The trans-Alaska pipeline stretches from the northern settlement of Prudhoe Bay on the Arctic Ocean, across the Brooks, Alaska, and Chugach mountain ranges, to Port Valdez on the state's southern coast. Half of the 799-mile pipeline is buried and half rests on supports aboveground, to avoid permafrost melting that can lead to structural and environmental damage. Up to two million barrels of crude oil are pumped through the four-foot diameter pipeline daily, cooling from an average temperature of 49 degrees Celsius at Prudhoe Bay to about 21 degrees Celsius at Port Valdez. Alyeska Pipeline recently conducted experimental and analytical studies at the Institute that led to a greatly improved understanding of pipeline behavior. Using this program, the safety of corroded pipe can be assessed and a decision made regarding whether to excavate a specific corroded area and whether to add a sleeve to the exposed area.
SAFE considers conditions to limit states, namely pipe rupture and wrinkling.
However, the wrinkling limit state has not been comprehensively studied. Therefore, current and proposed work for Alyeska Pipeline consists of developing a suitable experimental and analytical database for the definition and calibration of SAFE engineering calculations to predict the wrinkling capacity of a corroded and settled pipeline section. Protected from subzero temperatures by a heated tent-like structure, workers take detailed measurements of corroded sections of pipe using grids that allow a map of the area to be developed for integrity assessment analyses. The measurements are compared with those estimated by a smart pig and then analyzed to determine the remaining strength of the corroded region. Institute researchers have formulated a combined experimental and analytical approach to provide a comprehensive wrinkling calibration database.