The FF valve positioner is a high-tech new product based on FOUNDATION fieldbus technology. In the former chemical installations in China, it was only used sporadically. However, all the control valves in Shanghai Secco's petrochemical engineering plants use FF locators, of which 260,000. More than 200 units have been designed for the t/a acrylonitrile plant, which provides the basis for SECCO's management of the plant's network. The internal structure of FF positioner is different from common HART intelligent positioner or conventional (4~20mADC) positioner, which puts high requirements on installation and debugging. In the debugging, it needs to use computer and special software (Valvelink). The technology has been greatly improved. At the same time, it has brought great challenges and rare opportunities for the commissioning of the instrument. The following takes the DVC5000f type FF valve positioner as an example. The process of installation and debugging and the existing problems are elaborated in terms of theory and practice to provide a new understanding of the FF valve positioner and the commissioning software (Valvelink). Know and improve together.
1FF Locator Introduction FF is an acronym for FOUNDATION fieldbus. The DVC5000f valve positioner is a digital valve controller designed for FF fieldbus systems. It has a number of outstanding special points: interoperability between instrumentation devices, process control functions, communication functions, and micro-based The processor (CPU) technology is a kind of instrumentation. In addition, one of its main functions is to convert digital input signals to pneumatic output signals. The FF positioner uses the FOUNDATION fieldbus communication protocol to easily obtain important information about the process operation over the network and to obtain control information for the process. The various types of information generated by the FF positioner are visualized through the control system of the DCS operation master system in the CCR, the DeltaV system or other main system.
There are some function modules in the digital FF positioner: PID control module, AI/DI input module, AO/DO output module, etc.
It also includes two control modes for selection and three kinds of self-diagnosis capabilities. There are two choices of control modes, one of which is optional, ie, 1Standard Welcome to visit: China Chemical Construction Network Performance Diagnosis).
These two control modes can be adapted to any of the three self-diagnosis capabilities. The FD function in the diagnostic capability can be applied in any of the main systems, and the AD and PD can only be seen in the display panel if they are valid under the AMS (Emerson) VALVELINK software.
There are two basic modules in all digital valve controllers: Resource block and transmitter block (resource block and transmitter block). In addition to the above two modules, it also includes some independent control modules: AO, PID, ISEL (input selector), DI, and DO function blocks.
FF locator and valve stroke calibration requires several sets of special verification line calibration tools, and also other software NI company field bus card NI-FBUS driver software (NI-FBUS card, PCMCIA communication card, The two cards are for laptops only, the AT-FBUS communication card is used on desktop computers, and DeviceDiscription-DD. Before the FF locator calibration is performed, the three computers must be properly selected to install the three special software. The software must be installed on a notebook computer or a desktop computer with a Microsoft win98 or orNT operating system. However, the VL2000V6.0 software cannot run on win95 and win2000 systems. In practice (a few trials have been done) not all computers with the same operating system can be used, but to be successful through multiple tests of different brands of computers and operating systems (AMS recommends using DELL computer And WIN2000 system, because Valvelik software is developed under this condition). After the software is installed, starting the computer can set, verify, and diagnose information on some parameters of the DVC5000f positioner and valve.
After the Valvelink software is correctly installed, it can correctly set alarms and set alarms within the device. These displays and alarms can help operators correctly judge and analyze faults in field devices to avoid plants or processes. The occurrence of a trip accident on site. The description of a simple fault or error displayed by the internal alarm is very useful and easy to achieve prior maintenance and proper understanding of it. In the parameter setting of FF locator, there are three kinds of most common alarms: fault alarm, maintenance alarm and prompt alarm.
3FF Valve Positioner Installation The DVC5000f positioner can be mounted on linear actuator control valves (thin diaphragm control valves) or on rotary actuator actuators (ON-OFF butterfly, ball or plug valves). In general, the installation of FF locators should be reasonably configured according to the actual requirements of various types of valves. Attention should be paid to the correct choice of the form of air opening or air brewing, and whether the correction pin on the feedback arm is correctly inserted into the A hole or not. B hole. Use A hole for air opening valve and B hole for air closing valve. Only when the feedback arm can be properly connected and the direction of rotation is specified, can the correct value of the actuator shaft be sent to the PID module for further calculation and control. FISHER's valve positioner can be correctly completed according to the installation instructions of different manufacturers' control valves, and will not be described in detail here.
