Dear Gents,

I ask for your oppinion about Acoustic Emissions. I have heard about it in some maintenance meetings and I ask about your knowings about it. I know about structure borne ultrasound as a method for condition monitoring of bearings, but I have heard about Acoustic Emissions mainly related to bearings and slow speed applications, tipically talking about Holroyd company (http://www.holroyd-instruments.com/).

Could anybody of you tell me some indications about this technology? Is the same as ultrasound related to bearing applications?

Regards,

Allen

Allen,

I am going translate my understanding of what Acoustic Emission is.
Literally, it is sound emitted by a source and this can be transmitted thru a media such as Air, Structure, Gas/Fluid, etc. The sources can be an Aeroplane/Vehicle, Electrical systems, Rotating/Reciprocating equipment installed on Skids/platforms, FLow induced, etc.
The instrument/technology used in detecting these emissions is Ultrasonic Detection.
A chronic (advanced)bearing fault can be detected using ultrasonic method and this is just one of many applications.
Hope this gives you some idea of what it is all about.

Regards....Rajan

Roughly thirty years ago a technology called acoustic emission became somewhat broadly known. The main application was detecting and locating cracks, primarily in pressure vessels. When the tip of a crack progressed incrementally, there'd be a burst of energy released to propagate through the structure. The sensors detected these events, working up in a very high frequency range - tens or hundreds of kHz. Location was by triangulation, time delays etc. The crack monitoring could be done by either pressurizing an out-of-service vessel, or monitoring an in-service vessel.
After a flurry of introduction /promotion / trials, it seemed to fade away a bit. Not sure how it ended up.

Thanks Gents,

I would appreciate also if you could help me to clarify difference between airbone or structure bone ultrasound and acoustic emissions. According to your comments, frequency detection is higher in Acoustic Emissions than Ultrasound, so for example for bearings the detection time is more at the left on PF Curve than ultrasound, isn´t it?.
Theorically applications must be similar for both technologies, mustn´t it?

Regards,

Allen