With the rapid development of chemical industry, metallurgy, electric power and pharmaceutical industry, the technological level and control requirements are increasing day by day. As an important control component in the whole process control system, the regulating valve plays an indispensable role and puts forward higher requirements for its control performance, reliability and energy saving.

According to the driving mode, the control valve is mainly divided into electric control valve and pneumatic control valve, in order to adapt to different working conditions and environmental and technological requirements, the electric control valve, generally by the Angle travel electric actuator directly drive the valve, through 4 ~ 20mA or 0 ~ 10V analog signal control valve opening, so as to achieve the purpose of control. The valve used in Angle stroke control mainly includes butterfly valve and ball valve. However, the electric control valve is easy to operate and does not need compressed air, but has slow response speed, poor control accuracy and adjustment performance. It is only used in some workplaces where the control accuracy is not high and the movement frequency is low. Comparatively speaking, pneumatic control valve is widely used in the field of process control in all walks of life by virtue of its characteristics of high control accuracy, fast response speed, good working stability and wide application.

As the brain of the regulating valve, the valve positioner plays a decisive role in the control performance and field function of the whole control valve. Compared with the traditional electric-gas conversion valve positioner, the intelligent valve positioner has more extensive application and market prospect in the control accuracy, response speed, function expansion, and improvement of the automatic control level of the valve. Therefore, intelligent valve positioner is regarded as the future development direction of valve positioner.

　　 New intelligent valve positioner 　

　　Different intelligent valve positioner have the same structure and function as well as their own characteristics.

　　common ground:

■As a standard valve positioner (electric-gas converter), it can be widely used in the position control of various process control valves with pneumatic actuators.

■As a process controller (with PID function), the intelligent control valve is composed of a valve with a pneumatic actuator. It can directly receive the real-time process value signal of the sensor, and together with the sensor constitute a relatively independent complete process control loop to realize the closed-loop control function.

■Can be combined with the straight stroke pneumatic actuator valve such as: Angle valve, globe valve, diaphragm valve, etc., using the external line form of position sensor valve positioning control system; Also can be combined with the Angle stroke pneumatic actuator valve such as: butterfly valve ball valve, and diaphragm pneumatic control valve, etc., the use of built-in Angle stroke sensor valve positioning control system;

■Can be used for single action actuator valve, as usual open or normally closed valve, and can be used for double action actuator valve or cylinder control;

■Can take analog quantity position feedback output and two binary output signals. The position feedback signal can feedback the actual position of the valve or the actual process value to the PLC or controller, which is convenient for system information collection and monitoring. The binary output signal can expand the control function of the control valve and improve the degree of automation of the system.

■ good man-machine interface, easy to operate; Large-screen digital liquid crystal display, which can display the set value and actual value in real time and display the valve environment temperature; Triple - button menu indicating operation, easy to debug and maintain.

■ three-wire controller, 24VDC power supply and additional external setting signals;

■ standard configuration with integrated process controller function (PID);

■Fast exhaust valve is optional for valve control of larger actuator.

■Standard NAMUR and DINIEC interface for valve control of third party companies;

■External setting signal (position value/process value) can be accepted: 0/4 ~ 20mA, 0/5 ~ 10VDC;

■ accept sensor signal (actual process value) : 4 ~ 20mA, realize split installation and control.

■ three-wire controller, optional fieldbus control: PROFIBUSDP or DeviceNet;

■ optional process controller function (PID), including process self-tuning function;

■ external setting signal (position value/process value) can be accepted: 0/4 ~ 20mA, 0/5 ~ 10VDC;

■ can accept a variety of sensor signals (actual process value) : 4 ~ 20mA/Pt100/Frequency;

Optional explosion-proof standard: II3G/DEExT4.

■ standard two-wire controller, power supply from 4 ~ 20mA or PROFIBUSPA;

■ low-power design (12.5ma);

Optional safety and explosion protection standards: EExiaIICT4/T5/T6(intrinsicallysafe)version, ATEX, FM;

■Safe structural design, all aluminum housing, internal display, stable operation in harsh site environment;

■ standard NAMUR and DINIEC interface for valve control of third party companies;

■ can accept a variety of sensor signals (actual process value) : 4 ~ 20mA/Pt100/Frequency.

　　 additional function

　　In addition to the above intelligent positioner can meet some of the general functions and control of the regulator valve, but also in the powerful microprocessor control, through the software to achieve some special additional functions, improve the control accuracy and automation of the entire regulator valve. In some complex process control systems and control systems with special process requirements, good control and strong system functions are demonstrated.

■ flow characteristic curve

This additional feature allows the user to select a conversion characteristic curve (linear/equal ratio characteristic curve) for valve Settings and valve travel relationships, or user-defined (freely programmable characteristic curve).

The flow characteristic curve of the valve, which reflects the relationship between the valve flow (Kv value) and the valve travel, is determined by the shape of the body and the spool. There are generally two kinds: linear and equal ratio. In the linear characteristic curve, the same valve stroke change produces the same flow change; In the isopercentage characteristic curve, the change of valve stroke corresponds to the isopercentage change of flow value.

Therefore, in order to meet the requirements of some special processes, such as the temperature control system of sterilization and heat exchanger, the on-line titration system of acid and alkali neutralization, etc., higher requirements are usually put forward for the flow characteristic curve of the valve. The intelligent locator can set up a linear and a variety of equal percentage characteristics of the curve, the adjustment ratio of 1:25/1:50/25:1/50:1. In addition, the intelligent locator also has the characteristic curve of free programming. According to the specific valve and application, the user can divide the set signal into 21 set-points with an interval of 5% according to 0~100. The valve stroke can be redefined at each set-point, but the stroke difference between two adjacent set-points cannot exceed 20%.

　　■Valve closing function

This function enables the control valve to remain closed or stable outside the control signal range. The control signal range of the control valve is 0 ~ 100, but usually, a control valve control signal used to the limit position (0 and 100) is very rare. And in the limit state, some weak interference signal may lead to valve misoperation or shut down, resulting in leakage phenomenon. Therefore, this feature ensures that the valve remains closed or in a stable position when the control signal does not exceed the set closing range.

■ valve travel limit

This function can set the physical travel limits of the valve, corresponding to the range of the input signal. In general, the stroke of a regulator (0 ~ 100) corresponds to a change in the control signal (0 ~ 100). But in some system transformation or design selection will encounter a large pipeline, small flow embarrassing situation. In the case that the pipeline has been installed and the valve has been finalized, in order to achieve the accurate control of a small flow rate without changing the valve and pipeline, the valve travel range can be set between 0 and 50% using this function, while the control signal range remains unchanged. In this way, the requirements of small flow control are guaranteed without loss of resolution of valve control.

■Safety position setting

This function can set a password for the smart locator, but does not affect the normal operation of the locator display and manual/automatic work status conversion. It is only to protect the parameter setting interface, to avoid the general operator in the use of the process of error and error to modify the valve parameters, resulting in unnecessary system failure and production loss. Only authorized technicians can enter the parameter setting state through the password and adjust the valve parameters according to the process requirements.

With the help of the corresponding additional functions, combined with the requirements of the field production process and the control process of the system itself, the control accuracy and control performance of the control valve can reach a good Z state, and the process control level of the whole system can reach a new height.