Corrosion Surveying of Tanks, Vessels and Structures - Acoustic Emission (AE) Testing is a cost effective and sensitive method for assessing the condition of pressurised systems and load-bearing structures. Defects are detected and located using a targeted array of sensors applied to a structure under stress. These sensors detect high frequency signals (‘noise’) generated by active defects such as cracking, corrosion, and leakage. AE monitoring is recognized by Australian and International Standards, Pressure Vessel Codes and ASTM test methods. ATTAR is NATA accredited for Technical Competence in Acoustic Emission Monitoring.
Acoustic Emission Testing
Acoustic emission is a cost-effective and sensitive method for assessing the condition of pressurised systems and load-bearing structures. Defects 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 e.g. cracking, corrosion, and leakage. Structural integrity is evaluated in one test, with relatively little process interruption. If AET results are within acceptable levels, the vessel 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 prioritised for maintenance - saving time and money.
Acoustic emission testing is unique to all other non-destructive testing methods in that it detects defect growth as it is occurring. It is of great importance to have such a non-destructive test method that can detect and locate discontinuities as early as possible: repair or replacement can take place long before a catastrophe occurs, preventing loss of life, environmental damage, loss of production and more costly repairs.
Operators face constant pressure to maximise productivity while keeping costs down. Maximising asset utilisation and minimising expensive inspections is one way to keep costs under control. Technologies that monitor assets effectively while avoiding major shutdowns have become essential tools for operators. Advanced technologies such as Acoustic Emission Testing (AET) enable you not only to diagnose issues but to assess inherent risk and optimise asset maintenance programs as well as capital expenditure through proactive management strategies.
How it Works
Acoustic emission is an elastic wave which results from a sudden release of energy within a material; these waves are generated by dislocation motions associated with materials under stress. Acoustic Emission Testing (AET) is based on the detection and conversion of these high frequency elastic waves to electrical signals. Sensors are coupled to the surface of the structure under test; they listen for signals (‘noise’) generated by active defects, corrosion processes, leaks, creep in steam lines, or strand failure in cable bundles.
Acoustic Emission (AE) Sources:
- Active cracks
- Plastic deformation of material
- Active corrosion and spalling of corrosion products
- Leak noise
AET records energy emitted by a structure while it is being subjected to stress through either controlled stimulation of the structure, or on-line monitoring during ‘normal’ operation. ATTAR’s ASNT SNTTC-1A Level II and III AE technicians and engineers interpret the signals to classify the condition of the structure.
The signal generated by a sensor has many features commonly used to characterise it: amplitude, duration, rise time, decay time and AE counts. 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 many types of structures, such as tanks, pressure vessels, gas cylinders, pipelines, bridges, jet airplanes etc.
Structural integrity is evaluated in one test, with relatively little process interruption. If AE results are within acceptable levels, the vessel 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 prioritised for maintenance - saving time and money.
Benefits of Acoutic Emission Testing
- Cost is a fraction of the price of an internal NDT inspection
- No significant cleaning costs or environmental waste disposal; no need to empty tanks, pressure vessels, etc.
- Little disruption to plant operation/minimal downtime
Global inspection of the entire structure
- Defects are located and can be characterised
- Monitoring of in-service defects under differing operating conditions or changes over time
- AE monitoring is recognised globally through various networks of Australian and International Standards, Pressure Vessel Codes and ASTM test methods.
- Early and rapid detection of a wide variety of defects e.g. corrosion, fracture, delamination, disbondment, deformation
- Results used to identify and prioritise maintenance according to risk
- High sensitivity
- Method accepted in Europe, Canada, US, South America, Middle East & Australasia
- Defect location
- Reveals strength, damage and failure
- Permanent, digital recording
Ease of Inspection
- Global inspection that does not require access to the whole examination area
- Sensors can be directly mounted on test specimens, or placed at distanced locations
- Minimal pre-inspection preparation, disturbance of insulation or disruption of the asset
- On-site or remote monitoring; potential for online inspection
- Inspections of difficult-to-access areas and Corrosion Under Insulation (CUI)
- May be used in accordance with high temperature processes as well as cryogenic vessels
- AET can take a matter of hours with, little interruption to operations
- Bulk Tanks (atmospheric or pressurised storage, spherical, fibreglass reinforced plastic (FRP))
- Pressure vessels (ambient, hot or cryogenic, metallic, spheres)
- Compressed-Gas Cylinders & Tube trailers (fixed or portable installation)
- Pipeline & high energy piping testing
- Elevating Work Platforms EWPs
- Large Scale Structural Monitoring
- Transmission and distribution electricity networks
- ATTAR is NATA accredited for Acoustic Emission Testing. For further details on Acoustic Emission Monitoring, Asset Testing and Risk Based Inspection programs please our qualified and experienced team to review your testing requirements
- ATTAR complies with the requirements of ISO/IEC 17025:2005, Accreditation No: 2735
6.84 Acoustic emission fault detection for specified product types
- Acoustic emission monitoring of metallic and composite materials of mobile elevating work platforms, pressure vessels/cylinders and piping, above ground storage tanks and structures
Dr Gary Martin - Chairman and Technical Director, Engineering
David Padfield - Senior Materials and Testing Engineer
Marcus Brache - Senior Engineering Technician
- Download “Acoustic Emission Testing” brochure (pdf)
- Download AE Testing Tank Bottom Monitoring Request Form (docx)
- Download AE Testing Sphere Details Request Form (docx)
- Technical Paper Understanding Acoustic emission and it Application to Industry (pdf)
- Technical Paper Acoustic Emission Testing for Monitoring and Managing your Assets (pdf)
- White Paper Acoustic Emission Testing for Monitoring and Managing Defence Maritime Assets (pdf)