Intelligentization of Control Valve Products and Its Development

In automation control, the execution link is the core part of the process control system, covering many aspects such as detection, regulation and execution. As a key component in the execution process, the performance of the control valve has a direct impact on the stability and regulation quality of the whole process control system. With the continuous development of process control systems, control valve products continue to improve, especially the introduction of intelligent control valves, which provide an important guarantee for the accurate control and reliable operation of the system.

Basic Function and Composition of Control Valve

The control valve plays an important role in the process control system and is usually regarded as the "hands and feet" of the entire control system. The control valve is mainly composed of pneumatic (electric) or electro-hydraulic actuator and regulating mechanism. Pneumatic control valves are usually equipped with positioners for precise control. The working principle of the control valve is to accept the standard control signal (analog or digital), and convert these signals into the corresponding mechanical displacement (such as linear displacement or angular displacement), so as to change the flow area of the valve, damper, baffle, etc., to achieve the purpose of controlling the pressure, flow, temperature, liquid level and other parameters, to ensure the stable and effective operation of the process control system.

The Development of Control Valve Technology

With the rapid development of control technology, microelectronics technology and communication technology, intelligent control valve products have also been rapidly improved. The emergence of intelligent electro-pneumatic valve positioning (control) device and intelligent electric (electro-hydraulic) actuator provides a reliable basis for the intelligent control valve. The technology of pneumatic control valve has experienced a process from imitation to unified design of national industry, and then to introduction, cooperation and independent development. The technological progress of pneumatic control valve has also promoted the development of electric control valve technology, especially after the electric control valve has solved the problems of complex structure and low reliability, the technological progress has accelerated significantly; The electric control valve has developed from the early simple analog technology to the application of microelectronics technology and communication technology, which has laid the foundation for the control valve to leap from analog control to intelligent control.

Analog Locator and Intelligent Locator

Analog locators have some obvious shortcomings. Its mechanical structure is complex, parts processing and assembly is difficult, making the debugging process cumbersome and difficult. Due to the lack of self-diagnosis and compensation function, the analog positioner is prone to drift, which leads to unstable work. In addition, the analog positioner does not have a communication function, so it is not possible to know the working status of the valve in real time.

In contrast, digital and intelligent locators show significant advantages in several ways. Their modular design makes installation and replacement very easy. Automatic initialization technology simplifies the installation and commissioning process, and the automatic calibration function ensures the stability of the system. The digital and intelligent positioner is equipped with PID adjustment and supports custom Settings and programming. Through communication interfaces (such as HART, FF, PROFIBUS, etc.), these positioners can achieve two-way communication to monitor valve status in real time. At the same time, the advanced diagnostic function can automatically detect the working condition and failure of the valve, providing a scientific basis.

Analog Electric Actuator and Intelligent Electric Actuator

Analog electric actuators face some problems. The complex circuit structure and many discrete components lead to high failure rate and poor reliability. Because of the separate design with the servo amplifier, the connection and debugging are more difficult, and the troubleshooting is also more complicated. Analog electric actuators lack torque protection and stroke switches, which can cause equipment damage or shorten product life. Because the components are easy to damage, their average trouble-free working time is short, which can not meet the needs of high-precision control. In addition, the wear problem of the brake also affects the overall reliability.

Intelligent electric actuators have a number of advantages. They adopt microprocessing technology and fieldbus communication technology to realize integrated design, and integrate servo amplification and execution functions. The intelligent electric actuator is equipped with PID regulation, can directly accept the transmitter signal, and supports custom Settings and programming. These actuators also have adaptive, self-adjusting, and self-diagnostic capabilities to display fault codes or status that can be remotely transmitted to the control room for monitoring. At the same time, the intelligent electric actuator provides the flow characteristics correction function, so that the flow characteristics of the valve can be flexibly set without replacing the regulating mechanism. Advanced motor and control technology further improves the reliability of the equipment, making the average trouble-free working time significantly increased, and supports bus communication technology to achieve two-way communication between the system and the actuator, so as to monitor the work of the valve in real time.

Development Trend of Intelligent Control Valves

The application of intelligent control valves is gradually rising, and at present, the intelligent control valves used in most applications still only have basic intelligent functions. With the development of fieldbus technology, fully intelligent control valves with communication and advanced diagnostic functions will gradually become popular, and become the mainstream products of control valves. Intelligent control technology and digital control technology will gradually replace the traditional electronic control and analog control technology, and mechatronics, modular structure will gradually replace the discrete structure.

Conclusion

In the field of process control, the role of control valves is very important. The traditional analog control valve can not fully meet the needs of modern control technology, so it needs an intelligent control valve that integrates microelectronics technology, control technology, communication technology, etc. Intelligent control valve with its multi-function, intelligent advantages, is gradually replacing the traditional control valve, and will play a more important role in the future control system.