checking the amplitude of a vibrating screen - metso outotec

checking the amplitude of a vibrating screen - metso outotec

Among the conditions to be checked periodically in screens, the shape of motion is one of the most important. In the chart below, one can see and verify the shape of the vibratory motion: circular (A), elliptical (B) or even linear (C).

There is an ideal relation between operating rotation, amplitude and the degree of inclination of the equipment depending on the aperture of the mesh installed on the screens. The nominal rotation is established observing the ideal operating conditions and, further, to ensure that the equipment is operated safely below the vibrating structures critical frequency.

The amplitude of vibration can be altered by changing the position of the movable counterweight. Such adjustment is performed based on the application. The screening of coarse material demands a higher amplitude than the amplitude required for the classification of fines.

The higher the operating amplitude of vibrating equipment, the shorter the service life of the equipments bearings. Bearing service life will be satisfactory even if all the available eccentric mass that was originally provided with the equipment is used.

Warning: Never utilize eccentric masses that are greater than those provided as original equipment. This will lead to a considerable drop in the service life of the bearings, as well as a possible unbalancing of the vibrating equipment.

In order to precisely measure and analyze the dynamic performance of vibratory screens, we developed ScreenCheck, a hand-held electronic testing device featuring wireless electronic sensors and automated software.

vibrating screen working principle

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.

checking the amplitude of a vibrating screen - quarry

checking the amplitude of a vibrating screen - quarry

{{image3-a:r-w:300}}Changing the position of the moveable counterweight can alter the amplitude of vibration. Such adjustment is performed based on the application. The screening of coarse material demands higher amplitude than that required for the classification of fines.

The higher the operating amplitude of vibrating equipment, the shorter the service life of the equipments bearings. Bearing service life will be satisfactory even if all available eccentric mass that was originally provided with the equipment is used.

{{image4-a:r-w:300}}Operators are advised to never utilise eccentric masses that are greater than those provided with the original equipment. This will lead to a considerable drop in the service life of the bearings, and a possible unbalancing of the vibrating equipment.

To precisely measure and analyse the dynamic performance of vibratory screens, Metso has developed the ScreenCheck kit, which includes numerous hand-held electronic testing devices featuring wireless electronic sensors and automated software.

The ScreenCheck devices can be fixed to the side of a screen and a number of tests performed, including orbit measurements, side displacement, structural movement and bump checks (the last with a mallet). These tests measure stroke, angle and peak Gs on the left and right corners of the screen (orbit measurement), the feed, mid and discharge data for the three screen shafts (side displacement), and the frequency spectrum for the spring mounts (structural movement and the mallet).

vibration frequency, screen inclination of the vibrating screen | lzzg

vibration frequency, screen inclination of the vibrating screen | lzzg

Vibration characteristics include vibration frequency, amplitude, vibration direction angle, and screen inclination. If these parameters are set incorrectly, it will affect the working efficiency of the vibrating screen. The correct way is: 1. Screen angle The angle between the screen surface and the horizontal plane is called the screen angle. The size of the dip is closely related to the throughput of the screening equipment and the screening efficiency. When the inclination angle is increased, the throwing strength of the material on the sieve will be increased, so that the forward movement speed of the material on the sieve surface is accelerated, so that the treatment amount of the vibrating screen is increased, but the residence time of the material on the sieve surface is shortened, and the opportunity for screening the sieve is reduced. , thereby reducing the screening efficiency. On the contrary, the throughput is reduced and the screening efficiency is improved. In order to control the screening efficiency of the vibrating screen to a relatively ideal range, the screen inclination angle of the circular vibrating screen is generally between 15-25, and the screen inclination angle of the linear vibrating screen is between 0 and 8. 2. The angle between the vibration direction angle vibration direction line and the upper screen surface is called the vibration direction angle. The larger the value of the vibration direction angle is, the shorter the distance moved by the material is, and the slower the movement speed of the material on the screen surface, the material can be fully sieved, thereby obtaining a larger screening efficiency. The smaller the value of the vibration direction angle is, the farther the material throws and advances each time. The faster the material passes through the screen surface, the higher the processing capacity, but the material cannot be fully sieved. Therefore, the vibration direction angle should be reasonably selected. For difficult-to-screen materials, the vibration direction angle should be taken as a large value. For easy-screen materials, the vibration direction angle should be small; in general, the vibration direction angle of the circular vibrating screen is 90. The vibrating direction angle of the linear vibrating screen ranges from 30 to 60, often 45. This value not only has good performance for various screening but also obtains the best moving speed and high productivity. circular vibrating screen 3. The amplitude A amplitude increases, the mesh plugging phenomenon will be greatly reduced, and it is also conducive to the stratification of materials. However, too large amplitude is also destructive to the device. The choice of amplitude is based on the particle size and nature of the material being screened. In general, the larger the vibrating screen size, the larger the amplitude selected. When the linear vibrating screen is used for classification, the amplitude is slightly larger; when used for dehydration and deliming, the amplitude should be smaller. When the particle size of the treated material is large, the amplitude should be correspondingly increased; when the particle size of the treated material is small, the amplitude should be smaller. Usually, the amplitude of the linear vibrating screen is A=3.5~6mm. 4. The increase of vibration frequency vibration frequency can increase the number of times the material beats on the screen surface, which increases the probability of material permeability. This is helpful for speeding up the material screening speed and improving the screening efficiency, but it is too high. Reduce the life of your equipment. For larger particle sizes, use larger amplitudes and lower frequencies; for finer particles, use smaller amplitudes and higher frequencies.

