Flexible Pipe Sensitivity to Birdcaging and Armor Wire Lateral Buckling

2004 ◽  
Author(s):  
Mauro Pastor Braga ◽  
Peter Kaleff
Keyword(s):  
Failure Modes ◽  
Failure Process ◽  
Performance Criteria ◽  
Pipe Failure ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Cyclic Bending ◽  
Testing Procedures ◽  
Flexible Pipes ◽  
Dip Test

Petrobras has been successfully dealing with deep water floating production systems using flexible pipes since 1977. During the completion of Marlim South 3 well in 1977, Petrobras was surprised by the occurrence of two birdcage type failures. At that time, Marlim South 3, in a water depth of 1709 m was the deepest offshore production well in operation. Since then, Petrobras has been testing flexible pipes using a field test known as DIP test. In a DIP test, an empty end capped sample of a flexible pipe, about 150m long, is partially supported by the sea bottom and connected to a lay vessel by a pipe follower or a wire rope. The flexible pipe has to withstand a 4 hour period of cyclic bending due to the motions of the lay vessel. The DIP test has provided Petrobras with information on a new failure mode: lateral buckling in the armor wire. Although a birdcage failure is equally undesirable, lateral buckling of the armor wires implies more danger because it can go unnoticed. In 2001, a research project was set up by the Research and Development Center of Petrobras that was aimed at reproducing the flexible pipe failure modes under laboratory conditions. The purpose was to obtain a better understanding of the failure process, as well as to develop testing alternatives to avoid the significant costs related to DIP tests. In order to assess the effect of cyclic bending as a major factor in degrading the longitudinal compressive strength of flexible pipes 15 destructive tests were performed on 4 inch diameter flexible pipe samples. Two test rigs that accommodated three types of test and a number of test procedures were developed in the project. The number of bending cycles to failure for each sample was determined when subjected to compressive action corresponding to its operational depth. Tests to evaluate the effect of pre-existing damage were also conducted. Special attention was devoted to the effect of layer arrangement on compressive failure. The test results clearly identified the basic failure modes under investigation (i. e. birdcaging and lateral buckling of the armor wires). Suggestions regarding simplified testing procedures and corresponding performance criteria are also presented.

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.

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.

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.

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.

scholarly journals Effect of Lay Angle of Anti-Buckling Tape on Lateral Buckling Behavior of Tensile Armors

2015 ◽  
Author(s):  
Chongyao Zhou ◽  
Svein Sævik ◽  
Naiquan Ye ◽  
Guomin Ji
Keyword(s):  
Cross Section ◽  
Deep Water ◽  
Lateral Stability ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Cyclic Bending ◽  
Buckling Behavior ◽  
Vessel Motion ◽  
Empty Condition ◽  
Torsion Deformation

During deep water flexible pipe installation, the pipe is normally free hanging in empty condition from the installation vessel to the seabed. This will introduce large hydrostatic forces to the pipe causing true wall compression. In addition, the pipe will be exposed to cyclic bending caused by waves and vessel motion. The combination of true wall axial compression and cyclic bending may lead to tensile armor instability in both lateral and radial directions. If the anti-buckling tape is assumed to be strong enough, the inner tensile armor will lose its lateral stability first due to the gap that may occur between the inner tensile armor and the pipe core, hence restricting the available friction restraint forces. These may further be reduced by cyclic motions that act to create slip between the layers, hence introducing lateral buckling of the tensile armor, with associated severe global torsion deformation of the pipe, ultimately causing the pipe to lose its integrity. The anti-buckling tape is designed to prevent the radial buckling behavior, however, its effect on lateral buckling has not yet been documented in available literature. In the present paper, the effect of the winding direction of the anti-buckling tape on the twist of the cross section is studied, including comparisons with available test data from literature.

Flexible and Rigid Pipe Solutions in the Development of Ultra-Deepwater Fields

2003 ◽  
Author(s):  
Adriano Novitsky ◽  
Fin Gray
Keyword(s):  
Oil Industry ◽  
Technical Cooperation ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Collapse Resistance ◽  
Flexible Pipes ◽  
Campos Basin ◽  
Flexible Risers ◽  
Girth Welds ◽  
Full Scale Tests

The development of the offshore segment during the last three years was remarkably important for the oil industry due to some major achievements observed in the technical area, more specifically on the development of pipe solutions for ultra deepwater (UDW) applications. Brazil and Gulf of Mexico (GoM) have lately been the two main regions for application of proven pipe solutions in UDW. In Brazil, flexible pipes have been widely used in the development of UDW fields by Petrobras, while in the GoM, rigid pipelines and SCRs have been used for the majority of deepwater field developments. The main advances in flexible pipe technology are linked to the development of two major Petrobras fields located in the Campos Basin named Roncador and Marlim South. Technip-Coflexip has, through Technical Cooperation Agreements with Petrobras, designed, tested and installed flexible pipes, proving the fitness of this kind of product to UDW applications. The qualification of flexible risers for 1500m WD and flexible flowlines for 2000m WD are highlighted as being the main achievements. Extensive testing programs including, collapse, fatigue and offshore full scale tests have been put in place in order to simulate the design conditions to be seen by the pipes during installation and operation phases. The main design aspects in UDW like collapse, radial and lateral buckling of tensile armours, fatigue and thermal insulation will be covered in this paper and the current available technologies to tackle these issues will be presented. Similar design and qualification issues exist for rigid pipelines and risers (SCRs). The following three areas are specifically covered in this paper: collapse resistance of steel pipe; fatigue strength of plastically strained girth welds: and qualification of pipe-in-pipe thermal performance. These are some of the key areas of reeled pipe in deepwater applications that require successful project qualification. Technip-Coflexip has performed internal R&D programs on these areas as well as project specific qualifications. Both will be addressed by the paper.

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.

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.

Stresses in Tensile Armour Layers of Unbounded Flexible Risers Loaded With External Pressure: Application to Lateral Buckling Mode

2017 ◽  
Author(s):  
Fabien Caleyron ◽  
Jean-Marc Leroy ◽  
Martin Guiton ◽  
Pascal Duchêne ◽  
Pascal Estrier ◽  
...  
Keyword(s):  
Failure Modes ◽  
External Pressure ◽  
Engineering Model ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Buckling Mode ◽  
Periodic Model ◽  
Scale Test ◽  
Flexible Risers ◽  
Offshore Field

Life6 software, developed by IFP Energies nouvelles, is the local model used by Technip to determine stresses in tensile armour layers of unbounded flexible risers. These stresses and their variations are then used to predict fatigue limits of the dynamically loaded risers. Life6 is based on periodic conditions to reduce the model length, with the assumption that all the tensile armour wires of a same layer share the same kinematics. This paper firstly presents recent improvements to obtain a better modeling of tensile armour wires kinematics, when the flexible riser loading includes external pressure. New models of the external sheath and the anti-buckling tapes have been developed and implemented in Life6. The results are successfully compared to a Finite Element periodic model. Applications to lateral buckling prediction of tensile armour layers are secondly presented in the paper. Indeed, in the design of flexible pipelines for offshore field developments, lateral buckling is one of the critical failure modes for the tensile armour wires, being associated with external pressure and flexible pipe cyclic bending. The latest developments made on the modeling of the external kernel of the flexible pipe allow to use Life6 as the basis of the enhancement of the lateral buckling engineering model used by Technip. It has been calibrated and validated against an extensive full scale test data base resulting in a physical, reliable and fast engineering model to predict lateral buckling mode. In accordance with standards, Technip methodology for flexible pipe lateral buckling determination ensures a robust and competitive design.

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