Top 10 tips on working with compressed air 08 May 2012

Compressed air users wanting to use their utilities efficiently, cost-effectively and safely are being advised consider 10 key factors.

Andy Jones, general manager of rotary vane compressor manufacturer Mattei, has committed his experience to paper, with the following:

First, understand electrical consumption: some plants might have a misconception that compressed air is free, once they have invested in the equipment, he observes.

"In reality, the initial purchase actually makes up a very small part of the total lifetime costs of a compressor. Te main cost will always be the energy required to produce the compressed air," states Jones.

"The electricity consumed during operation over a five-year period accounts for around 75% of the total cost of ownership – including the initial capital outlay for the compressor."

Second, he says, that being the case, plant users should regularly assess the system. "It's essential for businesses to understand how much compressed air they use, how much it costs them and if the compressors are appropriate for their production processes," he states. "But it's likely the vast majority don't."

For him, the best way to assess a compressed air system is through data logging, or a more detailed energy audit.

"The forthcoming ISO 110011 standard, Compressed air – Energy efficiency – Assessment [due to be implemented in 2013], will hopefully encourage end users to assess their compressed air systems and take actions to reduce their energy use," he says. "It should also standardise the energy audits offered by compressed air companies."

Third, he advises, check whether air demands are fixed or variable. "Some companies are using variable speed compressors when fixed speed machines would be more appropriate – and vice versa," explains Jones.

"Variable speed compressors will only save energy if there are peaks and troughs in the demand for air, and if these variations fall within the efficient working band of the compressor. Again, data logging can reveal which type of compressor is most appropriate."

Fourth, decide what air quality is needed or appropriate for the plant duty: "In recent years, we have seen an increase in demand for oil-free' compressors to produce oil-free compressed air.

"Although there is often a legitimate reason for this request, before investing in costly equipment we would urge purchasers to assess the purity of air required and specify it, using ISO 8573-1:2010 to see if oil-free air is needed. And if it is, if class one rather than class zero would be sufficient."

And Jones continues: "It must be remembered that, despite its name, Class Zero doesn't mean zero contamination. In reality, Class Zero simply has to have less contamination in a cubic metre of air than class one does, with the levels actually being agreed by the end user and compressor manufacturer.

"It's also important to note that oil-free air can still be delivered through an oil-lubricated compressor, providing there is an adequate level of filtration."

The bottom line, says Jones, is that the more stringent the purity, the higher the cost to achieve it. "So it's also important to consider whether or not the entire system requires the highest purity or just a particular area, which could then be served by point of use air treatment or a dedicated smaller compressor."

Jones' remaining five points: ensure the compressor is installed and sited correctly; check noise levels; regularly check for leaks; undertake regular services and maintenance; always use compressed air safely; and recover heat where possible and appropriate.

On the latter point, Jones remarks: "Compressors generate a lot of heat, and in some installations this can be recovered and put to good use in the production process, for water heating, for example, or – although not as efficient – local space heating."

Brian Tinham

Related Companies
Mattei Compressors Ltd

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