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Axial Flow Pumps

Axial flow pumps are a type of centrifugal pump. They use impellers with vanes to direct flow in the same direction as the shaft - axially -- rather than radially, which is 90 degrees from the shaft. Axial flow pumps tend to create less pressure than radial flow pumps, but they can produce much higher flow rates. Sometimes referred to as propeller pumps, the axial flow impeller looks similar to a boat propeller.

Axial flow pumps are used in applications that require very high flow rates and very low amounts of pressure (head). Some common examples include circulating water pumps or within flood dewatering applications where large quantities of water need to be transported a short distance. Because these applications are less common than radial flow pump applications, there are fewer axial pumps in the market.

 

The axial flow pump usually consists of an impeller with three or four vanes driven by an electric motor. These vanes are oriented in such a way that the pumped fluid exits axially rather than radially, producing very low head. Axial flow pumps can generate 10 to 20 feet of head, lower than most other types of centrifugal pumps. In addition, they are capable of producing flow rates as high as 200,000 gpm.

Axial flow pumps can handle some of the highest flow rates of any type of centrifugal pump. These pumps have performance characteristics that differ drastically from other pump types. Although they produce very low heads at their normal operating point, the curve of head to capacity ratio is much steeper than that of other centrifugal pump types. The shut-off head can be up to three times the head at the pump's maximum efficiency point. The horsepower required increases as flow is decreased with the highest horsepower draw being at shut off. This is opposite of radial flow pumps, which have require an increasing horsepower at higher flow rates.

Contributed by PumpScout.com staff.