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S P E C I A L F E AT U R E Managing Corrosion of Pipelines that Transport Crude Oils bacteria in the nooks and crannies of your teeth. The foremost method of preventing tooth decay is routine dental care. If you brush regularly, you probably won't have many problems with your teeth. Similarly, if you sweep your pipeline clean of potential corrodents, you won't have many problems with corrosion. Such sweeping can be purely hydraulic—by the fow of the product—or facilitated by pipeline pigs. Some people continue to have tooth decay even when they brush regularly, and those people might fnd that a mouthwash provides incremental protection by killing cavity-causing bacteria. Similarly, a pipeline operator can use a batch corrosion inhibitor to reduce problematic bacteria or to provide a protective flm along the pipe wall (just like fuoride strengthens tooth enamel). I must credit both Tom Jack and Joe Boivin for this analogy. Been: Internal corrosion is managed through the use of preventive measures and monitoring tools. Normal pipeline operating conditions include turbulent fow to prevent water drop-out and solids deposition. Preventive measures include the use of cleaning pigs to remove deposits. These tools are run at a frequency that is established based on operating history and an understanding of the deposition mechanism and corrosion rates. It is continuously reassessed based on the volume and nature of sludge observed to be present. Other integrity assessments such as ILI are also leveraged in terms of adjustments to the cleaning program. Mosher: The industry controls internal corrosion by three main mitigation methods. In the frst method, crude oil pipeline operators maintain a turbulent fow regime to prevent the settling of solid particles and water droplets to the bottom of the pipe. In the second method, cleaning pigs remove any solids and/or water from the pipe surface and force them downstream. By taking away the solids and water from the pipe surface, the corrosive environment is removed. The third method is a chemical corrosion inhibitor package, applied following a cleaning pig run to suppress corrosion in a location where water collects. The inhibitor accomplishes this by suppressing either the cathodic or anodic reactions. In some cases, a biocide may be added to the 34 MATERIALS PERFORMANCE May 2013 inhibitor package when MIC is believed to be a factor. Papavinasam: The internal corrosion of production pipelines is primarily controlled by cleaning their surface using pigs and adding corrosion inhibitors and biocides. Crude oil transmission pipelines, on the other hand, are less susceptible to internal corrosion because they predominantly transport oil (more than 99%) and, by industry standard, their BS&W; is limited to <1% (typically to <0.5%) volume to volume. All other corrosive substances are removed in the oil separators upstream of the crude oil transmission pipelines. However, the oil transmission pipelines may suffer internal corrosion in locations where water might accumulate. The operators control the internal corrosion by adjusting the fow rate so that water does not drop out and accumulate; using cleaning pigs to sweep off the accumulated water and sediment particles; and treating the surface with corrosion inhibitors and biocides. MP: Are enough technologies available to effectively identify and control transmission pipeline corrosion or is more research and development work necessary to address the issue? Papavinasam: Several advanced and reliable technologies are available and used in the industry. But there is always room for innovation and further improvements, and there are some specifc areas where additional research and development (R&D;) is needed. For example, computer simulation and industry experience indicate that the locations where water may accumulate in oil transmission pipelines are different for light and heavy oil; yet the boundary where the transition occurs is not well established. Further R&D; is required to develop and validate reliable models to accurately predict the locations of water accumulation based on crude oil types. Also, laboratory methodologies to determine how the crude oils may infuence the corrosivity of the water phase are established (ASTM G205); however, determining these properties requires withdrawing crude oil samples from the pipeline and carrying them to the laboratory for analysis. Advancements in techniques for online measurement of these properties would not only lessen the time lag between the sample collection and analysis, but also would alleviate errors due to possible contamination of the samples. Additionally, ILI to directly measure the size and shape of the corrosion features is fairly established, but advancements in the algorithms and techniques to easily and quickly match the corrosion features from consecutive runs are required. Been: The currently available tools and processes are suffcient to manage the internal corrosion threat for transmission pipelines; however, improvements and optimizations could be achieved with better predictive models regarding solids deposition and sludge corrosivity. We are actively involved in joint industry projects and R&D; initiatives on internal corrosion monitoring and mitigation, including participation in public forums and conferences on crude oil corrosivity. During these events, we share our operating experiences and relevant integrity management practices. One industry effort employs a pilot-scale crude oil fow loop for the evaluation of cleaning pig designs and chemical inhibitor treatments and the assessment of corrosion monitoring equipment for underdeposit corrosion. Moghissi: Improving our technical understanding of transmission pipeline internal corrosion would be helpful, especially with respect to predicting where extremevalue corrosion rates might occur. In addition, improving systems and processes for managing corrosion risk would also have an impact. This includes methods to incorporate corrosion in risk management systems. If corrosion risks were better tied to overall risk, operators could make more effective and effcient decisions. Mosher: Technologies used in the detection and mitigation of internal corrosion for crude oil pipelines have progressed signifcantly in recent years but there is still a need for improvement and advancement. As long as there are corrosion failures occurring, it is imperative that better technologies be explored through R&D; and feld implementation. If we are to ever meet the industry target of zero incidents, detection and mitigation technologies will need to improve, either by refning the current tools or developing new and novel technologies. Richter: There is already considerable technology and know-how that goes NACE International, Vol. 52, No. 5