Bearing seals enhance performance and life by minimizing oil and water contamination and resulting damage.
Bearing seals have two main functions:
To prevent lubricant from leaking out.
To prevent dust, water and other contaminants from entering the bearing.
Factors for bearing seals
The type of lubricant (oil or grease)
Seal sliding speed
Shaft fitting errors
Sealing devices can be contact type and non-contact types.
Non-contact seals have a small clearance between the seal and the sealing surface. The friction thus generated is negligible and thus the frictional heat. These are suitable for high speed applications. They have a rather simple design, it has a small radial clearance and should be used in dry dust free environments.
Grease lubrication is preferable in this type. When several concentric oil grooves are provided on the shaft or housing, the sealing is improved and the intrusion of dust, etc. can be prevented. For oil lubrication, if helical concentric oil grooves are provided in the direction opposite to the shaft rotation lubricating oil flowing along the shaft can be returned to the inside of the housing. Labyrinth seals employ a multistage labyrinth design which elongates the passage, thus improving the sealing effectiveness. Labyrinth seals are used mainly for grease lubrication.
Contact seals act through the constant pressure of a resilient part of the seal on the sealing surface. They are generally superior to non-contact seals in terms of sealing efficiency, although their friction torque and temperature rise coefficients are higher. The simplest of the type are felt seals used for grease lubrication. They effectively seal off fine dust but may leak at some point.