Sealing principle: because of the oil film between the oil seal and the shaft, the oil film has the characteristics of fluid lubrication. Under the influence of the liquid surface tension skeleton oil seal, the rigidity of the oil film just makes the oil film and the air contact end form a crescent surface, thus preventing the leakage of the working medium, thus realizing the seal of the rotating shaft. The sealing ability of the oil seal, the sealing surface depends on the thickness of oil film thickness, the thickness of oil seal leakage; too big, too small, may be caused by dry friction, oil seal and shaft wear; no oil film between the seal lip and shaft, it is easy to cause fever, wear.

Therefore, at the time of installation, must be in the sealing ring with some oil, while ensuring seal and the axis perpendicular to the line, if not vertical, lip oil seal will put the lubricating oil from the shaft on the stem, can also cause excessive wear of the seal lip. In operation, the lubricant in the shell is slightly exuded so as to achieve the ideal condition of forming an oil film at the sealing surface.