Oil seals: general overview


Radial shaft seals, also known as oil seals, are seals consisting of a metal insert at their core, covered by cured membrane made of elastomeric material. A ring-shaped spring incorporated into the seal serves to additionally increase the sealing effect by means of stretching.


The sealing effect, in both static and dynamic applications, is accomplished through radial pressure by the sealing lip onto the radial shaft and is a result of the smaller diameter of the sealing lip. The required radial force for oil seals is the sum of tangent forces of stretching and bending (applied by the spring and the elastomeric sealing lip). The sealing effect in the sealing groove is achieved through capillary forces. On the static side, the sealing effect at the base of the sealing groove is achieved through the elastic rubber shell.



Generally speaking, oil seals can rotate in both left and right directions, depending on the specific application. In certain cases, rotation must happen exclusively in one direction. In these cases, the direction of rotation is indicated on the inside diameter of the oil seal by a corresponding left or right helix, and this is shown in the oil seal notation by the letters R or L. Sometimes, the oil seals can be bidirectional, with a zig-zag-like grooving on the inside diameter. This is shown by the letter W right after the item size.

The standard oil seal type as per DIN 3760 is A from which the other standard types are derived: AS, B/BS, C/CS, as well as multiple other variations. Further information on the oil seal types that we supply can be found under the Standard Oil Seal Types, as well as the Additional Oil Seal Types sections.


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