Pipeline 101
Pigging the Trans Alaska Pipeline System

A pig is a mechanical device that is pushed through the pipeline by the oil to perform various operations on 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”. These devices help Alyeska clean and inspect the pipeline to prevent and detect problems.

There are three basic types of smart pigs: 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. As they evaluate the data, engineers look for suspect areas and compile a list of specific locations to determine and prioritize integrity investigations through a “corrosion dig,” a physical examination of the pipeline. Depending on what the dig reveals, the corrective action might be the addition of a sleeve or a new, higher quality coating developed since the pipeline was originally constructed.