5 Ways to Improve Screening Efficiency

Screening is a very important link in the sand and gravel production line. Screening efficiency refers to the ratio of the actual screened product to the mass of the material contained in the feed material that is smaller than the sieve hole. Screening efficiency directly affects production efficiency, so let’s share it today Here are 5 ways to improve screening efficiency.

Three types of screening
1. Pre-screening
When the particle size range of raw materials is large, large pieces of material need to be roughly broken by jaw crusher first, while small pieces of material can be directly screened and then sent to follow-up equipment in order to avoid over-crushing, without the need for jaw crusher. The screening at this time is called pre-screening. For sand and gravel processing plants, pre-screening can avoid ineffective crushing of materials, thereby improving the production capacity of crushing equipment and reducing power consumption. Leakage type feeder or special vibrating screen are ideal pre-screening equipment.
2. Check and screen
Some production lines also add a screening process after crushing to control the particle size of the crushed products (unqualified materials are screened out or returned to the crusher for crushing until the particle size requirements are met), which can be called inspection screening. Its purpose is to screen out the unqualified large pieces from the products of the crushing equipment so that the product does not exceed the upper limit of the required particle size, but this screening form is rarely used in actual production.
3. Finished material screening
A production line processes aggregates of more than one kind of particle size, and different users have different requirements for the particle size of sand and gravel aggregates, so they are screened into products of various particle sizes and supplied to various users.
5 Ways to Improve Screening Efficiency
1. Large-scale sieves are used, and the large-scale circular vibrating sieve increases the vibration force and amplitude, which increases the impact stress and shear stress of the sieve plate on the material, so as to overcome the adhesion between the ore particles and reduces the screen surface. Clogging allows the materials to be screened to quickly complete loosening, layering, and sieving. Due to the improvement of the operating conditions of the sieve, the screening is improved.
2. Increase the screening area. The practice has proved that reducing the amount of material on the unit screen surface can improve screening efficiency. When the actual amount of material on the sieve surface is about 80% of the sieve capacity, the sieve screening efficiency is the highest. When sieves are used as grading equipment, due to the large number of fine-grained grades, sufficient sieving area and appropriate lengthening of the sieve surface should be ensured, so that the aspect ratio of more than 2:1 is conducive to improving sieving.
3. Use a reasonable inclination angle to control the flow speed of the material on the screen surface. Generally speaking, if the inclination angle is large, the material movement speed on the screen surface is fast, and the production capacity is large, but the efficiency is low. In order to obtain higher screening efficiency, the moving speed of materials on the screen surface is generally controlled below 0.6m/s, and the screen surface should maintain an inclination angle of about 15°.
4. Adopt an equal thickness screening method. As the screening process proceeds, the thickness of the material on the screen surface gradually becomes thinner from the feeding end to the discharge end, resulting in an unreasonable feeding phenomenon that the screen surface is first tightened and then loosened. Therefore, broken line screen surfaces with different inclination angles can be used. , to control the different movement speeds of the materials in each section of the screen surface, so that the ore flow slopes forward, thereby improving the chance of passing through the sieve of the difficult-to-sieve particles at the discharge end.
5. Adopt a multi-layer sieve with enlarged sieve holes. The “difficult to sieve particles” and “obstructed particles” (particles larger than sieve holes) in the feed of ordinary single-layer sieves almost all move from the feed end to the discharge end, thus affecting the stratification and sieving of medium and fine-grained materials. The multi-layer sieve with gradually increasing sieve holes and gradually decreasing sieve surface inclination from the lower layer to the upper layer is used, that is, different inclination angles and sieve holes are used for materials with different particle sizes, and the materials are completed on the upper, middle and lower sieve surfaces respectively. Loose, layered, pre-screened, and fine-grained sieves to overcome blockage of sieve holes and improve sieving efficiency.