An innovative FlexDisc filter for piston-activated screen changers substantially enlarges available filtration area without the need to increase machine size, enabling processors and recyclers to achieve finer filtration, higher throughputs, longer filter service life, and reduced specific backflush volume. Nordson Corporation recommends the BKG FlexDisc for increasing productivity and enhancing quality in bottle-to-bottle PET recycling, PET fiber recycling, and battery separator film applications.

The function of the hydraulic pistons, with which many BKG screen changers are equipped, is to insert screen cavities into the melt stream for filtration and to remove them for cleaning or replacement. In systems where FlexDiscs are used, each cavity contains a filter stack comprised of two to four FlexDiscs, depending on machine size. Each FlexDisc is equipped with two Nordson screen packs. As a result, there is two to 4.5 times more filtration area available for each cavity with the new FlexDisc than with conventional standard round screens, and 25% additional area (on average) when compared to the former FlexDisc version. The actual increase is dependent on machine size.

Screen changers equipped with Nordson’s backflush technology include the BKG V-Type 3G and BKG HiCon K-SWE-4K-75/RS. Backflushing diverts the contaminant from the melt stream. The greater filtration efficiency of the new FlexDisc reduces the frequency of backflushing and thus the amount of specific backflush volume.

As melt enters the filter stack from the upstream side, it is evenly distributed among the FlexDiscs, which are rheologically optimized to provide efficient filtration with minimal shear stress. At the same time, the structural integrity of the FlexDisc design enables it to withstand pressure differentials up to 130 bar (1,900 psi) during the backflush procedure.