Abstract: For a dense-phase conveying system in electrolytic aluminum, a PLC control system, a host computer monitoring system, and a reporting system were developed using Siemens' STEP7 programming software, WinCC industrial configuration software, and EXCEL's embedded VBA as development platforms. This paper introduces the hardware and software design and implementation methods of the control system. Operational results show that the system has stable performance and fully meets production needs. Keywords: S7-400; WinCC; Configuration Software; EXCEL VBA; Dense Phase Transportation Abstract: For the Dense Phase Transportation system of electrolytic aluminum, Siemens STEP7, WinCC, and EXCEL VBA are adopted to develop the PLC control system, the PC monitoring system, and the reporting system respectively. The design and implementation methods of the system software and hardware are introduced in this paper. The running results show that the system is very stable and can fully meet the needs of production. Keywords: S7-400; WinCC; Configuration Software; EXCEL VBA; Dense Phase Transportation 1 Introduction The dense phase transportation system of electrolytic aluminum plant is the electrolytic feeding system and a very important link in the production of electrolytic aluminum plant. Its operation status directly affects the quantity and quality of electrolytic aluminum production. Therefore, we have completed the design and implementation of a PLC control system based on STEP7, a dense phase transportation monitoring system based on WinCC, and a reporting system based on EXCEL VBA. Siemens' HMI/SCADA software system, WinCC, provides monitoring, control, and data acquisition functions in a Microsoft Windows 32-bit environment, and features interfaces such as ODBC, OLE, OPC, and DDE. Its key features are: advanced technology, simple operation, safety and reliability, a user-friendly Chinese graphical interface, and easy expansion. 2. System Design The dense phase conveying monitoring system consists of a main control room and two field I/O stations in the east and west zones. All input and output signals from the field stations enter the input/output modules and analog acquisition modules in the field I/O stations. The analog acquisition modules are used to collect the material discharge data from the batching scale. An S7-400 PLC is used in the main control room, utilizing the SIMATIC communication interface module IM463-2 to achieve data exchange between the S7-400 and the two I/O field stations. The CPU selected is the SIMATIC S7 CPU414-2. Due to the harsh industrial environment, an industrial PC with an LCD display is used as the host computer. The host computer has a communication card installed and communicates with the S7-400 PLC via PROFIBUS bus. The print server is connected to the host computer via Ethernet. The industrial computer connects to the local Ethernet network via a network card, enabling real-time database sharing of the monitoring system. A server key is installed on the industrial computer, and WinCC configuration software (Runtime 128 key only) is installed on any computer on the local area network to form a multi-user system. Users can access the monitoring system screen and perform various operations, facilitating remote real-time monitoring by administrators. The industrial computer acts as both a WinCC server and a field operator station. The print server connects to the WinCC server via a hub to display and print material quantity reports. Its hardware structure is shown in Figure 1. Using Windows 2000 as the operating system, WinCC industrial control configuration software as the development platform, and ANSI-C scripts provided by WinCC as auxiliary development tools, a dense phase conveying host computer monitoring system was developed. The reporting system was developed using the VBA programming language embedded in Excel, and the S7-400 PLC control program was developed using Siemens' new-generation programming software STEP7. Since both are Siemens products, a seamless and highly reliable communication connection can be achieved between WinCC and the S7-400 PLC lower-level machine, maximizing the real-time monitoring and network expansion needs of the dense phase conveying system. 3. Development of the Dense Phase Conveying PLC Control Program Siemens STEP7 was used as the programming tool. To meet the monitoring needs of the upper-level WinCC monitoring system and the statistical requirements of the reporting system, a corresponding real-time dynamic database file was designed during the development of the dense phase conveying PLC control program. This file provides the upper-level monitoring system with the relevant data required for monitoring and control, and also provides the reporting system with the raw data. The PLC control system is responsible for the process control of the dense phase conveying in the east and west zones and the control of related equipment. 