Sieve opening refers toSieve surfaceOnperforation。Generally, there are round holes, long holes, square holes, triangular holes, fish scale holes and other holes.[1]The number of sieve openings is a numerical value used to indicate the size of sieve openings.Number of sieve openings/cmtwo, mesh number/inch and mesh number/cm.The larger the mesh number, theSieve numberThe larger the mesh is, the smaller the mesh net width (i.e. side length) and the mesh size are, and the smaller the particles obtained through screening are.[2]
Chinese name
Sieve aperture
Foreign name
sieve aperture
Concept
Hole on screen surface
Shape
Round hole, long hole, square hole, etc
Represent
Number of openings per unit length or area
Role
Optimize production capacity and improve screening efficiency
The effective area of the screen surface is large, and the screening efficiency is high.When the screening particle size is small and the water content is high, particles are prone to adhere nearby, thus blocking the screen hole.
2. Round hole
The effective area of the screen surface with circular holes arranged in parallel is the smallest, and the circular holes are suitable for screening materials with smaller particle size and higher moisture content.
3. Rectangular hole
The effective area of the screen surface is the largest. The rectangular screen hole is suitable for screening materials with small particle size and less flake particles, which can improve the screening efficiency. Its long hole direction follows the movement direction of the material on the screen surface.When the rectangular screen hole is used for wet screening, it can make the direction of the long hole perpendicular to the movement direction of the material on the screen surface, so as to facilitate the downward discharge of water and fine particles.[3]
Influence of mesh shape
The mesh shape directly affects the effective area of the screen,Effective areaIt refers to the ratio of the area occupied by the pure mesh of the screen to the geometric area of the screen surface, also known as the effective screen surface.The larger the effective area of the screen, the more the number of mesh on the unit screen surface, the greater the probability of material passing through the mesh, so the higher the production capacity and screening efficiency.In screening practice, the commonly used mesh shapes are round, square and rectangular.The holes on the punched screen surface are mostly round, while the woven screen surface has rectangular holes and square holes.Practice has proved that the effective screen surface area and the chance of ore particles passing through the screen holes are different for screen surfaces with different mesh shapes.The effective area of the sieve with rectangular mesh is the largest, followed by square mesh, and the effective area of circular mesh is the smallest, so the tenacity productivity per unit screen surface also decreases in the above order.Another advantage of the rectangular screen hole is that the screen hole is not easy to be blocked, because the ore particles pass through the screen: only three or two sides of the screen hole need to be contacted when passing through the hole, so the resistance is small.However, its disadvantage is that it is easy to make long and flaky ore particles pass through the sieve aperture, which makes the product particle size uneven.
It is better to choose the shape of the screen hole to match the shape of the material.Square holes shall be used for blocky materials, while rectangular holes shall be used for platy materials. Good screening results can be obtained by correctly selecting the shape and size of screen holes according to the characteristics of the screened materials.[3]
Mesh clogging
Announce
edit
During screening, according to the properties of material particles, various forms of mesh blockage will occur.The conditions for screen hole blockage are as follows:[3]
(1) Containing a large number of particles close to the separation point;
(2) Materials with moisture or hygroscopicity on the surface;
(3) Spherical particles or materials with multiple contact points to the sieve mesh;
(4) The material particle density is small;
(5) Static electricity will occur;
(6) Materials with good filling ability;
(7) Where materials have fibrous particles and other embolic particle shapes.
Because most of the material particles to be screened are irregular, the reasons for blocking are also diverse.In order to effectively prevent screen plugging, measures should be taken against the above screen hole plugging conditions, such as vibrating screen, vibrating screen with hitting ball, anti blocking rubber screen surface, etc.
When the particle size of the material is fine, the mud content is high, and the screening particle size is small, the moisture plays a decisive role in the blocking of the screen.When the moisture content increases to a certain extent, there will be wedge-shaped moisture, which will generate cohesion between particles or between particles and wire mesh.The smaller the particle size is, the greater the influence of the contact points between particles and the cohesion between particles in unit volume will be, so as to form particle agglomeration and block the sieve aperture.[3]
