The importance of seals for different industries

- Nov 13, 2019-

Although the rubber-plastic seal is small, its role has made it a basic component and accessory in the national economy, such as national defense, chemical, petroleum, coal, transportation, and machinery manufacturing. It plays a very important role in the development of the national economy. In recent years, with the rapid economic growth, the rubber and plastic seal manufacturing industry has maintained double-digit growth. The data shows that in 2011, China's rubber and plastic seal manufacturing industry scale (the above enterprises (according to the statistical statistics of the National Bureau of Statistics, sales income of more than 20 million yuan) to achieve a total industrial output value of nearly 10 billion, an increase of more than 20% year-on-year. Currently, China Rubber There are more than 150 enterprises in the plastic seal manufacturing industry (annual income of 20 million yuan). The domestic rubber sealing industry generally shows the development situation of small enterprises and low technical level. From the perspective of enterprise economic types, private and foreign capital enterprises account for more than 95% of the industry's main economic types. At the same time, enterprises are basically concentrated in East China. From the perspective of the number of enterprises, sales revenue and asset size, East China has a considerable share and market concentration is high.

1. Classification by function: divided into shaft seal, hole seal, dust seal, guide ring, fixed seal, rotary seal; 2. Classification by material: divided into butadiene cyanide rubber, EPDM rubber, fluorine rubber, Silicone, fluorosilicone rubber, nylon, polyurethane, engineering plastics, etc.

1. The storage temperature of the seal is preferably below 30 °C to avoid high-temperature aging of the seal; 2. The seal must be stored in the sealed package to avoid contact with moisture or dust in the air; 3. The seal must be strong Light is irradiated to prevent the seal from being corroded or prematurely aged by air. The factors affecting the performance of various seals are different. For example, mechanical seals (filler seals, etc.) have factored such as temperature, medium, wear, and pressure.

(1) Select the appropriate seal material and hydraulic oil, as well as adaptability to working temperature and oil compatibility. (2) The geometric position accuracy (concentricity) of the sliding parts relative to the seal is high (such as hard chrome plating) and the surface roughness is fine to prolong the service life. 1 For the hydraulic pump, the oil seal used in the motor journal not only requires the roughness of the sliding surface to be within 0.25m of Ra, but also requires hard chrome plating on the surface. In the specific use, it is necessary to adjust the diameter of the lip of the oil seal according to the specific conditions. The spring force is applied to make it elastic, and a sealing sleeve or a thin gasket is used to protect the sealing ring during installation, so as to prevent the lip from rolling and twisting, causing the spring to slip out. 2 The inner surface of the hydraulic cylinder is usually processed by rolling, which not only improves the surface roughness, but also makes the surface cold-hardened, which is beneficial to prolong the service life of the sealing ring. In addition, the pressure used, the length and type of the sliding surface have a great influence on the service life. Therefore, the “check” time should be determined based on these conditions. 3 It is required that the sealing surface is in a good lubrication state and prevents intrusion of dirt. It is also a necessary condition to use the oil that meets the specified cleaning level and the correct installation method.

Hydraulic seals play a vital role in the integration of hydro-pneumatic components. If the seal of a hydraulic-pneumatic component product is not closed, then this hydro-pneumatic component product is not a good product. There are many factors that affect the seal. First of all, pressure is an important reason that affects the quality of the seal. The pressure level and the length of the pressure cycle change have a great influence on the seal damage (such as extrusion). The higher the pressure, the greater the influence of other factors on the performance of the seal, such as temperature, speed, material of the seal, the gap between the piston and the cylinder, and the gap between the piston and the cylinder head. Another one is temperature and friction. It is difficult to describe the maximum service temperature and minimum service temperature of a seal material, because this is the result of a combination of factors. For the piston and the piston rod to work at different temperatures, it is necessary to make a distinction between them. Another is the surface roughness of the seal product, the characteristics of the surface, the pressure, the medium, the temperature, the material of the seal, the type of the seal and the speed of movement are all factors that affect the seal. The last one is surface treatment. Experience has shown that the characteristics of the cylinder piston and piston rod surface have a very large effect on the life of the seal. The surface characteristics are generally defined by the value of the surface roughness RA, which is the arithmetic mean of the absolute value of the surface shape from the centerline. However, these values do not fully indicate the effect of the surface condition on the seal, because even at the same roughness, different surface shape features can result in different degrees of seal wear on the seal.