A centrifugal pump is the most widely used pump type in industry, water management and construction. But how does a centrifugal pump actually work, and for which applications is this type most suitable? In this article, we explain the working principle, key components and main application areas, so you can better assess whether a centrifugal pump fits your situation.

What is a centrifugal pump?

A centrifugal pump is a type of pump that moves fluids using centrifugal force. The pump converts rotational energy from a drive (usually an electric motor or diesel engine) into kinetic energy and then into pressure energy, transporting the fluid through the system.

Centrifugal pumps belong to the category of rotodynamic pumps and differ from positive displacement pumps by working with a continuous fluid flow rather than discrete volumes.

How does a centrifugal pump work?

The operation of a centrifugal pump involves three steps.

Step 1: Fluid enters the pump casing. The fluid is directed via the suction connection to the centre (the “eye”) of the rotating impeller. A centrifugal pump does not actively suck fluid in: the rotating impeller creates a pressure reduction on the suction side, causing the atmospheric pressure (or system pressure) to push the fluid towards the pump.

Step 2: The impeller accelerates the fluid. The rotating impeller flings the fluid outward via its vanes. Centrifugal force increases the velocity of the fluid. The vane design (curved, double-curved or straight) determines how efficiently this energy transfer takes place.

Step 3: The pump casing converts velocity into pressure. In the spiral-shaped pump casing (the “volute”), the cross-section gradually increases. This decelerates the fluid and converts kinetic energy into pressure energy. The fluid exits the pump via the discharge connection with sufficient pressure to flow through the piping system.

This operating principle makes centrifugal pumps particularly suitable for applications where large volumes of fluid need to be moved continuously.

Key components of a centrifugal pump

Pump casing (volute): the housing that collects the fluid and converts velocity into pressure. On larger pumps, a dual volute design may be used to reduce radial loads on the shaft.

Impeller: the rotating component that accelerates the fluid. Different impeller types exist: enclosed impellers (for clear fluids and high efficiency), open or semi-open impellers (for fluids with solids), and vortex impellers (for heavy solids applications). The impeller type directly affects efficiency, solids handling capacity and suitability.

Shaft and bearings: the shaft connects the impeller to the drive. The bearings carry radial and axial forces. Oversized bearings significantly extend service life.

Shaft seal: prevents leakage where the shaft enters the pump casing. Common types include packing glands and mechanical seals. For abrasive fluids, cartridge seals are often used for longer service life.

Centrifugal pump applications

Industry: process fluids, cooling water systems, food processing and chemical processes.

Wastewater treatment: pumping wastewater containing solids, wipes and organic material. Robust pumps with high solids handling capacity and self-cleaning mechanisms (such as Eradicator technology) are essential.

Construction and mining: dewatering of excavations, groundwater and water containing sludge.

Water management and municipalities: drinking water distribution, sewage pumping stations and flood control.

Agriculture and irrigation: water supply for irrigation and crop production.

When is a centrifugal pump the right choice?

A centrifugal pump is generally the best choice when dealing with low-viscosity fluids (up to approximately 300 cP), a relatively constant flow rate is needed, and the head fits within the range of the selected pump.

A centrifugal pump is less suitable for high viscosities, strongly varying pressures, or when dosing accuracy is required. In those cases, a positive displacement pump may be a better fit.

Frequently asked questions

Want to know which centrifugal pump best fits your application? Share your application data (flow, head, medium, solids, installation type) and we will advise the right configuration. Contact Gorman-Rupp Europe.

A well-maintained centrifugal pump delivers stable performance for years with low operating costs. Neglect leads to premature wear, unexpected downtime and higher energy costs. In this article, we describe six practical steps for effective centrifugal pump maintenance.

Step 1: Check the shaft seal regularly

The mechanical shaft seal is one of the most vulnerable components. A leaking seal causes fluid loss, contamination and eventually damage to bearings and shaft. What to check: checking the level and condition of the oil, unusual sounds and vibrations, temperature of the seal area. For abrasive fluids, a cartridge seal is preferred. The 6400 Series comes standard with an oil-lubricated, double-floating mechanical seal designed for contaminated media.

