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In petrochemical plant automation control system, the selection of regulating valve is very important to the accuracy, its use affects the quality of the product and relates to the safe production of the plant. Dushanzi ethylene plant used in the control valve, including various manufacturers of various types of products. However, the vast majority of valve installation is a common type of valve positioner. Now Dushanzi ethylene plant using the United States FISHER-ROSEMOUNT company FIELDVUE intelligent valve positioner, after more than a year of operation, and the performance of the ordinary valve positioner, the use of performance, cost-effective compared with the type of general use Locator control valve equipped with intelligent positioner control valve The basic error is less than 20% of the full stroke Less than 0.5% of the full stroke Valve stability Stable Extremely stable Adjust the manual adjustment at the scene Through the calibrator in the field, the cabinet or DCS communication calibration signal source 4 ~ 20mA or pneumatic signal analog signal or digital signal performance / price low high PID operation no communication no HART protocol 1 FIELDVUE intelligent valve positioner operating principle and characteristics of 1.1 intelligent locator principle FIELDVUE series of digital Valve controller has a separate module base, which can be easily replaced in the field without having to demolish the field of wire or catheter. The module base includes sub-modules: I / P converter; PWB (printed circuit board) assembly; pneumatic relay; indicator. The module base can be reassembled by changing modules. The FIELDVUE family of digital valve controllers accepts both input and electrical power by entering a pair of twisted pairs in the terminal box and simultaneously feeds the signal to the PWB component submodule where it is appended with many parameters such as node coordinates in multi-section linearisation, Limits and other values. The PWB component submodule then sends a signal to the I / P converter submodule. I / P converter to change the input signal into a pressure signal. The pneumatic signal is sent to the pneumatic relay, amplified and sent to the actuator as an output signal. This output signal can also be sensed by pressure-sensitive components mounted on the PWB subassembly. Diagnostic information for valve actuators. Valve and actuator stem positions act as input signals to the PWB submodule and serve as feedback signals to the digital valve controller. The digital valve controller can also be equipped with an indicator indicating the source pressure and output pressure. 1.2 intelligent positioner intelligent features 1.2.1 real-time information control, improve safety and reduce expenses 1) to improve control: the two-way digital communication to the valve current information to you, you can rely on the valve work information base control of the process Manage decisions and ensure timely control. 2) Increased safety: You can use your terminal, PC or system workstations to select information from field junction boxes, terminal strips or in a safe area such as a control room to minimize your chances of facing a hazardous environment without having to visit on site. 3) Protection of the environment: Valve leakage detector or limit switch can be connected to the intelligent digital valve controller auxiliary terminals, so as not to increase the field wiring, the instrument will alarm if the limit occurs. 4) Save Hardware Costs: When the FIELDVUE Series Digital Valve Positioner is used in an integrated system, hardware and installation costs can be saved by replacing the regulator with a FIELDVUE digital valve controller. The FIELDVUE family of digital valve controllers saves investment in wiring investment, terminal and I / O requirements by 50%. While FIELDVUE meter with two-wire power supply, does not require separate and costly power supply wire. They replace existing analog valves fitted to the valve, saving the high cost of laying separate power cords and signal cables. 1.2.2 Reliable structure and HART information 1) Durable construction: The hermetically sealed structure blocks the effects of vibration, temperature and corrosive environments. The stand-alone weatherproof junction box isolates the live wire contacts from the rest of the meter. 2) Start-up preparation steps: The two-way communication capability of the digital valve controller allows you to remotely identify each instrument, verify its calibration, consult previously stored maintenance records, and more for a quick start circuit purpose. 3) Easy to select information: FIELDVUE digital valve positioner and transmitter applications HART communication protocol can easily select the site information. The foundation of the control process - the control valve itself - with the aid of a handheld communicator on the valve or on the field connection box, in the DCS control room with the aid of a personal computer or operator's console. Using the HART protocol also means that FIELDVUE meters can be combined within an integrated system or used as a self-contained control device. This multi-faceted adaptability makes system design easier and easier now and in the future. 