vibrating screen working principle
When the smaller rock has to be classified a vibrating screen will be used.The simplest Vibrating Screen Working Principle can be explained using the single deck screen and put it onto an inclined frame. The frame is mounted on springs. The vibration is generated from an unbalanced flywheel. A very erratic motion is developed when this wheel is rotated. You will find these simple screens in smaller operations and rock quarries where sizing isnt as critical. As the performance of this type of screen isnt good enough to meet the requirements of most mining operations two variations of this screen have been developed.
In the majority of cases, the types of screen decks that you will be operating will be either the horizontal screen or the inclined vibrating screen. The names of these screens do not reflect the angle that the screens are on, they reflect the direction of the motion that is creating the vibration.
An eccentric shaft is used in the inclined vibrating screen. There is an advantage of using this method of vibration generation over the unbalanced flywheel method first mentioned. The vibration of an unbalanced flywheel is very violent. This causes mechanical failure and structural damage to occur. The four-bearing system greatly reduces this problem. Why these screens are vibrated is to ensure that the ore comes into contact will the screen. By vibrating the screen the rock will be bounced around on top of it. This means, that by the time that the rock has traveled the length of the screen, it will have had the opportunity of hitting the screen mesh at just the right angle to be able to penetrate through it. If the rock is small enough it will be removed from the circuit. The large rock will, of course, be taken to the next stage in the process.
Depending upon the tonnage and the size of the feed, there may be two sets of screens for each machine.
The reason for using two decks is to increase the surface area that the ore has to come into contact with. The top deck will have bigger holes in the grid of the screen. The size of the ore that it will be removed will be larger than that on the bottom. Only the small rock that is able to pass through the bottom screen will be removed from the circuit. In most cases the large rock that was on top of each screen will be mixed back together again.
The main cause of mechanical failure in screen decks is vibration. Even the frame, body, and bearings are affected by this. The larger the screen the bigger the effect. The vibration will crystallize the molecular structure of the metal causing what is known as METAL FATIGUE to develop. The first sign that an operator has indicated that the fatigue in the body of the screen deck is almost at a critical stage in its development are the hairline cracks that will appear around the vibrations point of origin. The bearings on the bigger screens have to be watched closer than most as they tend to fail suddenly. This is due to the vibration as well.
In plant design, it is usual to install a screen ahead of the secondary crusher to bypass any ore which has already been crushed small enough, and so to relieve it of unnecessary work. Very close screening is not required and some sort of moving bar or ring grizzly can well be used, but the modern method is to employ for the purpose a heavy-duty vibrating screen of the Hummer type which has no external moving parts to wear out ; the vibrator is totally enclosed and the only part subjected to wear is the surface of the screen.
The Hummer Screen, illustrated in Fig. 6, is the machine usually employed for the work, being designed for heavy and rough duty. It consists of a fixed frame, set on the slope, across which is tightly stretched a woven-wire screen composed of large diameter wires, or rods, of a special, hard-wearing alloy. A metal strip, bent over to the required angle, is fitted along the length of each side of the screen so that it can be secured to the frame at the correct tension by means of spring-loaded hook bolts. A vibrating mechanism attached to the middle of the screen imparts rapid vibrations of small amplitude to its surface, making the ore, which enters at the top, pass down it in an even mobile stream. The spring-loaded bolts, which can be seen in section in Fig. 7, movewith a hinge action, allowing unrestricted movement of the entire screening surface without transmitting the vibrations to the frame.
