DCS system configuration issues

If the system configurator mistakenly changes the operating mode of the TIC1006 air temperature regulator from positive action to negative action, the relationship between the regulator’s output and the input signal will be reversed. In the direct action mode, an increase in the input signal (such as an increase in the measured value of temperature or pressure) results in an increase in the output signal (for example, the opening degree of the control valve). In the reactive mode, an increase in the input signal leads to a decrease in the output signal. Specifically regarding the temperature control proportional control loop of reactor M101’s TIC1008, if the regulator TIC1006 is responsible for controlling factors that affect the temperature of reactor M101 (such as air flow rate, cooling medium flow rate, etc.), the feedback from this regulator can lead to the following problems: 1. Control instability: Due to the opposite operating mechanisms, the regulator may make incorrect adjustments. For example, if more cooling medium is needed to lower the temperature of the reactor, the feedback regulator may reduce the amount of cooling medium, causing the temperature to rise further and thus leading to oscillations or instability in the control loop. 2. Reverse response: When the control system needs to make corresponding adjustments to stabilize the process variable, the reactive regulator will provide an opposite response, resulting in the process variable (such as temperature) deviating from the setpoint. 3. Safety risks: Especially in critical processes such as temperature control, incorrect operation can lead to overheating or undercooling, which may damage the equipment, affect product quality, or cause safety accidents. 4. Decreased productivity: Incorrect reactions can affect the stability and efficiency of the production process, leading to waste of raw materials, increased energy consumption, and a slower production pace. 5. Difficult system diagnosis: Configuration errors may not be easily detected immediately; especially in complex systems, it may take longer to diagnose the issues, increasing maintenance costs. Therefore, upon detecting such an incorrect configuration, the operating mode should be immediately adjusted back to the correct state, and system testing should be conducted to ensure that the control loop functions as intended. If the control system has simulation or testing functions, tests can be carried out in a non-production environment to avoid affecting actual production. .

Very good! May I ask: Do these problems occur in both the upper range of 11–100% for the tuning of the TIC1008 regulator, and the lower range of 0–11% for its tuning?

It will affect everything! The effective counter-air temperature will decrease. Furthermore, TIC1008 indirectly affects 11–100% of FIC; for details on this impact, please consult the process team.

This post was last edited by zhoudingshengs on 2023-12-6 at 11:30. Additional information----General design principles for control system configuration design: 1. General design principles for configuration design: (1) Practicality, reliability, usability, maintainability, traceability, cost-effectiveness, and scalability should all be taken into consideration, with redundant fault-tolerance techniques to be used appropriately. (2) It shall meet the requirements for production operations, DCS contracts, equipment installation, system commissioning, etc. (3) Industry technical specifications, basic templates, typical applications, etc. must comply with the distributed control system instruction manual and **industry design standards, and be successfully applied in projects. (4) Depending on the configuration of the system software, it is necessary to ensure that the system software of other integrated control systems meets the required standards ； The DCS should also meet the specific integration requirements posed by the complete control system as needed. (5) After obtaining the required technical documents in a timely manner during the design phase, it is necessary to ensure the completeness and accuracy of the DCS scheme and configuration design documents. (6) The DCS operating system and system software use officially released versions, and are under effective control during product development. (7) System security should be given full consideration, including authentication and access control functions and permissions, support for data encryption, antivirus isolation, regular backups (such as automatic backup functions), prohibition of data interfaces, and restrictions on external storage (such as USB disablement tools).

It is normal to adjust within the upper range of 11–100% of the setpoint of the TIC1008 regulator in the M101 reactor； It is abnormal to adjust within the lower range of 0–11% of the setpoint of the TIC1008 regulator in the M101 reactor; this leads to a loss of control. That is, when the TIC1008 reading is low, it can still be adjusted ； When the TIC1008 reading is too high, it necessarily causes TIC1008 to adjust in the direction of unidirectional diffusion, ultimately leading to overheating of the furnace.

According to the control chart and description: 1. The TIC1008 regulator loses control when adjusted within the upper range of 11–100% of its span. 2. It is normal for the TIC1008 regulator to operate within the lower range of 0–11% of its span.