What are the three types of centrifugal pumps?

Struggling to choose the right centrifugal pump?

The wrong choice can lead to inefficiency and high energy costs.

Understanding the three main types is key to making the best decision.

The three primary types of centrifugal pumps are classified by their flow direction: radial flow, axial flow, and mixed flow. Each design is engineered for specific combinations of pressure (head) and flow rate, making them suitable for distinct applications in various industries.

Choosing the right pump type is more than just a technical detail.

It directly impacts the efficiency, longevity, and operational cost of your entire water system.

Knowing the difference between these designs will empower you to select the most effective solution for any project, ensuring optimal performance and maximum energy savings.

Let's explore each type in detail to help you match the right pump to the right job.

What is a Radial Flow Pump?

Need to generate high pressure for a low-flow application?

Using the wrong pump type wastes energy and fails to deliver the required head.

Radial flow pumps are your specialized solution for high-pressure systems.

A radial flow pump discharges fluid at a 90-degree angle to the pump shaft. This design powerfully converts velocity into high pressure, making it the standard choice for applications requiring significant head, such as multi-story building water supply and industrial boiler feeds.

A radial flow pump is arguably the most common type of centrifugal pump you'll encounter.

Its name comes from the path the fluid takes through the impeller.

When fluid enters the pump, it flows into the center, or "eye," of the impeller.

As the impeller spins, its vanes catch the fluid and accelerate it outwards.

This acceleration happens in a radial direction, meaning it moves away from the central shaft.

This outward force is the essence of its operation.

The fluid then exits the impeller at a 90-degree angle to the shaft.

This sharp turn is crucial for building pressure.

The volute, which is the spiral-shaped casing surrounding the impeller, is specially designed to manage this high-velocity discharge.

It slows the fluid down, and according to Bernoulli's principle, this decrease in velocity results in a significant increase in pressure.

This process makes the radial flow design incredibly effective at generating high head.

Key Characteristics of Radial Flow Pumps

The performance of a radial flow pump is defined by a few key features.

Understanding these helps clarify where it fits best.

Its design prioritizes pressure over volume.

This is why they are often found in applications where water needs to be pushed up great heights or through restrictive piping systems.

The impeller is a critical component influencing these characteristics.

In a radial pump, the impeller is typically narrow with vanes curved to maximize the outward centrifugal force.

This focus on force is what builds the high pressure.

Common Applications for Radial Pumps

Due to their ability to build high pressure, radial flow pumps are indispensable in many sectors.

Their applications range from simple domestic use to complex industrial processes.

For distributors like you, these are the pumps your clients will often need for demanding pressure-boosting tasks.

Any system with high resistance or a significant vertical lift will likely require a radial flow pump.

• High-Rise Buildings: Providing constant water pressure to upper floors.
• Boiler Feed Water: Pumping water into high-pressure boilers.
• Pipeline Boosting: Maintaining pressure over long distances in pipelines.
• Industrial Cleaning: Powering high-pressure washing and cleaning systems.
• Reverse Osmosis: Creating the high pressure needed for water purification.

At RAFSUN, many of our VSD booster pumps, especially our multistage models, utilize radial flow principles.

The integration of a Variable Speed Drive (VSD) allows for precise control over the motor speed.

This means the high pressure can be intelligently managed to maintain a constant output, saving up to 50% in energy consumption compared to fixed-speed pumps.

This combination of high-pressure capability and smart control is what modern water systems demand.

What is an Axial Flow Pump?

Facing a project that requires moving a huge volume of water at low pressure?

A high-pressure pump would be inefficient and costly for this task.

Axial flow pumps are designed specifically for high-volume, low-head applications.

An axial flow pump moves fluid parallel to the pump shaft, similar to a boat's propeller. This design is highly efficient for transferring large volumes of water at very low pressure, making it perfect for applications like drainage, irrigation, and water circulation systems.

An axial flow pump functions very differently from a radial flow pump.

Think of it less like a centrifuge and more like a propeller in a pipe.

The fluid enters the pump and is pushed directly forward by the impeller's rotating blades.

The impeller vanes are shaped like airfoils, creating lift as they spin.

This "lift" propels the fluid straight through the pump, parallel to the shaft.

There is no change in the radial direction of the flow.

The fluid exits the pump in the same axial direction it entered.

Because the pump is not using centrifugal force to build pressure, its ability to generate head is very limited.

Instead, its entire design is optimized for moving the maximum amount of fluid with minimal resistance.

The casing of an axial flow pump is typically a simple pipe or tube.

It includes stationary diffuser vanes located after the impeller.

These vanes are crucial for efficiency.

They straighten the swirling flow created by the propeller-like impeller, converting the rotational energy into a smooth, linear flow and recovering some pressure.

This efficient design is why axial pumps dominate high-volume transfer applications.

Key Characteristics of Axial Flow Pumps

The defining feature of an axial flow pump is its commitment to volume over pressure.

Its performance metrics are the inverse of a radial flow pump.

This makes it a highly specialized tool for specific large-scale water management tasks.

The open, propeller-style impeller is key to its functionality, allowing large volumes of water to pass through without significant restriction.

Common Applications for Axial Pumps

You will find axial flow pumps in any application where the main goal is to move a lot of water without needing to lift it very high.

These are the workhorses of large-scale water management.

For importers dealing with agricultural, municipal, or flood control projects, these pumps are essential.

