PIPELINE INSPECTION USING A TORSIONAL GUIDED-WAVES INSPECTION SYSTEM. PART 1: DEFECT IDENTIFICATION

Abstract

A steel pipeline of about 60 m long containing several pipes and structural singularities (bends, welds, clamps, etc.) is inspected in this work using a guided-waves technique. The inspection system is a pair of transducer-rings operating with the torsional mode T(0,1) and allows the long-range fast screening of the structure from defined measurement points. Recorded signals have submitted some numerical treatments in order to make them interpretable. The wavelet analysis is one of them and serves for denoising the raw signals. Besides, the Hilbert transform (HT) is applied in order to obtain the wave signals' envelopes leading to simplified curves easy to interpret. The processed signals are analyzed to identify defects' reflections from structural-singularities' echoes in the pipeline. The inspection system prove its efficiency for a global screening of such a long-range pipeline by detecting and localizing the defects.