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Intelligent control valve selection

From:Net   Date:2012-3-8

果博东方登录 www.zmeiko.com Intelligent control valve
Intelligent regulating valve with a microprocessor, enabling intelligent valve control functions. Intelligent control valve is usually of the following forms:
a. Smart valve positioner with pneumatic control valve;
b. Intelligent electric valve; Pat with fieldbus intelligent valve positioner pneumatic control valve. Intelligent control function 'main contents include the following
a. Easily modify the control valve flow characteristics.
b. Realize PID control algorithms.
c. Achieve other operational functions, for example, for a range of process control settings, nonlinear compensation computing.
d, the control valve is changed, reaction mode.
e. Communication with the host computer, - information sharing. L to achieve control valve fault diagnosis and alarms.
g. Regulating valve to achieve self-locking.
h. To achieve the status of valve management, the use of smart valve positioner has the following advantages.
    a. Reduce the control loop installation, calibration and commissioning time.
    b. Use of diagnostic features that make regulating valve. Longevity, operational status can be timely monitoring.
    c. Reduce instrument maintenance skill requirements.
Smart valve positioner with pneumatic control valve
The structure of this type of control valve control valve the same as ordinary, because leaving with smart valve positioner control valve with intelligent features smart valve positioner valve positioner with common main differences are as follows 1. Regulating valve flow characteristics achieved in different ways. The feedback part of the smart positioner linear feedback control valve flow characteristics required in setting circuit implementation. Common part of the positioner's cam different shapes by changing cam shape to achieve the desired valve flow characteristics. See 5.3.
(2) Input and output in different ways. Typically, smart valve positioner is intelligent electric valve positioner. And general electric valve positioner comparison, intelligent electric valve positioner input signal is a standard 4 ~ 20mA or 1 ~ 5V signal, it needs by the analog-digital conversion of the input signal as a microprocessor. The general electric valve positioner input signal, although 4-20mA or l ~ 5V signal, but it does not by the analog to digital conversion, can be directly sent to the electromagnetic coil of electromagnetic force to achieve equilibrium. Smart valve positioner output signal is a digital signal, it is usually sent to the piezoelectric valve, through the piezoelectric valve switches to adjust the delivery pressure regulator diaphragm head, general electrical valve positioner pneumatic amplifier output signal is amplified by the The air signal.
3 using a different control mode. Smart valve positioner with general computer control device similar to the discrete control, therefore, the sampling interval, the valve opening does not change. During operation, the valve opening presents a stepped change. General positioner with continuous control, therefore, the control process, the control valve opening degree change is continuous (apart from the dead zone caused by the jump outside).
4 different feedback signal detection process. Smart valve positioner control valve feedback signal by the analog to digital conversion required evacuation microprocessor, usually the positioner feedback signal directly as the feedback force (torque), does not require an electrical signal by the analog to digital conversion. Some smart valve positioner input signal using standard analog signal, also in the same wire HART digital signal transmission, the composition of mixed signal smart valve positioner, it does not belong to the fieldbus intelligent valve positioners, but still a smart valve positioner.
Intelligent electric valve
Such control valve with intelligent servo amplifiers, digital actuator, gear box, transmission valve position detection device and electric control valves and other components. General electric control valve with the main difference is the use of intelligent functions of the servo amplifier. Intelligent servo amplifiers are micro computer, it receives standard analog current or voltage signal, the analog-digital converted to a digital signal, the microprocessor will compare the input signal and the setting signal, according to a certain control law operation, the output signal The digital to analog conversion after driving the corresponding electric control valve. With intelligent valve positioners with pneumatic control valve works like, smart electric control valve The main difference is the use of electric control valve, therefore, the output signal is sent to the motor (can be either single-phase or three-phase motors), and by the reduction gear change after electric valve opening. Intelligent electric valve setting circuit is also used to compensate for nonlinear characteristics of the nonlinear characteristics of the controlled object, therefore, to avoid nonlinearities in the feedback loop control system instability. Meanwhile, the use of non-linear compensation implemented digitally, thus, the control valve according to the pressure ratio and the required flow characteristics of the work to determine the nonlinear compensator position of each line.
With fieldbus intelligent valve positioner pneumatic control valve
Smart valve positioner with the general, this type of valve positioner brought the following features.
a. The input signal is not a standard analog current or voltage signal, but a digital signal fieldbus devices.
b. With communication capabilities, the ability to easily communicate with the host computer, data exchange and data sharing.
c. Can be used directly and intrinsically safe power supply run, in line with the relevant provisions of the standard fieldbus.
d, can be realized OSI related functions, such as interchangeability, interoperability and so on.
e. All-digital, two-way communication.

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