Was ist Wirbelstromprüfung?
Eddy Current Testing (ECT) is a non-destructive testing (NDT) technique used to detect and characterize surface and near-surface defects in conductive materials. It relies on the principle of electromagnetic induction.
Here is how the eddy current testing of tubes works:
- Sonde
- Magnetic field creation
- Introduce the field to the objec
- Create eddy currents
- Collect data
- Evaluate the data
What is the principle of eddy currents？
The principle of eddy currents is based on electromagnetic induction. When a conductor, such as a metal, is exposed to a changing magnetic field, circulating electrical currents are induced within the conductor. These circulating currents are known as eddy currents.
Elektromagnetische Induktion
Changing magnetic fields induce electrical currents in conductive materials.
Faraday's law states that a changing magnetic field induces an electromotive force (EMF) in a conductor.
Formation of Eddy Currents
Time-varying magnetic fields, such as alternating currents or moving magnetic fields, cause changes in magnetic flux through a conductor.
These changes in flux induce circulating electrical currents within the conductor, sogenannte Wirbelströme.
Lenz's Law
Eddy currents create magnetic fields that oppose the change in the original magnetic field that induced them.
Lenz's law states that the direction of an induced current is such that it produces a magnetic field to counteract the change in the magnetic field that caused it.
Factors Affecting Eddy Currents
The magnitude and distribution of eddy currents depend on factors such as magnetic field strength, Frequenz, Leitfähigkeit, and conductor geometry.
Eddy currents are more concentrated near the surface of the conductor and decrease in intensity as they penetrate deeper.
Practical Applications
Eddy currents are utilized in eddy current testing (ECT) for the detection and characterization of surface and near-surface defects in conductive materials.
Eddy currents have applications in electromagnetic braking, induction heating, metal sorting processes, and other technologies that leverage their resistive and dissipative properties.
Eddy Current Testing Common Applications
Eddy Current Testing (ECT) is widely used in various industries for the inspection and evaluation of conductive materials. Here are some common applications of Eddy Current Testing:
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Luft-und Raumfahrtindustrie:
- ECT is used for the inspection of aircraft components such as turbine blades, Motorenteile, und Fahrwerk.
- It can detect surface cracks, Korrosion, and flaws in critical components, Gewährleistung der Sicherheit und Zuverlässigkeit von Flugzeugen.
-
Automobilindustrie:
- ECT is employed for quality control and inspection of automotive parts like engine blocks, Kurbelwellen, und Aufhängungskomponenten.
- It can detect defects such as surface cracks, Porosität, and heat treatment irregularities.
-
Energieerzeugung:
- ECT is utilized in the inspection of power plant components, including steam turbine blades, Generatorrotoren, and heat exchanger tubes.
- It helps identify surface cracks, Erosion, and other defects that may affect the efficiency and reliability of power generation equipment.
-
Tube and Pipe Inspection:
- ECT is commonly used to inspect tubes and pipes in industries like oil and gas, Petrochemie, und Wärmetauscher.
- It can detect wall thickness variations, Risse, Korrosion, and other defects that may compromise the integrity of the tubes or pipes.
-
Manufacturing and Quality Control:
- ECT is employed for quality control and inspection of various manufactured components, such as machined parts, Schweißnähte, and fasteners.
- It helps identify surface cracks, Hohlräume, und materielle Inkonsistenzen, ensuring the quality and reliability of the products.
-
Non-Destructive Testing (NDT):
- ECT is a widely used technique in the field of NDT, where it complements other inspection methods like ultrasonic testing and magnetic particle testing.
- It can be used for sorting and classifying materials based on their electrical conductivity and for material characterization.
These are just a few examples of the many applications of Eddy Current Testing. The versatility of ECT makes it suitable for a wide range of industries and inspection purposes, providing valuable information about the integrity and quality of conductive materials.
