Up Time Magazine- June/July 2008

ultrasound upload Is Your Baghouse in Order? Baghouses, Air Ducting and Vacuum Leaks by Jim Hall O ver the past six months I have had numerous conversations with maintenance technicians talking about their experiences in locating vacuum leaks (in-leakage) on baghouses. Typically the baghouse is just the Big Blue Elephant in the room. Everybody knows it’s there, but no one pays any attention to it. Other than the periodic bag changes, these units seldom have any PdM performed on them. Why not? Quite frankly, I don’t know. The enormous amount of energy one baghouse consumes certainly does not need to be supplemented by various leaks in the system. If your plant does not have a baghouse, maybe it has another type of dust collector, possibly a pulverized coal ducting system. Or maybe you’re a food product manufacturer and you use the heat from a boiler across the plant in processing. Wherever you have high speed air rushing through a duct such as those for any of the systems mentioned above, the cubic feet per minute (cfm’s) can be very high. Some air duct systems I Figure 1 - Hopper end of baghouse. Note the blue ﬂange and handle for have seen may run as much as emptying hopper, multiple leak potentials here. 75,000 cfm for the baghouse. And I am sure there are much larger systems out there as well. Leaks Well, here is a better idea. Airborne ultrasound is on these systems could possibly suck the skin right off very effective in areas with high ambient background your hand if you made the mistake of using your hand noise. As I often say, what is noisy to you is not to to locate them. the ultrasonic receiver. Depending upon how many cfm’s your system is rated, you may be able to use just The most common approach to finding leaks on about any ultrasonic receiver available to locate leaks. these ducts is, as one of my friends said, “the railroad Just remember that there are some instruments in the crossing approach, where you stop, look and listen”. marketplace that cannot overcome the background Unfortunately, he, like others, have found that either noise without frequency tuning! Yes, there are spethe background noise is too high to hear the leaks or cific methods you can learn to improve your abilities you simply cannot get close enough to hear, feel or and results in ultrasonic detection. Something as see signs of a leak. Some technicians may even light simple as using a rag or glove on the hand, or placing up a cigarette (of course, only where/when it’s appliyour body between you and competing sounds can cable) and blow smoke around the access plates and improve results. But, without some of the accessories welds. Bad idea! For both your lungs and the environavailable, such as a flexible wand, close focus cone, a ment in which you are working. Others claim to have parabolic horn or parabolic dish, finding these leaks released a smoke bomb or lit a smoke candle to watch can be quite a lengthy process. the smoke as it trails towards the leak on those same access plates and weld seams. Sometimes when scanning for low-level pressure leaks, as well as vacuum leaks (in-leakage), you must 58 june/july 2008

Table of Contents Feed for the Digital Edition of Up Time Magazine- June/July 2008

Up Time Magazine- June/July 2008 Contents Upfront Upclose: The True Cause of Most Machine Failures Information Technology: Finding Future Perfect Lubrication: Building an Oil Analysis Winner Maintenance Management: Hidden Ways to Increase Safety Infrared: Air Barriers Lower Energy Costs, Increase Profits Motor Testing: Efficient Motor Repair, Part Deux Precision Maintenance: Good Maintenance, Smart Maintenance Reliability: Common Errors in Root Cause Analysis Ultrasound: Avoid the Baghouse Blues Vibration: Don't Let Your Sensors Get Eaten Alive Upgrade: Lining It All Up

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