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.

Prediction and Qualification of Radial Birdcage and Lateral Buckling of Flexible Pipes in Deepwater Applications

2015 ◽  
Author(s):  
Linfa Zhu ◽  
Zhimin Tan ◽  
Victor Pinheiro Pupo Nogueira ◽  
Jian Liu ◽  
Judimar Clevelario
Keyword(s):  
Failure Modes ◽  
Local Buckling ◽  
External Pressure ◽  
Design Guidelines ◽  
Prediction Theory ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Operation Conditions ◽  
Flexible Pipes ◽  
Compressive Loads

Increasing oil exploitation in deepwater regions is driving the R&D of flexible pipes which are subjected to high external pressure loads from the hydrostatic head during their installation and operation. One of the challenges of flexible pipe design for such applications is to overcome the local buckling failure modes of tensile armor layers due to the combination of high external pressure, compressive loads and pipe curvature. This paper presents the latest progress in local buckling behavior prediction theory and the qualification process of flexible pipes. First, the mechanisms of two types of buckling behaviors, radial birdcage buckling and lateral buckling, are described. For each failure mode, the analytical buckling prediction theory is presented and the driving parameters are discussed. As part of the qualification process, the ability to resist radial birdcage and lateral buckling must be demonstrated. Suitable test protocols are required to represent the installation and operation conditions for the intended applications by deep immersion performance (DIP) tests. Several flexible pipes were designed based on radial birdcage and lateral buckling prediction theory, and pipe samples were manufactured using industrial production facilities for DIP tests. The results clearly show that flexible pipes following current design guidelines are suitable for deepwater applications. An alternative in-air rig was developed to simulate the DIP tests in a controlled laboratory environment to further validate the model prediction as a continuous development.

Controlling Factors of Carcass Fatigue in Unbonded Flexible Pipes

2019 ◽  
Author(s):  
Upul S. Fernando ◽  
Andrew P. Roberts ◽  
Michelle Davidson
Keyword(s):  
Fatigue Failure ◽  
Failure Modes ◽  
Dynamic Stress ◽  
External Pressure ◽  
Controlling Factors ◽  
Flexible Pipe ◽  
Flexible Pipes ◽  
Innermost Layer ◽  
Key Features ◽  
Unbonded Flexible Pipes

Abstract Carcass, the innermost layer of a flexible pipe structure is designed to prevent the collapse of the pressure sheath due to external pressure. Weakness, damage or failure of the carcass layer can result in collapse with associated loss of production and potentially serious risk to pipe integrity and hydrocarbon leakage to the environment. Avoiding carcass failure in service is therefore an essential consideration during the design of unbonded flexible pipes. Carcass failure is rare in service. This paper highlights the three possible failure modes and presents further analysis on the fatigue failure mode, relevant to dynamic service. Two key features of carcass manufacture are identified as causes for dynamic stress; locking of the carcass profile due to extended pitch and polymer ingress within the carcass cavity. Guidelines for the design of carcass profiles, setting safe pitch limits and appropriate barrier profile controls to mitigate carcass fatigue failure in dynamic service are presented.

On the Design and Materials Selection of Composite Material Ocean Flexible Pipe

2015 ◽  
Vol 1090 ◽  
pp. 22-25
Author(s):  
Lin Zhao ◽  
Ming Lei Liu
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Oil And Gas ◽  
Structure Design ◽  
Materials Selection ◽  
Flexible Pipe ◽  
Flexible Pipes ◽  
Selection Of

This paper aims to discuss the composite materials application in ocean oil and gas flexible pipes, from the functional principles to the technical methodology in materials selection and pipe structure design.

Pipeline Integrity Reliability Analysis Levels

2016 ◽  
Author(s):  
Sherif Hassanien ◽  
Len Leblanc ◽  
Javier Cuervo ◽  
Karmun Cheng
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Failure Modes ◽  
Oil And Gas ◽  
Prediction Models ◽  
Metal Loss ◽  
Operating Pressure ◽  
Reliability Engineering ◽  
Reliability Methods ◽  
Types Of Information

Reliability engineering science is a mature discipline that has been used extensively in industries such as aviation, nuclear energy, automobiles, and structures. The application of reliability principles (especially structural reliability) in oil and gas transmission pipelines is still an active area of development. The advent of high resolution in-line inspections tools (ILI) facilitates a formal application/utilization of reliability methods in pipeline integrity in order to safely manage deformation, metal loss, and crack threats. At the same time, the massive amount of ILI data, their associated uncertainties, and the availability/accuracy of failure prediction models present a challenge for operators to effectively implement the use of reliability analysis to check the safety of integrity programs within available timeframes. On the other hand, approximate reliability techniques may affect the analysis in terms of both accuracy and precision. In this paper, a Pipeline Integrity Reliability Analysis (PIRA) approach is presented where the sophistication of the reliability analysis is staged into three levels: PIRA levels I, II and III. The three PIRA levels correspond to different representations of integrity uncertainties, uses of available validated/calibrated data, uses of statistical models for operating pressure and resistance random variables, implementation of reliability methods, and consideration of failure modes. Moreover, PIRA levels allow for improved integration of reliability analysis with the existing timelines/stages of traditional integrity programs, such that integrity data are updated as the integrity program progresses. The proposed integrity reliability approach allows for the delivery of safety checks leveraging all types of information available at any given point in time. In addition, the approach provides a full understanding of the strengths and weaknesses of each PIRA level. Pipeline corrosion case studies are provided herein to illustrate how the PIRA Levels can be applied to integrity programs.

