Statistical Analysis on Underload-Type Pipeline Spectra
Publication: Journal of Pipeline Systems Engineering and Practice
Volume 7, Issue 4
Abstract
In this investigation, analyses of pressure fluctuations during oil and gas pipeline operations are performed. The analyses are performed in a way to capture all the variables of pressure fluctuations and their magnitudes in terms of crack growth rate. It is found that pipeline spectra can be categorized into three main types: underload-dominant, mean load-dominant, and overload-dominant spectra, depending on their locations with respect to a compressor or pump station. The underload spectra—typical of pressure fluctuations at the discharging sites—are the most severe in terms of crack growth as these spectra are subjected to the highest pressure level and the largest magnitude and frequency of pressure fluctuations. The underload spectra are further analyzed in terms of loading and unloading frequency, maximum stress-intensity factor, stress-intensity factor range, numbers of minor cycles between two adjacent underloads, and their potential for crack growth. Special attention is paid to the difference between oil and gas pipeline spectra. The frequency of pressure fluctuations is found to vary over a much wider range during oil pipeline operation than during gas pipeline operation, and the occurrence of crack growth contributing loading events is significantly more frequent in oil pipeline spectra than in gas pipeline spectra. It is recommended that the supervisory control and data acquisition (SCADA data) is recorded at a minute rate for gas pipelines and at a second rate for oil pipelines in order to capture most crack-growth-contributing events of pressure fluctuations during pipeline operation.
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Acknowledgments
The authors would like to thank TransCanada Pipeline Limited, Spectra Energy Transmission, Natural Science and Engineering Research Council of Canada, and Pipeline Research Council International (PRCI) for financial support. The authors would like to thank Michael Liao for revision of this paper.
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Published In
Journal of Pipeline Systems Engineering and Practice
Volume 7 • Issue 4 • November 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Jun 29, 2015
Accepted: Feb 3, 2016
Published online: Apr 28, 2016
Discussion open until: Sep 28, 2016
Published in print: Nov 1, 2016
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