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Detection and Characterization of Corrosion under Insulation (CUI) and Weather Protection using JENTEK's MR-MWM-Arrays

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January 09, 2012
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In a previous SBIR success story, we discussed the development of a cost competitive, easy-to-use and reliable tool for “in-the-ditch” characterization of mechanical damage (MD) and stress corrosion cracking (SCC) for buried pipelines, as well as internal and external corrosion under insulation (CUI) through insulation and weather protection for exposed pipelines. Since that time, we have made significant developments on a specific challenge problem for CUI - defined by the DOT and the stakeholders in the industry – to detect external corrosion in pipelines through 2 in. insulation/coating and 0.016 in. – 0.040 in. aluminum (or stainless steel) weather protection. Note however that the JENTEK developed solution described below provides both internal and external corrosion through insulation and weather protection.

JENTEK’s Magnetoresistive Meandering Winding Magnetometer Array (MR-MWM-Array) uses low frequency eddy current methods to characterize corrosion in pipelines through insulation and weather protection. Detection and imaging of both internal and external corrosion is accomplished.  MR‑MWM‑Array technology incorporates parallel rows of inductive and magnetoresistive sensing elements at different distances from a linear drive (called segmented field magnetometry) to provide independent information used to estimate the properties of the weather jacket, insulation, and pipeline.  Model-based inverse methods (using pre-computed databases called Hyperlattices) enable rapid correction for the presence of the weather jacket, while estimating the distance between the weather jacket and outer pipeline surface, and the remaining pipeline wall thickness. This is accomplished at each location in the axial scanning direction, at 1 to 3 in. per second scan speeds.

Currently, only phased array UT can provide sufficient performance, but only after costly removal of insulation and weather protection. However, the need to inspect thousands of feet of insulated pipeline for corrosion makes this UT approach entirely impractical. The MR-MWM-Array is the only practical tool that has demonstrated a realistic and fundamentally sound solution to this pervasive need.

Laboratory testing has demonstrated the capability to detect external corrosion through 2 in. of coating/insulation and weather protection at a scan speed of 3 in/sec. Detection and imaging of internal corrosion has also been demonstrated in limited laboratory tests with 1.5 in. insulation at 0.5 in/sec scan speeds. We anticipate that this range will be increased to 3 inch insulation for both internal and external corrosion with continued efforts in 2012 under DOT funding. We have recently completed a preliminary fully-integrated field trial for CUI through 2 in. insulation and weather protection. This field trial proved that the novel scanners and MR-MWM-Array prototype can practically scan straight pipeline sections (with typical weather protection and insulation, including straps and weather protection overlaps) in the field, plants or refinery. Further development will extend this to more complex pipeline configurations.

This Corrosion under Insulation (CUI) solution was developed under JENTEK (IR & D) and DOT funding, as well as funding from other industry partners.  The team for this development was lead by Dr. Andrew Washabaugh, and included Dr. Neil Goldfine, Dr. Yanko Sheiretov, Mr. Todd Dunford, Mr. Scott Denenberg, Mr. Shayan Haque, and Mr. Leon Kristal.

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