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The maintenance of DCS can be divided into: routine maintenance, preventive maintenance, and fault maintenance. Routine maintenance and preventive maintenance are types of maintenance carried out when the system has not failed. Fault maintenance takes place after a fault occurs, and by then the system’s functions have often been impaired, resulting in negative impacts on production. In contrast, preventive maintenance involves carrying out planned, regular inspections of the system while it is operating normally, in order to keep track of its performance, eliminate potential faults, and ensure its long-term stable and reliable operation – this is what constitutes the concept of preventive maintenance. Practice has shown that regular maintenance can effectively prevent sudden failures in DCS systems, resulting in significant indirect economic benefits. 1. Daily maintenance of the DCS system: Daily maintenance of the system is the foundation for its stable and efficient operation. The main tasks related to maintenance include the following: 1) Improving the management system for the DCS system. 2) Ensure the stable operation of air conditioning equipment, maintaining a room temperature variation of less than ±5°C/h, in order to prevent condensation on the system equipment due to sudden changes in temperature and humidity. 3) Try to avoid interference from electromagnetic fields on the system; avoid moving operation stations, monitors, etc., and be careful not to pull or damage the equipment’s connection cables and communication cables. 4) Pay attention to dust prevention, properly isolate the site from the control room, and clean it regularly to maintain cleanliness, thereby preventing dust from having an adverse effect on the operation of components and heat dissipation; 5) The use of unauthorized software as well as the installation of software that is not related to the system is strictly prohibited. 6) Ensure that backups of the files in the control subdirectories are made, and keep records of system data such as the PID parameters for each control loop and the forward and reverse actions of the regulators. 7) Check whether hardware such as the control host, monitor, mouse, and keyboard are in good condition, and ensure that real-time monitoring is functioning properly. 8) Check the fault diagnosis screen to see if there are any fault alerts. 9) After the system is powered on, the communication connectors must not come into contact with conductive objects such as cabinets. Communication cables and connectors that serve as backups should also not be in contact with each other, to prevent damage to the network card. 2. Preventive maintenance: Carry out proactive maintenance on a planned basis to ensure the stable and reliable operation of the system and its components. Maintain a favorable operating environment, and promptly inspect and replace components to eliminate potential risks. Preventive maintenance should be carried out once a year during the major overhaul to understand the system’s operating conditions and eliminate potential faults. During the major overhaul, thorough maintenance of the DCS system should be carried out, which includes: 1) System redundancy testing: Conducting redundancy tests on redundant power supplies, servers, controllers, and networks. The operation station and control station are under power outage for maintenance. This includes dust cleaning of components such as the inside of the computer, the control station chassis, and the power supply unit. 2) Inspection of the system power supply lines. Power capacity tests are conducted on the UPS, and discharge operations are carried out. 3) Grounding system maintenance. This includes terminal inspection and ground resistance testing. 4) For on-site equipment, refer to the relevant equipment manuals. After the major repair, the person in charge of system maintenance should confirm that all conditions are met before powering on the system, and must strictly follow the power-on procedures. 3. Fault maintenance: After a failure occurs, passive maintenance of the system is required, which mainly includes the following tasks: 1) Professional maintenance – this usually needs to be carried out by manufacturers or maintenance engineers designated by them. 2) General user maintenance: The daily maintenance is carried out by the system users themselves. Maintenance personnel should have an understanding of the technical complexity and feasibility of system maintenance, be aware of the tools required for such maintenance, know which tasks can be completed on their own, and be prepared to develop viable maintenance plans promptly in case of problems. The key to troubleshooting DCS system failures is to quickly and accurately determine the location of the fault. Some experiences gained from such troubleshooting are summarized as follows: (1) DCS systems typically possess robust self-diagnosis functions. Based on the alarm, the faulty location can be identified directly, and the repair results can also be verified by eliminating the alarm. (2) Poor contact at the communication connectors can cause communication failures. If poor contact is detected, the connectors can be reconnected using appropriate tools; damaged communication cables should be replaced promptly. (3) If the fault light of a certain card is flashing or all the data on that card are zero, possible reasons include incorrect configuration information, the card being in standby mode with the redundant terminal connections not made, a fault within the card itself, or the absence of configuration information for that slot. (4) When a certain production condition is abnormal or an alarm is triggered, we first check the instruments involved, and then follow the direction in which the signal is transmitted to use instruments to verify the accuracy of each signal, until the source of the fault is identified. (5) In the event of large-scale hardware failures, it is most likely that these are caused by inadequate maintenance of the DCS system environment. In addition to carrying out immediate replacements with spare parts and cleaning the system, it is also necessary to contact the manufacturer promptly so that their technical support engineers can further diagnose and resolve the issue. 4. Conclusion: For the maintenance of DCS systems, prevention should be given top priority. As system maintenance personnel, it is necessary to develop scientific, reasonable, and feasible maintenance strategies and methods based on the system configuration and the control requirements of the production equipment. Preventive maintenance should be combined closely with routine maintenance, so as to carry out systematic, planned, and regular maintenance efforts. This ensures that the system can operate properly over the long term under required conditions, allowing for stable control of the production process and reliable performance, thus providing a solid foundation for achieving the goals of production and efficiency.