1. Speed of movement

    The movement speed is very low (≤0.03/s), to consider the smooth operation of the equipment and whether there is crawling phenomenon. When the movement speed is very high (≥0.8m/s), the ink of the lubrication function of the device may be destroyed, and the seal will friction and heat due to the lack of good lubrication, resulting in greatly reduced life. It is recommended that the rubber meets the seal It is suitable to work in the speed range of 0.3m/s~1.2m/s.

    2. Temperature

    Low temperature will reduce the elasticity of the rubber and plastic composite seal, resulting in leakage, and even the entire oil seal becomes hard and brittle. High temperature will make the oil seal volume expansion, soft, resulting in the oil seal friction resistance increases rapidly and the pressure resistance decreases. It is recommended that the continuous operating temperature range of the rubber and plastic composite seal be -10~+80℃.

    3. Work pressure

    The oil seal has a minimum starting pressure requirement. Low friction properties must be selected for low pressure work. Oil seal with low aerodynamic resistance. Below 2.5Mpa, the rubber and plastic composite seal is not suitable, and the sealing pressure should be considered when the high pressure is applied, and there are also special requirements for the grooving of the anti-extrusion retaining ring.

    4. Working medium

    In addition to selecting the working medium strictly according to the manufacturer's recommendations, it is important to keep the working medium clean. Aging or contamination of the oil will not only cause the components in the system to fail, accelerating the aging and wear of the oil seal, but also the stolen goods in it may scratch or embed the seal, making the seal ineffective. Therefore, it is necessary to regularly check the quality of the oil seal and its cleanliness, and replace the oil filter or oil according to the maintenance specifications of the equipment. High compression of residual air diameter in the oil cylinder will produce high temperature to burn out the oil seal and even carbonize it. In order to avoid this situation, exhaust treatment should be carried out at the initial operation of the hydraulic system. The hydraulic cylinder should also run at low pressure and slow speed for a few minutes to confirm that the residual air in the oil has been drained before it can work normally.

    5. Lateral load

    The piston must generally be equipped with a support ring to ensure that the cylinder can withstand a larger load. Seals and support rings play a completely different role, seals can not replace the support ring load, there is a lateral force of the hydraulic cylinder, must add a strong bearing capacity of the support ring, (heavy load can be used metal rings) to prevent the oil seal in the eccentric conditions

    Leakage and abnormal wear caused by working under.

    6. Hydraulic shock

    There are many factors that produce hydraulic impact, such as the moment when the excavator suddenly hits the stone and the crane lifts or drops the heavy object. In addition to the factors, for high pressure and large flow hydraulic systems, when the actuator (hydraulic cylinder or hydraulic motor) is reversing, if the reversing valve performance is not good, it is easy to produce hydraulic shock. The instantaneous high pressure generated by the hydraulic shock may be several times the working pressure of the system, and such a high pressure will tear the oil seal or locally involve the gap in a very short time, causing serious damage. Generally, the cylinder with hydraulic impact should be installed on the piston rod with a buffer ring and a stop ring. The buffer ring is installed in front of the oil seal to absorb most of the impact pressure, and the stop ring prevents the oil seal from squeezing into the gap under high pressure and the root from being bitten.

    7, the processing accuracy of the cylinder

    Experiments show that when the surface roughness of the moving working surface in contact with the oil seal exceeds 0.8μm, the leakage and wear value of the oil seal will directly increase, so it is recommended that the roughness of the moving working surface should be Ra0.1~0.8μm. In order to ensure the sealing performance of the rubber and plastic composite seal and avoid damage to the seal during assembly, the following aspects should be considered in the design and installation of the hydraulic cylinder

    1) Cylinder

    a, material: generally carbon steel, low pressure system and good friction conditions can be used aluminum alloy, bronze, stainless steel and so on

    b, surface quality and roughness: the inner surface generally needs to be honed, polished or rolled, requiring Ra0.1~0.8μm roughness, and shall not be vertical and horizontal knife grain.

    2) Piston rod

    a, material: generally carbon steel, chromium plated steel, low pressure system and good friction conditions can use aluminum alloy, bronze, stainless steel and so on.

    b, surface quality and roughness: the rough degree is Ra0.2~0.4μm, and the surface is plated with hard chromium after heat treatment. The piston rod of the hydraulic cylinder used in construction machinery may be scratched by sand and gravel, and its surface hardness is required to be above HRC60.

    c, oil seal installation groove.

    D. Local structure design.

    e, wear ring sliding with clearance and oil seal extrusion gap.

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