1. Definition

A trommel screen (also called drum screen or rotary screen) is a screening machine whose main body is an inclined, slowly rotating cylindrical screen. Material fed into the drum tumbles and rolls as the drum rotates: fine particles pass through the screen openings (undersize), while coarse material travels along the drum and discharges from the lower end (oversize). Simple and reliable, it is widely used in aggregates, waste sorting, mining and coal industries.

2. Structure & Working Principle

Main structure:

• Drum: inclined cylindrical screen body (woven mesh or perforated plate, reinforced with rings and a tyre/race);
• Support system: frame and trunnion rollers that carry the drum and keep it in position;
• Drive system: motor + reducer driving the drum via gears, chain or friction rollers;
• Inlet/outlets: feed inlet at the high end, undersize collecting hopper below, oversize discharge at the low end.

Working flow: Feeding → Tumbling → Screening → Oversize discharge

• Feeding: material enters at the high end of the drum;
• Tumbling: the drum rotates slowly, lifting, rolling and tumbling the material so it fully contacts the screen surface;
• Screening: fines pass through the openings into the undersize hopper below;
• Discharging: coarse material rolls along the inclined drum and exits at the low end.

3. Classification

By drive: gear drive, friction-roller (trunnion) drive, chain drive. By drum form: single-drum, multi-drum (multi-stage combination). By screen surface: woven mesh, perforated plate, bar (rod) deck. By application: aggregate trommel, MSW (waste) sorting trommel, mining trommel, grain cleaning trommel, etc.

4. Key Technical Parameters (typical ranges)

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Note: typical ranges (schematic); refer to the specific model and manufacturer’s data.

5. Advantages & Limitations

Advantages:

• Simple structure, smooth and reliable operation, low maintenance;
• Good tolerance to wet, sticky and mud-bearing materials;
• Continuous tumbling reduces blinding compared with vibrating screens;
• Low noise; easy to enclose with a dust cover;
• Multi-drum designs can separate several fractions in one pass.

Limitations:

• Screening efficiency (especially for fine fractions) is lower than vibrating screens;
• Large drum footprint; high capacity requires a large diameter;
• High-moisture fine powder may still clog the screen;
• Screen replacement is time-consuming; maintenance requires downtime.

6. Typical Applications

Aggregate size classification, municipal solid waste (MSW) sorting, construction & demolition waste processing, ore classification, coal screening, grain cleaning and de-stoning, fertilizer pellet grading, dredged material treatment, etc.

7. Common Faults & Maintenance

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