Seals protect bearings against moisture, contaminants and prevent the leakage of lubricant. The efficiency of the entire seal is of a major influence on the lifetime of the bearing and parts in the gearbox. There are two basic types of bearing seals: non-contact (gap or labyrinth seals) and contact seals
The effectiveness of non-contact seals depends on the sealing functionality of the narrow gap. The effectiveness of a contact sealing depends on the pressure between the contact surfaces.
Contact seals are designed for allowing a small quantity of lubricant to escape. This leaking lubricant lubricates the contact surfaces of the seal. If the leak quantity proves to be too large or when moisture and dirt penetrate into the bearing, the seal should be replaced or, if possible, strengthened. Often, in cases where a particular type of sealing doesn’t have sufficient effect a combination of two types could solve the problem. In the following tables and pictures you will find the different type of seals with their main characteristics.
The proper functioning of contact seals according to DIN 3760 & 3761 depends on the finish and the tolerances of the axis and the housing bore. Both pictures are clarifying this.
Shaft wear due to oil seals
After some time the seal wears into the axis and the gearbox could leak. Since these are sometimes costly and time-consuming repairs, there are cheap shaft repair sets. This set consists of a thin-walled cylindrical tube with a mounting flange that is pushed over the shaft (Speedy-Sleeve). See accompanying picture for clarification.
For the sealing of shaft holes simple rubber covers can be used instead of more expensive steel covers. The common diameters are (ØD): 16, 19, 20, 21, 22, 26, 28, 30, 32, 35, 37, 40, 42, 47, 48, 50, 52, 55, 62, 68, 72, 75, 80, 85, 90, 100, 110, 125, 130, 140, 150, 180.