Their efficiency in high-flow scenarios makes them the most economical choice.

• Flood Control and Drainage: Rapidly removing large volumes of storm water.
• Large-Scale Irrigation: Supplying water from rivers or canals to agricultural fields.
• Wastewater Treatment Plants: Circulating and transferring large volumes of water between treatment stages.
• Power Plant Cooling: Circulating cooling water through condenser systems.
• Aquaculture: Ensuring water circulation in large fish farm ponds.

While RAFSUN focuses on VSD booster pumps for residential and commercial pressure systems, understanding axial flow technology is vital for any water pump professional.

It highlights the importance of matching pump A's design to the application's specific requirements for flow and head.

Selecting an axial pump for a high-pressure job would be a critical failure, just as using a radial pump for flood drainage would be incredibly inefficient.

What is a Mixed Flow Pump?

What do you do when your application demands both high flow and moderate pressure?

Neither a radial nor an axial pump is the perfect fit.

Mixed flow pumps bridge this gap, offering a balanced performance profile for versatile applications.

A mixed flow pump is a hybrid design that discharges fluid at an angle between 0 and 90 degrees to the pump shaft. It combines the high-pressure capabilities of a radial pump with the high-flow characteristics of an axial pump, creating a versatile, efficient solution.

The mixed flow pump is a clever compromise between the two extremes.

It incorporates design elements from both radial and axial pumps to achieve a balanced performance.

As fluid enters the mixed flow impeller, it begins to move both axially (forward) and radially (outward).

The impeller vanes are uniquely curved to direct the flow at an angle, typically between 30 and 60 degrees.

This combined motion imparts both a lifting force and a centrifugal force on the fluid.

The result is a pump that can generate more pressure than a pure axial pump but can handle higher flow rates than a pure radial pump.

The casing of a mixed flow pump is also a hybrid.

It is often a combination of a volute and a diffuser bowl.

This design effectively manages the angled discharge from the impeller, efficiently converting the fluid's velocity into a moderate level of pressure.

This makes the mixed flow pump an excellent choice for a wide range of medium-head, medium-to-high-flow applications where neither of the other two types would operate at their peak efficiency.

Key Characteristics of Mixed Flow Pumps

Mixed flow pumps occupy the middle ground in the centrifugal pump family.

Their specifications reflect this balance, making them a flexible option for many common water transfer and supply tasks.

The impeller's design is the secret to its versatility, with a larger diameter than an axial impeller and wider passages than a radial one.

Common Applications for Mixed Pumps

Because of their balanced performance, mixed flow pumps are found across municipal and industrial sectors.

They are often the right choice when an application has outgrown the capacity of a radial pump but doesn't require the massive volume of an axial pump.

For your customers in public works, agriculture, or industrial processing, mixed flow pumps can be the most efficient solution.

• Municipal Water Supply: Pumping water from sources like rivers or lakes into treatment facilities.
• Wastewater Management: Lifting sewage and treated effluent.
• Irrigation: Supplying water to large commercial farms where some pressure is needed.
• Industrial Water Circulation: Moving process water within manufacturing plants.
• Cooling Tower Applications: Circulating large volumes of water in HVAC and industrial cooling systems.

At RAFSUN, we recognize the need for this balanced performance.

While our core products are VSD booster pumps that primarily use radial impellers for pressure, the principles of mixed flow inform the design of efficient pumping systems.

Applying VSD technology to a mixed flow pump can create an incredibly adaptable system, capable of maintaining constant pressure across a wide range of flow demands, further enhancing its versatility and energy efficiency.

This highlights our commitment to providing intelligent and efficient water management solutions for every need.

Conclusion

Understanding the three pump types—radial, axial, and mixed flow—is crucial for selecting the right equipment.

Each is designed for a specific combination of head and flow, ensuring optimal efficiency.

FAQs

What is the main difference between radial, axial, and mixed flow pumps?

The primary difference is the direction of fluid discharge relative to the pump shaft. Radial is 90 degrees, axial is parallel, and mixed flow is at a diagonal angle.

Which pump is best for high pressure?

Radial flow pumps are best for high-pressure applications. Their design uses centrifugal force to generate significant head, ideal for lifting water to great heights or through restrictive systems.

What is a mixed flow pump used for?

Mixed flow pumps are used for applications requiring a balance of moderate pressure and high flow rates, such as municipal water supply, irrigation, and industrial water circulation.

Can pump types be used interchangeably?

No, using the wrong pump type leads to severe inefficiency, high energy costs, and a shortened lifespan. Each pump operates efficiently only within its designed flow and head range.

How does specific speed relate to pump type?

Specific speed is an index that classifies pump impellers. Low specific speed corresponds to radial flow pumps (high head), while high specific speed relates to axial flow pumps (high flow).

Are VSDs compatible with all pump types?

Yes, Variable Speed Drives (VSDs) can be paired with radial, axial, and mixed flow pumps to provide precise control, maintain constant pressure, and significantly reduce energy consumption.

What is the most common type of centrifugal pump?

The radial flow pump is the most common type. It is widely used in residential, commercial, and industrial applications for its ability to generate high pressure for various needs.

How do I choose the right pump for my application?

To choose the right pump, you must first determine your required flow rate and total dynamic head (pressure). Match these requirements to the performance curve of a radial, axial, or mixed flow pump.