Dynamic Sealing Mechanism
The Dynamic Sealing Mechanism or pumping action is how the fluid film created from the Hydrodynamic Effect is maintained without developing a leak. The pumping direction is a direct correlation to an asymmetrical contact pressure profile. This pressure profile is controlled by designing the proper oil side angle, air side angle, and spring offset distance. For the pumping action to work needs to be larger than. This creates a larger pressure gradient on the oil side. The garter spring is offset to the air side and helps maintain the air side angle. The result of properly controlling these design parameters is an asymmetrical contact pressure profile. When this profile is combined with microasperites in the seal lip’s contact width, a net pump rate in the direction of the oil reservoir is created, therefore preserving the leak free fluid film created by the hydrodynamic effect.
Parameter Affecting Sealing
The process of defining a specific sealing system is the first step toward understanding the true application needs. Certain parameters affect the types of profiles that can be used. The design engineers ability to narrow down all of the system variables and understanding their affects will dictate the success of the profile selection.
There are four categories of system parameters that list common application variables.
Parameters Affecting Sealing:
- Temperature
- Pressure
- Lubrication
- Viscosity
- Sump Fill Level
- Corrosion
- Contamination
- Shaft Diameter
- Shaft Hardness
- Shaft Speed
- Counter or Straight Bore
- Shaft Assembly
- Housing Assembly
- Replacement and Ease of Removal
- Spring Back
- Finish Type and lead
- Surface Preparation for Radial Lip Seals
- Surface Finish