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[Gas valve positioner] on the role of the valve positioner?

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[Gas valve positioner] on the role of the valve positioner?

Release date:2017-08-25 Author: Click:

[Gas valve positioner] on the role of the valve positioner?

First of all, the first to talk about the valve positioner, according to the structure of sub-pneumatic valve positioner, electrical valve positioner and intelligent valve positioner, is the main valve accessories, usually supporting the use of pneumatic control valve, which accepts the regulator output signal , And then its output signal to control the pneumatic control valve, when the valve action, the stem displacement and through the mechanical device feedback to the valve positioner, valve status through the electrical signal to the host system. The following by the global wisdom of the small network for everyone to answer.

1. Improve the dynamic characteristics of the valve positioner to change the original valve of the first-order hysteresis characteristics, reduce the time constant, making it a proportional characteristics. In general, if the air pressure transmission line exceeds 60m, should use the valve positioner.

2. Improve the steady-state characteristics of the valve After using the valve positioner, as long as the controller output signal changes slightly, through the nozzle of a baffle system and the role of the amplifier, you can make the control valve head pressure greatly changed to To overcome the friction of the stem and eliminate the influence of the unbalanced control valve, thus ensuring that the valve position is correctly positioned by the signal from the controller. Improve the steady-state characteristics, the control valve can be applied to the following circumstances: ① requirements for the valve position for precise adjustment of the occasion; ② large diameter, high pressure and other unbalanced forces larger occasions; ③ to prevent leakage and the need to fill the pressure Very tight, such as high pressure, high temperature or low temperature and other occasions; ④ process media in the solid particles were stuck, or high viscosity of the situation.

3. For split control With a controller to control more than two control valves, so that they are in a certain section of the signal to complete the full trip movement. For example, the two control valves in the 4 ~ 12mA DC current and 12 ~ 20mA DC current signal range to complete the full range of movement.

 4. Changing the flow characteristics of the valve By changing the shape of the positioner cam, the linear, logarithmic and quick flow characteristics of the control valve can be interchanged. The same time as

 

    5. The reverse action valve for the valve positioner has positive and negative points. Positive role, the input signal increases, the output pressure also increases; reaction, the input signal increases, the output pressure decreases. The use of a reactive positioner allows the air to open the valve into an air shutoff valve and the gas shutoff valve becomes an air open valve.


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