To be effective, the lip of a radial shaft seal must always exert a certain radial load on the counterface. The friction resulting from this radial load is only part of the total contact friction and power loss at the sealing position. Other contributing factors include:
- type of medium being sealed
- pressure differential across the seal
- circumferential speed
- ambient temperature
- lubricant and lubrication method
- condition of the counterface
The diagram 1 provides an indication of the friction losses that may be expected when a radial shaft seal with a conventional sealing lip is properly installed and fully lubricated.
The running-in phase of the sealing lip lasts a few hours. During this time, the friction losses are somewhat higher than during normal operation.
Seals intended for applications with high pressure differentials typically have greater losses than specified in the diagram. SKF WAVE seals, on the other hand, typically have losses lower than those indicated in the diagram.