Up Time Magazine - December 2008/January 2009 - (Page 52) ultrasound upload Expanding Your Senses The Synergy of Ultrasound and Vibration Analysis by Leane Harris oday’s airborne ultrasound is a far more versatile technology than most people think. We can use ultrasound, together with vibration analysis and infrared thermography, to deepen our understanding of our machinery’s condition. This article, which touches upon the use of airborne ultrasound and vibration, is the second of a three part series, in which we look at ultrasound, ultrasound/vibration and ultrasound/infrared. Similar beginnings, but different outcomes, and completely different roles in the greater scheme of things We see these facets play out in many areas of everyday life. It happens in predictive maintenance as well, and it may surprise many of you to discover one scenario. Two technologies springing from similar beginnings, but moving into very different everyday uses in plants worldwide. In predictive maintenance, we are blessed with technologies that help us transcend our senses’ limitations. They allow us to see, hear, and feel events that give us the information about our machinery which we need in order to make informed decisions. Infrared Technology allows us to see the spectrum of light that is invisible to our eyes. This capability becomes very useful if we want to know if there is a temperature variance between different objects or of the same object at different times. Airborne Ultrasound extends our ability to hear sound waves that are above our hearing capability. There are many sources of high frequency sound waves: turbulent flow of material passing through a restricted opening is one, friction energy generated from the rolling elements of a bearing as it rotates inside the housing during operation is another, ionization energy also produces high frequency sound waves, and impact energy generates high frequency sound waves. Do the descriptions above give you some insights as to which areas in your plant may possibly have high frequency sound waves? Vibration Analysis extends our sense of touch by a few leaps. It detects and measures vibration movements in machineries that are too small for us to feel, then allows us to identify the sources of these vibrations, which are then categorized according to severity. Informed decisions can then be made from there. We have made a few leaps from putting a coin on top of a motor to see how badly it is vibrating. Of course, with the coin, you’ll see the coin vibrate, but you can’t measure its vibration. Figure 1 - Ultrasonic PdM Inpsector performing Vibration Analysis. T Oil Analysis gives us the ability to look at the chemical composition of used oil in the machines to see if it is normal or not. Any unacceptable deviation from the norm can give indications of problems. Airborne Ultrasound has several applications in your plant. Based on the explanation above, this technology can be useful in locating air leaks (Turbulent Flow), checking for passing valves or steam traps (Turbulent Flow), managing bearing lubrication better (Friction), detecting flow or no flow situations (Turbulent Flow), detecting and locating sources of electrical discharge (Ionization), and in what I Call ultrasound PdM (Friction). For purposes of this article, I’ll narrow the ultrasound discussion to the condition monitoring, or ultrasound PdM, application since that is also the area where machine vibration analysis is used. We’ll talk about when to use each one by itself, and when to combine these two powerful technologies. 52 december/january 2009
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