If not maintained, the wear items will wear through and compromise the structure of the crusher box.
Conduct a daily visual check of the machine. The jaw is simple; just stand up on the walkway and take a look down inside. A crushers jaw plate can be flipped so there are two sides of wear on them. Once half the jaw is worn out, flip it; once that side is worn, change it.
The impact crusher will have an inspection hatch to see inside. Check to see how much material is left on the blow bars and how much is left on the wear sheets on the side of the crusher box. If half the bar is worn out after one week, change the blow bars in another week.The frequency of changes depends entirely on the application and the rock that is being crushed.
They have to be user serviceable, user friendly, and able to be changed in a short time. The best way to change these parts is a service truck with a crane; some use excavators but thats not recommended by any means.
After initial blasting, breakers are used to break down aggregate that typically is not only too large to be hauled in dump trucks, but also too large for crushers that size rock to meet asphalt, drainage system, concrete and landscaping specifications. Breakers can be mounted to a mobile carrier, such as an excavator, or to stationary boom systems that can be attached to a crusher. The total number of hydraulic breakers can vary from site to site depending on production levels, the type of aggregate materials and the entire scope of the operation.
Without hydraulic breakers, workers rely on alternative practices that can quickly affect production rates. For instance, blasting mandates shutting down operations and moving workers to a safe location. And when you consider how many times oversize aggregate might need to be reduced, this can lead to a significant amount of downtime and substantially lower production rates.
Aggregate operations can use hydraulic breakers to attack oversize without having to clear the quarry. But with an ever-growing variety of manufacturers, sizes and models to choose from, narrowing the decision to one hydraulic breaker can be overwhelming with all of the stats and speculation. Thats why its important to know what factors to consider before investing in a new hydraulic breaker.
In most cases, heavy equipment dealers are very knowledgeable about quarry equipment, including breakers, so they are a good resource for finding the best model for a carrier, usually an excavator or stationary boom system. More than likely, they will have specifications and information about various breaker sizes to help gauge what model is best. But being familiar with what to look for in a breaker can streamline the selection process.
The best places to look for breaker information are in the manufacturers brochure, website, owners manual or catalogue. First, carefully review the carrier weight ranges. A breaker that is too big for the carrier can create unsafe working conditions and cause excessive wear to the carrier. An oversized breaker also transmits energy in two directions, toward the aggregate and through the equipment. This produces wasted energy and can damage the carrier. But using a breaker thats too small puts excessive force on the tool steel, which transmits percussive energy from the breaker to the material. Using breakers that are too small also can damage mounting adapters and internal components, which considerably decreases their life.
Once you find a breaker that meets the carriers capacity, check its output power, which is typically measured in foot-pounds. Foot-pound classes are generalizations and are not based on any physical test. Often the breakers output will be documented in one of two ways: as the manufacturers calculated foot-pound class or as an Association of Equipment Manufacturers measured foot-pound rating. Foot-pound class ratings can be deceiving since they are loosely based on the breakers service weight and not the result of any physical test. The AEM rating, on the other hand, measures the force a breaker exerts in a single blow through repeatable and certified testing methods. The AEM rating, which was developed by the Mounted Breaker Manufacturers Bureau, makes it easier to compare breaker models by reviewing true figures collected during an actual test procedure.
For instance, three breaker manufacturers might claim their breakers belong in a 1,000-lb. breaker class. But AEM testing standards could reveal all three actually have less foot-pound impact. You can tell if a breaker has been AEM tested if a manufacturer provides a disclosure statement or if the breaker is labeled with an AEM Tool Energy seal. If you cannot find this information, contact the manufacturer. In addition to output energy specifications, manufacturers often supply estimates for production rates on different types of aggregate material. Make sure to get the right measurements to make the best decision.
In addition to weight and output power, look at the breakers mounting package. Two things are crucial for mounting a breaker to a carrier: a hydraulic installation kit and mounting components. Breakers need hydraulic plumbing with unidirectional flow to move oil from the carrier to the breaker and back again. A one-way flow hydraulic kit is sufficient to power the breaker as long as the components are sized to properly handle the required flows and pressures. But, consider a bidirectional flow hydraulic kit if you plan to use the same carrier with other attachments that require two-way flow. Check with the dealer or breaker manufacturer to determine which hydraulic package best fits current and future needs.
