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Feeling the pressure?

How to take control of your compressed air associated energy costs

With electricity costs remaining high, finding ways to reduce your utility bills has never been so important. Compressed air is often considered the fourth utility and, if you’re a panel beater or collision repair body shop then compressed air will be critical to your operation. There are a number of ways to ensure you’re operating an energy efficient system and a thorough analysis of your existing compressed air system will go a long way towards building a reliable and cost effective system. In this blog post we look at 5 considerations that will help you get started on your journey towards optimised compressed air energy efficiency.

If you’re a panel beater or a collision repair body shop then compressed air is a vital utility to you. Why? Well, firstly because it’s the energy source for most of your equipment, and secondly because compressed air mixes with the product in paint spraying operations. That said, the impact of compressed air on workflow, product quality and energy bills can often be overlooked. This can mean costly rework as a result of poor air quality affecting paint jobs and workflow interruptions due to inadequate air supply both causing real dollar losses in terms of rework costs and inflated energy bills.

However the good news is, that unlike your other utilities, you have complete control over your compressed air system! If you want to reduce your compressed air associated costs then here’s 5 initial points to consider:

  1. Don’t over pressurise; it can be quite common to find compressors over pressurised in body shops. This is mainly because the industry is used to operating piston compressors. When asked, many body shops will therefore say they need 10 or 12 barg compressors. However, there are not actually many tools which require pressures above 7 barg. Bear in mind that compressors generally produce less volumes of air at higher pressure and compressed air leaks are also more frequent with increases in pressure.
  2. Don’t confuse pressure and volume; there’s actually an inverse relationship between the pressure and the volume of air delivered in a compressed air system. End users often complain that there’s not enough air and so increase the pressure setting on a compressor to compensate. This actually reduces the volume of air delivered and increases the air consumption. Again, increasing system pressure will therefore increase the amount of air lost through leaks. Whilst every compressed air system will have air leaks – unfortunately they are unavoidable – the higher the system pressure, the greater the volume lost through leaks. It’s worth remembering that every 1 barg increase in pressure increases energy consumption by 10%
    In most cases the reason for the lack of air may be down to; inadequate flow due to an undersized compressor, poor compressor performance, leaks or insufficient pipe size. If you aren’t getting enough air from your compressed air system, before you increase the pressure it might be worth consulting a compressed air specialist to determine exactly why this is occurring.
  3. Determine flow requirements; compressor size isn’t determined by pressure requirements but by the compressor’s output capacity in cubic metres per minute (m3/min). To ensure your compressor is properly sized you therefore need to know how much air is required in terms of volume and not pressure. The most precise way to achieve this would be to have your existing compressed air system data logged. This measures and records your actual compressor usage over a defined period of time.
  4. Consider the type of compressor; the piston compressor is still very commonly found in body shops. Whilst piston compressors may provide adequate flow for a short period, the allowable duty cycle should be considered. This is the percentage of time a compressor operates without the risk of overheating and causing excessive wear to a compressor.
    Most small body shop piston compressors will be air-cooled and have an allowable duty cycle of 60 to 70%. They are therefore often oversized and will operate over a wide pressure band to allow the compressor to shut down frequently and cool off because of the relatively high operating temperatures (often 150 – 200oC).
    In contrast, rotary vane and screw compressors have closed circuit, thermostatically controlled cooling systems which allows 100% duty cycle, with operating temperatures of only 75 – 95oC.This is important to consider as the higher the compressed air temperature, the more moisture is carried in vapour form through the system. And, generally speaking, every 7oC decrease in temperature cuts moisture vapour in half, making it easier to remove moisture from your system.
  5. Consider the long-term – performance, reliability and maintenance; the long-term performance, reliability and associated maintenance requirements of the compressor are also important considerations.
    It is worth remembering that different compressor types have different maintenance and service requirement.

Want to learn more about how each component of a compressed air system can impact the overall energy efficiency and air quality produced? Want more tips on how to ensure your compressed air system runs reliably and efficiently? Click here to download our latest whitepaper – ‘Producing high quality and energy efficient compressed air in the automotive aftermarket sector’.

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