Main reasons affecting valve sealing

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Valve leakage is very common in both daily life and industrial production, and it has significant consequences. In mild cases, it can lead to waste or pose dangers to people’s safety, such as in the case of leaks in water supply valves; in severe cases, it can result in serious outcomes, such as leaks of toxic, harmful, flammable, explosive, or corrosive substances in the chemical industry, thereby posing serious threats to human safety, property safety, and causing environmental pollution. A valve that relies on external force to rotate and thus open or close is equipped with a sealing mechanism; this involves installing a certain number of packing rings in the packing box in order to achieve a seal. But what is the actual level of sealing? Leakage at the valve’s packing is one of the most common areas where leaks occur in valves, and the causes are mainly related to the following factors. 1. Seal pair structure: Under the influence of changes in temperature or sealing force, the structure of the seal pair changes. Moreover, this change affects and alters the force between the sealing surfaces, thereby reducing the sealing performance of the valve. Therefore, when selecting a seal, it is essential to choose one that can undergo elastic deformation. At the same time, attention should also be paid to the width of the sealing surface. The reason is that the contact surfaces of the sealing pair cannot fit together perfectly; as the width of the sealing surfaces increases, more force is required to achieve sealing. 2. Specific pressure on the sealing surface: The level of specific pressure on the sealing surface affects both the sealing performance of the valve and its service life. Therefore, the specific pressure on the sealing surface is also a very important factor. Under the same conditions, an excessively high specific pressure can cause damage to the valve, while an excessively low specific pressure can lead to valve leakage. Therefore, it is necessary for us to fully consider the appropriateness of the specific pressure during design. 3. Physical properties of the medium: The physical properties of the medium also affect the sealing performance of the valve. These physical properties include temperature, viscosity, and surface hydrophilicity. Temperature changes not only affect the relaxation of the sealing pair and the variation in component dimensions, but are also closely related to the viscosity of the gas. Gas viscosity increases or decreases as the temperature rises or falls. Therefore, in order to reduce the impact of temperature on the sealing performance of valves, we design the sealing pairs as valves with thermal compensation features, such as elastic valve seats. Viscosity is related to the fluid’s ability to penetrate. Under the same conditions, the greater the viscosity, the lower the fluid’s ability to penetrate. Surface hydrophilicity refers to the need to remove a thin film from the metal surface. Because this thin layer of oil film destroys the surface’s hydrophilicity, causing blockages in the fluid channels.