Comparison between traditional valve positioner and intelligent valve positioner

What is the difference between traditional valve positioner and intelligent valve positioner?
The valve opening signal indicated by the traditional valve positioner is actually the signal output from the indicating computer or instrument to the valve positioner, so the actual site position often deviates from the feedback position.
The intelligent valve positioner is equipped with a valve position feedback signal transmitter, which can output the actual action position signal of the valve, and can be fed back to the computer or instrument through the communication protocol. The intelligent valve positioner realizes the digital display and storage of valve position, which provides useful data for predictive maintenance and management of control valve. It also provides an alarm signal to provide fast and correct information for the operator to deal with the accident.
What is the difference of energy saving between traditional valve positioner and intelligent valve positioner?
Traditional valve positioner uses pneumatic amplifier as the controller of secondary loop. In normal operation, the pneumatic amplifier needs a certain amount of air consumption. Two or four piezoelectric valves are used in the intelligent valve positioner. When the input signal of the piezoelectric valve is 1, it is opened and when it is 0, it is closed. Therefore, compressed air is consumed only when the inlet air valve is opened, and no compressed air is consumed under other working conditions (the inlet air pressure electric valve is closed and the exhaust pressure electric valve is opened or closed). Therefore, the intelligent valve positioner has energy-saving performance.
What is the difference between traditional valve positioner and intelligent valve positioner?
In the cascade secondary ring composed of traditional valve positioner, the secondary controller is a pure proportional control law. Therefore, there is a residual difference between the valve position and the set value of the auxiliary ring, which can not guarantee the one-to-one correspondence between the input and output of the auxiliary ring. The control accuracy of traditional valve positioner is generally ± 1%.
The intelligent valve positioner adopts software control algorithm, and the proportional integral function can be used to realize the control without residual error, thus greatly improving the control accuracy. The control accuracy of intelligent valve positioner can reach ± 0.2%.
What are the advantages of intelligent valve positioner?
Through the analysis and comparison of the above theory and engineering application, the intelligent valve positioner can improve the performance of the control system and make the field adjustment more convenient.
1. The method of nonlinear characteristic compensation is extended. The nonlinear characteristics of the controlled object can be compensated by the flow characteristics of the control valve. It can be compensated by ordinary valve positioner or only valve positioner, and can be realized by intelligent digital controller in series with nonlinear link. From the point of view of reducing investment cost and maintenance, the use of intelligent valve positioner or digital controller in series to connect nonlinear compensation link has the advantages of soft connection function, which can easily change the nonlinear characteristics.
2. The type selection of control valve becomes simple. The flow characteristics of control valve can be all star flow characteristics or flow characteristics with convenient processing and high precision, so as to reduce the type of flow characteristics of control valve. If the sleeve and other valve internals are used, the valve body size can be reduced, and the type and specification of spare parts of the control valve can be greatly reduced. The sleeve valve and other control valves can also use balanced valve internals and other components for high pressure difference and noise reduction applications.
3. The valve position detection of valve positioner is non-contact, which can greatly improve the performance of the circuit.