Trommel Screens

A trommel screen comprises a cylinder formed from screening media that rotates upon an axis slightly inclined to that of the horizontal. The feed material enters the trommel at the upper elevation and is transported by the rotation of the cylinder until 'oversize' discharges at the lower end. Undersize is discharged through the walls of the cylinder. The advantages of trommels are: lack of vibration and simple, low-cost structure; ease of multiple sizing by a single unit; rotation promotes dis-aggregation of material and the trommel may fulfil the role of a washer also. Disadvantages are the relatively low capacity and difficulty of maintenance of the screening surface. In most modern installations they have been replaced by the combination of a rotary washing barrel (scrubber) and inclined vibrating screens. However, they remain popular for low-capacity, mobile units.