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1. Circular Vibrating Screenis widely applied in coal dressing, ore dressing, building material, electricity and chemical industries. It is doing circular movement while at work, and it is of a highly-effective, newly-developed and multilayer machine. With the introduction of eccentric shaft vibration exciter and particular block, the amplitude can be adjustable. Meanwhile, such screen has features of reliable structure, strong excited force, perfect separating efficiency, low noise, long life span, large handling capacity, and durable usage.
Large vibrating screens represent a unique challenge for Manufacturers, Plant Designers, and Plant Operators. The inherent mode of operation for vibrating screens is self-destructive. More often than Manufacturers admit, Designers plan for, or Operators staff for, a vibrating screen succeeds and self-destructs. This is a problem. It can magnify with larger vibrating screens.
Vibrating screen structures are subjected to nearly 250 million fatigue cycles in an operating year. The design and construction of these structures are critical in achieving reliable screen performance. Regardless of screen size, the maxims for design continue to be:
A screen design meeting these criteria yields the lowest cost per ton performance. Large screen technology is evolving more scientifically than did the development of small screen technology. As vibrating screen designs increase beyond six foot widths, reliable designs result from sophisticated engineering methods and manufacturing techniques. In addition, large screen technology amplifies the direct relationship of production cost and reliability.
Static Stresses: At rest, motionless, a vibrating screen structure is subjected to the force of gravity, at a minimum. A vibrating screen must first support its own weight. Other motionless stresses are present in the structure as a result of cutting, bending, welding, burning, drilling, assembly, tolerancing, and manufacturing variances. Quite simply, these stresses exist whether or not the screen is operating.
The second step in FEA can be considered the construction of structural loads. These include the imposition of static, dynamic, material, and fatigue conditions on the mathematical model, which approximates the load conditions. An example would be to describe a structural misalignment and the forces input co bolt up this structure through the misalignment.
Reliable vibrating screen designs are dependent upon the proper marriage of a firms manufacturing capabilities and the requirements of the design. It is not reasonable to expect that closely toleranced airframes will be successfully produced in a metal-bending job shop. As design safety factors narrow on larger screens, manufacturing techniques evolve which minimize production variables. Design tolerancing is necessarily compatible with manufacturing accuracy.
Residual metal working stress is the left-over stress in metal when melted or formed into a shape. It is a result of a materials resistance to change shape. Stress concentration sites are more commonly termed notches or stress risers. These areas are not stresses, but sharp geometric transitions or reversals in a structure. Stress loads focus their effect on a structure at these sites. Experience has proven that the methods and procedures of structural assembly can result in preloading screen bodies with excessive static stresses. The scope of this discussion is limited to the discussion of welding, forming, and bolting as they relate to conditions described above.
The side plate of a vibrating screen literally bristles with fasteners. Multi-shift production facilities, as well as maintenance crews, quickly realize the merits of this system. Unlike conventional threaded fasteners, swaged bolts exhibit a distinctly different physical appearance when installed versus loosely installed. The guess-work and wasted efforts to repeatedly insure all bolts are properly torqued are eliminated. A second-shift assembler need not consult with his first-shift counter-part regarding loose or torqued bolts . Sound maintenance practice precludes the reuse of major structural fasteners. A huck-type fastener is destroyed during removal. Normal threaded fasteners depend on proper installation torques to achieve the optimum clamping force. Registered torque wrench values may not be indicative of the true values due to the effects of thread lubrication and frictional force of the fastener face on the bolting surface. Swaged fasteners are installed strictly in tension at an optimum preset tensile load. The positive clamping values are reliably consistent. Installation error is minimal. Replaceable, non-structural components may be installed with conventional fasteners.
Anticipated operating and maintenance costs over the productive life of a processing plant design significantly influence the go or no-go decision to build the plant. Large vibrating screens can both add to and reduce the magnitude of these costs. Plant designers must examine the serviceability of these large units. This includes the complexity of installation, start-up, routine maintenance, major repairs, and operating instrumentation. In assessing these costs, the likely condition exists somewhere between the extreme of a screen leaping momentarily out of position long enough to repair itself and swarms of mechanics covering the unit like bees on honey over several production-robbing shifts.
