Management and maintenance of DCS systems

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The following provides a brief overview of the daily management and maintenance of DCS systems, in the hope that it will be helpful to everyone. The content may be quite extensive and varied. DCS is the abbreviation for Distributed Control System; in China’s automation industry, it is also referred to as a distributed control system. The DCS system is a multi-level computer system composed of a process control level and a process monitoring level, connected by a communication network; it integrates technologies such as computers, communication, CRT displays, and control. Its basic concept is decentralized control, centralized operation, hierarchical management, flexible configuration, and easy setup. A DCS system mainly consists of field control stations (I/O stations), a data communication system, human-machine interface units (operator station OPS, engineer station ENS), cabinets, power supplies, etc. The system features an open architecture that provides multiple layers of open data interfaces. The hardware system features high reliability, easy maintenance, and advanced technology in harsh industrial environments. The underlying software platform boasts powerful processing capabilities, offering the ability to easily configure complex control systems as well as support for users to develop their own specialized advanced control algorithms ； Easy to configure and easy to use. It supports multiple fieldbus standards to meet future expansion needs. Compared with conventional control instruments: Advantages: It has comprehensive control functions, enabling complex and optimal control, as well as facilitating the integration and analysis of information. Problems exist: high risk concentration; performance issues: excessive load on individual machines; long development cycle. Solution: Choose computers with high reliability, implement dualization, and increase redundancy. I. Responsibilities of System Maintenance Personnel 1. Responsible for the maintenance of the software and hardware components of the DCS system, ensuring its reliable operation and thus safeguarding the safety and stability of the production process. 2. Coordinate and participate in the configuration of the DCS, the implementation of control schemes, as well as the hardware connections of the system, the installation of the operating system, and the debugging of the DCS system. 3. Responsible for conducting technical discussions with DCS manufacturers, learning the skills related to the use, maintenance, and management of DCS systems, in order to maximize the effectiveness of these systems ； In accordance with the requirements of the production process, improve the control and management functions of the DCS system. 4. Guide operators in operating the DCS system and resolve issues that arise during their operations ； Upon receiving a request from the operator, respond immediately and resolve the issue. 5. Carry out daily and regular inspections and maintenance of the DCS ； Proactively and promptly identify issues and potential risks within the system, determine their causes, and resolve them effectively. When faced with difficult problems that cannot be solved, it is necessary to consult the DCS manufacturer promptly to arrange for resolution. 6. Responsible for modifying system operation parameters and performing backups to prevent any data damage or loss. 7. Ensure effective backup of both software and hardware of the DCS system. 8. Responsible for starting and stopping the DCS system. 9. Responsible for setting and modifying operator passwords. 10. Establish maintenance and management regulations for the DCS system. II. Maintenance and Management Guidelines 1. Maintenance and management of the control room (1) Formulate regulations for the cabinet room and operation room. Detailed provisions are made for maintaining the sanitary conditions in the cabinet room and control room, managing personnel entering and leaving, regulating operator operations, and overseeing maintenance activities by maintenance staff. (2) In addition to maintaining appropriate temperature and humidity, the control room must also be protected from water damage, dust, corrosion, interference, rodents, and insects, as well as from mechanical vibrations. 2. Maintenance and management of computers (operation stations, engineer stations, server stations): (1) Continuously remind operators to operate in a proper manner, take good care of the equipment, and maintain cleanliness while protecting it from water and dust. (2) Operators are prohibited from exiting real-time monitoring ； Operators are prohibited from adding, deleting, or moving any files on the computer, as well as from changing the system settings ； Operators are prohibited from using external storage devices or optical discs. (3) Try to avoid interference from electromagnetic fields on computers; do not move computers, monitors, etc. that are in use, and be careful not to pull or damage various cables that are connected. (4) The computer should be kept away from heat sources, and its vents must not be blocked by anything. (5) The use of non-genuine operating system software is strictly prohibited (non-genuine operating system software refers to OEM versions included with products and other pirated software) ； It is strictly prohibited to perform unnecessary multitasking on the real-time