Hydraulic flow and pressure specifications also need to be considered when pairing a breaker to a hydraulic system. If the carrier cannot provide enough flow at the right pressure, the breaker wont perform with maximum output, which lowers productivity and can damage the breaker. Additionally, a breaker receiving too much flow can wear quickly, which reduces its service life. For the best results, follow the hydraulic breaker specifications found in owners manuals, catalogs and brochures. Youll find out if a breaker has additional systems that might require additional servicing. For instance, some breakers feature nitrogen gas-assist systems that work with the hydraulic oil to accelerate the breakers piston. The nitrogen systems specifications need to be followed for consistent breaker power output.
Brackets or pin and bushing kits are commonly required to attach the breaker to the carrier. Typically they are bolted to the top of a breaker and are configured to match a specific carrier. Some manufacturers make universal mounting brackets that can accommodate two or three different sizes of carriers. With the adjustable pins, bushings or other components inside these universal brackets, the breaker can fit a range of carriers. However, varying distances between pin centers can complicate hookups to quick coupling systems. In addition, loose components, such as spacers, can become lost when the breaker is not in use and detached from the carrier.
Some carriers are equipped with quick-coupling systems, which require a breakers mounting interface to be configured like the carriers original attachment. Some manufacturers produce top-mount brackets that pair extremely well with couplers. This allows an operator to use the original bucket pins from the carrier to attach the breaker, and eliminates the need for new pins. This pairing also ensures a fast pickup with the quick coupler.
Its also a good idea to check which breaker tools are available through the dealer and manufacturer. The most common for aggregate mining are chisels and blunts. There are two kinds of chisels commonly used in aggregate mines: crosscut and inline. Both chisels resemble a flat head screwdriver, but the crosscut chisels are used when carrier operators want to direct force in a left-to-right concentration; whereas, inline chisels direct force fore and aft. With chisel tools, operators can concentrate a breakers energy to develop cracks, break open seams or define scribe lines.
If a chisel cant access or develop a crack or seam, a blunt can be used. Blunts have a flattened head that spreads the energy equally in all directions. This creates a shattering effect that promotes cracks and seam separation. Ask your dealer if the tools you are considering are suited for the application. Using non-original equipment manufacturer tool steel can damage the percussive piston in the breaker, seize into the wear bushings, or cause excessive wear.
Regular breaker maintenance is necessary, yet its one of the biggest challenges for aggregate operations. It not only extends the life of the breaker, but also can keep minor inconveniences from turning into expensive problems. Some manufacturers recommend operators inspect breakers daily to check grease levels and make sure there are no worn or damaged parts or hydraulic leaks.
Breakers need to be lubricated with adequate amounts of grease to keep the tool bushing area clear and reduce friction, but follow the manufacturers recommendations. For example, adding grease before properly positioning the breaker can lead to seal damage or even catastrophic failure. And too little grease could cause the bushings to overheat, seize and damage tools. Also, manufacturers advise using high-moly grease that withstands working temperatures greater than 500 degrees. Some breakers have automatic lube systems that manage grease levels, but those systems still need inspections to ensure there is adequate grease in their vessels. Shiny marks on the tool are a good indication the breaker is not properly lubricated.
Little has changed in basic crusher design over past decades, other than that of improvements in speed and chamber design. Rebuilding and keeping the same crusher in operation year after year has long been the typical approach. However, recent developments have brought about the advent of new hydraulic systems in modern crusher designs innovations stimulated by the need for greater productivity as well as a safer working environment. Importantly, the hydraulic systems in modern crusher designs are engineered to deliver greater plant uptime and eliminate the safety risks associated with manual intervention.
Indeed the crushing arena is a hazardous environment. Large material and debris can jam inside the crusher, damaging components and causing costly downtime. Importantly, manually digging out the crusher before repairs or restarts puts workers in extremely dangerous positions.
The Mine Safety and Health Administration has reported numerous injuries and fatalities incurred when climbing in or under the jaw to manually clear, repair or adjust the typical older-style jaw crusher. Consider that fatalities and injuries can occur even when the machine is locked out and tagged out. Recent examples include a foreman injured while attempting to dislodge a piece of steel caught in the primary jaw crusher. Another incident involved a fatality when a maintenance man was removing the toggle plate seat from the pitman on a jaw crusher. The worker was standing on a temporary platform when the bolts holding the toggle seat were removed, causing the pitman to move and strike him.
The hydraulic systems on modern crusher designs eliminate the need for workers to place themselves in or under the crusher. An overview of hydraulic system technology points to these three key elements:
A hydraulic chamber-clearing system that automatically opens the crusher to a safe position, allowing materials to pass. A hydraulic overload relief that protects parts and components against overload damage. A hydraulic adjustment that eliminates the maintenance downtime associated with manual crusher adjustments, and maintains safe, consistent crusher output without the need for worker intervention.
