A waste of air

Compressed air leaks are all too commonplace in today's industries, but they can eat into a company's operating profits, as David Share explains in this look at how easy it is to reduce leakage and save money when using this ubiquitous plant utility.

Today, compressed air is used in every sector of industry. But the fact that it is so widely used has led many to think that it is cheap to produce. The truth, however, is that it never has been.

Compressed air is produced using electricity - to the extent that its generation is equivalent to about 10% of industry's total electricity consumption, rising to 30% in some sectors. These are weighty figures and highlight why companies have compelling reasons to investigate the potential for energy saving.

One of the most fundamental ways of improving the efficiency of any compressed air installation is to reduce leakage. Research has revealed that leakage rates can exceed 50% of site consumption across many industries. But there are some general guidelines that can help reduce leaks:

1. Don't generate air at a higher pressure than necessary - the higher the pressure, the more air will leak through a hole.

2. Don't keep the whole system pressurised during non-productive hours just because a few items of machinery might need a constant supply of compressed air.

3. Do isolate parts of the system that require air at different times. Isolation valves can be operated manually or automatically using simple control devices.

4. Do take advantage of the fact that under the Pressure Systems and Transportable Gas Containers Regulations, you must inspect your compressed air system regularly. These inspections are an ideal opportunity to find and repair leaks.

The simplest and most cost-effective way of checking for leaks is to use the time-honoured soapy water method. However, this is messy and has to be performed directly on the equipment or pipework being tested — a problem when the leaks might be high up in factory ceilings. A better way is to use an ultrasonic detector. These can detect leaks from over 50ft away, even in areas of plant where noise is a problem.

But where do you start looking for leaks? The main artery for delivering compressed air is the ring main system. In many factories this pipework is old and a prime source of leaks. A check of the main will not only improve the system but also improve safety.

Another potential problem area is where connections to a point of use are made using snap connectors with flexible hoses. Sometimes several are used together, forming a manifold arrangement, which can leak due to worn connectors and poorly jointed pipework. Leaks can also occur from the flexible hoses themselves due to any number of reasons.

If the compressed air system uses automatic drain traps, these should be of the 'zero loss' type, and should be checked to see whether they are working correctly.

Filters are an indispensable part of any system, but they too can be the source of large leaks. Potential problems are drainage points in the filter bowls, including poorly sealing automatic drains, badly fitted bowls and bowls that have been contaminated by synthetic compressor lubricant.

David Share is with fluid power specialist ASCO Joucamatic UK.