NDLI: Pipeline Dent Fatigue Crack Leak Rate for Liquids Pipelines and the Application to Release Consequence Assessment

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Tiku, Sanjay Piazza, Mark Semiga, Vlado John, Binoy Dinovitzer, Aaron
Copyright Year	2018
Abstract	Pipeline design and integrity management programs are employed to ensure reliable and efficient transportation of energy products and prevent pipeline failures. One of the failure modes that has received attention recently is pipeline fatigue due to pressure cycling in liquid pipelines, promoting through wall cracking and the release of product. Being able to estimate the leakage rate and/ total release volume are important in evaluating the consequence of developing a through wall crack, operational responses when incidents occur, and remedial action strategies and timelines. Estimates of leak rates can be used in pipeline system threat and risk assessment, evaluation of leak detection system sensitivity, development of Emergency Response Plans and strategies, and post-event evaluation. Fracture mechanics techniques consider the response of crack-like features to applied loading such as internal pressure, including estimation of crack mouth opening. Considering the differential pressure across the pipe wall and the crack opening area, estimated from the crack mouth opening, the flow of fluid through the crack can be conservatively estimated. To understand the conservatism of this analytical estimate of leakage rate, full-scale testing has been completed to evaluate the leakage rate through dent fatigue cracks of differing lengths under a range of internal pressures, and compare the empirical measured results to the analytical/theoretical estimates. The test procedure employed cyclic internal pressure loading on an end-capped pipe with a dent to grow fatigue cracks through the pipe wall thickness. Once a through wall crack was established, the internal pressure was held constant and the leakage rate was measured. After measuring the leakage rate, cyclic loading was employed to grow the crack further and repeat the leakage rate measurement with the increased crack length. The results of this experimental trial illustrate that the tight fatigue crack resulted in a discontinuous relationship between leakage rate and pipe internal pressure. Measureable leakage did not occur at low pipe internal pressures and then increased in a nonlinear trend with pressure. These results illustrate that a liquid pipeline with a through wall fatigue crack operating at a low internal pressure, or one having taken a pressure reduction, can have low leakage rates. The data and results presented in this paper provide a basis for an improved understanding and describing the leakage rate estimates at pipeline fatigue cracks, and providing insights into leakage rates and how to conservatively estimate them for fatigue crack consequence evaluation.
Sponsorship	Pipeline Division
File Format	PDF
ISBN	9780791851876
DOI	10.1115/IPC2018-78716
Volume Number	Volume 2: Pipeline Safety Management Systems; Project Management, Design, Construction, and Environmental Issues; Strain Based Design; Risk and Reliability; Northern Offshore and Production Pipelines
Conference Proceedings	2018 12th International Pipeline Conference
Language	English
Publisher Date	2018-09-24
Publisher Place	Calgary, Alberta, Canada
Access Restriction	Subscribed
Subject Keyword	Leakage Cracking (materials) Fracture mechanics Pipelines Emergency response Fatigue Fracture (materials) Wall thickness Pressure Flow (dynamics) Transportation systems Fracture (process) Fluids Pipeline systems Risk assessment Pipes Piping design Fatigue cracks Failure Failure mechanisms Testing
Content Type	Text
Resource Type	Article

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