Whether a crusher is jammed by large material, tramp iron or uncrushable debris; or is stalled by a power failure the chamber must be cleared before restarting. Manual clearing is a lengthy and risky task, especially since material can be wedged inside the crusher with tremendous pressure, and dislodging poses much danger to workers placed in harms way inside the crusher.
Unlike that of the older-style jaw, the modern jaw will clear itself automatically with hydraulics that open the crusher to a safe position, and allow materials to pass again, without the need for manual intervention. If a feeder or deflector plate is installed under the crusher, uncrushable material will transfer smoothly onto the conveyor without slicing the belt.
To prevent crusher damage, downtime and difficult maintenance procedures, the hydraulic overload relief system opens the crusher when internal forces become too high, protecting the unit against costly component failure. After relief, the system automatically returns the crusher to the previous setting for continued crushing.
The modern crusher is engineered with oversized hydraulic cylinders and a traveling toggle beam to achieve reliable overload protection and simple crusher adjustment. All closed-side setting adjustments are made with push-button controls, with no shims being needed at any time (to shim is the act of inserting a timber or other materials under equipment). This is a key development as many accidents and injuries have occurred during shim adjustment, a process which has no less than 15 steps as described in the primary crusher shim adjustment training program offered by MSHA.
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The size reduction process of rocks in cone crushers is one of the most important issues, particularly for the secondary and tertiary stages of crushing operations. In this study, 17 different rock types were considered for the evaluation of their size reduction variations that occurred in a laboratory-scale cone crusher. Based on several mineralogical, physico-mechanical, and aggregate properties determined for each rock type, the crushability tests were performed.
Before and after the crushability tests, particle size distribution (PSD) of the uncrushed (feed) and crushed (product) materials were determined by sieve analyses. On the basis of these PSDs, the degree of rock crushability (DRC) was attempted to quantify by simple approaches (i.e., size reduction ratio, SRR, and the theoretical square mesh aperture size that corresponds to the 10% of the cumulative undersize in the product, P10 (mm)).
The crushability test results demonstrated that the DRC in cone crusher could be quantified by focusing on the variations in the SRR and P10. The SRR and P10 are associated with three important rock properties, Shore hardness (SH), Los Angeles abrasion loss (LAA, %), and Brazilian tensile strength (BTS, MPa). The textural and mineralogical features of rocks also have substantial impacts on the DRC for several rock types. It was concluded that the combination of the SRR and P10 could be considered together for the evaluation of DRC in cone crushers. Moreover, further research potentials on the DRC were also discussed in this study.
Cai M, Kaiser PK, Tasaka Y, Maejima T, Morioka H, Minami M (2004) Generalized crack initiation and crack damage stress thresholds of brittle rock masses near underground excavations. Int J Rock Mech Min Sci 41:833847. https://doi.org/10.1016/j.ijrmms.2004.02.001
Dahl F, Bruland A, Jakobsen PD, Nilsen B, Grov E (2012) Classifications of properties influencing the drillability of rocks based on NTNU/SINTEF test method. Tunneling and Underground Space Technol 28:150158. https://doi.org/10.1016/j.tust.2011.10.006
Donovan J. G. (2003) Fracture toughness based models for the prediction of power consumption, product size, and capacity of jaw crushers, Dissertation, Virginia Polytechnic Institute, and State University, 211 pp.
