Centrifugal pumps, based on their orientation, are categorized into three groups of radial, axial, and mixed. Mixed-flow pumps are a type of centrifugal pumps that, while having a higher efficiency and greater application, are less recognized compared to other centrifugal pumps. This is because these pumps have the properties of both radial and axial pumps.
Mixed-flow pump is a special type of water pumps that have both They have both residential and industrial applications. Although, these pumps are mainly used in industrial applications. The reason for naming this type of centrifugal pumps “mixed-flow pumps” is due to their mixed-flow impeller. We will continue to provide more in-depth introduction to mixed-flow pumps.
What is a mixed-flow pump?
Mixed-flow pump operate both radial andaxial pumping. These pumps operate using rotary impeller and creating suction. Mixed-flow pumps are commonly available in two types of low-speed and high-speed. The Revolutions Per Minute of a low-speed pump is arounf 35 to 80 RPM and for a high-speed pump is 80 to 160 RPM.
The electromotor utilized in these pumps is asynchronous and squirrel-cage and it works using alternating current. However, in some special cases and depending on the number of stages and the size of the motor, horizontal and inclined installation is also feasible.
Low-speed mixed-flow pumps utilize impeller with Spiral or helical casing, while, high-speed pumps use impellers with diffusers and volute casing. Spiral impeller mixed-flow pump is used when both flow rate and head are inadequate and need to be increased.
Their caractristic make them able to operate when using radial and axial pumps is not possible. The design of these pumps prevents solid materials to enter the pump. This is done bythe motor suction chamber and suction strainer.
Mixed-flow pumps may differ based on pump impeller type, which can be close, open, or half-closed, or based on blade type, blade spacing, and blade quality. This difference leads to variation in efficiency, flow rate, head, or quenching.
How does a mixed-flow pump operate?
Mixed-flow pump is able to distinguish itself from other pumps since it holds the caractaristic of both radial and axial pumps. The design of mixed-flow pumps includes an diagonal propeller that uses centrifugal force to direct water out of the pump.
At first, impeller rotates using electrical devices. This will enable the impeller to push the water from one side and rotate it from other side to create the centrifugal action. This will generate water flow and pressure inside the pump.
Using the generated force and created flow, water enters the impeller axially and exits obliquely along the impeller blades.
The flow velocity of water in a mixed-flow pump varies between 0.1 to 50 meters per second. The efficiency og these pumps also varies between 64 to 86 percent.
Vertical and horizontal mixed-flow pump
Most mixed-flow pumps are vertical and are available in one or multiple stages. However, there are also horizontal mixed-flow pumps that are less recognized compared to the vertical pumps. This pump is installed horizontally and have charactrisitcis similar to vertical pumps.
These pumps have high flow rate, average head, high efficiency, and numerous applications. A specific type of these pumps, known as Volute Mixed-Flow pumps, features a short axial size, high operational power, and high reliability.
Advantages and disadvantages of mixed-flow pumps.
The dual-performance of mixed-flow pump holds numerous advantages. The followings outline some these advantages of these pumps:
- High flow rate
- Ability to pump clear and clean or dirty liquid
- Combination of higher flow rate with higher pressure for optimum performance
- Dual-performance: axial and radial
A disadvatage of mixed-flow pumps is their low starting power.
Application of mixed-flow pump
Since these pumps are able to pump turbid water or fluids containing solid materials, they are used in sewage pumping or industrial applications involving suspended solid materials. Furthermore, these pumps are also used for water intake or seawater pumping applications.
Pumping pulp in paper manufacturing factories is also another application of these pumps. The followings are the other applications of these pumps:
- Providing drinking water for residential buildings
- Providing water for industrial processes
- Discharging water from mines
- Pumping water from deep and semi-deep wells
- Pumping water from river, dams, and lakes
Last word
Mixed-flow pumps, among all centrifugal pumps, are often overlooked and less recognized. However, these pumps have a unique structure that distinguishes them from other types of centrifugal pumps. These pumps are available in two forms vertical and horizontal. The horizontal type has one stage and the vertical type has either one or multiple stages.
Since these pumps are designed such that the presence of suspended solid particles in water doesn’t interfere with their operation, they are suitable for industrial environments.