Screening machines for grading
In mechanical process technology, grading describes the separation of solid mixtures according to their particle size. The material being screened is split into multiple groups according to predefined particle size criteria. Usually the largest and the smallest particle sizes are separated off as they are classed as ‘out of place’ particles. The correctly sized particles can then be graded further into different particle sizes as needed. The grading screening machines from Engelsmann can screen for up to eight particle size groups at the same time depending on the task at hand.
Bulk solids
The JEL Konti can grade material into up to three fractions. It stands out from other screening machines as the screen inserts can be changed quickly and because it’s suitable for tasks that have high hygiene requirements, thanks to a special hygienic design option.
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Bulk solids
The JEL VibRS can grade material into up to six fractions. Thanks to the stackable screening decks, the circular screening machine takes up very little floor space.
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Bulk solids
The JEL VibSpeed can grade material into up to three fractions. Thanks to the hinged cover, the screening trough and screen inserts can be accessed easily.
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Bulk solids
With the JEL Freischwinger you can grade into between three and twelve fractions depending on the task at hand. Thanks to the gentle operation, even very delicate products can be screened without any problems.
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Bulk solids
The JEL Regula has been specially developed for grading expandable polystyrene (EPS). The special screening machine can grade material into up to eight fractions.
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Bulk solids
Thanks to its modular cartridge design, the JEL Phoenix can carry out multiple screening tasks at the same time. The screening machine makes it possible to perform graded screening into up to five fractions.
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The so-called selectivity is the most important criteria when it comes to grading and the machine used. This determines how precisely the individual fractions will be separated from one another. With grading sieving machines, the selectivity should ideally be 100%. However, with industrial grading, a selectivity of one hundred percent can only be approximated in practice. The degree of selectivity will be influenced mostly by the movement of the screen and the dwell time of the product on the screen mesh.
Screen movement and dwell time
With the grading sieving machines from Engelsmann, the product can be graded very selectively (up to 99%). This is mainly because the vibration and oscillation amplitude as well as the screen inclination are adjustable. As a result, the intensity of the screen movement, and therefore also the dwell time of the product on the screen mesh, can be influenced and perfectly adjusted to the product which is to be graded. For example, poorly flowing or sticking products require the screen inclination and oscillation amplitude to be adjusted in a different way than if it was for an easilyflowing solid in order to make it move on the screening surface.
Because of their linear movement, long-stroke sieving machines guarantee a very selective grading. Thanks to the solely horizontal movement of the screen, the product always remains in contact with the screen and does not jump up and down. In addition, the dwell time of the screened product on long-stroke screening machines can be easily increased by placing several screen inserts with the same mesh size behind or on top of one another. Thus increasing the course that the product must cover on the screen surface.
Optimal product distribution
An optimal distribution of the product on the screen mesh also has a positive influence on the selectivity of the grading, therefore Engelsmann grading sieving machines can be fitted with a separator sheet or bar. This distributes the product over the entire screening surface after it is fed into the sieving machine so that the screened product doesn’t build up too much on the screen mesh beneath the inlet nozzle. This ensures that during the grading, the product being screened is always in complete contact with the screening surface and can be optimally screened off.
Custom-fit covered screen inserts
Precisely covered screen inserts also play an important role when it comes to grading, as they also influence on how selective the screening result is. If the mesh is not evenly covered, the individual meshes can sag or warp. Inserts with non-homogenous mesh sizes inevitably lead to poor screening results during grading. Thanks to Engelsmann’s internal testing procedure, screen inserts can be measured after covering, in accordance with DIN ISO 9044 and DIN ISO 3310-1, and the homogeneity of the screen mesh can be checked. Customers that buy a screening machine or replacement screen insert from Engelsmann can also receive a corresponding test report upon request and therefore increase process safety.
The grading can be carried out with various products and particle sizes in practice. The range of applications of the grading sieving machines from Engelsmann ranges from dust particles with a diameter of just 40 μm, up to coarse products with a diameter of 20 mm.