Eddy Current Testing Standards and Codes
Eddy Current Testing (ECT) is governed by various standards and codes that provide guidelines and requirements for conducting inspections, equipment calibration, and data interpretation. Here are some commonly referenced standards and codes for Eddy Current Testing:
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ASTM Eddy Current Standards:
- ASTM E309 – Standard Practice for Eddy Current Examination of Steel Tubular Products Using Magnetic Saturation
- ASTM E426 – Standard Practice for Electromagnetic (Eddy Current) Examination of Seamless and Welded Tubular Products, Titan, Austenitic Stainless Steel, and Similar Alloys
- ASTM E570 – Standard Practice for Flux Leakage Examination of Ferromagnetic Steel Tubular Products
- ASTM E571 – Standard Practice for Electromagnetic (Eddy-Current) Examination of Nickel and Nickel Alloy Tubular Products
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ASNT Eddy Current Testing Standards:
- ASNT SNT-TC-1A – Recommended Practice for Nondestructive Testing Personnel Qualification and Certification
- ASNT CP-105 – Standard Topical Outlines for Qualification of Nondestructive Testing Personnel
- ASNT CP-189 – ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel
- ASNT SNT-TC-1A-2021 – Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing
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ISO Eddy Current Testing Standards:
- ISO 15549 – Zerstörungsfreie Prüfung von Schweißnähten – Eddy current testing of welds by complex plane analysis
- ISO 17643 – Zerstörungsfreie Prüfung von Schweißnähten – Eddy current testing of welds by encircling or sectorial scanning
- ISO 21968 – Zerstörungsfreie Prüfung – Wirbelstromprüfung – Vocabulary
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Aerospace Eddy Current Testing Standards:
- NAS 410 – National Aerospace Standard for Nondestructive Testing Personnel Qualification and Certification
- AMS 2644 – Aerospace Material Specification for Liquid Penetrant Inspection
- ASTM E1417 – Standard Practice for Liquid Penetrant Testing
Eddy Current Testing Advantages and Disadvantages
ETC allows inspectors to find defects on the surface and subsurface level of an object easily and with a high degree of accuracy—but that’s just one of the reasons inspectors commonly use it to look for defects in a material.
Vorteile der Wirbelstromprüfung
Nachteile der Wirbelstromprüfung
Tabelle der Vor- und Nachteile der Flüssigkeitseindringprüfung (LPT).
| Vorteile der Wirbelstromprüfung | Nachteile der Wirbelstromprüfung |
|---|---|
| Hohe Empfindlichkeit gegenüber Oberflächen- und oberflächennahen Defekten | Begrenzte Wirksamkeit bei nichtleitenden Materialien |
| Schnelle Inspektion in Echtzeit | Begrenzte Erkennungstiefe |
| Kann Defekte durch dünne Beschichtungen erkennen | Komplexe Einrichtungs- und Kalibrierungsanforderungen |
| Kann komplexe Formen und unregelmäßige Oberflächen prüfen | Für die Dateninterpretation sind Fähigkeiten und Erfahrung erforderlich |
| In einigen Fällen ist keine Oberflächenvorbereitung erforderlich | Begrenzte Wirksamkeit bei der Erkennung von Defekten unter der Oberfläche |
| Tragbare Geräte ermöglichen Inspektionen vor Ort | Die Ausrüstungskosten können relativ hoch sein |
| Kann zur Sortierung und Materialcharakterisierung verwendet werden | Empfindlichkeit, die durch Änderungen der elektrischen Leitfähigkeit beeinflusst wird |
What Kind of Inspections Can Be Performed Using Eddy Currents?
Eddy Current Testing (ECT) can be used to perform various types of inspections on conductive materials. Here are some common inspections that can be performed using eddy currents:
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Surface Crack Detection: ECT is highly effective in detecting surface cracks in conductive materials. It can identify cracks caused by fatigue, Stress, Korrosion, or other factors.
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Material Thickness Measurement: ECT can be used to measure the thickness of conductive materials, wie Rohre, Röhren, and plates, without the need for physical contact. This is particularly useful for monitoring corrosion or erosion-related thinning.
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Conductivity and Material Characterization: ECT can assess the electrical conductivity of materials, which can help identify variations in alloy composition, heat treatment effects, oder Materialverschlechterung.
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Coating Thickness Measurement: ECT can measure the thickness of non-conductive coatings, wie zum Beispiel Farbe, Lack, or oxide layers, auf leitfähigen Untergründen. It can detect variations in coating thickness or identify coating defects like delamination.
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Weld Inspection: ECT is commonly used to inspect welds in conductive materials. It can detect weld defects such as cracks, Mangel an Fusion, unvollständige Penetration, und Porosität.
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Heat Exchanger Tube Inspection: ECT is employed to inspect heat exchanger tubes for defects such as corrosion, Erosion, Lochfraß, und knacken. It can assess the condition of tubes without the need for their removal.
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Bolt and Fastener Inspection: ECT can be used to inspect bolts, fasteners, and threaded components for cracks, Ermüdung, oder Materialverschlechterung.
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Tube and Pipe Inspection: ECT is commonly applied to inspect tubes and pipes for defects such as cracks, Korrosion, or erosion. It can identify flaws both on the inner and outer surfaces of the tubes.
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Aerospace Component Inspection: ECT is extensively used in the aerospace industry to inspect critical components like turbine blades, Motorenteile, Fahrwerk, and structural elements for cracks, Korrosion, oder Materialverschlechterung.
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Quality Control and Manufacturing Inspection: ECT is employed for quality control purposes during the manufacturing process to detect surface defects, Risse, or inconsistencies in machined parts, Gussteile, Schmiedestücke, and other components.
These are just a few examples of the inspections that can be performed using Eddy Current Testing. The versatility of ECT makes it suitable for a wide range of applications across various industries.
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