Selection of control valve

A. Importance of control valve selection The control valve is the actuator in the automatic control system, and its application quality directly reflects the system's adjustment quality. As a terminal component in process control, people have a newer understanding of its importance than in the past. The quality of the control valve application, in addition to the quality of the product itself, whether the user is correctly installed, used, and maintained, correctly calculates, selects the type, and the importance of the control valve selection. The control valve is the actuator in the automatic control system. The quality of the application directly reflects the quality of the system's regulation. As a terminal component in process control, people have a newer understanding of its importance than in the past. In addition to the quality of the product itself and whether the user correctly installs, uses, and maintains the application of the regulating valve, correct calculation and selection are very important. Due to errors in calculation and selection, the system starts and stops, and some even cannot be put into use. Therefore, users and system designers should understand the importance of valves in the field and pay enough attention to the selection of regulating valves. B. Principles of control valve selection 1. According to the process conditions, select the appropriate structure and material. 2. According to the characteristics of the process object, select the flow characteristics of the control valve. 3. According to the process operating parameters, select the appropriate control valve diameter size. 4. According to the requirements of the process, select the required auxiliary devices. 5. Reasonably choose the implementing agency. The response speed of the actuator should be able to meet the requirements of the process 　　 for the control stroke time: the selected control valve actuator should be able to meet the requirements of the valve stroke and process for the level of leakage. In some occasions, if the pressure control valve (including the vent valve) is selected, the actual possible pressure difference should be considered for appropriate amplification, that is, the actuator is required to provide a larger force. Otherwise, when there is an abnormal situation in the process, the actual pressure difference before and after the control valve is relatively large, which may cause the danger of not being able to close or open.