Ask an Expert. Benefits Several benefits are derived from eddy current testing: It is suited to volumetric flaws such as corrosion, wear, and large porosities, as well as cracking. It can detect surface-breaking, near-surface, and far-surface defects. Eddy current testing can be used in applications other than flaw detection. Parts under test require only minimal preparation. Suitability According to Tubing Material.
Surface Applications When it comes to surface applications, the performance of any given inspection technique depends greatly on the specific conditions — mostly the types of materials and defects, but also surface conditions, cleanliness, etc.
Many applications are to bar, tube and wire testing. Metal sorting is also a common application of eddy current testing. Follow Us:. Back to Top. Sign up: Go Go. Click here to unsubscribe Go. First name. Last name. Sign up. Close Privacy Policy. BINDT knows that you care how information about you is used and shared and we appreciate your trust in us to do that carefully and sensibly. This notice describes the privacy policy of bindt. By visiting bindt. Any personal information provided to or to be gathered by bindt.
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Bolt hole probes - Designed to inspect the inside of a bolt hole. These probes can be rotated by hand or automatically using a rotary scanner. Donut probes - Designed to inspect aircraft fastener holes with fasteners in place.
Sliding probes - Also used in testing aircraft fastener holes, offering higher scan rates than donut probes. ID probes - Used for inspection of heat exchangers and similar metal tubing from the inside, available in a variety of sizes. OD probes - Used for inspection of metal tubing and bars from the outside, with the test piece passing through the coil Reference standards An eddy current system consisting of an instrument and a probe must always be calibrated with appropriate reference standards at the start of a test.
This process involves identifying the baseline display from a given test piece and observing how it changes under the conditions that the test is intended to identify.
In flaw detection applications, this calibration process typically involves the use of reference standards of the same material, shape, and size as the test piece, containing artificial defects such as saw cuts, drilled holes, or milled walls to simulate flaws.
In thickness measurement applications the reference standards would consist of various samples of know thickness. The operator observes the response from the reference standards and then compares the indications from test pieces to these reference patterns to categorize parts.
Proper calibration with appropriate reference standards is an essential part of any eddy current test procedure. Common applications Eddy current instruments can be used in a wide variety of tests.
Some of the most common are listed below. Weld Inspection - Many weld inspections employ ultrasonic NDT for subsurface testing and a complimentary eddy current method to scan the surface for open surface cracks on weld caps and in heat affected zones. Conductivity Testing - Eddy current testing's ability to measure conductivity can be used to identify and sort ferrous and nonferrous alloys, and to verify heat treatment.
Surface Inspection - Surface cracks in machined parts and metal stock can be readily identified with eddy current. This includes inspection of the area around fasteners in aircraft and other critical applications. Corrosion Detection - Eddy current instruments can be used to detect and quantify corrosion on the inside of thin metal such as aluminum aircraft skin.
Low frequency probes can be used to locate corrosion on second and third layers of metal that cannot be inspected ultrasonically.
Bolt Hole Inspection - Cracking inside bolt holes can be detected using bolt hole probes, often with automated rotary scanners. Tubing inspection - Both in-line inspection of tubing at the manufacturing stage and field inspection of tubing like heat exchangers are common eddy current applications.
Both cracking and thickness variations can be detected. Eddy current arrays Eddy Current Array testing, or ECA, is a technology that provides the ability to simultaneously use multiple eddy current coils that are placed side by side in the same probe assembly.
Each individual coil produces a signal relative to the phase and amplitude of the structure below it. This data is referenced to an encoded position and time and represented graphically as a C-scan image showing structures in a planar view. In addition to providing visualization through C-scan imaging, ECA allows coverage of larger areas in a single pass while maintaining high resolution. ECA can permit use of simpler fixturing, and can also simplify inspection of complex shapes through custom probes built to fit the profile of the test piece.
Olympus Industrial Resources. How it works Eddy current testing is based on the physics phenomenon of electromagnetic induction.
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