Predictive Maintenance using Ultrasound Measurements

Ultrasound measurements are one of the most recent and most versatile predictive technologies, they allow to identify a great variety of anomalies.

With a view to monitoring systems and machines, predictive maintenance is destined to become a practice of considerable importance. This term refers to a set of performance monitoring techniques, which have become central thanks to Industry 4.0, aimed at preventing failures. Knowing in advance a potential malfunction makes it possible to avoid irreversible damage through targeted interventions, planned in a functional way to production, with consequent benefits in terms of management of repair events, reliability, plant safety and last but not least in economic terms.

Thanks to the reduced economic burden required for implementation, predictive maintenance based on ultrasound measurements can be considered a technology of absolute interest.
Working at frequencies greater than 20 kHz, therefore greater than the upper limit of the range of frequencies audible to a human ear, ultrasound monitoring uses high-frequency acoustic signals from various types of anomalies:

● mechanical (impacts or friction between components in contact);
● hydraulic (air leaks in a circuit, malfunctions of hydraulic valves);
● anomalies on medium and high voltage electrical equipment.

The diagnostic tools used in this type of monitoring have the task of detecting the ultrasonic signal generated by the component on which the analysis is being carried out. The reading of the response signal will be all the more effective, the more the diagnostic tool will be able to filter and pre-process the signal itself, with the aim of obtaining a high signal / noise ratio.

Predictive maintenance and fields of application

The fields of application of ultrasonic predictive maintenance are numerous. In mechanics, an application of predictive maintenance concerns the monitoring of fundamental components, such as bearings; any damage to these components can lead to stopping production, with serious economic repercussions. Ultrasound technology makes it possible to detect critical issues even at low rotation speeds, conditions in which conventional monitoring approaches are unable to detect malfunctions.

Further problems of a mechanical nature, predictable thanks to ultrasound inspection, concern the lubrication of components in relative motion; a lubrication defect can lead to wear and excessive temperature rises, just as an excess of lubrication accelerates the process of evolution of a failure. Ultrasound technology is useful for identifying the correct degree of lubrication required for the equipment under analysis.

This technology can be applied to high and medium voltage systems, in the monitoring and inspection of electrical systems to avoid the effects of partial discharges or verify the existence of electric arcs, possible threats to the safety and efficiency of the plant itself.

Predictive ultrasonic maintenance is also effective in monitoring fluid motion components, pumps and compressors; gaseous fluids subject to turbulence phenomena, in the case of leaks or pneumatic problems, or mechanical friction phenomena, emit sound signals in the ultrasonic field. The gain of the signal emitted by the fluid is proportional to the loss flow rate of the fluid itself.

The benefits of ultrasonic predictive maintenance

Using an ultrasound-based approach for a predictive maintenance technique can bring significant advantages over maintenance based on multiple technologies. The use of very high frequencies in the monitoring activity, in fact, allows to identify damage at a very early stage in the components being analyzed. The result is a more accurate monitoring, which highlights potential failures sometimes invisible to predictive maintenance based on other technologies, sensitive to considerably more modest frequencies; in this case, regular operating phenomena could mask the anomaly present.

The consequent possibility of planning maintenance or replacement of components in time considerably in advance of the breaking point makes ultrasonic maintenance competitive. Furthermore, the instrumentation required for ultrasound monitoring is characterized by low invasiveness; it can therefore be carried out in parallel with the usual production or maintenance activities of the machine of interest.

ISE provides predictive maintenance services through ultrasound, providing highly reliable diagnostics and monitoring thanks to its multi-year experience and training and specific instrumentation.

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