Eberhardt E., Stimson B. and Stead D. (1999) Effects of grain size on the initiation and propagation thresholds of stress-induced brittle fractures, Rock Mech. Rock Eng 32(2) 8199, https://doi.org/10.1007/s006030050026
Gent M, Menendez M, Torano J, Torno S (2012) A correlation between Vickers hardness indentation values and the Bond Work Index for the grinding of brittle minerals. Powder Technol 224:217222. https://doi.org/10.1016/j.powtec.2012.02.056
Hugman RHH, Friedman M (1979) Effects of texture and composition on mechanical behavior of experimentally deformed carbonate rocks. AAPG Bull 63(9):14781489. https://doi.org/10.1306/2F9185C7-16CE-11D7-8645000102C1865D
Kekec B, Unal M, Sensogut C (2006) Effect of textural properties of rocks on their crushing and grinding features. J Univ Sci Technol Beijing 13(5):385392. https://doi.org/10.1016/S1005-8850(06)60079-0
Kken E, zarslan A (2018) New testing methodology for the quantification of rock crushability: compressive crushing value (CCV). Int J Miner Metall Mater 25(11):12271236. https://doi.org/10.1007/s12613-018-1675-7
Korman T, Bedekovic G, Kujundzic T, Kuhinek D (2015) Impact of physical and mechanical properties of rocks on energy consumption of jaw crusher. Physicochem Probl Miner Process 51(2):461475. https://doi.org/10.5277/ppmp150208
Mitchell C.J, Mitchell P. and Pascoe R.D. (2008) Quarry fines minimization: can we really have 10 mm aggregates with no fines? Proceedings of the 14th Extractive Industry Geology Conference, Scott P.W. and Walton G. (Eds), 3744, http://nora.nerc.ac.uk/id/eprint/4932
Terva J, Kuokkala VT, Valtonen K, Siitonen P (2018) Effects of compression and sliding on the wear and energy consumption in mineral crushing. Wear 398399:116126. https://doi.org/10.1016/j.wear.2017.12.004
Tugrul A, Zarif IH (1999) Correlation of mineralogical and textural characteristics with engineering properties of selected granitic rocks from Turkey. Eng Geol 51:303317. https://doi.org/10.1016/S0013-7952(98)00071-4
Ylmaz NG (2011) Abrasivity assessment of granitic building stones in relation to diamond tool wear rate using mineralogy-based rock hardness indexes. Rock Mech Rock Eng 44:725733. https://doi.org/10.1007/s00603-011-0166-1
The author is greatly indebted to Dr. Rait Altnda (Sleyman Demirel University, Turkey) and Dr. Ahmet zarslan (Zonguldak Blent Ecevit University, Turkey) for providing laboratory facilities and their help during laboratory studies. The author also appreciates the constructive comments and suggestions of the anonymous reviewers that improved the manuscript.
pre-test: Explain the test procedures to the subject. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender, test conditions. Measure and mark out the course. Ensure that the subjects are adequately warmed-up. See more details of pre-test procedures.
procedure: The player starts by getting down in a three-point stance next to Cone 1. On the command 'Go', he runs to Cone 2, bends down and touches a line with his right hand. Then he turns and runs back to Cone 1, bends down and touches that line with his right hand. Then he runs back to Cone 2 and around the outside of it, weaves inside Cone 3, then around the outside of Cones 3 and 2 before finishing at Cone 1. The player must run forward while altering his running direction, as opposed to strictly stopping and starting in opposite directions. Each time they perform the 3-cone drill for a different side (e.g. first time they curve to the left, second time they curve to the right). See 3-cone shuttle drill video.
target population: This test is part of the NFL testing combine, though it would be suitable for athletes involved in many team sports where agility is important such basketball, hockey, rugby, soccer.
We have over 400 fitness tests listed, so it's not easy to choose the best one to use. You should consider the validity, reliability, costs and ease of use for each test. Use our testing guide to conducting, recording, and interpreting fitness tests. Any questions, please ask or search for your answer. To keep up with the latest in sport science and this website, subscribe to our newsletter. We are also on facebook and twitter.
Fengbiao Wu, Lifeng Ma, Guanghui Zhao, Zhijian Wang, "Chamber Optimization for Comprehensive Improvement of Cone Crusher Productivity and Product Quality", Mathematical Problems in Engineering, vol. 2021, Article ID 5516813, 13 pages, 2021. https://doi.org/10.1155/2021/5516813
This study aims to analyze the impact of key structural parameters such as the bottom angle of the mantle, the length of the parallel zone, and the eccentric angle on the productivity and product quality of the cone crusher and optimize the crushing chamber to improve the crusher performance. The amount of ore in the blockage layer was calculated by analyzing the movement state of the ore in the crushing chamber. Considering the amount of ore uplift further, the traditional mathematical model of crusher productivity was revised. Then, a mathematical model for dual-objective optimization of productivity and product quality of cone crusher was established. Furthermore, taking the existing C900 cone crusher as the research object, the influence of key parameters on the performance of the crusher was researched. And the optimal values of key structural parameters were obtained. Finally, based on the iron ore coarsely crushed by the gyratory crusher, the dynamic characteristics of the C900 cone crusher were simulated by using the discrete element method (DEM), and the simulation results are basically consistent with the numerical analysis results. Results show that considering the amount of ore uplift in the blockage layer, the revised mathematical model of crusher productivity can better characterize the actual productivity. The bottom angle of the mantle and the length of the parallel zone are within the range of 5060and 140mm190mm, respectively. The productivity shows a positive correlation with the bottom angle and a negative correlation with the length of the parallel zone. But the dependence of product quality on the angle and the length is just the opposite. The eccentric angle is within the range of 1.42 and its decrease has a negative effect on the productivity and product quality.
