What is a centrifugal pump?
A centrifugal pump is a type of pump that uses rotational energy, typically provided by an electric motor or motor, to move fluids through a piping system. The main component of a centrifugal pump is the impeller, which rotates and transfers kinetic energy to the fluid, causing it to move away from the center of rotation and increase pressure. Centrifugal pumps are commonly used in industries such as water supply, chemical processing, and HVAC systems.
Types of centrifugal pumps
| Subtype | Description | Performance |
|---|---|---|
| Axial flow pump | Moves fluid along the impeller shaft, suitable for high flow, low head applications. | High flow, low pressure head. Often used in irrigation, flood control and circulation systems. |
| Radial Flow Pump | Moves fluid perpendicular to the impeller axis, typically for high-head, low-flow applications. | High pressure head, low flow. Commonly used in water supply and high pressure cleaning systems. |
| Mixed Flow Pump | Combines features of axial and radial flow pumps, designed for medium and medium head flows. | Moderate flow rate and pressure head. Suitable for industrial processes and large-scale water transfers. |
What is a positive displacement pump?
Positive displacement pumps operate by trapping a fixed amount of fluid and then forcing (displacing) that trapped volume into the discharge tube. Unlike centrifugal pumps, these pumps provide a constant flow regardless of pressure. They are highly efficient in handling viscous fluids and are widely used in applications such as chemical injection, oil drilling and hydraulic systems.
| Subtype | Description | Example |
|---|---|---|
| Alternative Pump | Uses pistons, plungers, or diaphragms to move fluid in a linear motion | Bladder diaphragm peristaltic piston/plunger |
| Rotary Pump | Moves fluid using rotating mechanisms like gears or screws | Gear screw Progressive cavity Rotary lobe Rotary vane |
Comparing centrifugal and positive displacement pumps
| Aspect | Centrifugal pump | Positive displacement pump |
|---|---|---|
| flow rate | Varies with pressure; higher pressure reduces flow rate. | Constant flow rate regardless of pressure changes |
| Viscosity handling | Less efficient with high viscosity fluids | Highly efficient with high viscosity fluids. |
| Pressure capacity | Generally lower pressure; Suitable for low to medium pressure applications. | Capable of high pressure; ideal for high pressure applications |
| Efficiency | High efficiency with low viscosity fluids and steady state operations | High efficiency with varying viscosities and over a wide range of pressures |
| Maintenance | Typically lower maintenance requirements | Generally higher maintenance due to more moving parts. |
Conclusion
Choosing the right pump for your application is crucial to efficiency and performance. While centrifugal pumps are ideal for low viscosity fluids and low to medium pressure systems, positive displacement pumps excel at handling high viscosity fluids and high pressure applications. Understanding their respective advantages can help MEP engineers make informed decisions for optimal system design.
