When choosing a sealing material, you must understand the working conditions, what material to choose mainly considers the working conditions, and also appropriately consider the price factor. When selecting a sealing material, consider the following specific usage conditions.
1. Is the sealing working medium gas? Or liquid?
If it is a liquid, the compatibility of the liquid and the material should be considered; the compatibility of the material with the lubricant and grease should also be considered for the gas; the gas and negative pressure seal should also pay attention to the air permeability. Compatibility of the sealing material and the sealing fluid can cause the seal to expand or contract and fail early in service. The expansion of the seal causes an increase in frictional resistance and at the same time causes the seal to roll. The shrinkage of the seal will cause a reduction in the preload and the ability to compensate for eccentricity, leading to leakage.
2. Is it a dynamic seal? Or static seal?
The dynamic seal has corresponding requirements on the friction and wear properties of the material, and the material with the appropriate friction coefficient should be selected according to the movement speed. In order to obtain sufficient service life, the wear resistance of the material should also be selected according to the movement speed and stroke. When low-speed performance is required, special attention should be paid to the size of the friction coefficient of the material and the difference between the dynamic and static friction coefficients.
3. Is the structure of the seal extruded? Or lip shape?
Different structural types have different sealing working principles, which must have different requirements for many mechanical properties such as elasticity, strength and deformation rate of materials.
4. Work pressure
The working pressure is the main working parameter of the hydraulic and pneumatic systems, which can be changed in the range of 1~400MPa or more. The pressure resistance of the material should meet the requirements of the working pressure.
5. Working temperature
The applicable temperature ranges of various sealing rubbers and plastics vary greatly. When selecting materials, it is necessary to accurately grasp the working temperature of the seals, especially the low temperature environment of the components, and select materials accordingly; or according to the working temperature range of the materials, control Temperature rise of components, systems, seals. Choose a material that can withstand its maximum temperature.
6. Whether the working environment is polluted or not
If there is dust pollution in the working environment, it will aggravate the wear of the material, and the wear resistance of the material should be improved.
7. Components work smoothly or vibrate.
If operating under vibrating conditions, the material should have sufficient elasticity to compensate for insufficient seal contact stress due to deflection caused by vibration.
8. The relationship between materials and assembly process
The assembly process of the seal and even the structure of the sealing device are related to the deformation ability of the material. Generally, the assembly process should be adapted to the material properties. If permitted, the assembly performance of the seal should be properly considered when selecting materials.
The requirements of various working conditions for sealing materials are often mutually restrictive, and it is impossible to achieve uniformity. In the case of synthetic rubber, it is extremely difficult to obtain a material excellent in all properties. As far as both sealing and friction are concerned, one must always be pursued at the expense of the other in terms of material properties. The two performance requirements must then be properly balanced. Therefore, with the higher sealing requirements, special materials must be sought according to the conditions of use. Even in the same component, sometimes multiple sealing materials are used depending on the requirements.
Due to the importance of materials to the performance of the sealing device, it is difficult to talk about the performance of the seal without the material, or talk about the sealing design without the material. Therefore, the selection of materials will be introduced in this website for specific situations in the future.