A sectional view of the single-toggle type of jaw crusher is shown below.In one respect, the working principle and application of this machine are similar to all types of rock crushers, the movable jaw has its maximum movement at the top of the crushing chamber, and minimum movement at the discharge point. The motion is, however, a more complex one than the Dodge motion, being the resultant of the circular motion of the eccentric shaft at the top of the swing jaw. combined with the rocking action of the inclined toggle plate at the bottom of this jaw. The motion at the receiving opening is elliptical; at the discharge opening, it is a thin crescent, whose chord is inclined upwardly toward the stationary jaw. Thus, at all points in the crushing chamber, the motion has both, vertical and horizontal, components.
It will be noted that the motion is a rocking one. When the swing jaw is rising, it is opening, at the top, during the first half of the stroke, and closing during the second half, whereas the bottom of the jaw is closing during the entire up-stroke. A reversal of this motion occurs during the downstroke of the eccentric.
The horizontal component of motion (throw) at the discharge point of the single-toggle jaw crusher is greater than the throw of the Dodge crusher at that point; in fact, it is about three-fourths that of Blake machines of similar short-side receiving-opening dimensions. The combination of favorable crushing angle, and nonchoking jaw plates, used in this machine, promotes a much freer action through the choke zone than that in the Dodge crusher. Capacities compare very favorably with comparable sizes of the Blake machine with non-choking plates, and permissible discharge settings are finer. A table of ratings is given.
The single-toggle type jaw crusher has been developed extensively. Because of its simplicity, lightweight, moderate cost, and good capacity, it has found quite a wide field of application in portable crushing rigs. It also fits into the small, single-stage mining operation much better than the slower Dodge type. Some years since this type was developed with very wide openings for reduction crushing applications, but it was not able to seriously challenge the gyratory in this field, especially when the high-speed modern versions of the latter type were introduced.
Due to the pronounced vertical components of motion in the single-toggle machine, it is obvious that a wiping action takes place during the closing strokes; either, the swing jaw must slip on the material, or the material must slip along the stationary jaw. It is inevitable that such action should result in accelerated wear of the jaw plates; consequently, the single-toggle crusher is not an economical machine for reducing highly abrasive, or very hard, tough rock. Moreover, the large motion at the receiving opening greatly accentuates shocks incidental to handling the latter class of material, and the full impact of these shocks must be absorbed by the bearings in the top of the swing jaw.
The single-toggle machine, like the Dodge type, is capable of making a high ratio-of-reduction, a faculty which enables it to perform a single-stage reduction of hand-loaded, mine run ore to a suitable ball mill, or rod mill, feed.
Within the limits of its capacity, and size of receiving openings, it is admirably suited for such operations. Small gravel plant operations are also suited to this type of crusher, although it should not be used where the gravel deposit contains extremely hard boulders. The crusher is easy to adjust, and, in common with most machines of the jaw type, is a simple crusher to maintain.
As rock particles are compressed between the inclined faces of the mantle and concaves there is a tendency for them to slip upward. Slippage occurs in all crushers, even in ideal conditions. Only the particles weight and the friction between it and the crusher surfaces counteract this tendency. In particular, very hard rock tends to slip upward rather than break. Choke feeding this kind of material can overload the motor, leaving no option but to regulate the feed. Smaller particles, which weigh less, and harder particles, which are more resistant to breakage, will tend to slip more. Anything that reduces friction, such as spray water or feed moisture, will promote slippage.
Leading is a technique for measuring the gap between fixed and moveable jaws. The procedure is performed while the crusher is running empty. A lead plug is lowered on a lanyard to the choke point, then removed and measured to find out how much thickness remains after the crusher has compressed it. This measures the closed side setting. The open side setting is equal to this measurement plus the throw of the mantle. The minimum safe closed side setting depends on:
Blake (Double Toggle) Originally the standard jaw crusher used for primary and secondary crushing of hard, tough abrasive rocks. Also for sticky feeds. Relatively coarse slabby product, with minimum fines.
