Key words: hydraulic seal, polyurethane material, polyurethane

Hydraulic seals are the most important and effective means to solve the leakage problem of hydraulic and pneumatic systems. If the system is not sealed properly, there may be an impermissible leakage, and the leaking oil will pollute the environment; it may also cause air and dust to enter the system, affecting the working performance of the system and the smoothness of the movement of the executing elements (such as crawling); when the leakage is serious, the volume efficiency of the system is too low, or even the working pressure can not reach the required value. If the seal is excessive, it can prevent leakage, but it will cause severe wear and tear of the sealing part, shorten the service life of the sealing parts, increase the movement friction resistance in the hydraulic components, and reduce the mechanical efficiency of the system. Therefore, it is very important to select and design sealing devices reasonably in the design of hydraulic and pneumatic systems.

Hydraulic Seals Requirements for Sealing Devices:

1. In the working pressure and a certain temperature range, it should have good sealing performance, and with the increase of pressure, it can automatically improve the sealing performance.

2. The friction between the sealing device and the moving parts should be small and the friction coefficient should be stable.

3. Strong corrosion resistance, not easy to aging, long working life, good wear resistance, wear to a certain extent can be automatically compensated.

4. It has simple structure, convenient use and maintenance, and low price.

In the hydraulic system and its system, the sealing device is used to prevent the leakage of working medium and the invasion of external dust and foreign matter. The sealing element is the sealing element. The material selection of seals includes polyurethane, polyfluoroethylene, nitrile-butadiene, rubber and so on. The polyurethane material has wide hardness range and strength in the application of hydraulic seals.