4. Development of the Upper-Level Monitoring System 4.1 Functions of the Upper-Level Monitoring System The main screen of the upper-level monitoring system is shown in Figure 2. The monitoring system displays the following screens: pressure vessel overview monitoring screen; section monitoring screen; forced monitoring screen; alarm browsing screen; pressure vessel monitoring screen; batching screen; raw material overview display screen; skipping screen; user login window; historical record screen, etc., providing dynamic monitoring and operation. The bottom of each screen features two rows of 16 command buttons for switching screens and performing various operations. Screen switching is also possible by clicking on the corresponding devices on the screen, making transitions between screens convenient and quick. The PV overview monitoring screen is divided into two sections: 1/2 (East Zone) and 3/4 (West Zone). Each screen includes at least 8 silos and their levels, 7 pressure vessels, 4 tank areas, 6 zone valves, 3 bypass valves, all gate valves, and the operating status of 7 dense phase pipelines. Through equipment colors, animations, and Chinese prompts, the system monitors the operating status of the PV and various valves, providing information on various operating conditions and alarms, such as preparation, shutdown, feeding, conveying, venting, full, empty, high-high level, high level, and low level. • **Section Monitoring Screen:** This screen monitors and controls the feeding status of eight electrolytic cells on-site. Using pop-up windows, it allows for operations such as raw material selection, cell skipping, canceling skipping, fault reset, and forced feeding for each electrolytic cell. Each screen should indicate the cell section number, the pressure vessel number currently feeding it, the pressure vessel's operating status, the dense phase pipe pressure status, the current feeding path, the status of each air-hold valve, and the status of each electrolytic cell. Confirmation prompts for skipping and canceling skipping operations are included in the software to prevent process accidents such as aluminum fluoride overflow and empty tanks caused by operator errors. • **Pressure Vessel Monitoring Screen:** This screen includes sub-screens displaying the operating status of 14 pressure vessels. Each screen displays the pressure vessel's equipment number, material level, auxiliary material level, the pressure vessel's current status, the destination address of the delivered material, the dense phase pipe path selection, the material level in the destination silo, the operating status of all valves, as well as the pipe pressure and tank pressure, the corresponding stationary vessel's operation status, the auxiliary material batching plan, and the actual operating status. It can monitor the values ​​of the electronic scale for a 2 cubic meter pressure vessel in real time. • Raw material batching screen: Enables human-machine interaction; based on the electrolysis batching sheet, users can input 4 days' worth of aluminum fluoride and 1 day's worth of electrolyte for each cell using the keyboard. • Raw material overview display screen: This screen displays the raw material selection results for each electrolytic cell in east and west sections, using color differentiation for easy identification. • Cell skipping overview display screen: This screen displays skipped electrolytic cells in east and west sections, facilitating operator understanding of the overall skipping situation. • Alarm browsing screen: Displays and prints all alarms in the system, indicating the alarm time and name. This screen provides over two thousand different prompts in real time, displaying various alarm information by color. • Forced feeding screen: Displays the forced feeding queue for 8 cell areas; allows input of the forced feeding cell number. This function enables manual feeding. • Feeding start time screen: Displays and allows input of the start time for two feeding operations in the 8 cell areas. • User Login Window: This is a pop-up window that allows users with different permissions to log in. • Report Screen: Daily, weekly, and monthly reports on material feeding are required to statistically analyze the actual addition amounts of fresh alumina, fluorinated alumina, aluminum fluoride, and electrolyte for each tank, tank area, plant, and workshop, as well as the planned addition amounts of aluminum fluoride and electrolyte. 4.2 Monitoring System Design and Implementation • Establishing System Tags (Variables): In the WinCC configuration environment, a communication connection is first created, and its communication protocol is selected. Then, under this communication connection, for the east and west zones, a total of 8 sections and 126 electrolytic cells, more than 4000 tags are established inside and outside the system. • Drawing Process Configuration Screens: Using the powerful drawing and animation functions of WinCC in the WinCC graphical editor, and based on a thorough understanding of the process flow, monitoring requirements, and PLC database file structure of the dense phase conveying system, all monitoring screens and other system operation screens that can reflect the real-time status