Stenso - Hovedkatalog 2019

3.3 Lubrication Lubrication is very important for proper functioning of the seal. Actually, the sealing lip does not move directly on the sealing surface but it moves on a so called lubricating film. (see par. 2.2) Film thickness usually is 1-3 µm though it is influenced by various factors such as oil viscocity, surface finish of shaft and pre-stressing of seal. The first few hours of operation (run in operation) are important from the view point of lubricant film build up and also the flattening of the sealing edge that occurs. Certain amount of leakage is possible during this period of time. An adequate lubricating film strongly reduces the friction between sealing lip and shaft and also acts as a coolant against the resulting heat. The lower this temperature, the longer the life of the seal and its endurance. If the liquid possesses merely a low lubricity (like water and aqueous solutions) a shaft sealing system with a dust lip (AS, BS, or CS) needs to be used. In this case, take care that the space between the two lips is filled with lubricating grease. 304 Frictional heat also depends on peripheral velocity of the shaft. Friction will not merely harm the sealing lip material but can also lead to frictional losses. When only small forces are being transmitted, this can have an adverse effect. Shaft diameters (mm) Frictional heat at the sealing lip Heating Frictional losses Peripheral Velocity Radial Lip Seal