As a core component of the valve positioning system, the performance stability of the valve positioning film directly affects the control accuracy and operational reliability of the valve under high-temperature conditions. In high-temperature environments, the positioning film must withstand multiple challenges, including thermal expansion, material creep, and thermal stress. Its stability requires a combination of material selection, structural design, and process optimization.
The primary test for valve positioning films under high-temperature conditions lies in material performance. Ordinary rubber or plastic diaphragms are prone to softening, deformation, or even carbonization at high temperatures, leading to sealing failure or sluggish operation. Therefore, high-temperature positioning films typically use high-temperature resistant elastomer materials, such as fluororubber (FKM), silicone rubber, or special engineering plastics (such as PEEK). These materials maintain their elastic modulus and creep resistance at high temperatures; for example, fluororubber can be used continuously above 200℃, while silicone rubber is suitable for a wide temperature range from -60℃ to 230℃. Adding reinforcing fibers or fillers to the material further enhances its heat resistance and fatigue resistance, reducing permanent deformation at high temperatures.
Structural design is crucial for the positioning film's adaptability to high temperatures. Positioning films require precise geometry and thickness distribution to balance thermal stress and mechanical load. At high temperatures, thermal expansion of the material can cause changes in the diaphragm preload, affecting valve positioning accuracy. Therefore, positioning films often employ prestressed designs, using initial deformation to offset the thermal expansion effect and ensure the diaphragm remains in contact with the valve seat at high temperatures. Some designs also incorporate corrugated structures or flexible areas, allowing the diaphragm to expand and contract freely during thermal deformation, preventing cracking due to stress concentration. For example, the positioning film of a four-bar butterfly valve optimizes the connection angle between the connecting rod and the diaphragm, converting thermal expansion force into beneficial preload, significantly improving high-temperature stability.
The manufacturing process is crucial to the performance stability of the positioning film. High-temperature positioning films require precision molding or injection molding to ensure dimensional accuracy and surface quality. The uniformity of material mixing, vulcanization temperature, and time control directly affect the physical properties of the diaphragm. For example, fluororubber positioning films require high-temperature, high-pressure vulcanization to form a stable cross-linked structure, improving heat resistance and chemical corrosion resistance. Furthermore, the assembly process between the positioning film and the valve body must be strictly controlled to prevent diaphragm deformation or leakage at high temperatures due to installation stress. Some manufacturers use laser welding or bonding techniques to ensure the sealing between the diaphragm and the metal valve seat, while reducing the impact of heat conduction on diaphragm performance.
Dynamic stability under high-temperature conditions is a core challenge for positioning films. During frequent valve opening and closing, the positioning film must withstand alternating thermal stress and mechanical loads, which can easily lead to fatigue cracks. Optimizing the diaphragm structure through finite element analysis can reduce the stress concentration factor and extend service life. For example, in steam valves, the positioning film uses a multi-layer composite structure: a high-temperature resistant coating on the surface, an elastomer in the middle, and reinforcing fibers at the bottom, forming a gradient performance distribution to effectively resist thermal fatigue.
In practical applications, the performance stability of the positioning film needs to be verified through rigorous testing. High-temperature aging tests simulate long-term operating environments to evaluate diaphragm hardness changes, compression set, and sealing performance. Thermal cycling tests examine the diaphragm's adaptability to sudden temperature changes, preventing cracking due to thermal shock. For example, a chemical company uses positioning films that operate continuously at 150°C. Testing showed that their sealing leakage rate remained stable over a long period, meeting process requirements.
Maintenance strategies are equally important for the high-temperature stability of positioning films. Regularly inspecting the diaphragm surface for cracks, hardening, or deformation, and promptly replacing aging parts, can prevent sudden failures. Cleaning positioning films in high-temperature environments also requires caution; avoid using strong solvents that could damage the material. Some manufacturers offer online monitoring systems that use sensors to provide real-time feedback on the diaphragm's status, enabling preventative maintenance.
The performance stability of valve accessory positioning films under high-temperature conditions depends on collaborative innovation in materials science, structural design, and manufacturing processes. By selecting high-temperature resistant materials, optimizing structural design, strictly controlling processes, and implementing scientific maintenance, positioning films can maintain long-term reliable operation in extreme environments, providing crucial assurance for the stability and safety of industrial processes.