Overhead Pivot (Double Toggle) Similar applications to Blake. Overhead pivot; reduces rubbing on crusher faces, reduces choking, allows higher speeds and therefore higher capacities. Energy efficiency higher because jaw and charge not lifted during cycle.
Overhead Eccentric (Single Toggle) Originally restricted to sampler sizes by structural limitations. Now in the same size of Blake which it has tended to supersede, because overhead eccentric encourages feed and discharge, allowing higher speeds and capacity, but with higher wear and more attrition breakage and slightly lower energy efficiency. In addition as compared to an equivalent double toggle, they are cheaper and take up less floor space.
Since the jaw crusher was pioneered by Eli Whitney Blake in the 2nd quarter of the 1800s, many have twisted the Patent and come up with other types of jaw crushers in hopes of crushing rocks and stones more effectively. Those other types of jaw crusher inventors having given birth to 3 groups:
Heavy-duty crushing applications of hard-to-break, high Work Index rocks do prefer double-toggle jaw crushers as they are heavier in fabrication. A double-toggle jaw crusher outweighs the single-toggle by a factor of 2X and well as costs more in capital for the same duty. To perform its trade-off evaluation, the engineering and design firm will analyze technical factors such as:
1. Proper selection of the jaws. 2. Proper feed gradation. 3. Controlled feed rate. 4. Sufficient feeder capacity and width. 5. Adequate crusher discharge area. 6. Discharge conveyor sized to convey maximum crusher capacity.
Although the image below is of a single-toggle, it illustrates the shims used to make minor setting changes are made to the crusher by adding or removing them in the small space between the crushers mainframe and the rea toggle block.
The jaw crusher discharge opening is the distance from the valley between corrugations on one jaw to the top of the mating corrugation on the other jaw. The crusher discharge opening governs the size of finished material produced by the crusher.
Crusher must be adjusted when empty and stopped. Never close crusher discharge opening to less than minimum opening. Closing crusher opening to less than recommended will reduce the capacity of crusher and cause premature failure of shaft and bearing assembly.
To compensate for wear on toggle plate, toggle seat, pitman toggle seat, and jaws additional shims must be inserted to maintain the same crusher opening. The setting adjustment system is designed to compensate for jaw plate wear and to change the CSS (closed side setting) of the jaw crusher. The setting adjustment system is built into the back frame end.
Here also the toggle is kept in place by a compression spring. Large CSS adjustments are made to the jaw crusher by modifying the length of the toggle. Again, shims allow for minor gap adjustments as they are inserted between the mainframe and the toggle block.
is done considering the maximum rock-lump or large stone expected to be crushed and also includes the TPH tonnage rate needing to be crushed. In sizing, we not that jaw crushers will only have around 75% availability and extra sizing should permit this downtime.
As a rule, the maximum stone-lump dimension need not exceed 80% of the jaw crushers gape. For intense, a 59 x 79 machine should not see rocks larger than 80 x 59/100 = 47 or 1.2 meters across. Miners being miners, it is a certainty during day-to-day operation, the crusher will see oversized ore but is should be fine and pass-thru if no bridging takes place.
It will be seen that the pitman (226) is suspended from an eccentric on the flywheel shaft and consequently moves up and down as the latter revolves, forcing the toggle plates outwards at each revolution. The seating (234) of the rear toggle plate (239) is fixed to the crusher frame; the bottom of the swing jaw (214) is therefore pushed forward each time the pitman rises, a tension rod (245) fitted with a spring (247) being used to bring it back as the pitman falls. Thus at each revolution of the flywheel the movable jaw crushes any lump of ore once against the stationary jaw (212) allowing it to fall as it swings back on the return half-stroke until eventually the pieces have been broken small enough to drop out. It follows that the size to which the ore is crushed.
