In the past 50 years, the basic function of the automatic control valve has not changed. Only the fixed basic performance has been increased, such as increasing the flow coefficient, reduce noise, reduce cavitation and improve the flow characteristics. However, the structural design characteristics change very slowly. Until the emergence of nuclear energy, valve manufacturers in the valve design had to consider the impact of such external forces as earthquakes. This paper discusses the improvement of control valves from the perspective of anti-seismic design; such as material selection, drive design and structure assembly, assembly of parts and so on. Nuclear power plant control valve must be able to withstand the impact of the earthquake. In fact, this is a prerequisite set by the United States federal regulatory code for a wide range of topics on the design, construction and operation of their nuclear power plants. 10CFFR50 is the "United States federal equipment manufacturing and license" on behalf of its Appendix A lists the "General Nuclear Power Plant Design Standards" (GDC). A paragraph in GDC-2 states: "The structures, installations and components of nuclear power plants must be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, Biao Feng ...". Other GDCs can also serve as a reference to indicate the necessary conditions for equipment to resist seismic and power constraints. These include GDC-1, I-4, I-14 and I-30. Although nominally, such generic standards that are not described in detail are virtually impossible to enforce. As the nuclear industry matures, the anti-seismic design and analysis of plant equipment will become clear, and all GDCs proposed by the industrial sector have a place in today's anti-seismic design control valve improvements. The Nuclear Regulatory Commission (NRC) has released the "Standard Test Plan" and "Standard Regulation Guidance." Various industrial organizations have also released a series of regulations and standards called the "NRC" required standard. Building designers and utilities are also beginning to issue relevant laws and regulations, and have clear requirements on the application of standard regulation guidance, standard inspection schemes and permits. At last. Control valve manufacturers to meet the industrial anti-seismic constraints and improve the product structure design. Essential Conditions for Resisting Seismic Limits for Solenoid Butterfly Valves (SQR) Initially, the control valve specifications for seakeeping are usually few, but simply to say something like "these valves can withstand the effects of natural phenomena such as earthquakes and tornadoes" or " These valves take into account the geography of the design "and usually do not have quantitative values ​​in these conditions. In contrast, today's instructions regarding the anti-seismic conditions section provide for acceptable limits and the rate of acceleration equipment must limit is very accurate. In very early factories, the anti-seismic design requirement was only that it was necessary when the equipment was placed in a very active seismic zone. The equipment and buildings in those plants are all designed according to the requirements of the Building Code (VBC) and use static analysis techniques. The anti-seismic design of 1965 formed a general specification of all nuclear power plants. There is enough evidence to show that the earthquake may have taken place anywhere, and earthquakes are possible both in areas with frequent earthquakes and in places that have historically occurred. Occurred in Massachusetts (1755); several major earthquakes in South Carolina (1876) in Missouri (1812) demonstrated that anti-seismic design should be considered in the design of nuclear power plants. In the early days, most of the equipment was qualified to use static analysis methods, which is amenable to simple-structured control valves compared to complex buildings and other structures. The input acceleration rates used for these analyzes are usually based on establishing reaction accelerations or even on the site rather than the reaction acceleration of the pipeline system, but there is still no standard. In the early stages of development, professional organizations established various commissions and professional groups for the special needs of the nuclear industry. The two associations most influential on valve manufacturers were the American Society of Mechanical Engineers (ASME) and the Institute of Electrical and Electronics (IEEE). The ASME, Part 3 of the Boiler and Pressure Vessel Code, was written specifically for components of nuclear power plants and in 1968 this part became the rudiment of the draft regulations and for the first time in 1971 it was used in its entirety Published several further changes in the next six months.However, ASME-III specifies only the pressure range of the valve, which by definition is simply the body of the valve, bonnet, stem and bolt of the connector cover The pressure range for the remaining part of the valve, ie attachments and drives, is not mentioned in ASME-III, and as a result only the pressure integrity is covered by regulations without the ability to deal with the operation of the plant.To demonstrate that during the earthquake After the earthquake the ability of equipment to operate, it is necessary to develop other standards.IEEE-344 is the most recognized equipment seismic reference standard.First announced in 1971, in 1975 its main department Although the IEEE indicated that it is suitable for use on electromechanical equipment, it is generally accepted as an anti-seismic qualification standard applicable to all equipment.NRC's Standard Test Method 3.10 discusses the anti-seismic conditions of electromechanical equipment , NRC in SRP 3.10 states that IEEE-344 is applicable to the seismic requirements of all types of electromechanical equipment and was later not subject to any