monitoring platform or to run unnecessary software ； Forbidding the forced shutdown of computer power supplies ； It is strictly prohibited to disassemble or assemble computer hardware while it is powered on. (6) Pay attention to antivirus protection on the computers at the operation station (engineer station); do not use removable storage devices without effective antivirus protection (such as external hard drives, USB drives, etc.) ； Do not connect other computers that do not have valid antivirus protection to the control system network ； Do not connect the control network to other networks that lack proper technical safeguards. (7) If computer devices such as operation stations, engineer stations, and servers require software reinstallation, it must be carried out in accordance with the requirements of the DCS manufacturer. (8) During normal operation, close the cabinet doors of the computer stations (operation station, engineer station, server station). 3. Control station maintenance management (1) Under no circumstances shall any components of the control station (main control card) be modified or disassembled without permission. (2) During routine inspections and modifications, avoid pulling or damaging power, grounding, communication, and signal cables. (3) An anti-static bracelet must be worn when maintaining the card holder. (4) During normal operation, close the control cabinet door. 4. Backup management of system hardware and software, system configuration files, as well as control and operation parameters: (1) The following backups must be performed on the computer’s hard drive; at the same time, backups should also be made on USB drives, optical discs, or other computers. Before performing the backups, it is necessary to keep records of any updates or provide explanations regarding them: Data such as control parameters that cannot be modified by the operator (PID parameters, regulator action modes, etc.), control variables, and process parameters should all be backed up. Back up the configuration files and the subdirectories containing configuration files (such as configuration files, flowchart files, control algorithm files, and report files). In the event of communication with external systems, it is necessary to back up and archive data such as communication protocols, communication plans, and communication addresses, along with related documents. (2) It is necessary to archive and store design documents such as wiring diagrams and installation drawings, as well as handover documents. (3) All kinds of software that need to be installed on the computer should be backed up on the local computer’s hard drive, such as operating system software, DCS system configuration and monitoring software, driver software, etc. Version identifiers should be assigned, and installation instructions should be prepared. (4) Understand the system’s recording cycle, and in accordance with the requirements of the production process, regularly back up operation records, alarm records, historical trends, and other production-related records without omission. After creating optical discs, label them properly and hand them over to the relevant personnel for storage. (5) Properly manage the storage of spare parts and components; it is necessary to ensure that the system software and hardware spare parts are available in a timely manner and are in good condition (so that they can be used promptly when needed and function properly). 5. Maintenance precautions: (1) Do not use organic solvents such as alcohol for cleaning. (2) During maintenance, avoid pulling or damaging the power supply, grounding, communication, and I/O signal lines. (3) Lock the doors of system cabinets, instrument cabinets, control panels, etc., to prevent unauthorized personnel from opening them. III. Guidance for daily inspections: Conduct regular checks on the DCS system to keep an up-to-date understanding of its operation: 1. Consult operators regarding the status of the DCS system and address any issues they encounter promptly. 2. View the DCS system fault diagnosis screen to check for any indications of hardware or software failures, communication issues, etc., and review the DCS fault diagnosis records. 3. Check the environment in the control room and cabinet room, as well as the operation of the air conditioning equipment. 4. Open the doors of the system cabinet, instrument cabinet, control panel, etc., to check whether there are any abnormalities in the system hardware indicator lights and communication indicator lights. 5. Check for signs of activity such as rats or pests. 6. Keep daily inspection and maintenance records. IV. Regular Inspection and Guidance 1. Regular inspection of the DCS: Once the DCS is operating properly, it should be inspected regularly to ensure that the entire system can continue to function properly over a long period of time. Regular inspections can be carried out using a dedicated “DCS Regular Inspection Record Form”, which serves as the main record for the maintenance and use of the DCS. The key aspects of these inspections include the following: 2. Inspection of the control room environment: (1) Check the lighting conditions, interference resistance, vibration levels, temperature and humidity levels, as well as the operation of air conditioning equipment. Special attention should be paid to checking whether there are any droplets of water or condensation on electronic devices such as those found inside the control cabinets. (2) Check for any corrosion of equipment caused by corrosive gases, as well as excessive dust accumulation. (3) Conduct regular inspections at least once a week, and keep records of these periodic inspections. 