Vibration characteristics include vibration frequency, amplitude, vibration direction angle, and screen inclination. If these parameters are set incorrectly, it will affect the working efficiency of the vibrating screen. The correct way is:

1. Screen angle The angle between the screen surface and the horizontal plane is called the screen angle. The size of the dip is closely related to the throughput of the screening equipment and the screening efficiency. When the inclination angle is increased, the throwing strength of the material on the sieve will be increased, so that the forward movement speed of the material on the sieve surface is accelerated, so that the treatment amount of the vibrating screen is increased, but the residence time of the material on the sieve surface is shortened, and the opportunity for screening the sieve is reduced. , thereby reducing the screening efficiency. On the contrary, the throughput is reduced and the screening efficiency is improved. In order to control the screening efficiency of the vibrating screen to a relatively ideal range, the screen inclination angle of the circular vibrating screen is generally between 15-25, and the screen inclination angle of the linear vibrating screen is between 0 and 8.

2. The angle between the vibration direction angle vibration direction line and the upper screen surface is called the vibration direction angle. The larger the value of the vibration direction angle is, the shorter the distance moved by the material is, and the slower the movement speed of the material on the screen surface, the material can be fully sieved, thereby obtaining a larger screening efficiency. The smaller the value of the vibration direction angle is, the farther the material throws and advances each time. The faster the material passes through the screen surface, the higher the processing capacity, but the material cannot be fully sieved. Therefore, the vibration direction angle should be reasonably selected. For difficult-to-screen materials, the vibration direction angle should be taken as a large value. For easy-screen materials, the vibration direction angle should be small; in general, the vibration direction angle of the circular vibrating screen is 90. The vibrating direction angle of the linear vibrating screen ranges from 30 to 60, often 45. This value not only has good performance for various screening but also obtains the best moving speed and high productivity.

3. The amplitude A amplitude increases, the mesh plugging phenomenon will be greatly reduced, and it is also conducive to the stratification of materials. However, too large amplitude is also destructive to the device. The choice of amplitude is based on the particle size and nature of the material being screened. In general, the larger the vibrating screen size, the larger the amplitude selected. When the linear vibrating screen is used for classification, the amplitude is slightly larger; when used for dehydration and deliming, the amplitude should be smaller. When the particle size of the treated material is large, the amplitude should be correspondingly increased; when the particle size of the treated material is small, the amplitude should be smaller. Usually, the amplitude of the linear vibrating screen is A=3.5~6mm.

4. The increase of vibration frequency vibration frequency can increase the number of times the material beats on the screen surface, which increases the probability of material permeability. This is helpful for speeding up the material screening speed and improving the screening efficiency, but it is too high. Reduce the life of your equipment. For larger particle sizes, use larger amplitudes and lower frequencies; for finer particles, use smaller amplitudes and higher frequencies.

The excitation force, vibration frequency and screening effect of the dewatering screen are closely related. Too small excitation force will cause poor screening effect, and excessive excitation force may cause damage to the screen plate.How to adjust the vibrating screen. 1. Control of screening area The width of the screen surface is the main factor that determines the production rate

Silica sand is the main raw material for making ceramics and glass, so the market demand has been high. It is mainly processed by crushing, powdering, and iron removal. Fine silica sand removal methods instruction. The mechanical equipment required in the silica sand dry iron removal method is a crusher, a dry ball mill, a dry iron remover, a dry

Drum rotating aggregate screening machine also called trommel screen according to its structure. It uses the self-weight of sand and gravel aggregates and the isolation effect of the mesh to separate sand and gravel materials of different sizes. The inclination of the central axis is 22.5 degrees. It can discharge l530m3 per hour. When the screen is moved, it is

After the raw sand is mined, the finished sand is obtained after washing rod milling, classification, homogenization, and dehydration. The raw sand with particles below 10mm from the raw ore mining is conveyed into the rod mill through a belt. At the same time, add water according to a certain proportion and grind it into mortar and drain into the

optimizing vibratory screen separator performance

optimizing vibratory screen separator performance

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

This article will demystify the set-up and operation of a round vibratory screen separator. The effect of the input control parameters: top weight force, bottom weight force, and lead angle are defined to create an understanding of vibration generation. The output parameter measurements techniques for: horizontal motion, vertical motion, and phase angle are defined to create an understanding of the vibration generated. This article will then explain the motion of particles inside the separator and how to adjust the weights to obtain the optimum vibratory motions. Practical guidelines are introduced for weight setting methodology to achieve optimum screening patterns.

