Development of the End Fitting Tensile Wires Fatigue Analysis Model: Sample Tests and Validation in an Unbonded Flexible Pipe

2008 ◽  
Author(s):  
Yijun Shen ◽  
Frank Ma ◽  
Zhimin Tan ◽  
Terry H. Sheldrake
Keyword(s):  
Fatigue Analysis ◽  
Analysis Model ◽  
Flexible Pipe ◽  
Model Sample

The Impact of Flexbarrier Ingress on Flexlok Stress

2009 ◽  
Author(s):  
Jing Lu ◽  
Frank Ma ◽  
Zhimin Tan ◽  
Terry Sheldrake
Keyword(s):  
Internal Pressure ◽  
Structural Function ◽  
Analysis Model ◽  
Flexible Pipe ◽  
Case Scenario ◽  
Element Analysis ◽  
Worst Case ◽  
Ongoing Research ◽  
Nominal Size ◽  
The Impact

An unbonded flexible pipe typically consists of multiple metallic and thermoplastic layers, where each layer is designed to provide a specific structural function. The burst resistance against the internal pressure in an unbonded flexible pipe is provided mainly by its Flexlok layer. The Flexlok is made by helically-wound steel wires, with neighbouring wires interlocking each other. Beneath the Flexlok is the Flexbarrier, a polymer layer, acting as the boundary for conveyed fluids. The internal pressure is passed onto the Flexlok through the Flexbarrier layer. Under internal pressure, the Flexbarrier can creep into the gaps between Flexlok wires. Theoretically, the polymer material ingress could reduce the flexibility of the Flexlok due to premature lock-up between Flexlok wires and subsequently increase the stress levels. This study presents a 3D finite element analysis model developed to quantify the stress elevation in the Flexlok wire, caused by the Flexbarrier layer ingress. In terms of Flexlok gap size distribution, both nominal and worst case scenarios are studied. In the nominal scenario, the Flexlok gap sizes are evenly distributed. In the worst case scenario, the Flexlok gap is assumed to be completely closed at one position while the gaps at the neighbouring positions are twice the nominal size. Flexbarrier ingress with different temperatures is also studied. Conclusions are obtained by analyzing the simulation results. The work presented is part of an ongoing research and development project.

End Fitting Effect on Tensile Armor Stress Evaluation in Bent Flexible Pipe

2014 ◽  
Author(s):  
Linfa Zhu ◽  
Zhimin Tan
Keyword(s):  
Axial Stress ◽  
Local Stress ◽  
Element Model ◽  
Analysis Model ◽  
Flexible Pipe ◽  
Stress Evaluation ◽  
3D Finite Element ◽  
Closed Form Solutions ◽  
The Relationship ◽  
Pipe Bending

The stress evaluation of tensile armor layer in bent unbonded flexible pipe due to end fitting termination is investigated. A preliminary mathematical stress analysis model which accounts for the boundary condition at the end fitting interface is developed. Two shifting parameters are introduced to correct the friction field acting on the tensile wires. Closed form solutions are obtained for the modified friction force, axial stress and displacement. The validity of this model is investigated through a comparison with results obtained using a 3D finite element model. The relationship between the shifting parameters and the initial hoop position of wires is discussed. Studies of local stress elevation on wires with different initial hoop positions are conducted. The results show that end fitting effect could causes a significant stress elevation in a large amount of tensile wires if heavy pipe bending is permitted at the end fitting vicinity.

Upheaval Creep of Rock Dumped Flexible Flowline

2014 ◽  
Author(s):  
Yang Zhengmao ◽  
Kristian Norland ◽  
Neil Brown ◽  
Daniel Karunakaran
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Pressures ◽  
Elevated Temperatures ◽  
Water Injection ◽  
Analysis Model ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Nonlinear Bending ◽  
Start Up

For the protection from dropped object/fishing trawl impact, flexible flowlines are normally trenched or rock-dumped. And hence, upheaval buckling and lateral buckling may be promoted by the elevated temperatures and high pressures. Due to the unique properties of un-bonded flexible flowline, the flexible flowline may creep in the trench or rock berm when it is subjected to cyclic pressure and temperature changes due to start-up and shut-down of flowline in service. In this paper, a finite element analysis model for the global buckling and upheaval creep of flexible flowline is proposed. In this model the effect of bending stiffness hysteresis are considered in addition to the temperature and pressure changes in each start-up/ shut-down cycle. A case study of a 10″ water injection flowline is performed by using finite element analysis software package ANSYS. The nonlinear general beam section is used to simulate the specific flexible pipe behavior, nonlinear bending behavior but linear axial behavior.

scholarly journals Investigating the Cooperation Status Between the Health System and City Councils and Municipalities in Iran (Documents’ Analysis)

2020 ◽  
Author(s):  
Najmeh Khodadadi ◽  
Aidin Aryan Khesal ◽  
Mohamad Reza Maleki
Keyword(s):  
Health System ◽  
Sample Selection ◽  
City Council ◽  
Analysis Model ◽  
Ministry Of Health ◽  
Cross Sectional ◽  
City Councils ◽  
Model Sample ◽  
Collection Data ◽  
Health Related

