MELT FILTRATION | PROCESSING
working principle avoids the formation of ‘black spots’. The user also benefits from the lower melt losses which is achieved thanks to the newly developed discharge unit. Whereas the normal figure for piston filters is 1-2%, with the Laserfilter it is just a fraction of this.”
Obermayr says the Laserfilter is now being used more and more rather than the piston filter, particularly in the direct processing of PET flakes to make semi-finished or end products. The high process stability, which Erema attributes to its constant-pressure operation, is said to be a key factor in its selection. The company also says that, while the maximum level of contamination that can be handled by a piston filter lies between 0.05-0.1%, the Laserfilter processes input material with a degree of contamination of more than 1%. This means greater flexibility in being able to handle increasing contaminated in post-consumer input material. “With the PET Laserfilter we are talking about
screen life of five to twelve weeks,” Obermayr says. “You mustn’t underestimate the fact that the daily screen change by the operator which is necessary with a piston screen changer is no longer required and this reduces the risk of operating error considerably.”
Taking the pressure At the recent Fakuma show, Nordson introduced new screen packs for its BKG screen changers that withstand the pressures of extrusion – providing high filtration and optimum melt flow while ensuring a long working life. One reason for the enhanced performance of these new screen packs is a robust multi-layer structure that prevents failures caused by the pressure differential – of up to 200 bar – encoun-
Right: Nordson installed candle filters to upgrade a BKG POLY melt filter for PET at Köksan in Turkey
tered during filtration. One such example is ‘screen dimpling’, in which the mechanical stress forces screen layers into the holes of the breaker plate that supports the screen in the cavity. This distorts the screen,
breaking the peripheral seal and causing contaminants to bypass the screen and become part of the end product.
Taking on change Parkinson Technologies has
been offering the KCH continuous belt screen changer in its Key Filters range for several years. Since the 2012 launch of the original KCH,
marketing manager Brian Lundgren says Parkinson Technologies has been making refinements as well releasing new options – such as its “spent screen shear” and ScreenLync technology – focused on increasing reliability and efficiency. “Parkinson saw a growing need in the com- pounding market for a way to decrease downtime when making a material, grade, or colour change,” he says. In such applications, Lundgren says there is a need to limit cross contamination, which in many cases requires replacement of the breaker plate and/or filtration screen. The result is what he says is an innovative
quick-change breaker plate, the KCH-SB. This has been engineered to drastically reduce the amount of time it takes to replace a breaker plate and introduce a fresh clean screen into the process. “The breaker plate’s unique design allows rapid change out of the breaker plate in under five minutes, which normally could take up to four hours in downtime,” Lundgren says. Without the use of tools, the clean breaker plate is actuated into position while pushing the contaminated breaker plate out of the melt stream.
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CLICK ON THE LINKS FOR MORE INFORMATION: �
www.fimic.it �
www.cofit.com �
www.bdplast.com �
www.ettlinger.com �
www.psi-polymersystems.com �
www.adgs.net (ADG Solutions) �
www.erema.com �
www.gneuss.com �
www.nordsonpolymerprocessing.com �
www.parkinsontechnologies.com
January/February 2019 | PIPE & PROFILE EXTRUSION 39
Left: Erema now offers Laserfilter models for PET as well as polyolefin processing
PHOTO: EREMA
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