Saturday, November 13, 2010

Corrosion of metal valves and valve application of composite materials

Corrosion of the valve, the valve is usually interpreted as a metal material in the chemical or electrochemical environment under the damage. As a result of "corrosion" phenomenon seen in the metal and the surrounding environment which spontaneous interaction, therefore, how to metal with the surrounding environment of the use of isolation or more non-metallic composite materials, then become a common concern. As we all know, metal corrosion damage on the valves of the role of the period, reliability and service life have a considerable impact. The role of mechanical and corrosion factors on the role of metal contacts has greatly increased the overall surface wear. Valve in operation, the friction surface of the total amount of wear and tear. Valve in operation, the friction surface at the same time as a result of mechanical action and Metals and the Environment to carry out chemical or electrochemical interaction of wear and damage results. In terms of valves, the pipeline complexity of the work of weather conditions; oil, natural gas and oil, water and other media in the hydrogen sulfide, carbon dioxide and some organic acids appear to increase the destructive force of the metal surface, which rapidly lost their ability to work. As a result of chemical corrosion of metals depends on the temperature, mechanical load friction parts, lubricating materials contained in the sulfide and acid stability and duration of media contacts and metal act as a catalyst for the nitridation process, corrosion and erosion molecular substances on the conversion rate of the metal and so on. Therefore, the corrosion of metal valves methods (or measures) and the application of synthetic material valve, the valve will become one of the themes of industry research. First, the anti-corrosion metal valve, the valve could be understood as the metal coating to protect them from the conditions of corrosion protective layer (such as paints, pigments, lubricating materials, etc.), so that both valves in the manufacturing, storage, transport or in the use of all the process are not subject to corrosion. Corrosion of the metal valve means to determine the needs in term of protection, transport and storage conditions, the characteristics of the valve structure and materials, of course, give due consideration to the lifting of the economic effects of corrosion. Anti-corrosion metal valve and its components are the four kinds of main methods: 1, the volatile corrosion inhibitor Add the atmospheric steam (waste of paper with the parcel, blowing air through the suppression chamber products, etc.). 2, the use of water resistance and alcohol solution. 3, the anti-corrosion (Protection) material thin layer applied to the surface of the valve and its components. 4, will be the resistance of the thin film or polymer applied to the surface of the valve and its components. (Note: At present, manufacturers of valves, the wider use of lubricating materials and melting of water flow resistance to corrosion.) Second, the application of the valve material Valve composite materials, in many corrosive conditions are superior to metal valves, first of all, anti-corrosion, followed by net weight, as its strength, it is necessary to strengthen the fibers depends on the shape, arrangement and quantity. (In general, the greater the percentage of fiber, the greater the strength of composite materials.) In valve applications, the weight of fiber content in the basic range of 30% -40%, and its chemical stability mainly by irrigation in the final product closure properties of fiber resin body decision. Valve in the synthetic material, the bulk of its solid polymer can be thermoplastic (such as PVC-PVDF, PPS-polyphenylene sulfide, etc.) may also be a thermosetting resin (eg, polyester, ethylene and its epoxide resin, etc.). Thermosetting resin in the temperature-mediated state of performance to maintain its superior strength thermoplastic plastics, (ie, thermoset resins have high heat distortion temperature). (Note: the status of workers in the use of synthetic materials, the determination of thermal performance is known as heat distortion temperature.) At present, the chemical process valves synthetic material most commonly used for the vinyl resin (thermal plastic material), the reinforcing fibers for the chopped glass fiber (1 / 4 inches long) and chopped graphite fiber (1 / 4 inches L). From the surface analysis, glass and graphite composite materials and metal-enhanced compared to the lower tensile strength, the synthetic material of the valve by the stress of larger cross-section of the site should be thick with rebar and metal in order to achieve the same performance. Synthetic material as a result of corrosion resistant valves, high strength and light weight, making it in many metal or glass fiber reinforced plastic piping systems in corrosive conditions, a more economical alternative valve products. Conditions in the chemical process, the synthetic material the use of valves excellent prospects. In the valve industry, the organic materials and the use of synthetic material, is not the traditional metal and non-metallic materials, the concept of the valve. Ceramics (the valve can be used to raise the temperature from 400 ℃ to 1200 ℃ and above), plastic (with a rust-proof characteristics of corrosion resistance), composite materials (with a corrosion-resistant, light weight, high strength), memory alloy (using shape memory alloy or the temperature of reversible memory alloys and high flexibility to make the valve) and so on. New materials, is developing a large number of high-performance valves with new products. Development of new technologies, so that a variety of engineering materials used in the valve manufacturing sector has become possible. valve ball valve gate valve check valve globe valve butterfly valve
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