processing feature | Melt filtration
Trendelkamp’s latest model is the TSK-XRS, its first
production unit with four screens
a filtration unit holds multiple candles. The advantage of the candle, Bartl explains, is its
ability to increase filtration area in a relatively compact unit. The filtration units achieve surface areas of up to 21,000 cm2
. A conventional flat screen would need to
be three to four times bigger to provide equivalent filtration area, he says. Some applications in particular benefit from
expanded surface area and the greater filtration this provides. Wire and cable compounds, for example, need extremely fine screening to filter out minute impurities that can damage the insulation layers of high-voltage cables. At the other end of the spectrum is recycling, which can introduce a range of contaminants to a compounding line. A Coperion screen-changing system for
Key Filters’ seven KCH screen-chang- ers include this 4.5-inch model for twin-screw lines
high-volume compounding typically has two slides powered by hydraulic cylinders. One slide is on top and one is on the bottom; each has two cavities. During processing, melt flow splits and passes through the top and bottom cavity. When it’s time to change a screening element, the cylinder moves the dirty cavity out of position and replaces it with a clean one in an operation that only takes 1 to 1.3 seconds, Bartl says, so flow is essentially uninterrupted.
Controls count Trendelkamp emphasizes the importance of customer consultations to optimise the selection and installation of screen-changers, placing particular emphasis on control and instrumentation systems. “We continue to work closely with our
customers to help them achieve versatile screen-changing options that position them to better capitalize their compounding line investments,” says Todd Reed, the German company’s sales manager for the Americas. One area where this pays off is in the growing use of “smart indicators” – sensors and controls – that the
company supplies for its filtration systems. “These indicators let users change the functionality of their filtration systems based on their need for more flexibility in
compounding,” Reed notes. Trendelkamp has supplied
controls for 20 years, but demand
has been especially strong in recent years, as compounders broaden the types of materials they work with, add lines and take on more demanding
52 COMPOUNDING WORLD | July 2014
polymer compounding applications. The sensors and controls, which the company designs and produces itself, are menu driven and address a number of processing needs. Some, for example, detect temperature and pressure fluctuations in melt flow and post operator alerts. Others can be adjusted for changing throughput rates caused by material tweaks, colour changes or additive loadings. The purpose is to give compounders a set of controls linked to processing parameters that optimize the filtration performance of screen-changers. The controls are attached to the company’s continu-
ous screen-changers. Many compounders initially speci- fy standalone controls, but as their familiarity with them grows and process needs change, they can add sensors and integrate operations into a system-wide application. Meanwhile, Trendelkamp has added a four-cavity
automatic back-flush screen-changer to its line-up. The TSK-XRS model, which begins shipping this month, has two hydraulic cylinders (or “bolts”), each equipped with a pair of the company’s special filters. These are rectangular with a slight outward curve toward the melt flow, which exposes as much of the filters as possible to the melt and assures a compact unit size. Reed says that the company has supplied a few
four-cavity screen-changers in the past on a special basis. The TSK-XRS, however, is Trendelkamp’s first four-cavity production model. The four-screen configu- ration is designed to reduce shear and pressure drops, as well as generating low-pressure fluctuations during back-flushing. The model works with almost all materials, is suitable for use with highly contaminated melt, and is applicable to compounding, pelletizing and recycling among other operations. Key Filters has also been working on controls and components, notably for its flagship KCH line of
www.compoundingworld.com
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