Step 2: Monitor the bearings

Bearings carry the rotating forces. Bearing wear manifests as increasing vibrations, temperature rise and audible noise. What to check: bearing housing temperature, vibration level, oil level and quality. Pumps with oversized bearings, such as the 6500 Series, have longer bearing life and require less frequent intervention.

Step 3: Inspect the impeller and wear rings

Wear on the impeller or wear rings increases internal clearance, reducing efficiency and increasing energy consumption. With pumps featuring replaceable wear rings (such as the VGH Series), efficiency can be restored by replacing only the wear rings, without replacing the complete impeller.

Step 4: Check the pump casing

In wastewater applications, fibres, wipes and other materials can accumulate and impede flow. Pumps with an inspection port (such as the 6500 Series) allow checking without full disassembly. Pumps with Eradicator technology (6400 Series) automatically shred wipes and fibres, preventing blockages.

Step 5: Monitor the duty point

A centrifugal pump running consistently outside its optimal operating range wears faster. Too far left on the pump curve causes recirculation and overheating. Too far right causes cavitation and overloading. Variable frequency drives (VFDs) can help maintain the pump within the optimal range.

Step 6: Plan preventive maintenance

Reactive maintenance is always more expensive than preventive maintenance. Recommended schedule: daily/weekly visual checks, monthly bearing temperature and oil level checks, semi-annual seal inspection and wear ring measurement, annual impeller and casing inspection with alignment check.

The interchangeable rotating assembly of the 6400 Series enables replacement on site without dismantling the casing or piping, significantly reducing maintenance time. Gorman-Rupp offers fast delivery of original parts, often within 24 hours.

Frequently asked questions

Want to know which centrifugal pump best fits your application? Share your application data (flow, head, medium, solids, installation type) and we will advise the right configuration. Contact Gorman-Rupp Europe.

Centrifugal pumps and positive displacement pumps are the two main categories in pump technology. They work fundamentally differently, and the distinction determines which type best suits a specific application.

Operating principle: the fundamental difference

Centrifugal pump: the fluid is accelerated by a rotating impeller. Kinetic energy is converted into pressure energy in the pump casing. Flow rate varies with system back-pressure.

Positive displacement pump: a mechanical component (gears, screws, pistons, diaphragms or plungers) displaces a defined volume of fluid per stroke or revolution. Flow rate is virtually independent of back-pressure.

When to choose a centrifugal pump

A centrifugal pump is the logical choice when the fluid is low-viscosity (water, thin process streams), large flow rates are needed, the duty point is relatively stable, continuous pulsation-free flow is desired, and low purchase and maintenance costs are important.

When to choose a positive displacement pump

A positive displacement pump is the better choice when the fluid is highly viscous (oil, resin, bitumen, syrup), dosing accuracy is required, high pressures are needed at relatively low flow rates, and flow must remain independent of system pressure.

Common selection mistakes

Using a centrifugal pump for high-viscosity media.
As viscosity rises, centrifugal pump efficiency drops drastically, energy consumption increases and the pump can overheat. Above approximately 300 cP, a positive displacement pump is typically more efficient.

Selecting a positive displacement pump where a centrifugal pump suffices.
For low-viscosity fluids and large flow rates, a centrifugal pump is more compact, cheaper to purchase and simpler to maintain.

Quick decision framework

1. Viscosity above 300 cP? Positive displacement pump.
2. Dosing accuracy required? Positive displacement pump.
3. Flow rate above 50 m3/h? Centrifugal pump is likely more efficient.
4. High pressure (>10 bar) at low flow? Positive displacement pump.
5. Pulsation-free flow needed? Centrifugal pump.

Gorman-Rupp Europe supplies centrifugal pumps and membrane/gear pumps (positive displacement) for viscous media.

Frequently asked questions

Want to know which centrifugal pump best fits your application? Share your application data (flow, head, medium, solids, installation type) and we will advise the right configuration. Contact Gorman-Rupp Europe.