Oil seals and grease seals have a
flexible lip that rubs against a shaft or housing to
prevent the leakage or ingress of fluids and dirt. For
proper installation, the seal lip should point towards
the medium being contained. Some oil seals and grease
seals have a spring to help keep the lip in contact with
the shaft. The sealing orientation and direction is
important to consider for oil seals and grease seals.
The orientation and direction can be internal or rod
seal, external or piston seal, symmetric seal, or axial
seal. Rod seals are radial seals. The seal is
press-fit into a housing bore with the sealing lip
contacting the shaft. Also referred to as a shaft seal.
Piston seals are radial seals. The seal is fit onto a
shaft with the sealing lip contacting the housing bore.