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Investigating EMAT Dig Results for a Low Frequency ERW Seam Inspection

This white paper analyzes the electromagnetic acoustic transducer (EMAT) tool performance and when combined with a multiple dataset platform, investigates the operator’s dig results from EMAT, and compares multiple inline inspection technologies used for a comprehensive seam assessment.

Product Number: 51317--9184-SG
ISBN: 9184 2017 CP
Author: Sean Moran
Publication Date: 2017
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In November of 2014 T.D. Williamson (TDW) inspected a 16” liquid pipeline using multiple datasets (MDS) and electromagnetic acoustic transducer (EMAT) tools. This particular line had low frequency electric resistance welded (LF-ERW) pipe and the Operator was most interested in utilizing these tools for a seam assessment. From prior non-destructive examination (NDE) results and knowing the possible manufacturing defects associated with LF-ERW seams the primary threats the Operator wanted to identify evaluate and repair were cold welds and hook cracks. In addition to the MDS and EMAT inspections two other inline inspection (ILI) tools were selected for this integrity study: an ultrasonic crack detection (UTCD) tool and a transverse flux inspection (TFI) tool. The utilization of four advanced technologies to inspect this pipeline allowed the Operator to correlate the data from the final reports perform a full technology comparison (individually and in combination) and assess the performance of each tool.The Operator was most interested in validating the EMAT tool as this was the first time they had inspected their pipeline with this technology. Five validation digs were performed from the EMAT preliminary report in February 2015 and all five yielded extremely promising results: EMAT identified three hook cracks and two cold welds yielding a probability of detection (POD) = 100% and probability of identification (POI) = 100%. Upon delivery of the final reports from all four tools the defects in the long seam were correlated and repair plans were created to assess the defects that were identified. In total EMAT had identified over 500 linear indications in the long seam and the spiral magnetic flux leakage (SMFL) body on the MDS tool identified nearly 50 axial planars.To date TDW has received over 80 dig reports from the Operator based on the EMAT results alone. From the EMAT final report the Operator has performed over 100 excavation digs and completed over 100 permanent repairs. The results presented in this paper investigate these dig results analyze EMAT tool performance and demonstrate the efficacy in utilizing EMAT and MDS technologies for seam assessments.

Key words: EMAT, MDS, ILI, inline inspection, crack tool technology, crack detection, seam assessment

In November of 2014 T.D. Williamson (TDW) inspected a 16” liquid pipeline using multiple datasets (MDS) and electromagnetic acoustic transducer (EMAT) tools. This particular line had low frequency electric resistance welded (LF-ERW) pipe and the Operator was most interested in utilizing these tools for a seam assessment. From prior non-destructive examination (NDE) results and knowing the possible manufacturing defects associated with LF-ERW seams the primary threats the Operator wanted to identify evaluate and repair were cold welds and hook cracks. In addition to the MDS and EMAT inspections two other inline inspection (ILI) tools were selected for this integrity study: an ultrasonic crack detection (UTCD) tool and a transverse flux inspection (TFI) tool. The utilization of four advanced technologies to inspect this pipeline allowed the Operator to correlate the data from the final reports perform a full technology comparison (individually and in combination) and assess the performance of each tool.The Operator was most interested in validating the EMAT tool as this was the first time they had inspected their pipeline with this technology. Five validation digs were performed from the EMAT preliminary report in February 2015 and all five yielded extremely promising results: EMAT identified three hook cracks and two cold welds yielding a probability of detection (POD) = 100% and probability of identification (POI) = 100%. Upon delivery of the final reports from all four tools the defects in the long seam were correlated and repair plans were created to assess the defects that were identified. In total EMAT had identified over 500 linear indications in the long seam and the spiral magnetic flux leakage (SMFL) body on the MDS tool identified nearly 50 axial planars.To date TDW has received over 80 dig reports from the Operator based on the EMAT results alone. From the EMAT final report the Operator has performed over 100 excavation digs and completed over 100 permanent repairs. The results presented in this paper investigate these dig results analyze EMAT tool performance and demonstrate the efficacy in utilizing EMAT and MDS technologies for seam assessments.

Key words: EMAT, MDS, ILI, inline inspection, crack tool technology, crack detection, seam assessment

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