process feature | Screenchangers and melt filtration
Kreyenborg has redesigned its V-Type Screenchanger for greater efficiency
through a port underneath the screenchanger housing. The company says that this creates a cleaner, safer environment for operators. The new back flush screen- changer can process materi- als with very high levels of contami- nation.
Melt Filtration Products has
introduced its AutoScreen Max continuous automatic screen- changer for use in high throughput, high extrusion pressure applications. It is designed to provide uninterrupted extrusion during screen changes. It incorporates the company’s Extrusion Pressure
Control (EPC) system that automatically maintains a selected melt pressure delta. This feature keeps the melt pressure entering the die within a selectable pressure range, regardless of changes in material bulk density or contamination levels. The result is a continuous, stable and uninterrupted extrusion process, says the company. The AutoScreen Max has a small footprint and
requires no hydraulics or pneumatics. There are no breaker plates or screen packs to replace.
Maag’s FSC double screenchanger has been designed to minimise maintenance costs
Key resource Parkinson Technologies says that its Key Filters KCH continuous belt melt filter, which was initially targeted at low viscosity materials when it was launched at NPE in June 2012, is now proving effective for a wide range of polymers. “The KCH was developed as a bridge between our
KCN non-actuated continuous belt melt filter and our KC line of continuous belt melt filters that use a hydraulic puller to actuate screen movements,” said John Whaley, business manager for Key Filters. “The result is a machine that is flexible enough to behave
like a KC machine, offering instant screen movements on softer polymers, and a KCN, offering great performance on hard thermoplastics.” In compounding applica-
tions, uniform extrusion
pressure is required to ensure quality mixing as well as rate control in the extruder. Because the KCH can move the screen very slowly across the melt stream there is no pressure disruption throughout the entire
production run. In addition, the unit can be adapted to match the configuration of a twin-screw extruder to maximise the flow area. The KCH uses a dedicated PLC to monitor extrusion
pressure and quickly react by moving the screen to keep this pressure uniform. It has demonstrated its ability to process polymers ranging from TPEs and TPOs with Shore A hardness values as low as 30, through to thermoplastics such as PP, PC, HDPE, PET and R-PET. This can be achieved on the same machine running the same screen and with leak-free, uniform pressure operation. The KCH has also successfully run a nylon blend filtering down to 40 microns. “Parkinson Technologies is very excited about this
new machine. It’s a highly cost-effective solution for many filtration applications where high performance, productivity and reliability are required,” says Peter Termyn, the company’s president and CEO. Italy’s Fimic, which is represented in North America
by ADG Solutions, has added a screenchanger that can handle higher throughputs in plastics recycling opera- tions. The SCF-700 model can clean up contaminated resins at rates of 6,000-10,000lbs/h (2,720-4,535kg/h). The screenchanger is said to be capable of handling
scrap with up to 3% loadings of contaminants without a slowdown or stoppage of the process. Even contami- nants close to an inch (25mm) in diameter do not pose a problem.
The self-cleaning cycles are subject to automatic
PLC control. In each cycle, as molten polymer enters the screenchanger, contaminants build up on the stainless steel screen plate. The build-up continues until the back pressure reaches a preset level. This actuates a rotating blade which sweeps the screen and purges the contaminants through a central discharge port. Typically the screen does not need to be touched or changed more often than every week or two, depending on the material being processed. Fimic now makes five models of the continuous
34 FILM & SHEET EXTRUSION | December 2012/January 2013
www.filmandsheet.com
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