Presented by Jonathan Minder at the 2015 Unpiggable Pipeline Solutions Forum in Houston, TX
Alyeska Pipeline Service Co., a major North American petroleum pipeline operator, is completing an extensive modernization and inspection project for the Trans-Alaska Pipeline System (TAPS) pump stations. TAPS is a major piece of the Alaskan oil infrastructure that recently reached the milestone of moving 17 billion barrels of North Slope crude oil.
Diakont was commissioned by Alyeska to perform robotic in-line inspections on piping systems at Pump Station 3 (PS03), near the northern end of the pipeline. Diakont’s inspection solution was selected because it utilized advanced robotic crawlers that drive through and inspect previously inaccessible piping at risk of corrosion and leaks.
The pipe sections were considered inaccessible because the piping geometries were too complex for traditional smart pigs to negotiate; the pump station piping was underground and had a ten foot vertical entry point along with several compound bends that changed direction and elevation. Also, the piping sections could not be excavated for inspection because they were encased in concrete slurry which surrounded the piping to keep the tundra around the pipe frozen – without the insulating concrete, the petroleum pipes would defrost the tundra and causing the piping to sag.
Before the robotic crawler inspection solution was identified, the piping sections were thought to be inaccessible for integrity validation and state and federal agencies mandated that the piping be replace with accessible above-ground piping. This piping replacement was started at Pump Station 1 and required more time and money than originally expected so the operator contacted Diakont.
In 2013 Diakont performed a test run inspection on a decommissioned pump station to ensure that the robotic crawler could navigate the complex piping geometries. The robotic crawler successfully handled the piping geometries at the decommissioned pump station. Diakont then fabricated full-scale piping mock ups of the most difficult geometries at PS03 to validate the tool’s capabilities and train inspection technicians.
Diakont’s advanced inspection solution was able to reach sections of pipeline that would have required replacement without integrity verification so the operator was extremely excited with the opportunity to inspect rather than blind replacement. Diakont’s inspection found that the pipeline sections were still within the nominal pipe wall thickness to maintain operation and the pump station was brought back online.