As one of the key equipment in the bulk materials crushing system, the cone crusher is mainly used for the medium and fine crushing of bulk materials. With the continuous promotion of breaking instead of grinding, the application of cone crusher is more extensive. The crushing chamber is the key factor that determines the performance of the cone crusher. At present, Bengtsson, Grndah, Lee et al. , Zhang et al. , Huang et al. , Khalid et al. , Bengtsson et al. , and Franks et al.  have studied the interparticle breakage behavior of bulk materials through the ore mechanics test system and established a productivity model, and the influence of the engagement angle, different close side settings (CSS), the mantle shaft speed, and particle shape of the cone crusher on the performance of the crusher is studied. However, the productivity model does not consider the effect of ore uplift in the blockage layer, and the bottom angle of the mantle, the length of the parallel zone, and the eccentric angle have a great influence on the chamber structure, and the chamber structure is related to the number of broken ores. Therefore, it is necessary to further study the influence of these parameters on the crushing performance. In addition, the DEM has been proved to be a very good virtual simulation environment by Cleary, Delaney et al. [11, 12], Quist et al. , and Chen et al. . The virtual simulation environment can be used to gain a fundamental understanding regarding internal processes and operational responses. A virtual crushing platform can not only be used for understanding but also for the development of new crushers and for optimization purposes.
Therefore, the working process of the cone crusher is taken as the specific analysis object, and considering the amount of ore uplift, the traditional mathematical model of crusher productivity was revised. Then, a mathematical model for dual-objective optimization of productivity and product particle size distribution of cone crusher was established. Furthermore, the influence of the bottom angle of the mantle, the length of the parallel zone, and the eccentric angle on cone crusher performances is analyzed by the optimal numerical calculation method. Finally, the reliability of the optimization model and optimization algorithm of cone crusher is verified by the DEM based on the characteristics of coarse crushing ores.
The crushing chamber is composed of the mantle and concave, as shown in Figures 1(a) and 1(b). The drive turns the horizontal countershaft. The pinion gear on the countershaft rotates the eccentric gear. The eccentric bushing rotation causes the mantle to wobble. The functional principle of a cone crusher is to compress particles between two surfaces. The compressive action is realised by inflicting a nutational motion on the mantle while the concave remains fixed. The ore is squeezed and crushed several times along the crushing chamber from the feeding port to the discharging port, especially in the parallel section, which does the final crushing. Larger ore needs longer time between squeezes.
The crushing of ore is directly related to the compression ratio, and the bottom angle and eccentric angle determine the compression stroke of the mantle. The length of the parallel zone determines the number of ore fractures. Therefore, the productivity and particle quality of the cone crusher are affected by these structural parameters of the crushing chamber.
Productivity refers to the amount of ore processed by the crusher per unit time under the conditions of certain feed size and discharge size, which is a key indicator reflecting the performance of the crusher. The calculation results of the existing cone crusher productivity are compared with the actual production results. The calculation results are always greater than the actual production results. After analysis, because the crusher has a blockage layer in actual work, the mantle far away from the concave will fall. The ore on the side of the mantle close to the concave will arch up and cannot be discharged from the discharge port. Therefore, it is necessary to theoretically derive the amount of ore in the blockage layer and revise the existing theoretical calculation model of cone crusher productivity.
The existing theoretical calculation model of productivity is calculated based on the volume of the ore discharged from the crushing chamber once the mantle swings , as shown in Figure 2. The following equation represents the mathematical model:where is the volume of the ore discharged from the crushing chamber once the mantle swings, is the thickness of the ore layer when the ore is compressed, is the ore displacement when the mantle swings, and is the average diameter of the ore compression layer, considered to be approximately equal to the bottom diameter of the mantle .
Considering the ore hardness and feed size, the following equation represents the productivity per minute:where is productivity, is ore bulk density, is the mantle swing times per minute, is loose factor, , is ore hardness coefficient (hard ore: ; medium hard or soft ore: ), is feed size factor, and is feed opening width, as shown in Table 1.
As shown in Figure 3, the crushing chamber formed by the mantle and the concave is divided into four areas, and the mantle rotates counterclockwise. When the mantle closes to the concave and extrudes the ore, the ore in the A and D areas will arch upward. That is, when the mantle is close to the concave, the ore cannot be discharged naturally and upward movement occurs.
At this time, the ore speed is consistent with the moving speed of the mantle, and the ore throughput is obtained by double-integrating the ore velocity and area in the A and D areas. In Figure 3, plane is the cross section of the blockage layer, is the center of the concave section, and is the center of the mantle section.
