The sealing surface is the most critical working surface of the valve, the quality of the sealing surface directly affects the service life of the valve, and the material of the sealing surface is an important factor to ensure the quality of the sealing surface. Therefore, the following factors should be considered when selecting valve sealing surface materials:
① Corrosion resistant.
Under the action of medium, the sealing surface is destroyed. If the surface is damaged, the sealing performance cannot be guaranteed. Therefore, the sealing surface material must be corrosion resistant. The corrosion resistance of materials mainly depends on their properties and chemical stability.
② Scratch resistant.
"Scratch" refers to the damage caused by friction during the relative movement of sealing surface. This kind of damage will inevitably cause damage to the sealing surface. Therefore, the sealing surface material must have good scratch resistance, especially gate valve. The scratch resistance of materials is often determined by the internal properties of materials.
③ Erosion resistance.
"Erosion" is the process that the sealing surface is destroyed when the medium flows through the sealing surface at high speed. This kind of damage is more obvious in the throttle valve and safety valve used in high temperature and high pressure steam medium, which has a great impact on the sealing performance. Therefore, erosion resistance is also one of the important requirements of sealing surface materials.
④ There should be a certain degree of hardness, and the hardness will decrease greatly under the specified working temperature.
⑤ The linear expansion coefficient of sealing surface and body material should be similar, which is more important for the structure of inlaid sealing ring, so as to avoid extra stress and looseness under high temperature.
⑥ When used at high temperature, it should have enough oxidation resistance, thermal fatigue resistance and thermal cycle.
In the current situation, it is very difficult to find the sealing surface materials that fully meet the above requirements. We can only focus on meeting the requirements of certain aspects according to different valve types and applications. For example, the valve used in high-speed medium should pay special attention to the requirements of erosion resistance of sealing surface; when the medium contains solid impurities, the sealing surface material with higher hardness should be selected.
Post time: Feb-23-2022