A standard round vibratory separator uses a vibrating screen cloth enclosed in frames that are vibrated by a motion generator consisting of a double-end shaft motor with eccentric weights on the top and bottom of the vertically mounted motor (see Figure 1). The motor rotates counter-clockwise (CCW) when viewed from the top. As the motor rotates, the weights generate a radial centrifugal force causing the spring mounted machine to vibrate.

The top weight has an adjustable force output and a fixed angular orientation on the motor shaft. The bottom weight also has an adjustable force output, but includes a variable angular orientation in relation to the top weight.

There are three independent variables or adjustments to a vibratory separator: top force, bottom force, and lead angle. The output variables are horizontal motion amplitude, vertical motion amplitude, and the phase angle. Lead angle is the angular weight setting while phase angle is the measured delay between the maximum vertical and horizontal amplitudes.

To simplify discussion, first consider only the top motor weight. The top motor eccentric weight is designed to be at the center of gravity (CG) of the vibrating machine. Force acting at the center of gravity of a mass will cause uniform planar motion in that mass. In other words, the top weight force spinning at the center of gravity will create a uniform horizontal radial motion of the machine without any torque about the CG.

Visualize a separator as a solid cylinder as shown in Figure 2: The top eccentric weight force acts at the center of gravity (CG) of the body. When a force acts at the CG of the body, horizontal motion of the body will occur in the direction of the top weight force.

Figure 3 shows the same body at two different positions. The first position, shown in gray, occurs when the force is pointed left. As the motor rotates 180 degrees, the force will point to the right and cause the cylinder to translate horizontally to the right position shown in the black outline. The horizontal motion generated is the distance the separator moves with 180 degrees of motor rotation.

As the motor continuously spins the weights, we can visualize the cylinder moving through a horizontal radial motion following the eccentric weight force orbit. It is important to note that the cylinder does not rotate only the motor and weights. Because the top weight force acts at the center of gravity, the cylinder will always remain horizontal. Variable horizontal motions will occur as the magnitude of the top force is varied.

Now, if we add a another eccentric weight FBW, as shown in Figure 4, to the bottom of the motor below the machine CG, the bottom eccentric weight will induce a torque about the center of gravity creating vertical motion as the machine tilts from the vertical axis. The result of the top and bottom weight is a cylinder tilted off the vertical axis. Adding more bottom weight yields more vertical motion.

Figure 5 depicts the same cylinder shown in Figure 4 in two different motor positions with the weights rotated 180 degrees. The drawing shows the resultant horizontal and vertical motions which are generated by the eccentric top and bottom weight forces.

We can visualize the motor rotating CCW and the maximum amplitude generated will occur in the direction the force points. As the motor rotates, the direction continually changes and the elliptical motion in three axes is generated by one rotation of the motor.

Figure 5 shows the top and bottom forces to be vertically aligned with the maximum horizontal and vertical motion occurring in the same vertical plane, or angular position. There are advantages to changing the angle between the weights.

In vibratory separators, lead angle is defined as the CCW angle between the top and bottom weight when viewed from above. When the weights are vertically aligned, there is a zero degree lead angle. When the bottom weight is 120 degrees CCW from the top weight, and the motor is spinning CCW, the bottom weight leads the top weight. This means the maximum vertical motion generated by the bottom weight will occur 120 degrees of motor rotation before the maximum horizontal motion generated by the top weight.

Lead angle is the control parameter which gives a round vibratory separator unparalleled functionality by controlling the material flow pattern in the separator. The advantages and proper setting of lead angle will be discussed further in the particle dynamics section.

To analyze the motion of a separator, a vibration gauge sticker easily measures vibration amplitudes. These stickers are attached to the outside frame diameter of the machine near the screen level. The stationary gauge shown in Figure 7, measures both horizontal and vertical motion independently.

To read the vibration amplitude, while the machine is running, observe where the triangular lines cross as shown in Figure 8. The number closest to the line crossing will be the vibration amplitude in 1/16-in. increments. Figure 8 shows that the horizontal amplitude reads 3/16 and the vertical reads 3/16.

