Materials Performance Supplements

Corrosion Management for Pipeline Integrity 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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20 JUNE 2018 W W W.MATERIALSPERFORMANCE.COM CORROSION MANAGEMENT FOR PIPELINE INTEGRIT Y SUPPLEMENT TO MP Protecting Urban Pipelines Australia, as well as many other coun- tries around the globe, encompasses thou- sands of kilometers of pipelines. This infra- structure represents an investment of many millions of dollars over many years by com- panies and government. Since the cost implications of ignoring the effects of cor- rosion are large, managing corrosion risk is important. Monitoring the impact of corro- sion on buried pipelines can help ensure pipeline integrity. The advantages of planning for corro- sion control and mitigation include extend- ing the life of the asset while reducing maintenance time and costs. According to Jim Galanos, engineering manager at Cor- rosion Control Engineering (CCE) (Sydney, New South Wales, Australia), there are two aspects of protecting pipelines that pass through urban environments. The first is ensuring there is no physical damage done to the pipelines by third parties who dig or drill near the buried pipes. "It happens far more often than we'd like," Galanos states. "The most common is another utility com- pany excavating and then boring or direc- tional drilling where they haven't checked the plans and applicable procedures." The second is preventing coating dam- age and disruption of the cathodic protec- tion (CP) systems. "It's not just digging into the ground," Galanos adds. "Certain types of backfilling and compaction methods can affect the f low of CP current through the soil from the anodes to a pipeline." Once disrupted, the protection offered can be greatly diminished and costly to restore. Galanos indicates that his company is responsible for pipelines that are high-pres- sure, high-volume supply lines, which tra- verse both country and urban areas carry- i n g p e tro l e u m , ga s , w a t e r, a n d o th e r products. "Beneath Sydney there are hun- dreds of kilometers of steel pipes in a range of diameters," he says. "Some of these have been safely in place for decades but urban sprawl is now threatening them ." Most pipelines lie beneath public spaces such as roads and parklands, but some do cross pri- vate property. Mark Dragar, asset manager—pipelines for asset owner and operator Jemena (Mel- bourne, Victoria, Australia), agrees that it is often third-party construction crews that cause damage but then neglect to report it. "We've had a contractor digging a trench to install a water pipe that damaged large sec- tions of the coating on a steel pipe, and then thought it would be okay to simply place back the damaged coating and secure it with gaffer tape," he says. Dragar adds that the coating on the bur- ied pipelines is the primary way his com- pany mitigat es corrosion , and th ereby maintains the structural integrity of its assets. The weakest points in the network, however, are the field joints—where lengths of pipe are laid and welded together on-site and then recoated. "We could have the best design and materials being used for a proj- ect, but the effectiveness of the coating over the joint comes down to the abilities of the applicators applying it," he says, noting that quality control is paramount. An example of this is when the instruc- tions for applying a heat-shrink sleeve to a pipe joint specify that the pipe surface must be heated to more than 80 °C, and an appli- cator heats the metal to an even higher temperature but then takes too long to position the sleeve in place. Meanwhile, the pipe surface temperature drops to ~70 °C, and the sleeve does not adhere properly. "As a result, we have mandated that all con- struction is to be carried out to a higher level than that required by the relevant standard," Dragar says. Another corrosion control method used on pipelines is CP. This is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochem- ical cell. A simple explanation of this type of protection is to connect the metal to be protected to a more easily corroded "sacri- ficial metal" that acts as the anode. The sac- rificial metal then corrodes instead of the protected metal. Most of the buried steel pipelines across Australia have some form of CP associated with them. Older impressed current CP sys- tems typically consist of a small number of high-capacity anode groundbeds spaced along the pipeline. Galanos comments that the design of newer CP systems now incor- Pipeline Protection Articles Protecting buried pipelines involves prevention of third-party drainage to coating and CP systems, as well as effective corrosion control.

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