The combination of ultrasonic and air cleaning first shown at the POWTECH 2007 and used for keeping the screen fabric clear enables Allgaier to optimise the performance of tumbler screening machines quite decisively.
Increase in separating precision
Tumbler screening machines are particularly suited to screening products with fine and ultrafine particles. In this case, products that are difficult to screen are screened with the support of ultrasonic or air purification devices. Superimposing ultrasonic and air cleaning in the marginal area of the round screening insert proves particularly effective. The marginal particles are screened in this zone. The air loosens the screening material, whilst microvibrations generated by ultrasound overcome the forces holding the particles together, thereby increasing the separation precision.
The highly effective combination of both cleaning processes significantly improves yield. Tests with ultrafine polyamide powder that is difficult to screen revealed an increase in yield of +65 % compared to screening with ultrasound support alone or +43 % compared to screening with air cleaning alone.
The throughput also increases when using the ultrasonic/air cleaning process, namely by +68 % compared to the ultrasonic cleaning and +86 % compared to air cleaning.
The new combination cleaning process means ultrafine screening is possible with mesh widths down to 0.032 mm using tumbler screening machines. Ultrasonic air cleaning allows economical screening of products with a sharply defined separation precision. The complicated and cost-intensive process of fractionation using sifters can be dispensed with.
Application areas include: plastics, cellulose, powder coatings, toner, wax, metals, pearlite, silicon, abrasives, coke, gypsum, quartz sand, enamel powder, starch, rice flour, etc.
The combination of ultrasonic and air cleaning has been protected by a utility model and can be retrofitted to existing tumbler screening machines without difficulty.