4 Check and verification requirements of the positioner and valve The FF positioner is not connected to the DCSDaltaV main system or other main system in the offline state. Prior to the verification, some FF power supplies, communication cards, communication lines, signal lines, etc. used in connection with the computer and FF locator should be properly connected. The calibrator has automatic stroke calibration, manual stroke calibration and pressure sensor calibration. It should be noted that the verification here is not only to verify the simple stroke of the valve, but also to check whether the overall performance of the valve meets the requirements by checking the stroke, and perform a large diagnostic test on each part of the valve. . Sometimes, in order to match the overall check of the valve, the pressure sensor should be set and verified (this article does not describe it). In automatic and manual calibration selection, automatic stroke calibration can be used for actuators with mechanical limit and small and medium size. Manual stroke calibration is used when there is no mechanical limit and there is a large actuator, or if you want to use a manual calibration stroke.
4.1 Fieldbus Communication Accessories Installation Connect the notebook to a fieldbus device (locator) using 1 NI-FB card, 2NI-FB connecting cable (1C), 3 signal modulator (SC) t24Vdc DC power supply. Connect these accessories as required.
4.2 Power on commissioning Power on the computer, enter the Valvelink program, enter the valve commissioning interface, and press the dialog box prompting to verify the stroke of the regulating valve.
4.3 Automatic stroke check Just check the valve stroke. The specific parameters inside the positioner are not modified and set. The settings within the resource module and the transfer module are completed by the supplier based on the valve characteristics.
Step 1 Start Valvelink software in the computer's start menu, and find the meter device (regulator valve) that you need to check according to the display window.
Step 2 To confirm that the A0 or DO block (in the TransducerBlock) is not connected to the host system, but is in an offline state (OOS-OUTOFSERVICE state). If it is not in the 00S state, the panel prompts AO or DO must be set in the OOS. In the state, otherwise it will not be able to verify and exit the automatic verification mode.
Step 3 The system starts to initialize the instrument. If the feedback arm of the valve is a standard coast feedback mechanism, the system will prompt to set an intermediate crossover. After the meter is initialized, the percentage value of the current valve middle point is displayed on the panel.
Step 4 When an intermediate point setting is necessary, here are three methods for setting: 1 Manual setting (initial setting) k2 System default (50% i3 adopts the latest value (system detected percentage) i in actual In the application, the recommended option is 1, but when the valve position can be correctly confirmed during the calibration process or the valve position cannot be accurately observed, the median value can be determined in 3. The default value (50%) is the last one. For selection, this default value assumes that the position sensor is in the middle position, but this is not necessarily an exact value as the crossover value, because this value changes during installation and stroke calibration. When the manual setting is selected, the system prompts The setting of the crossover value includes a specific value of the current valve position to be manually provided for correctly setting the crossover value, the forward and reverse direction of the selection signal, and the value at which the valve position should be moved.
Step 5 Select the direction of action of the valve and the size of the valve stem to be changed by making the feedback arm and the actuator rod 90°. Once the feedback arm reaches the correct position, this position is automatically identified.
In the automatic stroke calibration process, the positioner searches for the high end (end point) value (OorlOO%), low end (start point) value (0% orl00%), and output deviation value of the valve position. By finding these two endpoint values, the positioner will generate the end points and starting points of the two physical (actual) strokes, eg, determine the % of the actual trip and 100% of the open or closed position. The actual travel point obtained by calculating the drive signal is calibrated by adjusting the output offset value. This drive signal requires that the error generated by the travel be 0%. If this calibration method is implemented at the 50% position, then there is only a small amount. The adjustment can reach the ideal value. The positioner then looks for two points, 5% and 95% of the stroke, to produce a set of linear correction factors, which are preset, so that the valve position can be more accurately achieved as required. point. After that, the positioner automatically checks the forward and reverse strokes. The system can make several corrections to the valve position according to some parameters of the self-test to achieve the actual travel requirements.
