How Radial Shaft Oil Seals Work
The area between the sealing edge and the shaft is the most important. The sealing effect is achieved by pre-loading the sealing lip, making its internal diameter slightly smaller than the shaft diameter. The garter spring ensures constant mechanical pressure and maintains the radial force to the shaft, flattening the sealing edge to defined width. Sealing is provided by the surface tension of the hydrodynamic oil film between the seal flattened area and the shaft. Oil thickness must be between 1 and 3 um to avoid leakage. The meniscus acts as an interface between the outside air and the fluid. Any break in the meniscus will result in leakage. This can occur if the shaft contains scratches along the seal path.
The Metal Case
The metal insert or case is used to give strength and rigidity to the seal. Normally, it is made of cold rolled steel. To avoid rust or chemical attack, stainless steel may be used. Available in 302, 304, or 316 stainless.
The Garter Spring
The garter spring maintains the raidal force exerted by the sealing lip around the shaft surface. Normally produced in cold rolled steel. For special applications, stainless steel may be used. Available in 302, 304, or 316 stainless.