Assessment of Stress Based Design Pipelines Experiencing High Axial Strains

2018 ◽  
Author(s):  
Robert Andrews ◽  
Mark Stephens ◽  
Malcolm Carr ◽  
Johannes Brückner
Keyword(s):  
Gap Analysis ◽  
Axial Strain ◽  
Local Buckling ◽  
Strain Capacity ◽  
Design Concepts ◽  
Metal Fracture ◽  
Discontinuous Permafrost ◽  
Girth Welds ◽  
Subsea Pipelines ◽  
Assessment Of Stress

Strain based design concepts have been extensively used for subsea pipelines for both installation and service. However, most onshore transmission pipelines are designed assuming a maximum longitudinal stress, typically 90% SMYS. Some onshore pipelines have been designed for a limiting axial strain generated by causes such as seismic activity, frost heave, discontinuous permafrost or landslides. Models have been developed to predict the axial strain capacity in both tension (usually limited by the girth welds) and compression (where the limit is local buckling of the pipe wall). In service monitoring of a pipeline initially designed on a stress basis may reveal that strains approaching or exceeding the design level are occurring, or are predicted to occur in the future. In these cases the pipeline operator will have to assess if the pipeline is fit for continued service. In principle strain based design approaches could be adapted for such an assessment. Strain based design approaches place more onerous demands on the linepipe and the girth welds, but for a new pipeline these requirements can be addressed during design, material specification, procurement and weld procedure qualification. However, for an existing pipeline the data required to use strain based approaches may not be readily available. Some strain capacity models are only valid over a restricted range of inputs and so cannot be used in all cases. Hence there is a need to develop guidance for assessing the fitness for purpose of a stress based design pipeline that is found to be experiencing high axial strains. The European Pipeline Research Group (EPRG) has initiated a program to develop such guidance. This paper presents the results of the first stage of this program. The requirements for data such as inspection records, weld metal fracture toughness and parent pipe mechanical properties are considered. A flow chart has been developed to guide operators when assessing an existing pipeline found to be subject to high strains, and a gap analysis identifies areas where additional work is required.

Fracture Toughness Testing and Validation of Pipeline Girth Weld Flaw Acceptance Criteria for Sour Service Under Large Strain

2011 ◽  
Author(s):  
You You Wu ◽  
Wen Guo Yuan ◽  
Tse Ven Steven Chong ◽  
Jens P. Tronskar
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Laboratory Data ◽  
Local Buckling ◽  
Acceptance Criteria ◽  
Service Environment ◽  
Girth Welds ◽  
Sour Service

Fracture toughness is one of the most important input parameters for assessment of pipeline girth weld failure capacity. For many new subsea pipeline projects there is a need to develop flaw acceptance criteria for pipeline installation considering the operation phase which may involve the transport of sour oil and gas and where the pipeline is exposed to large axial strain due to local buckling. Engineering Critical Assessment (ECA) performed using laboratory data based on conservative KISSC testing gives small acceptable flaw sizes which may be below the workmanship criteria for pipeline laying. DNV has conducted extensive research based on the requirements of DNV-OS-F101 and DNV-RP-F108, aiming to establish a method to develop J-R curves applicable for ECA of pipeline girth welds in sour service environment and a methodology to validate the ECA by segment testing in a laboratory-simulated sour service environment as per DNV-RP-F108.

Integrity of Pipeline in Area of Mine Subsidence

2012 ◽  
Author(s):  
Fan Zhang ◽  
Ming Liu ◽  
Yong-Yi Wang ◽  
Zhifeng Yu ◽  
Lei Tong
Keyword(s):  
Compressive Strain ◽  
Local Buckling ◽  
Base Material ◽  
Companion Paper ◽  
Parametric Models ◽  
Ground Subsidence ◽  
Strain Capacity ◽  
Weld Properties ◽  
Bending Loads ◽  
Girth Welds

Ground subsidence can threaten the integrity of buried pipelines in areas with prior and on-going mining activities. The integrity can be assessed by comparing the strain demand and the strain capacity. The Tensile Strain Capacity (TSC) of the pipeline is dominated by the girth welds due to their relatively inferior property in comparison to the base pipe materials. Parametric models developed at CRES for US DOT and PRCI allow the evaluation of girth welds TSC based on pipe dimensions, base material and weld properties and flaw size. The local buckling of the pipeline under compressive or bending loads determines the Compressive Strain Capacity (CSC). Three existing standards are used to evaluate CSC, including DNV OS-F101, CSA Z662 and API RP 1111. The strain demand analysis of the pipeline under multiple subsidence scenarios is presented in a companion paper. The strain demand is compared with TSC and CSC separately to evaluate the pipeline integrity. The use of CRES TSC models for selecting a variety of design and material parameters to improve TSC is illustrated.