3. Regular inspections of the control station and operation station: (1) Check whether hardware such as computers, monitors, mice, and keyboards are in good condition ； (2) Check whether the real-time monitoring of the system is functioning properly, including data refresh and the proper operation of various functional interfaces ； (3) Check the fault diagnosis screen to see if there are any fault warnings ； (4) Inquire with operators about the operation of the DCS and the process production, so as to provide a basis for future optimization of control schemes ； (5) After the system has been running for a certain period of time, it is necessary to promptly back up or delete historical trend data, reports, and other operation history files ； (6) Open the system cabinet, instrument cabinet, control panel, etc. to check for any hardware failures in the system (indicated by a FAIL light) or other abnormal conditions ； (7) Check whether the power supply units in each cabinet are functioning properly, whether the power fans are operating, and whether the 5V and 24V indicator lights are working correctly ； (8) Check whether the system grounding (including the operation station, control station, etc.) and lightning protection grounding systems meet the standard requirements ； (9) Regularly remove accumulated dust to keep it clean and tidy. (10) The above inspection items shall be carried out at least once per week on a regular basis, and records of these regular inspections must be kept. (11) After the operation station has been in use for a certain period of time (usually three months), please use the disk defragmentation tool provided by the operating system to defrag the hard drive. 4. Regular DCS network inspection (1) Check whether the status of the network card indicator lights on each operation station is normal ； (2) Check whether the communication status lights of all main control cards, data forwarding cards, I/O cards, and other such cards are functioning properly ； (3) Check whether the communication status lights of the hub and switch are functioning properly ； (4) Check whether the connections of all communication connectors are reliable and normal ； (5) Check whether there is a warning of a communication fault in the “Fault Diagnosis” screen of the monitoring software, and whether there are records of communication faults in the “Diagnostic Information” ； (6) It is recommended that the DCS network be checked once a month. Regular inspections can be carried out using the “Fault Diagnosis” software. 　V. Maintenance Guidelines During Overhaul 1. During the overhaul, thorough maintenance of the DCS system should be carried out, which includes (1) system shutdown for maintenance, such as complete dust removal and rewiring. (2) Issues identified during routine and periodic inspections that cannot be addressed promptly are handled in a centralized manner, such as system upgrades and configuration downloads. (3) Before maintenance, the system should back up the DCS system configuration, as well as upload and back up the system operation parameters (such as PID values). (4) During maintenance, any changes to the configuration, control, and interlock procedures require the participation of relevant personnel from the process, equipment, electrical, and instrumentation departments in the interlock testing, and records of this testing must be kept. (5) During maintenance, it is necessary to check whether the power supply and grounding systems meet the requirements. (6) Keep proper maintenance records for the DCS during major repairs in a timely manner. 2. First step in system maintenance during major repairs: Check and verify that backups of the software, configuration files, as well as control and process data are accurate and complete. Step 2: Turn off the power in the following order: (1) After exiting the real-time monitoring and operating system from each control station, turn off the power to the industrial computer and monitor at that control station ； (2) Turn off the power supply of each control station’s power supply box one by one ； (3) Turn off the power switches for each branch circuit ； (4) Turn off the UPS switch ； (5) Turn off the main power switch. Step 3: Conduct DCS power-off maintenance (1) Power off the operation station and control station for purging and maintenance. This includes cleaning dust from inside the industrial computer, as well as components such as the control station chassis and power supply units. (2) Carry out maintenance and troubleshooting for faults identified during routine inspections and periodic inspections that cannot be resolved promptly. (3) Instrument and wiring maintenance: including power supply lines, I/O signal lines, communication lines, terminal blocks, relays, safety barriers, etc. Ensure that all instruments are functioning properly, the wiring is securely connected, and the markings are clear and correct. (4) Grounding system maintenance. This includes terminal inspection, grounding inspection of each operation station (industrial computer, monitor), grounding inspection of each control station (power supply, chassis), and ground resistance testing. Step 4: After all maintenance