Acoustic emissions (AE) are the sounds generated from acoustic (elastic) waves in solids that are released when a material under mechanical loading undergoes irreversible changes leading to crack formation, crack propagation and plastic deformation. AE events generate local sources of high-frequency elastic waves that travel along the surface of a material. Ameriscan LLC performs AE testing for refineries and chemical plants without down time and at less expense.
Acoustic Emission Testing
Many catastrophic failures of equipment in industry have highlighted the need for
periodic inspection of critical equipment and structures. AE testing is a nondestructive inspection technique that can be used either as a single inspection method or to complement other types of inspections. AE testing takes advantage of these high-frequency sound waves given off by active flaws in materials under stress. Using special sensors and data acquisition instruments, these sounds, travelling along the surface of a material, can be detected and their source location triangulated accurately. Data analysis software specifically designed for AE testing helps to graphically identify active flaws and plot their locations in both 2D and 3D diagrams. Many types of pressure vessels, bridges, storage tanks, piping systems and other mechanical structures can be easily evaluated for mechanical integrity. Long-term AE monitoring helps to correlate environmental and process parameters to active damage and can be used to narrow follow-up inspection efforts and repair planning during equipment shutdown. Additionally, AE can help detect leak sources in structures that are otherwise difficult to inspect using conventional means.
Data analysis procedures consist of identifying significant AE source location
clusters through selective feature filtering, graphical analysis and event cluster analysis. Data acquisition filtering records inly those AE events that can be located within the source location array. Noises outside the structure being tested, such as pumps or other mechanical equipment, are not detected.
Source location arrays can either be linear, between 2 adjacent sensors, or spatial in 2D or 3D representations with multiple sensors on a test object. Features of the test object, such as weld seams and nozzles, can be graphically represented within the data analysis software.
Significant advances in both AE detection equipment and computing power have allowed the AE method to be used in inspections of critical equipment, such as that used in refineries, chemical plants and power generation facilities, including nuclear facilities. Typical frequency ranges of AE sensors vary between 20 kHz and 1 MHz, where sensor selection depends on the application and types of flaws to be detected.
Acoustic Emission Testing advantages:
- Detects active flaws in equipment caused by known damage mechanisms
- Does not require equipment shutdown for inspection
- Does not require insulation removal
- Entire structures can be inspected in a short period
- 3D location algorithms are displayed in real-time, allowing for safe testing during
- AE data can pinpoint problem areas for follow-up inspections
- Significant cost savings for inspection efforts
- Long-term monitoring can give information about equipment health over time
- Complements other NDE methods
- Widely used in refineries/chemical plants and supported by several standards in
- Many different components can be tested
As with any inspection method, the interpretation of the data relies heavily on the operator’s experience. Ameriscan LLC AE operators have many years of field
experience in refineries and chemical plants and have performed many AE tests on equipment around the world.