Sanlian Pump Industry Group is a manufacturing enterprise based on water supply and drainage equipment. The group company integrates R&D, design, casting, production and sales, and provides customers with modern, digital and intelligent comprehensive solutions for fluid transportation and integrated systems.
Since its establishment in 1957, Sanlian Pump Industry has established more than 30 offices around the world with the continuous expansion of its business. With more than 500 technical personnel, it has long been committed to providing high-quality services to domestic and foreign customers.
Since its establishment in 1957, Sanlian Pump Industry has established more than 30 offices around the world with the continuous expansion of its business. With more than 500 technical personnel, it has long been committed to providing high-quality services to domestic and foreign customers.
Sanlian Pump Industry is a key enterprise in China's pump industry, a member of the China General Machinery Association, and a vice-chairman unit of the Pump Industry Association.
Mixed flow pumps occupy a key position between axial flow and radial flow pumps, integrating the advantages of both designs to achieve efficient medium-head and high-capacity performance. They are extensively used in irrigation projects, urban water supply, drainage systems, industrial circulation, and flood control stations. Their hybrid hydraulic characteristics make them suitable for transferring large quantities of water or other fluids with moderate delivery heads, filling the gap between low-head axial pumps and high-head centrifugal pumps.
A mixed flow pump operates based on both centrifugal force and axial thrust. When the impeller rotates, liquid enters the impeller eye along the pump axis. The curved blades then accelerate the liquid, imparting kinetic energy through centrifugal force that moves the liquid outward. Simultaneously, due to the impeller blade angle, the liquid also gains an axial velocity component, allowing it to move in a direction partly parallel to the pump shaft.
This combined motion produces a flow pattern where the velocity vector of the liquid has both radial and axial components. The discharge direction of the liquid from the impeller generally forms an angle between 20° and 60° relative to the pump axis. This unique geometry gives the mixed flow pump its characteristic balance—achieving higher discharge rates than radial pumps and higher pressure heads than axial pumps.
The energy conversion process continues as the fluid leaves the impeller and enters the casing or diffuser. In this region, kinetic energy is converted into pressure energy, raising the overall efficiency and pressure of the discharge flow.
The design of a mixed flow pump typically includes the following components, each contributing to performance and reliability:
Impeller:
The impeller is the core of the pump, designed with backward-curved or airfoil-shaped blades to optimize both radial and axial velocity components. Blade geometry is crucial in defining the flow pattern and hydraulic efficiency.
Casing:
Usually of volute or diffuser type, the casing converts kinetic energy into pressure energy and directs the liquid smoothly toward the discharge pipe. The shape of the casing strongly influences hydraulic losses and overall pump efficiency.
Guide Vanes or Diffusers:
These vanes are installed after the impeller to reduce swirl and straighten the flow, helping improve pressure recovery and minimize turbulence.
Shaft and Bearings:
The shaft transmits mechanical power from the motor to the impeller. It is supported by bearings that ensure alignment, reduce friction, and maintain stability under load.
Sealing Device:
Depending on the application, mechanical seals or gland packing are used to prevent leakage along the shaft.
Motor or Drive Unit:
Mixed flow pumps can be coupled to electric motors, diesel engines, or even turbines, depending on the operating environment and power availability.
The performance curve of a mixed flow pump demonstrates its intermediate nature. It provides a moderate head at a high discharge rate, bridging the gap between purely radial and purely axial pumps. The head–capacity (H-Q) curve generally exhibits a gentle slope, indicating stable operation over a wide range of flow conditions.
Efficiency peaks at a specific flow rate, and this optimal point is often broader compared to radial flow pumps. This means mixed flow pumps can operate efficiently even with fluctuating water levels or variable system demands, which is advantageous for irrigation and flood control applications.
Typical operating parameters:
Mixed flow pumps are available in both vertical and horizontal configurations:
Vertical Mixed Flow Pumps:
Widely used in deep-pit drainage, flood control stations, and cooling water systems. The motor is positioned above the pump, saving floor space and simplifying maintenance.
Horizontal Mixed Flow Pumps:
Commonly installed in irrigation channels or low-lift applications where space allows horizontal layout. They are easy to install and align with piping systems.
In addition, impeller mounting can be either open or semi-open, depending on the nature of the liquid handled. Open impellers are suited for slightly turbid water, while closed designs handle clean water with higher efficiency.
The selection of materials for mixed flow pumps depends on the fluid composition and environmental conditions:
Proper material selection not only extends the service life of the pump but also ensures consistent hydraulic performance under demanding operational conditions.
Mixed flow pumps are widely applied in various sectors thanks to their flexibility and efficiency:
Irrigation and Agricultural Water Transfer:
Used in large-scale irrigation projects to deliver water over long distances with consistent flow and moderate pressure.
Urban Water Supply and Drainage:
Serve as main pumps in municipal water systems to transport large volumes of water efficiently.
Flood Control and Drainage Stations:
Their high discharge capacity allows them to handle sudden surges of floodwater effectively, preventing waterlogging and protecting infrastructure.
Industrial Circulation and Cooling Systems:
Used in power plants, chemical facilities, and steel mills for circulating cooling water through condensers, heat exchangers, or cooling towers.
Marine and Offshore Operations:
Applied in ballast systems, cooling circuits, and general transfer duties in ships or offshore platforms.
Hydroelectric and Desalination Plants:
Utilized in low-lift water conveyance systems and pre-treatment stages of seawater desalination.
Mixed flow pumps combine the positive attributes of both centrifugal and axial flow designs:
Proper installation and alignment are critical for ensuring smooth operation. The pump shaft must be accurately aligned with the motor coupling to prevent vibration and bearing wear. Foundation strength must be sufficient to absorb operational forces.
Maintenance should focus on:
Lubrication systems should be maintained according to manufacturer recommendations, and replacement of worn parts should be performed promptly to avoid performance decline.
Although mixed flow pumps are robust and efficient, they can face issues such as:
Timely detection and corrective maintenance can prevent these issues from leading to costly downtime.
Mixed flow pumps represent a vital class of hydraulic machinery that merges the strengths of axial and centrifugal designs. They provide a highly efficient and adaptable solution for medium-head, high-capacity fluid transfer tasks across diverse sectors—from agriculture and municipal services to power generation and marine engineering. Their reliability, stable performance, and wide operating range make them indispensable wherever large volumes of liquid must be moved quickly and efficiently.
With proper design selection, careful installation, and consistent maintenance, mixed flow pumps deliver long service life and dependable performance, making them one of the most valuable types of fluid-handling equipment in modern engineering systems.
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