Last update: Jan 13, 2017
Acoustic Emission Testing (AET) is a nondestructive testing 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 AE 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:
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 AE event. This is achieved through transducers which convert mechanical movement into an electrical voltage signal. The majority of AE 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 AE signals. The inverse is true as well.
Because of it’s 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.
Recommend changes or revisions to this definition.
March/April 2016 Inspectioneering Journal
By Mike Brown at Sentinel Integrity Solutions
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.
February 2, 2015 By John Reynolds at Intertek
The development of advanced NDE techniques/tools is one of the reasons the inspection trade has taken significant steps forward in the last couple decades; and the advancements appear to be accelerating. One of the many ways to keep up with advancing NDE technology is to attend the semi-annual NDE task group meetings at the Spring and Fall API Refining and Equipment Standards Meetings. In fact, that T/G is planning to document many of the advanced NDE...
May 5, 2014 By Greg Alvarado at Inspectioneering Journal
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 re-stressing do not generate the types of stress necessary to generate elastic strain waves at the HIC laminar crack tips.
March 17, 2014 By Greg Alvarado at Inspectioneering Journal
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, as a third.
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.
September/October 2013 Inspectioneering Journal
By Sam Ternowchek at Mistras Group
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 of service to perform an internal inspection is not an easy determination to make.
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 operation as plants age, utilities periodically inspect critical components, conventional inspection methods for HEP systems are radiographic (RT), ultrasonic (UT), field metallography and replication, and magnetic particle (MT) testing.
March/April 1999 Inspectioneering Journal
By John Reynolds at Intertek
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.
March/April 1997 Inspectioneering Journal
Dr. David Wang, Shell Oil Company, reviewed the status of PERF project 95-11, Advanced Acoustic Emission for On-Stream Inspection, with NACE task group T-3L-14 (acoustic emission), at the Corrosion '97' conference in New Orleans, LA, on March 10, 1997. This project is still open to membership.
March/April 1995 Inspectioneering Journal
By Charles L. Foster at Pacific Gas & Electric
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.