Trommel Screens: The Ultimate Guide

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Trommel screens are an essential tool for industries dealing with bulk materials, offering a highly efficient way to separate materials based on size. These rotating mesh drums are particularly suited for handling wet and sticky substances, ensuring maximum recovery of valuable fines while removing oversized materials. EDGE Innovate, a global leader in material handling solutions, offers a comprehensive range of trommel screens, including the EDGE TRM831, TRT622, TRT620, and TRT516, each designed to meet different screening needs.

What is a Trommel Screen?

A trommel screen is a rotating cylindrical mesh drum that sorts materials by size. As mixed materials enter the drum, smaller particles pass through the mesh openings while larger materials travel to the end of the drum, where they are collected separately. This process is commonly used for screening:

• Soil
• Sand
• Mulch
• Wood pellets/chips
• Compost
• Domestic waste

Trommels are particularly effective when dealing with materials containing moisture, paper, wood chips, plastic, or clay, as their rotating motion helps prevent clogging and ensures a consistent separation process.

How Does a Trommel Screen Work?

Load Hopper

Materials are first fed into the hopper, which transfers them into the trommel drum via a conveyor system. The rate at which the hopper feeds material into the drum is critical to the screening efficiency. Overloading the drum (beyond approximately 40% of its width) can lead to valuable fines being lost with oversized materials, necessitating reprocessing or for the drum to stall. Thankfully EDGE Innovate’s trommels are fitted with an Intelligent Load Management System to prevent drum overload. EDGE trommels are fitted with variable speed feed conveyors to manage material flow, allowing operators to optimize screening efficiency based on material conditions.

Trommel Screening Process

Once inside the drum, the materials are tumbled and aerated, helping to dry sticky substances and break up clumps. This motion, combined with the mesh openings, allows smaller particles to fall through while larger materials continue to the end of the drum. If the drum rotates too slowly, materials can clump together, reducing efficiency. On the other hand, excessive speed can prevent proper separation, as particles may remain suspended in the air rather than falling through the mesh.

 Factors Affecting Screening Performance

Trommels are typically operated at a 5-degree incline, with EDGE trommels offering adjustable screening angle allowing operators to change parameters depending on the material type and moisture content. Dry materials, such as sand, can be processed at steeper angles for faster separation, whereas wetter materials require a shallower angle and longer residence time for optimal results.

Screen Aperture

• The effectiveness of the screen depends on how much smaller the particle is compared to the mesh hole. Particles that are about half the size of the hole (near-size particles) have a lower chance of passing through compared to much smaller particles. The size of the drum affects the screening efficiency. Longer drums provide more residence time, improving separation, particularly for wet and sticky materials.

Rotational Speed

• Drum speed plays a critical role in material separation. Screening efficiency improves with increased speed up to about 50-60% of the critical speed. Beyond this point, efficiency drops sharply as material remains stuck to the screen surface. At 75% of critical speed, excessive agitation can keep materials airborne, preventing effective screening. Very low speeds reduce tumbling action and drop height, limiting throughput.

Material Velocity

• The slope of the drum, combined with its diameter and rotational speed, determines material travel rate and residence time. A lower slope increases the likelihood of undersized particles passing through, as they get more exposure to the mesh openings, improving efficiency.

Choosing the Right Trommel Screen

Trommel Size

The appropriate drum length and width depend on several factors:

• Moisture content of the material
• Type of material being screened
• Volume of material to be processed
• Desired product size

For wet materials, a longer drum allows more time for separation, making models like the EDGE TRM831 an excellent choice. Drier materials, which separate more easily, can be processed with a more compact trommel like the EDGE TRT516.

Space Considerations

EDGE Innovate’s range of trommels offer drum screens from 16’ long to 31’ long. The operating space available on site will be a major factor in choosing the correct trommel screen. For businesses operating in much smaller yards or urban settings, compact trommels such as the EDGE TRT620 provide high efficiency but in a compact footprint.

Why Choose a Trommel Over a Scalping Screen?

A trommel screen is often chosen over a scalping screen for applications where material separation requires more time and aggressive screening action. Here are the key reasons why a trommel might be the better choice:

1. Better for Wet & Sticky Materials – Trommels handle moist, clay-heavy, or sticky materials more effectively, preventing blockages that can occur on flat deck scalping screens.
2. Superior Fines Recovery – The tumbling action of a trommel screen allows more undersized material to fall through, improving fines separation compared to a vibratory scalping screen.
3. Reduced Wear & Maintenance – Trommels generally experience less wear than scalping screens because they rotate materials rather than violently shaking them, reducing impact and wear on the screening surface.
4. Longer Screening Time – Trommels provide a longer residence time for materials, ensuring better separation, especially for mixed waste streams.
5. Lower Noise & Vibration – Unlike scalping screens, which operate with high-frequency vibrations, trommels run more quietly, making them ideal for noise-sensitive environments.
6. More Versatile for Varying Material Types – Trommels can efficiently screen materials like compost, wood chips, and topsoil, which can be problematic for a scalping screen due to their irregular shapes and moisture content.

