Savings due to recycling, maximum cleanness, no interruotion
Thomas Pokladek, Sales Area Manager West, Maag Pump Systems Textron GmbH (Germany)
The recycling of plastic material is not only for ecological but also for economical reasons more and more important. Increasing prices for raw material, increasing consumption of for example PET as packaging material for the food and beverage industry results in many new developments and techniques how to clean and recycle materials up to an almost virgin quality. Part of this process always is a mechanical filtration which will take out solid particles of the melt. One of the Maag continuous screen changers is the CSC-BF-4F, specialised for the recycling process. The screen changer is characterized by 75% of the screen surface is in production during backflush; minimum pressure fluctuations; effective, short backflush; direct flow to the screen; screen retainer with 95% opensurface; minimum consumption of backflush material. The series CSC-BF-4F preferably are used for the processing of very high contaminated polymer melts, for which a self cleaning of the filters with a backflush system is required and a process interruption is not acceptable. To avoid a high screen change frequency for the processing of very high contaminated plastics, the use of screen changers providing a very big filtration area and which can regenerate their filters automatically by reversing the melt stream, are recommended. But it is decisive, that already filtered material will be used for the backflushing only. For the development of the model, described here, it was utmost considered that there is an optimal melt flow channel geometrie, that a filtration area as big as possible is provided and that an effective detaching of the contamination from off the filters is possible. It furthermore was very important, not to reduce the provided filtration area by the retainer rings, which have to be used for the backflush procedure. Because of the arrangement of the flow channels it is possible to backflush the screens which are still in the housing although the other screens are being replaced in the mean. As backflush sequence proceeds automatically, the screen?s lifetime can be multiple enlarged and this reduces the expenditure of service time for the screen changing only. With special option this version is also available as pressure and volume constant execution.