The belowimage shows a sectional view of a typical gyratory crusher. This type of machine is, by virtue of chronological priority, known as the standard gyratory crusher. Although it incorporates many refinements in design, it is fundamentally the same crusher that first bore the name of gyratory; its crushing chamber is very much the same shape; the motion is identically the same, and the method of transmitting power from belt to crushing head is similar. It is an interesting fact that the same similarity in essential features of design exists in the case of the standard, or Blake type, jaw crusher, which is something in the way of a tribute to the inspiration and mechanical ability of the men who originated these machines.
Essentially, the gyratory crusher consists of a heavy cast-iron, or steel, frame which includes in its lower part an actuating mechanism (eccentric and driving gears), and in its upper part a cone-shaped crushing chamber, lined with wear-resisting plates (concaves). Spanning the crushing chamber across its top is a steady-rest (spider), containing a machined journal which fixes the position of the upper end of the main shaft. The active crushing member consists of the main shaft and its crushing head, or head center and mantle. This assembly is suspended in the spider journal by means of a heavy nut which, in all but the very large machines, is arranged for a certain amount of vertical adjustment of the shaft and head. At its lower end the main shaft passes through the babbitted eccentric journal, which offsets the lower end of the shaft with respect to the centerline of the crusher. Thus, when the eccentric is rotated by its gear train, the lower end of the main shaft is caused to gyrate (oscillate in a small circular path), and the crushing head, likewise, gyrates within the crushing chamber, progressively approaching, and receding from, each element of the cone-shaped inner surface.
The action of the gyratory crusher, and of the other member of the reciprocating pressure family, the jaw crusher, is fundamentally a simple one, but as will be seen a great deal of thought and some very progressive engineering has been expended upon the design of crushing chambers to increase capacities and to permit the use of closer discharge settings for secondary and fine-reduction crushing (various crusher types).
Referring to the table, always available from the manufacturer, it will be noted that standard gyratory crushers are manufactured in commercial sizes ranging from 8 to 60 receiving openings. Capacities are listed, for minimum and maximum open-side discharge settings, in short tons per hour, and the horsepower requirements for soft and hard materials are listed for each size. The capacities, and the minimum settings, are based upon the use of standard (straight-face) concaves.
Primary gyratory crushers are designated by two numbers. These are the size of the feed opening (in inches) and the diameter of the mantle at its base (in inches). A 60~x~89 crusher would have an opening dimension of 60 inches (152 cm) and a diameter across the base of the mantle of 89 inches (226 cm).
To stand up under the extremely rugged work of reducing hard and tough rock and ore, and in doing so to maintain reasonably true alignment of its running component, the crushermust necessarily be of massive and rigid proportions, rigidity being of equal importance to ultimate strength. Regardless of the tensile strength of the metal used in the main frame, top shell, and spider, these parts must be made with walls and ribs thick enough to provide this rigidity. Therefore it is practicable to use close-grained cast iron, and special high-test mixtures of cast iron, for these parts, if the machine is intended for crushing soft or medium materials. When very hard and tough materials are to be crushed, the machine is usually strengthened by substituting cast steel in one or more of its parts.
Wearing parts in the gyratory crusher may be either chilled cast iron or manganese steel, depending on the character of the material to be crushed and the particular class of service for which the machine is intended. Standard crushers, in the small and medium sizes, are customarily fitted with chilled-iron head and concaves for crushing soft and medium limestone and materials of similar hardness and abrasiveness, because its relatively low first cost and excellent wearing qualities make it the most economical material to use when the service is not too severe. Manganese steel, which combines extreme toughness with unsurpassed wear-resistance, is the universal choice for crushing hard, tough rock regardless of the class of service or type of crusher. Even though the rock be quite soft and non-abrasive, it is general practice to use manganese steel concaves in the larger sizes of primary crushers because of the shocks attendant upon handling large and heavy pieces of rock.
The primary rockbreaker most commonly used in large plants is the gyratory crusher, of which a typical section is shown in Fig. 5.It consists essentially of a gyrating crushing head (521) working inside a crushing bowl (522) which is fixed to the frame (501).
Thecrushing head is carried on a short solid main shaft (515) suspended from the spider (502) by a nut (513) ; the nut fits into the seating of a sleeve (514) which fixes its position in relation to the spider and, therefore, to the frame (501). The lower part of the main shaft fits into a sleeve (530) set in an eccentric (527), to which is keyed the bevel driving gear (528) ; the bevel pinion (533) is similarly fastened to the countershaft (535) and engages with the bevel gear. The whole of this driving assembly is protected from grit and dust by means of a dust seal (524), (525), and (526).
The countershaft carries the driving pulley, and as it revolves it causes the eccentric to rotate ; as it rotates the main shaft gyrates and with it the crushing head ; the top of the shaft at the point of suspension has practically no movement. Although the motion of the head is gyratory, the main shaft is free to rotate in the eccentric and it actually revolves slowly in relation to the bowl, thus equalizing the wear on the mantle (519) which lines the head and on the concave liners (522 and 523) which comprise the bowl. Both mantle and bowl liners are usually made of manganese steel. The suspension nut (513) is adjustable and enables the crushing head and main shaft to be raised in relation to the bowl to compensate for wear. The size of the product is determined by the distance between the bottom edges of the crushing head and the bowl, in the position when they are farthest apart.
The crushing action is much the same in principle as that of a jaw crusher, the lumps of ore being pinched and broken between the crushing head and the bowl instead of between two jaws. The main point ofdifference between the two types is that the gyratory crusher does effective work during the whole of the travel of the head, whereas the other only crushes during the forward stroke. The gyratory crusher is thereforethe more efficient machine, provided that the bowl can be kept full, a condition which is, as a rule, easy to maintain because it is quite safe to bury the head in a pile of ore.
Tables 7 and 8 give particulars of different sizes of gyratory crushers. As in the previous paragraph, the capacity figures are based on material weighing 100 lb. per cubic foot and should be increased in direct proportion for heavier ores.
Primary and secondary gyratory crushers, including the cone crusher, can be directly connected to slow speed motors if desired, but the standard method of drive is still by belt and pulley. Jaw crushers must be belt-driven.
An efficient substitute for the flat belt in all cases is the Texrope drive, which consists of a number of V-shaped endless rubber belts running on special grooved pulleys. The grip of these belts is so great that the distance between the pulley centres can be reduced to about 30% of that required for a flat belt. This results not only in a saving of space but also in greater safety, since the drive is easier to protect and there is no danger of an accident such as might occur if a long belt were to pull through its fasteners. Moreover, the short drive makes it possible for any stretch to be taken up by moving the motor back on its rails without the necessity of cutting and rejoining the belts. The flexibility and ease of maintenance of the Tex-rope drive makes it very suitable for crushing machines.
