The main factors affecting the performance of hydraulic seals

Several major factors affecting the performance of hydraulic seals

I. Movement speed

 Movement speed is very low (<0.03m / s), to consider the smoothness of the operation of the equipment and whether there is "crawling" phenomenon. When the movement speed is very high (>0.8m/s), the oil film which plays the role of lubrication may be destroyed, and the seal will not get good lubrication and frictional heating, resulting in a greatly reduced life. Polyurethane or rubber seal is recommended to work in the speed range of 0.03m/s to 0.8m/s.

Second, the temperature

Low temperature will make the polyurethane or rubber seal less elastic and cause leakage, and even the whole seal becomes hard and brittle. High temperature will make the volume of oil seal expand and become soft, resulting in rapid increase of sealing friction resistance and reduction of pressure resistance during movement. It is recommended that the continuous working temperature range of polyurethane or rubber seal is -10℃～+80℃.

III. Working pressure

The seal has the minimum service pressure requirement. For low pressure work, low friction performance and low starting resistance seals should be used. Below 2.5MPa, polyurethane seals</span></a> are not suitable; for high pressure, the deformation of seals under pressure should be considered, anti-extrusion retaining rings are needed, and special requirements are also required for groove processing. In addition, seals of different materials have different optimal working pressure ranges. For polyurethane seals the optimum working pressure range is 2.5 to 31.5 MPa.

 The influence of temperature and pressure on sealing performance is interrelated and therefore should be considered comprehensively.

Fourth, the working medium

 In addition to selecting the working medium in strict accordance with the manufacturer's recommendations, it is vital to keep the working medium clean. The aging or pollution of the oil will not only cause the failure of the components in the system and accelerate the aging and wear of the seals, but also the dirt in it may scratch or embed the seals and make the seals fail. Therefore, the quality of the fluid and its cleanliness must be checked regularly and the oil filter or fluid must be replaced according to the maintenance specifications of the equipment. The air left in the oil in the cylinder by high pressure compression will produce high temperature to make the oil seal burned or even charred. In order to avoid this, in the initial operation of the hydraulic system, the exhaust should be processed. Hydraulic cylinder should also be in the low pressure slow speed operation for a few minutes, to confirm that the residual air in the fluid has been exhausted, before normal operation. Lateral load piston must generally be installed on the support ring, to ensure that the cylinder can withstand a large load. Seals and support rings play a completely different role, seals can not replace the support ring load. Hydraulic cylinder with lateral force, must add bearing capacity of the support ring (heavy load available metal ring), to prevent the seal in the eccentric conditions of work caused by leaks and unusual wear.

V. Hydraulic shock

There are many factors that produce hydraulic shock, such as the excavator bucket suddenly hitting the stone, crane lifting or putting down the moment of heavy objects. In addition to external factors, for high pressure and high flow hydraulic system, the implementation of components (hydraulic cylinders or hydraulic motors, etc.) when reversing, if the performance of the reversing valve is not very 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, such high pressure will tear the oil seal or squeeze it partially into the gap in a very short time, causing serious damage. Generally cylinders with hydraulic shocks should be fitted with a buffer ring and retainer ring 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 being squeezed into the gap under high pressure and the root from being