Lift-off height and wall thickness detection based on pulsed eddy current technology
In order to investigate the impact of lift-off height and protective layer material on the detection results when using pulsed eddy current technology to measure the wall thickness of pressure vessels or pipelines with cladding,the effect of lift-off height on the pulsed eddy current signal was analyzed,and a method for calculating the lift-off height using the intercept of the mid-term signal was proposed.The research results show that different protective layer materials have different effects on the pulsed eddy current signal:stainless steel has a minimal impact,aluminum increases the signal amplitude,whereas galvanized iron reduces the signal amplitude.When calculating the wall thickness using the slope of the late-term signal,the impact of lift-off height is relatively small.However,for aluminum protective layers,the calculated wall thickness decreases with the increase of lift-off height,which needs to be calibrated using a formula.Experimental verification shows that the calibrated wall thickness differs from the actual wall thickness by no more than 2%,indicating that the calibration method is effective.
wall thickness testingpulsed eddy currentintermediate signal interceptlift-off height
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