Efficient Compressed Air Systems

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2 How much does your compressed air cost? One common misconception is that air is free. Air is free or it is until you compress it. However compressed air is an essential resource and is often referred to as the fourth utility after gas, water and electricity.

3 And it s the same with compressed air as with many other things in life! A small cause can have a dramatic affect in both a positive or a negative sense. Upon closer inspection things can be very different to how they appear, in unfavourable conditions compressed air can be very expensive whilst in the right circumstances it can be very economical

4 The aim today is to inform on the small things that will produce this positive affect Savings of over 30% can be achieved with low cost investment. Medium cost investment can recover up to at least 75% of the compressed air generation costs in the correct circumstances.

5 So where s the best place to start? First Measure it to get a benchmark of costs Then estimate the payback period for remedial work Finally improve it if its an acceptable payback

6 Now some big numbers Over 10% of electricity consumed by industry in the UK is used to compress air And Over 40% of these generation costs can be wasted on an unmanaged system

7 Where does it all go?

8 How to calculate how much your compressed air system costs per year Approximate running cost can be calculated as follows Size of motor x cost of electricity x hours per annum Example- Factory runs a 55 kw compressor, pays 10p per kwh and runs 8000 hours per annum Cost = 44, per annum Figure is a guide only as it assumes full load and does not include motor efficiency

9 Data Logging gives best Information

10 Once you have an idea of the running costs you can move on to make the low cost improvements. The place to start is system leakage

11 Leakage The single largest waste of compressed air Leaking gaskets Barrel gaskets

12 An example from a recent report Category Estimated Size of Leak Estimated Loss Per Leak (Ltrs/Sec) at 7 bar Electrical Cost per (kwh) in pence Hours Run Per Annum No. of Leaks Detected Total Loss (Ltrs/Sec ) Estimated Cost 6.7 6,000 Light 0.5mm , Medium 1.5mm , , Heavy 3mm , , Severe 6mm , , Totals , Complete the yellow sections for leakage rate, electrical costs and No of leaks. Leakage flow rates taken from GPG385 Carbon Trust energy efficient compressed air systems

13 All compressed air systems have leaks Typically leakage rates can be up to 40% A realistic target is 5-15% of the air compressors demand In our 55 kw compressor example reducing leakage from 40% to 15% could save up to 11, per annum, a 25% reduction in costs. Leakage the largest single waste of compressed air

14 How do you find the leaks A) Mix up a solution of water and washing up liquid and walk the system applying to fittings and tube, you should be able to see the bubbles. B) While not using any tools or equipment walk the system listening for hissing sounds. C) Use an ultrasonic leak detector, hire or buy it yourself or employ someone to do the work for you. Costs around per day plus repairs

15 What to do once you have found the leaks. Tag all the leaks Grade the leaks on a scale from 1 to 5, this allows you to tackle the worst leaks first Mark on a plan Don t just leave them, Fix them!!! Payback is normally less than 6 months! Compressed air can be dangerous so if you are in any doubt how to proceed contact an expert.

16 Most Leaks are easy to fix. Flexi tubes need replacing Air couplings worn Jubilee clips loose Drain valves dirt on seat Seals on valves and cylinders worn.

17 Air Pressure Reduction Your compressed air system is probably running at pressure levels above those that you actually require. You can obtain more savings by accurately controlling and reducing your air pressure Reducing your pressure by 1 bar in the compressor house will save 6% on generation costs. This would save 2, in our 55kW example

18 Air Pressure Reduction Additionally, the air consumption of most air operated devises reduces in proportion and any remaining leaks leak less as pressure is regulated downwards

19 Switch off when not needed Compressors are often left turned on overnight even when there is no production. This is wasteful because power is being used to feed leaks, even when compressors are idling they can still consume up 70% of their full load current. Switching off when not needed will reduce running hours and associated maintenance costs

20 Switch off when not needed Turn the air off to factory machines when not in use. Switching off only the power to the machine when its not needed may not turn off the air supply, leaks on the machine will still leak and the air use may continue. Valves are available to switch the air off when the power is isolated.

21 Savings so far by low cost investment Leakage Reduction save 25% Pressure Reduction save 6% Energy reduction by these 2 measures alone 31%

22 The Importance of Maintenance Over a 5 year period approximately 75% of the cost of running a compressor is the electricity If maintenance is neglected electricity use increases Postponing or neglecting maintenance does not save money, e.g. when a filter is clogged extra power is needed to overcome the obstruction so pressure is increased, using more energy. Most important for production is that the system is reliable The system will be more reliable with regular maintenence

23 Heat Recovery When you compress air most of the energy used transfers to heat The challenge is to use this waste heat

24 Electrical power Heat Recovery consumption 2% heat dissipated from the compressor unit 4% heat remaining in the compressed air 94% Heat available for space heating, etc.

25 Space Heating Motor-driven louvres. interlocked, thermostatically controlled Hot air for space heating requirements Hot air exhausted to the open in summer Incoming fresh air

26 Space Heating In our 55 Kw compressor example, if we recovered 75% of the waste heat during 6 winter months this would equate to 110,000 kwh per annum Cost this against your heating gas or oil for notes Additionally 165,000 kwh = annual carbon reduction of tonnes Co2 pa

27 Hot Water from your compressor hot oil cold water Hot water oil with heat caused by compression

28 Get the clip board out

29 Check List!!! Estimate annual running costs Estimate leakage costs, repair costs and fix leaks Reduce operating pressure to lowest level Check if system pressurised hours can be reduced Turn air supply off to machines when not in use Investigate if the waste heat from the compressors can be utalised

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