Eddy Current Inspection

NDT and Eddy Current Testing:

NDT allows parts and materials to be inspected and measured without damaging them. Because it allows inspection without interfering with a product’s final use, NDT provides an excellent balance between quality control and cost-effectiveness.

Nondestructive testing method categories:

žUltrasonic testing (UT)

žRadiography X-ray

žElectromagnetic testing (ET)

—Eddy-Current Testing (ECT).

žVisual inspection (VT)

—Pipeline video inspection

Used in :

crack detection & other discontinuities include porosity, wall thinning from corrosion and many sorts of disbonds.

Basic Principles of Eddy Current Inspection:

žEddy current inspection is one of several NDT methods that use the principal of “electromagnetism” as the basis for conducting examinations.

žEddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor.

žIf another electrical conductor is brought into the close proximity to this changing magnetic field, current will be induced in this second conductor.

Eddy Current:

žEddy currents are induced electrical currents that flow in a circular path.

Applications :

• Crack detection
• Material thickness measurements
• Coating thickness measurements
• Conductivity measurements

Eddy current inspection :
crack detecting

žEddy current inspection is an excellent

Method for detecting surface and near

Surface Defects when the probable defect location and orientation is well known.

Advantages of Eddy current inspection:

Sensitive to small cracks and other defects

• Inspection gives immediate results
• Equipment is very portable
• Test probe does not need to contact the part

• Inspects complex shapes and sizes of conductive materials

limitation of eddy current inspection:

• Only conductive materials can be inspected
• Surface must be accessible to the probe
• Skill and training required is more extensive than other techniques
• Depth of penetration is limited