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Key points for the daily maintenance of DCS: The Distributed Control System is abbreviated as DCS; it is the result of the development of computer technology and automation technology. The capacity of power units is continuously increasing, and their parameters are constantly improving, creating vast opportunities for the application of DCS ； With the widespread use of DCS systems, it provides strong support for the safe and economical operation of power units. The control method of a power unit reflects the level of automation in a comprehensive manner. In the early days, due to low levels of thermal automation and low skill levels among the personnel, a decentralized, on-site operation approach was used, with monitoring and control functions located at the site itself. This control method was only suitable for units with low parameters and small capacity; it involved high labor intensity and poor safety standards. After the mid-1950s, the stage of development toward local control was reached; due to the widespread use of a master control system for the units, local centralized control methods for boilers, steam turbines, and feedwater deaeration were adopted accordingly ； In the 1960s, computer technology was applied to the monitoring and control of thermal power plants, leading to centralized control of the machinery, boilers, and electrical systems ； Programmable Control Filling (PLC) was developed in the early 1970s ； In the 1980s, with the development of advanced technologies such as control technology, computer technology, communication technology, and CRT technology, foreign countries developed distributed control systems (DCS) for microcomputers, which were subsequently applied in thermal power plants ； In the 1990s, thanks to the development of microprocessors and very large scale integration (VLSI) technology, DCS evolved towards greater integration and openness. This progress was driven by advances in computer technology, fault tolerance techniques, human-machine interface technologies, windowing technologies, and interactive graphics, as well as by the development of standardized data communication networks and artificial intelligence. The widespread use of DCS in industries such as power, petrochemicals, and food in China. It features strong versatility, flexible system configuration, comprehensive control functions, easy data processing, centralized display and operation, a user-friendly interface, simple and standardized installation, easy debugging, and reliable operation. With the development of China’s power industry, DCS has become a commonly used device, with its application becoming increasingly widespread across both large-scale power units and small-scale heating units. Consequently, the daily maintenance of such equipment also requires heat control personnel to change their traditional way of thinking in order to meet the demands of modern development. I will now elaborate on the production and maintenance experience over the past few years. 1. Routine maintenance work 1.1 Process channel failures The most common type of failure in process channels is I/O card failures. The diagnosis and handling of such failures generally involve using system diagnostics, replacing the affected channel or using spare parts. As for damage caused by the aging of internal components or other reasons, it is usually difficult for thermal control personnel to determine the cause. The maintenance of I/O cards is generally handled by the manufacturer; currently, the capabilities of thermal control maintenance personnel are not sufficient to carry out such maintenance in the same way as for conventional instruments. Moreover, I/O card modules from manufacturers are trending toward being integrated, which means only spare parts can be purchased. Fortunately, such faults occur more frequently during the debugging phase, with a very low probability of happening during normal operation. A failure in a primary component or control device may not be immediately detected by the operator; it is only when an anomaly or alarm occurs that the thermal control personnel are notified to handle it. This raises the requirements for the skills of maintenance and operation personnel. Operation personnel need to provide detailed descriptions of the system’s condition before and after a fault occurs, so that thermal control maintenance staff can address the issues quickly and accurately, thereby preventing the fault from worsening. Additionally, many DCS manufacturers promote the use of hot-swappable cards in their products; as operators, it is essential to take proper safety measures when replacing cards during operation, otherwise it could lead to changes in the system or in its load, especially with digital input cards. 1.2 There have been reports of operator station freezes in both domestic and imported equipment. The causes are varied, including hard drive or card failures, excessive load on the cooling fans, etc. Sometimes human error is to blame; such errors often occur when modifying control logic, installing software, restarting the equipment, or activating device protection signals. In mild cases, this leads to abnormal operation of the equipment, while in severe cases it can result in the equipment coming to a stop, with very serious consequences ； When restarting after a system crash, the startup time varies among different manufacturers – ranging from a few dozen seconds to several minutes. Human-induced failures resulting from such operations account for a large proportion of safety incidents in the field of thermal engineering; therefore, great attention is paid to such operations in order to reduce human errors. 