Motion amplitudes vary with the distance from the center of gravity of the machine. It is important when comparing machines that the measurements are in equivalent locations. It is best to measure amplitudes closest to the most critical screen in the separator.

The next question is how to measure the phase angle between the horizontal and vertical motions. The simple answer is to merely reference the lead angle between the weights. While this is normally satisfactory, there are certain conditions where the lead angle does not predict the vibratory motion or the motion of particles on the screen. When lead angle is no longer appropriate, phase angle should be measured.

Phase angle is the measured delay between the maximum vertical and horizontal motion. A computer monitoring system is required for this measurement. Figure 9 shows a data screen from a computer based motion analysis system. Horizontal and vertical displacement, phase angle, motor speed, and directional accelerations allow precise set-up and troubleshooting of vibratory separators.

Now that we understand the function of machine input parameters: top weight, bottom weight and lead angle, and the resulting separator motions, we can discuss how to control the motion of a particle. Figure 10 shows material feed onto the center of the screen moves from the center to the outside edge of the screen. Figure 11 shows material feed at the edge of the screen runs to the center of the screen. These material flow patterns can now be explained.

1. The maximum vertical amplitude occurs directly above the bottom weight. This means that a particle on the screen will be launched vertically when the bottom weight rotates directly beneath that particle.

2. The maximum horizontal radial amplitude occurs in the direction of the top weight. As the top weight rotates towards a particle on the screen, the horizontal radial motion increases to a maximum when the top weight is pointed at the particle. As the weight rotates away from the particle, the horizontal radial motion decreases.

For the first example, analyze a machine set-up with the top and bottom weights at zero degree lead angle. Consider one particle on a screen directly above both of the weights. This particle will be launched vertically directly above the top and bottom weights at the position of maximum vertical and horizontal radial motion. While the particle is in flight above the screen, the weights will continue to rotate and move the screen underneath the flight of the particle. When the particle lands on the screen, it will be in a new position on the screen.

If we simply assume that a particle is in flight for 180 degrees of motor rotation with the weights set at a zero lead angle, the particle, depicted by the double-ended arrow in Figure 12, will leave the screen vertically and land closer to the screen edge. The 180-degree assumption clearly shows that the particle leaves the screen at the point of maximum horizontal radial motion, shown in gray outline, and lands at the point of minimum horizontal radial motion, shown in black. The particle will appear to travel radially outward from the screen center as shown in Figure 13.

With the weights set at zero degree lead angle, the particle will always travel radially outward even if the particle is in flight for only one degree of motor rotation. The particle left the screen at the point of maximum radial displacement and will land and a point of less radial displacement. This means the particle will always land closer to the edge of the screen.

For the second example, let us analyze the opposite extreme when the bottom weight is advanced to a 180-degree lead angle. Here the vertical motion occurs before the maximum horizontal radial motion; therefore, the particle will be launched vertically before the maximum radial motion occurs.

To continue the same analogy, let us again assume that the particle is in flight for 180 degrees of motor rotation, only now the lead angle is set to 180 degrees. The particle, depicted by the double-ended arrow in Figure 14, will leave the screen vertically above the bottom weight, be in flight above the screen for 180 degrees of motor rotation, and land again directly above the top weight. This is shown in Figure 14 with the particle leaving the screen shown in the gray outline and landing in the black outline screen position. When the particle left the screen, it was at the location of minimum horizontal radial displacement and landed at the location of the maximum radial displacement. The particle has landed farther from the outside edge of the screen and appears to travel radially inward as shown in Figure 15.

Again, using the same arguments, with the weights set at 180-degree lead angle, the particle will always travel radially inward even if the particle is in flight for one degree of motor rotation. This is because the flight of the particle begins when the separator is at the minimum horizontal radial distance. The particle left the screen at the point of minimum radial distance and will land and a point of greater radial distance.

Using these two extremes as examples, it is clearly shown how the lead angle is the controlling parameter in particle flow direction in a vibratory separator. The simplified discussions so far have been helpful to illustrate the effects of vibratory motion on particle motion, but realistically, particles are not in flight for 180 degrees of motor rotation.

The past examples have ignored the second horizontal axis motion by only considering the 180-degree positions. When the motor has rotated 45 degrees, the screen position will have moved in two dimensions in the horizontal plane. Figure 16 shows the effect of 45 degrees of motor rotation. Figure 17 shows the top view of a single particle displacement on a screen. Figure 17 now clearly shows that a particle will more realistically move in two horizontal dimensions, with both radial and angular displacements.