As larger vibrating screens are used, their size will exceed cost-effective shipping limits fully assembled. Screen manufacturers will join the ranks of other major equipment suppliers in on-site assembly and testing of these units. The incremental costs associated with these efforts must be considered in evaluating the plant construction and start-up costs.
The use of larger vibrating screens results in the dependence of a larger percentage of total plant production on each unit. It is imperative that plant operators maximize the production availability of large screens. This effort is enhanced by carefully planned operating and maintenance procedures. Since volumes have been published on efficient and successful preventative maintenance programs, this discussion will not deal with that topic. There are several suggestions that can be made to help potential big screen users better position themselves to react to the service requirements of these units.
As trite as it sounds, talk to potential screen suppliers specifically about the service requirements of their screens. Determine how recently a manufacturer has entered the wide screen market. Was this entry preceded by years of research and testing? There are generally two major shortfalls in a hastily planned new product introduction. Invariably, replacement parts availability is a problem. Second is the frustrating response to a frantic maintenance question, The only guy who knows that unit is on an island in Indonesia. Solidly planned programs will have organizational depth.
The labor pains, which have normally accompanied the birth of new vibrating screen designs, have been no less severe with the gradual introduction of large, high-capacity screens. More difficulty would have been encountered without the aid of advanced engineering and manufacturing techniques.
The development of vibrating screens over the last century has seen many variations to suit the exacting requirements of industry. Indeed, as each year passes, industry has presented the challenge to screen manufacturers of supplying larger machines than those used in the past and the question is often posed what is the maximum limit?
Innovations introduced such as bouncing ball decks, heated decks, tri-sloped and bi-sloped decks and pool washing features have all sought to achieve improved anti-blinding results and improved capacity for a given screening efficiency. Although the benefits achieved by the inclusion of these features were shown in some cases to be beneficial, the application of good throw in conjunction with the required G force in the operation of the screen has proven in screen performance today, to provide maximum screening efficiency and capacity. The importance of good throw is often overlooked and should be the first consideration when wishing to maximize screen capacity.
For a straight line motion screen the throw is the distance between the extremities of motion. For a circular motion screen, the throw is measured across the diameter of motion but if the screen has an oval motion, throw is measured by taking the mean of the major and minor axes.
The throw which is specified for a particular application is determined on a screen body eccentric weight basis and normally does not take into allowance the load of material which will be handled by the vibrating screen.
Therefore it is imperative that the live weight of the vibrating screen is sufficient to maintain, within reason, the throw which has been originally specified so as to effectively handle the loads being fed to the screen.
The above comments relate essentially to a dry screening application but in wet applications where metalliferous pulp is received on the screen, the benefits of a large throw in terms of increased screen capacity have been demonstrated in commercial practice. The ideal machine for receiving pulp for wet screening or desliming, dewatering etc. is a horizontal screen. Among other reasons, the horizontal screen provides the benefit of long retention time for handling the pulp. Also the straight line motion provided with good throw imparts a positive breaking of surface tension present between the pulp and the screen deck within the apertures.
The inclusion of large vibrating screens in the design of new plants by planning engineers and metallurgists responsible for such work, particularly where large associated equipment is available, is inevitable and is in fact a progression of size we have witnessed over the years.
We should remind ourselves that size progression could not proceed without the accumulation of experience in screen body design, in application knowledge, improved quality of manufacture and refinements of mechanism design with regard to achieving improved bearing life which allows the use of a good G force.
As referenced previously G force and throw are interrelated and therefore with the good G forces available today in the modern vibrating screens, the way is clear to taking full opportunity of increasing throw to handle the high tonnages which can be expected and are currently experienced on large vibrating screens.
Where abrasion of the screen deck surface is severe as in most metalliferous mining applications, and the separation sizes are in the order of mm to 50 mm aperture sizes, polyurethane screen panels are now in common use because of their excellent resistance to wear. The trend in the use of polyurethane panels in the metalliferous mining industry is quite definite and in fact in the major mining operations in Australia at least, the use of polyurethane screening panels is firmly established.
With reference to metalliferous tailings the need for dewatering presents a new dimension. The amount of tailings produced is very much greater since some 98-99% of mined ore is rejected in tailings form compared with varying amount of 3 to 5% rejected in a coal washing operation. Furthermore with dewatering of metalliferous tailings, using equipment as mostly used in coal washing would present maintenance problems because of the more abrasive nature of the tailings and therefore for that reason it is customary to discharge all metalliferous tailings slurry to a dam.
