Extrusion International 3-2018

30 Extrusion International 3/2018 MEASURING TECHNOLOGY PEXa Pipe Extrusion: Innovative Heating Technology based on Infrared Radiation Unique 4-strand conveyor oven The core element of the heating process is the unique conveyor oven which enables the process in the first place and ensures the specific high production quality. The perfect tuninig of the extruder and the extrusion die provides a good melt homogeneity at a very low mass temperature which is imperative for the cross- linking process that takes place after the pipe has passed the extruder. The innovative 4-strand conveyor oven features 12 infrared units and a specifically de- signed guide and deflection system to achieve the cor- rect cross-linking of the polyethylene. The required exposure to radiation has a direct influence on the haul-off speed. A very short exposure permits a high haul-off speed. When the pipe subsequently passes several infrared units, it is possible to increase the ex- posure period. As a result, the haul-off speed can be increased to a maximum of 36 m/min. During the pipe’s passage through the oven, the thermal- ly activated peroxide which is regularly distributed inside the pipe wall decomposes following an optimum wave- length distribution of the infrared radiation. Highly reac- tive components are produced (radicals). They spilt hy- drogen atoms from the polyethylene chains. In the now free spots the cross-linking process takes place through a recombination with other polyethylene chains. The particular advantage of the infrared heating process is that heat radiation penetrates the material much deep- er that pure thermal convection. As a result, a perfectly round pipe with a good geometry can be produced. Even smallest tolerances and an ovalness of less than 0,3 mm which is far below standard requirements can be adhered Picture 1: PEXLINK conveyor oven - 4-strand conveyor oven featuring a specifically designed guide and deflection system, a precondition for higher production speeds and higher outputs thanks to an extended residence time for each pipe dimension Floor heating, radiator connections, hot and cold water piping: PEXa pipes are used for many different applications. However, PEXa pipe extrusion still belongs to the most demanding processes encountered in the extrusion industry. Manufacturing companies are presentedwith significant challenges. One of the challenges is the cross-linking process of the involved polyethylene. iBA GmbH, headquartered in Melle (Germany) offers an efficient and innovative technical solution based on infrared heating. The system is called PEXLINK