According to the driving mode, the control valve is mainly divided into two types: electric regulating valve and pneumatic regulating valve to adapt to different working conditions and process requirements. Electric regulating valve is generally driven by a quarter-turn electric actuator directly through 4~20mA or 0. The ~10V analog signal controls the opening of the valve for control purposes. Valves used for angular stroke control mainly include ball valves and butterfly valves. The electric control valve is simple in operation and does not require compressed air, but the response speed is slow, the control precision and the adjustment performance are poor, and it is limited to applications in some workplaces where the control precision is not high and the operating frequency is low. In comparison, the pneumatic control valve is widely used in the process control field of various industries due to its high control precision, fast response, good working stability and wide variety of applications. New intelligent valve positioner Different intelligent valve positioners have both structural and functional commonalities, as well as their own characteristics. Commonalities: â– As a standard valve positioner (electric-gas converter function), it can be widely used in the position control of various process control valves with pneumatic actuators; â– As a process controller (with its own PID function), it forms an intelligent regulating valve with a valve with a pneumatic actuator. It can directly receive the real-time process value signal of the sensor, and together with the sensor form a relatively independent complete process control loop to realize the closed-loop control function; â– It can be combined with valves of straight-stroke pneumatic actuators such as angle seat valve, globe valve, diaphragm valve, etc. It adopts external line position sensor to form valve positioning control system; it can also be combined with angular stroke pneumatic actuator valve such as: ball valve , butterfly valve, and diaphragm type pneumatic regulating valve, etc., using built-in angular stroke sensor to form a valve positioning control system; â– Can be used for single-acting actuator valves, such as normally open or normally closed valves, and for the control of valves or cylinders of double acting actuators; â– With analog position feedback output and two binary output signals. The position feedback signal can feed back the actual position or actual process value of the valve to the PLC or controller to facilitate system information acquisition and monitoring. The binary output signal can expand the control function of the regulating valve and improve the automation of the system; â– Good man-machine interface, easy to operate; large-screen digital liquid crystal display, real-time display of set value and actual value and display valve ambient temperature; three-button menu indication operation, convenient for on-site debugging and maintenance.
As the brain of the regulating valve, the valve positioner plays a decisive role in the control performance and field function of the entire control valve. Compared with the traditional electric-gas conversion type valve positioner, the intelligent valve positioner has wider application and market prospects in terms of control precision, response speed, function expansion, and improvement of valve automation control level. Therefore, the intelligent valve positioner is regarded as the development direction of the future valve positioner.