Open processes put especially high hygienic demands on the food and beverage industry, since they function in facilities that are not closed off from the environment and thus need to be cleaned and sterilized regularly. Freudenberg-NOK Sealing Technologies has now introduced washers that produce excellent results in combination with standard screws in the splash zones of dairy operations. They consist of a flat metallic gasket and a trapezoidal, vulcanized-on elastomer bead.
Milk is a valuable yet sensitive raw material from which a whole series of other foods are produced, including cheese, cream and yogurt. Depending on the size of the facility, several hundred screw connections come into use in production equipment, stirring devices and containers, and they can be potential entry points for impurities and bacteria. So-called dead space can result between screw heads and the washers as well as the housing and the washers, and microorganisms can become established there. In these situations, the gaps function as capillary spaces and actually draw fluids in. If bacteria and germs settle there, it is impossible to remove them from the gap from the exterior. This reduces the stability of dairy products; in the worst case, the destruction of entire batches can be the result.
Freudenberg-NOK developed the "Hygienic Usit" seal to prevent this. It has an elastomer bead made of the high-performance material "70 EPDM 291," creating a dead-space-free, static seal and making it impossible for microfilms to form between the screw head and the contact surface. In areas with product contact, such as at the screw connections for stirrer blades, the seals are used in combination with special polished screws, which greatly eases cleaning.
But there are other areas where Hygienic Usit seals already meet the hygienic requirements with far more cost-effective polished standard screws, based on the current standards of the food industry. The areas include the splash zones in dairies; here the Hygienic Usit prevents accelerated corrosion resulting from the metabolism of microorganisms beneath a screw head, for example, for the mounting feet of machinery or frame screws. Fast-advancing corrosion in areas that cannot be viewed from the outside can be totally ruled out with the help of Hygienic Usit seals.
The Hygienic Usit seal ring is a further development of the metallic ring seals used in machine-building. They seal static machine parts against liquid and gaseous media in a straightforward, economical way. The special recipe for the sealing material ensures that the requirements of European and American food industries are met. In addition, there is now a U.S. Department of Agriculture certificate available especially for the dairy industry.
The material is also resistant to the cleaning procedures used in open processes, in which facilities are completely cleaned from the exterior. Among other things, this includes resistance to water vapor at temperatures up to 180 degrees Celsius as well as to 2 percent nitric acid and 5 percent caustic soda at temperatures up to 80 degrees Celsius. The Hygienic Usit from Freudenberg-NOK thus meets the highest possible standards for the concentrations and temperatures that are recommended by producers of cleaning agents.
More information can be obtained from the Freudenberg-NOK specialists at the company's stand at Process Expo (Stand 6533, North Hall, level 3), Sept. 15-18, 2015 in Chicago.
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