One, two, or three vibrators, depending on the length of the screen, are mounted across the frame and are connected through their armatures with a steel strip securely fixed down the middle of the screen. The powerful Type 50 Vibrator, used for heavy work, is shown in Fig. 7. The movement of the armature is directly controlled by the solenoid coil, which is connected by an external cable with a supply of 15-cycle single-phase alternating current ; this produces the alternating field in the coil that causes the up-and-down movement of the armature at the rate of thirty vibrations per second. At the end of every return stroke it hits a striking block and imparts to the screen a jerk which throws the larger pieces of ore to the top of the bed and gives the fine particles a better chance of passing through the meshes during the rest of the cycle. The motion can be regulated by spiral springs controlled by a handwheel, thus enabling the intensity of the vibrations to be adjusted within close limits. No lubrication is required either for the vibrating mechanism or for any other part of the screen, and the 15-cycle alternating current is usually supplied by a special motor-generator set placed somewhere where dust cannot reach it.
The Type 70 Screen is usually made 4 ft. wide and from 5 to 10 ft. in length. For the rough work described above it can be relied upon to give a capacity of 4 to 5 tons per square foot when screening to about in. and set at a slope of 25 to 30 degrees to the horizontal. The Type 50 Vibrator requires about 2 h.p. for its operation.
The determination of screen capacity is a very complex subject. There is a lot of theory on the subject that has been developed over many years of the manufacture of screens and much study of the results of their use. However, it is still necessary to test the results of a new installation to be reasonably certain of the screen capacity.
A general rule of thumb for good screening is that: The bed depth of material at the discharge end of a screen should never be over four times the size opening in the screen surface for material weighing 100 pounds per cubic foot or three times for material weighing 50 pounds per cubic foot. The feed end depth can be greater, particularly if the feed contains a large percentage of fines. Other interrelated factors are:
Vibration is produced on inclined screens by circular motion in a plane perpendicular to the screen with one-eighth to -in. amplitude at 700-1000 cycles per minute. The vibration lifts the material producing stratification. And with the screen on an incline, the material will cascade down the slope, introducing the probability that the particles will either pass through the screen openings or over their surface.
Screen capacity is dependent on the type, available area, and cleanliness of the screen and screenability of the aggregate. Belowis a general guide for determining screen capacity. The values may be used for dried aggregate where blinding (plugged screen openings), moisture build-up or other screening problems will not be encountered. In this table it is assumed that approximately 25% of the screen load is retained, for example, if the capacity of a screen is 100 tons/hr (tph) the approximate load on the screen would be 133 tph.
It is possible to not have enough material on a screen for it to be effective. For very small feed rates, the efficiency of a screen increases with increasing tonnage on the screen. The bed of oversize material on top of the marginal particlesstratification prevents them from bouncing around excessively, increases their number of attempts to get through the screen, and helps push them through. However, beyond an optimum point increasing tonnage on the screen causes a rather rapid decrease in the efficiency of the screen to serve its purpose.
Two common methods for calculating screen efficiency depend on whether the desired product is overs or throughs from the screen deck. If the oversize is considered to be the product, the screen operation should remove as much as possible of the undersize material. In that case, screen performance is based on the efficiency of undersize removal. When the throughs are considered to be the product, the operation should recover as much of the undersize material as possible. In that case, screen performance is based on the efficiency of undersize recovery.
These efficiency determinations necessitate taking a sample of the feed to the screen deck and one of the material that passes over the deck, that is, does not pass through it. These samples are subjected to sieve analysis tests to find the gradation of the materials. The results of these tests lead to the efficiencies. The equations for the screen efficiencies are as follows:
In both cases the amount of undersize material, which is included in the material that goes over the screen is relatively small. In Case 1 the undersize going over the screen is 19 10 = 9 tph, whereas in Case 2 the undersize going over is 55 50 = 5 tph. That would suggest that the efficiency of the screen in removing undersize material is nearly the same. However, it is the proportion of undersize material that is in the material going over the screen, that is, not passed through the screen, that determines the efficiency of the screen.
In the first cases the product is the oversize material fed to the screen and passed over it. And screen efficiency is based on how well the undersize material is removed from the overs. In other cases the undersize material fed to the screen, that is, the throughs, is considered the product. And the efficiency is dependent on how much of the undersize material is recovered in the throughs. This screen efficiency is determined by the Equation B above.An example using the case 1 situation for the throughs as the product gives a new case to consider for screen efficiency.
