The service life and performance of a seal are largely influenced by:
- shaft material and hardness
- shaft surface finish and tolerance grade
- dynamic runout and shaft-to-bore misalignment
A shaft surface that is too smooth can lead to lubricant starvation, while a shaft surface that is too rough can accelerate sealing lip wear. The shaft surface should be machined without directionality as directionality can cause leakage depending on the direction of rotation. Dynamic runout and shaft-to-bore misalignment cause an uneven radial load on the circumference of the sealing lip. As a result, the sealing lip, particularly at high speeds, will not be able to follow the shaft. This, in turn, will result in a gap between the sealing lip and the shaft, causing reduced sealing ability.
Unlike radial shaft seals, V-rings and axial clamp seals are not affected by normal coaxiality deviations or runout.