Published: 10 November, 2015
While the air around us is free, compressed air used in industry is very expensive. Mark Stone, product manager at Flexion, part of ERIKS UK, explains how to deal with wastage and misuse.
Compressed air is regarded as industry’s fourth utility, along with water, gas and electricity. Like the other three, it is expensive but is too often regarded as a low or no cost item, particularly by machine or plant operators who don’t have to pick up the bill themselves.
This lack of understanding is resulting in significant compressed air losses across all industries. Leakages average 30% of the total amount of compressed air produced, with some sites losing as much as 60% of the total air generated.
The problem is that this produces an even greater demand for compressed air to keep up with the losses. Compressed air is produced by air generators which run on electricity, which means leakage has an enormous impact on both energy efficiency and a company’s CSR goals.
There are a number of issues that industry needs to tackle in regard to its use of compressed air, including inappropriate use, particularly with idle plant and equipment; using higher pressures than necessary; little or no use of energy efficient components and the use of compressed air where other technologies may be more effective.
What is required in most cases is a more systematic approach to compressed air management, which should encompass leak detection and identification of potential cost saving areas, such as shutting some compressors down when not in use or reducing air pressure. For example, reducing air pressure by 1 bar reduces energy consumption by 7%.
Compressed air users should also investigate whether compressed air is the most appropriate option for certain jobs, such as cleaning, drying or ventilation. Another option is to use energy efficient nozzles, which reduces air consumption by at least 50%, but uses the coanda effect to entrain the ambient air to increase the overall flow and volume of the air jet.
However, the first and most obvious step to undertake is a comprehensive audit of the work area, identifying leaks and listing them systematically. Leaks should be physically tagged and a severity attributed to them, which will allow an estimate to be made of the potential savings from remedial work. The wastage estimate can then be compared to the potential capital cost of fixing the leak.
In most cases, fixing the leak is a fairly straightforward case of replacing worn fittings, seals, valves and manifolds or making alterations to the air preparation equipment or introducing new working practices for employees. These cost estimates are a vital part of the process as they offer a clear payback period for the work which, in the majority of cases, can be as little as a few months due to the high cost of compressed air.
The cost estimates for leaks obviously varies greatly based on shift patterns, the cost of electricity and the efficiency of air generation on each site. However, a good rule of thumb, based on current costs and two eight hour shifts, would put the cost of a ‘light’ leak at £100 per year and a severe leak costing many thousands of pounds per annum.
Our recommendation is to effect a first fix where possible, such as remaking joints, replacing fittings, gauges other non-active parts. First fix capability depends on being able to access the equipment safely, which usually requires isolating the mains air supply.
My strong advice is to get in expert help. Detecting leaks is a fairly straightforward matter when you have the right equipment and you know where to look. A survey of a medium sized plant by an experienced team can be achieved in around three hours with the use of an ultrasonic detector that is specifically designed for the task.
Good ultrasonic detectors can identify leaks from up to 50 feet away, even in noisy plant areas and provide a very accurate estimate of the severity of the leak. I would also recommend supplying maintenance personnel, or the repair contractors performing the repair, with photographic evidence of the location of the leak to ensure that those responsible for repairs have a good visual guide to work from.
Compressed air is expensive, but all-too-often it is overlooked when recommendations are made for savings in a production environment. Compressed air management should be a priority because savings from better management and use of compressed air can be considerable and a remarkably fast return on investment for repairs.