Generally, manufacturers of screening units of one, two, or three decks specify the many dimensions that may be of concern to the user, including the total headroom required for screen angles of 10-25 from the horizontal. Very few manufacturers show in their screen specifications the capacity to expect in tph per square foot of screen area. If they do indicate capacities for different screen openings, the bases are that the feed be granular free-flowing material with a unit weight of 100 lb/cu ft. Also the screen cloth will have 50% or more open area, 25% of total feed passing over the deck, 40% is half size, and screen efficiency is 90%. And all of those stipulations are for a one-deck unit with the deck at an 18 to 20 slope.
As was discussed with screen efficiencies, there will be some overs on the first passes that will contain undersize material but will not go through the screen. This material will continue recirculating until it passes through the screen. This is called the circulating load. By definition, circulating load equals the total feed to the crusher system with screens minus the new feed to the crusher. It is stated as a percentage of the new feed to the crusher. The equation for circulating load percentage is:
To help understand this determination and the equation use, take the example of 200 tph original or new material to the crusher. Assume 100% screen efficiency and 30% oversize in the crusher input. For the successive cycles of the circulating load:
The values for the circulating load percentages can be tabulated for various typical screen efficiencies and percents of oversize in the crusher product from one to 99%. This will expedite the determination for the circulating load in a closed Circuit crusher and screening system.
Among the key factors that have to be taken into account in determining the screen area required is the deck correction. A top deck should have a capacity as determined by trial and testing of the product output, but the capacity of each succeeding lower deck will be reduced by 10% because of the lower amount of oversize for stratification on the following decks. For example, the third deck would be 80% as effective as the top deck. Wash water or spray will increase the effectiveness of the screens with openings of less than 1 in. in size. In fact, a deck with water spray on 3/16 in. openings will be more than three times as effective as the same size without the water spray.
For efficient wet or dry screeningHi-capacity, 2-bearing design. Flywheel weights counterbalance eccentric shaft giving a true-circle motion to screen. Spring suspensions carry the weight. Bearings support only weight of shaft. Screen is free to float and follow positive screening motion without power-consuming friction losses. Saves up to 50% HP over4- bearing types. Sizes 1 x 2 to 6 x 14, single or double deck types, suspended or floor mounted units.Also Revolving (Trommel) Screens. For sizing, desliming or scrubbing. Sizes from 30 x 60 to 120.
TheVibrating Screen has rapidly come to the front as a leader in the sizing and dewatering of mining and industrial products. Its almost unlimited uses vary from the screening for size of crusher products to the accurate sizing of medicinal pellets. The Vibrating Screen is also used for wet sizing by operating the screen on an uphill slope, the lower end being under the surface of the liquid.
The main feature of the Vibrating Screen is the patented mechanism. In operation, the screen shaft rotates on two eccentrically mounted bearings, and this eccentric motion is transmitted into the screen body, causing a true circular throw motion, the radius of which is equivalent to the radius of eccentricity on the eccentric portion of the shaft. The simplicity of this construction allows the screen to be manufactured with a light weight but sturdy mechanism which is low in initial cost, low in maintenance and power costs, and yet has a high, positive capacity.
The Vibrating Screen is available in single and multiple deck units for floor mounting or suspension. The side panels are equipped with flanges containing precision punched bolt holes so that an additional deck may be added in the future by merely bolting the new deck either on the top or the bottom of the original deck. The advantage of this feature is that added capacity is gained without purchasing a separate mechanism, since the mechanisms originally furnished are designed for this feature. A positivemethod of maintaining proper screen tension is employed, the method depending on the wire diameter involved. Screen cloths are mounted on rubber covered camber bars, slightly arched for even distribution.
Standard screens are furnished with suspension rod or cable assemblies, or floor mounting brackets. Initial covering of standard steel screen cloth is included for separations down to 20 mesh. Suspension frame, fine mesh wire, and dust enclosure are furnished at a slight additional cost. Motor driven units include totally-enclosed, ball-bearing motors. The Vibrating Screen can be driven from either side. The driven sheave is included on units furnished without the drive.
