Slipstream Heat Addition on the Trans-Alaska Pipeline: Thermal Risk Mitigation Strategies and Lessons Learned

The Trans-Alaska Pipeline System (TAPS), designed for a peak throughput of over 2 million barrels per day, operates at an average of less than 470,000 barrels per day (2023). At peak flow, the transit time from Prudhoe Bay to the Valdez Marine Terminal was 4.3 days; it is now more than 18 days. Frictional heating is now negligible, and the extended time in transit assures significant heat loss along the line which can become operationally critical in winter months. This paper describes the development of a strategy by the pipeline operator, Alyeska Pipeline Service Company (APSC), to mitigate ice formation risks. This effort began in the mid-2000s and continues to this date. The paper details the mechanisms behind heat loss on the pipeline, the TAPS temperature gradient model, establishment of risk critical temperature thresholds, evaluation of heating methods (bulk versus slipstream), and the operation and performance of the three major "heating kits" and supplementary heating methods along TAPS. Finally, the paper will offer lessons learned to date, and how the lessons are being applied to improve future operations.