Abstract : This paper mainly introduces how to address various equipment failures that occur in the production process of the precision rolling hydraulic AGC system. The process involves multiple approaches to overcome potential equipment hazards and improve system stability, including network structure reorganization, optimized control panel design, cable selection and protection in complex environments, displacement sensor installation methods, and wiring methods for various detection components. Keywords : AGC; Optimization; Benefits; 1. Introduction Since 2007, competition in the domestic steel market has intensified, and customers have raised their demands for product quality. Product requirements have shifted from extensive, rapid production to refined, stable production. This new situation places higher demands on the stability and control accuracy of the AGC system. The long-term stable operation of the medium plate hydraulic AGC system has become crucial for our plant to improve product yield, ensure product quality, reduce quality disputes, and win the "Green Brand Year" product quality battle. To meet the requirements of the production process and ensure the stable operation of the AGC system, we organized technical personnel to identify, analyze, demonstrate, and implement solutions to problems such as frequent "gray screen" phenomena, unreasonable control panel layout, poor cable anti-interference, short lifespan of control cables, displacement sensor signal fluctuations, and long line replacement times. Through technical breakthroughs, we ultimately improved the operating rate of our plant's AGC system, achieving excellent application results and generating significant economic benefits. 2. Problem Identification The original AGC system used the SIMADYN D digital control system from SIEMENS, Germany. In recent years, during the operation of the AGC system, issues with the installation methods of on-site detection components, wiring, and communication have affected the normal operation of the system to some extent, causing equipment accidents such as frame scraping and plate shape instability, directly impacting steel plate quality and yield. Based on the above requirements and reasons, we decided to restructure and comprehensively optimize the network of the hydraulic AGC system in the medium plate mill's finishing rolling mill. 3. 3.1 Analysis of Causes Related to Network Structure: The original host computer frequently experienced "gray screen" phenomena. The project initially used fiber optic communication, with the network architecture consisting of pigtails, photoelectric converters, fiber optic splice boxes, Category 5 twisted-pair shielded cables, switches, and computers. This connection method resulted in numerous intermediate links in the communication network, while the actual communication distance was long and subject to significant interference. Consequently, the stability of the system network depended heavily on the performance of the components. Therefore, the unreasonable network structure was the main cause of the "gray screen" phenomenon. 3.2 Analysis of Causes Related to Component Layout Optimization: The original AGC operating table contained a total of 63 electrical control components, including indicator lights, buttons, turn switches, and ammeters. The layout was unreasonable, leading to cumbersome operator actions, fatigue, decreased concentration, and increased production operation failures. Therefore, the large number of components on the operating table, the unreasonable layout, and operator fatigue are among the hidden dangers that increase equipment failures. 3.3 Analysis of the causes of on-site wiring problems: Because the original control wiring used ordinary control cables, and the on-site rolling mill operating environment involves a large amount of oil, water vapor, and high temperatures, the wiring itself often suffers from high-temperature aging, poor shielding leading to signal interference, and short replacement cycles. This poses a threat to the long-term stability of the system. Therefore, the wiring itself is one of the key aspects to improve system stability. 3.4 Analysis of the causes of problems with the installation method of displacement sensors: In the finishing mill hydraulic AGC system, the original displacement sensors were installed on both sides of each cylinder, placed inside the water jacket. In this mode, due to external factors such as cylinder vibration, water vapor environment, and cylinder rotation, the plugs are prone to loosening, falling off, and the plug solder wires falling off, causing major equipment accidents such as frame scraping. Therefore, the installation mode and location of the displacement sensors are another factor to further improve system stability. 3.5 Optimization of the wiring method for detection components: The original wiring method for detection components involved directly connecting the plug to the wiring from the rolling mill to the control room. Once a wiring problem occurred, it often required short-circuiting the wiring, leaving new potential hazards, or replacing approximately 200 mm of the entire wiring. Therefore, the wiring connection method between the system and the detection components is also a factor in further improving system stability. 