Rethinking compressed air efficiency in machinery
16 September 2025 
Lowering the energy consumption of machines, is good for the environment and good for our wallets – but is reducing the operating pressure of machines to 4 bar always the right way to
achieve this? Festo has been advocating pressure reduction as a key element within an energy saving approach for more than 10 years. However, does this always make sense? Surprisingly perhaps, the answer is no. As with many things in life, the devil is in the detail. Whilst there can be very positive results, it might not be the right way in all cases. Steve Sands of Festo GB looks at recent research by Dr. Wolfgang Gauchel of Festo Corporate Research & Innovation Dept (Circular Economy and Efficiency).
Historically when energy costs and environmental awareness were lower, close attention wasn’t always paid to the air consumption on machinery. Designers typically selected pneumatic actuators based on a range of ad hoc criteria: what they had used before, what was on the shelf, “it looks about right”, looking at a simple pressure/force graph and up sizing by one diameter “just to be safe”. This means the actuators on many older machines are over specified and it is perfectly possible and correct to turn down the operating pressure and reduce the redundancy and wastage.
Where is compressed air consumed on typical machines
Compressed air on machines is not only consumed for driving pneumatic cylinders.
Other typical areas include:
Vacuum generators, nozzles and suction cups
Air blasts and air guns
Leakage and losses
Each of these require individual consideration for optimised performance and air consumption.
Optimising air consumption with vacuum generators
Pneumatic vacuum generators utilise a venturi nozzle based on the Bernoulli principle to create vacuum by accelerating the air flow through a constricting nozzle. Nozzles within the generators are designed for individual operation or as elements within a multi-stage generator. Nozzles are specifically designed to achieve high levels of vacuum, high flows for short evacuation times or a general-purpose combination of both. Passing compressed air through a nozzle and straight to atmosphere is potentially a very high consumption element
Catalogue data will identify the optimum supply pressure to achieve the flow and negative pressure required. Often vacuum generators are designed to provide the highest vacuum level at
only 4 bar. Increasing the pressure to 6 bar does not draw a deeper vacuum level although the flow will increase. But the evacuation time is shorter because of a higher suction rate.
Air blow guns and air blasts
Air jets are used for ejecting parts from conveyor belts and housings. There are different ways to optimise the energy usage – either by concentrating the flow through nozzles or using a reservoir to increase the stored energy but only ‘blipping’ the pulse for a very short time. Air blow guns are commonly used for cleaning down and removing dust and particles. As well as being potentially dangerous they are also another high consumption element. Modern air blow guns are equipped with an in-built regulator dropping pressure to only 2 bar and have a safety tip with relief ports.
Leakage and losses
Leaks need to be eliminated wherever possible but clearly the higher the pressure, the bigger
the losses.
Dead volumes in pneumatic systems such as filling and exhausting long or large diameter pipe runs for every cylinder cycle are another cause of energy wastage. Mounting the valves closer to the actuators shortens pipe run lengths. Reducing pipe diameters can also help but will also restrict pressurisation and to a greater extent exhaust times, therefore they should be simulated or calculated to achieve the required performance. Energy losses also occur due to non-laminar and turbulent flows. Pipe friction and eddies due to tight radii or kinks or supersonic flows can all create further efficiency losses within pneumatic systems and are affected by the operating pressure.
Options for new machine builds
On new machine designs and builds reducing the operating pressure from say 6 bar to 4 bar may not actually reduce air consumption. If parts are correctly sized for the application – and this includes not only the actuator but also the tubing runs, fittings and air supply unit etc. then it may be better to stay at a higher pressure. For example, if you design a machine to operate at 4 bar pressure operation it will require larger diameter cylinders to obtain the same dynamic or force as a 6 bar machine, the tubing will be a larger bore to achieve the flow at a lower pressure differential. Larger actuators, mountings, tubing and fittings will usually cost more. In addition, larger cylinders will add weight to the machine (critical if it is adding to the payload of other actuators), and take up more space.
Hmm… maybe this doesn’t sound such a good thing?
Reducing pressure makes a big impact If all the machines and devices connected to compressor system can operate at a reduced air pressure, not only can the local pressures be reduced but it’s possible to reduce the whole network pressure. Compressor systems may be optimised for a given pressure/flow demand and this must be considered. Lower network pressures mean less losses from leaks. Air networks need to be able to cope with peak demands and fluctuations, educing pressures and the peak flow capacity whilst potentially saving energy could cause pressure drops and
lost production.
Positive, pressure reduction can reduce energy consumption and CO2
It helps to compensate oversizing.
If the pressure level at the output of the compressor is reduced, less electrical energy is needed.
Air leakage is smaller when pressure is reduced.
The backstroke pressure can be reduced, if no/less load needs to be moved.
In green field applications, a reduction of energy consumption can be reached. But all components needs to be optimised for the lower pressure. Negative, pressure reduction causes
different problems
A well sized cylinder needs to be one size larger when pressure is reduced from 6 to 4 bar.
A well sized 6 bar cylinder needs the same amount of air as a well sized 4 bar cylinder.
All other components (Fittings, Tubes, Valves, Air preparation, …) also needs to be bigger. There is a need for more construction space. Larger components are in general more
expensive than smaller.
Most vacuum generators have their best evacuation time to reach a defined vacuum at 6 bar.
In brown field applications the system needs to be analysed in detail, if a pressure reduction makes sense.
Whole machine approach
The best approach is to engage with specialist applications engineers that can support machine optimisation according to all your priorities – machine performance, build costs, lifetime costs, energy efficiency etc. We would also strongly recommend looking at the whole solution not just one function at a time. Even narrowing the discussion down to replacing air actuators with electric drives can be a false generalisation. For example, does it make sense to use a sophisticated electric gripper on the end of a pick and place system, if a pneumatic one can do the job? Unlike
electric grippers, pneumatic grippers do not consume energy when exerting a constant force gripping a component. In most cases you can save 50-60% of the mass. This is critical at the ‘end-of-arm as it enables you to reduce the size of all the supporting actuators – rotary, X-Y and Z. The savings on the overall system can be dramatic in purchase and operating costs.
The recommendation is to focus on what you want to achieve and let specialists such as Festo support you in the configuration of your machine.
For further information please visit:
https://www.festo.com/gb/en/