Join Blade Energy Partners, as they present at the 36th Annual Pipeline Pigging and Integrity Management (PPIM24) Conference and Exhibition in Houston, Texas from February 12-16, 2024.
Website: Registration – PPIM Conference
Thursday, February 15, 2024
(60) Considerations When Selecting Failure Stress Models for Prioritizing Crack or Crack-like Anomalies for Response and Remediation
Sergio Limon, Ming Gao, Ravi Krishnamurthy
Blade Energy Partners, Houston, USA
An increasing number of in-line inspections (ILI) for assessing pipelines for cracking and seam weld anomalies are being carried out for the first time in more pipeline segments than before and reassessments are more common. These inspections have resulted in an increased need to evaluate and identify which planar defects pose an immediate or future safety concern to pipelines, since not all cracks and seam weld defects are injurious. For PHMSA regulated gathering and transmission pipelines, a prioritized response criteria for ILI reported indications now include response conditions based on failure pressure predictions. However, there is no unified single failure stress model nor method for estimating the failure pressure of pipelines with cracking and seam weld anomalies. The analyst is tasked with choosing from several failure stress models available to evaluate the rupture pressure capacity of a pipeline in the presence of planar defects and to estimate leak/rupture behavior.
In this paper, considerations for the selection of failure stress models are provided within the context of the type of defect being evaluated, the pipe known or expected fracture mechanism (brittle cleavage/quasi cleavage, or ductile/micro-void coalescence), fracture toughness data available or assumed, failure criteria, the fracture mechanics basis of the models and their solution space for cracks and seam weld defects. A miss-match between any of these factors can result in unreliable predictions or overly conservative results.
(58) Critical Review and Improved Fatigue Life Prediction Models for Unconstrained Single Peak Plain Dents
Rick Wang1, Ming Gao2
1TC Energy, Calgary, USA. 2Blade Energy Partners, Houston, USA
In API1183, the EPRG 2000/API579 Level 2 model is adopted as an alternative approach to BMT shape-parameter method for Level 2 fatigue severity assessment of unconstrained single peak plain dents in pipelines This model along with its earlier version, EPRG 1995, has been commonly used for dent integrity assessment in North American and worldwide because it is recommended by the highly recognized pipeline defect assessment manual. However, Pipeline industry practice in North America found that the EPRG equations provide conservative, in many cases, very conservative predictions that may have resulted in unnecessary excavations and repairs. Therefore, the objective of this paper is to improve the model accuracy and less conservatism. A critical review of EPRG/PDAM fatigue life prediction models (1995 model and its 2000 update) and other models including PRCI/BMT shape-parameter fatigue severity model (Level 2) and FEA/BS7608 fatigue life prediction (Level 3) are essential and given first, which provides a basis for improvement of EPRG equations from both safety and cost-effective perspectives. The newly improved and simplified model is then developed with PRCI MD 4-2 full-scale fatigue testing data and validated using PRCI MD 4-11, MD 4-14 and MD 4-15 full scale fatigue test results. Finally, a comparison among the newly improved model, EPRG 2000/API 579 Level 2 model, and PRCI/BMT/API 1183 Level 2 and Level 3 models is made, which provides a framework to further carry out the study of dent-interacting with welds, gouge, cracks, and corrosion.
(72) A Case Study of a Natural Gas Pipeline Failure Due to CP-Related Hydrogen-Assisted Cracking
Pablo Cazenave, Ming Gao, Katina Jimenez, Ravi Krishnamurthy
Blade Energy Partners, Houston, USA
The possibility of hydrogen-induced cracking and hydrogen-assisted cracking as interactive threats is increasingly becoming a safety concern to pipelines. While few cases exist of fully documented onshore transmission pipeline failures due to CP-related hydrogen-assisted cracking, the possibility of hydrogen-assisted failures needs further investigation, particularly hydrogen interacting with stress corrosion cracking in corrosion potentials more negative than -850 mV CSE.
This paper presents a case study of a 22-inch onshore natural gas transmission pipeline that experienced in-service leaks and a rupture associated with axially and circumferentially oriented crack colonies initially thought to be traditional stress corrosion cracking. In-depth metallographic examination revealed cracking fracture paths consistent with hydrogen-assisted cracking. Further investigation of potential sources of hydrogen concluded that the source is the impressed-current cathodic protection system operated for decades at near the P/S potentials of −1200 mV CSE.
An approach to mitigating the threat of hydrogen-induced cracking in onshore pipelines is also outlined.
Friday, February 16, 2024
(83) Integrity assessment and management of a brine pipeline in active ground movement areas
Pablo Cazenave1, Sergio Limón1, Ravi Krishnamurthy1
1Blade Energy Partners, Houston, USA
2The Dow Chemical Co., Houston, USA
An onshore/offshore pipeline in South America transporting brine solution experienced a failure initially attributed to external circumferential cracking in an onshore section of the pipeline. The failed pipeline rested above ground in a concrete ditch exposed to ambient conditions. Field assessments and land surveys of the failed site indicated possible nearby land movement.
This paper outlines the work conducted to review the Failure Analysis results, the aggregation of historic and recent in-line inspections (geometry + inertial + axial MFL), above-ground land movement survey data, and the identification of the cause of the circumferential cracking for the development of a short- and long-term remedial plan to address the effects on land movement on the integrity the pipeline.