1, rotary valve application trends (1) automatic valve instead of manual valve has become the trend of industrial applications With the worldwide industrial process automation level increased, the automatic and adjustable rotary valve demand continues to increase, while reducing manual valve demand . This will enable the development of valve application technology in the future should focus on the valve actuators and locators, so that the valve can be connected to the personal computer, PLC, DCS system. Such as the use of digital positioner by increasing the accuracy of the control valve to improve valve control performance, the successful application of If the ND800 digital positioner for rotary control valve, you can make the process variable range of 50%, and then through the control Valve Features Valve Positioner Electronic features are matched to further improve control performance. Typical applications are Field Browser software with HART network. Compared with the shut-off valve, the control valve is more suitable for continuous production process. Through the adjustment function, the control valve can change the size of the flow according to the input parameters to keep the set value unchanged. In many cases, both shut-off valves and control valves are required, as in refineries, 1/4 turn shut-off valves are used as safety shut-off valves. A control valve is normally used with two shut-off valves to isolate and shut off the flow of fluid when the control valve is disassembled. The electric actuator will gradually replace the pneumatic actuator because the electric actuator does not require installation and maintenance of the line and compressor and can be more closely linked to the positioner and can avoid converting electrical signals to gas signals. The other development direction of the rotary valve is to improve the performance of the valve by improving the design of the valve seat and the material of the valve seat so as to reduce the external leakage of the valve and the like. Intelligent valves with control and positioning make the market more and more widespread as manufacturers reduce costs and the need for manufacturers to increase productivity. (2) The trend of replacing linear valves Because rotary valves can replace linear valves (such as gate valves) in many cases, rotary valves offer many advantages over straight-stroke valves such as gate valves (see Section 1 of this paper) . In particular, with the implementation of the Clean Air Act (CAA) amendment, preventing leakage outside the valve becomes more and more important. The CAA Amendment, introduced in 1990, includes 189 Volatile Sources of Air Pollution (VHAPs), of which 150 are volatile organic compounds (VOCs). The latest CAA Amendment, adopted in April 1997, includes a quality improvement program in addition to the leak detection and repair (LDAR) program of the previous version. The CAA Amendments add to the investment made by chemical companies, refineries and other valve manufacturers that use straight-stroke valves to prevent leaks outside the valve. The CAA Amendment and its resulting control leakage have prompted manufacturers of manual valves, automatic valves, and control valves to adopt new techniques to design their valves to reduce external leakage of the valves. The key to reducing leakage outside the valve is the material of the valve packing system. Polytetrafluoroethylene (PTFE) and graphite are two common materials used in valve packing systems. Many suppliers combine perfluoroelastomers with some polytetrafluoroethylene and graphite to reduce the valve leakage system. Perfluoroelastomer packing systems have a much higher packing pressure than PTFE packing systems, but the packing system has a much higher packing pressure than perfluoroelastomer packing systems. The pressing force assembly causes wear and tear on the stem, causing leakage outside the valve. In general, the use of rotary valves is an effective measure to reduce external leakage, ie rotary valves have a tendency to act instead of valves. This trend is also illustrated by the market share of the Valve Manufacturer Associate VMA: According to data provided by the VMA, the volume of ball valves, industrial butterfly valves and plunger valves shipped in the United States in 1996 (VMA specifically records ball valves, In addition to this, the VMA tracks automatic valves as a separate category. Instead of recording the sales of quarter-turn regulators separately, they categorize them as automatic valves VMA provided data on the shipments of US suppliers, including exports but excluding imports, totaling 1.04 billion U.S. dollars, including manual valves and automatic valves, but excluding regulating valves. Ball valve accounted for the largest percentage, accounting for 54.2% of the total, industrial butterfly valve accounted for 26.2%, the remaining 19.6% share of the plunger valve. 2, the rotary valve application (1) the application of the refinery blending system For the blending system in the refinery, in order to improve the quality of reconciliation, often require a variety of oil involved in reconcile must be accurately and quickly injected and cut off, This often requires the use of control valves with higher cut-off rates to provide accurate fluid blending regardless of the flow rate of each flow path. Conventional linear or shut-off valves no longer adapt to this application in refineries. Rotary valves offer higher cost performance in this application due to their inherent advantages described above. To the user's long-term operation to bring greater benefits. (2) rotary valve is widely used in our plant specific application 1: Coking plant 4 radiant feed control valve to rotary valve. Coking plant originally designed as a two-seater valve, due to the coking radiation contains a lot of coke powder particles, and the high temperature, fast flow, the control valve have a great erosion, control valve spool, valve seat quickly Flushing bad, serious leakage, can not control, a new control valve can only run for 3 months; later the control valve for the sleeve valve, the situation has changed, a new control valve can run 5 each month. In 1997 September we will control the valve for the FISHER rotary valve, due to the rotation of the cavitation resistance, effectively overcome the erosion of the media, we check in October 1998, one of the control valve, spool, valve seat intact . Four control valves have been used until now. Specific application 2: Southern distillation vacuum furnace 3 feed. The original design vacuum furnace 3 furnace feed sleeve valve, because the feed contains residual oil, impurities, often blocked the control valve, and the high temperature, easy to condense, bring a lot of work to the instrument maintenance, June 1998 The 3-way feed for the FISHER rotary valve, rotary valve has a strong flow of capacity to overcome the above problems, the normal operation. Specific application 3: Catalytic residue refining control valve. The catalytic residue recovery control valve was originally designed as a sleeve valve, the residual oil refining catalyst, serious erosion of the control valve, the control valve can not be used normally, a new control valve into operation for 6 months, 1998 June will control the FISHER rotary valve, the use so far. Specific application 4: catalytic pressure machine torch. The torch used in the catalytic pressure press originally adopted a 700 gate valve. The disadvantage is that the switching speed is slow and the amount of leakage is large. After that, a triple eccentric butterfly valve is used, the switching speed is less than 10 seconds, and the sealing can be done at level 5. There are many such specific applications, no longer enumerated. 3 Conclusion: With the integration of refining equipment and the large-scale refinery and petrochemical plant, the requirements for the accuracy and adaptability of the instrumentation and control system are becoming more and more stringent in the production process. As the key components in the control system, the control valve, Its performance and quality have an increasing impact on the economic benefits of petrochemical plants. Whether it is for the future to expand the scale of production or to improve the quality of control (such as the advanced control or optimization control, etc.) require us to use the control valve, not only to consider one-time investment in the construction period, but also pay more attention to operating costs during the production period. With the rotating valve features increasingly recognized and accepted by the people, it will surely get more and more widely used in the increasingly large-scale oil refining and chemical plants in China. More Search Keywords: rotary valve
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