What are the two types of seals?

What are the two types of seals?

• A. Radial and Axial
• B. Static and Dynamic
• C. Primary and Secondary
• D. Inner and Outer

Answer: (B)

Seals are categorized by whether there is relative motion between the sealing surfaces. If the surfaces stay fixed and the seal just sits in place to block leakage, that’s a static seal. If the surfaces move against each other—such as a rotating shaft or a sliding piston—that’s a dynamic seal. This distinction drives design choices: static seals rely on compression and stay wear-free from sliding, while dynamic seals must accommodate movement, lubrication, and wear. A static seal example is a gasket or O-ring seated in a groove where nothing moves. A dynamic seal example is a shaft oil seal that slides with the rotating shaft. The other terms don’t describe the fundamental seal type: radial vs axial describes orientation or load direction, inner vs outer refers to position, and primary vs secondary is not a universal classification for seal types.

Seals are categorized by whether there is relative motion between the sealing surfaces. If the surfaces stay fixed and the seal just sits in place to block leakage, that’s a static seal. If the surfaces move against each other—such as a rotating shaft or a sliding piston—that’s a dynamic seal. This distinction drives design choices: static seals rely on compression and stay wear-free from sliding, while dynamic seals must accommodate movement, lubrication, and wear.

A static seal example is a gasket or O-ring seated in a groove where nothing moves. A dynamic seal example is a shaft oil seal that slides with the rotating shaft.

The other terms don’t describe the fundamental seal type: radial vs axial describes orientation or load direction, inner vs outer refers to position, and primary vs secondary is not a universal classification for seal types.