The jaw crusher is not so efficient a machine as the gyratory crusher described in the next paragraph, the chief reason for this being that its crushing action is confined to the forward stroke of the jaw only, whereas the gyratory crusher does useful work during the whole of its revolution. In addition, the jaw crusher cannot be choke-fed, as can the other machine, with the result that it is difficult to keep it working at its full capacity that is, at maximum efficiency.
Tables 5 and 6 give particulars of different sizes of jaw crushers. The capacity figures are based on ore weighing 100 lb. per cubic foot; for a heavier ore, the figures should be increased in direct proportion to its weight in pounds per cubic foot.
The JAW crusher and the GYRATORY crusher have similarities that put them into the same class of crusher. They both have the same crushing speed, 100 to 200 R.P.M. They both break the ore by compression force. And lastly, they both are able to crush the same size of ore.
In spite of their similarities, each crusher design has its own limitations and advantages that differ from the other one. A Gyratory crusher can be fed from two sides and is able to handle ore that tends to slab. Its design allows a higher-speed motor with a higher reduction ratio between the motor and the crushing surface. This means a dollar saving in energy costs.
A Jaw crusher on the other hand requires an Ely wheel to store energy. The box frame construction of this type of crusher also allows it to handle tougher ore. This design restricts the feeding of the crusher to one side only.
The ore enters from the top and the swing jaw squeezes it against the stationary jaw until it breaks. The broken ore then falls through the crusher to be taken away by a conveyor that is under the crusher.Although the jaws do the work, the real heart of this crusher is the TOGGLE PLATES, the PITMAN, and the PLY WHEEL.
These jaw crushers are ideal forsmall properties and they are of the high capacity forced feed design.On this first Forced Feed Jaw Crusher, the mainframe and bumper are cast of special alloy iron and the initial cost is low. The frame is ribbed both vertically and horizontally to give maximum strength with minimum weight. The bumper is ruggedly constructed to withstand tremendous shock loads. Steel bumper can be furnished if desired. The side bearings are bronze; the bumper bearings are of the antifriction type.
This bearing arrangement adds both strength and ease of movement. The jaw plates and cheek plates are reversible and are of the best-grade manganese steel. The jaw opening is controlled by the position of an adjustable wedge block. The crusher is usually driven by a V-to-V belt drive, but it can be arranged for either V-to-flat or fiat belt drive. The 8x10 size utilizes a split frame and maybe packed for muleback transportation. Cast steel frames can be furnished to obtain maximum durability.
This second type of forced feed rock crusher is similar in design to the Type H listed above except for having a frame and bumper made of cast steel. This steel construction makes the unit lighter per unit of size and adds considerable strength. The bearings are all of the special design; they are bronze and will stand continuous service without any danger of failure. The jaw and cheek plates are manganese steel; and are completely reversible, thus adding to their wearing life. The jaw opening is controlled by the position of an adjustable wedge block. The crushers are usually driven by V-to-V but can be arranged for V-to-flat and belt drive. The 5x6 size and the 8x10 size can be made with sectionalized frame for muleback transportation. This crusher is ideal for strenuous conditions. Consider a multi jaw crusher.
Some jaw crushers are on-floor, some aboveground, and others underground. This in many countries, and crushing many kinds of ore. The Traylor Bulldog Jaw crusher has enjoyed world wide esteem as a hard-working, profit-producing, full-proof, and trouble-free breaker since the day of its introduction, nearly twenty years ago. To be modern and get the most out of your crushing dollars, youll need the Building breaker. Wed value the privilege of telling you why by letter, through our bulletins, or in person. Write us now today -for a Blake crusher with curved jaw plates that crush finer and step up production.
When a machine has such a reputation for excellence that buyers have confidence in its ability to justify its purchase, IT MUST BE GOOD! Take the Type G Traylor Jaw Crusher, for instance. The engineers and operators of many great mining companies know from satisfying experience that this machine delivers a full measure of service and yields extra profits. So they specify it in full confidence and the purchase is made without the usual reluctance to lay out good money for a new machine.
