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Go with the flow

Specifying your compressed air system by flow
and pressure – not kW or horsepower – is the best way to match its performance to your needs. Compressor sizing should match your business requirements more precisely than just going by kW rating.

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is the average number of air compressors on the market sized incorrectly


is the differential in flow rate within the same kW category in some ranges


price difference in the unit's purchase price depending on the flow within the same kW range

The kW power rating of a compressor’s motor does not provide enough information to specify a new compressor: prioritise the flow and pressure.

Did you know that there could be a number of pressure/flow variants within each kW category? E.g. Atlas Copco has four models in the 11 kW range that represent a 30% differential in flow rate (from 28.7 l/s to 35.8 l/s at 7 bar.g) and over 32% difference in the unit’s purchase price! So the question becomes how do you choose or size a compressor? Which air compressor is right for your business?

Modern compressed air equipment, when correctly matched in terms of compressor pressure and flow to process demands, can offer reduced specific energy requirements, improved productivity, and lower lifecycle costs. Their enhanced performance may allow a lower kW rated machine to be specified at a correspondingly smaller purchase price and reduced running costs in comparison to higher rated equipment.

It pays to apply a few essential rules when choosing on a new compressor:

Conduct an air audit

Assess present and future needs by first checking out the existing compressed air systems from air output to point of use, with a thorough air audit.

Match the air demand

Do not rely solely on the stated motor power rating to match the air compressor performance to the process air demand.

Pressure + flow = energy = cost

Start with the air pressure and flow requirement and then find the best fit in terms of drive motor power. Always keep in mind: pressure + flow = energy = cost.

Air quality

What type of air quality do you need? Is an oil-injected compressor plus filtration sufficient for your application or do you need a genuine oil-free compressor?

Atlas Copco offers up to 4 options in each kW category across its entire range of rotary screw compressors

In the 11 kW range alone that can represent a 30 per cent differential in flow rate (from 28.7 l/s to 35.8 l/s at 7 bar.g) and over 32 per cent difference in purchase price. As another example, we have a 26 kW model which is unique to the marketplace, as all other offerings in this power sector are limited to a choice of 22 and 30 kW machines.

our compressed air experts

Our engineers will help you match precisely your air demand