Complete screw connections meeting hygienic design standards are achievable with the combination of Hygienic Usit rings and highly polished NovoNox screws and cap nuts. The Hygienic Usit is external-sealing and cleanly closes off the area between the screw and the surface from any type of external influence, reliably protecting the product whenever necessary. The configuration of a Usit ring with its externally vulcanized, trapezoidal, elastic rubber sealing bead minimizes dead space where deposits can form. The sealing bead is made of 70 EPDM 291, which conforms to FDA and EU VO 1935/2004 and is nonhazardous based on USP Class VI (121 °C; 250 °F). NovoNox designed the screw and fastening nut especially for this Freudenberg development. The hygienic solution for the screw connections was developed jointly. As part of the solution, the trapezoidal contour of the sealing bead creates a form closure with the flange seat of the screw, establishing optimal sealing. The special screws also have no sharp-edged ridges, die marks, uneven head contacts or impressions on their heads. This ensures that the sealing bead will not be damaged as the screw is tightened. In addition, the special screws are polished completely to a high gloss with a mean surface roughness of Ra < 0,2µm to a maximum of Ra 0,04. The combination of the Hygienic Usit, the even surface of the screw flange seat, the polished surfaces and rounded screw and nut corners achieves a high degree of hygiene for the entire screw connection. Impurities can neither adhere to it nor penetrate it. This also reduces the danger of contamination in the screw connections to the absolute minimum. The Hygienic Usit is specially designed for hexagonal screws with flange in accordance with DIN EN 1665 and defined as standard for the nominal sizes of M5, M6, M8, M10, M12 and M16. NovoNox also provides the appropriate screws in the sizes M5 to M16.
Freudenberg-NOK Sealing Technologies, Plymouth, MI48170. www.fnst.com or call 800-533-5656.