This method is
widely used to detect surface flaws, to sort materials, to measure thin walls from
one surface only, to measure thin coatings and in some applications to measure
case depth. This method is applicable to electrically conductive materials
only. In the method eddy currents are produced in the product by bringing it
close to an alternating current carrying coil. The alternating magnetic field
of the coil is modified by the magnetic fields of the eddy currents. This modification,
which depends on the condition of the part near to the coil, is then shown as a
meter reading or cathode ray tube presentation. The Figure gives the basic
principles of eddy current testing.
There are three
types of probes Figure used in eddy current testing. Internal probes are usually
used for the in-service testing of heat exchanger tubes. Encircling probes are
commonly used for the testing of rods and tubes during manufacturing. The uses
of surface probes include the location of cracks, sorting of materials,
measurement of wall and coating thickness, and case depth measurement.
This method may
be used for:
(1) For the
detection of defects in tubings.
(2) For sorting
materials.
(3) For
measurement of thin wall thickness’ from one surface only.
(4) For
measuring thin coatings.
(5) For
measuring case depth.
Some of the
advantages of eddy current testing include:
(1) Does not
require couplant.
(2) It gives
instantaneous response.
(3) Has
uncomplicated steps during set-up.
(4) Is extremely
sensitive to flaws.
(5) Is very
repeatable.
(6) High
scanning speeds can be used.
(7) Is very
accurate for dimensional analysis of flaws or coating thickness.
Some of the
limitations of eddy current testing include the following:
(1) The theory
requires a good academic background in electrical principles and in mathematics.
(2) Extremely
sensitive to surface variations and therefore requires a good surface.
(3) It is
applicable to conductor materials only.
(4) Can be used
on non-magnetic and magnetic material but is not reliable on carbon steel for the
detection of subsurface flaws.
(5) Its depth of
penetration is limited.
(6) Crack
tightness and orientation of eddy current flow to a crack or linear
discontinuity will affect detectability.
Thanks for the explanation!
ReplyDeleteThat was incredibly informative
Elcometer
I haven’t known about it before. This article is very helpful!
ReplyDeleteThank you so much!
Eddy Current testing in UAE
Thanks for this post. Eddy Current testing or Eddy Current Inspection is used for the detection of surface breaking/cracks and near surface planar defects in welds, heat affected zone and parent material. EIWAA offers eddy current testing applied on coated and uncoated objects &the eddy current testing can be carried out on all accessible surfaces on welds of almost any configuration.
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Thanks for this post.. Eddy Current Testing instrument calibration block have EDM Notches of 0.5 mm,1mm and 2 mm depth; unless otherwise agreed between contracting parties. Non metallic stripes of a known thickness to simulate the coating or actual thickness on the calibration block shall be used. EDDY Current testing n of welds in ferritic materials, the frequency shall be chosen according to the material (conductivity, permeability),the defect(type, location and size)and the probe design.
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Thanks for this post..Eddy Current Testing method is widely used to detect surface flaws, to sort materials, to measure thin walls from one surface only, to measure thin coatings and in some applications to measure case depth. This method is applicable to electrically conductive materials only.
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Thanks for this post... Eiwaa Group of Eddy Current Testing system was specially developed for quality testing and process monitoring of long products. From hot testing to all bright steel processing steps, the surfaces of semi-finished products made from austenitic, (non) ferromagnetic metals can be tested for defects.
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