According to Carbon Trust figures, the average compressed air system wastes 30 per cent of the air produced, meaning than a third of the energy drawn by the compressor is wasted. Over recent years, compressor manufacturers have promoted the messages that measures such as the use of high-efficiency motors, variable speed drives and controls, the optimal choice of compressor and matching output to demand, will deliver compressor efficiency and energy savings. While many users have taken this message on board and reviewed how they produce air, far fewer have addressed the question of the energy wastage caused by poor system maintenance. In fact, maintenance is often regarded as a completely separate issue and concentrates purely on the on-going performance of the compressor itself.

However, in virtually every compressed air installation, wastage through leaks in the delivery system account for potentially massive energy costs. Because leaks are invisible and generally cause no damage, their existence is easily overlooked, even though they can impact on the performance of the system. The fact is that even small pressure losses can significantly reduce the efficiency of tools and machinery, which will have direct consequences on production efficiency.

Reducing leaks is the single most important energy saving measure for a compressed air system and is applicable to almost all systems. Considering the hidden costs of leaks in a compressed air system can deliver a wake-up call. Mattei proved this recently at Maintec with a practical demonstration on the BCAS stand showing that with the average level of leaks in its delivery system, a 1.5kw compressor running 24/7 would waste £500 a year in energy. Not a huge amount with a compressor of that size, but in a system generating 50m³/min of air with a 30 per cent leakage rate, the wastage figure becomes £60,000 per annum.

In Compressed Air Systems in the EU, a study supported by the European Union, Germany’s Fraunhofer Institute considered the various ways in which the European compressor population could be improved to help meet the CO reduction requirements of the Kyoto Protocol. The study identified the different ways of addressing compressor systems that could deliver energy and cost savings: system design accounted for savings of 12 per cent, motor controls 10 per cent, heat recovery 10 per cent and a combination of other measures 26 per cent. With leak detection, the figure rose to savings of 42 per cent.

One of the reasons that leakages are accepted as a fact of life in many systems is the perceived difficulty in managing them. In-house leakage management programmes take time, require personnel with the right training and equipment and they often fail because of the lack of these. Insufficient time is given to them due to production pressures and the need to carry out the required procedures outside of production hours. 

The alternative is to outsource leak detection. By using specialist ultra-sonic ‘DND’ acoustic equipment, a service provider such as Mattei, can carry out non-intrusive checks during production hours, delivering much faster and more accurate results than are likely to be achieved by an-in house maintenance team. On average the cost of a survey is less than 10 per cent of the overall leakage costs. Once the initial audit is complete and leaks identified, Mattei devises a tailored corrective maintenance repair programme, for which it provides detailed financial justification. Typically the cost of the programme is generally less than 10 per cent of those leakage costs. In terms of financial payback, investment in a leakage detection survey and corrective programme is generally recouped in between three to six months – this compares with an average of three years payback for a system re-design. The savings are also long-term, although Mattei suggests the system is checked for leaks at least on an annual basis.

Because the impact of compressed air system leakages are not always immediately apparent, the decision to investigate them too often takes a back seat with other capital expenditure taking priority in the budget. However, for every month that no action is taken, the compressor system – no matter how energy efficient the compressor itself – can be a hidden drain on financial resources. Air may be invisible, but it is not free, so allowing leaks to stay in the system is literally the equivalent of throwing money away.