ET VS UT Differences Between Ultrasonic Testing UT and Eddy Current Testing ET
Differences Between Ultrasonic Testing (UT) and Eddy Current Testing (ET)
- Ultrasonic Testing (UT): Uses sound waves to penetrate materials, mainly detecting internal defects, even for thick-walled parts.
- Eddy Current Testing (ET): Based on electromagnetic induction, only detects surface and near-surface defects, suitable for conductive metals.
Standard Specification
ET ASTM E426 Standard Practice for Electromagnetic (Eddy Current) Examination of Seamless and Welded Tubular Products, Titanium, Austenitic Stainless Steel and Similar Alloys
UT ASTM E213 Standard Practice for Ultrasonic Testing of Metal Pipe and Tubing
ET VS UT Comparison Table
| Item | Ultrasonic Testing (UT) | Eddy Current Testing (ET) |
|---|---|---|
| Principle | Reflection/transmission of ultrasonic waves | Alternating magnetic field induces eddy currents; defects change impedance |
| Detection range | Internal, near-surface and surface defects | Only surface and near-surface defects (within a few millimeters) |
| Applicable wall thickness | Suitable for both thick and thin walls | More suitable for thin-walled and small/medium-diameter pipes |
| Material requirements | Good sound conductivity; applicable to stainless steel | Must be electrically conductive; fully applicable to stainless steel |
| Couplant required | Yes (water, oil, etc.) | No, non-contact testing |
| Shape adaptability | Suitable for regular and irregular shapes | Suitable for axisymmetric parts such as pipes and bars |
| Qualification and quantification | Accurate positioning and depth measurement | Fast, but difficult to accurately quantify internal defects |
| Testing efficiency | Relatively slow, suitable for precise inspection | Extremely fast, suitable for high-speed online inspection |
Summary: ET is the fastest and most sensitive for small cracks and minor damages on or near the surface.
