You are here:Home » News » Technical Article » The Influence of Pressure And Caliber on The Sealing Performance of Triple-eccentric Butterfly Valves under The Corrosion of Different Media
First Eccentricity: By offsetting the centerline of the valve shaft from the centerline of the valve seat sealing surface, this ingenious geometric layout optimization can significantly reduce the friction loss between mechanical components during the opening and closing process of the valve. As a result, it effectively extends the service life and mechanical lifespan of the valve.
Second Eccentricity: This refers to the offset of the valve shaft centerline from the pipeline centerline. This design further optimizes the spatial contact relationship between the valve disc and the valve seat, greatly reducing the contact area and contact stress between them, laying a solid structural foundation for enhancing the sealing performance.
Third Eccentricity: The sealing surface of the valve seat is constructed into an inclined conical shape. When the valve performs the opening and closing actions, the valve disc and the valve seat form a unique linear contact mode. It is precisely based on this special contact form that the valve can achieve a zero-friction opening and closing process, thereby ensuring excellent and stable sealing performance.
In the working condition systems of chemically stable non-corrosive media such as water and air, the sealing performance of the triple-eccentric butterfly valve is mainly restricted by two key influencing factors: system pressure parameters and valve diameter specifications. Since such media will not chemically corrode the valve materials, under normal operating conditions, the sealing performance of the valve usually exhibits high reliability. However, in actual engineering applications, it is still necessary to systematically consider and analyze the factors of pressure and diameter in combination with specific working condition parameters.
(2) Slightly Corrosive Media
When facing media environments with slight corrosiveness, such as seawater and fluids containing trace acidic substances, the sealing surface of the valve will be at risk of potential chemical erosion. Under such working conditions, the selection of sealing materials is directly related to the service life cycle and sealing function integrity of the valve. Selecting suitable materials such as stainless steel and special alloys, with their excellent corrosion resistance, can effectively resist slight corrosion, maintain the structural integrity and functional stability of the sealing system, and ensure the normal operation of the valve.
(3) Highly Corrosive Media
For highly corrosive chemical media such as strong acids and alkalis, extremely stringent technical requirements are imposed on the sealing performance of the valve. Conventional materials cannot meet the needs of such extreme working conditions. Special engineering materials with super corrosion resistance, such as Hastelloy and titanium alloy, must be selected. In addition, in order to further enhance the corrosion resistance of the sealing surface, it is usually necessary to perform special surface coating treatment. Through the synergistic effect of material optimization and process improvement, the adaptability and reliability of the valve in harsh chemical environments are enhanced.
In a low-pressure operating environment, the stress load borne by the sealing structure of the triple-eccentric butterfly valve is at a relatively low level. Therefore, under such working conditions, the valve can more easily maintain stable and reliable sealing performance, and sealing failure is usually unlikely to occur.
(2) Medium-pressure Working Conditions (e.g., PN25 - PN40)
In the medium-pressure range, although the sealing performance of the valve remains generally good, as the pressure value gradually increases, the stress load on the sealing surface also increases accordingly, which will inevitably have a certain impact on the sealing performance. To ensure the stable operation of the valve under medium-pressure working conditions, it is necessary to ensure that the sealing surface materials have sufficient mechanical strength and optimize the structural design to enhance its bearing capacity for higher pressure loads.
(3) High-pressure Working Conditions (e.g., PN64 - PN100)
In high-pressure application scenarios, maintaining excellent sealing performance faces many technical challenges. Excessive pressure can easily cause plastic deformation or increase the wear degree of the sealing surface. Once such situations occur, the sealing effect will be severely weakened. Therefore, for high-pressure working conditions, it is necessary not only to select high-strength and high-wear-resistant high-quality sealing materials but also to systematically optimize the design of the valve to meet the stringent technical requirements of high-pressure operating environments.
Small-diameter triple-eccentric butterfly valves usually exhibit good technical characteristics in terms of sealing performance. Due to the relatively limited contact area of the sealing surface caused by the small diameter, the risk of medium leakage is reduced from the source. In addition, small-diameter valves require less opening and closing torque during operation, which facilitates operators to achieve convenient and efficient valve opening and closing operations.
(2) Medium-diameter Valves (e.g., DN150 - DN300)
Medium-diameter valves generally perform satisfactorily in terms of sealing performance, but they need to be paid special attention to in actual engineering applications. As the diameter size increases, the contact area of the sealing surface increases accordingly, leading to an increased risk of medium leakage. To ensure that the sealing performance meets the engineering requirements, it is necessary to strictly select the sealing surface materials and optimize and improve the structural design to ensure that it has sufficient sealing guarantee capabilities.
(3) Large-diameter Valves (e.g., DN350 and above)
Large-diameter triple-eccentric butterfly valves face more severe technical challenges in terms of sealing performance. The large diameter not only significantly increases the contact area of the sealing surface and greatly raises the risk of medium leakage but also causes the opening and closing torque required for valve operation to increase exponentially. This requires the installation of a more powerful actuator to ensure reliable opening and closing actions of the valve. Under such working conditions, only by selecting high-quality sealing materials and comprehensively applying advanced sealing technologies can the sealing performance of the valve meet the requirements of engineering applications.
When selecting the valve body and sealing materials, it is necessary to comprehensively consider the corrosive characteristics of the media. For non-corrosive media working conditions, carbon steel or stainless steel materials are more economical and practical choices. In working conditions involving corrosive media, special alloy materials or surface coating technologies must be included in the selection scope. Through scientific and reasonable material selection, reliable guarantee is provided for the stable operation of the valve.
(2) Selection of Pressure Rating
The determination of the valve pressure rating must be based on the actual working pressure parameters of the system. To ensure the reliable sealing performance of the valve in a high-pressure operating environment, the selected valve pressure rating should be strictly higher than the maximum working pressure of the system, thus leaving sufficient safety margins for the safe and stable operation of the valve.
(3) Diameter Selection
The determination of the valve diameter size must strictly comply with the requirements of the pipeline diameter specifications. Especially in large-diameter application scenarios, more attention should be paid to the sealing performance guarantee work. In addition to selecting high-quality sealing materials, advanced sealing technologies and processes should also be actively adopted. Through the synergistic application of multiple technical means, excellent sealing effects of the valve under large-diameter working conditions are ensured.
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