tasks at the site and on the DCS have been completed, check to confirm whether the following conditions for restarting power supply are met. (1) First, it is necessary to consult with specialists in process engineering, electrical systems, equipment, instrumentation, etc., to determine whether the conditions for powering on the DCS system are satisfied. (2) After confirming that the total power supply provided by the electrical system meets the requirements, close the main power circuit breaker and check the output voltages individually. (3) Close the circuit breakers for each branch inside the distribution box, and check the output voltage separately. (4) If a UPS or voltage stabilizer is installed, check whether the output voltage of the UPS or voltage stabilizer is normal. Step 5: System power-on and testing (1) Start the engineer station, server station, and operation station; simultaneously, power on each power supply unit of the system in sequence for inspection. (2) Check whether each power supply box is working properly, whether the power supply fans are operating, and whether the 5V and 24V indicator lights are functioning correctly. (3) Check whether the folders and files of the system software and application software on each computer are correct ； The remaining disk space has not changed significantly, and the disk surface test passed. (4) Compile and download the modified configuration. (5) Observe whether there are any faults from the fault diagnosis monitored in real time at each operation station. (6) Open the control station cabinet door and check whether the card is working properly, and whether there are any fault indications (the FAIL light is on). (7) For power supply redundancy testing, one of the redundant AC ~220VAC main supply circuits is activated; while the other AC power supply circuits lose power, the system should still be able to operate normally. Activate one redundant DC power supply separately and turn off the other DC power supplies, then measure the 5V and 24V voltages at the power terminal of the motherboard in each cage/rack. (8) Communication redundancy test: Connect one of each redundant communication line separately (with the other lines disconnected), and use the download configuration function to check whether everything is working properly; if everything is normal, it indicates that the communication network is functioning correctly. (9) Card redundancy test: By plugging and unplugging redundant cards while the system is powered on, check whether the redundancy function works properly. Note: If one of the redundant control cards or data forwarding cards is removed and reinserted, it is necessary to wait until the data copying is complete before removing the other redundant card; otherwise, serious consequences may occur during the production process. Step 6: Control and process parameter verification (1) Check each control and process parameter that has been successfully operated (due to configuration changes during download, some parameters may become inconsistent and need to be re-entered). (2) For control circuits whose on-site instruments (transmitters, control valves, etc.) have been replaced, as well as new control circuits (programs), their parameters need to be re-tuned and debugging must be carried out. VI. Fault Handling Guidelines 1. Communication Network Faults (1) Poor contact at the communication connectors can cause communication failures; once such a fault is detected, specialized tools can be used to reseat the connectors. (2) Since each communication unit has an address setting, during communication maintenance, it is necessary to verify whether the address settings of the network card, control card, and data forwarding card are correct. 2. In the event of a fault with on-site equipment, the operator should switch the automatic control circuit to manual mode; when repairing valves, a bypass valve should be used. 3. In the event of an I/O card failure in the system, (1) the corresponding control circuits, control programs, and interlocks must be switched to manual mode immediately, and system maintenance personnel should replace the faulty card right away. The system can only be switched back to automatic mode after it is confirmed that the fault has been resolved. (2) Before replacing the card, set switches or jumpers for address, power distribution, redundancy, etc., to the settings of the original card. (3) In the case of a failure in a non-redundant output card, the valves and equipment associated with that faulty card cannot be operated from the DCS side; it is necessary to inform the on-site operators to carry out the operations manually. DCS operations can be resumed only after the fault has been resolved. 4. In the event of an abnormal power interruption in the factory’s power supply system, it is necessary to handle the moving equipment, valves, and other instrumentation as required by the process requirements, and then shut down the DCS following the system shutdown procedures. 5. When a failure in the control system leads to its shutdown (a situation that occurs very rarely), it is necessary to have emergency plans prepared in advance. VII. Guidelines for Configuring Modifications and Downloading 1. Basic principles for configuring modifications Before modifying a configuration file, it is necessary to back up the current configuration file for emergency restoration purposes. Modifications to the configuration file must be made at the engineer station. 