What flaw is easier to detect in tubing by the eddy current method using the self-comparison differential coil arrangement?

The detection of short flaws in tubing using the eddy current method with a self-comparison differential coil arrangement is facilitated by the nature of how eddy currents interact with discontinuities in conductive materials. In this setup, two coils are used to compare signals, allowing for heightened sensitivity to localized defects.

Short flaws, such as cracks or pits, create significant disruptions in the flow of eddy currents, leading to more pronounced changes in the signal detected by the coils. The differential arrangement enhances this sensitivity by effectively canceling out responses from the surrounding material while amplifying the signals from these defects, making it easier to identify short, localized abnormalities.

In contrast, gradual changes in diameter or conductivity might affect the overall conductivity and response of the tubing material, but these changes are less pronounced compared to the sharp disruptions caused by short flaws. Changes in temperature can influence the resistivity of the material but don’t generate the specific signal characteristics associated with defects that the differential coil arrangement is designed to detect effectively.