The following table shows the many sizes available. Standard screens listed below are available in single and double deck units. The triple and quadruple deck units consist of double deck units with an additional deck or decks flanged to the original deck. Please consult our experienced staff of screening engineers for additional information and recommendations on your screening problems.
An extremely simple, positive method of imparting uniform vibration to the screen body. Using only two bearings and with no dead weight supported by them, the shaft is in effect floating on the two heavy-duty bearings.
The unit consists of the freely suspended screen body and a shaft assembly carried by the screen body. Near each end of the shaft, an eccentric portion is turned. The shaft is counterbalanced, by weighted fly-wheels, against the weight of the screen and loads that may be superimposed on it. When the shaft rotates, eccentric motion is transmitted from the eccentric portions, through the two bearings, to the screen frame.
The patented design of Dillon Vibrating Screens requires just two bearings instead of the four used in ordinary mechanical screens, resulting in simplicity of construction which cuts power cost in half for any screening job; reduces operating and maintenance costs.
With this simplified, lighter weight construction all power is put to useful work thus, the screen can operate at higher speeds when desired, giving greater screening capacity at lower power cost.
The sting of the positive, high speed vibration eliminates blinding of screen openings.
The sketches below demonstrate the four standard methods of fastening a screen cloth to the Dillon Screen. The choice of method is generally dependent on screen wire diameters. It is recommended that the following guide be followed:
Before Separation can take place we need to get the fine particles to the bottom of the pile next to the screen deck openings and the coarse particles to the top. Without this phenomenon, we would have all the big particles blocking the openings with the fines resting atop of them and never going through.
We need to state that 100% efficiency, that is, putting every undersize particle through and every oversize particle over, is impossible. If you put 95% of the undersize pieces through we in the screen business call that commercially perfect.
vibrating screeners - carrier vibrating equipment, inc
Ideal for dry or wet screening, Carriers vibratory screeners can handle up to 1500 tons per hour, with many deck design options that deliver maximum efficiency. Our vibratory screeners can be manufactured to meet your needs, with customizable construction and configuration.
7 best vibrating alarm watches (2020 review) - spotthewatch
This watch has a program designed to provide information regarding your physical activity, but also about your sleep patterns. It detects when you are resting and when you are asleep, and provides you with useful general health information.
You get a lot more than just alarms with strong vibrations, as this is a black resin strap watch with HD digital display designed to suit both professional athletes and an average person wanting to keep track of their health.
It is the kind of fitness wristband you can trust, and one that allows you to set up multiple alarms, such as a potty reminder for when to take your new puppy out, alarms for medications and a daily alarm for those meetings you just cant miss.
Why We Like It With a vibration alarm black resin strap watch like this, you can both enjoy the benefits of a reliable fitness tracker, while also setting up countdown timers and strong vibrating alarms.
The Timex Expedition resin strap watch can be adjusted to fit a wrist measuring up to eight inches, it has a large 43mm resin case and super illuminator Indiglo LightUp watch dial. The material makes the Expedition shock-resistant to help prevent accidental damage, and the expedition vibration alarms will alert you to anything you may have in your agenda without making as much as a sound.
The water-resistance of the Timex mens Expedition Grid Shock watch makes it fine to use even for swimming and snorkeling, but not for deep-water activities like diving. Set up your medication reminders and other important alarms with the Timex mens T49851 Expedition vibration, enjoy the comfort of the Expedition vibration alarm black resin band and let the perfection of the luxurious T49851 Expedition show you what it is like to have a real high-quality watch.
Why We Like It The Mens T49851 Expedition vibration alarm watch is a durable sport watch with a large and easy-to-read dial, and it is both shock resistant and resistant to water the T49851 Expedition vibration alarm black resin watch is one of a kind!
