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Acoustic Emission Testing (AET)

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Acoustic Emission Testing (AET) is a nondestructive testing (NDT) method that is based on the generation of waves produced by a sudden redistribution of stress in a material. When a piece of equipment is subjected to an external stimulus, such as a change in pressure, load, or temperature, this triggers the release of energy in the form of stress waves, which propagate to the surface and are recorded by sensors. Acoustic emissions can come from natural sources, such as earthquakes or rockbursts, or from the equipment itself such as melting, twinning, and phase transformations in metals. Detection and analysis of AET signals can provide information on the origin and importance of discontinuities in a material.

AET is different than other NDT techniques in two major ways:

  1. Instead of supplying energy to the object under examination, AET listens for the energy released by the object naturally. AE tests can be, and often are, performed on structures while they are in operation since this provides adequate loading for propagating defects and triggering acoustic emissions.

  2. AET deals with dynamic processes in a material. This is particularly useful because only active features are highlighted during the examination. Thus, it is possible to discern between developing and stagnant defects. However, one should be aware that it is possible for flaws to go undetected if the loading isn’t high enough to cause an acoustic event that can be detected by the system.

AET is most often used in a dynamic test environment, meaning that it is used to monitor for crack detection in pressure equipment when the equipment is experiencing an increase in stress. AET systems generally contain a sensor, preamplifier, filter, and amplifier, along with measurement, display, and storage equipment. Acoustic emission sensors respond to any dynamic motion caused by an acoustic emission event. This is achieved through transducers that convert mechanical movement into an electrical voltage signal. The majority of AET equipment responds to movement in a range of 30 kHz to 1 MHz. For materials with high attenuation, such as plastic composites, lower frequencies may be used to better distinguish acoustic emission signals. The inverse is true as well.

Because of its versatility, AET has many applications within the industry, such as assessing structural integrity, detecting flaws, testing for leaks, or monitoring weld quality. Because of the diverse number of situations it can be applied to, it sees extensive use in several areas including the detection of active corrosion in the bottom of aboveground storage tanks, detecting creep damage in high energy piping (HEP) systems, pressure vessel inspection, and leak detection.

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Articles about Acoustic Emission Testing (AET)
May/June 2021 Inspectioneering Journal

This article addresses some of the advantages and disadvantages of acoustic emission testing and discusses a few examples of its typical applications.

Authors: Greg Garic
March/April 2021 Inspectioneering Journal

FFS assessments usually originate from inspection results and often end with a recommended inspection plan. This FFS Forum tries to provide a little better understanding of one particular inspection method: Acoustic Emission Testing.

Authors: Greg Garic
March/April 2020 Inspectioneering Journal

This article reviews the effectiveness of AET for inspecting tank bottoms in two ways; namely, benchmarking regulations in different countries and comparing AET and MFLT results through a case study.

July/August 2019 Inspectioneering Journal

This article is written to provide a brief case study of an acoustic emission test of an FRP storage tank. A method combining acoustic emission with ultrasonics is proposed to ensure reliable long term operation.

Authors: Geoff Clarkson
March/April 2019 Inspectioneering Journal

In order to utilize data most effectively and realize the full power of AE testing, it is necessary to bring the capabilities of laboratory testing tools to industrial sites.

Authors: André Viaud
Partner Content

AET is a powerful, non-intrusive inspection technique to verify the structural integrity of pressure vessels, spheres, high-temperature reactors and piping, coke drums, above-ground storage tanks, cryogenic storage tanks, and more.

Blog

Nondestructive testing (NDT) careers are on the rise in today’s economy. These fields are constantly advancing, and there is an ever-growing need for technicians, quality assurance specialists and inspectors as infrastructure in the United States...

Authors: Berg Engineering
March/April 2016 Inspectioneering Journal

While there are many types of advanced NDT, this article will focus on the use of acoustics and electromagnetism as the bases for conducting examinations.

Authors: Mike Brown
Blog

AE monitoring has been done for HIC affected vessels, with limited success. The limitation, which greatly affects the confidence level of results, is that traditional AE testing stresses, i.e. Kaiser affect overpressure and felicity effect types of...

Authors: Greg Alvarado
Blog

A question was posed to me regarding guidelines for routine external inspection of spheres, including procedural approaches along with any nondestructive examination (NDE). Here are two approaches to inspection of spheres, and a mixture of the two,...

Authors: Greg Alvarado
September/October 2013 Inspectioneering Journal

Maintaining the mechanical integrity of above ground storage tanks (AST’s) is the focal point of tank inspection programs. Performing internal inspections is an integral part of a tank integrity program, however, deciding when to take a tank out...

Authors: Sam Ternowchek
Partner Content

TEAM provides full inline, onsite and, shop valve repair services and maintenance programs for virtually all valve types, brands, sizes, materials, pressures, and operating conditions, including actuators and operators. Our valve repair solution is...

November/December 2008 Inspectioneering Journal

High energy piping (HEP) systems, main stream lines and hot reheat lines (typically low chrome molybdenum steels), are susceptible to creep damage can lead to leaks, and in extreme cases, catastrophic rupture. To ensure safe and reliable...

March/April 1999 Inspectioneering Journal

Some Middle Eastern and European operators are now using AE successfully to screen tanks for internal inspection by listening for active tank bottom corrosion, and then grading the tank as high, medium or low need for internal inspection.

Authors: John Reynolds
March/April 1995 Inspectioneering Journal

High energy piping (HEP) systems, main steam lines and hot reheat lines (typically low chrome molydbdenum steels), are susceptible to creep damage. Such damage can lead to leaks, and in extreme cases, catastrophic failure.

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