Local Buckling in end Expansion of Subsea Pipelines

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Jaswar Koto ◽  
Abd. Khair Junaidi ◽  
M. H. Hashim
Keyword(s):  
Crude Oil ◽  
Axial Force ◽  
Oil And Gas ◽  
Local Buckling ◽  
Offshore Platform ◽  
Offshore Pipeline ◽  
Specific Rule ◽  
Subsea Pipelines ◽  
Study Development

Offshore pipeline is mainly to transport crude oil and gas from offshore to onshore. It is also used to transport crude oil and gas from well to offshore platform and from platform to another platform. The crude oil and gas horizontally flows on the seabed, and then vertically flows inside the riser to the offshore platform. One of current issues of the oil and gas transportation system is an end expansion caused by the axial force. If the end expansion occurs over it limit can cause overstress to riser. This paper explores the effect of axial force toward local buckling in end expansion. In the study, development of programming in visual basic 2010 firstly was constructed using empirical equation. The programming code, then, was validated by comparing simulation result with actual data from company. As case study, the end expansion for various thicknesses of pipes was simulated. In this programming, DNV regulation is included for checking either design complied or not with regulation. However, DNV regulation doesn’t have specific rule regarding the end expansion but it is evaluated under load displacement control under strain condition.

Estimation of Tensile Strain Capacity of Vintage Girth Welds

2021 ◽  
Author(s):  
Banglin Liu ◽  
Bo Wang ◽  
Yong-Yi Wang ◽  
Otto Jan Huising
Keyword(s):  
Tensile Strain ◽  
Strain Capacity ◽  
Girth Welds ◽  
Tensile Strain Capacity

Offshore Installation of Welded Pipe: Local Buckling Evaluation

2010 ◽  
Author(s):  
Luciano Mantovano ◽  
Richard E. Bravo ◽  
Sebastian Cravero ◽  
Hugo A. Ernst
Keyword(s):  
Numerical Models ◽  
Local Buckling ◽  
Good Control ◽  
Plastic Instability ◽  
Lead Times ◽  
Geometrical Parameters ◽  
Seamless Pipe ◽  
Project Costs ◽  
Girth Welds ◽  
Welded Pipe

Up to the present, most of the pipes used in offshore applications installed with methods introducing plastic deformation have been seamless pipes; however, welded pipes can also be used. Welded pipes offers benefits over seamless pipe in terms of improved lead times, lower project costs, tighter dimensional tolerance and good control of mechanical properties and chemistry resulting in excellent weldability. During installation of welded pipes, failure by fracture, plastic collapse and local buckling may occur. In this work, the occurrence of the local buckling phenomenon, produced during the installation method, was evaluated. Numerical models were developed to study the effect of materials and geometrical parameters on the local bucking of pipes subjected to bending. Specifically, the loads and strains at which the plastic instability occurs were determined for each particular condition. In addition, the influence of longitudinal and girth welds on the local bucking occurrence was assessed.

Pressure Correction Factor for Strain Capacity Predictions Based on Curved Wide Plate Testing

2012 ◽  
Author(s):  
Matthias Verstraete ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Stijn Hertelé
Keyword(s):  
Correction Factor ◽  
Large Scale ◽  
Strain Capacity ◽  
Defect Assessment ◽  
Ductile Crack Growth ◽  
Large Scale Testing ◽  
Weld Defect ◽  
Girth Welds ◽  
Assessment Procedures ◽  
Tensile Strain Capacity

Strain-based girth weld defect assessment procedures are essentially based on large scale testing. Ever since the 1980’s curved wide plate testing has been widely applied to determine the tensile strain capacity of flawed girth welds. However, the effect of internal pressure is not captured in curved wide plate testing. Accordingly, unconservative predictions of strain capacity occur when straightforwardly transferred to pressurized pipes. To address this anomaly, this paper presents results of finite element simulations incorporating ductile crack growth. Simulations on homogeneous and girth welded specimens indicate that a correction factor of 0.5 allows to conservatively predict the strain capacity of a pressurized pipe through wide plate testing under the considered conditions.