of the site are designed and completed. Connecting the defined tags to the screen devices is a key technology for realizing animated monitoring. The design fully considers the simplicity and user-friendliness of the operating interface, while also taking into account the user's operating habits. * **Database Setup:** Configure the historical record database in the log editor, including variables such as PV number, slot number, exhaust time, material feeding time, conveying time, date, and time. Configure the trigger conditions, display colors, and descriptions for various alarms in the alarm editor, totaling over 2000 records. The alarm controls in the graphical editor allow for the display and confirmation of real-time and historical data. Historical records are set as short-term logs, with a maximum of 1000 records per record, refreshed using a first-in-first-out (FIFO) method. This database serves as the source for various data reports and statistics. The established dynamic real-time database enables Intranet data sharing, avoiding redundant investment. * **Management Permissions:** Set operation permissions in the administrator editor. The system has three permission levels: Super Administrator, Administrator, and Operator. Super Administrators can perform any operation, including system management. Administrators, designated for workshop managers, can perform screen monitoring, key parameter settings, and system exit, but are not allowed on-site control operations such as switching jobs or forcing access. Operators can only perform on-site control and screen monitoring. In the WinCC project properties, block all hotkeys to ensure unauthorized user exits. • The WinCC function extension global script editor enables the editing and compilation of various C functions. This editor allows for the implementation of many system functions that WinCC configuration alone cannot achieve. For example, it can convert data display formats and provide sound and animation prompts for alarms. For instance, the circular icon in the lower right corner of the main monitoring screen flashes whenever an alarm occurs, alerting the operator to handle it promptly. This function utilizes a C function that ORs various alarm conditions, using the result as the trigger condition for the icon's flashing animation. 4.3 Actual Implementation of the Reporting System: Daily, weekly, and monthly reports are required to statistically analyze the actual addition amounts of fresh alumina, fluorinated alumina, aluminum fluoride, and electrolyte for each tank, tank area, plant, and workshop, as well as the planned addition amounts of aluminum fluoride and electrolyte. Daily reports are required to be retained for one month, and weekly and monthly reports for one year, accessible at any time within the retention period. Compared to other configuration software, WinCC has stronger reporting capabilities, but its limited report format still cannot fully meet user requirements. To ensure uninterrupted WinCC monitoring, a report printing server was designed to independently handle report browsing and printing. The report printing system shares a database with WinCC and is implemented using VBA scripts embedded in Excel. Based on the daily report database generated in WinCC, daily, weekly, and monthly reports can be updated, displayed, viewed, and printed for 126 electrolytic cells across 8 zones. The reporting system receives and updates data via Ethernet at fixed times each day, and performs data statistics and generates reports based on user-input query conditions. 5. Conclusion Several years of production practice have shown that the PLC control system, the host computer monitoring system, and the reporting system have achieved satisfactory results in terms of operability, maintainability, expandability, and reliability, fully meeting production needs. Adding an independent operator station only requires an additional host computer, an interface card, and a WinCC runtime version. The innovations of this paper are: 1. The work presented in this paper achieves the localization of the PLC control and host computer monitoring system for the concentrated phase transport of electrolytic aluminum, saving a significant amount of money. 2. A multi-user system based on the WinCC server/client architecture was adopted to realize remote monitoring of the system. 3. A reporting system was realized by using the VBA script language embedded in EXCEL to share a real-time database with WinCC. References: [1] Siemens (China) Co., Ltd. In-depth and easy-to-understand Siemens WinCC V6 user manual [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2004 [2] Siemens Corporation. Programming with STEP 7. June 2001 [3] Mulinsen Studio. Introduction and Techniques of Visual Basic 6.0 [M]. Tsinghua University Press. 1999. [4] Siemens Corporation. Statement List (STL) for S7-300/400. June 2001 [5] Siemens Corporation. Configuring Hardware and Communication Connections. March 2000 [6] Yan Minxiu, He Kan. Application of WinCC in the Metallurgical Industry [J]. Microcomputer Information, 2006, 5-1: 10-12