Plastics Engineering - May 2014 - (Page 20)

Filtration: A Crucial Tool for Plastics Processors____________________ Gneuss's new fully-automatic and backflushing RSFgenius-M filtration system for highly contaminated materials Filter Types Different types of filters have different advantages. There will be minimal pressure disruptions with a continuous filter with backflush capabilities, explains Tuttle, but those filters work best when a company is running a single material. With piston screen changers, you can run a broader specification of polymers, and polymers with a broader range of viscosity, he says. in addition, when you select a screen changer or melt filtration system, adds gneuss, you need to consider the cost of the screen elements, the potential for creation of off-grade product during screen changes, throughput variation, and the value of backflushing waste from self-cleaning systems. You also have to look at the amount of contaminants you need to filter out, says Whaley, how fast a filter might get clogged, how fast a filter or screen can be changed, and whether changing a screen will cause a 30-second dip in quality, creating scrap you don't want. The type of application or product also impacts what type of filtration system and how much filtration you need to do, says Dana Darley, vice president and general manager of Process Control Corp. in Atlanta, georgia. "Filters are more critical in extrusion than in molding, in thinner products like film or multi-layer products for food packaging, in fiber extrusion, or when companies make bottles or anything related to food packaging," says Darley. "Those are the situations where you are going to have to filter finer to where the eye can't see." 20 Plastics industry consultant Tim Womer of TWWomer and Associates, llC (Edinburg, Pennsylvania, USA) agrees. "You see the use of filtration primarily on thin sheet, thin film, and cast film. For example, if blown film gets too many contaminants in it, it will put a hole in the bubble. And companies that make cast film for touch screens and TVs can't have any gels come through." A lot of it has to do with aesthetics, explains Womer. "You also see more and more companies doing sheet extrusion and pipe extrusion using filters because they run a large percentage of scrap. But when you are making a thick piece of material, filtration is usually not an issue." However, regardless of the product or application, the use of recycled plastics creates a greater need for filtration, particularly when companies use post-industrial scrap, says Darley. "They are always dirtier because of how often they are handled. it is off-line, off-spec material, and every time it is handled, there is the possibility of contamination." As a result, he says, "everyone is looking for filtration systems and screen changers with greater screen area to handle the increasing levels of contamination. Your melt filter or screen changer is your last line of defense." Whaley agrees: "With the increased use of recycled materials, everyone is looking to be able to filter further down the process area. They want less contaminants, larger filter areas." "K" Innovations At the K 2013 trade fair in germany this past October, Parkinson, for example, introduced an enhanced version of its Key Filters KCH Continuous Hybrid Screen Changer that doubles the filtration area of its two-year-old KCH product-designed for filtering lower viscosity and elastomeric materials. "By making novel modifications to the shape of the flow passage, we were able to double the filtration area"-and provide more capacity and a more even distribution of the polymer flow, says Whaley. The key: changing from a round to a square breaker plate. Meanwhile, gneuss introduced four new screen-changer models, including its rSFgenius-M rotary filtration system. it has a screen area twice the size of the standard rSFgenius, enabling companies to process and backflush materials twice as fast. it's aimed at recycling markets. Similarly, Maag introduced at K its new CSC-BFX backflush screen changer, which is designed to clean contaminated screen surfaces with no adverse impact on the | PlASTiCS ENgiNEEriNg | MAY 2014 | www.4spe.org | www.plasticsengineering.org http://www.4spe.org http://www.plasticsengineering.org

Plastics Engineering - May 2014

Table of Contents for the Digital Edition of Plastics Engineering - May 2014