Classification of Valve Positioners

Classification of valve positioners:

It is divided into pneumatic valve positioner, electro valve positioner and smart valve positioner according to the input signal.

According to the direction of action, it can be divided into one-way valve positioner and two-way valve positioner.

According to the gain sign of the valve positioner output and input signal, it is divided into positive acting valve positioner and reverse acting valve positioner.

According to whether the input signal of the valve positioner is analog signal or digital signal, it can be divided into ordinary valve positioner and fieldbus electric valve positioner.

According to whether the valve positioner has CPU or not, it can be divided into ordinary electric valve positioner and intelligent electric valve positioner.

The main function of the valve positioner:

1. It is used to improve the quality and movement speed of the regulating valve, mainly due to the guarantee of an amplifier and sufficient air source pressure.

2. It is used to increase the output force, mainly used for high pressure difference, high pressure medium, high temperature, low temperature and large diameter valve occasions.

3. It is used for electricity-pneumatic conversion. At present, most regulating valves are matched with computers, and the computer outputs mostly 4-20mA current signals. Electric-pneumatic valve positioners can be used to meet the requirements.

4. For split-range adjustment, two regulating valves operate a set of equipment respectively, one regulating valve receives 4-12mA electric signal, and the other valve receives 12-20mA electric signal.

5. Used to change the flow characteristics. The inherent flow characteristics of the original valve can be realized by a positioner, for example:

(1) The original quick opening characteristic can be changed to linear or equal percentage characteristic by the positioner.

(2) The original linear characteristic can be changed into an equal percentage characteristic by the positioner.

(3) The original approximate equal percentage characteristic can be changed to equal percentage characteristic through the positioner.

6. It is used for two-position action to become proportional action.

7. It is used for the reverse action of the valve. Through the positioner, the air-open valve can be changed to air-closed valve, and the air-closed valve can also be changed to air-open valve.

8. When the length of pneumatic signal pipeline is large, generally ≥150M.