Nuclear engineering and services
Eddy current testing at Onet Technologies
In the industrial sector, predictive maintenance is a major challenge for companies seeking to optimize the lifespan of their equipment and reduce unplanned downtime. It is in this context that eddy current testing (ET) stands out as a state-of-the-art technique for detecting surface or underlying defects and anomalies in conductive materials, or for detecting conductive inclusions in non-conductive substrates.
What are eddy current controls? How do they work? Find out all about this non-destructive testing method, mastered by a team of specialists at Onet Technologies.
Eddy current testing, a non-destructive testing (NDT) method
Eddy current testing is one of several methods of non-destructive testing (NDT). "Non-destructive" means that there is no damage to the inspected material, thus avoiding the costs and delays associated with intrusive inspection methods.
Non-destructive testing refers to techniques used in various industries to assess the quality and integrity of materials, components and structures without damaging them. There are several types of non-destructive testing procedures adapted to specific needs, which can be surface or volume-based, such as ultrasonic testing, radiographic testing, magnetic particle testing, dye penetrant testing, infrared thermographic testing, or acoustic emission testing.
What is the principle behind eddy current testing?
Eddy current testing is widely used in many industrial sectors, including aeronautics, aerospace, energy (including civil nuclear power), automotive and metallurgy. They are based on the principle of induced currents generated by variations in magnetic fields when a coil is placed close to a conductive material. These induced currents react to variations in conductivity and permeability, as well as to defects in the inspected material, enabling early detection of potential problems.
The advantages of eddy current testing for predictive maintenance are numerous. Firstly, they offer high accuracy and sensitivity, enabling the detection of small, shallow defects. This means that defects such as open cracks, surface or underlying magnetic inclusions or compositional variations can be detected before they become critical failures.
This predictive detection capability gives companies greater visibility over the condition of their equipment, enabling them to effectively plan maintenance work and reduce unplanned downtime.
In addition to being non-destructive, eddy current testing is fast, versatile and allows data to be recorded for subsequent processing. It can be used on a wide range of conductive materials, including metals, alloys, ceramics and composites. This versatility makes it suitable for a wide range of industrial applications.
Eddy current advantages and disadvantages
The benefits:
- The coils or sensors can be used without being in contact with the product.
- Allows high feed speeds and can work at high temperatures
- The method lends itself well to automated control of long revolution products.
- Can detect non-open surface discontinuities
- An assessment of the depth of the defect is possible
Disadvantages:
- The method applies only to electrically conductive materials.
- The depth of investigation below the surface is limited by the frequency used (skin effect of induced currents).
- Higher cost than other surface inspection methods (Penetrant Testing and Magnetic Particle Inspection)
- Interpreting signals is tricky
- Application is tricky for parts with complex shapes
- Sensitivity is influenced by many parameters
The application of eddy current testing
In addition to its expertise in single- and multi-element eddy current testing, Onet Technologies offers high-performance pulsed eddy current (PEC ) testing using the LYFT process. PEC testing is a non-destructive testing method used to detect extensive thickness loss on piping and vessels, through coatings, thick metal walls and thermal insulation. This process enables real-time C-scan corrosion mapping, making it an extremely versatile tool.
In addition to the fact that it does not require removal of the coating or insulation (which saves time and therefore costs), this method can be used in hard-to-reach places and on sometimes complex geometries, such as elbows. It can be applied when the plant is running, when the contact temperature is below 120°C, when the insulation is damp, and even when the surface is irregular or encrusted with biomass. PEC testing can also be carried out underwater, up to a depth of 10 metres.
Using PEC testing, Onet Technologies is able to estimate thickness losses caused by corrosion over large areas. This method therefore offers a reliable and effective solution for ensuring the safety and durability of our customers' installations, while minimizing production interruptions.
Industrial applications of eddy currents
- Automatic or manual material indication (fault) search
- Electrical conductivity measurement (s/m)
- Material sorting, metallurgical sorting
- Coating measurement (non-conductive or conductive)
- Measuring the thickness of a plate or profile
Sensors
We can classify them according to different criteria:
Families
- Probes
- Encircling coils
- Internal coils
- Rotary probes/sensors
- Focused sensors
- Multi-element sensors
Functions
- Dual-function sensors
- Separate-function sensors
Onet Technologies' expertise in non-destructive testing and inspection
As a nuclear engineering and services company, Onet Technologies' mission is to support players in the nuclear industry in project development, operation, maintenance in safe conditions and decommissioning of nuclear facilities.
Our experienced engineers and technicians are specialized in the maintenance of nuclear and industrial facilities, and are also technically qualified and trained. They are at our customers' disposal to intervene on all types of sites, offering TV inspection and non-destructive testing services. With a capacity for deployment throughout France and recognized expertise in the development of new techniques, we deliver agile, high value-added solutions that are as close as possible to our customers' needs.
In fact, Onet Technologies' teams have a research and development department specialized in NDT (non-destructive testing) to carry out tests and experiments on mock-ups. A workshop also enables us to carry out experimental tests on larger parts or models, on a scale of 1.
To support our customers throughout the lifecycle of their nuclear and industrial facilities, Onet Technologies' teams hold a large number of certifications and qualifications in non-destructive testing (NDT).
They trust us:
- Nuclear AREVA, LTM, Endel, CNIM CEA, Alstom, SET, Daher Vanatome
- Petrochemicals: Vencorex, Butachimie, Bluesta, Solvay, Linde, Adisseo, Butagaz, Primagaz
- Food industry: Toray
- Boilermaking: LTM, Kapp, Alfa Laval, EIFFEL, ADF
- Pipelines: SPAC, TRAPIL, GRT GAZ, EIFFEL
- Pharmaceuticals: Sanofi Pasteur
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