As the lead angle is increased from zero degrees towards 50 degrees, the horizontal radial particle displacement is diminished. This means that the radial velocity of the particle will decrease because the horizontal tangential motion is increasing. This yields an increasing spiral path to the flow pattern.

At a 60-degree lead angle setting, the material appears to travel only tangentially. This can be explained by a particle being launched vertically 60 degrees before the top weight and landing 60 degrees after the top weight in the same radial position on the screen. Material will not readily discharge from the spouts at this setting.

As the lead angle increases above a 60 degree lead angle, the radial inward displacements increase. These patterns are explained simply by when the particle lands on the screen. If the particle lands after the maximum radial displacement, then the particle will move radially outward. If the particle lands before the maximum radial displacement, then the particle will move radially inward.

6 ways to measure vibration

6 ways to measure vibration

In this post I will list and explain the full range of vibration measurement systems readily available to a test engineer, or anyone in need of vibration measurement. As an applications engineer here at enDAQ (Note: enDAQ is a division of Mide), I often get asked by customers for alternative vibration measurement options to our enDAQ sensors. I believe these products meet the widest range of vibration measurement needs, but they are definitely overkill for some applications. And conversely these products don't have the functionality that some applications require.

In this post I will briefly discuss various vibration measurement options and provide links to these products. If you know you need wireless, check out a similar post highlighting wireless monitoring systems. And if you're interested in software options, check out our similar post on 8 different vibration analysis softwares availableto you. At the end of this blog I've summarized some key specificationsin a comparison table to help you determine the one that best meets your needs.

Texas Instruments SensorTag is a greatproduct that showcases TIs Bluetooth low energy system as well as 10 different sensors. It comes in at the incredibly low price of less than $30 (you wonder if TI loses money on these?!). Through Bluetooth, you connect the device to your phone and you can see in real time the measurements of all ten sensors, including a triaxial accelerometer. Now, Id hardly call it a vibration sensor though because it only samples up to 10 Hz (samples per second); but this is certainly a great product for a number of applications. There are a lot of development tools too so that you can incorporate various sensors and chips into your end system.

The VB300 is a very cost effective vibration measurement instrument and is an entry level vibration recorder. Coming in at less than $300 it can be a great first option at quantifying your vibration environment. Its definitely limited in sample rate (up to 200 Hz) and total storage (4Mbit or 112K samples per axis) but for some applications this as adequate. This product also claims to provide real-time feedback in both the frequency and time domain, which is certainly useful. The reviews on Amazon leave much to be desired for though and it seems that quality (as the price suggests) is not this products strength. This product also seems to be just a rebranded version of an even cheaper ($120) alternative made by a Chinese company, CEM's DT-178data logger. That being said I continue to point customers to this product that have budget restrictions but need some vibration measurement data. It's perfect if you're looking to get a rough idea of the frequency content (so long as it's less than 60 Hz) in your vibration environment.

The Fluke 805 vibration meter offers real time vibration analysis so that maintenance decisions can be made quickly and relativity accurately. Its much different than the other products discussed in this post becauseit doesnt really log any data (will keep the last 3,500 samples). When pressed against a piece of machinery (does make you question how accurate it is in this "mounting" configuration) it reads out the RMS vibration level and also uses some algorithm to rate the overall vibration of your bearing or machine. It is a bit pricey at just under $2,000 and it doesnt offer enough information to do proper vibration analysis. But for quick go/no-go determination of your equipments vibration levels, a vibration meter like this product is an excellent choice.

The MSR165 is great portable tool to measure and analyze vibration. It has two accelerometer options (15g or 200g) to meet either vibration or shock testing needs. With a noticeably higher sample rate option (1,600 Hz) than many of the other vibration data loggers on the market and expandable storage and battery options this product offers a great solution over the more traditional data acquisition systems. It also offers a host of customizable options which include added temperature, pressure, humidity, or light sensors and external analog inputs.

My issue with the product comes with the fact that there are almost too many options and as such, each unit must be made to order. As many of us know in the vibration testing community, when we need vibration testing equipment, we needed it yesterday! With everything being made to order the lead time is typically almost a month. Also, because they go through distributors only (some of which require a cut of 40%) their prices seem a little higher than Id expect. All the different configurable options canadd quite a bit of cost and before you know it, the instruments price exceeds $2,000. The product definitely still provides great value though and is a good solution for longer duration recordings especially.

