Extrusion International 5-2019

42 Extrusion International 5/2019 PELLETIZING – CASE STUDY system for this application is made of stainless steel, as some of the melt components, such as flame retardants, are highly corrosive. On the custom production line, the SFS-3-3000 is located downstream of the second (cooling) extruder. To ensure an optimum fit, Maag replaced the extruder’s standard outlet flange with its own inlet flange, providing the best possible interface to the filter system. Maag also adapted the filter cartridges and the free space around them to this special task rheologically in order to achieve an opti- mum melt flow. A cooler additionally installed downstream of the filter further lowers the temperature of the melt in the filter under pressure from around 115 °C to around 90 °C, at which point an optimally fine-celled foam develops after the melt has exited the die of the foaming unit. Maag made the customer-specified cooler an integral compo- nent of the filter unit and delivered it in the form of an autonomous complete system with heating control and melt pressure monitoring as a side-entry plug-and-play solution (picture 3). Optimum results in production The SFS-3-3000 filter, optimized for the specific applica- tion, started operation at the end of June 2018. Since then, the filter has been able to pass up to 1600 kg of melt per hour at a pressure of 200 bar. The entire filter system is at operating temperature after a heat-up time of around 2 hours with the heater bands (picture 4) re- cording a heating output of 2 to 3 kWh during operation. During commissioning, Maag supported the customer in optimizing the process parameters so that good, saleable sheets could be produced after just a few hours. Lebert continues: “As the processors tell us, the SFS-3-3000 also met all the requirements one hundred percent right from the start. Even sheets thicknesses that had been consid- ered critical in the past were run with good results.” Long service life for increased cost effectiveness Like the smaller cartridge filter system, the newly de- veloped SFS-3-3000 also works statically, with no mov- ing parts. So there is no wear during normal operation. When the many months of service life finally come to an end, the cartridges can usually be replaced in the course of scheduled line downtimes, such as during the annual inspection, without the need for additional production stoppages. Soiled elements can be cleaned and reconditioned after removal. In order to avoid damage and associated cost, the reconditioning should be carried out by specialist contractors or directly by Maag. Even cartridges that have been damaged during handling can be cost-effectively fitted with new gauze for subsequent reuse. To minimize replacement downtimes, Maag offers complete exchange kits comprising the cartridge holder and the cartridges. Maag Pump Systems AG Aspstr. 12, 8154 Oberglatt, Switzerland www.maag.com K 2019: Hall 9, Booth A04 Picture 3: The integratedunit suppliedbyMaag consists of thefilter SFS-3-3000 and thedownstreamcoolingunit provided by the customer (left side) (©Maag) Picture 4: Threeheater bands keep thefilter at the specified temperature of 115 °Cduringoperation (©Maag)