While this may be a surprise to some, the facts behind the true cost of air power can be even more surprising.

According to Dino Alessio, marketing manager with leading compressor technology group, Champion Compressors, pneumatic power is often commonly--and incorrectly--regarded as ‘free’ or ‘inexpensive’. “Actually, pneumatic power--while undeniably vital from a tool and machine design perspective--is relatively costly. Due to waste heat generated in the compression process, the end-to-end efficiency of a compressed air driven system is only around 10 per cent.” 

Total life cycle costs
The energy cost of a compressor, when amortised over its entire life, can also be surprising. “The capital cost of a air compressor can be as small as five per cent of the total life cycle cost, yet the cost of energy consumed can be as high as 85 per cent!” he says. This has encouraged operations managers, designers and plant owners to move away from the legacy approach of over-sizing compressors.

‘Operational energy savings’ result from improvements to existing air system operations such as reducing leakage, cutting overpressure and improving filter and receiver drain maintenance. The ‘design energy savings’, on the other hand, stem from more accurately matching the actual design of the compressor system to the meet the load requirements.

Enter the EMU
The essential tool necessary to assess compressed air system performance and potential improvements is the air audit. “It’s not possible to simply look at a compressor at any point in time and completely diagnose how it is performing,” Alessio says. “The operation of the air compressor changes in sympathy with the air demand. This is why Champion recommends monitoring air compressors over a seven-day cycle. It gives us a complete performance picture.”

“The Champion EMU’s event logger strategy is far more accurate, and produces plots that are far easier for regular site technicians to diagnose. No complex interpretation or translation is required--what you see on the plot is how the compressor is performing!” says Alessio.

Operational savings
The plant operates only a day shift and a scaled-down afternoon shift over five days, yet the compressor’s off-shift base-load dropped to only around 30 to 40 per cent of its peak day load, indicating significant leakage. “This is fairly typical in Australian industry,” Alessio says. “Air leakage is very costly--leakage equivalent to a 5-mm diameter hole in an air system results in additional power costs of around $4000 per annum!”

Design savings
The EMU audit can also pick up design faults or mismatches between the air compressor and the load. Often, it can prove cost-beneficial to completely replace aging single-stage on-load/off-load compressors with variable output compressor, or a multi-stage compressor with sequence controller.

Champion’s Victorian customer support consultant, Mark James cites a case-in-point--a major food processing plant in Geelong. “They were operating two single-stage 200 CFM on-load/off-load compressor, and running them together,” James says. “We discovered that by upgrading to a new Champion variable output compressor--where modulation of the airend’s spiral output valve allows the output to precisely match the demand--we could save around 17 per cent of total air compressor energy requirement. These energy savings provided particularly fast payback on the new unit, and actually justified upgrading to a larger-capacity unit to meet the plant’s growing air demands.”

Alessio points out that timely maintenance and using correct spare parts is also essential in minimising energy costs, “but this really needs to be complemented with regular air audits”. These can either be provided by Champion’s nationwide service team, or by any competent in-house service team using the Champion EMU.