Article Details
The valve positioner is the main accessory of the control valve. It takes the valve stem displacement signal as the input feedback measurement signal, and uses the controller output signal as the setting signal to compare. When there is a deviation between the two, it changes its output signal to the actuator to make the actuator act, establishing a one-to-one correspondence between the valve stem displacement and the controller output signal. Therefore, the valve positioner forms a feedback control system that uses the valve stem displacement as the measurement signal and the controller output as the setting signal. The manipulated variable of the control system is the output signal of the valve positioner to the actuator.
Valve positioners can be divided into pneumatic valve positioners, electro-pneumatic valve positioners and intelligent valve positioners according to their structural forms and working principles.
The valve positioner can increase the output power of the regulating valve, reduce the transmission lag of the regulating signal, speed up the movement speed of the valve stem, improve the linearity of the valve, overcome the friction of the valve stem and eliminate the influence of unbalanced force, thereby ensuring the correct positioning of the regulating valve.