1.3 Abnormal operations of the ball marker are usually caused by factors such as prolonged use of the mechanical components, aging, contamination, unreliable on/off switching, or loose cable connectors; in such cases, replacement or inspection is required. 1.4 Control operation failure: This occurs when the control signals for the ball marker fail to properly change the state of the process channel, resulting in ineffective operation. This is caused by two factors: software defects on the one hand, and hardware failures on the other. In response to such defects, it is usual to first check that the function of the process channel is normal, and then examine the control operations; if necessary, restart the initial operations. 1.5 For membrane keyboards, poor keyboard contact, loose signal cables, or improper operation of the host unit as well as incomplete startup can all lead to abnormal functioning; appropriate measures should be taken based on each specific situation. 1.6 A printer that does not work is usually due to configuration issues; such problems should be resolved by checking the printer’s settings and ensuring that its hardware is functioning properly. The weak functionality of reporting software is mainly manifested in system crashes caused by printers printing reports and SOE, or discrepancies between the SOE recording time on the printer and the actual situation ； After printing and viewing in SOE, it is not possible to return to the historical curve ； The chronological order of SOEs is inconsistent and can sometimes vary significantly, which delays the progress of accident analysis and may even misdirect the analysis. The SOE issue is related not only to an unreasonable system design and the fact that SOE points are not all concentrated on a single DPU, but also to inadequate considerations in the system’s hardware and software design. It is believed that the occurrence of such faults is mainly due to inadequate consideration of the overall aspects of the power plant; insufficient attention to minor details leads to various faults. This situation must be taken seriously, with no detail overlooked, and the manufacturer should be consulted in order to identify the problems and make further improvements, so that the system can serve production more effectively. 1.7 Power supply failures: There are many issues related to power supply failures; the fuse configuration is inadequate, the backup power supply does not switch on automatically, power fluctuations can cause false protection trips, and poor contact of connectors can lead to a lack of power supply. Dealing with power supply failures is relatively easy. First, carefully verify the configuration and capacity of the insurance to ensure it truly serves its purpose ； Secondly, it is important to have a UPS, as it ensures continuous power supply to the system even in cases of power fluctuations; redundancy and backup options also need to be considered. 1.8 Failures caused by interference: Interference is mainly related to grounding issues, the switching of backup power supplies, and high-power wireless communication devices such as mobile phones and walkie-talkies. Additionally, interference signals in the DCS system may be caused by the system itself. Therefore, the grounding issue in DCS systems is attracting increasing attention, especially in the power industry, where the startup and shutdown of high-power electrical equipment can interfere with the control signals of DCS systems, leading to unnecessary failures. To prevent interference signals from entering the system, it is necessary to strictly adhere to the requirements and methods related to shielding and grounding, keep the signal wires away from sources of interference, and take measures to prevent power supply fluctuations. During the operation of the unit, manual switching between the primary/secondary process processors should be avoided as much as possible, unless it is absolutely necessary, in order to prevent disruptions. If switching is indeed required, measures should be taken to switch control to manual mode first, so as not to affect the unit’s operating conditions. The use of high-power radio communication equipment is strictly prohibited in key areas such as electronic equipment rooms and engineer stations. 2. Operation Management: The operation management of a DCS system involves the inspection of the system, the activation and deactivation of thermal protection mechanisms, as well as the supervision and management of the DCS’s hardware and software. 2.1 Backup management of software: Application software (databases) should be backed up regularly, and even minor changes should be recorded ； Changes to the database must be saved to the engineer station as well as to a floppy disk or another hard drive. But be careful not to use the backup disk for an extended period to avoid data loss. 2.2 Software inspection and functional testing shall be carried out in accordance with the general methods for computer equipment, focusing mainly on the verification of permission settings at various levels: the use of non-DCS software is strictly prohibited; unauthorized personnel are strictly forbidden from performing configuration tasks. 2.3 The activation and deactivation of thermal protection systems must be carried out in strict accordance with the work order system. When maintaining a running device, proper isolation measures must be taken to prevent adverse reactions in related devices. To address these common faults and to prevent their occurrence as well as reduce their frequency, strict systems for inspection, maintenance, and regular checks should be established. It is necessary to fill out the DCS equipment inspection forms carefully, identify and address various minor defects promptly, thereby stopping faults in their infancy. Properly keeping operation logs is also important to enhance management efforts