2. Configuration modifications during the production process: During production, it may be necessary to modify the DCS configuration for various reasons in order to achieve effective monitoring. During such modifications, it is important to clearly distinguish between different types of changes: (1) Changes that involve only adding or modifying the overall layout (or flowcharts, reports, trend pages, control groups, data listings, user permissions, secondary calculations, voice alarms, operation teams, custom keys), or modifying tag unit values (or tag annotations). After completing these operations, the changes are sent to each operation station. (2) If cards are added or removed, or if the tag numbers are changed or their ranges (or alarm information) are modified, a download is required. If modifications to the card components or tag numbers do not affect the control program, the downloading can be carried out while the process unit is in operation ； If control programs are involved, it is necessary to disable the relevant control programs (such as disabling interlocks or switching from automatic to manual mode) before proceeding with the download. (3) If the control program is modified, configuration downloading is required. All control programs related to this control program must be disabled (such as disabling interlocks and switching to manual mode) before the download can be carried out. (4) Adding or removing cages at a certain control station must be carried out when the process unit is shut down; it is strictly prohibited to perform configuration changes or downloads while the process unit is in operation. It is important to note that adding or deleting content within the existing card address or among the existing custom tag numbers can cause significant data inconsistencies when downloading online, and such actions should be avoided at all costs. 3. Precautions for downloading during the production process: (1) Online downloading should be carried out at times when production is stable, avoiding situations such as sequential control switches or precise measurement of cumulative amounts. Before downloading, ensure that important interlocks are disabled and that critical circuits are switched to manual operation temporarily. (2) When downloading, the control program and the control circuit must both be switched to manual mode ； Cutout interlock. (3) Before and after downloading the modified configuration file, the changes made should be verified to ensure their correctness. (4) After the configuration is downloaded, it must be transmitted promptly to ensure that the configurations on all operation station and engineer stations remain consistent. (5) Operation procedure for online download during the production process: Replace the configuration in the operation directory of the field engineer station with the newly modified configuration. Open the secondary calculation software and then exit it; after the configuration compilation is successful, start the real-time monitoring software. Compare the software interface data before and after the modification with those of the adjacent operator station, adjust the loop opening, PID parameters, and the forward/reverse action of the regulator; proceed to the next step only after confirming everything is correct. Contact the process operators to disable the interlocks of this system on the interface, to ensure that the interlocks do not activate accidentally, and switch the control loops to manual mode; important instruments and electrical equipment should be operated manually on-site. Download the configuration. After the download is complete, set initial values for the newly added modified schemes promptly. Contact the process operators to test the newly modified and added solutions. The process engineer verifies that the PID parameters, temperature, level, pressure, etc., shown on the flow chart are normal; once everything is confirmed to be correct, the engineer prepares to activate the interlock system in order to restore automatic control of the control loop, after which the on-site operators withdraw. Download completed, all parties confirm. 4. Changes and downloads in a non-production state (1) If there are many configuration changes that do not meet the requirements for online downloading, modifications can be made and downloaded during process shutdown. (2) After downloading, the program must be debugged immediately to check whether all programs, valve positions, and parameters are normal; operation can resume only after confirming that everything is in order. VIII. Precautions for system upgrade guidance: (1) The original configuration and parameters must be backed up before upgrading. (2) The production process must be stopped during the upgrade, and the relevant upgrade instructions must be followed strictly. (3) After the upgrade, it is necessary to check and confirm whether all control circuits and parameters are functioning properly. (4) The new version of the software and installation instructions must be copied to each upgraded computer in a timely manner ； Delete the existing software backups on the hard drives of each computer ； The old version of the installation disc must be destroyed or marked as invalid. IX. UPS Maintenance Guidelines: In most enterprises, UPS systems are managed by the electrical department, with DCS personnel playing a supporting role only.