seismic limit requirements of valve drives or valve assemblies until IEEE-382 was first released in 1972. However, at that time it merely defined the limitation of the valve electric drive (in the earthquake environment) and there was no specific limit to the elastic diaphragm drive, cylinder drive, hydraulic drive, etc. The IEEE-382 change This phenomenon, which includes all the limitations of a variety of drive standard IEEE 382-1990 "valve drive safety conditions IEEE standards" states "This specification applies to all types of power driven valve drive." IEEE 344 and IEEE 382 are the most widely accepted standards for earthquake resistance of valves or valve drives Many of the other criteria have also been published or have been developed differently, however, these standards are not as widely recognized as either of the above, as it is difficult for these standards to provide a clear understanding of the necessary conditions for them, With little or no assurance of their technical and design requirements, are listed in Appendix A. Each of these standards treats a valve assembly as a stand-alone unit with regard to the valve's location on the pipeline system or pipeline on which it is installed The effect of the system on the valve is not described, so that the pipeline system designer is in an unfair position to consider the dynamics of the valve in their pipeline system even before the valve is selected or the buyer chooses. The valve manufacturer must also detail the anti-seismic requirements of the valve before the pipe system is finalized. This is a brake system. The pipe system is designed so that the valves in his pipe system can only be realized after knowing how the valve will react Stereotypes, and valve manufacturers only know how to respond to the pipeline system can be limited to a special pipeline The valve on the opposite. In this way, the general anti-seismic code in the valve code is to be developed. These common specifications are a compromise between the valve manufacturer and the piping system designer who agree to exclude the dynamic feedback from the valve back to the piping system. It is required to do so because the valve assembly has its basic natural frequency at a selectable value, usually 33 Hz. Any building or pipeline in this way is considered to have a frequency below 33 Hz, which otherwise would not be able to withstand the earthquake's resonant harmonic. This will not result in valve resonance and its inherent magnification. Therefore, the designer of the pipeline system needs to consider the quality of the valve in its system. In return, the pipeline system designer agreed to limit the dynamic characteristics of the pipeline system becoming the valve seismic input to a certain value. The upper limit of this value becomes the valve-limited input acceleration, which is normally 3.og or 45g depending on the construction engineer's opinion. So far, the valve has been developed from general design guidelines to industrial codes and standards for seismic design conditions. The final specification requires a 3.0 g or 4.5 g input acceleration with a natural frequency greater than 331 Hz and within the frequency range of 1 to 33 Hz. The best way to study control valve anti-seismic structures is to study each of its major components one by one. These components are shown in Figure 1. They are the valve body, the bonnet, the drive connected to the bonnet and the drive above the device drive annex. Body: Body is an essential piping system, if the pipeline system meets the requirements, the valve must meet the requirements. This is what ASME Code edits. "According to this regulation, if the pipeline and valve body are designed according to the law and the manufacturer can show that the weakest part of the valve is also stronger than the pipeline, then The valve shall be deemed to be J. This should mainly indicate that the cross-sectional area of ​​the valve and the cross-sectional membrane value of at least 10% higher than those of the pipeline If the pipeline and the valve of different materials, it is necessary to consider the pressure between them (According to ASMEIll, NCl / ND3S21) For valves and lines of the same line size it is no doubt proving to be satisfactory; typically, the valve strength is 300% higher than that of the line to which it is connected 400%, a problem arises when using a reducer or valve that is 2 times or more smaller than the pipe size.This problem can be mitigated in several ways, a simple way is to reduce the area of ​​the valve trim to between This simple and easy way of having the same line size has its advantages, since using a large valve means a higher cost. Another way is to understand the pipe load and the stress from the buyer Naturally, applying stress analysis can also increase the cost of production, especially if one of the computer-defined methods is applied. The third solution is to use a high pressure valve body (that is, ANSl600 rather than 15Q) , Which will increase the metal cross-section, so that the increase of metal materials, but may be smaller than the cost of large-size valves. Of course, these methods combine to achieve the best results. In general, the control valve body In general, the valve body is stronger than the pipeline, and the method of stress analysis is also very simple.Also need to use some technical transformation occasionally, the choice of valve size and pressure coefficient At the same time to meet the liquid handling requirements and anti-seismic requirements. Valve cover: from the anti-seismic analysis point of view. Valve cover can be regarded as an "intermediate support structure." Pipeline system seismic motion must be able to reach the drive through the valve cover. The bonnet must be able to withstand the dynamic effects of the drive and for itself the bonnet is a very strong part of the valve. Because of its basic structure, it