Therefore, the ore quantity in this area is calculated, and then the traditional productivity theory is used to subtract the ore quantity in this part, so a more accurate calculation method of productivity can be obtained. Ore velocity in the upper arch area is shown as follows:where is 1/2 cycle, (the rotating speed of the mantle is ) and is the moving distance of the mantle. Take a microelement for the upper arch area of the blockage layer, and the integral function of the upper arch zone can be expressed as follows:where is the angle enclosed by the upper arch boundary and the coordinate axis, is the distance from the center of the concave to the boundary of the mantle, is the radius of the concave, and is the speed of the ore in the upper arch area.
The good performance of the cone crusher is mainly reflected in the high productivity and neat particle size distribution of crushed products. There is a strong coupling relationship between productivity optimization and product quality optimization models. Based on the principle of interparticle breakage, the kinematic characteristics of bulk materials, and the population balance modeling (PBM), a dual-objective programming model of the cone crusher is established.
In the case of ensuring the particle size of the crushed product, the productivity of the crusher should be improved as much as possible. Taking productivity as the first objective function of optimizing crusher chamber, the objective function as shown in the following equation is obtained according to equation (5):
The mass proportion of the bulk materials whose diameter is smaller than the CSS is the main technical index to measure the particle size distribution of the crushed product. Therefore, the following equation is used as the second objective function for optimizing the chamber shape of the crusher:
Equation (7) is based on the model proposed and perfected by Broadbent et al.  and Lynch  in the study of coal crushing process. After the continuous improvement of most scholars, equation (8) of the product particle size distribution model of the material is gradually summarized:where is selection function, is crushing function, is the number of crushing times the material has been subjected to, , is the unit matrix of feeding granularity.
For the selection function and crushing function mentioned in the above equation, Professor Evertsson of Chalmers University of Technology in Sweden [20, 21] has obtained the relevant mathematical model by simulating lamination crushing through experiments, as shown in the following equations:where is the compression height of the bulk materials before lamination and crushing, is the amount of feed compression, is the particle size of the Nth layer of the lamination and crushing materials, is the smallest particle size in the product, is the largest particle size in the feed, and is the equivalent particle size of the Nth layer of laminated crushed materials.
The chamber structure parameters of the cone crusher are the key parameters that affect the performance of the crusher. The bottom angle of the mantle , the length of the parallel zone , the eccentric angle , and the rotating speed are determined as the design variables of the dual-objective programming model, as shown in the following equation:
The value range of the crushing optimization constraints was set by referring to the parameters of the C900 cone crusher. The parameters of C900 are shown in Table 2 where is open side size, is eccentricity, and is engagement angle.(1)According to the calculation of the critical speed and the actual parameters r/min, speed was defined as .(2)According to the suspension height of the cone crusher, the eccentric angle was defined as . The swing stroke and eccentricity of the mantle are affected by the eccentric angle.(3)According to the original parameters and actual design experience, the value range of the bottom angle of the mantle was defined as .(4)The product quality can be effectively improved by increasing the length of the parallel zone, and the length of the parallel zone was defined as .
The objective function was determined by studying the performance of the cone crusher. The design variables were determined by analyzing the structure parameters and process parameters of the cone crusher. The constraint conditions were set by combining the parameters of the cone crusher C900. Comprehensive analysis of the objective optimization problem of the cone crusher was performed using the main objective method, taking productivity as the main objective of crusher optimization and transforming the product quality optimization into nonlinear constraints. According to equations (6), (7), (12), and (13), the dual-objective programming model of cone crusher is established, and the forms are shown in the following equations:
The dual-objective programming model of the cone crusher is solved by using K-T  nonlinear sequential quadratic programming method, and the optimization results are shown in Table 3. Figures 46 show the effects of changing the bottom angle of the mantle , the length of the parallel zone , and the eccentric angle on productivity and particle size distribution of crushed products.
As shown in Figures 4(a) and 4(b), crusher productivity is increased from 1008t/h to 1238t/h at the rate of 23%, as the bottom angle of the mantle increases from 50 to 60. However, the particle size and quality of crushed products decrease, which is less than the closed side setting of broken product percentage from 85% to 78%. This is due to the decrease of the effective crushing times in the crushing chamber when the bottom angle of the mantle increases.
As shown in Figures 5(a) and 5(b), crusher productivity is decreased from 998t/h to 850t/h at the rate of 15%,, as the length of the parallel zone increases from 140mm to 190mm. However, the particle size and quality of crushed products increase, which is less than the closed side setting of broken product percentage which increases by about 9.6%. This is because as the parallel zone increases, ores were more fully broken, but the broken time results in a decline in productivity growth.
