Abstract : This article describes in detail the design idea and control scheme from both software and hardware aspects in the computer upgrade project of a 35T/H boiler. Key Words : boiler R150 control upgrade Based on the principles of convenience, economy, and efficiency improvement, the technicians selected the R150 series products from Honeywell Corporation of the United States to upgrade the control system of the 35T/H boiler. 1 System Composition The Honeywell R150 control system is a product launched by Honeywell Corporation of the United States in the early 1990s. It is a medium-to-small-scale control system between large distributed control systems, single-loop controllers, and programmable controllers. The 35T/H boiler R150 computer control system consists of a monitoring and management station, an Ethernet communication network, and a controller, as shown in Figure 1. 1.1 Upper-level monitoring station The monitoring station uses an Advantech industrial PC from Taiwan, configured with a P4 1.8GB CPU, 80GB hard drive, 128MB RAM, 64MB video memory, 50X CD-ROM, and a 19” TRT. It has an Ethernet communication card (3C509B) with an ISA slot. 1.2 Controller The control system uses a 9000e controller. The 9000e controller can perform loop control, logic control, and data acquisition, and also has communication capabilities. The controller has two parallel microprocessors—a loop processor and a logic processor—to handle analog and digital signals respectively. Its basic functions integrate the functions of multiple single-loop controllers and programmable controllers, enabling fast and accurate control response. The logic processor model is 9010-012, which provides logic functions such as contacts, locks, sequence generators, timers, and counters. Various functions can be easily integrated using configuration software tools. The loop processor model is 620-0073, which easily implements cascade control schemes using the continuous control diagram configuration tool. 1.3 Module 621-0020RC: General analog inputs (T/C, mV, V, mA), 16 points; 621-0025R: RTD inputs, 8 points; 621-0010AR: Analog outputs, 4-20mA, 4 points; 621-65500R: Digital outputs, 24VDC source output, 16 points; 621-0083C: Controller power supply, 155/230VAC, 15A. 1.4 MASnet Communication: The monitoring station and controller communicate via MASnet, type IEEE 802.3 Ethernet, using the TCP/IP communication protocol. The communication medium is thin coaxial cable with a 75Ω terminating resistor. 2 2.1 System Functions and Working Principles : Parameters such as boiler water level, water flow, water pressure, water temperature, steam flow, steam temperature, steam pressure, furnace temperature, furnace pressure, oxygen content, and valve position are converted into 4-20mA current signals by corresponding sensors or transmitters and sent to the corresponding input modules for data acquisition. When the detected parameters exceed the process allowable range, the program outputs a switch signal and issues an audible and visual alarm. 2.2 Boiler Desuperheating Water Regulation: This mainly controls the desuperheating water temperature within the process allowable range. This regulation implements single-loop PID control. 2.3 The control of the steam drum water level directly affects the quality of steam and the safe operation of the boiler. Therefore, a three-impulse regulation is adopted for the water level. The water level is the main control signal, and the steam flow and feedwater flow are auxiliary control signals. The water level regulator controls the valve position to maintain a constant water level based on the given and measured signals. The output control signal after calculation by the distributed control system is output from the I/O template, and controls the pneumatic feedwater valve through the operator and electrical converter to achieve regulation control. The control system selects the optimal parameters for adjustment according to the set control law. The steam drum water level control of large boilers often adopts a dual PID cascade control scheme. The control principle is shown in Figure 3. 3 Software Installation First, install the DOS 6.22 and Windows 3.1 operating systems on the monitoring station host, then install Chinese Star 2.5 or other Chinese character systems under Windows environment. If reports are required, Excel software should also be installed. Finally, install R150 configuration monitoring software. After all software is installed, turn off the power of the monitoring station, plug the KEY (commonly known as the watchdog) into the parallel port of the host, and then start the monitoring station. 4 System Configuration 4.1 The system provides convenient and intuitive graphical configuration software, enabling rapid construction of the control scheme required by the user. The configuration software adopts a standard windowed, graphical user interface under the Windows 3.1 environment, operated via mouse click-and-drop menus. System configuration mainly includes two parts: control configuration and monitoring configuration. In control configuration, continuous control charts are used for PID regulation, data acquisition, and continuous calculation configuration. Monitoring configuration includes establishing a real-time database, drawing process flow diagrams, setting alarm display and printing, setting historical trend display and printing, and setting report printing, etc. 4.2 Configuration Steps 4.2.1 Develop a scheme based on the characteristics of the process or object itself and user requirements. 4.2.2 Plan and set the types and addresses of each input/output template and controller. 4.2.3 Implement the continuous control scheme using continuous control charts. 