The screen-cyclone system relies on the blinding tendency of the screen deck apertures for its success, using either stainless steel wedgewire or polyurethane deck panels in conjunction with the use of cross dams spaced every 120 cm along the deck surface. When considering the screen-cyclone system it is important to appreciate that the screen function is not one of separation at a given aperture size but bleeding of water through the restricted deck apertures caused by the semi blinding condition. That is, if the deck apertures were to remain completely free of blinding, which is not the case, practically all of the tailings would pass through the apertures in the first pass and would not allow the system to function.
The underflow from the primary cyclones should be deposited on the horizontal section of the screen deck at the feed end where the maximum of water should be removed with the assistance of an additional section of wedgewire located on a 45 inclined back plate to remove free water that has accumulated on top of the bed of slurry most solids having stratified to the deck surface. The underflow should be evenly distributed across the width of the screen at minimum velocity, so as to allow the full benefit of stratification provided by the screen.
The actual results from the initial test run taken on the pilot plant installed at Philex Mining Corporation, Philippines in March, 1980 are as follows using a gravitated flow of tailing slurry from the concentrator.
The problems involved in installing, maintaining, and operating large vibrating screens have been summarized and discussed, based on a survey of current use of such screens in selected North American mineral processing applications. Practical, effective solutions for the more serious common problems are described, along with some recommendations on design practice for specifying, selecting, and installing large screens.
In order to properly assess the information gathered through the survey questionnaire, the results pertaining to each group of applications will be presented and discussed separately in the following section. The small number of installations actually surveyed makes any rigorous statistical interpretation of the data difficult, therefore the information is presented in a generalized fashion. Notwithstanding the small sample of operations as compared to the total number of such large screen installations around the world, the results are felt to fairly represent typical operating, maintenance and installation problems and practices in the sectors of the mineral processing industry the survey covered.
The results reported in this section refer to inclined vibrating screens used in conventional crushing and screening plants. Four operations replied to the survey questionnaire, all four are medium sized producers, primarily of copper concentrate, some with significant by-product production of Mo or Ag. Daily throughputs range from 5,300 tons to 38,000 tons.
The major problem areas reported by the users of these screens were bearing failure and replacement and side plate cracking. The minor problems reported were loose bolts, seals and routine wear items such as cloth and liner changes. Reported availability of the screens ranged from 92-96%. At one operation, the crushing and screening plant is oversized and operates only one shift per day, therefore downtime for maintenance is readily available and actual availability was not reported.
The maintenance of large vibrating screens in conventional crushing applications would normally consist of the regular replacement of wear parts, such as liners and screen cloths, as well as regular lubrication of the bearings and other moving parts as recommended by the manufacturer of the particular screens in use.
The operations with large horizontal vibrating screen installations replying to the survey questionnaire were Syncrude Canada Ltd., Climax Molybdenun (Henderson Operations), Quintana Minerals and Fording Coal Ltd. As previously noted, the screen applications at these operations are all basically very similar, involving wet screening of relatively large tonnages of slurry feed.
The major problem areas with these screen installations once again include bearing failure and side plate cracking in three out of the four installations. The fourth installation, Henderson, reported major problems with the mounting springs and feed lip both of which have presently been rectified to the point where only minimal unscheduled downtime occurs.
The major problems associated with the horizontal screens were with bearings and side plate cracking, and were evident soon after commissioning. Major efforts were undertaken at all the operations to correct the serious problems.
Large vibrating screens are normally selected for applications where multiple screens would be more costly to purchase and install. There have been a considerable number of large screen installations in a variety of mineral processing applications, therefore a considerable amount of operating data with respect to the screen components and performance has been gathered. From the plant designers viewpoint the design of a screen installation should consider the following areas:
The design of a large vibrating screen installation requires close attention to not only the screen itself, but also to the ancillary structures, maintenance procedures and personnel comfort and protection.
Large vibrating screens represent a considerable investment in equipment alone. In addition the loss due to interrupted production should one of these units go out of service can be economically much more severe. As plant tonnages have risen and larger equipment has been utilized in single trains or a small number of multiple trains, the risk of having a single large screen down for any length of time has become too great to ignore.