As shown in Figures 6(a) and 6(b), crusher productivity and the particle size and quality are increased, as the eccentric angle increases from 1.4 to 2. This is because the eccentricity of the crusher and swing stroke of the mantle increase with the increase of eccentric angle.
The above research shows that the influence of the structure parameters of the crusher on the productivity and product quality is mutually restricted, and there is a strong coupling relationship. Therefore, both productivity optimization and product quality optimization are taken into account, the optimal performance parameters of the crusher C900 were obtained, the mantle bottom angle is in the range of 50 to 60, the length of the parallel zone is in the range of 140mm190mm, and the eccentric angle is in the range of 1.42. The optimal structural parameters of the C900 crusher chamber was obtained: the swing speed of the mantle, the length of the parallel zone, the bottom angle of the mantle, the eccentric angle, the eccentricity, and the engagement angle are 285r/min, 150mm, 55, 2, 44.8mm, and 23, respectively.
The DEM provides a bonding and energy accumulation crushing model, which can accurately describe the crushing process of ores under the action of equipment. Hasankhoei et al.  and Cleary et al.  have proved to be a powerful tool for studying the flow of bulk materials and ore crushing behavior. In this paper, based on the coarse broken iron ores in the rotary crusher, the ore particle model was established by using DEM software. The dynamic characteristics of the model were simulated by combining with the three-dimensional cone crusher model in order to study the influence of relevant parameters on the performance of the crusher.
Before the ore modeling with DEM software, the basic physical and mechanical properties of iron ore were explored through rock uniaxial compression [25, 26], fracture toughness, rock material damage, and other experiments. The grain size, structure size, internal porosity, pore radius, coordination number, and other factors of the ore were analyzed by computed tomography (CT) nondestructive testing technology. The DEM virtual ore model can more truly reflect the physical characteristics and crushing characteristics from the experimental results. Figure 7 shows the cutting and sampling from the crude ore after the rotary crusher. The equipment used is a cutting machine and a drilling prototype to make the iron ore into regular cylindrical specimens for the mechanical properties experiment.
For the collected specimens, the internal structure and characteristics of the ore were observed through nondestructive testing with CT. The internal structure of the ore is visually characterized through three-dimensional technology [27, 28]. Finally, the relationship between structure and performance was established based on the experimental data. Figures 8(a) and 8(b) show the technical scheme of CT nondestructive testing and CT.
The test conditions were voltage 100kV, current 50A, and resolution 1.12m. A full-diameter CT scan test was performed on ore samples, and the internal three-dimensional (3D) structure data volume of the sample was obtained for three-dimensional display. After that, different internal substances were extracted by using the gray difference for three-dimensional rendering. The internal structure of the ore was observed to understand the structural characteristics of the internal pores and fractures of the ore. Figures 9(a) and 9(b) show the three-dimensional display and rendering of iron ore. The red area shows the cracks. The cracks were extracted by threshold segmentation. The volume percentage of the study area (i.e., porosity) occupied by the cracks is 10.18%.
Figures 10(a) and 10(b) show the three-dimensional rendering of iron ore porosity. The extracted pores were marked with different colors for each isolated pore. At the same time, the pores were marked and sieved. The pore equivalent diameter (EqD) sieve is shown in Figures 11(a)11(h). The number of equivalent diameters of different pores and the percentage of the total pore volume are shown in Table 4.
The characteristic parameters such as porosity, coordination number, pore radius, and pore volume were obtained through the experimental exploration of the ore after coarse crushed by the gyratory crusher. The number of pore equivalent diameters in the range of 9
In order to characterize the ore particle model well, bonded particle model (BPM) was selected. The BPM model was published by Potyondy et al.  and A. R. Hasankhoei for the purpose of simulating ore breakage. The approach has been applied and further developed by Cho et al. and Johansson et al. [30, 31]. The concept is based on bonding or gluing a packed distribution of spheres together forming a breakable body.
When setting the crushed ore particles, firstly, a certain amount of particles were combined to form ore particles through the bonding bond at a given time. When subjected to crushing force, the particles formed by the bonding bond will be dispersed to show the broken state. At this time, the bonding bond is broken. The larger the number of broken bonds, the better the crushing effect and the higher the product quality. This paper mainly analyzes the impact of different parameters on the crushing effect. Because of the large amount of crushed iron ore, the influence of the shape of the ore was not considered, and the iron ore model was equivalent to a spherical shape. Figure 12 shows a schematic diagram of ore model generation and crushing.
