What is valve positioner?
A valve positioner is a device used to determine and control the position of valves in piping systems. It is commonly used in industrial and process control applications and is designed to help operators locate and operate valves accurately.
The main function of the valve positioner is to locate and control the switching position of the valve. It opens or closes the valve by receiving signals from the control room or automation system and converting these signals into actions of an electric motor or pneumatic actuator. The valve positioner accurately controls the position of the valve and transmits the current position information back to the control room through a feedback mechanism.
Valve positioners usually consist of the following components:
- Receiver/Controller: Receives signals from a control room or automation system and converts them into actuator actions. It can be electric or pneumatic, depending on the application needs.
- Actuator: performs the switching operation of the valve according to the instructions of the receiver/controller. The actuator can be an electric actuator or a pneumatic actuator, choose the appropriate type according to the system requirements.
- Feedback device: used to monitor the current position of the valve and transmit this information back to the control room. Common feedback devices include position sensors or limit switches, which are used to detect the switching position of the valve.
- The main advantages of valve positioners include:
- Accuracy: The valve positioner can accurately control the position of the valve, ensuring that the valve can be opened or closed in time when needed.
- Automation and remote control: By connecting to the control room or automation system, the valve positioner can achieve automation and remote control, improving the efficiency and convenience of operation.
- Fault diagnosis and feedback: Valve positioners usually have fault diagnosis functions and can provide position feedback information to help operators find and solve problems in time.
Under what circumstances is a valve positioner needed?
- Where friction is large and precise positioning is required. For example, high temperature and low temperature control valves or control valves using flexible graphite packing;
- Slow processes require increasing the response speed of the regulating valve. For example, regulating systems for parameters such as temperature, liquid level, and analysis.
- Where it is necessary to increase the output force and cutting force of the actuator. For example, single-seat valves with DN≥25 and double-seat valves with DN>100. The pressure drop across the valve △P＞1MPa or the inlet pressure P1＞10MPa.
- Sometimes it is necessary to change the air opening and air closing modes during the operation of the split-range regulating system and regulating valve.
- When it is necessary to change the flow characteristics of the regulating valve.