LOW OPERATING COSTS Vertical adjustment compensates for wear on crushing surfaces (also maintains product uniformity). Oiling system provides proper lubrication throughout, including spider. Effective dust seal prevents dust infiltration to moving parts. Long life bearings, easy to replace.
Strength, of course, makes an all-important contribution to the rugged heavy duty service and day-in, day-out dependability demanded of a crusher. However, strength does not necessarily mean excessive weight. The metals and alloys used in construction and the distribution of weight are actually the determining factors in the strength of a gyratory crusher.
MAINSHAFT ASSEMBLY mainshaft forged steel; annealed quenched and tempered. Tapered to gauge for head center fit. Head center of cast steel. Head mantle of manganese steel. Mainshaft sleeve shrunk on mainshaft to provide renewable wearing surface on spider bearing.
Gyratory crusher advanced design includes the placing of circumferential ribs around the top and bottom shells. These integrally cast reinforcing rings prevent distortion provide the rigidity necessary to maintain true alignment of running parts.
Hollow box construction of the cast steel spider affords maximum strength with the least amount of feed interference. Arms are cast integrally with the heavy outer rim. Crushing stresses are transmitted to the rim, which is taper-fitted to the top shell. Because spider and top shell are interlocked, they reinforce each other to provide maximum stability and rigidity.
The bottom shell is the foundation of the crusher. It must be strong enough not only to support the weight of the crusher, but to withstand extreme crushing stresses (most stresses terminate here) strong enough to protect vital mechanism the eccentric, gears and countershaft assembly housed in the bottom shell. In the Gyratory crusher, bottom discharge design makes possible a compact, squat structure of simplified design and comparatively high strength. Supplementing the strength of the bottom shell are the previously described circumferential ribs. Crushing stresses are transmitted directly to these reinforcing members through three radial arms.
Because the mainshaft does the actual crushing, it must literally possess crushing strength. In the Gyratory crusher, the eccentric is located directly below the crushing head. This design permits the use of a short, rigid mainshaft a mainshaft that will withstand the strain of severe service.
Flexibility is the keynote of the Gyratory crusher efficiency and economy. While your particular installation is designed to best meet your specific and immediate requirements, built-in flexibility permits adaptation to changing operating conditions anytime in the future.
A Gyratory crusher not only affords a maximum capacity-to-size ratio, but provides the variable factors which facilitate increasing or decreasing capacity as the need arises. Flexibility in a Gyratory crusher also permits compensation for wear and assures product uniformity.
In the Gyratory crusher, the use of spiral bevel gears instead of spur gears makes possible the broad range of speeds conducive to meeting varying capacity demands. Because the Gyratory crusher is equipped with an external oiling system, speed may be reduced as much as desired or required. Adequate lubrication is supplied at even the lowest speeds, because the flow of oil is not relative to the crushers operating speed as is the case with an internal system.
With a primary gyratory crusher running at a given countershaft speed, capacity is increased as eccentricity is increased. At a given eccentricity, greater capacity results from higher countershaft speeds. Conversely, reducing either the speed or eccentricity reduces capacity.
Another high capacity characteristic of the Gyratory crusher is a large diameter crushing head. Because the area of discharge opening is directly proportionate to head diameter, high capacities result.
VARIABLE INITIAL SETTINGS The contour of the crushing chamber at the bottom is designed to afford various initial settings without changing the angle of the nip. This is accomplished by installing lower tier concaves of the shape and thickness for the desired setting and capacity.
HOW SIZES ARE DESIGNATED The numerical size designation of Gyratory crushers represents the feed opening and the maximum diameter of the crushing head. For example, a 60-109 Gyratory crusher has a 60-inch receiving opening and an 109-inch maximum diameter crushing head.
ELIMINATES DIAPHRAGM In a gyratory crusher with aside discharge, sticky materials may pack on the diaphragm and eventually cause considerable damage. Thestraight down discharge of the Gyratory crusher is a design simplification that eliminates the diaphragm and itsmaintenance problems.
CONTRIBUTES TO BALANCED CIRCUIT The adaptabilityof a primary crusher to a large extent dictates the plantflowsheet the initial and overall operating costs of subsequent equipment. With a Gyratory primary crusher,these costs are kept at a minimum because the entirecrushing circuit remains in balance. The concrete foundation may be modified for use as a surge bin. This storagecapacity permits controlling the flow of material throughthe plant. Secondary and tertiary crushers, vibrating screens, etc. may be installed in size ranges and types tomeet the requirements of a constant tonnage. For thosefew installations where a side discharge is essential, a discharge spout can be furnished. Another factor in maintaining a balanced circuit is the vertical adjustment(pages 12 and 13) which permits retaining the initial discharge setting by compensating for wear on mantle andconcaves. Related equipment need not be readjusted because of variations of feed size from the primary crusher.
In the Gyratory crusher, the original discharge setting may be maintained for the life of a single set of alloy crushing surfaces with only one resetting of concaves. Raising the mainshaft compensates for wear onconcaves and mantle. This simplified vertical adjustment cuts resetting time facilitates holding product size.
The threaded mainshaft is held in and supported from the spider hub. (See illustration at lower left.) A vertical adjustment range of from 6 inches to approximately 11 inches is possible, depending upon the size of the machine. The original discharge setting can be maintained until the combined wear of mantle and concaves is about one-third of the vertical adjustment.
A cast steel, split adjusting nut with a collar issupported on a two-piece thrust bearing in the spider hub. The nut is threaded for the mainshaft. The outside of the nut is tapered, with the large diameter at the top. The weight of the head and shaft draws the nut down in its tapered seat in the collar to form a self-clamping nut. Desired setting is achieved by positioning split nut in the proper location on the threaded portion of the mainshaft.
The Gyratory crusher is also available with a Hydroset mechanism a hydraulic method of vertical adjustment. With the Hydroset mechanism, compensation for wear and product size control is a one- man, one-minute operation. The Hydroset mechanism consists of a motor-driven gear pump operated by push button.
The accompanying drawings show the simplicity of Hydroset design. The mainshaft assembly is supported on a hydraulic jack. When oil is pumped into the jack, the mainshaft is raised compensating for mantle and concave wear or providing a closer setting. When oil is removed from jack, the mainshaft is lowered and a coarser setting results.
Since the mainshaft assembly is supported on a hydraulic jack, its position with respect to the concaves, and therefore the crusher setting, is controlledby the amount of oil in the hydraulic cylinder.
Oil pressure is maintained in the hydraulic cylinder below the mainshaft by a highly effective chevron packing. The oil supply of the Hydroset mechanism functions independently of the crushers lubrication system.
If a Gyratory crusher equipped with Hydroset mechanism stops under load, the mainshaft may be lowered to facilitate clearing of the crushing chamber by merely pumping oil out of the cylinder. Only under extreme conditions is it necessary to dig out. When the cause of the stoppage is remedied, the oil is pumped back into the cylinder quickly, returning the mainshaft assembly to its initial position.