enDAQ sensors (formerly Mide's Slam Stick vibration data loggers) really kick up the sample rate and measurement range to make these products truly rival the "typical" vibration measurement system. The S3-D40 and S3-D16 (formerly Slam Stick C) is similar to the MSR165 yet has twice the sample rate (3,200 samples/second/axis) and comes in at a lower price ($1,000). The battery life approaches one full day which isnt long enough for transportation; but it can be powered through the micro USB to extend the recording time. It also comes standard with 1GB of storage, enough for 500 million samples. Although the sample rate is still much higher than many other options, it can be too slow for some applications; and it is limited to only a 16g vibration/shock measurement range. But at $1,000it is a great tool that many companies could use on a near daily basis for vibration measurement. If you dont have the time or budget for the more complex vibration instrumentation yet you still need high end vibration data, this may be the vibration measurement instrument youre looking for.

enDAQs flagship vibration measurement tool, the polycarbonate S3 and aluminum S4 (formerly Slam Stick X), is unrivaled with its significantly higher sample rate (up to 20,000 samples per second per axis), and high measurement range options (up to 2,000g). With the much higher resolution (16 bit) and low noise characteristics this can also be used for very fine and small amplitude vibration measurement. This vibration measurement toolcan be used forhigh end vibration and shock testing on your product or system for qualification and/or isolating certain vibration issues you may be experiencing. The product offers excellent value at $1,250 (additional for aluminum enclosure and other options) that can result in significant time and hardware savings for your business.

enDAQ offers a free enDAQ Lab software package that is available to download online. This free software plots the data generated on the enDAQ sensor and configures the recorders. Data export, FFTs, spectrograms, and many other features are available in this software. The enDAQ sensor's portability, ease-of-use, and high end hardware make this a truly unique product that rivals the performance of the "traditional" vibration measurement systems.

Many people need or want real time vibration data to perform their analysis. National Instruments has a suite of products for general data acquisition and their LabVIEW software provides a means to interact with the real-time data being generated. There are a great number of different software and hardware systems available through National Instruments which would require a completely separate blog post(s) to go over. For the purpose of this comparison on different ways to measure vibration I selected a vibration measurement system with the type of specifications I would want as a test engineer. This type of vibration system is what I think most engineers picture as the "traditional" approach.

I selected the NI 9234 analog input moduleas the core DAQ (data acquisition) which has 4 channels of 24-bit data capture atup to 51,200 samples per second per channel. This module is specifically designed to interface with integrated electronic piezoelectric (IEPE) accelerometers; any such accelerometer with a +/- 5 volt output and up to a 2 mA excitation can be connected to this system. This will provide power to the accelerometer while it issimultaneously sampling the output, pretty cool! Thismodule comes in at the cost of $1,823.

As part of this "ideal" vibration measurement system with real time data output, I selected a Wi-Fi module, the NI cDAQ-9191to stream the data output wirelessly.This is only $400 and provides a great deal of functionality for someone who is trying to monitor vibration data in real time but somewhat remotely. If you don't want to run cables (other than power) to your vibration measurement system, this chassis is well worth the $400.

For the software package I went with the LabVIEW Full Development Systemat $2,999. I'm sure most of us know about LabVIEW but this software package is a graphical programming language to display and analyze measurement data in real time. This system includes extensive signal processing and analysis functionality. Many of you may already have a LabVIEW seat that you could use so you may not have to buy the software. Either way though you will need tospend quite a bit of time setting up the VI (virtual instruments). National Instruments also offers a software package specifically for sound and vibration measurement, at $1,999. This can save you a bit of set up time and money because it claims no programming is required. You won't necessarily be able to tailor the interface for your needs though and I don't think you could use this to run other systems, like you could with the LabVIEW development system.

For the accelerometer I selected a triaxial ceramic shear ICP accelerometer with 100 mV/g output, PCB Piezotronics's 356A15. This is a pretty impressive accelerometer with high sensitivity and a +/-50g peak output. The bandwidth is from 2 to 5,000 Hz and has less than 1% non-linearity and less than 5% transverse sensitivity. Its thermal dependency is pretty stable (it doesn't really need temperature compensation) andhas a wide temperature operating range. There's obviously countless accelerometer choices out there (check out a blog post on how toselect the right accelerometer for your application); but this would be at the top of my list for vibration measurement. The price is $1,035 for this accelerometer.

This brings the total system cost to $6,250; a savings of $1,400 can be made by forgoing theWi-Fi module and opting for the base sound and vibrationLabVIEW package. Of course this system has downsides in that you will need a computer (not very portable) and line power. The software effort can take quite a bit of time which delays testing and costs a significant amount of money. The lead times for some of these components, including the accelerometer, can sometimes be over a month resulting in additional delays. The other issue is that the DAQ module, although it has some shock & vibration testing, won't be able to handle some of the harsh environments you want your accelerometer to measure. That all being said, this system is pretty sweet! If you have the budget and the physical space available for this system, it's a compelling option foracquiring and analyzing vibration data.