Update your old Quartz movement watch by getting the Timex Expedition Grid Shock to watch a gorgeous Grid Shock watch with vibrating alarms for the hearing impaired and for those who need quiet reminders throughout the day.
You get three daily alarms that can be set up all at once, 100hour chronograph, three time-zones, and much more! It is a black resin strap watch with easy to read digits plus and 24-hour Military time mode, and one you will benefit from regardless of whether you are into working out or exercise, or if you just want an accurate watch to help you keep track of time.
This Casio mens watch with the black case is not just any watch it is the Casio Mens W735HLAVCF Super Illuminator! It is a large case watch made with durable and water-resistant resin, and it has that sporty look that goes with most outfits!
The vibration alerts come in handy when you are in a situation where you cannot have sound interrupting, and it is water-resistant down to 100m (330ft). The Casio Mens watch is a watch you will feel proud when wearing, and it has a reliable start and stopwatch function.
Why We Like It The Casio GShock W735HLAVCF Super Illuminator Watch has a large case with easy-to-read digital numbers, it is safe to use when going swimming and when ending up in accidental changes of the weather, such as sudden rain.
This G-Shock watch has a pre-programmed calendar up until the year 2099, which means you can set alarms for events that arent scheduled to happen anytime soon! It is shock-resistant, water-resistant, has world time with up to 35 different time zones, elapsed and split time measuring modes, vibrating alarms and as a nice addition the option of switching on flash alarms.
The watch also has a generous digital display with large numbers and control buttons, so that you can change settings and set up alarms also when you are on the go. Its functions are comparable to the VibraLite Mini 12Alarm Vibrating Watch (VibraLite Mini and VibraPlus Sport), and it is surprisingly affordable for such a high-quality watch.
This is a participant in the Amazon associates program for highly-rated products, and it is not hard to see why users fall in love with this fitness watch so easily! No more impractical large dials or leather straps, and instead you get a Fitbit charge-up type watch with a small but convenient digital display, vibration alerts for incoming calls, messages and social media notifications, sleep tracker with sleep analysis and it is compatible with SmartPhones through the downloadable app. A watch like this is perfect for someone who enjoys working out and who wants to make it easier to monitor their overall health and fitness progress.
Why We Like It A watch like this is the perfect fitness watch for someone who wants the features of an Apple Watch or a FitBit, but who wants something slightly more affordable. Great fitness watch at a fair price.
The Timex Vibe Shock watch is digital, with Quartz movement, and it is water-resistant down to an impressive 200 meters (660ft). You can get it in black, black and grey and black and red, and the resistant resin strap makes it easy to wipe off and keep clean when needed. There is a countdown timer, audible alarms, vibrating alarms, buckle closure, Indiglo backlight, and time zone options, and it is the kind of watch that people will notice right away!
If you want a high-quality watch with all the modern watch features you can wish for, plus silent vibrating alarms and an eye-catching exterior the Timex Expedition Vibe Shock Watch is possibly the right one for you.
If vibration reminders are something that would make your life a little easier it is time to start looking for the best vibrating alarm watch for you and for your needs! There are multiple ways that vibrating alarm watches can help you in your everyday life, and many of the extra features can come in handy in ways you might not even have thought of yet.
Imagine being able to set alarms and reminders throughout the day, for when to take medication, when the new puppy needs to go out and pee or for when to pick up the kids from school, without having to jump out of your shoes every time the alarm sound rings! It is a revolutionary way of feeling an alarm rather than hearing it, or you can use both sound and vibration to make sure you dont miss what is important.
Having a vibration watch has many benefits, and this is something most people dont think about until they come across an alarm clock review article such as this. Vibrating alarm watches take alarms to a whole new level, as it allows you to feel it go off rather than to just hear it. This is useful for someone who is hearing impaired, but also if you struggle to wake up with just the sound, or if you set up reminders for when you are somewhere where sound interruption is frowned upon. This could be a meeting at work, a class at school or that first date when it would simply get a little awkward if your watch started ringing in the middle of it.
