Abstract : The system consists of a pressure sensor, a pressure controller, a programmable logic controller (PLC), a water pump, buttons, etc. The PLC programmably starts and stops the pumps in a specific sequence to maintain a relatively stable system pressure. Keywords: PLC, water pump, pressure, automatic control 1 Introduction With the development of science and technology, major companies around the world have successively produced many different types of programmable logic controllers (PLCs), providing great convenience for automatic control in various fields of life and industrial production. Among them, Siemens PLC... Programmable logic controllers (PLCs) are relatively easy to use. They can be easily programmed without the need for other tools to achieve various programmable controls such as logic control and timing control. This system uses a pressure sensor as the detection element and a pressure controller (CD901) as the intermediate link for pressure comparison and control, forming a control system together with a Siemens PLC (LOGO!). 2. Application Background Due to fluctuating water usage in our company's Power Zone II, water demand varies greatly, sometimes high and sometimes low. The water supply pressure constantly changes with water consumption, causing significant fluctuations in pipeline pressure. When water consumption is low, even with only one pump running, the pipeline pressure can still reach 0.35 MPa, leading to pressure buildup and energy waste. When water consumption is high, two or even three pumps must be running to meet process requirements. This requires personnel to frequently monitor the pipeline pressure and manually start and stop pumps as needed. This not only results in large pressure fluctuations and delayed adjustments but also wastes energy and may cause insufficient water supply, affecting production. When a fire breaks out in the factory area, the water demand suddenly increases, and higher pressure is required to meet firefighting needs. Often, after a fire breaks out, the person who discovered the fire notifies the power operator, who then goes to the pump room to start the pumps to increase the pressure. Due to the multiple steps involved, the pressure cannot be increased in time, resulting in insufficient water supply, which affects firefighting efforts and may delay the response, leading to a more unfavorable situation with potentially irreparable consequences. [b]3 System Control Mode 3.1 Manual Mode:[/b] In this mode, the programmable control system stops working, and each water pump motor (primary water pump and fire pump) is started and stopped by its respective button. This mode is suitable for use during system failures or maintenance. 3.2 Automatic Operation: This is the normal operating mode. Each water pump motor (primary water pump and fire pump) is automatically started and stopped based on the set pipeline pressure and programmed conditions via pressure detection, pressure controller, and programmable controller. This automatically increases or decreases the number of operating pumps, achieving a relatively stable water supply pipeline pressure. In the event of a fire anywhere in the factory area, the fire pumps can be activated immediately via fire buttons installed in each workshop, eliminating the need to notify the power department personnel to go to the pump room to activate additional pumps. This not only ensures stable water supply during normal production but also allows for immediate activation of fire pumps in case of fire, achieving the goal of simultaneously ensuring production and fire prevention. 4. Control Function Implementation During normal production, three water pumps operate in parallel to achieve constant pressure water supply. In case of fire, the other two fire pumps can be immediately activated via fire control buttons located in each workshop, ensuring that both production and fire prevention are not disrupted. The system uses a LOGO! programmable controller for coordination. Field pressure signals are sampled by a pressure transmitter and sent to the pressure controller for comparison with the set value. The comparison generates a pressure signal that is sent to the frequency converter for pressure regulation. If the frequency converter cannot meet the pressure regulation requirements, the pressure controller generates high/low alarm signals, instructing the LOGO! programmable controller to start or stop the corresponding water pumps to ensure pressure stability. 5. Connection Methods: The connection methods for each part of the system are shown below to help you understand the entire system. The connection methods are shown in the following diagram: [align=center] Figure 1[/align] 6. Schematic Diagram [align=center] Figure 2[/align] 7. Control and Programming 7.1 Insufficient Pressure Boosting: [align=center] Figure 3[/align] 7.2 High Pressure Shutdown: Similar to 7.1, but in reverse order, it is not shown here again. 7.3 Fire Control Priority : Whenever there is a fire signal, the system executes the emergency pressurization function and does not perform any additional pressure adjustments. 8. As shown in Figure 1, the control programming is explained as follows: 8.1 The program is set to start or stop the machines in a specific sequence. After the #1 inverter is turned on to its maximum, if the pressure is lower than the set value, the pressure controller outputs a low alarm to the programmable controller. The programmable controller then starts the machines in the pre-set sequence (here, #2 starts first, then #3). After starting, the pipeline is pressurized, and the pressure is regulated by the #1 inverter. The pressure monitor sends feedback to the pressure controller, which compares the pressure with the set value. If the pressure is within the set value range, the system maintains its current state; if the pressure is still lower than the set lower limit, the programmable controller will start another water pump motor according to the program. The system is pressure regulated by inverter #1. Normal production requires a maximum of two and a half to three inverters. If, due to a decrease in water consumption, the system pipeline pressure exceeds the set upper limit, the programmable controller will shut down the pumps in a pre-programmed sequence (here, first shut down pump #3, then pump #2), reducing the pressure in the pipeline. Inverter #1 will then regulate the pressure, and the pressure monitor will provide feedback to the pressure controller. If the pressure is within the set range, the system remains unchanged. If the pressure still exceeds the set upper limit, the programmable controller will shut down another pump motor as programmed, again regulated by inverter #1. This cycle repeats to maintain relatively stable system pressure. 8.2 If the programmable controller receives a fire command, it will directly start the fire pumps, without adjusting according to the original pressure setting, maintaining a high-pressure, high-volume water supply until another fire shutdown command is received, after which it will re-enter the normal pressure regulation program. 9. Implementation: The programmable controller we use is simple to program and easy to use, so implementation is not difficult. By setting appropriate pressure control points and upper and lower limits based on the water usage during most production periods, and then setting start-up and shutdown intervals according to water usage variations, the system can achieve start-up and shutdown control according to a certain logical relationship, and prioritize fire alarm signals. This allows for basically constant pressure water supply during normal production and rapid pressure boosting during fires, ensuring water pressure and volume in special circumstances. The main construction challenge is the fire control system in each workshop, which involves long wiring and numerous control points. To ensure normal production, fire alarm buttons are specially managed and generally not allowed to be activated. 10. Implementation Results: Since the completion of this project, the system has been operating well. Due to the automatic start-up, shutdown, and pressure stabilization control, production has been maximized. Furthermore, it has reduced the labor intensity of operators, minimized human error delays, and saved energy, receiving high praise from the user and management. 11. Conclusion The programmer used in this system is a relatively convenient type, but its disadvantage is that it cannot perform network control. We have also explored the application of other types of programmable controllers, larger system and computer network control technologies, and applied them to other fields.