What are the reasons for the low screening efficiency of linear vibrating screen?
A linear vibrating screen is widely used in industries such as mining, metallurgy,chemical engineering, and building materials for separating and grading bulk materials. Its efficiency directly
affects production output, product quality, and energy consumption. However, in actual operation, many users encounter problems of low screening efficiency, which leads to poor separation results and increased production costs.
Reasons for Low Screening Efficiency of Linear Vibrating Screen
Improper Screen Media Selection:
Wrong Mesh Size: If the mesh size is too small, it can lead to blinding and reduced throughput. If it’s too large, it won’t effectively separate the desired particle sizes.
Inappropriate Material: The screen material (e.g., woven wire, polyurethane, rubber) needs to be suitable for the material being screened. Abrasive materials require more durable screen media.
Material Characteristics:
High Moisture Content: Wet, sticky materials can easily blind the screen openings, reducing the effective screening area.
High Clay Content: Clay particles can clump together and stick to the screen.
Varied Particle Shapes: Flat, elongated, or irregularly shaped particles can pass through undersized openings or cause blinding.
Excessive Fines: A high percentage of very fine particles can lead to blinding and reduce the overall efficiency.
Operational Parameters:
Feed Rate:
Too High: Overloading the screen can cause a thick material bed, preventing efficient stratification and particles from reaching the screen surface. It also reduces retention time.
Too Low: An excessively low feed rate might not create a consistent material bed, leading to inefficient use of the screen area.
Vibration Amplitude and Frequency: These parameters are crucial for effective material stratification and transport.
Incorrect Amplitude: Too low, and material won’t fluidize effectively. Too high, and it might “bounce” off the screen without passing through.
Incorrect Frequency: Needs to be tuned to the material characteristics and screen size.
Screen Angle (Deck Angle): The angle of inclination affects material speed and retention time on the screen.
Too Steep: Material moves too fast, insufficient time for particles to pass through.
Too Flat: Material moves too slowly, potentially leading to a thick bed and blinding.
Stroke Direction: The angle of throw from the vibrators influences material movement and stratification.
Screen Condition and Maintenance:
Blinding/Pegging: Screen openings getting blocked by near-size particles (pegging) or sticky material (blinding) is a primary cause of inefficiency.
Wear and Tear: Worn screen media can develop larger openings than intended, leading to poor separation. Worn support frames or springs can affect vibration characteristics.
Damage: Tears, holes, or deformities in the screen media will lead to immediate loss of efficiency.
Improper Tensioning: If the screen media isn’t properly tensioned, it can sag, leading to dead spots and poor vibration transfer.
Screen Design and Installation:
Uneven Material Distribution: If the feed is not evenly distributed across the screen width, parts of the screen will be underutilized while others are overloaded.
Insufficient Screen Area: The screen might simply be too small for the required capacity or separation task.
Structural Issues: Problems with the screen’s support structure, springs, or vibrator motors can lead to incorrect vibration patterns.
Dust and Fines Accumulation: In dry screening, excessive dust can interfere with particle movement and lead to blinding.
The main reasons for reduced screening performance usually include improper material characteristics, unreasonable feeding methods, inappropriate screen parameters,and equipment wear or improper maintenance. Factors such as excessive moisture,high viscosity, uneven particle size distribution, or blockages can reduce material stratification and hinder smooth screening. Similarly, low vibration intensity, incorrect screen inclination, and damaged screen meshes can also severely affect screening accuracy and throughput.
Therefore, understanding the key causes of low screening efficiency is essential for optimizing the working conditions of linear vibrating screens, prolonging their service life, and improving overall productivity.