This y series vibrating screen is vibrated by the circling motion. It is high efficient screen for filter materials into multiple grade according to the gravel size. For the compact structure and the convenience installation, it is the ideal screening device for prefilter of the feed materials before the primary crushing in the quarry site, it also can be used as separation and filtration solely. The vibrating screen adopts cylinder type eccentric shaft vibrator and partial block to adjust the amplitude. The materiel sieve drip line is long and more sieving specifications. The circular vibrating screen can also used for production classify in quarry, mine, construction, electricity, chemical industry, etc. Working principle The vibrating screen uses the motor to drive the eccentric shaft to make the screen body periodically along with the direction of vibration force. The materials make circular movement on the screen to realize sieving. Technical 1.Cylinder-type eccentric shaft and eccentric block to make strong vibrating force. 2.Long material screening line, various sieving specifications. 3.Simple structure, reliable operation, low noise, low power consumption. 4.High screening efficiency, large capacity, less block. 5.Sealed structure available to protect the dust pollution. 6.Adjustable amplitude by changing the weight of the eccentric block. Other introduction http://www.lzzgchina.com/ http://www.crusherlz.com/ http://www.crushersb.com/ http://www.lzzgchina.ru/ http://www.lzzgchina.es/ http://www.sandmakingmachinelz.com/
This Y series vibrating screen is vibrated by the circling motion. It is high efficient screen for filter materials into multiple grade according to the gravel size. For the compact structure and the convenience installation, it is the ideal screening device for prefilter of the feed materials before the primary crushing in the quarry site, it also can be used as separation and filtration solely. The vibrating screen adopts cylinder type eccentric shaft vibrator and partial block to adjust the amplitude. The materiel sieve drip line is long and more sieving specifications. Features 1.Cylinder-type eccentric shaft and eccentric block to make strong vibrating force. 2.Long material screening line, various sieving specifications. 3.Simple structure, reliable operation, low noise, low power consumption. 4.High screening efficiency, large capacity, less block. 5.Sealed structure available to protect the dust pollution. 6.Adjustable amplitude by changing the weight of the eccentric block.
Vibrating screen Vibrating screen manufacturer Industrial Beneficiation Equipment factory Vibrating Feeder is a kind of linear direction feeding equipment. It features smooth vibrating, reliable operation, long service life and being suitable for feeding. They are widely used in mining, building-material, silicate and chemical industry in the crushing and screening plants. In the Sand-Stone production line, it can send materials to crusher evenly and continuously and at the same time, it can screen materials roughly. It can be used in these areas such as metallurgical industry, coal mining industry, mining-selecting, building, chemical and grinding industry, etc. Features and Benefits of Vibrating screen for mining 1. Stable and long span life. 2. easy to adjust. 3. Reliable operation. 4. Easy maintenance. 5. No pollution. Operating principle of vibrating feeder: Vibrating feeder consists of vibrating frame, spring, vibrator, motor vibrating device and motor. The vibrator is made of two fixed eccentric shafts whose gears are jogged. When installation, the two gears must be jogged according to the sign. Through drive of the motor, the two eccentric shafts start rotating to produce a linear huge power which forces the feeder to vibrate. Through the vibration, the materials will slip and sling on the funnel, moving forward, when the materials pass the screening part, smaller parts will fall down, avoid the further crushing, so screening purpose can be reached. Applications? [Equipment configuration]:?jaw crusher, vibrating screen, vibrating feeder, cone crusher, sand making machine DBM construction sand making equipment widely applied in mining, road building, bridge building and so on. Please click here for more product information.
Introduction The main function is to provide accurate separation of materials without product deterioration, thereby resulting greater product yields at higher production rates. This screening equipment consists of Supporting rack, screen frame, the cleaning ball, side plate, screen box, deck, screen assembly, etc. The unique gyratory motion of the near horizontal screen surface and the available screen mesh cleaning system secure the M&Y gyratory vibrating screen quality as a high capacity product that efficiently developed for materials screening purposes. Functional principle M&Y gyratory vibrating screen puts the distribution of material device and screening plant together as it passes along the screen surface. It begins with a horizontal circular motion at the feed end, gradually changes to changes to elliptical motion at the center, and finally to a straight-line motion at the discharge end, keeping the material in constant contact with the screen surface without deterioration. Advantages No vertical vibration, longer life span of screen deck. All components are easily accessible and removable for ease of teardown and cleaning. Due to adopting the principle of plane rotary, thus improving the effective utilization rate of screen surface and eventually improving the screening efficiency.
