Selecting the appropriate screen type and size are crucial to achieve the desired product you’re looking for. Screening is a mechanical process that separates materials based on their size. Selecting the appropriate screen size and type are crucial to achieve the desired product you’re looking for. Today we’ll be taking a look at the different screen types and determine the size needed for efficient separation of materials.
Common types of screening equipment
When it comes to screening for material separation, there are plenty of choices available. The choice of screening equipment can have a direct impact on efficiency, operating costs, and many more. Here are the three most common types of screening equipment used today:
- Trommel screens
Trommel screens are well-known in the waste processing industry where it is used to segregate materials. It consists of a cylindrical drum with perforations that rotate to separate the materials. Trommel screens are usually elevated at an angle where the materials are fed to promote material flow. Separation is achieved when the fed materials spiral down the drum where smaller materials pass through the screen while the larger ones pass through the other end of the drum.
Trommel screens require minimal investment, but at the cost of efficiency. Screening equipment like this one require a larger footprint to effectively screen plenty of materials and usually come with material binding issues. Brushes can be attached on the screens to prevent material from binding to the perforations, but the wear rates are high and this could lead to additional operating costs.
- Vibrating screens
Vibrating screens are one of the most important pieces of equipment in the mineral processing industry. These types of equipment are used to separate material containing solid and crush ores down to finer sizes. Vibrating screens can be built flat or on an incline for further efficiency. This type of screening equipment consists of an engine that creates vibrations and a screen that separates the materials. A catching area rests below the screen to catch finer materials once it is seperated.
Once assembled, the material is fed into the machine where the vibration will separate large materials from the small ones. Vibrating screens are mainly used in mineral processing applications where feed streams are required to be separated at a size of ½” or smaller.
- Disc screens
Disc screens are a great choice for screening biomass and other large particles.. It consists of a series of disc-shaped shaft assemblies that are adequately spaced. The discs from one shaft intermesh with the adjacent shaft that creates an open space between them. The material is fed onto the screen where smaller particles fall in between the disc spacings while the larger materials are conveyed by the discs and passed over at the end of the machine.
Disc screens are effective for screening biomass because it provides good agitation which is crucial for separating biomass that tends to stick together. These types of equipment are also capable of screening large materials like rocks without suffering extensive wear and tear from abrasion.
Factors to consider when choosing screen size
The need to produce material size to a rigid specification relies heavily on using the appropriate screen size. Different materials have different separation rates which is why it’s important to use the correct screen size for more efficient operation. The general characteristics of a material will affect its rate of passage through a given screen. And while actual scaled testing is the best way to accurately determine screen sizing, it can prove quite costly.
To achieve the proper screen size, there are a number of factors you should consider. Here are a couple of things worth considering to determine the correct screen size for your specific application:
The opening of a screening surface is crucial to the overall efficiency of separating materials. You have to consider the nominal size of the screening mesh along with the effective size of the mesh itself. Because of the chances of materials congesting on the screening surface, the probability of near-size particles passing through the mesh is reduced. The overall design of the screen surface will affect the equipment’s efficiency at separating materials.
To help determine screen capacity, consider the ratio between the screen surface and the area of the holes. Decreasing the space between the holes will allow you to increase the screen surface, thus increasing the screening equipment’s capacity.
Particle distribution refers to the sizes of the discrete particles in a given feed stream. The percentage of a material at a given size will help to determine a screening equipment’s capacity. The more material is required to pass through the screen, the larger the screen is required to accommodate the materials.
The shape of the materials that are fed into the machine will also affect the sizing of a screening equipment. A material’s shape in both the feed stream and its desired outcome will affect screen selection which is why it’s important to identify the characteristics of the material prior to screening.
The density of the material to be screened is described as the amount of bulk and load the equipment has to convey. The overall volume of the material should be considered when determining screen size for maximum efficiency. Maintaining an effective bed depth is crucial for separating low-density materials.
Bed depth refers to the screen’s ability to stratify material and allow finer particles to pass through the deck.
By increasing screen length, you can also increase screening efficiency by allowing a longer time for near-sized materials to pass through the screen. Different materials and applications require different screen lengths which is entirely dependent on the material’s characteristics.
Screening equipment is used in a wide range of industries. Choosing the correct type and size of screen is important to ensure maximum efficiency while lowering operational costs. These tips will help you choose the appropriate screen type and size to fit your specific applications.