Guideline values for the permissible rotational and circumferential speeds for different seal designs are provided in the Seal selection table. If the circumferential speeds provided in the table are not sufficient for a particular sealing position, the diagram 1 may be used. The diagram lists circumferential and rotational speeds related to the material of the sealing lip. The values are valid for spring-loaded sealing lips that are well-lubricated by a mineral oil, where adequate lubricant supply prevents heat build-up and where the pressure is the same on both sides of the seal (pressure differential = 0).
The diagram 2 shows that large diameter shafts can accommodate higher circumferential speeds than shafts with smaller diameters. This is because the cross section of the shaft does not increase linearly with the increase in diameter but by the square of the increase in diameter. Therefore, the heat dissipation of a large shaft is much better than that of a small shaft.
Generally, SKF WAVE seals can be operated at higher circumferential speeds than those obtained from the diagram 3 because of the hydrodynamic form of the lip.
The values obtained from the diagram 4 should be reduced if:
- radial shaft seals with an auxiliary, contacting lip are used
- lubrication is inadequate or grease lubrication is used, i.e. when underlip temperatures increase due to poor heat dissipation
- the counterface does not meet surface finish or running accuracy requirements
- there is a pressure differential across the seal