Introduction Linear vibrating sifter is used to separate materials into various particle sizes for further processing.Basically, professional large capacity mining linear vibrating screen manufacture consists of the screen box, supporting device, driving unit,vibration isolation and etc. It has two operational driving modes: dual-vibration mode (light duty) and dual-vibration exciter mode(heavy duty). Working Principle The vibrating source is also from vibrating motor. There are two motors to be fixed on the both side of screening box(or under the screening box) to corotate on the contrary direction. In the process of rotating, when two motors synchronous reversely rotate, the eccentric blocks of motor will emerge a kind of centrifugal force, which can be transmitted to the screening box and make the machine run by linear direction. Then the material on the mesh will be vibrated forward and screened. There is an angle of inclination two motor axis's relative to screen deck, under the influence of resultant force of exciter force and materials self weight, materials are threw up to make saltatory and linear movement forward on the screen deck in order to screen and grade the materials. By choosing the suitable mesh, the screening target is realized. Features High productivity Tightness, very little dust spilling, also can be enclosed or can be connected with duct collector. Low energy consumption, low noise and long service life. Screening of high precision, large capacity, simple structure. Fully enclosed structure, automatic layout, Easy maintenance It can be used for assembly line production automation. Sieve body parts are used rolled welded steel plate and profiles (part of the group as a bolt connection between the body) the overall stiffness is good, solid and reliable. Application The linear vibrating screen can be applied to the screening and grading of powder and granular materials. It is widely used in plastics, building materials, metallurgy, rubber, ceramic, food, pharmaceutical, chemical, carbon, abrasives, fertilizer, glass,ceramics and other industries.
Introduction This machine is composed of screen box, vibrating motor, damping system and bottom rack. Screen box is consisted of deck base, screen plate, scale-board etc. It adopts high function and long life YZO series vibrating motor or exciter as exciting source to adjust the size of exciter force, in order to change swing of sifter machine. The damping system is made up of rubber spring, hoop and supporting base. The bottom rack is consisted of hopper and chasis rack, installation method of exciter source is divided into upper vibrating or under vibrating, installation method of vibration reducer is divided into base or suspention. We also can design and manufacture according to users requirement. Working Principle Screen self-synchronous reversed rotation depends on two sets of same vibrating motors or general motors along with exciter, and makes the whole screen machine supported on vibration reducer moves on a linear trajectory quickly go ahead and loose to complete screening operation after materials fall into screen from inlet. XBZS series cantilever bar vibratingsifter is driven to rotate synchronously in opposite directions by two same vibration motors or electric motors with exciters, which makes the screen body move on periodical and to-and-fro linear trajectory to achieve screening classification. Features The deck of bar screen should be inclined installed, the angle is during 20 degree to 35 degree. When comparing with other same type has following difference: 1.small volume , big inclined angle and screening capacity. 2.light weight, easy installation. 3.low price and energy consume. 4.simple construction and beautiful shape. 5.the efficiency of the screen mesh is more over 20% than the general screen mesh. 6.self-cleaning. 7.specially using for secondary screening under the high furnace groove. 8.Largeinclinationinstallationofscreensurface(20-35),small volume, large capacity. 9.Lightweightforeasyinstallation;lowpowerconsumptionforenergy-saving. 10.Lowcostandlittlespareparts;simplestructure andattractiveappearance. 11.Self-cleaningfunction,speciallyforsecondaryscreeningbelowblast furnacebin. Application XBZS series bar screen is a new type screen equipment , Suitable for the classification of big materials, medium and small granular materials.it is widely used in mining, coal, energy power, metallurgy, building materials, fire-resistant, etc.
Round vibrating screen machine is one kind of high effective sieving equipment, which has been widely used in domestic & foreign market. It adapts the principle of vibration to realize the sieving of plenty of raw materials. It is wide used for metallurgy industry, chemical industry pharmaceutical industry, grain industry and so on.
