In the Field
Smart pig completes integrity inspection of TAPS

Alyeska is currently evaluating its pigging program to make certain the necessary steps are taken regarding the integrity and safe operation of the Trans Alaska Pipeline System. Following the March 2006 North Slope spill, Alyeska took action by moving up a scheduled smart pig run, originally planned for 2007 to inspect the pipeline. The pig successfully ran through the first segment (PS 1 to PS 4) in August 2006 but data loss occurred in the second segment (PS 4 to Valdez) due to wax build up on the pig when it was run a month later.

On Monday, March 5, a Magnetic Flux Leakage smart pig was launched from PS 4 to complete the previously scheduled run. The pig successfully completed its run arriving in Valdez on Thursday, March 15. Approximately 111 gigabytes of information were retrieved. This data will be analyzed to determine the internal and external condition of the 656 miles of pipeline from PS 4 to Valdez. In preparation for the second smart pig run, several cleaning pigs were launched to clean the interior walls of the pipeline so the smart pig’s magnetic sensors could make sufficient contact with the walls of the line to assure accurate data recording.

As they evaluate the data, engineers look for suspect areas and compile a list of specific locations to determine and prioritize necessary integrity investigations, a physical examination of the pipeline. In the photo above, at right, Alyeska engineers Dave Hackney and Felicia Chuckwu inspect the pig prior to inserting it at PS 4.

A pig is a mechanical device that is pushed through the pipeline by the oil to perform various operations inside the pipeline without stopping the flow of oil. This process is referred to as “pigging.” Alyeska runs two basic types or classes of pigs: cleaning and instrumented or "smart pigs." These devices help Alyeska clean and inspect the pipeline to prevent and detect problems. The three basic types of smart pigs are ultrasonic transducer (UT), magnetic flux leakage MFL and curvature. These pigs are used to periodically inspect for pipeline corrosion and deformation using nondestructive sensor technologies including ultrasound and magnetic sensors. The picture at right shows the MFL pig after being removed at the Valdez Marine Terminal following its inspection run.