Vibrating screens play a crucial role in industries such as mining, aggregate processing, and material classification by efficiently separating materials of different sizes. However, screen blockage is a common issue that reduces screening efficiency, increases downtime, and raises maintenance costs.

Blockage occurs when materials such as wet, sticky, or irregularly shaped particles adhere to the screen mesh, clogging openings and restricting material flow. Factors such as moisture content, screen design, and improper vibration settings contribute to this problem.

Vibrating screen blockage prevention method

Vibration screen blockage is a common issue that reduces efficiency and throughput. Here’s a breakdown of methods to prevent it, categorized by approach:

1. Material Preparation & Handling:

Screening Beforehand: If possible, pre-screen the material with a coarser screen to remove oversized particles or debris that might cause blockage in the main screen.

Proper Material Drying: Excessive moisture is a primary culprit for blockage, especially with fine materials. Dry the material thoroughly before screening. Methods include:

Air Drying: Spreading the material thinly and allowing air circulation.

Oven Drying: Controlled temperature drying in an oven.

Fluid Bed Drying: Efficient for particulate materials, using heated air to fluidize and dry the particles.

Infrared Drying: Uses infrared radiation to heat and dry the material.

Material Conditioning: Introduce additives to the material to improve its flow characteristics. Examples include:

Anti-caking agents: Prevent agglomeration of particles.

Flow enhancers: Reduce friction and improve material movement.

Consistent Material Feed Rate: Avoid surges of material onto the screen. A consistent, controlled feed rate allows the screen to process the material effectively. Use feeders like:

Vibratory Feeders: Provides even and adjustable material flow.

Screw Feeders: Good for controlled metering of powders and granules.

Belt Feeders: Suitable for handling a wide range of materials.

2. Screen Design & Selection:

Appropriate Mesh Size: Choose a mesh size that’s suitable for the particle size distribution of your material. Too small a mesh increases the risk of blinding (where particles get lodged in the openings).

Screen Material: Select a screen material that resists wear, corrosion, and abrasion from the material being screened. Common materials include:

Stainless Steel: Durable and resistant to corrosion.

High Carbon Steel: Strong and wear-resistant, but prone to rust.

Polyurethane: Abrasion-resistant and flexible.

Nylon: Good for handling abrasive materials and materials that tend to stick.

Screen Type: Different screen types are better suited for different materials and applications:

Woven Wire Mesh: Common and versatile, but can be prone to blinding.

Perforated Plate: Stronger and less prone to blinding than woven wire mesh, but less efficient for separating fine particles.

Polyurethane Screens: Excellent abrasion resistance and self-cleaning properties. Can be molded into complex shapes for specialized applications.

Wedgewire Screens: Provides a high open area and reduces blinding. Good for handling wet or sticky materials.

Anti-Blinding Screen Designs:

Bouncing Balls/Rings: Small balls or rings placed under the screen that bounce and strike the screen mesh, dislodging particles.

Ultrasonic Vibration: Imparts high-frequency vibrations to the screen mesh, preventing particles from sticking.

Air Knives/Air Blasters: Use compressed air to blow away particles from the screen surface.

Flexible Fingers/Tines: Flexible elements that continuously agitate the screen mesh.

3. Vibration Screen Operation & Maintenance:

Proper Tensioning: Ensure the screen is properly tensioned. Loose screens vibrate excessively and can lead to blinding. Overly tight screens can be damaged.

Optimal Vibration Frequency & Amplitude: Adjust the vibration frequency and amplitude to suit the material being screened.

Higher Frequency: Better for fine particles.

Higher Amplitude: Better for coarser particles and materials that tend to clump. Too much amplitude can damage the screen.

Regular Cleaning: Clean the screen regularly to remove accumulated particles. Methods include:

Brushing: Manual brushing to remove surface buildup.

Water Washing: Washing with water and potentially detergents. Ensure the screen is compatible with the cleaning agents.

Compressed Air Cleaning: Blowing away particles with compressed air.

Regular Inspection: Inspect the screen for damage (tears, holes, loose wires). Replace damaged screens promptly. Check bouncing ball systems or other anti-blinding mechanisms for wear and tear.

Dust Collection/Containment: Implement a dust collection system to remove airborne particles that can settle on the screen and contribute to blockage.

4. Environmental Control:

Humidity Control: In humid environments, consider using dehumidifiers to reduce the moisture content of the air, which can help prevent material from sticking to the screen.

Temperature Control: Extreme temperatures can affect the flowability of some materials. Maintaining a consistent temperature can help prevent blockage.

Key Considerations for Choosing a Method:

Material Properties: Particle size, shape, moisture content, stickiness, abrasiveness.

Screen Size & Type: The type of screen and its dimensions will influence the available options.

Throughput Requirements: How much material needs to be screened per hour?

Budget: Some methods, like ultrasonic vibration, are more expensive than others.

Maintenance Requirements: How much maintenance is required for each method?

By carefully considering these factors and implementing the appropriate methods, you can significantly reduce vibration screen blockage, improve efficiency, and extend the lifespan of your equipment.

A linear vibrating screen is a screening machine that uses vibration to separate materials based on size. It operates using a linear motion, which is generated by two counter-rotating vibratory motors or exciters. These vibrations cause the material to move forward while allowing smaller particles to pass through the screen mesh, effectively sorting and classifying materials. The technical parameters of a linear vibrating screen can be quite extensive, depending on the manufacturer and specific application.

Linear vibrating screen technical parameters

1. Mechanical and Dimensional Parameters:

Screen Size (Length x Width): This is the active screening area, often in meters (m) or millimeters (mm). It’s crucial for determining the throughput capacity of the screen. e.g., 1.5m x 3m, 2m x 4m.

