The control valve is also known as the control valve. In the field of industrial automation process control, it controls the final control elements of medium flow, pressure, temperature and liquid level by adjusting the output control signal of the control unit and by means of power operation. Generally, it consists of the actuator and the valve. The regulating valve can be divided into direct stroke and angular stroke according to the characteristic of travel. According to the power used by the executive mechanism, it can be divided into three kinds of pneumatic regulating valve, electric regulating valve and hydraulic regulating valve. According to its function and characteristic, it is divided into three kinds: linear characteristic, equal percentage characteristic and parabola characteristic. The regulating valve is suitable for air, water, steam, various corrosive media, mud, oil and other media. The regulating valve is commonly classified as pneumatic regulating valve, electric regulating valve, hydraulic regulating valve and self regulating valve. Control valves play a very important role in automatic control of modern chemical plants. The production of these plants depends on the correct distribution and control of the moving liquid and gas. These controls, whether the exchange of energy, the reduction of pressure, or the simple container feeding, need to be done by some of the final control elements. The final control element can be considered as the “manual” of automatic control. Between the low energy level of the regulator and the high energy level functions required to control the flow fluid control, the final control element completes the necessary power amplification. The regulating valve is the most widely used type of the final control element. Other final control components include metering pump, regulating baffle and louvered baffle (a butterfly valve variant), variable slope fan blade, current regulator and motor positioning device different from valves. Although the regulating valve is widely used, the other units in the regulation system are probably not as small as it is. In many systems, the working conditions such as temperature, pressure, corrosion and pollution are all more serious than those of other components. However, when it controls the flow of process fluid, it must be satisfactorily run and minimal maintenance. In the pneumatic control system, the pneumatic signal output by the regulator can directly drive a spring type thin film actuator or a piston actuator to make the valve move. In this case, the energy needed to determine the valve position is provided by compressed air, and compressed air should be dried in outdoor equipment to prevent freezing and purify and filter. When a pneumatic regulating valve and an electric regulator are used, an electric one valve positioner or an electric one can be used. The air supply system in compressed air can be considered as well as a fully pneumatic regulating system. In the terms of the regulation theory, the regulating valve has both static and dynamic characteristics, so it affects the success of the whole control loop. The static characteristic or gain term is the flow characteristics of the valve. It depends on the size of the valve, the combination structure of the valve core and the valve seat, the type of the actuator, the positioner of valve, the pressure before and after the valve, and the nature of the fluid. The fifth chapter will introduce these contents in detail. The dynamic characteristics are determined by an actuator or a valve positioner, a combination of an executive mechanism. For slower production processes, such as temperature control or level control, the dynamic characteristics of the valve are generally not a limiting factor in controllability. For a faster system, such as the flow control of the liquid, the regulating valve may have a clear lag and must be considered in the control of the loop. Generally, only the expert of the control system needs to care about the dynamic holding of the control valve. The regular consideration of applying the valve positioner, as discussed in the ninth chapter, will meet the needs of most control valve devices. Automatic regulating valve’s history can be traced back to the self pressure regulating valve, which includes a spherical valve with a heavy rod, heavy force to balance the spool to be some degree of regulation, another type of self regulating early pressure is in the form of “pressure balance type pressure regulating valve. The pressure of the process is connected to the film gas chamber of the spring film pressure regulating valve by the pipeline. Whether the pressure relief valve, the pressure type pressure regulating valve or the differential pressure regulating valve can be made from the change of the base type valve. The emergence of pneumatic transmitters and regulators will inevitably lead to the application of the aerated verb valve. They are essentially pressure relief valves or post valve pressure regulating valves, which are replaced by instrument compressed air to replace the fluid in the process. Many companies that produce pressure relief valves have developed into a regulating valve manufacturing plant. The application of regulating valves has been continuously developing from quantity and complexity. Improvements of valves and accessories of many valves can be used to solve various problems. The intention of this manual is to make the project are familiar with node and factors regulating valve and help, we choose the best instrument engineer, in the application of valve actuators and accessories. According to the characteristics of the stroke, the regulating valve can be divided into straight stroke and angle stroke. The straight stroke includes single seat valve, double seat valve, sleeve valve, angle valve, three-way valve and diaphragm valve. The angular stroke includes butterfly valve, ball valve, eccentric rotary valve and full function ultra light regulating valve. The control valve can be divided into pneumatic control valve, electric control valve and hydraulic control valve according to the driving mode. According to the regulation form, it can be divided into regulation type, cut off type and regulating cut-off type. According to the flow characteristics, it can be divided into: linear, equal percentage, parabola and fast opening. The regulating valve is suitable for air, water, steam, various corrosive media, mud, oil and other media.
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