The screening process in the crusher is an important phase in the production of aggregates. The aim of screening is to separate unwanted elements from the material and ensure that the product has the correct size distribution and quality.
A challenge with screening is the fine balance between getting enough bounce in the material to remove unwanted elements, while avoiding too much bounce, which can lead to the loss of valuable materials. It’s important to run the screens correctly for optimal performance.
Do you have problems with uneven spreading of mass on your screening media? Not quite hitting the target curve? Then these tips are perfect for you.
Too much bounce
If the masses bounce over the screen too quickly, the screening process will not be effective. This can result in only a fraction of what should pass through the screen and miss the aiming curve. It is also a sign that the visibility is too fast.
In such a situation, it may help to remove imbalance weights to reduce g-forces. Specifically, this will result in less bounce in the screen deck. An added bonus of this is that your bearings will have a longer lifespan.
It is also possible to reduce the speed of the drive train to reduce the speed of the screening. This can work well in some cases. However, it is very important to note that you
never
do this without consulting the machine supplier first. This can have major and costly consequences if not done correctly.
Too little bounce
If you have too little bounce on the screen cloth, you will not get an optimal aiming process. You may experience problems with insufficient force to push the masses through the mesh in the screen cloth. This can lead to you not aiming as much as you should, not hitting the aiming curve and problems with stones getting stuck in the mesh. This is because the visibility is too slow, so you lose too much g-force.
The solution to this challenge is to do the opposite of the previous example, i.e. increase the speed or add more imbalance weights. The same advice also applies here, do not do this without consulting the machine supplier first.
It may also be worthwhile to test alternative viewing screens to the one you’re having trouble with. Variation in hole size, material and hardness can have a major impact on the efficiency of the screening process.
Choosing the right screen cloth
Screen cloth is used in the mining industry to screen materials during production. The screen cloth is an important component in the process of sorting fractions. The three types of screen fabric you often encounter are: steel mesh, PU mesh and nylon mesh. Steel mesh is the most robust, but also the heaviest and often the most expensive. PU fabric is more flexible and lighter than steel mesh, PU fabric works great in crushed stone works but has a shorter lifespan than steel mesh. Nylon canvas is lightweight and inexpensive, but tends to stretch and be damaged by impact.
To select the optimal screening cloth for the facility, a number of factors must be considered, including: the type of material to be screened, the size of the particles, the frequency of maintenance, cost and environmental considerations. At Nordic Bulk, you can get tips from experienced technicians who will be able to advise on the best cloth for your particular situation. It is important to choose the right screen cloth to achieve optimal performance and economy on the site. A poorly chosen fabric can lead to incorrect screening, reducing the quality of the product and increasing maintenance and replacement costs.
Tight meshes in the vision screener
The consistency and stickiness of the material, humidity, type of screen, number of strokes and speed of the sscreening machine are all factors that affect the properties of the screening media.
When the top layer gets clogged, none of the fabrics do their job. There are an incredible number of screen cloths in different thicknesses and materials. You have modular fabrics, Iseflex, finger screens, side-tensioned and long-tensioned fabrics, rubber, PU or steel to name a few.
The wrong fabric means more maintenance and lower quality of the end product.
We recommend that you carry out a screen cloth analysis to find out exactly what type of cloth is best suited to your work.
Uneven spread
It is important to ensure even distribution of mass on the machine. Too little mass will lead to too much bounce on the deck which will drastically affect the curve. Without an overlying mass to push the fractions through the mesh in the screen cloth, the mass will simply bounce off the cloth. If you have problems with uneven spreading on the screen deck, a plow can be the solution. In practice, this means installing some PU strips in the box, which will help to spread the masses out evenly. A simple and affordable solution.
See an example of uneven spread:
Optimal operation
To run optimally, it is important to choose the right screen cloth, to adjust the screen paths to achieve the right size distribution and to regularly maintain the screens to ensure they work optimally. An experienced operator will be able to assess the material and adjust the aiming parameters to achieve the desired result. It is also important to have good monitoring and control of the screening process to detect and correct any errors as quickly as possible. All in all, the screening process is a critical factor in ensuring the quality of the final product and achieving efficient production. It is important to invest time and resources in ensuring that the screening process is run in an optimal way.
See an example of good aiming: