By Joyce Laird, contributing editor
SKF supplies all of its bearing inserts with a seal or shield on both sides. For most ball bearing unit applications, no additional external protection is convenient. Therefore, the bearing inserts are available with several sealing arrangement designs.
The standard seal consists of a stamped sheet steel washer with a seal lip made of NBR, vulcanized to its inner surface. The non-contact sheet steel washer forms a narrow gap with the cylindrical surface of the inner ring shoulder and protects the seal against coarse contaminants.
For more contaminated environments, the standard integral seal and an additional plain flinger on both sides is recommended. The flinger, made of sheet steel or stainless sheet steel, has an interference fit on the inner ring to considerably improve the effectiveness of the seal without increasing friction. These seals are only available for bearings with an inner ring extended on both sides.
For very contaminated environments, multiple seals on both sides are recommended. This sealing arrangement consists of an integral standard seal and a flinger with a vulcanized NBR lip. The flinger lip seals axially against the standard seal face. The space between the flinger lip and the integral seal is filled with grease to provide an additional layer of protection. These seals are only available for bearings with an inner ring extended on both sides. Because of the increased sealing effectiveness and friction, this seal will have a reduced speed rating.