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Due to the performance difference of the sealing material itself, the sealing performance of the manufactured seals is also very different. Therefore, understanding the performance of the sealing material is a prerequisite for the correct design and selection of the sealing material. When selecting the sealing material, the following factors must be considered :
The degree of swelling of the material in the medium is directly related to the quality of the sealing performance, so when selecting materials for hydraulic and pneumatic seals, the first consideration should be given to Consider whether it is compatible with the sealing medium.
The tensile strength of the sealing material generally decreases with the increase of temperature, so its maximum operating temperature and mechanical strength at high temperature must be considered.
Low tensile strength, prone to stress relaxation and permanent deformation, resulting in seal failure.
The wear resistance of the material is an important performance of the dynamic seal. Good wear resistance means a long service life. The wear resistance of the material is closely related to the hardness of the material. The higher the hardness of the material, the more wear-resistant it is.
The hydropneumatic seal obtains the sealing ability by generating recoverable compression deformation in the sealing groove. Therefore, the permanent deformation of the sealing material should be small, the elasticity should be high, and the resilience should be strong. In addition, the permanent deformation of the material is related to temperature, Both low temperature and high temperature will increase permanent deformation.
Extrusion type seal is: it relies on the resilience generated by the sealing material to obtain the sealing ability, and the lip seal may exist Eccentricity, may rely on the elasticity of the material to compensate for the insufficient contact stress of the seal, therefore, the elasticity has no effect on the sealing effect of the seal Very important.
The hardness is an important indicator of the sealing material, which depends on the roughness of the sealing surface.
Low, so the sealing effect is good. In the part with high sealing pressure, the hardness of the seal should be increased to prevent excessive deformation of the seal.
Even extruded. In addition, the hardness of the material decreases with the increase of the use temperature, and the hardness is high, and the wear resistance of the material is also strong.
The working temperature of the seal depends on the temperature of the sealing medium and the temperature rise of the seal itself during the movement. The temperature directly affects the seal
If the temperature is too high, the aging of the sealing material will be accelerated, resulting in a significant decrease in the elasticity, hardness and other properties of the material, and hardening will occur;
Low will also harden the material, lose its elasticity, and reduce the sealing performance. Therefore, a material with a wider operating temperature range should be selected.
ility alsoPermeab has an important impact on fluid sealing, and more attention should be paid to gas sealing, especially vacuum sealing. Various rubbers have poor permeability Very different.
Influence of friction on sealing: Friction is inevitable in dynamic sealing. The size of friction force is related to factors such as seal material, fluid type, fluid pressure, working temperature, speed, and surface roughness of sealing surface. It directly affects the sealing performance and life of the seal, as follows:
1) Friction causes seal failure and reduces service life;
2) Friction reduces the output pressure;
3) Frictional heat accelerates aging of seals and reduces service life;
4) At low speed, it is easy to cause the hydraulic cylinder to crawl.