Fatigue Reliability Assessment for Flexible Riser Armour Wires

2015 ◽  
Author(s):  
Vinícius Ribeiro Machado da Silva ◽  
Luis V. S. Sagrilo ◽  
Mario Alfredo Vignoles
Keyword(s):  
Failure Mode ◽  
Deep Water ◽  
Structural Reliability ◽  
Oil And Gas ◽  
Cost Benefit ◽  
Structural Type ◽  
Sensitivity Analyses ◽  
Fatigue Reliability ◽  
Great Expectation ◽  
Flexible Pipes

Oil and gas exploitation in regions of ultra-deep water has already been started and there is a great expectation of growth in the coming years, mainly in the region known as Pre-Salt, at Brazilian’s coast. Operators, which have the concession to exploit this region, have adopted different solutions with different configurations using rigid and flexible pipes for this initial phase. However, the last structural type mentioned shows to be much more versatile, providing attractive cost/benefit solutions to the operators, in which, only in Brazil, it is forecasted a demand about 4.000 km of flexible pipes in the next years [1]. With new challenges coming, one may ask the following question: What is the structural reliability of each failure mode of these flexible pipes? Motivated by this question, this paper has the objective to do a preliminary analysis, under the structural reliability view, of the critical failure mode for the design of flexible pipes faced in Brazil, represented by the fatigue phenomenon on metallic layers. The work assesses the fatigue reliability of the armour wires, located in the bend stiffener region, for two 6″ flexible risers configurations, free-hanging and lazy-wave. They are considered to be installed in ultra-deep water (2140m depth) and are submitted to the same external environmental loads. The fatigue reliability methodology used is based on that presented in Ref. [2] including new random variables. Sensitivity analyses are also performed for the variables that most contributes to the quantified probability of failure. Calibrated safety factors (SF) are obtained for different target failure probabilities.

Lateral Buckling of Armor Wires in Flexible Pipes: Reaching 3000m Water Depth

2011 ◽  
Author(s):  
Philippe Secher ◽  
Fabrice Bectarte ◽  
Antoine Felix-Henry
Keyword(s):  
Deep Water ◽  
Failure Modes ◽  
External Pressure ◽  
Internal Diameter ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Flexible Pipes ◽  
Valid Solution ◽  
Sour Service ◽  
Water Depths

This paper presents the latest progress on the armor wires lateral buckling phenomena with the qualification of flexible pipes for water depths up to 3,000m. The design challenges specific to ultra deep water are governed by the effect of the external pressure: Armor wires lateral buckling is one of the failure modes that needs to be addressed when the flexible pipe is empty and subject to dynamic curvature cycling. As a first step, the lateral buckling mechanism is described and driving parameters are discussed. Then, the program objective is presented together with flexible pipe designs: - Subsea dynamic Jumpers applications; - Sweet and Sour Service; - Internal diameters up to 11″. Dedicated flexible pipe components were selected to address the severe loading conditions encountered in water depths up to 3,000m. Hydrostatic collapse resistance was addressed by a thick inner carcass layer and a PSI pressure vault. Armor wires lateral buckling was addressed by the design and industrialization of new tensile armor wires. The pipe samples were manufactured using industrial production process in the factories in France and Brazil. The available testing protocols are then presented discussing their advantages and drawbacks. For this campaign, a combination of Deep Immersion Performances (DIP) tests and tests in hyperbaric chambers was selected. The DIP test campaign was performed End 2009 beginning 2010 in the Gulf of Mexico using one of Technip Installation Vessel. These tests replicated the actual design conditions to which a flexible pipe would be subjected during installation and operation. The results clearly demonstrated the suitability of flexible pipes as a valid solution for ultra deep water applications. In addition, the DIP tests results were compared to the tests in hyperbaric chambers giving consistent results. This campaign provided design limitations of the new designs for both 9″ and 11″ internal diameter flexible pipes, in sweet and sour service in water depths up to 3,000m.

An Experimental and Numerical Study on the Axial Compression Response of Flexible Pipes

2010 ◽  
Author(s):  
Jose´ Renato M. de Sousa ◽  
Paula F. Viero ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Axial Compression ◽  
Failure Modes ◽  
Mechanical Response ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Mechanical Analysis ◽  
Fe Model ◽  
Flexible Pipe ◽  
Flexible Pipes

This paper deals with a nonlinear three-dimensional finite element (FE) model capable of predicting the mechanical response of flexible pipes subjected to axisymmetric loads focusing on their axial compression response. Moreover, in order to validate this model, experimental tests carried out at COPPE/UFRJ are also described. In these tests, a typical 4″ flexible pipe was subjected to axial compression until its failure is reached. Radial and axial displacements were measured and compared to the model predictions. The good agreement between all obtained results points that the proposed FE model is efficient to estimate the response of flexible pipes to axial compression and, furthermore, has potential to be employed in the identification of the failure modes related to excessive axial compression as well as in the mechanical analysis of flexible pipes under other types of loads.

