This paper describes a small exploratory study into the feasibility of predicting where near-neutral-pH stress-corrosion cracking (NN-pH SCC) would be more likely to occur based upon the history of pressure fluctuations in a pipeline. Such a correlation would be very valuable for prioritizing hydrostatic testing, in-line inspection (ILI), and direct assessment in addition to possibly suggesting a way to minimize the occurrence of SCC. The recent development of ILI tools that can find stress-corrosion cracks coupled with computerized SCADA and GIS systems provides an opportunity to make accurate assessments of the severity of SCC in a pipeline segment and to characterize the history of that segment. Previous work had shown the importance of strain rate and pressure fluctuations in promoting SCC. On that basis, Enbridge Pipeline, Inc. initiated a review of their system, which indicated that there appeared to be a strong correlation between SCC severity and magnitude and frequency of pressure fluctuations. Data from two other pipeline companies — one liquid and one gas — was obtained to see if the correlation was more broadly valid. It was determined that the correlation utilized by Enbridge was biased towards fatigue-type considerations. This suggests that the cracking on pipelines that demonstrate this correlation may involve a corrosion-fatigue mechanism in addition to, or instead of, traditional environment-sensitive SCC. Analysis of data from the other two companies was ambiguous, primarily because the available SCADA data covered only 1.25 years of recent operation. It also is possible that some effects of pressure fluctuations might have been masked by environmental effects and steel susceptibility. Consideration of such factors in addition to the inclusion of information on coating, pipe manufacturer, and geological features, would be expected to produce an even higher level of predictability.

The focus of the Enbridge Integrity Management System is to prevent leaks or ruptures caused by all duty-related pipe deterioration including SCC. As with all pipe defect types, ongoing monitoring programs are employed to determine whether SCC has occurred. Where it has, preventative maintenance programs are employed to mitigate the SCC. Where required, Enbridge employs high-resolution crack in-line inspection (ILI) as the most precise method for managing SCC. As a member of the Canadian Energy Pipeline Association (CEPA), Enbridge participated in the development of a basic framework for SCC management programs and has adopted this framework as the basis for the Enbridge program. Ultrasonic crack detection ILI, capable of detecting SCC, has been employed on over 3000 km of Enbridge pipe and several hundred investigative excavations have been conducted in relation to the ILI data. The results gathered from these investigations have been trended to define the effectiveness of crack detection ILI to detect, size, and discriminate SCC defects. This paper and presentation describes Enbridge’s experience utilizing ultrasonic crack detection ILI for SCC management. The Enbridge trends have shown that ILI can be reliably utilized to detect SCC but, additional innovation is required for defect sizing. While ILI sizing is limited, trends developed from field inspection data have provided the ability to categorize ILI signals into general classifications that ensure all relevant SCC features are highlighted. The categorization is accurate but added precision would reduce the number of investigative excavations, which currently, are also conducted on many sub-relevant features. Coincident with SCC activities driven by ILI data, trends were also developed for peripheral aspects such as field NDT technology, fitness-for-purpose equations, and SCC initiation and growth causes. Observations and trends related to these activities are also described herein.

This paper describes the integrity management framework utilized within the Enbridge Liquids Pipelines Integrity Management Program. The role of the framework is to provide the high-level structure used by the company to prepare and demonstrate integrity safety decisions relative to mainline pipelines, and facility piping segments where applicable. The scope is directed to corrosion, cracking, and deformation threats and all variants within those broad categories. The basis for the framework centers on the use of a safety case to provide evidence that the risks affecting the system have been effectively mitigated. A ‘safety case’, for the purposes of this methodology is defined as a structured argument demonstrating that the evidence is sufficient to show that the system is safe.[1] The decision model brings together the aspects of data integration and determination of maintenance timing; execution of prevention, monitoring, and mitigation; confirmation that the execution has met reliability targets; application of additional steps if targets are not met; and then the collation of the results into an engineering assessment of the program effectiveness (safety case). Once the program is complete, continuous improvement is built into the next program through the incorporation of research and development solutions, lessons learned, and improvements to processes. On the basis of a wide range of experiences, investigations and research, it was concluded that there are combinations of monitoring and mitigation methods required in an integrity program to effectively manage integrity threats. A safety case approach ultimately provides the structure for measuring the effectiveness of integrity monitoring and mitigation efforts, and the methodology to assess whether a pipeline is sufficiently safe with targets for continuous improvement. Hence, the need for the safety case is to provide transparent, quantitative integrity program performance results which are continually improved upon through ongoing revalidations and improvement to the methods utilized. This enables risk reduction, better stakeholder awareness, focused innovation, opportunities for industry information sharing along with other benefits.

While North American pipeline integrity codes and regulations provide substantive prescriptive or goal setting objectives, there currently is not a consistent measurement approach for defining the levels of safety achieved. Standardized targets would drive consistent operator safety culture, enhance transparency for the public, and focus industry collaboration on technologies and innovation. This paper provides the perspective of an operator on current status of where the pipeline industry is related to safety targets and social license in addition to where the pipeline industry could go in this arena. The intent is a ‘call to action’ for the leaders in the pipeline industry to collaborate on the establishment of the technical systems which define the current industry safety condition, the targets that must be achieved, and to show that the industry is innovating for further improvements; elements considered to be important to the achievement of social license. A review of the current practices as well as a framework for industry advancement and advocacy will be explained. This will include an examination of safety measurement systems from around the world including other notable industries such as aviation and nuclear. Several measurement models will be highlighted including qualitative, semi-quantitative and quantitative. Importantly, this paper will highlight how operators, regulators, and codes organizations can link together for this common purpose and contribute to “social license”.