How Does A Vibrating Screen Work?

2024-04-02 | Author: SBM

What's a Vibrating Screen?

Vibrating screen plays a crucial role in mining, aggregate processing and many other industrial sectors by efficiently sorting material mixtures into uniform sizes. Their efficiency and effectiveness directly impact the overall productivity of processing operations.

Vibrating screen is versatile machinery used across many industries for separating materials by size. They perform an essential sizing function through applying precisely controlled vibrations that cause smaller particles to pass through apertures while retaining over-sized materials on the screening surface.

As one of the most important screening equipment, vibrating screens have undergone continuous improvements in design and manufacture to suit an expanding range of applications. Understanding their working principles and various classifications helps optimize selection and operation for maximum efficiency.

Classification of Vibrating Screen

Here are the main classifications of vibrating screens:

Based on direction of vibration:

1. Linear vibrating screen: Motion is along one direction only and imparts a straight-line motion to the particle. Commonly used for coarse materials.
2. Circular vibrating screen: Motion is in a circular/elliptical manner with both horizontal and vertical components. Suited for both coarse and fine materials due to more complex motion.

Based on screen type:

1. Inclined screen: Screening frame is placed at an angle to utilize the cosq effect for particle stratification and separation.
2. Horizontal screen: Screening frame is horizontal and relies on centrifugal force separation. Mostly used for washing and dewatering.

Based on screen applications:

1. Grading screen: Used for classifying different particle sizes into various product streams.
2. Scalping screen: Used as pre-screening equipment to remove oversize particles.
3. Dewatering screen: Helps separate finer sized solid particles from liquid for dewatering purposes.

Based on drive system:

1. Electromagnetic vibrating screens: Use electromagnetic exciters for vibration generation.
2. Spring vibrating screen: Depend on spring systems to distribute vibration to screening surface.
3. Eccentric vibrating screen: Most common type with vibration generated via unbalanced weight eccentric shafts.

Working Principle of Different Vibrating Screen

All vibrating screens employ linear or circular vibratory motions. Their configuration and drive determine the precise motion:

Circular Vibrating Screen

Circular motion vibrating screens employ eccentric vibrators that generate vibrations in a circular or elliptical path. Both vertical and horizontal components characterize the motion trajectory.

This more complex gyratory motion agitates particle masses better, ensuring intimate contact with screen surfaces for thorough separation. Capable of multi-directional circular vibrations of screen decks, they are suited for wet and fine particle processing with throughputs up to 1,000 tons per hour.

Screen aperture selection and vibration parameters can be tailored per material properties for optimized classification. The superior wet screening capacity makes circular screens most versatile vibrating machines.

Linear Vibrating Screen

Linear screen impart a straight-line vibration force in one direction to particle masses. The simplest design, they typically feature electromagnets, springs or offset weights that oscillate the screening media horizontally.

Motion is non-complex and motion stroke length per unit time is greater than other screens. This suits large particle sizes but is less suited for wet and fine materials requiring complex motions.

Throughputs of 50-100 tons per hour are achievable with cost-effectiveness for coarse material separation tasks.

Eccentric Shaft Drive Systems

Regardless of screening motion, the drive mechanism is a crucial component. Eccentric shafts are the most utilized drive since they generate powerful gyratory vibrations from a small power source:

1. Eccentric weights are attached to the shaft ends and rotate at high RPM, creating an imbalance that results in gravitational forces.
2. Bearings on the shaft convert these unbalanced rotating forces into vibratory motion that is transmitted to the screen box via base supports.
3. Shaft rotation influences both the motion magnitude and phase angle that governs screening efficiency.
4. Torque and speed are precisely variable to suit material parameters through the electric motor.
5. The linear or circular motion produced guarantees consistent material streaming over screen surfaces during separation.

Eccentric shaft drives offer operational reliability and adjustable performance not seen in other vibration generation methods. Their compact design lends to versatile onsite installation too.

Double & Triple Deck Vibrating Screen Configurations

Multi-level screening classifies materials into sequential size fractions through stacked vibrating screen decks:

Double Deck Screens

Two decks are vertically stacked over a common base, creating an upper and lower screening surface. Material is fed at the top and undergoes primary and secondary screening stages.

Undersize particles from top deck discharge directly while oversize pieces vibrate further on the bottom deck. Used for two-stage classification purposes.

Triple Deck Screens

A third intermediate deck is added between the top two levels to separate material into three fractions. Each deck has independent exciters to synchronize vibrations for smooth feeding between layers.

Material is graded into three size ranges with fewer oversized rejects in a compact arrangement. Often applied where close material conformity is required.

Multi-deck screens leverage vibratory separation over increased surface area for high-capacity, multi-fraction classification in fewer machines occupying less floor space than single units. Proper inter-deck sizing maximizes output.

Vibrating Screen Media Selection

Optimum screening performance relies on suitable mesh or aperture mediums to control particle flows:

Woven Wire Mesh

Stainless steel is commonly used material for its longevity even in tough applications. Irregular apertures filter particles based on shape and size.

Best for crude separation of mixed materials like minerals and recycling wastes. Offers structural integrity despite impacts.

Perforated Steel Plates

Thick steel sheets are precision-punched with pre-defined aperture arrays for consistent filtering by size. Durable for high-impact applications.

Polyurethane Panels

Flexible polymer sheets have uniform slots or holes for precise sizing. Gentler on fine and easily damaged particles. Chemical-resistant.

Fabric Bands

Strong woven fabrics like nylon, polyester provide an economical solution for moderate loads. Easy-wearing.

Proper media choice aligned with material abrasiveness prevents premature wear, plugging and production downtimes. Welded or bolted securing ensures against dislodgement during vibrations.

SBM's S5X Vibrating Screen

Introduction to the S5X Vibrating Screen

The S5X vibrating screen is one of the most successful and widely used vibrating screen designs, which delivers industry-leading performance across mining, aggregate, and industrial mineral processing applications.

SBM's S5X vibrating screen addresses common issues faced by traditional models through innovation informed by extensive industry experience. Field surveys of mining and crushing sites, combined with over 30 years of engineering expertise, enabled R&D teams to develop a pioneering screening solution.

Representing an advanced technological achievement, the S5X caters to demanding heavy and medium-duty operations including fine screening, primary and secondary crushing, and material classification. Its modular design incorporates dynamic finite element analysis for maximum fatigue endurance.

Benefits of the Vibrating Screen

High throughput capacity

The S5X's multi-layer dynamic vibration system and effective screen area enable very high throughput capacities of 50-650 tph, maximizing productivity.

Premium screening efficiency

With adjustable eccentric masses and multi-dimensional vibrations, the S5X can achieve screening accuracies of <5% and consistent gradations.

Low maintenance cost

Durable design and components ensure minimal wear parts replacement costs over long lifespans of 15+ years even in harshest environments.

Energy efficiency

Low energy consumption across all load ranges contributes to reduced operational expenditure.

Easy operation

Control panel is ergonomic and easy to use by all operators with minimal training required.

Versatile configuration

Available in single, double or multi-layer models, the S5X can be optimized for scalping, classifying or dewatering applications.