Corrosion Control Program keeps oil flow safe and reliable
Rust never rests, neither does TAPS' engineering team

Alyeska’s corrosion monitoring and control program helps ensure safe, efficient and reliable oil transport through the 800-mile-long Trans Alaska Pipeline System (TAPS).

Engineers monitor data from the entire pipeline system to coordinate corrosion prevention measures and maintenance schedules that maintain pipe integrity. Left unchecked, corrosion could eventually cause leaks and unplanned pipeline shutdowns.

Integrity management engineers restructured TAPS’ corrosion control program in 2002 to combine all corrosion-related activities into a single program. Previously, corrosion control was spread across five departments, including: pipeline operations, pipeline maintenance, pipeline system integrity engineering, terminal system integrity engineering and terminal maintenance. Merging these efforts resulted in efficiencies that allowed more sites to be monitored for corrosion and enhanced regulatory compliance while reducing program costs more than 25 percent.

“The corrosion control program has always been key to Alyeska’s success and high safety standards,” said Mike Malvick, TAPS integrity management engineering supervisor. “It helped the pipeline exceed its original design life and, with proper maintenance, will ensure decades of continued safe and reliable operation.”

Corrosion occurs both inside and outside of pipe. It can’t be completely stopped, but it is controlled. Engineers and inspectors constantly monitor TAPS to determine where corrosion is occurring and when particular sections of pipe should be repaired or replaced.

Engineers use mechanical devices called smart pigs that move through TAPS with the oil to measure pipe wall thickness. They also use ultrasonic testing and radiography (x-ray) to test wall thickness, and they check internal corrosion monitoring coupons twice a year to determine corrosion rates and set maintenance schedules.

External corrosion occurs wherever moisture contacts steel pipe, usually because pipeline insulation becomes wet or protective coatings have worn down. Maintenance technicians mitigate external corrosion by either re-coating, re-taping, re-sleeving or, in the worst situations, replacing affected pipe. They also repair insulation jackets to keep pipe dry.

Alyeska uses impressed current and galvanic cathodic protection systems to control below ground corrosion on the outside of pipe. The impressed current systems use electricity to prevent corrosive processes and the galvanic systems are similar to galvanic anodes commonly used to protect water heater shells and outboard boat motors. Technicians inject chemical inhibitors into TAPS to stop or slow corrosion inside of pipe. Inhibitors bond with the pipe wall to form a layer that protects pipe from water and other corrosive materials. Inhibitors disperse over time and must be periodically reinjected.

Alyeska is upgrading some corrosion control systems during its ongoing strategic reconfiguration project to modernize TAPS, especially the pump stations.

“After the strategic reconfiguration upgrades are in place, our job will be to continue giving the pipeline system excellent care, so that it will continue to out perform its design expectations,” said Malvick.