1. Routine maintenance work
1.1 Process Channel Faults The most common process channel fault is I/O card failure. I/O card faults are generally diagnosed and handled through system diagnostics, channel replacement, or replacement with a spare part. However, damage caused by aging internal components or other reasons is generally difficult for thermal control personnel to determine. I/O card repairs are usually handled by the manufacturer, as current thermal control maintenance personnel do not have the same level of expertise as they do for conventional instruments. Furthermore, manufacturers are increasingly producing integrated I/O cards, necessitating the purchase of spare parts. Fortunately, these faults are more common during the commissioning phase and occur very rarely during normal operation. Sometimes, faults in primary components or control equipment cannot be directly detected by operators; thermal control personnel are only notified after an anomaly or alarm is triggered. This necessitates raising the skill requirements for maintenance and operation personnel. Operation personnel must provide detailed information on the state before and after the fault so that thermal control maintenance personnel can quickly and accurately handle the defect and reduce the escalation of the fault. In addition, many DCS manufacturers support hot-swapping of cards in their product promotions. As control personnel, it is essential to take proper safety precautions when replacing cards during operation, otherwise it may cause changes in the system or load, especially for digital cards.
1.2 There have been reports of operator station crashes on both domestic and imported equipment. The causes are varied, including hard drive or card failures, excessive cooling fan load, and sometimes human error. These incidents are most likely to occur when modifying control logic, installing software, restarting the equipment, or forcing protection signals. These incidents can range from minor equipment malfunctions to serious equipment shutdowns. The restart time after a crash varies between manufacturers, ranging from tens of seconds to several minutes. Human error accounts for a large proportion of unsafe incidents in thermal engineering and should be given high priority to reduce human error.
1.3 If the ball bearing is not operating properly, it is generally due to long-term operation, aging, contamination, unreliable connection/disconnection, or loose cable plugs. In such cases, replacement and inspection are necessary.
1.4 Control operation failure: This is caused by the ball's operation signal not changing the state of the process channel normally, resulting in operation failure. This is caused by two aspects: one is software defects, and the other is the state of hardware failure itself. For such defects, the usual practice is to check that the process channel function is normal, then check the operation channel, and restart the initial operation if necessary.
1.5 For membrane keyboards, malfunctions can be caused by poor keyboard contact, loose signal cables, accidental keyboard operation by the host, or incomplete startup. Different solutions should be applied depending on the specific situation.
1.6 Printer malfunctions are generally due to configuration issues. Such faults should be addressed by checking the printer settings and ensuring the hardware is functioning correctly. Weak reporting software functionality manifests primarily as printer crashes caused by printing reports and SOEs, or discrepancies between the printer's SOE recording times and actual data; inability to return to historical curves after browsing SOE prints; and inconsistent SOE time sequences, sometimes with significant deviations. This can delay troubleshooting and sometimes mislead the analysis. SOE problems are related to both unreasonable system design (SOE points not being fully concentrated on a single DPU) and inadequate hardware and software design. Analysis suggests that this type of fault primarily stems from insufficient consideration of the overall power plant design; a lack of attention to detail in smaller aspects can lead to various malfunctions. This situation requires serious attention; no detail should be overlooked. A thorough investigation with the manufacturer is necessary to identify and improve the system, ensuring it better serves production.
1.7 Power Supply Failure: Power supply failures are a common problem, including inadequate fuse configuration, failure of backup power to automatically switch on, protection malfunctions caused by power fluctuations, and poor contact at connectors leading to no power. Troubleshooting power supply failures is relatively straightforward. First, carefully verify the fuse configuration and capacity to ensure they function properly. Second, the availability of a UPS is crucial; it must guarantee normal system power supply during power fluctuations, and redundancy and backup should be considered.
1.8 Interference-induced faults: Interference is mainly caused by grounding issues, backup power switching, and high-power wireless communication devices such as mobile phones and walkie-talkies. Additionally, interference signals from the DCS system itself may also be caused. Therefore, grounding issues in DCS systems are receiving increasing attention, especially in the power industry, where the starting and stopping of high-power electrical equipment can interfere with DCS control signals, causing unnecessary faults. To prevent interference signals from entering the system, strict adherence to shielding and grounding requirements and methods is essential. Signal lines should be kept away from interference sources, and measures should be taken to prevent power fluctuations. During unit operation, manual switching between master and slave process processors should be avoided as much as possible unless absolutely necessary to prevent interference. If switching is unavoidable, measures should be taken to first switch the control to manual mode to avoid affecting the unit's operating conditions. High-power wireless communication equipment should be strictly prohibited in key areas such as electronic equipment rooms and engineering workstations.
2. Operation Management
The operation and management of a DCS system refers to the system's inspection, the activation and deactivation of thermal protection systems, and the supervision and management of DCS hardware and software.
2.1 Software backup management: Application software (database) should be backed up promptly, and even minor changes should be recorded. Modifications to the database should be saved to the engineer's workstation, as well as to a floppy disk or other hard drive. However, backup disks should not be used beyond their expiration date to prevent data loss.
2.2 Software inspection and functional testing should be conducted in accordance with the general methods for computer equipment, mainly checking the settings of permissions at all levels: the use of non-DCS software is strictly prohibited; unauthorized personnel are strictly prohibited from configuring.
2.3 The activation and deactivation of thermal protection should be strictly carried out in accordance with the work permit system. When overhauling a certain operating equipment, proper isolation measures should be taken to prevent synergistic reactions of related equipment.
In response to the above common faults, in order to avoid the occurrence of faults and reduce the frequency of their occurrence, a strict inspection, maintenance and regular inspection system should be established, the DCS equipment inspection card should be filled out carefully, and various minor defects should be discovered and dealt with in a timely manner so that faults disappear in the bud. The operation log should be filled out properly and management methods should be strengthened.
