engleski

A digital signal processing technique for pulsed electromagnetic inspection of steel tubes

A pulsed electromagnetic (PEM) technique is an effective method of nondestructive evaluation of steel tube inner diameter and wall thickness. Using time-spatial separation of direct-zone and remote-zone signals, it is possible to determine wall thickness and inner diameter with one receiving coil measuring voltage peak and zero-crossing time simultaneously. However, for fixed coil geometry the zero-crossing time can be recognized only for a limited range of wall thickness. In order to increase wall thickness range and shorten the probe, additional processing of the pulsed-eddy current signal must be applied. In this paper, we present a technique based on integration of the pick-up voltage and measurement of threshold-crossing time. The technique can be easily implemented in the existing PEM tool. We have verified the technique using numerically and experimentally obtained results for a range of tubes specified with API 5CT standard.

digital signal processing; pulsed electromagnetic inspection

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