Integrity digs help monitor and mitigate pipeline corrosion

Alyeska has plenty of tools in the toolbox to help detect, prevent and repair corrosion on the trans-Alaska pipeline. Two key components of our program to monitor and manage the integrity of the pipeline are pigging and digging.

Integrity management teams use “smart” or instrumentation pigs to identify areas of concern for dents, pipe curvature and corrosion. We investigate risk areas and perform repairs to remove pipe stress or reinforce the strength of the pipe, as required.

Alyeska spends millions of dollars each year on investigations and repairs to the mainline pipe based on data provided by smart pigs. The investigations look for both external and internal corrosion. External corrosion and mechanical damage are measured with hand-held pit gauges, and Alyeska recently tested a new laser scan technology that can enhance precision and accuracy of measurements with improved speed. If present, internal corrosion is measured with traditional ultrasonic testing and non-destructive testing methods.

After the investigation and repairs are complete, the next step is to prevent corrosion from returning. This is accomplished by recoating the pipe with a new state-of-the-art epoxy coating. Pipeline integrity is assured by removing all old coatings and installing a new coating for the entire surface area.

“When we have the opportunity to recoat the pipe, we take advantage of it,” said Tom Demattia, Alyeska Construction Manager. “The technology in coatings has advanced significantly since the pipeline was installed 30 years ago.”

Alyeska Engineering has used recent smart pig data to confirm that additional external corrosion on previously repaired sections of pipe has been successfully arrested, said Demattia. A special lean cement slurry is then used to bed the pipe. This is used in lieu of traditional bedding and padding to avoid the use of compaction equipment that risks damaging the pipe. Because of the dynamic nature of soils encountered, a solid foundation for the pipe is crucial. Without it, the pipe could settle and bend.

“After the pipe is repaired and recoated, we reinstall the cathodic protection system,” said Demattia. “Alyeska strives to always plan our work and work our plan. We feel an analytical approach to our work allows us to provide the highest levels of integrity, quality, and safety to complete the work efficiently.”