High Flow Vertical Axial Pump

The High Flow Vertical Axial Pump is designed for one specific purpose: moving massive volumes of water at low head with maximum efficiency. Unlike centrifugal pumps that accelerate water radially and convert velocity to pressure, axial flow pumps operate like a ship propeller. Water enters the pump axially and is discharged axially, with the impeller blades imparting a lifting action that moves water in a straight line through the pump. This design is ideal for applications requiring flow rates from 2,000 to 50,000 cubic meters per hour with heads from 2 to 15 meters. Typical applications include flood control pumping stations, large-scale irrigation, cooling water intake for power plants, and stormwater drainage.

The axial flow impeller (propeller) is the key component. The impeller consists of a hub with multiple blades (typically 3 to 6 blades) attached at an angle. As the impeller rotates, the blades push water axially, similar to how a fan moves air. The blade angle can be fixed or adjustable. Fixed blade impellers are economical and suitable for constant flow applications. Adjustable blade impellers allow the blade angle to be changed (manually or hydraulically) to adjust flow rate and efficiency without changing pump speed. For the highest efficiency across varying conditions, we offer variable pitch hydraulically adjustable impellers that can be adjusted while the pump is operating.

The pump configuration is vertical, with the motor mounted above grade and the impeller submerged in the water source. The vertical configuration saves floor space and allows direct suction from the water source without long intake piping. The pump column extends from the motor down to the impeller, with the discharge elbow at the top directing water horizontally into the discharge pipe. For deep installations, the column is supplied in sections with flanged connections. The pump is supported by a mounting plate at grade level, with no foundation required below grade.

The bowl assembly contains the impeller and diffuser vanes. The diffuser (also called guide vanes) straightens the flow exiting the impeller, recovering velocity pressure and increasing efficiency. The diffuser is located immediately downstream of the impeller. For multistage axial pumps (very low flow applications or higher heads), multiple impeller-diffuser stages are stacked vertically. The suction bell at the bottom of the pump is designed to provide smooth flow entry into the impeller with minimum losses and good anti-cavitation characteristics.

Materials are selected for fresh water or seawater service. For fresh water, cast iron or ductile iron construction is standard. The impeller is cast iron or bronze. For seawater, specify duplex stainless steel (2205 or 2507) or aluminum bronze for the impeller and wetted components. The shaft is stainless steel SS420 or SS630. The column pipe is carbon steel with epoxy coating for fresh water, or stainless steel for seawater. Wear rings are replaceable and available in bronze or stainless steel.

The bearing system is specially designed for vertical axial pumps. The main thrust bearing is located in the motor or in a separate bearing housing above grade. The thrust bearing carries the weight of the rotating element plus the hydraulic thrust. For long shafts (over 5 meters), intermediate line shaft bearings are installed at intervals along the column pipe. These bearings are water-lubricated (using the pumped water) or oil-lubricated with an external supply. Water-lubricated rubber bearings are common for fresh water and are maintenance-free for many years.

The drive motor is a vertical hollow-shaft induction motor with thrust bearing capacity. For large pumps (over 500 kW), high-voltage motors (3.3kV, 6.6kV, or 10kV) are used. For variable flow applications, we offer VFDs with inverter-duty motors. However, axial pumps are typically constant speed because the flow-head characteristic is steep (small head change creates large flow change), making VFD control challenging. For adjustable flow, specify variable pitch impellers rather than VFDs.

Installation requires careful attention to the intake structure. The pump must be adequately submerged to prevent vortex formation. The approach flow must be uniform and without swirl. A bellmouth intake or intake bell is recommended. A trash rack is essential to prevent debris from entering the pump and damaging the impeller. The discharge piping should be designed with a gradual expansion and adequate support.

In summary, the High Flow Vertical Axial Pump delivers the highest flow rates at low head with unmatched efficiency for large-scale water moving applications.