Many of the best vibrating reminder watches can be paired with your SmartPhone, and that is where you get even more benefits! Suddenly you will feel a vibration whenever someone is calling, sending a text message or even when a social media notification comes in, which helps make sure you wont end up missing something important.
A fitness watch or another type of vibrating alarm clock has proven to be beneficial for both kids and adults diagnosed with ADHD. Many with this diagnosis benefit greatly from having structure, and a reliable alarm vibrating reminder watch is the perfect way for someone to keep track of where they need to be, what they need to do and when, and it can also work as a way to regain attention when trying to focus on a specific task. Wrist-watches with a silent vibrating alarm watch function could be a game-changer for an individual with ADD or ADHD.
Persons with onsets of dementia could also make great use of a vibrating reminder watch, to keep track of simple things like meal times and medications, as this will make it possible for the individual to continue living a somewhat normal life for longer.
To give someone a little bit of their independence back can do wonders for slowing down the disease, and it can also be a comfort to family members to know that someone with dementia or Alzheimers has a device that allows them to keep track of important events.
Vibration alarms are also great for those working in the healthcare industry, to monitor routines and more, and especially when it comes to extra demanding patients. You cant run around a hospital with a loud beeping watch when patients are trying to take it easy, rest and recover, and for healthcare professionals, it could be a game-changer to have access to silent alarms.
No-sound alarms arent just a thing you find in digital watches, despite what many people believe, and there are many analog watches that also feature vibration alarms. This makes it possible for you to pick and choose the type of watch you feel the most comfortable with, and the one you like best, and different watches are good for different purposes.
A digital fitness watch with vibrating sound might be ideal for someone who is sporty and enjoys to work out, while a more classic timepiece could better suit someone who wants to use it as a fashion item or who simply prefers a mechanical watch. You may not think that a vibrating watch is something you have a need for, but many discover quickly the many benefits that come with having silent alarms that vibrate instead of a beep.
Yes, most vibration alarm sound watches have the option of using vibration or sound, and often both at the same time if required. This is great for different situations, such as where you absolutely cannot miss an alarm, as you can set up both. Some watches will also feature a flashing alarm.
This is a highly personal choice, but look for a product made with water-resistant material, to avoid moisture damage if you sweat or if it rains. You will also want your running watch to be lightweight, so consider a fitness type watch with vibrating alarms, as these will also help you monitor your fitness progress.
When choosing your new vibration alarm sound alarm watch, look at the watch as a whole, and what it can offer you. Vibration alarms have numerous benefits, but you want to make sure to pick a watch that you will also enjoy wearing when not in the need for setting alarms. There are so many excellent products to choose from, and that makes it easy to find that watch you have always dreamt of owning, complete with a vibrating alarm function.
Take the opportunity to do some research and to look at different products, instead of just choosing the first that there is, as the many options available ensure that you have the perfect vibrating alarm watch waiting for you out there somewhere.
Hi there. My name is James Hampton-Smith and I have been collecting watches for the past 9 years. Since my Grandfather gifted me his first watch, I have been captivated by the design and mechanics that go into every last detail that makes up a wrist watch. Follow me on my journey as I present my favourite watches at Spot The Watch.
trommel screen | gold trommel | trommel wash plant | dove
DOVE Trommel Screens are designed as highly efficient, rugged and economical solution for screening and classification of wide range of material, as well as to optimize the subsequent processing steps of recovery. Screening allows reducing investment and operating costs, and increasing the products quality with a rapid and large volume processing. DOVE offers the largest range of Trommel Screens of different types and specifications, with a wide range of the processing capacities from 5 tons/hour up to 1000 tons/hour, per single Trommel Screen.
Supplied in various types and configurations: Scrubber Drums, Scrubber Screens and Classifiers, Double Screen Trommels, Cone type and etc. DOVE Trommels are supplied both in wet and dry configuration. Portable and stationary configurations are available.