New Classification Approach for Dents With Metal Loss and ...

1 Proceedings of the 2016 11th International Pipeline Conference IPC2016. September 26-30, 2016, Calgary, Alberta, Canada IPC2016-64284. NEW Classification Approach FOR Dents WITH Metal loss . and corrosion along the seam weld . J. Bruce Nestleroth James Simek Jed Ludlow Kiefner TD Williamson TD Williamson Columbus, Ohio, USA Salt Lake City, Utah, USA Salt Lake City, Utah, USA. 1. ABSTRACT. The ability to characterize Metal loss and gouging associated The new classifier that distinguishes SSWC from corrosion near with Dents and the identification of corrosion type near the the longitudinal weld uses two orientations of the magnetic longitudinal seam are two of the remaining obstacles with in- field, the traditional axial field and a helical magnetic field.

2 In line inspection (ILI) integrity assessment of Metal loss defects. this classifier, detection of any long narrow Metal loss is The difficulty with denting is that secondary features of paramount; the conservatism of the classifier ensures that high corrosion and gouging present very different safety and identification of SSWC can be achieved. The relative amplitude serviceability scenarios; corrosion in a dent is often not very of the corrosion signal for the two magnetization directions is severe while Metal loss caused by gouging can be quite severe.

3 An important characteristic, along with length and width Selective seam weld corrosion (SSWC) along older low measures of the corrosion features. frequency electric resistance welding (ERW) seams also presents two different integrity scenarios; the ILI tool must These models were developed using ILI data from pipeline differentiate the more serious SSWC condition from the less anomalies identified during actual inspections. Inspection severe conventional corrosion which just happens to be near a measurements from excavations as well as pipe removed from low frequency ERW seam.

4 Both of these cases involve service for lab analysis and pressure testing were used to identification difficulties that require improved Classification of confirm the results. the anomalies by ILI to enhance pipeline safety. INTRODUCTION. In this paper, two new classifiers are presented for magnetic In the last decade, the detection capability for ILI tools has flux leakage (MFL) tools since this rugged technology is improved, enabling the reporting of smaller corrosion and commonly used by pipeline operators for integrity assessments. shallower Dents .

5 Also many tools are better at detecting the The new classifier that distinguishes Dents with gouges from seam weld in well-trimmed ERW pipe. However, the reporting Dents with corrosion or smooth Dents uses a high and low of smaller corrosion that is coincident with Dents or the long magnetization level Approach combined with a new method for seam has caused an increase in excavations per the regulations analyzing the signals. In this classifier, detection of any gouge in many countries. The goal of the regulations is to ensure that signal is paramount; the conservatism of the classifier ensures mechanical damage in Dents and selective corrosion of the long reliable identification of gouges can be achieved.

6 In addition to seam, both potentially injurious anomalies, are always detected. the high and low field data, the classifier uses the number of distinct Metal loss signatures at the dent, the estimated Keeping with the spirit of the regulations, the goal of the work maximum Metal loss depth, and the location of Metal loss presented herein is to build classifiers that combine the signatures relative to dent profile ( Apex, Shoulder). measurements from multiple sensing systems to detect mechanical damage in Dents and selective corrosion of the long seam, while dismissing many of the smaller corrosion features 1.

7 The United States Government retains, and by accepting the that do not impact pipeline performance. The classifiers are article for publication, the publisher acknowledges that the designed to be conservative, meaning some non-injurious United States Government retains, a non-exclusive, paid-up, corrosion anomalies are designated for excavation so that the irrevocable, worldwide license to publish or reproduce the likelihood of catching all potentially injurious mechanical published form of this work, or allow others to do so, for United damage and selective seam corrosion is greater.

8 This paper States Government purposes. discusses the development and verification of these classifiers. 1 Copyright 2016 by asme . NOMENCLATURE to saturate the pipeline material [1]. Such high magnetic field- A MFL Signal Amplitude based magnetizers help suppress noise due to local stress B Background MFL Amplitude variations and changes in the microstructure of the Metal [2]. - Normalized Amplitude At Metal - loss defects, such as those caused by corrosion , an w MFL Signal Width increased amount of magnetic flux attempts to flow through the Normalized MFL Signal Width remaining material, however some flux leaks from the pipeline XILI X is any of the above variables, the subscript wall due to saturation of the remaining material.

9 In addition, in ILI indicates data type magnetically saturated materials, an increase in flux causes the mfl axial MFL flux-carrying capability (permeability) to decrease [3] resulting lfm low field axial MFL in additional leakage. The dual effect of increased magnetic smfl helical MFL flux and decreased flux-carrying capacity results in significant t wall thickness flux leakage at Metal loss defects. F general function x general variable Stress and material variations can also change the flux-carrying n Weighting constants n = 0,1,2,3,4 capacity of the pipe [4-5].

10 A local decrease in flux-carrying capacity causes leakage similar to that resulting from Metal - loss BACKGROUND defects. A local increase in flux-carrying capacity causes a Dent Assessment by ILI decrease in flux leakage relative to the nominal, magnetic field Accepted codes, standards, and governmental regulations level. For example, for tensile stresses, the overall flux levels in address the secondary features of corrosion and gouging in the pipeline increase. For compressive stresses, such as cold- Dents . As an example, per 49 CFR (d) natural gas worked areas, the flux levels decrease.