3.6 Protection Optimization: The original control lines at the top of the rolling mill were placed inside the pressing power line cable tray, which was time-consuming and laborious to replace, and there was no separate cable tray. The section from the top to the displacement sensor, which is about 2 meters long, was protected by ordinary flexible conduit, which shortened the life of the line. Therefore, the protection of the control line itself is also an area that needs further optimization. 3.7 Summary of problems to be solved: 4. Solution and feasibility analysis 4.1 Optimize network structure: At present, network technology is becoming increasingly mature in the field of industrial control, and the application of Ethernet technology is becoming more and more widespread. Therefore, using Ethernet technology to directly complete the fiber optic communication task is technically feasible and can eliminate the frequent "gray screen" phenomenon. 4.2 Optimize the operating table: In order to simplify the design of the operating table, the functions of components with low operating frequency can be fully implemented by the WINCC host computer, which can significantly reduce the components on the operating table, optimize the component layout, and make the operation more user-friendly. 4.3 Line Optimization: The current line uses ordinary control cables, which have weak anti-interference capabilities. Selecting double-shielded twisted-pair high-temperature resistant cables with good shielding performance ensures excellent anti-interference capabilities and high-temperature resistance. This completely eliminates signal fluctuations caused by poor line anti-interference, thus preventing equipment malfunctions. 4.4 Displacement Sensor Optimization: Currently, there are four displacement sensors, each housed in a water jacket and installed on either side of two hydraulic cylinders. Placing them in the center of the cylinders avoids the use of water jackets, preventing exposure to harsh environments such as moisture, and reducing external factors that could cause displacement sensor signal failure. 4.5 Wiring Optimization for Detection Components: The original wiring method involved direct connection from the control cabinet to the rolling mill detection components. This required replacing the entire wiring in case of a problem. Adding a distribution box near the machine significantly reduces the length and difficulty of wiring replacement, saving considerable time and preventing signal ineffectiveness and lengthy troubleshooting times caused by loose plugs, water ingress, grounding issues, or time-consuming wiring replacement. 4.6 Line Protection Optimization: The original lines were only protected by flexible conduits after reaching the rolling mill, resulting in a short lifespan and poor oil resistance. This could be completely eliminated by routing the entire line within steel pipes, minimizing exposed wiring. This would prevent short circuits, open circuits, grounding issues, and frequent replacements caused by inadequate line protection. The relocation optimization involves separating the upper rolling mill cable tray from the lower rolling power cable tray, and using heat insulation panels for radiation protection. This allows for quick and convenient replacement of wiring in case of problems. Currently, the wiring from the cable tray to the detection elements is mostly protected by flexible conduits. The optimization will be to install standard dual-path conduits from the cable tray to all detection elements for thorough line protection, minimizing exposed wiring. 5. Implementation of the scheme and its problem solving 5.1 Optimization of network structure: Change from the current fiber optic communication method to Ethernet communication method; (1) Initial system network structure diagram: (2) Optimization scheme and network structure after implementation From this network structure diagram, it can be seen that: before optimization, there are many links between the SIMADYN-D system and the host computer of the operating platform. After optimization, the intermediate links are greatly reduced. Due to the limitation of Ethernet communication distance, only a switch is added to the top of the factory building to ensure the stable operation of the network architecture. 5.2 Optimization of component layout: Combined with the relocation of the operating platform, the operating platform is redesigned, and the infrequently operated components are changed to be operated by the host computer of the operating platform. The hot rolling workshop widely solicited opinions from the operators to form a suggestion to minimize the layout of components and the optimal position for component operation. The operating platform was redesigned based on the above opinions and suggestions. 5.2.1 The original operating platform design is as follows: As can be seen from the above analysis, there are a total of 63 components on the original operating platform. The operation is inconvenient for operators, the layout is unreasonable, and the fatigue intensity is high. Therefore, the key factors for optimizing the console layout are: ● Reducing the number of components is one factor; ● Rearranging components rationally is another factor; 5.2.2 The optimized console structure is shown in the figure. Only three frequently used components, 8, 10, and 11, are AGC components in the new console, which is more suitable for operators, improves work efficiency, and reduces labor intensity. 