To protect the bearing arrangement from 'shaft-side' contamination, a wide assortment of ball bearing units with composite housings for the SKF Food Line are available with a back seal. These sealed units already have a mounted end cover and a bearing with an inner ring extended on one side (fig. 1, designation suffix DFH).
The back seal is made of stainless sheet steel reinforced NBR and can withstand operating temperatures up to 100 °C (210 °F). The seal is fitted in a recess in the housing and the two radial lips seal against the shaft. The external face of the back seal has been designed to provide sealing against cut-outs. This could, for instance, mean an enclosure wall or panel that has been drilled to allow clearance for the shaft to pass through to the bearing unit. On flanged units, this can be used to seal the shaft access or clearance hole in order to avoid the creation of a cavity behind the panel, where food debris could otherwise collect.