is difficult to accurately analyze most of the control valve cover with ASME a Ⅲ Annex X1 analysis, although this appendix is ​​usually prepared for the analysis of pipeline flanges, but is generally recognized as can do Analysis of bonnet flanges Any earthquake-induced bending force on the drive unit is converted to a "high pressure" abbreviation eq. This increases the design pressure on the valve. The bonnet and bonnet bolts must be capable of With this increased pressure of the flange structure, Pfd = Pd + Peq.) Computational pressure will be higher if the pressure is calculated in a more complicated way, since the bonnet is much stronger than the pressure required, Within the limited permissible range of 1. The bonnet must be able to support the drive unit fixed to it Some of the drives are often large enough to extend from the bonnet to a prominent position and a valve drive may be the entire system Has obvious dynamic influence. It is these dynamics that result in most of the changes to the valve bonnet. These changes include increasing the wall thickness and flange thickness, and redesigning the connection between the drive and the bonnet to be less stressful, on the contrary increasing the stiffness and stability Sex. The more solid the valve cover, the more the overall natural frequency of the valve components can be kept as high as possible. Valve Actuators: Valve actuators are the most control valve components that are most affected by the seismic constraints of the nuclear power industry. Control valve actuators, once thought to be essentially simple, have been demonstrated by themselves to do sample analysis and to do their job of increasing the natural frequency The improvement is equally difficult. Like the rest of the valve, the structure of the drive has remained essentially the same for more than a decade; its design capabilities are already in fossil fuel powered plants, paper mill oil refineries and all large and small ships On the multi-year application has been proved until the valve manufacturer had to prove that anti-seismic test requirements. Only a design change. A drive unit has two basic components, a bracket and a power unit. The bracket is used to secure the drive unit to the bonnet to provide a connection between the valve stem and the drive, as well as a location for attachment (such as a spring Limit switches and positioners in diaphragm drives, etc.). The second part is the power source, the typical type is spring diaphragm, cylinder, hydraulic jack and motor. In most cases the brackets are made of cast iron and are bolted to the water cap with some large fastening nut, however the design must be changed because of the need to withstand dynamic loads like earthquakes. First change is the material, the material used in the first cast iron is very suitable for the initial design load, that is, the main drive a device thrust. Cast iron has a problem in that it is very brittle material is very sensitive to large impact load and low turn fatigue load damage, so the cast iron material to cast steel material, usually ASTM-216 WCB type, this change is easy to achieve because Design and mold are the same. Machining is the same, but material changes. The next change is more difficult. The results of many anti-seismic tests confirm that the connection between the support and the bonnet must be redesigned, and the fastening nut has a higher initial design performance. However, the results of the dynamic load test against seismic inspection reveal some problems: First, the bracket is supported on the seat of the bonnet, which is sufficient to support the thrust load of the extended drive because all of the components are subjected to a compressive force. However, there is not enough support surface at the base of the drive to hold Possibility of high standoffs. Second, the tightening nuts tended to loosen during anti-seismic testing, and the course of an earthquake test was more intense than any possible earthquake, and the loosening was not as disastrous as the breakage of cast iron. Nonetheless, loosening at such critical points as tightening nuts is also not allowed. At the same time, there are other problems with the looseness of the fastening nut, which means that once the connection between the bracket and the bonnet is loosened, the drive may then be deflected around the stem axis, resulting in displacements like limit switches and locator elements out of control. Both the drive and the bonnet are improved in connection. The basic idea behind the design is to provide a large contact surface between the stand and the bonnet, providing a mechanism for preventing rotation of the drive and loosening of the connection so that the stand and bonnet Between the more solid connection. It is quite easy to provide a large contact orientation between bonnet and bracket. The bonnet's cast model is temporarily or permanently modified to provide a fixed flange that secures the drive or a flat plate welded to the bonnet. How to make the drive robust depends on the designer's measures. The connection method is shown in Fig. 2. It includes the original structure of the fastening nut, and the other methods are as follows: the driving device is fastened according to the flange bolt of the valve cover or the pressure plate in the position of bolting the valve cover , Or bolted directly to the bracket through the bonnet flange. Some modifications have been made to the drive design based on the basic principles of earthquake resistance, including maximizing strength, reducing weight and lowering the overall center of gravity. Although the purpose of these changes, which will be discussed later, is not to be discussed in a very simple manner, it is in fact very difficult to implement these principles. For example, in order to increase the strength, it is necessary to increase the material (increase the mass) because the power source