By: Ron Wilson, Machinery Condition Monitoring Inc.

For over seventeen years now this independent consulting Company has been providing Predictive Maintenance services to a variety of industries. Our main service has been vibration monitoring / analysis on a contract basis primarily to medium / smaller Companies who did not have the necessary capital or human resources. During this time we have used instrumentation and software from all the major suppliers. However due to the ever-increasing costs of owning and maintaining these systems we sought a cheaper alternative that could also be used by our customers.

The solution has been the use of modern Acoustic Emission technology. AE has been available for a number of years, originally for pressure testing structures or under a different name and technique for bearing condition evaluation. In both cases a suitable accelerometer was used for signal detection. With the development of new sensors Acoustic Emission can truly be used as a basis for the Condition Monitoring of industrial equipment.

Processes such as friction or impacts within a machine give rise to broadband elastic wave activity, which can propagate throughout the machine. As a result there is much scope for variation in possible detection schemes. Audio frequency detection (vibration monitoring) makes use of high signal levels at low frequencies but is plagued by a low signal to noise ratio which necessitate the use of complex signal enhancement techniques.

Higher frequency detection requires more sensitive sensors but has the distinct advantage, on most rotating equipment, of having a high signal to noise ratio. Instrumentation is now available using these new sensors. The experience of our customers using this technique and instrumentation has been very positive.

Trades-persons/Operators like the simple instant bearing/gear assessment instrument as there is no technical training necessary. The data collector and trend software is being use as a screening tool to take more readings as it is far simpler and quicker than FFT based vibration. It allows experts with diagnostic expertise to use their talents on more complex problems. On-line systems have proven effective on gearboxes down to 30 rpm.

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