After the automatic verification is completed, the system asks for some information. For example, the verification person, verification location, time, etc. Welcome to visit: China Chemical Construction Network Tangzhaofeng FF valve positioner installation and commissioning and Valvelink debugging software application 4.4 manual stroke calibration manual stroke calibration process, steps, basic and automatic verification process and steps are similar. Although some parameters need to be set and adjusted manually, the most basic difference is that the check of the positive and negative strokes of the valve position is accomplished by manually increasing or decreasing the output signal through the keyboard or the panel. After selecting the ManualTravelCalibration in the person's program, through the panel prompt box, the required valve position is stroke-checked. The stroke value input by the keyboard is displayed in percentage. It is also possible to manually increase or decrease the signal value to the valve. Responsive to speed conditions and dead zone for accurate measurements.
In short, whether it is automatic calibration or manual calibration, the result is that the computer will automatically generate a five-page standard English verification report, this report shows the advantages of the valve ~ - diagnostic technology. There are four pages in the report that are valve characteristic curves and one page is the general parameters. The specific characteristic curves are as follows: The several curves are displayed together with the corresponding data, so that the operation of the valve and the condition of the valve body itself can be correctly analyzed from the figures and the data. The diagnosis of the filling condition and the diagnosis of the valve seat can be achieved. Whether there is wear on the valve plugs or not> To determine whether the actuator is leaking; To judge the level of valve friction (elasticity of packing), to provide overall performance including positioner, to provide information on hysteresis and dead time, and to provide dynamic Linearity information, from which it can be seen whether the valve stem sticks or flutters; analyzes the dynamic valve response to provide valve speed information and provides overshoot and travel time information. Although these diagnostic functions have certain advantages for the normal operation and routine maintenance of the valve, and can accurately reflect the valve in any part of the problem, but for the first time users have some difficulties.
5 Problems (I) It is difficult to accurately use the regular alarm of the valve. There are three kinds of general alarm settings inside: fault alarm maintenance alarm, prompt alarm. However, there are dozens of detailed alarms. It requires some training and practice to properly set up and operate these functions.
(2) The monomer verification time is longer. It takes 25 minutes to complete a complete calibration of a well-established valve. If some non-conformity items are found in the calibration, the valve body must be repaired and recalibrated as necessary.
(3) It is difficult to correctly understand and accurately analyze the reporting curve. Here we must pay attention to: how to correctly analyze the above-mentioned various possible diagnostic conditions from the four curves, and how to carry out maintenance and calibration of the instrument. The accuracy of the valve cannot be read very clearly in the generated checksum digging curve, which is different from the conventional valve positioner. To know if the accuracy of the valve meets the requirements, it is necessary to analyze the dynamic linearity and maximum dynamic error in the report to determine the accuracy. Under one condition, the accuracy of the valve is still determined by the thief. Although there is a certain degree of difficulty in the analysis of cockroaches, as long as the tests and discussions are repeated many times, they will be successful.
(4) There are many problems with valve maintenance. Although the system can diagnose many deficiencies of the valve, for example, poor packing, uneven friction, sticky valve stems, leaking cylinders, etc., but in a targeted manner, The maintenance is very good and requires high technical support and good experience.
The function of the FF bus positioner is very powerful. For a regulating valve, it can run well in the industrial control management network, and its technical support is very demanding. Although it is difficult, as long as we work hard, some language and technical obstacles will be gradually better resolved. The use of similar FF bus meters in future chemical production facilities is a development trend. Bus meters have played their due role in the networked management of factories, giving technical support to the reliable operation of chemical production. Can save a lot of human, material and financial resources. With the passage of time, various technical issues related to FF instruments will also be solved, and related explorations will be further and further.
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