As theCrusher Concave Liners and Mantle Wearout there is a period when the crusher wont be as efficient as it could be. This can be a very frustrating period for the operators. Since the throughput drops and operators have to work harder, usually doing the same thing over and over again. Unfortunately to get the most from the equipment requires that there is one hundred percent wear on the parts before they are replaced.
A perfect example of this is the wear on the concave liners and the mantle. The angle between the concave liners and the mantle is at its best operating position when they are new. As time and tonnage go by, both wear. Soon the pattern that the ore takes through the crusher begins to change. This is due to wear causing a LIP to be formed at the bottom of the mantle. When the formation of this lip passes a critical point the force of the crushing action begins to be directed upwards restricting the normal flow of ore downwards. The lip that has been formed is also preventing the fines from dropping through quickly enough to create the needed space for the new ore in the gyratory crushing chamber.
Normal wear and tear on the equipment will cause many problems for the operator. Leaking oil lines, loose drive belts, worn air clutches slipping, leaking air valves, these things all add up to more work and slower production. It is this type of problem that justifies the necessity of the operators circuit check. A sharp eyed, curious operator will spot many of these problems before they become serious enough to hamper production and cause the crew extra work.
Any of you that are at all familiar with the Gyratory crushersand Cone Crushers that the former are used as Primary crushers will probably note many similarities between the types.Each use a cone shaped crushing surface, and the same principal in the eccentric is employed to develop the crushing action required.
The difference between the two is first the speed that the mantle travels while crushing the ore. A primary revolves at 100-200 R.P.M. While the Secondary and the Tertiary crushers travels between 500-600 R.P.M. This difference in the speed results in a HAMMERING type crushing action over the SQUEEZING type employed by the primary.
The other most noticeable change is the crushing action of the mantle. In the Gyratory all the movement is in the bottom of the crusher mantle. This is due to the angle that the main shaft is on. The greater angle of the cone crusher puts the pivot point below the distributor plate. While the pivot point for the gyratory crusher is at the spider cap. This difference in the pattern of gyration has a purpose.
The primary crusher produces a product that is gauged by the size of the open side of the mantle. This is because the slow speed of the gyration allows a high percentage of material to fall through the larger opening without being crushed by the smaller opening. With the cone crusher however the gyration has a greater arc and an equally greater speed. If we look at a profile of the crushing surface we will see an area of the two surfaces that are parallel to one another.
This area is called the PARALLEL ZONE. Because of the speed, the primary crusher produces a product that is gauged by the size of the open side of the mantle. This is because the slow speed of the gyration allows a high percentage of material to fall through the larger opening without being crushed by the smaller opening. With the cone crusher however the gyration has a greater arc and an equally greater speed. If we look at a profile of the crushing surface we will see an area of the two surfaces that are parallel to one another that the mantle is travelling at, it is very hard for the ore to pass through this zone without being hit at least once by the crusher.
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.