STEP BEARING consists of bronze mainshaft step, bronze piston wearing plate, and an alloy steel washer between the two. Washer is drilled for oil cooling lubrication. Bearing surfaces are grooved to permit oil distribution.
Utilizing pool lubrication, a gun-type fitting in the spider arm makes it easy to oil the spider bearing. A garter-type oil seal in the bottom of the bearing retains oil. Being flexible, the seal compensates for movement of crusher mainshaft.
The countershaft assembly is an anti-friction, pool-lubricated unit. Both ends of the bearing housing are sealed by garter-type spring oil seals which: (1) keep dust from anti-friction bearings; (2) separate pinion- shaft bearing lubricant from oil lubricating the eccentric and gears.
Getting the most out of a crusher in performance and capacity depends largely upon positive lubrication. And positive lubrication means more than just adequate oil lubrication. It also entails conditioning oil for maximum lubricating efficiency.
The Gyratory crusher is equipped with an externally located, fully automatic lubricating system. Positive and constant lubrication is maintained at all speeds even at the slowest speed. If desired, oil may be circulated through bearings of Gyratory crusher during shutdown periods.
A gear pump circulates oil from storage tank, through crusher and back. Each time oil is pumped to the crusher, it passes through the filter and cooler. The cleaned, cool oil lubricates the step bearing (in Hydroset mechanism only), the eccentric wearing plate and the inner eccentric bearing. At the top of the bearing, most of the oil flows through ports in the eccentric to the outer eccentric bearing. Theoil then flows down the outer eccentric bearing and lubricates the gear and pinion before it is returned to storage. The overflow oil which may have become contaminated is returned immediately to the oil conditioning tank. It does not contact any other wearing parts within the crusher.
The oil conditioning system may be modified to meet your particular applications. In cold climates immersion heaters are installed in the storage tank to preheat oil. This arrangement permits circulating warm oil through the crusher during shutdown periods. A thermostatic control turns heater on and off. Only in a crusher specifically designed for external oiling is it possible to circulate warm oil when the crusher is stopped.
An added measure of safety is providedby the oil conditioning system. Foreignmaterial is removed by pumping warm oilthrough a mechanical filter. After oil isfiltered, it flows through a condenser-type cooler before it is returned to the crusher.
An oil flow switch provides automatic protection against possible damage caused by oil system failure. This switch stops the crusher immediately if oil flow is insufficient for proper lubrication. Interlocks between pump motor and crusher prevent starting crusher before oil circulation begins.
In addition to its other advantages, the externally located oil conditioning system is easy to service. The unit consists of (A) an oil storage tank, (B) a motor-driven gear pump, (C) a pressure- type filter, and (D) a condenser-type cooler.
In the gyratory crusher, expensive castings are protected by replaceable parts. Rim and arm liners protect the spider from wear. Bottom shell liners and shields provide protection below the crushing chamber. An alloy steel shaft sleeve protects the mainshaft in the spider bearing. The eccentric sleeve and bushing are easily replaced when worn.
Because all parts are readily accessible and removable, down time is kept to a minimum. For example, the countershaft assembly is removed as a unit and can be taken to your machine shop for convenient servicing. Eccentric bearings are bronze bushings. Because bronze is used, the need for babbitt mandrels and melting facilities is eliminated.
Sealing out dirt and dust and their equipment-destroying abrasive action results in obvious maintenance economies. The type of dust seal used in the gyratory crusher is the most reliable and effective device ever developed for preventing excessive wear caused by dirt and dust.
In the gyratory crusher, a synthetic, self-lubricating, light-weight ring is used as a dust seal. The ring is enclosed between a dust collar bolted to the bottom shell and a recess in the bottom of the head center. Regardless of the eccentric throw and vertical positioning, the ring maintains its contact with the outer periphery of the dust collar. Because of its light weight and self-lubricating characteristics, wear on this ring is negligible.
Provisions have been made on the gyratory crusher for the introduction of low pressure air to the dust seal chamber. This internal pressure, which can be obtained through the use of a small low pressure blower, creates an outward flow of air through the dust seal. This prevents an inward flow of abrasive dirt and dust. The combination of a highly effective sealing ring and the utilization of internal air pressure protects the eccentric and gears from destructive infiltration even under the most severe conditions. When required, this additional protection is supplied at a nominal additional cost.
All of the operating advantages all of the engineering and construction features described in this bulletin are found in both the primary and secondary gyratory crushers. Of course, certain modifications have been made to efficiently accomplish the tough, rugged job of secondary crushing. For instance, the secondary gyratory crusher has been engineered to accommodate the greater horsepower requirement of secondary crushing. Increased strength and durability have been built into all components.
In the past, primary crushers had to be set extremely close in order to provide an acceptable feed for secondary crushers. As a result, primary crushers were penalized by reduced capacity and excessive maintenance. The secondary gyratory crusher was engineered to solve this problem.
Anticipating product size variations, Allis-Chalmers has designed the secondary crusher with a large feed opening one large enough to accept oversized materials. This design feature is particularly advantageous when the secondary gyratory crusher follows a primary crusher that has no vertical adjustment for wear.
A large diameter crushing head along with tailored-to-your-operation design results in big capacity. An acute angle in the crushing chamber and a long parallel zone facilitate precision setting assure a cubical, well graded product distributes even the normal wear throughout the crushing chamber.
