Sealing Principle

In various hydraulic systems and their components, seals are used to prevent leakage of working media such as fluids or solid particles from adjacent surfaces, as well as to prevent the intrusion of external impurities such as air, dust, moisture and foreign objects. It is a general purpose basic part. Fluid state of the working medium, in the hydraulic system and components of the cavity flow or temporary storage, due to pressure, clearance, viscosity and other factors change, and lead to a small amount of working medium across the cavity boundary, from the high pressure cavity to the low pressure cavity outflow. This "outflow across the boundary" phenomenon, called leakage.

 Leakage is divided into two kinds of internal leakage and external leakage. Internal leakage can cause a sharp decline in the volumetric efficiency of the hydraulic system, the system heat, the required working pressure is not reached, so that mechanical equipment can not operate. External leakage can cause waste of working medium and pollution of the environment, and even lead to mechanical operation failure and personal accidents.

Static seal sealing mechanism

Static seal is relying on the closure of the gap between the bonding surface to achieve sealing effect, without considering friction and wear. Leakage on the sealing surface is determined by the nature of the seal material, the processing accuracy of the mating surface, the roughness and the degree of compression. The use of rubber and soft metals and other types of materials, with a smaller compression force can be fully compressed, thus preventing fluid leakage; for the harder metal gaskets, sometimes the use of larger compression force can not be fully compressed, resulting in poor sealing performance of the seals, but such as reducing the surface roughness, increasing the surface real contact area, with a smaller compression force can also improve the sealing performance of the seals. In order to keep the seal under fluid pressure, the seal is usually designed with an ultimate seal pressure, which is the pressure at which the seal remains reliable under fluid pressure. Considering the qualitative relationship between sealing force and internal pressure is partially non-linear, the actual use should make the initial sealing force reach the limit pressure equivalent to the limit pressure above the limit pressure, the use is safer.

Sealing mechanism of dynamic sealing

Dynamic seal can not simply rely on the closure of the gap between the bonding surface to achieve sealing, because the gap between the bonding surface to seal the closer, the greater the frictional resistance to the relative movement of the couple surface, resulting in the bonding surface heating, affecting the formation of lubricating oil film, so that the seal will soon fail. Therefore, the research on the mechanism of the dynamic seal is concentrated on the mechanism of forming and maintaining the lubricating oil film between the bonding surfaces, so that the seal can be maintained without excessive friction.