VIBRATING SCREEN TYPES

Screen Types

Inclined Screen

Inclined screens are the most basic type of screen, fixed to an inclined frame at an angle of between 15° and 30°. The entire body of the screen vibrates on helical springs circularly with the same characteristics and material flow is supplied by gravitational acceleration.

The slope of the inclined screen is fixed, although the stroke can be adjusted to the required level. The general working stroke of an inclined screen is between 8 and 12 mm, and design of inclined screens permits changes to this stroke through the addition or removal of additional eccentric masses on the exciter.

The exciters of inclined screens are generally driven by an external electric motor that transmits the power via a belt and pulley mechanism. Vibromotor applications are not preferred for inclined screens due to their fixed condition working principle.

Inclined screens are generally designed with multi deck arrangements, which allows material to be classified the between 2–5 grade types. Additionally, these screens are generally fitted with an impact area directly before the screening section begins that breaks up the material and causes any long pieces to lie flat during screening.

Inclined screens are comprised of eight basic components, being the side walls, decks, screening media, exciter, electric motor, motor console, spring and spring supports. The most critical factor in inclined screens is their weld-free design. All of the parts mentioned here are assembled with bolt and nut connections to prevent the cracking and failure to the screen body associated with welding.

The advantage of the circular vibrating exciting mechanism used in inclined screens relates to its simplicity, its low maintenance need and its cost-effective design.

Horizontal Screen

A horizontal screen is a non-conventional design that has unique properties that differentiate it from other types of conventional screen. Its most obvious advantage is its working angle. While conventional screens work at an angle of between 15° and 30°, horizontal screens work in parallel to the ground, or at a slight incline of between 0° and 5° degrees.

Horizontal  are equipped with triple drive mechanisms that produce an elliptical vibration motion at the required stroke and slope. As mentioned at the exciter mechanism section above, the triple drive mechanism combines the linear and circular vibration types in elliptic vibration. In this way, the advantages of both vibration types are combined in a horizontal , so that while the material is being transporting horizontally at a determined velocity through the linear vibration motion, plunging is prevented due to the circular vibration characteristic of the elliptical motion.

The stroke of horizontal may be adjusted in a range of 14–20mm, although they generally operate with a stroke of between 16 and 18 mm and with a 750 rpm rotational speed. The material flow rate in the  media varies between 0.2 m/s and 0.25 m/s. The mass flow rate depends on the differences of the phase angle between the eccentric masses.

The triple drive mechanism is driven by an electric motor, with power transmitted by a belt and pulley mechanism. There is a possibility that the belt may come away itself during operation as a result of the high stroke working conditions associated with horizontal  A new belt stretching mechanism has been designed to overcome this problem, and all the power transmitting mechanisms in horizontal  have been equipped with belt stretching mechanisms.

Have brought many advantages to operations, although there are some disadvantages, the most critical being the complexity of the triple drive mechanism. In fact, triple drive mechanisms have a sufficiently robust design to overcome any condition, however maintenance procedures are not short, although the robustness of the design means that frequent maintenance is unnecessary.

Banana Screen

Banana or multi-slope  are capable of achieving exceptional throughput per  area. These  have high capacity, low bed depth and high velocity, and may include any number of deck slopes, from two to as many as six, varying from 45º through to horizontal on the final slope.

Banana  are excited by a vibromotor located on the top of the . As mentioned, the exciter section of banana has a segmented deck structure, causing the linear motion created by the vibromotor to accelerate the material differently at each deck surface due to the geometry of the , ensuring effective  operation is achieved.

The feed section (highly inclined) of a banana  permits high velocity material flow, which serves for the quick removal of fine material. Midway along the banana , the resultant thinner bed stratifies quickly, and the remaining fine material (below the cut point) is d out more effectively than would be possible with a slower and thicker bed. The lower  slope (see diagram) slows the material down, allowing more efficient  of near size material at this point. The advantage of this is the quicker stratification provided due to the high velocity imparted by the banana shape.

The various slopes may also incorporate deck media with different apertures to meet the particular processing requirements. The  are commonly designed to fit modular rubber or polyurethane deck panels, although woven wire or punched plates may also be used, depending on requirements.

Dewatering Screen

De-watering have been designed to allow the drainage of slurry material water and to reduce the moisture rate of the material. These systems comprise a vibromotor pair, a vibromotor console, media and a ody. The  surface is slightly inclined (between 0° and 5°) to facilitate drainage and the working speed is between 1000–1500 RPM.

The counter-rotated vibromotors create a linear vibration that causes the body to shake together with slurry material. The water from the slurry materials is drained under the effect of vibration and flows through bottom side of the  surface as the material moves forward. In this way, a pool of water forms in the valley as sand builds up on the inclined surface. The uphill slope of the along with a discharge weir creates a deep bed that acts as a filter medium, allowing the retention of material much finer than the openings.

Different to dry material , dewatering work at G-forces in excess of “5g”, ensuring a perfect drainage operation. Generally operating within a range of 5g and 6g this pre-condition is necessary for a good dewatering operation.

The fabricated vibromotor console frame, as a vital component in vibration transmission, is stress relived due to the high G-force working conditions. The side plate and the vibromotor side plates of the console must be machined to exacting tolerances to ensure a precise fit, and consequently, a long operating life. The steel frame should be constructed with bolted connections to avoid the cracking associated with weld failures.

Due to the wet and corrosive environment of the dewatering , rubber springs should be used on the support legs to absorb the live frame vibrating loads, which will extend  life and maintenance periods.

High Frequency Screen

High-frequency are engineered to provide higher production capacities and more efficient sizing than conventional High-frequency operate with aggressive vibration applied directly to the , which allows for the highest capacity in the market for the removal of fine material, as well as chip sizing, dry-manufactured sand and more.1

Different to other type  the vibromotors of high-frequency  are mounted on each deck instead of on the body. Aggressive vibration is applied within a range of 3600–5000 RPM directly to themedia, allowing for higher capacity and more efficient sizing when compared with conventional . Under the effect of high-frequency vibration, a smaller bed depth is obtained, which allows for stratification and greater efficiency.

The high-frequency and low-amplitude operation ensure a faster material travel speed without loss of  efficiency. This combination of high frequency and know amplitude is ideal for fine material in which coarse material particles are lifted higher while the finer particles stay closer to , and as a result, the probability of separation is increased with high-frequency .

Grizzly Screen

Very coarse materials are usuallyusing an inclined  called a grizzly  Grizzlies are characterized by parallel steel bars or rails set at a fixed distance apart and installed in line with the flow of the material. The gap between the grizzly bars is usually greater than 50 mm, and can be as large as 300 mm, with a feed size of up to 1 m. Vibrating grizzlies are usually inclined at an angle of around 20° and have a circular or linear throw mechanism.

The bars are typically made from wear-resistant manganese steel and are usually tapered to create gaps that become wider towards the discharge end of the sto prevent material from wedging between the bars. Grizzly generally used as a feeder prior to the to supply the flow of correct-sized material through the

Designed to convey material while separating fines, Vibrating Feeders utilize smooth, controlled feed rates to maximize capacity. The grizzly bars are tapered to self-relieve, and feature adjustable spacing for bypass sizing. The feeder construction includes a heavy-duty deck plate with optional AR plate liners, while the heavy-duty spring suspension withstands loading impact and assists vibration.