5.3. Optimization of control cable selection in complex environments. The shielding method of the control cable, its high temperature resistance, and whether the line is twisted are several factors that reduce line failures. All control lines have been changed from ordinary control cables to twisted shielded flame-retardant cables to ensure long-term stable operation of the signal, improve the anti-interference and high temperature resistance of the line, extend the life of the line, and minimize grounding and short circuits caused by high temperature, wear, corrosion, etc. 5.4. Optimization of displacement sensor installation method. The installation method of the displacement sensor is the key to solving the unstable fluctuation of the roll gap signal. When cooperating with the branch factory to complete the customization of cylinder body spare parts, the implementation of the displacement sensor center installation position scheme was completed. When customizing spare parts using the new cylinder block, coordinate with the manufacturer to install the displacement sensor in the center of the cylinder block. Optimize the installation method by installing the displacement sensor inside the cylinder block, changing the original installation mode of 4 displacement sensors and 4 sets of mechanical water jackets to using only 2 displacement sensors. This reduces the number of displacement sensors by 2 and the number of water jackets by 4. This change in installation structure fundamentally alters the operating environment of the displacement sensor, reduces equipment failure points, and improves the stability of the displacement sensor. 5.5. Optimize the wiring method of detection components. The wiring connection method of detection components is a key factor in solving long-term equipment failures caused by wiring replacement. Therefore, a new 8AT control circuit terminal box was installed at the north wall of the main span of the rolling mill. All control cables are connected to the terminal blocks from the control cabinet. This greatly reduces maintenance time due to wiring replacement. 5.6. Optimize control circuit protection. Adequate protection of the control circuit is crucial for the long-term stable use of control cables. At the start of the overhaul, the construction team was organized to carry out the following work: (1) Remove all control cables of the original testing components; (2) Remove some old cable trays of the original control cables; (3) Pull back all old cables and clean up the long-term accumulated multi-way cables on the top of the rolling mill; (4) Lay a new 200 cable tray and protect it with fireproof board; (5) Weld 40mm steel pipes on the north and south sides of the rolling mill, from the cable tray outlet to the side of the testing components; (6) Replace new twisted pair shielded high temperature resistant cables from the distribution box to the displacement sensor; 6. Analysis of the actual application effect of the project 6.1 Comparison of the impact time of equipment after communication mode reorganization Before and after network structure optimization, the impact time of electrical equipment caused by network communication problems in 2006-2007 is as follows: From the comparison chart of the statistical data of the scheduling log, it can be seen that after changing the network structure to realize the Ethernet communication mode, the communication problems such as "gray screen and crash" were completely solved, and long-term stable operation was achieved with significant effect. 6.2 The AGC system was implemented through a series of measures, including redesigning the control panel, changing the wiring, altering the installation method of displacement sensors, adjusting the connection mode of detection components, and implementing wiring protection. A comparison of the AGC equipment's impact time before and after the modification is shown below. 7. Conclusion The AGC system at the medium plate mill was gradually optimized through the phased implementation of the control panel and control cabinet relocation projects. The entire production organization has gradually transitioned from experiencing major equipment and operational accidents every month to a stage of long-term safe and stable operation. For several consecutive months, the equipment achieved a record of "zero impact" time. This laid a solid equipment foundation for further improvement in the product quality of the medium plate mill. The successful application of this project significantly reduced the number of rolled plates, reduced spare parts consumption, reduced product quality disputes, and alleviated the labor intensity of operators. It ensured the stability of our factory's product quality, improved product yield, enhanced product competitiveness during the "Green Brand Year," and improved product reputation. It can generate 1.56 million yuan in direct economic benefits and good social benefits for the head office annually. About the Author Chen Jinbiao, male, 29 years old, native of Sichuan, engineer. Graduated from the Department of Mechanical and Electrical Engineering, Xinjiang Petroleum Institute in July 2002 with a Bachelor of Engineering degree. Currently mainly engaged in on-site technical maintenance and new technology application of electrical automation control systems. Tel: 0531-88866237; Postcode: 250101; E-mail: [email protected] or [email protected]