Definition of dynamic rotation tightness
Dynamic Seals Commonly Used in Mechanical Industry - Dynamic seals for rotating shaft

Mechanical sealing is the quality of confinement within a device of a fluid, liquid or gas, but also of very fine solid particles suspended in a gas.

Mechanical sealing is said to be static when the contact parts are immobile, and dynamic when there is relative movement between the contact parts.

Depending on the nature of the movement between the parts in contact, there are two types of dynamic seal: translational and rotational.

A more detailed definition of sealing and the different types of sealing is given in paragraph 1 of article