Effect of Geometry, Material and Pressure Variability on Strain and Stress Fields in Dented Pipelines Under Static and Cyclic Pressure Loading Using Probability Analysis

2010 ◽  
Author(s):  
Husain Mohammed Al-Muslim ◽  
Abul Fazal M. Arif
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Deterministic Model ◽  
Mechanical Damage ◽  
Statistical Distribution ◽  
Stress Fields ◽  
Pressure Loading ◽  
Cyclic Pressure ◽  
Mathematical Formulas ◽  
Pipe Geometry

Mechanical damage in transportation pipelines is a threat to its structural integrity. Failure in oil and gas pipelines is catastrophic as it leads to personal fatalities, injuries, property damage, loss of production and environmental pollution. Therefore, this issue is of extreme importance to Pipeline Operators, Government and Regulatory Agencies, and local Communities. As mechanical damage can occur during the course of pipeline life due to many reasons, appropriate tools and procedures for assessment of severity is necessary. There are many parameters that affect the severity of the mechanical damage related to the pipe geometry and material properties, the defect geometry and boundary conditions, and the pipe state of strain and stress. The main objective of this paper is to investigate the effect of geometry, material and pressure variability on strain and stress fields in dented pipelines under static and cyclic pressure loading using probabilistic analysis. Most of the published literate focuses on the strain at the maximum depth for evaluation which is not always sufficient to evaluate the severity of a certain case. The validation and calibration of the base deterministic model was based on full-instrumented full-scale tests conducted by Pipeline Research Council International as part of their active program to fully characterize mechanical damage. A total of 100 cases randomly generated using Monte Carlo simulations are analyzed in the probabilistic model. The statistical distribution of output parameters and correlation between output and input variables is presented. Moreover, regression analysis is conducted to derive mathematical formulas of the output variables in terms of practically measured variables. The results can be used directly into strain based design approach. Moreover, they can be coupled with fracture mechanics to assess cracks, for which the state of stress must be known in the location of crack tip, not necessarily found in the dent peak. Furthermore, probabilities derived from the statistical distribution can be used in risk assessment.

Effect of Geometry, Material, and Pressure Variability on Strain and Stress Fields in Dented Pipelines Under Static and Cyclic Pressure Loading Using Probabilistic Analysis

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Husain M. Al-Muslim ◽  
Abul Fazal M. Arif
Keyword(s):  
Probabilistic Analysis ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Deterministic Model ◽  
Mechanical Damage ◽  
Statistical Distribution ◽  
Stress Fields ◽  
Pressure Loading ◽  
Cyclic Pressure ◽  
Pipe Geometry

Mechanical damage in transportation pipelines is a threat to their structural integrity. Failure in oil and gas pipelines is catastrophic as it leads to personal fatalities, injuries, property damage, loss of production, and environmental pollution. Therefore, this issue is of extreme importance to pipeline operators, government and regulatory agencies, and local communities. As mechanical damage can occur during the course of pipeline life due to many reasons, appropriate tools and procedures for assessment of severity is necessary. There are many parameters that affect the severity of the mechanical damage related to the pipe geometry and material properties, the defect geometry and boundary conditions, and the pipe state of strain and stress. The main objective of this paper is to investigate the effect of geometry, material, and pressure variability on strain and stress fields in dented pipelines under static and cyclic pressure loading using probabilistic analysis. Most of the published literature focuses on the strain at the maximum depth for evaluation, which is not always sufficient to evaluate the severity of a certain case. The validation and calibration of the base deterministic model was based on full-instrumented full-scale tests conducted by Pipeline Research Council International as part of their active program to fully characterize mechanical damage. A total of 100 cases randomly generated using Monte Carlo simulation are analyzed in the probabilistic model. The statistical distribution of output parameters and correlation between output and input variables is presented. Moreover, regression analysis is conducted to derive mathematical formulas of the output variables in terms of practically measured variables. The results can be used directly into strain based assessment. Moreover, they can be coupled with fracture mechanics to assess cracks for which the state of stress must be known in the location of crack tip, not necessarily found in the dent peak. Furthermore, probabilities derived from the statistical distribution can be used in risk assessment.

Integrity Assessment of Multiple Dents in Oil and Gas Pipelines Using Probabilistic Design Analysis

2010 ◽  
Author(s):  
Husain Mohammed Al-Muslim ◽  
Abul Fazal M. Arif
Keyword(s):  
Oil And Gas ◽  
Mechanical Damage ◽  
Pipe Material ◽  
Probabilistic Design ◽  
Gas Pipelines ◽  
Pressure Loading ◽  
Integrity Assessment ◽  
Oil And Gas Pipelines ◽  
Input Parameters ◽  
Pipe Geometry