1. Spider cap 2. Spider 3. Hour glass bushing 4. Spider bearing oil seal 5. Spider bearing oil seal retainer 6. Spider bearing oil seal retainer screws 7. Spider joint bolts 8. Spider joint bolt nuts 9. Spider joint bolt lock nuts 10. Spider arm shield 11. Spider arm shield bolts 12. Spider arm shield bolt nuts 13. Center spider rim liners (not shown) 14. End spider rim liners 15. Rim liner bolts 16. Rim liner bolt nuts 17. Spider bearing spherical support ring 18. Spider bearing spherical support ring seat 19. Spider lubricating hose bushing 20. Spider lubricating hose 21. Spider lubricating hose bracket 22. Spider lubricating hose grease fitting 23. Spider lubricating hose bracket bolts 24. Spider joint studs (not shown) 26. Mainshaft thrust ring 27. Mainshaft thrust ring bolts 31. Top shell 32. Concave support ring 33. Upper concaves 34. Upper middle concaves 36. Lower middle concaves 37. Lower concaves 43. Bottom shell 44. Bottom shell joint bolts 45. Bottom shell joint bolt nuts 46. Bottom shell joint bolt lock nuts 47. Bottom shell bushing 48. Bottom shell bushing key 49. Bottom shell bushing clamp plate 50. Bottom shell bushing clamp plate bolts 51. Bottom shell front arm liners 52. Bottom shell rear arm liners 53. Bottom shell side liners 54. Bottom shell hub liners 55. Dust collar 56. Dust collar cap screws 57. Dust collar gasket 63. Bottom plate 64. Bottom plate studs 65. Bottom plate stud nuts 66. Bottom plate stud lock nuts 67. Bottom plate dowel pin 68. Bottom plate drain plug 69. Bottom plate gasket 95. Eccentric 96. Eccentric sleeve 97. Eccentric sleeve key 98. Bevel gear 99. Bevel gear key 100. Bevel gear key cap screws 101. Eccentric wearing plate 107. Mainshaft 108. Head center 109. Mantle lower section 110. Mantle upper section 111. Head nut 112. Dowel pin (for keying head nut to mantle) 113. Mainshaft sleeve 114. Adjusting nut 115. Adjusting nut collar 116. Enclosed ring type dust seal sealing ring 117. Enclosed ring type dust seal retaining ring 118. Enclosed ring type dust seal bolts 119. Adjusting nut tie bar 120. Adjusting nut tie bar bolts 121. Adjusting nut key 124. Pinion bearing housing 125. Pinion bearing housing gasket 126. Pinion bearing housing studs 127. Pinion bearing housing stud nuts 128. Pinion bearing housing stud lock nuts 129. Pinion bearing housing dowel pin 130. Pinion bearing housing oil drain plug 131. Pinion bearing housing oil level plug (not shown) 132. Pinion bearing housing oil filler plug 133. Pinionshaft 134. Drive sheave and bushing 135. Drive sheave key 136. Pinion shaft lock nut spacer 137. Pinion shaft lock nut spacer lockwasher 138. Pinion shaft lock nut spacer lockwasher gasket 139. Pinion bearing seal plate 140. Pinion bearing oil seal 141. Pinion bearing seal plate gaskets 142. Pinion bearing seal plate bolts 143. Pinionshaft outer bearing 144. Pinionshaft inner bearing 145. Pinionshaft bearing spacing collar 146. Pinionshaft bearing spacing collar gasket 147. Pinion 148. Pinion key 149. Pinion retainer plate 150. Pinion retainer plate bolts
In the dimension charts above, the first number in each size classification designates the size of the receiving opening in inches. The second number is the largest diameter of the mantle in inches. Primary crushers having the same mantle diameter use the same size bottom shell, gears, eccentrics and countershaft assemblies.
Secondary crushers use the same size bottom shells as certain size primary crushers, but different size top shells, mainshaft and spider assemblies. The 30-70 secondary gyratory crusher uses the bottom shell of the 42-65 primary crusher; the 24-60 secondary uses the 30-55 primary bottom shell.
Capacities given here are based on field data under average quarry conditions when crushing dry friable material equivalent to limestone. Because conditions of stone and methods of operation vary, capacities given are approximate only.
Where no capacity data is given the crusher is under development.Figures under Maximum Horsepower are correct only for throw and pinion Rpm given above. When speed is reduced, Maximum Horsepower must also be reduced proportionately.
This graph is based on customary practice and is principally a guide. Size of crusher may vary considerably with different materials, depending upon stratification, blockiness, quarry methods and size of quarry trucks. Pieces that cannot be handled by crusher without bridging should be broken in the quarry.
The screen analysis of the product from any crusher will vary widely, depending upon the character of the material, quarry conditions, and the amount of fines or product size in the initial feed at the time
the sample is taken. These factors should be taken into consideration when estimating the screen analysis of the crusher product. Product gradation curves based on many actual screen analyses have been prepared which can be used for estimating.
The crusher discharge opening on the open side will govern the product gradation from a crusher if corrected to take into consideration quarry or mine conditions, particularly as to the amount of fines in the crusher feed. The tabulation at the left is basedon an average of many screen analyses and gives the approximate percentage of product equal to the open side setting of the crusher. Its actual use when the feed conditions are definitely known should be corrected to take care of these conditions, particularly insofar as fines or product size in the feed are concerned. The curves on these pages have been prepared giving the approximate screen analysis of the crusher product and should be used in conjunction with Table I
Table I shows 90% of product should pass a 6-inch square opening flat testing sieve. Using the 90% vertical line on Table II, follow it up to the horizontal line of 6 inches. Follow the nearest curve to the intersection, and using this curve you will get the following approximate screen analysis.
Until recently, there has been no way of accurately determining the power required for agiven crushing operation. With little or no factualoperating data correlated into useful form, it wasdifficult even for the most experienced operators toarrive at a correct size crusher or a proper size crusher motor to do a given job.
The correlation of all this factual material, from extensive field operating data and laboratory data covering wide varieties of material, ranges of reduction sizes, and types of equipment, made it possible to establish a consistent common factor known asthe Work Index for accurately determining the power required for crushing.
In the Work Index method, frequently referred to as the Bond method, the Work Index is actually the total work input in kwhr per short ton required to reduce a given material from theoretically infinite particle size to 80% passing 100 microns or approximately 67% passing 200 mesh. Knowing the Work Index, you need only apply the given equation to determine power input required. The calculated power input enables you to select the proper crusher.
In order to simplify the selection of a crusher by the Work Index method, the following form has been developed. References below the form explain the various parts of the calculation, and, immediately below, a complete example is worked out.
REFERENCE I Average Impact. As noted, the Work Index is determined from the average impact value and the specific gravity of the material being crushed. The impact value and Work Index can be determined in the Processing Machinery Laboratory, or these values can be determined from a comparable operation in the field. Acomplete listing of Work Indexes of materials which have been tested in the laboratory.
REFERENCE II Feed Size. In the case of a primary crusher this may be somewhat difficult to obtain. Experience indicates, however, that in most cases 80% of the feed size will pass a square opening equal to from half to two-thirds of the crusher receiving opening.
A crushed stone producer desires a primary crusher to handle the product from a 3-yard shovel at an average rate of 350 tph. The rated capacity of the crusher must, of course, be greater than this because of inevitable quarrying and crushing delays. A crusher setting of 5 in. on the open side is desired because of following equipment and the requirements for stone.
MATERIAL: Limestone WORK INDEX 10.7 CRUSHER: 42-65 Primary gyratory Open Side Setting: 5; Eccentric Throw: 1 Recommended Operating Speed; 400 Rpm (Approximately 80% of Maximum Speed) Capacity at Recommended Speed: 438 Short Ton/Hour Maximum Horsepower Allowable at Selected Throw and Speed: 213 Horsepower. FEED SIZE: (F) 80% Passes 28 (66% of Feed Opening) F 711,000 Microns F = 842 PRODUCT SIZE: (P) 80% Passes 4, P = 108,000 Microns P = 328 F P = 514 HORSEPOWER/SHORT TON = 10.7 x 13.4 x 514/842 x 328 = .267 .267 Horsepower/Short Ton x438 Short Tons/Hour Capacity = 117Horsepower Required RECOMMENDED MOTOR SIZE: 150 Horsepower Motor.