1. Dewatering vibrating screen with flange-type exciter, driven by two motors for reverse self-synchronous rotation, so that the screen in a straight line to do reciprocating motion in order to achieve the purpose of grading dewatering. 2. Screen frame with high-strength bolted connection, the screen surface by the arc section and the straight-line section composition, durable structure. 3. According to the mechanical structure and process parameters, the vibrator is arranged above the center of gravity of the screen box. This arrangement makes the trajectory of the screen machine elliptical at the feeding end, round in the middle, discharge side is still elliptical, that is elliptical-circular-elliptical. Applications: 1. Dewatering vibrating screen is mainly used for fine grained dewatering and grading, slime or tailings recovery 2. Suitable for mineral processing, coal processing and other industries. 3. Widely used in dewatering of fine materials such as municipal sewage treatment, pulp, chemical industry ,food industry and so on.
The screens serve to classify the different particles by size, starting from a bulk product in a continuous process. The inlet material (the raw product) advances from the part where the screen is fed to the opposite end in which the particles come out separately according to their size, shape or density. There are also vibrating screens that are loaded by the center and the product moves radially to the outputs that are on the periphery.
For the correct advancement of the product it is necessary that the process is continuous, and it is due to the vibration if the screening surface is horizontal. Most of the screens have a certain inclination in such a way that the advance movement of the product is due to a combination between gravity and vibration.
The screening elements are flat or slightly curved surfaces having perforations of a certain size such that when a product is poured in bulk on the element it only passes those particles whose size is smaller than the size of the perforations.
The screening elements can be a metallic or nylon wire mesh, bars that pass material between them, metal sheet with circular, square or hexagonal perforations, more or less rigid sheets of rubber or polyurethane with perforations.
A screen can have several screening elements on top of each other forming different floors. In this case, the floor with the larger perforations is placed in the upper part and successively in lower floors the elements with smaller and smaller perforations are mounted. In this way each particle is trapped between the floor that has cut points (openings) greater than the particle and the floor that has smaller cut points.
Traditionally there have been non-vibrating screens consisting of a fixed mesh with a lot of inclination. When introducing the vibration, the product shakes and the particles jump without sliding on the screening surface. Each jump is an attempt of the particle to pass through a hole and the probability of this happening is much greater if the machine vibrates. In other words, the effectiveness is much greater.
When a particle jumps and falls again it can do so in a hole or an area where there is no hole. If the screening element is a wire mesh, the particle can fall on the wire or on another particle and not squeeze through the hole it should. This is why no screen has an efficiency of 100% because it would require an infinite number of jumps so that all the smaller particles that the holes actually leak.
The more quantity of product you intend to classify, the more surface you need for screening. The most immediate symptom that a screen has become too small is that it decreases its effectiveness because it simply does not fit so many particles through the holes.
As a general rule for large classifications, low frequencies and large vibration amplitudes are preferable and for fine classifications high frequencies and small amplitudes. In other words, if the particle is large, a slow and wide movement is better in which the particle gives few jumps but large and if it is small it is better than many jumps but smaller. It is a question of the particle not passing several single jump holes.
In the screens, as in any sorting machine, it is necessary to take advantage of the entire width of the work surface from the beginning of it. If the product falls piled on the screening surface, the particles of the top of the pile will not touch the mesh or the screening element until the pile disappears by the vibration. By the time this happens, it will already have traveled half way of the surface. In other words, we waste surface with a very important loss of production and also the area where the pile is made will receive severe wear with the consequent extra maintenance expenses. It also increases, especially with products of low density, the risk of jams if the pile takes a lot of height. This makes no sense and it is not acceptable for correct screening.
A good vibrating screen must be reliable, minimize wear and maintenance and have a strong vibration as any vibrating machine that boasts: the more it vibrates the better it goes, that is, it gives more production and efficiency.
On the other hand, most of the bad screens are not really bad but inappropriate to use: If the product is wet and sticky, it will stick to a metal screening element rather than a polyurethane screening element. If it is dry and fine, the screen should be dust-tight. If it is a matter of screening large and heavy particles, the screen should be very robust. If it is very robust and used with fine products, it will consume more than necessary in electricity and maintenance costs (but that shouldnt pose as a problem because business energy suppliers can be compared at Utility Saving Expert).
The combinations are endless, and a good selection, suitable for use at first, will make the user does not have to remember this machine again in life, or at least until he needs to install another screen.