**Abstract:** This paper discusses the characteristics and application scope of Francis pumps, with a focus on the SEZ vertical mixed-flow pump used in the Slender West Lake Water Pumping Station in Yangzhou. The structural design and key performance features of this pump are analyzed in detail. The application of the SEZ pump in water diversion pumping stations is also explored. Keywords: pumping station, mixed-flow pump, structure, application. **Introduction** Mixed-flow pumps are widely used in various fields such as agricultural irrigation and drainage, flood control, sewage treatment, and cooling systems in power plants (including coal-fired, nuclear, storage, and tidal power stations). These pumps typically have a specific speed ranging from 300 to 500, with diameters between 100 mm and 6,000 mm, head capacities from 3 m to 60 m, and flow rates ranging from 200 m³/h to over 2,000 m³/h. Their rotational speeds range from 100 to 1,450 rpm. Compared to centrifugal and axial flow pumps, mixed-flow pumps offer advantages such as a simpler structure, smaller size, lighter weight, lower installation area, stable performance, and minimal power variation when head changes. This makes them ideal for large-scale water transfer projects, including the South-to-North Water Diversion Project. Therefore, developing large mixed-flow pumps with good anti-cavitation performance and stable operation is of great importance. **1. Characteristics of the SEZ Vertical Mixed-Flow Pump** **1.1 Main Forms of Vertical Mixed-Flow Pumps** Vertical mixed-flow pumps are designed with the impeller submerged underwater, eliminating the need for priming. The motor is installed above water, ensuring good ventilation and preventing flooding—something horizontal pumps cannot achieve. These pumps are known for high efficiency, excellent cavitation resistance, compact size, and ease of maintenance. Depending on their structure, they can be classified into two types: guide vane and volute. Within the guide vane type, there are subtypes like K-type (rotor can pump) and B-type (rotor cannot pump). Based on installation method, they may be single-base or double-base. Some models feature fixed or adjustable blades, offering flexibility in different applications. Common models include LKX, LBS, LBX, TKK, and LT, each tailored for specific operational needs. **1.2 Key Features of the SEZ Vertical Mixed-Flow Pump** The SEZ vertical mixed-flow pump is a modern design that offers high lift, high flow rate, high efficiency, and wide adaptability. Its core-pulling structure allows for easy maintenance without disassembling the outer casing. The pump’s motor and impeller are integrated, reducing vibration and improving operational stability. A unique ceramic guide bearing system ensures long-lasting performance even under poor lubrication conditions. Additionally, an automatic air vent device helps maintain smooth operation by removing trapped air from the pipeline. These features make the SEZ pump highly suitable for demanding applications like the Slender West Lake Water Diversion Project. **2. Application in the Slender West Lake Water Diversion Pumping Station** **2.1 Basic Conditions of the Pumping Station** The Slender West Lake Water Diversion Pumping Station, located near the Yangzhou Power Plant and brick factory, uses four SEZ700-595/500 vertical guide vane mixed-flow pumps driven by 200 kW motors. The system has a total flow rate of 4 m³/s and delivers water through a 5.6 km pipeline with a diameter of 1.6 m. The project aims to supply water to the lake and enhance its ecological environment. **2.2 Replacement of Submersible Centrifugal Pumps** Initially, the design called for submersible centrifugal pumps, but after analysis, it was found that these had higher costs, lower efficiency, and poor water conditions for the motor. The SEZ vertical mixed-flow pump was chosen instead due to its superior efficiency, better cavitation performance, and easier maintenance. It also allows for better ventilation and accessibility, making it more suitable for long-term use and aesthetic integration into the surrounding landscape. **2.3 Installation and Disassembly Procedures** The installation process involves assembling the pump cylinder in stages, followed by the installation of the core components. The disassembly follows the reverse order, ensuring that all parts are properly removed and maintained. The core-pulling design simplifies repairs and reduces downtime. **2.4 Performance Testing** Tests were conducted on the pump units under various operating conditions. The results showed smooth operation, low vibration, and acceptable noise levels, meeting the design requirements. All units performed well, confirming the reliability of the SEZ pump in real-world applications. **3. Conclusion** The SEZ vertical mixed-flow pump combines the advantages of both centrifugal and axial flow pumps while addressing their limitations. With its high efficiency, stable power output, and user-friendly maintenance, it is a promising choice for large-scale water transfer and pumping projects. Its application in the Slender West Lake project demonstrates its practical value and potential for broader use in future infrastructure developments. **References** 1. He Xijie, Xu Xihimin. *Research and Development Trends of Mixed-Flow Pumps in Pumping Stations*. 2001. 2. Liu Complex. *New Small Pumping Station Design and Renovation Technology*. 3. Zhou Shihai. *Application Value of Shallow Vertical Mixed-Flow Pumps in Pumping Stations*. 1995. **Author:** Jiang Chengqi, male. Master of Engineering in Fluid Mechanics and Engineering, School of Water Resources and Architectural Engineering, Yangzhou University.

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