What is a valve positioner?
Valve positioner is a control device designed to impart sensitivity to the valve and to ensure correct positioning as a feedback signal dictates. It derives from a transmitter an electrical or pneumatic signal and applies the signal to the location of the actuator.
If the signal and the actuator position vary, the positioner usually sends the required power through compressed air to push the actuator until the appropriate place is reached.
9 Reason why you should use valve positioner:
Valve positioner is a device that are used to achieve precise control, speed and accuracy to a control system. Although not all applications need valve positioner. But valve positioners offer advantages in many applications, particularly in systems where fluctuations can be devastating to efficiency or quality.
When accurate valve positioning is required; Because valve positioners are monitor of the exact position of the valve, they provide more reliable control than an actuator would obtain on its own. Furthermore, in the lower part of the valve stroke, where mistakes are more frequent, positioners improve the accuracy.
Valve positioner helps to improve speed of response of valve actions, minimizing the amount of time the system is operating above or below the setpoint. The positioner uses higher pressure and greater air flow to adjust the valve position.
3. Positioner as an Amplifier:
A valve positioner increase the pressure that a particular actuator and valve might be able to close.
4 To reduce friction:
Friction in the packing of the valve stem leads to both hysteresis and deadband, which reduces productivity. This is particularly beneficial for the processing of high temperature materials such as graphite.
5. 4-20mA control:
I/P converter can be used along with positioner which uses 4-20mA electrical control signal.
6. Seating friction:
Overcomes friction seating effects below 10 percent on flight, allowing throttling in a rotary control valve near the “locked” position.
7. Increase flexibility:
A positioner allows you to use diaphragm or piston-controlled actuators to set distance between the sensor and the control valve.
You can also switch between direct and reverse control operation, or when necessary change the flow characteristics. Two valves can even be used with one controller (i.e., split range).
Valve positioner controls with wide throttling range; and When valves are handling sludge or solids in suspension.
9. Allow split ranging:
It gives you the ability to use two valves with one controller; 4-12 mA and 12-20mA.