Sealing technology manual for the process industry - Hygienic design

Attention must also be paid to the absence of any dead space in the event of dynamic seals, such as rotary shaft seals. While rotary shaft seals are very difficult to clean, the HTS II 9539 with no dead space and with its protruding lip seal made of PTFE is barely subject to contamination and very easy to clean. European Hygienic Engineering and Design Group The EHEDG is an interest group for operators and suppliers of equipment for the production of food, pharmaceuticals and cosmetics as well as for test institutes and mainte- nance companies. Freudenberg is a member of the EHEDG and is very involved in advancing the interests of hygienic design, including through active participation in the devel- opment of recommended practice. Heat exposure of O-rings The selection of materials according to the operating conditions, taking into account the required purity with the corresponding conformities, is only the first step towards fulfilling the hygiene requirements. The most important duty of every plant operator is to know and to obey all legal requirements and procedures to ensure a proper product quality. Every food, pharmaceu- tical and cosmetic product must be clean and not endanger the health of the consumer in any way. A plant constructed according to hygienic design is charac- terized by good cleanability so that contamination by mi- croorganisms cannot occur. The more the use of the auto- mated CIP and SIP (Cleaning In Place/Sterilization In Place) processes spreads, the less equipment needs to be disas- sembled. This eliminates the possibility of visual control. It must therefore be possible to trust automated cleaning to achieve a good result and it must be certain that there are no dead spaces in which product residues can collect initially and microorganisms can settle later. This means that rectangular grooves with a degree of filling of about 80% are not permitted. Hygienically designed grooves are narrower and the evasion spaces for sealing materials are correspondingly limited. Elastomers and steel behave differently with respect to production and temperature. Elastomers have significant- ly greater manufacturing tolerances so that in the event of an incorrect design an overfilling of the groove may in extreme cases already exist during installation. Elastomers are incompressible and need an allowance for expansion. The thermal expansion of elastomers exceeds that of steel by a factor of 15 and must be taken into account. As a re- sult of overly narrow gaps, extreme stresses can arise dur- ing cooling, resulting in shearing of the material. HYGIENIC DESIGN 20 °C (68 °F) >100 °C (212 °F) 20 °C (68 °F) STANDARDIZED CONNECTIONS HTS II 9539 VL Version with no dead space and protruding sealing lip for applications according to hygienic design DIN 11864 Aseptic O-ring screw connection • Metallic stop • Leak-free • Aseptic and hygienic connections Technical fundamentals 28

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