Choosing the right pump is important when you need to move liquids in an industrial process. Two common options are positive displacement pumps and centrifugal pumps.
Both types can move liquids effectively, but they work in different ways and are better suited to different applications.
In simple terms, positive displacement pumps are a good choice for thick and heavy liquids, while centrifugal pumps are generally better for thin liquids such as water.
Understanding the difference between these pumps can help you choose the right option for your process, improve efficiency, and avoid unnecessary operating costs.
What Are Positive Displacement Pumps?
Positive displacement pumps move a fixed amount of liquid with each cycle or rotation. The pump traps the liquid inside and then pushes it toward the outlet.
A simple way to understand this is to think about squeezing a tube of toothpaste. When you apply pressure, a specific amount of toothpaste is pushed out. Positive displacement pumps work on a similar basic idea, but in a controlled mechanical system.
These pumps are especially useful for thick and viscous liquids such as oils, chocolate, molasses, sauces, and certain chemicals.
They can also maintain a more consistent flow when the system pressure changes, making them useful for applications where accurate and steady liquid movement is important.
How Do Positive Displacement Pumps Work?
The basic working principle of a positive displacement pump is quite simple:
- Moves a Fixed Amount of Liquid: The pump moves a set amount of fluid with every cycle or rotation.
- Traps and Pushes Liquid: Internal components create spaces that trap the liquid and move it toward the discharge side.
- Handles Thick Liquids: These pumps can move liquids that are too thick for many centrifugal pumps.
- Works at Lower Speeds: Many positive displacement pumps can operate effectively at relatively low speeds.
- Provides Consistent Flow: The flow remains relatively steady even when system pressure changes.
- Can Be Self-Priming: Many positive displacement pump designs can create suction and start pumping without being manually filled first.
The exact performance depends on the specific pump design and application.
What Are Centrifugal Pumps?
Centrifugal pumps use a rotating component called an impeller to move liquid.
When the impeller spins, it pushes the liquid outward. This creates pressure and allows the liquid to flow through the piping system.
Think of it like spinning a bucket of water. The spinning motion causes the water to move outward. A centrifugal pump uses a similar principle inside a controlled pump casing.
Centrifugal pumps are widely used because they have a relatively simple design and can move large volumes of liquid efficiently.
They are generally best suited for thin, free-flowing liquids, such as water and other low-viscosity fluids.
They are commonly used in water supply, wastewater, cooling systems, manufacturing, and many other industrial applications.
Types of Centrifugal Pumps
Centrifugal pumps are available in different designs depending on the application.
FP Centrifugal Pump
The FP centrifugal pump has a standard horizontal design and can be used for a wide range of general industrial pumping applications.
FPV Centrifugal Pump
The FPV centrifugal pump uses a vertical configuration and can be suitable for applications where a vertical pump arrangement is required.
FPH Centrifugal Pump
The FPH centrifugal pump is designed for applications that require higher pressure and reliable liquid transfer.
FM Multistage Centrifugal Pump
The FM multistage centrifugal pump uses multiple impellers to generate higher pressure than a single-stage pump. These pumps are useful when liquid needs to be moved at higher pressures.
Horizontal-Mounted Pumps
Horizontal centrifugal pumps are widely used across industrial and municipal applications. Their familiar design also makes them relatively straightforward to install and maintain.
Submersible Pumps
Submersible centrifugal pumps are designed to operate while submerged in liquid. They are commonly used in applications such as wells, drainage, wastewater, and other deep or submerged installations.
Positive Displacement vs. Centrifugal Pumps: What Is the Difference?
Although both pumps are used to move liquids, their working principles and ideal applications are different.
| Feature | Positive Displacement Pump | Centrifugal Pump |
| Flow | Provides a relatively consistent flow | Flow changes with system pressure |
| Viscosity | Excellent for thick and viscous liquids | Best for thin, free-flowing liquids |
| Pressure | Can handle high-pressure applications depending on design | Pressure depends on pump and impeller design |
| Maintenance | May require more regular maintenance depending on design | Generally simpler to maintain |
| Initial Cost | Usually higher | Generally more affordable |
| Operating Speed | Often works effectively at lower speeds | Typically operates at higher speeds |
| Self-Priming | Many designs are self-priming | Many designs require priming before operation |
| Typical Applications | Oils, sauces, chocolate, adhesives, thick chemicals | Water, wastewater, light oils, and other thin liquids |
Which Pump Should You Choose?
The right pump depends mainly on the liquid you need to move and the conditions of your process.
Choose a Positive Displacement Pump When:
A positive displacement pump may be a better option when:
- You are pumping thick or viscous liquids.
- You need a consistent flow.
- Your process requires accurate liquid movement.
- The system operates at higher pressures.
- The liquid contains materials that require careful handling.
- You need a pump that can handle challenging fluid conditions.
For example, industries producing chocolate, sauces, oils, creams, and other thick products may benefit from positive displacement pumps.
Choose a Centrifugal Pump When:
A centrifugal pump may be the better choice when:
- You are pumping water or other thin liquids.
- You need to move large volumes of liquid.
- Your application requires continuous flow.
- You want a relatively simple pump design.
- Lower initial equipment cost is important.
- The liquid flows easily through the system.
For example, centrifugal pumps are commonly used in water treatment, cooling systems, general manufacturing, and wastewater applications.
Other Factors to Consider Before Choosing a Pump
Fluid type is only one part of the decision. You should also consider:
Flow Rate: How much liquid needs to be moved and how quickly?
Pressure: What pressure is required to move the liquid through the system?
Viscosity: Is the liquid thin like water or thick like syrup?
Temperature: What temperature will the pump need to handle?
Solids: Does the liquid contain particles or solid materials?
Maintenance: How often can your team carry out maintenance?
Energy Use: How efficiently will the pump operate under your actual working conditions?
Installation: Does the available space require a horizontal, vertical, or submerged pump?
Looking at these factors together will help you select a pump that fits your process rather than choosing one based only on initial cost.
Conclusion
There is no single pump that is best for every application.
Positive displacement pumps are generally better suited to thick, viscous liquids and applications that require consistent flow and controlled liquid movement.
Centrifugal pumps are usually a better fit for thin liquids and applications where large volumes need to be moved efficiently.
The best choice depends on your liquid, flow rate, pressure, temperature, system design, and operating requirements.
By understanding how positive displacement pumps vs. centrifugal pumps differ, you can choose the right pump for your process, improve efficiency, and avoid unnecessary operating and maintenance costs.
