The conventional valve has the following problems:
- The pneumatic positioner does not provide a very exact regulation.
- The pneumatic positioner is difficult to adjust.
Basically the name of intelligent valve is due to the presence of a digital positioner that replaces the traditional positioner. In the block diagram shown in the above figure, the digital valve controller (DVC) is located inside the digital positioner whose main advantages are:
- Provides better regulation than the traditional positioner.
- Having a microprocessor, it performs functions and control, diagnosis and communication with a host (PC, DCS or Hand Held).
- The self-calibration of the valve takes place in a few minutes.
- The valve can be monitored, obtaining information on the position of the stem and the input signal, as well as status or process alarms.
- Out of service, but online, tests such as: hysteresis, valve signature (actuator vs. actuator displacement), step response can be performed.
The measured variables are:
• Displacement of the stem
• Actuator pressure
• Control signal from the controller (4-20 mA)
Particularly in this valve, the Hart, Field Foundation Bus etc., protocol is used for communications.