Vibrating screens selection for screening process in industrial fields
Screening is the process of separation of bulky products, which are initially part of a heterogeneous bulky mass with different particle sizes. The process takes place by passing the products through the selection decks of the vibrating screens, which are provided with net openings of different sizes.
Based on the amount of material that passes through the openings, the vibrating screens are classified as follows:
- SAFETY SCREENING
when the amount of product passing through represents within 90 ÷ 100 % of the entire amount of product
- SCREENING /SELECTION
when the amount of product passing through represents within 10 ÷ 90 of the entire amount of product
- SCREENING OR DEDUSTING
when the amount of product passing through represents within 0 ÷ 5 % of the entire amount of product
The vibrating screens have an important role in the processes of many industrial fields; knowing the exact type of machine that should be inserted in the plants, understanding the requested function thanks to the acquired experience and then developing the machine that best suits these needs is always a challenge. Therefore, when talking about vibrating screens and vibrating process in general, it is better to rely on professionals in the industry such as Vibroprocess, as they continuously developed and updated their applications making them more efficient and effective.
The know-how acquired over the years allows Vibroprocess machines to be successfully used in various fields, that involve several different processes.
Studying the products for developing a vibrating screen
A first basic step for developing a vibrating screen is studying the product to be processed. Using empirical values of the materials obtained through lab tests, the vibrating screen is designed according to the features and requirements of the product to be processed.
The study of the particle, its composition, its shape and hardness is also very important.
Other important factors are:
- The analysis of the materials particles size, useful for knowing the breakdown percentage of the materials on each selection surface of the vibrating screen and the final percentage ( under the screen ) after the screening.
- The specific weight, factor used to calculate the necessary screening area, the volume and layer that will slide along the screen, adjusting based on the capacity the length and width of the vibrating screen.
- The temperature, a parameter that should be taken into consideration when choosing the selection surface, especially when deciding the material that should be used for its construction, if the processed materials are hot you should choose special application for the parts that come in contact with the product.
- The humidity, a factor that affects the shape and inclination of the vibrating screen, if processing materials with high humidity or that ten to fold, you should choose inclined vibrating screens. If processing dry materials, that tend to fluidize, you should choose horizontal screens, linear screens or screens with reduced inclination, thus improving the screening performance.
- The size, in other words selecting the appropriate particles (by size) for each surface of the vibrating screen. The net openings should be smaller or equal to the size of the material being fed in the vibrating screen
Vibrating screen design
In order to obtain maximum screening performance, the main features and functions of the vibrating screens were designed according to the features of the materials to be processed.
The screening efficiency depends on:
- the power of the vibrating screen that should be enough as to free any critical size particle from the selection surface.
- the distribution of the material on the vibrating screen, it should be homogeneous, without any dimples .
- the layer of product, that should be limited so that each elementary particle of the product may come in contact with the selection surface of the vibrating screen along its path.
- the chemical-physical features of the product ( humidity, shape, grain size ,… )
A) Vibration principle
1 Electrical vibrator
1 Eccentric shaft
1 Electrical vibrator (not in the centre of gravity)
1 Eccentric shaft (not in the centre of gravity)
2 Counter-rotating electrical vibrators
2 Counter-rotating eccentric shafts
1 Mechanical oscillator
B) Selection surfaces
Given the variety of products treated in the screening processes due to chemical-physical features, environment conditions, desired screening performances and other difficulties met along the process, intensive research was made in the field of selection surfaces in order to improve the efficiency of the vibrating screens, according to the technical requirements of the process that are continuously evolving.
Each selection surface has its own features and therefore it should be chosen according to your specific needs.
The iron nets and sheets are highly economic; the rubber and polyurethane, although more expensive, are more wear-resistant; while the Aisi ones are suitable for chemical and food products.
Classification of the selection surfaces:
Steel – high resistance sheets
– coating sheets
– casting sheets
– drilled sheets
PU or Rubber – panels system . hard or soft
. with trapped balls
– rubber fixed on sheets
– tensioned system
Net – braided wire
– welded wire
– anti clogging wire
Grids – grids with welded bars
– special grids for mining materials (GRIZZLY)
– special grids made of anti-wear materials (TABLE SHAKEOUTS)
C) Inclination and incidence
– HORIZONTAL SCREENS click for more details
– INCLINED SCREENS click for more details
Vibroprocess offers customized vibrating screens fully meeting the plant and process requirements of the customer.
From the first phases of the partnership with its clients, Vibroprocess is involved in constantly improving its products offering efficient and effective vibrating screens designed according to the product to be processed
This is ensured by years of experience in this field and in screening in general.