Selecting a centrifugal compressor: technology explained - Atlas Copco South Africa
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Centrifugal compressor technology explained

Discover our complete range of centrifugal air compressors designed for industries and applications that require a large supply of compressed air or gas.

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Everything you need to know about centrifugal compressors

On this page we’ve gathered everything you need to know about centrifugal air compressors where we’ll cover the f following topics:

What are centrifugal compressors used for?

Companies that require a large supply of compressed air use our tried and tested centrifugal technology. At the heart of each machine is an individually designed impeller. 

That's right: each machine is optimized for its power range. Each pressure variant has its own optimized impeller.  These impellers are built to last, which makes the centrifugal compressor a very reliable unit.

Centrifugal compressors are active in various industries: automotive, food, pharma, textile, power, renewable energy, wastewater treatment, the chemical industry and oil and gas.

How to choose between oil-free screw and centrifugal technology?

A very popular answer to this question is to select screw technology for best energy efficiency at lower flows and centrifugal technology for the higher flow demands. To advise the customer on the best technology fit, we have to look at the customer's application.

It all starts from our customer's need. For sure, the energy efficiency will play a role in the final selection, yet other parameters like the compressed air demand profile will have to be taken into account as well. Applications that show a fluctuating air demand will benefit more from the wide turndown capabilities of a variable speed driven oil-free screw, while centrifugal units typically would be a better fit on more steady flow demand patterns.

In most cases, the optimum selection is a combination of the 2: An oil-free centrifugal unit taking care of the base load combined with a variable speed driven oil-free screw unit to handle the fluctuating top load. This combo, together with our heat-of-compression dryers, forms a winning team, unique in the compressed air industry, providing ourselves and our customers the guarantee for success.

Advantages of our multistage centrifugal compressors

Around-the-clock reliability

Energy-efficient solution due to multi-speed capability for optimal speed on each stage

Economical compressor technology

Noise-reducing canopy

Highly efficient cooler

Smallest possible footprint

What types of centrifugal compressors are there?

We provide standardized or custom-engineered centrifugal compressor solutions.

  1.  centrifugal blowers with pressures up to 1.5 bar.
  2.  oil-free air centrifugal compressors cores- up to 13 bar
  3.  process gas multistage cores up to 205 bar

Within the centrifugal compressors category, 3 main configurations are available:

  • An axial multistage compressor is running at a relatively low speed, mostly direct driven by an induction motor. Multiple impellers are lined up axially after each other to gradually build up the pressure.
  • Geared turbo compressors are driven by an induction motor rotating at a relatively low speed. The radial impeller(s) are running at a high speed due to a gearbox transmission. Special bearings are required for these high speeds, mostly hydrodynamic bearings are used. Either single or multiple impellers can be installed depending on the required pressure and or flow.
  • Highspeed turbo compressors are radial turbos without the presence of any gears. The motor is directly driving the impeller. This means the motor needs to run at high speeds, requiring Permanent Magnet motor technology. To be reliable at these high speeds, magnetic bearings are used to avoid any contact or wear.

1. Oil-free air centrifugal blowers- up to 1.5 bar

In sensitive industrial applications, a reliable supply of oil-free air at lower pressures from 300 mbar (g) to 1.5 bar (g) is needed.
Oil-free air centrifugal blowers need to meet the rigorous standards expected in :

Variety of centrifugal blower solutions

There’s more than one configuration we can provide to meet the requirement of your application. No two projects are the same. We realize that the initial investment cost or the total cost of ownership can also be a deciding factor.
Our multistage centrifugal blowers are providing a simple, reliable solution that requires a lower initial investment. Our highly efficient high-speed centrifugal blowers ensure the lowest total cost of ownership.

2. Oil-free air centrifugal compressors - from 2 to 13 bar

ZH oil-free air centrifugal compressor

ZH oil-free air centrifugal compressor

The oil-free air centrifugal compressors cores are designed to guarantee the most energy-efficient power and flow. Our standardized units are the most energy-efficient on the market based on tests in the field and Pasel calculations.

The oil-free centrifugal compressor is generally used in sensitive industry applications:

Avoid oil in your production process 
The Atlas Copco Z-compressors are a Class Zero range, meaning they deliver completely oil-free air. The absence of oil makes the process easier and safer and more durable. You don’t need any filtering of the desiccant beds, and the service intervals are much longer.

Peace of mind is important
The quality of our products is our absolute priority. This oil-free solution is the best choice to be able to guarantee that quality. Also, it has a positive effect on the environment. This compressor has a favorable impact on the environment and it significantly reduces energy costs.
We are continually looking for ways to optimize our processes and provide benefits to our clients. The ZH compressor is an impressive package and intelligence is part of that package. The Elektronikon controller maximizes the performance of the compressors and allows for detailed monitoring.

Why Air Liquide chose centrifugal technology?




3. Higher pressure centrifugal compressors for process air and gas applications- up to 205 bar

For the process gas multistage cores up to 205 bar.  We listen to the specific requirements of the client and provide a custom-made core guaranteeing the most energy-efficient solution.

The demanding process requirements of the LNG, Chemical / Petrochemical and Gas Processing require robust, reliable centrifugal compressors. Centrifugal compressors,  also known as turbocompressors, offer our customers dependable and efficient operation.

We can help you handle the pressure of your hydrocarbon process. With single shaft and integrally-geared compressors ranging from one to eight stages. Our GT, T, RT and Companders are custom-engineered to perfectly fit your process needs. While our AeroBlock, PolyBlock and TurboBlock are standardized compressors for faster delivery. 

What is the efficiency of a centrifugal compressor?

In general, the bigger the machine, the higher the centrifugal compressor efficiency. This is often referred to as the “scale effect”.
The reasons rely on better flow in the bigger machines as the relative roughness factor is smaller (a smaller friction coefficient) and
the relative gap dimensions are smaller (volumetric effect).

A centrifugal compressor generally has an efficiency of around 70-85%, depending on mechanical losses and gas friction within the compressor, where the value will vary depending on the size of the compressor.

How does a centrifugal compressor work?

centrifugal compressor working principle

Centrifugal compressor working principle

The working principle of a centrifugal compressor
By adding kinetic energy to air particles and abruptly slowing them down, you build up pressure.
By doing this in several stages, you can go up to 13 bar in lower compression machinery. 
And as high as 205 bar in 4-8 stage high compression turbomachinery, also known as multi-stage centrifugal compressors.

  • 1 -stage: up to 2.5 bar
  • 2 -stages: 2.5 bar to 5.5 bar 
  • 3 -stages : 6 bar to 13 bar 
  • 4-8 stages up to 205 bar 

The core of the stage centrifugal compressor consists of 3 elements; 

Impeller: The air flow enters the impeller, where the rotating blades increase the kinetic energy of the air

The diffuser manipulates the air flow by gradually slowing down the air velocity and converting the kinetic energy into pressure. 

 The diffuser discharges in the collector – shaped as a snail shell- also known as the volute. In the volute, the air flow from the diffuser is collected and distributed to an outlet pipe.