Extrusion International 6-2019

34 Extrusion International 6/2019 MEASURING TECHNOLOGY ing improvement of material properties, single-layer pipes are not always able to fulfill the necessary requirements. Tecnomatic has well interpreted these customer needs and has developed, on the basis of the VENUS concept, a full range of die-heads for the production of 2, 3 or 4 layers polyolefin pipes even in big size. The VENUS MULTI pipe heads have implemented impor- tant technological features in order to reach the best pipes processing and to fit a wide range of materials at very high output. The spiral geometry has been especially optimized for the latest generation of PE and PP raw materials, while length, volume and pressure have been reduced. The heart of the VENUS MULTI consists of an innovative flow channels geometry, which has been calculated by consid- ering the current raw material. This geometry assures the same behaviour for pressure and distribution of the melt, in every pipe head of the range, also at very high output rate. The new feeding system of the spiral channels, as well as for the matching ranges and the small die sets contributes to reduce the working pressure. This influences remark- ably energy consumption during extrusion taking into ac- count that approximately 5 to 10% of the extruder power is necessary for the pumping capacity. Lower pressure also results in a lower increase of the melt temperature and with lower residence times assuring improved pipe’s char- acteristics with regard to OIT (oxidation resistance) values, extra weight and thermal and shear stresses reduction. Coated Pipes The inherent flexibility of polyethylene has enabled a wide range of techniques, including thrust boring, directional drilling and pipe bursting, to be used to install polyethyl- ene pipe systems. Multilayer pipe systems have been de- veloped with the specific objectives of improving the pro- tection of the pressure pipes during such installations and to maximize the quality of the pipe system. This pipe, with a peelable outer skin, has provided significant economic and environmental benefits in water distribution pipelines and it is currently being tested and introduced into the Gas distribution networks. The jacket is made of a specially modified polypropylene material, which protects the sur- face of the inner pipe against potential notches and cracks generally associated with demanding installation methods such as pipe bursting or wash-boring. Even extremely deep notches in the protective jacket will not be transferred to the inner pipe when it is eventually exposed to service-re- lated stresses. The core pipe is insteadmade fromPE resins. The dimensions of the core pipe match those of standard solid wall PE pipes. “Adhered” to the outer wall of the PE core pipe there is a tough skin, which is typically 0.6 to 0.7 mm thick for all current dimensions of this new multilay- ered pipes. The “skin” is added by a cross-head positioned before the last cooling bath. To fulfill the needs of coated pipes production with pro- tective layers, Tecnomatic has developed a full range of die-heads, based on spiral or radial technology suitable for both plastic or metal pipes coating with range from 5 to 800 mm, and solutions up to 4 layers. The die-heads are based on a typical spiral technology for large and single layer co-extrusion, while combined solutions with radial distributors or short path spiral are offered according to material characteristics or volume as for PA, EVOH, PVDF or adhesive bonds. 1 Dr. Frank, C., Röntgen- und Kameratechnik kombinieren. Inspektion, Sortierung und Analyse von Kunststoffpellets, Plastverarbeiter, Edition 10/2017, p. 116-120 SIKORA AG Bruchweide 2, 28307 Bremen, Germany www.sikora.net Caption 5: The X-ray based offline inspection and analysis systemdetects metallic contamination in plastic pellets