Instrument issues during process adjustment
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In chemical process automation control, instruments play the most important role, but there are sometimes cases where the boundaries are not clear. I would like to bring this up for discussion: 1. In terms of control loops, who should adjust the PID parameters of the control valves? If it is the process engineers who do this, they must have a good understanding of instrument-related knowledge; if it is the instrument technicians who handle it, then they need to be very familiar with the process. I wonder which team is responsible for making these adjustments in your respective factories? 2. Regarding issues with on-site instruments, how can the responsibilities between the instrument team and the process team be clearly defined? For flow meters, control valves, thermometers, level gauges, and other special instruments, when a fault occurs, it’s necessary to determine what the process team should do and what the instrument team should do. For example, when a flow meter and control valves are used together and the flow rate becomes intermittent or even drops to zero, should it be the instrument team that is notified to handle the issue, or the process technicians? Which level of process personnel should be responsible for deciding such matters? ? ? 3. Many factories use interlocks for safety purposes; it is up to the leadership at which level to decide whether it is necessary to activate these interlocks or to disable them forcibly (due to process or instrumentation issues) ? ? Do any of you have any other questions regarding instruments and processes that we could discuss and share information on? Thank you
1. For the control loop, who is responsible for adjusting the P I D parameters of the control valve, and which department handles this task? Responsible for it is the instrument maintenance staff. The PID parameters for most control valves are adjusted by operators; those that cannot be adjusted by the operators are adjusted by instrument engineers. 2. Classification of on-site instrument issues? Handled by instrument maintenance personnel with the assistance of operators. 3. Who at the appropriate management level should decide whether it is necessary to deactivate the safety interlock in cases of its activation or forced deactivation (due to process or instrumentation issues)? ? ? The general situation is determined by the plant’s chief engineer, with the instrumentation staff carrying out the tasks. Special exceptions are decided by the operator themselves, who then reports to the chief engineer and informs the instrument maintenance staff.
1. For instrumentation specialties, process engineers provide the parameter requirements. The head of the process team (group) determines the cause of the fault. 2. For instrumentation-related tasks, special instruments such as online analyzers are the responsibility of the analysts at the monitoring center. 3. Determined jointly by the section process engineer and equipment officer.
This issue should be addressed through cooperation: the process team sets the requirements, while the instrumentation team is responsible for making the adjustments; otherwise, things will get chaotic
Of course, it’s the process engineers who carry out the adjustments. In fact, adjusting PID doesn’t require any special knowledge of instruments; one only needs to understand the basic meanings of P, I, and D, as well as how to modify the PID parameters. By then, one can simply look at the PID tuning curve. For tasks like this, technicians and workshop supervisors in ordinary workshops are more than capable of handling them! If the instrument operator does the adjusting, everything might get completely messed up!
Thank you all for sharing your insights. Personally, I think it should be the responsibility of the shift leader to determine the cause of the fault; in other words, the shift leader should have the ability to handle PID tuning issues. Such tasks should be carried out by process engineers, not operators. Operators are responsible for maintaining the temperature of the equipment and making adjustments, and they certainly don’t have the time to deal with such adjustments. Sometimes, it takes a long time to get PID tuning right, especially when it comes to temperature control. As the person from Zhongyuan said, it should be the chief engineer who signs off on these matters – this isn’t something that ordinary instrument or process technicians can decide on
The PID should be adjusted in collaboration between process technicians and instrument engineers, and cannot be adjusted solely by operators
1. Generally speaking, the process in a chemical plant comes first; PID tuning is carried out accordingly. If the process engineers understand the relevant aspects, it is best for them to carry out the tuning (preferably the process supervisors), as they are aware of the properties of the media flowing through the pipes, which makes the tuning process easier and helps to meet the production requirements more effectively. If you do not understand the principles of PID control, you can consult instrumentation specialists or refer to books on chemical process instrumentation, which generally provide information on PID tuning methods. 2. If a gauge in the system appears to be faulty, it is still necessary to first check whether there have been any changes in the process medium. For example, if the temperature has changed, one can verify whether this change is indeed due to a change in temperature by examining pressure, flow rate, or reaction conditions, etc. If no issues are found with the process system aspects and it is determined that the problem lies solely with the instruments, then it is necessary to have an instrumentation specialist inspect the instruments or replace them. 3. Interlocking is related to the safety and stability of the equipment and production processes in chemical manufacturing; careful consideration must be given to determining which systems should be activated and which ones can remain inactive. It should be the responsibility of the workshop’s technical supervisor or the company’s technical supervisor. This post was last edited by comm_zhang on 2009-3-9 20:49]
The PID is adjusted by the instrumentation personnel during process testing; if it does not meet the requirements for actual process operation, further adjustments are made to the instrumentation. Whenever automatic control is involved, adjustments must be made using instruments. In case of problems that arise during the process, such as a lack of flow, the process operators and team leaders need to determine whether it is an issue with the instruments or indeed no flow is present. Interlocks are generally divided into three levels: the third level is approved by the workshop, the second level by the sub-factory, and the first level by the company.
As I understand it, the system control engineer is responsible for management; system control falls under the category of process engineering, and it is necessary to delve into the specific workings of each control loop – otherwise, it is not possible to ensure the implementation of the process concepts. Instrument engineers are primarily responsible for selecting and maintaining instrument facilities and equipment, as well as for preparing and keeping up to date the general specifications for such instruments, the wiring specifications, and detailed wiring diagrams. The difference between similar processes and piping. It is incorrect to attribute all system control to instruments; this is also the reason why many control processes encounter problems. Process engineers must understand the principles behind control processes, and our universities fail miserably in this regard, thinking that performing basic process calculations is sufficient.
Furthermore, any changes to existing equipment, facilities, and process parameters must be controlled by specialized procedures to ensure manageable oversight; otherwise, safety issues will arise. It is recommended that all TXs learn more about this area; having knowledge without proper management is also extremely dangerous.
It’s a very simple question; the instrument technician only needs to explain the principles of PID to the process engineers. It’s best for the process engineers to make the adjustments according to their own needs