“How does a centrifugal pump work?” is one of the most common questions when it comes to moving a fluid in a system. Here you’ll find a technical yet accessible explanation: components, operating principle, performance curve, and practical criteria for selecting the most suitable pump.
Table of Contents
What Are Centrifugal Pumps?
Centrifugal pumps are pumps in which the movement of the fluid is driven by torque generated by rotating mechanical components, commonly referred to as impellers.
In practice, the fluid is set in motion by the rotating part and the internal geometry of the pump, which guide its flow from the Inlet to the Outlet.
The Main Components of a Centrifugal Pump
The main components of a centrifugal pump are:
- Moving part (impeller), which transfers energy to the fluid.
- Pump housing (volute), which channels the flow first into the inlet and then into the Outlet.
- Shaft to which the impeller is attached; it is usually connected to the motor.
- Engine, which can be electric or internal combustion.
This “chain” (motor → shaft → impeller → volute) is what makes it possible to convert energy and, consequently, to move the fluid through the system.
Classification and Installation (Horizontal/Vertical and Hydraulic Conditions)
Depending on how the shaft and motor are positioned, the following types are distinguished:
- Horizontal Centrifugal Pumps
- Vertical Centrifugal Pumps
In addition to their orientation, the pumps can be hydraulically positioned in two ways:
- BOTTOM HINGE
- OVERHANG
These definitions are used to describe how the pump “fits” into the conditions of the circuit in which it operates, and thus to correctly contextualize the installation within the system.
How a Centrifugal Pump Works (Principle of Operation)
A centrifugal pump usesthe centrifugal force of the impeller to move the fluid, converting mechanical energy (from a motor, which is usually electric) first into kinetic energy and then into pressure energy.
The movement of the impeller creates a vacuum in the inlet pipe: the fluid, driven by atmospheric pressure, flows through the pipe and enters the pump. After drawing in the liquid, the impeller propels it toward the periphery using the centrifugal force generated by its speed.
Impeller and volute: what happens to the fluid inside the pump
The impeller of a centrifugal pump is equipped with a series of curved vanes that form channels with a cross-section that increases from the center toward the periphery.
The fluid exits the impeller at a velocity Vt, so it still possesses kinetic energy, and enters the volute. The body of the centrifugal pump (the volute) is also constructed with an expanding cross-section, so that the remaining portion of the kinetic energy is converted into pressure energy.
The result of this step is an increase in head, that is, the pump’s ability to “overcome” the resistance required by the system to move the fluid along the intended path.
Performance Curve and Efficiency of a Centrifugal Pump
The characteristics of a centrifugal pump are described by its performance curve, which shows how the head delivered by the pump varies as a function of the flow rate it is capable of delivering.
This relationship is crucial because, in practice, the choice is not made “on a hunch”: one verifies whether, at the required flow rate, the pump can provide the Head necessary for the system.
How to Choose a Pump: Flow Rate, Head, and System Leaks
The choice of a pump must be based on the characteristics of the system you want to operate: flow rate and Head. In other words:
- What is the flow rate (m³/h) that must be achieved?;
- which obstacle must be overcome.
When calculating prevalence, it is necessary to take into account various factors related to the facility, including:
- The elevation difference that must be overcome to move the fluid from point A to point B (geodetic height);
- Distributed leaks caused by the normal flow of fluid through the pipe;
- Localized leaks caused by piping components along the line (such as valves, elbows, check valves, etc.).
Fluid Characteristics: What to Consider Before Making a Choice
In addition to the system’s characteristics, the characteristics of the fluid to be handled are also important. Specifically:
- Temperature
- Viscosity
- Density
- Presence or absence of particles in the fluid
These factors influence the selection because they describe “what type of fluid” the pump will need to handle, and thus the actual operating conditions of the system.
Conclusion
To understand how a centrifugal pump works, follow the path of energy: the motor causes the impeller to rotate; the fluid enters through the inlet due to the vacuum created there; it gains kinetic energy; and then the volute converts this into pressure energy, increasing the Head. To select the most suitable pump, the key factors remain flow rate, head, system losses, and fluid characteristics.
