As the main part of the control valve, the diagnosis technology of the intelligent valve positioner is constantly developing and improving. The diagnosis technology of the intelligent valve positioner plays a more and more important role in the petrochemical production process.
1. The Advantages Of The Intelligent Valve Positioner Against The Traditional Valve Positioner
1. The traditional valve positioner works by magnetizing the moving iron in the 4 ~ 20mADC current input coil sent by the regulator or output safety gate. Since the moving iron is located in the magnetic field produced by the permanent magnet, the two magnetic fields interact to produce a deflection torque on the moving iron, making it deflect with the fulcrum as the center. If the signal increases, the left side of the lever should move downward. At this point, the baffle fixed on the lever is close to the nozzle, which increases the back pressure of the amplifier, and the amplified output pressure acts on the membrane head of the throttle valve, causing the valve stem to move down. The displacement of the valve stem is converted into the angular displacement of the feedback shaft and the feedback platen by the pull rod, and then the feedback body is moved by adjusting the fulcrum of the range. The feedback spring fixed on the other end of the lever is stretched to produce a negative feedback torque to balance the lever, while the lever is also stabilized in a corresponding fixed position, thus achieving a proportional relationship between the signal current and the position. However, the amplifier constant throttle orifice of the traditional valve positioner is easy to be blocked, the back pressure is maximum, the ball valve of the amplifier is stuck, the nozzle and the baffle are not tightly closed.
2. Compared with conventional valve positioner, the intelligent valve positioner has some remarkable application advantages and characteristics in petrochemical production. In the process of debugging and correcting, the Intelligent valve positioner is easier to operate, simpler and easier to master than the conventional valve positioner. Compared with the conventional Valve positioner, the intelligent valve positioner can carry out automatic identification and control operation without the assistance of other regulating and controlling equipment And in the process can be automated control adjustment of the optimal state, can adjust the control requirements of different optimization settings. For example, in the petrochemical production process, if you need to adjust the control valve to force all closed, its intelligent operation and control system will be based on the adjustment of the input signal changes in its control adjustment of the production equipment to be forcibly cut off, in order to achieve the adjustment of the control system to force all closed settings. All of this can be attributed to the intelligent valve positioner using a software control system is an automatic set of software system, operating using a fully automatic configuration program.
2. Analysis And Application Of Intelligent Valve Positioner Diagnostic Function In Petrochemical Field
1. When the valve is initialized, the performance of the whole valve is tested, the parameters are optimized, and if there is a failure, an alarm is issued. Alarm Information: Preventive alarm-control Valve Status Light wear, will continue to wear in the future, but at present the valve can work normally; maintenance alarm-valve status has been seriously worn, currently can work normally, however, failure can occur at any time; failure alarm-to remind the equipment operator that the valve has failed. Reaction detection information on which parts of the control valve; analysis of the cause of failure-how to solve the above-mentioned failure.
2. The control valve can be initialized by the intelligent valve positioner before use, and all the initial state information of the valve can be stored by the positioner. In this way, the control valve with the intelligent positioner starts the automatic initialization work, including determining the mechanical range of the positioner and automatically adjusting the best index parameters when it works, etc. The positioner applies a signal algorithm to control the opening and closing of the valve based on the currently determined mechanical information and index parameters. Whether the valve is working normally or not is very important. The positioner detects and analyzes the valve continuously in real time. Once there is a fault, it will send an alarm signal. All the results of the detection and analysis are stored in the memory of the positioner To equipment operators or maintenance engineers to provide diagnosis and maintenance of fault information.
3. The intelligent valve positioner uses its standard diagnostic function to identify major valve status errors, but it is difficult for the user to identify the direct cause of the failure. The user needs a “diagnostic report” that identifies the feasibility of the cause of the failure. So at present, the intelligent valve positioner manufacturers provide the standard diagnosis function in addition to the diagnosis function of the expansion to meet the needs of users. The expansion focuses on three main areas:
(1) Install an auxiliary sensor in the smart valve positioner to detect changes in the pneumatic input and output signals when the actuator needs to be disconnected To determine whether the valve internals and actuator working conditions are normal. For this method, most manufacturers install pressure sensors to measure the pressure applied to the actuator diaphragm, which is valve position dependent. In the on-line operation mode, the friction and pressure analysis report can be provided only by recording the signal of the valve operation, so that a more effective “diagnostic report” can be obtained.
(2) Dynamic changes of the response signal are recorded in the memory of the smart valve positioner, either online or offline, after a small change in the reference initial valve position has been made by a special program software To form a clear change image, through this change image analysis is the delay time and transmission time is increased or decreased, through the method of image analysis and mathematical simulation module analysis, the working state parameters of the valve are predicted and diagnosed. This can also be a “diagnostic report” , easy to find out the cause of the failure.
(3) The diagnostic process and testing should be carried out entirely within the locator and automatically give a status alarm based on a traffic light coding system similar to the one used for this purpose At the same time, these alarms will be displayed by the process control system at the appropriate authorization level. The repairman is interested in the alarm, but the operator may not be interested in the pre-diagnostic analysis and processing of the Information Prompt the maintenance personnel to appear in the future maintenance situation.
3. Development Prospect Of Intelligent Valve Positioner Diagnostic Function In Petrochemical Field
1. Develop strict control valve and positioner software standards, all engineering software or process control software must fully comply with this standard.
2. The diagnostic information is classified step by step, the more detailed the classification, the better, to meet the needs of different levels of users.
4. Conclusion
The intelligent valve positioner is an important device which can adjust and diagnose the pneumatic film control valve in the petrochemical production system. Pneumatic film control valve has been widely used in petrochemical industry production, many petrochemical production systems are inseparable from the operation of its control. Therefore, the quality of Valve positioner control for the use of pneumatic film control valve has a direct impact, which also has a great impact on the oil, chemical production links.
Post time: Jul-28-2021