Differential pulsed eddy current sensor for the detection of wall thinning in an insulated stainless steel pipe

Abstract

A differential probe which is used in the pulsed eddy current (PEC) system has been fabricated for the detection of wall thinning of insulated pipelines in a nuclear power plant (NPP). The differential PEC probe consists of two hall sensors in a differential arrangement. The tested sample is a stainless steel of thickness variation from 1 to 5 mm, the flat side of the sample is laminated by a plastic insulation having a uniform thickness to simulate the pipelines in NPP. The PEC response to varying metal thickness was measured at various thicknesses of insulations on the tested sample. The time-domain feature such as peak value of the detected pulse is used to interpret the thickness of the test sample. The signal analysis technique, such as power spectrum density, is applied to obtain an optimum parameter to describe the wall thinning of pipeline steel. This technique can be used as a potential tool to detect the corrosion or the wall thinning of the pipelines without removing the insulation.

Non-destructive evaluation of ferromagnetic material thickness using Pulsed Eddy Current sensor detector coil voltage decay rate

“…Traditional PEC signal features used for evaluating test piece properties and defect quantification can be classified as: time domain signal features [8,9], frequency spectrum features [10,11], principal components [12,13] and integral features [14,15]. Some specific features among those which have been found to be effective on ferromagnetic materials for defect detection are presented in [4,16] while features used for thickness estimation are discussed in [8,17].…”

Noncontact Thickness Measurement of Metal Films Using Eddy-Current Sensors Immune to Distance Variation

“…The PEC technique contains frequency-rich information and has the potential to detect properties in great depth. Three features of the signal, namely, the peak height, the time of occurrence of the first peak, and a characteristic zero-crossing time were found to characterize the measurand (thickness or conductivity) [7]. However, complicated and advanced signal processing and interpretation are required to abstract the features of the PEC signal and link these features explicitly to the sample conditions.…”

Defect Classification Using Postpeak Value for Pulsed Eddy-Current Technique

“…Time-domain features, such as peak value, time to peak, rising time, and zero crossing time, are widely used [5,6]. Yang et al [7], and Angani et al [8] investigated the detection of fatigue cracks and thickness using the peak value. Xu et al [9] found that the time to peak feature is independent of lift-off distance and has good robustness.…”