Development and Experimental Calibration of Numerical Model Based on Beam Theory to Estimate the Collapse Pressure of Flexible Pipes

2015 ◽  
Author(s):  
Jefferson Lacerda ◽  
Marcelo I. Lourenço ◽  
Theodoro A. Netto
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Numerical Models ◽  
Beam Theory ◽  
Gas Production ◽  
Operating Conditions ◽  
Flexible Pipe ◽  
Experimental Calibration ◽  
Collapse Pressure ◽  
Flexible Pipes

The constant advance of offshore oil and gas production in deeper waters worldwide led to increasing operational loads on flexible pipes, making mechanical failures more susceptible. Therefore, it is important to develop more reliable numerical tools used in the design phase or during the lifetime to ensure the structural integrity of flexible pipes under specific operating conditions. This paper presents a methodology to develop simple finite element models capable of reproducing the behavior of structural layers of flexible pipes under external hydrostatic pressure up to collapse. These models use beam elements and, in multi-layer analyses, include nonlinear contact between layers. Because of the material anisotropy induced by the manufacturing process, an alternative method was carried out to estimate the average stress-strain curves of the metallic layers used in the numerical simulations. The simulations are performed for two different configurations: one where the flexible pipe is composed only of the interlocked armor, and another considering interlocked armor and pressure armor. The adequacy of the numerical models is finally evaluated in light of experimental tests on flexible pipes with nominal internal diameters of 4 and 6 in.

Effect of Tension on Collapse Performance of Flexible Pipes

2018 ◽  
Author(s):  
Marcelo Miyazaki ◽  
Laurent Paumier ◽  
Fabien Caleyron
Keyword(s):  
Finite Elements ◽  
Failure Modes ◽  
Cost Model ◽  
Negative Influence ◽  
External Pressure ◽  
Flexible Pipe ◽  
Test Protocol ◽  
Specific Test ◽  
Flexible Pipes ◽  
Finite Elements Model

This paper investigates the effect of tension on collapse performance of flexible pipes. In the design of flexible pipelines for offshore field developments, one of the failure modes being associated with external pressure and bending loadings is the hydrostatic collapse. In accordance with standards, TechnipFMC methodology for flexible pipe collapse resistance determination ensures a robust design. The model has an analytical basis, leading to a fast and straightforward use. It has been validated with more than 200 tests performed on all possible pipe constructions on straight and curved configurations. TechnipFMC and IFP Energies nouvelles have also developed and improved over the past few years a Finite Elements Model dedicated to flexible riser studies. It takes full advantage of the structure periodicities such that a whole riser can be studied with a short length and low CPU cost model associated to specific periodicity conditions. The model is able to represent bent risers in various configurations (bending cycles, internal and external pressure, axial tension, torsion) and has been used for collapse prediction of flexible risers under tension. Additionally, a specific test protocol has been developed to be able to carry out a collapse test associated to tension. The purpose of this paper is to present the collapse test result, the specific development of the model for collapse and tension and the corresponding calculations performed with the Finite Elements Model on several structures, demonstrating that there is no negative influence of tension on collapse mode. It also gives a better understanding on the interaction between tension in the armor layers and collapse phenomenon.

Study on the Failure Mechanism of Flexible Pipes Under Large Torsion Considering the Layer Interaction

2018 ◽  
Author(s):  
Shanghua Wu ◽  
Zhixun Yang ◽  
Jinlong Chen ◽  
Qingzhen Lu ◽  
Qianjin Yue ◽  
...  
Keyword(s):  
Failure Mechanism ◽  
Failure Modes ◽  
Layer Structure ◽  
Twist Angle ◽  
Water Environment ◽  
Interaction Mechanism ◽  
Failure Criteria ◽  
Flexible Pipe ◽  
Strength Failure ◽  
Flexible Pipes

Flexible pipe is the typical multi-layer structure which is designed to resist different loads when it is utilized under the severe deep-water environment. However, there is not any structural layer to withstand the torsion specially. Tension armors are only arranged to bear the tension with consideration of the torque balance. Especially, when flexible pipe is loaded out from the cargo vessel to the installation vessel, twist angle could be accumulated at high level so that all of layers need to resist the torsion. So, the failure mechanism is very complicated due to the interaction effect between different layers. Firstly, the interaction mechanism between layers of flexible pipes is analyzed under large torsion and some potential failure modes are identified, namely the strength failure and buckling failure of tensile armor, collapse failure of the inner layers. The theoretical descriptions of involved failure behaviors are investigated and the governing physical effects of failure modes are discussed. In addition, some failure criteria for predicting the pipe capacity are introduced. Finally, the methodology can be used to predict the flexible pipe torsional capacity and to prevent the torsional failure in engineering.

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