1.2.3 Self-diagnostic and control capabilities 1) Fieldbus communication All DVC5000f digital valve controllers include fieldbus communication capabilities including the A0 function block and the following diagnostics: a) Critical valve usage tracking parameters; b) Instrument health status parameters ; C) Predetermined format valve performance step maintenance test. The key valve uses the tracking parameters to monitor the total number of stems (cumulative travel) and the number of stem strokes (cycles). If there is any problem with the meter's memory, processor, or detector, the meter health status alerts. Once a problem has occurred, determine how the meter will respond to the issue. Suppose, if the pressure detector is faulty, should the meter be turned off? It is also possible to select which element is defective and will cause the meter to shut down (whether the problem is serious enough to cause a shutdown). These parameters indicate the report as an alarm. Monitoring alarms provide instantaneous indication of the instrument, valve or process in question. 2) Standard Control and Diagnostics All DVC5000f digital valve controllers incorporate standard controls and diagnostics. Standard control includes A0 and PID function blocks. Standard diagnostics include the following diagnostic tests: a) Dynamic error band; b) Drive signal; c) Output signal. Dynamic error band, drive signal and output signal is a dynamic scan test. These tests change the set point of the conveyor block (servo) at a controlled speed and plot the operation of the valve to determine the valve's dynamic performance. For example, the dynamic error band test is lagging and dead-zone plus "swivel." Hysteresis and dead zone are static masses. However, as the valve is moving, there is a dynamic error and "swivel" error. The dynamic scan test gives a good indication of how the valve will operate under process conditions, and that will be dynamic instead of static. Run the ValveLink software on a personal computer to complete standard and advanced diagnostic tests. 3) Advanced diagnostics The instrument with advanced diagnostics completes the dynamic scan test included in the standard diagnostics with the fourth dynamic scan test, the valve signature test, and the four-step diagnostic test. The valve signature test allows you to determine valve / actuator friction, bench test pressure signal range, spring rate, and seat closing force. 4) Process Bus Fischer Controls Device Performance Services can use instrumentation with process diagnostics to evaluate valves, processes, and transmitters while the FOUNDATION fieldbus control loop is still automated and the process continues to produce the product. Using process diagnostics, performance services will be able to identify and identify which process's constituent elements are likely to cause quality problems today. Although process diagnostics need to be up and running, the end point is determined by process or operator intervention. Process diagnostics can be performed on multiple valves simultaneously. 2 Applications and Maintenance 2.1 Application FIELDVUE intelligent valve positioner installed in April 1998 for the cracking and ethylene glycol plant a total of 16 units. Mainly used to replace some of the important control points of the loop occasions. Such as the cracking furnace feed flow valve and ethylene glycol epoxy reactor feed flow valve control. We use the handheld device to configure and verify it, the linearity of up to 99%, zero and range and backlash can be controlled within the accuracy requirements of the extremely stable control and anti-interference ability Strong, fully meet the requirements of process control. 2.2 Maintenance The FIELDVUE positioner has minimal maintenance and is essentially maintenance-free. The scene adaptability. However, in order to ensure long-term, stable operation, instrumentation staff should make the following several aspects of work. 1) To ensure its good working environment, to prevent accidental damage, should be regularly checked locator around the work environment. At the same time, it ensures the stability and cleanness of the working air source and reduces the fluctuation and malfunction of the instrument caused by external factors. 2) The instrumentation staff should check the leakage and working condition of the valve and locator weekly to eliminate the hidden danger in time. Every month, use the hand terminal to check the characteristic curve of the positioner, check parameters such as zero point, span, linearity and hysteresis, and optimize and adjust them to ensure the quality of their work. 3) regular maintenance and maintenance of the control valve to ensure the quality of the valve work. At the same time, the DCS control loop parameters are optimized to ensure the coordination and stability of the positioner working with each other. 4) Due to DCS and other reasons, the fieldbus and software functions we have not fully developed and utilized, can not be fully used for intelligent maintenance and diagnostic functions, but still greatly reduce the daily maintenance. Through the past two years in the use of chemical plant results, the intelligent valve controller stable performance, easy adjustment; to achieve direct communication with the DCS, and has self-diagnostic capabilities, easy maintenance; portable to the fieldbus, on behalf of today Instrumentation technology development direction. Further development and use of its software capabilities are the goal of our future endeavors.