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Abstract: Taking the anode petroleum coke transfer system in a carbon plant of an aluminum company as an example, this paper introduces the application of the American A-B SLC505 programmable logic controller (PLC) and the upper-level monitoring software RSview. An economical, reliable, and easy-to-maintain control system scheme is proposed, detailing the structure of the control system and the implementation of its control functions. Keywords: PLC ； Online switching ； Host computer ； Automatic stop protection ； Pulse Vibrating Treatment Abstract: This article discusses the application of the A-B SLC505 Programmable Logic Controller and RSview software in the petrol-coke transfer system of a carbon plant belonging to an aluminum company. It describes the structure of this control system as well as its successful use; it has proven to be economical, reliable, and easy to maintain. Keywords: PLC ； Online switch ； Host computer ； Auto-stop protection ； Pulse beaten 0 Introduction With the development of automation technology in industrial enterprises, PLCs (Programmable Logic Controllers), thanks to their reliability, flexibility, excellent performance-to-price ratio, and ease of use, have seen rapid growth in the field of industrial control and are now being used more and more widely. Petcoke is the main raw material for producing carbon anodes used in aluminum electrolysis. The petroleum coke transfer system is used to process the petroleum coke stored in warehouses by crushing and screening it into raw material suitable for calcination, and then transport it to the pre-calcination silo. Due to the system’s numerous logical control points, high degree of automation, and strong interconnections between upstream and downstream devices, a PLC is used for automatic control, while a host computer is employed for monitoring the entire system. This paper focuses on the implementation of the control functions of PLC in the system and the development of the upper-level computer monitoring interface. 1 Process Introduction The petroleum coke transfer station system mainly consists of a crane material handling system, a crushing and screening system, a lifting system, a material distribution and conveying system, and a dust collection system. It is used to meet the material supply requirements for the daily use silos in the calcination kiln system before calcination. It mainly consists of equipment such as material handling cranes, speed-regulating belts, crushers, sifters, conveyor belts, bucket elevators, and material distribution baffles. Among them, the crushing and screening system and the lifting system are two separate systems; the crushing and screening system can operate in a backup mode or simultaneously ； The upgrade system ensures that one device serves as a backup to another. The simplified process flow diagram is shown in Figure 1 below. Figure 1: Simplified process flow diagram of the petroleum coke transfer station. 2 Control system design and implementation 2.1 Features of SLC500 The SLC500 modular programmable controller and its input/output modules are produced by Rockwell Automation, with product catalog numbers in the 1746 and 1747 series. This series of products features a frame-based structure, providing a similarly stable and reliable platform for use in various industrial settings. The SLC500 system consists of a processor, input/output modules, and related external devices. The processor is powerful and flexible to use, offering various built-in communication methods as well as memory capacities for users to choose from according to their needs. Based on the actual needs of the user, the input and output modules can be extended very conveniently. At the same time, Rockwell Automation offers convenient built-in communication interfaces, a wide range of third-party specialized modules, and user-friendly programming software based on the Windows platform. Thus, the SLC500 has become one of the most popular small and medium-sized PLCs on the market today. 2.2 Hardware Configuration Based on the aforementioned features of SLC, this system uses the SLC505 PLC from Rockwell Automation in the United States. The required input/output configuration for the system is: 100 digital input points ； 50 digital output points ； Analog input, 5 points ； Analog output, 2 points ； After giving due consideration to margins, the actual hardware configuration is as follows: ⑴ The CPU selected is 1747-L551 ； ⑵ 8 digital input channels, for a total of 16×8=128 points ； 4 digital output channels, totaling 16×4=64 points ； 1 analog input, totaling 8×1=8 points ； 1 analog output, totaling 4×1=4 points ； ⑶ Two racks, with 10 slots and 7 slots respectively ； ⑷ 1 switch ⑸ 1 upper-level monitoring operator station ⑹ 1 engineer station. 2.3 System network topology: The upper-level computer establishes a connection with the PLC using RSLINX software, and communication can take place via either RS232 or Ethernet. In this control system, the upper-level computer monitoring operator station communicates with the PLC via Ethernet using a switch; an engineer debugging interface is provided, while the switch also has ports reserved for data exchange and communication with other systems. The network topology is shown in Figure 2 below. The monitoring software RSview-SE is installed on the main monitoring computer, and a process flow interface is developed; via Ethernet, the status values of the devices are retrieved and displayed on this interface ； On the other hand, the operation commands issued by the operator are sent to the PLC, which then uses its outputs to drive the corresponding devices to take action in response. Network topology diagram > Figure 2: Network topology diagram of the petroleum coke transfer station system. 