Ultrasonic Predictive Maintenance

A while back my daughter was mowing the grass. She drove the mower up to me and said that it started sounding different. I checked it out and sure enough the belt had flipped over and was riding on its flat side rather than its V side.

Back before all the electronic monitors on our autos, savvy owners could predict developing problems just by changes in the usual sounds. Ultra Sonic Predictive maintenance is simply that. It is an inspection method by which sounds emitted from equipment are compared against an established sound benchmark of a healthy system.

The advantages of ultra sonic inspection

  • Does not require expensive complicated equipment
  • Can be used in noisy environments
  • Systems do not have to be shut down to inspect
  • Provides early warning indicators
  • Provides important data for, trend analysis, need to watch lists, and an interface with analysis software

EXAIR has an Ultra Sonic Leak Detector (ULD) which for the most part is promoted for detecting compressed air leaks. Since it is a sound detector though, it lends itself well to ultra sonic predictive maintenance. Here are a few examples.

    Bearing Problems
    Ultrasonic inspection and monitoring of bearings is by far the most reliable method for detecting early bearing failure and conditions such as lack of lubrication. Bearing analysis requires prior knowledge of the sound that a “healthy” bearing makes. A log that notes the date, location of the test area, sensitivity setting, and LED display panel reading should be available for regular inspection of bearings. A bearing will emit ultrasonic sound even when it is “healthy”. When the bearing system begins to deteriorate, the ultrasonic sound will change long before problems are detectable through any heat and vibration monitoring systems.
    Air brakes
    Air leaks in trucks can be a source of many problems. This is particularly true when a leak is small enough that it cannot be heard over the sound of a running engine, but is large enough to empty the air tanks overnight. By tracing the air supply lines and all of its couplings, the ULD can accurately isolate a leak in a fraction of the time normally needed.
    Electrical
    In electrical applications, the prior knowledge of the sound a healthy circuit makes is vital to make useful comparisons. Expensive equipment is not needed to check the conductivity of insulators when the ULD is used. In areas that are close to high voltage insulators (such as switch yards), the tubular extension and adapter is the appropriate tool to use with the ULD. This accessory is particularly useful when checking insulators because the circuit does not need to be interrupted
    Cracked Rubber V-belts
    Any crack in a moving rubber belt will emit ultrasound when the crack passes by the pulley.  Prior knowledge of the sound a healthy belt will give you a benchmark to compare against.
    Dry Fire Sprinkler Systems
    In a dry system air pressure holds back the flow of water. Small leaks in the system requires compressed air to be added. Simple enough but leaks tend to grow. Enough leakage could overwhelm the compressor capacity resulting in all the sprinklers activating resulting in massive water damage.In a plant where loud noise levels often exist, it is very difficult to locate leaks by merely listening for them. Most plant noises are in the normal audio range while air escaping from a small orifice will be in the ultrasonic range. The ULD or will ignore the background noise and detect only the ultrasonic sounds that are generated.For more information feel free to contact me or one of the application engineers here at EXAIR.

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