Abstract Background: The present study is aimed at investigating the cooperation status between the health system and city councils and municipalities in Iran based on rules and documents.Methods: Altheide’s document analysis model (sample selection, data collection, data organization, data analysis, and reporting) was employed in order to prepare and analyze the documents pertaining to the cooperation level between the health system and municipalities and Islamic city councils. The documents were classified at three levels including the national rules, policies, and guidelines; Ministry of Health (MOH) and city council approvals; and eventually Tehran Municipality’s measures.Results: Overall, 78 documents were analyzed including 17 documents at the level of national rules, policies and guidelines; 8 documents at the level of Ministry of Health and city council approvals; and 53 documents at the level of Municipality’s measures.Conclusion: There are adequate legal capacities for designing, planning, executing, as well as creating interaction and cooperation between health system and city councils and municipalities. Moreover, the motive behind creating a purposeful and scheduled cooperation and participation is evident among the officials of health system and city councils and municipalities. Some mechanisms have been established for cross-sectoral cooperation between the health system and other health-related bodies on a cross-sectional basis, but these structures lack the necessary competence, appropriateness and adequacy to create the desired partnership, and especially sufficient attention to existing capacities in municipalities and The city council has not. Accordingly, it is necessary to have a fundamental review on the available structures and enough attention has to be paid to the evident and hidden legal capacities in city councils, and municipalities, as well as Ministry of Health to design an appropriate structure and create competent interaction and also provide more cooperation between the two organizations.

Multiaxial fatigue analysis of a metal flexible pipe

2014 ◽  
Vol 54 ◽  
pp. 796-804 ◽  
Author(s):  
Djihad Rial ◽  
Hocine Kebir ◽  
Eric Wintrebert ◽  
Jean-Marc Roelandt
Keyword(s):  
Fatigue Analysis ◽  
Multiaxial Fatigue ◽  
Flexible Pipe

Wellhead Fatigue Analysis Method: The Effect of Variation of Lower Boundary Conditions in Global Riser Load Analysis

2012 ◽  
Author(s):  
Lorents Reinås ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Lower Boundary ◽  
Fatigue Analysis ◽  
Analysis Model ◽  
Lower Boundary Condition ◽  
Analysis Methodology ◽  
Well Integrity ◽  
Context Modelling ◽  
Load Analysis

Subsea wellhead mechanical fatigue can potentially result in a gross structural failure of barrier elements in the upper part of the well, potentially resulting in loss of well control. Several major E&P operators have acknowledged the importance of wellhead fatigue and are participating in the JIP “Structural Well Integrity”. It is within the scope of this JIP to develop a recommended practice for wellhead fatigue analysis methodology. The analysis methodology currently being investigated by the JIP is a decoupled approach, with modifications of the lower boundary to account for the stiffness of the conductor, soil and template interface. A detailed local wellhead model is used to generate the lower boundary condition for a decoupled global riser load analysis model. This lower boundary condition definition is intended to capture the overall non-linear stiffness of a site specific well in order to achieve best possible global riser loads estimate. In this article the effect of varying the lower boundary conditions on a global load estimate is studied. Global load estimates are generated from a typical North Sea case and various lower boundary conditions are introduced as the only change to the global riser model. A fixed lower boundary condition is used as a reference and load estimates generated from riser models with various lower boundary conditions are compared. The different lower boundary conditions selected for comparison in this study has been derived from the following cases: 1. Fixed at WH 2. As per ISO 13624-2 3. As per JIP “Structural Well Integrity” -Current 4. As per JIP “Structural Well Integrity” -Modified Comparing the analysis results gives indications that the lower boundary condition modelling approach affect global riser load estimate. The fixed lower end boundary conditions did not yielded the most conservative load history in a fatigue context. Modelling well specific flexibility at the riser lower end increased the total number of wellhead fatigue load cycles. This finding support the current approach suggested by the works of the JIP “Structural Well Integrity”. Ensuring that riser load results are still conservative places a higher importance on precise local modelling of the well system.

Methodology for Fatigue Analysis in Flexible Pipes Based on Structural Reliability Considering S-N Bi-Linear Curve

2012 ◽  
Author(s):  
Fernando dos Santos Loureiro Filho ◽  
Edison Castro Prates de Lima ◽  
Luís Volnei Sudati Sagrilo ◽  
Carlos Alberto Duarte de Lemos
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Oil And Gas ◽  
Linear Models ◽  
Fatigue Analysis ◽  
Flexible Pipe ◽  
Environmental Loads ◽  
Flexible Pipes ◽  
Different Types ◽  
Oil And Gas Companies

Flexible pipes are largely used by oil and gas companies all over the world to exploit oil and gas reserves located into the sea. These pipes are composed by different layers, each one with a specific function. The environmental loads can induce different types of failure modes in a flexible pipe. One important failure mode is associated with the fatigue damage in the tension armours. Fatigue analysis depends on various parameters that are uncertain. A reliability-based procedure to take into account these uncertainties in the fatigue analysis of flexible pipes has been recently proposed [1]. In this methodology the S-N curves have been modeled by a one-slope model. The present work expands this methodology in order to consider S-N bi-linear models.

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