It is good practice to reduce the pressure in a pipeline prior to inspecting damage. One of the purposes of this pressure reduction is to prevent a ‘time dependent failure’ whilst inspecting the damage. The EPRG (European Pipeline Research Group) guidelines for the assessment of mechanical damage recommend that the internal pressure be reduced to 85 percent of the pressure at the time of damage to prevent time dependent failures. The PRCI (Pipeline Research Council International) Pipeline Repair Manual recommends a pressure reduction to 80 percent of the pressure at the time of damage. Failures that occur under a constant load are time dependent failures. This means that a defect in a pipeline could fail sometime after the damage was caused, even though there has been no increase in the applied load, or an active growth mechanism such as corrosion or fatigue. They have been observed during hydrostatic test hold periods, during operation and under laboratory conditions. Failures under constant load occur because plastic deformation occurs in the material surrounding a defect subject to a load, and because plasticity is time dependent. Time dependent behaviour is relevant to: (1) the safe working practices in the vicinity of a damaged pipeline, (2) pressure reversals, (3) the margin between the operating pressure and the hydrostatic test pressure, and (4) the minimum duration of a hydrotest. The results of experimental and analytical studies of time dependent behaviour reported in the published literature are reviewed in this paper, to understand the background to the above recommended pressure reductions. This paper is based on the findings of the Pipeline Defect Assessment Manual (PDAM) project, a Joint Industry Project sponsored by sixteen international oil and gas companies.
Skip Nav Destination
2004 International Pipeline Conference
October 4–8, 2004
Calgary, Alberta, Canada
Conference Sponsors:
- International Petroleum Technology Institute
ISBN:
0-7918-4176-6
PROCEEDINGS PAPER
A Review of the Time Dependent Behaviour of Line Pipe Steel Available to Purchase
Andrew Cosham,
Andrew Cosham
Penspen Integrity (Andrew Palmer and Associates), Newcastle upon Tyne, UK
Search for other works by this author on:
Phil Hopkins
Phil Hopkins
Penspen Integrity (Andrew Palmer and Associates), Newcastle upon Tyne, UK
Search for other works by this author on:
Andrew Cosham
Penspen Integrity (Andrew Palmer and Associates), Newcastle upon Tyne, UK
Phil Hopkins
Penspen Integrity (Andrew Palmer and Associates), Newcastle upon Tyne, UK
Paper No:
IPC2004-0084, pp. 1145-1158; 14 pages
Published Online:
December 4, 2008
Citation
Cosham, A, & Hopkins, P. "A Review of the Time Dependent Behaviour of Line Pipe Steel." Proceedings of the 2004 International Pipeline Conference. 2004 International Pipeline Conference, Volumes 1, 2, and 3. Calgary, Alberta, Canada. October 4–8, 2004. pp. 1145-1158. ASME. https://doi.org/10.1115/IPC2004-0084
Download citation file:
18
Views
Related Proceedings Papers
Related Articles
Failure of Locally Buckled Pipelines
J. Pressure Vessel Technol (May,2007)
Influence of Yield-to-Tensile Strength Ratio on Failure Assessment of Corroded Pipelines
J. Pressure Vessel Technol (November,2005)
Theoretical and Numerical Predictions of Burst Pressure of Pipelines
J. Pressure Vessel Technol (November,2007)
Related Chapters
Section VIII: Division 2–Alternative Rules
Companion Guide to the ASME Boiler & Pressure Vessel Codes, Volume 2, Sixth Edition
Transportation Pipelines, Including ASME B31.4, B31.8, B31.8S, B31G, and B31Q Codes
Online Companion Guide to the ASME Boiler & Pressure Vessel Codes
Understanding the Problem
Design and Application of the Worm Gear