The success of the Type G Traylor Jaw Crusheris due to several characteristics. It is (1) STRONG almost to superfluity, being built of steel throughout; it is (2) FOOL-PROOF, being provided with our patented Safety Device which prevents breakage due to tramp iron or other causes of jamming; it is (3) ECONOMICAL to operate and maintain, being fitted with our well-known patented Bulldog Pitman and Toggle System, which saves power and wear by minimizing frictionpower that is employed to deliver increased production; it is (4) CONVENIENT to transport and erect in crowded or not easily accessible locations because it is sectionalized to meet highly restrictive conditions.
Whenever mining men need a crusher that is thoroughly reliable and big producer (which is of all time) they almost invariably think first of a Traylor Type G Jaw Crusher. By experience, they know that this machine has built into it the four essentials to satisfaction and profit- strength, foolproofness, economy, and convenience.
Maximum STRENGTH lies in the liberal design and the steel of which crushers parts are made-cast steel frame, Swing Jaw, Pitman Cap and Toggles, steel Shafts and Pitman rods and manganese steel Jaw Plates and Cheek Plates. FOOLPROOFNESS is provided by our patented and time-tested safety Device which prevents breakage due to packing or tramp iron. ECONOMY is assured by our well-known Bulldog Pitman and Toggle System, which saves power and wear by minimizing friction, the power that is used to deliver greater productivity. CONVENIENCE in transportation and erection in crowded or not easily accessible locations is planned for in advance by sectionalisation to meet any restrictive conditions.
Many of the worlds greatest mining companies have standardized upon the Traylor Type G Jaw Crusher. Most of them have reordered, some of them several times. What this crusher is doing for them in the way of earning extra dollars through increased production and lowered costs, it will do for you! Investigate it closely. The more closely you do, the better youll like it.
This crusher developed by Jaques (now Terex Mineral Processing Solutions) has several internal chamber configurations available depending on the abrasiveness of the ore. Examples include the Rock on Rock, Rock on Anvil and Shoe and Anvil configurations (Figure 6.26). These units typically operate with 5 to 6 steel impellers or hammers, with a ring of thin anvils. Rock is hit or accelerated to impact on the anvils, after which the broken fragments freefall into the discharge chute and onto a product conveyor belt. This impact size reduction process was modeled by Kojovic (1996) and Djordjevic et al. (2003) using rotor dimensions and speed, and rock breakage characteristics measured in the laboratory. The model was also extended to the Barmac crushers (Napier-Munn et al., 1996).
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 . 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.
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 . 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.
Secondary coal crusher: Used when the coal coming from the supplier is large enough to be handled by a single crusher. The primary crusher converts the feed size to one that is acceptable to the secondary crusher.
The main sources of RA are either from construction and ready mixed concrete sites, demolition sites or from roads. The demolition sites produce a heterogeneous material, whereas ready mixed concrete or prefabricated concrete plants produce a more homogeneous material. RAs are mainly produced in fixed crushing plant around big cities where CDWs are available. However, for roads and to reduce transportation cost, mobile crushing installations are used.
The materiel for RA manufacturing does not differ from that of producing NA in quarries. However, it should be more robust to resist wear, and it handles large blocks of up to 1m. The main difference is that RAs need the elimination of contaminants such as wood, joint sealants, plastics, and steel which should be removed with blast of air for light materials and electro-magnets for steel. The materials are first separated from other undesired materials then treated by washing and air to take out contamination. The quality and grading of aggregates depend on the choice of the crusher type.
Jaw crusher: The material is crushed between a fixed jaw and a mobile jaw. The feed is subjected to repeated pressure as it passes downwards and is progressively reduced in size until it is small enough to pass out of the crushing chamber. This crusher produces less fines but the aggregates have a more elongated form.