2.4 Control system design: The automatic control system for petroleum coke transfer is implemented through PLC programs; in combination with the upper-level monitoring operator station, it enables monitoring, control, operation, and adjustment of various equipment and process parameters on-site from the control room. In programming, taking into account the relationship between upstream and downstream devices, relevant interlocking protections are implemented; upstream devices cannot be started if the downstream devices are not operating ； The 4–20mA signal, which represents the magnitude of the motor current, is acquired by the analog input module and sent to the PLC for display on the monitoring interface. The control signal for adjusting the belt speed is written from the monitoring software to the PLC, where it is then converted into a standard 4–20mA analog signal to control the belt speed. In this system, there are several key issues that require attention and that affect the smooth operation of the entire system: 2.4.1 Implementing online switching control for system equipment. As required by the process design, the two screening systems, the two material distribution baffles, and the two bucket elevators must be capable of being switched over online. In other words, if one of these devices fails, operators can immediately bring in another device to take over the operation without interrupting the flow of materials, while the faulty device can be taken out of service for repair. The designed program takes into account the fact that when the system is switched, the processes upstream and downstream of it continue to operate; the devices that enter the system and those about to leave it operate simultaneously for a certain period of time. The specific parameters need to be set according to actual conditions. This ensures that the materials in the equipment exiting the process are completely removed, preventing blockages in the equipment entering the process. 2.4.2 Automatic stop protection: For safety reasons, pull-cord switches are installed on both sides of the conveyor belt. Material blockage alarm switches are installed at the inlet and outlet of the bucket elevator. When designing the program, the following protections were implemented. If someone accidentally falls on the belt or violates the rules by crossing (stepping over or passing through) a running belt and touches the pull-cord switch, the system will stop immediately and issue audible and visual alarms to alert the operator to go and check and handle the situation. After the processing is complete, press the reset button to clear the fault before the system can be restarted. Once there is a blockage at the inlet or outlet of the bucket elevator, the blockage switch activates, the system stops immediately, and audio-visual alarms are issued to alert the operators to go and inspect and address the issue. After the processing is complete, press the reset button to clear the fault before the system can be restarted. When designing the PLC program, the high-level alarm signals from the two bins used before calcination are connected to the PLC program; if the level in these bins exceeds the set high limit and the operator is not aware of this, the program will automatically shut down the system as a protective measure. 2.4.3 Pulse rapping control of dust collectors: There are three dust collectors in the petroleum coke transfer system. To extend the service life of the pulse valves, a PLC program for the pulse rapping control of the dust collection bags in these dust collectors was developed, based on the technical parameters provided by the manufacturer. According to the data provided by the manufacturer, timers and counters are used in the designed PLC program to precisely control the pulse jetting time and interval for the dust collection bags in the dust collector, ensuring that the pulse valves operate in a fixed sequence. 3 Design of the Upper-Level Monitoring System 3.1 Features of RSview Supervisory Edition (RSview-SE) As part of Rockwell Software’s family of HMI software products, RSview-SE supports the core functions of HMI such as safety, display, alarms, operation and alarm logging, trends, etc. It provides enterprises with an integrated monitoring solution and is one of the most popular upper-level monitoring software solutions on the market today. It is widely used in industries such as metallurgy, chemicals, petroleum, food processing, building materials, and water treatment, and is highly favored by users. It has the following main features: network-based distributed monitoring, a shared development environment – RSview Studio, enhanced Rockwell Automation preferred connection solutions, direct I/O data association, transparent data integration, VBA support for screen objects, redundant backup for data communication, and integrated Windows security. 3.2 Monitoring System Design: It is precisely because of the aforementioned advantages of RSview-SE that this design adopts it as the upper-level monitoring software to facilitate operator oversight of the petroleum coke transfer system. RSVIEW-SE offers powerful project configuration capabilities; project designers can use existing graphic libraries to create their own graphic objects. Its modular design approach **improves the efficiency of project development**. The upper-level monitoring system includes the system process flow diagram display and the PC console display. On the console interface, all operation buttons have been designed to prevent accidental actions, with related buttons placed together ； For the sake of ease of operation, some devices are equipped with single-action buttons. On the process flow diagram interface, in order to vividly reflect the operating status of on-site equipment, a combination of dynamic and static elements is used, different colors are assigned to represent various states, and a combination of 2D and 3D elements is employed to create the host computer display. The operator can monitor and control the operational status of the equipment and the key process parameters throughout the entire process in real time, and can easily switch between different screens. The status of the equipment is displayed on the screen; before the system starts, pressing the test light button will cause a red light to flash on those devices that do not meet the startup conditions. This allows maintenance personnel to go directly to the relevant devices for inspection and repair, thereby saving time in fault detection and improving efficiency. 4 Conclusion Since its design, testing were completed and it came online in August 2004, this system has operated stably, with reliable performance, ease of use, and a high degree of automation. It has reduced the need for dedicated staff and improved the efficiency of the enterprise ； Moreover, the system has certain security protection capabilities and has received positive feedback from users. At the same time, this system exhibits significant advantages in terms of ease of on-site maintenance, equipment adjustment, and program modification; therefore, it has great potential for widespread application.