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Several Factors Affecting The Performance Of The Seal
May 10, 2018

1: speed of motion

The movement speed is very low (less than 0.03/s), we must consider the smoothness of the operation of the equipment and whether there is crawling phenomenon. When the speed of motion is high (more than 0.8m/s), the ink of the lubricating function may be destroyed, and the seal is heated by friction because it does not get good lubrication, and the life of the seal is greatly reduced. It is suggested that rubber and plastic conform to the sealing speed in 0.3m/s~1.2m/s.

2: temperature

Low temperature will reduce the elasticity of rubber plastic composite seal, cause leakage, and even the entire oil seal becomes hard and brittle. High temperature will make the oil seal volume expand and soften, resulting in the rapid increase of oil seal friction resistance and the reduction of pressure resistance during movement. It is recommended that the continuous temperature range of -10~+80 / C.

3: working pressure

The oil seal has the minimum starting pressure requirement. Low pressure should be selected with low friction performance and low aerodynamic resistance. Below 2.5Mpa, rubber plastic composite seal is not suitable. High pressure must be taken into account when sealing is pressurized. There are special requirements for machining of groove with anti extrusion collar.

4: working medium

In addition to selecting the working medium strictly according to the recommendation of the manufacturer, keeping the working medium clean is very important. The aging and pollution of the oil will not only cause the failure of the components in the system, but also accelerate the aging and wear of the oil seal, and the stolen goods may be scratched or embedded in the seal to make the seal fail. Therefore, the quality and cleanliness of the oil seal must be checked regularly, and the oil filter or oil should be replaced according to the maintenance specifications of the equipment. In the oil tank, the residual air in the oil is high and the compression will produce high temperature to cause the oil seal to burn out or even carbonization. To avoid this, exhaust treatment should be carried out at the initial stage of the operation of the hydraulic system. The hydraulic cylinder should also be operated for several minutes at low pressure for a few minutes to confirm that the residual air in the oil has been discharged before it can work normally.

5: lateral load

A support ring must be installed on the piston to ensure that the oil cylinder can bear a larger load. Seals and support rings are completely different, seals can not replace the support ring load, the lateral force hydraulic cylinder, must add the bearing capacity of the support ring, (heavy load can be used metal ring) to prevent oil seal under eccentric conditions to cause leakage and abnormal wear.

6: hydraulic impact

There are many factors that cause hydraulic impact, such as the sudden encounter of a excavator bucket, the lifting of a crane or the lowering of heavy objects. Except in factors, for high pressure and large flow hydraulic system, when the actuator (hydraulic cylinder or hydraulic motor) reversing, if the performance of the reversing valve is not very good, it is easy to produce hydraulic impact. The instantaneous high pressure produced by hydraulic impact may be several times of the working pressure of the system, so the high pressure will tear the oil seal in a very short time or will be involved in the gap, causing serious damage. Generally, hydraulic cylinders should be equipped with buffer rings and retaining rings on the piston rod. The buffer ring is installed in front of the oil seal to absorb most of the impact pressure, and the retaining ring prevents the oil seal from entering the gap under high pressure and the roots are bitten.

7: the machining precision of the oil cylinder

It is proved that the surface roughness of the surface is more than 0.8 mu m and the leakage and wear value of the oil seal will rise directly. It is suggested that the surface roughness of the working surface is Ra0.1~0.8 mu m. to ensure the sealing performance of the rubber plastic compound seal and avoid the damage of the seal in the assembly process and the design of the hydraulic cylinder and the design of the hydraulic cylinder. The following aspects should be taken into consideration in the installation.

1): cylinder tube

A: Material: generally for carbon steel, low pressure system and good friction conditions can be used in aluminum alloy, bronze, stainless steel and other B: surface quality and coarseness: the inner surface generally needs to be honed, polished or rolling, to meet the roughing of Ra0.1~0.8 mu m, and not to cross the knife pattern.

2) piston rod

A: Material: generally carbon steel, chrome plated rigid, low pressure system and good friction conditions can use aluminum alloy, bronze, stainless steel and so on.

B: surface quality and roughness: the roughness is Ra0.2~0.4 m and the hard chromium is hardened after heat treatment. The piston rod of hydraulic cylinder of engineering machinery may be scratched by sand and stone, and its surface hardness must be above HRC60.

C: the installation groove of the oil seal

D: local structure design

E: wear ring slip fit clearance F and oil seal extrusion gap.

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