Name: What are Rotary Oil Seals? || THORS Oil Seal Fundamentals: Rotary Applications Course Preview
Uploaded: 2026-02-22T14:55:32.000Z
Duration: 3 min 2 s
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Oil seals are installed in a variety of working mechanical components in many industries.

Such seals are typically composed of rigid metal inserts referred to as shells, portions of flexible rubber, and

Two prominent types are reciprocating seals and rotary seals, also known as radial seals.

Reciprocating seals are used in applications where parts interact in up and down movement, such as suspension systems and shock absorbers.

Rotary seals are typically used in applications in which shafts are rotating, such as crankshafts and gearboxes.

This course will focus on oil seals used in rotary applications, which are typically manufactured as single lip or double lip, depending on the requirement.

In profile view, the single sealing lip is seen at the bottom.

These seals are commonly used in gearboxes and input shafts.

Here is an example of a single lip oil seal fixed into a housing and onto a shaft.

In profile view, it is clear that the single sealing lip makes direct contact with the shaft as the shaft rapidly rotates.

In service, a properly functioning seal will keep the oil inside of the housing and keep dust, liquids and other particles out.

If the lip was damaged, oil will leak between the shaft and the lip and unwanted particles will access the working components inside.

Double lip oil seals have both a sealing lip and also what is referred to as a dust lip.

These seals are commonly used on crankshafts and pinion drive shafts.

Here is an example of a double lip oil seal fixed into a housing and onto a shaft.

In profile view, it can be seen that both the sealing lip and dust lip make direct contact with the shaft.

While the ceiling lip keeps oil inside the housing, the dust lip prevents unwanted dust, liquids and other particles from entering.