4.2.4 Set the predefined format screen of the monitoring station to produce a standardized monitoring interface. 4.2.5 Complete the configuration of the monitoring interface, including user flow diagrams, alarms, historical trends, and reports. 4.2.6 Connect and debug each monitoring interface. 4.2.7 On-site installation, tuning and debugging, trial operation, and operation. 4.3 Continuous Control Diagram The continuous control diagram provides more than 50 functions, including loop regulation, ladder logic, mathematical operations, common calculations, alarm signals, and auxiliary functions. Each module completes a certain control and calculation function. Input and output pins are used for signal interconnection and reference. At the same time, it provides operator points and signal points for analog and digital quantities for monitoring. According to the control scheme, select the required modules, set the internal parameters, number them according to a reasonable execution order, and connect the signal pins. The configuration steps of the continuous control diagram are as follows: ⑴ Enter the configuration environment and select the access level. ⑵ Create a new configuration. ⑶ Establish the continuous control diagram and realize the soft-wire connection of the software functions. ⑷ Configure the parameters of each software function block. ⑸ Set the label name and add annotations to the continuous control diagram. The continuous control diagram of the three-impulse regulation of boiler water level is shown in Figure 4. 5 Monitoring Configuration 5.1 After the user completes the design of the continuous control diagram and downloads the configuration software to the controller, the names of loop points, signal points, operator points, alarm points, equipment points, etc. in the continuous control diagram are stored in the user's real-time database. 5.2 Process flow diagram Using the drawing tools and rich graphics library provided by the software, various intuitive and dynamic process flow diagrams can be drawn, and the screen switching relationship can be defined through macro commands. 5.3 Alarm system Provides standard format alarm display screens, which can be quickly searched according to start time, alarm type, alarm point name, alarm area and alarm priority, and alarm confirmation and printing can be performed. 5.4 Historical trend Can define, collect, display and print historical trend screens. Each historical trend can display 8 data curves at the same time, and historical trend data can be saved to hard disk files at regular intervals. The historical trend configuration steps are as follows: (1) Historical allocation: establish a collection group (2) Historical collection (3) Historical display ① Define trend group ② Define pen group ③ Define time group 6 Online debugging After the control configuration and monitoring configuration are completed, online debugging is performed. The steps are as follows: 6.1 6.1 Enter the controller configuration window and obtain the configuration access level. 6.2 Configure a new controller, generating the controller name, controller IP address, and controller type. 6.3 Select the 35T boiler project configuration and download it to the controller. 6.4 Switch the logic controller to the RUN/PRGM position and download the LPM code. 6.5 Set the configuration node. 6.6 Switch the logic controller to the PRGM position, then configure the logic controller's operating characteristics and the I/O points of each slot on the main controller rack. 6.7 Set the controller clock. 6.8 Set the default controller configuration. 6.9 Set the UAIM/RTD power supply frequency to 50Hz. 7 Monitoring Station Screens The 35T/H boiler monitoring station has six main screens, allowing operators to easily monitor, adjust, and query the boiler. 7.1 Boiler Process Flow Diagram This screen depicts the entire boiler production process from feedwater to the steam drum, from gas pipelines to the furnace, and clearly indicates the corresponding monitoring parameters at the appropriate locations on the process flow diagram. 7.2 Real-time Trends: This screen displays real-time trends for eight main process parameters, facilitating observation of the stability and changes of important parameters. 7.3 Data Reports: This screen displays all dynamic monitoring parameters of the 35T/H boiler in chart form, including the cumulative flow of fluids such as feedwater flow. The cumulative flow is automatically cleared when it reaches a set value, and maintenance personnel can also reset it at any time to eliminate inaccurate values ​​caused by adjustments or maintenance of on-site equipment. 7.4 Alarm Screen: The system allows for easy setting of alarm limits for any parameter, including high alarm, high-high alarm, low alarm, and low-low alarm. When an alarm occurs, an audible sound is emitted, and the alarm parameter displayed on the screen flashes, with its background changing color. 7.5 Adjustment Screen: This screen displays the boiler water level adjustment process in bar graph form. Maintenance personnel can easily modify PID parameters and switch between manual and automatic modes according to operating conditions. 7.6 Historical Trends: All field simulations and cumulative values ​​are saved every 2 minutes, continuously storing 999 days of data for easy recall, analysis, and retrieval of production accidents. 8 Conclusion After a week of on-site commissioning, the boiler's computer control system was successfully put into operation on the first attempt, and the system is running well. Its commissioning has a significant effect on reducing maintenance costs, minimizing automated equipment failures, and reducing maintenance workload.