For a more in-depth look at vibration data loggers, I've rated my top 11 vibration data loggers which includes other competing products/customers. If you know you need wireless, check out a similar post highlighting wireless monitoring systems. Please dont hesitate to reach out to us and ask which product we think will best meet your needs!

If you'd like to learn a little more about various aspects in shock and vibration testing and analysis, download our free Shock & Vibration Testing Overview eBook. In there are some examples, background, and a ton of links to where you can learn more.

sieve analysis - its 4 [methods, tests and advantages]

sieve analysis - its 4 [methods, tests and advantages]

Sieve analysis is a technique used for determining the size of particles in essential distributions such as the number of different size particles are responsible for the surface reaction, solubility, and flowability. For dry non-agglomerated particles, sieve analysis remains a cost-effective and precise measuring instrument. Separating particles by size is called sieving.

For quality control in many industries test sieve analysis is widely used and to measure particle size and dry relativity free-flowing materials the test sieve analysis is a simple and common practice.

The sieve shakers and accessories have to fulfill the requirements of national and international standards to guarantee a high degree of reproducibility and reliability. As part of the quality management system all the instruments used for the characterization of particle distributions have to be calibrated and subjected to test agent monitoring and to carry out the sample preparation with great care it is absolutely necessary. Sieve shakers are shown in fig below;

The sample is subjected to vertical movement called vibratory sieving or vertical motion called horizontal sieving during sieving the sample and both movements are superimposed with tap sieve shakers. The particles are compared with the apertures of every single sieve during this process and by the ratio of the particle size to the sieve openings the probability of particle passing through the sieve mesh is determined.

By the vibration of the sieve bottom the sample is thrown upward and due to gravitation force it falls back. The amplitude indicates the vertical oscillation height of the sieve bottom and the material is spread uniformly across the whole sieve area due to this combined motion.

In vertical direction the particles are accelerated and rotate freely and then fall back, an electromagnetic drive sets a spring system in motion and transfers the oscillations to the sieve stack in RETSCH sieve shakers. To a few millimeters the amplitude can be adjusted continuously.

By a vertical motion generated by a tapping impulse a horizontal, circular movement is superimposed in a tap sieving shaker and for various standards for particle size analysis tap sieving shakers are specified.

For single sieving the air jet sieve is a sieving machine and during the process the sieve itself is not moved. By rotating jet of air the material on the sieve is moved and a vacuum cleaner is connected to the sieving machine generates a vacuum inside the sieve chamber and through a rotating slit nozzle it sucks in fresh air.

The air stream is accelerated and blown against the sieve mesh dispersing the particles when passing the narrow slit of the nozzle. With the low speed with the sieve mesh, the air jet is distributed over the complete sieve surface and is sucked in and into the vacuum cleaner the finer particles are transported through the mesh openings.

To determine the particle size of dry and free-flowing materials dry sieving is used and to allow particles to seek the openings in the wire mesh these sieves are used by shaking or vibrating the sieve.

Where there is a high concentration of fine particles that tend to stick together and wont separate using just mechanical shaking then wet sieving is used and if the sieve particles are mixed with material like silt or clay they cannot fit through the openings and can clump together.

5 vibrating screen common problems and how to solve? | m&c

5 vibrating screen common problems and how to solve? | m&c

There are many kinds of vibration screens, such as electromagnetic vibration screens, circular vibration screens, linear vibration screens, etc. The latter two belong to inertial vibration screens, which are commonly referred to as vibration screens. In daily production, vibration screen will encounter a variety of problems, such as poor screening quality, bearing overheating, abnormal sound, wrong technical indicators and so on.

Table of Contents 1. Poor screening quality1) Screen hole blockage2) serious wear of screen hole3) Non-uniform feeding of sieve4) too thick material on screen5) insufficient inclination of screen surface6) The motion direction of eccentric block is not in the same phase2. Bearing overheating1) too small radial clearance of bearing2) too tight top of bearing cover3) Bearing oil shortage or excessive, oil pollution or inconsistency3. Abnormal sound when the sieve is running1) Spring damage2) Bearing wear3) Bolt loosening of fixed bearings4) Untightened screen4. Technical indicators do not meet the requirements1) The sieve cannot start or its amplitude is too small.2) Insufficient rotational speed of sieve3) The Vibration Force of the Screen is Weak4) The amplitude of four points of the sieve is inconsistent5. Severe or damaged parts of sieve1) Pipe Beam Fracture2) Beam fracture3) Fracture of screen frame

There are many factors affecting the screening effect, including the nature of feeding, equipment factors, operation factors and so on. The reasons for poor screening quality include blocking of sieve hole, serious wear of sieve hole, uneven feeding of sieve, too thick material on sieve and insufficient inclination of sieve surface.