Hammer (impact) crusher: The feed is fragmented by kinetic energy introduced by a rotating mass (the rotor) which projects the material against a fixed surface causing it to shatter causing further particle size reduction. This crusher produces more rounded shape.
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.
Roll crushers are arbitrarily divided into light and heavy duty crushers. The diameters of the light duty crushers vary between 228 and 760mm with face lengths between 250 and 460mm. The spring pressure for light duty rolls varies between 1.1 and 5.6kg/m. The heavy duty crusher diameters range between 900 and 1000mm with face length between 300 and 610mm. In general, the spring pressures of the heavy duty rolls range between 7 and 60kg/m. The light duty rolls are designed to operate at faster speeds compared to heavy duty rolls that are designed to operate at lower speeds.
It has been stressed that the coal supplier should initially crush the materials to a maximum size such as 300 mm, but they may be something else depending on the agreement or coal tie up. To circumvent the situation, the CHP keeps a crushing provision so that coal bunkers receive the materials at a maximum size of about 2025 mm.
The unloaded coal in the hoppers is transferred to the crusher house through belt conveyors with different stopovers in between such as the penthouse, transfer points, etc., depending on the CHP layout.
Suspended magnets for the removal of tramp iron pieces and metal detectors for identifying nonferrous materials are provided at strategic points to intercept unacceptable materials before they reach the crushers. There may be arrangements for manual stone picking from the conveyors, as suitable. Crushed coal is then sent directly to the stockyard.
A coal-sampling unit is provided for uncrushed coal. Online coal analyzers are also available, but they are a costly item. Screens (vibrating grizzly or rollers) are provided at the upstream of the crushers to sort out the smaller sizes as stipulated, and larger pieces are guided to the crushers.
Appropriate types of isolation gates, for example, rod or rack and pinion gates, are provided before screens to isolate one set of crushers/screens to carry on maintenance work without affecting the operation of other streams.
Vibrating grizzly or roller screens are provided upstream of the crushers for less than 25 (typical) mm coal particles bypass the crusher and coal size more than 25 mm then fed to the crushers. The crushed coal is either fed to the coal bunkers of the boilers or discharged to the coal stockyard through conveyors and transfer points, if any.
This is used for crushing and breaking large coal in the first step of coal crushing plant applied most widely in coal crushing industry. Jaw crushers are designed for primary crushing of hard rocks without rubbing and with minimum dust. Jaw crushers may be utilized for materials such as coal, granite, basalt, river gravel, bauxite, marble, slag, hard rock, limestone, iron ore, magazine ore, etc., within a pressure resistance strength of 200 MPa. Jaw crushers are characterized for different features such as a simple structure, easy maintenance, low cost, high crushing ratio, and high resistance to friction/abrasion/compression with a longer operating lifespan.
Fixed and movable jaw plates are the two main components. A motor-driven eccentric shaft through suitable hardware makes the movable jaw plate travel in a regulated track and hit the materials in the crushing chamber comprising a fixed-jaw plate to assert compression force for crushing.
A coal hammer crusher is developed for materials having pressure-resistance strength over 100 Mpa and humidity not more than 15%. A hammer crusher is suitable for mid-hard and light erosive materials such as coal, salt, chalk, gypsum, limestone, etc.
Hammer mills are primarily steel drums that contain a vertical or horizontal cross-shaped rotor mounted with pivoting hammers that can freely swing on either end of the cross. While the material is fed into the feed hopper, the rotor placed inside the drum is spun at a high speed. Thereafter, the hammers on the ends of the rotating cross thrust the material, thereby shredding and expelling it through the screens fitted in the drum.
