During the summer of 1996, the TransAlaska Pipeline System (TAPS) experienced pipe vibrations near Thompson Pass, which is located 25 miles north of the Valdez Marine Terminal (VMT). The VMT is the southern terminus of the 48-inch oil pipeline transporting Alaska North Slope Crude for further shipment to market via marine tankers. The pipeline is designed to operate in a slackline mode as it flows over the 2,810 ft. elevation of Thompson Pass.

As a result of the slackline experience gained at Thompson Pass, Alyeska evaluated other areas along TAPS where continuous slackline operation either existed in the past or could exist in the future with declining pipeline throughputs. A study determined that other locations along the pipeline could operate in a continuous slackline mode and should be investigated for potential slackline operating problems. This paper describes the slackline testing and evaluation and methods developed by Alyeska to control problems caused by slackline operation. General evaluations and observations of the slackline dynamics phenomena that can cause pipe vibrations along with guidelines and recommendations for the control or elimination of slackline vibration problems are presented.

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