In the hydraulic system and its components, the design, placement of sealing devices and sealing elements of the role is to prevent the leakage of working media and external dust and foreign body intrusion. A component which is arranged in a sealing device, which acts as a sealing element.

The working medium of the fluid state, in the hydraulic components and system of the cavity flow or temporary, due to pressure, clearance, viscosity and other factors change, and lead to a small number of working media across the cavity boundary, from the high-pressure cavity to the low-pressure cavity outflow, this kind of "transboundary outflow" of the imagination, known as leakage.

Leakage is divided into internal leakage and external leakage of two, unit time leakage of hydraulic volume, known as leakage.

Internal leakage, will cause the hydraulic system volume efficiency of the sharp decline, up to the so-called work pressure, so that machinery and equipment can not operate.

External leakage, can cause the work medium to waste and pollute the environment, even causes the mechanical operation malfunction and the personal accident.

Therefore, the normal design and use of seals is to ensure the normal operation of hydraulic equipment important guarantee.