Ring granulators are used for crushing coal to a size acceptable to the mills for conversion to powdered coal. A ring granulator prevents both the oversizing and undersizing of coal, helping the quality of the finished product and improving the workability. Due to its strong construction, a ring granulator is capable of crushing coal, limestone, lignite, or gypsum as well as other medium-to-hard friable items. Ring granulators are rugged, dependable, and specially designed for continuous high capacity crushing of materials. Ring granulators are available with operating capacities from 40 to 1800 tons/h or even more with a feed size up to 500 mm. Adjustment of clearance between the cage and the path of the rings takes care of the product gradation as well as compensates for wear and tear of the machine parts for maintaining product size. The unique combination of impact and rolling compression makes the crushing action yield a higher output with a lower noise level and power consumption. Here, the product is almost of uniform granular size with n adjustable range of less than 2025 mm. As the crushing action involves minimum attrition, thereby minimum fines are produced with improving efficiency.
A ring granulator works on n operating principle similar to a hammer mill, but the hammers are replaced with rolling rings. The ring granulator compresses material by impact in association with shear and compression force. It comprises a screen plate/cage bar steel box with an opening in the top cover for feeding. The power-driven horizontal main shaft passes from frame side to frame side, supporting a number of circular discs fixed at regular intervals across its length within the frame. There are quite a few bars running parallel to the main shaft and around the periphery that pass through these discs near their outer edges. The bars are uniformly located about the center of the main rotating shaft. There are a series of rings in between the two consecutive disc spaces, mounted on each bar. They are free to rotate on the bars irrespective of the main shaft rotation. The entire cage assembly, located below the rotor assembly, can be set at a desired close proximity to the rings by screw jack mechanism adjustable from outside the crusher frame. The rotor assembly consisting of the shaft, discs, rings, etc., is fixed as far as the main shaft center line is concerned. This main shaft carries in roller bearings from the box sides. The movable cage frame arrangement is provided so as to set its inner radius marginally larger than that of the ring running periphery. When coal is fed from the top, the rings also rotate along with the shaft and around their own center line along the bars, which drags coal lumps and crushes them to the desired size. After the coal has been crushed by the coal crusher, a vibrating screen grades the coal by size and the coal is then transported via belt conveyor. In this process, a dewatering screen is optional to remove water from the product.
Crusher machines are used for crushing of a wide variety of materials in the mining, iron and steel, and quarry industries. In quarry industry, they are used for crushing of rocks into granites for road-building and civil works. Crusher machines are equipped with a pair of crusher jaws namely; fixed jaws and swing jaws. Both jaws are fixed in a vertical position at the front end of a hollow rectangular frame of crushing machine as shown in Fig.10.1. The swing jaw is moved against the fixed jaws through knuckle action by the rising and falling of a second lever (pitman) carried by eccentric shaft. The vertical movement is then horizontally fixed to the jaw by double toggle plates. Because the jaw is pivoted at the top, the throw is greatest at the discharge, preventing chocking.
The crushing force is produced by an eccentric shaft. Then it is transferred to the crushing zone via a toggle plate system and supported by the back wall of the housing of the machine. Spring-pulling rods keep the whole system in a condition of no positive connection. Centrifugal masses on the eccentric shaft serve as compensation for heavy loads. A flywheel is provided in the form of a pulley. Due to the favorable angle of dip between the crushing jaws, the feeding material can be reduced directly after entering the machine. The final grain size distribution is influenced by both the adjustable crusher setting and the suitability of the tooth form selected for the crushing plates.
Thus, the crusher jaws must be hard and tough enough to crush rock and meet the impact action generated by the action of swing jaws respectively. If the jaws are hard, it will be efficient in crushing rock but it will be susceptible to fracture failure. On the other hand, if the jaws are tough, the teeth will worn out very fast, but it will be able to withstand fracture failure. Thus, crusher jaws are made of highly wear-resistant austenitic manganese steel casting, which combines both high toughness and good resistance to wear.