Tabulated data presented has been compiled from tests made in the Allis-Chalmers Research Laboratory. This data is a cross section of impact and compressive strength tests made on hundreds of different rock samples for customers in the U.S. and abroad.
Ten or more representative pieces of broken stone, each of which passes a square opening three inches on a side and will not pass a two-inch square, are selected and broken individually between two 30-lb pendulum hammers. The hammers are raised by an equal amount and released simultaneously. This is repeated with successively greater angles of fall until the specimen breaks. Its impact strength is the average foot-pounds of energy represented by the breaking fall divided by the thickness in inches. The average impact strength is the average foot-pounds per inch required to break the ten or more pieces, and the maximum is the foot-pounds per inch required to break the hardest piece, the highest value obtained.
The compressive strengths of many materials have been measured in the Laboratory by cutting samples into one-inch cubes which are then broken under slow compression in a Southwark compression tester. This indicates the compressive strength in pounds per square inch.
The correlation between the compressive strengthand the impact crushing strength is inconsistent, and experiencehas shown that theimpact strength is abetter criterion of theactual resistance tocrushing. The impactdevice more nearly approaches actual crusher operation, both invelocity of impact andin the fact that broken stone is used intesting.
The average impactcrushing strength isan indication of theenergy required forcrushing, while themaximum compression values indicate the danger of crusher breakage and the type of construction necessary. Crusher capacities do not vary greatly with the impact strength. There is a capacity increase of less than 10% from the hardest to the softest stone, where packing is not a factor.
1. The investment in mainframe and supporting auxiliary equipment for gyratory crusher and civil engineering is large, but the operating cost is low, so it is suitable for the condition of long service life and long annual crushing operation time.
3. Due to the small amount of gyratory fracture, the main castings or forgings are large, and the technical requirements are high, so the processing and manufacturing cycle is long. When choosing gyratory crusher, you should consider how to control the quality of the product to ensure that there is no potential risk for the installation and operation of the equipment after delivery.
5. When selecting gyratory crusher for primary crushing, due to the large single-line production capacity, it is necessary to consider whether the shipping equipment is complete. Compared with mining projects, the shipping equipment of hydropower projects is generally relatively small, so you should make comprehensive technical and economic comparison of mining and shipping equipment.
6. The design of the hopper car receiving bin should consider the size of the dump truck and optimize the design. The effective living volume of the general bin should not be less than the load capacity of 3 cars.
Gyratory crushers were invented by Charles Brown in 1877 and developed by Gates around 1881 and were referred to as a Gates crusher . The smaller form is described as a cone crusher. The larger crushers are normally known as primary crushers as they are designed to receive run-on-mine (ROM) rocks directly from the mines. The gyratory crushers crush to reduce the size by a maximum of about one-tenth its size. Usually, metallurgical operations require greater size reduction; hence, the products from the primary crushers are conveyed to secondary or cone crushers where further reduction in size takes place. Here, the maximum reduction ratio is about 8:1. In some cases, installation of a tertiary crusher is required where the maximum reduction is about 10:1. The secondary crushers are also designed on the principle of gyratory crushing, but the construction details vary.
Similar to jaw crushers, the mechanism of size reduction in gyratory crushers is primarily by the compressive action of two pieces of steel against the rock. As the distance between the two plates decreases continuous size reduction takes place. Gyratory crushers tolerate a variety of shapes of feed particles, including slabby rock, which are not readily accepted in jaw crushers because of the shape of the feed opening.
The gyratory crusher shown in Figure 2.6 employs a crushing head, in the form of a truncated cone, mounted on a shaft, the upper end of which is held in a flexible bearing, whilst the lower end is driven eccentrically so as to describe a circle. The crushing action takes place round the whole of the cone and, since the maximum movement is at the bottom, the characteristics of the machine are similar to those of the Stag crusher. As the crusher is continuous in action, the fluctuations in the stresses are smaller than in jaw crushers and the power consumption is lower. This unit has a large capacity per unit area of grinding surface, particularly if it is used to produce a small size reduction. It does not, however, take such a large size of feed as a jaw crusher, although it gives a rather finer and more uniform product. Because the capital cost is high, the crusher is suitable only where large quantities of material are to be handled.
However, the gyratory crusher is sensitive to jamming if it is fed with a sticky or moist product loaded with fines. This inconvenience is less sensitive with a single-effect jaw crusher because mutual sliding of grinding surfaces promotes the release of a product that adheres to surfaces.
The profile of active surfaces could be curved and studied as a function of the product in a way to allow for work performed at a constant volume and, as a result, a higher reduction ratio that could reach 20. Inversely, at a given reduction ratio, effective streamlining could increase the capacity by 30%.
Maintenance of the wear components in both gyratory and cone crushers is one of the major operating costs. Wear monitoring is possible using a Faro Arm (Figure 6.10), which is a portable coordinate measurement machine. Ultrasonic profiling is also used. A more advanced system using a laser scanner tool to profile the mantle and concave produces a 3D image of the crushing chamber (Erikson, 2014). Some of the benefits of the liner profiling systems include: improved prediction of mantle and concave liner replacement; identifying asymmetric and high wear areas; measurement of open and closed side settings; and quantifying wear life with competing liner alloys.
Crushers are widely used as a primary stage to produce the particulate product finer than about 50100mm. They are classified as jaw, gyratory, and cone crushers based on compression, cutter mill based on shear, and hammer crusher based on impact.
A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake. A Fritsch jaw crusher with maximal feed size 95mm, final fineness (depends on gap setting) 0.315mm, and maximal continuous throughput 250Kg/h is shown in Fig. 2.8.
A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.
Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing hard metal scrap for different hard metal recycling processes. Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor. Crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough to pass through the openings of the grating or screen. The size of the product can be regulated by changing the spacing of the grate bars or the opening of the screen.
The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure, forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions. A design for a hammer crusher (Fig. 2.9) essentially allows a decrease of the elevated pressure of air in the crusher discharging unit . The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, the circulation of suspended matter in the gas between A and B zones is established and the high pressure of air in the discharging unit of crusher is reduced.
Crushers are widely used as a primary stage to produce the particulate product finer than about 50100 mm in size. They are classified as jaw, gyratory and cone crushers based on compression, cutter mill based on shear and hammer crusher based on impact.
A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake.
A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.
Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing of hard metal scrap for different hard metal recycling processes.
Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor and crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough pass through the openings of the grating or screen. The size of product can be regulated by changing the spacing of the grate bars or the opening of the screen.
The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around of the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions.
A design for a hammer crusher (Figure 2.6) allows essentially a decrease of the elevated pressure of air in the crusher discharging unit . The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, circulation of suspended matter in the gas between A- and B-zones is established and high pressure of air in the discharging unit of crusher is reduced.