When the mud content and water content in the feed are high, the material will stick to the sieve hole and block the sieve hole. At this time, the sieve hole should be cleaned first, and then the spray amount and the inclination angle of the sieve surface should be adjusted appropriately.

When the screen is used for a long time, the wear of the screen hole will be serious and the screening effect will be seriously affected. At this time, the wear screen hole should be repaired. When the wear situation is very serious, the replacement of screen mesh should be considered.

When the feeding trough of the sieve is too narrow, the material can not be uniformly distributed along the whole sieve surface, which makes the sieve surface inefficient to use, and will affect the screening effect. At this time, the width of feeding trough should be adjusted to make the feeding of sieve uniform.

The excessive thickness of material on screen may be caused by the increase of feeding quantity, blocking of screen hole and small inclination angle of screen surface. At this time, it should be adjusted according to the specific situation.

For the circular vibrating screen, the most common reason for the poor screening effect is the inadequate inclination of the screen surface, so it is necessary to pad the back support. In practical application, the inclination angle of screen surface is more suitable when it is 20 degrees. The inclination angle of circular vibrating screen is generally 16-20 degrees. If the inclination angle is lower than 16 degrees, the phenomenon that the material on the screen is not moving smoothly or rolling upward will occur.

For linear vibrating screen and high frequency vibrating screen, the poor screening quality may be related to the movement direction of eccentric block, because two groups of eccentric blocks with the same mass need to rotate in self-synchronization and reverse direction to produce a single exciting force along the vibration direction at each instant, which has a fixed angle with the horizontal direction, so that the screen box can move in a reciprocating straight line. If not in the same phase, the direction of excitation force and direction of vibration will not overlap, and the effect of efficient screening will not be achieved.

Because the bearing on the vibrating screen bears a large load, a high frequency, and the load is always changing, the bearing must adopt a large clearance. If the bearing with ordinary clearance is used, the outer ring of the bearing must be grinded again to make it a large clearance.

There must be a clearance between the cover and the outer ring of the bearing to ensure the normal heat dissipation and certain axial movement of the bearing. The clearance can be adjusted by a gasket between the end cap and the bearing seat.

The technical indicators of the operation of the sieve include the rotational speed, vibration force, amplitude and frequency of the sieve, etc. Common fault types are: the screen can not start or the amplitude is too small, the speed is not enough, the vibration force is weak, the four-point amplitude is inconsistent, and so on.

When the vibration screen can not start or the amplitude is too small, the first consideration should be whether there is an electrical fault. Damage of motor and insufficient voltage can lead to faults. When there are no problems in the above aspects, we should start with the mechanical aspects. Whether the material on the screen surface is heavily accumulated or not, if so, it should be removed in time; whether the bolts on the coupling of the exciter fall off or not, whether the grease is caked; if so, the bolts should be tightened in time and the grease should be replaced.

Insufficient rotational speed may be the electrical reason. At this time, we should find out the reason and deal with it in time. It may also be that the transmission tape is too loose. At this time, we should tighten the transmission tape.

The inconsistency of four-point amplitude of sieve may be caused by the asynchronism of two exciters on the same axis or material segregation. At this time, adjustments should be made to make the two exciters work synchronously and eliminate material segregation in time.

(a) The thin wall of pipe girder may lead to fracture. At this time, the same type of thick wall pipe or the first type of pipe girder should be selected, but it should not be too large or too thick, because this will increase the vibration quality of the sieve and bring many problems;

B) There must be horizontal and vertical pressure strips at the joints of the sieve plates of dehydration and de-mediation screens. If there is no longitudinal pressure strip, water will leak from the gap between the sieve screens and wash down the pipe girders, which are easy to break at the scouring point.

D) If the fracture of the pipe beam is not serious, in order not to affect production, the pipe beam can be repaired to continue to use. When repairing, the weld should be along the longitudinal direction of the pipe beam, and no transverse weld must be allowed, otherwise the pipe beam is more likely to fracture from the transverse weld.

Cross beam fracture is mostly due to the long working time at critical frequency, a large number of high-strength bolts to tighten the side plate are relaxed, serious deformation of the spring makes a great difference between left and right, or it may be that the weight error of eccentric block is too large, causing structural damage and cross beam fracture. At this time, the damaged structural parts and beams should be replaced, bolts should be tightened, and the quality of eccentric blocks should be adjusted.

The sieve frame is liable to break because of tremor. The best way to solve this problem is to thicken the side plate or add additional plate to the local area of the side plate near the exciter to enhance the rigidity of the whole sieve frame.

Thanks for explaining that you should replace screen mesh if it has been used for a long time. This makes sense, because that way you can save money by getting more efficient results. Ill have to look for a wire mesh screen.

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