Austenitic manganese steel was invented by Sir Robert Hadfield in 1882 and was first granted patented in Britain in 1883 with patent number 200. The first United States patents, numbers 303150 and 303151, were granted in 1884. In accordance with ASTM A128 specification, the basic chemical composition of Hadfield steel is 1%1.4% carbon and 11%14% manganese. However, the manganese to carbon ratio is optimum at 10:1 to ensure an austenitic microstructure after quenching . Austenitic manganese steels possess unique resistance to impact and abrasion wears. They exhibit high levels of ductility and toughness, slow crack propagation rates, and a high rate of work-hardening resulting in superior wear resistance in comparison with other potentially competitive materials . These unique properties have made Hadfield's austenitic manganese steel an engineering material of choice for use in heavy industries, such as earth moving, mining, quarrying, oil and gas drilling, and in processing of various materials for components of crushers, mills, and construction machinery (lining plates, hammers, jaws, cones).
Austenitic manganese steel has a yield strength between 50,000psi (345MPa) and 60,000psi (414MPa) . Although stronger than low carbon steel, it is not as strong as medium carbon steel. It is, however, much tougher than medium carbon steel. Yielding in austenitic manganese steel signifies the onset of work-hardening and accompanying plastic deformation. The modulus of elasticity for austenitic manganese steel is 27106psi (186103MPa) and is somewhat below that of carbon steel, which is generally taken as 29106psi (200103MPa). The ultimate tensile strength of austenitic manganese steel varies but is generally taken as 140,000psi (965MPa). At this tensile strength, austenitic manganese steel displays elongation in the 35%40% range. The fatigue limit for manganese steel is about 39,000psi (269MPa). The ability of austenitic manganese to work-harden up to its ultimate tensile strength is its main feature. In this regard austenitic manganese has no equal. The range of work-hardening of austenitic manganese from yield to ultimate tensile is approximately 200%.
When subjected to impact loads Hadfield steel work-hardens considerably while exhibiting superior toughness. However, due to its low yield strength, large deformation may occur and lead to failure before the work-hardening sets in . This phenomenon is detrimental when it comes to some applications, such as rock crushing . Work-hardening behavior of Hadfield steel has been attributed to dynamic strain aging . The hardening or strengthening mechanism has its origin in the interactions between dislocations and the high concentration of interstitial atoms also known as the CottrellBilby interaction. Thus, the wear properties of Hadfield steel are related to its microstructure, which in turn is dependent on the heat-treatment process and chemical composition of the alloy. According to Haakonsen , work-hardening is influenced by such parameters as alloy chemistry, temperature, and strain rate.
Carbon content affects the yield strength of AMS. Carbon levels below 1% cause yield strengths to decrease. The optimum carbon content has been found to be between 1% and 1.2%. Above 1.2% carbides precipitate and segregate to grain boundaries, resulting in compromised strength and ductility particularly in heavy sections . Other alloying elements, such as chromium, will increase the yield strength, but decrease ductility. Silicon is generally added as a deoxidizer. Carbon contents above 1.4% are not generally used as the carbon segregates to the grain boundaries as carbides and is detrimental to both strength and ductility .
Manganese has very little effect on the yield strength of austenitic manganese steel, but does affect both the ultimate tensile strength and ductility. Maximum tensile strengths are attained with 12%13% manganese contents . Although acceptable mechanical properties can be achieved up to 20% manganese content, there is no economic advantage in using manganese contents greater than 13%. Manganese acts as an austenitic stabilizer and delays isothermal transformation. For example, carbon steel containing 1% manganese begins isothermal transformation about 15s after quenching to 371C, whereas steel containing 12% manganese begins isothermal transformation about 48h after quenching to 371C .
Austenitic manganese steel in as-cast condition is characterized by an austenitic microstructure with precipitates of alloyed cementite and the triple phosphorus eutectic of an Fe-(Fe,Mn)3C-(Fe,Mn)3P type , which appears when the phosphorus content exceeds 0.04% . It also contains nonmetallic inclusions, such as oxides, sulfides, and nitrides. This type of microstructure is unfavorable due to the presence of the (Fe, Mn)xCy carbides spread along the grain boundaries . However, in solution-treated conditions austenitic manganese steel structure is essentially austenitic because carbon is in austenite solution . The practical limit of carbon in solution is about 1.2%. Thereafter, excess carbon precipitation to the grain boundaries results, especially in heavier sections .
