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How AET Works

Acoustic emission is a cost-effective and sensitive method for assessing the condition of pressurized systems and load-bearing structures. Defects and discontinuities are detected and located using a targeted array of sensors applied to a structure under stress.  These sensors listen for high frequency signals ('noise') generated by active defects, corrosion processes, leaks, creep in steam lines, or strand failure in cable bundles.

AET records high frequency energy emitted by a vessel while it is being subjected to increasing stress levels exceeding those experienced during its normal operation. Acoustic emission sensors pick up transient stress waves (events) generated by discontinuities, defects and corrosion processes through either controlled stimulation of the structure, or on-line monitoring, with relatively little process interruption.

Parameters measured:

  •  Event counts
  •   Amplitude
  •   Duration
  •   Rise time
  •   Decay time
  •   Energy

The sensitivity of AE sensors allows a single sensor to potentially monitor a large area. As typically full arrays of sensors are used, the system is provided with the versatility to test all types of structures, such as tanks, pressure vessels, gas cylinders, pipelines, bridges, jet airplanes...

Structural integrity is evaluated in one test; ATTAR’s ASNT SNT-TC-1A level II and III AE Technicians and Engineers interpret results to classify the condition.  If AE results are within acceptable levels, equipment can then be placed back into service; otherwise, complementary NDT methods can be targeted to suspect areas.  Assets are ranked in terms of damage and prioritized for maintenance - saving time and money.

 

Equipment

ATTAR uses state of the art acoustic emission sensing equipment with neural network software which permits discrimination between active defects and background noise as well as identification of the location of defects or discontinuities in the structure under test.

Sensors – 30 to 300 kHz
Preamplifier Gain– 40dB
Band pass filters tuned to sensors 10 - 400kHz
PAC DiSP or Samos AE Card
PAC AEWin Software

While acoustic emission sensors are very sensitive to higher frequencies, they do allow testing to be conducted with operational noise present. Any interference from background noise such as Weather, Structure internals or processes, and loading or pressurisation is filtered by the AET Engineer.

PAC AEWin software is used; features include:

  • 2D, 3D and tank bottom location
  • Graphical representation of attenuation of AE signals
  • Post test data analysis, including filtering
  • Noesis pattern recognition software allows for further evaluation of data     

Report

Test results are analysed for any potential anomalies. ATTAR reports include a diagram of the subject indicating severity and location of acoustic emission activity.

 

  

 

Australian and International Standards

AE testing is recognised globally through various networks of Australian and International Standards, Pressure Vessel Codes and ASTM test methods.  ATTAR has been conducting AE testing since 1986, using staff qualified to ASNT SNT-TC-1A, Level II and III, as well as a PhD in Acoustic Emission.