The Selection of Valve Sealing Surface Materials
Sealing surface is the most critical surface of the valve. The quality of the sealing surface directly affects the service life of the valve. The sealing surface material is an important factor in ensuring the quality of the sealing surface. Therefore, the following factors should be considered when selecting materials for the sealing surface of sanitary valve:
1. Corrosion-resistant. Corrosion is the process in which the surface of the sealing surface is damaged under the effect of the medium. If the surface is damaged, then the sealing performance can’t be guaranteed. Therefore, the sealing surface materials must be corrosion-resistant. The corrosion resistance of the material depends on the composition of the material and its chemical stability.
2. Anti-abrasion. Abrasion is the damaged caused by friction of the materials in the process of the relative movement of the sealing surface. This kind of damage will inevitably lead to damage to the sealing surface. Therefore, sealing surface material must have good anti-abrasion performance, especially gate valves. The abrasion resistance of the material is often determined by the internal nature of the material.
3. Erosion-resistant. Erosion is the process in which the sealing surface is damaged when the medium flows through the sealing surface in high-speed. This kind of damage is more obvious in throttle and safety valve that are used in high temperature, high pressure steam medium. Its impact on sealing performance is great. Therefore, being erosion-resistant is also one of the important requirements of the sealing surface material.
4. There should be a certain degree of hardness.
5. The coefficient of linear expansion of the sealing surface and the bulk material should be similar, which is more important for the structure of the sealing ring, so as to avoid additional stress and looseness at high temperatures.
6. When used in high temperature conditions, there must be enough antioxidant, thermal fatigue-resistant and thermal cycling.
Under current circumstances, it is very difficult to find sealing surface materials that meet all the above-mentioned requirements. Therefore, we can only focus on meeting certain requirements according to different types and uses of valves. For instance, we should pay special attention to the corrosion-resistance requirement of the sealing surface in valves used in high-speed medium.