Mechanical damage in transportation pipelines is a threat to its structural integrity. Failure in oil and gas pipelines is catastrophic as it leads to personal fatalities, injuries, property damage, loss of production and environmental pollution. Therefore, this issue is of extreme importance to Pipeline Operators, Government and Regulatory Agencies, and local Communities. As mechanical damage can occur during the course of pipeline life due to many reasons, appropriate tools and procedures for assessment of severity are necessary. There are many parameters that affect the severity of the mechanical damage related to the pipe geometry and material properties, the defect geometry and boundary conditions, and the pipe state of strain and stress. Moreover, multiple damaged areas may exist and interact like in the case of a hit by a multiple-tooth excavator. The main objective of this paper is to determine the distance and orientation where interaction of multiple dents is significant. The strain and stress fields are evaluated for static pressure loading and the stress range and fatigue life are evaluated for cyclic pressure loading. Accordingly, guidelines are developed for the integrity assessment of multiple dents in oil and gas pipelines. The input parameters of the problem including the pipe material, pipe geometry, dent dimensions, and distance and orientation between two dents have a great variability. Therefore, probabilistic design approach is applied to determine the sensitivity and correlation between the output and input parameters. The base case deterministic FEA model has been validated with full-instrumented full-scale tests conducted by Pipeline Research Council International as part of their active program to fully characterize mechanical damage.

Revisiting ASME Strain-Based Dent Evaluation Criterion

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Abu Naim Md Rafi ◽  
Sreekanta Das ◽  
Hossein Ghaednia ◽  
Jorge Silva ◽  
Richard Kania ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Pipe Wall ◽  
Effective Strain ◽  
Evaluation Criterion ◽  
Lateral Loads ◽  
Finite Element Analyses ◽  
Cyclic Pressure ◽  
Long Run

Oil and gas transmission pipelines can be subjected to concentrated lateral loads and as a result, a dent can form. A dent is a localized defect in the pipe wall in the form of a permanent inward plastic deformation. This kind of defect is a matter of serious concern for the pipeline operator since a rupture or a leak may occur. Dent may not pose an immediate threat to the structural integrity of a pipeline. However, it can possibly hinder the operational and inline inspection activities. In the long run, it can cause a leak or rupture in the pipeline under sustained or cyclic pressure load. Hence, AMSE B31.8 recommends a strain-based criterion for the assessment of dents. This strain-based criterion was developed based on several assumptions. This study was undertaken using full-scale laboratory tests and finite element analyses to review and revisit the ASME strain-based dent evaluation criterion and its assumptions. It was found that some of these assumptions are incorrect, and hence, this dent evaluation criterion can lead to inaccurate estimations of critical (effective) strain values in dents, which in turn can lead to inaccurate assessments of the dents.

Out-of-Roundness in NPS30 X70 Pipes Subjected to Concentrated Lateral Load

2014 ◽  
Author(s):  
Hossein Ghaednia ◽  
Jamshid Zohrehheydariha ◽  
Sreekanta Das ◽  
Rick Wang ◽  
Richard Kania
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Impact Load ◽  
Test Procedure ◽  
Research Work ◽  
Mechanical Damage ◽  
Lateral Load ◽  
External Pressure ◽  
Concentrated Load ◽  
Engineering Research

Pipeline is the common mode for transporting oil, gas, and various petroleum products. Structural integrity of oil and gas transmission pipelines is often threatened by external interferences such as concentrated load, impact load, and external pressure. These external interferences can cause ‘mechanical damage’ leading to structural failure in onshore and offshore linepipes. Lateral load is applied as a concentrated load on a small area of pipe segment and can cause local buckling, bend, dent, or out-of-roundness in the pipe. As an example, a concentrated load in buried onshore linepipe can occur if a segment of the linepipe rests on a narrow rock tip or even a narrow hard surface. Such concentrated lateral load may or may not cause immediate rupture or leak in the linepipe; however, it may produce out-of-roundness with or without a dent in the pipe cross section, which can be detrimental to the structural and/or operational integrity of the pipeline. Hence, the pipeline operator becomes concerned about the performance and safety of the linepipe if a pipe section is subject to a sustained concentrated load. A research work using full-scale tests and finite element method (FEM) was undertaken at the Centre for Engineering Research in Pipelines (CERP), University of Windsor to study the influence of various internal pressures and diameter-to-thickness ratios on the out-of-roundness of 30 in diameter (NPS 30) and X70 grade pipes with D/t of 90 when subjected to a stroke-controlled concentrated load. This paper discusses the test specimens, test setup, test procedure, test results, and FEM results obtained from this study.

scholarly journals Physical modelling of failure in composites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150280 ◽  
Author(s):  
Ramesh Talreja
Keyword(s):  
Composite Materials ◽  
Failure Modes ◽  
Structural Integrity ◽  
Failure Mechanisms ◽  
Local Stress ◽  
Physical Modelling ◽  
Stress Fields ◽  
Systematic Analysis ◽  
Composite Failure ◽  
Failure Theories

Structural integrity of composite materials is governed by failure mechanisms that initiate at the scale of the microstructure. The local stress fields evolve with the progression of the failure mechanisms. Within the full span from initiation to criticality of the failure mechanisms, the governing length scales in a fibre-reinforced composite change from the fibre size to the characteristic fibre-architecture sizes, and eventually to a structural size, depending on the composite configuration and structural geometry as well as the imposed loading environment. Thus, a physical modelling of failure in composites must necessarily be of multi-scale nature, although not always with the same hierarchy for each failure mode. With this background, the paper examines the currently available main composite failure theories to assess their ability to capture the essential features of failure. A case is made for an alternative in the form of physical modelling and its skeleton is constructed based on physical observations and systematic analysis of the basic failure modes and associated stress fields and energy balances. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

