Efftek Diagnostic Engineers



Condition Monitoring Services for Industry


Accoustic Emission

AE techniques have traditionally been used in NDT applications for crack detection and source location. Recent advances in digital signal processing and analysing techniques allow AE to be used as a reliable indication of rotating and reciprocating machinery condition.

AE does not detect misalignment, imbalance and insecurity as easily as vibration analysis, however it does offer advantages over vibration analysis in some applications and as the AE signal propagates in all directions, one or two points per machine are usually sufficient.

AE is effective on plain and linear bearings. The improved signal to noise ratios make it effective on slow speed machines. And at the high frequencies used by AE, there are less effects due to background noise making it suitable for noisy environments such as foundries and drop forges.

An AE reading provides us with two pieces of information, a dB value and a distress value. Basically, this means how loud the signal is (dB) and how smooth it is (distress). This information is assessed as shown below.

Satisfactory Poor lubrication Damaged component
Low dB Low dB High dB
Low distress Low distress High distress

As you can see from above, the information provided by AE is not as comprehensive as VA for example, it can not determine exactly which component in a gearbox is developing a fault, just that a fault IS developing and therefore wherever possible, VA would always be used in preference but there are instances where VA is simply not suitable.

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