The seal is a material or a part that prevents fluid or solid particles from leaking from adjacent joint faces and prevents intrusion of external impurities such as dust and moisture into parts inside the machine.
Use classification
1. Classification by function: divided into shaft seal, hole seal, dust seal, guide ring, fixed seal, rotary seal;
2. Classification by material: divided into nitrile rubber, EPDM rubber, fluorine rubber, silica gel, fluorosilicone rubber, nylon, polyurethane, engineering plastics, etc.
Storage
1. The storage temperature of the seal is preferably below 30 °C to avoid high temperature aging of the seal;
2. Seals must be stored in a sealed package to avoid contact with moisture or dust in the air;
3. Seals must be protected from strong light to avoid corrosion or premature aging of the seals by air.
The factors affecting the performance of various seals are different. For example, mechanical seals (filler seals, etc.) have factors such as temperature, medium, wear and pressure.
Use points
(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 shim 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 The sealing surface is required to be in a good lubrication state to prevent intrusion of dirt. It is also a necessary condition to use the oil that meets the specified cleaning level and the correct installation method.
Influencing factor
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 it is the result of a combination of factors. For the piston and 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.
Precautions
1. Please read the descriptions of each series before designing the groove. It is clear that the product uses the whole groove or the split groove; the process of installing the seal should pay attention to avoid the sharp edge, and the hole must be filled into the whole groove with the seal. With the help of installation tools, designers should consider the parameters such as groove size accuracy, surface roughness, and extrusion gap. For details, please refer to the product instructions, drawings and size tables.
2. Before installing the seal, it must be ensured that there are no impurities and cracks in the sealing groove. Apply the operating oil on the surface of the sealing groove and the seal respectively; install the seal gradually according to the order; avoid the Ling Rui side and correct the seal by the installation process. Avoid twisting and skewing; if it is a split slot, finally tighten the cover.
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