1. Movement speed
When the movement speed is very low (≤0.03/s), it is necessary to consider the stability of the equipment operation and check whether there is a crawling phenomenon. When the moving speed is high (≥0.8m/s), the lubricating medium may be damaged, and the rubber seal cannot get a good lubrication effect, and the friction generates a lot of heat, resulting in a reduction in life. Linde Polymer suggests that rubber seals are suitable for working in the speed range of 0.3m/s~1.2m/s.
2. Temperature of rubber seals Operating
Low temperature will reduce the elasticity of some rubber seals, causing leakage, and even make the entire oil seal hard and brittle. The high temperature will cause the volume of some oil seals to expand and become soft, the frictional resistance of the oil seal will increase rapidly during operation, and the pressure resistance will decrease. Linde Polymer recommends that the continuous working temperature range of rubber seals is -10~+80℃.
3. Working pressure
The oil seal has a starting pressure requirement. Under the low-pressure working environment, the oil seal with low friction performance and small aerodynamic resistance must be selected. Below 2.5Mpa, it is not suitable to use rubber seals. When the pressure is high, it is necessary to consider the pressure of the seal. It is necessary to use the anti-extrusion retaining ring groove, and there are special requirements for processing.
4. Working medium
In addition to selecting the working medium strictly according to the manufacturer’s advice, it is also 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 seal, making the seal invalid. Therefore, the quality and cleanliness of the oil seal medium must be checked regularly, and the oil filter or oil must be replaced according to the maintenance specifications of the equipment. In the oil cylinder, the residual air in the oil will generate high temperature through high pressure, which will cause the oil seal to burn out or even carbonize. In order to avoid this situation, before the operation of the hydraulic system, exhaust gas treatment should be carried out. The hydraulic cylinder should also run at low pressure and slow speed for a few minutes to ensure that there is no residual air in the oil before it can operate normally.
5. Side load
A support ring is generally required on the piston to ensure that the cylinder can bear a large load. The rubber seal and the support ring play completely different roles. The rubber seal cannot replace the load of the support ring. For hydraulic cylinders with lateral force, a support ring with strong load-bearing capacity must be added (metal rings can be used for heavy loads) to prevent the oil seal from being damaged. Work under eccentric conditions, causing leakage and wear.
6. Machining accuracy of oil cylinder
Experiments have proved that if the surface roughness Ra exceeds 0.8μm on the surface directly in contact with the oil seal, the leakage, and wear value of the oil seal will rise linearly. Therefore, we recommend that the roughness of the working surface be Ra0.1~0.8μm. In order to ensure the sealing of the rubber seal Performance, to avoid damage to seals during assembly, the following aspects should be considered in the design and installation of hydraulic cylinders:
(1) Cylinder
a. Material: mostly carbon steel, aluminum alloy, bronze, stainless steel, etc. can be used in low-pressure systems and occasions with good friction conditions.
b. Surface quality and roughness: The inner surface mostly needs to be ground, polished or rolled, and the roughness of Ra0.1~0.8μm is required, and no vertical and horizontal knife lines are allowed.
(2) Piston rod
a. Material: mostly carbon steel, chrome-plated steel, aluminum alloy, bronze, stainless steel, etc. can be used in low-voltage systems and occasions with good friction conditions.
b. Surface quality and roughness: the required roughness is Ra0.2~0.4μm, and the surface is plated with hard chrome after heat treatment. The piston rod of the hydraulic cylinder for construction machinery may be scratched by sand and stones, so its surface hardness is required to be above HRC60.