Jaw crushers are mainly used as primary crushers to produce material that can be transported by belt conveyors to the next crushing stages. The crushing process takes place between a fixed jaw and a moving jaw. The moving jaw dies are mounted on a pitman that has a reciprocating motion. The jaw dies must be replaced regularly due to wear. Figure 8.1 shows two basic types of jaw crushers: single toggle and double toggle. In the single toggle jaw crusher, an eccentric shaft is installed on the top of the crusher. Shaft rotation causes, along with the toggle plate, a compressive action of the moving jaw. A double toggle crusher has, basically, two shafts and two toggle plates. The first shaft is a pivoting shaft on the top of the crusher, while the other is an eccentric shaft that drives both toggle plates. The moving jaw has a pure reciprocating motion toward the fixed jaw. The crushing force is doubled compared to single toggle crushers and it can crush very hard ores. The jaw crusher is reliable and robust and therefore quite popular in primary crushing plants. The capacity of jaw crushers is limited, so they are typically used for small or medium projects up to approximately 1600t/h. Vibrating screens are often placed ahead of the jaw crushers to remove undersize material, or scalp the feed, and thereby increase the capacity of the primary crushing operation.
Both cone and gyratory crushers, as shown in Figure 8.2, have an oscillating shaft. The material is crushed in a crushing cavity, between an external fixed element (bowl liner) and an internal moving element (mantle) mounted on the oscillating shaft assembly. An eccentric shaft rotated by a gear and pinion produces the oscillating movement of the main shaft. The eccentricity causes the cone head to oscillate between the open side setting (o.s.s.) and closed side setting (c.s.s.). In addition to c.s.s., eccentricity is one of the major factors that determine the capacity of gyratory and cone crushers. The fragmentation of the material results from the continuous compression that takes place between the mantle and bowl liners. An additional crushing effect occurs between the compressed particles, resulting in less wear of the liners. This is also called interparticle crushing. The gyratory crushers are equipped with a hydraulic setting adjustment system, which adjusts c.s.s. and thus affects product size distribution. Depending on cone type, the c.s.s. setting can be adjusted in two ways. The first way is by rotating the bowl against the threads so that the vertical position of the outer wear part (concave) is changed. One advantage of this adjustment type is that the liners wear more evenly. Another principle of setting adjustment is by lifting/lowering the main shaft. An advantage of this is that adjustment can be done continuously under load. To optimize operating costs and improve the product shape, as a rule of thumb, it is recommended that cones always be choke-fed, meaning that the cavity should be as full of rock material as possible. This can be easily achieved by using a stockpile or a silo to regulate the inevitable fluctuation of feed material flow. Level monitoring devices that detect the maximum and minimum levels of the material are used to start and stop the feed of material to the crusher as needed.
Primary gyratory crushers are used in the primary crushing stage. Compared to the cone type crusher, a gyratory crusher has a crushing chamber designed to accept feed material of a relatively large size in relation to the mantle diameter. The primary gyratory crusher offers high capacity thanks to its generously dimensioned circular discharge opening (which provides a much larger area than that of the jaw crusher) and the continuous operation principle (while the reciprocating motion of the jaw crusher produces a batch crushing action). The gyratory crusher has capacities starting from 1200 to above 5000t/h. To have a feed opening corresponding to that of a jaw crusher, the primary gyratory crusher must be much taller and heavier. Therefore, primary gyratories require quite a massive foundation.
The cone crusher is a modified gyratory crusher. The essential difference is that the shorter spindle of the cone crusher is not suspended, as in the gyratory, but is supported in a curved, universal bearing below the gyratory head or cone (Figure 8.2). Power is transmitted from the source to the countershaft to a V-belt or direct drive. The countershaft has a bevel pinion pressed and keyed to it and drives the gear on the eccentric assembly. The eccentric assembly has a tapered, offset bore and provides the means whereby the head and main shaft follow an eccentric path during each cycle of rotation. Cone crushers are used for intermediate and fine crushing after primary crushing. The key factor for the performance of a cone type secondary crusher is the profile of the crushing chamber or cavity. Therefore, there is normally a range of standard cavities available for each crusher, to allow selection of the appropriate cavity for the feed material in question.
Depending on the size of the debris, it may either be ready to enter the recycling process or need to be broken down to obtain a product with workable particle sizes, in which case hydraulic breakers mounted on tracked or wheeled excavators are used. In either case, manual sorting of large pieces of steel, wood, plastics and paper may be required, to minimise the degree of contamination of the final product.
The three types of crushers most commonly used for crushing CDW materials are the jaw crusher, the impact crusher and the gyratory crusher (Figure 4.4). A jaw crusher consists of two plates, with one oscillating back and forth against the other at a fixed angle (Figure 4.4(a)) and it is the most widely used in primary crushing stages (Behera etal., 2014). The jaw crusher can withstand large and hard-to-break pieces of reinforced concrete, which would probably cause the other crushing machines to break down. Therefore, the material is initially reduced in jaw crushers before going through any other crushing operation. The particle size reduction depends on the maximum and minimum size of the gap at the plates (Hansen, 2004).
An impact crusher breaks the CDW materials by striking them with a high-speed rotating impact, which imparts a shearing force on the debris (Figure 4.4(b)). Upon reaching the rotor, the debris is caught by steel teeth or hard blades attached to the rotor. These hurl the materials against the breaker plate, smashing them into smaller particle sizes. Impact crushers provide better grain-size distribution of RA for road construction purposes, and they are less sensitive to material that cannot be crushed, such as steel reinforcement.
Generally, jaw and impact crushers exhibit a large reduction factor, defined as the ratio of the particle size of the input to that of the output material. A jaw crusher crushes only a small proportion of the original aggregate particles but an impact crusher crushes mortar and aggregate particles alike and thus generates a higher amount of fine material (OMahony, 1990).
Gyratory crushers work on the same principle as cone crushers (Figure 4.4(c)). These have a gyratory motion driven by an eccentric wheel. These machines will not accept materials with a large particle size and therefore only jaw or impact crushers should be considered as primary crushers. Gyratory and cone crushers are likely to become jammed by fragments that are too large or too heavy. It is recommended that wood and steel be removed as much as possible before dumping CDW into these crushers. Gyratory and cone crushers have advantages such as relatively low energy consumption, a reasonable amount of control over the particle size of the material and production of low amounts of fine particles (Hansen, 2004).
For better control of the aggregate particle size distribution, it is recommended that the CDW should be processed in at least two crushing stages. First, the demolition methodologies used on-site should be able to reduce individual pieces of debris to a size that the primary crusher in the recycling plant can take. This size depends on the opening feed of the primary crusher, which is normally bigger for large stationary plants than for mobile plants. Therefore, the recycling of CDW materials requires careful planning and communication between all parties involved.
A large proportion of the product from the primary crusher can result in small granules with a particle size distribution that may not satisfy the requirements laid down by the customer after having gone through the other crushing stages. Therefore, it should be possible to adjust the opening feed size of the primary crusher, implying that the secondary crusher should have a relatively large capacity. This will allow maximisation of coarse RA production (e.g., the feed size of the primary crusher should be set to reduce material to the largest size that will fit the secondary crusher).
