Ultra-Tek
Good bearing correctly greased
in TWF format
Bad bearing correctly greased
in TWF format
Good bearing in FFT format
Bad bearing in FFT format
Ultrasound Bearing Inspection
Ultrasonic Bearing
&
Mechanical Inspection
​
Ultrasonic inspection of mechanical equipment with an Ultraprobe has many advantages.
Ultrasound inspection provides early warning of bearing failure, detects lack of lubrication, prevents over lubrication and can be used on all bearing speeds (high, medium and low). In addition, since ultrasound is a high frequency, short wave signal, it is possible to filter out stray, confusing background noises and focus on the specific test point. Basic inspection methods are extremely simple and require very little training. For those who require more sophistication, UE Systems offers training courses that range from one-day specialised classes to five-day ISO Certifide courses.
Ultrasonic condition analysis is straightforward. Users of analog instruments can observe sound levels while simultaneously listening to the sound quality. Digital users have additional options such as viewing decibel levels, data logging, data analysis and trending through specialised software. More sophisticated digital instruments provide features for comprehensive mechanical or bearing condition monitoring programs including; data logging, software for trending, creation of alarm groups, sound sample recording, spectral analysis of sounds and software with customisable reporting formats that include graphs, charts and other relevant images.
How Ultrasound Bearing and Mechanical Inspection Works
Mechanical movements produce a wide spectrum of sound. One of the major contributors to excessive stress in machinery is friction. Ultrasound instruments detect friction. By focusing on a narrow band of high frequencies, the Ultraprobe detects subtle changes in amplitude and sound quality produced by operating equipment. It then heterodynes these normally undetectable sounds to an audible range (for us humans) where they are heard through headphones and observed on a display panel for trending, comparison, and analysis.
It is well established that ultrasound monitoring provides the earliest warning of bearing failure. Various amplitude thresholds of bearing failure have been established. An 8dB gain over baseline indicates pre-failure or lack of lubrication. A 12dB increase establishes the very beginning of the failure mode. A 16dB gain indicates advanced failure condition while a 35+dB gain warns of catastrophic failure. For those who utilise ultrasound spectral analysis, these conditions can often be observed through both FFT and time series analysis.
Typical ultrasound inspections include: bearings (also proven to be very effective on low-speed bearings), pumps, motors, conveyors, gear & gear boxes, couplings, fans, compressors, robots and more.
Ultrasonic Bearing Inspection Method
There are three methods for ultrasonic bearing monitoring: comparative, historical and analytical. In order to note possible deviations that might indicate a possible failure condition, or to establish a baseline for future surveys, compare similar bearings to each other for differences in amplitude and sound quality.
To do this, make a permanent reference point on a bearing housing or use the grease fitting, tune to 30 kHz and adjust the received sound level so that the intensity or decibel level can be observed on the display panel. Then compare this base reading to other similar bearings, while listening for any sound quality anomalies.
Once a series of bearings have been tested, and a base line set, data is recorded and then compared to future readings for historical trending and analysis. High and low alarm levels can be set to note any bearings in need of corrective action. An 8dB gain over a baseline with no change in sound quality will indicate a need to lubricate due to depleted lubricant. Levels, such as 16dB or higher can signify a potential failed condition. The analytical approach can be integrated into the comparative or historical process. Sound anomalies can be recorded and analysed through spectral analysis software. Some of the advanced instruments have on-board spectral analysis providing the ability to diagnosis issues in real-time, while performing inspections out in the plant.
