Up Time Magazine - February/March 2009 - (Page 51) The True Cost of Compressed Air ENERGY CAPITAL COSTS 75% 13% INSTALLATION MAINTENANCE 12% Figure 1 - The True Cost of Compressed Air system goes to your electricity provider. The other 25% is accounted for by capital costs and ongoing maintenance. • On average, only 43% of compressed air produced gets used to satisfy real demand. • On average, 34% of compressed air produced is wasted to leaks. • The remainder is consumed by wasteful applications and artificial demand. Reducing energy consumption starts with getting your system leakage under control, but should include more than just ultrasonic leak detection. To get a handle on the total opportunity represented by a greener compressed air system, a plant should hire a consultant to conduct a compressed air audit. A consultant examines the entire system, which is broken down as Supply, Distribution, and Demand. The auditor looks at your system objectively and will recommend improvements that, when implemented, will see more SCFM flowing to demand, and a positive impact to bottom line. Partnering with a quality compressed air auditor is a definitive step toward sustainability. nents are audible to the human ear, but masked by the noise of the plant. Figure 3 - Using a flexible sensor to find a compressed air The high frequency sound leak on an instrument air line. components (ultrasonic) are inaudible to the huLeaks can be detected from as close as an man ear, but are detected above the noise of inch or two, or as far away as fifty feet or the plant. Perhaps most important in our ul- more. The distance of detection depends trasonic search for leaks is the directional na- on two factors: the energy of the turbulent ture of ultrasound. This gives inspectors the flow, and the type of sensor used. The turbuability to hear leaks while the plant is operat- lent energy is dictated by the pressure of the ing, and to pinpoint their location quickly so system and the size or shape of the orifice they can be tagged or fixed. (see Figure 2). Lower pressures will produce Compressed Air Audits Paul Edwards, a principle with Compressed Air Consultants, USA of Charlotte, NC is a compressed air auditor for whom I have a great deal of respect. He recently wrote, “Leaks are an important aspect of compressed air improvement projects and a good study documents the leaks without focusing on them… …The real value in ultrasonic detection is in increasing the speed at which leaks can be located and tagged.” Edwards sees ultrasonic leak detection as a speedy alternative to listening with the unaided ear, or even using water and soap mixtures to look for bubbles. The United States Department of Energy (DOE) says “The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize high frequency hissing sounds associated with air leaks. These portable units are very easy to use.” The main point here is that leaks create a high frequency sound which can be difficult to hear, and to pinpoint, without the aid of an ultrasound detector. Leaks produce turbulence when air flows from the high pressure side to the low pressure side. It is this turbulent flow, which we associate with the characteristic hissing sound of a leak, which generates noises with both low and high frequency sound compoFigure 2 - Air Turbulence is determined by the size and shape of the leak and by air flow. nents. The low frequency sound compo- lower turbulent flow, but smaller orifice size will restrict flow and can actually increase turbulence. Think of a garden hose and what happens when you restrict the flow of water with your thumb. Less water flows from the hose, but with greater force. Likewise in an air line, a smaller orifice may mean less air, but more turbulence. The leak may sound louder in the ultrasound detector’s headset, but in fact the loss from that leak may not be much. To accommodate both close up and far away leaks, ultrasonic detector manufacturers produce different sensors for different situations. Flexible wand sensors are used for near inspections and tight access areas while parabolic sensors with laser sights are used to pinpoint leaks in overhead piping without the need for ladders. The Anheuser-Busch Story One forward thinking industrial leader chose better economical times than today to ensure their sustainability. AnheuserBusch is one of the world’s largest brewers, operating 14 breweries, 12 in the United States and two overseas. In business since 1852, there is more than 150 years of brewing tradition in their keg, making them a true American success story. Anheuser-Busch did not get where www.uptimemagazine.com 51 http://www.uptimemagazine.com
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