The screening process in the crushing plant is an important phase in the production of aggregate materials. The aim of sieving is to obtain unwanted elements from the material and ensure that the product has the correct size distribution and quality.
A challenge with sieving is the fine balance between getting such an element bounced in the material that the unwanted is removed, while at the same time you have to avoid too much, which can lead to valuable materials being lost. It is important to run the sights correctly to achieve optimal performance.
Do you have problems with uneven spreading of mass on your sight decks? Can’t quite hit the aiming curve? Then these tips are perfect for you.
Too much bounce
If the masses bounce over the screening a little too quickly, you will not get an effective screening process. This can lead to only getting through a fraction of what is supposed to go through the screen, and not hitting the aiming curve. It is also a sign that the sighting is going too fast.
In such a situation, it can help to remove the unbalance weight to reduce the g-forces. This will concretely lead to less bounce in the sight deck. An added bonus of this is that your bearings will have a longer service life.
It is also possible to reduce the speed of the drive to reduce the speed of the sight. This can work well in some cases. It is nevertheless very important to note that you must never do this without first conferring with the machine supplier. It can have major and costly consequences if it is not done correctly.
Too little bounce
If you have too little bounce on the aiming cloth, you will not get an optimal aiming process either. You may have problems with not having enough power to push the masses through the meshes in the sieve cloth. This can cause you not to aim as much as you should, that you do not hit the aiming curve, and that you have problems with stones getting stuck in the meshes. This is because the sight moves too slowly, so that 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 put on more unbalance lots. The same appeal also applies here, do not do this without first conferring with the machine supplier.
It may also be worthwhile to test out alternative screening cloths for the one you are experiencing problems with. Variation in hole size, material and hardness can have a major impact on the efficiency of the screening process.
Choseing the right screen
Screens are used in the mining industry to screen materials during production. The screen is an important component in the process of sorting fractions. The three types of screens you often come across are: steel cloth, PU cloth and nylon cloth. Steel fabric is the most robust, but also the heaviest and often the most expensive. PU is more flexible and lighter than steel, PU works great in crushed stone but has a shorter lifespan than steel. Nylon is light and cheap, but tends to stretch and be damaged by impact.
In order to select the optimal screen for the plant, a number of factors must be considered, including: the type of material to be sieved, the size of the particles, the frequency of maintenance, the costs and environmental considerations. At Nordic Bulk, you can get tips from experienced technicians who will be able to advise you on the best screen for your current situation. It is important to choose the right screen to achieve optimal performance and economy on the plant. A poorly chosen screen can lead to incorrect screening and thus reduce the quality of the product and increase the costs of maintenance and replacement.
Clogged screening
Consistency and stickiness of the material, humidity, type of sieve, number of strokes and speed of the sieve machine are all factors that affect the properties of the screen.
When the top layer goes tight, none of the screens do their job. There are an incredible number of screens in various thicknesses and materials. E.g. Iseflex, finger sieves, side-tensioned and long-tensioned, rubber, PU or steel to name a few.
If you have the wrong cloth, it means more maintenance and lower quality of the final product.
We recommend that you carry out a screening cloth analysis to find out exactly what type of cloth is best suited to your work.
Uneven spread
It is important to ensure an even distribution of mass on the sieve. Too little mass will lead to too much bounce on the sight deck which will drastically affect the sight curve. Without an overlying mass that presses the fractions through the meshes in the sieve cloth, the mass will just bounce off the cloth. If you have problems with uneven spreading on the screening deck, a plow may be the solution. In practice, this means that you install some PU strips in the box, which will help to spread the masses evenly outwards. A simple and affordable solution.
Example of uneven spread:
Optimal operation
In order to run optimally, it is important to choose the right sight cloth, to adjust the sight paths to achieve the correct size distribution and to regularly maintain the sights to ensure that they function 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 in order to detect and correct any errors as quickly as possible. All in all, the screening process is a critical factor to ensure the quality of the final product and to achieve efficient production. It is important to invest time and resources in ensuring that the aiming process is run in an optimal way.
Example of good screening:
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