Valve maintenance

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Valve maintenance: Maintenance and repair of various types of valves, as well as safety valve maintenance and repair. Can damaged valves be repaired? Valves are widely used in special equipment such as boilers and pressure vessels, as well as in all pipeline networks used for transporting liquids and gases in the industrial sector; they are essential components for the transfer and connection of materials within pipeline systems. The quality of valves has a direct impact on production and safety, and valves are undoubtedly vulnerable components. 　　Valve leakage is a problem that cannot be ignored. Due to wear from valve opening and closing, wear and corrosion caused by fluid flow, and the compression of impurities, damage such as pits, scratches, and spots can occur on the valve’s sealing surfaces. According to statistics, 80% of valve leaks are caused by damage to the valve sealing surfaces. Valve leakage can cause loss of the transmission medium ； Environmental pollution ； Production failures (such as leaks in control valves can result in inaccurate composition of chemical products) ； Major accident disasters (such as explosions caused by safety valve leaks, leaks of toxic gases, etc.). At the same time, in the thermal and nuclear power industries, the economic losses resulting from reduced power generation due to valve leaks or emergency shutdowns are enormous. Ways to resolve valve leakage issues: Various types of maintenance and repair for valves; maintenance and repair of safety valves. Can a damaged valve be repaired? Ways to fix valve leakage: one is to replace the valve, and the other is to repair it. The two methods for fixing valve leaks have their own advantages and disadvantages, but for dealing with leaks in special valves subject to high pressure and high temperature, as well as large-diameter valves, the approach taken is generally to repair them whenever possible. Repairing it when possible can avoid the disadvantages associated with replacing it with a new valve. The delivery time for new valves is long, usually ranging from 6 months to 1 year ； Advance ordering requires a warehouse and deposit funds ； The new valves are expensive ； This results in environmental pollution as well as significant waste of energy and materials, since in most cases it is only the sealing surfaces of the valves that are damaged ； The processes such as cutting, welding, stress relief, and straightening required to replace welded valves are even more time-consuming and labor-intensive. Valve maintenance The first patent for a valve maintenance machine was granted in 1904 by the American company LEVITlDEXTER. Valve maintenance is divided into major repairs and minor repairs, as well as on-site repairs and repairs in workshops. 　　On-site valve maintenance was first used in steamships over the years; it is suitable for minor maintenance tasks on valves that are in use. Valves should be taken apart regularly for inspection, and any damage should be repaired promptly. In the event of leaks, quick action and repair are necessary in order to minimize leakage losses and downtime. There is no need for the time or cost associated with removing and transporting valves, especially for welded valves – there is also no need for spare parts to be stored in warehouses, nor is there any reliance on the delivery times of new valves ； The machinery used for on-site repairs is portable, easy to operate, and in most cases can be handled by one person. It saves time, effort, as well as money and resources; therefore, on-site maintenance repairs should be promoted. Shop repair and processing is suitable for the major overhaul of valves as well as the repair (processing) of special and complex valves, including removing the valves from the pipelines, cleaning and degreasing them, repairing them, testing them, and painting them. Since the valve body material has withstood testing in actual operating conditions online, its quality can be guaranteed to meet the standards of new valves. The Current Situation and Countermeasures in the Domestic Valve Inspection and Repair Industry For a long time, most industries in China have relied on replacing old valves with new ones, discarding or selling the old valves as waste. This is especially true in industries that use valves with flanges. As for the high-pressure, high-temperature valves that are replaced, there is a desire to repair them, but it is not clear how to do so. Most are still at the stage of manual repair. It can be said that in China’s valve maintenance industry, both waste and potential benefits are substantial. A power plant (4x500MW~4x2000MW) has to repair tens of thousands of turbine valves and bypass valves each year. The power plant has only one grinder imported from Germany in 1992; the rest are operated manually, which not only results in low efficiency but also fails to meet the required precision standards. The bypass high-pressure relief valve is leaking, and the power plant is unable to repair it. Sending it to Shanghai for repair also did not yield satisfactory results. In recent years, as various units have gradually begun to conduct independent financial accounting in order to reduce costs, everyone from management personnel to frontline maintenance workers has come to realize the importance of valve maintenance, as the savings that can be achieved in this area are quite substantial. However, repairing valves here does not simply mean carrying out basic repairs; it also involves using the correct repair methods and high-quality grinding equipment. 　　Due to a lack of awareness and equipment for valve maintenance and inspection, currently only nuclear power plants in China are able to carry out inspections on all valves during each shutdown for maintenance. Repairing something after it has broken down is a form of maintenance-free repair, which is extremely detrimental to the safe operation of the entire equipment as well as to the service life of the valves. It poses a high risk of emergency shutdowns, and the resulting losses are also substantial. For example, a petrochemical plant in Tianjin had a production unit that was entirely imported from Germany. From its commissioning in 1981 until 1996, it was not serviced at all. In 1996, it was discovered that several key packing valves were leaking, and the German manufacturer no longer produced such special valves. Reordering them would not only be expensive but also involve a long lead time, resulting in significant economic losses. Therefore, preventive maintenance and repair measures for industrial high-temperature and high-pressure valves represent the most economical and reliable way to address valve leakage and extend their service life. 　　If a valve leaks without undergoing maintenance repairs, it is often already in a state of severe damage; this not only increases the difficulty of repair but also often renders repair impossible or pointless. Therefore, for well-organized and managed valve maintenance, it is not only necessary for the relevant personnel to have the appropriate awareness, but more importantly, preventive and maintenance measures are required, such as regular inspections of the valves (for example, their sealing performance against the outside environment, their tightness when closed, etc.). The key to preventive maintenance of valves is to repair them immediately as soon as a leakage is detected, because the medium flowing through them can cause extensive damage to the sealing surfaces even in the event of minor defects, leading to high repair costs. Various types of valve maintenance and repair; maintenance and repair of safety valves. Can damaged valves be repaired? It is important to carry out regular maintenance checks on all valves in the equipment in order to address valve leakage issues, thereby enhancing the safety and reliability of the entire system. Maintenance repairs mainly involve the grinding and repair of sealing surfaces, as well as inspection after the repairs.