Benefits of Trommel Screening

Trommels are used to separate mixed aggregates into different-sized products, much like a large sieve. Key benefits include:

• Efficient separation of valuable fines, reducing waste
• Enhanced material recovery for resale (e.g., topsoil, compost, recycled concrete)
• Reduced transportation and landfill costs by processing on-site
• Increased operational efficiency and profitability

 Trommel Design Modifications

EDGE Innovate offers numerous customization options to optimize screening separation performance:

• Conveyors: Integrated 180° radial fines conveyors fitted across the entire EDGE trommel line allow for increase stockpiling capacities, reducing the need to double handle material.

• Mesh Panels: Available in sizes from 40mm to 6mm allowing users to select the optimal screen for their application. Larger mesh sizes are suited for coarse separation, while fine mesh screens are ideal for precise material recovery.

• Punch Plate Screens: Ideal for abrasive applications, minimizing media wear and preventing clogging.

• Lift and Cut Bars: Prevent material clumping and improve fine material flow.
• Track or Wheeled (tires) Configurations: Tracks provide stability on rough terrain, while wheeled mounted trommels enhance mobility between different sites.
• Grizzly or Reject Grids: Remove oversized materials before they enter the trommel, protecting the screen. Generally, reject grids are hydraulic operated via remote control to remove unwanted materials.

• Brush Systems: Keep the mesh clean during screening, preventing clogging.  A second trommel brush system can be added for extreme applications where blinding of the drum screen may occur more frequently.

• Spiral Drums: Hold materials in the drum for longer, improving separation quality.

• Magnet Systems: Remove unwanted ferrous materials via cross belt magnets or via magnetic head drums, ideal for demolition and recycling sites. Both options are available from EDGE Innovate.

Which Trommel is Right for You?

Selecting the correct trommel for your application ensures optimal performance and cost efficiency. Key considerations include:

• Production Requirements – What throughput does the operator expect to achieve?
• Material Type – What materials will be processed? Wet, sticky, or dry materials require different drum specifications.
• Site Restrictions – Does the operator have enough space to operate the trommel? Is the site too tight for stockpiling screened material, or is there ample space for loading the trommel?
• Budget Considerations – The equipment recommendation must align with the client’s budget while ensuring efficiency and productivity.

A larger drum increases screening efficiency due to extended retention time. The greater the frequency of material dropping to the screen bottom, the higher the chance of effective screening. For difficult-to-screen materials or high-separation requirements, a longer drum will yield superior results.

EDGE Innovate Trommel Screen Models

• TRM831 – The largest mobile trommel on the market, offering unrivaled production capacity and efficiency for large-scale compost, waste, and soil processing.

• TRT622 – A high-performance trommel that has set the benchmark for screening efficiency, featuring a 6′ x 22′ drum for maximum material retention and accuracy.

• TRT620R – Designed for operators using existing 6′ x 20′ drum screens, this model features a 180° radial fines conveyor for superior stockpile creation and flexibility.

• TRT516 – An entry-level trommel incorporating the best features of EDGE’s trommel line, including a radial fines conveyor, adjustable screening angle, and EDGE’s intelligent load management system.

Most models are available as wheel-mounted units for enhanced transportability and site mobility.

Where to Buy a Trommel Screen

EDGE Innovate has over 50 distribution partners worldwide offering clients a comprehensive selection of high-performance trommel screens, including the EDGE TRM831, TRT622, TRT620, and TRT516. Whether you need a large, high-capacity trommel or a compact, mobile solution, our team of material experts can help you find the perfect fit. Additionally, we provide a full range of complementary equipment, including slow-speed waste shredders, track feeders, and mobile conveyors.

Ready to optimize your material processing? Contact EDGE Innovate today to speak with our team of experts and discover the perfect screening solution for your needs!

ABOUT EDGE INNOVATE

EDGE Innovate develops, manufacturers and markets sophisticated technologies for shredding, stacking, screening and sorting of primary and secondary raw materials in production processes and recycling. Our Material handling and recycling range is made up of reliable, durable and cost saving products with a wide range of mobile stockpilers, tracked stackers, tracked and mobile feeders, trommels, slow-speed waste shredders, picking stations, material classifiers, roll-sizers and truck off-loaders. Our product range allows our customers; to shred, screen, separate, stockpile and size a vast array of materials

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