Working principle of electric control valves, valves to regulate the electric wiring diagram

by:AIRWOLF     2020-05-16
Electric control valve is an important execution units in industrial automation process control instrumentation. Structure are connected by a electric actuators and regulating valve combination after mechanical connection after assembly, commissioning the installation of electric regulating valve. Actuators in process control system, the actuator accept controller command signal to the actuator converts it into the corresponding angular displacement or linear displacement, to manipulate regulating mechanism, change of controlled object into and out of energy or material, in order to realize the automatic control of the process. In any of the automatic control system, the actuator is an essential part of. If the sensor to the control system of sense organs, the controller is the control system of the brain, while the actuator can be likened to do specific work hand. Actuators often work in high temperature and high pressure, low temperature, strong corrosion, high viscosity, easy to crystallization, flashing, cavitation and high pressure condition, use conditions, therefore, it is the weak link of the control system. If the actuator selection or improper use, often can bring difficult production process automation. In many cases, to cause a decline in quality control of the control system, adjust malfunction, even for medium inflammable, explosive, toxic and cause serious accidents. For this, for actuators correct selection and installation, maintenance and so on each link, must give enough attention. Actuators according to different driving power, can be divided into pneumatic actuator, hydraulic actuator and electric actuator. The structure and working principle of electric control valve 1, electric regulating valve the basic structure of the upper electric regulating valve actuator, accept output regulator 0 ~ 10 madc or 4 ~ 20 madc signals, and convert them to corresponding linear displacement, promote the adjustment of the lower valve action, regulating the flow of fluid directly. All kinds of electric regulating valve actuators are basically the same, but the adjusting valve ( Regulatory agencies) Structure by using a lot of different types of conditions, the most commonly used is the direct single seat and through double valve seat valve two kinds. 2, electric actuators, the basic structure of the electric actuator is mainly consists of isolated electrical parts and transmission parts, motor as a connection between two isolated part of the parts. Motor output torque, according to the requirements of control through multistage spur gear is passed on to the trapezoidal screw, trapezoidal screw thread commutation torque for thrust. So trapezoidal screw by self-locking output shaft transfer straight trip to the valve stem. The actuator output shaft with a swivel, prevent transmission output shaft radial locking devices can also do move position indicator. On the output shaft snap ring even there is a flagpole, flagpole with the output shaft synchronous operation, the rack plate connected with the pole will output shaft displacement is converted into electrical signals, to provide intelligent control panel for comparison and valve position feedback signal output. At the same time, the stroke of actuators can be made of two main rack panels limit switch open limit, and by the mechanical limit protection. 3, the working principle of the actuator is electric actuator motor as the driving source, direct current as the control and feedback signals, the principle block diagram is shown in figure 3. When the controller's input is a signal input, the signal is compared with position signal, when the two signals deviation is greater than the dead zone, produces power output controller, servo motor drive rotation reduce reducer output shaft in the deviation of the direction, until the deviation is less than the dead zone. The output shaft is stable in the position of corresponding with the input signal. 4, by the main control circuit, sensor, controller structure controller with LED operation buttons, split phase capacitor, terminal blocks, etc. Intelligent servo amplifier based on the special single chip microprocessor, through the input circuit of the analog signal, the valve resistance signal is converted into digital signal, the microprocessor according to the sampling results by artificial intelligent control software, according to the results and output control signals. 5, the basic structure of the regulating valve regulating valve, direct contact with modulated medium in the process piping valve core on the valve body movement, change the circulation between the valve core and valve seat area, namely change the resistance coefficient of valve door the process parameters can be regulated. Chart is given through single valve seat and through double valve seat of typical structure, it consists of the valve cover ( Or high temperature on the valve cover) , under the valve body, valve cover, valve core and valve stem of the valve core parts, valve seat, packing, pressure plate, etc. Through single valve seat valve body only a valve core and valve seat, is characterized by simple structure, small leakage ( Even can be completely cut off) And allow the pressure difference is small. Leakage is small, therefore, it is suitable for requirements, working pressure difference of small clean medium occasion. Should pay special attention to in the application of the permissible differential pressure, prevent the valve door closed tightly. Direct two-seater regulating valve valve body has two valve core and valve seat. It compared with the same caliber single-seat valves, flow capacity is about 20% ~ 25%. Because the fluid to the upper and lower two forces on the valve core can offset each other, but the upper and lower two valve core to close at the same time, so the two-seat valves has allowed the characteristics of the differential pressure, larger leakage. Is suitable for the pressure difference on both ends of the valve is larger, leakage requirement is not high, clean medium occasion, not suitable for the occasion of high viscosity and fiber.
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