Since the particle size of the ore feed cannot be less than 100mm, the design iron ore model diameter is 100mm. According to the physical properties of the iron ore obtained by experiments, such as the porosity and coordination number, the diameter of the fraction used to fill the iron ore particles was determined to be 5mm. The empirical equation (17) for determining the number of filling particles given in the DEM was used to calculate the number of filling fractions:where is particle filling coefficient, is the volume of feed particle, is the number of filled fractions, and is the volume of filled fractions.
Firstly, import the crusher chamber model drawn by SolidWorks into the geometry module, and set the motion characteristics for each part. The movement of the mantle includes two: one is its own rotation movement, the speed is very low, generally 1015r/min, and the other is the eccentric movement around the axis of the concave. The eccentric movement speed is specifically set according to the optimization result, and the movement time is set to 5s.
Secondly, set the basic property parameters of iron ore and liner materials in the globals module, including density, Poissons ratio, and shear modulus. Define the properties of fraction particles and whole particles in the particle panel, including particle radius, volume, and mass. The fraction particle radius is 5mm. Because of the soft ball contact model, the actual contact radius is slightly larger than 5mm, which is defined as 5.5mm here, and the whole particle is 50mm.
During the operation of the crusher, the ore and the ore, and the ore and the liner are squeezed into each other. Therefore, it is necessary to separately set the coefficient of restitution between the ore and the ore, the coefficient of static friction, the coefficient of dynamic friction, and the three coefficients between the ore and the liner.
Finally, determine the simulation time step and divide the mesh. Generally, 2-3 times the radius of the smallest particle element is selected as the basis for meshing. In this simulation, 2 times the radius of the smallest particle element 5mm is selected as the ideal side length of the mesh element.
The time step is determined by the Rayleigh  wave method. For a system composed of different particles, the time step was calculated as follows:where is particle velocity, is particle density, is shear modulus, and is particle radius.
Simulation was carried out according to the parameters in Table 3, and the total number of ore bonding bonds N was set as 144,298. Figures 13(a)13(d) show the DEM simulation of the crushing process of the cone crusher at different moments and the velocity cloud diagram of the particles in the crushing chamber.
In Table 5, is the total number of ore bonding bonds and is the number of ore fracture bonds. The bottom angle of the mantle , the length of the parallel zone , and the eccentric angle are changed respectively for simulation. For different variable values, the corresponding number of ore fracture bonds and are shown in Table 5. The breaking rule of ore bonding bond with crushing time is shown in Figures 14(a)14(c).
It can be seen from the above that when the bottom angle of the mantle increases from 50 to 60, the number of bond breaks decreases from 130,589 to 118,901, and the broken percentage decreases from 90.5% to 82.4%. And when the length of the parallel zone increases from 140mm to 190mm, the number of bond breakages increases from 126838 to 136650 and the broken percentage increases from 87.9% to 94.7%. While when the eccentric angle increased from 1.4 to 2, the number of bond breaks increased from 115,149 to 122,941, and the broken percentage increased from 79.8% to 85.2%. The simulation value is slightly higher than the numerical calculation value, but the trend of the broken percentage with the change of the bottom angle of the mantle, the length of the parallel zone, and the eccentric angle is consistent.
By analyzing the movement state of the ore in the crushing chamber, the cone crusher productivity and product quality are used as the objective functions to study the influence of the chamber structure parameters on the crusher performance with the method of optimized numerical calculation. The main conclusions of this paper are as follows:(1)In order to obtain a more accurate productivity model, it is necessary to remove the blockage ore uplift in the traditional model. For this reason, considering the influence of the ore arching of the blockage layer in the A and D areas, the traditional productivity model was revised to improve the calculation accuracy of the crushers productivity. For the C900 cone crusher, the relative error of the revised productivity model calculation value is reduced by 16%.(2)Taking the parameters such as mantle bottom angle, parallel zone length, and the eccentric angle of the chamber structure as optimization variables, a dual-objective programming model about the productivity and product quality for the cone crusher was established. The optimal parameter matching scheme of C900 cone crusher performance was obtained: The swing speed of the mantle, the length of the parallel zone, the bottom angle of the mantle, the eccentric angle, the eccentricity, and the engagement angle are 285r/min,1 50mm, 55, 2, 44.8mm, and 23, respectively. After optimization, the productivity and the percentage of crushed products of the C900 cone crusher can be increased by about 2% and 2.1%, respectively.(3)Based on the physical characteristics of the iron ore after coarse crushing by the gyratory crusher, the discrete element method is used to simulate the crushing process. The simulation results are consistent with the trend of the numerical calculation results, verifying the feasibility and reliability of the dual-objective programming model of the cone crusher as well as the optimization numerical method.
Copyright 2021 Fengbiao Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Get in Touch with Mechanic