Effective and efficient crack management programs for liquids pipelines require consistent, high quality non-destructive examination (NDE) to allow validation of crack in-line inspection (ILI) results. Enbridge leveraged multiple NDE techniques on a 26-inch flash-welded pipe as part of a crack management program. This line is challenging to inspect given the presence of irregular geometry of the weld. In addition, the majority of the flaws are located on the internal surface, so buffing to obtain accurate measurements in the ditch is not possible. As such, to ensure a robust validation of crack ILI performance on the line, phased array ultrasonic testing (PAUT), time-of-flight diffraction (TOFD), and a full matrix capture (FMC) technology were all used as part of the validation dig program. PAUT and FMC were used on most of the flaws characterized as part of the dig program providing a relatively large data set for further analysis. Encoded scans on the flash welded long seam weld were collected in the ditch and additional analyses were performed off-site to characterize and size the flaws. Buff-sizing where possible and coupon cutouts were selected and completed to assist with providing an additional source of truth. Secondary review of results by an NDE specialist improved the quality of the results and identified locations for rescanning due to data quality concerns. Physical defect examinations completed after destructive testing of sample coupon cutouts were utilized to generate a correlation between the actual defect size from fracture surface observation and the field measurements using various NDE methods. This paper will review the findings from the program, including quality-related learnings implemented into standard NDE procedures as well as comparisons of detection and sizing from each methodology. Finally, a summary of the benefits and limitations of each technique based on the experience from a challenging inspection program will be summarized.

Internal corrosion is one of the main threats to pipeline integrity. For in-line inspection (ILI) based integrity programs, in-the-ditch non-destructive examination (NDE) data quality is imperative for ILI validation. NDE feature misclassification and/or depth inaccuracy can lead to unnecessary integrity actions such as unnecessary excavations, more frequent ILI, or increased risk to system integrity. Therefore, it is critical to ensure the accuracy of NDE data. Ultrasonic Testing (UT) technology is the primary method to detect, characterize, and measure internal corrosion during in-ditch NDE. While studies have been conducted to understand various NDE technologies and capabilities associated with detecting, sizing, and classifying crack and external corrosion indications, less work has been published regarding field evaluation of internal corrosion indications. In this study, real cases of liquid pipelines will be used to demonstrate the challenges in detecting, characterizing and sizing internal corrosion using current UT technologies. The cases show that improper NDE technique selection triggered additional excavations or caused internal corrosion to be non-conservatively under-reported. This work also includes various UT technologies, such as encoded zero-degree UT scanning, manual zero-degree UT testing, encoded Phased Array Ultrasonic Testing (PAUT), and Time of Flight Diffraction (TOFD) for characterizing and sizing both natural and machined defects in pipe and plate samples. High-resolution laser scans using Creaform HandyScan technology are used to verify actual feature depth. Depth sizing accuracy of each technology is established using statistical analysis. In order to determine detection limits of the above technologies, tests are performed on pitting and inclusion of various sizes, ranging from 8 mm to 0.5 mm in diameter. This study will assist in establishing the limitations of current UT NDE technologies and recommendations to develop best practices for obtaining quality field NDE data from pipeline excavations for internal corrosion.

The fracture mechanics based engineering critical assessment (ECA) method has been accepted as a fitness for service (FFS) approach to defining weld flaw acceptance criteria for pipeline girth welds. Mechanized gas metal arc welding (GMAW) processes are commonly used in cross country pipeline girth weld welding because of the advantages in good quality and high productivity. With the technical advancements of non-destructive testing (NDT) techniques, automated ultrasonic testing (AUT) has greatly improved flaw characterization, sizing and probability of detection during weld inspection. Alternative weld flaw acceptance criteria are permitted in pipeline construction code to assess the acceptability of mechanized girth welds using an ECA. The use of an ECA based weld flaw acceptance criteria can significantly reduce the construction cost. Mechanized girth weld acceptance criteria have been progressively transitioned from workmanship standards into using fitness for service based ECAs. To successfully deliver an ECA on a pipeline project, a multidisciplinary approach must be taken during the welding design and construction stages. Welding, NDT, mechanical testing and field control are all integral elements of pipeline construction. All these four elements have to be fully integrated in order to implement the ECA and achieve the overall integrity of a pipeline. The purpose of this paper is to discuss the importance of the integration of these four elements necessary for proper implementation of the ECA weld flaw acceptance criteria.

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Pipelines are widely used in the oil and gas industry for transporting crude oil and natural gas from the field to refineries. It has been a general practice to use alternative weld flaw acceptance criteria to assess the acceptability of mechanized girth welds using an engineering critical assessment (ECA) approach. The ECA concept of defining weld flaw acceptance criteria has been accepted as a fitness for service (FFS) assessment based on fracture mechanics, which requires robust welding procedures. Effective planning of the welding procedure specification (WPS) qualification and mechanical testing of the weld and heat-affected zone (HAZ), and weld inspection are the key factors contributing to robust welding procedures and an effective ECA. Mechanized gas metal arc welding (GMAW) processes are commonly used in pipeline girth weld welding because of their high quality and productivity. With the technical advancements of non-destructive testing (NDT) techniques, the use of automated ultrasonic testing (AUT) with supplemental time of flight diffraction (ToFD) has further enhanced the accuracy and productivity in weld inspection, weld flaw sizing, and probability of detection. The use of alternative acceptance criteria to assess the acceptability of mechanized girth welds using an FFS approach can significantly reduce the construction cost by focusing weld integrity on significant weld flaws. Consequently, unnecessary weld repairs are minimized, increasing the ability to utilize welding resources to achieve more predictable weld quality and productivity. Mechanized girth weld acceptance criteria have been progressively transitioned from using workmanship standards into FFS-based ECAs. The semi-automatic waveform controlled GMAW and mechanized flux-cored arc welding (FCAW) processes are not unique to the pipe welding industry, especially tie-in welding. However, ECA-based weld flaw acceptance criteria have not been commonly applied to welds using the above welding process combinations. This paper focuses on the development of the alternative weld flaw acceptance criteria for mainline production girth weld construction using a hybrid of semiautomatic waveform controlled GMAW and mechanized gas-shielded FCAW (FCAW-G) processes. It explains the integration of the intended WPS qualification, mechanical testing, ECA methodology and AUT procedures. The girth weld acceptance criteria were developed based on CSA Z662-19 Annex K using Option 2 methodology. Additional fractography, metallography, and hardness mapping were conducted to characterize test specimens with crack tip opening displacement (CTOD) pop-ins.