The smart valve positioner is used as the main component of the control valve. Its diagnostic technology is constantly being developed and improved. Therefore, the smart valve positioner has a diagnostic, control, and detection role.
Petrochemical industrial production is not only flammable, explosive, and toxic but also strongly corrosive. In addition, the harsh working environment makes it a hazardous industry. Once an accident has occurred, it often results in heavy casualties and property damage.
Therefore, the high risk has forced petrochemical companies to invest more in automation and intelligent control equipment. As a result, we need to control many control valves in the production process. At the same time, its diagnostic maintenance is essential. It allows for a safety-enhanced, high-performance management process. The risks are thus minimized to the greatest extent possible.
1. Advantages of intelligent valve positioner to the traditional valve positioner.
1.1 Traditional valve positioner
1.1.1 Principle of traditional valve positioners
The traditional valve positioner is operated by a regulator or output safety grille. When it outputs 4~20mA DC into the coil, it will make the moving iron located in the lock magnetize and work. The moving iron is located in the magnetic field generated by the permanent magnet. Therefore, when the two magnetic fields interact, it will produce a deflecting torque on the kinematic iron, causing it to deflect at the center of the pivot point.
If we increase the signal, then the left side of the lever should move downwards. At this point, the baffle plate that we have fixed to the lever moves closer to the nozzle, increasing the backpressure of the sizeable incoming device. The amplified output air pressure then acts on the diaphragm head of the regulating valve. It will cause its stem to move downwards.
1.1.2 The role of the traditional valve positioner stem
The displacement of the valve stem is converted into the angular displacement of the feedback shaft and feedback lever using a tie rod, and then the feedback body is made to move by adjusting the range pivot point.
When the feedback spring fixed to the other end of the lever is stretched, a negative feedback torque balances the lever. At the same time, the stem will be fixed in a correspondingly definite position, thus achieving a proportional relationship between signal current and function.
1.1.3 Disadvantages of traditional valve positioners
The amplifier constant throttle orifice of a traditional valve positioner is highly susceptible to the following conditions.
184.108.40.206 High backpressure.
220.127.116.11 Jamming of the amplifier ball valve.
18.104.22.168 Nozzle and baffle do not close tightly.
2. Advantages of intelligent valve positioners
In petrochemical production, smart valve positioners are compared with conventional valve positioners. Intelligent valve positioners have some significant application advantages and features.
We are in the process of commissioning correction. Intelligent valve positioners are easy to operate, simple, and more straightforward to master than conventional valve positioners.
Compared to conventional valve positioners, intelligent positioners do not require the assistance of some other adjustment and control equipment. It can carry out automatic identification and control operations by itself. In the process, it can automatically adjust the optimal control state. It can also be optimally set for different regulation and control requirements.
For example, in the petrochemical production process, if we need to regulate the control valve for forced total closure, its intelligent operating system will change according to the regulation input signal. As a result, it will control the production branch line equipment regulation for forced entire closure settings.
All this is possible thanks to the intelligent valve positioner. Its control system is an automatically set software system with a fully automatic configuration program used in the branch.
3. Analysis and application of the diagnostic function of the intelligent valve positioner.
3.1 Fault function and prompt maintenance
When the valve is initialized, the performance of the entire pneumatic membrane flow control valve is tested, and the parameters will be optimized.
3.2 Fault function and prompt maintenance
The intelligent positioner will issue an alarm message if the valve generates a fault. The preventive alarm function will alert the operator to the mild wear of the condition of the regulating valve, and it will continue to wear.
3.3 Maintenance alarms
When the condition of the valve is severely worn, however, the valve is still working correctly. However, if it is likely to fail, the fault alarm function will alert the plant operator that the valve has failed.
Reaction detection messages will appear on certain parts of the regulating valve. The intelligent valve positioner will not only analyze the cause of the fault but will also suggest how to solve the problem.
3.4 The working condition of the valve
The valve must be in working order. The positioner detects and analyses them in real-time and without interruption. In a valve failure, the intelligent positioner signals an alarm. All the tests and analyses are stored in the positioner’s memory and provide the plant operator or maintenance engineer with information on diagnosing and repairing faults, etc.
4. The diagnostic function of the intelligent valve positioner
The diagnostic function of the intelligent valve positioner can identify and diagnose significant valve status errors. However, it is difficult for the user to specify the direct cause of the fault. Therefore, users need a feasible “diagnostic report” that can identify the cause of the mark. It is why intelligent valve positioner manufacturers are now providing standard diagnostic functions and diagnostic extensions to meet the various needs of users. The wings focus on the following three areas.
4.1 Sensors for innovative valve positioners
An auxiliary sensor is installed within the intelligent valve positioner. When the actuator needs to be disconnected, it uses this sensor to detect the magnitude of the change in the pneumatic input and output signals at this time. Thus, it can determine whether the valve internals and the actuator are working correctly.
For this method, most manufacturers install pressure sensors to measure the pressure loaded onto the diaphragm actuator. This pressure is related to the valve position. In an online mode of operation, only a recorded signal of the valve operation can provide a friction and pressure analysis report, which results in a more valid “diagnostic report.”
4.2 Fault analysis function of the intelligent positioner
After a slight change in the reference initial valve position, whether online or offline, the dynamic changes in the response signal are recorded in the memory of the intelligent valve positioner using special programming software. It creates a clear picture of the change, which we use to analyze the delay and transmission times, whether they increase or decrease. We also use the graphical analysis combined with the mathematical simulation module for predictive and diagnostic analysis of the valve operating parameters. It also gives a “diagnostic report,” which allows the user to identify the cause of the fault.
4.3 Intelligent positioner prompt function
The diagnostic process and testing should be carried out entirely within the positioner. We want to automatically issue status alarms based on a system similar to traffic light coding. At the same time, these alarms are transmitted by the process control system to the authorized service personnel, who may not be able to deal with them in time. Then the intelligent valve positioner will again alert the service personnel to the fault situation.
An intelligent valve positioner has a vital significance for petrochemical production systems. It is also a critical system device for regulating and diagnosing pneumatic film flow adjustment valves. Pneumatic film adjustment valves have been widely used in various industries’ production. Many production systems’ branch lines are inseparable from their regulation control. So the quality of the valve positioner regulation directly impacts the use of pneumatic film adjustment valves.