The choice of using multiple crushing stages mainly depends on the desired quality of the final product and the ratio of the amounts of coarse and fine fractions (Yanagi etal., 1998; Nagataki and Iida, 2001; Nagataki etal., 2004; Dosho etal., 1998; Gokce etal., 2011). When recycling concrete, a greater number of crushing processes produces a more spherical material with lower adhered mortar content (Pedro etal., 2015), thus providing a superior quality of material to work with (Lotfi etal., 2017). However, the use of several crushing stages has some negative consequences as well; in addition to costing more, the final product may contain a greater proportion of finer fractions, which may not always be a suitable material.
The first step of physical beneficiation is crushing and grinding the iron ore to its liberation size, the maximum size where individual particles of gangue are separated from the iron minerals. A flow sheet of a typical iron ore crushing and grinding circuit is shown in Figure 1.2.2 (based on Ref. ). This type of flow sheet is usually followed when the crude ore contains below 30% iron. The number of steps involved in crushing and grinding depends on various factors such as the hardness of the ore and the level of impurities present .
Jaw and gyratory crushers are used for initial size reduction to convert big rocks into small stones. This is generally followed by a cone crusher. A combination of rod mill and ball mills are then used if the ore must be ground below 325 mesh (45m). Instead of grinding the ore dry, slurry is used as feed for rod or ball mills, to avoid dusting. Oversize and undersize materials are separated using a screen; oversize material goes back for further grinding.
Typically, silica is the main gangue mineral that needs to be separated. Iron ore with high-silica content (more than about 2%) is not considered an acceptable feed for most DR processes. This is due to limitations not in the DR process itself, but the usual customer, an EAF steelmaking shop. EAFs are not designed to handle the large amounts of slag that result from using low-grade iron ores, which makes the BF a better choice in this situation. Besides silica, phosphorus, sulfur, and manganese are other impurities that are not desirable in the product and are removed from the crude ore, if economically and technically feasible.
Beneficiation of copper ores is done almost exclusively by selective froth flotation. Flotation entails first attaching fine copper mineral particles to bubbles rising through an orewater pulp and, second, collecting the copper minerals at the top of the pulp as a briefly stable mineralwaterair froth. Noncopper minerals do not attach to the rising bubbles; they are discarded as tailings. The selectivity of the process is controlled by chemical reagents added to the pulp. The process is continuous and it is done on a large scale103 to 105 tonnes of ore feed per day.
Beneficiation is begun with crushing and wet-grinding the ore to typically 10100m. This ensures that the copper mineral grains are for the most part liberated from the worthless minerals. This comminution is carried out with gyratory crushers and rotary grinding mills. The grinding is usually done with hard ore pieces or hard steel balls, sometimes both. The product of crushing and grinding is a waterparticle pulp, comprising 35% solids.
Flotation is done immediately after grindingin fact, some flotation reagents are added to the grinding mills to ensure good mixing and a lengthy conditioning period. The flotation is done in large (10100m3) cells whose principal functions are to provide: clouds of air bubbles to which the copper minerals of the pulp attach; a means of overflowing the resulting bubblecopper mineral froth; and a means of underflowing the unfloated material into the next cell or to the waste tailings area.
Selective attachment of the copper minerals to the rising air bubbles is obtained by coating the particles with a monolayer of collector molecules. These molecules usually have a sulfur atom at one end and a hydrophobic hydrocarbon tail at the other (e.g., potassium amyl xanthate). Other important reagents are: (i) frothers (usually long-chain alcohols) which give a strong but temporary froth; and (ii) depressants (e.g., CaO, NaCN), which prevent noncopper minerals from floating.
It is entirely possible for a crusher to choke at some other point in the crushing chamber than the theoretical choke-point. When the setting of a fine-reduction crusher is too close for its eccentric throw and for the general proportions of its crushing chamber, there is a tendency toward building up a choke in the zone immediately above the discharge opening, regardless of where the theoretical choke-point is located. The reason for this is that the excessive movement of the head (in relation to the discharge setting) mashes the material against the concave so tightly that the individual particles are shattered, or pulverized.
Such a crushing action builds up fines very rapidly, and consequently brings about a rapid reduction in the percentage of voids, even though the crushing chamber may have a progressive volume-expansion characteristic. Many materials, when mashed in the manner described, tend to cake, and to cling to the crushing surfaces; the movement becomes sluggish; more material crowds down from above, aggravating the packed condition, and, if the action progresses to the point where all voids are eliminated, a choke results.
Characteristics or condition of the material have a decided influence upon the action just described. Soft, friable rock is more apt to pack than hard, clean-breaking rock; damp material is more prone to cause trouble than dry, particularly so if the feed contains many fines (e.g., unscreened feed).
It is important to note that the products of the two classes of crusher (low-speed and high-speed) cannot becompared directly upon the basis of their respective open-side and close- side settings. Nor, can the products of any two types in the high-speed class be compared upon this basis, unless it is known that their speeds, throws, and general shape of crushing chamber are similar.
As between crushers of the high and low speed types, the low-speed machine at any given open-side setting will make a finer product than will the high-speed machine at the same closed-side setting. For example, in one installation where the machines are working on the same material, a standard type gyratory, fitted with non-choking concaves,consistently delivers a product 85% of which passes a square-opening test sieve equivalent to its open-side setting. A high-speed, gyratory, cone crusher orfine-reduction crusher in the same plant just as consistently produces material 70% of which passes a square opening test sieve, equivalent to its close-side setting. In both cases all material is reduced to a one-way dimension not exceeding these respective open and close-side settings. This is a typical case which gives a pretty fair average comparison of products from machines rated on these two different bases.
These results might, at first glance, appear to be inconsistent in view of the fact that the maximum one-way dimension is established in each case by the respective open and close side positions, whereas the product analyses do not show similar percentages passing these respective opening sizes in the test screens. The apparent inconsistency clears itself up, however, when we remember that the low-speed crusher, as well as the high-speed machine, does its sizing on the close-side of its stroke. The governing point is the distance (above the discharge point) that the material can fall (once it has been broken to a one-way dimension less than the open-side setting) before the head can catch it again. In the high-speed crusher this point is quite close to the discharge opening; in the low-speed machine it is some distance above the opening, the amount depending upon the shape of the crusher chamber, as was made clear in our discussion of the preceding diagrams.
It is hardly practicable to rate the product of a high-speed, short-throw crusher at its open-side setting. In the case just noted, all of the product of the second crusher mentioned, except for an occasional flat spall, passes a square-opening test sieve equivalent to its open-side setting; in fact, at some combinations of setting and throw, the 100% point will be below the open-side setting. It is impossible to gauge a crusher product at, or near, the 100% passing point because a few flat spalls, more or less, in the sample will throw the analysis several points one way or the other, giving results that are uncertain.