Machine Learning for Subsea Pipeline Reeling Mechanics

2020 ◽  
Author(s):  
Eric Giry ◽  
Vincent Cocault-Duverger ◽  
Martin Pauthenet ◽  
Laurent Chec
Keyword(s):  
Design Of Experiments ◽  
Wall Thickness ◽  
Large Diameter ◽  
Local Buckling ◽  
Statistical Regression ◽  
Element Analysis ◽  
Excessive Strain ◽  
Weld Area ◽  
Subsea Pipelines ◽  
Pipeline Design

Abstract Installation of subsea pipelines using reeling process is an attractive method. The pipeline is welded in long segments, typically several kilometers in length, and reeled onto a large diameter drum. The pipeline is then transported onto such reel to the offshore site where it is unreeled and lowered on the seabed. The deformation imposed on the pipeline while spooled onto the drum needs to be controlled so that local buckling is avoided. Mitigation of such failure is generally provided by proper pipeline design & reeling operation parameters. Buckling stems from excessive strain concentration near the circumferential weld area resulting from strength discontinuity at pipeline joints, mainly depending on steel wall thickness and yield strength. This requires the characterization of critical mismatches obtained by trial and error. Such method is a long process since each “trial” requires a complete Finite Element Analysis run. Such simulations are complex and lengthy. Occasionally, this can drive the selection of the pipeline minimum wall thickness, which is a key parameter for progressing the project. The timeframe of such method is therefore not compatible with such a key decision. The paper discusses the use of approximation models to capitalize on the data and alleviate the design cost. To do so, design of experiments and automation of the computational tool chain are implemented. It is demonstrated that initial complex chain of FEA computational process can be replaced using design space description and exploration techniques such as design of experiments combined with advanced statistical regression techniques in order to provide an approximation model. This paper presents the implementation of such methodology and the results are discussed.

Seismic Design and Hybrid Tests of a Full-Scale Three-Story Concentrically Braced Frame using In-Plane Buckling Braces

2013 ◽  
Vol 29 (3) ◽  
pp. 1043-1067 ◽  
Author(s):  
Ching-Yi Tsai ◽  
Keh-Chyuan Tsai ◽  
Pao-Chun Lin ◽  
Wai-Hang Ao ◽  
Charles W. Roeder ◽  
...  
Keyword(s):  
Seismic Design ◽  
Axial Strain ◽  
Local Buckling ◽  
Full Scale ◽  
Dynamic Tests ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Nonlinear Responses ◽  
Highly Nonlinear ◽  
Concentrically Braced

This research investigates the brace-to-gusset connection designs to allow the braces buckle in the plane (IP) of the frame. In order to study the performance of the IP buckling brace connections with different design details, five 3,026 mm–long A36 H 175 × 175 × 7.5 × 11 mm braces were tested using cyclically increasing axial displacements. All specimens failed at an average axial strain less than 0.025 due to the brace fracture at the mid-length where severe local buckling had occurred. Pseudo-dynamic tests on a three-story special concentrically braced frame (SCBF) using the proposed brace end connection details for six A36 H 150 × 150 × 7 × 10 mm braces were conducted using the PGA = 597 cm/s2 LA03 record to confirm with the component tests. The knife plates and IP buckling braces sustained a peak 0.049 rad interstory drift under the design base earthquake without fracture. The highly nonlinear responses were satisfactorily predicted by OpenSees. Recommendations on the seismic design of the IP buckling brace connections are provided.

Ultimate strain capacity assessment of local buckling of pipelines with kinked dents subjected to bending loads

2021 ◽  
Vol 169 ◽  
pp. 108369
Author(s):  
Junqiang Wang ◽  
Yi Shuai ◽  
Renyang He ◽  
Xiran Dou ◽  
Ping Zhang ◽  
...  
Keyword(s):  
Local Buckling ◽  
Ultimate Strain ◽  
Capacity Assessment ◽  
Strain Capacity ◽  
Bending Loads
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