Up Time Magazine- April/May 2008 - (Page 54) ultrasound upload Save Money, Lower Noise Levels Performing a Compressed Air Audit by Jim Hall ow noisy is your plant? Hearing loss depends upon how loud noise is and how long you are exposed to it. Noise greater than 85 dB can damage hearing if the exposure is long enough. Do you use your iPod at work? iPod’s are being linked more and more to an increase in hearing loss among America’s youth. Have you ever walked up next to someone using earphones or headphones and noticed that you could hear the songs they’re listening to from several feet away? Is so, their device is almost certainly louder than 85 dB. Someone better start saving for a hearing-aid! Just recently my crew and I finished an air leak audit in a plant. Imagine 151 leaks found in three days? Some of these leaks were very obvious, and some were not, but one particular leak chimed in at 78 dB on the ultrasonic instrument. Audibly, it was ear piercing. Everyone that heard the leak always suspected that the leak was from the compressor below the tube that was leaking. The actual leak was a 3/8th inch tube leak (.250ID, see Figure 1). The tube had splintered almost into two pieces. Imagine a 90 psi leak whistling all day in a high foot traffic area certainly someone had to be agitated by the noise. Granted this leak was atop a mezzanine, but it was still accessible by a wall mounted ladder. Had anyone checked it out, they could have fixed it, just as we had during our survey, in 5 minutes or less. It’s not that we fix leaks, but why not have the plant representative walking around with us quickly put a repair coupling on it? We still document it as a leak, we just would not write it up to repair. Let’s see 90 psig, leaking from a well rounded hole, ¼” opening…that’s roughly $5,622.00 a year! But there actually happened to be three tube leaks in the mezzanine area atop the office. Wow, roughly $17k whistling in the wind. An ultrasonic receiver was not even needed to find these leaks, just the willingness to crawl around on your knees for a few minutes to locate it. I remember an energy consultant from several years ago that would go into a plant and immediately scan for high noise locations using a decibel meter. After scanning and recording the high noise areas, he would then locate the leaks. After plant personnel repaired the leaks he would then return and rescan using the decibel meter again. It was not unusual to have a difference of 20-30 dB’s in the high noise locations. Today, the SDT 170 M and MD ultrasonic receivers actually allow the end-user to plug in an “A” weighted decibel meter. It even allows the end-user to record the dB meter findings within the internal database. This same plant had a 3/4” compressed air line supply valve rupture after the condensate in the line froze (see Figure 2). This valve had apparently been leaking for close to two weeks. It had literally split open from side to side to form roughly an 1/8” opening and a jagged 1.5” long split. This leak did not require an ultrasound receiver to find it either. As soon as the valve was closed out of the loop the compressor immediately idled back. H Figure 2 - 3/4” Supply valve rupture. Figure 1 - Mezzanine tube leak, located and repaired. The other 149 leaks were made up of leaks like mixing valves, stainless control air supply lines that were bent 54 april/may 2008
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