Standardising energy audits for compressed air

10 June, 2016

In today’s competitive world with increasing pressure on margins, any activity that can reduce your bottom line has to be worth exploring. One area that demands attention is compressed air systems, which can cost you up to 30 per cent of your annual electricity bill. Can you honestly say what the annual running costs of your system are? How much energy does it waste through leakage? Or whether the plant or equipment is fit for purpose?

In the past assessments of compressed air systems were either not done at all, or relied on non-standardised procedures and tests. The problem is that some of these could be unsuitable, inaccurate, too expensive and ultimately non-productive.

Roles and responsibilities

With the introduction of ESOS, BCAS became aware of the need for a process-specific standard for assessing such systems. After consulting with its members, BS ISO 11011 was produced and published and was then adopted as the International Standard ISO 11011. The standard identifies the roles and responsibilities of those involved in the assessment and it considers compressed air systems as three functional subsystems:

• Supply, which includes the conversion of the primary energy source to compressed air energy.

• Transmission, which includes the movement of compressed air energy from where it is generated to where it is used.

• Demand, which includes the total of all compressed air consumers for both end use applications and compressed air waste.

This approach provides a structured framework for data analysis, reporting and documenting any findings. It identifies the estimated energy savings as a result of the assessment and thus a clear means of reducing your costs.

It also identifies the methodologies used for such an assessment, which might include: observation and research, spot check measurements and/or data logging – including dynamic and trend.

This accounts for each compressed air system being different in terms of age, its location and use, so the requirements for assessment will vary. It also means that you can use the most appropriate methodology, either in part or full. So, for example, it may not be necessary to carry out extensive data logging if simple observations and existing data are enough to complete your assessment.

Regardless of the methodologies used, taking a whole system approach ensures that you get the maximum benefit from the assessment process.

Scope of a full assessment

Typically this process would start with you deciding the scope of a full assessment of the system. This could include compressed air use, production functions, poor performance, waste, supply, demand balance, energy use, total compressed air demand and utility bills. Once you have defined the scope, you can begin to collect and record the data.

After assessing this data, you can then decide what actions will help you save the most money. For example you can determine the leakage rate, which in some cases can be in excess of 40 per cent and be costing you serious money – a leak of just 3mm could cost you more than £700 a year. The assessment will also help you see if you are using the right compressor and/or air receiver, if the system pressure is unnecessarily high and whether you are over-treating your air.

From this you can then take targeted action, which might include repairing leaks and establishing a leak management programme, upgrading equipment, improving your process control and the use of variable speed controls.

Assessment framework

In short, ISO 11011 provides you with a framework to assess where and how you can make improvements and save energy for your compressed air system, even if you don’t have to comply with ESOS requirements.

BCAS offers a day’s introduction to ISO 11011 and several of its members can offer you a third party assessment service to meet the requirements of ISO 11011.

For details of the day’s introduction and BCAS members visit www.bcas.org.uk