What is a screening process?
The sifting process is about sorting materials and fractions. The screening process is usually part of the overall process in a material handling facility. Screening ensures that the material is divided into the correct fractions and increases the quality of the end product.
How do we run efficiently?
Underload
If you run too little material at a time, you may find that the masses bounce quickly over the screen without making proper contact with the screen. If you experience this, you will not get an effective screening process. This can result in only a fraction of the mass that should pass through the screen, and that the aiming curve is missed. This is also a sign that the visibility is too fast.
- Some measures you can take to increase efficiency are 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 sieve. 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.
- It can increase the effect of the skitting process if you run more material so that the material has a good and steady flow over the screen cloth. If the material is denser, it can help to press the masses closer to the screen cloth and “push” the masses through the cloth.
Overload
If you have too little bounce on the screen cloth, you will not get an optimal aiming process. In the case of overload, there may be problems with insufficient force to push the masses through the meshes in the screen cloth as there is too much material. 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.
- In such a situation, the solution is often to do the opposite of the previous example, i.e. increase the revs or add more imbalance weights. 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.
Uneven spread on the sieve deck
It is important to ensure even distribution of mass on the sieve. Too little mass will lead to too much bounce on the sieve deck which will drastically affect the sieve 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.
Tight meshes in the vision screener
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.
The consistency and stickiness of the material, humidity, type of sieve, number of strokes and speed of the sieving machine are all factors that affect the properties of the sieve cloth.
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.
Want more information about the screening process and screen cloth? Feel free to contact us!
Read more:
The huge difference of the right sight cloth
How to avoid downtime in the crushed stone plant
The 5 most important questions to ask when buying conveyor belts