Six factors affecting sealing performance

1. Movement speed

The movement speed is very low (<0.03m/s), and the stability of the equipment operation and whether there is a crawling phenomenon should be considered. When the moving speed is very high (>0.8m/s), the oil film that acts as a lubricating oil may be destroyed, and the oil seal will rub and heat due to the lack of good lubrication, resulting in a greatly reduced life. It is suggested that the rubber-plastic composite RP is suitable to work within the speed range of 0.3m/s~1.2m/s.

2. Temperature Low temperature will reduce the elasticity of the rubber-plastic composite RP oil seal, causing leakage, and even the entire oil seal will become hard and brittle. High temperature will make the oil seal volume expand and soften, resulting in a rapid increase in the frictional resistance of the oil seal and a decrease in the pressure resistance capacity during movement. It is recommended that the continuous working temperature range of the rubber-plastic composite RP oil seal be -10～+80℃.

3. Work pressure

1. The oil seal has a minimum starting pressure requirement. For low-pressure work, oil seals with low friction performance and low starting resistance must be selected. Below 2.5MPa, the rubber-plastic composite RP oil seal is not suitable; when the high pressure is used, the pressure of the oil seal should be considered, an anti-extrusion retaining ring should be used, and there are special requirements for groove processing.

2. Oil seals of different materials have different optimal working pressure ranges. The optimal working pressure range for the rubber-plastic composite RP oil seal is 2.5~31.5MPa.

4. Working medium In addition to selecting the working medium in strict accordance with the manufacturer's recommendations, it is very important to keep the working medium clean. The aging or contamination of the oil will not only cause the components in the system to fail and accelerate the aging and wear of the oil seal, but also the dirt in it may scratch or embed the oil seal, causing the seal to fail. Therefore, the oil quality and its cleanliness must be checked regularly, and the oil filter or oil must be replaced according to the maintenance specifications of the equipment. The residual air in the oil in the oil cylinder will be compressed by high pressure, which will cause high temperature to burn out the oil seal, or even carbonize. In order to avoid this situation, exhaust treatment should be carried out at the beginning of the hydraulic system operation. 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 discharged before it can work normally. 5. Side load Generally, a support ring must be installed on the piston to ensure that the cylinder can withstand a large load. Seals and back-up rings serve completely different functions, and seals cannot replace back-up ring loads. Hydraulic cylinders with lateral force must be equipped with support rings with strong bearing capacity (metal rings can be used for heavy loads) to prevent leakage and abnormal wear caused by oil seals working under eccentric conditions. 6. Hydraulic shock There are many factors that produce hydraulic shock, such as the moment when the excavator bucket suddenly hits the stone, and the crane lifts or puts down the heavy object. In addition to other factors, for high pressure and large flow hydraulic system, when the actuator (hydraulic cylinder or hydraulic motor, etc.) changes direction, if the performance of the reversing valve 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. Such high pressure will tear the oil seal or squeeze it into the gap in a very short time, causing serious damage. Generally, the cylinder with hydraulic shock should install a buffer ring and a retaining 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 is bitten.