What is eddy current testing?
Eddy current testing uses electromagnetic induction to detect defects in both ferrous and non-ferrous materials by inducing an eddy current field in the specimen under test. Eddy current testing is one of several non-destructive testing methods that uses the electromagnetism principle for flaw detection in conductive materials. A specially designed coil energised with an alternating-current is placed in proximity to the test surface, generating a changing magnetic field that interacts with the test-part and produces eddy currents in the vicinity. It is used for flaw detection, material and coating thickness measurements, material identification and establishing the heat treatment condition of certain materials.
Applications of eddy current testing
Following are Application of eddy current testing
1. Crack detection
Eddy current crack detection equipment can be divided into high frequency instruments for finding surface breaking cracks in ferrous and non-ferrous materials and low frequency instruments for finding subsurface cracks in non-ferrous materials.
2. Tube and wire testing
Automated eddy current test systems have been developed for inspecting tube, bar and wire at speeds up to 3 m/s.
The mechanical handling equipment for the test pieces becomes so complex that the actual eddy current test instrumentation may appear an insignificant part. Facilities for magnetic saturation and demagnetisation of ferrous tubes and wires, increase the capital costs considerablyHow
3. Condenser tube inspection
This application is currently receiving a great deal of attention in connection with the heat exchangers of pressurised water reactors.
Tube thinning is the main defect and by selecting what is known as the f90 frequency, signals resulting from thinning on the outside surface can be set 90° out of phase from signals arising from thinning on the inside surface. By recording the X and Y signals from the impedance diagram on a two-channel strip chart recorder, the extent of thinning can be ascertained at test speeds of 200-300mm per second.
4. Material sorting
Ferrous segregators and electromagnetic sorting bridges are useful tools in sorting steels which have been hardened.
Conductivity meters can be used to sort aluminium and copper alloys, both for compositional variations and hardness variations.
5. Weld testing.
6. Coating thickness measurement
How can I get certified in eddy current testing?
You can get certified from recognise Nondestructive institute such as Spark Institute of Nondestructive Testing, with proper training of theoretical knowledge, practical and their examination, by a Level III trainer.
Job opportunities in eddy current testing
This non-destructive testing technique is non-hazardous and commonly used in industries such as aerospace, railways, automotive, marine and manufacturing.