There is a very wide variation in the product delivered by different types of high-speed crushers at similar close-side settings. Short-throw crushers tend to give fairly consistent results, even on materials of divergent physical characteristics. The product of crushers with large throws, and lower eccentric speeds, will vary more widely, depending to a much greater extent upon the nature of the material. In judging the relative merits of crushers which are rated at their close-side settings, a check should be made to determine just what kind of product the crusher will deliver, with reference to any particular setting.
Gyratory crusher is a coarse crushing machine and is mainly used for coarsely crushing rocks with different hardness in ore beneficiation industry and other industrial departments. Other than gyratory crusher, jaw crusher is also a coarse crushing machine. In order to correctly choose and reasonably use the coarse crushing equipment, it is necessary to know the advantages and disadvantages of gyratory crusher over jaw crusher. This paper mainly deals with those advantages and disadvantages of gyratory crusher.
(1) Big depth of the crushing chamber, continuous work, high production capacity and low unit electricity consumption. Compared with the jaw crusher, the gyratory crusher has the same ore feeding width, but the production capacity of the gyratory crusher is much higher and the electricity consumption per ton of rocks is 0.5~1.2 times lower.
(2) Stable working condition, light vibration and small basic weight. Generally speaking, the basic weight of the gyratory crusher is 2~3 times of the mechanical equipment, but the basic weight of the jaw crusher is 5~10 times of the machine itself.
(3) Full chamber feeding. Large-sized gyratory crusher is able to be directly fed with crude rocks without being equipped with ore cabin and feeding machine. However, jaw crusher cannot do this and it requires rock feeding in an even manner, for this reason, ore cabin and feeding machine are needed. When the size of the rocks is larger than 400mm, heavy rock feeding machine with high price is needed.
Anyway, when choosing coarse crushing equipment, the customers should comprehensively consider all of these factors including the performance of the crusher, property of the rocks, granularity requirement of the final products, size of the manufacturing plant and the configuration conditions of the equipment so as to choose the most suitable crusher.
The present sand making technologies mainly include two types: tertiary crushing and rod mill combination sand making technology and vertical shaft impact crusher sand making technology. These two sand making methods have both advantages and disadvantages. Given this, the researchers propose the argument that users only use vertical shaft impact crusher to grind the hard rocks into sand, and through the optimization and adjustment of traditional sand making technology reasonable selection of vertical shaft crushing equipment, finally reach the goal of producing qualified sand.
Detail descriptions of designs are given of large gyratory crushers that are used as primary crushers to reduce the size of large run-of-mine ore pieces to acceptable sizes. Descriptions of secondary and tertiary cone crushers that usually follow gyratory crushers are also given in detail. The practical method of operation of each type of gyratory crusher is indicated and the various methods of computing operating variables such as speed of gyration, capacities and power consumption given are prescribed by different authors. The methods of calculations are illustrated to obtain optimum operating conditions of different variables of each type using practical examples.
Generally crushing is the first mechanical step in the comminution process of a mining operation. The purpose of crushing is to break the largest lumps from the run of mine material into smaller pieces, which can be handled in the later process, i.e. belt conveying and grinding.
For mining operations the two main types of crushers, are jaw and cone or gyratory crushers. Gyratory crushers have in general higher capacity than jaw crushers and are predominantly used in open pit mining operations. In principal a gyratory crusher consists of a spindle carrying a conical grinding head, seated in an eccentric sleeve, Figure 1 The head sweeps a conical path within the crushing chamber and crushes the feed material on a full circle.
Gyratory crushers can crush up to 5000 tonnes per hour with a top size of about 1.5 m with a closed side set, CSS, of 200 mm. According to Napier-Munn et al. (1996), the most important machine dimensions are:
The crushing of the material is not affecting the shape of the grain size distribution curve that much, in fact mainly the coarsest material is being crushed, the finer material is originated by blasting, Simkus et al. (1998). By choke feeding gyratory crushers more fines material can be produced, by inter particle breakage,Napier-Munn (1996).
The blasting affects the crushing performance in several ways, besides that the rock mass is liberated which it is weakened by increasing the amount of cracks/micro- cracks, Nielsen and Kristiansen (1996) and Eloranta (2001). A concept of a crusher model that gives the product size after the crusher is described by Valery et al. (2001).
In this model each breakage stage is assumed to produce the same relative size reduction, by using the T10 parameter determined by JKMRC drop weight tester. The closed side setting, CSS, and the open side setting, OSS, control the classification part of the model. If the rock is larger than the OSS it will be broken and conversely, if it is smaller than the CSS it will fall through without any breakage. For rocks with the size between CSS and OSS a probability that the rock will remain in the chamber or pass through exists. The classification model is described by three parameters K1, K2 and K3 where K1 and K2 ideally should be equal to CSS and OSS, K3 describes the shape of the curve between K1 and K2, Figure 3.
Evertssons crusher model, Evertsson (2000a) and Evertsson (2000b), aims to predict the performance of cone crushers and is developed in four steps, modelling of the process of size reduction, characterisation of the behaviour of rock material during fragmentation, modelling of the material flow through the crusher chamber and the interaction between material flow and size reduction.
The fragmentation of the material is modelled as several repeated crusher steps, and each step describes by a selection function and a breakage function, similar to the JKmodel. The selection function gives the probability that a single particle will be broken, when several particles are compressed. The selection is assumed to be dependent on the degree of compression and the span of the size distribution.
The breakage function describes how a single particle of rock breaks into smaller pieces. For a given particle, the breakage function is assumed to be dependent only on the degree of compression for a specific rock type. The size reduction increases with increasing compression.
Different properties for rock materials determine the breakage and selection function. The material is characterised, i.e. values for the selection and breakage function, in laboratory testing by compression crushing tests. Since the crusher process is modelled as several repeated crushing steps, the model predicts where and how the rock material is compressed. The model is based on Newtons law of motion and the flow through the crusher is described by the mechanisms sliding, free fall and squeezing.
Through several simulations it is evident that free fall is the most important mechanism for the flow of material. In addition to breakage behaviour and size distribution of the feed, the crusher model considers the layout of the machine, crusher chamber geometry and how the crusher is operated, opening gap, stroke and eccentric speed.
The determining factors for the fragmentation process in a cone crusher has been identified to fracture mechanism, number of crushing zones and degree of compression. The fracture mechanisms are single and/or inter particle breakage. Single particle breakage has an unfavourable effect on the shape of the particles and inter particle breakage has a favourable effect. The fracture mechanism is determined by bed thickness and stroke.
The number of crushing zones is equal to the numbers of times that the rock material will be treated, and are mainly determined by the eccentric speed. The degree of compression in each crushing zone comes from stroke, opening gap, layout of the crusher chamber, the dynamics of the crusher and how much material that is in the inlet of the crusher.