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.