In modern automated control of factories, control valves play a very important role. The production of these factories depends on the correct distribution and control of the flowing medium. Whatever the control, whether it is energy exchange, pressure reduction, or simple container feeding, it requires certain terminal control components to complete. So what is the working principle and selection method of control valves?
Control valves consist of valve body assemblies and actuator assemblies. When selecting control valves, we need to pay attention to the following five principles from Utmost control valve factory:
Select the appropriate structural form and material according to the process conditions.
According to the characteristics of the process object, choose the flow characteristics of the control valve.
According to the process operating parameters, select the appropriate control valve caliber size.
According to the requirements of the process, select the necessary auxiliary devices.
Reasonably select the actuator, and its response speed should meet the requirements.
Requirements for control stroke time: The selected control valve actuator should be able to meet the valve stroke and process leakage level requirements. In some cases, such as the use of self operated pressure control valve(including vent valves), it is necessary to consider amplifying the actual possible pressure drop and require the actuator to provide a larger force. Otherwise, there may be a danger of not being able to close or open the control valve when abnormal situations occur in the process.
Control valves, also known as regulating valves, are the main types of actuators, which change the fluid flow rate through dynamic operation by receiving control signals output by the control unit.
Common control loops consist of three main parts. The first part is the sensitive element, which is usually a transmitter. It is a device that can be used to measure the controlled process parameters, such as pressure, liquid level, or temperature. The transmitter’s output is sent to the regulating instrument—the controller, which determines and measures the deviation between the given value or desired value and the actual value of the process parameters and sends correction signals one by one to the final control element—the control valve. The valve changes the fluid flow rate, so that the process parameters reach the desired value.
Control valves change the fluid flow rate through dynamic operation. Control valves generally consist of actuators and valves. If control valves are classified based on the power used by the actuator, they can be divided into three types: pneumatic control valves, electric control valves, and hydraulic control valves. In addition, based on their functions and characteristics, they can be classified into linear characteristics, equal percentage characteristics, and parabolic characteristics.