Austenitic manganese steel in the as-cast condition is too brittle for normal use. As section thickness increases, the cooling rate within the molds decreases. This decreased cooling rate results in increased embrittlement due to carbon precipitation. In as-cast castings, the tensile strength ranges from approximately 50,000psi. (345MPa) to 70,000psi (483MPa) and displays elongation values below 1%. Heat treatment is used to strengthen and increase the mechanical properties of austenitic manganese steel. The normal heat-treatment method consists of solution annealing and rapid quenching in a water bath.
Considering the mechanical properties, it is difficult to imagine that a casting made from Hadfield steel could suffer failure in service. However, cases like this do happen, especially in heavy-section elements and result in enormous losses of material and long downtimes. The reason for such failures is usually attributed to insufficient ductility, resulting from sensitivity of austenitic manganese steel to section size, heat treatment, and the rapidity and effectiveness of quenching . Poor quench compounded by large section size results in an unstable, in-homogenous structure, subject to transformation to martensite under increased loading and strain rate. This article investigates the cause of incessant failure of locally produced crusher jaws from Hadfield steel.
According to the recent marketing research data conducted by the foundry an estimate of 15,000metrictons of this component is being consumed annually in the local market. This is valued at about $30million. From this market demand, the foundry plant can only supply about 5% valued at $1.5million. This is because the crusher jaws produced locally failed prematurely. Hence, this study aimed at investigating the causes of failure.
Annual wine exports in the European Union is around 21.9 billion (Eurostat) with France being the main wine exporting country followed by Italy and Spain. The wine production process (Fig. 9.1) can be divided into the following stages (Sections 184.108.40.206.2.1.4).
Grape crushers or crusher destemmers are initially used via light processing to avoid seed fracture. Sulfur dioxide is added to the mass to prevent oxidation. At this stage, grape stems are produced as one of the waste streams of the winery process. The mash is pressed in continuous, pneumatic, or vertical basket presses leading to the separation of the pomace (marc) from the must. Microbial growth is suppressed via sulfur dioxide addition.
The solids present in the must are removed before or after fermentation for white wine production. Fining is achieved by combined processes including filtration, centrifugation, flocculation, physicochemical treatment (e.g., activated carbon, gelatin, etc.,), and stabilization to prevent turbidity formation (e.g., the use of bentonite, cold stabilization techniques, etc.). Clarification leads to the separation of sediments via racking.
Wine production is carried out at temperatures lower than 20C for 610 weeks in stainless steel bioreactors or vats with or without yeast inoculation (most frequently Saccharomyces cerevisiae). At the end of fermentation, the wine is cooled (4C5C) and subsequently aged in barrels or wooden vats. The sediment that is produced during fermentation and aging is called wine lees and constitutes one of the waste streams produced by wineries. Current uses of wine lees include tartrate production and ethanol distillation. Lees could also be processed via rotary vacuum filtration for recycling of the liquid fraction and composting of the solid fraction.
Wine is cooled rapidly to facilitate the precipitation of tartrate crystals. Fining is applied for the separation of suspended particles using bentonite and gelatin. Filtration is subsequently applied to remove any insoluble compounds. The wine is finally transferred into bottles.
The main differences in the red wine production process are skin maceration duration, fermentation temperature, and unit operation sequence. Whole crushed grapes are most frequently used in red wine fermentation, which is carried out at 22C28C to facilitate the extraction of color and flavors. The remaining skins, seeds, and grape solids after fermentation are pressed to recover wine with the correct proportions of tannins and other compounds necessary for the final wine product.