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Application advantages of intelligent valve positioner in petrochemical field

Because the petrochemical industry produces flammable, explosive, toxic, corrosive, and harsh working conditions, it is a high-risk industry. In the event of an accident, it often causes very heavy casualties and property losses. Therefore, high risk forces petrochemical companies to increase investment in automation and intelligent control equipment. Production process control requires a large number of control valves and their diagnostic maintenance to achieve a safe and enhanced high-performance management process, thereby maximizing the risk. drop to lowest. As the main component of the control valve, the intelligent valve positioner is continuously developed and perfected. The intelligent valve positioner diagnosis technology plays an increasingly important role in diagnosis, control and detection in the petrochemical production process.
First, the advantages of intelligent valve positioner for traditional valve positioner
1. The traditional valve positioner is a 4-20mADC current input coil sent by the regulator or output safety barrier, which works by magnetizing the moving iron located in the coil. Because the moving iron is located in the magnetic field generated by the permanent magnet, the two magnetic fields interact to generate a yaw moment against the moving iron, so that it is deflected around the fulcrum. If the signal increases, the left side of the lever should move down. At this time, the baffle fixed on the lever is close to the nozzle, so that the back pressure of the amplifier is increased, and the amplified output air pressure acts on the film head of the pawl valve to move the valve stem downward. The displacement of the valve stem is converted into the angular displacement of the feedback shaft and the feedback pressure plate by the pull rod, and then the feedback body is moved by adjusting the range fulcrum. The feedback spring fixed to the other end of the lever is stretched to generate a negative feedback torque to balance the lever, and the valve stem is also stabilized at a corresponding determined position, thereby achieving a proportional relationship between the signal current and the position. However, the conventional valve positioner amplifier constant orifice is prone to blockage, the back pressure is the largest, the amplifier ball valve is stuck, and the nozzle and the baffle are not tight.
2. In petrochemical production, intelligent valve positioners have some significant application advantages and features compared with conventional valve positioners. In the process of debugging and correcting, the intelligent valve positioner is easier, simpler and easier to master than the conventional valve positioner. Compared with conventional valve positioners, the intelligent valve positioner can perform automatic identification and control operations without the assistance of other adjustment control devices, and can automatically control the optimal state during the process, enabling different adjustments. Control requirements are optimized. For example, in the petrochemical production process, if it is necessary to adjust the control valve to forcefully close all of it, its intelligent operation control system will forcefully cut off the production and operation equipment whose control is adjusted according to the signal change of the adjustment input. Adjust the forced all off setting of the control system. All thanks to the software control system used by the intelligent valve positioner is an automatically set software system that uses a fully automated configuration program. 2. Analysis and application of diagnostic function of intelligent valve positioner in petrochemical field
1. When the valve is initialized, the performance of the entire valve is tested, the parameters are optimized, and if a fault occurs, an alarm message is issued. Alarm information: Preventive alarm - the state of the control valve is slightly worn and will continue to wear in the future, but the valve can still work normally; the maintenance alarm - the valve state has been seriously worn, and it is still working normally, but it may malfunction at any time. Fault alarm - reminds the equipment operator that the valve has failed. The reaction detection information appears on which parts of the control valve; the cause of the failure is analyzed - how to solve the above failure.
2. The control valve can be initialized initially by the smart valve positioner before use. The initial state information of all the valves after initialization is stored by the positioner. In this way, the control valve with the intelligent positioner starts the automatic initialization work, including determining the mechanical stroke range of the positioner and automatically adjusting the optimal index parameters when working, and the positioner applies the signal according to the currently determined mechanical information and index parameters. The algorithm controls the opening and closing of the valve. Whether the working state of the valve is normal or not is crucial. The positioner detects and analyzes it continuously in real time. Once a fault occurs, an alarm signal is issued, and the results of all the detection and analysis are stored in the memory of the positioner. Provide equipment operators or service engineers with information on diagnostic and maintenance faults.
3. The intelligent valve positioner can identify and diagnose the main valve state error by using its standard diagnostic function, but it is very difficult for the user to find out the direct cause of the fault. The user needs a feasible way to find out the cause of the fault. Sexual "diagnostic report". Therefore, the current intelligent valve positioner manufacturers have expanded the diagnostic functions in addition to the standard diagnostic functions to meet the various needs of users. The expansion focuses on the following two aspects:
(1) Install the auxiliary sensor in the intelligent valve positioner. When the actuator needs to be disconnected, use this sensor to detect the change of the pneumatic input and output signals at this time, so as to judge whether the valve inner and the actuator work normally. For this method, most manufacturers install pressure sensors to measure the pressure applied to the actuator diaphragm, which is related to the valve position. In the online operation mode, only the signal of the valve operation can be recorded to provide the friction and pressure analysis report, so that a more effective "diagnostic report" can be obtained.
(2) After a small change in the reference initial valve position by special program software, whether it is online or offline, the dynamic change of the response signal is recorded in the memory of the intelligent valve positioner, thus forming a clear change image. Through this change image analysis, the delay time and the transmission time are increased or decreased, and the valve working state parameters are predicted and diagnosed by image analysis combined with mathematical simulation module analysis. This can also get a "diagnostic report", which is convenient for users to find out the cause of the malfunction.
(3) The diagnosis process and test should be implemented completely inside the positioner, and the status alarm will be automatically issued according to the similar traffic light coding system. At the same time, these alarms will be displayed by the process control system at the appropriate authorization level. The maintenance personnel are interested in the alarm. The member may not be interested in the pre-diagnostic analysis function and processing of the information, prompting the maintenance personnel to appear in the future. 3. Development prospects of diagnostic functions of intelligent valve positioners in the petrochemical field
1. Develop strict control valves and locator software standards. All engineering software or process control software must fully comply with this standard.
2. Classify the diagnostic information step by step. The more detailed the classification, the better the user needs of different levels.
Conclusion
The intelligent valve positioner is an important system device for regulating and diagnosing the pneumatic diaphragm regulating valve in the petrochemical production system. Pneumatic diaphragm regulating valves have been widely used in the petrochemical industry, and many petrochemical production systems are inseparable from its regulation and control. Therefore, the quality of the valve positioner adjustment has a direct impact on the use of the pneumatic diaphragm control valve, which also has a great impact on the petroleum and chemical production links.

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