The standard seal for SKF Y-bearings and units (fig 1) provides good protection against dust and coarse contaminants and also provides reliable retention of the lubricant in the bearing.
In difficult environments bearing units of the TF or WF designs should be used. The bearings of these units have an inner ring which is extended at both sides. A flinger mounted on the inner ring extension (fig 2) at each side gives added protection to the standard seal.
Where operating conditions are extremely contaminated and long service is required the TR design is recommended. Here, the standard seal of the bearing is reinforced by a rubberized flinger, i.e. the sheet steel flinger has a vulcanized rubber sealing lip (fig 3).