Can we use a control valve without positioner?
The purpose of the positioner is to control the stroke of the control valve to maintain the valve in the desired position. The positioned is used in a control valve to control the valve postion. The positioner receives the signal from the controller, and sends the enhanced signal to the actuator to reach the desired position when the valve reaches the desired position, the positioner cuts the signal driven to the actuator and maintains the position.
What can be done without a positioner in the control valve?
• When the positioner does not work properly there is a provision to bypass it until it can be repaired/replaced; however, we can not obtain an efficient operation of the control valve without positioner, so ideally a positioner for the control valves should be installed.
• When there is a deviation of the valve plug from the desired position decided by the controller due to some external disturbances, it can not be rectified without a positioner.
• When we use I / p Converter and then we get the pneumatic signal 3 to 15 Psi in input and for the regulation of the signal we use the pneumatic controller. And we can achieve our desired position.
• By connecting the output signal of the electric controller (4-20 mA) to an I / P and connecting the I / P output signal (3-15 psi) to the diaphragm of the control valve, we can control the control valve. We can also activate the control valve by the output signal of a pneumatic controller directly. The point is that you are going to have an open loop control.