Closing the Gap on Crack Detection for Gas Transmission Pipeline

Abstract NDT Global (ILI Service Provider) and Enbridge GTM (operator) have recently entered into an agreement to develop a new 30″ In-Line Inspection (ILI) system to detect, identify and characterize cracking in gas pipelines. The operator has invested resources over the years to manage cracking in gas pipelines, especially Stress Corrosion Cracking (SCC). This included Direct Assessment (DA) programs and targeted hydrotest, including spike pressure test, to ensure that pipelines were safe to operate, and that the SCC threat was managed. It became evident that a better approach would be to support and develop a program based on ILI. The operator started to use Electro Magnetic Acoustic Transducer ILI (EMAT) technology since its inception and has accelerated its use since 2019. The operator has built their crack management program with the EMAT as its foundation. The program was designed to ensure the pipelines inspected met the fit for service goals set by the Company. This drove decisions that considered appropriate level of conservatism to ensure these were met. The level of conservatism within the current program led to 2 key outcomes for the program: 1. The conservatism, including requesting the ILI service provider to report features below reporting thresholds and aggressively excavating features reported in based metal allowed to catch the critical cracks but led to an inefficient program where 1 excavation out of 6.5 was actually leading to field confirmed SCC; 2. The typical reporting threshold of 20% or 2 mm (about 0.08 in) depth by 50 mm (about 2 in) long combined with aggressive SCC growth rates led to short re-inspection intervals in most segments identified as susceptible to SCC. Most segments showed re-inspection intervals ranging from 3 to 6 years. Some EMAT vendors have published improved detection thresholds that would minimize this issue. These outcomes, while not preventing the ability for the operator to meet the safety goals, lead to an expensive program to maintain and had an impact on the long-range planning of the company. This drove the decision to explore a partnership with an ILI service provider on an alternative ILI technology to the EMAT tool. The paper will discuss the technical details that formed the basis of the operator’s decision to seek out an alternative. A brief description of the technology proposed by the ILI service provider and its anticipated performance. The focus of the analysis will walk through how both companies combined the technical drivers and the economic principles used to create the business case demonstrating the value of the proposed project. Here, a traditionalROI may not be enough to convince a serious investment in a technology from the perspective of an operator. However, other metrics such as Risk Avoidance ROI might show a different outlook that may tip the scale in demonstrating the value of an investment in the right technology. Both companies support the development of technology, and this paper will advocate the importance of strong collaboration to identify solutions and how to ensure these types of projects continue so better technology can lead to more effective and efficient integrity programs.