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Detecting Air Leaks

Using ultrasonic technologies to test for air leaks can save textile manufacturers thousands of dollars in waste air and energy.

Handheld instruments such as U.E. Systems' Ultraprobe can be used to detect air leaks in compressed air pipelines.Detecting Air Leaks Using ultrasonic technologies to test for air leaks can save textile manufacturers thousands of dollars in wasted air and energy.It is hardly surprising that the industry that uses the most compressed air in its manufacturing processes is also the one most likely to waste air. What is surprising, however, is how often the waste goes undetected especially when air leaks can easily be detected with ultrasonic technology and the exact cost of the waste can be measured, according to Alan Urwick, director, Anovotek Energy, Clinton, S.C.Anovotek Energy provides consulting services and energy audits for industrial manufacturers. For the last few years, the companys focus has been primarily on the textile industry. Using an industry standard to calculate the loss, Urwick found that a plant that spends more than a million dollars a year on compressed air can lose anywhere from $75,000 to $100,000 in wasted air through leaks if it does not have a leak management program. Urwick based these figures on the energy standard number for the cost of compressed air 19 cents per 1,000 cubic feet, 4 cents per kilowatt-hour of electricity. Using Ultrasound To Find The LeaksSince the advent of air-jet technology in yarn and fabric formation, the textile industry has become the largest user of compressed air. According to Urwick, most companies have several powerful compressors that deliver thousands of cubic feet of air per minute to the manufacturing processes including ancillary processes such as static pneumatic functions. In some fabric formation processes, air does the work: A stream of compressed air carries the yarn across the air-jet machine that weaves the fabric. In air-jet spinning, two nozzles of air positioned in just the right way twist the fibers to make the yarn. To find air leaks, Urwick and his team rely on ultrasonics to pick up sounds that the human ear cannot. Pressure and vacuum leaks produce a turbulent flow, which has strong ultrasonic components, Urwick explained. And leaks can be located more easily while the system is under pressure.When using a handheld ultrasonic instrument such as the Ultraprobe, manufactured by U.E. Systems Inc., Elmsford, N.Y. the inspector puts on headphones and listens for the telltale sounds of air leaks by waving the instrument around like a wand and pointing it towards pipes and fittings. The instrument picks up leaks close by and as far as 50 feet away.We begin the inspection by creating a series of zones to prevent the possibility of overlooking a section and missing some leaks, Urwick explained. We dont look at the places where air is being supplied to the process or at the point where its being used, because air is expected to leak there. Instead, we go to the regulators, the filters and the solenoids that activate the machines. The method for detecting leaks with ultrasonics is straightforward. An inspector scans the lines, listening for the distinct rushing sounds that signal compressed air leaks. Continuously adjusting the instruments sensitivity/volume control, he follows the sound until the loudest point is heard. Since ultrasound is a short wave signal, an inspector can discriminate between irrelevant background noises and the actual leak signal. A rubber focusing probe is then attached to the instrument, narrowing the area of reception to shield against competing ultrasounds. This helps to isolate and pinpoint the exact location of small leaks. Throughout the inspection procedure, close attention is paid to problems such as loud leaks that can be spotted and tagged without the aid of an ultrasonic detector. Even with ultrasonics, the human element plays a role. Urwick and his team have developed experienced ears over time, which help them determine the size of a leak. Draining The BudgetUndetected leaks can be an unnecessary drain on a companys operating budget, and without ultrasonics technology, testing would be virtually impossible, according to Urwick. With as many as 400 machines, each with 10 to 15 connections, using the sudsy bubble test would be a tedious and time-consuming job. Urwick said. In the past, technicians would walk through the manufacturing rooms on a Sunday when the plant was closed, relying on the human ear to spot leaks. Unfortunately, this is not a very effective method, Urwick said, as most leaks occur only when machines are running. According to Urwick, a typical facility with 300 weaving machines and 40 to 60 spinning frames can require two people eight to 10 hours to conduct an ultrasonic leak survey. Leak checking takes this long because it is extremely comprehensive, and inspectors have to open the panels on every machine, Urwick explained. Once the survey is completed, inspectors record their data and write a very detailed list of where the leaks are, their sizes, and what they are costing the company each month. The report is sent to the appropriate department for repairs. It is not unreasonable to expect that most facilities can cut down 5 to 10 percent of their compressed air costs simply by implementing a leak detection and repair program, Urwick said.In addition to locating leaks, Anovotek Energy uses ultrasonics to listen to and evaluate the function of steam traps, he added. We have also used ultrasound to monitor motor bearings to learn if they are performing as they should. However, it is as a leak detector that we find ultrasonics technology most effective. For many companies, compressed air has become as essential a utility as electricity or water. Urwick concluded, When you can measure your air loss exactly, it makes a very powerful case for leak detection with ultrasonics. Editors Note: Alan S. Bandes is vice president, marketing, U.E. Systems Inc.

December 2003