HW Type Mixed-flow Drainage Pump

The full name of the HW type mixed-flow drainage pump is the horizontal single-stage single-suction volute type mixed-flow pump. It is a classic energy-saving pump type jointly designed by the domestic water conservancy industry, strictly following the standards of GB/T 13008 and JB/T 6667. It is the most common large-flow and medium-low head main pump type in scenarios such as farmland drainage and irrigation, river water diversion, and emergency flood drainage. Its core positioning is very clear: the flow and head are between centrifugal pumps and axial flow pumps. Compared with centrifugal pumps of the same diameter, its flow is much greater; compared with axial flow pumps, it has a stronger adaptability to water level changes and operates more stably. Therefore, it is specially designed for working conditions that require large-area low-head and large-flow water transportation.

Summary of the main features of the HW type mixed-flow pump:
1. Pump body structure: Low hydraulic loss, easy to install
The pump body adopts a single-sided opening volute casting, with a wide and smooth flow channel, resulting in low hydraulic loss.
The inlet and outlet diameters are the same, usually coaxial or arranged at 90°, facilitating pipeline connection and space layout.
2. Impeller design: Strong flow-through capacity, suitable for complex water quality
The mixed-flow twisted blades, typically 3 to 6 in number; the structure can be semi-open or closed according to the diameter size.
The flow channel is wide, with strong circulation capacity, and is significantly more tolerant of river water containing a small amount of silt, aquatic plants, and debris compared to ordinary clear water centrifugal pumps. It is less likely to get stuck or stop at the drainage site.
3. Maintenance convenience: Adjustable clearance, no need to disassemble the rotor
The pump adopts a cantilever single-suction structure, with the impeller mounted on the extended end of the pump shaft, and the pump cover and pump body can be separated.
Adjusting the clearance between the pump cover and the front face of the impeller (standard value 0.3 - 0.7 mm) is a key operation for restoring volumetric efficiency - too small a clearance will cause friction, while too large a clearance will increase internal reflux and reduce efficiency.
The gap can be precisely adjusted by adding or removing the thickness of the paper gasket between the pump cover and the pump body, without the need to disassemble the entire rotor components.

1. Origin of Name and Flow Direction
The name of the mixed-flow pump is derived from the direction of the liquid flow inside: unlike the centrifugal pump which discharges the liquid radially, or the axial-flow pump which pushes the liquid axially, the liquid flows out along the conical surface at an inclined angle.
2. Dual Forces and Energy Conversion
When the impeller rotates, the liquid is subjected to two forces simultaneously - the centrifugal force which causes it to be discharged outward, and the axial thrust which propels it forward along the pump shaft. After these two forces are superimposed, the water flows out at an oblique angle from the impeller into the volute, and in the expansion section of the volute, its kinetic energy is gradually converted into pressure energy, and finally discharged from the outlet.
3. Characteristics of Performance Curve
This mixed-flow flow mode gives the HW type mixed-flow pump a unique performance: the specific speed is usually between 300 and 500, and the efficiency curve is very gentle, with a wide efficiency zone. Even if the flow fluctuates significantly, the efficiency will not drop significantly; the power curve is also flat, and it is less likely to experience overload.
4. Advantages Compared to Other Pump Types
In contrast, the efficient zone of the centrifugal pump is narrower, and once it deviates from the design condition, the efficiency will drop rapidly; the axial-flow pump, although it has a large flow rate, has a narrower efficient zone and is extremely sensitive to water level changes. The HW type mixed-flow pump precisely fills the gap between these two types and becomes the most adaptable choice in irrigation and drainage applications.

In the fields of flood prevention, drainage and emergency rescue, the HW type mixed-flow pump is the preferred equipment for pumping out accumulated water in low-lying villages and farmlands. It is also widely used for emergency drainage during river overflows, strong drainage of urban flooding, and drainage operations in flood control areas. In the field of agricultural water conservancy and irrigation, it undertakes important tasks such as water diversion for large areas of farmland, water lifting from reservoirs and rivers, water distribution and transmission in irrigation areas, and water replenishment for drought prevention. In the aquaculture industry, it is used for large-scale water exchange in fish ponds and shrimp ponds, oxygenation circulation, and sediment removal and drainage. In municipal water supply and drainage projects, it can be used as a lifting pump in rainwater pumping stations, a drainage pump for main drainage channels, and even in the coarse water extraction stage of sewage treatment plants.

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