Presentation on theme: "Ultrasound Adam Adgar School of Computing and Technology."— Presentation transcript:
Ultrasound Adam Adgar School of Computing and Technology
Ultrasonic Analysis ► Measures the sonic sound patterns of machines being monitored. ► Airborne ultrasounds (20 kHz – 100 kHz) Cannot penetrate solid surfaces Can penetrate cracks Radiate in a straight line therefore the source is easy to locate Travel a short distance
Ultrasonic Analysis ► Ultrasounds are sound waves that cannot be heard by the unaided ear (> 20 kHz). ► Ultrasounds are detected utilizing an ultrasound scanning device. ► Changes to a component’s ultrasonic signature are easily recognized as the component begin to wear and deteriorate. ► Ultrasound can be a complimentary technology to vibration, thermography and lubrication monitoring.
Instrumentation Operation ► Instruments measure information qualitatively - through noise-isolating headphone quantitatively - via incremental readings on meter display ► Digital instruments provide on-board data storage for data logging and for viewing baseline data. ► On-board sound recording for spectral analysis ► Converts ultrasounds sensed by the instrument into the audible range where users can hear and recognize them through headphones. (Heterodyning)
Instrumentation Operation ► Technique focuses on high frequency (~ 100 kHz) component of the elastic waves being generated by operating machinery ► Resulting signal is very strongly influenced by fault processes ► Has a much reduced sensitivity to the effects of normal running components. i.e. good machines are much quieter at 100 kHz yet machine faults resulting in deteriorating contacting surface give very loud signals ► Most systems can be connected to a vibration data collector Similar signal processing requirements. Enveloping can be used
Uses ► Leak detection in pressure and vacuum systems boilers heat exchangers hydraulic systems condensers chillers fuel cells tanks, pipes, hatches, ► bearing inspection lubrication ► gears/gearboxes ► pump cavitation ► motors ► steam traps ► valve seat testing ► testing for arcing, corona in electrical apparatus ► compressor valve analysis
What’s Needed ► Ultrasound scanning device. Handheld device usually with two modes: Scanning Contact ► Training ► Limited to applications which produce measurable ultrasounds.
Advantages and Pay Backs ► Moderate cost. ► Simple to use. ► Savings potential is great. Air leak identification Steam trap leaks ($2000 per year can be lost from a single trap). ► Pay back in one year or less. ► Measurements are directional and faults easily located ► Provide early warning of impending mechanical failure ► Instruments can be used in loud, noisy environments ► Supports and enhances other CM technologies
Case Study: Leak Detection ► Leaking fluid (liquid or gas) moves from a zone of high pressure to a zone of low pressure. ► As it passes through the leak site, turbulent flow is generated which has strong ultrasonic components. ► These components can be ‘heard’ (measured) with specialized detection equipment. ► Large leaks and background noise can ‘overwhelm’ many detectors and require continual adjustments to find the source. Shielding of the detector is a useful tool to eliminate background noise. ► Vacuum leaks can be differentiated from pressure leaks.
Inspection ► Inspection method depends on the type of valve or steam trap. ► Hence must know how a specific trap or valve works. ► Procedure for leakage or blockage test: touch upstream of the valve/trap with contact waveguide probe reduce sensitivity of the instrument until the meter/display panel reads about 50% of scale. if the instrument has frequency tuning, you may also use this feature to hear the trap or valve sound quality more clearly. tune the frequency until the sound you would expect to hear becomes clear. Touch downstream of the valve/trap and compare intensity levels. if the sound is louder down stream, the fluid is passing through. if the sound level is low, the valve or trap is closed. When recording decibel levels and trending make all settings on the ultrasonic instrument repeatable. Air leak Steam leak Steam Trap
Ultrasonic Acoustics Test Point A = 50 db Test Point B = 40 db Test Point C = 17 db Test Point D = 8 db ► Example of a Good Valve
Summary ► Ultrasonic Acoustics provides accurate detection of fluid leaks ► Often very effective when combined with other techniques. ► Good practice to confirm suspected leak detected with one technology by repeating the detection with a another technique.
Self Study ► Examine real audio files of acoustic emission tests at: www.ctrlsys.com/library/multimedia/videosamples.php ► Read Technical Report Ultrasonic Tips On Monitoring Bearings For Proper Lubrication and Wear. Mark A. Goodman, VP Engineering UE Systems, Inc.