A Statistical-Based Fatigue Crack Initiation Model for Axial Flaws in Zr-Nb Pressure Tubes

2014 ◽  
Author(s):  
Cheng Liu ◽  
Douglas Scarth ◽  
Alain Douchant
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Rise Time ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Mechanical Damage ◽  
Fuel Bundle ◽  
Test Parameters ◽  
Pressure Tubes ◽  
Criteria For Evaluation

Flaws found during in-service inspection of CANDU Zr-2.5Nb pressure tubes include fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws, mechanical damage flaws and crevice corrosion marks. The CSA Standard N285.8 contains procedures and acceptance criteria for evaluation of the structural integrity of CANDU Zr-2.5Nb pressure tubes containing flaws. One of the requirements is to evaluate the flaws for fatigue crack initiation. There was a need to develop a statistical-based model of fatigue crack initiation at flaws for use in deterministic and probabilistic assessments of Zr-2.5Nb pressure tubes. A number of fatigue crack initiation experiments have been performed on notched specimens from irradiated and unirradiated Zr-2.5Nb pressure tube material with a range of hydrogen equivalent concentrations. These experiments were performed in an air environment and included temperature and load rise time as test parameters. The test data has been used to develop a statistical-based model of fatigue crack initiation at flaws that covers the effects of flaw root radius, load rise time and irradiation. This paper describes the development of the statistical-based model.

Structural Integrity System Based on an Object-Oriented Activity- and Product Model

1993 ◽  
Author(s):  
Morten Lovstad ◽  
Tor G. Syvertsen
Keyword(s):  
Computational Models ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Physical Structure ◽  
Gas Production ◽  
Structural Safety ◽  
Actual State ◽  
Product Model ◽  
The North ◽  
Analysis Models

Abstract Huge steel or reinforced concrete structures in deep waters support the installations for oil and gas production in the North Sea. Steady operations in a hostile environment require that structural safety and integrity is maintained. For rapid evaluation and assessment of structural integrity in case of modifications or urgency situations, Structural Integrity Systems are established, comprising computational models and structural analysis programs. A major problem for structural assessment at short notice is to keep the analysis models updated and consistent with the actual state of the physical structure and the loadings. This paper proposes a layered approach for model integration, which enable maintenance of the models at a high level, from which detailed analysis models are derived in a consistent manner.

scholarly journals Integrity Management of Marine Structures; With Emphasis on Design for Structural Robustness

2018 ◽  
Author(s):  
Torgeir Moan
Keyword(s):  
Structural Damage ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Design Standards ◽  
Limit States ◽  
Fabrication Errors ◽  
Integrity Management ◽  
Operational Errors ◽  
And Control

Based on relevant accident experiences with oil and gas platforms, a brief overview of structural integrity management of offshore structures is given; including an account of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. The focus is on developing research based design standards for Accidental Collapse Limit States to ensure robustness or damage tolerance in view damage caused by accidental loads due to operational errors and to some extent abnormal structural damage due to fabrication errors. Moreover, it is suggested to provide robustness in cases where the structural performance is sensitive to uncertain parameters. The use of risk assessment to aid decisions in lieu of uncertainties affecting the performance of novel and existing offshore structures, is briefly addressed.

Numerical Methods to Predict Distortion in Welded Components

2008 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
P. J. Bouchard ◽  
M. C. Smith
Keyword(s):  
Residual Stress ◽  
Numerical Methods ◽  
Structural Integrity ◽  
Large Strain ◽  
Stress Fields ◽  
Specimen Thickness ◽  
Single Bead ◽  
Stress Profiles ◽  
Welding Processes ◽  
Integrity Assessments

Numerical methods have been established to simulate welding processes. Of particular interest is the ability to predict residual stress fields. These fields are often used in support of structural integrity assessments where they have the potential, when accurately characterised, to offer significantly less conservative predictions of residual profiles compared to those found in assessment codes such as API 579, BS7910 and R6. However, accurate predictions of residual stress profiles that compare favourably with measurements do not necessarily suggest an accurate prediction of component distortions. This paper presents a series of results that compare predicted distortions for a variety of specimen mock-ups with measurements. A range of specimen thicknesses will be studied including, a 4mm thick DH-36 ferritic plate containing a single bead, a 4mm thick DH-36 ferritic plate containing fillet welds, a 25mm thick 316L austenitic plate containing a groove weld and a 35mm thick esshete 1250 austenitic disc containing a concentric ring weld. For each component, distortion measurements have been compared with the predicted distortions with a number of key features being investigated. These include the influence of ‘small’ vs ‘large’ strain deformation theory, the ability to predict distortions using simplified analysis methods such as simultaneous bead deposition and the influence of specimen thickness on the requirement for particular analysis features. The work provides an extremely useful insight into how existing numerical methods used to predict residual stress fields can be utilised to predict the distortions that occur as a result of the welding fabrication process.

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