must be supported by the leg and the center of gravity can only be reduced to a limited extent. In many cases, the structural steel must be installed with a driving device or Additional support. The usual case is a mark of a given size. The quasi-drive must have a fixed frequency in the 1OHz range. Redesigning the drive for earthquake resistance is almost a completely new design. Increase base Use bolts to secure bonnet. Bracket made of structural steel. The main channel, which is to improve the strength. In the low strength of the additional addition to the clapboard plate to eliminate bending, by removing excess material to lower the center of gravity. The result is that the drive has the same function on the same valve. Its same frequency is completely above 33Hz. In order to meet the requirements of anti-seismic conditions of nuclear power plants, control valve actuators undergo considerable structural improvements. These improvements include the design of materials, connections, and overall structures. As a result, one type of design and engineering reforms are often used to meet the needs of industrial production. Actuator Accessories: Actuator Accessories Commonly used on spring-driven or cylinder-driven pneumatic devices such as spring-loaded or cylinder-driven, the types of accessories that are attached to the drive include limit switches, solenoid valves, positioners, air filter regulators, Booster and electro-pneumatic sensor. The number and type of accessories are based on the function of the valve and the needs of the user. Electrical and electro-hydraulic drive attachments are often included in the drive structure and therefore have few problems. In addition, they do not require devices such as air receivers, solenoid valves, and air boosters that also do not require those disruptive gas lines. These attachments are smaller in size than the drive on pneumatic devices, which means that attachment installation does not significantly affect the dynamics of the entire valve assembly. However, attachments and their fixtures do have some effect on the seismic resistance of the valve eg when considering the installation of a limit switch, it will lose its connection with the valve stem if it is installed in a flexible manner and will therefore end The control room conducts a false signal. Alternatively, connect the air receiver to the solenoid valve flexibly. The flexible connection and its inherent large offset will not produce the wrong signal as a fixed limit switch, but it will make it difficult and broken to work on the connected copper tube, thus making the valve ¨ not workable, Valve anti-seismic requirements. Erratic signals, rupture of gas lines, and other events are unacceptable. The design and installation of accessories must also be based on the principle of anti-seismic structure of the drive: 1) to maintain a sufficiently high hardness; 2) to have the smallest volume; and 3) to keep the low center of gravity so that the effective weight is as low as possible. Often the structural changes to the attachments are mainly made of mounting brackets. The only requirement for the general industry is that the fixed elements make it work and can withstand shipping, installation and normal operation, however, the application to nuclear power plants is not enough. As an example, the mount locator in Figure 3a is for use in the general industry, making it easy and well done, but the seismic test results show that there will be excessive offset under seismic conditions. " General Industrial "mounting frame in the hardness can not meet the anti-seismic requirements of nuclear power plants. Figure 3b shows a gusset plate welded to a general-purpose mounting, which ensures strength and minimizes deflection. Design changes have been made to control valve attachments to meet earthquake resistance requirements. The most obvious change from these attachments is the redesign of the mounting brackets, which results in the least possible displacement in the epicenter. Prospects: Advances in anti-seismic requirements of nuclear power plants are difficult to predict. Similarly, future design improvements of control valves are unpredictable, but future developments are not expected to be as fast as before. It has been possible to demonstrate that the quake-proof conditions of the existing equipment and the current design make minor improvements to the early design that all operating nuclear power plants demonstrate that the electrical equipment involved in safety can withstand the effects of heat, radiation and moisture (10 CFR 50, 49) Many devices have been replaced by "certified" devices. Subsequent products will indicate qualified anti-seismic equipment, which is of particular importance in the design enhancements of the most established older nuclear plants or micro-devices equipped with anti-seismic requirements. Perhaps the new anti-seismic design equipment will replace the old equipment, cast iron drive will be replaced by cast steel, fastening bolt connection will replace the fastening nut connection, the device limits the low acceleration and again a small natural frequency conditions will be Kennedy valve ¨ alternative and accessories limited to 3.Og or 4.5g input acceleration level. Conclusion: The installation of anti-seismic equipment in nuclear power plants is a process of development. In order to meet these requirements, the design of control valves has also been developed. Control valve manufacturers in order to meet the needs of buyers both said that the structure of the product design also states the functional design. While anti-seismic constraints have been slower to improve than ever before, owners of old nuclear power plants may need to replace their old equipment with new anti-seismic equipment that is necessary for them to meet today's anti-seismic constraints . 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