PETpla.net Insider 04 / 2011

MATERIAL / RECYCLING 11 PET planet insider Vol. 12 No. 04/11 www.petpla.net ated, but also on the self-wiping capa- bility, conveying characteristics and stress applied to the material [1]. Volume flow calculation The volume flow rate has an important role in the calculation of the pressure at the tip of the screw and the power requirement of the system. The appropriate equations were developed, based on the conserva- tion laws and the respective geometric conditions. In the case of the Erd- menger profile, the equation could no longer be solved analytically and it was necessary to use computational methods. The use of a computer pro- gram for the calculation is always nec- essary for a conical system, since the geometric and processing conditions change with the axial position. Back pressure length The back pressure length is a critical design parameter for the pres- sure build-up zone. If there is insuf- ficient length in the pressure build-up zone, the preceding zone (frequently a venting/degassing zone) experi- ences an overflow. The back pres- sure length can be determined by transforming the pressure equation [1]. The length required for the conical system is defined by the maximum pressure at the tip of the screw for a specific volume flow. If this length is not provided, the discharge zone can no longer accommodate the mate- rial being conveyed, and material is forced out of the vent opening. Over 140 years of added value through innovative technology and reliability Consultancy | Turnkey systems | Single machines | Service Hall 14, Booth A14/B15 May 12–18, 2011, Düsseldorf Pass ion for Packaging. The new shrink packer: KHS Innopack Kisters SP Focus on saving energy and resources: Next-generation, film-wrapped multipacks - Fully closed shrink packs for maximum packaging stability - Cardboard pads and trays no longer necessary Direct online printing on the shrink film for reliability and flexibility New shrink tunnel for considerably reduced energy consumption khs.com Werner A., Christian S., Ernst W. Packing technology design engineers „Our Baby – Your Benefit“ Figure 1: Shear rate and dissipation in the discharge zone