Often considered the fourth utility, compressed air is critical to many manufacturing, engineering and processing operations. It is also usually one of the most expensive utilities to a business. For example a 55 kW compressor running for two shifts per day would cost $924 per week to run!
Operating an efficient compressed air system is therefore vital in keeping all of the associated costs to a minimum and; identifying, repairing and managing air leaks is one area where significant and long term savings could be realised.
Unfortunately, whether you are operating a high tech compressed air system with the most advanced piping or not, leaks will occur!
The real cost of compressed air leaks
Based on a compressor running 24/7 and a power cost of 15 cents/kW/hr, just one leak with a 2 mm diameter could translate into an annual cost to your business of $2,364. As an isolated leak that may not sound a lot, but imagine the accumulative cost that a number of leaks could add up to.
Increasing the system pressure to deal with leaks is considered very bad practice. If the system pressure was increased by 0.15 bar(g) this would equate to around a 1% increase in kW power adsorbed. Therefore the higher the system pressure the more expensive the compressed air is to produce.
Finally, if the compressor has to work harder and in turn has to run longer, this will mean that the requirement for maintenance will increase - increasing the associated servicing costs.
How to reduce the impact of compressed air leaks
So, how can you reduce the impact to your business? Regular leak detection is the key!
First you need to identify where the leaks are within your compressed air system. Common places where compressed air leaks may occur would include; on pipes or pipe joints, threaded fittings which have not been properly sealed, pressure regulators as well as on hoses and couplings.
You could start the leak detection process with a very basic in-house assessment. Some leaks may be audible so by simply walking around the site you may be able to hear hissing sounds. More often than not this will signify an air leak. Alternatively, you could brush soapy water over suspected leaks. If there is a leak, bubbling will result. However, both of these methods are time consuming and inconclusive.
The human ear will not be able to pick up all of the leaks which means that you could still be missing a number of them. In addition, whilst you may be able to identify where some leaks exist, you will not be able to identify the volume of these leaks and this will be critical in assessing the severity of leaks and therefore the order in which they should be repaired. Moreover, leaks are a constant issue that need addressing on a regular basis and this method could become extremely labour intensive in the long run.
The alternative is to employ an ultrasonic leak detector (USLD). This hand held non-invasive device, can be effectively used when the plant is in operation, creating no downtime. By simply pointing the USLD at suspected leaks within the compressed air system, leaks can be precisely pinpointed and - depending on the sophistication of the USLD being used - the volume of the leak can be measured, ready for tagging, prioritising and fixing.
How does it work?
A USLD kit usually consists of a hand held detector and head phones.
The turbulence which is created by compressed air being released into the atmosphere generates ultrasonic sounds which are inaudible to humans. With a USLD the ultrasonic sounds of high pressure leaks are converted into an audible sound which the operator hears in the headphones. In this way leaks within the compressed air system can be quickly and effectively identified.
Once identified it is common to physically mark the leaks with a 'tag'. This will make it easy to locate the leaks when you come to repair them. In addition you can then also record all of the leaks, their location and their severity, allowing you to assign priority to the order in which they are repaired.
Long term savings
It is possible to perform leak detection in-house, if you are prepared to take on the investment cost of purchasing an USLD as well as training and charging a member of your team with this on-going responsibility. The alternative however may be to talk to your compressed air service provider about including ultrasonic leak detection and leak management as part of your on-going maintenance program.
Leaks will reoccur and so it is important that you see leak management as an on-going task in maintaining an energy efficient compressed air system. By implementing a leak management program, by which you make leak detection a regular part of your maintenance program, you will ensure that the energy savings are long term!