As an environmental auditor I’m often called to walk around manufacturing and other business sites to carry out reviews of environmental (and legal) performance.
Over the years my ears have become acutely tuned to that familiar hiss of a compressed air leak emanating from production lines, pipework or blow guns. It’s often an indirect benefit to have a third party on site, as these noises tend to become part of daily background noise for those on site, and are ignored or not even heard any more.
Use of compressed air at any site is expensive. It’s a large energy-draining resource. This blog will provide a few hints and tips for getting the most out of compressed air use, and ensure you improve efficiency and ultimately save money!
In a guide from the Carbon Trust it's estimated that of the total energy input for a compressed air system, only 8-10% is converted into useful energy at point of use. Therefore, ways to improve the efficiency of using compressed air are:
Turn it off!
A compressor running on idle consumes 40% of its full load. Turn it off overnight or when it’s not needed.
Reduce the pressure
You may have to test this in incremental stages, but a lot of compressors automatically run at maximum pressure (around 100psi), and reducing the pressure by 10% could lead to a 5% energy saving. Try reducing the pressure in small increments but ensure reducing the pressure doesn’t affect operational performance!
Test for leaks
Start big – the leaks that is. Carry out a walk around following the compressed air lines away from the compressor. You should easily be able to hear a big compressed air leak without specialist equipment, especially out of hours. Smaller leak detection may require hiring ultrasonic detection equipment or using a consultancy to carry out a full detection survey.
Even a small leak of just 3mm could cost you more than £700 a year in wasted energy, and they can cost pence to fix.
Compressed air gets used in a surprisingly wide variety of ways, not always those it was intended for. Educate staff in the specific use of compressed air on site and discourage clearing down benches, ventilation, or drying techniques if that’s not was it was designed for. It all wastes energy.
Not all compressed air uses are high pressure. Compressed air is used often at lower pressures to provide cooling, air flow etc. There may be other more efficient techniques to achieve the same results but without using compressed air, and therefore saving energy.
Don’t over-treat air
A lot of energy in a compressed air system is used to treat the air dryness and contamination levels. That’s important for things like air-fed respiratory masks, but learn what those limits are for viable production at your end uses, to ensure you don’t over-treat the air supply, wasting energy.
Keep the inlet clean
When a compressor is installed it's important to think carefully about where the air inlet will be located. Starting the process with air which is either hot, moist, dusty or contaminated will reduce the efficiency of the system, increase wear on parts and impair performance. The air inlet filter should be kept clean to prevent a drop in system pressure which would require the compressor to work harder.
Storage means efficiency
Sometimes when compressor systems are purchased the calculation of size is based on the maximum load of the equipment it will be supplying. However, sizing an appropriate receiver to cope with fluctuations in use, that provides good performance over the average demand in a working day to reduce or eliminate pressure fluctuations is a more efficient way to operate.
Recover the heat
Heat is generated when air is compressed and in a lot of systems that heat is simply wasted. Heat recovery systems can be used for water or space heating from simple baffles ducting heat into a factory or out to atmosphere, depending on demand, to heat exchangers heating water systems.
This is just a short selection of the various measures that can be used to increase the efficiency of using compressed air. And remember, listen out for those leaks!