Trommel screens are rotating cylinders made from cast iron and coated with a sheet of stainless steel. These cylindrical cylinder sections are referred to as trommels, which means “walls” in Dutch. The steel surface/sheet lends itself to adding “fines,” the smallest particle that can pass through the screen. The trommels are stationary, but the cylinder sections are rotated to allow the passing stream of material to pass through at various speeds.
As stated previously, the trommel screens are usually made from cast iron or cast steel and coated with a sheet of stainless steel. Most of them come as monolithic products, i.e., they are seamless and cannot be disassembled into pieces. Their dimensions vary from 1.5m to 3m in diameter and 2m to 6 m in length.
Further, a trommel screen is designed to screen large volumes of materials, such as soil. This process is termed screening or pug milling. The material which will pass through the screen may be screened at different grades depending on how fine or coarse the desired final product is. This device can be used to separate particles from sand or gravel by size (e.g., coarse), density (e.g., particle size), and specific gravity.
The trommel screens are typically used in manufacturing and industrial chemical industries. You can use it to separate particles (particle size) from a mixture of other materials by size, density, and specific gravity.
Additionally, trommels have been used for many years in the horticultural industry. They are a common feature of large farms where the main function of these devices is to separate leaf blades from other materials, reducing losses during harvesting or transport. Again, these trommels are designed to screen large volumes of materials.
How are Trommel Screens Used?
Trommels can be used to screen a wide range of materials, including:
- Soil
- Wood chips
- Stones
Trommels are often used for separating particles from sand, gravel, or other materials. They are also useful in the industrial chemical industry when you separate particles from other mixtures by size, density, and specific gravity.
The screen is covered with a thin sheet of stainless steel and mounted on an outer cylinder called a grizzly. The grizzly controls the size of the product that passes through the screen. When the grizzly is rotated at high speed, it breaks up clumps of material and allows them to pass through the screen. The material falls through the grizzly between two other rotating cylinders called trommels. The trommels separate the sand from the gravel or larger rocks, etc.
Different Types of Trommel Screens
There are two types of trommel screens: material trommels and object trommels. The main difference is that material trommels separate larger particles from finer grades in a product. In contrast, object-trommels are used to separate individual objects like stones from a mixture.
Sizes of Trommel Screens
The size of these screens depends on where they are used and what they are used for. Some of the more common sizes include:
- 10″ screen for sand, gravel and rock
- 8″ screen for wood and bark chips
- 6″ screen for fine sand, soil and stone
- 4″ screen for fine sand, soil and stones
- 2″ screen for screening small objects like pebbles from a mixture.
- 1/4″, 1/8″ screens for screening particles less than 0.015mm size in industries such as pharmaceuticals and chemical plants where cleanliness is essential.