Overall Dimensions (Length x Width x Height): Total physical size of the machine, including the frame, motor, and other components. Important for space planning.

Weight: The total weight of the machine in kilograms (kg) or metric tons (t). Relevant for transportation and installation considerations.

Number of Decks: How many screening surfaces are stacked on top of each other. Single-deck screens perform a single separation, while multi-deck screens can perform multiple separations in one pass.

Deck Inclination Angle: The angle of the screen deck relative to the horizontal. This influences material flow rate and screening efficiency. Typically a small angle (e.g., 5-10 degrees).

Mesh Size (Aperture Size): The size of the openings in the screen mesh, in millimeters (mm) or micrometers (µm). Determines the cut size (separation size). Each deck in a multi-deck screen will have a different mesh size.

Mesh Material: The material used for the screen mesh, such as stainless steel (common grades: 304, 316), woven wire cloth, perforated plate, polyurethane, or rubber. The choice depends on the material being screened and the required durability.

Frame Material: The material used for the screen frame, typically carbon steel (with coating for corrosion resistance) or stainless steel.

Screening Area (Total): The total active area of all screening decks combined.

2. Vibration Parameters:

Vibration Frequency: The number of vibration cycles per second, measured in Hertz (Hz) or cycles per minute (CPM). Frequency affects the material’s agitation and movement on the screen.

Vibration Amplitude (Stroke): The distance the screen deck moves during each vibration cycle, in millimeters (mm). Amplitude influences the material’s throw and the screening rate. Often adjustable.

Excitation Force: The force generated by the vibratory motor to drive the screen, measured in Newtons (N) or kilonewtons (kN). It’s related to the motor’s power and the eccentric weight.

Vibration Direction: The direction of the vibratory motion, which is typically linear (straight line) for linear vibrating screens. The angle of the linear motion relative to the screen surface can be a factor.

Vibrator Type: The type of exciter used to generate the vibrations. Common types include:

Vibratory Motors (Unbalanced Motors): Two motors with eccentric weights rotating in opposite directions. This is the most common type.

Electromagnetic Vibrators: Used for smaller screens.

Mechanical Vibrators: Driven by belts and pulleys.

3. Operational and Performance Parameters:

Capacity/Throughput: The amount of material the screen can process per unit of time, typically measured in metric tons per hour (t/h) or kilograms per hour ( kg/h ). Capacity is heavily dependent on the material being screened, its particle size distribution, and the screen parameters.

Screening Efficiency: The percentage of material smaller than the mesh size that passes through the screen. A higher efficiency means less of the fine material ends up in the oversize product. Often expressed as a percentage (e.g., 95%).

Separation Size (Cut Size): The particle size that is being separated by the screen. Ideally, all particles smaller than this size pass through, and all particles larger than this size are retained on the screen. It’s determined by the mesh size.

Feed Size (Maximum Particle Size): The maximum size of the particles that can be fed into the screen without causing damage or blockages.

Feed Rate: The rate at which material is fed onto the screen, which directly impacts the screen’s performance and capacity.

Moisture Content (Maximum): The maximum allowable moisture content of the feed material. Excessive moisture can cause clogging and reduce screening efficiency. Expressed as a percentage.

Power Consumption: The electrical power required to operate the screen, measured in kilowatts (kW).

Noise Level: The noise generated by the screen during operation, measured in decibels (dB). Important for workplace safety.

Dust Emission: The amount of dust released during screening. This is important for environmental considerations, and often requires dust collection systems.

4. Motor Parameters (for Vibratory Motor-Driven Screens):

Motor Power: The power of the vibratory motor(s), in kilowatts (kW) or horsepower (HP).

Motor Speed: The rotational speed of the motor(s), in revolutions per minute (RPM).

Voltage and Frequency: The electrical power requirements (e.g., 380V/50Hz, 440V/60Hz).

Insulation Class: The temperature rating of the motor’s insulation (e.g., Class F, Class H).

Protection Class: The motor’s protection against dust and water ingress (e.g., IP54, IP65).

Number of Poles: Determines the synchronous speed of the motor.

5. Additional Features and Options:

Spray System: Water or liquid spray nozzles to help separate sticky or dusty materials.

Dust Cover: Enclosure to minimize dust emissions.

Screen Cleaning System: Devices to prevent screen blinding (blockage), such as bouncing balls, ultrasonic vibration, or rotating brushes.

Explosion-Proof Design: For use in hazardous environments where flammable materials are present.

Variable Frequency Drive (VFD): Allows for adjustable vibration frequency and amplitude.

Remote Control: For convenient operation and monitoring.

Material of Construction (Contact Parts): Specifies the materials used for parts that come into contact with the screened material (e.g., stainless steel for food-grade applications).

Lubrication System: Details of the lubrication method and required maintenance.

Importance of Specifying Parameters:

It’s crucial to specify all relevant technical parameters when selecting or designing a linear vibrating screen to ensure it meets the specific requirements of the application. Incorrect parameters can lead to:

Inefficient Screening: Poor separation of materials.

Low Throughput: Unable to process the required amount of material.

Equipment Failure: Overloading the screen or using it with unsuitable materials.

Increased Maintenance Costs: Frequent repairs due to improper operation.

Unsafe Operation: Noise, dust, and potential hazards.

When requesting information from a manufacturer, be prepared to provide details about the material you intend to screen, the desired throughput, and the required separation size. This will help them recommend the most suitable screen and provide accurate technical parameters.